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Albert Bursik

ABSTRACT

The polyamine/amine treatment is applied in hundreds

and hundreds of fossil plant cycles, particularly in the

industry. Over the last decade, the extent of its appli-

cation in utilities has been increasing. This paper fo-

cuses on the polyamine/amine regime in cycles with

drum boilers, although one case study is presented

which reports on application of this treatment in unitswith once-through steam generators. The major hin-

drance with respect to the use of this treatment in util-

ities is the fact that the cation conductivity of steam

increases slightly when this treatment is applied.

Operation experience in industrial power and steam

generation and in utilities demonstrates that a slight

cation conductivity increase in the steam does not

cause any turbine-related problems, assuming that the

pH is correctly set by low-molecular volatile amines

being a part of the polyamine/amine formulation.

Steam cation conductivity-related studies for estab-

lishing the actual interaction of slightly contaminated

steam and turbine materials in the presence of an ad-

equate alkalizing agent (a low-molecular amine with a

favorable distribution behavior), i.e., when the early

condensate is adequately alkaline, are suggested.

AN ALTERNATIVE PLANT CYCLE CHEMISTRY

TREATMENT

The Problem with Organics

In recent years, many publications in the cycle chemistry-

related literature have dealt with a very attractive topic,

namely with organics. A complete listing of all the relevant

references would make use of more space than is at the

author's disposal. One gets the strong impression that this

topic is the only important plant cycle chemistry issue. The

most frequent causes of component failures in plant cy-

cles seem to fall into oblivion or at least become negligi-

ble: flow-accelerated corrosion (a corrosion mechanism

that represents a major potential danger to cycle equip-

ment and staff), corrosion fatigue (not rare with compo-

nents or component parts which come into contact with

both water and steam), underdeposit corrosion (still rela-

tively common in utility boilers and heat recovery steam

generators), and stress corrosion cracking of turbine

blades or discs all seem to be no trouble at all. None of

the problems mentioned count in comparison to the in-

dustry problem with organics [1].

Organic treatment chemicals have been suspect for many

decades. Operators using them have been derided; the

additives themselves have been deprecatingly called

"snake oils." It is not clear who was the first to adopt this

designation, typically used for additives to lubricants or

fuels, for non-traditional and non-conventional additives

to plants and soils, for additives used in the cosmetic in-

dustry (e.g., in skin- and hair-care products), in alternative

medicine, and in many other areas. With the term "snake

oils," the organic cycle additives were put on the same

level withgimcrack[2].

Probably for this reason, the application of organic fossil

plant cycle treatment chemicals organics is considered

very negative and is not covered in any internationally ac-

knowledged cycle chemistry guideline. Dooley's contin-

uum of treatments (Figure 1 [3]) does not include the ap-

plication of organic treatment chemicals either.

Current Situation

The current situation is very interesting. Despite the fact

that the use of organic cycle treatment chemicals is not

advised in any major international cycle chemistry guide-

line, many variations of the amine treatment have been

used for decades in industrial steam and power genera-

tion. The extent of amine treatment use in fossil power

plants is also increasing [2].

Polyamine/Amine Treatment in Industrial und Utility

Power Generation

In an application report, theoretical discussions of pros

and cons of amine use for conditioning a fossil plant cycle

are inappropriate. Nevertheless, some of the most impor-

tant reasons for an operator to decide in favor of feedwa-

ter alkalizing with amines for his or her particular cycle(s)

are:

reduction of corrosion generation and corrosion prod-

uct transport into the boiler,

improvement in the feedwater purity, which results indecreased blowdown losses,

faster startups (lower corrosion product transport dur-

ing startup).

Polyamine/Amine Treatment A Reasonable Alternative

549PowerPlant Chemistry 2004, 6(9)

Polyamine/Amine Treatment A Reasonable Alternative for

Conditioning High Pressure Cycles with Drum Boilers

2004 by PowerPlantChemistry GmbH. All rights reserved.

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550 PowerPlant Chemistry 2004, 6(9)

All the abovementioned advantages are the result of an

increased pH in the condensing steam (due to a more fa-

vorable distribution behavior of amines in comparison to

ammonia), even in the presence of decomposition prod-

ucts of the amines themselves. The combination of poly-

amines with low-volatile amines dealt with in this paper

reveals further benefits:

as a rule, an additional boiler water treatment is not re-

quired,

the steam generator is self-cleaning (polyamines in

combination with dispersants),

there is an increase in turbine efficiency, and

there is less corrosion during idle periods.

