ENERGY OPTIMIZATION IN TURBINE AND BOILER AUXILIARIES OF THERMAL POWER PROJECT

The main objective of the project is to improve the performance of the plant equipment & improving the thermal cycle efficiency

This can be achieved by

Reheating of steam Condenser vacuum improvement Reheat spray control Regenerative feed heating

OBJECTIVE

In India 70% of the electricity consumed is generated by thermal power plants

the efficiency of these plants is around 35 % only and the coal reserves are limited so we need to conserve this energy for future

From above limits we understood that the power plant should be operate at their best performance conditions

In this project energy optimization in the turbine & boiler auxiliaries by regenerative feed heating, condenser vacuum improvement, feed water temperature improvement, reheat spray improvement and unit loading are studied(heat rate )

INTRODUCTION

PLANT LAYOUT

RANKINE CYCLE

The Rankine cycle efficiency can be improved by increasing average temperature at which heat is supplied, decreasing or reducing the temperature at which heat is rejected.

i.e.Super heating of steamRegenerative heatingReheating of steam

EFFECTED OF OPERATING CONDITIONS ON RANKINE CYCLE EFFICIENCY:

REHEAT CYCLE

There is an increasing output the turbine. Erosion and corrosion problems in the steam turbine are

eliminated. There is an improvement in the thermal efficiency of turbines. Final dryness fraction of steam is improved. There is an increase in the nozzle and blade efficiency.

ADVANTAGES OF REHEATING:

REGENERATIVE CYCLE

The thermal stress set up in the boiler are minimized this is due to the fact that temperature ranges in the boiler are reduced.

The thermal efficiency is improved because the average temperature of heat addition to the cycle is increased

Heat rate is reducing. Due to much extraction there is an improvement in the turbine

drainage and it reduces erosion due to moisture. A small size condenser is required.

ADVANTAGES OF REGENERATIVE CYCLE:

Back Pressure of Vacuum Final Feed water Temperature Reheat inlet parameters Reheat spray

CYCLE EFFICIENCY CONTROL PARAMETERS

The exhaust steam of the turbine is condensates into water by the condenser To obtain the highest operating efficiency the temperature diff. between the exhaust

steam & circulating water should be minimum Condenser temp. diagram

Heat transfer in the condenser is

affected by the cleanliness of the

tubes, amount of air present in the

steam space, velocity of circulating

water any also by the circulating water temp.

Condenser Performance:

Causes of poor condenser performance: 1) contamination of the circulating waterside of the tubes by slim

and dirt 2) Excessive air in the steam space 3) Poor vacuum

Condenser performance optimization: Chlorination of circulating water to remove the organic deposits in the

tubes Bulleting(mechanical method) to remove the inorganic matter in the tubes Acid cleaning is preferred if the scale forms in the tubes Air in the condenser steam space reduces the vacuum and under cools the

condensate so it should remove from the steam space

Bulleting in condenser tubes

As the no of heaters increases then the cycle efficiency goes on increasing it can be observed by below T-S diagrams

Regenerative Feed Heating:

The cycle efficiency = (useful work )/(heat supplied) As more and more steam has been extracted from the turbine for feed

heating by the increasing number of heaters it is seen that the useful work area in above figures has been progressively reduced. However, the energy lost to the condenser (heat rejected from the cycle) has been reduced at a greater rate so there is an improvement in cycle thermal efficiency

Regenerative Feed Water Heating

Data collectionS.NO  

DESCRIPTIN

 

UNIT

 

DESIGN

VALUES

UNIT-1

FULL

LOAD

UNIT-1

PART

LOAD

UNIT-2

FULL

LOAD

UNIT-2

PART

LOAD

1 Load MW 210 212.0 197.3 215.5 180

2 Feed water flow(Hr avg) TPH 636.74 703.1 656.7 718.8 628.6

3 RH spray TPH 0 9.6 0.0 18.1 1.8

4 Main steam flow TPH 636.74 670.6 642.4 672.2 562.1

5 Main steam pressure before strain Kg/cm2 150 152.1 148 152.1 153.1

6 Main steam temp before Esv1/Esv2 oC 535 537.6 536.2 536.5 537.4

7 HP turbine 1.stage balding pressure Kg/cm2 134.23 133.2 125.9 132.6 114.9

8 CRH steam pressure at HPT exhaust Kg/cm2 38.56 37.2 34.7 38.6 33.5

9 CRH steam temperature At HPT

exhaust

oC 342.4 342.8 339.3 345.2 333.5

10 HRH steam pressure at IPT inlet Kg/cm2 35/36 36.1 33.7 37.5 32.6

11 HRH steam temperature at IPT inlet oC 535 540.7 535.4 536.4 536.6

12 LP turbine exhaust hood temperature oC 42.1 48.6 47.7 49.7 47.1

13 HPH 5 inlet feed water temperature oC 168 170.6 167.4 169.6 162.8

14 HPH 6 outlet feed water temperature oC 244.8 233.1 232.8 235.3 234.8

15 HPH 6 inlet feed water temperature oC 201.2 200.1 196.7 200.6 194.6

16 HPH 6 inlet feed water pressure Kg/cm2 185.42 181.3 181.6 185.8 181.4

17 HPH 6 outlet feed water pressure Kg/cm2 184.56 185.1 177.8 184.5 180.2

18 Economizer inlet feed water

temp(L/R)

