energy audits in thermal power station

PRESENTATION ON ENERGY AUDITS

IN

THERMAL POWER STATION

BY

H.S.BediSr. Vice President (Power)

Energo Engineering Projects Ltd.A-57/4, Okhla Industrial Area,Phase – II, New Delhi - 110020

““You cannot Manage what you You cannot Manage what you cannot Measurecannot Measure””

(Accurately)(Accurately)

-- Jack Welch, CEO, General ElectricJack Welch, CEO, General Electric

PATTERN OF ENERGY CONSUMPTION

IN

THERMAL POWER STATION

TYPICAL PLANT LOSSES

TYPICAL BOILER LOSSES

TYPICAL CYCLE LOSSES

1.0 USEFULNESS OF ENERGY AUDIT IN THERMAL POWER STATION

Contd Contd ……

• Identifies Wastage areas of Fuel, Power and Water & Air Utilization.

• Reduction in cost of generation by implementing findings of EA.

• Increases power generation by efficient utilization of steam in turbine cycle and reduction in Aux Power Consumption.

• Maintenance planning and availability improvement.


• Provides guidance in Loading Sequences of the Units.

• Identification and Rectification of errors in on-line Instruments.

• Leads to reduction in Green House Gases. • Utilizes specialized services of experienced

Engineers.• Training of O&M staff for Efficient Control of

Unit Operation.

Contd Contd ……

• Improves competitiveness by reducing unit generation.

• Creates bench mark for all equipments and systems.

• Fulfills bureau of energy efficiency mandatory requirement of Energy Audit.


A. Plant on-line instruments with few audit instruments Accuracy around 3.0%.

B. Accurate calibrated instruments as per ASME-PTC-6 for steam turbine& ASME-PTC-4-1 for Boilers.Accuracy around 0.5 %

ERROR OF PROCEDURE OF ENERGY AUDIT OTHER THANASME-PTC-6 for steam turbines and ASME – PTC-4.1 for boiler

– Error in Boiler Energy Audit – around 2.0%– Error in steam turbine Energy Audit – around 3.0%

Total error because of Instrumentation & Procedure 6.0%

EFFECT OF INSTRUMENTATION ON ENERGY AUDITS

Contd….

IMPORTANCE OF ACCURACY IN ENERGY AUDITS

– 1.0% Deviation in findings means 25000 tons of coal loss/annum for 200 MW Unit or approx Rs. 5 crores / year (4000Kcal coal GCV & Rs.2000/ton coal cost)

– Difference in cost of Energy Audit between B & A is 12 to 14 lacs as against 6 to 8 lacs.

SHORT FALL LOSS IN CRORES PER ANNUM

TURBINE CYCLE HEAT RATE 1.0 % 5.0TG OUTPUT 1.0% 5.0BOILER EFFICIENCY 1.0% 1.75AUX. POWER CONSUMPTION 5.0 % 2.5

NOTE:TG CYCLE HEAT RATE IS TAKEN AS 2000 KCAL / KWhCOAL CV IS TAKEN AS 4000 KCAL / KgPRICE OF COAL TAKEN AS Rs. 2000 / TONLOSS INCREASES WITH MACHINE SIZE

ECONOMIC ASPECTS OF INEFFICIENT MACHINES (200 MW)

Description Effect on Effect onTG HR KW

1% HPT Efficiency 0.16% 0.3%

1% IPT Efficiency 0.16% 0.16%

1% LPT Efficiency 0.5 % 0.5 %

Output Sharing by Turbine Cylinders are around

HPT 28%IPT 23%LPT 49%

Impact of Turbine Efficiency on HR/Output

HP/IP Turbine EfficiencyInstrument Inaccuracy / lack of corrections

Main Steam HPT Exhaust

PressureKg/cm2

TempDeg C

PressureKg/cm2

TempDeg C

1 1 1 1HPT

Efficiency 0.6 % 0.6 % 2.0 % 0.7 %

IPT Efficiency

IPT Inlet IPT Exhaust

PressureKg/cm2

TempDeg C

PressureKg/cm2

TempDeg C

1 1 1 1

1.2 % 0.3 % 6.0 % 0.4 %

Effect of Condenser Vacuum on Heat Rate

10 MM HG IMPROVEMENT IN CONDENSER VACUUM

LEADS TO 20 Kcal/kwh (1%)IMPROVEMENT IN HEAT RATE FOR A

210 MW UNIT

EFFECT ON HEAT RATE FOR PARAMETER DEVIATION (500MW UNIT)

