advanced power plants coal fired steam power plant

Technische Universität München

Advanced Power Plants

Coal Fired Steam Power Plant

Prof. Dr.-Ing. H. Spliethoff

Lehrstuhl für Energiesysteme

Technische Universität München

Content

1. Situation today

2. Efficiency: achievements and outlook

3. Future – discussion of the energy concept

4. Flexibility of power plants

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1. Today

Requirements: today (Germany)

Today (2010): Share of renewables 16 %, Wind 26 GW, PV 17 GW

Source: Spliethoff: et. al, CIT 2011

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1. Today

Power Plant Capacity and Production (2010)

Economic and environmental motivation for an efficiency increase

13%

31%

14%

3%

3%

3%

33%

Capacity [%] Total: 168 GW

nuclear

coal

domestic gas

oil

pump storage

others*

renewables

23%

42%

14%

1%

1%

3% 16%

Production [%] Total: 621 TWh :

full load hours

(calculated)

Total:

1825 h/a (21%)

Coal

5000 h/a (58 %)

Source: Spliethoff: et. al, CIT 2011

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2. Efficiency

Possibilities to increase efficiency

• Increasing the average temperature of heat

addition

• Decreasing the average temperature of heat

removal

• Reducing losses • Design

• Operation

• Part load

• Start-up, shut-down

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2. Efficiency

Temperature of heat addition

• Live steam pressure and

temperature: 200 bar/540°C/540 °C

300 bar/ 600°C/620 °C

Δη =2,5 %

• Double RH

• Feed water preheating:

+30-40 k 0,7 %

0%

2%

4%

6%

8%

10%

12%

550 575 600 625 650 675 700

Live steam temperature =Reheat temperature [°C]

Re

lati

ve

ch

an

ge

in

eff

icie

nc

y [

%]

190 bar

250 bar300 bar350 bar

Source: Spliethoff: Power Generation from Solid Fuels, Springer 2010

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2. Efficiency

Limitations by materials

MS-Pressure

MS-Temperature

RH-Temperature

Membrane wall Pipes Headers

Source: Alstom

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2. Efficiency

Temp. heat extraction – Wet Cooling

2-8

• Reduction of condenser temperature by 10 K 1,2 %

• lowest possible condensation temperature: wet bulb or wet air temperature

• difference is caused by:

– terminal temperature difference of the condenser

– cooling range (= warm-up margin)

– approach

• Economic optimization

Kondensat-temperatur= 36 °C

Warmwasser-temperatur= 28 °C

Kaltwasser-temperatur= 20 °C

Feuchtluft-temperatur= 6,6 °C

Kondensator-grädigkeit

Kühlzonenbreite

Kühlgrenz-abstand

Trockenluft-temperatur= 8,5 °C

terminal temperature

difference of condenser

Condensate

temperature

= 36 °C

Warm water

temperature

= 34,5 °C

Cold water

temperature

= 20 °C

Wet-bulb

temperature

= 6.6 °C

cooling range

Approach

dry air

temperature

= 8.5 °C

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3. Efficiency

Losses

– Steam generator losses

– Turbine losses

– Pipe losses

– Generator losses

– Auxiliary power demand

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2. Efficiency

Steam Generator Losses

Steam Generator Losses Old Plant (1980) Modern Plant

air ratio 1,3 1,15

exhaust temperature 130 C 110 C

exhaust losses 5,3 % 3,8 %

radiation losses steam generator 0,25 % 0,3 %

losses through unused fuel

flue ash 0,2 % < 0,3 %

coarse ash 0,1 % < 0,2 %

sensible heat

flue ash 0,02 % 0,03 %

coarse ash 0,04 % 0,04 %

total 5,9 % 4,6 %

Source: Spliethoff: Power Generation from Solid Fuels, Springer 2010

Technische Universität München

82

84

86

88

90

92

94

96

1940 1960 1980 2000 2020

Ise

ntr

op

ic t

urb

ine

eff

icie

ncy

[%

]

Year

Werte aus Diagramm

Zusatzwerte

3. Efficiency

Isentropic turbine efficiency

Billotet 1995

Add.values

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2. Efficiency

Brown coal – External Predrying

• External pre-drying leads to

efficiencies comparable to

hard coal, because

– Steam generator losses

are limited (seperated

vapors removal)

