The Conversion Characteristics Of By-product Contaminant During The Gasification Of Municipal Solid Waste

As one of the most promising technologies for the development of municipal solid waste energy recycling,the fundmental researches on gasification are becoming more and more improvement.However,it is not well known about the generation of environmental pollutants in the gasification process.In order to promote the establishment of the environmenta-friendly garbage gasification production system,in order to study the effective control of mechanism scientifically and lay the necessary theoretical bases for the maximum inhibition of pollutants,the paper mainly investigates the conversion characteristics and the factors of various pollutants in the process of gasification.Respectively,the three units for the study,such as refuse gasification process,modified process and purification system,and the effects of operating factors,such as temperature,gasification factor and upgrading catalyst,on the formation and transformation of various pollutants during gasification of synthesis gas were investigated in details.Combined with the gas purification unit for the removal of various types of pollutants,and with reference to the relevant pollutant emission standards for the gasification of synthetic gas production system,the paper scientifically analyzes the potential of the pollution characteristics.The Research indicates:During the gasification of municipal solid waste,it will produce various types of environmental pollutants.Among them,the N and the S elements contained in the municipal solid waste are directly converted to the gas components H2S and NH3 with the occurrence of thermal decomposition reaction,and the heavy metals including Cu,Pb,Zn,Cu and Hg in the municipal solid waste are volatilized in different degrees,which are associated with the synthesis gas in gaseous or liquid form respectively.In addition,a large number of phenolic substances are also present in the synthesis gas.These pollutants directly hinder the safe use of syngas;(1)The conversion characteristics of by-product contaminant during the gasification of municipal solid waste are mainly affected by the gasification temperature,and the influence of the oxidant and water vapor is also limited by the temperature conditions.The increase of gasification temperature promotes the volatilization of heavy metals and promotes the formation of NH3,but inhibites the H2S and the phenolic compounds.Oxygen can convert part of the H2S gas oxidation into SO2,but the oxidation of NH3 is limited.The addition of steam supply has different inhibitory effects on all kinds of pollutants;(2)In the modified process,the pollutants are changed correspondingly by the catalyst application and the modification elements.With the increase of catalytic modified temperature,NH3 is showed an increasing trend,and H2S increases firstly and then decreases.Meanwhile,the concentrations of heavy metals Cd,Pb,Zn,Cu and Hg decreases and the decomposition of phenol is promoted,the concentration generally descends.The modified catalysts show different effects on the transformation of pollutants due to the difference of components.When the catalyst No.1 is used,the concentration of H2S,NH3,SO2 and NOx is lower than that of catalyst No.2,however,the concentrations of Cu,Pb,Zn,Cu and Hg are higher than that of the catalyst with No.2.From the perspective of reducing the occurrence of phenol,the modified effects of the No.1 catalyst is good,but when the temperature reaches 750?,the No.1 catalyst losts the advantage of the modified;(3)The removal of phenols was 100%when the pollutants are purified by a purification system consisting of water treatment,alcohol washing and activated carbon adsorption.The concentration of phenolic substances is in line with the "Integrated Emission Standard for Air Pollutants"(GB16297-1996)non-organized emission monitoring concentration limition.SO2 and NOx gas emissions meet the emission standards for pollutants.The concentration of H2S and NH3 gas emissions is higher than the corresponding factory boundary emission standards,and the purified gas emissions need to set a 15 meters high exhaust pipe.The adsorption rate of activated carbon on acidic gas H2S is very high,and the removal effects are obvious.The average purification efficiencies of Cu,Pb,Zn,Cu and Hg are above 50%after the purification unit treatment;(4)The contents of five heavy metals Cr,Pb,Zn,Cu and Hg in the residue do not exceed the limits of the second class environmental quality standards of the soil inorganic pollutants in the " Soil Environmental Quality Standard”(GB 15618-2008).