Combustion of mechanically agitated lumpy solid fuels
Project Number 377
Within this research project the effect of mechanical agitation and local cooling on the thermal conversion of non-spherical fuel particles within a moving bed will be investigated through experiments and numerical simulation. The aim is to predict the influence of operational parameters (stoking rate, heat extraction, air flow) and currently not sufficiently identified physical fuel properties (particle geometry, local bulk porosity) on the combustion of lumpy biomass in grate incineration plants of arbitrary design. For this purpose, a very recently developed and in its application unique CFD/DEM simulation tool for reacting, moving assemblies of thermally thick non-spherical particles will be employed.
At first DEM simulations are used to compute the effect of mechanical agitation, local cooling and the particle geometry on the overall conversion time, the resulting temperatures of flue gas and solid fuels, the heat fluxes, and the emission of pollutants (especially carbon monoxide) in a well-defined generic system. The aim is to prove the predictive reliability of the simulation tool prior to an application on combustion systems of industrial scale.
Simultaneously, missing experimental data is obtained to successively cover each essential sub-process involved in the thermal conversion of fuel particles. The experiments are carried out in one single experimental rig, in which all relevant aspects of reacting particle assemblies can be studied isolated as well as in direct interaction with each other. Well defined conditions and a good accessibility for measurements are assured and the effort for a systematic variation of fuel and operational parameters stays in an economical reasonable scope. Due to the compliance with minimum dimensions and fuel quantities the results obtained are directly transferable to decentralized small scale combustion units.
Finally the verified CFD/DEM code will be used to simulate the conversion of biomass in a grate combustion system.
The project is funded by the German Federal Ministry of Economics via the AiF (funding no. 17949 N). It is carried out from December 2013 to May 2016 at Bochum University (LEAT). The VGB technically supports the investigations via the European Working Group Biomass and the European Technical Committee Use of Renewables and Distributed Generation.