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Microalgae are a sustainable rich source of high-added value metabolites, as omega-3 and carotenoids, for their ability to grow and accumulate these compounds also in wastewaters or in seawaters. Molecular distillation is a valid techinque respect to conventional distillation for fractionation of these thermosensitive products without affecting their nutritional and biological values. In this work a fractionation process using molecular distillation for separating fatty acids (in part omega-3) as esters and carotenoids from a microalgal lipidic extract, was designed and optimized. A Response Surface Method (RSM) analysis was carried out in order to find the optimal operative conditions of the molecular distiller in terms of temperature, pressure and purification ability. Furthermore, to complete the process scheme, also the design of the other equipments, including in particular the esterification reactor and the dewatering column, was done. In order to complete the feasibility study of the process, an estimation of the Operating Expense (OPEX) and Capital Expenditure (CAPEX), using the results of the simulations in terms of energy and utilities’ consumption, was done. All of these informations, both technical and economical, will be the basis for future industrial implementations of the designed process.

Vapor permeation seems to be a more suitable separation process than pervaporation in bio-ethanol recovery from fermentation broth because of its non-direct contact trait. The unsatisfactory flux and selectivity of polymeric membranes limit their utilization in industrial application. Here, we tailored the physical and chemical structure of commercial available polyacrylonitrile (PAN) ultrafiltration membrane to serve in vapor permeation. The membrane porosity was reduced till dense enough for separation while preserving an ultra-high flux by hydrolyzing in alkali. The hydrophilicity/hydrophobicity was controlled by grafting fluoroalkyl chains to ensure an acceptable ethanol selectivity. The changes of physical structure and chemical property were systematically characterized by Fourier transform infrared-attenuated total reflectance (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), water contact angle and pure water permeance. Tested at 60 °C, the optimized membrane exhibited a high flux of ca. 10.5 kg m−2 h−1 and a permeate ethanol content similar to vapor-liquid equilibrium curve, which outstripped most polymeric membranes (applied in pervaporation or vapor permeation) in both flux and selectivity.

In process industries, separation techniques need to be employed to match product quality and purity specifications. Most vapour-liquid based separation techniques involving the separation of close-boiling or azeotropic as well as gaseous mixtures are energy intensive. Downstream separations from bioreactors are, on the other hand, difficult because of relatively small amounts of products in large amounts of reactants and carriers such as water. With growing energy and environmental challenges, novel, sustainable and innovative separation techniques are receiving increasing attention. Because of their non-volatility and other tuneable properties, ionic liquids (ILs) based separation techniques are promising alternatives. In this work, a systematic method that combines group contribution (GC)-based property prediction and IL-based separation process design is presented. That is, the optimal IL molecular structure and the corresponding optimal flowsheet configuration for a specific IL-based separation process are simultaneously identified. Case studies involving the separation of azeotropic mixtures such as ethanol-water and acetone-methanol are presented to highlight the application of the method for synthesis-design of the IL-based separation technology.

Melt crystallization is a promising and widely used method for obtaining pure compounds. Nonetheless, separation of 3,3-dilauryl thiodipropionate (DLTP) has not yet been realized by melt crystallization. Solid-liquid equilibrium is the fundamental for the separation process design. In this work, we evaluated the feasibility of the purification of DLTP from the DLTP/lauryl alcohol (LA) binary mixture by melt crystallization technique. For this purpose, the solid-liquid equilibrium data were measured using differential scanning calorimetry (DSC) technique. The experimental data were correlated by Wilson, Margules-3-suffix and Non-Random Two-Liquid (NRTL) activity coefficient models to obtain the binary parameters of the three models. Eutectic composition and temperature were calculated using NRTL model, which were xLA = 0.961 (molar fraction) and 295.79 K, respectively. On the basis of the solid–liquid equilibrium, the multistage countercurrent separation configurations were proposed for the separation of the binary system. The formulated Mixed Integer Nonlinear Programming (MINLP) problem was solved using the branch-and-bound algorithm. The conceptual designs for multistage countercurrent configuration were derived based on MINLP optimization by comparing results at various conditions. Results showed that at least 3 crystallization stages with keff ≤ 0.4 are required to obtain the 99% (mass fraction) DLTP product within the initial concentration range from10% to 30% (mass fraction).

