Download - Execution and Evaluation of Kiln Performance Tests

T R A N S L A T I O N

GERMAN ASSOCIATION OF

CEMENT WORKS (VDZ)

Tannenstrasse 2

4 Düsseldorf Germany

Execution and

Evaluation of Kiln

Performance Tests

PROCESS TECHNOLOGY

COMMITTEE

KILN PERFORMANCE

TESTS TASK FORCE

May 1992

Specification Vt 10

May 1992 Specification Vt 10

TABLE OF CONTENTS

1. PRELIMINARY REMARKS...........................................................................7

2. DESCRIPTION OF THE CLINKER BURNING PROCESS ...........................8

2.1 Reactions of the kiln feed............................................................................................................... 8

2.2 Burning process............................................................................................................................ 10

3. EXECUTION OF KILN PERFORMANCE TESTS.......................................16

3.1 Mode of operation of the kiln system.......................................................................................... 16

3.2 Duration of the performance test................................................................................................ 16

3.3 Measuring methods...................................................................................................................... 17

3.3.1 Solid substances.................................................................................................................... 17 3.3.1.1 Sampling .......................................................................................................................... 17 3.3.1.2 Analysis ........................................................................................................................... 18 3.3.1.3 Mass flows ....................................................................................................................... 25

3.3.2 Gases..................................................................................................................................... 27 3.3.2.1 Sampling .......................................................................................................................... 27 3.3.2.2 Analysis ........................................................................................................................... 28 3.3.2.3 Volume flows................................................................................................................... 28

3.3.3 Liquids.................................................................................................................................. 30 3.3.3.1 Heating oil ....................................................................................................................... 30 3.3.3.2 Water................................................................................................................................ 30

3.3.4 Temperatures ........................................................................................................................ 31 3.3.5 Pressures ............................................................................................................................... 32 3.3.6 Strokes and rotational speeds................................................................................................ 32 3.3.7 Electricity consumption ........................................................................................................ 33 3.3.8 Ambient conditions............................................................................................................... 33 3.3.9 Ensuring the precision of the measurements and analyses ................................................... 34

4. EVALUATION OF KILN PERFORMANCE TESTS.....................................35

4.1 Balancing of the entire system..................................................................................................... 35

4.1.1 Solid substance mass flows .................................................................................................. 40 4.1.2 Gas volume flows ................................................................................................................. 42


4.1.2.1 Dry gas............................................................................................................................. 42 4.1.2.1.1 Minimum air volume flow.......................................................................................... 42 4.1.2.1.2 Air proportionality factor............................................................................................ 45 4.1.2.1.3 Infiltrated air at the kiln hood ..................................................................................... 46 4.1.2.1.4 Secondary air .............................................................................................................. 47 4.1.2.1.5 Cooler intake air ......................................................................................................... 48 4.1.2.1.6 Raw gas ...................................................................................................................... 48 4.1.2.1.7 Gas downstream from the burning area ...................................................................... 50 4.1.2.1.8 Gas downstream from the rotary kiln (kiln inlet) ....................................................... 50

4.1.2.2 Water vapor...................................................................................................................... 51 4.1.2.2.1 Humidity in the air...................................................................................................... 51 4.1.2.2.2 Water from the kiln feed............................................................................................. 51 4.1.2.2.3 Water from the fuel..................................................................................................... 52 4.1.2.2.4 Injection water ............................................................................................................ 52

4.1.2.3 Moist gas.......................................................................................................................... 52 4.1.2.3.1 Air............................................................................................................................... 52 4.1.2.3.2 Raw gas ...................................................................................................................... 53

4.1.3 Liquid mass flows................................................................................................................. 53 4.1.4 Energy flows......................................................................................................................... 53

4.1.4.1 Energy input..................................................................................................................... 53 4.1.4.1.1 Fuel ............................................................................................................................. 53 4.1.4.1.2 Kiln feed ..................................................................................................................... 57 4.1.4.1.3 Air............................................................................................................................... 60 4.1.4.1.4 Injection water ............................................................................................................ 62 4.1.4.1.5 Mechanical performance ............................................................................................ 62

4.1.4.2 Energy output................................................................................................................... 62 4.1.4.2.1 Reaction enthalpy of the kiln feed .............................................................................. 62

4.1.4.2.1.1 C3S, C2S, C3A and C4AF in the clinker ............................................................... 64 4.1.4.2.1.2 CaCO3 and MgCO3 in the kiln feed and in the raw gas dust ............................... 65 4.1.4.2.1.3 CaCO3 and C2S in the bypass dust....................................................................... 66 4.1.4.2.1.4 Balance equations ................................................................................................ 66

4.1.4.2.2 Water evaporation....................................................................................................... 70 4.1.4.2.3 Waste gas losses ......................................................................................................... 70 4.1.4.2.4 Dust losses .................................................................................................................. 71 4.1.4.2.5 Incomplete combustion............................................................................................... 72 4.1.4.2.6 Clinker ........................................................................................................................ 72 4.1.4.2.7 Radiation and convection ........................................................................................... 74 4.1.4.2.8 Uncoupled heat ........................................................................................................... 78

4.1.4.3 Energy balance................................................................................................................. 79

4.2 Balancing of the partial systems.................................................................................................. 80

4.2.1 Clinker cooler ....................................................................................................................... 80 4.2.1.1 Solid substance mass flows.............................................................................................. 83 4.2.1.2 Gas volume flows ............................................................................................................ 84 4.2.1.3 Energy flows ........................................................................................................................... 84

4.2.1.3.1 Energy input ............................................................................................................... 84 4.2.1.3.1.1 Hot clinker ........................................................................................................... 84 4.2.1.3.1.2 Cooler intake air .................................................................................................. 85 4.2.1.3.1.3 Injection water ..................................................................................................... 85 4.2.1.3.1.4 Mechanical performance ..................................................................................... 85


4.2.1.3.2 Energy output ............................................................................................................. 85 4.2.1.3.2.1 Clinker, clinker dust ............................................................................................ 85 4.2.1.3.2.2 Radiation and convection .................................................................................... 86 4.2.1.3.2.3 Uncoupled heat .................................................................................................... 86 4.2.1.3.2.4 Cooler vent air, secondary air, tertiary air ........................................................... 86 4.2.1.3.2.5 Water evaporation................................................................................................ 86

4.2.1.3.3 Energy balance ........................................................................................................... 86 4.2.1.4 Evaluation quantities........................................................................................................ 87

4.2.1.4.1 Pre-cooling zone ......................................................................................................... 87 4.2.1.4.2 Energy loss flow of the cooling area .......................................................................... 89 4.2.1.4.3 Cooling area efficiency............................................................................................... 89 4.2.1.4.4 Cooler efficiency ........................................................................................................ 90

4.2.2 Calcinator (only for kiln system with cyclone preheater)..................................................... 90 4.2.2.1 Determination of the degree of precalcining.................................................................... 92

4.2.3 Preheater (only for kiln system with cyclone preheater) ...................................................... 93 4.2.3.1 Degree of separation of individual cyclone stages........................................................... 94

5. EVALUATION OF THE SUBSTANCE CIRCULATION SYSTEMS ............98

6. EVALUATION OF THE CEMENT CLINKER ..............................................99

6.1 Degree of burning......................................................................................................................... 99

6.2 Particle-size distribution.............................................................................................................. 99

6.3 Grindability ................................................................................................................................ 100

6.4 Chemical composition ................................................................................................................ 100

6.5 Phase composition ...................................................................................................................... 103

6.6 Microscopic examination........................................................................................................... 103

6.7 Cement testing ............................................................................................................................ 104

7. EVALUATION OF THE EMISSIONS ........................................................105

8. FORMULA SIGNS AND INDICES ............................................................106

9. LITERATURE REFERENCES...................................................................112

9.1 General literature references .................................................................................................... 112

9.2 Technical literature references.................................................................................................. 113


10. EVALUATION EXAMPLE 1 (KILN SYSTEM WITH A CYCLONE PREHEATER, CALCINATOR AND TERTIARY AIR DUCT) ...........................118

10.1 Balancing the entire system .................................................................................................. 118

10.1.1 Solid substance mass flows ................................................................................................ 118 10.1.2 Gas volume flows ............................................................................................................... 119

10.1.2.1 Dry gas ...................................................................................................................... 119 10.1.2.1.1 Minimum air volume flow...................................................................................... 119 10.1.2.1.2 Air proportionality factors ...................................................................................... 120 10.1.2.1.3 Infiltrated air at the kiln hood ................................................................................. 120 10.1.2.1.4 Secondary air .......................................................................................................... 121 10.1.2.1.5 Cooler intake air ..................................................................................................... 121 10.1.2.1.6 Raw gas .................................................................................................................. 122 10.1.2.1.7 Gas downstream from the burning area .................................................................. 123 10.1.2.1.8 Gas downstream from the rotary kiln (kiln inlet) ................................................... 124 10.1.2.1.9 Infiltrated air (preheater)......................................................................................... 125 10.1.2.1.10 Infiltrated air (calcinator)...................................................................................... 125

10.1.2.2 Water vapor............................................................................................................... 125 10.1.2.2.1 Humidity in the air.................................................................................................. 125 10.1.2.2.2 Water from the kiln feed......................................................................................... 126 10.1.2.2.3 Water from the fuel................................................................................................. 127 10.1.2.2.4 Injection water ........................................................................................................ 127

10.1.2.3 Moist gas (examples) ................................................................................................ 128 10.1.3 Liquid mass flows............................................................................................................... 128 10.1.4 Energy flows....................................................................................................................... 128

10.1.4.1 Energy input .............................................................................................................. 128 10.1.4.1.1 Fuel ......................................................................................................................... 128 10.1.4.1.2 Kiln feed ................................................................................................................. 129 10.1.4.1.3 Air........................................................................................................................... 130 10.1.4.1.4 Injection water ........................................................................................................ 130 10.1.4.1.5 Mechanical performance ........................................................................................ 130

10.1.4.2 Energy output ............................................................................................................ 131 10.1.4.2.1 Reaction enthalpy of the kiln feed .......................................................................... 131

10.1.4.2.1.1 C3S, C2S, C3A and C4AF in the clinker ........................................................... 131 10.1.4.2.1.2 CaCO3, and MgCO3 in the kiln feed and in the raw gas dust........................... 132 10.1.4.2.1.3 CaCO3 and C2S in the bypass dust................................................................... 132 10.1.4.2.1.4 Balance equations ............................................................................................ 132

10.1.4.2.2 Water evaporation................................................................................................... 134 10.1.4.2.3 Waste gas losses ..................................................................................................... 134 10.1.4.2.4 Dust losses .............................................................................................................. 135 10.1.4.2.5 Incomplete combustion........................................................................................... 136 10.1.4.2.6 Clinker .................................................................................................................... 136 10.1.4.2.7 Radiation and convection: ...................................................................................... 137 10.1.4.2.8 Uncoupled heat ....................................................................................................... 137

10.1.4.3 Energy balance .......................................................................................................... 137

10.2 Balancing of the partial systems........................................................................................... 138 10.2.1 Clinker cooler ..................................................................................................................... 138

10.2.1.1 Solid substance mass flows ....................................................................................... 138


10.2.1.2 Gas volume flows...................................................................................................... 138 10.2.1.3 Energy flows ............................................................................................................. 139

10.2.1.3.1 Energy input ........................................................................................................... 139 10.2.1.3.2 Energy output ......................................................................................................... 139 10.2.1.3.3 Energy balance ....................................................................................................... 141

10.2.1.4 Evaluation quantities................................................................................................. 142 10.2.1.4.1 Pre-cooling zone ..................................................................................................... 142 10.2.1.4.2 Energy loss flow of the cooling area ...................................................................... 142 10.2.1.4.3 Cooling area efficiency........................................................................................... 143

10.2.2 Calcinator ........................................................................................................................... 143 10.2.3 Preheater ............................................................................................................................. 144

10.3 Estimation of error................................................................................................................ 145

10.4 Tables...................................................................................................................................... 146


1. Preliminary remarks

In cement plants, kiln performance tests not only serve to gather data on the performance

of the kiln system (clinker output, specific fuel-energy consumption), but also to create a

reliable foundation for the optimization of individual system components, of the opera-

tion and of the cement quality, as well as for the reduction of the level of emissions. The

important aspect here is the absolute value of the measured values. For this reason, this

specification, in addition to the evaluation, specifically contains information for carrying

out performance tests, including significant remarks pertaining to measurement technol-

ogy.

The units indicated in Section 8 apply to all numerical value equations. The practical fea-

sibility of the evaluation is always the main priority in the formulation of the numerical

value equations. The evaluation equations are employed in two practical examples in

Sections 10 and 11.

This specification deals primarily with energy and mass balances. Information on pres-

sure levels, stroke numbers and rotational speeds as well as on the consumption of elec-

tricity, in contrast, only serves to assess the kiln operation. Additional information in this

context would be necessary in order to obtain a precise measurement.


2. Description of the clinker burning process

2.1 Reactions of the kiln feed

Portland cement clinker is made from a finely-ground raw material mixture consisting of

limestone, marl, clay and sand. The oxidic main components are calcium oxide (CaO),

silicon dioxide (SiO2), aluminum oxide (Al2O3) and iron oxide (Fe2O3).

The raw material mixture is heated up and burned in the rotary kiln to form clinker, a

process in which several chemical reactions take place, some of them consecutively, and

some of them in parallel to each other (see Figure 1).

Figure 1 - Schematic representation of the clinker formation reaction.


The clinker formation reactions can be depicted as a model broken down into the fol-

lowing temperature stages:

• starting composition:

calcite (CaCO3), quartz (SiO2), clay minerals (SiO2-Al2O3-H2O) and iron ore (Fe2O3);

• up to about 700°C [1292°F], activation of the silicates through water expulsion and

modification change;

• between 700°C and 900°C [1292°F and 1652°F], calcination of the CaCO3 and concur-

rent binding of Al2O3, Fe2O3 as well as of activated SiO2 and CaO;

• once a maximum of 1200°C [2192°F] is reached, the formation of belite (“C2S”) from

SiO2 on CaO (“free lime”) is completed;

• starting at 1250°C [2282°F], and forced above 1300°C [2372°F] due to melt formation,

reaction of the belite with the remaining free lime to form alite (“C3S”);

• upon cooling, crystallization of the melt to form C3A and C4AF. In this process, the

alite and the belite remain virtually unchanged in their form and composition.

First of all, the physically bound water is removed when the kiln feed is preheated, while

the chemically bound water is removed up to a temperature of about 700°C [1292°F].

This is followed by the calcination (decarbonation, dissociation) of the calcium carbonate

into CaO and CO2, which practically takes place between 800°C and 900°C [1472°F and

1652°F]. After the complete decarbonation, the kiln feed has lost about 35% of its dry

weight.

Owing to solid-state reactions, the formation of the dicalcium silicate (2CaO · SiO2, in

short, C2S) already starts at about 700°C [1292°F]. Moreover, various calcium aluminate

and calcium ferrite compounds are formed as transition phases which, however, disinte-

grate again once the clinker melt starts to form at about 1280°C [2336°F]. At a sintering

temperature of around 1450°C [2642°F], it reaches a fraction of about 20% to 30% by

weight. The melt plays a significant role in the finishing burn of the clinker, since it pro-


motes the formation of tricalcium silicate (3CaO · SiO2, in short, C3S) from solid dical-

cium silicate and CaO, which is indispensable for the strength properties of the cement.

As the melt cools down, essentially tricalcium aluminate (3CaO · Al2O3, in short, C3A)

and aluminate ferrite (4CaO · Al2O3 · Fe2O3, in short, C4AF) crystallize out.

After completion of the sintering, the cement clinker has to be cooled off so quickly that

the tricalcium silicate does not disintegrate, and the tricalcium aluminate crystallizes with

the finest grain possible. On the other hand, the cooling rate should not be so high that the

melt becomes glassy as it solidifies. In this context, qualitative differences occur which

depend on the composition of the kiln feed [48-53]. Consequently, the cooling of the

cement clinker has to be optimally harmonized with the required clinker properties.

2.2 Burning process

In Germany nowadays, cement clinker is produced in rotary kiln systems with kiln feed

preheaters located upstream and clinker coolers located downstream (for other process

techniques, see [2-4, 6-9 and 11-15]).

Rotary kilns are fire-proof, brick-lined tubes, having diameters of up to 6 meters and

inclined at an angle ranging from about 2.5° to 4.0°, which are operated at 1.5 to 3 rpm.

As a result of the inclination and rotation, the kiln feed coming from the preheater moves

towards the main burner of the rotary kiln, which is located at the lower end of the rotary

kiln. Rotary kilns with preheaters located upstream have a length that is 10 to 17 times

longer than their diameters. In order to reach the sintering temperature of about 1350°C

to 1500°C [2462°F to 2732°F] that is necessary for the formation of the clinker phase and

in view of the unfavorable heat-conduction conditions in the kiln feed, burning tempera-


tures ranging from 1800°C to 2000°C [3272°F to 3632°F] or even higher are needed. In

order to be able to reach such high temperatures, the combustion air is preheated to about

600°C to 1000°C [1112°F to 1832°F] in a clinker cooler located downstream from the

sintering process, and it is then fed to the rotary kiln burner as so-called secondary air.

Grate-type coolers, satellite coolers and rotary coolers are employed as clinker coolers in

the cement industry. With grate-type coolers, the clinker that drops out of the rotary kiln

after the sintering operation is cooled in a crosscurrent. In the case of the rotary coolers or

satellite coolers, which usually consist of 10 satellite tubes attached around the periphery

of the rotary kiln, the clinker dissipates its energy to the cooling air that is flowing in a

cross current or countercurrent.

