Energy Audit Procedure

for

Coal Handling Plant

Contents

Objective.

Instrumentation used.

Audit procedure.

Report Preparation Format.

Auditor tools.

Saving potential sheets.

Observation sheets.

Objective

To evaluate the performance of coal handling plant on following lines-

(1) To measure the relevant electrical parameters i.e. power drawn (Kw) or current

/power factor /voltage at various load conditions.

(2) Evaluation of energy requirement in bunkering, stacking & reclaiming.

(3) To evaluate specific energy consumption (kwh/Ton).

(4) To evaluate the normal coal throughput on an average basis.

(5) Estimation of average hours of operation of the CHP towards bunkering, stacking

& reclaiming modes.

(6) Observation & Analysis of

(a) Drive Speed

(b) Belt tension

(c) Condition of rollers

(7) Identification of areas of improvement / retrofit / modification leading to better

system capacity utilization.

INSTRUMENTS REQUIRED

1) Energy meter (0.2 Class accuracy) - 2 Nos

or,

a) Kw meter - 1 Nos

b) Volt meter - 1 Nos

c) Ampere meter - 1 Nos

d) Power factor meter - 1 Nos

2) Tachometer - 1 Nos

3) Tensiometer - 1 Nos

AUDIT PROCEDURE

STEP-1 (COMPILE THE CHP EQUIPMENTS DATA)

- Compile all data of main CHP equipments in respect of rated specifications as

well as performance guarantee test values.

- A schematic diagram of the coal handling plant.

STEP-2 (COMPILATION OF IMPORTANT SYSTEM DATA)

- Collect last 1 year data on the following – on a month wise basis (day wise would

be preferable) (Refer Annexure-I)

Total coal handled (tons)

Total power consumption in CHP

CHP utilization factor

Equipment wise utilization hours

Evaluate average load of the system from the past data.

STEP -3 (MEASUREMENT OF PARAMETERS)

- Measure the input electrical parameters like Kw or PF, Voltage; Current of all

motor drives both LT & HT for no load & average load conditions.

- Note the average equipment wise operating hours using time totalizes.

STEP -4 (EVALUATION OF COAL THROUGHPUT RATE)

- Study track hopper management / coal unloading. If necessary, do time motion

study.

- Note the average coal throughput rate using coal totalizer.

STEP – 5 (EVALUATION OF LOADING OF EQUIPMENTS)

- Determine equipment wise % loading (i.e. actual TPH / rated TPH) as well as the

motor % loading (i.e. Actual Kw / Rated Kw)

- Also make a table, listing each of the equipment and their actual & design

electrical parameters like Kw, pf, V, A.

STEP-6 (CALCULATION OF SPECIFIC ENERGY CONSUMPTION)

- Calculate Kw /Ton for existing operations i.e. bunkering, stacking, reclaiming

both activity wise & equipment wise for last one year.

- Refer annexure-II

STEP -7 (DEVELOPING MONTH WISE SPECIFIC ENERGY

CONSUMPTION PLOT)

- Based on energy meter reading & coal receipt data calculate month wise kwh /

Ton for last one year.

- Plot kwh/Ton on Y axis & months on X axis.

STEP -8 (COAL SAMPLE ANALYSIS)

Send 2-3 samples of coal taken from the belts feeding to the crushers for sieve

analysis to determine extent of coal particles below 20 mm size. (Refer annexure-

III)

STEP -9 (DRIVE SPEED ANALYSIS & BELT TENSION)

- Measure drive speed N1 (with the help of tachometer), Dia of drive and driven

pulley D1,D2.

- Calculation theoretical value of driven rpm (N2)

N1 D1

……. = ……..

N2 D2

- Measure actual driven rpm(Na) by tachometer.

- Calculate liner speed of belt (Sb)

- Sb = !! D2Na

- Measure actual linear speed of belt (Sa)

- Calculate slip = Sb -Sa

- Tolerances of slips should be < 4% for conveyor belts.

- Recommendations maybe made accordingly.

Step-10 (Lub oil inspection)

- Collect the oil sample.

- Get the sample analysed.

- If the metal traces are found beyond permissible limits, recommend for

complete oil change or inspection of bearings.

REPORT PREPARATION FORMAT

The audit report may be prepared in the following format.

a) Foreword

b) Audit team

c) Recommendation

-Energy conservation option

- Saving potential

d) Observation

e) Present Practices : Explain in detail present status.

f) Technical specifications

g) Single line Diagram.

AUDITORS TOOLS

1) Installing power saver device in major LT motors.(conveyor belt etc.)

Major HT /LT motors i.e. conveyors, crushers etc. are often partially loaded & also there

is frequent starts /stops. Hence to mitigate the above problem, it is proposed to provide

power saver devices in major motors. Advantages of power saver devices are described

below.