DEVIATION IN PARAMETER

EFFECT ON HEAT RATE (KCAL/KWH)

1. HPT inlet press. by 5.0 ata 6.25

2. HPT inlet temperature by 10.0deg C

6.0

3. IPT inlet temperature by 10.0deg C 5.6

4. Condenser pressure by 10.0 mm of Hg

9.0

5. Re spray water quantity by 1.0% 4.0

6. HPT Cylinder efficiency by 1.0% 3.5

7. IPT Cylinder efficiency by 1.0% 4.0

Instrument calibration interval

Calibration intervals should be based on the Specifications given by OEM / trended calibration observations.

An example of Accuracy degradation as a function of time is:

06 mth 12 mth 18 mth 24 mth

Accuracy 0.2 0.2 0.2 0.2

(% of span)

Repeatability) 0.05 0.05 0.05 0.05

(of calibrated span)

Drift (@06months) 0.1 0.2 0.3 0.4

Overall Instrument 0.30 0.40 0.50 0.60 accuracy

CONFORMITY FOR ENERGY AUDITS

FOLLOW TEST CODES

• ASME PTC - 6 For Steam Turbines

ASME PTC - 4.1 for Boilers

CALIBRATION LAB• Govt. Accredited i.e. NABL Labs

TEST SCHEME • To be Furnished And Approved Sample enclosed

HEAT LOSS METHOD

BOILER EFFICIENCY = 100 - % AGE LOSSES

1. Heat Loss in Dry flue gasa. Hg = 0.24 wg (Tg – Ta) as percentage of heat input

G.C.V

a. Hg = K (Tg – Ta) /1.8 K=0.32 for fuel oil

% CO2 in flue gas K=0.35 for Bituminous coal

2. Heat loss due to evaporation of moisture & H2 in fuelHm = Wm+9H (100 – Tf) + 540 – 4.6 (Tg -100) %of heat input

G.C.V3. Heat loss due to moisture in air

Ha = 0.26 Wma (Tg – Ta) % of heat inputG.C.V

4. Heat loss due to Incomplete combustion to CoHco = 2414 C x CO x 1 as % of heat input

CO+CO2 G.C.V5. Heat loss due to unburnt carbon “C”

Hc = Wc x 7831 as % of heat inputG.C.V

6. Heat loss due to Blow DownHbd = Wb (hbw – hw) as % of heat input

G.C.V7. Heat loss due to Radiation

HR = Difficult to evaluate & thus take design values only

In aboveWg =Wt of dry flue gasW..G = [44.01 *CO2 + 32*O2 28.02 * N2 + 28.01*CO]*[Cb + 12.01 * S/32.07]

12.01 * (CO2 + CO)Tg = Tempt. Of flue gas at exit of BoilerTa = Tempt. Of air at inlet (ambient)Tf = Tempt. Of fuel inlethbw-hw = Heat in blow downWm = Weight of moistureWma = Wt of waterin Kg/Kg of air X Wt of air in Kg supplied / Kg of fuelWc = Weight of unburnt “C”Wb = Wt of water blow down

All wts are / kg of fuel

Economizer

FG

APH

SamplingLocations

FG

APH

ExpansionBellow

HVS

Annexure - IBOILER EFFICIENCY AND APH TEST SCHEME &

INSTRUMENTATION DIAGRAM

1.Grid measurement for gas composition and gas temp. at air pre heater inlet / outlet.

