The Effect Of Particle Fraction On Powder Flowability And Discharge Characteristic

Based on the application of feeding system in pressured entrained flow gasification of pulverized coal, the flowability and discharge characteristics of fuel powder were studied qualitatively and quantitatively by powder rheomoter, powder comprehensive characteristics analyzer and discharge facility. Samples of petroleum coke and coal with narrow particle size distribution were characterized to assess the effect of particle size on packing characteristics and flowability. The relationship between particle size, packing characteristics and flowability was established. Angle of repose and basic flow energy results show that the petroleum coke has worse flowability than coal when particle size is below 70 μm. And the flowability is similar when particle size is larger than 70 μm. But there is not much difference of flowability by shear test. The error comes from different packing characteristics of powder.The effects of fine particle and particle size distribution on packing, flowability and fluidization of coal were studied experimentally. The results show that as the fine particle content decreasing, the cohesion, angle of internal friction and wall friction decreases. As a result, the flowability of coal and stability of discharge become better. And the particle flow is transforming from intermittent flow to continuous flow during the discharge. When the fine particle content is larger than 40%, the discharging would be discontinuous or jamming. Besides, for the samples with similar mean particle size, reducing the width of particle size distribution would greatly enhance flowability and friction characteristics. So bridging or jamming in industrial process would be prevented by reducing the fine particle content or the width of particle size distribution.Furthermore, the effect of particle size on discharge and pneumatic conveying stability were studied based on the industrial operation data. The discharge rates of high pressure condition is significantly lower than that of atmospheric pressure. The pneumatic conveying of middle particle size(60-80 μm) is most stable.