Study On Application Of Dividing Wall Column To Extractive And Azeotropic Distillation Systems

Disllation is an unit operation with high energy consumption in chemical industry. To save energy, researchers in the area of process systems engineering are interested in developing new process systems with high energy utilization efficiency. There are mainly two methods can be used for this intention, namely: thermally coupled technology, such as dividing wall column (DWC) and integration of distillation process and other process, such as distillation - membrane separation technology. Extractive and azeotropic distillations are commonly used in industry to separate close boiling point mixtures and azeotropes by using an additional entrainer to alter the relative volatility of the components to be separated.This paper applies DWC technology to extractive and azeotropic distillation systems, and makes a study of two new types of distillion columns: extractive dividing wall colomn (EDWC) and azeotropic dividing wall colomn (ADWC). In the present work, the design and optimization procedures of EDWC intended for the separation of methanol/acetone mixture are evaluated first and then the univariate analysis is implemented with Aspen Plus to obtain the optimum operation parameters. In addition, the cross-sectional analysis of EDWC is made and compared with the conventional extractive process(CEP).The results shows that EDWC can decrease the degree of back-mixing and reduce energy consumption.Based on the optimum process, the reasons for exergy loss of EDWC are illustrated through exergy loss profiles and then the thermodynamic analysis of EDWC is carried out. The results show that the thermodynamic efficiency of EDWC is improved apparently compared with CEP; Moreover, the total annual cost (TAC) of EDWC is recduced, which indicates that EDWC has more economic advantages. At last, the explicit estimation of CO2 emissions reduction due to energy savings of EDWC is carried out and the environmental benefits of EDWC are confirmed. As for the study of ADWC, the same research methods as those of EDWC are introduced and the case assessed in this paper is isopropanol dehydration. The results show that compared with conventional azeotropic process(CAP), ADWC can decrease the degree of back-mixing and has reductions in energy consumption and CO2 emissions and higher thermodynamic efficiency as well. So the economic and environmental benefits can be obtained.