Joachim Scholta, Ludwig Jörissen Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg. Hydrogen Technology

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1 Hydrogen Generation Joachim Scholta, Ludwig Jörissen Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg Hydrogen Technology Hydrogen is considered as a Secondary Energy Carrier In nature, it is observed only in trace amounts therefore, it must be produced from a primary energy source Hydrogen will be used in a (solar) Hydrogen Economy as clean fuel saisonal energy storage intercontinental medium of energy transport raw material for chemical processes ( regenerative Petrochemistry )

2 Hydrogen: Physico-Chemical Data H 2 CH 4 (Natural Gas) C 3 H 8 (LPG) 20 C 0,089 kg/nm 3 0,718 kg/nm3 2,011 kg/nm 3 Boiling 1 bar -252,77 C -161,5 C -42,1 C Heat of combustion 2,995 kwh/nm 3 9,968 kwh/nm 3 25,893 kwh/nm 3 10,8 MJ/Nm 3 35,9 MJ/Nm 3 93,2 MJ/Nm 3 39,4 kwh/kg 141,890 kj/kg 13,9 kwh/kg 55,530 kj/kg 12,88 kwh/kg 50,410 kj/kg Flashpoint 530 C 645 C 510 C Ignition limits 4,1-72,5 Vol% 5,1-13,5 Vol% 2,5-9,3 Speed of combustion 275 cm/sec 43 cm/sec 47 cm/sec Color of flame Invisible Visible Visible Use of Hydrogen in Chemical Industry

3 Hydrogen as Fuel Hydrogen is already today widely used in different technical applications food technology fertilizer oil refineries Hydrogen can be used in a (solar) hydrogen economy as clean fuel seasonal energy storage intecontinental Energy vector chemical raw material ( regenerative petrochemistry ) However: Hydrogen is a rather bulky fuel Fuel Cell System CH 4 + 2H 2 O => 4H 2 + CO 2 (CO) Natural gas nat. gas compress reformer shiftreactor HT a) Reformer-Heating b) cat-burner (thermal utilization) residual gas 9% CO 3% CO shiftreactor NT COcleaner. PEMfuel cell heat 0,5% CO Air (O 2 ) H 2, CO 2 < 0,005%CO E-Energy

4 Liquid fuels Fuel Cell Technology and H2 Purity Increasing efficiency Evaporation Fuel cell types Natural gas Sulphur removal 500 C Conversion to to H 2 and CO C 300 C to Increasing 500 C complexity of fuel processing Shift reaction H 2 and CO 2 CO selective oxidation SOFC Thermally integrated Reformer MCFC Thermally integrated Reformer PAFC, HT-PEMFC CO < 5% PEMFC CO < 10 ppm) 800 C to 1000 C 650 C 200 C 80 C Source: B.C.H. Steele, Nature 99 From coal C + H 2 O CO + H 2 CO + H 2 O CO 2 + H 2 From natural gas CH H 2 O CO H 2 From Electrolysis Hydrogen Production (I) Thermal processes (ISPRA Mark II) 700 C CaBr H 2 O Ca(OH) HBr 200 C 2 HBr + Hg HgBr 2 + H C HgBr 2 + Ca(OH) 2 CaBr 2 + HgO + H 2 O 600 C HgO Hg + 1/2 O 2 H 2 O H 2 + 1/2 O

5 Hydrogen Production (II) Sources natural gas (CH 4 ) LPG (C 3 H 8 ) Alcohols Methanol (CH 3 OH) Ethanol (C 2 H 5 OH) Processes Steam reforming autothermal reforming partial oxidation with or without use of catalyst Gasoline Diesel Reactions Occuring During Processing of Natural Gas Combustion CH O 2 CO H 2 O -802 kj/mole CH 4 + 3/2 O 2 CO + 2 H 2 O -277 kj/mole Reforming CH H 2 O CO H kj/mole CH 4 + H 2 O CO + 3 H kj/mole Shift CO + H 2 O CO 2 + H 2-41 kj/mole Carbon (Soot) Deposition CO + H 2 C + H 2 O +111 kj/mole CO H 2 C + 2 H 2 O -90 kj/mole 2 CO C + CO kj/mole CH 4 C + 2 H kj/mole

6 Poly MW Natural Gas Reformer Refoming = State-of-the-art! KW Scale Natural Gas Reformer H2-production: Dimensions: (dxh) Weight: Volume: 1.5 Nm³/h 250 x 420mm ca. 15 kg 20 l Applications: Micro-KWK in single family homes Decentralized power generation Battery charging