When it comes to kiln systems, a distinction is made as to whether they are operated with

a grate-type preheater or with a cyclone preheater. Grate-type preheaters consist of a

traveling grate on which the kiln feed that has been made into granules or briquettes trav-

els through a closed tunnel that is divided into a hot chamber and a dry chamber. An

intermediate gas fan blows the process gas of the rotary kiln from the top to the bottom

through the layer of granules in the hot chamber. After the coarse dust has been separated

out, the gas is once again blown from the top to the bottom through the moist granules in

the dry chamber.

The cyclone preheater essentially consists of four to five cyclone stages arranged one

above the other in a tower that is 50 to 100 meters high, depending on the clinker output.

The process gases coming from the rotary kiln flow through the cyclone preheater from

the bottom to the top. The dry, raw meal mixture is fed into the waste gases prior to

entering the uppermost cyclone stage, and it is once again separated from the gas in the

cyclones; afterwards, it re-enters the gas stream prior to the next-lower cyclone stage.


Both with cyclone preheater systems and with grate-type preheater systems, the process

gas from the rotary kiln has a temperature of about 1000°C to 1200°C [1832°F to

2192°F]. The kiln feed entering the rotary kiln reaches temperatures of 820°C to 850°C

[1508°F to 1562°F] at precalcining degrees of up to about 90%. Upon leaving the cyclone

preheater, the waste gases have a temperature of around 290°C to 400°C [554°F to

752°F], depending on the number of stages and capacity flow ratio. As a function of the

process, the waste gases of the grate-type preheater have a temperature of about 90°C to

120°C [194°F to 248°F].

Figure 2 shows a schematic representation of a cement rotary kiln system with a cyclone

preheater and waste gas utilization. Figure 3 schematically shows a rotary kiln system

with a grate-type preheater.

Figure 2 - Schematic representation of a cement rotary kiln system

with cyclone preheaters and waste gas utilization.



with a grate-type preheater.

Since about 1970, the further development of kiln systems has led to the process involv-

ing precalcining. In this process, the fuel energy is divided up over two burners and, with

the secondary burner located between the rotary kiln and the preheater, the amount of

energy supplied is such that 70% to 95% of the calcium carbonate of the kiln feed has

already decarbonated by the time it enters the rotary kiln. For this purpose, new systems

with cyclone preheaters are provided with an enlarged combustion chamber between the

rotary kiln inlet and the lowermost cyclone, which is designated as the calcinator.

The combustion air for the secondary burner can be conveyed through the rotary kiln,

that is to say, together with the waste gas from the main burner. This method is employed

with old systems in particular. In the case of new systems with cyclone preheaters, how-

ever, the combustion air is conveyed in a separate gas duct, the so-called “tertiary air

duct”, which leads from the clinker cooler past the rotary kiln, and from there to the sec-

ondary burner. The principle involved in both techniques for conveying the combustion


air is shown in Figure 4. A rotary kiln system with precalcining, consisting of a four-

stage cyclone preheater, calcinator, rotary kiln, reciprocating grate-type cooler and terti-

ary air duct, is shown in Figure 5. In rotary kiln systems having a calcinator but without a

tertiary air duct, up to 30% – in systems with a tertiary air duct, up to 60% – of the total

fuel energy needed can be employed in the secondary burner.

Figure 4 - Precalcining process with and without tertiary air duct.



with a cyclone preheater, calcinator and tertiary air

duct.


3. Execution of kiln performance tests

3.1 Mode of operation of the kiln system

The considerations elaborated upon below apply exclusively to the stationary operation a

kiln system. The latter has to be safeguarded by means of appropriate measures.

The essential operating data (for instance, the mass flow of the kiln feed, the energy frac-

tion of the secondary fuel, types of fuel, composition of the kiln feed, type of combined

drying and grinding operation) should already have been determined during the planning

phase of the performance test and, in cases of major changes vis-à-vis normal operations,

should already have been established one week prior to the start of the performance test.

Neither shortly before nor during the performance test should there be any changes in the

composition of the kiln feed or of the fuel (for example, by changing the mixed bed).

Possible criteria for interrupting the performance test should also be laid down in

advance.

3.2 Duration of the performance test

A kiln performance test should last for at least 24 hours, preferably 48 or 72 hours. If the

type of combined drying and grinding operation changes (in, out, partial load), the per-

formance test should preferably last 72 hours.


3.3 Measuring methods

3.3.1 Solid substances

3.3.1.1 Sampling

The objective of sampling is to obtain a random sample of each solid substance mass

flow that is representative of the parent population being examined.

The samples are taken from the belt (for instance, conveyor belt, apron conveyor), at the

discharge end of the conveyors (for instance, bucket elevator, screw conveyor) or from

the meal pipes (for example, the hot-meal pipe of a cyclone). The safety regulations that

apply in such cases must be observed. It must be ensured that the sample is taken over the

entire width of the material stream in order to take into account possible de-mixing phe-

nomena. Thus, for instance, when two partial streams having different concentrations of

the component to be examined are combined, which could give rise to insufficient

blending by the time the sampling site is reached, then this non-homogeneity has to be

taken into consideration by enlarging the scope of the sampling, that is to say, the sam-

pling amount and the sampling frequency have to be adapted to the prevailing test con-

ditions. Table 1 shows an example of a sampling plan.

Table 1 - Sampling amount and sampling frequency in rotary kiln performance tests.

Material

Sampling amount in kg

Sampling frequency

clinker ≥ 1 every hour

coal dust (main burner) ≥ 0.5 every four hours

coal dust (secondary burner) ≥ 0.5 every four hours

kiln feed ≥ 0.5 every four hours

raw gas dust ≥ 0.5 every four hours 1)

tertiary air dust ≥ 0.5 every four hours 1)

bypass dust ≥ 0.5 every two hours

Kiln feed in the preheater ≥ 0.5 every four hours 1) With partial-stream suction, every 12 hours.


A partially decarbonated kiln feed should be cooled off rapidly and air-tight so as to

avoid, for example, further decarbonation of CaCO3 or a residual burn-out of carbon.

For practical reasons, the samples can also be taken at time-staggered intervals. Samples

of solid substances from flowing gases (raw gas dust, tertiary air dust) can also be taken

by means of isokinetic suction of a partial stream. In this process, care should be taken to

ensure that the suction is representative.

The individual samples are pre-comminuted (for example, clinker), homogenized and

combined to form a weighed average sample for the duration of the performance test.

As a matter of principle, the individual and average samples should be stored air-tight in

order to avoid a falsification of the H2O and CO2 contents. High levels of moisture (for

instance, in the raw material) should be determined on larger individual samples; the

average sample is subsequently formed on the basis of the pre-dried individual samples.

3.3.1.2 Analysis

Table 2 shows an example of an analysis plan. As a matter principle, the laboratory

should be informed about the source and presumed composition of the samples. This

ensures that the best suited decomposition and analysis methods will be selected for each

particular case.


Table 2 - Analysis and analysis method for rotary kiln performance tests.

Material

Analysis

Analysis method

Coal dust

sampling, sample preparation

DIN 51701 (Part 3), ISO 1988, ISO 2309

calorific value DIN 51900, ISO 1928

H2O DIN 51718, ISO 331, ISO 348, ISO 579, ISO 589, ISO 687, ISO 1015

ash DIN 51719, ISO 1171

ash composition DIN 51729

volatile components DIN 51720, ISO 562

C and H DIN 51721, ISO 609, ISO 625

S DIN 51724 (Part 1), ISO 334, ISO 351

Cl – DIN 51727, ISO 352, ISO 587

N DIN 51722 (Part 1), ISO 333

O subtraction

Oil

sampling

DIN 51570 (Parts 1 to 3)

calorific value DIN 51900, ISO 1928

H2O DIN 51777, ISO 3733

ash DIN EN 7

C and H DIN 51721 1)

S DIN EN 41, DIN 51400

Cl – DIN 51722 1)

N subtraction

Natural gas

composition

DIN 51872

O DIN 51856

S DIN 51855

Clinker, tertiary

air dust

sample preparation

Grinding for complete passage through the sieve, 0.09 mm (for CaOfree 0.063)

loss on ignition 1000°C [1832°F] ± 25 K (10 min) or 950°C [1742°F] ± 25 K until weight constancy is achieved


X-ray fluorescent

full analysis 2) a) fluxing agent tablet (≤ 1000°C [1832°F]; 81%

by weight of Li2B4O7 + 8.1% by weight of LiF + 8.9% by weight of SrO + 2% by weight of V2O5 as the decomposition agent; dilution of 1:5 to 1:20); analysis including SO3 and alkali

b) fluxing agent tablet (1050°C [1922°F]; 90% by weight of Li2B4O7 + 10% by weight of LiF as the decomposition agent; dilution of 1:10); determination of SO3, K2O and Na2O with other analytical methods, subsequent correction of the results

c) fluxing agent tablet (1200°C [2192°F]; 100% by weight of Li2B4O7 as the decomposition agent; dilution of 1:5); determination of SO3, K2O and Na2O with other analytical methods, subsequent correction of the results

Cl – (including Br and I) 3) Decomposition:

a) nitric acid (1 part of concentrated nitric acid + 19 parts of water)

b) acetic anhydride (7+6)

c) thermal reaction in a moist O2 stream at 1000°C [1832°F] so as to form hydrogen chloride

Analysis:

a) potentiometric titration with silver nitrate

b) titration according to Volhardt

c) introduction of the hydrogen chloride into an acetic silver nitrate solution and coulometric titration

The weighed-in amount has to be adapted to the low Cl – content of the clinker (5 to 10 g)

Σ SO3 a) gravimetric

b) thermal reaction of the sulfur compounds with additives in the oxygen stream. Measurement of the SO2 by means of an IR detector or else iodometrically

K2O, Na2O J.L. Smith decomposition, hydrofluoric acid decomposition / perchloric acid decomposition (observe the safety regulations!) or melt decompo-sition (< 1000°C [1832°F]) with Li2B4O7, flame photometry (emission, absorption)

CaOfree a) method according to Franke

b) method according to Schläpfer and Bukowski Depending on the boundary conditions, the results can deviate from one method to another


Kiln feed

sample preparation

Grinding for complete passage through the sieve, 0.09 mm

CO2 Thermal degradation in the inert gas stream at 1000°C [1832°F] or chemical degradation with acid

a) gravimetric

b) coulometric

c) IR detection

H2O < 110°C [230°F] 4) Weighing, drying at 110°C [230°F], cooling in a desiccator, weighing

Σ H2O Thermal desorption in an inert gas stream at 1000°C [1832°F]

a) KF titration

b) IR detection

c) gravimetric

Corg Decarbonation with hydrochloric acid, thermal reaction of the carbon compounds in an oxygen stream

a) gravimetric

b) coulometric

c) IR detection

X-ray fluorescent full analysis 2)

a) fluxing agent tablet (≤ 1000°C [1832°F]; 81% by weight of Li2B4O7 + 8.1% by weight of LiF + 8.9% by weight of SrO + 2% by weight of V2O5 as the decomposition agent; dilution of 1:5 to 1:20); analysis including SO3 and alkali








Analysis:





Σ SO3 a) oxidation with bromine water, gravimetric


K2O, Na2O J.L. Smith decomposition, hydrofluoric acid

decomposition / perchloric acid decomposition (observe the safety regulations!) or melt decompo-sition (< 1000°C [1832°F]) with Li2B4O7, flame photometry (emission, absorption)

S2– Dissolution with hydrochloric acid containing SnCl2 in the presence of Cr (metallic), pick-up in a cooled (≤ 15°C [59°F]) ammoniacal ZnSO4 or CdCl2 solu-tion, iodometry

sample preparation Grinding for complete passage through the sieve, 0.09 mm

Raw gas dust 5)

(cyclone preheater

kiln) CO2 Thermal degradation in an inert gas stream at 1000°C [1832°F] or chemical degradation with acid

a) gravimetric

b) coulometric

c) IR detection


a) KF titration

b) IR detection

c) gravimetric


a) gravimetric

b) coulometric

c) IR detection


X-ray fluorescent

full analysis 2) a) fluxing agent tablet (≤ 1000°C [1832°F]; 81%

by weight of Li2B4O7 + 8.1% by weight of LiF + 8.9% by weight of SrO + 2% by weight of V2O5 as the decomposition agent; dilution of 1:5 to 1:20); analysis including SO3 and alkali







Analysis:










sample preparation

Grinding for complete passage through the sieve, 0.09 mm

Bypass dust 5)

Kiln feed in the

preheater5)

Raw gas dust 5)

(grate-type pre-

heating kiln)

CO2 Thermal degradation in an inert gas stream at 1000°C [1832°F] or chemical degradation with acid

a) gravimetric

b) coulometric

c) IR detection


a) KF titration

b) IR detection

c) gravimetric


a) gravimetric

b) coulometric

c) IR detection





Analysis:



c) coulometric titration

d) gravimetric





1) Since there are no specifications for mineral oils, the analysis method for fuels is employed. 2) SiO2, Al2O3, TiO2, P2O5, Fe2O3, Mn2O3, CaO, MgO, SO3, K2O, Na2O. (Σ SO3, K2O, Na2O should be

checked by other analytical methods. In addition to the above-mentioned compounds, the solid materials might also contain fluoride, barium oxide and strontium oxide or S2–. During the reducing burning proc-ess, clinker contains FeO and MnO. If this is already known to be so, the laboratory should be informed to this effect.)

3) Nitric acid extraction does not always dissolve all of the halides out of the sample matrix. This can lead to erroneously low results at low levels of Cl– in the raw material.

4) Alternatively, < 105°C [221°F]. 5) Dust as well as the kiln feed in the preheater can also contain highly volatile compounds such as, for

instance, (NH4)2SO4. In the case of sensitive samples that are hygroscopic or that react during the drying process, the examinations should be performed in the delivery state.

3.3.1.3 Mass flows

Clinker:

The clinker is loaded onto trucks or railroad cars and weighed on calibrated scales (for

example, shipping scales). In each case, the trucks or railroad cars are weighed both

empty and fully loaded (varying amounts of fuel in the tank, dirt). An interim result

should be determined every 4 to 6 hours in order to obtain information about the time

course of the mass flow. The duration of the clinker weighing can differ from the per-

formance test duration, but it should not be shorter than 24 hours. The maximum error is

smaller with a duration of 48 hours. Prior to the test, the weighing procedure should be

checked.

Continuously operating clinker scales can be adjusted by the above-mentioned method,

even over shorter periods of time. For this purpose, several measuring intervals are

needed, for example, every 4 hours with different clinker production. The measured value

from the performance test is then multiplied by the resulting correction values.


In the case of immediately consecutive kiln performance tests, a second clinker weighing

procedure is not necessary if it is ensured that all of the dust mass flows remain constant.

The following relationship applies:

Fuels:

Fuels are weighed on industrial scales which have been previously adjusted. However,

the precision levels achieved in this manner are often not sufficient for evaluating the kiln

system. For this reason, the fuel energy consumption is usually balanced by means of a

comparison of the energy output with the energy input (see Section 4.1.4.3).

Kiln feed:

The kiln feed mass flow is calculated. It results from the component balance of the sum

of the non-volatile substances (see Section 4.1.1).

Dust:

Dust is preferably weighed on calibrated scales (for example, shipping scales). Here, care

should be taken to ensure that the cleaning of the filter is switched to continuous opera-

tion before the dust is discharged. If weighing is not possible, the dust mass flow is

determined by means of an isokinetic partial stream suction (in this context, also see the

VDZ Specification titled “Dust quantity measurements in cement plants” [17]).

Translator’s note: See Section 8 for the list of abbreviations used in the formulas.


3.3.2 Gases

For the gas analysis, more information can be obtained from the VDZ Specification titled

“Continuous gas analysis in cement plants” [20]), while information on volume flow

measurement is to be found in the VDZ Specification titled “Quantity measurement of

gases by means of velocity measurements” [16]). Table 3 shows an example of a meas-

urement plan.

Table 3 - Volume flow measurement and gas analysis in rotary kiln performance tests.

Measuring site

Volume flow measurement

Gas analysis

raw gas pitot tube CO2, O2, CO

bypass gas (with cooling air) pitot tube CO2, O2, CO 1)

bypass gas (without cooling air) – CO2, O2, CO 1)

downstream from the burning area – CO2, O2, CO

kiln inlet – CO2, O2, CO

tertiary air pitot tube –

cooler intake air – –

cooler vent air pitot tube –

burner air (main burner) pitot tube + rated values –

burner air (secondary burner) pitot tube + rated values –

conveying air (kiln feed) rated values –

1) Discontinuous measurement is often sufficient.

3.3.2.1 Sampling

In the raw gas, in the bypass gas and in the gas downstream from the burning area, vari-

ous gas compositions can occur over the cross section of the duct. Moreover, in the case

of double-string cyclone preheaters, there are also differences in the individual strings. In

the gas downstream from the burning area, the time intervals at which the probes need to


be cleaned can be extended by placing the measuring gas sampling opening as far as pos-

sible from the meal inlet pipes. The probe in the gas downstream from the burning area

should be cooled.

In the rotary kiln inlet, the process gas usually displays great differences in concentration,

both with respect to location and to time. For this reason, it is not possible to specify a

representative measuring site. Sampling sites in the upper third of the rotary kiln cross

section are recommended. The sampling opening should project about 0.5 m into the

rotating part of the kiln in order to avoid falsifications of the measured results due to

infiltrated air that gets into the inlet gasket or as a result of falling kiln feed material.

