Particle characterization for angularity and the effects of particle size and angularity on erosion in a fluidized bed environment

A number of parameters for characterizing the angularity of particles have been proposed in the literature. These parameters serve as good indicators of irregularity as opposed to roundness, but fail to provide a good measure of angularity. The relevant parameter in erosion is angularity and not irregularity. In this work, a new parameter for characterizing the angularity of particles is proposed. It takes into account the sharpness of particle corners and the probability of these corners contacting the target surface. The particles of SiO2, garnet, Al2O3 and SiC are characterized for angularity in terms of this parameter and compared with other measures, P-2/A and W/L, where P, A, W and L denote the perimeter, area, width and length of the particle, respectively. It is found that the new parameter provides the characterization for angularity even where the other measures fail. In addition to the above, the effect of particle angularity and size on the erosion of 1020 HR steel in a fluidized bed atmosphere at 500 degrees C and 5 m s(-1) impingement velocity is studied, It was found that the erosion rate increases with increases in both particle angularity and size. The erosion features have been studied as a function of these variables and the erosion mechanisms are discussed. (C) 1997 Elsevier Science S.A.