A review of cleaning technologies for biomass-derived syngas
TL;DR: In this article, a review of the technologies for removing contaminants from raw syngas is presented, which are classified according to the gas temperature exiting the cleanup device: hot, cold, and warm.
Abstract: Syngas from gasification of carbonaceous feedstocks is used for power production and synthesis of fuels and commodity chemicals. Impurities in gasification feedstocks, especially sulfur, nitrogen, chlorine, and ash, often find their way into syngas and can interfere with downstream applications. Incomplete gasification can also produce undesirable products in the raw syngas in the form of tar and particulate char. This paper reviews the technologies for removing contaminants from raw syngas. These technologies are classified according to the gas temperature exiting the cleanup device: hot (T > 300 °C), cold (T < ∼100 °C), and warm gas cleaning regimes. Cold gas cleanup uses relatively mature techniques that are highly effective although they often generate waste water streams and may suffer from energy inefficiencies. The majority of these techniques are based on using wet scrubbers. Hot gas cleaning technologies are attractive because they avoid cooling and reheating the gas stream. Many of these are still under development given the technical difficulties caused by extreme environments. Warm gas cleaning technologies include traditional particulate removal devices along with new approaches for removing tar and chlorine.
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TL;DR: In this paper, an assessment on the fundamentals such as feedstock types, the impact of different operating parameters, tar formation and cracking, and modelling approaches for biomass gasification is presented.
Abstract: Biomass gasification is a widely used thermochemical process for obtaining products with more value and potential applications than the raw material itself. Cutting-edge, innovative and economical gasification techniques with high efficiencies are a prerequisite for the development of this technology. This paper delivers an assessment on the fundamentals such as feedstock types, the impact of different operating parameters, tar formation and cracking, and modelling approaches for biomass gasification. Furthermore, the authors comparatively discuss various conventional mechanisms for gasification as well as recent advances in biomass gasification. Unique gasifiers along with multi-generation strategies are discussed as a means to promote this technology into alternative applications, which require higher flexibility and greater efficiency. A strategy to improve the feasibility and sustainability of biomass gasification is via technological advancement and the minimization of socio-environmental effects. This paper sheds light on diverse areas of biomass gasification as a potentially sustainable and environmentally friendly technology.
779 citations
TL;DR: In this paper, a review of the progress in gasification techniques and key generation pathways for biofuel production, process design and integration and socio-environmental impacts of biofuel generation are discussed, with the goal of investigating gasification-to-biofuels credentials as a sustainable and eco-friendly technology.
478 citations
TL;DR: In this article, the options of converting sewage sludge to energy and fuel via three main thermochemical conversion processes namely pyrolysis, gasification and combustion are reviewed, and various alternative approaches deserving further consideration, such as the incorporation of pre-processing and co-utilization, are discussed.
Abstract: Sewage sludge, the inevitable by-product of municipal wastewater treatment plant operation, is a key issue in many countries due to its increasing volume and the impacts associated with its disposal. Thermochemical processing offers a new way of managing sewage sludge, not only by providing effective volume reduction, but also enabling transformation of carbon-rich organic fraction into valuable energy and fuel. Owing to some unique properties, sewage sludge differs from other solid fuels such as lignocellulosic biomass and coal, making its thermochemical conversion application somewhat complicated and challenging. This paper reviews the options of converting sewage sludge to energy and fuel via three main thermochemical conversion processes namely pyrolysis, gasification and combustion. The fundamental aspects of sewage sludge and its behaviour in each of thermochemical process are summarised. The challenges in adopting thermochemical conversion technology in sewage sludge management are addressed, and various alternative approaches deserving further consideration, such as the incorporation of pre-processing and co-utilisation, are discussed.
411 citations
TL;DR: In this paper, the authors reviewed and evaluated some aspects related to tar formation, laboratory and industrial methods and technologies for its reduction-removal, as well as research and development in this area.
Abstract: One of the main problems that happen during biomass gasification is tar formation, which could make this technology unsuccessfully from a commercial point of view. Tar content present in syngas defines its application, considering that limits - according to desired application - can be very demanding. There are two ways to overcome this problem: by optimizing gasification operation conditions and removal of tar from gas through in-situ (primary methods) or post-gasification (secondary methods) treatments. This way, multiple technologies have been developed considering the balance between efficiency and economy of the process, besides being (ecofriendly) environmentally acceptable. Some aspects related to tar formation, laboratory and industrial methods and technologies for its reduction-removal, as well as research and development in this area are reviewed and evaluated in this paper.
372 citations
TL;DR: In this paper, a comprehensive review of cold gas and hot gas syngas cleanup for major contaminants (tar, NH3, H2S, HCl and trace metals) is presented.
343 citations
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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.
1,352 citations
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 article, the authors present the major issues concerned with biomass combustion with special reference to the small scale fluidized bed systems (small to pilot scale). Problems have been identified, mechanisms explained and solutions have been indicated.
1,012 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
TL;DR: In this paper, the technical feasibility and economics of biomass integrated gasification-Fischer Tropsch (BIG-FT) processes in general, identifies most promising system configurations and identifies key R&D issues essential for the commercialisation of BIG-FT technology.
Abstract: This paper reviews the technical feasibility and economics of biomass integrated gasification–Fischer Tropsch (BIG-FT) processes in general, identifies most promising system configurations and identifies key R&D issues essential for the commercialisation of BIG-FT technology. The FT synthesis produces hydrocarbons of different length from a gas mixture of H2 and CO. The large hydrocarbons can be hydrocracked to form mainly diesel of excellent quality. The fraction of short hydrocarbons is used in a combined cycle with the remainder of the syngas. Overall LHV energy efficiencies, 1 calculated with the flowsheet modelling tool Aspenplus, are 33–40% for atmospheric gasification systems and 42–50% for pressurised gasification systems. Investment costs of such systems ( 367 MW th ) are MUS$ 280–450, 2 depending on the system configuration. In the short term, production costs of FT-liquids will be about US$ 16/GJ. In the longer term, with large-scale production, higher CO conversion and higher C5+ selectivity in the FT process, production costs of FT-liquids could drop to US$ 9/GJ. These perspectives for this route and use of biomass-derived FT-fuels in the transport sector are promising. Research and development should be aimed at the development of large-scale (pressurised) biomass gasification-based systems and special attention must be given to the gas cleaning section.
841 citations