Influence of swirling intensity on lump coal particle pickup velocity in pneumatic conveying

Abstract

Pickup velocity, defined as the airflow velocity requirement of the initial movement of solid particles, is the well-recognized minimum conveying velocity required of a pneumatic conveying system. To reduce the airflow velocity, the influence of swirling intensity on lump coal particle pickup velocity was studied via experimental measurements. The pickup velocity of lump coal particle was determined by the weight loss method and the whole process was recorded by a high-speed camera. Initially, a side inlet guide vanes swirling generator was developed and used to measure the effect of swirling airflow. The impact of the swirling intensity was discussed and regressed, considering the tangential flow rate, the total inlet airflow rate, and the measurement position. Subsequently, the pickup velocities of 5 to15 mm lump coal particles in axial and swirling flow field were separately determined. In addition, a normative gradual change of tangential flow rate was utilized to examine the pickup velocity variation with swirling intensity. Two points in particular are worth highlighting: (1) the lump coal particle pickup process is prone to rolling up from coal particle bed fore-end, rather than the locally layer-by-layer peeling off in axial flow field; and (2) the pickup velocity of lump coal particle first increases and then decreases with swirling number, and a cubic polynomial function has favorable adaptability to fit the relationship between the lump coal particle pickup velocity and swirling intensity. The fitting results show good agreement with the measurements, with the fitting errors being <3%.