Compression properties of dust cake of fine fly ashes from a fluidized bed coal combustor on a ceramic filter

Dust cake compressibility of fine fly ashes (from a coal power plant of fluidized bed combustor) on a ceramic filter was carefully investigated under well-controlled conditions and by measuring the cake thickness under filtration conditions using a laser displacement measuring system. Overall cake porosity and pressure drop of dust cake of three different particles of geometric mean diameters: 1.2, 2.2, and 3.6 μm and the adjusted dynamic shape factors: 1.15, 1.28 and 1.64, respectively, were investigated, at face velocities of 0.02–0.08 m/s. Overall cake porosity was strongly dependent on face velocity and mass load but less dependent on particle sizes. It was understood that dust cake was compressed by reduction of previously formed cake layers with drag forces of lately formed dust layers. The expressions for overall cake porosity and pressure drop across the dust cake, based on the equation proposed by Endo et al. [Powder Technol. 98 (1998) 241] and considering the compression effect, were developed with good agreement with experimental results.