Study On The Vacuum Volatilization Separation Process

Throughout the chemical and pharmaceutical industries many azeotropic mixtures are frequently encountered, which can not be completely separated by standard distillation. Their separation sometimes can be improved by adding an agent in extractive and azeotropic distillation, but this complicates the process by introducing a new component. Seeking new methods for separating azeotropic mixtures has always been a puzzle in the field of separation.A new method to separate azeotropic mixtures was proposed in the paper, that is, vacuum volatilization separation process. It is undertaken in vacuum and the temperature must be controlled under the azeotropic point to avoid forming of azeotrope. It depends on the difference of volatilization rate and diffusion rate between two components to break through the limit of azeotrope. The process does not need the third component, so it is an environmentally friendly technique and supplies a new choice for separating azeotropic mixtures.In this paper, batch vacuum volatilization separating azeotropic mixtures was studied using ethanol-water, ethanol-toluene, ethanol-cyclohexane and n-butanol- m-xylene system under different pressure. On this basis, continuous vacuum volatilization separation experimental apparatus with a layer of packing for enlarging volatilization surface was built up. Then ethanol-toluene was studied systematically and got obvious separation effects. The experiment was operated adopting different feed concentration, feed rate, pressure and temperature and other conditions to examine their effects on separation.The separation mechanism of vacuum volatilization process was analyzed applying gas-liquid mass transfer theory, diffusion coefficient theory and evaporation heat of these components. The experiment results were also given a satisfactory explanation, which further verified the feasibility of this new process.