Study On The Process Of Producing Anhydrous Ethanol From Distillation Decompressed

To produce anhydrous alcohol by using azeotropic distillation have lots of merits and now is the most popular process in anhydrous alcohol preparation. But there exits high energy consumption and entrainer pollution. For example, as a kind of entrainer, benzene cannot be used in cosmetic, medicine industries due to its toxicity. So a low power consumption and green distillation decompressed method begin to show the potential market. We study on the process of producing anhydrous ethanol from distillation decompressed through experiment, at the same time, the process is simulated by ASPEN PLUS 11.1 software, which is used in chemical processes extensively. Based on the regression of literature data, binary interaction parameter is revised which can predict ethanol-water system decompression distillation accurately. An annual output of 10,000 tons of anhydrous ethanol from distillation decompressed is simulated, and a new process added with heat pump is proposed and analysed, which has a guiding significance in ethanol industry amplification, process renovation and production adjustment and save large amount of manpower and material resources. And some important conclusions have been achieved in these investigations and summarized as follows:(1)The current interacting parameters in ASPEN PLUS database can accurately predict atmospheric distillation composition, but can't accurately predict ethanol concentration from distillation decompressed. Ethanol-water system phase diagram and its partial enlargement figure is analysed in 6.7KPa,9.3KPa,12.7KPa and13.3 KPa. The results indicate that the phase equilibrium calculating has strayed from the actual curve, the azeotropic composition 97.73% in 13.3KPa and 98.31% in 6.7KPa. In fact, ethanol-water boiling mixture would disappear when belowl2.7KPa.So binary interaction parameter should been revised.(2) Based on the regression of literature data in 6.7KPa, new binary interaction parameter is obtained. And Ay=-8.88099, Aji=3.76722, Bij=2585.555, Bji=-699.4163. The new simulation results are better agreement with experimental value, so the new binary interaction parameter can predict ethanol-water system decompression distillation accurately.(3)The simulation of producing anhydrous ethanol from distillation decompressed is carried out by the software of ASPEN PLUS, with an annual output of 10,000 tons of anhydrous ethanol. Under different conditions, the simulation and optimization of the pre-distillation column and the main distillation column were made and the optimal operation parameters were obtained. Pre-distillation column:the mass of distillate rate is 1480kg/h, the reflux ratio is 2.5,the numbers of theory stage is 50, and the number of feed stage is 25.Main distillation column:the mass of distillate rate is 1389.5 kg/h, the reflux ratio is 1.7,the numbers of theory stage is 240, and the number of feed stage is 150.On this basis, in order to save energy, the whole process is optimized, thus selecting distillation to 91%in 1.013 X 105Pa air pressure.(4)In order to reduce the effective energy loss, we developed a new process added with pump technology. The simulation results demonstrate that the best energy-saving effect is 84% and 150kt water is saved compared with azeotropic distillation, but investment cost only increased 24%. Therefore, the new process added with pump technology is a kind of economical, energy-saving and environmental process.