Since the measuring site is also frequently exposed to falling material, the sampling probe

should be built laterally into the refractory brickwork. So as to prevent falsifications of

the concentration values due to the scrubbing out of individual gas components, the

measuring gas should be sampled dry, that is to say, without injection water or scrubbing

water. The probe should be cooled.

3.3.2.2 Analysis

The gas analysis should be carried out continuously. At the very least, determinations of

CO2, O2 and CO are required.

3.3.2.3 Volume flows

The volume flows are primarily measured with a pitot tube. With volumes flows that

fluctuate markedly (for instance, cooler vent air), the pitot tube should be installed in the


gas duct and the differential pressure as well as the appertaining temperature should be

recorded continuously.

There are three methods for measuring the raw gas volume flow:

a) direct measurement with a pitot tube (in the case of unfavorable measuring condi-

tions, for example, deflection of the gas upstream from the measuring site, substantial

pressure fluctuations or a high amount of dust [for instance, > 50 g/m³], this is often

very imprecise);

b) calculation on the basis of a CO2 and an H2O balance of the kiln system (imprecise

when secondary fuels are used) [30];

c) conversion of the clean gas volume flow to raw gas conditions using an O2 or CO2

balance or an H2O balance (additional gas analysis and measurement of the volume

flow in the clean gas is necessary; only possible if clean gases of the kiln can be

detected in their entirety; expensive but accurate).

There are three methods for measuring the volume flow of the cooler intake air:

a) inlet nozzles (often very imprecise);

b) fan characteristic curves (only possible for fans with adjustable rotational speeds);

c) air balance of the cooler (often the most precise way with continuous volume flow

measurement of the cooler vent air after the dust removal).

The bypass gas is measured with a pitot tube after admixing the cooling air. The bypass

gas volume flow prior to the admixture is derived from the gas analysis before and after

the admixture of the cooling air.


The volume flow of infiltrated air at the kiln hood is calculated on the basis of the open

cross-sectional area and of the differential pressure at the kiln hood (see Section 4.1.2.3).

The cross-sectional surface area is either measured or estimated.

The conveying air volume flow of the coal dust and, if applicable, of the kiln feed is

derived from the nominal data of the fan.

Heating gas that has been measured volumetrically has to be converted to the standard

conditions.

3.3.3 Liquids

3.3.3.1 Heating oil

Heating oil can be sampled either by means of an automatic sampling system or else a

sample is taken from the oil tank. The amount of oil that passes through the burner nozzle

per unit of time is for the most part measured volumetrically by means of an oil meter. In

order to determine the actual volume flow that passes through, the result that is read off

the meter has to be corrected by means of a calibration curve. Moreover, it is necessary to

take into account the density, which changes as a function of the temperature.

3.3.3.2 Water

The water mass flow of a cooling chute (cooling water) or into the clinker cooler (injec-

tion water) is measured with water meters that have to be installed in advance.


3.3.4 Temperatures

Table 4 shows the example of a measuring plan.

Table 4 - Temperature measurement in rotary kiln performance tests.

Measuring site Measuring device Frequency

cold clinker compensation temperature in adiabatic vessel, Pt 100

every hour

hot clinker quotient pyrometer continuously

kiln feed in the preheater (e.g. hot meal) NiCr Ni twice per day

bypass dust Pt 100 or NiCr Ni once per day

raw meal (for instance, kiln feed)

Pt 100 or surface temperature of the conveying line with partial-radiation pyrometer

once per day

fuels Pt 100 or surface temperature of the conveying line with partial-radiation pyrometer

once per day

raw gas Pt 100 or NiCr Ni continuously

bypass gas (with cooling air) Pt 100 or NiCr Ni continuously

gas downstream from the burning area NiCr Ni continuously

tertiary air upstream from the preheater NiCr Ni once per day

tertiary air downstream from the cooler NiCr Ni continuously

cooler intake air meteorological station continuously 1)

cooler vent air Pt 100 or NiCr Ni continuously

burner air (main burner) Pt 100 or NiCr Ni once per day

burner air (secondary burner) Pt 100 or NiCr Ni once per day

conveying air (kiln feed) like kiln feed –

surface temperature - rotary kiln partial-radiation pyrometer (ε = 0.9)

twice per day

surface temperature - cooler partial-radiation pyrometer (ε = 0.9) once per day 2)

twice per day 3)

kiln hood partial-radiation pyrometer (ε = 0.9) once per day

calcinator partial-radiation pyrometer (ε = 0.9) once per day

preheater partial-radiation pyrometer (ε = 0.9) once per day 1) if available 2) with grate-type coolers 3) with rotary coolers or satellite coolers


3.3.5 Pressures

In order to evaluate the kiln operation, the following differential pressures should be

measured or recorded by the operating measuring pick-ups:

• cooler (chambers 1 through N);

• kiln outlet;

• kiln inlet;

• preheater (stages 1 through N);

• upstream from the waste gas fan;

• downstream from the waste gas fan.

The above-mentioned differential pressures have to be measured with damped measuring

pick-ups.

3.3.6 Strokes and rotational speeds

In order to evaluate the kiln operation, the strokes and rotational speeds of the following

aggregates should be measured or recorded by the operating measuring pick-ups:

• cooler;

• kiln;

• grate-type preheater;

• waste gas fan;

• bag house fan / ESP fan;

• cooler vent fan;

• bypass fan.


3.3.7 Electricity consumption

In order to evaluate the kiln operation, the meter readings of the main consumers should

be recorded at intervals of, for example, 8 hours.

A large proportion of the electricity is converted into heat in the kiln system. Conse-

quently, when the balancing space is calculated, the consumption of electricity should be

considered as an input item of the energy balance.

If several consumers are connected to one meter, the energy distribution should be meas-

ured with prong-type instruments. The following consumers should be taken into consid-

eration:

• cooler fans;

• cooler vent fan;

• cooler drives;

• burner air fan;

• rotary kiln drive;

• bypass fan;

• waste gas fan;

• kiln feed feeding system;

• fuel feeding system.

3.3.8 Ambient conditions

The temperature, pressure and relative humidity of the ambient air are recorded by a

meteorological station.


3.3.9 Ensuring the precision of the measurements and analyses

The precision of a kiln examination depends on the systematic maintenance and upkeep

of the measuring instruments. In addition to regularly checking the status and settings

during the performance test, it is also necessary to routinely replace wearing parts as pre-

ventive maintenance and to conduct function tests with comparative measured values

(calibration). Checks and corrections should be documented and should be indicated on

the measuring equipment used, together with the date.

Status checks should be made every hour and setting checks should be carried out at least

before and after the performance test. The time schedule for replacing wearing parts and

for the function tests with comparative measured values depends on the measuring instru-

ments and should be laid down appropriately.

Table 5 provides an overview of possible comparative measuring methods.

Table 5 - Comparative measuring instruments or method for rotary kiln performance tests.

Measuring instrument

Comparative measuring instrument or method

gas analyzer gas analyzer with another measuring principle wet-chemical analysis

gas meters testing by the Board of Weights and Measures

thermal elements resistance thermometer

test thermometer and normal thermometer (for instance, plati-num resistance thermometer)

pyrometer black body radiator tungsten band lamp (only above 500°C [932°F])

pressure transducer liquid pressure gage (for instance, miniscope or U-tube)

humidity measuring device sealed container with several aqueous saturated salt solutions

The solid substance analyses have to be conducted by a laboratory that has sufficient

experience with the execution of the analyses listed in Table 2.


4. Evaluation of kiln performance tests

4.1 Balancing of the entire system

When the mass balance is drawn up, the gas and solid substance mass flows should be

balanced together, since there are interactions between both of these as a result of chemi-

cal reactions.

Figure 6 shows the balancing space of a kiln system with a cyclone preheater (V), calci-

nator (C), tertiary air duct (T), rotary kiln (D) and cooler (K) with the mass and energy

flows that exceed the balance limit as an example. With other kiln types, the changes are

only gradual, as a result of which a separate presentation has not been provided. The fol-

lowing mass and energy flows have been taken into account:

Incoming solid substance mass flows:

S1m& for the kiln feed

B7m& for the fuel (main burner) *)

B3m& for the fuel (secondary burner) *)

Outgoing solid substance mass flows:

S10m& for the clinker

St5m& for the bypass dust

St1m& for CFl,H& raw gas dust

St12m& for the discharged tertiary air dust (only relevant in kiln systems with a terti-

ary air duct and high levels of dust in the tertiary air)

*) Liquid or gaseous fuel can also be fed in.


Incoming gas volume flows **)

L10V& for the cooler intake air

L7V& for the burner air (main burner)

L3V& for the burner air (secondary burner)

L1V& for the conveying air (kiln feed)

DFl,V& for the infiltrated air (kiln hood)

C Fl,V& for the infiltrated air (calcinator)

V Fl,V& for the infiltrated air (preheater)

Outgoing gas volume flows:

L11V& for the cooler vent air

G1V& for the raw gas

G5V& for the bypass gas

Incoming liquid mass flows:

O,10H 2m& for the cooler injection water

Incoming energy flows:

S1H& for the kiln feed

B7H& for the fuel (main burner)

B3H& for the fuel (secondary burner)

**) The formula sign V& below designates the volume flow related to standard conditions (0°C [32°F], 1013

hPA), while the formula sign trV& designates the volume flow related to standard conditions after removal

of the water-vapor fraction.


L10H& for the cooler intake air

L7H& for the burner air (main burner)

L3H& for the burner air (secondary burner)

L1H& for the conveying air (kiln feed)

DFl,H& for the infiltrated air (kiln hood)

CFl,H& for the infiltrated air (calcinator)

VFl,H& for the infiltrated air (preheater)

BR,H&∆ for the reaction enthalpy of the fuels

10 O,H2H& for the cooler injection water

mechP for the mechanical performance

Outgoing energy flows:

S10H& for the clinker

St5H& for the bypass dust

St1H& for the raw gas dust

St12H& for the discharged tertiary air dust

L11H& for the cooler vent air

G1H& for the raw gas

G5H& for the bypass gas

SR,H&∆ for the reaction enthalpy of the kiln feed

OHV, 2H&∆ for the evaporation enthalpy of the cooler injection water

KK,Q& for the uncoupled heat (cooler)


COR,H&∆ for the incomplete burning

VW,Q& for radiation and convection losses (preheater)

CW,Q& for radiation and convection losses (calcinator)

DW,Q& for radiation and convection losses (rotary kiln)

TW,Q& for radiation and convection losses (tertiary air duct)

KW,Q& for radiation and convection losses (cooler + kiln hood)


Figure 6 - Balancing spaces for preheater, calcinator, tertiary air duct, rotary kiln and cooler with incoming and outgoing mass and energy flows.


With rotary and satellite coolers, the cooling air volume flow is used completely as com-

bustion air in the process, whereas in contrast, it is only partially used as such with grate-

type coolers. In the case of the latter, excess cooling air is released as cooler vent air.

When the waste gas leaves the preheater, it still contains relatively large amounts of dust.

Therefore, the waste gas is designated as “raw gas” and the dust as “raw gas dust”. With

grate-type coolers, some of the cooler vent air can be returned to the cooler as intake air

via a fan once the dust has been removed and cooled (duothermal configuration). This

was taken into consideration in the figure by the uncoupled heat flow KK,Q& . Cooler vent

air dust has not been taken into account.

4.1.1 Solid substance mass flows

Measured quantities: clinker, fuel (main burner), fuel (secondary burner), bypass

dust, raw gas dust, discharged tertiary air dust.

Operands: mass flow of the kiln feed.

In order to balance the mass flows, a component balance is drawn up of the sum of the

non-volatile substances (for example, SiO2, Al2O3, TiO2, P2O5, Fe2O3, Mn2O3, CaO,

MgO) whose mass concentration in the individual substance flows is designated by xNF *).

The following applies:

*) The formula sign x below stands for the mass concentration of the solids at the balance limit (= delivery

condition in the laboratory).


The loss on ignition can also be used for a rough estimate. By using xG to designate the

mass concentration of the substances that are released during calcination at about 1000°C

[1832°F] until weight constancy is achieved, the following applies analogously:

The kiln feed mass flow necessary for the clinker burning process then results from

Equation (2):

As an approximation, the following applies to the kiln feed mass flow that actually

becomes clinker (including discharged tertiary air dust):

The ratio of kiln feed to clinker necessary for the clinker burning process then results

from Equation (4):


Analogously, the following applies:

4.1.2 Gas volume flows

Measured quantities: fuel (main burner), fuel (secondary burner), cooler vent air

(if present), burner air (main burner), burner air (secondary

burner), bypass gas, raw gas, conveying air (kiln feed).

Operands: infiltrated air, secondary air, cooler intake air (see Section

3.3.2.3).

4.1.2.1 Dry gas

4.1.2.1.1 Minimum air volume flow

In order to calculate the dry, minimum air volume flow, the burning of all combustible

substances has to be taken into consideration. For this reason, in addition to the fuel mass

flows B7m& and B3m& , the combustible components (organically bound carbon, sulfide sul-

fur) of the kiln feed also have to be taken into account.


By designating the carbon content of the kiln feed as xC,S1, the carbon content of the raw

gas dust as xC, St1 and the carbon content of the bypass dust as xC, St5, the following results

for the carbon mass flow S eff,C,m& effectively fed into the kiln system:

Analogously, the following applies for S eff, S,m& :

Frequently, St5C,x and St5S,x are approximately zero. The minimum air volume flow

minL,V& to burn all of the combustible substances then amounts to the following:

lmin is the minimum air demand of the fuel in question in its raw state. This value can be

calculated on the basis of elementary analyses of the fuel according to Equation (11):


Accordingly, the numerical value equation is the following:

For oil and coal, lmin can be calculated as an approximation using the lower calorific

value of the fuel *). The following applies:

For lignitic coal and coal:

For heating oil:

Table 6 shows examples of elementary analyses and calorific value-related combustion

gas quantities of lignitic coal and coal. Calorific value-related combustion gas quantities

of secondary fuels can differ markedly from the indicated uppermost and lowermost val-

ues.

*) The formula sign hu below stands for the lower calorific value of the coal at the balance limit threshold

(= delivery condition in the laboratory).


Table 6 - Elementary analyses of lignitic coal dust and coal dust

with the combustion gas quantities calculated therefrom

and related to the lower calorific value in the raw state.

Lignitic coal dust

Coal dust

Analyses (raw) in % by weight:

L M U L M U

water 8.7 11.8 14.0 0.8 1.9 2.9

ash 3.4 4.5 8.3 11.9 19.1 29.3

C 56.1 59.2 61.4 57.3 65.8 71.7

H 3.9 4.2 4.5 2.6 3.6 4.4

O 16.1 19.4 23.7 4.5 7.2 8.7

N 0.4 0.5 0.6 0.7 1.3 2.0

S 0.2 0.3 0.7 0.6 1.0 2.1

calorific value (raw) in MJ/kg: 20.22 21.92 22.76 21.35 25.05 27.80

Calorific value-related combus-

tion gas quantity in kg/MJ:

minimum air demand 0.332 0.339 0.347 0.339 0.341 0.344

carbon dioxide 0.096 0.098 0.101 0.094 0.096 0.099

water vapor 0.021 0.022 0.024 0.011 0.014 0.016

moist flue gas 0.374 0.382 0.392 0.370 0.373 0.375 L = lowermost value; M = mean value; U = uppermost value

4.1.2.1.2 Air proportionality factor

The following applies in general:


The air proportionality factor in the waste gas results as an approximation from the values

of the gas analysis (in the case of Orsat analyses and measuring methods that work with

extraction, as a rule related to dry measuring gas):

The expression in the denominator of the lower fraction corresponds to N2.

4.1.2.1.3 Infiltrated air at the kiln hood

The volume flow of infiltrated air at the kiln hood can be roughly calculated using the

Bernoulli equation. The following applies theoretically:

Equation (17) presupposes a frictionless flow and an incompressible medium. In reality,

neither is present. As a consequence, the equation yields an excessively high gas velocity.

Consequently, for actual practice, the gas velocity has to be multiplied by a dimension-

less factor which lies between 0.6 and 0.9, Here, it has been set at 0.75. Thus, the fol-

lowing applies:


With /FVv &= for the gas velocity and with the density ratio ρ L /ρ L,N for dry air (the

water present in the air is ignored here), the result is a calculation equation for the volume

flow of infiltrated air:

wherein

∆p = differential pressure at the kiln hood in Pa

ρ L = density of the air in the cross section F in kg/m³

ρ L,N = density of the ambient air under standard conditions (s.c.) in kg/m³

F = open cross-section area in m²

tr D,Fl,V& = volume flow of infiltrated air in m³ (s.c.)/s

As a simplification, the density of the ambient air can be taken as the basis for ρ L.

4.1.2.1.4 Secondary air

The following applies for the volume flow of the secondary air (also see Figure 12):

Due to non-representative gas analyses in the kiln inlet, trL8,V& can only be calculated very

imprecisely.


4.1.2.1.5 Cooler intake air

The following applies for the volume flow of the cooler intake air (also see Figure 12):

4.1.2.1.6 Raw gas

1. Calculation on the basis of the CO2 balance

The following applies for the CO2 balance:

S,CO2V& stems from the decarbonation and the combustion of organic components of the

kiln feed. The following applies:

wherein

and

Seff,,Cm& according to Equation (8).


