Gas Characteristics Of Yunnan Xianfeng Lignite By Microwave Pyrolysis Coupling Gasification

With the sharp reduction of China’s high-quality coal resources,the rational utilization of lignite resources with relatively abundant reserves and low metamorphic degree has attracted wide attention both at home and abroad.Lignite accounts for 45%of the world’s coal reserves.However,because of its high water content,low calorific value,high chemical reactivity and flammability,it is limited to use as raw material.Pyrolysis and gasification of lignite is one of the effective ways for the conversion and utilization of lignite resources.It is of great significance to alleviate the shortage of energy supply and reform the energy structure of China.Compared with the traditional heating methods,microwave heating has been widely used in various fields of technology and science because of its advantages of high efficiency,fast heating,selective heating,energy saving,easy control and no pollution.In this paper,the pyrolysis characteristics of the Xianfeng lignite in Yunnan were studied by means of microwave heating.The effects of microwave stirrer,microwave power,coke ratio and coal particle size on the production rate,yield and content of pyrolysis gas were investigated to improve the efficiency of microwave pyrolysis of lignite.At the same time,the characteristics of gaseous product formation of lignite pyrolysis were studied by microwave heating and conventional heating.The aim of the study was to maximize the utilization of lignite resources.Gasification experiment is based on the microwave pyrolysis gas as the gasifier,the product of semi coke as raw material,through the coupling of the gasification process,compared with the conventional gasification method,the effect of microwave power,steam coal ratio and catalyst of gaseous products of effective components of CO,H₂,CH₄ production rate,yield and content were investigated in order to improve the efficiency of the lignite char gasification by microwave,and find a method of lignite gasification coupled microwave dehydration.The conclusion is summarized as follows:（1）Yunnan Xianfeng lignite is a typical low rank coal with low carbon content,high oxygen content,high moisture content and high volatile content.Its molecular structure contains a large number of oxygen-containing functional groups,unsaturated bonds,long chain branched structures and associated hydrogen bonds.With a dense surface structure and a large number of pores;350～750℃is the main temperature range of pyrolysis reaction of Xianfeng lignite.（2）The higher the microwave power,the higher the heating rate of coal sample and the temperature of final pyrolysis.Adding the microwave stirrer can significantly increase the production rate of pyrolysis gas and gaseous product yield.The proper increase of microwave power and coal coke ratio,decreasing coal particle size can accelerate the rate of gas production and gas production.When the isothermal pyrolysis temperature is 900℃,the maximum gas production rate is about 1040ml/min,and The total yield of the active ingredient of pyrolysis gas is 3.36 L.When the microwave pyrolysis power is 800 W,the maximum gas production rate is 2636ml/min,and the total output of the active ingredient of pyrolysis gas is 7.04 L.Under the optimal conditions,the maximum gas production rate of microwave pyrolysis is2.53 times of that of conventional pyrolysis,and the total yield of the active ingredient of pyrolysis gas is 2.1 times of that of conventional pyrolysis.（3）The higher the microwave power,the faster the heating of the semi coke,the higher the final temperature of gasification.Increasing the microwave power,increasing the water flow rate and increasing the amount of catalyst can improve the gas production rate and the production of gaseous products.When the microwave power is 1000 W,the maximum gas production rates of CO and H₂ are 984.43 and1043.51ml/min,respectively,and the total yield of the active ingredient of gaseous products is 28.27 L.When the isothermal gasification temperature is 1000℃,the maximum gas production rates of CO and H₂ are 746.34 and 915.05 ml/min,respectively,and the total yield of the active ingredient of gaseous products is 16.97 L.Under the optimal conditions,the maximum gas production rate of microwave gasification is obviously higher than that of conventional gasification,and the total yield of the active ingredient of gaseous product is 1.67 times of conventional gasification.（4）Compared with the conventional heating methods,microwave heating is a fast and efficient way of heating.The characteristics of microwave pyrolysis and gasification of lignite are short time,low energy consumption and so on.When microwave heating is used in the pyrolysis and gasification of lignite,the production rate and output of the active ingredient of gaseous products can be greatly increased,which is in accordance with the concept of low carbon environmental protection,and has good prospects for development and application value.