Syngas from Biomass Problems and Solutions en route to technical Realisation

Transcription

1 Syngas from Biomass Problems and Solutions en route to technical Realisation International Conference Synthesis Gas Chemistry Dresden, October 2006

2 Motivation Biomass is the only renewable carbon source! Biomass should be used favourably for organic chemicals and fuel production instead of electrical power and heat generation! Syngas and its main constituent, Hydrogen, are key intermediates for synthetic chemistry! Synthetic fuels are most promising products!

3 Main uses of syngas and hydrogen Thermochemical via intermediates Biological direct and via intermediates Hydrogen Ammonia Hydrocarbons Waxes CO + H 2 Methanol Aldehydes Alcohols

4 Fuel options of syngas and hydrogen Hydrogen Fuel Cells MTBE Gasoline Diesel CO + H 2 Methanol DME Gasoline CH 4 (SNG) Medium BTU gas I. Wender, Fuel Proc. Techn. 48 (1996) 189

5 Thermochemical gas formation from biomass Dry Biomass CO, H 2 Fischer- Tropsch Methanol DME... C 6 H 12 O 6 6 CO + 6 H 2 6 CO + 6 H 2 O 6 CO H 2 Wet Biomass H 2, CH 4 Fuell cells Gas engines... C 6 H 12 O H 2 O 6 CO H 2

6 Gasification of dry biomass Dry Biomass CO, H 2 C 6 H 12 O 6 6 CO + 6 H 2 6 CO + 6 H 2 O 6 CO H 2

7 Hurdles in biomass utilization Usually low volumetric energy density Widely distributed occurrence Heterogeneous solid fuels High ash and salt contents Direct gasification is problematic (tar and methane formation) Unfavourable H 2 :CO ratio after gasification Downstream syntheses require high pressures (Fischer-Tropsch 30 bar, Methanol, DME 80 bar) Use of catalysts sensitive to impurities

8 The slurry gasification concept Energy density [GJ/m 3 ] Distributed biomass Transport radius Straw 1,5 25 km Slurry 20 Regional intermediate fuel production regionale Pyrolyse- Anlagen Diesel 36 Zentraler Central syngas and fuel production 250 km

9 Straw Fast pyrolysis Slurry Stroh preparation De-central central High pressure entrained flow gasification Gas conditioning The process chain basing on a review an technologies suitable to be adapted to biomass feedstocks Fuel synthesis Synfuel

10 Fast pyrolysis using a twin screw mixer reactor Stroh, Straw, Heu wood, u.a.... Chopper Häcksler M Cold chopped straw kaltes Strohhäcksel heisser Sand ca. 500 C Hot sand 550 C Heater, Heizer Heat Sandkreislauf carrier loop Pyrolysis segas Kühler Cooler Pyrolysis Pyrolyseöl oil Slurry Pyrolysekoks Pyrolysis char M Doppelschnecken-Reaktor Twin screw mixer reactor

11 Reactor principle Forschungszentrum Karlsruhe Gases, vapors and pulverised Sand hotsand Straw-cut ratio 5-15 Sand loop Char Mechanically fluidised sand at 500 C (no dilution by gas), fast transport with good radial mixing (2 s gas retention time) fast heat transfer, ball milling effect

12 Mass distribution Forschungszentrum Karlsruhe Straw retention in the mixing reactor 0,25 0, kg Sand pro h plus 3 g Stohhäcksel 0,15 4 0, Hertz 0, t (s)

13 Variation of heat transfer carriers Optimisation of the heat transfer medium for: - spherical particles reduced abrasion of the medium - higher heat capacity low heat carrier / biomass ratio - coarse-grained particles better milling of the char and its separation from the heat carrier medium Steel SiC SiO 2 c p,wt (at 600 C) [kj/(kg K)] 0,6 1,2 1,25 (T aus -T ein ) WT [K] m WT /m Bio (wet) [ - ] , m WT /m Bio (dry) [ - ]