B,CO2V& stems from the combustion of the fuel. The following applies:

If the elementary analysis is not available, Equation (26) can be employed:

wherein

2COµ = 5.01 · 10 –

5 m³ of CO2/kJ for lignitic coal

and 2COµ = 4.87 · 10

– 5 m³ of CO2/kJ for coal.

G5,CO2V& results from the gas analysis and from the measurement of the gas volume flow

in the bypass gas:

With

the result is the calculation equation for the raw gas volume flow:


2. Calculation on the basis of the clean gas volume flow

This calculation is only possible if the entire clean gas volume flow of the kiln system

can be determined and if no auxiliary burner is operated in the combined drying and

grinding mill.

CO2 balance:

O2 balance:

4.1.2.1.7 Gas downstream from the burning area

trG2,V& is calculated according to Equations (30) or (31) on the basis of the raw gas vol-

ume flow. A gas analysis downstream from the burning area is needed for this purpose.

4.1.2.1.8 Gas downstream from the rotary kiln (kiln inlet)

trG6,V& can be calculated according to [30]. Due to non-representative gas analyses in the

kiln inlet, the calculated values are often very imprecise.


4.1.2.2 Water vapor

4.1.2.2.1 Humidity in the air

The humidity in the air results from the relative humidity and from the saturation pressure

of water-vapor at ambient temperature. The following applies:

wherein

xD = water content in kg of H2O/kg of dry air

ϕ = relative humidity

ps (ϑ L,U) = saturation pressure of the water vapor in Pa

p = ambient pressure in Pa

and

Then, the following applies for the moisture volume flow of the air:

4.1.2.2.2 Water from the kiln feed


4.1.2.2.3 Water from the fuel

4.1.2.2.4 Injection water

4.1.2.3 Moist gas

4.1.2.3.1 Air

The following applies in general:

Altogether,

is fed into the kiln system. λ G1 should be calculated with the gas concentration values

which would result after the mixing of raw gas and bypass gas.


4.1.2.3.2 Raw gas

λ G1 should be calculated with the gas concentration values which would result after the

mixing of raw gas and bypass gas. With grate-type coolers, O,10H 2V& often equals zero.

G5O,H 2y often equals G6O,H 2

y .

4.1.3 Liquid mass flows

Measured quantities: fuel (main burner), fuel (secondary burner), water.

4.1.4 Energy flows

Since standard reaction enthalpies and calorific values are related to 25°C [77°F], a refer-

ence temperature of 25°C [77°F] was likewise selected for the calculation of the individ-

ual enthalpy flows.

4.1.4.1 Energy input

4.1.4.1.1 Fuel

Combustion:


Sensible enthalpy flows: *)

For dry coal, the following applies (also see Figure 7):

wherein xF,B = sum of the volatile components in the coal.

Equation (43) also applies, as an approximation, to dry lignitic coal. Here, however, the

water content of the lignitic coal has to be taken into account. The following then applies:

wherein OH 2c ≈ 4.2 kJ/kg K for 0°C [32°F] < ϑ < 100°C [212°F].

The following applies in the case of oil (also see Figure 8):

wherein ρ = density of the oil in kg/m³ at 15°C [59°F].

*) The formula sign c or cp below stands for the mean specific thermal capacity

ϑF][77 C25pc °° .


Figure 7 - Mean specific thermal capacity of dry coal (reference temperature = 25°C [77°F]).


Figure 8 - Mean specific thermal capacity of oil (reference temperature = 25°C [77°F]).


The specific thermal capacity of the heating gas is calculated on the basis of the mean

specific thermal capacities of the individual gas components according to Table 7. The

following applies here:

Table 7 - Mean specific thermal capacity cp of the fuel gas compo-

nents (reference temperature = 25°C [77°F]).

Specific thermal capacity cp in kJ/m³ (s.c.) K

Fuel gas component

25°C [77°F] 100°C [212°F] 200°C [392°F] methane

CH4

1.582

1.700

1.817

ethylene C2H4 2.270 2.402 2.519

acetylene C2H2 1.985 2.137 2.246

propadiene C3H4 2.631 2.918 3.172

n-butane C4H10 4.579 5.156 5.717

propylene 1) C3H6 4.101 4.555 5.113

hydrogen sulfide H2S 1.531 1.579 1.602

1) Use C3H6 use for CmHn.

s.c. = under standard conditions

4.1.4.1.2 Kiln feed

Sensible enthalpy flows:


The following applies as an approximation for the commonly employed composition of

the kiln feed:

The specific thermal capacities of individual components of the kiln feed are shown in

Figure 9.


Figure 9 - Mean specific thermal capacity of kiln feed components

(reference temperature = 25°C [77°F]).


4.1.4.1.3 Air

Sensible enthalpy flows:

wherein

(For the calculation of cp, j according to Equations (85) through (87), also see Figure 10).

As an approximation, it is also possible to use the specific thermal capacity of dry air for

the calculation. The following applies in this case:


Figure 10 - Mean specific thermal capacity of gas components (ref-

erence temperature = 25°C [77°F]).



As a rule, the sensible enthalpy flow of the injection water can be ignored.

4.1.4.1.5 Mechanical performance

Within the balancing space, the mechanical performance of the electric drives has to be

taken into consideration. This is particularly true of the intake air fans and of the kiln

drive. In simplified form, the following applies:

4.1.4.2 Energy output

4.1.4.2.1 Reaction enthalpy of the kiln feed

For the calculation of the reaction enthalpy of the kiln feed, the degradation reactions of

the starting materials and the reactions for the formation of the clinker phases have to be

taken into account. Table 8 is a compilation of the main reactions that take place during

the clinker burning process, with the standard reaction enthalpies needed in each case (for

the additional reaction enthalpies, see [22, 23 and 25 through 27]). The data shown in the

two right-hand columns are each related to the substance in the left-hand column. The

actual reaction enthalpies to be employed result from balance equations. For this purpose,

it is first necessary to calculate the contents of C3S, C2S, C3A, C4AF in the clinker, the

contents of CaCO3 and MgCO3 in the kiln feed and in the raw gas dust as well as the

contents of CaCO3 and C2S in the bypass dust.


Table 8 - Reactions of the kiln feed and reaction enthalpies (298 K)

during the production of Portland cement clinker.

Reaction

Reaction equation

Reaction enthalpy 1)

at 298 K

kJ/kg kJ/mole

I. Formation of oxides and

degradation reactions

1. Evaporation of H2O H2O (fl) � H2O (g) + 2446 + 44

2. Decomposition of

• kaolinite (relative to Al2O3)

kaolinite � α-Al2O3 + 2 · β-SiO2 + H2O (fl)

+ 1519 + 155

• montmorillonite (relative to Al2O3)

montmorillonite � α-Al2O3 + 4 · β-SiO2 + n · H2O (fl)

+ 744 + 76

• illite (relative to Al2O3)

illite � α-Al2O3 + 4 · β-SiO2 + m · H2O (fl)

+ 884 + 90

3. Organic clay components (relative to C)

C + O2 � CO2 – 32786 – 394

4. MgCO3 dissociation MgCO3 � MgO + CO2 + 1396 +118

5. CaCO3 dissociation CaCO3 � CaO + CO2 + 1772 + 178

6. Pyrite (FeS2) 2 FeS2 + 5½ O2 � α-Fe2O3 + 4 SO2 – 6902 – 828

II. Formation of the clinker phases

7. Formation of C4AF 4 CaO + α-Al2O3 + α-Fe2O3 � C4AF – 67 – 33

8. Formation of C3A 3 CaO + α-Al2O3 � C3A + 74 + 20

9. Formation of β-C2S 2 CaO + β-SiO2 � β-C2S – 700 – 121

10. Formation of C3S 3 CaO + β-SiO2 � C3S – 495 – 113

11. Formation of K2SO4 K2O = SO2 + ½ O2 � α-K2SO4 – 4452 – 776

1) Related to the substance in the left-hand column.


4.1.4.2.1.1 C3S, C2S, C3A and C4AF in the clinker

For normal Portland cement clinker or tertiary air dust, which consists primarily of C3S,

C2S, C3A and C4AF (TM > 0.64), the clinker phases can be calculated according to

Bogue [45 and 46]. In this context, the value employed for the CaO bound in the clinker

phases is the one that is obtained after the subtraction of the free CaO and of the CaO

bound to SO3. The following applies:

For S10 O,NaS10 O,KS10 ,SO 223x292.1x85.0x ⋅+⋅≤ , the following applies:

For S10 O,NaS10 O,KS10 ,SO 223x292.1x85.0x ⋅+⋅> , the following applies:

The following results from this:


4.1.4.2.1.2 CaCO3 and MgCO3 in the kiln feed and in the raw gas dust

The content of CaCO3 and MgCO3 of the kiln feed results from the content of CO2 and

CaO. Assuming that the CO2 is primarily bound to the CaO, the following applies in the

case of

1.274 · CaOCO xx2

≤ :

and

in the case of

1.274 · CaOCO xx2

> :

and


4.1.4.2.1.3 CaCO3 and C2S in the bypass dust

The content of CaCO3 results from the content of CO2 in the bypass dust.

For purposes of calculating the C2S content, it is assumed that Al2O3 and Fe2O3 have

completely reacted with CaO to form C4AF and C12A7. The following then applies:

The calculation of St5,CaO 3SOx is made according to Equations (55) or (56).

4.1.4.2.1.4 Balance equations

The balance equations are based on the following assumptions and simplifications:

1) 0x St5 O,H 2=

2) xC, St5 = 0

3) 0x St5 ,MgCO3=

4) xS, St5 = 0

5) The formation enthalpy of C4AF and of C12A7 in the bypass dust is negligibly small.

6) The starting materials as shown in Table 8 are present.

7) The fuel ash is present in the form of oxides.


According to Figure 6, the following applies for the balance equations:

1) Evaporation of H2O:

2) Decomposition of clay:

100%-kaolinite:

100%-montmorillonite:

100%-illite:

3) Organic clay components:


4) MgCO3 dissociation:

5) CaCO3 dissociation:

6) Pyrite:

7) Formation of C4AF:

8) Formation of C3A:


9) Formation of β-CsS:

10) Formation of C3S:

11) Formation of K2SO4:

In Equation (79), the actual SO3 contents (without sulfide sulfur) should be used.

In order to calculate the reaction enthalpy of a special clinker, for instance, TM < 0.64, or

of a clinker from a kiln feed with calcareous fly ash, blast-burner slag or gypsum from

flue gas desulfurization plants, or of a clinker from a burning process involving other

substance flow configurations, the balance equations need to be changed or supple-

mented. Moreover, in the case of fly ash and blast-burner slag, assumptions also have to

be made pertaining to the devitrification enthalpies.


The following applies to the sum of the reaction enthalpies of the kiln feed:

4.1.4.2.2 Water evaporation

Evaporation enthalpy for cooler injection water:

4.1.4.2.3 Waste gas losses

Raw gas:

wherein

The following approximation equations apply for the essential components of the waste

gas (also see Figure 10):


Bypass gas:

Cooler vent air:

4.1.4.2.4 Dust losses

Raw gas dust:

(for cSt1, see Section 4.1.4.1.2; ϑ St1 = ϑ G1).


Bypass gas dust:

(for cSt5, see Section 4.1.4.1.2; ϑ St5 = ϑ G5).

Discharged tertiary air dust:

(for cSt12, see Equation (95); ϑ St12 = ϑ L9).

Losses due to cooler vent air dust are usually negligibly small.

4.1.4.2.5 Incomplete combustion

In cases of high energy losses due to incomplete combustion (for example, yCO,G1 > 0.01),

an analyzer that operates continuously should be used for the calorific value of the gas for

the balancing.

4.1.4.2.6 Clinker


The following applies for the specific thermal capacity of the clinker (also see Figure 11):

Figure 11 - Mean specific thermal capacity of Portland cement

clinker (reference temperature = 25°C [77°F]).


4.1.4.2.7 Radiation and convection

Rotary kiln:

First of all, the heat flow of individual tube elements is calculated on the basis of the

mean circumferential temperature ϑ W,m of the tube element and of the ambient tempera-

ture ϑ L,U:

wherein

and

αconv results from approximation equations. The following applies for wind velocities

w ≤ 2 m/s:

wherein

a = 0.3

a0 = 4.0


a1 = 3.5

a2 = -0.85

a3 = 0.076

Scope of validity:

w ≤ 2 m/s

100°C [212°F] ≤ ϑ W,m ≤ 500°C [932°F]

2 m ≤ Da ≤ 8 m

10°C [50°F] ≤ ϑ L,U ≤ 30°C [86°F]

The following applies for wind velocities w > 2 m/s:

wherein

Diameter range in m

b

b0

b1

*1b

2.75 ≤ Da < 3.25 2.37 4.98 0.73 - 0.244

3.25 3.75 2.27 5.05 0.79 - 0.243

3.75 4.25 2.18 5.11 0.83 - 0.238

4.25 4.75 2.11 5.19 0.88 - 0.236

4.75 5.25 2.05 5.27 0.92 - 0.233

5.25 5.75 1.98 5.40 0.93 - 0.227

5.75 6.25 1.93 5.48 0.97 - 0.227

6.25 6.75 1.87 5.66 0.97 - 0.220

6.75 7.25 1.83 5.70 1.00 - 0.219


Scope of validity:

2 m/s < w ≤ 10 m/s

100°C [212°F] ≤ ϑ W,m ≤ 500°C [932°F]

2.75 m ≤ Da ≤ 7.25 m

10°C [50°F] ≤ ϑ L,U ≤ 30°C [86°F]

The following applies for αStr:

wherein

ε W = 0.9

σ = 5.67 · 10 –

8 W/(m² · K4)

TW,m = mean surface temperature in K

TL,U = ambient air temperature in K

The radiation and convection loss flow DW,Q& for the entire rotary kiln results from the

addition of the radiation and convection loss flows of the individual tube elements:

More details on the calculation of the radiation and convection loss flow can be found in

literature references [28 and 31].


Cooler:

Equations (96) through (101) can be employed directly for the rotary cooler. For satellite

coolers, it is recommended to employ the imaginary surface area of a cylinder surround-

ing the satellite cooler as the heat-transfer surface area. The diameter of this surrounding

cylinder can then be used to calculate the heat-transfer coefficient αtotal as an approxima-

tion according to Equations (98) through (101). The mean circumferential temperature ϑ

W,m is calculated as an arithmetic mean value of all of the individual temperature meas-

ured values calculated over the circumference, that is to say, the satellite temperatures as

well as the temperatures in the interstitial spaces. Moreover, an empirical factor of 1.6

should be used for the calculation of the heat flow. The following applies:

The following applies as a good approximation for the grate-type cooler and the kiln

hood:

wherein

αconv = 7 W/(m²·K)

ε W = 0.9

At higher wind velocities, Equation (104) yields a heat loss flow that is too low. In such

cases, the surface temperature should be measured only on the side facing away the wind.


Preheater and calcinator:

Equations (104) should be employed accordingly.

Tertiary air duct:

Equations (96) through (102) should be employed accordingly.

4.1.4.2.8 Uncoupled heat

The following applies as an approximation for the heat uncoupling via a cooling chute:

wherein

OH2c ≈ 4.2 kJ/kg K for 0°C [32°F] < ϑ < 100°C [212°F].

The following applies for the heat uncoupling through the cooling of the cooler circula-

tion air:


4.1.4.3 Energy balance

The following applies for the sum of the energy input and energy output:

and

With kiln performance tests, the energy input and the energy output are compared to each

other. Usually the input and the output do not offset each other completely, so that a bal-

ance deficit remains which, however, should not make up more than ± 3% of the total

energy output.

Since the reaction enthalpy flow of the fuel as energy input can often only be determined

very imprecisely, it should be calculated on the basis of the difference between the

energy output and the other energy input values according to Equation (109); it is also

designated as fuel energy consumption.


4.2 Balancing of the partial systems

4.2.1 Clinker cooler

A complete mass and energy balance can only be drawn up for the clinker cooler within

the limits set by its design. For this reason, the fact that considerable dust circulation can

occur between the rotary kiln and the clinker cooler has to be taken into account. More-

over, the hot clinker temperature can only be measured in a very imprecise manner.

Figure 12 - Balancing space of the cooler with the incoming and

outgoing mass and energy flows.


Figure 12 shows the balancing space of a clinker cooler with the mass and energy flows

that exceed the balance limit. Thus, for example, several exhaust air flows can be dis-

charged from the cooler. In the case of rotary and satellite coolers, the exhaust air volume

flow, in contrast, has to be set as zero. The following mass and energy flows have been

taken into consideration:

Incoming solid substance mass flows:

S8m& for the hot clinker

Outgoing solid substance mass flows:

S10m& for the clinker

St8m& for the secondary air dust

St9m& for the tertiary air dust

Incoming gas volume flows:

L10V& for the cooler intake air

Outgoing gas volume flows

L8V& for the secondary air

L9V& for the tertiary air (cooler)

L11V& for the cooler vent air

Incoming liquid mass flows:

10 O,H 2m& for the cooler injection water


Incoming energy flows:

S8H& for the hot clinker

L10H& for the cooler intake air

10 O,H2H& for the cooler injection water

Kmech,P for the mechanical performance (cooler)

Outgoing energy flows:

S10H& for the clinker

St8H& for the secondary air dust

St9H& for the tertiary air dust

L8H& for the secondary air

L9H& for the tertiary air

L11H& for the cooler vent air

KW,Q& for radiation and convection losses (cooler + kiln hood)

KK,Q& for the uncoupled heat (cooler)

O HV, 2H&∆ for the evaporation enthalpy of the cooler injection water


4.2.1.1 Solid substance mass flows

Measured quantities: clinker, discharged and returned tertiary air dust.