With the gradual depletion of petroleum resources, the one-step synthesis of acrylic acid/ methyl acrylate from acetic acid/methyl acetate and formaldehyde via aldol reaction, instead of propylene selective oxidation, has stimulated researchers’ interest. Current research in this field focus on catalyst modification, structure–activity relationships, catalytic mechanism and kinetics, and separation process design. The faced challenging problems are efficient catalyst development, mechanism-based kinetics calculation for reactor design and separation process optimization, which hinder the industrial progress, although great efforts have been made in the last decades. Therefore, it is necessary and meaningful to review the achievements as the basis for the further exploration and application in this area. This review aims to systematically summarize and analyze the catalytic performance and structure–activity relationships of developed catalysts, catalytic mechanism and kinetics, and separation process design, as well as suggest the prospective research.

An innovative permselectivity test bench is used in order to determine the axial distribution of two properties of a stainless steel porous tube, which are the permeance and the gas selectivity. The effects of the operating conditions (inlet mass flowrate and inlet pressure) have been studied. A new radial form of the gas permeability equation has been developed for this work and its relationship with Darcy‘s permeability is established for a cylindrical configuration of the test. The pressure variation along the centre axis of the tube is determined. The effects of this pressure variation on the physical properties of gases such as density and viscosity are determined and their influence on the selectivity of gases is studied. It is found that the gas density and gas viscosity decrease along the flow. This decrease leads to an increase in the gas permeability for N 2 and a decrease for CO 2 . Consequently, the selectivity (N 2 /CO 2 ) increases. The obtained results can be useful to understand the factors affecting gas separation in case of a porous tube for continuous industrial processes.

The phase separation of liquid/liquid systems consisting of oil, water and amphiphilic molecules is a function of temperature and composition. The phase separation is fastest in liquid three phase systems, where the organic and aqueous excess phases are separated by a microemulsion middle phase. In this work, a detailed analysis of the relevant physical properties (density, rheology, interfacial tension) of the phases in combination with drop size distribution measurements and image analysis of the droplet interactions is performed using an endoscope measurement system. This methodology enables to directly quantify influencing effects of droplet size and droplet interactions on dispersion and phase separation processes. The duration and character of the separation process strongly depends on the droplet interactions (e.g. formation of multiple emulsions) of the dispersed phases.

Microemulsion systems may enable innovative and highly efficient synthesis paths for the chemical industry. When expensive catalysts are involved in the process, an efficient separation of products together with an extremely low catalyst leaching are of utmost importance. In order to optimize the separation process and improve the settler design, a thorough understanding of droplet-droplet interactions is required. In this work, computational fluid dynamics (CFD) has been used to study the multiphase flow in a horizontal settler using the Eulerian two-fluid framework. Droplet coalescence, which is the most important physical phenomenon in gravity-driven separation, has been modeled using a spatially inhomogeneous buoyancy-based kernel, and the resulting population balance equation has been solved using the quadrature-based method of moments (QMOM). After calibrating the model parameters using selected experiments, a very good description of the observed separation is obtained, opening the door for process understanding and optimization.

