稀醋酸共沸精馏脱水工艺的模拟

醋酸是一种重要的化工原料,其水溶液广泛存在于各类工业过程中。由于醋酸与水会缔合使得两者的相对挥发度不大,生产中用于分离醋酸/水的工艺能耗较高,因此研究者和工业界都在寻求更好的分离方法。本文以醋酸正丙酯做挟带剂,应用Aspen Plus流程模拟软件,汽相逸度采用Hayden-O’Connell方程,液相活度系数采用NRTL方程计算,实现了稀醋酸共沸精馏脱水工艺的模拟。本文详细讨论了全塔理论板数、进料位置、回流比等因素对脱水塔性能的影响。结果表明,在理论板数50块,回流比3.2,醋酸进30块板,挟带剂与进料比0.15条件下,塔釜得到醋酸浓度高于95%。模拟结果对醋酸脱水工艺的设计和改造具有重要的指导意义。

Simulation of azeotropic distillation to separate water from acetic acid

Acetic acid is an important chemical material and solvent in the production of many chemicals and intermediates. Being vapor phase association of acetic acid and water, their relative volatility is small, and the typical processes for separating acetic acid solvent characterize high energy consumption. Therefore, researchers and industry are looking for a better separation process. In this paper, an azeotropic distillation process was applied for dehydration of dilute acetic acid solution by using n-Propyl acetate as entrainer and simulated by Aspen Plus. To account for the non-ideal vapor–liquid equilibrium (VLE) and possible vapor–liquid–liquid equilibrium (VLLE) for these quaternary systems, the NRTL activity coefficient model was adopted. The second viral coefficients of Hayden-O’Connell were used to account for vapor phase association of acetic acid due to dimerization and trimerization. The effects of number of theoretical stages, feeding position, feed temperature, and the ratio of reflux to feed on the performance of the azeotropic distillation column were studied in detail by using Aspen Plus. The results showed that under the conditions of number of theoretical plates 50, reflux ration 3.2, dilute acetic acid(37%, wt%) feed at 30 th plate and the solvent ratio 0.15, acetic acid (>95%, wt%) were obtained from the bottom of the azeotropic distillation column. The simulation results have important guiding significance for the design and reconstruction of the acetic acid dehydration process.