Study On MSW Combustion Characteristics And A New CFB Incineration Technology

Municipal solid waste (MSW) has become a serious environmental problem besetting each country. Because of its advantage of maximum volume/quantity reduction and energy recovery, MSW incineration has received wide application in the developed countries. With rapid development of the economy, MSW incineration has been adopted or paid attention to by more and more cities in China. Therefore, how to ensure efficient and clean combustion of MSW becomes an emergent subject which needs further research.This dissertation is composed of three main parts:Ⅰ. Study on the fundamental combustion characteristics of typical combustible components of MSW.Based on the basic hypothesis that each stage of MSW combustion indicates one part of independently reacting material and the corresponding kinetic parameters do not change within the range of experiment temperature, a consecutive combustion kinetic model of MSW was set up and the kinetic parameters of main typical combustible components of MSW were gained through thermogravimetric analysis. The TG and DTG curves regressed on the basis of the model give good agreement with the experimental results over the temperature range of room temperature to 1000℃. Furthermore, the combustion characteristics (including combustion efficiency, devolatilization characteristics and char combustion ), the emission of main gas pollutants (CO, NO, HCl,dioxins) and the effect of operating conditions (including such parameters as excess air, bed temperature and moisture content etc. ) on combustion and pollutants emission were also investigated.Ⅱ. Study on the fundamental characteristics of pipe-distributed gas fluidized bed.The pressure drop characteristics and flow evenness of pipe distributor were studied through theoretical analysis and experiments. The theoretical calculationagrees well with the experimental results. The hydrodynamic characteristics of pipe-distributed fluidized bed,such as minimal fluidizing velociy, bed material pressure drop ,critical pipe interval and the mixing of bed materials and model wastes ,were investigated through cold test. Test shows that the air unevenness in pipe distributed fluidized bed is helpful to the longitudinal mixing of bed materials and wastes. Based on the movement characteristics of solids in pipe-distributed fluidized bed, the bed is divided into two regions, moving region and fluidized region. The hydrodynamic model of pipe-distributed fluidized bed was built up in each region by mass and momentum balance analysis. The general movement regulation of gas and solids in pipe-distributed fluidized bed was calculated and analysed.Ⅲ. Design and Experimental Research of pilot pipe-distributed fluidized bed incinerator.A large scale pilot pipe-distributed fluidized bed incinerator to dispose crude MSW was designed and experimented. Experiments indicated that the novel fluidized bed incinerator had good performance in residue discharging and stable combustion. Under appropriate working conditions, high bed temperature and high combustion efficiency (greater than 96%) can be obtained, and at the same time the pollutants emission, such as SO2,HC1 , NO,dioxins ,heavy metal,can reach or overreach the National emission control standard for MSW incineration.