FLUID FLOW AND MASS TRANSFER IN ROTATING PACKED BEDS WITH COUNTERCURRENT GAS-LIQUID FLOW

A rotating packed bed was constructed to investigate its mass-transfer and flooding characteristics. Flooding tests with an air-water system and glass beads showed that Sherwood's correlation underestimates the flooding gas velocities by 40% to 70%. Theoretical correlations for the liquid-side (gas-liquid) and liquid-solid mass-transfer coefficients were developed based on models for laminar liquid film-flow on the rotating blade and on the rotating disk. It was shown that, even though the liquid films in high gravity fields are very thin, penetration theory can be used to predict mass transfer coefficients in the normal operating range of rotational speed. Both the liquid-side and the liquid-solid mass-transfer coefficients increase with rotational speed. The chemical method was successfully used for determining experimentally the liquid-side mass-transfer coefficients and the gas-liquid interfacial area. The results show that the gas-liquid interfacial area increases with the rotational speed. The gas-liquid contacting efficiency was found to be two to three times higher than the corresponding value for the gravity-flow packed bed. As predicted by the theoretical correlation, the liquid-side mass-transfer coefficient also increases with rotational speed and it is two to three times higher than the corresponding coefficients in gravity flow. The developed theoretical correlation gives a satisfactory prediction of the experimental values.; Dissolution of naphthalene into water was used to determine the liquid-solid volumetric mass-transfer coefficients. The results show that these are four to six times higher than the corresponding values in the gravity-flow packed bed. The theoretical correlation gives a fair prediction of the estimated experimental liquid-solid mass-transfer coefficients. Liquid-solid volumetric mass-transfer coefficients can also be used to estimate the end effects in the measured gas-liquid interfacial area.; Two design cases were studied to illustrate the advantages and disadvantages of the rotating packed bed. A correlation was developed to estimate the increase in power requirements above those for gravity flow beds.