oC 244.8 233.1 233.3 233.9 233.5

19 CW temp at condenser I/L-O/L(L/R) oC 27/36 29/39 29.2/38.9 31.1/40 32/39.4

20 Steam pressure at ejector nozzle Kg/cm2 7.5 10.0 10.0 10.2 11

21 No 6 extraction steam pressure Kg/cm2 36.91 37.1 34.6 34.7 33.6

22 No 6 extraction steam temperature oC 340.7 346.9 343.6 350.5 340.7

23 IP casing exhaust steam temperature oC 314.8 336.8 332.3 342.6 325.9

24 HPH 6 drip temperature oC 206 205.5 201.9 207.4 199.8

25 IP casing exhaust steam pressure Kg/cm2 7.2 7.7 7.2 7.8 7.4

26 Steam temperature at ejector nozzle oC 200 199.8 198.7 266.7 217

S.No. Re-heat inlet parameters %Cycle efficiency

Heat rate(kJ/kWh)

Pressure(bar) Temperature (0C)

1 100 470 48.30 7453.4

2 80 430 48.60 7407.4

3 70 415 48.70 7392.0

4 60 380 48.79 7378.5

5 50 350 48.84 7371.0

6 40 325 49.03 7342.4

7 30 290 45.15 7973.4

Heat Rate w.r.t. to reheat inlet parameters

Reheat Spray (TPH) Heat Rate (KJ/kWh) Cycle efficiency (%)

15 11143.2 32.30

12 11108.6 32.40

9 11074.0 32.50

6 11039.4 32.61

3 11004.8 32.71

0 10970.2 32.82

S.No. Feed water parameters Heat Rate (kJ/kWh)

Cycle efficiency (%)

Temperature(0C)

Pressure(kg/cm2)

1 200 160 11145.88 32.23

2 210 164 11110.63 32.40

3 220 168 11075.45 32.50

4 230 172 11040.32 32.61

5 240 176 11005.23 32.71

6 250 180 10970.20 32.81

UNIT – 2 AT DESIGN VALUES

HEAT RATE= [Qms (Hhpti-Hecoi) +Qrh (Hipti-Hhpto) +Qrhs (Hipti - Hecoi)] / LOAD

= [636.74(3380-1061.6) +571.62(3520-3050) +0(3520- 1061.6) / 210 = (1476218+268661.4+0) / 215.5 = 8308.9 kJ / Kwh

UNIT – 2 AT FULL LOAD

HEAT RATE= [Qms (Hhpti-Hecoi) +Qrh (Hipti-Hhpto) +Qrhs (Hipti - Hecoi)] / LOAD

= [672.2(3360-1013.8) +622.14(3500-3050) +0(3500- 1013.8) / 215.5 = 8397.5 kJ / Kwh

UNIT 2 AT PART LOADHEAT RATE = [Qms (Hhpti-Hecoi) +Qrh (Hipti-Hhpto) +Qrhs (Hipti - Hecoi)] / LOAD

= [562.1(3365-1013.8) +503.6(3500-3060) +0(3500-1013.8) / 180= 8571.25 kJ / Kwh

HEAT RATE ANALYSIS

S.NO Parameter Units Design

data

Operating data

actual After Performance optimization

1 Load MW 210 210 210

2 Condenser vacuum mm of Hg 684 624 686

3 C.W inlet temperature 0C 33 34 32

4 C.W outlet temperature 0C 41.17 44 40

5 C.W temperature rise 0C 8.17 10 08

6 C.W inlet pressure Kg/cm2 2.0 2.2 2.0

7 C.W outlet pressure Kg/cm2 1.7 1.7 1.7

8 C.W flow TPH 28900 28800 28850

9 Steam flow into the condenser

TPH 600 600 600

10 Velocity of water m/sec 1.89 1.85 1.86

Condenser vacuum improvement practical data

For the energy optimization the Reheat inlet pressure and temperatures should be

40 bar and 3250C At this parameters cycle efficiency is 49.03% At this parameters the heat rate value is 7342.4 kJ/kWh

For the energy optimization the Condenser vacuum pressure should be -0.95 kg/cm2

At this parameter cycle efficiency is 48.94% At this parameter the heat rate value is 7355.94 kJ/kWh

For the energy optimization the the Reheat spray value should be ‘0’ TPH At this parameter cycle efficiency is 32.82% At this parameter the heat rate value is 10970.2kJ/kWh

For the energy optimization the Feed water parameters at economizer inlet should be

180 kg/cm2 and 2500C At this parameter cycle efficiency is 32.81% At this parameter the heat rate value is 10970.2kJ/kWh

RESULTS AND DISCUSSION

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