Possible utilization pathways of char from biomass thermochemical conversion: Char as a catalytic filtering medium for tar cracking
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This work investigates the potential of char as catalytic filtering medium for gasification tar cracking. As a first step, chars from representative small-scale gasification plants installed in South-Tyrol (Italy), have been collected, characterized, and compared with chars obtained experimentally under controlled conditions. The results of the characterization show a specific surface area between 352.41 and 427.93 m2/g, higher heating value between 23.04 and 35.73 MJ/kg, and carbon content between 48.03% and 90.60%. As expected, different technologies produced different quality of char. In addition, the preliminary design of a fixed char bed reactor, currently in the setting up phase, is presented. The system will consist of a mixing station for preparing a synthetic tar mixture to be fluxed at controlled flow rate into the char bed reactor. The tar will be collected by means of a tar sampling apparatus and analyzed with a gas-chromatograph before and after the char bed, in order to evaluate the tar cracking effect of the char. The aim is to identify the conditions that maximize the tar-char interactions thus promoting the tar cracking. Moreover, the system will be used to test the effects of the char bed on “real” tar in a pilot scale open-top gasifier.