Improvement of power plant flexibility by coupling of power generation

Transcription

1 11 th ECCRIA University of Sheffield Improvement of power plant flexibility by coupling of power generation with syngas-based chemical synthesis Clemens Forman, Matthias Gootz, Christian Wolfersdorf, Bernd Meyer Institute of Energy Process Engineering and Chemical Engineering, TU Bergakademie Freiberg 6th September 2016, Sheffield, UK

2 OUTLINE 1. Background and motivation 2. Power generation cases 3. Coupling interfaces 4. Modeling results 5. Summary 2

3 1. BACKGROUND AND MOTIVATION lignite-fired power plant 650 1,100MW(el) electric grid renewable energy sources lignite coal combustion flue gas path steam cycle flue gas, ash, gypsum electric energy drying residual gas water electrolysis 50 MW(el) Annex plant auxiliaries steam O MW(th) carbon residue coal gasifier entrained-flow (EFG) fluidized-bed (FBG) water scrubbing CO-shift sour gas CO 2 /H 2 S scrubbing waste water pretreatment CO 2 H 2 Fischer Tropsch synthesis MeOH synthesis MtG synthesis MtO synthesis small-scale chemical synthesis wax, diesel gasoline olefins 3

4 1. BACKGROUND AND MOTIVATION MIN MAX MIN Annex plant serves MAX as a power sink: RES RES RES RES electric grid electric grid electric grid load elasticity of power plant rises incorporation of surplus RES improved power plant flexibility electric grid auxiliary power MAX MIN or shut tdown MA AX auxiliary power auxiliary power IN M power power power Annex power Annex plant plant plant + plant plant + plant 4

5 2. POWER GENERATION CASES Existing power plant Design data Future power plant built in 1970s to be built ,725 MW rated thermal input* 2 x 1,155 MW (30 % dry lignite) 672 t/h coal demand 2 x 450 t/h 650 MW gross electric output 1,100 MW 607 MW net electric output 1,046 MW 37.7 % gross efficiency* 47.6 % 35.2 % net efficiency* 45.3 % 1,853 t/h live steam generation 2 x 1,387 t/h 170 bar; 530 C live steam parameter 285 bar; 605 C 34/30 bar; 300/540 C cold/hot reheat steam 56/51 bar; 340/620 C 66 mbar condenser pressure 35 mbar wet cooling tower cooling system hybrid cooling tower (natural draft) (forced draft) * thermal input / efficiencies based on LHV 5

6 2. POWER GENERATION CASES Power plant modeling: steady-state simulation part load performance flue gas path sliding pressure boiler curves pressure drops plant modeling heat losses efficiency curves auxiliary power steam cycle relativ ve net plant efficiency (%) EPP: existing power plant FPP: future power plant EPP FPP BRACHTHÄUSER 1998 CHALMERS 2007 LINNENBERG 2009 ELSNER 2011 ZIEMS 2012 ROEDER 2014 HANAK 2015 RUPPRECHT

7 2. POWER GENERATION CASES Key performance data: net plant efficiency; specific auxiliary power 0, ,0 0, ,0 ncy change (% %-points) ne et plant efficie -0, , , , , , net efficiency change specific auxiliary power 7.5 7, , , , , ,0 (%) specific aux xiliary power ncy change (% %-points) ne et plant efficie -0, , , , , , , ,75 net efficiency change specific auxiliary power 6.5 6, , , , , , , ,0 specific aux xiliary powe er (%) -3, , , , existing power plant: % load future power plant: % load in DUO block operation ( ) % load in MONO block operation (- -) 7

8 3. COUPLING INTERFACES Existing power plant ECO Target: coupling interfaces require little constructional effort only 1 2 CAPH RHT SHT HP IP LP ~ 50 Hz MP steam: injection into the cold reheat pipeline air ESP EVAP HP FWH LP steam: installation of an additional feedwater heater bypassing the existing LP feedwater heating section Carbon residue & gases: combustion / thermal treatment in the after-burning section of the furnace IDF FGD clean gas DM lignite residue & gases 1 2 FWT LP FWH BFWP CP C CT ANNEX CWP 8

9 3. COUPLING INTERFACES Future power plant clean gas air ECO 1 Target: adjustment due to load-dependent operation conditions FGD FGTS I CAPH II RHT SHT HP IP LP ~ 50 Hz MP steam: injection into feed line of BFWT/FWH and cold reheat pipeline I EVAP 2 x HP FWH LP steam: feedwater heating and injection into feed line of FBD IDF 1 2 FBD DM lignite residue & gases FWT BFWP BFWT C 3 Carbon residue & gases: after-burning section (one/both blocks) ESP II CAPH HP-ABEco LP-ABEco LP FWH CP 2 3 C CWP CT ANNEX 9

10 3. COUPLING INTERFACES Residual & sour gases: positive pressure; ~30 C; major components (at STP) Sour gas: vol.-% CO vol.-% H 2 S vol.-% COS MeOH synthesis: purge gas vol.-% H vol.-% CH 4 light ends vol.-% H vol.-% CH 3 OH MtG synthesis: off gas ~ 92 vol.-% C1-C4 FG: vol.-% SO 2 : +10 % at FGD 2 CO 2 : up to 27 g/kwh Carbon residue (FBG only): 1 atm; ~100 C 34 wt.-% carbon; 66 wt.-% ash 14.8 MW thermal input (11.5 MJ/kg LHV) 10

