PRESENTATION SLIDES: Fluidized Bed Combustion for Clean Energy

Transcription

1 Refereed Proceedings The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering Engineering Conferences International Year 2007 PRESENTATION SLIDES: Fluidized Bed Combustion for Clean Energy Filip Johnsson Chalmers, Dept Energy Convers,, fijo@chalmers.se This paper is posted at ECI Digital Archives. xii/131

2 Johnsson: Fluidized Bed Combustion for Clean Energy FLUIDIZED BED COMBUSTION FOR CLEAN ENERGY Filip Johnsson Department of Energy and Environment, Energy Technology , Göteborg Fluidization XII - New Horizons in Fluidization Engineering May 13-18, 2007 Published by ECI Digital Archives,

3 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] Structure of presentation Introduction - energy market Climate change Boiler market Example of FB related bridging technologies The FBC market FBC and fluidization Flow characteristics R&D need New concepts Conclusions 2

4 Johnsson: Fluidized Bed Combustion for Clean Energy Large investments required in the energy sector over the next decades: - battle climate change - maintain security of supply - maintain competitiveness Published by ECI Digital Archives,

5 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] 370 ppm 280 ppm Atmospheric CO2 concentration 4

6 Johnsson: Fluidized Bed Combustion for Clean Energy Summary for Policymakers, IPCC Fourth Assessment Report, Working Group III, (Draft May 5, 2007) Published by ECI Digital Archives,

7 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] Per Capita CO 2 Emissions 12 OECD Tonne CO2/capita 8 4 Middle east Former USSR Non-OECD Europe China World average Latin America Asia Africa Population [million] 6

8 Johnsson: Fluidized Bed Combustion for Clean Energy Global Power Generation by Fuel 5,000 Generation (BkWh) 4,000 3,000 2,000 1,000 Renewables Nuclear Hydro Thermal 0 North America Latin America W. Europe E. Europe & FSU Middle East Africa Asia & Oceania Published by ECI Digital Archives,

9 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] Alternatives towards Sustainable Energy Systems -General To use less energy Population Technology affluence and life style efficiency measures To shift fuel Renewable energy Nuclear Coal to gas To Capture and Store CO 2 From large point sources (power plants, industry, hydrogen from fossil fuels) Carbon sequestration (Land Use Change and Forestation- LUCF) 8

10 Johnsson: Fluidized Bed Combustion for Clean Energy Power generation Large need for investments in boiler capacity Published by ECI Digital Archives,

11 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] Age distribution of US coal fired power plants FOSSIL FUEL POWER GENERATION - STATE-OF-THE-ART PowerClean Thematic Network, 2005,

12 Johnsson: Fluidized Bed Combustion for Clean Energy Net capacity of operating and planned thermal power plants in EU-25 distributed by fuel and age GWe (Nuclear) 0.6 (Oil) 2.6 (Lignite) 2.5 (Coal) 1.6 (Nuclear) 0.1 (Oil) 2.4 (Lignite) > 30 years years years 0-10 years Construction Planned Natural gas Coal incl peat Lignite Oil Nuclear Kjärstad, J., Johnsson, F., The European power plant infrastructure Presentation of the Chalmers energy infrastructure database with applications, Energy Policy 35, 2007, pp Published by ECI Digital Archives,

13 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] Power generation capacity - Germany (Hydro) 0.2 (Bio) (Bio) 5,6 0.2 (Bio) 2,2 1.1 (Hydro) 0.8 (Bio) 28,4 GWe 30 3,1 1,2 13,8 0.2 (Hydro) 20 8,4 0,8 0.2 (Bio) 1.1 (Wind) 17,3 1,2 3,7 9,8 5,4 0,9 13, ,3 2,1 0.4 (Oil) 5,6 0 8,5 3,8 6,0 1,9 1,4 6,2 0.1 (Bio) 2,1 2,4 7,6 > 30 years years years 0-10 years Construction Planned Natural gas Coal Lignite Oil Nuclear Wind Bio/Waste Hydro Kjärstad, J., Johnsson, F., The European power plant infrastructure Presentation of the Chalmers energy infrastructure database with applications, Energy Policy 35, 2007, pp

