A review of the primary measures for tar elimination in biomass gasification processes
TL;DR: In this paper, a review of the research and development in this area are reviewed and cited in the present paper, and the concepts of two-stage gasification and secondary air injection in the gasifier are of prime importance.
Abstract: 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.
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TL;DR: Hydrogen Production by Water−Gas Shift Reaction 4056 4.1.
Abstract: 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
7,067 citations
TL;DR: In this article, the state of the art in modeling chemical and physical processes of wood and biomass pyrolysis is reported, and the main achievements of numerical simulations are discussed.
1,495 citations
TL;DR: In this article, the main steps of pyrolysis and the composition of the products obtained from each constituent were synthesized and the results were used to predict the reactivity and energy content of these products and evaluate their potential use as biofuels in renewable applications.
Abstract: The conversion of biomass by thermochemical means is very promising for the substitution of fossil materials in many energy applications. Given the complexity of biomass the main challenge in its use is to obtain products with high yield and purity. For a better understanding of biomass thermochemical conversion, many authors have studied in TG analyzer or at bed scale the individual pyrolysis of its main constituents (i.e. cellulose, hemicelluloses and lignin). Based on these studies, this original work synthesizes the main steps of conversion and the composition of the products obtained from each constituent. Pyrolysis conversion can be described as the superposition of three main pathways (char formation, depolymerization and fragmentation) and secondary reactions. Lignin, which is composed of many benzene rings, gives the highest char yield and its depolymerization leads to various phenols. The depolymerization of the polysaccharides is a source of anhydro-saccharides and furan compounds. The fragmentation of the different constituents and the secondary reactions produce CO, CO2 and small chain compounds. For temperature higher than 500 °C, the residues obtained from the different constituents present a similar structure, which evolves towards a more condensed polyaromatic form by releasing CH4, CO and H2. As the aromatic rings and their substituent composition have a critical influence on the reactivity of pyrolysis products, a particular attention has been given to their formation. Some mechanisms are proposed to explain the formation of the main products. From the results of this study it is possible to predict the reactivity and energy content of the pyrolysis products and evaluate their potential use as biofuels in renewable applications.
1,234 citations
Book•
23 Jun 2010
TL;DR: In this article, the authors provide a comprehensive coverage of the design, analysis, and operational aspects of biomass gasification, the key technology enabling the production of biofuels from all viable sources.
Abstract: This book offers comprehensive coverage of the design, analysis, and operational aspects of biomass gasification, the key technology enabling the production of biofuels from all viable sources--some examples being sugar cane and switchgrass. This versatile resource not only explains the basic principles of energy conversion systems, but also provides valuable insight into the design of biomass gasifiers. The author provides many worked out design problems, step-by-step design procedures and real data on commercially operating systems. After fossil fuels, biomass is the most widely used fuel in the world. Biomass resources show a considerable potential in the long term if residues are properly handled and dedicated energy crops are grown. 5 years of the author's research in the area Biomass fuel production First book devoted to Biomass Gasification Includes step-by-design procedures, cases studies and worked out numerical examples
1,169 citations
Cites background from "A review of the primary measures fo..."
...The naphthalene and benzene content of the gas increases with temperature (Devi et al., 2003)....
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...Tar is a complex mixture of condensable hydrocarbons, including, among others, oxygen-containing, 1- to 5-ring aromatic, and complex polyaromatic hydrocarbons (Devi et al., 2003)....
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TL;DR: The analysis indicates that gasification is a technically viable option for the solid waste conversion, including residual waste from separate collection of municipal solid waste, and can have a remarkable effect on reduction of landfill disposal option.
952 citations
Cites background or methods from "A review of the primary measures fo..."
...Anyway, a tar-free gasifier does not exist and tar removal and/or conversion is required in most cases (Devi et al., 2003; Arena et al., 2010)....
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...In the updraft reactors the waste is fed in at the top of the gasifier, and the oxidant intake is at the bottom, so that the waste moves counter-currently to the gases, and passes trough different zones (drying, pyrolysis, reduction and oxidation) successively....
