Effect of fine coal accumulation on dense phase fluidized bed performance

Abstract

System for the dry separation of 50×6-mm coal is described. It consists of an air dense-medium fluidized bed as the separation medium (using 0.15×0.30-mm magnetite powder as the main medium solid). The bed density stability is a key operational parameter during separation, as the feed coal is separated according to the bed density. In separating process, the fine coal (<1 mm) will continuously accumulate in the fluidized bed, thus inevitably resulting in the fluctuation of bed density. The distribution of fine coal in an air dense-medium fluidized bed was studied. We learn from the study that fine coal can mix with magnetite powder and distribute uniformly in the fluidized bed. Experiment results in the pilot system show that a mixture of magnetite powder and fine coal can also be used as medium solid, and the 50×6-mm coal can be separated efficiently with an E p value of about 0.05 under 8.8 cm/s gas velocity. The stability of bed density can be maintained through split-flow of used medium solids and complement of fresh medium solids (magnetite powder) in continuous coal separation.