Multi-orifice plate distributors in gas fluidised beds — a model for design of distributors

The use of a suitable gas distributor is essential for satisfactory performance of gas—solid fluidised beds. Multi-orifice plate type gas distributors in fluidised beds are frequently used in industrial practice. This paper analyses the factors governing the operating characteristics of the multi-orifice plate type of gas distributor. Results of the experiments carried out in a 100 mm diam. glass tube assembly with a distributor plate having 20 orifices are presented. Rutile and zircon sands and alumina powder (70 – 150 μm) were used as the bed material, while air — up to ten times the minimum fluidising velocity (Umf) — was used as the fluidising medium. It has been observed that all the orifices become operative at a gas velocity UM and the ratio UM/(UM — Umf) is related to the pressure drop (distributor/bed) ratio (ΔPd/ΔPb) by a constant K0 which is independent of system parameters. A theoretical model for the estimation of K0 and the experimental values are presented.