“A CASE STUDY OF MTPS, DVC”

Presented by :1. Dr. Jagannath Munda, Sr. Divisional Engineer (Mechanical)2. Mr. Arjunlal Mandal, Sr. Divisional Engineer (Mechanical)3. Ms. Kalyani Pyne, Executive Engineer (Electrical)4. Mr. Sumit Anand, Executive Engineer (Mechanical)

Damodar Valley Corporation

OPTIMUM CONDENSER PRESSURE FOR BETTER TURBINE OPERATION AND

PERFORMANCE WITH REDUCTION IN GHG

Maithon DAM

Tilaiya DAM

POWER GENERATING INSTALLATIONSTHERMAL POWER STATIONS & HYDEL POWER STATIONS

Panchet DAM

Bokaro’B’ TPS

Mejia TPS

Durgapur TPS

Chandrapura TPS

Bokaro TPS-A Koderma TPS

MPL, JV

Durgapur STPS

Raghunathpur TPS Ph-I & II

BPSCL, JV

KONAR DAM

Type of Power Station Capacity (MW)Thermal Power (DVC) (Commissioned Units)

Mejia TPS 2340 (4X210+2X250+2x500)Bokaro TPS ‘B’ 630 (3X210)Chandrapura TPS 890 (3X130+2x250)Durgapur TPS 350 (1X140+1X210)DSTPS 1000 (2x 500)KTPS 1000 (2x 500)Total Thermal 6210

Hydel Power (DVC)

Maithon Hydel Station 63.2 (2X20 + 1x23.2)Panchet Hydel Station 80 (2X40)Tilaiya Hydel Station 4 (2X2)Total Hydel 147.2

Total DVC Generation Capacity 6357.2Thermal(JV) BPSCL 338

MPL 1050 (2x 525)

Total DVC Generation Capacity including JV 7745.2

GENERATION CAPACITY:COMMISSIONED

Name of Thermal Power Station

Station Dt. Of commission

UnitCapacity (MW)

Mejia Thermal Power Station

Durlavpur, Bankura, West Bengal

2340 = (4X210+2X250+2x500)MW

Unit # 1 Dec.1997 210

Unit # 2 Mar.1999 210

Unit # 3 Sep.1999 210

Unit # 4 Feb.2005 210

Unit # 5 Feb.2008 250

Unit # 6 Sep.2008 250

Unit # 7 Aug.2011 500

Unit # 8 Aug.2012 500

GENERATION CAPACITY:COMMISSIONED

INTRODUCTION The electricity generated from TPP constitutes 68.14 % of total generation. India’s

present total installed capacity is 308834.28MW out of which 214003.90MW isthermal and majority of which 187802.88MW is coal fired.

India ranks fourth among the top emitter of greenhouse gases and contributes6.96% of the total emission.

By adopting best practices in operation through energy and exergy analysisspecific coal consumption can be reduced.

This study is being carried out by analysing the data of 500MW Mejia ThermalPower Plant, DVC at different condenser pressures .

Modified Rankine Cycle is used in thermal powerplant.

Inefficient cyclic operation produce moregreenhouse gases

CV

SCHEMATIC DIAGRAM OF 500MW TPP

TheORy

The control volumes on which analyses have been done are clearly marked by dotted linein schematic diagram. In the present analysis, the turbine heat rate and total exergy atturbine inlet in a control volume is evaluated as below.

STEAM I/L TO TURBINE (HP+IP)

CONTROL VOLUME (TURBINE + GENERATOR)

GEN OUT PUT (MW)

TURBINE HEAT RATE CALCULATION

Turbine Heat rate (THR) is commonly used to measure the turbine efficiency in a

steam power plant. It is defined as "the energy input to turbine (in Kcal) divided by the

electricity power generated, (in kW). Heat rate is simply the inverse of efficiency.

Turbine Heat Rate (THR)

= (Heat Added to Feed Water + Heat added to SH Attemperation + Heat Added

CRH + Heat added to RH Attemperation) /(Unit load)

mfw (h1 – h11) + msh_spray (h1-h11)+m2 (h3 - h2 )+ mrh_spray(h3-h18)

= -------------------------------------------------------------------- …Eqn1

Unit Load

There are two provision of SH attemperation:

a) HPH out let,

b) Kicker stage of boiler feed pump.