Existing Problem:

a) At no load & partial load motor draws the same power.

b) Higher starting current leads to over heating which in turn produces thermal

stresses resulting in reduction of life of the motor.

c) Due to higher starting current, life of motor and power contactor will be reduced.

Advantages of power saver:

a) Power consumption will vary according to lead.

b) Starting current gets reduced to almost half.

c) Increase in supply voltage starts the motor smoothly & starting currents are also

limited.

1) Power factor correction

Induction motors are characterized by power factors less than unity, leading to lower

overall efficiency (and higher overall operating cost) associated with a plant’s electrical

system. Capacitors connected in parallel with the motor are typically used to improve the

power factor . The impacts of pf correction include kVA demand (and hence reduced

utility demand charges), reduced I2R losses in cable upstream of capacitor (and hence

reduced energy charges), reduced voltage drop in cables (leading to improved voltage

regulation), and an increase in the overall efficiency of the plant electrical system.

The size of capacitor required for a particular motor depends upon the no-load reactive

power (KVARs) drawn by the motor, which can be determined only from no-load testing

of the motor. In general, the capacitor is than selected in such a way that capacitor rating

does not exceed 90% of the no load KVARs of the motor. (Higher capacities could result

in over voltages and motor burn-outs.) Alternatively, typical power factors of standard

motors can provide the basis for conservative estimates of capacitor ratings to use for

different size motors (Table 1).

Since a reduction in line current, and associated energy efficiency gains, is reflected

backwards from the point of application of the capacitor, the maximum improvement in

overall system efficiency is achieved when the capacitor is connected across the motor

terminals, as compared to somewhere further upstream in the plant’s electrical system.

However, economies of scale associated with the cost of capacitors and the labor required

to install them will place an economic limit on the lowest desirable capacitor size.

Savings are also a function of cable lengths and resistance (Table 2) and the electricity

tariff.

3)Lighter Synthetic Belting

Use of higher synthetic (Nylon / Polyester / Polyamide etc.) belting in place of heavier

cotton belting has resulted in reduction of power consumption by coal conveyors.

4) Use of chemicals for reduced water spray

Mixing of chemical compounds in water for suppression of dust provides much better

atomization of water spray, by way of reduction in surface tension of water. Thus for the

given application of dust suppression, lesser quantity of water us sprayed which also

result in lesser wastage of latent heat in the steam generator.

5) Maximum Mechanical Handling: Minimum Bulldozing

Sequence of coal handling operations like receipt unloading stacking and reclaiming and

the selection of machinery is made in such a way that all the handling operations are

accomplished without the use of semimechanised means like bulldozers which are more

energy intensive equipments.

6) Reduced Number of Fillings.

Live storage capacity of raw coal bunkers and the filling pattern of bunkers is so planned

that 24 hours coal requirement of the generating units is met by not more than two fillings

per day. This does not require the CHP to be started and stopped again and again.

TABLE-1

Capacitor ratings for power factor correction by direct connection to induction

motors capacitor rating (KVARs) for motor speed

Motor Rating(hp)

3000(rpm) 1500(rpm) 1000(rpm) 750(rpm) 600(rpm) 500(rpm)

5 2 2 2 3 3 37.5 2 2 3 3 4 410 3 3 4 5 5 615 3 4 5 7 7 720 5 6 7 8 9 1025 6 7 8 9 9 1230 7 8 9 10 10 1540 9 10 12 15 16 2050 10 12 15 18 20 2260 12 14 15 20 22 2575 15 16 20 22 25 30100 20 22 25 26 32 25125 25 25 30 32 35 40150 30 30 35 40 45 50200 40 40 45 50 55 60250 45 45 50 60 65 70Note:- The values here are based on average conditions and efficiency to maintain a power factor of 0.95 to 0.97 between 33.3% and 125% of rated load, and are applicable to 50-Hz motors of 220,400/440, and 3300 volts.

Table-IIAnnual savings in energy charges from power factor correction by shunt capacitor across motor terminals as a function of motor load and length of cable between control panel and motor .a

Annual savings in energy charges (Rs.) b for cable length (meters)c of :

25m 50m 100m 150m

165 330 661 991

150 299 599 898

120 241 481 722

127 254 508 761

Note;-(a) For a 15-kw motor operating 86.4% efficiency and 0.84 power factor at 100 %load. A 6 kVAR capacitor would be installed to correct the power factor. (b) Assuming an electricity tariff of 1.4 Rs /kWH and 7920 operating hours per year.(c) Assuming a cable cross-sectional area of 35 mm2 and resistance pf 0.00104 ohm/meter.

