Fluidization Characteristics And Separation Regulation Mechanism Of Trapezoid Type Gas-solid Fluidized Bed

Air-heavy media fluidized bed separation technology has great development prospects in coal-rich and water-scarce areas,while the discharge scraper of industrial air-heavy media fluidized bed cannot be widened in one go due to material limitation is the key problem that restricts its large-scale development.In order to meet the growing demand of coal separation and improve the competitiveness of fluidized bed sorting equipment.In this paper,a trapezoid-type fluidized bed separation system is constructed to increase its effective sorting width to increase the processing capacity based on the formation of a steady-state separation bed.The influence of solid phase particle motion and operating parameters on the fluidization and separation characteristics of the trapezoid-type fluidized bed is investigated by exploring the fluidization characteristics and density distribution patterns of the trapezoid fluidized bed part and whole.Based on the above study,the steady-state separation environment of the trapezoid-type fluidized bed is constructed,which is important for the large-scale of gas-solid fluidized bed separation equipment.In this thesis,based on the special configuration of trapezoid-type fluidized bed,we divide it into flat section and inclined section,and build inclined air-bleed fluidized bed and square fluidized bed respectively on the basis of trapezoidal fluidized bed for experimental study.Firstly,the fluidization characteristics and density distribution of the fluidized bed of inclined air-bleed fluidized bed were studied,and the solid phase particle motion law was summarized based on Fluent simulation.From the test results,it can be seen that the fluidized bed density of the tilted air-board fluidized bed gradually decreases along the deep bed area to the shallow bed area at lower fluidized gas velocity,and the fluidized bed density tends to be lower in the axial direction and higher in the upper direction,and the overall density tends to decrease along the tilted air-board;with the increase of fluidized gas velocity,the density tends to be lower in the lower direction,highest in the middle direction and slightly higher in the upper direction in the axial direction,and the fluidized bed density of the tilted air-board fluidized bed The distribution of fluidized bed density along the midpoint of radial Y-axis is symmetrical;the solid phase and heavy mass make counterclockwise circulation movement in the tilted air-board fluidized bed,which is not conducive to the normal fluidization of the bed;the research and test on the fluidization characteristics and axial and radial density distribution of the square fluidized bed under different fluidization numbers show that:the axial density of the square fluidized bed varies from 1.0,1.2,1.4 and 1.6 during the change of fluidization number N The extreme differences are 0.27g/cm³,0.22g/cm³,0.15g/cm³,0.32g/cm³,showing a trend of decreasing and then increasing.The standard deviations of its axial density fluctuations are 0.0972,0.0734,0.0626and 0.121,respectively.Combined with its radial density distribution diagram,it can be seen that the bed stability is better when the fluidization number N is 1.2 and 1.4for the square-shaped fluidized bed.By simulating the solid phase motion in the trapezoid-type fluidized bed,the effect of gas velocity ratio on the motion of weighted mass in the bed was explained:when the gas velocity ratio was 1.4/1.2,the relative motion of weighted mass in the plane section and the inclined section of the trapezoid-type fluidized bed cancelled each other,and the counterclockwise circular motion was curbed.By designing the single-factor test and orthogonal test of gas velocity ratio,variable aperture air distribution plate and static bed height,the influence of each factor and factor combination on the fluidization characteristics of the trapezoid-type fluidized bed is studied,and the standard deviation of bed density and density skewness are introduced for comprehensive evaluation,which explains the bed stability state under different parameters and clarifies the regulation mechanism of bed density stability of the trapezoid-type fluidized bed.According to the experimental results,the best fluidized bed stability is obtained when the static bed height H₀=150mm,the gas velocity ratio is 1.4/1.2,and the aperture diameter of inclined air distribution plate is6-2mm;and the regression equation between the combination of factors and the standard deviation of bed density is proposed based on Quadratic model.The separation experiment of raw coal of-13+6 mm size class was carried out by selecting three factors of gas velocity ratio,static bed height and air distribution plate aperture according to the fluidization test,and evaluated using fine coal yield,ash segregation and possible deviation.The test results showed that under the optimum operating parameters,the coal yield of the selected coal sample was 71.66%,the ash separation was 1.42 and the possible deviation was 0.140g/cm³.The effect of raw coal volume on the separation effect was studied,and the test results showed that the yield of fine coal was 71.66%,74.35%and 72.64%,and the ash separation degree was 1.42,1.37 and 1.41 when the raw coal volume was 230g,300g and 400g,respectively,and the separation test did not produce any significant decrease in the yield of fine coal and ash separation degree after increasing the raw coal volume.This trapezoidal fluidized bed separation system can achieve the purpose of widening the sorting space and improving the fluidization quality.The dissertation consists of 66 Figure s,24 Table s and 86 references.