Reforming of Model Gasification Tar Compounds
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Reforming of Model Gasification Tar Compounds Agata Łamacz Æ Andrzej Krzton´ Æ Andrea Musi Æ Patrick Da Costa
Received: 14 July 2008 / Accepted: 26 September 2008 / Published online: 7 November 2008 Ó Springer Science+Business Media, LLC 2008
Abstract Gasification tar, causing various process equipment problems, is an undesirable product during biomass gasification therefore catalysts for its decomposition are needed. Toluene as a model tar compound was tested on steam reforming reaction using ceria-zirconia based Ni and Co catalysts. Keywords Biomass Toluene steam reforming Ni/CeZrO2 Co/CeZrO2
1 Introduction Beside of hydropower, solar, and wind, biomass is found to be a very good source of renewable energy. Its main advantage over fossil fuels is neutral emission of greenhouse gas such as CO2. Due to increasing petroleum price, biomass process is getting more and more eligible [1, 2]. Biomass gasification has attracted a lot of interest by producing a gas rich in CO and H2 which is used for chemicals production, Fischer-Tropsch and methanol synthesis [3]. Among CO and H2, gasification products are CO2, water, nitrogen (in case of air application), small amount of methane, and higher hydrocarbons. The impurities present in the gas consist of ash, volatile alkali metals, and tar, which is a complex mixture of aromatics [1]. Depending on A. Łamacz (&) A. Krzton´ Polish Academy of Sciences, Centre of Polymer and Carbon Materials, Marii Curie-Sklodowskiej 34, 41-819 Zabrze, Poland e-mail: [email protected] A. Musi P. D. Costa Laboratoire de Re´activite´ de Surface, Universite´ Pierre et Marie Curie, CNRS UMR 7609, case 178, 4 place Jussieu, 75252 Paris, France
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the type of gasifier and feedstock characteristics, concentrations of gas impurities range from 5 to 30 g/N m3 for particles [4] and from 0.5 to 30 g/N m3 for volatile alkali metals [5]. In fluid bed gasifiers tar content varies from 5 to 75 g/N m3 [6, 7], what exceeds the maximum allowed for diesel engines and gas turbines. Tar can condense or polymerize to more complex structures in the pipes, filters or heat exchangers, causing process equipment problems (as choking and attrition), decreasing total efficiency, and increasing the cost of the process [3]. Because of the prohibition of direct gas stream utilisation, gas purification systems are needed. Tar removal technologies including cracking and mechanical separation using scrubbers or cyclones take place downstream the gasifier (hot gas cleaning). Tar treatment inside the gasifier may eliminate the need for downstream cleanup. For both tar removal technologies, catalytic steam reforming is very promising [3] however it is a endothermic process and the external source of heat is needed [8]. This process usually involves tar components oxidation on supported nickel-based catalyst, with the use of steam, at the temperatures above 650 °C. Tar steam reforming leads to CO and H2, enriching gas from biomass gasification in these components. The reaction pathway is described by reactions
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