These additional benefits are predominantly the result of

polyamine film forming on all surfaces in the cycle.

Adsorption of surface-active polyamines on metal sur-

faces, e.g., in waterwalls, creates a local high-pH environ-ment and inhibits corrosion even in the presence of cer-

tain contaminants or when the pH in the bulk is lower than

expected. All operators applying polyamines report on ex-

tremely clean turbine blades. It is easy to understand that

doing without phosphates when conditioning boiler water

results in less mechanical carryover of phosphates and,

for this reason, less turbine blade deposit buildup. In ad-

dition, the presence of surface-active polyamines in the

steam helps in the removal of older turbine blade deposits

and prevents the formation of new deposits even if the

concentration of contaminants in steam is relatively high.

To be honest, amine application also has some disadvan-

tages. In most cases, the cation conductivity of steam (and

condensate and in units without condensate polishers

of feedwater) in units on amine treatment is slightly in-

creased. For this reason, the monitoring of the plant cycle

chemistry may become somewhat complicated. However,

a multiplicity of operators, particularly in industrial steam

and power generation, has decided to capitalize on the

advantages of this treatment and to master the possible

disadvantages.

In the following, the use of a non-traditional polyamine/

amine treatment is demonstrated in some case studies. In

all cases reported, Helamin1, a proprietary product con-

taining both polyamines and volatile amines, was used as

the plant cycle treatment chemical. The pressure range

covered in the examples is very wide, as is the range of

main steam temperatures.

APPLICATION EXAMPLES

Case Study 1

A large European refinery operates steam generators (con-

ventional drum boilers, heat recovery steam generators,

and refinery-typical steam-generating systems) with a to-

tal steaming capacity of about 2 050 t h1

. The two high

pressure boilers (steaming capacity 700 t h1

each) sup-

ply superheated steam with the following parameters:

pressure 9 MPa (1 305 psi) and temperature 520 C

(968 F). The steam generated in the high pressure and

other boilers is used at different pressure levels in the

range between 0.4 MPa (58 psi) and 8.9 MPa (1 291 psi).

The total length of the steam pipelines is more than

70 000 m (more than 43.5 miles); the condensate lines are

of a corresponding length.

1Helamin is a registered trademark of Filtro, SA, Geneva,Switzerland

Figure 1:

Continuum of treatments [3].

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The use of the polyamine/amine treatment started in 1993

in the old power plant and later this treatment was used in

all types of boilers (conventional and heat recovery) and in

all other steam-generating refinery systems. There were

several reasons for the conversion from a typical phos-

phate/ammonia/hydrazine treatment to the polyamine/

amine treatment: heavy corrosion and corrosion product

transport in the steam/condensate systems, deposition of

corrosion products in the boilers, and deposits on the tur-

bine blades. It is probably worth mentioning that an equiv-

alent polyamine/polyacrylate proprietary mixture was also

used for preoperational boil-out of the high pressure boil-

ers.

After the application of the new treatment, the corrosion

product transport in the whole system was significantly

reduced, the subsequent boiler and turbine inspections

revealing clean surfaces in both the boilers and the tur-

bines. Figure 2 shows the boiler drum of one of the steam

generators. The photograph was taken during a majorboiler overhaul.

A slight increase in cation conductivity in the cycles is a

typical attendant circumstance of the polyamine/amine

application. The operator reports on cation conductivity in

the range of 0.15 to 0.35 S cm1

during prolonged oper-

ating periods. Due to problems with raw water organics

passing the makeup system during a few months of the

year, the cation conductivity peaks up to 0.5 S cm1

.

Even in such situations, the corrosion product generation

and transport is successfully controlled.

The use of the polyamine/amine treatment in a complex

multipressure steam-generating system demonstrates an

important treatment advantage: the same chemical is used

in the same concentration in boilers regardless of the par-

ticular individual system pressure. In comparison to phos-

phate treatment, this fact markedly simplifies both the

boiler water chemistry (pressure-dependent phosphateconcentrations vs. uniform conditions) and its surveillance.