7 Tem peratur / C Steam Reforming Brennerabgas Ref o rm ergas Reaktionsw eg 25% CH 4 75% H 2 O Rauchgas Konvektiver W ärmeübergang Reformierreaktor H 2 (75-78 Vol%,tr) CO 2 (10-12 Vol%,tr) CO (8-10 Vol%,tr) CH 4 (2-5 Vol%,tr) H 2 O B : CH O 2 CO H 2 O -802 kj/mole R : ( C ) CH 4 + ( S ) H 2 O CO + 3 H kj/mole CH H 2 O CO H kj/mole R/B and S/C characterize the reforming process, R/B 1,9, S/C 2 Temperatur / C 1600 Catalytic Partial Oxidation Ref ormergas Reaktionsweg CH 4 O 2 N 2 Reformierreaktor H 2 (24-34 Mol%) CO 2 (0,6-2 Mol%) CO (14-18 Mol%) CH 4 (0 Mol%) N 2 (43-52 Mol%) H 2 O (3-9 Mol%) CH 4 + 1/2 O 2 CO + 2H Strahlungsbrenner -13-

8 Temperatur / C Autothermal Reforming Refo rm erg as Reaktionsw eg Source: Wikipedia: Einteilung der klassischen Reformierverfahren, Copyright 2006 jmsanta CH 4 O 2 N 2 H 2 O Reformierreaktor CH 4 + H 2 O CO + 3 H kj/mole CH 4 + 3/2 O 2 CO + 2 H 2 O -277 kj/mole 2 CH 4 + 3/2 O 2 2 CO + 3 H 2 + H 2 O CO + H 2 O CO 2 + H 2-41 kj/mole 2 CH 4 + 3/2 O 2 CO + CO H 2 H 2 (28-32 Vol%,tr) CO 2 (8-10 Vol%,tr) CO (9-11 Vol%,tr) CH 4 (0,2-4 Vol%,tr) N 2 (48-52 Vol%,tr) H 2 O 100 Steam Reforming: Steam to Carbon Ratio -Thermodynamic equilibrium- Methanumsatz (%) p Ref =1 bar S/C = dn/dt(h 2 O) / dn/dt(ch 4 ) S/C= 4,0 S/C= 3,5 S/C= 3,0 S/C= 2,5 S/C= 2, Reaktionstemperatur ( C)

9 Steam Reforming: Pressure Dependence of CH 4 -Utilization -Thermodynamic equilibrium S/C= 3 Methanumsatz (%) bar 3 bar 5 bar Reaktionstemperatur ( C) -16- CH 4 Reforming Shift Reaction Konvertierung CO + H 2 O --> H 2 + CO 2 c(co): appr. 10 % appr. 0,5 % 2-stage: 1-stage: HT-Shift ( C), Fe/Cr catalyst LT-Shift ( C), Cu/Zn catalyst MT-Shift ( C) Why? High reaction kinetics at high temperatures Good thermodynamic equilibrium at low temperatures - 17-

10 1,4% CO Konzentration (Mol-%,trocken) 1,2% 1,0% 0,8% 0,6% 0,4% 0,2% S/C=0.77 S/C=1 S/C=2 S/C=3 0,0% Reaktionstemperatur ( C) CO + H 2 O CO 2 + H 2 Hight temperature shift at C Low temperature shift at C -18- Gas Composition after Steam Reforming -Thermodynamic equilibrium + reaction kinetic realistic case CH4 CO CO 0 Reformer Shift 1 Shift 2 Temperature Dependence of CO-Concentration after Shift Reaction -Thermodynamic equilibrium- -19-

11 (Fine) Purification of Hydrogen for Use in Fuel Cells Separation of hydrogen Diffusion through selective membranes (e.g. Pd/Ag) Pressure swing adsorption Separation of CO 2 and CO Washing with Amines and Methanization Separation of CO selective oxidation selective Methanization Selective Catalytic Oxidation (PROX) Reformate: H 2, CO 2, CO, H 2 O purified reformate Catalyst Pt, Ru, Au Oxygen (air) Reactions: CO + 1 / 2 O 2 CO 2 H / 2 O 2 H 2 O

