Microwave Drying Experiment And Numberical Simulation Study On Baorixile Lignite

With its advantages in stability,scale and economy,coal resources have always been the main source of primary energy supply in China.With the gradual depletion of high-quality coal resources,the rich reserves of lignite resources have attracted increasing attention.However,lignite has high water content and is easy to absorb water after drying,which restricts its large-scale application.Therefore,lignite must be dried before it can be used.Microwave drying compared to traditional drying in selectivity,flexibility and rapidness,as well as advantages,and after microwave drying lignite moisture relapse behavior obtained the certain inhibition,therefore,the microwave drying lignite has become a current research hot spot.However,researchers mostly the experimental study on the microwave drying lignite,lack of quantitative understanding of lignite microwave drying process,a few numerical simulation was carried out on the microwave drying lignite,the applicability of the model is not good,the simulation accuracy is not high,the mock object bigger deviation with actual situation.To establish a quantitative understanding of lignite microwave drying process,to deepen understanding of mechanism of microwave drying lignite,optimization of microwave drying lignite mention operating conditions,it is necessary to further study.Taking treasure on lignite coal shearer as the research object,firstly studied the operating conditions on the thin layer of the influence law of lignite microwave drying characteristics,in addition to a thin layer of lignite microwave drying process are analyzed in dynamics.It is found that increasing microwave power,particle size of coal sample and reducing coal sample quality have positive effects on enhancing microwave drying effect of thin layer lignite.With the increase of microwave power,the effective diffusion coefficient of water based on Fick diffusion equation increases.The microwave drying activation energy of thin layer lignite based on Arrhenius formula was 45.601W/g.Then based on the Maxwell equations,the equation of conservation of energy,the diffusion equation,set up theory model for describing the thin layer of lignite microwave drying process,using COMSOL Radio frequency module,solid heat transfermodule and loose material transfer module was carried out on the thin layer of lignite microwave drying process numerical simulation research.It was found that the electromagnetic field distribution of the thin layer lignite was not uniform during microwave drying,and the field intensity in the central area was high.The higher the microwave power was,the greater the field intensity gradient from the center to the edge was.Lead to uneven distribution of electromagnetic field and dry uneven distribution of temperature field,the early central area temperature is very high,the microwave power,the greater the thin layer of lignite average temperature is higher,but the more serious the center also to the tendency of local overheating.Finally,the effect of microwave extraction on lignite physicochemical structure and water resorption behavior was studied.Study found that the microwave after mass of coal sample,the surface microscopic structure more compact,the microporous proportion increase,cut down the content of oxygen containing functional group and fat structure,coal rank,coal sample moisture relapse behavior has been suppressed.The microwave power and processing temperature were increased,and the physicalchemical structure of coal sample was changed more obviously after quality extraction,and the moisture resorption behavior was further inhibited.When water vapor is present in the atmosphere,the content of oxygen-containing functional groups in coal samples after microwave extraction is lower and the moisture resorption is lower.The research results of this paper are of great significance to optimize the operation conditions of lignite microwave drying and quality extraction,understand the mechanism of lignite microwave drying,and guide the design of lignite microwave drying reactor.