Improving the Performance of Extractive Dividing-Wall Columns with Intermediate Heating

Abstract

In spite of the fact that using extractive dividing-wall columns (EDWCs) lead to a considerably reduced reboiler heat duty in comparison with conventional extractive distillation column (CEDC) flowsheets, the involvement of a heavy entrainer frequently requires a relatively high-pressure steam for process heating and incurs consequently adverse steady-state economics. To address the potential deficiency, we proposed, in the present study, to facilitate the EDWC with intermediate heating because the great boiling-point difference between the components in the azeotropic mixture and entrainer results in steep temperature profiles and allows effectively recovering sensible heat from the recycled entrainer and using relatively lowpressure steam. When the extractive separation operation dominates the EDWC, intermediate heating should be arranged in the left side of the dividing wall and feed preheating is frequently the most favorable option. On the other hand, when the entrainer recovery operation dominates the EDWC, intermediate heating should be arranged below the lower end of the dividing wall, i.e., in the stripping section, and an intermediate reboiler is the favorable option. Under both circumstances, the heat recovery from the recycled entrainer should be considered prior to the use of available utilities, thereby permitting great improvement in the steady-state economics. The strategy features simplicity in principle and requires a relatively small number of trial and error searches. It is evaluated in terms of extractive separations of two binary azeotropic mixtures: dimethyl carbonate and methanol (with aniline as the entrainer) and acetone and methanol (with dimethyl sulfoxide as the entrainer). It is found that intermediate heating could substantially enhance the performance of the EDWC with the resultant steady-state economics overwhelmingly above that of the CEDC flowsheet. Even compared with the CEDC flowsheet reinforced with intermediate heating, the EDWC is still likely to yield comparable steady-state economics. These outcomes indicate that intermediate heating should be taken into account in the synthesis and design of the EDWC and the EDWC with intermediate heating should be regarded as a potential option for the extractive separations of binary azeotropic mixtures.

Optimization and control of vertical double wall dividing‐wall column for separating a quaternary system

“…[ 2 ] Therefore, the study of process intensification and energy saving related to distillation has gained much attention. [ 3 ] The dividing‐wall column (DWC) is a typical example of process integration and intensification. [ 4 ] The special construction of the DWC can perform the prefractionator before the main column, which allows the separation of three or four component mixtures in one distillation column.…”

Proportional-Integral Control and Model Predictive Control of Extractive Dividing-Wall Column Based on Temperature Differences

“…Extractive distillation (ED) is the predominant technology for the separation of liquid mixtures with azeotrope and/or low relative volatility in the chemical and pharmaceutical industries, which cannot be realized by the conventional distillation. , An additional entrainer (also known as solvent) is added to alter the relative volatility of liquid mixtures in ED, and two pure components can then be obtained at the top of two columns together with entrainer at the bottom of the second column . However, the thermal efficiency of ED based on conventional two-column sequence is low at 5–20%. , Various approaches have been developed to intensify and improve the ED process, e.g., extractive dividing-wall column (EDWC), − ED with varying pressure, and heat-integrated ED. − …”

Energy-Saving Optimal Design and Effective Control of Heat Integration-Extractive Dividing Wall Column for Separating Heterogeneous Mixture Methanol/Toluene/Water with Multiazeotropes

“…The divided-wall at the top of the DWC configuration divides the column into two rectifying sections and a shared stripping section, and the dividing-wall is often implemented in the extractive separation denoted as extractive dividing-wall column (EDWC) for separating an azeotropic mixture (see Figure a). − A thermodynamically equivalent process of the EDWC in Aspen Plus is demonstrated in Figure b. Note that MC and RC in Figure represent main column and rectifying column of the EDWC, respectively.…”