Experimental And Numberical Studies On Mixing Between Reducing Agent And Boiler Flue Gas

Nitrogen oxides are some of important atmospheric pollutants discharged by the boilers. Developing with the emission regulations by the national and local governments, post-combustion NOx control technologies are being in urgent need. Selective Non-Catalytic Reduction (SNCR) of NOx is suitable for China's national conditions because of low cost, convenience of installation and easy hybridization with other NOx control techniques. The good mixing of N-agent and flue gas is one of the important factors to guarantee higher NOx removal efficiency in the SNCR applications.Focused on the evaporation and diffusion of reductant solution in the furnace in the SNCR process and the methods to improve mixing performance in the furnace, numerical simulations by Fluent software are done to research the evaporation and diffusion of a single jet of liquid reductant in high temperature furnace. Flow velocity, flow temperature, droplets velocity, the injecting rate of liquid droplets flow rate and droplets size were concerned and their effects on droplets evaporation and diffusion were analyzed.The cold testes were carried out on the reductant injections of SNCR based on a waste grate incinerator. The effects on the mixing of droplets injection velocity and the injection rate are experimentally researched by the heat balance method. And the evaporation process of reductant droplets in the furnace was researched by the way of adding water and measuring the water distribution.Finally, the effects of the injectors arrangement on the mixing in the furnace were studied based on the waste incinerator and the optimal case of injectors arrangement was achieved. The simulation calculations were carried out aiming at the optimal case by CFD and Chemkin software. The NOx removal efficiency of SNCR operation is predicted, which could provide some guidance on the practical application.