AVT - Research - Research project

Development of a modelling approach to simulate the chemical conversion processes in the combustion chamber of a biomass-fired power plant

Instead of fossil fuels biomass can be combusted in order to generate electric energy and heat. Long transportation distances for the biomass can be avoided by reasonably located small plants and thus the carbon dioxide balance of the process can be kept almost neutral. In the plants analysed in the project at hand, used wood is burnt corresponding to the german Erneuerbare-Energien-Gesetz (EEG). The biomass is combusted in a moving grate furnace. Primary air and recirculated exhaust gas are supplied through the grate and enable drying, degasification, and char burnout of the fuel. Secondary air is injected into the combustion chamber above the grate and combustible gases which have been released during degasification are burned. Gas cleaning includes SCR denitrogenation by injection of urea, de-dusting in a cyclone and desulphurisation with calcium hydroxide.

The plant is modelled by a combination of thermochemical and flow simulation tools. The combustion chamber is simulated in CFD which yields information about the mixing conditions. These conditions are reproduced by the thermochemical cell-model which enables detailed prediction concerning the distribution of volatile heavy metal compounds into the different ash streams.