Foundation Research On Selective Non-Catalytic Reduction Process

NO emitting from coal combustion in power plant is one of major sources of air pollution which affect environment seriously. Selective non-catalytic reduction (SNCR) process is a technology which reduce NOx availably. Simple system and lower cost is the strong suit of SNCR process. This paper studied SNCR process by numerical simulation and test drawing on the predecessors.To sdudy the influence of mixing process, SNCR process on lab-reactor was simulated by Chimkin. The plug flow reactor (PFR) model and the Zwietering model were used respectively to simulate the SNCR process in an entrained flow reactor (EFR). Comparison of simulation and experimental results shows that the mixing process of central jet flow and annular jet flow can be described by the Zwietering model. Below 900℃, the reaction rate is lower and the SNCR process is mainly controlled by the reaction dynamics and the mixing process has little effect on the SNCR process. Above 950℃, the reaction rate increases. The SNCR process is mainly controlled by the mixing process. With the increasing of the mixing time, above 950℃, the denitration efficiency of SNCR process decreases, and the temperature window of SNCR process becomes narrow.Additives have obvious effect on improving denitration efficiency of SNCR process at lower temperature. This paper put forward and simulated a way using biomass-gasified gas as additives of SNCR process. It proved that biomass-gasified gas can be used as additives of SNCR process and improve denitration efficiency of SNCR process at lower temperature. The three main components of biomass-gasified gas are H2,CH4 and CO, of which H2 and CH4 have obvious effects on temperature window while CO has less effect. Additives improve the denitration reaction by increasing the OH radical.To studies Thermal DeNOx and NOxOUT process, a thermal horizontal reactor was biulded. The influence of the molar ratio of NH3/NO, mix process and so on was studied. Experimental results showed that with the increase of the molar ratio of NH3/NO, NO removal efficiency rises. As the flux of carrier gas was increased, NO removal efficiency rises because of the improvement of mix process. Thermal DeNOx and NOxOUT process have different temperature window. The temperature window of NOxOUT process is higher than Thermal DeNOx process. But the NO removal efficiency is lower because of decomposition of urea and gasification of water from urea solution. In allusion to the neglect of decomposition of urea in numerical simulation of SNCR process, an overall reaction model considered decomposition of urea was proposed. The influence of different urea decomposition model on NO removal efficiency was compared by simulating SNCR process in CRF (Combustion Research Facility). It showed that the model considered decomposition of urea is more accurate. SNCR process with different molar ratio of NH₃/NO and temperature, as well as SNCR process in reducing atmosphere was studied using the urea decomposition model.