11 3. COUPLING INTERFACES Total heat input: steam; gases; carbon residue MP steam LP steam Residue & gases Energy Exergy FBG FBG tion scenarios s Annex integra FT MTO MTG EFG FBG EFG FBG EFG tion scenarios s Annex integra FT MTO MTG EFG FBG EFG FBG EFG thermal rating (MW) thermal rating (MW) 11

12 3. COUPLING INTERFACES Annex integration: mass and heat balancing Power plant efficiency stand-alone (LHV) power plant el: electric aux: auxiliaries Power plant efficiency with Annex integration Annex plant C: coal S: steam W: feedwater G: gases R: carbon residue P: product(s) 12

13 4. MODELING RESULTS Net plant efficiency: reference case vs. Annex integration 0, ,0 0.0 ne et plant efficie ency change (% %-points) -0, , , , , , , , , , , EFG-MTG FBG-MTG EFG-MTO FBG-MTO EFG-FT FBG-FT reference (existing plant) ne et plant efficie ency change (% %-points) -0, , , , , , , , , , , EFG-MTG FBG-MTG EFG-MTO FBG-MTO EFG-FT FBG-FT reference (future plant) -6, ,

14 4. MODELING RESULTS Net plant efficiency: reference case vs. Annex integration 0, ,0 0.0 ne et plant efficie ency change (% %-points) -0, , , , , , , , , , , EFG-MTG FBG-FT reference (existing plant) ne et plant efficie ency change (% %-points) -0, , , , , , , , , , , EFG-MTG FBG-FT reference (future plant) -6, , existing power plant: (100 %) (50 %) future power plant: (100 %) (40 %) 14

15 4. MODELING RESULTS Coal savings: heat input by Annex integration results in less coal demand (and CO 2 emissions) 8 8 coa al savings com mpared to refe erence (%) EFG-MTG EFG-MTO EFG-FT FBG-MTG FBG-MTO FBG-FT existing power plant coa al savings com mpared to refe erence (%) EFG-MTG EFG-MTO EFG-FT FBG-MTG FBG-MTO FBG-FT future power plant existing power plant: g CO 2 / kwh(el) future power plant: g CO 2 / kwh(el) 15

16 4. MODELING RESULTS Coal savings: heat input by Annex integration results in less coal demand (and CO 2 emissions) 12 8 coa al savings com mpared to refe erence (%) EFG-MTG EFG-MTO EFG-FT FBG-MTG FBG-MTO FBG-FT future power plant: MONO operation coa al savings com mpared to refe erence (%) EFG-MTG EFG-MTO EFG-FT FBG-MTG FBG-MTO FBG-FT future power plant: DUO operation future power plant: g CO 2 / kwh(el) [MONO] future power plant: g CO 2 / kwh(el) [DUO] 16

17 4. MODELING RESULTS Load elasticity: coupling enables lowering of minimum power plant load relativ ve net electric city generatio on (%) reference Annex integration Annex integration including electrolysis Note: Annex integration averaged amongst all scenarios 0 existing power plant SINGLE future power plant DUO future power plant MONO existing power plant SINGLE future power plant DUO future power plant MONO 17

18 5. SUMMARY Overall evaluation: SWOT analysis from power plant point of view Strengths: Annex integration results in coal savings (and less CO 2 emissions) Weaknesses: slight efficiency loss compared to reference plant cases Opportunities: improvement of flexibility respectively load elasticity via Annex integration Threats: possible limitations for coupling interfaces towards minimal boiler capacity 18

19 ACKNOWLEDGEMENT Project Concept studies of coal-based Polygeneration-Annex-plants (03ET7042A) Supported by: Participating companies: RWE Power AG Forschung und Entwicklung 19

20 THANK YOU FOR YOUR ATTENTION! For enquiries or further questions, please contact: Clemens Forman Phone: +49 (0) Fax: +49 (0) Website: 20

21 APPENDIX References C. Wolfersdorf, K. Boblenz, R. Pardemann, B. Meyer; Syngasbased annex concepts for chemical energy storage and improving flexibility of pulverized coal combustion power plants; Applied Energy 156 (2015) ; doi: /j.apenergy M. Gootz, C. Forman, B. Meyer; Coal-to-Liquids: An attractive opportunity for improved power plant capacity utilization?; 8th International Freiberg Conference on IGCC & XtL Technologies Innovative Coal Value Chains, Cologne, Germany, C. Forman, R. Pardemann, B. Meyer; Differentiated evaluation of the part load performance of an industrial CHP; COAL-GEN Conference 2015, Las Vegas, Nevada/USA, Nomenclature (Annex plant) EFG Entrained-flow gasifier FBG Fluidized-bed d d gasifier FT Fischer Tropsch synthesis MTG Methanol-to-Gasoline synthesis MTO Methanol-to-Olefins synthesis Nomenclature (power plant) ABEco air bypass economizer FBD fluidized-bed drying BFWP boiler feed water pump FGD flue gas desulfurization BFWT boiler feed water turbine FGTS flue gas transfer system C condenser FPP future power plant CAPH combustion air preheater FWH feed water heating CP condensate pump FWT feed water tank CT cooling tower HP high pressure CWP cooling water pump IDF induced draft fan DM drying mills IP intermediate pressure ECO economizer LP low pressure EPP existing power plant MP medium pressure ESP electrostatic precipitator RHT reheater EVAP evaporator SHT superheater 21