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ENERGY AUDIT METHODOLOGY FOR FOR TURBINE CYCLE
Presented By
M.V.Pande
Dy.Director
NPTI, Nagpur
COAL TO ELECTRICITY PROCESS
STEAM CYCLE FOR 210 MW UNIT
EFFECT OF STEAM PARAMETERS
Effect of Increasing Steam Temperature
On Available Energy
Effect of Increasing Pressure on Available
Energy
Effect of Increasing Steam Pressure &
Temperature Both on Available Energy
P1 P2P3
T1
P1
T2
T3
P1
P2
T1
T2T1
H
S
H
S S
H
EFFECT OF STEAM PARAMETERS
Effect of Changing Reheat Pressure Effect of Changing Reheat Temp.
S S
HH
THERMAL PROCESS LOSSES
Description Effect on Effect on TG HR KW
1% HPT Efficiency 0.16% 0.3%
1% IPT Efficiency 0.16% 0.16%
1% LPT Efficiency 0.5 % 0.5 %
Impact of Turbine Cylinder Efficiency on HR/Output
FOLLOW TEST CODES
• ASME PTC - 6 For Steam Turbines
• ASME PTC - 4.1 or BS- 845: 1987 for Boilers
210 MW KWU STEAM TURBINE STEAM & WATER CYCLE
TURBINE CYCLE LOSSES
STEPS INVOLVED IN CONDUCTING THE TURBINE ENERGY AUDIT
Data collection
Observations and Analysis
Exploration for energy conservation measures
Report preparation
DATA COLLECTION
Design Specification of turbine and associated equipment:
Type of the turbine, make and model Number of cylinders No of stages (for HP, IP and LP) No of main and reheat valves Construction details of HP, IP LP Turbine extraction systems Control systems Type of governing Type of sealing Year of installation Major modifications carried out during the recent past
DATA COLLECTION
Turbine Cycle Heat Rate Kcal/kwh
DATA COLLECTION
INSTRUMENTS REQUIRED
Temperature Indicator & Probe
Pressure gauges
Flow measuring instrument (steam and water)
Ultrasonic leak detector
MEASUREMENTS & OBSERVATIONS TO BE MADE
Feed water at Inlet & Outlet of Heaters
Main steam parameters
HP turbine extraction
Hot reheat steam, Cold reheat Steam
IP extraction
IP Exhaust
Condenser back pressure
Cooling water flow and temperatures
Generator output
Barometric pressure
Reheater spray (flow)
Superheater spray (flow)
Feed water (flow)
Pressure
Temperature
Flow
MEASUREMENTS & OBSERVATIONS TO BE MADE
Past performance trends on turbine loading, operation, PLF
Major constraint in achieving the high PLF, load or efficiency
Major renovation and modifications carried out in the recent past
Operational failures leading to inefficient operation
Tripping
Performance of associated equipment (condenser, boiler, etc)
Plant side initiatives to improve the performance and efficiency of the Turbine
TURBINE HR EVALUATION AND EFFICIENCY
Turbine heat rate is defined as the heat input (Kcal) required to generate one unit of Electrical output (KWh). The trials are to establish heat rate (Kcal/kWh) and turbine efficiency under, as run conditions have to be carried out
The efficiency method given in this procedure is the enthalpy drop efficiency method. This method determines the ratio of actual enthalpy drop across turbine section to the isentropic enthalpy drop
This method provides a good measure for monitoring purposes. Each section of the turbine must be considered as a separated turbine
Each section should be tested and results are trended separately. While conducting the tests, it has to be ensured that, it is conducted over normal operating load range
TURBINE HR EVALUATION AND EFFICIENCY
Turbine Cycle Efficiency = 860
Heat RateX 100
kW
kCal/hr
Turbine Heat Rate = Q1 x (H1 – h2) + Q2 X (H3 – H2) Gross Generator Output
TURBINE HR EVALUATION AND EFFICIENCY
Comparison of Actual Expansion with Isentropic Expansion in Turbine
Actual Expansion in HP, IP & LP Cylinder
Actual Process
1-2-3-4-5
TURBINE HR EVALUATION AND EFFICIENCY
Heat Rate Characteristics with Condenser Exhaust Pressure
Variation of Heat Rate with Load
TURBINE EFFICIENCY EVALUATION DATA
Kcal/kg/oK
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 (500 MW 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 10.0 deg C 6.0
3. IPT inlet temperature by 10.0 deg 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
IDENTIFYING FACTORS FOR HR DEVIATION
After evaluating the turbine heat rate and efficiency, check for the deviation from the design and identify the factors contributing for the deviations. The major factors to be looked into are: Main steam and reheat steam inlet parameters
Turbine exhaust steam parameters
Reheater and super heater spray
Passing of high energy draining
Loading on the turbine
Boiler loading and boiler performance
Operations and maintenance constraints
IDENTIFYING FACTORS FOR HR DEVIATION
Condenser performance and cooling water parameters
Silica deposition and its impact on the turbine efficiency
Inter stage sealing, balance drum and gland sealing
Sealing fins clearances
Nozzle blocks
Turbine blade erosion
Functioning of the valves
Operational status of HP heaters
Performance of reheaters
FEED WATER HEATERS PERFORMANCE
inlet
inlet
outlet
0 C
FEED WATER HEATERS PERFORMANCEWhile collecting the heater wise parameters, collect the following data:
Unit load MW
Main steam pressure, temperature & flow
Feed water flow
Super heater & Reheater attemperation flow
Boiler feed pump discharge pressure
HP Heater levels
Condenser vacuum, Barometric pressure
FEED WATER HEATERS PERFORMANCE
After the collecting the above data, evaluate the following
Terminal temperature difference – TTD
Heater drain cooler approach temperature difference – DCA
Feed water temperature rise across heater – TR
TTD = t sat – t fw outlet
FEED WATER HEATERS PERFORMANCE
DCA = t drains – t fw inlet
TR = t outlet – t fw inlet
HEATER PERFORMANCE DEVIATION Check following if TTD, DCA, TR are deviating from the design and actual rise in feed water temperature is low:
High terminal temperature difference, TTD
Excessive venting (worn vents, altered set point, vent
malfunctioning)
Excessive make up
High water level (tube leaks, improper setting)
Header partition leaks
Non condensable gases on shell side
Excessive tube bundle pressure drop (excessive number of tubes plugged, tubes folded internally)
HEATER PERFORMANCE DEVIATION High drain cooler approach temperature, DCA
Drain cooler inlet not submerged
Low drain water level (improper setting, excessive FW heater drain bypass – bypass valve left open - bypass valve malfunctioning / leaking)
Excessive tube bundle pressure drop (excessive number of tubes plugged / tubes folded internally)
Feed water heater bypassed
FW heater bypass valve leaking
Note: Similar approach shall be followed for LP Heaters
ADDITIONAL LOAD ON ECONOMIZER
Based on the above, if the HP heaters performance is poor, then additional load on economizer can be estimated by using the data sheet
economizer