Experimental determination of the minimum agitation speed for complete liquid-liquid dispersion in mechanically agitated vessels

A new method was developed to experimentally determine the minimum agitation speed for complete dispersion of two immiscible liquids in stirred vessels. The method consists of taking samples from the liquid mixture at different agitation speeds and plotting the volumetric fraction of the dispersed phase vs the agitation speed. In correspondence of the visually observed minimum agitation speed, the typical plot showed a significant change in slope or a maximum point. The plots were analyzed with a mathematical method to unequivocally determine the minimum agitation speed value. A comparison between the values so obtained and those obtained with the visual observation method showed an excellent agreement. This approach is independent of sampling point position and type of agitation. No isokinetic sampling is required. The proposed method is expected to replace the visual observation approach especially in large scale, closed, industrial reactors where the visual method cannot be used