Particle Attrition in a Fluidised Bed

Particle attrition in fluidised beds and circulating fluidised beds causes operational problems as well as material losses. Prevailing mechanical, thermal and chemical stresses bring about a gradual degradation of the particles and formation of fines. The main mechanical sources of particle attrition in a fluidised bed are the gas jets, bubbling region of the bed and cyclones.

In this work a pilot scale fluidised bed is used to assess the particle attrition induced by a jet and the bubbling part bed of “Geldart group B” manganese dioxide particles, intended for use in the Chemical Looping Combustion. The effects of the jet gas velocity and orifice size on the rate of attrition are analysed. The study includes both ambient condition and operation at 700 °C.

The jet penetration height, for both cold and hot tests, is measured by monitoring the gas pressure using a pitot tube and compared with that obtained from an Eulerian-Eulerian CFD simulation. This is then used in the modelling of the effect of the jet velocity on the overall attrition rate. The model predictions of the rate of elutriated fines are compared with those of the existing models in literature.