Study On The Effect Of Pressure And The Application Of A Loop Foam Column In A Foam Fractionation Process

Foam fractionation offers an attractive method of separating proteins which have a range of surface activities from dilute solutions because of its low cost and mild operation conditions.The influences of pressure on bubble size, bubble size distribution, gas holdup, interfacial area, of rising foam and separation efficiency was studied systematically. Experiments were conducted to obtain the values of the average bubble size, bubble size distribution, gas holdup, interfacial area, the recovery rate and the enrichment ratio. The results show that as the pressure in foam column increased, great changes occurred in bubble size, foam layer structure, foam stability and hydrodynamic characteristics of rising foam, which led to an intensified effect on separation efficiency. The higher enrichment ratio 17.3 and lower recovery 13.5% were found under increased pressure 0.15MPa compared with the ones under atmospheric pressure.A new loop column was also designed by adding draft tube in liquid layer to enhance the drainage of BSA foam and increase enrichment ratio. The effects of pressure, froth/solution ratio (K), BSA concentration and pH on the recovery and the enrichment ratio were studied to optimize the conditions. The results show that the enrichment ratio increased with pressure and the K increased, surfactant concentration decreased, and was higher at pH 6.0-7.4 than at other pH value. Under the optimum conditions, the enrichment ratio was 12.86% and the recovery was73.63%.Foam fractionation was performed in the loop column using BSA as the model solution and the influence of pressure, K, BSA concentration and gas flow rate on the average liquid fraction of the foam leaving the top of the columnεout was investigated. The experimental results show that the K decreases the ?out slightly, while the superficial gas velocity significantly enhances the ?out, theεout was higher at the pH close to the isoelectric point of BSA than at other pH value. At the same time we also find that an higher can reduce the ?out effectively. By the analysis of the experimental results and theoretical, we extended the hydrodynamic theory of rising foam to the loop column for the draining process and explained the newly developed device successfully as well.