Research On Separation Schemes Of Mixture Of Water, Propanediol And 1, 2-propyleneglycol-1-monomethylether

Propylene oxide product obtained from the reaction of propylene and hydrogen peroxide will continually react with methanol to get by-product1,2-propyleneglycol-l-monomethylether(PGME) solution, which is usually a mixture of PGME, propanediol and a great quantity of water. Because water will form azeotrope mixture with PGME and this mixture's azeotropic point is so close to water's boiling point that it is very difficult to separate them to get eligible PGME product by traditional distillation method.A three-tower separation technology to separate the mixture of water, ethylene-glycol and PGME, the propylene epoxidation products, is presented in this paper. By using azeotropic distillation method to separate water from PGME and calculating with UNIFAC thermodynamic equation as state equation, the process simulation is conducted and corresponding technological coefficients are worked out.Meanwhile, for purpose of reducing energy consumption, simulation of a separation scheme combining azeotropic distillation with penetrative evaporation for pre-reducing different content of water is also conducted. When pre-reducing more than 80% content of water, the original three-tower separation technology is transformed to a two-tower one. Both the subsequently formed back-reducing water process and pre-reducing water process for two-tower technology are also studied and compared here.All of the important technological parameters are optimized in order to get minimal energy cost, thus providing certain rational technological process' for design of industrial plants.