Distillation-based Processes Research Articles

Cryogenic CO2 capture from oxy-combustion flue gas by a hybrid distillation + physical absorption process

Hybrid flowsheets are defined, in the context of process intensification, as alternatives suitable for replacing energy-intensive separation methods through the combination of more than one unit operation. Given the undoubted importance of carbon capture, utilization, and storage (CCUS) in the next decades in the path to net-zero emissions and even negative emissions scenarios, this work focuses on CO2 capture from an oxy-combustion flue gas by means of a distillation-based hybrid process that avoids CO2 freeze-out, which is capable of delivering a liquid CO2-rich stream that can in principle be pumped to transport pressures with lower energy consumption in comparison to conventional post-combustion CO2 capture processes based on chemical absorption. A distillation-based process and a hybrid distillation + physical absorption process have been studied based on simulations in Aspen Hysys® V11 using the Peng-Robinson Equation of State and the “Acid Gas – Physical Solvents” thermodynamic property package. Firstly, a CO2 capture process based on cryogenic distillation has been proposed and a sensitivity analysis on the operating pressure and specified CO2 recovery has been performed in order to determine the most convenient configuration, balancing capital and operating costs. Then, a hybrid capture process has been proposed and analyzed, where cryogenic distillation is the bulk removal step and physical absorption into a mixture of homologues of the dimethylether of polyethylene glycol (DEPG) is the finishing step. Energy and economic analyses have shown that the hybrid process, delivering a CO2 product respecting the stringent purity requirement on the oxygen content for application for Enhanced Oil Recovery (EOR) and in the food industry is less energy intensive than the standalone cryogenic distillation, though it is characterized by higher capital costs.

Production of Biofuel Additives Using Catalytic Bioglycerol Etherification: Kinetic Modelling and Reactive Distillation Design

Glycerol is an unavoidable by-product of the biodiesel production process. The conversion of glycerol into valuable biofuel additives is essential in the fuel industry. The goal of this work is to develop a reactive distillation-based process for the production of biofuel additives by bio-glycerol etherification. In this study, a kinetic model using a lumping approach for glycerol etherification with tert-butyl alcohol (TBA) over Sn (II) phosphomolybdate (Sn1.5PMo12O40) catalyst was developed. Aspen Plus was used to validate the kinetic model by simulating the glycerol etherification with TBA in a batch reactor. The model predictions were in good agreement with the experimental data. A reactive distillation-based process to produce glycerol ethers was developed, and heat integration was conducted to reduce energy consumption. The energy requirements of the integrated process and the CO2 emissions were decreased by 17% and 14%, respectively. An economic evaluation was performed to study the profitability of the process for an annual capacity of 33,000 metric tons of glycerol ethers. It was found that the process is economically attractive, with a return on investment of 29.40% and a payback period of 2.2 years. The reactive distillation-based process is green and promising for producing biofuel additives that are sustainable and environmentally friendly.

Process intensification from conventional to advanced distillations: Past, present, and future

This perspective paper features the process intensification (PI) application for advanced distillation-based processes. Starting with the historical background of generic PI, we subsequently narrow down the discussion to extractive distillation (ED), reactive distillation (RD), and hybrid reactive-extractive distillation (RED). We categorize the existing PI techniques onto internal and external intensification, where the former does not involve altering the distillation configuration while the latter does. Instead of deliberating the technical aspects, we explicitly highlight the contribution of PI applied to ED, RD, and RED towards societal impact covering energy, economic, environmental, control, and safety perspectives. The future perspectives of PI are discussed in the last section, covering the development of hybrid PI technologies, exploring the energy efficiency of different PI configurations, prioritizing PI beyond energy by considering some other sustainability aspects, and linking PI with the ever-increasing Industry 4.0 applications.

