Zhaoyou Zhu

Flow characteristic prediction for liquid-liquid system in a stirred tank based on RNG k-ε model

The RNG k-e model was adopted to calculate liquid–liquid turbulent flow in stirred tanks based on Eulerian–Eulerian model. The radial and tangential velocities of numerical calculation were compared with that of reported experiment. The results show that the calculation results are in satisfactory agreement with the experimental data. The complex liquid-liquid flow characteristics in the stirred tank were successfully predicted by the RNG k-e model which means that the established calculation model can be an alternative method with inexpensive computing costs and high computational accuracy.

An improvement scheme for pressure-swing distillation with and without heat integration through an intermediate connection to achieve energy savings

Abstract Pressure-swing distillation is widely studied in academia and industry. Energy consumption is a key criterion for judging whether a pressure-swing distillation is better than other distillation methods. An improved process with an intermediate connection was developed based on the two-column pressure-swing distillation for separating a binary azeotropic mixture to save energy and reduce the total annual cost. The proposed pressure-swing distillation was applied to three case systems, two minimum-boiling azeotropic mixtures of ethyl acetate/ethanol and methanol/chloroform and one maximum-boiling azeotropic mixture of ethylenediamine/water. According to our analysis, the proposed pressure-swing distillation and heat-integrated scheme can reduce energy consumption and total annual cost. The pressure-swing distillation with the intermediate connection is promising for saving energy. This advantage assists in promoting the application of pressure-swing distillation and overall energy savings in the chemical process industry.

Phase Behavior and Thermodynamic Model Parameters in Simulations of Extractive Distillation for Azeotrope Separation

Extractive distillation (ED) processes for separating ternary mixtures of benzene-cyclohexane-toluene with dimethyl formamide (DMF) and N-methyl-2-pyrrolidone (NMP) were studied using Aspen Plus and PRO/II simulators. The Aspen Plus built-in binary interaction parameters for the toluene-DMF, benzene-NMP and cyclohexane-NMP systems resulted in inaccurate phase behavior calculations. The vapor-liquid equilibrium (VLE) for the three binary systems was regressed to illustrate the importance of using accurate model parameters. The obtained binary interaction parameters described the phase behavior more accurately compared with the built-in binary interaction parameters in Aspen Plus. In this study, the effects of the regressed and built-in binary interaction parameters on the ED process design are presented. The total annual cost (TAC) was calculated to further illustrate the importance of the regressed binary interaction parameters. The results show that phase behavior and thermodynamic model parameters should receive more attention during the research and development of ED processes.