Comparison study of riser geometry effect on the solids distribution in CFBs

The axial and radial solids holdup profiles were studied by measuring with an optical fibre probe in a 7.6 m rectangular circulating fluidized bed with a narrow 19x114 mm cross-section riser under a wide range operating conditions. Comparing the rectangular riser with the other cylindrical columns, it is found that the general shapes of the axial and radial profiles of solids holdup in rectangular riser are quite similar to that in cylindrical risers, but more uniform. It is concluded that the geometry of the riser is a factor affects the solids distribution due to the perimeter per unit cross-sectional area and the distance from the wall to the centre. In some extent, the two-dimensional and three-dimensional risers are more comparable under fast fluidization conditions. Generally, the solids distribution along the axial and the radial direction in rectangular riser are close to that in cylindrical risers, and the main differences have been known by the study of this paper.