Analysing divided wall columns

preview not available - see full-text PDF article.

This paper presents simulation and analysis of multiple steady states (MSS) in dividing wall column (DWC). First steady state simulation of benzene–toluene–xylene (BTX) separation in DWC is run to obtain its four different solutions using Aspen Plus software, and then detailed comparisons and analysis of these solutions are carried out. From simulation results, it can be concluded that MSS inevitably exists in DWC, which is important for its design, operation and control but has not been declared in open literature up to now. In addition, obvious grouping feature is found among the four solutions of BTX DWC case, and light component benzene and heavy component xylene have, respectively, two different recoveries at the top of the side column among the four solutions. The grouping feature is interesting and important for DWC, which may be explained by the existence of impurities in side product stream and their different flow paths from the feed to the side product stream, that is, above or under the dividing wall. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.

The divided wall column (DWC) can achieve sharp separations of three or more components in a single shell, substituting conventional sequences of two or more binary<br /> distillation columns, with lower expenses. Despite these advantages, DWC models are not available in commercial chemical process simulators. To simulate DWC, users must employ instances of conventional column model and couple them in different configurations. In this paper, a DWC model was developed in EMSO (Environment for Modeling, Simulation and Optimization). DWC model was then used for simulating the separation of an equimolar mixture of three hydrocarbons. Results show that, depending on the number of trays, DWC presented energy savings compared to two ordinary distillation columns. Better separation was obtained when the number of divided trays was close to half the number of total trays. However, the liquid and vapor flow rates split into the divided section play a key role in the separation.

Energy, exergy, economic and environmental analysis of a novel steam-driven vapor recompression and organic Rankine cycle intensified dividing wall column

Innovative biodiesel production in a reactive dividing-wall column

This study focuses on the energy-efficient separation process of styrene monomer, avoiding the formation of an azeotrope by using a vacuum distillation, derived from the pyrolysis of waste polystyrene (PS). The direct-indirect sequence, which positions the separation column of ethylbenzene and styrene monomer as the last step, exhibited a 30% reduction in the total utility consumption and a 37% reduction in the total annual cost compared to that of the direct-direct sequence that separates lighter components sequentially. A dividing wall column (DWC) configuration derived from the direct-indirect sequence showed the most significant reduction of 40% in utility consumption. However, when the feed capacity was low, the increased capital cost of DWC resulted in a total annual cost similar to that of the direct-indirect sequence. As the capacity of the entire distillation system increased, the reduction in the total operating cost of the DWC was amplified, indicating the advantages of using the DWC in high product throughputs from both energy and economic perspectives. Therefore, implementing the DWC in large-scale PS recycling processes demonstrates superior performance compared to the conventional distillation process, resulting in a more streamlined process with substantial energy savings and CO2 emissions.

Enhancing multi-component separation of aromatics with Kaibel columns and DWC

Novel side-reactor dividing wall column and reactive distillation process for enhanced electronic-grade propylene glycol monomethyl ether acetate production

The energy demand and better utilization of by-products are areas with large potential improvements in the ethanol production process. The ethanol industry in Brazil has experienced successive increases in demand and production. This expansion of ethanol productivity will allow more profitable uses of products such as fusel oil, a mixture of various alcohols such as isobutanol, ethanol, propanol and, especially, isoamyl alcohol. Such alcohols have applications in various industries. However, current applications of fusel oil present low economic benefits for ethanol mills. Energy demand is another point that has great impact on increasing the sustainability and profitability of bioethanol production. The development of more efficient distillation technologies is very important because this unit operation is responsible for a considerable part of the utilities and investment costs in ethanol production. Moreover, this reduction in steam consumption can increase the quantity of bagasse available to be used for bioelectricity or cellulosic ethanol production. In these circumstances, the present study aims to investigate processes that increase the economic benefit and sustainability of ethanol production by reducing utilities and equipment distillation costs or by manufacturing of products with higher added value. With the premise of having relative ease application, the following processes are investigated: integrated process for isoamyl alcohol and ethanol production; use of high energy efficiency columns distillation for multi-component separations (divided wall column and multi-effect columns; energy demand optimization of the conventional distillation process of ethanol; distillation process of fusel oil to obtain ethanol, isoamyl alcohol and butanol. The integrated production of ethanol and isoamyl alcohol allows increasing the recovery of ethanol and producing isoamyl alcohol and its isomer active amyl alcohol with high purities from fusel oil. However, energy integration using a multi-effect distillation column for the integrated process was not an economically viable alternative due to the small temperature differentials obtained for energy transfer between columns. To make better use of other constituents of fusel oil, the investigation of an autonomous plant configuration for butanol, isoamyl alcohol and ethanol recovery from fusel oil was investigated, this process shows high recovery rates of these components by a process that does not use solvents and employs only conventional distillation columns and decanters. An additional contribution of this thesis is to demonstrate the influence of phlegm concentration on energy demand costs of industrial ethanol distillation. The optimal economic conditions allow savings in energy demand of about 15% in the current ethanol plants, only by controlling the composition of phlegm. The process of hydrated ethanol production using a Divided Wall Column (DWC) was developed and optimized. Compared with the conventional sequence of two distillation columns, the DWC proposal presented lower costs of utilities and equipment.

Chapter 5 - Dividing-Wall Columns

This study gives a brief overview about using dividing-wall column (DWC) technology in azeotropic and extractive distillation processes aimed to break azeotropes. The relevant case study considered here is the bioethanol dehydration process that requires significant energy to overcome the azeotropic behaviour of ethanol-water mixture. The results of the rigorous Aspen Plus simulations show that energy savings of 10– 20 % are possible for the novel process intensification alternative based on DWC, while using less equipment units as compared to the conventional azeotropic and extractive distillation configurations.

A novel two-parts heat integrated dividing wall column with middle vapor recompression

Data-driven surrogate optimized and intensified extractive distillation process for clean separation of isopropanol from water: A sustainable alternative

Intensified Separation Processes for the Recovery and Dehydration of Bioethanol from an Actual Lignocellulosic Fermentation Broth

Dividing-wall column (DWC) is very attractive as the most energy saving alternative for conventional distillation columns. Hence, the main objective of this study is to develop general procedures for simulation and optimization of DWCs for industrial applications. For this, six examples involving typical industrial conditions are selected, and then the relative importance of various design variables of DWCs is examined through rigorous simulation using a commercial simulator, in order to gain insight into the design of such columns. The results show that vapor and liquid splits in the column have significant impact on the energy requirements of DWCs although their effect on condenser and reboiler duty is less pronounced within the optimum region. Further, simulation results show that DWC optimization does not need to include the variation of the number of stages as its effect on reducing the total annual cost is small. Based on the simulation and design results for the six examples, a simplified procedure for the quick design of DWCs using process simulators is proposed.