Calculation of Reheat Steam FlowCRH flow is calculated as follow:

CRH Flow (m2) = Steam Flow (m1) – Extraction Steam Flow (m19) to HPH - HPT Leak Off Steam flow …..Eqn2

a) Leak off steam flow derived from design leak off flow as per load from HBD.b) Extraction flow to all HP Heaters having extraction from HP Turbine exhaust to be considered for computing CRH Flow.Calculation of Extraction Steam Flow in HPH#6A/6B

mfw (h11 – h20) + m21h21(m2) = ------------------------------ …..Eqn3

(h19 – h21)

Exergy calculation at turbine inletThe specific thermo-mechanical exergy (neglecting kinetic and potential energy) is evaluated from the following equation:

ej=(hj─ h0) – T0(sj – s0) ..…Eqn4

where, ej: specific exergy, hj: Enthalpy at jth state, h0: enthalpy at zero state or atmospheric condition, T0: temperature enthalpy at zero state or atmospheric condition, sj: Specific entropy at jth state, s0:Entropy at zero state or atmospheric condition.The total rate of exergy in a stream is obtained from its specific value as

Total exergy, Ej = mjej …Eqn5

Where, mj: mass flow rate.

Turbine heat rate decreases with increase in load. At lower load throttling lossincreases due to lesser steam flow into the turbine. Turbine inlet steam pressuredecreases at lower load, causes entropy generation or exergy destruction.

VARIATION OF TURBINE HEAT RATE WITH LOAD

Four different sets of data at the maximum unit load in different condenser pressure have been collected and tabulated in table 1. Parameters Value Value Value ValueCondenser pr(ksc) 0.0640 0.0717 0.0810 0.1030Load(MW) 502.60 500.35 500.51 502.00Main Steam Pr -R (ksc) 174.9 174.6 174.16 175.8Main Steam Pr -L (ksc) 174.9 174.6 174.16 175.8Main Steam Temp -R (oC) 540.5 538.8 537.16 533.48Main Steam Temp -L (oC) 540.5 538.8 537.16 533.48Main Steam Flow (TPH) 1608 1604.3 1604.63 1632Feedwater Flow(TPH) 1611 1602.2 1595.37 1653FW Temp. HPH #5A inlet(oC) 168 168.1 168.7 168.09FW Temp. HPH #5B inlet(oC) 168 168 168.56 168.5FW Temp. HPH #5A Outlet(oC) 208.5 208.5 208.97 209

FW Temp. HPH #5B Outlet(oC) 209 209.1 209.63 209.6FW Temp. HPH #6A Outlet(oC) 256 257.2 257.4 257FW Temp.HPH #6B Outlet(oC) 259.2 259.5 259.77 259

FW Pr. HPH #5 Inlet(ksc) 203 201.5 201.65 204FW Pr.HPH #6 Inlet(ksc) 202 199.5 200 204

HPH #5A drain Temp(oC) 176.2 176.3 176.58 176.4HPH #5B drain Temp(oC) 176.2 176.7 177.13 177HPH #6A drain Temp(oC) 215.5 216.1 216.26 217HPH #6B drain Temp(oC) 216 216.4 216.52 217HPH #5A Ext Steam Temp(oC) 404.6 403.7 410.01 401.4HPH #5B Ext Steam Temp(oC) 404.6 403.6 409.97 401HPH #6A Ext Steam Temp(oC) 351.8 350.2 353.5 346HPH #6B Ext Steam Temp(oC) 351 349.5 352.73 345.6HPH #5A Ext Steam Pr(ksc) 17.6 17.9 17.84 17.6HPH #5B Ext Steam Pr(ksc) 17.8 18.1 18.08 17.8HPH #6A Ext Steam Pr(ksc) 45.6 45.8 45.53 46.2HPH #6B Ext Steam Pr(ksc) 45.5 45.9 45.48 46.15CRH Steam pr.(R)(ksc) 46.18 46.9 46.22 47CRH Steam pr.(L)(ksc) 46.18 46.9 46.22 47CRH Steam Temp.(R) (oC) 359.2 357.7 361.29 353.7

CRH Steam Temp.(L) (oC) 359.2 357.7 361.29 353.7HRH Steam pr.(R)(ksc) 45.03 45.3 44.99 45.76HRH Steam pr.(L)(ksc) 45.03 45.3 44.99 45.76HRH Steam Temp.(R)(oC) 529.3 526.3 534.16 523.4HRH Steam Temp.(L)(oC) 528.6 526.8 534.13 523.86SH spray water flow (TPH) 9.17 27.8 38 17SH spray water Temp(oC) 240 250.5 251.8 251SH spray water pr.(ksc) 198.7 198.3 197.37 200IPT Exhaust Temp(oC) 283 5 284 292 281