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15 Representative results 1000 Produktausbeute g/kg Gas Schwelteer Schwelwasser Koks Wood Material Nr. Straw Focus on more difficult biomass like straw less condensates, more ash (solids) Lab scale plant (10 kg/h)

16 Slurry preparation Forschungszentrum Karlsruhe Highly porous char from straw, soaked with 78 wt.% tar Is liquefied by milling and heating char particle volume fraction ~ 50 % porosity %

17 Influence of milling on slurry preparation Suitable for entrained flow gasification Original char particles suspended in alcohol Mass distribution Slurry 1: 21 wt.% weat straw char Slurry 4: 40 wt.% weat straw char Char particles after colloidal milling Particle size / μm Better milling with increasing viscosity and particle content

18 Viscosity of slurrys with high particle load near the sedimentation limit: a few Pas good atomization below 0.3 Pas Temperature[ temperature o C -- ] Pre-condition: Enough liquid phase to cover all particles with a liquid film Short storage: rearrangement of the organic molecules after mixing: increase of viscosity. Long time storage: char particles improve their arrangement, less liquid is contained in the space between the particles, decrease of viscosity. logarithm Viscosity of viscosity ln (η) [ ln ( η ) ] % char %% char %% Koks char 33 % char 10 1,0 0, Viscosity viscosity [ Pas ] Reciprocal reciprocal temperature [ 1000/Kelvin ]

19 Continuous slurry preparation Supply of pyrolysis oil (8 t) and char (4 t) at Future Energy Continuously operated slurry mixer (1 t/h) at FZK

20 High pressure entrained flow (GSP) gasifier Tar free synthesis gas Suitable for feeds rich of ash Gasification with pure O 2 High pressures, 30 to 100 bar Temperatures around 1200 C pilot fuel steel pressure shell flame oxygen Residence time of seconds, complete C-conversion 4 gasification campaigns with different feed materials, process parameters, 500 kg/h (2-3 MW th ) water cooled radiation screen ~ 1200 C ~ 50 bar raw syngas molten slag

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22 Results of slurry-gasification Gas composition H 2 CO CO 2 N 2 Feeds: Solids: 0 39 wt.% Ash: 3 % Heating value: MJ/kg Density: 1250 kg/m 3 Operation conditions: Throughput: t/h Pressure: 26 bar Temperature: C Feed-Temperature: 40, 80 C no tar, < 0.1 vol.% methane C-conversion 99 % operation without problems Equilibrium: (CO 2 H 2 ) / (CO H 2 O) = K(T) Slag melting point < 1200 C

23 Influence of the water content No tar, < 0,05 Vol.% Methane, 0.5 t/h C, 24 MPa, % char H 2 0 % Conversion % HHV kj/kg η 62-1/ Versuch Nr H 2 CO CO 2 N , Gas yield / vol.% Gasausbeute / Vol.% * Gasifcation campaigns 2003 and 2005

24 Lignocellulose 100 % Energy- and mass balance ~ 7 % ~ 1 % Schnellpyrolyse Fast pyrolysis ~ 3 % Kondensat/Koks Condensate/char Slurry ~ 90 % Flugstrom Entrained - Druckvergasung flow gasification ~ 3 % Synthese Synthesis-raw -Rohgas Reaktionswärme Heat of reaction Synthese Synthesis-clean -Reingas ~ 76 % ~ 13 % 7.5 t Wood or Straw with 15 wt.% H 2 O 5.4 t Condensate/char - slurry plus ~ 1,8 t O 2 Heat losses: Sum ~ 6 % ~ 1 % ~ 1 % FT- Synthesis Synthese FTS - Heat Reaktionswärme of reaction ~ 18 % Syntheseprodukte Synthesis products ~ 51 % nicht Not umgesetztes converted Syngas ~ 6 % Trennung Separation C 5- - Produkte Products ~ 5 % El. Power and HT steam: ~ 42 % ~ 40 % C 5+ FTS - Produkte Synfuel, waxes, olefines ~ 5 % valuable C 5 -products C t FTS-raw products 1 t Synthetic fuel By-products: Chemicals, Steam, Electricity

