Experimental Study On No_x Release Rule Of Different Waste Components During Thermal Conversion

With the rapid development of China’s economy,the production of municipal solid waste（MSW）has increased year by year.MSW incineration has become the fastest growing technology in waste treatment.Kinds of pollants are produced during the MSW incineration,and NO_x is relatively harmful.The nitrogen content in MSW is relatively high.The conversion processes and mechanism of nitrogen in MSW incinerators are quite different from those in coal incinerators.NO_x generated during combustion not only causes air pollution,but also destroys ecology.The existing denitration technology has problems such as large investment,large ammonia escape,and easy poisoning of the catalyst.Threrfore,it is economic and convenient to control nitrogen in the combustion process.In order to better control the emission of NO_x emissions in the combustion process,it is necessary to study the conversion mechanism of nitrogen from different fuels.Although some studies have carried out some research on the nitrogen conversion,the mechanism research on the MSW nitrogen transformation is not enough.Four typical components of MSW were selected in this study and the formation of NO_x and its precursors was studied experimentally with respect to the changes of additives and atmosphere.Three different atmospheres include O₂,CO₂ and H₂O（0%,2%,5%and 10%respectively）.The release concentration of NO_x from paper,wood,soybean powder and nylon during thermal conversion was studied.The four materials were paper,biomass,kitchen waste and organic polymer respectively.In different gas atmospheres,the release concentration of NO_x varies greatly.It is beneficial for inhibiting the formation of NO_x by reducing the concentration of O₂ and increasing the concentration of CO₂and H₂O properly.When the content of O₂ is 5%,the content of CO₂ is 5%,and the content of H₂O is 2%,the release of NO_x is the least.The effect of lignin on the thermal conversion process was studied by the method of thermogravimetric analysis combined with Fourier infrared spectroscopy,and the changes of NH₃,HCN and NO_x content were measured.The main nitrogen-containing gases in the pyrolysis process of soybean were NH₃ and HCN.NH₃ mainly comes from the direct pyrolysis of amino group in soybean,while HCN mainly comes from the secondary pyrolysis of volatile matter.It was found that the content of NH₃ increases due to the impediment of soya protein,and HCN decreases due to the competitive reaction after adding lignin.NH₃ content in nylon is low due to the inhibition of amino separation,while HCN content increases.When soya was co-combusted with lignin at a rate of 3:1,the NO_x emission was reduced to 28.1%of the calculated value.The nitrogen-containing gases were analyzed online by tube furnace-spectrophotometry at different temperatures,and soybean chars were analyzed by X-ray photoelectron spectroscopy.It was found that the higher the temperature,the higher the HCN/NH₃ ratio.N-6 is the main nitrogen component in char.N-X decreases,OH radicals increase,and HCN increases with the increase of temperature.