Biomass Gasification : Fundamentals, Experiments, and Simulation

Biomass gasification has received tremendous research attention all over the world because (a) biomass is abundant, diverse, renewable, and environmentally friendly, (b) the produced biogas/syngas is clean, versatile, efficient, and easily controllable, and (c) the system used is generally simple. This book aims to present up-to-date research on biomass gasification. The content of this book is divided to three parts or sections: the fundamentals of biomass gasification as presented in chapters 1 to 4, experimenting of biomass gasification as presented in chapters 5 and 6, and simulation of biomass gasification as presented in chapters 7 to 8. In chapter 1 (An introduction to biomass), biomass is introduced, and these mainly include biomass resources, biomass and energy, biomass and environment, benefits of biomass, etc. In chapter 2 (Biomass properties), the properties of biomass are introduced, and these include structural compositions (cellulose, hemicellulose, lignin, starch, extractives, proteins, etc.), physical properties (moisture content, particle size, bulk density, porosity, etc.), chemical properties (elemental compositions, chemical compositions, heating value, etc.) and the other properties (thermal conductivity, ignition temperature, specific heat, etc.). In chapter 3 (Biomass gasification technologies), biomass gasification technologies are classified and introduced according to the gasification agents used (air, oxygen, steam, hydrogen, supercritical water, carbon dioxide and the combination of the above gases), and some factors that have significant impacts on gasification technologies (or performances) are also discussed. Then the emerging gasification technologies (microwave gasification, solar gasification and plasma gasification) using new heat sources are also detailed, and the effects of heat source on biomass gasification are also discussed. In chapter 4 (Biomass gasifiers), the main gasifier structures are introduced, and these include fixed bed gasifiers (updraft and downdraft), fluidized bed gasifiers (bubbling fluidized bed, circulating fluidized bed and dual fluidized bed), entrained flow gasifiers (Koppers-Totzek (K-T) gasifier, shell gasifier and Gas Schwarze Pumpe (GSP) gasifier and Colin gasifier). The other gasifier structures are also presented, and these include solar gasifier, microwave gasifier and plasma gasifier, etc. In chapter 5 (High-temperature gasification of biomass), the effects of physical and chemical properties of biomass on high-temperature gasification are analyzed, and these mainly include high-temperature pyrolysis of biomass, thermal cracking of biomass tar, and high-temperature gasification of biomass char. In chapter 6 (Supercritical water gasification of biomass), the properties of SCW (supercritical water) are detailed and the effects of different operating parameters on CE (carbon conversion efficiency) and GE (gasification efficiency) are summarized. The operating parameters include feedstock characteristics, biomass concentration, gasification temperature, reactor pressure, residence time and catalyst types and concentration. In chapter 7 (Simulation of biomass gasification using thermodynamic equilibrium model), the two thermodynamic equilibrium models of stoichiometric thermodynamic equilibrium models and non-stoichiometric equilibrium models (using Gibbs free energy minimization approach) are initially introduced, and the simulation results obtained from biomass gasification using thermodynamic equilibrium models based on Aspen Plus are then presented. In chapter 8 (Simulation of biomass gasification using intrinsic reaction rate submodel), the numerical simulation of biomass gasification using the intrinsic reaction rate submodel was introduced. The kinetic model for char-gas reaction as well as the intrinsic kinetic data for various biomass materials are detailed. A CFD (computational fluid dynamic) model based on the intrinsic kinetics is developed for biomass entrained flow gasification, and the effects of operating conditions including gasification temperature, equivalence ratio, CO2/biomass mass ratio and average particle size on the gasification performances in a lab-scale entrained flow reactor are investigated. Multi-objective optimization of biomass gasification based on response surface method is then studied to improve the gasification performances. Hopefully, the content of this book can supply a helpful guide to the up-to-date research on the fundamentals, experimental, and simulation of biomass gasification.