25 State of development Fundamental studies in lab scale equipment, parameter determination for various feed materials and conditions, selection of appropriate process technologies Demonstration of the principal technical feasibility in technical relevant plants, process variants in bench scale plants Construction and operation of a pilot plant proving practicability, allowing for scale-up and reliable cost estimates

26 Pilot plant (500 kg/h) Stepwise construction : 1. Biomass conditioning Fast pyrolysis, slurry preparation Gasifier Gas conditioning Fuel synthesis 2008

27 State of construction Pyrolysis plant Conditioning Slurry mixing

28 Gasification of wet biomass Wet Biomass H 2, CH 4 C 6 H 12 O H 2 O 6 CO H 2

29 Hydrothermal gasification of biomass is an option to generate hydrogen directly from wet biomass and organic residues using a renewable resource could fill the lack in hydrogen as present in the dry biomass conversion process, because for methanol production a CO/H 2 of 2 is required is favourable, when zero cost residual biomass or waste are used

30 Hydrogen for synfuel production Syngas composition after gasification 2 CO + H 2 H 2 -deficit Hydrogen from single gasification process: CO + H 2 O H 2 + CO 2 Shift-reaction CO + 2 H 2 H 2 O + -CH 2 - Synthesis 2 CO + H 2 CO 2 + -CH 2-1t product -CH 2 - from 4.2 t product gas bad carbon efficiency External hydrogen, e.g. by hydrothermal gasification of e.g. bio-ethanol C 2 H 5 OH + 3 H 2 O 6 H CO 2 C 2 H 5 OH + H 2 O CH 4 + CO H 2 (H 2 :CH 4 = 4:1) 1 t Hydrogen from 7.5 t ethanol C 2 H 5 OH + 2 (2 CO +H 2 ) 2 CO 2 + H 2 O + 4-CH 2-1 t Product from 2.1 t product gas and 3.2 ethanol higher carbon yield in the fuel no need for CO 2 -separation

31 Hydrothermal gasification of biomass C 6 H 12 O 6 6 CO + 6 H 2 6 CO + 6 H 2 O 6 CO H 2 C 6 H 12 O H 2 O 6 CO H 2 No drying prior to the process Classical gasification Water-gas-shift-reaction Hydrothermal gasification Δ r H o = 158 kj/mol (Glucose) High H 2 -yield obtained under pressure, nearly no CO integrated water gas shift reaction, catalysts included Short reaction times, high space/time-yields No tar and char under optimal conditions due to solvation of the reaction intermediates, solvent like environment Easy CO 2 -separation under pressure Inorganic components are not volatile

32 What thermodynamics predict? CH 4 H 2 CO 2 CO T / C Wood, CH 1,44 O 0,66, 25 MPa, 10 wt.%

33 R&D demand Process technology High pressure feeding and pre-treatment Handling of solids precipitations Adaptation to different feed stocks and products Experience with real feed stocks by operation of the pilot plant VERENA and special test facilities Process fundamentals for reaction engineering and optimization Optimisation of H 2 -yield Optimisation of H 2 / CH 4 ratio Avoidance and reduction of tar formation by identification of main reaction pathways and their dependencies via key components

34 Feeding 100 kg / h 5-20 % dmc Reactor 35 L Volume 0,11 m i.d., 3,7 m length Inconel Ni-Alloy External Heating

35 Test facility VERENA Biomass Water Gas tank Pre-heater Reaktor Separator Feed Economizer CO 2 - Scrubber HP-Pump Cooler Colloidal mill Res. Water tank Feed section Reaction section Separation section

36 Hydrothermal gasification of maize silage Results before and after CO 2 -separation CO 1% CO2 44% C2H6 8% CO 2% C2H6 5% CH4 39% H2 51% 7.5 wt.% DS, 700 C, 250 bar, min, Avarage from 7 independent test runs CH4 22% H2 28%