14 1200 Johnsson: Fluidized Bed Combustion for Clean Energy The challenge Example Germany Phase out of fossil and nuclear generation in Germany together with estimated maximum realistic deployment of renewables (RES) HIGH MED TWh 600? LOW Existing system Max RES Hard Coal Lignite Oil Gas Nuclear Wind Hydro Biomass Other RES Others MOD MED BAU Kjärstad, J., Johnsson, F., The European power plant infrastructure Presentation of the Chalmers energy infrastructure database with applications, Energy Policy 35, 2007, pp Published by ECI Digital Archives,

15 RES and Energy efficiency not likely to be sufficient The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] We need bridging technologies: 1. Nuclear (life time extensions + new installations) 2. Fossil with CO2 capture 3. Co-firing biomass with coal 4. Coal to gas (but feasible?) 5. CHP with waste as fuel (increased use of DH) 2, 3 and 5 are possible markets for FBC together with biomass and waste in CHP with FBC technology 14

16 Johnsson: Fluidized Bed Combustion for Clean Energy CO 2 Capture and Storage as a bridging technology Published by ECI Digital Archives,

17 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] CO 2 Capture, Transport & Storage (CCS) 16

18 Johnsson: Fluidized Bed Combustion for Clean Energy Storage 1 Mt/year pilot project in the North See since 1996 Published by ECI Digital Archives,

19 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] CO2 Capture main technologies 18

20 700 Johnsson: Fluidized Bed Combustion for Clean Energy Example UK 60% CO2 reduction by 2050, Fuel costs and demand from EU Energy & Transport Trends 2030 (2005 edition), extrapolated to Electricity generation [TWh] CCS (coal) Hydro Wind Biomass & waste others Hard coal Nuclear Oil Gas CCS Published by ECI Digital Archives,

21 Storage sites by reservoir type and coal and lignite fuelled power plants within EU-25 plus Norway Blue = oil fields Red = gas fields Crossed grey = aquifers Black = coal plants Brown = lignite plants The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] 20

22 Johnsson: Fluidized Bed Combustion for Clean Energy Co-firing as a bridging technology Published by ECI Digital Archives,

23 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] Power generation capacity - Poland , ,7 0.1 (Oil) 10 1,2 GWe 8 2, ,8 7,2 1,7 1,5 0.1 (Hydro) 0.1 (Wind) > 30 years years years 0-10 years Construction Planned Natural gas Coal Lignite Oil Wind Bio/Waste Hydro 0,7 1,8 0,7 0,5 0,8 0,8 0,8 Kjärstad, J., Johnsson, F., Chalmers power plant database 22

24 Johnsson: Fluidized Bed Combustion for Clean Energy Example of repowered power plant - FB boilers in Turow (Bogatynia) Published by ECI Digital Archives,

25 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] Co-firing opportunities in 2010 and Low wood supply estimate (TJ/year) High wood supply estimate (TJ/year) Boiler capacity surplus Woody biomass supply surplus Poland Fuel Supply Type Cost Heat value Conversion Boiler- -Type -Cost Electricity production from biomass in co-firing Low-cost CO 2 avoidance option Availibility -Size Emissions -Age -Main fuel -Location Cost for implementing co-firing Cost optimisation Johnsson, F., Berndes, G., Berggren, M., World Bioenergy Conference & Exhibition, 30 May-1 June 2006, Jönköping 24

26 Johnsson: Fluidized Bed Combustion for Clean Energy The FBC market Published by ECI Digital Archives,

27 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] Fluidized Bed Combustion Originates from the need to burn difficult low grade fuels of varying quality Ability to burn various fuels in the same unit Good load following characteristics Possibility for in-bed sulphur removal and low NOx emissions (low combustion temperature) and that without any need for special DeSOx or DeNOx equipment For reviews on history of the FBC development see Banales and Norberg-Bohm (Energy Policy 30, 2002, p 1173) and Koornneef et al. (Prog. Energy and Combustion Science 33, 2007, p 19) For FBC reviews see e.g. Leckner (Prog. Energy and Combustion Sci. 24, 1998, p 31) and previous Proc of Fluidization conf, FBC conf and CFB conf. 26

28 Johnsson: Fluidized Bed Combustion for Clean Energy FBC installations (year of commissioning and fuel) FBC reference lists from Alstom, Foster Wheeler and Metso Power GWth Coal Bark Wood Sludge Peat Oil Gas MSW Published by ECI Digital Archives,

