DEVELOPMENT OF SOLVENTS ALCOHOL MIXTURE SEPARATION TECHNOLOGY

Abstract

The paper is devoted to the development of a technology for the regeneration of caprolactam solvents containing n-butanol, amyl alcohol, cyclohexanone, cyclohexanol, as well as isoamyl alcohol and cyclopentanone in impurity amounts. To study the phase equilibrium and the separation process, a computational experiment using AspenPlus V.10.0 was selected. The parameters of the Non Random Two Liquid equation allow reproducing the vapor-liquid equilibrium data and azeotropic properties of the system with a relative error not exceeding 5%. Separation of the mixture by conventional distillation is difficult, which is caused by the presence of three binary azeotropes, as well as three pairs of components characterized by close volatility. The structure of the vapor-liquid equilibrium diagram becomes more complex due to the appearance of new azeotropes with a decrease in pressure. A technological flowsheet for solvent regeneration based on the use of continuous distillation was proposed. The flowsheet contains five columns. At the first stage, preliminary fractionation of the mixture is assumed (the mode of sharp distillation in the first column) with complete separation of cyclohexanone and cyclohexanol in the bottom (vacuum distillation is used to separate this pair) and of a mixture of butanol and amyl alcohol with impurity components in the distillate. Extractive distillation with ethylene glycol was proposed to purify butanol and amyl alcohol from impurities. In the presence of the latter, the volatility of butanol increases in relation to other components. The fourth column is designed for the regeneration of the separating agent. Amyl alcohol separation is provided on the bottom of fifth column. The column operation parameters (the number of stages, the feed stage, the reflux ratio, the ratio of the quantities of the initial mixture and the separating agent) that meet the minimum energy consumption and ensure the production of commercial-quality substances are determined.