Numerical Simulation of Simultaneous NO and SO2 Reduction by Reburning

A reaction model including NO reduction by reburning with pulverized coal and SO₂ absorption by CaO is presented. It includes the coal combustion model, which covers coal devolatilisation, combustion of volatiles, and combustion of char. The NO conversion model by reburning includes the formation of NO from fuel nitrogen and the reduction of NO by hydrocarbon, HCN, NH₃ as well as char. Sulfation of CaO is controlled by solid state diffusion through the product layer. The model is validated by comparing the predicted NO and SO₂ emissions with the measurements obtained from simultaneous NO/SO₂ removal experiments in an entrained-flow reactor reburning with pulverized coal together with calcium-based sorbent CaO. Low SR is beneficial for NO reduction, but high SO₂ reduction needs higher SR. It is suggested that the reburn fuel and Calcium-based sorbent CaO should be injected in different area to ensure high efficiencies of NO and SO₂ reduction.