This work presents a systematic framework for solvent design and selection based on optimum economic and controllability separation process performance. Solvents are initially designed in a solvent-process screening stage where conceptual process models are optimized to identify solvent options and process features of optimum economic performance. The integration of solvent and process design is facilitated computationally by a data mining approach which allows a reduced number of solvents to be evaluated in process design optimization. Highly performing solvents identified in the first stage are introduced into rigorous separation process design, supported again by the proposed data mining approach. At this stage detailed process models enable identification of operating process characteristics which can be used as targeted set-points in a subsequent control design problem. Selected solvents and design configurations which are able to match the targeted set-points are then investigated for their performance in compensating the effects of multiple and large in magnitude process disturbances. A non-linear sensitivity analysis approach is employed that calculates the optimum steady-state effort for the solvent-process design-control structure configuration. The focus of the work is maintained in the formal mathematical presentation and implementation of the data mining procedure and the controllability assessment of different solvents as well as in the use of rigorous process design models. In this respect alternative solvents and process designs are evaluated based on their economic and static controllability performance.

For design of ionic liquid (IL) solvents for a specific separation process, a computer-aided ionic liquid design (CAILD) method based on multi-scale simulations is presented. A new group contribution based approach GC-COSMO for ILs is established for estimating the σ-profiles and cavity volumes of cations, where ILs are structured by three parts, i.e., one anion, one cation skeleton, and substituents on cation skeleton. Prediction models, including the COSMO-SAC model for thermodynamic properties and semi-empirical models for physical properties, are integrated into a computational IL design framework. A mixed-integer nonlinear programming (MINLP) problem is then formulated to optimize the separation performance combing the constraints of structural feasibility and physical properties. The optimal IL solvents are identified using a deterministic optimization method with branch and bound algorithm. The CAILD method is successfully tested for two typical separation examples, i.e. extraction of benzene from cyclohexane and post-combustion CO2 capture.

Liquid-vapor separation process is a widely used process in many industrial and domestic applications. Liquid-separation condenser using header-orifice as liquid-vapor separator has been widely studied, confirming its superiority of higher heat transfer coefficient and lower pressure drop simultaneously over the conventional condenser. However, research on flow and separation mechanism of the header-orifice liquid-vapor separator is rarely found in existing literatures. Herein, we propose a numerical simulation model based on Volume of Fluid for the header-orifice liquid-vapor separator. The model is verified and applied to study the liquid-vapor separation mechanism of the header-orifice. The major parameters that influence the liquid-separation efficiency are analyzed, including the diameter of a liquid-separation hole, header height and inlet mass flow rate. Multi-factor analysis is also performed to investigate the synergetic effects of the parameters on the liquid-separation efficiency. A correlation of liquid-separation efficiency as a function of cross-section area, two-phase Reynolds number, and modified Weber number is obtained based on the orthogonal experimental method.

New approaches and materials for inexpensive carbon capture are important areas of research. Herein, we report a new material (i.e., zeolitic imidazolate framework-67 (ZIF-67)/glycol-2-methylimidazole (mIm) slurry) that can be used to capture CO 2 similar to a liquid absorbent, and ZIF-67 was synthesized on a pilot scale. This flowable slurry was formed by suspending ZIF-67 in a glycol–mIm solution. The results from the gas-–slurry equilibrium experiments indicate that this method provides a more efficient approach for the low cost capture of CO 2 compared to conventional technologies. The selectivities for CO 2 /H 2 , CO 2 /N 2 , and CO 2 /CH 4 were 1409, 723, and 222, respectively. The apparent solubility of CO 2 in the slurry was 1.3 mol L −1 , and the sorption enthalpy was only −33 kJ mol −1 at 1 bar and 303.2 K. To simulate an actual separation process for carbon capture using the ZIF-67/glycol–mIm slurry, a series of column breakthrough tests were performed in a stainless steel bubbling column to investigate the influence of temperature, ZIF-67 mass fraction in the slurry, feed gas flow rate, and composition. The slurry was completely regenerated via helium purging and heating at 323–343 K. The CO 2 capture ability of the regenerated slurry was the same as that of the fresh slurry, even after 10 adsorption/desorption cycles.