29 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] FBC installations (thermal rating and fuel) FBC reference lists from Alstom, Foster Wheeler and Metso Power 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% MWth Coal Bark Wood Sludge Peat Oil Gas MSW 28

30 Johnsson: Fluidized Bed Combustion for Clean Energy FBC installations (thermal rating, year and fuel) FBC reference lists from Alstom, Foster Wheeler and Metso Power Coal Other 600 MWth Year Published by ECI Digital Archives,

31 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] FBC market Boilers of a capacity of less than ~ 100 MW th burning waste derived fuels, including biomass, typically operating in CHP schemes (or as heat only boilers, mainly in Sweden) Competing technology grate fired boilers Large power boilers (up to ~1,000 MW th mainly burning coal (bituminous coal or lignite), Competing technology PC boilers Fuel flexibility will be increasingly important? 30

32 Johnsson: Fluidized Bed Combustion for Clean Energy Future of FBC technology in a CO 2 constrained world If climate target to be met, coal plants must be equipped with CO 2 capture! Current EU target is that all new coal fired plants should have capture from 2020 and on (even stricter target is required if to meet new IPCC target for max 2 ºC temperature increase ) Also FBC power boilers must be with capture! Increase in biomass and waste combustion and CHP schemes can be expected Development of new concepts such as CLC New FB gasification concepts (biomass, coal with biomass) Published by ECI Digital Archives,

33 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] FBC and fluidization Flow characteristics R&D need related to Fludization 32

34 Johnsson: Fluidized Bed Combustion for Clean Energy FBC characteristics A height to diameter (aspect) ratio of the riser (H 0 /D eq ) of the order of or less than 10 A ratio of settled bed height (the bed formed if the solids are not fluidized) to riser diameter of less than 1 (H b,settled /D eq < 1) Fluidized solids belonging to group B in the Geldart classification For CFB units a solids net flux (G s,net ) typically ranging from 0.5 to 20 kg/m 2 s G s,net not known and should not be input in CFBC models Primary operational parameters of the furnace (with respect to fluid dynamics) are the riser pressure drop and the gas flows (i.e. fluidization velocity, secondary gas injection) Published by ECI Digital Archives,

35 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] Circulating FBC Bubbling FBC 34

36 Johnsson: Fluidized Bed Combustion for Clean Energy Without and with EHE + 55,4 m + 2,3 m Published by ECI Digital Archives,

37 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] Bottom bed with exploding bubbles High through flow High fluctuations in gas flow Interaction with air plenum Reducing conditions Freeboard Splash zone with strong solids back mixing (cluster phase dominates) Transport zone with backmixing at furnace walls (disperse phase flow dominates) Solids segregation Freeboard Exit Exit duct Cyclone Flow characteristics 36

38 Johnsson: Fluidized Bed Combustion for Clean Energy Application of Johnsson & Leckner (1995) freeboard model (with a and K decay factors) SOLIDS CONCENTRATION [kg/m3] 1E+3 1E+2 1E+1 1 slope of line determines K slope of line determinesa Chalmers 12MW CFB u 0 = 2.7 m/s, p ref = 7 kpa d p = 0.20 mm, H x = 0.51 m 0.32 mm, 0.49 m 0.44 mm, 0.60 m HEIGHT ABOVE BOTTOM BED h - H x [m] LEVEL BELOW H x [m] (From Johnsson & Leckner, 1995) Published by ECI Digital Archives,

39 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] Exploding bubble in bottom bed Primary gas flow varies with time and with spatial location Air distributor 38

40 Johnsson: Fluidized Bed Combustion for Clean Energy Momentum probe signals from three elevations in the Turow CFB boiler Impact pressure [Pa] Impact pressure [Pa] Impact pressure [Pa] Time [s] Wall layer ER, 50 mm from wall L5f, 50 mm from wall Time [s] L2f3, 50 mm from wall Time [s] Impact pressure [Pa] Impact pressure [Pa] Impact pressure [Pa] Time [s] Core ER, 2550 mm from wall L5f, 2500 mm from wall Time [s] L2f3, 2000 mm from wall Time [s] 36.7 m above air distributor 17.7 m above air distributor 3.8 m above air distributor Front wall Published by ECI Digital Archives,

41 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] Need for FBC research related to fluidization 40

