Characteristics of bubble, cloud and wake in jetting fluidised bed determined using a capacitance probe

Abstract

Detailed properties of bubble, cloud and wake in a jetting fluidised bed are studied by a capacitance probe method in this paper. In a jetting fluidized bed, when smaller particles are fluidised, bubble size and rising velocity initially increase near the distributer and maintains almost constant values with the increase in bed height. When bigger particles are fluidized, the bubble size and rising velocity decreased with the increase in bed height. The bubbles in bed when bigger particles are fluidised are smaller than those when smaller particles are fluidised under the same operating conditions. Background gas velocity has a more significant influence on bubble size, whereas the jetting gas velocity has a more significant influence on bubble rising velocity. The effect of operating conditions and bubble size on the averaged voidage of cloud or wake is negligible. Besides, the thickness of cloud and wake increases with bubble size, and the thickness of cloud is greater than that of wake.