Flotation is a density separation process which is influenced by physico-chemical interaction between a particle and a bubble. In biotechnology, it finds application in the solid-liquid separation of biomass. The process mechanism depends on the formation of stable microorganism-bubble-complexes by collision and adsorption. The difference in density of these complexes and the surrounding liquid medium causes them to rise to the liquid surface, where a foam develops. This microorganism enriched foam can then be removed. An economical comparison of the separation technologies centrifugation, cross-flow-filtration and flotation showed, that flotation is a financially and energetically interesting alternative process step for the harvest of microorganisms. In this work separation results with a model microorganism S. cerevisiae are presented. Experiments were conducted batch-wise in a 6L-laboratory dissolved air flotation setup, where bubble generation classically results from expanding air from supersaturated medium. Goal was the optimization of the flotation rate and the energy efficiency of the flotation process by adaptation of operational parameters, such as gas- and recycle flow rate and saturation pressure. Flotation models show proportional dependency between the flotation rate and the bubble size and bubble surface area flow rate. Therefore, the effect of operational parameters, such as saturation pressure, recycle and gas flow rate, on the bubble size and surface area flow rate was analyzed. The positive effect of an increasing bubble surface area was possible with increasing gas flow rate, recycle flow rate and saturation pressure. Decreasing bubble sizes were measured for increasing recycle flow rate and saturation pressure, meanwhile the contrary was the case with an increasing gas flow rate. Evaluation of the flotation rate and flotation energy efficiency showed, increasing the recycle flow rate and the saturation pressure both improved the flotation rate, but had low effect on the energy efficiency. Increasing the gas flow rate improved both flotation rate and energy efficiency. It is the most interesting operational parameter for enhancing the process efficacy.

Microfluidics-based particle separation has attracted much attention in a wide range of chemical, environmental, and biological applications. However, most of the existing methods require complex channel designs to generate inertial flows or external forces such as electric fields. In this work, we demonstrate a facile particle separation technology with extremely simple straight channel geometry not relying on any external force. In viscoelastic flow, larger particles are enriched downstream of a straight channel in a self-modulated manner by sheathless elasto-inertial focusing mechanism (Yang et al., Lab Chip, 2011, 11, 266-273). We evaluated the performance of a microfluidic separator based on this mechanism, and found significant effects for polymer and particle concentrations, as well as flow rate. In particular, we determined an upper limit for the polymer concentration, which was attributed to the occurrence of shear-thinning behavior, and we found optimal flow rates for the separation. In addition, we found that particle-particle interaction plays an important role in the separation process and the purity of separated particles is gradually degraded with increasing particle concentration. This work will contribute to the design of microfluidic particle separators and the fundamental understanding of particle dynamics in polymer solutions flowing through confined geometries.

While CO 2 capture has been extensively investigated in different metal–organic frameworks (MOFs), their performance under practical process conditions is scarcely examined. In this study, a multi-scale modeling study is reported to examine CO 2 capture from flue gas by vacuum swing adsorption (VSA) process using cation-exchanged rho zeolite-like MOFs ( rho -ZMOFs) as adsorbents. Three rho -ZMOFs namely Na-, Mg- and Al- rho -ZMOFs are considered and compared with 13X Zeolite, which is the current benchmark for post-combustion capture from dry flue gas. First, Monte Carlo (MC) simulations are conducted to estimate the adsorption isotherms of pure CO 2 and N 2 in the range from 0 to 100 kPa and their mixtures of varying composition at a total pressure of 100 kPa. The pure gas isotherms are then fitted by the dual-site Langmuir model. Subsequently, the extended dual-site Langmuir model is used to satisfactorily predict the equilibrium behavior of CO 2 /N 2 binary mixtures over a wide range of composition. In addition, micropore diffusivities are calculated from molecular dynamics (MD) simulations and compared with the estimated macropore diffusivities in order to determine the controlling mechanism of mass transfer. Macropore is expected when these adsorbents are pelletized before using in a separation process. For each rho -ZMOF adsorbent, a four-step VSA process with light product pressurization for CO 2 capture and concentration (CCC) from dry flue gas containing 15% CO 2 in balance N 2 is then simulated using a non-isothermal, non-isobaric model. The process is optimized using multi-objective optimization based on a genetic algorithm for minimizing the energy penalty and maximizing the process productivity, subject to the purity and recovery constraints of 95 and 90%, respectively. The operating spaces of the three rho -ZMOFs are similar to that of 13X zeolite. However, the minimum energy penalty in Al- rho -ZMOF (156 kW h/t CO 2 ) is lower than in 13X (165 kW h/t CO 2 ). While identifying the cation-exchanged rho -ZMOFs as interesting candidates for CO 2 capture, this study also demonstrates that the multi-scale modeling approach adopted here is an effective methodology to screen and design novel MOFs for CCC and other separation applications.

