Experiences with the improvement of minimum …...Experiences with the improvement of minimum load in coal fired power stations Manfred Schesack Outline 2017-12-01 Improvement of flexibility

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


STEAG


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.


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)


▪ 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


Outline


STEAG


1

2

3 Frequency control

4 Roadmap

STEAG‘s fleet


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)


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)


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)


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


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


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


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


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


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



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









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


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


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


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


Outline


STEAG


1

2

3 Frequency control

4 Roadmap

Frequency control


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


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


Example: 780 MW unit


Outline


STEAG


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


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Thank you very much for your attention!

For further information please visit us at www.steag.com

Documents

Experiences with the improvement of minimum …...Experiences with the improvement of minimum load in coal fired power stations Manfred Schesack Outline 2017-12-01 Improvement of flexibility