On dense phase voidage and bubble size in high pressure fluidized beds of fine powders

Abstract

AbstractDense phase voidage, εD, dense phase superficial gas velocity, uDo, and absolute bubble rise velocity, uB, were measured at pressures up to 8300 kPa in a pilot‐scale, fluidized bed of Group A and boundary Group A/B powders. The mean equivalent bubble diameter, db, near the top of the bed was inferred from uB, and known bed operating conditions. Increased pressure at fixed superficial gas velocity, uo, increased εD and uDo and decreased db for Group A powders. The marked decrease in inferred maximum bubble size, d with increased pressure could not be explained by a decrease in gas contributing to bubble flow, uBo, but rather appeared to be the result of a bubble instability phenomenon limiting bubble growth.