Characteristic Studies On Middle And Low-temperature Pyrolysis Of Municipal Household Garbage

Owing to the shortage of energy and resources all over the world and theemergence of different utilization of municipal waste, recent years, the traditionalwaste disposal such as simple collection and direct burying have been graduallysubstituted by some new methods which not only can restrain the yield of trash butalso can effectively utilize waste as one kind of resource. By introducing thedomestic and overseas disposal status of MSW (municipal solid waste), andcomparing the advantages and disadvantages of some disposal methods, such aslandfill, compost, incineration and pyrolysis, it proves that the pyrolysis technologyis a main disposal method of MSW in the future, and that studies on this filed hasbecome an important direction to be developed.To simulate the pyrolysis characteristics of real facility, an externally heatedfixed-bed pyrolysis furnace was built. Compounds made by typical pyrolysiscomponent of municipal solid waste were taken as the testing materials. While thepyrolysis temperature rising from 300℃ to 700℃, its effects on temperature field ofpyrolyzed waste, pyrolysis time, pyrolysate distribution, removal rate of volatilefraction have been studied by a series pyrolysis tests.The change rules of pyrolysis gas components, as important pyrolysates, has adirectly influence on the use of pyrolysis gas. Both the content of pyrolysis gascomponent and its average heat value vary with the pyrolysis temperature as definiterules. During the examination of present research, namely the pyrolysis temperaturefrom 300℃ to 700℃, the heat value of pyrolysis gas varied from 5.4 MJ/m3 to15.13MJ/m³. The main components of pyrolysis gas were H₂, CO, CH₄, CO₂, C₂H-4,C₂H₆. The pyrolysis gas also concluded other components such as NOX, HCl, H₂S,NH3, O2, C3, C4, C5, and hydrocarbon, the content of which increased with thepyrolysis temperature rising.Elemental analyses and industrial analyses of semi-coke, the pyrolysis remains,were also proposed in this paper. The heat value of semi-coke was between20.99MJ/kg and 24.7MJ/kg, so that it can be used as solid fuel. However, thecomponents of semi-coke changed with the pyrolysis temperature, whichsimultaneously affected the combustion characteristic of semi-coke.Analyzing the whole process of waste pyrolysis, it s apparently indicated thatthe pyrolysis product can provide total energy for waste pyrolysis,and there were noother auxiliary heat source needed.Considering the trait of municipal solid waste, the complicated heat transferprocess of waste pyrolysis was simplified to a pure heat conduction process in thispaper by using equivalent conduction method, accordingly, the heat transfer modelused to obtain the temperature field of pyrolysis material in the fixed-bed reactorwas built. Comparing with the test data, it was proved that this heat transfer model ispartly practical.