Study On The Microwave Pyrolysis Of The Low Rank Coal Under Different Environmental Atmospheres

The microwave pyrolysis of the low rank coal is a new technology, which solves theutilization problems of coal cleaning conversion. On basis of experiments, this paperinvestigated the characteristics of microwave pyrolysis under different environmentalatmospheres, respectively N2, CO2, CH4, H2and recycle gas. The characteristics ofmicrowave pyrolysis products, which were produced in different factors by the low rankcoal, were under test. This paper studied the microwave powers, pyrolysis time, gasflow rates and coal particle size on the influence of product yield and composition,analysed the mechanism of pyrolysis, scientifically put forward and further verifies thatthe coal-recycle gas co-pyrolysis technology was feasible, and it will be a new researchdirection for coal thermal processing.Researches showed that: by integrating different environmental atmospheres, themicrowave pyrolysis technology condition reached its better when the microwavepower was800W, pyrolysis time was40min, the sample size was15mm, and the rate offlow was0.4L/min. When the microwave pyrolysis was under N2environmentalatmosphere, the solid product yield was65.8%, the liquid products yield was18%; whenthe microwave pyrolysis under CO2environmental atmosphere, the solid product yieldwas62%, the liquid products yield was20.6%; when the microwave pyrolysis underCH4, H2and recycle gas environmental atmosphere, the solid product yield were62.8%,61.6%and61.4%, the liquid products yield were23.4%,25.8%and26%.A similar law was observed under different environmental atmospheres that as themicrowave powers and pyrolysis times increased, the pyrolysis solid productiondecreased, in contrast to the liquid production. It decreased under CO2, CH4, H2andrecycle gas environmental atmosphere along with the reduction of the pyrolysis solid production, the liquid product production was deceased with the coal particlesizeincreasing; When the environmental atmosphere was CO2, as the rate of flowaccelerates, the pyrolysis solid production drops, in opposite to the liquid productproduction. When the environmental atmosphere was CH4, with the rate of flowspeeding up, the pyrolysis solid production and the liquid product production went upreversely.After evaluating the pyrolysis solid, liquid and gas products production andcomposition, it could be concluded that the prime choice for the low rank coal withdifferent environmental atmospheres to achieve co-pyrolysis effect was environmentalatmosphere of H2, followed by environmental atmospheres of recycle, CH4, CO2,and N2respectively. H2and recycle gas environmental atmospheres could all realize thehydrocracking of the low rank coal, improved the production rate of coal tar, and madethe tar light. Therefore, the technology of the microwave pyrolysis of the low rank coal,in which gas was produced by microwave coal pyrolysis, and partially cycled to themicrowave pyrolysis, it was economic, energy saving and feasible.