W/6 W/3T1

W/3T2

W/6T3

N11 N21 N31

D/6

N12 N22 N32

D/3

N13 N23 N33

D/3

D/6

DEPTH

D = Duct Depth (Internal)

W = Duct Width (Internal)

Tx = Traverse (x) (Pockets)

x =1 to 5 (Width wise)

Nxy = Nodexy

(Sketch for one half of flue gas duct cross - section)

Grid measurement for gas sampling and temperature measurement at 3 to 5 locations on APH inlet & at 3 to 5 locations on APH outlet ducting as close to APH as possible shall be taken provided test pockets are available for inserting sampling probes. Flue gas sampling and temperature measuring probe shall be inserted at each location and traversed to collect data at these points in each location. This shall eliminate effect of gas stratification.Air temperature at inlet and outlet of APH shall be measured at two points each in case spare pockets are available.Ambient temperature, barometric pressure & RH is measured near F.D. fans.

Note1 : WBPDCL to provide the test pockets in each of the Air and Gas path for inserting test instrument.

Note2 : Test instruments shall be used for the above.

b) Turbine cycle heat rate.This varies with the system changes in cycle i.e.

1.Location of Aux. Stm. Tapping.

2.Whether Reheater spray is reqd. or not.

3.Whether spray for superheater attemperation is tapped off from BFP discharge or after top heater.

i.Cycle with Aux. Steam from MS or No Aux. Stm.;No. RH Spray, ;

H. Rate = M1 (H1 – hF) + M2 (H3 – H2 )Pg

ii.Same as (a) but Aux. Steam from CRHH. Rate = [M1 (H1 – hF) + M2 (H3 – H2) – MAS (H3 – Hc )]

Pg

iii.Same as (a) but with Reheat Spray.H. Rate = M1 (H1 – hF) + M2 (H3 – H2) + MRHS (H3 – hRHS )

Pg

iv.Same as (a) but Spray for Superheater from BFP discharge H. Rate = M1 (H1 – hF) + M2 (H3 – H2) + MSHS (hF – hSHS )

Pg

ENERGY AUDIT SCHEME FOR 210 LMW STEAM TURBINE

PERFORMANCE TEST PROCEDURE FOR PUMPS

Measured flow Q M3 / HR

Suction pressure Ps kg / m2

Discharge Pressure PDkg / cm2

Test speed NrpmLiquid temp. T ° CSpecific weight of liquid W kg / M3

Based ion characteristic curve of the pump the expected flow Q2M3 / Hr shall be worked out at H1MLC of total dynamic head (TDH)

CONCLUSION

For Normal Pump performance Q1M3 / Hr should be more than or equal to Q2 M3 / HrQ1 > Q2

Total dynamic head at test speed NH = (PD – PS) X 10 / W MLC

Total dynamic head at design speed N1H1 = HX (N1 / N)2 MLC

Fluid flow at design speed N1Q1 = QX (N1 / N) M3 / Hr

FREQUENCY OF READINGS FOR ACCURATE DATA COLLECTION

TURBINE CYCLE AUDIT

Pressure - 5 MinutesTemperature - 5 MinutesFlow - 1 MinutePower - 1 MinuteLevels - 10 Minutes

BOILER UNIT AUDIT

Temperature - 15 to 30 MinutesFlue Gas Composition - ½ to one hour

DURATION OF AUDIT TEST

Turbine Cycle - 2 HrsBoiler Unit - 4 Hrs

TEST INSTRUMENTS ACCURACY, CODE & CALIBRATION LAB

Accuracy of Energy Audit Instruments

• Pressure Measuring Instruments 0.1 % Acc.• Temperatures 1/2 DIN Tolerance

Or ASME CLASS ‘A’• Aux. Power Measuring Instruments 0.2 % Acc.• Generator Power Measurement 0.1 % Acc.• Flue Gas Analysis 0.5 % Acc.• Data Logger 0.03 % Acc.• Ultrasonic Flow Meter 0.5 % Acc.

