Pressure drop through multiorifice gas distributors in fluidized bed columns

Good grid design is essential for the satisfactory performance of large gas fluidized beds and requires the accurate prediction of the grid pressure drop. Experiments conducted with various perforated plate distributors in a 0.6 m I.D. fluidized bed column showed that the presence of fluidized solids could increase the grid pressure drop by more than 100%. This increase was around 25% for a grid pressure drop to bed pressure drop ratio of 0.4. It was greatly affected by the bed height. An investigation of various possible causes for this increase demonstrated that it is primarily caused by the backflow of fluidized solids into the grid holes under the influence of waves at the bed surface.