42 Johnsson: Fluidized Bed Combustion for Clean Energy τ dispersion τ conversion Bottom bed and Freeboard To increase the knowledge and modeling capabilities for prediction of mixing of fuel and combustion air Depends on the fuel conversion time and the characteristic mixing length. Comparison of the characteristic times for fuel dispersion and conversion: L * Da = τ τ dispersion conversion = τ r dispersion conversion dispersion = characteristic time for fuel dispersion, r dispersion = mixing rate, conversion = characteristic time for fuel conversion, L * = characteristic mixing length Published by ECI Digital Archives,

43 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] Fuel feed distribution (Turow 235 MW e ) REAR WALL (fuel and recycle ash) R1 R2 2.3 m above distributor F1 F2 F3 F4 FRONT WALL (fuel only) page 6 42

44 Johnsson: Fluidized Bed Combustion for Clean Energy D sr from modeled drying rate of fuel and measured concentrations of H 2 O above the bed + Drying rate + Dispersion of fuel Distribution of H 2 O above the bed Comparison between modeled and measured concentrations of H 2 O gives best fit for D sr 0.1 m 2 /s Most measurements from narrow units lower dispersion rates Not a dispersion process Published by ECI Digital Archives,

45 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] Influence of bottom bed fluctuations on freeboard mixing flow Bed surface 44

46 Johnsson: Fluidized Bed Combustion for Clean Energy Exit zone and exit duct To model the ratio of the solids which leave the furnace and the solids which are internally recirculated, i.e. the back-flow ratio For conditions corresponding to those in boilers, it seems as if the exit geometry has little influence on the back-mixing ratio, but that is not to say that the net solids flux can be predicted Published by ECI Digital Archives,

47 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] Cyclone To find primary particle separation systems with a more compact design (e.g. integrated with furnace, U-beam separators) 46

48 Johnsson: Fluidized Bed Combustion for Clean Energy Particle seal and downcomer To integrate a external heat exchanger (EHE) in the loop seal is advantageous due to the high in-bed heat transfer and the CFB loop will provide a self controlled power output from the EHE The solids flow and solid size distribution becomes crucial for the design of the heat transfer surfaces in the EHE EHE flow is complex. Few studies (e.g. Werderman, and Werther, Proc. 12th Int. FBC Conf, 1993, p 985, Johansson et al., J. Energy Resources Technology, 128, 2006, p 135) Published by ECI Digital Archives,

49 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] Entire loop in the case of CFB boiler Integrating the above zones in a model requires knowledge on the particle size segregation For a given set of operational parameters (pressure drop and gas velocities), particle size distribution determines: internal solids backmixing net solids flux cyclone efficiency (i.e. the design of cyclone) solids size (and size distribution) in the loop seal Modelling of solids size segregation may require that momentum transfer between solids of different size and weight is taken into account 48

50 Johnsson: Fluidized Bed Combustion for Clean Energy Solids size segregation in CFB boiler AVERAGE PARTICLE DIAMETER, dp [mm] u t, 0.20 mm u t, 0.44 mm d p = 0.44 mm d p = 0.20 mm FLUIDIZATION VELOCITY, u 0 [m/s] (From Johnsson & Leckner, 1995) Published by ECI Digital Archives,

51 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] New concepts Oxyfuel CFB for CO2 capture Chemical looping combustion Integrated gasifier in FB boiler 50

52 Johnsson: Fluidized Bed Combustion for Clean Energy Process and cost study of a large scale lignite fired O2/CO2 PC power plant Reference plant (current): Lignite-fired 2x933MW el 2x115MW heat Commissioned in million tons CO 2 /year! Proposed O2/CO2 scheme: ( 99.5% reduction in CO2 emissions to the atmosphere) o O N o 2 21 Air inlet 20 CO 2 out 27 C B A 1. Air compressor 2. Compressor cooling 3. Direct contact air cooler 4. Evaporative cooler 5. Molecular sieves 6. Heat exchanger 7. Expansion turbine 8. Destillation column 9. Boiler 10. Super heater 11. Economizer 12. TEG heat exchanger 13. Flue gas condensation unit 14. Flue gas cooler 15. Compressor unit 1, 30 bar 16. TEG 17. Compressor unit 2, 58 bar 18. CO condenser Heat exchanger (CO 2 /CO 2 ) 20. Gas/Liquid separator 21. Subcooler 22. High pressure pump 23. HP Steam turbine 24. IP Steam turbine 25. LP Steam turbine 26. Condenser 27. Cooling tower 28. District heating 29. Feed water preheater 30. Feed water preheater 31. Nitrogen heater Published by ECI Digital Archives, 2007 Study yields CO2 capture cost of approx 20 /t CO2 Andersson et al.(2003) VGB Power Tech Journal No 10 51

