Experiences with the improvement of minimum load in coal fired power stations Manfred Schesack
Outline 1 2 STEAG Minimum load reduction 3 Frequency control 4 Roadmap 2017-12-01 Improvement of flexibility in coal fired power stations 2
Outline 1 2 STEAG Minimum load reduction 3 Frequency control 4 Roadmap 2017-12-01 Improvement of flexibility in coal fired power stations 3
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 2016 2017-12-01 Improvement of flexibility in coal fired power stations 4
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. 2017-12-01 Improvement of flexibility in coal fired power stations 5
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 ) 2017-12-01 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
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 2017-12-01 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
Outline 1 2 STEAG Minimum load reduction 3 Frequency control 4 Roadmap 2017-12-01 Improvement of flexibility in coal fired power stations 8
STEAG s fleet PP 10 PP 9 PP 8 PP 7 PP 6 PP 5 PP 4 PP 3 PP 2 PP 1 0 5 10 15 20 25 30 35 40 Load [in % of net capacity, based on unit design capacity] 2017-12-01 Improvement of flexibility in coal fired power stations 9
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 18 160 140 120 100 16 14 12 10 80 60 40 65 MW 58 MW 8 6 4 20 7 MW 2 0 0 18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00 Zeit [hh:mm] 2017-12-01 Improvement of flexibility in coal fired power stations 10
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 18 160 140 120 100 80 60 16 14 12 10 8 6 40 20 19 MW 12 MW 4 2 0 7 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 2017-12-01 Improvement of flexibility in coal fired power stations 11
Net power (MW) Example: 750 MW unit (1-mill operation) Test runs 300.0 250.0 200.0 150.0 100.0 50.0 0.0 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) 2017-12-01 Improvement of flexibility in coal fired power stations 12
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 2017-12-01 Improvement of flexibility in coal fired power stations 13
Kesselwirkungsgrad [%] elektrischer Wirkungsgrad [%] Efficiency 95 Kesselwirkungsgrad elektrischer Wirkungsgrad 50 94 45 93 40 92 91 90 89 88 87 86 85 35 30 25 20 15 10 5 0 0 20 40 60 80 100 120 140 160 elektrische Leistung [MW] 2017-12-01 Improvement of flexibility in coal fired power stations 14
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 2017-12-01 Improvement of flexibility in coal fired power stations 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 2017-12-01 Improvement of flexibility in coal fired power stations 16
IR Flame detection [%] Limitations Flame stability and flame detection 1-mill operation 120 98 100 98 94 Burner 21 Burner 22 60 IR-Signal BRN21 [%] IR-Signal BRN22 [%] IR-Signal BRN23 [%] IR-Signal BRN24 [%] 0 22:00 0:00 2:00 4:00 6:00 08.09.2011 Time [hh:mm] Burner 23 2017-12-01 Improvement of flexibility in coal fired power stations 17
1 62 123 184 245 306 367 428 489 550 611 672 733 794 855 916 977 Limitations Flame stability and flame detection 120 100 80 60 40 20 0 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 2017-12-01 Improvement of flexibility in coal fired power stations 18
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) 2017-12-01 Improvement of flexibility in coal fired power stations 19
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 1 26 51 76 101 126 151 176 201 226 251 276 301 326 351 376 401 426 451 476 0 50 100 150 200 250 300 350 400 450 1 24 47 70 93 116 139 162 185 208 231 254 277 300 323 346 369 392 415 438 461 Limitations Steam temperatures 190 550.00 600 580 560 540 520 500 Superheater Temp(C) Set Point Superheater Temp(C) Reheater Temp(C) Set Point Reheater Temp(C) 185 180 175 170 165 160 155 150 545.00 540.00 535.00 530.00 525.00 520.00 515.00 510.00 120 100 80 60 40 20 0 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 (%) 545.00 540.00 535.00 530.00 525.00 520.00 515.00 510.00 Time [min] Time [min] Frequent problem: Inappropriate spray water control 2017-12-01 Improvement of flexibility in coal fired power stations 20
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 2017-12-01 Improvement of flexibility in coal fired power stations 21
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 2017-12-01 Improvement of flexibility in coal fired power stations 22
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 1 2 STEAG Minimum load reduction 3 Frequency control 4 Roadmap 2017-12-01 Improvement of flexibility in coal fired power stations 24
0 50 100 150 200 250 300 350 400 450 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 60.00 50.00 40.00 30.00 20.00 10.00 HPCV-1 POS ( LHS ) HPCV-2 POS ( RHS ) 0.00 Time [min] Measures: Sliding pressure operation / inherent storage capabilities 2017-12-01 Improvement of flexibility in coal fired power stations 25
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 2017-12-01 Improvement of flexibility in coal fired power stations 26
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 1 2 STEAG Minimum load reduction 3 Frequency control 4 Roadmap 2017-12-01 Improvement of flexibility in coal fired power stations 29
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 www.automaxs.de 2017-12-01 Improvement of flexibility in coal fired power stations 30
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