Flow Characteristics and Particle Size Distribution in Pneumatic Conveying with Attrition
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چکیده
Introduction This work presents an analysis of gas-solids flow in a pneumatic conveying line wherein by collisions with the wall, the particles undergo breakage. A measure of particle attrition, the often-undesirable damage to particles, is necessary for design of many fluid-particle operations. For example, proper design of cyclones requires knowledge of the amount and size of fines produced from attrition. Additionally, an estimate of energy consumption from particle breakage is needed to ensure that pneumatic conveying lines operate in the flow regime as designed. Population balances and kinetic theory are used in this study to describe how the local variables, such as the particle velocity and average particle volume at a specific point in the system, affect the rate of attrition at that point. Particle breakage, which modifies the average size of the particles, affects the characteristics of the multiphase flow. Specifically, the kinetic theory constitutive models proposed by Lun et al. (1984) for the particle phase stress tensor are dependent upon the diameter of the particles. In this work, the typical equations for multiphase flow, conservation of mass, momentum and energy for both the gas and particulate phases (as implemented by Sinclair and Jackson (1989) and others), are coupled with an additional equation for the average particle size.
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تاریخ انتشار 2004