Study On Occurrence Characteristics Of Rare Earth Elements In Coal And Simulation Of Dry Preconcentration Based On X-ray

Rare earth elements are very important strategic resource and are widely used in13 fields and more than 40 industries such as new energy,military industry and precision electronic components.In 2018,China's rare earth production accounted for70.5%of the world's total rare earth production,and its consumption accounted for about 60%of the world's rare earth consumption.It is the country with the highest production and consumption of rare earths in the world.However,due to the inadequate selection level and the large amount of exports from abroad,the rare earths in my country can only be supplied for decades.Coal contains up to 74 trace elements and 12major elements including rare earth elements.Some studies show that the total amount of rare earth contained in coal is about 50million tons,which is about 50%of the reserve of traditional rare earth deposits.The average level of rare earth element content in world coal is 69 ppm,while that in China is about 138 ppm,which is twice the average level of world coal.Rare earth element content in some coal seams in northwestern China can reach 1350 ppm.If the rare earth in coal and coal by-products can be enriched effectively,it will not only alleviate the demand of rare earth resources in China,but also have a long-term strategic significance.In this paper,HE coal and ZD coal are taken as the research objects to study the change of rare earth elements content with density and particle size,and to explore the adhesion relationship between rare earth elements and mineral components through the change of mineral composition with the change of density.The results show that the highest density level of rare earth element content is 1.8-1.9g/cm~3 for HE samples,and1.7-1.8g/cm~3 for ZD coal samples.The total content of rare earth elements in the two mines increases with the increase of dissociation degree.After density and particle size separation,the total content of rare earth elements is several times to more than ten times higher than that of raw coal.By means of XRD,EPMA and other analysis and testing means,it is concluded that rare earth elements coexist with clay minerals represented by Al/Si Group in the state of ion adsorption,and have strong affinity with Ti,Ca and Fe,and elements have strong affinity.On the basis of the above research,based on the theory of ray separation,using3D-XRM equipment to explore the changes of ray intensity,gray value and transmittance of samples with different density levels,combined with the way of machine learning,the particle swarm optimization algorithm feedforward neural network prediction model of each density level of the two mines is established,and the accuracy of the model is analyzed,which can provide reference for the accurate separation of rare earth rich density level coal.It provides the basis for the selection.Finally,an accurate separation process for rare earth-rich carbon has been proposed.Numerical simulation methods are used to investigate the effects of particle density,airspeed,and nozzle angle on the horizontal displacement of particle movement.On this basis,orthogonal experiments are designed to explore the movement of particles under different conditions.According to the simulation results,the gas velocity has the greatest influence on the horizontal displacement of particles,while the density has no obvious influence on the displacement of particles.Through response surface model optimization,the significance order of three factors was obtained:gas velocity>angle>density.