PRESENTATION ON ENERGY AUDITS IN THERMAL POWER STATION BY H.S.Bedi Sr. Vice President (Power)
Energo Engineering Projects Ltd. A-57/4, Okhla Industrial Area, Phase – II, New Delhi - 110020
“You cannot Manage what you cannot Measure” (Accurately) - Jack Welch, CEO, General Electric
PATTERN OF ENERGY CONSUMPTION IN THERMAL POWER STATION
TYPICAL PLANT LOSSES
TYPICAL BOILER LOSSES
TYPICAL CYCLE LOSSES
• • •
USEFULNESS OF ENERGY AUDIT IN THERMAL POWER STATION 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. Contd …
1.0 • • • • •
USEFULNESS OF ENERGY AUDIT IN THERMAL POWER STATION Provides guidance in Loading Sequences of the Units. Identification and Rectification of errors in online 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 …
• • •
USEFULNESS OF ENERGY AUDIT IN THERMAL POWER STATION Improves competitiveness by reducing unit generation. Creates bench mark for all equipments and systems. Fulfills bureau of energy efficiency mandatory requirement of Energy Audit.
EFFECT OF INSTRUMENTATION ON ENERGY AUDITS A.
Plant on-line instruments with few audit instruments Accuracy around 3.0%.
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 THAN ASME-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%
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.
ECONOMIC ASPECTS OF INEFFICIENT MACHINES (200 MW) SHORT FALL
LOSS IN CRORES PER ANNUM
TURBINE CYCLE HEAT RATE
AUX. POWER CONSUMPTION
NOTE: TG CYCLE HEAT RATE IS TAKEN AS 2000 KCAL / KWh COAL CV IS TAKEN AS 4000 KCAL / Kg PRICE OF COAL TAKEN AS Rs. 2000 / TON LOSS INCREASES WITH MACHINE SIZE
Impact of Turbine Efficiency on HR/Output Description
Effect on TG HR
Effect on KW
1% HPT Efficiency
1% IPT Efficiency
1% LPT Efficiency
Output Sharing by Turbine Cylinders are around HPT IPT LPT
28% 23% 49%
HP/IP Turbine Efficiency Instrument Inaccuracy / lack of corrections
Temp Deg C
Temp Deg C
Temp Deg C
Temp Deg C
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)
HPT inlet press. by 5.0 ata
HPT inlet temperature by 10.0deg C
IPT inlet temperature by 10.0deg C 5.6
Condenser pressure by 10.0 mm of Hg
Re spray water quantity by 1.0%
HPT Cylinder efficiency by 1.0%
IPT Cylinder efficiency by 1.0%
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: 18 mth
Overall Instrument accuracy
(% of span) Repeatability) (of calibrated span)
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 gas a. Hg
= 0.24 wg (Tg – Ta) G.C.V
as percentage of heat input
= 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 fuel Hm = Wm+9H (100 – Tf) + 540 – 4.6 (Tg -100) G.C.V 3. Heat loss due to moisture in air Ha = 0.26 Wma (Tg – Ta) G.C.V 4. Heat loss due to Incomplete combustion to Co = 2414 C x CO x 1 Hco G.C.V CO+CO2 5. Heat loss due to unburnt carbon “C” = Wc x 7831 Hc G.C.V
%of heat input
% of heat input
as % of heat input
as % of heat input
6. Heat loss due to Blow Down Hbd = Wb (hbw – hw) G.C.V 7. Heat loss due to Radiation HR
as % of heat input
= Difficult to evaluate & thus take design values only
In above Wg =Wt of dry flue gas W..G = [44.01 *CO2 + 32*O2 28.02 * N2 + 28.01*CO]*[Cb + 12.01 * S/32.07] 12.01 * (CO2 + CO) = Tempt. Of flue gas at exit of Boiler Tg Ta = Tempt. Of air at inlet (ambient) = Tempt. Of fuel inlet Tf hbw-hw = Heat in blow down = Weight of moisture Wm Wma = Wt of waterin Kg/Kg of air X Wt of air in Kg supplied / Kg of fuel = Weight of unburnt “C” Wc Wb = Wt of water blow down All wts are / kg of fuel
FG Expansion Bellow
APH Sampling Locations APH FG
Annexure - I BOILER 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/6 T3 D/6
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.
