Validation of CFD-models for non-stoichiometric oxycoal combustion

To compensate the drawback of high flue gas recirculation rates specific for oxyfuel processes, a new concept based on staged combustion, called controlled staging with non-stoichiometric burners (CSNB) was investigated. A combination of over- and sub-stoichiometric burners avoids inadmissible high flame temperatures even with oxygen concentrations up to 40 vol.-% in the oxidant. The non-stoichiometric burners are arranged in such a way that the overall stoichiometry at the combustion chamber outlet is slightly over-stoichiometric similar to conventional combustion processes, so that full burn out is secured. This concept aims at a more efficient oxyfuel process due to the decreasing effort in the recirculation loop and a new designed, more cost effective, steam generator. For further process optimization of the CSNB concept and the adjacent steam generator layout are validated CFD simulations urgently required. This paper shows first steps in validation of the CSNB combustion concept against state of the art CFD codes. The CFD code was optimized for oxyfuel combustion including a new char combustion and gas radiation model. Experimental investigations and CFD modelling are showing good agreement in concerns of temperature, CO and CO₂ profiles. However the prediction of the oxygen concentration differs significantly between experiment and simulation.