Experiences with the improvement of minimum load in coal fired power stations. Manfred Schesack

Transcription

1 Experiences with the improvement of minimum load in coal fired power stations Manfred Schesack

2 Outline 1 2 STEAG Minimum load reduction 3 Frequency control 4 Roadmap Improvement of flexibility in coal fired power stations 2

3 Outline 1 2 STEAG Minimum load reduction 3 Frequency control 4 Roadmap Improvement of flexibility in coal fired power stations 3

4 Facts and figures We are specialists in all matters relating to the generation and marketing of electricity and heat open to any technology. 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 Improvement of flexibility in coal fired power stations 4

5 Our mission 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. 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. 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 Improvement of flexibility in coal fired power stations 5

6 Worldwide in demand Termopaipa IV Coal Power Plant Colombia (165 MW el ) Crucea North Wind Farm Romania (108 MW el ) Mindanao Coal Power Plant Philippines (232 MW el ) Own power plants / investment projects Engineering / projects STEAG headquarters Representative offices / subsidiaries Operation and maintenance contracts Disposal and marketing of power plant by-products Arenales Concentrated Solar Power Plant Spain (50 MW el ) Improvement of flexibility in coal fired power stations Vishakhapatnam Coal Power Plant India (1,040 MW el ) 5% shareholding and O&M Iskenderun Power Plant Turkey (1,320 MW el ) 6

7 Operation & Maintenance Our focus We focus on our strengths: planning, developing, building and operating power plants, and marketing the energy and by-products they produce. Project development Project implementation Hard coal Natural gas Mine gas Renewable resources Scrap wood Engineering services Energy contracting Recycling and marketing of power plant by-products Improvement of flexibility in coal fired power stations Construction of new power plants Hard coal fired power plants Power plants based on renewable sources of energy Refinery power plants Industrial power plants Natural gas fired power plants Electricity District heating Coal Gas Emissions certificates 7

8 Outline 1 2 STEAG Minimum load reduction 3 Frequency control 4 Roadmap Improvement of flexibility in coal fired power stations 8

9 STEAG s fleet PP 10 PP 9 PP 8 PP 7 PP 6 PP 5 PP 4 PP 3 PP 2 PP Load [in % of net capacity, based on unit design capacity] Improvement of flexibility in coal fired power stations 9

10 E-Leistung [MW], Frischdampf [10 t/h], CO-Gehalt [mg/nm 3 ] O 2 -Gehalt [Vol.-%] Example: 150 MW unit (2-mills operation) 180 E-Leistung BTS E-Leistung DTS E-Leistung gesamt Frischdampf CO-Gehalt O2-Gehalt MW 58 MW MW :00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00 Zeit [hh:mm] Improvement of flexibility in coal fired power stations 10

11 E-Leistung [MW], Frischdampf [10 t/h], CO-Gehalt [mg/nm 3 ] O 2 -Gehalt [Vol.-%] Example: 150 MW unit (1-mill operation) 180 E-Leistung BTS E-Leistung DTS E-Leistung gesamt Frischdampf CO-Gehalt O2-Gehalt MW 12 MW MW 0 18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00 Zeit [hh:mm] CO emission was main limitation Improvement of flexibility in coal fired power stations 11

12 Net power (MW) Example: 750 MW unit (1-mill operation) Test runs Time (min) Variation of firing rate 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) Improvement of flexibility in coal fired power stations 12

13 Example: 400 MW CHP unit Δ = 50 MW Δ = 10% Δ = 10% Δ = 50 MW P el m fuel m Evap SP P el P el 20% No process modifications required Improvement of flexibility in coal fired power stations 13

14 Kesselwirkungsgrad [%] elektrischer Wirkungsgrad [%] Efficiency 95 Kesselwirkungsgrad elektrischer Wirkungsgrad elektrische Leistung [MW] Improvement of flexibility in coal fired power stations 14

