efficient operation at part load the need of hour · comparison of life consumption based on cold,...

Efficient operation at part load – The need of hourSandeep Chittora, Power Generation Services, Siemens Limited

Restricted © Siemens AG 2018

Restricted © Siemens AG 201801.11.2019 Sandeep Chittora Services and Digital

Plant OptimizationFlexibility is the new efficiency

A Balance of Plant (BoP) Optimization makes a significant contribution to economic values

An improved efficiency leads to lower CO2

emissions!

Improved I&C and combustion for stable

operation at lower loads

Reduced startup-times and earlier power

productions by improved I&C and hardware

measures

Higher ramp rates up to 15MW/min

Reduced Electricity Production Cost and Increased Competitiveness *

3x higher

@ 75% load, including aging recovery effects by new hardware in HP and LP turbine at constant

coal consumption

Down to 30% 16 MW more Up to 5% lower >60min earlier

Improved Ramp Rates

Increasing Efficiency and

Performance (MW)

Reduced Costs for Starting and earlier Power Production

Reducing CO2Emissions

Reducing technical minimum plant

load

* Values are based on a 500 MW reference steam power plant


Plant OptimizationTotal Plant Evaluation is key for successful operation in deep part load

Balance of Plant (BoP) Assessment for Boiler, Condenser, Steam Turbine & Auxiliaries

BoilerFuel SupplyInstrumentation & ControlsCombustion Concept & OperationThermal DesignFans and Pumps

Feed Water Heaters

Boiler Feed Pump (incl. Motor orturbine drive)

Turbine

Blading

Operation

Steam Seal

Drains

CondenserTerminal Temperature Difference (TTD)

Condensate Pump

Cooling Water System

Steam Piping System


40% Technical Minimum is Possible – NTPC Dadri

0

50

100

150

200

250

300

350

400

450

500

550

3:00

3:30

4:00

4:30

5:00

5:30

6:00

6:30

7:00

7:30

8:00

8:30

9:00

9:30

10:0

010

:30

11:0

011

:30

12:0

012

:30

13:0

013

:30

14:0

014

:30

15:0

015

:30

16:0

016

:30

17:0

017

:30

18:0

018

:30

19:0

019

:30

UNIT LOAD

GCV (kcal/kg) VM% Ash %

3000 22% 35%


Influence on Ramps on Temperature Transient

510

520

530

540

550

560

570

7:00

7:30

8:00

8:30

9:00

9:30

10:00

10:30

11:00

11:30

12:00

12:30

13:00

13:30

14:00

14:30

15:00

MS TEMP

500

510

520

530

540

550

560

570

7:00

7:30

8:00

8:30

9:00

9:30

10:00

10:30

11:00

11:30

12:00

12:30

13:00

13:30

14:00

14:30

15:00

HRH TEMP

DT = 1 K/min

DT = 1.5 K/min


Lower technical minimum is better than two shift operation

Comparison of life consumption based on cold, warm and hot start

Start Life Consumption IEC 45 permissiveCold Start 23 – 75 hours 100Warm Start 15 -17 hours 700Hot Start 10 -12 hours 3000Load Change 3 hours -

140%155%

170%

100%120%140%160%180%

210 MW 500 MW 660 MW

Incremental O&M costs

Base Load Technical Minimum 2 shift


Transient Operation (Ramp Up / Ramp Down)increased temperature gradient results increased life consumption

Crack depth: 50% wall thickness

Main steam valve


Time for crack initiation

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

100 1000 10000 100000

Tem

pera

ture

gra

dien

ts [K

]

Number of (thermal) cycles to crack initiation [cycles]

Pre-Damagee.g. due to starts Load changes with

DT=100 K

Load changes withDT=50 K

N (50K) >> N(100K)

Curve based on Manson-Coffin-Model(at 550°C)

Initiation of cracks

50

100

150

200

250

300

350

400

450

500 Operational Strategy

• Part load may lead to steam temperature changes, especially hot reheat temperature

• Thermal stresses due to temperature changes across thick wall components are detrimental to life consumption

• Careful analysis and suitable modification would lead to improved fatigue behavior and reduce maintenance requirements


Power on DemandReduction of Wall Thickness to Improve Start Up & Cycling Capabilities

Example: Reduced Casing thickness & reduced thermal piston loading by HP bypass cooling

Significant improvement in LCF

coolingsteammixed steam main steam

0

20

40

60

80

100

Load

in %

Time

Design with internal bypass

cooling

Design without internal bypass

cooling

Interstage admission


Performance at lower part load factor

210 MW modernization leads to 25 paisa savings in cost of generation with payback period of ~3 years

Zone of interest

660 MW supercritical unit

500 MW subcritical unit

500 MW modernized unit


Part Load Efficiency: Turbine hardware upgradeHP Turbine

* Relative to aged condition (both in fixed pressure operation)