A micro-impinging stream reactor (MISR) at the size of ~1 mm has been built from commercial T-junctions and steel micro-capillaries, which has advantages of intensified micromixing and easy construction. By using a big-sized and very short outlet tube, the two injecting streams could impinge intensely within the limited chamber of the T-junction to achieve a quick mixing at the micro-scale. The effects of both operating parameters and geometric parameters of MISR, e.g., inlet jet Reynolds number (Rej), volumetric flow ratio (R), outlet configuration, outlet length (L), and inlet diameter (di), on the micromixing efficiency have been studied by experiments with the Villermaux–Dushman reaction as well as by computational fluid dynamics (CFD) method. Both experimental and numerical results agreed well and demonstrated that the inlet jet Reynolds number (Rej) and inlet size played a key role for the micromixing performance. The outlet configuration also had a great influence on micromixing, but the effects of the length of outlet channel were insignificant. This work showed that MISR will have a great potential for both reaction and separation process intensifications.

This paper discusses experimental investigations and mathematical modelling of pervaporation for binary and ternary mixtures of acetone, isopropyl alcohol and water using the hydrophilic polymeric membrane PERVAP™ 1210. The experimental results show a strong increase of water and organic permeances with increasing water mass fractions in the feed while selectivities are decreasing. The increasing organic permeances result from coupling effects between water and organic molecules during the transport through the membrane. However, no coupling between both organic permeances could be identified for the ternary system. The influence of the feed temperature on permeances and selectivities is comparatively smaller. The experimental results are used to identify appropriate trans-membrane mass transfer models for pervaporation and to determine the respective model parameters. The mass transfer models are integrated in a detailed rate-based model for pervaporation and simulated separation characteristics agreed well with experimental data. The applicability of the investigated membrane in a membrane-assisted separation process and the suitability for using the respective mass transfer models in an optimisation-based process design are assessed for the ternary system.

A falling film micro reactor has been investigated as a contactor for a separation process in order to be implemented in fine chemical and pharmaceutical production. Nitrogen stripping of a pure solvent was performed allowing straightforward mass transfer measurements due to the absence of resistance in the liquid side.Two mass transfer models were developed in this study, a semi-analytical one based on the mass balance equations combined with an existing Sherwood correlation for laminar flow in micro channels and a numerical model solving the hydrodynamics and mass transport equations. Very good agreement was found between the two models, which were then compared with experimental data. The experimental values of stripping efficiency agree with the calculated ones with an error of ±15% showing good modelling prediction. The calculated gas side mass transfer coefficients of the investigated micro contactor are in the range of 0.007–0.01 m s−1.

Seeking alternative olefin/paraffin separation techniques have been attracting great interest due to the high operating and capital costs of current commercially practiced separation processes. An olefin/paraffin separation scheme using membrane based facilitated transport/chemical absorption techniques offers great advantages such as reducing the operating and capital costs, as well as eliminating the operating drawbacks occurring in absorption processes such as flooding, foam formation, etc. Consequently, the utilization of a facilitated transport/chemical absorption scheme with a suitable membrane system for olefin/paraffin separation would be an attractive option for the replacement of the current separation technologies. A comprehensive review is presented for application of membranes for light olefin/paraffin separation. This article covers all types of membrane based facilitated transport/chemical absorption techniques which include various conventional liquid membranes configurations, membrane contactors and more advanced solid membrane electrolytes. The performance evaluation, shortcomings, and advantages are discussed in details.

