Study On Release Of Typical Pollutants Characteristics For Co-disposal Solid Waste In Fluidized Bed Boiler

With the development of economy,our country’s solid waste generation has increased sharply,and the market for hazardous waste disposal is in great demand.In this regard,the industrial kiln co-processing technology gradually developed in recent years has become an important way for solid waste disposal.The fluidized bed boiler is the main type of industrial kiln.Its co-processing of solid waste is still in the preliminary experimental exploration stage.The experimental foundation is weak and lacks engineering practice.The corresponding technical standards have yet to be formulated.Therefore,it is necessary to carry out research on the release characteristics of typical pollutants in the co-processing of solid wastes by fluidized bed boilers,and to provide theoretical and technical support for the co-processing of solid wastes(especially hazardous wastes)in fluidized bed boilers.In this paper,the fluidized bed boiler co-processing solid waste is studied by the laboratory simulation test and field engineering test.Laboratory simulation experiments explored the volatile characteristics of heavy metals Pb,Cd,Zn,As and the degradation characteristics of organic pollutants benzene and p-dichlorobenzene.In engineering tests,antibiotic bacteria residues were selected for co-processing on a large fluidized bed boiler.The release characteristics of typical pollutants(heavy metals and dioxins)and conventional pollutants in the process of co-processing were analyzed,and their environmental risks were analyzed.Finally,combined with the results of heavy metal simulation tests,an analysis was conducted to verify the law of migration and transformation of heavy metals in the fluidized bed boiler.Research indicates:(1)Under laboratory simulation conditions,no matter the initial form of three kinds of heavy metals—Pb,Cd,Zn is oxide,chloride or sulfide,and As existing in the form of sulfide,their volatilization rate increases with temperature and time gradually increasing.When the combustion temperature exceeds 825℃ and the residence time is90 minutes,the volatilization rates of Pb,Cd,Zn,and As all reach more than 60%,which is easy to exist in boiler fly ash or flue gas.Through engineering test analysis and verification,the heavy metals Pb,As and Zn are mainly distributed in the fly ash,the distribution rate is more than 81%;followed by slag;while the boiler flue gas emissions are minimal,the highest is only 0.55%;the distribution rate of Pb,As and Zn in desulfurized gypsum is also low,Pb and As are almost absent.Heavy metal Cd is easy to exist in fly ash or flue gas.Other heavy metals V,Cr,Mn,Co,Ni,Cu,Mo and Sn are also easy to migrate to fly ash,followed by slag,desulfurized gypsum and boiler flue gas distribution rate are low.(2)Under laboratory simulation conditions,750℃～975℃,the thermal degradation rate of organic pollutant benzene is lower than p-dichlorobenzene.At a temperature above 825℃ and a residence time of 5s,the thermal degradation rate of benzene only reaches 99.95%,while p-dichlorobenzene reaches 99.99%;the thermal degradation rate of p-dichlorobenzene meets the requirements of pollution control standards for hazardous waste incineration.Organic solid waste of containing p-dichlorobenzene and thermal stability grades lower than p-dichlorobenzene can be fully degraded in the fluidized bed boiler.(3)The co-processing of antibiotic bacterial slag in the fluidized bed boiler has no significant impact on the stability of the boiler’s operating conditions.However,there are some environmental risks in the process of collaborative disposal of boiler flue gas.The co-processing of antibiotic bacterial slag increases the emission concentration of heavy metal Zn in boiler flue gas,and the emission concentration of CO and HF exceeds the standard limit of pollution control standards for hazardous waste incineration,so measures should be taken to reduce its concentration.