53 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] Air N 2 Air Separation Unit Flue gas recycle Boiler N 2, O 2, Ar, NO x, SO x Flue gas treatment and compression CO 2, (SO 2 ) Oxyfuel (O 2 /CO 2 recycle) FBC combustion (Alstom) Lignite H 2 O CFB Steam Generator Unit INDUCED DRAFT FAN CO 2 -RICH PRODUCT TO GAS PROCESSING SYSTEM Cyclone AIR INFILTRATION COMBUSTOR BACKPASS HEAT EXCHANGERS CONDNESATE Gas Cooler PFWH COAL LIMESTONE External Heat Exchanger OXYGEN HEATER PARTICULATE REMOVAL SYSTEM GAS RECIRCULATION FAN OXYGEN ASH COOLER FLUIDIZING GAS BLOWER AIR AIR SEAPARATION UNIT NITROGEN 52

54 Johnsson: Fluidized Bed Combustion for Clean Energy Chemical looping combustion N 2, O 2 CO 2, H 2 O flue gas M y O x 2 Airreactor M y O x-1 Fuelreactor 1 3 H O 2 Air Fuel air fuel CO 2 (2n+m)Me x O y + C n H2 m (2n+m)Me x O y-1 + mh 2 O + nco 2 Me x O y-1 + ½O 2 Me x O y Published by ECI Digital Archives,

55 Chalmers 10 kw chemical-looping combustor 2003 convective cooling of flue gases The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] reactor system filters 54

56 Johnsson: Fluidized Bed Combustion for Clean Energy Chemical-Looping Combustion Reactor system (fluidized beds): - well established - commercially available - simple - moderate costs Oxygen-carrier particles: - very encouraging results - scale-up of particle manufacture - raw materials - long-term testing needed Published by ECI Digital Archives,

57 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] Applications of chemical-looping combustion for CO 2 capture: Combustion of gaseous fuel, natural gas, refinery gas, syngas Chemical-looping reforming, i.e. hydrogen production Combustion of solid fuels 56

58 Johnsson: Fluidized Bed Combustion for Clean Energy Integration of biomass gasification in existing boiler infrastructure a new low cost gasification concept Circulating fluidized bed (CFB) Bubbling fluidized bed (BFB) Heat, Electricity, Steam Heat, Electricity, Steam Flue gas Bio Product Gas Flue gas Fuel Hot bed material Biomass Fuel Hot bed material Bio Product Gas Biomass Air Fluidization gas Air Fluidization gas Published by ECI Digital Archives,

59 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] Chalmers gasifier for demonstration och research Advantages Heat balance always fulfilled Minimization of char losses Optional fluidization medium Operation at any temperature Possibility to gasify wet fuel with a high efficiency Possibility to burn fuel with high moisture content in combustor The gasifier does not have any negative effect on the combustor Can be integrated in existing energy system infrastructure 58

60 Johnsson: Fluidized Bed Combustion for Clean Energy Published by ECI Digital Archives,

61 The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering, Art. 131 [2007] Conclusions Large investments in the energy system are required over the coming decades, both as a result of an increased demand for heat and power, as well as due to replacement of old plants The prospects for the FBC technology for clean energy is high, but there are competing technologies Research and development is required in order to improve the FBC technology establish models for reliable design and scale up of the technology (fuel mixing, solids segregation) Rather than competing with the PC technology, the FBC technology (CFBC) will take important niche markets, where fuel flexibility is or can be foreseen to be of future importance New concepts (oxyfuel, CLC, indirect gasifiers) 60

62 Johnsson: Fluidized Bed Combustion for Clean Energy Alstom, Foster Wheeler and Metso Power are gratefully acknowledged for providing the boiler figures and boiler reference lists. Mr Fredrik Normann is acknowledged for compiling the data from the lists. Published by ECI Digital Archives,