Process parameters for operating 1-butanol gas stripping in a fermentor

In this study, effects of the agitation speed, the flow rate, and type of non-polar gases on the performance of gas stripping was systematically investigated. Macroscopically, the stripping rate of butanol is linearly proportional to the concentration of butanol in the feed solution. Nevertheless, a decrease in butanol selectivity was observed with the increasing butanol concentrations up to 0.01 g/cm3. This can be attributed to the thermodynamics reason that with increasing butanol concentrations in the feed, more stripping gas will dissolve in the feed solution that decrease the activity of butanol for mass transfer from liquids to gas bubbles. This can be supported by the use of highly soluble gas of carbon dioxide as the stripping gas where the Ksa dropped 48% compared to the nitrogen stripping. By the parameter sensitivity analysis, it has been shown that the dominant variable is the flow rate. The best strategy of maximizing the performance of 1-butanol gas stripping at a given flow rate is to bubble the gases at a high superficial velocity, which leads to a less resistance on the liquid side for mass transfer.