Biomass gasification in a 100kW fast internal circulating fluidised bed gasifier

Authors: J. W. Brown, R. M. Dobbs, S. Devenish, I. A. Gilmour
Publication: New Zealand Journal of Forestry, Volume N.Z.J.For. 2006, Issue N.Z.J.For. 51(2) 2006, pp 19-22, Aug 2006
Publisher: New Zealand Institute of Forestry

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Abstract: At the University of Canterbury a 100 kW Fast Internal Circulating Fluidised Bed (FICFB) gasification system has been built, commissioned and is currently operating to characterize the product gas under a range of conditions. This system was chosen for its advantages over fixed bed gasifiers and was based on the successful design originally developed by the Vienna University of Technology. It incorporates two closely coupled fluid bed stages, a bubbling bed for gasification and a fast circulating bed for combustion. This duality provides a medium calorific value producer gas suitable for use as a fuel in a gas engine or gas turbine. Steam gasification is used in the bubbling fluid bed at approximately 800 °C to form a product gas which is rich in hydrogen. Residual char is transferred with bed material to the circulating fluid bed, where it is combusted along with LPG to heat the bed material. The hot bed material is circulated back to the gasification stage providing heat for the endothermic gasification reactions. Currently the gas is being directly burnt in an afterburner but will require cleaning and removal of tars before it can be burnt in a gas engine for generating electricity. The results will be used to select suitable gas cleaning and tar removal technology and provide a database for scale up and computer modelling in support of the wider program. Variable conditions tested include the biomass to steam ratio, sand and char circulation rate, circulating bed material temperature and bubbling bed temperature. Moisture content and fuel type will be additional variables tested in future work but currently dry uniform moisture fuel is being used. Characteristics of the product gas measured include the gas composition and tar composition.

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