Evaluation of airlift pump performance for vertical conveying of coal particles

One of the crucial aspects of reducing air consumption when conveying particles with an airlift pump is to know the factors that affect the process of particle motion at an initial velocity of zero.To determine the influence of submer-gence ratio and physical properties of particles(such as size,shape,and mass)on the onset of vertical particle motion,the airlift pump was taken as the research object,and spherical glass together with irregular shaped coal were used as experimental test particles.The results show that unlike the water-solid environment,the start of particle motion in the water-air mixture does not always occur at a certain value of superficial water velocity and this value also increases with increasing submergence level.Among the parameters considered,the role of submergence ratio is much more effective than the dimensions and the shape of the particle,because by increasing submergence from 0.3 to 0.8,it is possible to reduce air consumption by up to 8 times.Based on this study the corresponding theoretical model derived by Fujimoto et al.is optimized,wherein the overall agreement between the modified theory and present experimental data is particularly good.Contrary to Fujimoto,the minimum superficial water velocity for lifting solids in the air-water mixture is not always smaller than water ambient which indicates on optimum submergence ratio higher than 0.7.Finally,a new criterion was introduced to describe the moment of onset of the particle motion as a function of the superficial fluid velocity ratio for each submergence value.