Limiting Conditions for Maintaining a Fixed Bed within a Coil-Shaped Rotating Spiral Gas-Solid Contacting Device under Gas Feeding

A novel rotating coil-shaped spiral gas-solid contacting device was proposed. A cold model of a 1.5-cycle spiral structure was made by combining 180 degrees elbows of half-octagonal shape using ID 24 mm transparent plastic tube. Pressure drop in the solid bed during gas feed was measured. Co-current flow and counter-current flow of gas were employed. Below a certain gas flow rate (threshold gas flow rate), pressure drop in the bed increased monotonically with increasing gas feed rate. However, when the gas flow rate exceeded the threshold, the pressure drop suddenly decreased. ibis sudden decrease in pressure drop is attributable to the gas passing through the channeling formed in the bed for co-current flow, and to the formation of a fluidized region in the vertical section for counter-current flow. The relationship between the maximum pressure drop observed for the co-current flow and particle-wall friction force or particle-particle friction force is discussed. For counter-current flow, the relationship between the superficial gas velocity at maximum pressure drop and minimum fluidizing velocity of the solids is discussed.