– The drying medium is used

at low temperatures

• Efficiency is higher than that of

hard coal, if the condensation

heat of vapors is used

• Improvement by 5 % is

possible

dryer flue

gas

mill coal dust and

carrier gas

superheated steam ~150°C

brown coal

condensation

heat

water

carrier gas

pre-drying at low

temperatures

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2. Efficiency

Reference power plant

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2. Efficiency

Data Hard Coal Steam Power Plants

Circuit Zolling Staudinger Rostock NRW

R&D

Thermie

R&D

Thermie

initial Operation 1985 1992 1994 Projekt Projekt Projekt

net Output [MW] 450 510 510 556 556 556

LS-pressure [bar] 247 250 262 285 350 375

LS-temperature [°C] 536 540 545 600 700 700

RH-temperature [°C] 538 560 562 620 720 720 / 720

RH-pressure [bar] 49 53 54 60 60 120 / 23,5

condensation

pressure [bar] 0,04 0,038/0,052 0,027/0,033 0,045 0,045 0,045

cooling

cooling

tower/river

cooling

tower

cooling

tower/ocean

cooling

tower

cooling

tower

cooling

tower

feed water

temperature [°C] 270 270 270 304 304 335

number of preheaters 8 7 7 8 8 8

efficiency [%] 41,3 42,7 43,8 45,9 48,7 50,1

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2. Efficiency

Average operational efficiency

0 100 200 300 400 500 600

30

32

34

36

38

40

42

44

46

48

50

> 2004

< 1990

1990 - 2004

best point <2004

full load 6000 >2004

best point 1990-2004

full load 5000 1990-2004

best point <1990

full load 5000 <1990

Eff

icie

ncy

Capacity (MWe netto))data from Theis 2005

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3. Future

Goals of the energy concept

-100

0

100

200

300

400

500

600

700

2008 2020 2030 2040 2050

ele

ctr

icity [T

Wh

]

year

import/export conventional renewable energies consumption of electricity

Source: Spliethoff et. al, CIT 2011

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3. Future

Goals Energy Concept

2008 2020 2030 2040 2050

Power generation D 637

TWh

- 8-10

%

-20-27

%

-30 -38 -45-48

Share of coal 43 % 37 % 30 % 20 % 18 %

Full load operation

hours Bit. C.

Brown C.

4500

6800

3300

6300

3400

4000

3700

3000

4800

5200

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4. Flexibility

Requirements: tomorrow (Germany)

Morgen

Tomorrow (2020)

• Installed capacity:

Wind 46 GW

PV 50 GW

• Constant consumption

Tomorrow (xxxx)

• Installed capacity:

Wind 75 GW

50 GW PV

Requirement for low minimum load

Source: Spliethoff: et. al, CIT 2011

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3. Flexibility

Change of power from Renewables 2020

0

10.000

20.000

30.000

40.000

50.000

0 6 12 18 24

ca

pa

city [M

W]

time [h]

-3.000

-1.500

0

1.500

3.000

0 6 12 18 24gra

die

nt [M

W/1

5m

in]

time [h]

Forcast of a winter

day (27.1.2010):

• 46 GW Wind

• 50 GW PV

Requirement for fast load change and start-up

Source: Spliethoff: et. al, CIT 2011

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4. Flexibility

Load change capability

Data from Lambertz, RWE

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25

load [

%]

time [min]

dry lignite technology hard coal CCP nuclear power plant

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4. Flexibility

Load range – Minimum load – Coal

• Load range 30/40 % -100 %

• Firing stability determines minimum load

– Requirement: safe operation in case of a mill failure

• Minimim load

– Pure coal firing: 35-40 % 25 %

– oil/ ng support: 25 %

• Change of once-through to circulation results in limitations

• Brown coal appr.50 %,

• Dried brown coal comparible to hard coal

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4. Flexibiliy

Load Change Capability

• Secondary Control

– Only by fuel mass flow

• Delay of the mill (Storage of the mill)

• Pressure increase of boiler (Gliding pressure)

– Big load changes > 20 % 3-6 % / min

• Limit by turbine inlet temp. 1-2 k/min

– Small load changes < 20 % 1-2 % / min

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4. Flexibility

Start-up, Shut-down

Old Coal

Plant

New

Coal

Plant

CC new

Hot start up (8h) 2 h 1-2 h 0,5-1 h

Warm start-up (48 h) 4-5 h 3 h 1-1,5 h

Cold start-up (72 h) 4 h 2-3 h

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Conclusions for coal fired power plants

- Substantial efficiency increase in the past

- Flexibility requirements

- Minimum load and load change capability comparable to CC

- Start-up slower

- Full load operation hours of coal fired pp will decrease

Economic conflict: efficiency

- Coal: Gasification concepts become more attractive

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Thank You

for Your Attention