Operands: secondary air dust, hot clinker.

Only in the case of kiln systems with a tertiary air duct can the secondary air dust mass

flow be calculated on the basis of the discharged and returned tertiary air dust assuming

equal dust contents in the secondary air and in the tertiary air. The secondary air dust

mass flow then results from the dust mass flow measured in the tertiary air and from the

fraction calculated on this basis for the secondary air volume flow:

In other cases, the dust concentration in the secondary air should be estimated. With a

“clear” kiln discharge, the dust concentration is about 30 to 50 g/m³. In the case of a pro-

nounced dust circulation, this value can rise to more than 200 g/m³.

The following applies for the hot clinker mass flow:


4.2.1.2 Gas volume flows

Measured quantities: cooler vent air (if present), tertiary air.

Operands: cooler intake air, secondary air.

The secondary air volume flow results from Equations (20) and (38), and the cooler

intake air volume flow results from Equations (21) and (38). The water vapor from the

water injection should also be taken into account.

4.2.1.3 Energy flows

A reference temperature of 25°C [77°F] is selected for the calculation of the individual

energy flows.

4.2.1.3.1 Energy input

4.2.1.3.1.1 Hot clinker

(cS8 according to Equation (95) or Figure 11).


Only the surface temperature of the hot clinker can be measured by means of instruments.

Therefore, the calculated hot clinker energy flow is fundamentally too low. This error

increases as the temperature drops and the particle size increases. Therefore, the hot

clinker energy flow is associated with a high level of uncertainty.

4.2.1.3.1.2 Cooler intake air

4.2.1.3.1.3 Injection water

See Section 4.1.4.1.4.

4.2.1.3.1.4 Mechanical performance

4.2.1.3.2 Energy output

4.2.1.3.2.1 Clinker, clinker dust



4.2.1.3.2.2 Radiation and convection


4.2.1.3.2.3 Uncoupled heat


4.2.1.3.2.4 Cooler vent air, secondary air, tertiary air


4.2.1.3.2.5 Water evaporation


4.2.1.3.3 Energy balance

If a reliable measured value for the secondary air temperature is available, the hot clinker

enthalpy flow S8H& can be calculated on the basis of the energy balance. As a rule, this is

the case whenever tertiary air is removed from the kiln hood (ϑ L9 = ϑ L8) or when the

secondary air can be measured error-free (for example, with sound-over-time measure-

ment or a suction-type thermometer). The following then applies:


The hot clinker enthalpy flow calculated according to this equation serves as the basis for

the calculation of the cooler efficiency (see Section 4.2.1.4.4).

4.2.1.4 Evaluation quantities

4.2.1.4.1 Pre-cooling zone

For the evaluation of the clinker cooler, it is necessary to take into account the fact that

the first cooling of the clinker already takes place inside the rotary kiln, in the so-called

pre-cooling zone, which is where radiation and convection losses occur. Figure 13 shows

the principle of the balance limits of the burning area and of the cooling area and its sub-

division into the pre-cooling zone and the cooler.

Figure 13 - Balance limits of the burning area and cooling area, of

the pre-cooling zone as well as of the cooler with the

example of a kiln system with a rotary cooler.


In order to calculate the radiation and convection losses in the pre-cooling zone, it is nec-

essary to know their length Lpre-cool. Since this length cannot be measured and no calcula-

tion method is known for this at the present time, the position of the burner lance serves

as the reference point for estimating this length (also see Figure 13).:

wherein

Lpre-cool = length of the pre-cooling zone, in m

Lburner = length of the burner in the rotating part of the kiln, in m

Da = outer diameter of the rotary kiln, in m

The estimation according to Equation (116) diverges from that described in the VDZ

Specification titled “Grate-type, satellite and rotary coolers in the cement industry” [33].

It was selected because of the high degree of measuring uncertainty associated with the

determination of the hot clinker temperature.

The radiation and convection loss coolpreW,Q −& in the pre-cooling zone of the rotary kiln

amounts to the following:

Here, αtotal stands for the mean heat-transfer coefficient, which can be calculated accord-

ing to Equations (98) through (101) with a superimposition of the radiation (rad) as well

as free and forced convection (conv).


4.2.1.4.2 Energy loss flow of the cooling area

The energy consumption of a rotary kiln system depends to a decisive degree on the

extent to which the enthalpy of the clinker in the cooling area can be recovered for the

process. The fraction that is not recovered constitutes the energy loss of the cooling area,

which has to be replaced by fuel energy.

The energy loss flow areacoolingloss,E& is the sum of the heat and enthalpy flows that are

released by the cooler into the atmosphere. In this context, for the clinker and cooler vent

air, those enthalpy flows that would be released during the cooling procedure from the

appertaining outlet temperature to the ambient air temperature should be seen as energy

flows,

In this equation, h(ϑ L,U) stands for the specific enthalpy at the ambient air temperature.

4.2.1.4.3 Cooling area efficiency

For comparisons, it is advantageous to relate the energy loss flow of the cooling area to a

theoretical enthalpy flow change on the part of the clinker and thus to define a cooling

area efficiency:


For the sake of harmonization, a sintering temperature of 1450°C [2642°F] was presup-

posed, which should prevail at the site of transition from the burning area to the cooling

area. Future improvements of the burning process or special compositions of the kiln feed

could make it necessary to stipulate a sintering temperature that differs from this.

The cooling area efficiency makes it possible to thermally evaluate the cooling in the

entire process.

4.2.1.4.4 Cooler efficiency

The efficiency values of the cooler are described in the VDZ Specification titled “Grate-

type, satellite and rotary coolers in the cement industry” [33]. The limitations outlined in

Section 4.2.1.3.1.1 apply when using the formulas.

4.2.2 Calcinator (only for kiln system with cyclone preheater)

The balancing space of the calcinator starts at the rotary kiln inlet and ends downstream

from the lowermost cyclone (Figure 14). The lowermost stage of the cyclone preheater

counts as part of the calcinator. With degrees of precalcining below approximately 90%,

the equilibrium temperature of the calcium carbonate dissociation sets in at the lowermost

stage, irrespective of the burning or pre-heating conditions. Thus, at this site, the waste

gas acquires a chemically determined temperature that is very well-suited for determining

this balance limit. In contrast, this does not apply for the “rotary kiln inlet” balance limit

where the energy and mass flows can only be determined very imprecisely. For this rea-

son, the calcinator is often balanced together with the rotary kiln, since it is in these

aggregates that the essential reactions of the kiln feed and of the fuel take place.


Figure 14 - Balancing space of the calcinator with incoming and



4.2.2.1 Determination of the degree of precalcining

The degree of precalcining can be used to evaluate the progress of the decarbonation of

the kiln feed in the preheater and in the calcinator. In this context, the degree of precal-

cining refers to the degree of dissociation of the calcium carbonate contained in the kiln

feed prior to its entry into the rotary kiln. The actual degree of precalcining ϕ actual is

defined according to Equation (120) as the ratio of the carbon dioxide mass flow

VCCO ,2m& that has escaped from the kiln feed in the preheater and in the calcinator to the

carbon dioxide mass flow 0CO ,2m& that was originally bound in the kiln feed as carbonate:

The degree of precalcining calculated according to Equation (120) can only be deter-

mined by using complete gas or solid substance balances. More details on this can be

found in literature reference [30].

As a simplification, the degree of precalcining can also be determined on the basis of the

solid substance analyses. It is designated as the apparent degree of precalcining ϕ apparent.

Provided that the raw gas dust St1m& has the same chemical composition as the kiln feed

S1m& , and by ignoring the dust in the rotary kiln inlet gas, the apparent degree of precal-

cining ϕ apparent results from the CO2 concentrations 2COx and the concentrations of non-

volatile components xNF of the kiln feed (index S1) and of the kiln feed at the kiln inlet

(index S6):


In reality, however, the more highly decarbonated dust St4m& and St6m& influences the

composition of the kiln feed mass flow S6m& . For this reason, the apparent degree of pre-

calcining ϕ apparent calculated according to Equation (121) generally simulates a higher

decarbonation of the kiln feed. If the dust mass flows St4m& and St6m& have been com-

pletely decarbonated, the following relationship exists between the apparent and the

actual degree of precalcining:

4.2.3 Preheater (only for kiln system with cyclone preheater)

Figure 15 shows the balancing space of the preheater. As a rule, it consists of 3 to 5 pre-

heating stages in which gas and the kiln feed are fed in a countercurrent with respect to

each other. The degrees of separation of the individual cyclone stages are relevant for an

evaluation of the preheater.


Figure 15 - Balancing space of the preheater with incoming and


4.2.3.1 Degree of separation of individual cyclone stages

Figure 16 shows the incoming and outgoing solid substance mass flows of a preheating

stage. According to it, the following applies for the degree of separation:


The mass flows iS,m& and 1iSt,m +& result from the mass and energy balance of the ith stage.

The following applies as an approximation for the solid substance balance:

The following applies for the energy balance:

In this context, iW,Q& stands for the radiation and convection loss flow of the ith cyclone

stage and iR,H&∆ stands for the reaction enthalpy flow of the raw material in stage i.

Equations (124) and (125) yield the mass flows iS,m& and 1iSt,m +& :

Equations (126) and (127) can be employed in the area of the preheater where hardly any

solid/gas reactions (decarbonation) occur. As a rule, this is the case with the uppermost

cyclone stages (ϑ < 600°C [1112°F]). In this context, it is assumed that there is tempera-

ture equilibrium between the gas and the kiln feed in the cyclone stage.


Figure 16 - Incoming and outgoing solid substance mass flows of a

preheating stage with a cyclone separator.

If the alkali compounds in the kiln feed differ sufficiently, the mass flows can also be

ascertained on the basis of component balances. This generally applies to the lower stages

of the preheater, but also to the cyclone separator of the calcinator. If effNF,m& stands for

the mass flow of non-volatile substances effectively fed into the kiln system,

and if effalk,m& stands for the mass flow of alkali compounds that are effectively fed into

the system by means of the kiln feed,

then, provided that the dust and solid substance mass flows exiting from each individual

stage have the same chemical composition, it is possible to determine the mass flows of

the kiln feed and the dust between the individual cyclone stages:


From a technical standpoint, xNF, N+1 and xalk, N+1 (N= cyclone separator of the calcinator)

are very difficult to measure, as a result of which, for purposes of simplification, both

concentration values should be pre-defined.

Equations (126) and (127) as well as (130) and (131) constitute very rough approxima-

tions, as a consequence of which only changes in these operands, for example, between

two performance tests, should be interpreted, but not the absolute value.


5. Evaluation of the substance circulation systems

Relevant substance circulation systems should be measured during a kiln performance

test or else calculated on the basis of measured and analytical data.


6. Evaluation of the cement clinker

As a rule, new systems are only examined once the clinker properties and thus also the

cement properties have been achieving the desired quality requirements for quite some

time. In contrast, kiln performance tests with old systems can also serve to optimize the

quality of the cement and clinker.

6.1 Degree of burning

The degree of burning of the cement clinker is usually monitored on the basis of the bulk

density (weight per unit volume) of a narrow particle range, for instance, 5 to 7 mm,

whose values lie between 1.2 and 1.6 kg/dm³. The bulk density, however, is not only

dependent on the degree of burning, but also on the chemical composition and on the

porosity of the clinker. Moreover, the content of free CaO also provides information

about the degree of burning.

6.2 Particle-size distribution

The coarse and fines fractions of the clinker (for example, < 2 mm and > 25 mm) provide

information about the kiln operation and the clinker quality. They are ascertained by

means of sieve analysis.


6.3 Grindability

The grindability of the clinker provides information about the necessary work in the

cement mill. It is primarily tested with the device according to Zeisel.

6.4 Chemical composition

The chemical composition yields the lime standard (KSt), the silica ratio (SM), the

alumina/iron ratio (TM), the sulfatization degree (SG), the total alkali fraction (A) and

the melt phase fraction (S).

The lime standard indicates the content of CaO actually present in the raw material mix-

ture or clinker as a percentage of the maximum CaO content that can be bound to SiO2,

Al2O3 and Fe2O3 under industrial burning and cooling conditions.

Several formulas, which do not differ markedly from each other, are commonly

employed to calculate the lime standard. According to F.M. Lea and T.W. Parker, for

example, the following applies [7]:


The silica modulus is the ratio of silicon dioxide to the sum of aluminum oxide and iron

oxide. The following applies:

Since the silicon dioxide is primarily bound in the solid phases tricalcium silicate and di-

calcium silicate at the sintering temperature, but since aluminum oxide and iron oxide are

present in the melt, the silica modulus refers to the solid-to-liquid ratio in the sintering

zone of the cement kiln. Generally speaking, the silica modulus lies between SM = 1.8

and SM = 3.0, most frequently and most advantageously between SM = 2.3 and SM =

2.8.

The alumina/iron ratio (TM) is the ratio of the aluminum oxide content to the iron oxide

content. The following applies:

It provides information about the quantity ratio of calcium aluminate to calcium alumi-

nate ferrite and consequently about the clinker melt. With clinker having a commonly

employed composition, this value lies between 1.5 and 4.0. With an alumina/iron ratio of

0.638, the calculation indicates that all of the aluminum oxide contained in the clinker is

bound as calcium aluminate ferrite having the assumed composition

4 CaO · Al2O3 · Fe2O3.


The sulfatization degree (SG) indicates the percentage of alkalis in the clinker, which are

present as alkali sulfate:

The total alkali fraction (A) results from the conversion of the fraction of potassium

oxide into the equivalent sodium fraction according to the following equation:

The following applies as an approximation for the melt phase (S):

(for ϑ S = 1338°C [2440.4°F] and TM > 1.38).

(for ϑ S = 1338°C [2440.4°F] and TM < 1.38).

(for ϑ S = 1400°C [2552°F]).

(for ϑ S = 1450°C [2642°F]).


xMgO enters into the formulas with xMgO = 0.02 at the maximum; at higher contents,

xMgO = 0.02.

6.5 Phase composition

The phase composition of the clinker can be calculated on the basis of the values of the

chemical analysis, for instance, according to equations (54) through (60). However, it is

necessary to assume that the clinker phases have the composition indicated by their for-

mulas and that the clinker melt is in a continuous state of thermodynamic equilibrium

with the solid phases of the clinker, not only at the sintering temperature but also and

especially when they crystallize during the cooling procedure. For these reasons, the cal-

culation only provides an approximation of the actual clinker composition [7].

6.6 Microscopic examination

The microscopic examination of the clinker provides information about the type, consti-

tution and distribution of the clinker compounds. Whereas the type of the compounds

depends primarily on the chemical composition of the kiln feed, the structure, that is to

say, the constitution and distribution of the clinker compounds and their coalescence,

provide information about the preparation of the raw material mixture and about the con-

ditions during the burning and cooling of the clinker.


6.7 Cement testing

The results of the quality tests with the ground-up cement types within the scope of our

own as well as outside monitoring also provide essential information about the properties

of the cement clinker. They are of decisive significance for the optimization of opera-

tions.


7. Evaluation of the emissions

Relevant emissions have to be measured and/or recorded during a kiln performance test.


