Improving the asymmetric phenomenon effects on the combustion characteristics in an opposed-fired pulverized coal boiler

Numerical investigations were performed on an opposed-fired boiler to better understand the formation of the asymmetric phenomenon and its effects on the combustion characteristics. It is revealed that with the increasing of the inlet Reynolds numbers, the in-furnace flow and temperature fields evolve from symmetry to asymmetry under the symmetric combustion conditions. Nonlinearity was elaborated to explain this phenomenon. Three asymmetric combustion modes were proposed to optimize the deflected flowfield. The final optimal combustion pattern was established via comprehensive consideration of the general air stoichiometric ratio and reduction zone heights. Compared to the original symmetric combustion mode, asymmetric air disturbance creates better internal flowfield recirculation and improves the combustion performance, which obtains a significant NOx reduction from 369.16 mg/Nm(3) to 216.16 mg/Nm(3) and lowers the carbon content in fly ash from 3.465% to 2.07%, respectively.