Load 50% 75% Full load

Savings (coal) * ≈ 1.3% ≈ 1.3% ≈ 1.5%


Part Load Efficiency: Turbine hardware upgradeHP + LP Turbine


Savings (coal) * ≈ 2.7% ≈ 2.7% ≈ 2.9%



Part Load Efficiency: Turbine hardware upgradeHP Turbine with control stage


Savings (coal) * ≈ 3.5% ≈ 2.9% ≈ 1.0%



Part Load Efficiency: Turbine hardware upgrade with control stageHP + LP Turbine with control stage


Savings (coal) * ≈ 4.7% ≈ 4.1% ≈ 2.2%

Savings (coal) ** ≈ 2.7% ≈ 3.2% ≈ 1.3%

* Relative to aged condition (both in fixed pressure operation)** Relative to new and clean conditions


Part Load Efficiency: Turbine hardware upgrade with control stageHP + LP Turbine with control stage

* Aging applied to HP/IP&LP-section** Aging applied to IP/LP-section*** Aging applied to IP-section

8300

8500

8700

8900

9100

9300

9500

40 60 80 100

Pla

nt

He

at R

ate

[kJ

/kW

h]

Plant Load [%]

Base - T2 - Fixed Pressure *

Base - T2 - Sliding Pressure *

HP-CS/3DS - Fixed pressure **

HP-CS/3DS_LP 3DS - Fixed Pr. ***

0

5

10

15

20

25

40 60 80 100

DP

to

Bas

e (

T2-F

ixe

d p

ress

ure

) ["g

ree

n"

MW

]

Plant Load [%]


Return on investment with hardware upgradePotential Benefits

0 1 2 3 4 5 6 7 8 9years

HP-CS & LP

HP-CS only

typical I&C-measure

Initial IncrementalInvestment *

Investment Break Even Point *

* This example is based on a modernization of a 500MW-coal-fired power plant in India (KWU-design)

For the corresponding 500MW steam power plant the modernization of the Turbine

Hardware (new HP module with control stage / new LP rotor and inner casing) would

result in significant savings for coal.

Taking this into account, the return of invest period accounts to 4 - 5 years. Additional

benefits like the avoided CO2 and the enhanced ability for fast load changes are not

even considered here.


Reduced Startup-times: Heating blanketsST Warm Standby Operation to prepare for fast start-up

Technology

• Electrical heating system for ST in turning gear

• Maintains rotor shaft temperature at warm startup conditions

Benefit

• Significant reduction of startup time

• > 60 min. earlier power production

• Reduction of EOH consumption per start

• Less energy is bypassed to condenser

• Reduced costs per start up

Electric heating coils to keep HP/ IP Turbine casing and shaft in warm start conditions


Key Takeaway

• Lower Technical Minimum is better operation than two shift

operation

• Subcritical fleet is more suitable for flexible operation with respect

to loss in performance

• Lower Technical Minimum with part load performance

improvement is possible, unit specific changes needs to be applied

• Means of improving part load efficiency by upto 4% are available

• Need based R&M is the approach for part load performance

improvement


Contact information

Sandeep ChittoraHead – Portfolio ConsultingSiemens Limited, IndiaPhone: +91 124 2842650Mobile: +91 9971170337

E-mail: [email protected]

mailto:[email protected]


Power on DemandMonitoring of flexibility consequences: steam turbine EOH counter 4.0

Solution• Evaluation of operational history• Implementation of a state of the art EOH counter considering

load changes

Benefits• More accurate EOH counting• Improved outage planning• Enhanced operational flexibility

Task• Part load may lead to steam temperature changes,

especially hot reheat temperature• Thermal stresses during operation are not considered in

standard counting of equivalent operating hours (EOH counter)

• Maintenance needs may not be recognized

I. Generation

II. Generation

III. Generation

IV. Generation

Introduction of three start-up modes with fixed EOH consumption

Maintenance interval defined by operating hours and number of starts

EOH consumption is a function of actual thermal stress

EOH counting also considering load changes


Maintenance FlexibilityFatigue Monitoring System

Don’t Guess when you can actually measure it

How much fatigue is it?

Old minimum sustainable load

NEW, minimum sustainable load

Load

Time


Maintenance FlexibilityFatigue Monitoring System

Online calculation of Boiler Fatigue Components is possible

Both Creep Fatigue and Low cycle fatigue calculated

Depending upon the actual operating mode, residual life of critical components is determined

efficient operation at part load the need of hour · comparison of life consumption based on cold,...

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