Numerical Simulation Of NO_X And SO_X Pollutant Formation And Distribution In Waste Incinerator

As the production of municipal solid waste（MSW）increases,incineration technology has been widely applied in China.It gradually becomes a main way for MSW treatment because it can realize harmlessness,reduction and resource utilization.However,a large amount of NO_X and SO_X gas pollutants will be generated in the process of incineration,which endangers the environment and people’s health.In order to solve this problem,this paper establishes a nitrogen and sulfur model regarding the incinerator bed,which is based on the self-developed software BASIC.Five nitrogen gaseous pollutants NO,NH₃,HCN,HNCO,N₂O and five sulfur gaseous pollutants SO₂,SO₃,H₂S,CS₂,COS are involved in the model.The reliability of the model is verified by comparing with the experimental results.In addition,the changes of the relevant reaction rates are also predicted,the effects of different chemical reactions on different NO_X and SO_X gases production are studied from the perspective of the chemical mechanism.In this way,the main chemical reactions that promote and inhibit the formation of NO_X and SO_X can be determined.Furthermore,the productions of different nitrogen and sulfur gases are studied under different initial parameters（initial temperature,pressure,particle size,primary air volume）.And the optimal operating conditions for reducing the generation of NO_X and SO_X pollutants are predicted which can provide suggestions for the actual operation of MSW incinerator.The simulation results show that:（1）When the initial temperature is 1373 K,the production of NO is the lowest,the oxidation reaction of NH₃ and the reduction reaction between NO and H₂ are the main control reactions of NO,while the production of SO₂ and SO₃ presents downward trend with the increase of initial temperature;（2）The pressure has little influence on the formation of the most nitrogen and sulfur gases.However,the decline time of all gases is advanced with varying degrees with the increase of pressure;（3）For different average particle sizes,the production of NO precursors（NH₃,HCN,HNCO）gradually decrease with the increase of particle size,and the production of NO decreases first and then increases when the particle size increases.When the particle size is 30 mm,the production of NO is the lowest.And the production of sulfur pollutants especially for SO₃ increases with the increase of particle size.（4）The production of NO,N₂O and SO₃ increases with the increase of primary air volume.The precursors NH₃,HCN,HNCO and other sulfur compounds are oxidized with a larger primary air volume,which results in the downward trend.