Shortcut design methods can be valuable tools for rapid screening of different separation process alternatives to assess feasibility and determine minimum energy demand. This work presents a variant of the feed angle method ( Kraemer et al., 2011 ), which applies to single- and double-feed reactive distillation columns. The proposed method relies on pinch point analysis and determines the minimum energy demand from the calculation of a tray at the feed pinch. It is fully algorithmic and insensitive to impurities in product specifications. Its validity and performance is illustrated by a variety of case studies covering multi-component and multi-reaction systems, mixtures with potential liquid–liquid phase split, and double-feed columns. The results show that the method is sufficiently accurate and computationally efficient, even for highly non-ideal systems and complex configurations.

Ethanol is a biofuel, produced through the fermentation of sugars derived from biomass. Its usefulness as a fuel is limited by the energy intensive nature of the ethanol separation process. The ethanol recovery process is inefficient due to the dilute nature of the fermentation product and the presence of the ethanol−water azeotrope. This investigation presents a new hybrid separation process for energy efficient ethanol recovery. The new process is a hybrid of distillation and pervaporation. However, as opposed to most other hybrid processes, the distillation and pervaporation processes are combined into single unit. An overview of the proposed system was provided and differences to the conventional separation process were highlighted. A mathematical model was derived to explain the transport phenomena occurring in the hybrid process. The model was then used to compare the process to distillation. It was shown that the hybrid process is capable of breaking the ethanol-water azeotrope. It was also demonstrated that the pervaporation process, which is associated with both material and energy transfer, induces partial condensation of the vapor and thereby affects the efficiency of vapor−liquid contacting. Simulations were presented to show the impact of reflux ratio and pervaporation flux on the performance of the process.

Ethane was extracted from a synthetic natural gas mixture at 298 K and 101.3 kPa using modified ETS-10 as a packed bed adsorbent. Ethane was completely separated from the mixture for a prolonged period until the initial stages of breakthrough. The adsorptive properties of several cation-exchanged forms of ETS-10, a large-pored titanosilicate molecular sieve, were compared. Na-, Ba- and Ba/H-ETS-10 were all found to be selective for ethane over methane. Na-ETS-10 showed the highest Henry's selectivity (α=52) for ethane over methane of the three ETS-10 materials tested. Ideal Adsorbed Solution Theory (IAST) models indicate that significant selectivity should persist at high pressures. Ethane is commonly removed from raw natural gas by energy-intensive cryogenic methods and these results reflect the potential for an alternative and efficient separation process using cation-exchanged ETS-10 as an adsorbent.

A novel gas separation process is described and analysed in the context of carbon capture. It involves a highly selective absorbent fluid below its saturation pressure pre-mixed with the gas to be separated and adsorbed into a porous solid. This fluid mixture simultaneously forms gas-like and liquid-like regions within the porous solid depending on the pore size. The gas component to be separated is selectively absorbed by the liquid-like regions, and a novel ‘pressure-swing wetting layer absorption’ process is used to recover the absorbed gas. This work examines the equilibrium behaviour of this process in the context of carbon capture using the density functional theory (DFT) of classical fluids. The DFT model employed represents the porous solid in terms of ideal graphitic slit-pores, and a ternary fluid model is calibrated to represent mixtures of tetrahydrofuran (the absorbent fluid), carbon dioxide and nitrogen. Under the conditions investigated here we find that the equilibrium behaviour of this system is superior to the analogous pressure-swing adsorption process without solvent. This result motivates further experimental and dynamical process modelling studies of this system.

