HYDRODYNAMICS OF A SPOUTED BED WITH A POR OUS DRAFT TUBE

The flow rate of the gas in the annular section, the particle circulat ion rate, the pressure drop and the particle hold-up in the tube secti on were measured for a spouted bed fitted with a porous draft tube. Th e results were more or less different from the data of a spouted bed f itted with a conventional (solid) draft tube. The experimental relatio nships between the items as described above and the design factors of distance of entrainment zone and its diameter, and operating factors s uch as the gas velocity and the particle diameter were determined. A c orrelation concerning the particle circulation rate was presented in t he operating region where the particle circulation rate increased in p roportion to the gas velocity. In addition, three patterns of particle flow in both porous and solid draft tubes were recognized by determin ing the pressure drops and the particle hold-up in the tube. These thr ee patterns could be described as follows: a stable spouting region in which the particle hold-up was insensitive to the gas velocity; a pul sing spouting region in which the particle hold-up varied with the gas velocity; and a clogging region within the tube.