Note: - Price and Quality / Grade of Energy Audit Depends largely on Instrument Accuracies

3.0 METHODOLOGY TO BE ADOPTED FOR ENERGY AUDIT

3.1 INTERACTION WITH PLANT ENGINEERS AND OBTAIN DATA ON

• Various equipment problems.

• Present performance level i.e. unit heat rate, fuel

consumption, DM Water and raw water consumption etc.

• Plant design data for the main and auxiliary equipments.

• Boiler TG Cycle layout, condensate, feed and steam pipe line

schematics.

• Performance / Guarantee test reports of the tests carried out

on equipments.

• Plant electrical power distribution system and transformer

etc

• Auxiliary power distribution system and transformer etc.

• Evaluation procedure for day to day monitoring i.e. plant M.I.S. systems

• Loading / requirement during test.

3.2 Follow enclosed Test scheme for boiler and turbine testing.

3.3 Develop Energy Audit procedure covering following for each equipment

• Object of energy audit

• Scheme and list of measurements

• Range, make & class of accuracy of instruments.

• Frequency of instrument readings.

• Duration of instrument readings.

• Required man power.

• Interconnected plant data required.

• Finalize procedure with customer / consultants

3.4 CHECK UP THE AVAILABILITY OF INSTRUMENTMOUNTING POINTS AND ORGANIZE FOR MISSINGPOINTS. (CUSTOMER TO ARRANGE OR SPAREALTERNATE POINTS)

3.5 ARRANGE CALIBRATED INSTRUMENTS.

3.6 PLAN SCHEDULE OF ACTIVITIES FOR ENERGYAUDIT.

3.7 Customer to Arrange shutdown if required for providing non available / missing points and attending defects noticed during walk down survey.

3.8 Conduct test as per above plan.

3.9 Prepare preliminary energy audit report.

3.10 Evaluate Final Results.

3.11 Conduct mass and energy balance in Turbine cycle components and boiler.

3.12 Make comparison with design Acceptance test data and establish shortfall areas.

3.13 Furnish recommendations in the form of cost benefit analysis.

3.14 Give presentation on findings with backup data

SCOPE FOR CONSULTANT

• Frame SPECS for Energy Audits

• Approve Energy Audit Schematics

• Approve Procedure Covering Evaluation Procedure, Type

and Class of Accuracy of Instruments & their Calibrations

• Installation of Instruments and Ensure Compatibility of Data

Thermodynamically

• Supervise Conductance of Energy Audit

• Review & Acceptance of Audit Report

SCOPE OF WORK FOR ENERGY AUDIT OF THERMAL POWER PLANT UNITS

Energy Audit should cover evaluation of the present performance

level of all major equipments, identify the controllable losses and

suggest remedial measures for improvements with cost benefit

analysis and pay back period. The detailed scope of work covering

the following is given as under.•Boilers•Turbine including regenerative cycle and condenser•Electrical system•Fans and Pumps in the above areas•Insulation•Balance of Plant including Station auxiliaries power consumption, Coal Handling plant, ash handling system, DM Plant, Station Compressed air system, CW system and Air conditioning.

Preliminary Energy Audit, Preliminary Checking / Hot

walk downEnergy Auditing agency to check the complete unit steam, condensate

and feed water system along with the functioning of Heat cycle

equipment like Boiler, Condenser Regenerative system Turbine

Cylinders etc. during HOT WALK DOWN. Problem if any, shall be

brought to the notice of the authority for rectification and arranging

provisions for mounting audit instruments during Audit Preparatory

Activities, prior to start of the detailed EA.

A Energy Audit Of Boilers

Performance of Boiler and APH be established by measuring exit flue

gas temperature and its analysis at around nine to fifteen points in flue

gas duct cross section before and after APH to eliminate effect of gas

stratification as per international practice (Refer enclosed boiler test

scheme Annexure – I). This is because boiler efficiency differs by

around 2.0% by this method than if the measurements are taken at

single point. Scope will include the following

DETAILED ENERGY AUDIT

• Conduct boiler efficiency measurements as per above test

scheme by indirect method i.e heat loss method, evaluate Boiler

efficiency and identify potential areas for improvements such as.

a. Heat loss due to heat in dry flue gas.

b. Heat loss due to moisture in as fired fuel.

c. Heat loss due to moisture from burning of hydrogen in fuel

d. Heat loss due to moisture in air.

e. Heat loss due to surface radiation and convection.

f. Heat loss due to formation of carbon monoxide.

g. Heat loss due to combustibles in bottom and fly ash

Check up air ingress in boiler from LTSH area downwards

upto I.D fans.