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 CRH H. 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
Ps kg / m2
PD kg / cm2
Specific weight of liquid
W kg / M3
Total dynamic head at test speed N H = (PD – PS) X 10 / W MLC Total dynamic head at design speed N1 H1 = HX (N1 / N)2 MLC Fluid flow at design speed N1 Q1 = QX (N1 / N) M3 / Hr 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 / Hr Q1 > Q2
FREQUENCY OF READINGS FOR ACCURATE DATA COLLECTION TURBINE CYCLE AUDIT Pressure Temperature Flow Power Levels
5 Minutes 5 Minutes 1 Minute 1 Minute 10 Minutes
15 to 30 Minutes ½ to one hour
BOILER UNIT AUDIT Temperature Flue Gas Composition
DURATION OF AUDIT TEST Turbine Cycle Boiler Unit
2 Hrs -
TEST INSTRUMENTS ACCURACY, CODE & CALIBRATION LAB Accuracy of Energy Audit Instruments • •
Pressure Measuring Instruments Temperatures
• • • • •
Aux. Power Measuring Instruments Generator Power Measurement Flue Gas Analysis Data Logger Ultrasonic Flow Meter
0.1 % Acc. 1/2 DIN Tolerance Or ASME CLASS ‘A’ 0.2 % Acc. 0.1 % Acc. 0.5 % Acc. 0.03 % Acc. 0.5 % Acc.
Note: - Price and Quality / Grade of Energy Audit Depends largely on Instrument Accuracies
METHODOLOGY TO BE ADOPTED FOR ENERGY AUDIT
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.
Follow enclosed Test scheme for boiler and turbine testing.
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
CHECK UP THE AVAILABILITY OF INSTRUMENT MOUNTING POINTS AND ORGANIZE FOR MISSING POINTS. (CUSTOMER TO ARRANGE OR SPARE ALTERNATE POINTS)
ARRANGE CALIBRATED INSTRUMENTS.
PLAN SCHEDULE OF ACTIVITIES FOR ENERGY AUDIT.
Customer to Arrange shutdown if required for providing non available / missing points and attending defects noticed during walk down survey.
Conduct test as per above plan.
Prepare preliminary energy audit report.
Evaluate Final Results.
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 down Energy 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.
DETAILED ENERGY AUDIT 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 •
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.
Heat loss due to heat in dry flue gas.
Heat loss due to moisture in as fired fuel.
Heat loss due to moisture from burning of hydrogen in fuel
Heat loss due to moisture in air.
Heat loss due to surface radiation and convection.
Heat loss due to formation of carbon monoxide.
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.
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.
HP and IP cylinders efficiency
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.
• Assessment of the health & Transformer load loss of GT, UAT, Station Service transformers etc. • Identification of possible Energy conservation options in this area. • 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).
• 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 Opportunities.
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 the corrected 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
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.
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 transmitters better than
Power Meter for generator &
Unit Aux Power measurement iv
Power transducers / Load Analyser
Flue gas analyser
Ultrasonic flow meters
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.
METHODS / OBSERVATION FOR SAVINGS ENERGY IN 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. Contd….
METHODS / OBSERVATION FOR SAVINGS ENERGY IN POWER PLANT 7)
HP heater no. 5 out of service.
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.
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….
METHODS / OBSERVATION FOR SAVINGS ENERGY IN POWER PLANT 12)
Condenser air ingress and dirty tubes.
Under loading of motors
Excessive air leakage in compressed air system
Drain valves passing
Air ingress to Boiler furnace
FAD of compressors low
Thanks… Energo Engineering Projects Ltd. A-57/4, Okhla Industrial Area, Phase – II Phone: +91 - 11 - 26385323/ 28/ 29/ 38 Fax: +91 – 11 – 26385333 E-mail: ener[email protected] [email protected]