EFFECT OF CONDENSER PRESSURE ON TURBINE HEAT RATE AT FULL LOAD

Sl. No. Unit load: 500MWCondenser

Pressure (Kg/cm2)

Turbine Heat Rate (Kcal/kwh)

1. 0.0640 20282. 0.0717 20203. 0.0801 20154. 0.1030 2042

Turbine heat rate decreases with decrease in condenser pressure as cycle efficiency increases. Itbecame minimum at 0.078 kg/cm2. With further decrease in condenser pressure, exit turbine lossincreases, as steam from last stage of LP turbine is directly damped into the condenser withoutdoing any useful work.

Table:2

Figure-4

EFFECT OF CONDENSER PRESSURE ON TOTAL EXERGY AT TURBINE INLET TO GENERATE 500MW

Sl. No.

Unit load: 500MWUnit load

Condenser Pressure

(Kg/cm2)

Total Exergy at Turbine

Inlet (Kcal)1 500MW 0.0640 9453750.42 500MW 0.0717 9417284.93 500MW 0.0801 9401233.74 500MW 0.1030 9534858.2

At design condenser pressure, i.e., at 0.1033 kg/cm2 total exergy requirement at turbine inlet ismaximum and decreases with reduction in condenser pressure due to improvement in workingcycle efficiency. It became minimum at around 0.078 kg/cm2 and again increases with furtherreduction in condenser pressure as exit steam loss increases.

Fig.5

Table:3

EFFECT OF CONDENSER PRESSURE ON THR WITH AT 380MW UNIT LOAD. SL. NO. Unit load: 380MW

Condenser Pressure (kg/cm2)

Turbine Heat Rate

(Kcal/Kwh)1 0.0465 20502 0.0563 20453 0.0669 20564 0.0853 2082

THR decreases with increasein condenser pressure. THRbecame minimum at around0.055 kg/cm2 cond. Pr. THRincreases with furtherreduction in condenserpressure as exit steam velocityincreases and steam isdamped into the condenserwithout doing any useful work.

Fig.:6

Tab.:4

2040204520502055206020652070207520802085

0.04 0.06 0.08 0.1Condenser pressure (kg/cm2 )

Turb

ine

hea

trat

e (K

cal/K

wh)

INFLUENCE OF CONDENSER PRESSURE ON TURBINE VIBRATION

Influence of condenser pressure on turbine vibration (at unit load: 380MW)

Influence of condenser pressure on turbine vibration (at unit load: 500MW)

GHG EMISSION REDUCTIONTHR improvement by optimising condenser pressure is directly related to reduction in greenhouse gas emission.

At 0.103 kg/cm2 cond. pressure THR was obtained 2042 Kcal/Kwh.

At 0.0801 kg/cm2 THR obtained 2015 kcal /kwh.

Deviation in HR=(2042-2015)= 27Kcal/kwh

Total Energy saved in a year if unit is considered to run 365*24 days in full load with 34% plant efficiency,=500*365*24*1000*27/0.34= 347823529411.76 Kcal

Average GCV of coal=3600 Kcal/Kg.So total coal saving in a year =96617647.06 kg =96617.64706 ton, considering 42.8 % of carbon by weight in 1 kg of coal.

CO2 emitted by burning 1kg of coal=(mol wt. of CO2/mol wt of Carbon)*percentage of carbon by wt in per kg of coal = (44/12)*0.428=1.498kgSo total CO2 emission reduction = 144733.24 ton/year.

CONCLUSION The country is committed to the development of clean coal technology

applications to mitigate climate impacts in a way that is consistent withsustainable development.

Power generators have wide latitude in designing their strategies to reduceemissions. Viable means for substantially reducing specific CO2 emissions fromcoal-fired power generations need to be developed and widely adopted byimplementing best practices in operation.

Through our study, by adopting best practices in operation at MTPS throughenergy and exergy analysis at different condenser pressures, specific coalconsumption got reduced, and hence total CO2 emission reduced to144733.24 ton/year.

This study also analyze the effect of condenser pressure on turbine health interms of TG vibration and optimum value has been found out for lower TGvibration.

Exergy and energy analysis to be carried out at site to re-optimise the variousinfluential parameters for better efficiency and finally to mitigate globalclimate change through reduction in GHG emission.