advanced power plants coal fired steam power plant
TRANSCRIPT
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