In this work, the influence of surface properties on the flow characteristics and mass transfer performance of two immiscible liquids are investigated in the opposed and cross-flow configuration microchannels, as the volumetric flux ratio is far

Modelling of gas/vapour–liquid separation processes usually requires experimentally determined parameters, e.g., mass transfer coefficients. This results in expensive experimental work, especially for new types of column internals. A novel modelling approach based on hydrodynamic analogies (HA) has recently been developed for distillation units equipped with structured corrugated sheet packings. The HA model takes the packing geometry directly into account whereas the experimental determination of mass transfer coefficients is not required. In this work, the HA approach is extended to cover heterogeneously catalysed reactive stripping processes. Experimental investigations are performed with a test system, esterification of hexanoic acid and 1-octanol, using different types of catalytically coated supports as column internals (one corrugated sheet packing and three film-flow monoliths with different channel geometries). Simulation results obtained with the extended HA model are in a good agreement with experimental values.

A mechanical separation process in a hydrocyclone is described in which disperse water droplets are separated from a continuous diesel fuel phase. This separation process is influenced by droplet–droplet interaction effects like droplet breakup and coalescence resulting in a change of droplet size distribution. A simulation model is developed coupling the numerical solution of the flow field in the hydrocyclone based on computational fluid dynamics with population balances. The droplet size distribution is discretized and each discrete droplet size fraction is assumed to be an individual phase within a multiphase-mixture model. The droplet breakup and coalescence rates are defined as mass transfer rates between the discrete phases by the aid of user-defined functions. All model equations are solved with the CFD software package FLUENT™. The investigations show the impact of the cyclone geometry on the coupled population and separation dynamics. Cyclone separators with an optimized geometry show less steep velocity gradients increasing the coalescence rates and improving the separation efficiency. The calculated droplet size distributions at the cyclone overflow and at the underflow show good accordance with experimental data. The basic modeling approach can be extended and adapted to other disperse multiphase flow systems.

The separation of carbon dioxide from light hydrocarbons is a vital step in multiple industrial processes that could be achieved by pressure swing adsorption (PSA), if appropriate adsorbents could be identified. To compare candidate PSA adsorbents, carbon dioxide, methane, and ethane adsorption isotherms were measured for cation exchanged forms of the titanosilicate molecular sieves ETS-10, ETS-4, and RPZ. Mixed cation forms, such as Ba/H-ETS-10, may offer appropriate stability, selectivity, and swing capacity to be utilized as adsorbents in CO 2 /CH 4 PSA processes. Certain cation exchanged forms of ETS-4 were found to partially or completely exclude ethane by size, and equivalent RPZ materials were observed to exclude both methane and ethane, while allowing carbon dioxide to be substantially adsorbed. Adsorbents such as Ca/H-ETS-4 and Ca/H-RPZ are strong candidates for use in PSA separation processes for both CO 2 /C 2 H 6 and CO 2 /CH 4 , potentially replacing current amine scrubber systems.

The separation of propane/propylene mixtures is the most energy-intensive operation practiced in the petrochemical industry. Adsorptive processes are currently viewed as a promising alternative to cryogenic distillation for the separation of these mixtures. In this paper, we explore the possibility of using a new metal-organic framework material, CuBTC, in adsorptive separation processes, particularly in a simulated moving bed (SMB) context using isobutane as a potential desorbent. A gravimetric method has been used to measure the adsorption equilibrium isotherms of propylene, propane and isobutane onto a commercial CuBTC powder over a temperature range from 323 to 423K and pressures up to 100kPa. These were complemented by a detailed experimental characterization of the structure of CuBTC using XRD and SEM techniques. Comparison of experimental isotherms with grand canonical Monte Carlo simulations in CuBTC showed that propane adsorption occurs preferentially in small octahedral pockets, while isobutame is excluded from these pockets due to its bulky structure. Propylene was seen to interact strongly with unsaturated metal sites, due to specific pi-Cu bonds. These interactions significantly enhance the affinity of this MOF for unsaturated hydrocarbons. Furthermore, in a range of temperatures and pressures, the affinity of CuBTC for isobutane is intermediate to that of propane and propylene. Our results suggest that CuBTC-isobutane is a very promising adsorbent-desorbent pair for use in SMB processes for propane/propylene separations.

