Study On The Heterogenous Azeotropic Batch Distillation Process

The heterogenous azeotropic batch distillation is an integrated process of batch distillation and heterogenous azeotropic distillation, which is used to separate close-boiling mixture and azeotropes. It has many advantages, such as low equipment investment, separation of multi-component mixture by a single column and flexibility.N-ethylpiperazine and monoethanolamine were separated by the heterogenous azeotropic batch distillation with p-xylene and cyclohexane as the entrainers, respectively. The feasibility and the effects of different operation parameters of the heterogenous azeotropic batch distillation process were studied via theoretical analysis, experiments and simulation.The vapor-liquid equilibrium data for binary systems of N-ethylpiperazine- monoethanolamine, p-xylene-N-ethylpiperazine and p-xylene-monoethanolamine were obtained by the vapor-liquid equilibria experiments at ambient pressure, also the azeotropic points for binary azeotropic systems were obtained. The experimental results were tested for thermodynamic consistency and the parameters of NRTL equation for these binary systems were correlated by the experimental data. The liquid -liquid equilibrium for ternary systems of N-ethylpiperazine-monoethanolamine- p-xylene was obtained by the liquid-liquid equilibrium experiment at 20℃and 50℃, and the feasibility of the separation by the heterogenous azeotropic batch distillation was analyzed with residue curve maps. The vapor-liquid equilibrium data for binary systems of cyclohexane-monoethanolamine and cyclohexane -N-ethylpiperazine at ambient pressure were estimated by UNIFAC group contribution method. Based on the above resluts, the heterogenous azeotropic batch distillation experiments for the separation of the azeotropic mixture of N-ethylpiperazine-monoethanolamine were carried out. And the experiments results proved that p-xylene and cyclohexane were the effective entrainers.The mathematical model of the heterogenous azeotropic batch distillation was established, and the heterogenous azeotropic batch distillation process for the separation of the azeotropic mixture of N-ethylpiperazine-monoethanolamine with p-xylene as the entrainer was simulated. The effects of operation parameters such as reflux ratio, theoretical stages and feed charge to the heterogenous azeotropic batch distillation process were obtained by simulation.