Simulation Of Lignite Rapidly Drying By Hot Flue Gas At Low Temperature And The Analysis Of Heat And Mass Transfer

Selecting Mondon lignite whose moisture content is 29.86% as the research object,we established the System for Lignite Rapidly Dried by Hot Flue Gas at Low Temperature on the basis of the coal industry analysis and thermogravimetric analysis in this article.With hot smoke from the burning of lignite as drying medium,crushing and drying simultaneously within the coal mill,we can not only ensure the lignite drying quality,but also possess the characteristics of environmental protection and energy saving.In order to study further on the drying mechanism of The System for Lignite Rapidly Dried by Hot Flue Gas and improve the efficiency of drying,this article establishes a three-dimensional scale model of coal mill where the drying takes place in by Fluent.Through the simulation of particle distribution,particle velocity and residence time in different moment of the coal mill,this article research the flow characteristics of raw coal in the process of drying,avoiding bad situation such as pulverized coal accumulation.By changing the influence factors such as spindle speed,lignite particle size and flue gas flow rate,it showed When lignite particle size increased within a certain range,the flow condition would be better;Mill output goes well when spindle speed is 500-700r/s.According to simulation results such as particle temperature,moisture content,and the heat transfer coefficient,it showed that the drying effect is was better as the particle size decreases,but the efficiency of mill output was lower.Lignite whose diameter was 3 mm could meet the requirements of the two aspects of mill output and dry.Selecting 200? hot flue gas could reduce the moisture content of lignite significantly under guaranteeing no pyrolysis.The change of the flue gas flow had little influence on flow behavior and drying effects.For a deeper research in heat and mass transfer mechanism of lignite dehydration process,a one-dimensional spherical coordinates single grain drying mathematical model which shows evaporation interface migration by outside and inside is established under the results of lignite constant temperature hot air drying experiment.It showed that the effective diffusion coefficient of Mondon lignite under hot air drying is 1.24×10-10-5.097×10-9.