Numerical simulation and experimental analysis on nitrogen and sulfur oxides emissions during the co-combustion of Longyan anthracite and sawmill sludge

Abstract

The cold flow, co-combustion, SO2 and NO emissions’ simulation of dried sawmill sludge (DSS) and Longyan anthracite (LYA) in a CFB pilot device were implemented by using Euler-Euler method, the emissions of SO2 and NO were studied in experiments. The cold flow simulation results showed that air-particle phases finally reached stable flow conditions and backflow occurred in the pilot device. The coal mono-combustion simulation results indicated that when the combustion calculation was stable, the maximum furnace temperature tended to be stable. The co-combustion simulation results were conformed to the relevant combustion theory. The distributions of gas component concentrations of O2, CO and CO2 were reasonable in the furnace. Molar concentrations of CO, CO2, SO2 and NO in dense zone of co-combustion were higher than those of firing LYA separately, outputs of SO2 and NO were accelerated in co-combustion, both of which indicated that the addition of DSS could strengthen and promote the combustion of LYA. Both the simulation and experiment results showed that SO2 and NO mainly released during the early combustion stages, SO2 emission in co-combustion were all lower than that in LYA mono-combustion. In this research, NO concentration was far below the national emission standard. The reasons for low NO emission were deduced.