Research on the reforming of ethanol

Transcription

1 Research on the reforming of ethanol LAMNET Workshop, Brasilia, Dec. 2-4, 2002 Dr.-Ing. Peter Hübner CH 3 CH 2 OH H 2 O Introduction - regenerative energy sources for hydrogen fuel cells - motivation for ethanol as fuel H 2 -rich gas Reforming of fossil fuels - allothermal reforming - partial oxidation - autothermal reforming European Project: - reformer and shift conversion device - burner development - catalyst screening Summary, Outlook Seite 2

2 Introduction regenerative energy sources for hydrogen fuel cells regenerative power sources: until now neglegible market penetration 1. Electrolysis of water with electricity from regenerative sources like - windenergy - hydropower - solar energy bio-ethanol - can be reformed most easily - is economically attractive (see following slides) motivation for ethanol 2. Reforming of biogenic (CO 2 -neutral) fuels - solid biomass (wood, wood pellets) - biogas - pyrolysis oil - biogenic ethanol Seite 3 Introduction: motivation for ethanol as fuel - economic potential Preliminary estimation of worldwide market penetration: potential contribution of ethanol to energy supply is significant 550 million tons per year in the transport sector (20 % of present consumption) 500 million tons per year for co-generation capacity (10 % of present capacity) several hundred million tons per year in the domestic market 200 million tons per year for the chemicals market Source: Guiliano Grassi, Bioethanol - Industrial world perspectives in Renewable Energy World, May-June 2000, p Seite 4

3 Introduction: Motivation for ethanol as fuel 1 Barrel = 159 liter Cost reduction potential: the Brazilian example assumption: 1 Dollar = 1 Euro cost in $/barrel 80 cost in EUROC/l , , , Source: José Goldberg in Tagungsband zur Veranstaltung Biotreibstoffe, 22. Juni 1999, Rüschlikon, Switzerland Seite 5 Reforming of fossil fuels Temperature/ C allothermal reforming Off-gas burner 800 heat is transferred via a burner, special burner design required Reformer Reaction path high hydrogen content of the reformate 25 % C of HC 75 % H 2 O Off-gas convective heat transfer Reforming reactor Radiative burner H Vol % CO Vol % CO 8-10 Vol % CH Vol % H 2 O Seite 6

4 Reforming of fossil fuels partial oxidation without catalyst at 1300 C C good dynamic behaviour simple construction Temperature / C Reaction path lowest hydrogen content (24-30 Vol%) HC CO O Reforming reactor 2 (0,6-2 Vol%) 2 CO (14-18 Vol%) N 2 H 2 CH 4 (0 Vol%) (43-52 Vol%) O N 2 H2 Seite 7 Reforming of fossil fuels autothermal reforming heat is released in the catalyst bed quick start-up Temperature / C Reaction path good dynamic behaviour temperature peak at the reactor inlet HC O 2 N 2 H 2 O Reforming reactor H 2 (28-32 Vol%) CO 2 (8-10 Vol%) CO (9-11 Vol%) CH 4 (0,2-4 Vol%) N 2 (48-52 Vol%) H 2 O Seite 8

5 Reforming of fossil fuels steam reforming of alcohols, general equation C n H 2n+1 OH + (2n -1) H 2 O 3n H 2 + n CO 2 steam reforming of ethanol C 2 H 5 OH + 3H 2 O 6 H CO 2 R H = 173,5 kj/mol endothermal cracking of ethanol C 2 H 5 OH + H 2 O 4 H CO R H = 255,9 kj/mol exothermal CO-conversion CO + H 2 O H 2 + CO 2 R H = -41,2 kj/mol Seite 9 Bioethanol as fuel for fuel cell vehicles and small scale stationary applications JOR3-CT Partnership: Fraunhofer ISE Universtity of Duisburg Nuvera Reforming of bioethanol, CO-conversion Co-ordination Fine purification by PSA Fuel cell requirements, implementation and dissemination of the results Summary of results: May, 2001 Seite 10

6 Reformer- PEM fuel cell system with ethanol as fuel Seite Reformer und CO-conversion device at Fraunhofer ISE 1. Water/ethanol pump 2. Reformer 3. HT-shift reactor 4. NT-shift reactor 5 5. Gas cooling heat exchanger 1 Reformer C HT-shift C NT-shift C Seite 12

7 Experimental set-up: Reformer: Height: 150 mm Diameter: 121 mm Catalyst Volume: 600 cm 3 Burner: Height: 150 mm Diameter: 81 mm Seite 13 advantages of the porous burner high effective heat conduction of the pore material ( higher then the effective heat conduction of gas) large combustion reaction zone ( flame burner reaction zone thickness 1 mm) lower temperature in the reaction zone homogeneous temperature profile lower NO x - and CO-emission high flame velocity in the pore medium without flame instability ( 8-10 higher then a flame burner) large performance modulation range 1:20 ( flame combustion 1:3) Seite 14