37 Hydrothermal gasification of maize silage Before CO 2 separation C2H6 5% CO2 44% After CO 2 separation CO 1% H2 51% CH4 39% C2H6 8% CO 2% 5 wt.% DS 0 C, 250 bar min CH4 22% H2 28%

38 Lab scale plants exhibiting different reactor characteristics, model compounds and biomass Tumbling reactor (Batch) 500 C, 50 MPa, 1 L Tubular reactor 600 C, 30 MPa, ca. 20 ml Cont. Stirred tank reactor 600 C, 100 MPa, 190 ml

39 Gas yield and gas composition - Glucose vs. biomass Gas yield / (mol/kg) Phytomass Glucose / K 2 CO 3 45% 47% CH 4 CO Ca. 5% DM, 500 C, 30 MPa; τ / min 0.5 % (g/g) K 2 CO 3 H 2 40% H 2 0% 38% CO 2 CH % 15% CO 15%

40 Influence of alkali salts Vol.- % dd CH4 CO2 H2 CO Gas com ponent Mit with KHCO3 Ohne without Conzentration / (mg/l) HOH 2 C O CHO O CHO O CHO H 3 C Mit with KHCO3 ohne without KHCO3 25 MPa, 400 C 1,5 % (g/g) Glucose; 0,2 % (g/g) KHCO 3 OH CH 2 OH OH O OH OH 0 HMF FU MF Furfurals

41 Concluding remarks Both, dry and wet biomass can be utilized for syngas and hydrogen production by technical feasible and economical ways

42 Energy balance Energy demand El. Energy 2 kw e Forschungszentrum Karlsruhe 41 kw th Product gas 85 kw th : H 2 90 % CH 4 6 % CO 4 % (after CO 2 -separation) 44 kw th Energyproduction Feed: 15 % MeOH 95 kg/h (79 kw th ) Losses ( 26 kw) 3-6 kw e El. power for CO 2 scrubbing Warm water (T max 166 C, 40 C reflux ) 11 kw th 15 wt.% methanol, 95 kg/h, reaction temperature = 571 C, yield 98.4 %, mass balance 98 %

43 Energy consumption vs. production LHV/time (gas) LHV / time (CH3OH) product Energy / time (kw) Heat dissipation (flue gas) educt consumption c(ch3oh) / wt %

44 Feed materials for hydrothermal gasification Residual biomass Organic waste Fuels Energy plants Disposal & energy Disposal & energy Decentralized Energy Enduring energy Food & beverage Wine trash Agricultural production Liquid manure Paper & cellulose Pharmaceutical & chemical industry Biotechnology Sewage sludge Bio-alcohol Rape oil MeOH Hydrocarbons Pyrolysis oil Suitable ground and aquatic fresh plants Corn silage Mash (bioethanol) Sludge (biogas) Wet Wet / toxic Without catalyst Use of complete plant

45 State of development Fundamental studies in lab scale devices (reaction mechanism, kinetics, catalytic effects by salts contained in the biomass), parameter studies (influence of composition, temperature, pressure, concentration, heating rate), investigation of reactor materials Pilot plant operation (100 kg/h) for further process development, e.g. in regard to solids handling (precipitating salts and minerals)and corrosion, optimization in regard to H 2 /CH 4 ratio, operational reliability, and economics

46 Concluding remarks For syngas production from biomass to large extent, thermochemical processes adapted from fossil fuel treatment are well suited, operational practicability and economics have to be proved Biomass as the only carbon containing renewable energy preferentially should be used for the production of fuels and organic chemicals (consuming ca. 10 % of the primary energy). Heat and electrical power can be produced from other renewable energy sources Since C/H-ratio available from biomass is worse than that from fossil fuels, additional hydrogen should be produced from other renewable resources

47 Financing R&D budget of Forschungszentrum Karlsruhe Supplementary support by HGF Ministerium für Ernährung und ländlichen Raum Baden-Württemberg MELR Ministerium für Verbraucherschutz, Ernährung und Landwirtschaft BMVEL und FNR EU-Commission Federal Ministry of Education and Research