8. Formula signs and indices

Roman letters

a factor (Section 4.1.4.2.7)

A total alkali fraction in kg/kg

b factor (Section 4.1.4.2.7)

c mean specific thermal capacity of solids and liquids in kJ/kg K

cp mean specific thermal capacity of gases in kJ/m³ under standard condi-

tions (s.c.) K

D diameter in m

E& energy flow in kJ/s

f ratio of kiln feed to clinker in kg/kg of clinker

F surface area in m²

hu lower calorific value in kJ/kg

h specific enthalpy in kJ/s

H& sensible enthalpy flow in kJ/s

RH&∆ reaction enthalpy flow in kJ/s

VH&∆ evaporation enthalpy flow in kJ/s

KSt lime standard in %

L length in m

lmin minimum air demand in m³ of air (s.c.) / kg of fuel

m& mass flow in kg/s

M molecular weight in kg/mole

N stage number in the cyclone preheater, chamber number in the grate-type

cooler

p pressure in Pa


P performance in kJ/s

Q& heat flow in kJ/s

S melt phase content

SG sulfatization degree in %

SM silica modulus

T absolute temperature in K

TM alumina/iron ratio

v gas velocity in m/s

V& volume flow under standard conditions (0°C [32°F] and 1013 hPa) in m³/s

w wind velocity in m/s

x mass concentration in kg/kg

y volume concentration in m³/m³

Greek letters

α heat transition coefficient in W/m² · K

∆ difference

εW emission ratio of the wall surface

η cooling area cooling area efficiency

ϑ temperature in °C

λ excess air coefficient

µ combustion product per energy unit in m³ (s.c.) / kJ

ξ degree of separation of a cyclone

ρ density in kg/m³

σ Stefan-Boltzmann constant

σ = 5.67 · 10 –

8

42Km

W

ϕ degree of precalcining, relative humidity


Indices

0 initial state

0 through 11 reactions of the kiln feed (Section 4.1.4.2.1.4)

0 through 12 balance limits

1 preheater (kiln feed, raw gas)

2 preheater / calcinator

3 calcinator (secondary burner)

4 calcinator (tertiary air duct)

5 calcinator (bypass)

6 calcinator / rotary kiln

7 rotary kiln (main burner)

8 rotary kiln / cooler

9 tertiary air duct / cooler

10 cooler (clinker, cooler intake air)

11 cooler (cooler vent air)

12 tertiary air duct (discharged tertiary air dust)

a outside

Alk alkali compounds

out balance output

Out outlet

B fuel

burner burner

C calcinator, carbon

D rotary kiln, vapor under standard conditions (0°C [32°F] and 1013 hPA)

eff effective

in balance input

In inlet


F sum of the volatile substances

Fl infiltrated air

total total

G gas, loss on ignition

surr surrounding cylinder

i variable

K cooler, uncoupled

Kl clinker

con convection

L air

m mean value

max maximum

mech mechanical

min minimum

N standard conditions (s.c.) (0°C [32°F] and 1013 hPA)

NV sum of non-volatile substances

p at constant pressure

R reaction

clean gas clean gas

grate grate-type cooler

s saturation

app apparent

S solid, sulfide sulfur

Sat satellite cooler

St dust

Str radiation (rad)

actual actual

theor theoretical


tr dry

T tertiary air duct

U ambient

Um circulation air

V preheater, evaporation enthalpy

loss loss

pre-cool pre-cooling zone

W radiation and convection losses

Chemical formula signs

C3A tricalcium aluminate (3 CaCO · Al2O3)

C12A7 (12 CaO · 7Al2O3)

C4AF aluminate ferrite (4 CaO · Al2O3 · Fe2O3)

C2S dicalcium silicate (2 CaO · SiO2)

C3S tricalcium silicate (3 CaO · SiO2)

Al2O3 aluminum oxide

C carbon

CaCO3 calcium carbonate

CaO calcium oxide

Cl – chloride

CO carbon monoxide

CO2 carbon dioxide

Fe2O3 iron(III)-oxide

H hydrogen, atomic

H2O water

K2O potassium oxide

K2SO4 potassium sulfate

MgCO3 magnesium carbonate


MgO magnesium oxide

Mn2O3 manganese(III)-oxide

N2 nitrogen

Na2O sodium oxide

O oxygen, atomic

O2 oxygen

P2O5 phosphorus pentoxide

S2– sulfide

SiO2 silicon dioxide

SO3 sulfur(VI)-oxide (sulfate)

TiO2 titanium dioxide


9. Literature references

9.1 General literature references

[1] Kühl, H.: Zement-Chemie. Band 1. Die physikalisch-chemischen Grundlagen der

Zement-Chemie. VEB Verlag Technik, Berlin 1956. [2] Kühl, H.: Zement-Chemie. Band 11. Das Wesen und die Herstellung der hydrau-

lischen Bindemittel. VEB Verlag Technik, Berlin 1958. [3] Keil, F: Zement-Herstellung und Eigenschaften. Springer-Verlag, Berlin 1971. [4] Seidel, G., Huckauf, H., und Stark, J.: Technologie der Bindebaustoffe. Band 3.

Brennprozeß und Brennanlagen. VEB Verlag für Bauwesen, Berlin 1978. [5) Baehr, H.D.: Thermodynamik. Springer-Verlag, Berlin 1981. [6] Labahn, O.: Ratgeber für Zementingenieure. Bauverlag GmbH, Wiesbaden 1982. [7] Locher, F. W: Zement. Ullmanns Enzyklopädie der technischen Chemie, Band 24,

pp. 545-574, Verlag Chemie GmbH, Weinheim 1983. [8] Duda, W.H.: Cement-Data-Book. Band 1. Internationale Verfahrenstechniken der

Zementindustrie. Bauverlag GmbH, Wiesbaden 1985. [9] Stark, J., Huckauf, H., und Seidel, G.: Bindebaustoff-Taschenbuch. Band 3. Brenn-

prozeß und Brennanlagen. VEB Verlag Für Bauwesen, Berlin 1985. [10] Brandt, F: Brennstoffe und Verbrennungsrechnung. FDBR-Fachbuchreihe, Band 1.

Vulkan-Verlag, Essen 1991.


9.2 Technical literature references

Description of the clinker burning process [11] Sprung, S.: Technologische Probleme beim Brennen des Zementklinkers, Ursache

und Lösung. Schriftenreihe der Zementindustrie, Vol. 43,1982. [12] Garrett, H.M.: Precalciners today - a review. Rock Products, July (1985) pp. 39-61. [13] Wolter, A.: Einfluß des Ofensystems auf die Klinkereigenschaften. Zement-Kalk-

Gips 38 (1985) Vol. 10, pp. 612-614. [14] Bonn, W., und Lang, Th.: Brennverfahren. Zement-Kalk-Gips 39 (1986) Vol. 3, pp.

105-114. [15] Rosemann, H.: Theoretische und betriebliche Untersuchungen zum Brennstoff-

energieverbrauch von Zementofenanlagen mit Vorcalcinierung. Schriftenreihe der Zementindustrie, Vol. 48,1987.

Execution of kiln performance tests [16] VDZ-Merkblatt “Mengenmessung von Gasen durch Geschwindigkeitsmessung”,

Verein Deutscher Zementwerke e.V., Düsseldorf 1961. [17] VDZ-Merkblatt “Staubmengenmessungen auf Zementwerken”, Verein Deutscher

Zementwerke e.V., Düsseldorf 1962. [18] Hengstenberg, J., Sturm, B., und Winkler, O.: Messen, Steuern und Regeln in der

Chemischen Technik. Band 1. Messung von Zustandsgrößen, Stoffmengen und Hilfsgrößen. Springer-Verlag, Berlin 1980.

[19] Hengstenberg, J., Sturm, B., und Winkler, O.: Messen, Steuern und Regeln in der

Chemischen Technik. Band 11. Messung von Stoffeigenschaften und Konzentra-tionen. Springer-Verlag, Berlin 1980.

[20] VDZ-Merkblatt “Kontinuierliche Gasanalyse in Zementwerken”, Verein Deutscher

Zementwerke e.V., Düsseldorf 1990.


Evaluation of kiln performance tests [21] Schwiete, H.E.: Die spezifische Wärme des Portlandzementklinkers. Tonindustrie-

Zeitung 56 (1932) Nr. 22, pp. 304-306. [22] Schwiete, H.E., und Ziegler, G.: Beitrag zur Thermochemie von Zementrohstoffen.

Zement-Kalk-Gips 9 (1956) Vol. 6, pp. 257-262. [23] zur Strassen, H.: Der theoretische Wärmebedarf des Zementbrandes. Zement-Kalk-

Gips 10 (1957) Vol. 1, pp. 1-12. [24] VDZ-Merkblatt “Berechnungsunterlagen für Ofenversuche”, Verein Deutscher

Zementwerke e.V., Düsseldorf 1959. [25] Petrosjan, M.: Thermodynamik der Silikate, VEB Verlag für Bauwesen, Berlin

1966. [26] Barin, I., und Knacke, O.: Thermochemical properties of inorganic substances.

Springer-Verlag, Berlin 1973, [27] Barin, I., Knacke, O., und Kubaschewski, O.: Thermochemical properties of inor-

ganic substances. Supplement. Springer-Verlag, Berlin 1977. [28] Gardeik, H.O., Ludwig, H., und Steinbiß, E.: Berechnung des Wandwärmeverlustes

von Drehöfen und Mühlen. Teil 1: Grundlagen. Zement-Kalk-Gips 33 (1980) Vol. 2, pp. 53-62.

[29] VDI-Wärmeatlas, Berechnungsblätter für den Wärmeübergang, VDI-Verlag

GmbH, Düsseldorf 1983. [30] Rosemann, H., und Gardeik, H.O.: Rechnergesteuerte Meßdatenerfassung und -

verarbeitung bei der Durchführung von Ofenversuchen. Zement-Kalk-Gips 37 (1984) Vol. 9, pp. 465-473.

[31] Gardeik, H.O., und Ludwig, H.: Berechnung des Wandwärmeverlustes von Dreh-

öfen und Mühlen. Teil 2: Näherungsgleichungen und Anwendungen. Zement-Kalk-Gips 38 (1985) Vol. 3, pp. 144-149.

[32] Wolter, A.: Phase composition of calcined raw meal. Proc. 8th International Con-

gress on the Chemistry of Cement, Rio de Janeiro, 1986, pp. 89-94.


[33] VDZ-Merkblatt “Rost-, Satelliten- und Rohrkühler in der Zementindustrie”, Verein Deutscher Zementwerke e.V., Düsseldorf, 1989,

Evaluation of the substance circulation systems [34] Weber, P.: Warmeübergang im Drehofen unter Berücksichtigung der Kreislauf-

vorgänge und der Phasenneubildung. Dissertation, Bergakademie Clausthal-Zellerfeld 1959, Zement-Kalk-Gips, Sonderausgabe Nr. 9 (1960).

[35] Goes, C.: Ober des Verhalten der Alkalien beim Zementbrennen. Schriftenreihe der

Zementindustrie, Vol. 4, 1960. [36] Weber, R: Alkaliprobleme und Beseitigung bei wärmesparenden Trockenöfen.

Zement-Kalk-Gips 17 (1964) Vol. 8, pp. 335-344. [37] Sprung, S.: Das Verhaften des Schwefels beim Brennen von Zementklinker

Schriftenreihe der Zementindustrie, Vol. 31, 1964. [381 Ritzmann, H.: Kreislaufe in Drehofensystemen. Zement-Kalk-Gips 24 (1971) Vol.

8, pp. 338-343. [39] Locher, F W, Sprung, S., und Opitz, D.: Reaktionen im Bereich der Ofengase.

Zement-Kalk-Gips 25 (1972) Vol. 1, pp. 1-12. [40] Locher, F. W: Stoffkreisläufe und Emissionen beim Brennen von Zementklinker.

Fortschritte der Mineralogie 60 (1982) Vol. 2, pp. 215-234. [41] Kreft, W: Methode zur Vorausberechnung von Schadstoffkreisläufen in Zement-

öfen. Zement-Kalk-Gips 35 (1982) Vol. 9, pp. 456-459. [42] Rosemann, H., und Gardeik, H.O.: Einflüsse auf die Energieumsetzung in Calci-

natoren bei der Vorcalcination von Zementrohmehl. Zement-Kalk-Gips 36 (1983) Vol. 9, pp. 509-511.

[43] Kreft, W: Alkali- und Schwefelverdampfung in Zementofen in Gegenwart hoher

Chloreinnahmen. Zement-Kalk-Gips 38 (1985) Vol. 8, pp. 418-422. [44] Schütte, R., und Kupper, D.: Die Bedeutung von Kreislaufbetrachtungen für Pro-

duktqualität und Umweltverträglichkeit der Zementherstellung. Zement-Kalk-Gips 43 (1990) Vol. 12, pp. 565-570.


Evaluation of the cement clinker [45] Bogue, R.H.: Calculation of the compounds in portland cement. Industrial and

Engineering Chemistry 1 (1929) pp. 192-197. [46] Bogue, R.H.: The chemistry of portland cement. Reinhold Publishing Corporation,

New York 1955. [47] Locher, F W: Berechnung der Klinkerphasen. Schriftenreihe der Zementindustrie,

Vol. 29,1962, pp. 7-29. [48] Locher, F.W: Einfluß der Klinkerherstellung auf die Eigenschaften des Zements.

Zement-Kalk-Gips 28 (1975) Vol. 7, pp. 265-272. [49] Sylla, H.-M.: Einfluß der Klinkerkühlung auf Erstarren und Festigkeit von Zement.

Zement-Kalk-Gips 28 (1975) Vol. 9, pp. 357-362. [50] Locher, F. W: Verfahrenstechnik und Zementeigenschaften. Zement-Kalk-Gips 31

(1978) Vol. 6, pp. 269-277. [51] Sylla, H.-M.: Einfluß der Ofenatmosphäre beim Brennen von Zementklinker.

Zement-Kalk-Gips 31 (1978) Vol. 6, pp. 291-293. [52] Locher, F.W, Richartz, W., Sprung, S., and Sylla, H.-M.: Erstarren von Zement.

Teil III: Einfluß der Klinkerherstellung. Zement-Kalk-Gips 35 (1982) Vol. 12, pp. 669-676.

[53] Sprung, S.: Einflüsse der Verfahrenstechnik auf die Zementeigenschaften. Zement-

Kalk-Gips 38 (1985) Vol. 10, pp. 577-585.


Evaluation of the emissions [54] Kroboth, K., und Xeller, H.: Entwicklungen beim Umweltschutz in der Zement-

industrie. Zement-Kalk-Gips 39 (1986) Vol. 1, pp. 1-14. [55] Sprung, S.: Spurenelemente - Anreicherungen und Minderungsmaßnahmen.

Zement-Kalk-Gips 41 (1988) Vol. 5, pp. 251-257. [56] Locher, F W: Entwicklung des Umweltschutzes in der Zementindustrie. Zement-

Kalk-Gips 42 (1989) Vol. 3, pp. 120-127. [57] Kroboth, K., und Kuhlmann, K.: Stand der Technik der Emissionsminderung in

Europa. Zement-Kalk-Gips 43 (1990) Vol. 3, pp. 121-131. [58] Wischers, G., und Kuhlmann, K.: Ökobilanz von Zement und Beton. Zement-Kalk-

Gips 44 (1991) Vol. 11, pp. 545-553.


10. Evaluation example 1 (kiln system with a cyclone pre-heater, calcinator and tertiary air duct)

10.1 Balancing the entire system

10.1.1 Solid substance mass flows

S10m& = 18.00 kg/s S10 NF,x = 0.9760

St12m& = 0 kg/s St12 NF,x not applicable

B7m& = 1.29 kg/s B7NF,x = ashNV,B7ash, xx ⋅ = 0.04 · 0.8007

B3m& = 1.24 kg/s B3NF,x = ashNF, B7ash, xx ⋅ = 0.04 · 0.8007

St1m& = 0.84 kg/s St1 NF,x = 0.6454

St5m& = 0 kg/s St5NF,x not applicable

S1 NF,x = 0.6316

Kiln feed mass flow (Equation 4):

0.6316

6454.084.08007.004.0)24.129.1(976.000.18mS1

⋅+⋅⋅+−⋅=& = 28.55 kg/s.

Ratio of kiln feed to clinker necessary for burning clinker (Equation 6):

000.18

28.55fS1

+= = 1.586 kg/kg.


10.1.2 Gas volume flows

10.1.2.1 Dry gas

10.1.2.1.1 Minimum air volume flow

S1m& = 28.55 kg/s S1 C,x = 0.0015 S1 S,x = 0.0004

St1m& = 0.84 kg/s St1 C,x = 0.0021 St1 S,x = 0.0008

B7m& = 1.29 kg/s B7u,h = 22684 kJ/kg

B3m& = 1.24 kg/s B3u,h = 22684 kJ/kg

The carbon mass flow (Equation 8) and the sulfide mass flow (Equation 9) effectively fed

in with the kiln feed:

S eff, C,m& = 28.55 · 0.0015 – 0.84 · 0.0021 = 0.0411 kg/s

S eff, S,m& = 28.55 · 0.0004 – 0.84 · 0.0008 = 0.0107 kg/s

Minimum air demand of the fuels (Equation 13):

lmin, B7 = lmin, B3 = 0.44 + 0.000245 · 22684 = 5.998 m³/kg

Minimum air volume flow (Equation 10):

trmin, L,V& = (1.29 + 1.24) · 5.998 + 0.0411 · 8.88 + 0.0107 · 3.32 = 15.58 m³/s


10.1.2.1.2 Air proportionality factors

G1tr,,CO2y = 0.2925 G1tr,CO,y = 0.0007 G1tr,,O2

y = 0.0489


y = 0.0318


y = 0.0302

Air proportionality factors in the waste gas downstream from the preheater, from the

burning area and from the rotary kiln (Equation 16):

)0489.00007.00.2925(1

0007.05.00489.03.7621

1G1

−−−

⋅−−

=λ = 1.3843

)0318.00006.00.3290(1

0006.05.00318.03.7621

1G2

−−−

⋅−−

=λ = 1.2278

)0302.00005.00.2108(1

0005.05.00302.03.7621

1G6

−−−

⋅−−

=λ = 1.1745

10.1.2.1.3 Infiltrated air at the kiln hood

F ≈ 0.25 m² ∆p = 5 Pa ϑ U = 5°C [41°F]

ρ L,N = 1.29 kg/m³ p = 1010 hPa


Density of the ambient air:

ρ L = 1.29 · 277

273

1013

1010⋅ = 1.268 kg/m³

Infiltrated air volume flow (Equation 19):

2268.1529.1

25.075.0V trD,Fl, ⋅⋅⋅

⋅≈& = 0.52 m³/s

10.1.2.1.4 Secondary air

λ G6 = 1.1745 B7m& = 1.29 kg/s trL7,V& = 1.39 m³/s

lmin, B7 = 5.998 m³/kg trD,Fl,V& = 0.52 m³/s

Secondary air volume flow (Equation 20):

trL8,V& = 1.1745 · 1.29 · 5.998 – 1.39 – 0.52 = 7.18 m³/s

10.1.2.1.5 Cooler intake air

trL8,V& = 7.18 m³/s trL9,V& = 6.73 m³/s trL11,V& = 23.17 m³/s

Cooler intake air volume flow (Equation 21):

trL10,V& =7.18 + 6.73 + 23.17 = 37.08 m³/s


10.1.2.1.6 Raw gas

S1m& = 28.55 kg/s S1,CO2x = 0.3380

St1m& = 0.84 kg/s St1,CO2x = 0.3256

St5m& = 0 St5,CO2x not applicable

Seff,C,m& = 0.0411 kg/s

B7m& = 1.29 kg/s B7u,h = 22684 kJ/kg (lignitic coal)