8 catalyst screening name composition sign. operation range nickel-cat. nickel on Al 2 O 3 Ni t react ion ruthenium-cat. ruthenium on Al 2 O 3 Ru t react ion platinum cat. platinum on Al 2 O 3 Pt t react ion palladium cat. palladium on Al 2 O 3 Pd t react ion Perovskite-cat. lanthanum, manganese, cobalt, strontium Pe t react ion nickel-platinum-cat. nickel; platinum on Al 2 O 3 PtNi t react ion nickel-palladium-cat. nickel; palladium on Al 2 O 3 NiPd t reakt ion investigation parameters Temperature: 600; 700; 800 C steam to carbon ratio: 2; 3; 4 pressure: 2; 5; 9 bar gas hourly space velocity: sl educts /(l cat h) Seite 15 operation parameters of the Fraunhofer ISE-Reformer Operation load [%] Porous burner temperature [ C] Temperature of the fixed catalyst bed [ C] Pressure 7,3 7,3 [bar] S/C ratio 4 4 [mole H2O /atom C ] Reformer ethanol inlet stream 3,45 10,36 [mole/h] Enthalpy stream of the ethanol 1,19 3,57 [kw] Product gas stream 42,89 128,9 [mole/h] Hydrogen stream of the product gas 14,90 44,63 [mole/h] Enthalpy stream hydrogen reformer 1,00 3,00 [kw] Burner hydrogen stream 7,5 22 [l N /min] Enthalpy stream hydrogen burner 1,35 3,96 [kw] Burner exhaust stream 23,7 64,3 [l N /min] Seite 16

9 Ni Pd Pt Ru Pe Pt Ni NiPd catalyst screening T = 700 C S/C = 4 selection of Nicatalyst H 2 -yield [(mole/h) H2 /(mole/h) Eth. ] 1 0,9 0,8 0,7 0,6 0, pressure [bar] Seite 17 Ni catalyst T = 700 C p = 2 bar influence of S/C S/ C-ratio 4 3 0,5 1,0 8,7 10,9 16,4 18,4 71,2 70,5 H2 CH4 CO2 CO 68,5 2,4 2 14,0 13,9 0,0 10,0 20,0 30,0 40,0 50,0 60,0 70,0 80,0 molar fractionl [%,dry] Seite 18

10 Ni catalyst 4 4,3 19,3 67,7 T = 700 C p = 9 bar influence of S/C higher pressure due to PSA H2 CH4 CO2 CO S/ C-ratio 3 2 7,7 7,3 8,8 10,3 10,3 18,5 17,4 61,5 65,1 0,0 10,0 20,0 30,0 40,0 50,0 60,0 70,0 80,0 molar fraction [%,dry] Seite 19 temperature top temperature middle temperature bottom CO content HTS Fe-oxide-catalyst GHSV = 4000/h S/C = 4 temperature [ C] , ,23 2,03 3 2,5 2 1,5 1 0,5 CO content [mole %] pressure [bar] 0 Seite 20

11 temperature top temperature middle temperature bottom CO content LTS , ,14 0,12 Cu/Zn-catalyst GHSV = 4000/h S/C = 4 temperature [ C] ,087 0,086 0,10 0,08 0,06 0,04 CO content [mole%] 0, pressure [bar] 0,00 Seite 21 CH4 CO CO2 H2 H2O Results of reformer and CO-shift device S/C = 4 p = 9 bar With CO fine purification: Reformate suitable for PEM- fuel cell gas composition [mole%] ,7 10,3 38,5 45,4 42,4 40,5 41,7 43,4 13,6 14,9 1,2 0,1 1,1 1,1 1,2 Reformer HT-shift LT-shift CH4 CO CO2 H2 H2O Seite 22

12 Summary Summary Hydrogen generation from biogenic ethanol is attractive due to - good availability, - competitive costs, - easy realisation of reforming process Research of at Fraunhofer ISE: - development of a compact steam reformer with preheating of liquid reformer feedstream (with burner exhaust gas) and of the air for the burner (with the reformer product gas) - development of a porous burner with stable combustion for offgas, methane, or ethanol - optimisation of heat losses and performance Outlook: - reduction of volume and weight of the reforming unit - reduction of start-up time - further improvement of performance - cost reduction - longtime-operation to show catalyst stability Seite 23 Outlook 5 kw Fuel processor unit for stationary electricity generation Source: Nuvera Fuel Cells Europe, Milan, methanol reformer Seite 24

13 Thank you very much for your attention! Seite 25