15 Limitations Overview Flue gas temperature Economizer Catalyst Further FG Cleaning Emissions Unit control Frequency control Boiler protection system (ESS) Turbine ventilation and erosion Reheaters Steam temperatures HP MP + NP G Benson vessle Superheaters Extraction pressures (in particular CHP) Condenser Evaporator Mills Flame stability Once-through operation / circulation mode HP-Preheaters Feed water pump Feed water tank LP-Preheaters Improvement of flexibility in coal fired power stations 15

16 Limitations Overview Flue gas temperature Economizer Catalyst Further FG Cleaning Emissions Unit control Frequency control Boiler protection system (ESS) Turbine ventilation and erosion Reheaters Steam temperatures HP MP + NP G Benson vessle Superheaters Extraction pressures (in particular CHP) Condenser Evaporator Mills Flame stability Once-through operation / circulation mode HP-Preheaters Feed water pump Feed water tank LP-Preheaters Improvement of flexibility in coal fired power stations 16

17 IR Flame detection [%] Limitations Flame stability and flame detection 1-mill operation Burner 21 Burner IR-Signal BRN21 [%] IR-Signal BRN22 [%] IR-Signal BRN23 [%] IR-Signal BRN24 [%] 0 22:00 0:00 2:00 4:00 6: Time [hh:mm] Burner Improvement of flexibility in coal fired power stations 17

18 Limitations Flame stability and flame detection Intensidad llama quemador 11 Intensidad llama quemador 12 Intensidad llama quemador 13 Intensidad llama quemador 14 Intensidad llama quemador 21 Intensidad llama quemador 22 Intensidad llama quemador 23 Good prerequisites but inappropriate (zonal) flame detection Improvement of flexibility in coal fired power stations 18

19 Limitations Flame stability and flame detection 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) Improvement of flexibility in coal fired power stations 19

20 Limitations Steam temperatures Superheater Temp(C) Set Point Superheater Temp(C) Reheater Temp(C) Set Point Reheater Temp(C) Position of spray Water Control Valve SH-2 (%) Position of spray Water Control Valve SH-1 (%) Position of spray Water Control Valve RH-A (%) Position of spray Water Control Valve RH-B (%) Time [min] Time [min] Frequent problem: Inappropriate spray water control Improvement of flexibility in coal fired power stations 20

21 Limitations Steam temperatures Intentional reduction of temperature set-points Main steam temperatures cannot be kept T MS depends on mill activated (upper levels preferred) Inadmissible thermal stress to be avoided SP T MS 500 C 480 C 540 C 520 C P min,new P min,old SP P el Improvement of flexibility in coal fired power stations 21

22 Limitations Circulation mode Superheater Start-up separator Reheater Steam Turbine Evaporator Atmosph. flash tank Boiler water flash tank Recirculation pump HP- Heaters Feedwatertank Feedwaterpump LP- Heaters Condenser Condensate storage water tank Efficient way: Recirculation pump Improvement of flexibility in coal fired power stations 22

23 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 Improvement of flexibility in coal fired power stations 23

24 Outline 1 2 STEAG Minimum load reduction 3 Frequency control 4 Roadmap Improvement of flexibility in coal fired power stations 24

25 Frequency control 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 HPCV-1 POS ( LHS ) HPCV-2 POS ( RHS ) 0.00 Time [min] Measures: Sliding pressure operation / inherent storage capabilities Improvement of flexibility in coal fired power stations 25

26 Inherent storages Economizer T P :transient loadchange potential T : delay time delay capacity :storage capacity (time) Reheater HP Bypass HP MP + LP G Superheaters HP Steam duct Mills T T P high delay capacity 5s 40s Condenser Evaporator Depends on mill type Condensate pump HP Preheaters P 5% T T delay capacity 10s 5min Feedwater pump Feedwater tank P 5% T T delay capacity 30s 5min LP Preheaters P 2.5% T T delay capacity 30s 5min Condensate tank Improvement of flexibility in coal fired power stations 26

27 Requirements in Germany Improvement of flexibility in coal fired power stations 27

28 Example: 780 MW unit Improvement of flexibility in coal fired power stations 28

29 Outline 1 2 STEAG Minimum load reduction 3 Frequency control 4 Roadmap Improvement of flexibility in coal fired power stations 29

30 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 Improvement of flexibility in coal fired power stations 30

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