Experimental Study On Microwave Drying Of Lignite And Energy Consumption Analysis

The world's energy consumption intensifies so lignite with large reserves and low difficulty in mining is taken seriously.However,the characteristics of lignite,such as high moisture content,low calorific value and spontaneous combustion,have limited its development and deep utilization.In order to explore a new method of improving lignite quality by modification.In this paper,microwave drying of lignite is used to explore the characteristics of microwave drying of lignite assisted by biomass charcoal and to reveal its drying mechanism.Firstly,the effects of microwave power and initial mass on microwave drying characteristics of lignite were investigated.The results show that the optimum dry power of lignite is different from the optimum drying power,and the optimum drying power of 15g,20g,25g lignite is 231W,539W,539W respectively.The energy calculation shows that he mass of lignite is 15g,microwave power is increased from 231W to 700W,the energy utilization ratio of lignite is reduced by 47%,and energy consumption is increased by 106%.Secondly,study on moisture migration law in different layers of lignite during microwave drying.The results show that the drying efficiency of middle layer of lignite is obviously higher than that of other layers and the moisture content in the middle layer is 5.3%different from that in the other layers,which conforms to the principle of microwave internal heating.Finally,the physicochemical properties of lignite after drying were tested,and it was found that the specific surface area,total pore volume and average pore size of lignite were reduced as a whole.The specific surface area and average pore volume were decreased by 10.4%and 8.2%respectively,the sulfur content decreased by 76%and the calorific value increased by 8.82%.The influence of different bio-char on the microwave drying of lignite was analyzed.Based on the analysis of bio-char dielectric properties,microwave drying rate and spontaneous combustion time factor,the auxiliary additive is selected from pine charcoal as lignite microwave drying.The constant temperature time of lignite added with pine charcoal is obviously prolonged,and the maximum temperature of secondary heating stage is 153?.The drying process of lignite with pine charcoal was accelerated,energy consumption and activation energy decreased,and moisture diffusion coefficient increased.Compared with pure lignite,the energy consumption of lignite added 10%,pine charcoal decreased 26.8%,activation energy decreased 30%and water diffusion coefficient increased 72.5%by 231W power drying 15g lignite.