Cross-scale Analysis And Parameter Optimization Of Lignite Vibrating Fluidization And Low Temperature Upgrading

Lignite has the disadvantages of high water content,low degree of coalification and poor thermal stability,but the storage of lignite is huge,and high value-added products can be obtained after upgrading.The lignite vibration fluidization and upgrading process is widely used because of its good quality improvement effect and suitable for large-scale industrial production.Therefore,this paper studies the low-temperature upgrading of lignite vibrating fluidization,analyzes the mechanism and internal variation of lignite vibrating fluidization and upgrading,and explores the morphology and internal structure of lignite after vibrating fluidization.The main research contents of this paper are as follows:(1)In this paper,the CFD method is used to study the vibrating fluidization and upgrading process of lignite.Firstly,the Euler-Eulerian two-fluid model is selected as the CFD model,then the Gunn Model is selected as the heat transfer model of the gas-solid particle two-phase flow;the dynamic meshing technique is combined with the static mesh technology to obtain the simulation model of the vibration fluidization.Finally,the gas-solid heat transfer of the vibrating fluidization is simulated according to the empirical formula.(2)The Fluent software was used to analyze the general fluidized upgrading process and the vibrating fluidization upgrading process.The effects of inlet velocity,particle size and vibration parameters on fluidization and heat transfer were determined by simulation.Inlet velocity,particle size and vibration intensity provide a reference for vibrating fluidization and quality improvement experiments.(3)The CFD-DEM coupling method is used to analyze the vibrating fluidized bed on the particle scale.Firstly,the spatial distribution of three kinds of particles in the vibrating fluidized bed is studied.Secondly,the velocity changes of the three kinds of particles are studied.Finally,the collision and trajectory of three kinds of particles are studied.Through the visualization of the vibration fluidization process,the motion law of the particles under different vibration parameters is summarized,and the optimal vibration amplitude and frequency are determined.(4)According to the above simulation results,the intake air velocity is determined to be 0.8 m/s,the inlet air temperature is 400?,the pyrolysis time is 300 s.the lignite particle size is 0 to 1 mm.the vibration amplitude is 2 mm,and the vibration frequency is 20 Hz.The lignite with vibrating fluidization and upgrading of this parameter was characterized.The content of each component before and after upgrading was determined by industrial analysis of coal.The surface morphology changes before and after upgrading were observed by electron microscopy.The quality of the surface was determined by thermogravimetric analysis.The change of the characteristic temperature before and after;the Fourier transform infrared spectroscopy analysis,the change of functional groups and chemical bonds before and after the upgrading.