Determine Air preheater performance to establish.

a. Gas Side Efficiency – As ratio of gas temperature drop corrected

for no air leakage to temperature heads.

b. Air leakage as percentage of air passing from airside to gas side.

c. X-Ratio I,e heat capacity of air passing through the air heater to the

heat capacity of gas passing through the air heater.

d. Air side and gas side pressure loss across the air heater.

Input power measurement of ID FANS / FD fans, PA fans, Fan

Loading & combined efficiency of fan and motor and their specific

power consumption

Energy Audit test has to be carried out for four hours by recording

parameters at every 15 minutes and average of data to be utilized

for evaluation.

B Energy Audit of steam turbine cycle and it auxiliaries

For Energy Audit of steam turbine cycle, all the parameters as per the

enclosed scheme in Annexure – II are to be measured

simultaneously by hooking up these calibrated instruments to

a data logger. The recording has to be at least for a minimum

period of two hours with each measurement being recorded at an

interval of one minute. Average of the data so collected to be

utilized for evaluation of the following and suggestions for

deficient areas for improvements to be made.

1. Turbine cycle heat rate.

2. HP and IP cylinders efficiency

3. Turbine pressure survey

4. TTD & DCA of HP / LP heaters performance

5. Condenser performance i.e

• Condenser back pressure after duly considering the effect of

present C.W inlet temp. C.W flow, heat load on condenser

and air ingress to condenser vis-à-vis design conditions

• C.W side pressure drop in condenser

6. Cycle losses

7. Performance of turbine glands

8. Ejector performance

For accurate heat rate determination, Turbine inlet flow and reheat

flow need to be evaluated as per international practice by

measuring condensate flow through measurement of ∆p of plant

condensate flow orifice after checking its condition and using

evaluated drip and extraction to deaerator flows through heat and

mass balance across heaters and deaerator as per scheme. Fall in

deaerator level and HPTV and IPV leak off flow are also considered.

Alternately by mass balance across deaerator if flow orifices are

installed in drip and extraction lines to deaerator. Deaerator outlet

feed flow shall then be taken as the main steam flow after

considering for RH spray tap off from Boiler feed line.

C. Electrical system

1 Transformers • Assessment of the health & Transformer load loss of GT, UAT, Station Service transformers etc.

• Identification of possible Energy conservation options in this area.

2 Motors • Assessment of Loading condition of HT and LT motors of Boiler area, Turbine area and Balance of Plant area.

• Assessment of operating parameters like load variation, Power factor, of HT and LT motors consuming power more than 50 KW.

• Identification of possible Energy conservation options in this area (with latest techniques).

Capacitors • Assessment of health of capacitors.

Plant Lighting system • Lighting load survey and Assessment of

installed load efficacy (I.L.E) and I.L.E

ratio at various areas of plant.

• Assessment of present lighting controls

• Identification of Energy Conservation

Opportunities.

D Fans and Pumps Performance

Performance of fans consuming power more than 50 KW such as ID,

FD, PA fans etc.•Input power measurement•Fan loading and combined efficiency of fan and motor•Specific energy consumption

Pump performance for BFPs, CEPs, Aux C.W.P & C.W.Pand

pumps consuming power more than 50 KW etc. •Check Performance of the pumps by comparing the corrected measured flow at operating speed to design speed with that of the expected flow derived from the characteristic curves against thecorrected total dynamic head at design speed.•Determine Pump efficiency as the ratio of power input to the pump shaft to hydraulic power.•Specific power consumption

E Insulation Audit:A. Walk through survey of Boiler, Turbine and associated steam

piping to identify the damaged and Hot spot area.B. Surface temperature measurement at the damaged and Hot

spot area by infrared temperature indicator.C. Estimation of heat loss in the hot spots and damaged

insulation area.