ANNEXURE -I

DATA SHEET COAL HANDLING PLANT

MONTHLY DATA REQUIRED

PARAMETER UNIT1. Total coal receipt

2. Total electrical connected load

3. Over all operating load

4. Plant equipment operating hours

5. Operating hours of wagon trippler

6. Plant utilization factor

7. Total gross generation of station

8. Total auxiliary power consumption of the station

9. % Auxiliary power consumption

10. Total power consumption by the CHP plant

11. % of power consumption of CHP wrt APC

Lakh tons

MW

MW

Hrs

Hrs

%

MU

MU

%

MU

%

ANNEXURE-I

EQUIPMENT DATA

Equipment Rated Actual % Loading

PF Kw A V PF Kw1. Paddle feeder

2. Belt conveyor

3. Crushers

4. Vibro feeders

5. Vibro greezly feeder

6. Belt feeder

7. Dust extraction fans

8. Dust suppression pumps

CHP KEY EQUIPMENT SPECIFICATION DATA

EQUIPMENT REFERENCE

CAPACITY TPH

MOTOR INPUT POWER

SPEED OF DRIVEN EQUIPMENT(RPM OR LINEAR SPEED)

LENGTH (IN CASE OF BELTS)

HOURS OF OPERATION PRODUCTION

Paddle Feeders

Belt conveyors

Vibro feeders

Grezzly feeders

Belt feeders

Dust extraction fans

Dust suppression pumps

ANNEXURE-I

RUNNING HOUR DETAILS

Month Stage---Track Hopper Bunkering Stacking Reclaiming

Hr Hr Hr Hr

AprMayJunJulyAugSepOctNovDecJanFebMar

MonthlyAverage

ANNEXURE –I

UTILIZATION FACTOR OF CHP

MonthStage

Track hoper Bunker endAprMayJunJulyAugSeptOctNovDecJanFebMarAprMay

ANNEXURE-1

MGR Details

1. No of rakes with NTPC ----

2. Circuit Rate Length ---km

3. Time required for a rake to ---hrs complete circuit a. Placement at mine ---minutesb. Sampling (manual) ---minutesc. Loading ---minutesd. Mine to track hopper ---minutese. Rake Unloading ---minutesf. Track hopper to mine ---minutes

4. Rakes detail ---Wagons per rake (First wagon remains empty due to placement problem)---MT coal / Wagon.

5. No. of rakes received per day ---(In General)

6. Coal per rake ---MT

ANNEXURE-II

BUNKERING

STAGE---

RATED CAPACITY T/HAVERG CAPACITY T/H

S.NO Equipment Rated kw

Voltage No load Avg load Specific Energy Consumption

No load Average Rated

Amp Kw Amp Kw Kw/Ton Kw/Ton Kw/Ton1 PF-122 PF-3/43 C-1A/

1B(P)4 C-1A/

1B(S)5 C-2A/

2B(P)6 C-2A/

2B(S)7 VS-1/28 VS-3/49 CR-1/210 CR-3/411 BF-1/212 BF-3/413 C-CA/3B14 C-4A/4B15 C-5A/5B16 C-6A/6B17 C-7A/7B18 C-8A/8B

TOTAL

ANNEXURE-II

RECLAIMING

STAGE-

RATED CAPACITY T/HAVERAGE CAPACITY T/H

S no

Equipment Rated KW

Rated Volt

No load Average Load

Specific Energy Consumption

No load Average Rated

Amp Kw Amp Kw Kw/Ton Kw/Ton Kw/Ton1 Bucket

wheel2 Boom

cony3 C-9A/

9B(P)4 C-9A/

9B(S)5 C-10A/

10B6 C-11A/

11B7 C-5A/5B8 C-6A/6B9 C-7A/7B10 C-8A/8B

TOTAL

ANNEXURE-II

STACKING

STAGE-

RATED CAPACITY T/HAVERAGE CAPACITY T/H

S no

Equipment rated Kw

Rated Volt

No load Average load Specific Energy ConsumptionNo Load

Average Rated

Ampear Kw Ampear Kw Kw/Ton Kw/Ton Kw/Ton1 PF-1/22 PF-3/43 C-1A/

1B(P)4 C-1A/

1B(S)5 C-2A/

2B(P)6 C-2A/

2B(S)7 VS/-1/28 VS-3/49 CR-1/210 CR-3/411 BF-1/212 BF-3/413 C-3A/3B14 C-4A/4B15 C-9B(P)16 C-9B(S)17 Boom con

TOTAL

ANNEXURE –III

COAL SAMPLE SIEVE ANALYSIS

Crusher inlet (%)i.e. from belt feeder to crusher

Crusher outlet (%)

+ 40 mm -40 +20 mm -20 mm +40 mm -40 +20 mm -20 mm