The SNCR(selective non-catalytic reduction) denitrification technology was applied on a 600 t/d MSW(municipal solid waste) incinerator to control the NOx emission.Numerical simulation on mixing process of urea solution and flue gas in the SNCR system was conducted by using the Fluent software.The influence of such factors as temperature

NSR(normalized stoichiometric ratio)

jet velocity and droplet sized on NOx removal efficiency and ammonia leackage was discussed.The simulation results agreed well with the experimental data

indicating the simulation was reliable.The best NOx removal efficiency was obtained between 960 ℃ and 1 000 ℃.The NOx removal efficiency can reach 60% when the NSR equaled 1.8 and increased slowly when the NSR was larger than 1.6.The simulation results showed that

at fixed NSR and injection flow

the NOx removal efficiency first rose then decreased and finally went up again with an increase in droplet size.The ammonia leackage decreased with an increase in both droplet size and temperature

and the best droplet size was 100 μm.The great difference between the simulation and experimental data of ammonia leackage was mainly due to the adsorption of slipped ammonia by fly ash.The adsorbed ammonia by fly ash was within range of 40 μg/g to 90 μg/g.