Case Study 2

On a large chemical industry site in Europe (in a nitric acid

production unit), polyamine/amine cycle chemistry treat-

ment was introduced, replacing the classic European

phosphate treatment. Both the boiler (drum pressure

8 MPa (1 160 psi)) and the turbine were supplied by well-

known European original equipment manufacturers. The

major reason for converting the unit from phosphate treat-

ment to polyamine/amine treatment was trouble with tur-bine fouling. The turbine had to be frequently cleaned

(washed) to recover the turbine performance. After intro-

ducing the new chemical treatment, the turbine washes

were no longer required. Figure 3 depicts the performance

improvement. During the application of the phosphate


Figure 2: Boiler drum unit on polyamine/amine

treatment.

Figure 3: Turbine performance phosphate treatment vs. polyamine/amine treatment.


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treatment, the mean turbine output was approximately

22.7 MW. After 9 months operation on polyamine/amine

treatment, the plate rating of 25 MW was achieved (with-

out any turbine wash).

Improvement in the boiler and turbine operation and the

efficiency increase realized result in non-negligible sav-

ings. The reader may transfer the improvement achieved

(22.7 MW 25 MW) and thereby the savings realized to

his or her own unit or utility operated on phosphate treat-

ment.

Case Study 3

Inadequate thermal stability of organic cycle treatment

chemicals is often cited as evidence against their use in

fossil plant cycles. It is assumed that these chemicals are

completely decomposed, the final decomposition prod-

ucts being low-molecular organic acids and carbon diox-ide. In arguing thus, the main residence time of organics

in water-touched and steam-touched boiler parts is com-

pletely disregarded. Considering a particular 14 MPa

(2 030 psi) drum boiler unit as an example, Tavast esti-

mates that the period during which the chemical remains

in the drum system is in the order of one hour (the precise

time depends on the percentage of blowdown), and in the

superheater only in the order of a few tens of seconds [4].

In cycles with once-through boilers, the residence time is

markedly shorter. This case study demonstrates that for

this reason a successful use of polyamine/amine treat-

ment is possible even in cycles with once-through boilers

with high pressures and temperatures.

In one European combined heat and power generating

plant, two cycles with subcritical once-through steam gen-

erators (main steam pressure/temperature 200 bar/

540 C, reheat steam temperature 540 C) have been

treated with the polyamine/amine treatment chemical

since 1996. The units are equipped with condensate pol-

ishers. Another unit was recently commissioned and is

treated with the same chemical. The reason for the plant

cycle treatment selection was long holds during startups

due to a high concentration of iron oxides in the feedwa-

ter when applying the all-volatile treatment (AVT) in units

being subject to frequent shutdowns/startups and load

variations.

During the conversion from the AVT to polyamine/amine

treatment, two parameters have controlled the treatment

chemical dosage: the pH (pH target value > 9) and the

cation conductivity ( 0.2 S cm1) in the cycle. The op-

eration practice shows that after the startup, the cation

conductivity reaches values about 0.5 S cm1

and falls

down to 0.2 S cm1

in continuous operation.

In 2001/2002, early condensate measurements were car-

ried out, revealing that the early condensate pH is higherthan the bulk steam/condensate pH even in the presence

of low-molecular acids [5]. The early condensate pHs de-

picted in Figure 4 are measured (not calculated) values.

Case Study 4

In a large paper mill, polyamine/amine treatment is applied

in a unit with a drum-type boiler with a steaming capacity

of 125 t h1

(276 000 lb h1). The main steam parameters

are: pressure 9.5 MPa (1 378 psi) and temperature 525 C

(977 F). After commissioning, the treatment used was

ammonia/hydrazine AVT combined with phosphate dos-

ing into the boiler water. As is typical in paper mills, long

steam and condensate lines between the boiler house and

the individual paper machines and frequent air ingress into

the low pressure and high pressure condensates resulted

in heavy corrosion in the boiler peripheral paper mill equip-


Figure 4: pH of the early condensate samples a unit

with a once-through steam generator on

polyamine/amine treatment.

Figure 5: Paper mill parts taken from the equipment vs.

a part from the spare part stock.

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ment. The unit suffered from heavy corrosion product

transport into the boiler and fast buildup of boiler tube de-

posits. A boiler tube hot side deposit weight of

760 g m2

was determined. The boiler had to be chemi-

cally cleaned.

