1.0. Introduction 4044 2.0. Biomass Chemistry and Growth Rates 4047 2.1. Lignocellulose and Starch-Based Plants 4047 2.2. Triglyceride-Producing Plants 4049 2.3. Algae 4050 2.4. Terpenes and Rubber-Producing Plants 4052 3.0. Biomass Gasification 4052 3.1. Gasification Chemistry 4052 3.2. Gasification Reactors 4054 3.3. Supercritical Gasification 4054 3.4. Solar Gasification 4055 3.5. Gas Conditioning 4055 4.0. Syn-Gas Utilization 4056 4.1. Hydrogen Production by Water−Gas Shift Reaction 4056

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Synthesis of transportation fuels from biomass: chemistry, catalysts, and engineering.

This paper provides an updated review on fast pyrolysis of biomass for production of a liquid usually referred to as bio-oil. The technology of fast pyrolysis is described including the major reaction systems. The primary liquid product is characterised by reference to the many properties that impact on its use. These properties have caused increasingly extensive research to be undertaken to address properties that need modification and this area is reviewed in terms of physical, catalytic and chemical upgrading. Of particular note is the increasing diversity of methods and catalysts and particularly the complexity and sophistication of multi-functional catalyst systems. It is also important to see more companies involved in this technology area and increased take-up of evolving upgrading processes. © 2011 Elsevier Ltd.

Review of fast pyrolysis of biomass and product upgrading

Progress and recent trends in biofuels

Modeling chemical and physical processes of wood and biomass pyrolysis

Tar formation is one of the major problems to deal with during biomass gasification. Tar condenses at reduced temperature, thus blocking and fouling process equipments such as engines and turbines. Considerable efforts have been directed on tar removal from fuel gas. Tar removal technologies can broadly be divided into two approaches; hot gas cleaning after the gasifier (secondary methods), and treatments inside the gasifier (primary methods). Although secondary methods are proven to be effective, treatments inside the gasifier are gaining much attention as these may eliminate the need for downstream cleanup. In primary treatment, the gasifier is optimized to produce a fuel gas with minimum tar concentration. The different approaches of primary treatment are (a) proper selection of operating parameters, (b) use of bed additive/catalyst, and (c) gasifier modifications. The operating parameters such as temperature, gasifying agent, equivalence ratio, residence time, etc. play an important role in formation and decomposition of tar. There is a potential of using some active bed additives such as dolomite, olivine, char, etc. inside the gasifier. Ni-based catalyst are reported to be very effective not only for tar reduction, but also for decreasing the amount of nitrogenous compounds such as ammonia. Also, reactor modification can improve the quality of the product gas. The concepts of two-stage gasification and secondary air injection in the gasifier are of prime importance. Some aspects of primary methods and the research and development in this area are reviewed and cited in the present paper.

A review of the primary measures for tar elimination in biomass gasification processes

Tar formation under different biomass gasification conditions

The State of Hawaii is interested in converting the large volume of agricultural residues, principally sugarcane bagasse, that is generated in the state into transportation fuels. One of the technologies that is currently being evaluated is steam explosion as a pretreatment for conversion of the bagasse into ethanol. In order to identify the optimum conditions of the steam explosion cycle, a range of operating temperatures (188–243°C) and residence times (0.5–44 min) were used to pretreat bagasse in a 10 l batch reactor. The analytical results were also used to evaluate the “reaction ordinate” concept. The exploded bagasse samples were examined as to total mass recovery, weight loss by water extraction, composition of water extracts, total sugar recovery, and conversion of the polysaccharide of the exploded biomass to monosaccharide by a cellulosic enzyme mixture. Steam explosion followed by enzymatic saccharification was found to be an effective pretreatment for converting biomass into monosaccharides. However, the total sugar recovery, and thus the ethanol “potential”, of the process was relatively insensitive to changes in reaction conditions due to the trade-off between xylose recovery and glucose recovery. Furthermore, it was found that the reaction ordinate concept was not universally valid for the variety of sample characteristics examined in this study.

Steam explosion of sugarcane bagasse as a pretreatment for conversion to ethanol

Inorganic constituents of ash in biomass fuels are responsible for equipment failure and operating difficulties in thermochemical energy conversion facilities. Alkali metals, in the presence of chlorine and sulfur, are the leading contributors to this problem. Banagrass, a herbaceous species being considered for use as a dedicated energy crop, contains high levels of potassium and chlorine. Some inorganic elements are water soluble and the opportunity exists to remove them by mechanical dewatering and leaching as part of the feedstock preparation process. Laboratory-scale equipment, representative of processes employed in the commercial extraction of sugar from cane, was used to prepare banagrass fuel treatments that included two degrees of comminution (coarse and fine) and two dewatering schemes (mechanical dewatering only, and a multi-step process consisting of initial mechanical dewatering followed by a water rinse and second dewatering). The treatment that included fine comminution and multi-step dewatering resulted in a fuel with substantial reductions in ash (45%), K (90%), Cl (98%), S (55%), Na (68%), P (72%) and Mg (68%). The coarse comminution and multi-step dewatering scheme also resulted in reductions, but generally with 10–20% more of the initial constituent mass retained in the fuel. These two treatments produced fuels containing 0.11 and 0.23 kg (Na2O + K2O) GJ−1, respectively, with corresponding ash fusion temperature estimates of 1250 and 1075°C. By comparison, bagasse, the fibrous by-product of sugar cane, contains 0.06 kg (Na2O + K2O) GJ−1 and has an estimated ash fusion temperature of roughly 1500°C. Banagrass subjected to the most severe treatment, fine comminution with multi-step dewatering, should produce a boiler fuel with characteristics similar to those of bagasse.

Removal of inorganic constituents of biomass feedstocks by mechanical dewatering and leaching

Gasification of four biomass feedstocks (leucaena, sawdust, bagasse, and banagrass) with significantly different fuel-bound nitrogen (FBN) content was investigated to determine the effects of operational parameters and nitrogen content of biomass on the partitioning of FBN among nitrogenous gas species. Experiments were performed using a bench-scale, indirectly heated, fluidized-bed gasifier. Data were obtained over a range of temperatures and equivalence ratios representative of commercial biomass gasification processes. An assay of all major nitrogenous components in the gasification products was performed for the first time, providing a clear accounting of the evolution of FBN. Important findings of this research include the following:  (1) NH3 and N2 are the dominant species evolved from fuel nitrogen during biomass gasification; >90% of FBN in feedstock is converted to NH3 and N2; (2) relative levels of NH3 and N2 are determined by thermochemical reactions in the gasifier; these reactions are affecte...

Release of fuel-bound nitrogen during biomass gasification

Parametric tests on catalytic reforming of tars produced in biomass gasification are performed using a bench-scale, fluid-bed catalytic reformer containing a commercial nickel-based catalyst. The product gas composition and yield vary with reformer temperature, space time, and steam: biomass ratio. Under certain catalytic tar reforming conditions, the gas yield increases by 70%; 97% of the tars are cracked into gases; and benzene and naphthalene, the predominant tar species, are virtually eliminated from the product gas.

C.M. Kinoshita

Papers

Tar formation under different biomass gasification conditions

Steam explosion of sugarcane bagasse as a pretreatment for conversion to ethanol

Removal of inorganic constituents of biomass feedstocks by mechanical dewatering and leaching

Release of fuel-bound nitrogen during biomass gasification

Effect of Reformer Conditions on Catalytic Reforming of Biomass-Gasification Tars