"ENERGY AUDIT METHODOLOGY FOR FOR TURBINE CY"
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 P1 P2 P1 P3 P1 P2 T2 T1 T3 T2 T1 T1 H H H S S S Effect of Increasing Effect of Increasing Effect of Increasing Pressure on Available Steam Temperature Steam Pressure & Energy On Available Energy Temperature Both on Available Energy EFFECT OF STEAM PARAMETERS H H S S Effect of Changing Reheat Pressure Effect of Changing Reheat Temp. THERMAL PROCESS LOSSES Impact of Turbine Cylinder Efficiency on HR/Output 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 % 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 Pressure HP turbine extraction Temperature Hot reheat steam, Cold reheat Steam Flow 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) 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 Q1 x (H1 – h2) + Q2 X (H3 – H2) Turbine Heat Rate = Gross Generator Output 860 kW Turbine Cycle Efficiency = X 100 Heat Rate kCal/hr TURBINE HR EVALUATION AND EFFICIENCY Actual Process 1-2-3-4-5 Comparison of Actual Expansion Actual Expansion in HP, IP & LP with Isentropic Expansion in Turbine Cylinder TURBINE HR EVALUATION AND EFFICIENCY Variation of Heat Rate with Load Heat Rate Characteristics with Condenser Exhaust Pressure 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 0C FEED WATER HEATERS PERFORMANCE While 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 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