Recent progress on hybrid reactive-extractive distillation for azeotropic separation: A short review

The reactive-extractive distillation (RED) has the advantages of combining the beneficial features of both reaction and separation processes. Relative to the conventional reactive or extractive distillation-based processes, the RED is also less energy intensive as it relies on the reaction heat produced for the subsequent separation process. Therefore, the application of RED for ternary azeotropic separation has become the subject of popular interest, as evident by the increasing number of publications since 2020. This review paper is the first that puts together, in a chronological manner, all the existing studies on the RED to date, starting from the initial three column reactive-extractive distillation (TCRED) to the most recent dividing wall reactive-extractive distillation (DW-RED), for ternary azeotropic separation, so that the rapid progress in this area is summarised and any existing gaps in these studies become easier to identify for future work. The last part of this review provides three potential areas for future work, i.e. analysis of the sustainability of RED, combination of different process intensification strategies to improve the energy efficiency and separation performance, and further exploration on the control studies for the RED.

Insights on sustainable separation of ternary azeotropic mixture tetrahydrofuran/ethyl acetate/water using hybrid vapor recompression assisted side-stream extractive distillation

The energy-efficiency of the traditional distillation-based processes are low, which results in waste of resources and environmental pollution. Therefore, a sustainable extractive distillation (ED) process should be developed to reduce energy consumption and CO2 emissions while improve the energy efficiency. In this work, a systematic approach is developed for the first time, for the separation of ternary azeotropic mixture containing Tetrahydrofuran (THF)/Ethyl acetate (EtAC)/Water via the combination of side-stream distillation and vapor recompression heat pump techniques. Firstly, the conceptual design of the various intensified schemes such as single (or double) side-stream(s) ED configurations are developed. Subsequently, the developed configurations were optimized using mesh adaptive direct search algorithm to obtain the optimal operating conditions of the established processes. Vapor recompression heat pump technique is used to further reduce the energy consumption. The sustainability of the various established configurations is assessed via the comparison of total annual cost (TAC), CO2 emissions, energy consumption, and thermodynamic efficiency. Overall, it was revealed that the TAC, CO2 emissions, and energy-consumption for the integrated vapor recompression assisted side-stream ED process were reduced by 33%, 49%, and 38%, respectively, relative to the conventional triple column ED. Likewise, the thermodynamic efficiency was improved by 52%.

Review: membrane materials for the removal of water from industrial solvents by pervaporation and vapor permeation

Organic solvents are widely used in a variety of industrial sectors. Reclaiming and reusing the solvents may be the most economically and environmentally beneficial option for managing spent solvents. Purifying the solvents to meet reuse specifications can be challenging. For hydrophilic solvents, water must be removed prior to reuse, yet many hydrophilic solvents form hard-to-separate azeotropic mixtures with water. Such mixtures make separation processes energy intensive and cause economic challenges. The membrane processes pervaporation (PV) and vapor permeation (VP) can be less energy intensive than distillation-based processes and have proven to be very effective in removing water from azeotropic mixtures. In PV/VP, separation is based on the solution-diffusion interaction between the dense permselective layer of the membrane and the solvent/water mixture. This review provides a state-of-the-science analysis of materials used as the selective layer(s) of PV/VP membranes in removing water from organic solvents. A variety of membrane materials, such as polymeric, inorganic, mixed matrix, and hybrid, have been reported in the literature. A small subset of these are commercially available and highlighted here: poly(vinyl alcohol), polyimides, amorphous perfluoro polymers, NaA zeolites, chabazite zeolites, T-type zeolites, and hybrid silicas. The typical performance characteristics and operating limits of these membranes are discussed. Solvents targeted by the U.S. Environmental Protection Agency for reclamation are emphasized and ten common solvents are chosen for analysis: acetonitrile, 1-butanol, N,N-dimethyl formamide, ethanol, methanol, methyl isobutyl ketone, methyl tert-butyl ether, tetrahydrofuran, acetone, and 2-propanol.

Shortcut-based optimization of distillation-based processes by a novel reformulation of the feed angle method

The conceptual design of distillation-based separation processes is a well known and thoroughly investigated research subject in chemical engineering science. Nevertheless, there are only few shortcut methods available that are derived without simplifying assumptions, such as constant relative volatilities or constant molar overflow, allowing for a thermodynamically sound evaluation of the minimum energy demand for the separation of non-ideal mixtures. The current article presents a novel reformulation of the previously introduced feed angle method, which represents a geometrical shortcut method that is based on a direct calculation of characteristic pinch points. The reformulation retains the beneficial properties of the original formulation, providing high accuracy and an equation-based formulation that can be embedded in an optimization problem, while being numerically simpler and requiring significantly less case-specific modifications. The benefit of the so-called FAM+ formulation and the applicability to complex design problems are illustrated on several case studies, including the optimization of a closed-loop flowsheet and a superstructure with two reactors and several distillation columns.

