Study On Pseudo-component Materials Of Combustible Solid Waste Pyrolysis And Gasification With TGA And Macro-tGA

In recent years, the amouts of municipal solid waste(MSW) in China have been keeping increasing at great rates, which results in terrible environmental problems and great waste of sources. Waste to energy technologies, based on the clean and efficient thermochemical conversion for combustible solid waste(CSW), are vital and necessary. However, it brings modelling, design and operation of thermochemical treatment systems a huge challenge for a large variety in CSW composition and differences in thermal behavior of CSW components.The pyrolysis and gasification characteristics of 9 pseudo-component materials of CSW including cellulose, hemicellulose, lignin, starch, pectin, poly Ethylene(PE), poly Styrene(PS), polyethylene terephthalate(PET) and polyvinyl chloride(PVC) were investigated by a thermogravimetric analyzer(TGA) and Macro-TGA in this paper, respectively. Comparison of pyrolysis behavior of pseudo-components on TGA and MacroTGA was performed. The discrete distributed activation energy method was applied to analyze the kinetics of each thermal decomposition process. Finally, pseudo-components method was proposed to describe the characteristics of thermochemical conversion process of CSW.The results showed that lignin had mass loss all over the temperature range of 200~1000oC, while other materials played at a narrow range. The process of thermal decomposition at CO2 atmosphere can be devided into two stages: the first stage derived from devolatilization which was identical to the process of pyrolysis; the second stage involved Boudouard reaction(C(s) + CO2â†'2CO), which happened above 700 oC. Lignin and pectin with high fixed carbon content had significant mass loss above 700 oC in their gasification process. It was found that DTG peak temperature of pyrolysis process in Macro-TGA was 30 to 60 oC higher than those of TGA due to the influence of heat and mass transfer. The main way of heat transfer was radiation in Macro-TGA. The quantitative relationship of DTG peak temperatures between Macro-TGA and TGA could be describled as Tmacro-TGA=TTGA+(68.832-0.0717TTGA).Kinetic analysis of thermal decomposition process showed that the distribution of activation energy for each material corresponded to its DTG curves. The thermal decomposition process of the pesudo-components with relatively simple composition, such as cellulose, PE, PS and PET, could be described by one 1st-order reaction. Comparison between the activation energy distributions of lignin’s and pectin’s pyrolysis process and gasification process showed that the activation of Boudouard reaction was about 321kJ/mol with the fixed pre-exponential factor of 2.2?1013s-1.A new pseudo-component method was proposed, in which the pyrolysis or gasification of CSW could be re-expressed by overlap of individual pyrolysis or gasification of its pseudo-components. This method was test and verified by pyrolysis and gasification of poplar stem, Chinese cabbage and orange peel with TGA and Macro-TGA. The results suggested the method was effective within a certain error.