B3m& = 1.24 kg/s B3u,h = 22684 kJ/kg (lignitic coal)

trG5,V& = 0 G5tr,,CO2y ; G5tr,CO,y not applicable


y = 0.0489

trgas,pureV& = 60.42 m³/s gaspuretr,,CO2y = 0.1262 gas puretr,,O2

y = 0.1426

1. Calculation on the basis of the CO2 balance:

Carbon dioxide mass flow (Equation 24) effectively fed in with the kiln feed:

Seff,,CO2m& = 28.55 · 0.3380 – 0.84 · 0.3256 = 9.376 kg/s

CO2 from the kiln feed (Equation 23):

97.1

1

12.01

44.010411.0376.9V S,CO2

+=& = 4.84 m³/s

CO2 from the fuel (Equation 26):

B,CO2V& = (1.29 + 1.24) · 5.01 · 10

– 5

· 22684 = 2.88 m³/s


Raw gas volume flow (Equation 29):

0007.02925.0

088.284.4V trG1,

+

−+=& = 26.33 m³/s

2. Calculation on the basis of the clean gas volume flow:

Raw gas volume flow (Equations 30 and 31):

a) CO2 balance:

2925.0

1262.042.60V trG1, =& = 26.07 m³/s

b) O2 balance:

0489.021.0

1426.021.042.60V trG1,

−

−=& = 25.28 m³/s


trG1,V& = 0.5 (26.07 + 25.28) = 25.68 m³/s

10.1.2.1.7 Gas downstream from the burning area

G1tr,,CO2y = 0.2925 G1tr,,O2

y = 0.0489 trG1,V& = 25.68 m³/s

G2tr,,CO2y = 0.3290 G2tr,,O2

y = 0.0318

Gas volume downstream from the burning area (Equations 30 and 31):

a) CO2 balance:

3290.0

2925.068.25V trG2, =& = 22.83 m³/s


b) O2 balance:

0318.021.0

0489.021.068.25V trG2,

−

−=& = 23.22 m³/s


trG2,V& = 0.5 (22.83 + 23.22) = 23.03 m³/s

10.1.2.1.8 Gas downstream from the rotary kiln (kiln inlet)


y = 0.0489

trG1,V& = 25.68 m³/s

G6tr,,CO2y = 0.2108 G6tr,,O2

y = 0.0005 G6tr,,O2y = 0.0302

B3m& = 1.24 kg/s lmin,B3 = 5.998 m³/kg

S eff, C,m& = 0.0411 kg/s lmin,C = 8.88 m³/kg

S eff, S,m& = 0.0107 kg/s lmin,S = 3.32 m³/kg

Gas volume flow downstream from the rotary kiln [30]:

/sm32.9

21.0

0302.02108.01

0007.068.2521.0

5.032.30107.088.80411.0998.524.179.0

21.0

0302.02108.01

21.0

0489.00007.02925.0168.25

V

3

trG6,

=

−−

⋅⋅−⋅+⋅+⋅

−

−−

−−−

=&


10.1.2.1.9 Infiltrated air (preheater)

trGl,V& = 25.68 m³/s trG2,V& = 23.03 m³/s L1V& = 1.60 m³/s

10.1.2.1.10 Infiltrated air (calcinator)

B3m& = 1.24 kg/s lmin,B3 = 5.998 m³/kg

S eff, C,m& = 0.0411 kg/s lmin,C = 8.88 m³/kg

S eff, S,m& = 0.0107 kg/s lmin,S = 3.32 m³/kg

trG2,V& = 23.03 m³/s G2tr,,O2y = 0.0318 G2tr,,O2

y = 0.0006

trG6,V& = 9.32 m³/s G6tr,,O2y = 0.0302

trL4,V& = 6.73 m³/s trL3,V& = 0.19 m³/s

Infiltrated air volume flow (calcinator) according to [30]:

21.0

1V Ctr,Fl, =& (23.03 · (0.0318 – 0.5 · 0.0006) – 9.32 · 0.0302) + 1.24 · 5.998 +

0.0411 · 8.88 + 0.0107 · 3.32 – 6.73 – 0.19 = 3.03 m³/s

10.1.2.2 Water vapor

10.1.2.2.1 Humidity in the air

p = 101000 Pa ϑ L,U = 4°C [39.2°F] ϕ = 0.4


Saturation pressure of the water vapor at ambient temperature (Equation 33):

ps (ϑ L,U) = 611.5 + 43.87 · 4 + 1.470 · 42 + 2.564 · 10

– 5

· 43 + 2.877 · 10

– 4

· 44 + 10

– 6

· 45 =

812.2 Pa

Water content of the dry air (Equation 32):

xD = 0.622 2.812

4.0

1010002.812

−

= 0.0020 kg/kg

Humidity volume flows (Equation 34):

a) downstream from the preheater

trmin,L,G1LO,H VV2

&& ⋅= λ · 1.608 · xD = 1.3843 · 15.58 · 1.608 · 0.002 = 0.07 m³/s

b) downstream from the burning area

LO,H2V& = 1.2278 · 15.58 · 1.608 · 0.002 = 0.06 m³/s

c) downstream from the rotary kiln (kiln inlet)

LO,H2V& = 1.1745 · 1.29 · 5.998 · 1.608 · 0.002 = 0.03 m³/s

10.1.2.2.2 Water from the kiln feed

S1m& = 28.55 kg/s S1O,H2x = 0.0204 DO,H2

ρ = 0.8 kg/m³

St1m& = 0.84 kg/s St1O,H2x = 0.0190


Moisture volume flow from the kiln feed (Equation 35):

8.0

1)019.084.00204.055.28(V SO,H 2⋅⋅−⋅=& = 0.71 m³/s

10.1.2.2.3 Water from the fuel

B7m& = 1.29 kg/s B7O,H2x = 0.087 B7H,x = 0.0453

B3m& = 1.24 kg/s B3O,H2x = 0.087 B3H,x = 0.0453

Moisture volume flows (Equation 36):

a) Main burner

8.0

1

2

180453.0087.029.1V B7O,H 2

+=& = 0.80 m³/s

b) Secondary burner

8.0

1

2

180453.0087.024.1V B3O,H 2

+=& = 0.77 m³/s


10O,H 2m& = 0


10.1.2.3 Moist gas (examples)

Raw gas volume flow (Equation 40):

G1V& = 25.68 + 0.07 + 0.71 + 0.80 + 0.77 = 28.03 m³/s

Volume flow downstream from the burning area:

G2V& = 23.03 + 0.06 + 0.80 + 0.77 = 24.66 m³/s

Volume flow downstream from the rotary kiln (kiln inlet):

G6V& = 9.32 + 0.03 + 0.80 = 10.15 m³/s

10.1.3 Liquid mass flows

Does not apply.

10.1.4 Energy flows

10.1.4.1 Energy input

10.1.4.1.1 Fuel

B7m& = 1.29 kg/s B7u,h = 22684 kJ/kg B7ϑ = 32°C [89.6°F]

B3m& = 1.24 kg/s B3u,h = 22684 kJ/kg B3ϑ = 32°C [89.6°F]

B7O,H2x = B3O,H2

x = 0.087 B7F,x = B3F,x =)087.01(

496.0

−


Mean specific thermal capacity for dry lignitic coal (Equation 43):

−

⋅+≈

087.01

496.0803.0846.0c trB, (1 + 1.5 · 10

– 3

· 32 – 8 · 10 –

10

· 323) = 1.344 kJ/kg K

Mean specific thermal capacity for the water in the coal:

OH2c ≈ 4.2 kJ/kg K

Mean specific thermal capacity for moist lignitic coal (Equation 44):

cB7 = cB3 = (1 – 0.087) · 1.344 + 0.087 · 4.2 = 1.592 kJ/kg K

Reaction enthalpy flow of the fuel (Equation 41):

BR,H&∆ = (1.29 + 1.24) · 22684 = 57391 kJ/s

Sensible enthalpy flow of the fuel (Equation 42):

BH& = (1.29 + 1.24) · 1.592 · (32 – 25) = 28 kJ/s

10.1.4.1.2 Kiln feed

S1m& = 28.55 kg/s S1ϑ = 63°C [145.4°F]

Mean specific thermal capacity of the kiln feed (Equation 49):

cS1 ≈ 0.8 + 7.3 ·10 –

4 · 63 – 4.6 ·10

– 7 · 632 + 5.2 · 10

– 11 · 633 = 0.844 kJ/kg K

Enthalpy flow of the kiln feed (Equation 48):

S1H& = 28.55 · 0.844 · (63 – 25) = 916 kJ/s


10.1.4.1.3 Air

G1λ = 1.3843 trmin,L,V& = 15.58 m³/s xD = 0.002 kg/kg

trL11,V& = 23.17 m³/s ϑ L,U = 4°C [39.2°F]

Sum of the air volume flows fed in (Equation 39):

∑i

LiV& = (1.3843 · 15.58 + 23.17) (1 + 1.608 · 0.002) = 44.88 m³/s

Mean specific thermal capacity of the air fed in (Equation 52):

cp,L,tr = 1.297 + 5.75 · 10 –

5 · 4 + 8.06 · 10

– 8 · 42 – 2.86 · 10

– 11 · 43 = 1.297 kJ/m³ K

Enthalpy flow of the air fed in (Equation 50):

totalL,H& = 44.88 · 1.297 · (4 – 25) = -1223 kJ/s


Does not apply.

10.1.4.1.5 Mechanical performance

Pmech, air-intake fan = 337 kJ/s Pmech, kiln drive = 117 kJ/s

Mechanical performance (Equation 53):

Pmech = (337 + 117) · 0.9 = 409 kJ/s


10.1.4.2 Energy output

10.1.4.2.1 Reaction enthalpy of the kiln feed

Chemical analyses of the solid substance average samples, each according to Table 10.

10.1.4.2.1.1 C3S, C2S, C3A and C4AF in the clinker

SO3 bound to the CaO in the clinker (Equation 55 or 56):

0.85 · 0.0083 + 1.292 · 0.0010 = 0.0083 > 0.0067

The following then results: S10,CaO3SO

x = 0

CaO bound in the clinker phases (Equation 54):

S10,CaO*x = 0.6641 – 0.0143 – 0 = 0.6498

Clinker phases (Equations 57 through 60):

S10S,C3x = 4.071 · 0.6498 – 7.602 · 0.2137 – 1.43 · 0.0234 – 6.718 · 0.0632 = 0.563

S10S,C2x = 2.868 · 0.2137 – 0.754 · 0.563 = 0.188

S10A,C3x = 2.65 · 0.0632 – 1.692 · 0.0234 = 0.128

S10AF,C4x = 3.043 · 0.0234 = 0.071


10.1.4.2.1.2 CaCO3, and MgCO3 in the kiln feed and in the raw gas dust

a) kiln feed (Equations 61 through 64):

1.274 · 0.3380 = 0.4306 > 0.4304

The following then results: S1,CaCO3x = 1.785 · 0.4304 = 0.7683

S1,MgCO3x = 1.916 · (0.3380 – 0.785 · 0.4304) = 0.0003

b) raw gas dust (Equations 61 through 64):

1.274 · 0.3256 = 0.4148 < 0.4235

The following then results: St1,CaCO3x = 2.274 · 0.3256 = 0.7404

St1,MgCO3x = 0

10.1.4.2.1.3 CaCO3 and C2S in the bypass dust

Does not apply.

10.1.4.2.1.4 Balance equations

S1m& = 28.55 kg/s St5m& = 0 kg/s St12m& = 0 kg/s

St1m& = 0.84 kg/s S10m& = 18.00 kg/s

Reaction enthalpy flows (Equations 67 through 79):

1) Evaporation of H2O:

R1H&∆ = 2446 (0.0204 · 28.55 – 0.0190 · 0.84) = 1386 kJ/s


2) Decomposition of clay:

assumption: 100%-illite

R2H&∆ = 884 (0.0402 · 28.55 – 0.0499 · 0.84) = 978 kJ/s

3) Organic clay components:

R3H&∆ = -32786 (0.0015 · 28.55 – 0.0021 · 0.84) = -1346 kJ/s

4) MgCO3 dissociation:

R4H&∆ = 1396 (0.0003 · 28.55 – 0 · 0.84) = 12 kJ/s

5) CaCO3 dissociation:

R5H&∆ = 1778 (0.7683 · 28.55 – 0.7404 · 0.84) = 37895 kJ/s

6) Pyrite:

R6H&∆ = -12914 (0.0004 · 28.55 – 0.0008 · 0.84) = -139 kJ/s

7) Formation of C4AF:

R7H&∆ = -67 · 0.071 · 18.00 = -86 kJ/s

8) Formation of C3A:

R8H&∆ = 74 · 0.128 · 18.00 = 170 kJ/s

9) Formation of β-C2S:

R9H&∆ = -700 · 0.188 · 18.00 = -2369 kJ/s


10) Formation of C3S:

R10H&∆ = -495 · 0.563 · 18.00 = -5016 kJ/s

11) Formation of K2SO4:

R11H&∆ = -9690 (0.0067 · 18.00 + 0.0014 · 0.84 – 0.0010 · 28.55) = -903 kJ/s

Sum of the reaction enthalpy flow of the kiln feed (Equation 80):

SR,H&∆ = 1386 + 978 – 1346 + 12 + 37895 – 139 – 86 + 170 – 2369 – 5016 – 903 =

30582 kJ/s

10.1.4.2.2 Water evaporation

Does not apply.

10.1.4.2.3 Waste gas losses

G1V& = 28.03 m³/s ϑ G1 = 330°C [626°F] G1O,H2y = 0.0838

L11V& = 23.25 m³/s ϑ L11 = 278°C [532.4°F]

G1,CO2y = (1 – 0.0838) · 0.2925 = 0.2680

G1,O2y = (1 – 0.0838) · 0.0489 = 0.0448

G1,N2y = 1 – 0.0838 – 0.2680 – 0.0448 = 0.6034


a) Raw gas

Mean specific thermal capacity of the raw gas (Equations 83 through 87):

2COp,c = 1.633 + 9.631 · 10 –

4 · 330 – 4.606 · 10

– 7 · 3302

+ 8.90 · 10 –

11

· 3303 = 1.904 kJ/m³ K

OHp, 2c = 1.489 + 9.52 · 10

– 5 · 330 + 2.021 · 10

– 7 · 3302

– 7.35 · 10 –

11

·3303 = 1.540 kJ/m³ K

2Np,c = 1.301 + 3.05 · 10 –

5 · 330 + 9.65 · 10

– 8 · 3302

– 3.22 · 10 –

11

·3303 = 1.320 kJ/m³ K

2Op,c = 1.304 + 1.916 · 10 –

4 · 330 – 9.4 · 10

– 9 · 3302

– 1.01 · 10 –

11

·3303 = 1.366 kJ/m³ K

G1p,c = 0.268 + 1.904 + 0.0838 · 1.54 + 0.6034 · 1.32 + 0.0448 · 1.366 = 1.497 kJ/m³ K

Enthalpy flow of the raw gas (Equation 82):

G1H& = 28.03 · 1.497 (330 – 25) = 12798 kJ/s

b) Cooler vent air

Mean specific thermal capacity of the cooler vent air (Equation 52):

cp, L11 ≈ 1.297 + 5.75 · 10 –

5 · 278 + 8.06 · 10

– 8 · 2782 – 2.86 · 10

– 11 · 2783 = 1.319 kJ/m³ K

Enthalpy flow of the cooler vent air (Equation 89):

L11H& = 23.25 · 1.319 (278 – 25) = 7759 kJ/s

10.1.4.2.4 Dust losses

St1m& = 0.84 kg/s ϑ St1 = 330°C [626°F]

Mean specific thermal capacity of the raw gas dust (Equation 49):

CSt1 ≈ 0.8 + 7.3 · 10 –

4 · 330 – 4.6 · 10

– 7 · 3302 + 5.2 · 10

– 11 · 3303 = 0.993 kJ/kg K


Enthalpy flow of the raw gas dust (Equation 90):

St1H& = 0.84 · 0.993 (330 – 25) = 254 kJ/s

10.1.4.2.5 Incomplete combustion

trG1,V& = 25.68 m³/s y CO,tr,G1 = 0.0007

Reaction enthalpy flow (Equation 93):

COR,H&∆ = 25.68 · 0.0007 · 12645 = 227 kJ/s

10.1.4.2.6 Clinker

S10m& = 18.00 kg/s ϑ S10 = 120°C [248°F]

Mean specific thermal capacity of the raw gas dust (Equation 95):

CS10 = 0.729 + 5.921 · 10 –

4

· 120 – 5.369 · 10 –

7 · 1202

+ 2.124 · 10 –

10

· 1203 = 0.793 kJ/m³ K

Enthalpy flow of the clinker (Equation 94):

S10H& = 18.00 · 0.793 (120 – 25) = 1355 kJ/s


10.1.4.2.7 Radiation and convection:

For calculation examples, see [31]:

VW,Q& = 720 kJ/s

CW,Q& = 360 kJ/s

DW,Q& = 4266 kJ/s

TW,Q& = 486 kJ/s

KW,Q& = 252 kJ/s

10.1.4.2.8 Uncoupled heat

Does not apply.

