Research On Combustion Characteristics Of Municipal Solid Waste In Circulating Fluidized Bed Incinerator

Technology of Circulating Fluidized Bed (CFB) Incineration has gradually become an important method to deal with Municipal Solid Waste (MSW). In order to grasp the whole combustion process of MSW in CFB, and to provide theoretical support to optimize design of CFB incinerator, combustion characteristics of MSW in CFB was studied through experiment results and theoretical analysis in this thesis.The first part of this thesis is research on basic combustion characteristics, including element analysis, industrial analysis and thermalgravity analysis, and some plastics and paper are selected as samples. It is concluded through the research that MSW contains much volatile and is easy to get burnt. Basic research also includes fluidization experiment on a cold rig, and it is found that MSW moves up and down only inside the dense zone due to its large radius. Experiment of combustion is also carried out for further investigation.The second part is devaporization model of one single MSW particle, and the physical and chemical changes of a particle are concretely described before it is ignited. It is concluded that MSW finishes its course of devaporization when moving up and down in the dense zone, and the gaseous productions move up to reach the velocity of air as soon as they are emitted out. The light and fragile MSW, such as paper and leaf, are considered to bypass their movement in the dense zone and move up to get the velocity of the air once they are feed into the furnace.Another part is the proposition of 3-parameter model and the conception of "Intensity of Combustion and Diffusion", the latter describing the combustion rate of the gaseous productions. Two more parameters are proposed to modify heat transfer coefficients between air flow and the wall. The temperature distribution of the whole bed can be solved once the 3 parameters are determined. Experimental data can be used to fit out the 3 parameters. The 3-parameter model agrees with experimental data quite well and can also fit data from a real CFB incinerator. The last part of this thesis is research on combustion characteristics of real CFB incinerator. The man difference between real CFB incinerator and the experimental stage is that real incinerator has much circulating bed materials in it which contains much carbon, and the fraction of carbon combustion is much bigger than that of MSW combustion. So the changes of MSW composition and shape do not take much effect on the working status of the incinerator. This is the reason why CFB technology fit MSW procession very well and should be generalized.