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Experiences with the improvement of minimum …...Experiences with the improvement of minimum load...
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Experiences with the improvement of
minimum load in coal fired power stations
Manfred Schesack
Outline
2017-12-01 Improvement of flexibility in coal fired power stations 2
STEAG
Minimum load reduction
1
2
3 Frequency control
4 Roadmap
Outline
2017-12-01 Improvement of flexibility in coal fired power stations 3
STEAG
Minimum load reduction
1
2
3 Frequency control
4 Roadmap
Facts and figures
4
›7 hard coal fired power plants and 1 refinery power plant in Germany
›3 hard coal fired power plants in Colombia, Turkey and the Philippines
›2 waste to energy facilities in Germany
›More than 200 distributed generating facilities on the basis of renewable sources
and for energy supply to industry and heat supply
› Installed gross capacity of about 5,300 MW in Germany and 1,950 MW abroad
›6,104 employees in Germany and abroad
›Total sales of EUR 3.9 billion and EBITDA of EUR 281 million in 2016
› Investment volume of about EUR 223 million in 2016
We are specialists in all matters relating to the generation and marketing
of electricity and heat – open to any technology.
2017-12-01 Improvement of flexibility in coal fired power stations
Our mission
5
Our contribution
We make our contribution to the
successful transition to
sustainable energy supply.
With our strong and highly
efficient power plant portfolio
and our installed capacity of
around 5,300 MW in Germany.
Innovative solutions
We understand the ongoing
changes in the electricity and
heat markets and develop
innovative solutions to
complement our range of
products and services.
Energy mix
In our energy mix in Germany
and abroad, we rely on fossil
and renewable sources of
energy and develop sustainable
generation and supply concepts.
2017-12-01 Improvement of flexibility in coal fired power stations
Worldwide in demand
6
Mindanao Coal
Power Plant
Philippines
(232 MWel)
STEAG headquarters
Own power plants /
investment projects
Representative offices /
subsidiaries
Operation and
maintenance contracts
Engineering / projects
Disposal and marketing
of power plant by-products
Termopaipa IV
Coal Power Plant
Colombia
(165 MWel)
Arenales
Concentrated
Solar Power Plant
Spain
(50 MWel)
Iskenderun
Power Plant
Turkey
(1,320 MWel)
Vishakhapatnam
Coal Power Plant
India (1,040 MWel)5% shareholding and O&M
Crucea North
Wind Farm
Romania
(108 MWel)
2017-12-01 Improvement of flexibility in coal fired power stations
▪ Hard coal fired power plants
▪ Power plants based on
renewable sources of energy
▪ Refinery power plants
▪ Industrial power plants
▪ Natural gas fired power plants
Our focus
7
We focus on our strengths: planning, developing, building and operating
power plants, and marketing the energy and by-products they produce.
▪ Electricity
▪ District heating
▪ Coal
▪ Gas
▪ Emissions certificates
▪ Hard coal
▪ Natural gas
▪ Mine gas
▪ Renewable resources
▪ Scrap wood
▪ Project development
▪ Project implementation
▪ Engineering services
▪ Energy contracting
▪ Recycling and marketing of power plant by-products
Op
era
tio
n &
Ma
inte
na
nc
e
Construction
of new
power plants
2017-12-01 Improvement of flexibility in coal fired power stations
Outline
2017-12-01 Improvement of flexibility in coal fired power stations 8
STEAG
Minimum load reduction
1
2
3 Frequency control
4 Roadmap
STEAG‘s fleet
2017-12-01 Improvement of flexibility in coal fired power stations 9
0 5 10 15 20 25 30 35 40
PP 1
PP 2
PP 3
PP 4
PP 5
PP 6
PP 7
PP 8
PP 9
PP 10
Load [in % of net capacity, based on unit design capacity]
Example: 150 MW unit (2-mills operation)
2017-12-01 Improvement of flexibility in coal fired power stations 10
0
20
40
60
80
100
120
140
160
180
18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00
Zeit [hh:mm]
E-L
eis
tun
g [
