Title: CFD simulation of ash deposit formation in fixed bed biomass furnaces and boilers

Authors: Martin Forstner, Georg Hofmeister, Markus Joller, Jonas Dahl, Markus Braun, Stefan Kleditzsch, Robert Scharler, Ingwald Obernberger

Addresses: Austrian Bioenergy Centre GmbH, Inffeldgasse 21 b, 8010 Graz, Austria. ' Austrian Bioenergy Centre GmbH, Inffeldgasse 21 b, 8010 Graz, Austria. ' Austrian Bioenergy Centre GmbH, Inffeldgasse 21 b, 8010 Graz, Austria; Graz University of Technology, Institute for Resource Efficient and Sustainable Systems, Inffeldgasse 21 b, 8010 Graz, Austria. ' Austrian Bioenergy Centre GmbH, Inffeldgasse 21 b, 8010 Graz, Austria; Graz University of Technology, Institute for Resource Efficient and Sustainable Systems, Inffeldgasse 21 b, 8010 Graz, Austria. ' Fluent Deutschland GmbH, Birkenweg 14 a, 64295 Darmstadt, Germany. ' Fluent Deutschland GmbH, Birkenweg 14 a, 64295 Darmstadt, Germany. ' Austrian Bioenergy Centre GmbH, Inffeldgasse 21 b, 8010 Graz, Austria; Graz University of Technology, Institute for Resource Efficient and Sustainable Systems, Inffeldgasse 21 b, 8010 Graz, Austria; BIOS BIOENERGIESYSTEME GmbH, Inffeldgasse 21 b, 8010 Graz, Austria. ' Austrian Bioenergy Centre GmbH, Inffeldgasse 21 b, 8010 Graz, Austria; Graz University of Technology, Institute for Resource Efficient and Sustainable Systems, Inffeldgasse 21 b, 8010 Graz, Austria; Technical University of Eindhoven, Department of Mechanical Engineering, Section Process Technology, Den Dolech 2, P.O. Box 513, 5600 MB Eindhoven, the Netherlands; BIOS BIOENERGIESYSTEME GmbH Inffeldgasse 21 b, 8010 Graz, Austria

Abstract: In order to describe and predict the formation of ash deposits in biomass fired combustion plants, a mathematical model is being developed and implemented into the CFD code Fluent® as a post processing tool. At the present state of development the model covers the release of coarse ash particles and ash-forming vapours from the fuel bed, the transport to furnace and boiler surfaces and the deposition of particles and vapours. Changes in the flue gas composition due to chemical reactions are considered by performing thermodynamic equilibrium calculations in order to determine the gas phase composition. The build-up of the deposit layer depending on wall temperature, deposit porosity and chemical composition is also taken into account. First results of modelling deposit formation for the furnace and fire tube of a grate fired combustion unit (boiler capacity 440 kWth) show plausible results but have yet to be validated.

Keywords: CFD; biomass combustion; deposit formation modelling; computational fluid dynamics; ash deposits; fixed bed furnaces.

DOI: 10.1504/PCFD.2006.010034

Progress in Computational Fluid Dynamics, An International Journal, 2006 Vol.6 No.4/5, pp.248 - 261

Published online: 09 Jun 2006 *

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