The flow pattern of solids in a gravity column

Flow pattern of solids in a gravity column (150 mm diam.) with peripheral discharge was studied by measuring the residence time distribution (RTD) of coloured solids tracer in the exit stream. The data were used to calculate dispersion numbers and flow volumes by applying a dispersion model and a multiparameter model respectively. The results show that the flow pattern of solids in the upper 75% of the column height was plug and that this flow pattern was virtually unaffected by the flow rate in the range investigated (35 – 75 g/s millet seed). The flow pattern of the solids in the bottom section of the column is shown to be markedly mixed and to depend on the flow rate. The paper also notes the usefulness of RTD analysis in providing flow models of bulk flow equipment which can give supplementary design and operating information not available by traditional methods.