MW
], F
risch
dam
pf
[10 t
/h],
CO
-Geh
alt
[m
g/N
m3]
0
2
4
6
8
10
12
14
16
18
O2-G
eh
alt
[V
ol.-%
]
E-Leistung BTS FrischdampfE-Leistung DTS CO-GehaltE-Leistung gesamt O2-Gehalt
65 MW
7 MW
58 MW
Example: 150 MW unit (1-mill operation)
2017-12-01 Improvement of flexibility in coal fired power stations 11
0
20
40
60
80
100
120
140
160
180
18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00
Zeit [hh:mm]
E-L
eis
tun
g [
MW
], F
risch
dam
pf
[10 t
/h],
CO
-Geh
alt
[m
g/N
m3]
0
2
4
6
8
10
12
14
16
18
O2-G
eh
alt
[V
ol.-%
]
E-Leistung BTS E-Leistung DTS E-Leistung gesamt
Frischdampf CO-Gehalt O2-Gehalt
7 MW
12 MW19 MW
CO emission was main limitation
Example: 750 MW unit (1-mill operation)
2017-12-01 Improvement of flexibility in coal fired power stations 12
Variation of firing rate
0.0
50.0
100.0
150.0
200.0
250.0
300.0
Net
po
wer
(MW
)
Time (min)
Test runs
Source: Heinzel, T.; Meiser, A.; Stamatelopoulos, G.-N. and Buck, P.:
Implementation of Single Coal Mill Operation in the Power Plant Bexbach and Heilbronn Unit 7, VGB PowerTech (2012)
Example: 400 MW CHP unit
2017-12-01 Improvement of flexibility in coal fired power stations 13
Δ = 50 MWΔ = 10%Δ = 10%Δ = 50 MW
P el
m fuel
m Evap
SP P el
P el ≈ 20%
No process modifications required
Efficiency
2017-12-01 Improvement of flexibility in coal fired power stations 14
85
86
87
88
89
90
91
92
93
94
95
0 20 40 60 80 100 120 140 160
elektrische Leistung [MW]
Ke
ss
elw
irk
un
gs
gra
d [
%]
0
5
10
15
20
25
30
35
40
45
50
ele
ktr
isc
he
r W
irk
un
gs
gra
d [
%]
Kesselwirkungsgrad elektrischer Wirkungsgrad
Limitations – Overview
2017-12-01 Improvement of flexibility in coal fired power stations 15
G
Condenser
HP MP + NP
Feed water tank
Catalyst
Feed water pump LP-PreheatersHP-Preheaters
Further
FG
Cleaning
Mills
Reheaters
Superheaters
Economizer
Evaporator
Benson
vessle
Flue gas temperature
Steam temperatures
Once-through operation / circulation mode
Turbine ventilation and erosion
Extraction pressures
(in particular CHP)
Flame stability
Unit control
EmissionsFrequency control
Boiler protection system (ESS)
Limitations – Overview
2017-12-01 Improvement of flexibility in coal fired power stations 16
G
Condenser
HP MP + NP
Feed water tank
Catalyst
Feed water pump LP-PreheatersHP-Preheaters
Further
FG
Cleaning
Mills
Reheaters
Superheaters
Economizer
Evaporator
Benson
vessle
Flue gas temperature
Steam temperatures
Once-through operation / circulation mode
Turbine ventilation and erosion
Extraction pressures
(in particular CHP)
Flame stability
Unit control
EmissionsFrequency control
Boiler protection system (ESS)
Limitations – Flame stability and flame detection
2017-12-01 Improvement of flexibility in coal fired power stations 17
08.09.2011
1-mill operation
22:00 0:00 2:00 4:00 6:00
IR-Signal BRN21 [%]
IR-Signal BRN22 [%]
IR-Signal BRN23 [%]
IR-Signal BRN24 [%]
9498
98 100
120
60
0
IR F
lam
e d
ete
cti
on
[%
]
Time [hh:mm]
Burner 21 Burner 22
Burner 23
Limitations – Flame stability and flame detection
2017-12-01 Improvement of flexibility in coal fired power stations 18
Good prerequisites but inappropriate (zonal) flame detection
0
20
40
60
80
100
120
162
12
318
424
530
636
742
848
955
061
167
273
379
485
591
697
7
Intensidad llamaquemador 11
Intensidad llamaquemador 12
Intensidad llamaquemador 13
Intensidad llamaquemador 14
Intensidad llamaquemador 21
Intensidad llamaquemador 22
Intensidad llamaquemador 23
Limitations – Flame stability and flame detection
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1-mill operation improves flame stability / detection
Source: Heinzel, T.; Meiser, A.; Stamatelopoulos, G.-N. and Buck, P.:
Implementation of Single Coal Mill Operation in the Power Plant Bexbach and Heilbronn Unit 7, VGB PowerTech (2012)
Limitations – Steam temperatures
2017-12-01 Improvement of flexibility in coal fired power stations 20
500
520
540
560
580
600
124
47
70
93
11
613
916
218
520
823
125