10.1.4.3 Energy balance

Energy output (Equation 108):

outE& = 30582 + 12798 + 7759 + 254 + 227 + 1355 + 720 + 360 + 4266 + 486 + 252 =

59059 kJ/s

Reaction enthalpy flow of the fuel including the balance remainder (Equation 109):

BR,H&∆ = 59059 – 28 – 916 + 1223 – 409 = 58929 kJ/s

Balance deficit: 58929 – 57391 = 1538 kJ/s

This corresponds to 2.6% of the balance sum.


10.2 Balancing of the partial systems

10.2.1 Clinker cooler

10.2.1.1 Solid substance mass flows

S10m& = 18.00 kg/s trL8,V& = 7.18 m³/s

St9m& = 0.35 kg/s trL9,V& = 6.73 m³/s

Secondary air dust mass flow (Equation 110):

73.6

18.735.0mSt8 ⋅=& = 0.37 kg/s

Hot clinker mass flow (Equation 111):

S8m& = 18.00 + 0.35 + 0.37 = 18.72 kg/s

10.2.1.2 Gas volume flows

trL8,V& = 7.18 m³/s trL10,V& = 37.08 m³/s xD = 0.0020 kg/kg

Secondary air volume flow (Equation 38):

L8V& = 7.18 (1 + 1.608 · 0.002) = 7.20 m³/s

Cooler intake air volume flow (Equation 38):

L10V& = 37.08 (1 + 1.608 · 0.002) = 37.20 m³/s


10.2.1.3 Energy flows

10.2.1.3.1 Energy input

L10V& = 37.20 m³/s ϑ U = 4°C [39.2°F] Pmech, intake air fan = 337 kJ/s

cp,L10 = 1.297 kJ/m³ K (for the calculation, see above)

The enthalpy flow of the hot clinker results from the balance remainder from the energy

balance.

Enthalpy flow of the cooler intake air (Equation 113):

L10H& = 37.20 · 1.297 (4 – 25) = -1014 kJ/s

The enthalpy flow of the injection water does not apply here.

Mechanical performance (Equation 114):

Pmech, K = 337 · 0.9 = 303 kJ/s

10.2.1.3.2 Energy output

L9V& = L4V& = 6.75 m³/s St9m& = St4m& = 0.35 kg/s ϑ L4 = 853°C [1567.4°F]

L8V& = 7.20 m³/s St8m& = 0.37 kg/s TW,Q& = 486 kJ/s


Enthalpy flow of the clinker (for the calculation, see above):

S10H& = 1355 kJ/s

Radiation and convection loss flow of the cooler including the kiln hood:

KW,Q& = 252 kJ/s

The uncoupled heat flow does not apply here.

Enthalpy flow of the cooler vent air (for the calculation, see above):

L11H& = 7759 kJ/s

Enthalpy flow of the tertiary air at the calcinator (Equations 52 and 89):

cp,L4 = 1.297 + 5.75 · 10 –

5 · 8.53 + 8.06 · 10

– 8 · 8532 – 2.86 · 10

– 11 · 8533 = 1.387 kJ/m³ K

L4H& = 6.75 · 1.387 · (853 – 25) = 7752 kJ/s

Enthalpy flow of the tertiary air dust at the calcinator (Equations 95 and 99):

CSt4 = 0.729 + 5.921 · 10 –

4

· 8.53 – 5.369 · 10 –

7

· 8532 + 2.124 · 10

– 10

· 8533 = 0.975 kJ/kg K

St4H& = 0.35 · 0.975 · (853 – 25) = 283 kJ/s

Energy balance for the tertiary air duct:

T W,St4L4St9L9 QHHHH &&&&& ++=+ = 7752 + 283 + 486 = 8521 kJ/s

The iterative calculation then results in the following: ϑ L9 = ϑ St9 ≈ 901°C [1653.8°F]


Enthalpy flow of the secondary air (Equations 52 and 89):

Cp,L8 = 1.297 + 5.75 · 10 –

5

· 901 + 8.06 · 10 –

8

· 9012 – 2.86 · 10

– 11

· 9013 = 1.390 kJ/m³ K

L8H& = 7.2 · 1.39 (901 – 25) = 8767 kJ/s

Enthalpy flow of the secondary air dust (Equations 95 and 94):

CSt8 = 0.729 + 5.921 · 10 –

4

· 901 – 5.369 · 10 –

7 · 9012

– 2.124 · 10 –

10

· 9013 = 0.982 kJ/kg K

St8H& = 0.37 · 0.982 (901 – 25) = 318 kJ/s

The evaporation enthalpy flow of the water does not apply here.

10.2.1.3.3 Energy balance

Enthalpy flow of the hot clinker (Equation 115):

S8H& = 8767 + 318 + 8521 + 7759 + 1355 + 252 + 1014 – 303 = 27683 kJ/s

Hot clinker temperature:

25cm

H

S8S8

S8S8 +

⋅=

&

&

ϑ

cS8 (1389°C [2532.2°F]) = 1.084 kJ/kg K S8m& = 18.72 kg/s

The following then results: 251.08472.18

27683S8 +

⋅=ϑ = 1389°C [2532.2°F]


10.2.1.4 Evaluation quantities

10.2.1.4.1 Pre-cooling zone

LB = -0.2 m ϑ W,m ≈ 200°C [392°F] ϑ U = 4°C [39.2°F]

Da = 3.2 m

Heat-transition coefficients (Equations 98, 99 and 101):

αconv = 0.3 · 3.2 + 4.0 + 3.5 100

200 – 0.85

2

100

200

+ 0.076

3

100

200

= 9.168 W/m² K

αrad = 0.9 · 5.67 · 10 –

8

277473

277473 44

−

−= 11.499 W/m² K

αtotal = 9.168 + 11.499 = 20.667 W/m² K

Radiation and convection loss flow of the pre-cooling zone (Equation 117):

coolpreW,Q −& = 20.667 · π · 3.2 (3.2 – 0.2) (200 – 4)

1000

1= 122 kJ/s

10.2.1.4.2 Energy loss flow of the cooling area

Enthalpy flow of the clinker at 4°C [39.2°F]:

S10H& (4°C [39.2°F]) = 18.00 · 0.731 · (4 – 25) = -276 kJ/s

Enthalpy flow of the cooler vent air at 4°C [39.2°F]:

L11H& (4°C [39.2°F]) = 25.25 · 1.298 · (4 – 25) = -688 kJ/s


Energy loss of the cooling area (Equation 118):

area coolingloss,E& = 1355 + 276 + 7759 + 688 + 252 + 122 = 10452 kJ/s

10.2.1.4.3 Cooling area efficiency

Enthalpy flow of the clinker at 1450°C [2642°F]:

S10H& (1450°C [2642°F]) = 18.00 · 1.106 · (1450 – 25) = 28370 kJ/s

Cooling area efficiency (Equation 119):

η cooling area = 1 – 27628370

10452

+= 0.635

10.2.2 Calcinator

S6,CO2x = 0.0532 xNF,S6 = 0.9016 (sum 1 to 8 in Table 10)

S1,CO2x = 0.3380 xNF,S1 = 0.6316 (sum 1 to 8 in Table 10)

Apparent degree of precalcining of the kiln feed at the kiln inlet (Equation 121):

6316.0

3380.09016.0

0532.0

1apparent −=ϕ = 0.89


10.2.3 Preheater

Calculation of the mass flows and degrees of separation according to Equations (123),

(126), (127), (130) and (131).

Assumptions made for the calculations:

1) The conveying air volume flow for the kiln feed enters into stage 1.

2) One-fourth of the moisture volume flow from the kiln feed is desorbed in each of the

four uppermost stages.

3) The infiltrated air volume flow of the preheater is uniformly distributed over the four

stages.

4) The following aspects are taken into account for the reaction enthalpy flow in the

preheater:

• evaporation of H2O

• degradation of clay

• organic components

• MgCO3 dissociation

• pyrite

5) The sum of the reaction enthalpy flows in the preheater is uniformly distributed

among the four stages.

6) The cyclone of the calcinator is assigned the number 5.

7) The dust from the rotary kiln and from the tertiary air duct contains 10% alkalis and

90% non-volatile components.


Results:

energy balance alkali balance

i

ϑ

cS

GV&

cp,G

WQ&

RH&∆ Sm& Stm& Sm& Stm&

ξ

0 63 0.844 – – – – 28.55 – 28.55 – –

1 330 0.993 28.02 1.497 180 223 43.14 0.84 – 0.84 0.98

2 480 1.050 25.97 1.555 180 223 34.67 15.43 34.67 – 0.69

3 638 1.092 25.53 1.595 180 223 49.26 6.96 48.62 7.19 0.87

4 744 1.110 25.09 1.619 180 223 – 21.55 62.03 21.31 0.80

5 – – – – – – – – 23.26 28.92 0.35

6 – – – – – – – – – 3.87 –

10.3 Estimation of error

Table 16 provides an overview of how possible errors in the measured or input quantities

(column 2) impact on the fuel energy consumption when it is calculated according to

Equation (109) or according to Equation (41) and then related to the clinker mass flow

(columns 3 and 4). Thus, the table provides information about the necessary measuring

precision for the individual measured quantities during a performance test.


10.4 Tables

(The operands are printed in boldface!)

Table 9 - Solid substance mass flows (kiln system with a cyclone

preheater, calcinator and tertiary air duct).

Designation

t/d

kg/s

Clinker

Discharged tertiary air dust

1555

–

18.00

–

Kiln feed

a) meter status

b) calculated

lignitic coal (main burner)

lignitic coal (secondary burner)

2506

2466

111.4

107.3

–

28.55

1.29

1.24

Raw gas dust

Bypass dust

Returned tertiary air dust

73.0

–

30

0.84

–

0.35


Table 10 - Chemical analyses of the solid substance average sam-

ples in % by weight of the substance entailing loss on

ignition (kiln system with a cyclone preheater, calcinator

and tertiary air duct).

Kiln feed downstream from the cyclone

No.

Components

Kiln

feed

Raw gas

dust

Clinker

Fuel

ash 1a 1b 2 3 4 5

1 SiO2 13.91 14.72 21.37 8.13 14.25 13.65 14.12 14.84 15.85 19.76

2 Al2O3 4.02 4.99 6.32 3.36 4.13 3.95 4.12 4.42 4.59 5.82

3 TiO2 – – – 0.32 – – – – – –

4 P2O5 – – – 0.02 – – – – – –

5 Fe2O3 1.51 1.70 2.34 12.23 1.51 1.51 1.50 1.58 1.62 2.15

6 Mn2O3 – – – 0.25 – – – – – –

7 CaO 43.04 42.35 66.41 48.22 43.60 42.57 43.92 45.22 47.45 61.42

8 MgO 0.68 0.78 1.16 7.54 0.64 0.63 0.64 0.70 0.72 1.01

9 SiO3 0.10 0.14 0.67 17.04 0.49 0.31 0.45 0.45 0.44 0.61

10 S2 – 0.04 0.08 – – – – – – – –

11 Cl – 0.008 0.05 0.001 – 0.03 0.02 0.05 0.15 0.30 0.47

12 K2O 0.57 0.72 0.83 0.15 0.57 0.57 0.57 0.77 1.03 1.85

13 Na2O 0.23 0.22 0.10 0.45 0.30 0.31 0.26 0.23 0.25 0.30

14 ignition loss 35.64 34.00 0.26 2.10 34.58 34.75 34.43 31.72 27.85 6.51

15 sum 1-14 99.75 99.75 99.46 99.81 100.10 98.27 100.06 100.08 100.10 99.90

16 sum 1-8 63.16 64.54 97.60 80.07 61.13 62.31 64.30 66.76 70.23 90.16

17 C 0.15 0.21 – – – – – – – –

18 CO2 33.80 35.56 0.14 – 33.80 33.80 33.76 31.48 27.40 5.32

19 H2O (< 110°C) 0.08 0.07 – – – – – – – –

20 H2O (> 110°C) 1.96 1.83 – – – – – – – –

21 CaOfree – – 1.43 – – – – – – –


Table 11 - Fuels (kiln system with a cyclone preheater, calcinator

and tertiary air duct).

Designation

Unit

Fuel (main burner)

Fuel (secondary burner)

lower calorific value kJ/kg 22,684 22,684

water wgt.-% 8.70 8.70

ash wgt.-% 4.00 4.00

carbon wgt.-% 60.20 60.20

hydrogen wgt.-% 4.53 4.53

sulfur wgt.-% 0.27 0.27

nitrogen wgt.-% 0.56 0.56

oxygen wgt.-% 21.74 21.74

volatile components 1) wgt.-% 49.60 49.60 1) Relative to the dry substance.


Table 12 - Temperatures (kiln system with a cyclone preheater,

calcinator and tertiary air duct).

Designation

Temperature (°C [°F]) Kiln feed

Raw gas

Kiln feed (cyclone 2)




Tertiary air (calcinator)

Kiln inlet gas

Hot clinker

Secondary air

Cooler vent air

Clinker

Ambient air

Fuel (main burner)

Fuel (secondary burner)

63°C [145.4°F]

330°C [626°F]

480°C [896°F]

638°C [1180.4°F]

744°C [1371.2°F]

845°C [1553°F]

853°C [1567.4°F]

1024°C [1875.2°F]

1389°C [2532.2°F]

901°C [1653.8°F]

278°C [532.4°F]

120°C [248°F]

4°C [39.2°F]

32°C [89.6°F]

32°C [89.6°F]


Table 13 - Gas volume flows and composition (kiln system with a

cyclone preheater, calcinator and tertiary air duct).

Gas composition, related to

Dry gas

Moist gas

dry gas moist

gas

Designation

m³(s.c.)/h m³(s.c.)/h m³(s.c.)/h m³(s.c.)/h CO2 O2 CO vol-%

… … H2O vol-%

clean gas 217500 60.42 244000 67.76 12.62 14.26 0.03 – – 10.8

raw gas 92400 25.68 100900 28.03 29.25 4.89 0.07 – – 8.4

gas after burning area 82900 23.03 88700 24.66 32.90 3.18 0.06 – – 6.6

kiln inlet gas 1) (33600) (9.32) 36500 (10.15) 21.08 3.02 0.05 – – 8.0

secondary air 1) (25900) (7.18) (26000) (7.20)

tertiary air 24200 6.73 24300 6.75

cooler vent air 83400 23.17 83700 23.25

cooler intake air 133600 37.08 134000 37.20

conveying air (kiln feed) 5800 1.60 5800 1.61

burner air (secondary burner) 700 0.19 700 0.19

burner air (main burner) 5000 1.39 5000 1.39

infiltrated air (preheater) 3800 1.05 3800 1.05

infiltrated air (calcinator) 1) (10900) (3.03) (10900) (3.04)

infiltrated air (kiln hood) 1900 0.52 1900 0.52

air with 0.3 vol-% of H2O

1) Calculated, but often very imprecise since gas analysis at the kiln inlet is not representative.

s.c. = under standard conditions


Table 14 - Energy balance of the kiln system (kiln system with a

cyclone preheater, calcinator and tertiary air duct).

Designation

kJ/s

kJ/kg Kl

Input

Fuel main burner secondary burner sensible enthalpy balance remainder

Kiln feed

Air

Mechanical performance

Sum

29262

28129

28

1538

916

–1223

409

59059

1626

1563

1

85

51

–68

23

3281

Output

Reaction enthalpy of the kiln feed

Water evaporation

Waste gas losses

raw gas cooler vent air

Dust losses

Incomplete combustion

Clinker

Radiation and convection Preheater Calcinator Rotary kiln Tertiary air duct cooler + kiln hood

Heat uncoupling

Sum

30582

—

12798

7759

254

227

1355

720

360

4266

486

252

—

59059

1699

—

711

431

14

13

75

40

20

237

27

14

—

3281

Fuel energy consumption including the balance remainder 58929 3274


Table 15 - Energy balance of the cooler (kiln system with a cyclone

preheater, calcinator and tertiary air duct).

Designation

kJ/s

kJ/kg Kl

Input

Hot clinker (balance remainder)

Cooler intake air

Mechanical performance

27683

–1014

303

1538

–57

17

Sum 26972 1498

Output

Clinker

Radiation and convection

Cooler vent air

Tertiary air and tertiary air dust

Secondary air

Secondary air dust

Heat uncoupling

Water evaporation

1355

252

7759

8521

8767

318

–

–

75

14

431

473

487

18

–

–

Sum 26972 1498

Evaluation quantities

Energy loss of the cooling area in kJ/kg Kl

Cooling area efficiency (1450°C [2642°F])

581

0.635


Table 16 - Influence of measuring errors on the calculated fuel

energy consumption (kiln system with a cyclone pre-

heater, calcinator and tertiary air duct).

Input quantity

Relative error

in the input

parameter in %

Relative error in

the fuel energy

consumption in %

(Equation 109)

Relative error in

the fuel energy

consumption in %

(Equation 41)

Hu fuel 2 0 2

Ash content of fuel 10 –0.08

Mass flow of fuel 10 0.15 10

Mass flow of raw gas dust 50 0.22

Mass flow of clinker 3 –1.42 3

Volume flow of dry raw gas 10 2.12

Volume flow of dry cooler vent air 10 1.43

Temperature of clinker 5 0.09

Temperature of raw gas 2 0.51

Temperature of kiln feed 10 –0.27

Temperature of cooler vent air 2 0.3

Radiation and convection loss of preheater

50 0.93

Radiation and convection loss of kiln 10 0.74

SiO2 content in the clinker –2 0.29

CO2 content in the kiln feed 5 1.28

CO2 content in kiln feed and raw gas dust

5 1.24

Translation by:

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