After the chemical clean, the unit cycle treatment was con-

verted to polyamine/amine treatment. As a result of the

cycle treatment conversion, the iron content of the con-

densates after a short period with higher iron levels

(cleaning of surfaces in paper mill equipment, outside of

the boiler system) has dramatically decreased to

levels customary in non-industrial power stations

(

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cation exchanger) may have a high or a low pH; i.e., it may

be non-corrosive or strongly corrosive with respect to iron-

based materials [9]. Industry experience proves that even

at increased cation conductivity, failure- and damage-free

operation of the cycle in the presence of organic alkalizing

agents is possible. This is a result of favorable distribution

coefficients of low-molecular volatile amines. For this rea-

son, in the phase transition zone of a low pressure turbine,

amines are capable not only of coping with their own de-

composition products (e.g., acetates and formates), but

also with certain levels of inorganic contaminants possibly

present in the steam.

The experience in the industrial steam generation proves

that cation conductivities in the range of 0.5 S cm1

do not cause any turbine-related problems, assuming that

pH is correctly set by low-molecular volatile amines. A se-

rious and deep study of this topic is desirable. The major

turbine manufacturers should carefully investigate whether

the materials and the design of low pressure turbines areactually so inadequate that the turbines cannot accept

steam with a cation conductivity somewhat higher than

the ominous 0.2 S cm1

, even though the pH of the early

condensate is markedly higher than 9 and the specific

conductivity of the early condensate is, e.g.,

< 10 S cm1

. Such evaluations should only focus on

technical issues and not be prejudged by possible war-

ranty aspects. The long-term experience with the poly-

amine/amine treatment demonstrates that a slightly in-

creased cation conductivity does not endanger low pres-

sure parts of condensing turbines.

Bursik et al. have in a somewhat provocative manner

suggested that polyamine/amine treatment should be in-

corporated into Dooley's continuum of treatments [2]. The

more operation experience that is gained with this treat-

ment, the more justifiable this opinion becomes [Figure 7].

REFERENCES

[1] Bursik, A., Staudt, U. W., PowerPlant Chemistry

2001, 3(3), 136.

[2] a) Bursik, A., Bezzoli, P., Graf, A., The Seventh

International Conference on Cycle Chemistry in Fossil

Plants (Houston, TX, U.S.A.), 2003. Electric Power

Research Institute, Palo Alto, CA, U.S.A.

b) Bursik, A., Bezzoli, P., Graf, A., PowerPlant

Chemistry2003, 5(6), 373.

[3] a) Dooley, B., Shields, K., The Seventh International

Conference on Cycle Chemistry in Fossil Plants

(Houston, TX, U.S.A.), 2003. Electric Power ResearchInstitute, Palo Alto, CA, U.S.A.

b) Dooley, B., Shields, K., PowerPlant Chemistry

2004, 6(3), 153.

[4] Tavast, J., PowerPlant Chemistry Seminar "Com-

bined Cycles and Heat Recovery Steam Generators

Development, Boiler Tube Failures, Chemistry, and

Monitoring", 2002, Contribution to the discussion.

PowerPlant Chemistry GmbH, Neulussheim,

Germany.

[5] Bursik, L., PowerPlant Chemistry2002, 4(2), 81.

[6] Grabli, A., Massalha, L., VGB Symposium Industrie-und Heizkraftwerke, BHKW 2004 (Bochum,

Germany), 2004. VGB PowerTech, Essen, Germany.


Figure 7:

Continuum of treatments

including polyamine/amine

treatment [2].

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[7] Galt, K. J., Proc. (on CD), ESAA Power Station

Chemistry 2004 Conference (Pokolbin, NSW,

Australia), 2004 . Energy Supply Association of

Australia, Melbourne, VIC, Australia.

[8] Roofthooft, R., Eyckmans, M., Verheyden, K., de

Pourcq, D., VGB PowerTech 2001, 81(3), 83.

[9] Bursik, A., PowerPlant Chemistry2002, 4(10), 597.

THE AUTHOR

Albert Bursik (Ph.D., Chemical Engineering, Institute of

Chemistry and Chemical Technology in Prague, Czech

Republic, Mechanical Engineering, University of Stuttgart,

Germany) has worked for over 35 years as a chemist in

several utilities. Albert Bursik is an Honorary Fellow of the

International Association for the Properties of Water andSteam and has published more than 200 scientific and

technical publications. He is a professor at the University

of Stuttgart and works as the editor of the PowerPlant

Chemistry journal.

CONTACT

Albert Bursik

PowerPlant Chemistry GmbH

P.O. Box 1269

68806 Neulussheim

Germany

E-mail: [email protected]

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