12 H 2 - and CO-Content of Autothermal Reformate after Shift 80% 16% H2-Gehalt 70% 60% 14% 12% CO-Gehalt Autotherme Methan- Reformierung H2-Gehalt 50% 40% 30% 10% 8% 6% Nach Shift- Konverter S/C 1,5 TP: 60 C 20% 4% 10% 2% 0% 0% Temperatur / C -22- Comparison of Reforming Processes Autothermal Steam reformer CH 4 + 1,5 H 2 O CH H 2 O 100 EE 100 EE Q: 27 EE Autoth.-Reformer H 2 : 84 EE Q: 49 EE Dampf-Reformer H 2 : 104 EE HT-Shift H 2 : 90 EE Q HT : 2 EE HT-Shift H 2 : 109 EE Q HT : 7 EE NT-Shift H 2 : 96 EE Q HT : 2 EE NT-Shift H 2 : 116 EE Q HT : 5 EE PROX Q HT : 1 EE PROX Q HT : 4 EE H 2 : 90 EE Q NT : 2 EE H 2 : 103 EE Q NT : 17 EE W el : 38 EE W el : 43 EE Brennstoffzelle H 2 -Umsatz: 70 % El. Wirkungsgrad 60 % Q NT : 53 EE Brennstoffzelle H 2 -Umsatz: 70 % El. Wirkungsgrad 60 % Q NT : 39 EE Abgas (H 2 +CH 4 ): 29 EE Abgas (H 2 +CH 4 ): 34 EE -23-

13 Examples for Gas Processing Units in Systems Ballard 200 kw Stationary System

14 Evolution in System Layout First Generation Wasser Zuluft befeuchtet Luft Reformer WT HT-Shift WT NT-Shift WT SelOx WT Brenner Stack 1 Stack Zellen Abluft Rauchgas Luftzuführung Third Generation Wasser Trockene Zuluft Reformer WT Single- Shift Methanisierung WT Stack 60 Zellen Brenner Luft Rauchgas Abluft zur Doppelmantelkühlung Quelle Viessmann (2003) -26- Optimized Gas Processing Concept (Viessmann, 2003) Process Simplification Low temperature operation of the reformer Low CO content But unconverted methane Only a single Shift-stage CO-removal via selective methanization Lower heat release than SELOX, similar temperature to Shift -27-

15 SOFC-Systems are Apparently Less Complex Exhaust Water Heater Reaction Water H O 2 Separator Waste Air Waste Air Condensor Recuperator Water PEM DC AC Stack Cooler Inverter DC SOFC Generator AC Inverter Exhaust with residual H 2 H 2 Humidifier Blower Air Steam Generator CO - Cleaning Compressor Air Desulphurization Blower Fuel Exhaust Compressor Reformer Desulphurization Shift Converter Fuel Source: Siemens Pre Reformer Pre reformed Gas CH CO 4 H O 3H 2 H O 2 H 2 2 CO CO 2 H O / CH 2 4 2,5 30% pre reformed H 2 : 26,26 % CH :17,1 % 4 H 2O : 49,34% CO : 2,94% CO 2 : 4,36% Gas Quelle: FZJ Natural gas

16 Fuel Cell System for Stationary Application Methanee Compressor Pre-reformingg Currentt SOFC Air Compressor Pre-heater Afterburner Vaporizer Water Heat t exchanger Heat Exhaust Example: SULZER SOFC-System

17 Electrolytic Hydrogen Generation H 2 O H 2 + 1/2 O 2 G (l)25 C = -237,141 kj/mole 1,23 V H (l)25 C = -285,830 kj/mole 1,48 V Alkaline Electrolysis conventional Electrolysis advanced Electrolysis Membrane electrolysis Polymer electrolyte High temperature electrolysis Solid state electrolyte Thermodynamics of Water Splitting [kj/mol] Delta H(g) -Delta G (g) -Delta H(liq) -Delta G(liq) T [ C]

18 Losses in an Electrolytic Cell U Z E Anode Cathode i R Ohmic Resistance Concentration of the electrolyte Electrode distance gas bubbles Concentration overvoltage Depletion zone in front of the electrode Activation overvoltage Kinetics of the electrochemical Reaction (oxygen evolution) Electrocatalysis Advanced Alkaline Electrolysis Minimization of Electrode distance Electrodes are in direct contact with the separator (diaphragm) Form of electrodes Diameter of holes in perforated sheets Cathode (hydrogen evolution: 0.5 mm) Anode (oxygen evolution: 1 mm) Form of holes (e.g. conical) Separator / Diaphragm Wettability, thermal Stability Catalytically coated Electrodes Cathode: Nickel (and alloys) Anode: Metal oxides (e.g. Ni Co 2 O 4, LaNiO 3, LaSrCoO 3 )

19 Alkaline Electrolysis (advanced) Alkaline Electrolyzer

20 Membrane Electrolysis Energy Flow in Water Electrolysis heute erwartet

21 Impact of Process Efficiency in a Future Hydrogen Economy Hydrogen technologies will start from a fossil fuel basis The public acceptance of a future hydrogen economy is crucially depending on cost and the impact caused to the environment. Efficient processes will be required for hydrogen generation when using fossil fuels. Emissions of CO 2 and other pollutants during production Total energy efficiency Balancing from well to wheel Only surplus renewables will be available to trigger a hydrogen economy Cost availability Energy- and Material (circular) Flow