Process for n-butyl acrylate production using reactive distillation: Design, control and economic evaluation

n-Butyl acrylate is produced at industrial scale from acrylic acid and n-butanol using strong acidic homogeneous catalysts. The associated well-known problems (corrosion, product purification, and disposal of spent catalyst) lead to high operating costs and a continuously increasing difficulty to comply with environmental regulations. Employing solid catalysts and process intensification technologies can overcome these drawbacks. However, the literature is scarce in studies describing the development of complete plants.Here, the design, control and economic evaluation of a reactive distillation-based process are presented. Since n-butanol is not completely converted in one pass, a decanter–flash system is used to recover and recycle the alcohol, and obtain a high purity waste water stream. To control the purity of the acrylate product when throughput changes or fresh reactants get contaminated, direct control using concentration measurement is required. Indirect control using temperature measurement alone is insufficient; since constant tray temperature cannot hold constant the concentration profile in the column, the acrylate purity always shows an offset. The process robustness is proved by rigorous simulations in Aspen Plus Dynamics. The economic analysis shows key economic indicators similar with those of other solid-based catalytic processes presented in literature.

Economic comparison of a reactive distillation-based process with the conventional process for the production of ethyl tert-butyl ether (ETBE)

•Modelling and design of reactive distillation systems.•Economic evaluation of reactive distillation systems.•Comparison of conventional and RD-based processes for the production of ethyl tert-butyl ether.

A Comparison of Membrane Technologies for Engine Coolant Recycling

Abstract Recycling of used engine coolants containing ethylene glycol and other glycols would appear to be well established, particularly for reverse osmosis and nanofiltration membrane, electrodialysis, and distillation-based processes. Both literature and recycling facilities indicate success in employing these techniques. However, many recyclers, particularly those employing a single treatment technology, are not capable of producing recycled product meeting original equipment manufacturer (OEM) requirements for coolant, and these typically fall far short of approaching virgin (nonrecycled) coolant quality. In addition, some recycling facilities have produced and marketed product that led to coolant system damage and engine failure, either as a result of not sufficiently removing contaminants or inadequately reformulating with corrosion inhibitors and other additives. The danger of process upsets resulting in inadequate product is particularly high for those facilities that receive feeds with varying contaminant levels and coolants containing a range of corrosion inhibitors and additives (silicates, organic acids, etc.). However, no study to date has focused on a fundamental assessment of the separation characteristics and interactions of the various classes of coolant technologies with the commercially available reverse osmosis, nanofiltration, and electrodialysis ion exchange membranes typically seen in recycling operations. This study presents results of a comprehensive evaluation of the separation characteristics of a wide range of these membranes with a wide range of coolant types. In particular, the study examined production rate characteristics, inhibitor and other additive separation, and contaminant removal for reverse osmosis, nanofiltration, and electrodialysis. Residual inhibitors remaining in the recycled coolant are examined, with guidance provided on how these residuals might affect coolant reformulation and performance.

Synthesis of distillation-based processes for non-ideal mixtures

Our understanding of how to design distillation-based processes to separate mixtures displaying azeotropic behavior has grown enormously in the past quarter century. We elegantly sketch distillation column behavior on a composition diagram where we display VLE and column behavior using residue and distillation curves. In the presence of azeotropes, these curves partition composition space into distillation regions that trap the performance of individual columns. We can view liquid–liquid behavior as a tearing of composition space, a tear that always spawns from a minimum binary azeotrope. A material balance across a column section leads to a difference point, which we can use to understand column tray-by-tray and limiting behavior for ordinary, extractive and even reactive distillation. We demonstrate how to synthesize alternative separation processes, concentrating on those that produce pure products. We use boundary curvature, solvent addition, extractive agents, liquid–liquid behavior and strategically placed reaction to step across distillation boundaries. We show that these processes always contain recycles to gain feasibility but also to have economically attractive processes.