427
730
032
334
636
939
241
543
846
1
Superheater Temp(C)
Set Point SuperheaterTemp(C)
Reheater Temp(C)
Set Point ReheaterTemp(C)
0
20
40
60
80
100
120
1
26
51
76
10
1
12
6
15
1
17
6
20
1
22
6
25
1
27
6
30
1
32
6
35
1
37
6
40
1
42
6
45
1
47
6
Position of spray WaterControl Valve SH-2 (%)
Position of spray WaterControl Valve SH-1 (%)
Position of spray WaterControl Valve RH-A (%)
Position of spray WaterControl Valve RH-B (%)
Frequent problem: Inappropriate spray water control
510.00
515.00
520.00
525.00
530.00
535.00
540.00
545.00
550.00
150
155
160
165
170
175
180
185
190
0
50
10
0
15
0
20
0
25
0
30
0
35
0
40
0
45
0
Time [min]
510.00
515.00
520.00
525.00
530.00
535.00
540.00
545.00
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
Time [min]
Limitations – Steam temperatures
2017-12-01 Improvement of flexibility in coal fired power stations 21
Intentional reduction of temperature set-points
• Main steam temperatures cannot be kept
• TMS depends on mill activated (upper levels preferred)
• Inadmissible thermal stress to be avoided
SP Pel
480 °C
SP TMS
Pmin,old
500 °C
540 °C
520 °C
Pmin,new
Limitations – Circulation mode
2017-12-01 Improvement of flexibility in coal fired power stations 22
Efficient way: Recirculation pump
Condensate storage
water tank
Boiler water
flash tank
Start-up
separator
Superheater
Evaporator
Reheater
HP-
Heaters
Feed-
water-
tank
Feed-
water-
pump
LP-
HeatersCondenser
Recirculation
pump
Atmosph.
flash tank
Steam Turbine
Further common limitations
• Emissions
• Flue gas system (DeNOx, DeSOx, ESP)
• Dew points
• Controls optimized for nominal load
• Safety system does not allow 1-mill operation
• Inadmissible throttling of turbine valves (IP)
• Turbine
• Stockyard
• Frequency control
2017-12-01 Improvement of flexibility in coal fired power stations 23
Outline
2017-12-01 Improvement of flexibility in coal fired power stations 24
STEAG
Minimum load reduction
1
2
3 Frequency control
4 Roadmap
Frequency control
2017-12-01 Improvement of flexibility in coal fired power stations 25
0.00
10.00
20.00
30.00
40.00
50.00
60.00
0
50
10
0
15
0
20
0
25
0
30
0
35
0
40
0
45
0
Time [min]
HPCV-1 POS (LHS )
HPCV-2 POS (RHS )
Measures: Sliding pressure operation / inherent storage capabilities
• Internationally frequency control is a basic requirement for coal-fired power plants
(up to 5%)
• To be provided over the entire load range (also at minimum load)
• Frequency control solely by means of throttling of turbine control valves
• Turbine control valves already severely throttled at current minimum load
Inherent storages
2017-12-01 Improvement of flexibility in coal fired power stations 26
Depends on
mill type
G
Condensate
tank
LP PreheatersFeedwater tankFeedwater
pumpHP Preheaters
Mills
HP Bypass
Condenser
Reheater
Super-
heaters
Evaporator
Economizer
HP Steam duct
s40
s5
high
capacity
delay
T
T
P
min5
s30
%5
capacity
delay
T
T
P
min5
s30
%5.2
capacity
delay
T
T
P
min5
s10
%5
capacity
delay
T
T
P
(time)capacity storage:
timedelay :
potential change load transient:
capacity
delay
T
T
P
HP MP + LP
Condensate
pump
Requirements in Germany
2017-12-01 Improvement of flexibility in coal fired power stations 27
Example: 780 MW unit
2017-12-01 Improvement of flexibility in coal fired power stations 28
Outline
2017-12-01 Improvement of flexibility in coal fired power stations 29
STEAG
Minimum load reduction
1
2
3 Frequency control
4 Roadmap
Roadmap to a proper 1-mill operation
• Analysis of status quo and definition of suitable measures
• Discussion with OEMs (boiler, turbine) to evaluate potential limitations
• Identification of relevant interlocks in the DCS (in particular safety
system)
• Discussion with related authorities
• Test runs to confirm and identify limitations
• Implementation of measures to
overcome limitations
2017-12-01 Improvement of flexibility in coal fired power stations 30
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