Pyrolysis Gas Formation Characteristics During Microwave Pyrolysis Of Lignite

In recent years, high quality coal resources decline sharply while the consumptionincreases and the environmental conditions go down gradually. Then lignite with largereserve has gained extensive attention. But low heat value, high moisture andeasy self-ignition make it utilization efficiency very low. So study of cleanly andefficiently utilization of lignite mean a great deal to alleviate the scarce problem ofenergy and environment stress. Pyrolysis of lignite has much technological superiority,such as low energy consumption, short pyrolysis time, high conversion rate and cleanand green, which makes it has great research value.The conventional pyrolysis experiment was performed on Dongsheng lignite tostudy the effects of heating method, pyrolysis temperature and coal species on pyrolysisgas formation characteristics. Microwave pyrolysis experiment was also carried out tostudy microwave power, coal species and proportion of char added to coal on pyrolysisgas formation characteristics.Conventional pyrolysis of lignite experiment showed that more high heating valuegas was obtained under isothermal heating pyrolysis in less time which makes it a morepreferable method than pyrolysis via programmed temperature. The yield of pyrolysisgas and heating value reached the maximum when the temperature was700℃, with3418Kcal/m3for heating value. The concentration of CO, CO2, CH4, CnHm and H2was20.2%,19.9%,19.1%,0.9%and39.8%respectively.Microwave pyrolysis of lignite experiment showed that pyrolysis time reduceddramaticly, pyrolysis gas yield firstly increased then remained nearly unchanged, andthe heating value ranged from2900to3100Kcal/m3while microwave power andproportion of char went up. The concentration of CO, CO2, CH4, CnHm and H2was31.0%,7.1%,6.5%,0.3%and55.1%respectively, when the microwave was3000W.When the microwave power was1500W and the ratio of char and lignite was2:10, theconcentration of CO, CO2, CH4, CnHm and H2was28.2%,11.3%,9.3%,0.4%and 50.7%.Compared to isothermal heating pyrolysis of lignite, more H2and higher yield ofpyrolysis gas was obtained during microwave pyrolysis of lignite while pyrolysis timereduced dramaticly, which made the latter an energy-saving and efficient pyrolysismethod.