F Balance Of Plant(i) Compressed air system:•Free Air Delivery i.e. Capacity evaluation of the Plant and Instrument air compressors.•Checking volumetric efficiency of compressors.•Assessment of compressed air leakage quantity.•Assessment of Energy performance of the air compressors/ specific power consumption.•Study of the compressed air network and suggest suitable energy saving options.

(ii) Air conditioning system:•Performance evaluation of AC Plant w.r.t net cooling / refrigeration capacity along with heat load of Air handling unit and energy requirements at the operating conditions vis-à-vis design condition to be determined.

(iii) Ash Plant•Performance of ash Slurry pumps through power measurement and flow measurement.•Ash water ratio assessment and recommendations for optimization in water and power consumption.

(iv) Cooling Tower Performance•It shall include establishment of •Liquid/Gas ratio•Fan efficiency as the ratio of shaft power developed and the work done by the fan•Cooling Tower Effectiveness, approach and range.•Cooling capacity.

V Coal Handling Plant

Input Power measurement of all the key equipment of the CHP area

like: Paddle feeders, Conveyors, Stacker & Re-claimer, Wagon

Tipplers, Crushers,

Establishment of specific energy performance indicators.

Accuracy and calibration of the instruments

The proposed instruments should have following level of accuracy.

i.Thermocouples and PRTs – ASME special class ‘A’ i.e ½ DIN

tolerance

ii.Pressure and differential pressure - 0.1%

transmitters better than

iii. Power Meter for generator & - 0.1%

Unit Aux Power measurement

iv Data Logger - 0.03%

v Power transducers / Load Analyser - 0.5%

vi Flue gas analyser - 0.5%

vii Ultrasonic flow meters - 0.5%

viii Anemometer - 1.0%

xi Infrared Thermometer - 1.0%

x Lux meter - 1.0%

xi RH meter - 1.0%

These should be duly calibrated from NABL accredited lab.The above accuracies for S.No. I to V are as per ASME specified for

Performance Evaluation of Thermal Power Plants.

OUR EXPERIENCE OF ENERGY AUDITS OF THERMAL POWER PLANTS

–Two 2 x 210 MW units of M/s WBPDCL Kolaghat

Thermal Power Plant.

–15 units of Saudi Electric company of Saudi Arabia

having unit sizes varying from 60 MW to 660 MW.

–Two 2 x 18 MW units of M/s Shree Cements Captive

Power Plant.

1) Operation of machine at very low turbine I/L parameters.

2) Operation of turbine at lower loads.

3) HP and IP turbine cylinder efficiencies are very low.

4) Main steam and HRH inlet temperature to turbine very low.

5) RH pressure drop high

6) High quantity of SH Spray and its tapings before HPH-5 resulting of loss in heat because of changed cycle.

METHODS / OBSERVATION FOR SAVINGS ENERGY IN POWER PLANT

Contd….

7) HP heater no. 5 out of service.

8) Turbine cycle not operating as per design scheme i.e. Ejector and Deaerator pegging steam from PRDS header as against normal source from deaerator & extraction steam respectively.

9) Passing of turbine cycle drain valves.

10) Make up quantity to cycle is very high which indicates

excessive system steam (heat) loss.

11) TTD & DCA of heaters high


Contd….

12) Condenser air ingress and dirty tubes.

13) Under loading of motors

14) Excessive air leakage in compressed air system

15) Faulty insulation

16) Drain valves passing

17) Air ingress to Boiler furnace

18) FAD of compressors low


Thanks…Energo Engineering Projects Ltd.A-57/4, Okhla Industrial Area, Phase – II Phone: +91 - 11 - 26385323/ 28/ 29/ 38Fax: +91 – 11 – 26385333E-mail: [email protected]

[email protected]: www.energoindia.com

energy audits in thermal power station

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