ATTRITION OF POROUS-GLASS PARTICLES IN A FLUIDIZED-BED

Fluidisation is frequently accompanied by unwanted attrition of the be d material. This paper focuses on the mechanical aspects of fines crea tion by attrition in fluidised beds supported by multi-orifice distrib utor plates. The attrition rates of low-density porous glass particles were measured; these particles show abrasive wear behaviour rather th an breakage. Positron emission particle tracking (PEPT) was used to fo llow particle motion in three dimensions within the fluidised bed. For a single orifice distributor with background fluidisation, the attrit ion rate increased exponentially with increasing orifice gas velocity. For a multi-orifice distributor, however, attrition rates were roughl y proportional to excess gas velocity, except near to a critical ratio of particle to orifice diameter; as this ratio approached 2, attritio n was observed to increase by an order of magnitude. A method is propo sed for estimating attrition rates from a combination of small-scale e xperimental results and theoretical calculations of distributor jet en trainment rates. (C) 1998 Elsevier Science S.A. All rights reserved.