Multi-stage fluidized bed column: Hydrodynamic study

In our recent work we carried out mass transfer study on the multi-stage fluidized bed ion exchanger column with solids and liquid flowing in the counter current directions and demonstrated improved separation efficiency of dissolved anions from waste water in comparison to that achieved in a fixed bed operation. In this study, we report the results pertaining to hydrodynamic study with a view to ascertaining the type of fluidization prevailing on the column's stage and the operating range of liquid and solid flow rates for the steady and stable operation of the column without loading or flooding with excess solid or water flow rates. Residence time distribution (RTD) study was carried out to investigate the extent of mixing on the stages. In addition, the experimental measurements for pressure-drops were made over a wide range of operating conditions including number of stages, height of the downspout on every stage, and the liquid and solid flow rates. Based on the data, empirical correlations were developed using scale-up analysis for predicting pressure-drop, bed porosity and average bed height during cross-flow fluidization apparently prevalent on the stage. The results in this study assume significance from the perspective of design and stable operation of staged fluidized bed ion exchangers.