The bubble phase in high-pressure fluidised beds.

Abstract

The slugging/bubbling behaviour of a wide-size range of powders has been investigated at gas pressures up to 25 bar in a 0.1 m diameter fluidised bed, by X-ray photography of slugs within the system and by direct observation of the bed surface. It is found that in a well-fluidised bed the bubble phase is only affected when fine powders (typically 100MUm) are fluidised at evaluated pressure. The bubbles then become smaller, more unstable, and the two-phase theory of fluidisation increasingly invalid as the pressure is increased. For larger powders, the bubbles are the same size and just as stable at 25 bar as at 1 bar provided the bed is fluidised at the same value of (U-U SUB m SUB f). The two-phase theory is valid with these systems over the full range of pressure. (A)