Oxifuel combustión for CO2 capture. Application of computacional fluid dynamics techniques

The overall combustion behaviour for coals of different rank was experimentally and numerically studied in air and oxy-fuel conditions in an entrained flow reactor. High CO2 concentrations seemed to affect volatile yield and nitrogen distribution, and also the subsequent char reactivity. To obtain similar or better ignition and combustion properties under oxy-firing conditions to those attained in air, the oxygen concentration in the CO2 and H2O(v) mixture must be about 30%. During oxy-fuel combustion, lower NO emissions were produced in comparison with air-firing conditions, although an increase on fuel-N conversion to NO was observed when increasing the oxygen concentration. The experimental findings related to coal burnout and NO emissions were used to test the accuracy of the CFD model developed for oxy-coal combustion. The CFD model predicted accurately oxy-coal combustion in the entrained flow reactor, and it was a useful tool for describing the differences in temperature, species concentration and burning profiles, during the combustion of different coals in both air an oxy-firing conditions.