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