Dipl. Ing. Matthias Mayerhofer Technische Universität München ...

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18 Biomass Gasification Figure 9: Langmuir-Hinshelwo and Eley-Riedeal mechanism The Mars-Van Krevelen Mechanism This mechanism is used to describe the kinetics of reactions such as selective oxidation of hydrocarbons and it is more applied for the hydrodesulfurization and NOx removal. Because steam reforming is a highly endothermic reaction the maximum conversion is achieved with high temperature and low pressure and high steam-to-hydrocarbon ratio. Their basic advantage is that their use does not reduce the heating value of the gas. The Mars-van Krevelen mechanism is based on the idea that adsorption of one molecule occurs on top of another molecule which had previously been adsorbed (Ross, 2012). The tar decomposition is significantly affected by the presence of methane due to the catalytic reforming reactions (Hepola,1997b). The basic processes in which they are used are hydrogenation reactions, steam reforming (production of H2 or syngas), and methanation (Sehested,2006). 2.4.4.3 State of the art The basic criteria that a catalyst should fulfill to commercially feasible are listed below (Sutton,2001), (Courson,2000), (Hepola,1997b): 1. Effectiveness in the removal of tars 2. Capability of reforming methane 3. Should provide a suitable syngas ratio depending on the desired application 4. Resistance to deactivation due to carbon deposition, sintering and sulfur poisoning 5. Easily regenerated 6. Resistance to mechanical stresses 7. Inexpensive 8. Compatible with the continuous oxidation and reduction cycles 9. The catalyst life time is also a basic factor that can control the viability of the whole process
Biomass Gasification 19 Groups of Catalysts that have been tested for tar elimination so far (Abu El-Rub,2004): -Fluid catalytic Cracking Catalysts -Alkali metals are less active for carbon conversion and hard to recover (Xu,2010).They are mixed directly into the biomass as it is fed into the gasifier and the char formation is enhanced (Dayton,2002). -Calcinated Rocks (dolomites, olivine etc.) -Olivine -Clay Minerals -Char -Activated Alumina -Metal Based (Nickel and precious metals) -Ferrous metal Oxides
Page 1: Betreuer der Arbeit: Dipl. Ing. Mat
Page 5: Acknowledgements This work was acco
Page 8 and 9: II Content Content Acknowledgements
Page 10 and 11: IV List of Figures List of Figures
Page 12 and 13: VI List of Abbreviations List of Ab
Page 14 and 15: VIII Notation Notation ΔH [Kj/mol]
Page 17 and 18: Introduction 1 1 Introduction The d
Page 19 and 20: Introduction 3 1.2 Tasks The presen
Page 21 and 22: Biomass Gasification 5 2 Biomass Ga
Page 23 and 24: Biomass Gasification 7 Spouted Bed
Page 25 and 26: Biomass Gasification 9 2.2 Gas Clea
Page 27 and 28: Biomass Gasification 11 types of ca
Page 29 and 30: Biomass Gasification 13 Mechanical
Page 31 and 32: Biomass Gasification 15 Partial oxi
Page 33: Biomass Gasification 17 The followi
Page 37 and 38: Nickel Based Catalysts 21 even show
Page 39 and 40: Nickel Based Catalysts 23 The conte
Page 41 and 42: Nickel Based Catalysts 25 ing press
Page 43 and 44: Nickel Based Catalysts 27 3.4 Proce
Page 45 and 46: Iron Based Catalysts 29 4 Iron Base
Page 47 and 48: Iron Based Catalysts 31 Measurement
Page 49 and 50: Iron Based Catalysts 33 The percent
Page 51 and 52: Iron Based Catalysts 35 4.6 Catalys
Page 53 and 54: Iron Based Catalysts 37 Reduction i
Page 55 and 56: Iron Based Catalysts 39 and MgO (Di
Page 57 and 58: Precious Metal Catalysts 41 5 Preci
Page 59 and 60: Precious Metal Catalysts 43 Bimetal
Page 61 and 62: Experiments 45 Table 3: Biomass fee
Page 63 and 64: Experiments 47 6.3.1Experimental Pr
Page 65 and 66: Experiments 49 6.3.2 Tar Sampling M
Page 67 and 68: Results and Discussion 51 7 Results
Page 69 and 70: Results and Discussion 53 7.2 Sampl
Page 71 and 72: Results and Discussion 55 Wet Gas C
Page 73 and 74: Results and Discussion 57 er, the v
Page 75 and 76: Results and Discussion 59 7.3.1. Ef
Page 77 and 78: Results and Discussion 61 The conve
Page 79 and 80: Results and Discussion 63 7.3.3 App
Page 81 and 82: Results and Discussion 65 7.4 Blank
Page 83 and 84: Summary/Outlook 67 The aim is to pr
Page 85 and 86:
References 69 (Aznar,1993) Aznar, M
Page 87 and 88:
References 71 (Hepola,1997b) Hepola
Page 89 and 90:
References 73 (Sarvaramini,2012) Sa
Page 91 and 92:
75 Appendix Appendix A: Iron based
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Dipl. Ing. Matthias Mayerhofer Technische Universität München ...

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