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...…the power gasifier configuration – where the syngas is properly treated to meet the specifications of an internally-fired cycle or a synthesis process – presents a clear distinction of the gas production stage from those of gas cleaning and better utilizes the potential of the gasification plant....
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...A sort of atmospheric moving bed downdraft gasifier is the vertical shaft-furnace proposed by Nippon Steel as ‘‘Direct Melting System’’....
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...…the energy conversion device that can be reasonably utilized, taking into account the technical and economical performance of the cleaning techniques that can be applied inside the reactor (primary measures) and/or downstream of it (secondary measures) (Devi et al., 2003; Arena et al., 2010)....
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References
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TL;DR: In this article, an extensive literature review of the three main groups of catalysts, which have been evaluated for the elimination of these hydrocarbons, are dolomite, alkali metals and nickel.
1,126 citations
TL;DR: In this paper, the costs and technologies involved in an integrated system for the production of electricity from biomass in general and wood in particular are reviewed, and the main conclusions are that wood handling, storage, drying, comminution and screening are well established and present no uncertainties in operation and performance.
992 citations
Book•
01 Jan 2000
TL;DR: In this paper, the authors discuss the linkage between energy and economic, social, environmental, and security issues, and analyzes the contradictions between current patterns of use and objectives in these areas.
Abstract: This report is based on the premise that energy is an essential component of sustainable development of social and economic progress that meets the needs of both present and future generations. The report discusses the linkage between energy and economic, social, environmental, and security issues, and analyzes the contradictions between current patterns of use and objectives in these areas. Key features include reviews of energy resources and technology options from the point of view of sustainability including better end-use efficiency, greater reliance on renewable sources of energy, and next-generation nuclear and fossil-fuel technologies; examination of plausible scenarios for combining various options to achieve a sustainable and relatively prosperous future; and consideration of policy options for producing and using energy in ways that are compatible with sustainable development.
799 citations
TL;DR: In this paper, the catalytic behavior of olivine, a common, naturally occurring mineral containing magnesium, iron oxides and silica, was investigated in a laboratory scale, biomass gasification unit.
Abstract: Naturally occurring catalytic substances are employed in biomass steam-gasification processes to enhance the yield of fuel gas and reduce its tar content by cracking and reforming the high molecular weight organic components. Calcined dolomite is widely used for this purpose; it exhibits good catalytic activity under the operating conditions of the gasifier. However, due to its poor mechanical strength, it gives rise to a large production of fines in a fluidised-bed environment. This work reports an investigation into the catalytic behaviour of olivine, a common, naturally occurring mineral containing magnesium, iron oxides and silica: iron is known to play a positive role in tar decomposition reactions. The gasification runs, performed with a laboratory scale, biomass gasification unit, show that the olivine activity is close to that exhibited by dolomite under comparable operating conditions. Olivine has the additional advantage, however, that its resistance to attrition in the fluidised bed is much greater, similar to that of sand. Parametric sensitivity studies of a gasification process, utilising olivine as the fluidised-bed inventory, indicate an optimum gasification temperature of just above 800°C, and little influence of the steam/biomass ratio in the range 0.5–1.
657 citations
TL;DR: In this paper, the equivalence ratio (from 0.20 to 0.45), temperatures of the gasifier bed (750−850 °C) and of its freeboard (500−600 °C), H/C ratio in the feed, use of secondary air (10% of the overall) in the freeboard, and addition (2−5 wt %) of a calcined dolomite mixed with the biomass used as the feedstock.
Abstract: Biomass gasification with air in a bubbling fluidized bed is studied in a small pilot plant. Variables analyzed are equivalence ratio (from 0.20 to 0.45), temperatures of the gasifier bed (750−850 °C) and of its freeboard (500−600 °C), H/C ratio in the feed, use of secondary air (10% of the overall) in the freeboard, and addition (2−5 wt %) of a calcined dolomite mixed with the biomass used as the feedstock. Using advanced tar and gas sampling and analysis methods, the gas composition and tar content in the gas are determined and their variation with the operation parameters is given. A statistical analysis of the effects of the gasification variables is also here presented.
617 citations