Chiral separation of racemic mixtures is essential in the production of many pharmaceutical compounds. The present work describes a novel chiral separation technique that combines cooling crystallization and a membrane separation that is used in DL-glutamic acid resolution. The process utilizes two crystallization chambers that are separated by a membrane that prevents transport of crystals from one chamber to another. Importantly, conditions must be controlled so that only a pure species crystallizes in each of the chambers. This is done by appropriate addition of seed crystals to each chamber and by restricting the formation of new crystals to secondary nucleation mechanisms. The seed crystals may grow or participate in secondary nucleation, but conditions must be controlled so as to prevent primary nucleation, which would result in the formation of both crystal species in each chamber. Experiments were conducted with different amounts of seed crystals to determine operating conditions that produce the high product yield and purity. The results show that this novel chiral separation process is promising: the product purity was over 94% (with a separation factor of 16) and the product yield was increased by as much as 56% more than could be obtained with simple cooling crystallization.

This paper describes the separation of vaporous alcohol-water mixtures using the FricDiff separation technology. This separation process is based on a difference in interspecies friction between the components of a feed mixture and a sweep gas. A comparison is made between the performances of tubular and plate FricDiff-modules for several dimensions of the module using the finite element program COMSOL MultiphysicsTM [Comsol, 2006. COMSOL Multiphysics User's Guide, version 3.3]. It is shown that these configurations give different results when the fluxes through the porous barrier (which separates the feed mixture compartment from the compartment where the sweep gas is flowing) increase. These differences can be attributed to the resistances to mass transfer located in flow channels adjacent to the porous barrier. These resistances are different for the two configurations and when they become dominant, the tubular and plate FricDiff-modules behave differently. Sherwood correlations are derived to describe the resistances to mass transfer in the flow channels. Both the developing and fully developed boundary layer regimes are taken into account. In the developing regime, the derivation is based on that of a pseudo-binary system, consisting of one of the feed components and the sweep gas. In the fully developed regime the true multi-component behavior of the system is taken into account. It is shown that these Sherwood correlations give a very accurate description of the separation process in a FricDiff-module. © 2009 Elsevier Ltd. All rights reserved.

We recently illustrated the strong effect of local Soret-transport-induced “enrichment” in raising condensation-onset temperatures for surfaces exposed to hydrocarbon vapors dilute in compressed gaseous N 2 at pressures up to ca. 100 atm [Rosner, D.E., Arias-Zugasti, M., 2007a. Chemical Engineering Science 62 (15), 3962–3969]. Because of current interest in the processing of compressed CO 2 containing more condensable hydrocarbon vapors, we generalize our previous methods to now include the phenomenon of carrier gas dissolution in the incipient condensate, which becomes especially important for systems like C 12 H 26 / CO 2 , even at pressures of the order of “only” 10 atm. As before, binary Soret factors and vapor-phase non-ideality are estimated using gas kinetic theory and a virial EOS, truncated at the binary encounter level [see e.g., Rosner, D.E., Arias-Zugasti, M., 2007b. A.I.Ch.E. Journal 53 (7), 1879–1890]. Carrier gas dissolution and liquid phase non-ideality are now accounted for using an extended form of regular solution theory shown to be successful for dilute CO 2 / n -alkane binary solutions by King et al. [1977. Chemical Engineering Science 32 (10), 1247–1252]. For the example of dodecane (our surrogate for jet- or diesel-fuel) vapor dilute in compressed CO 2 at, say, 20 atm near 1000 K, we predict condensation-onset surface temperatures which are higher than those expected on purely thermodynamic grounds (i.e., neglecting vapor-phase Soret enrichment) by ca. 24 K corresponding to 5.5% dew-point “shift” at a mainstream composition of 10 4 ppm ( v ) . Put another way, if measured dew-point temperatures were being used to infer mainstream vapor mole fractions ( y 1 , e ), neglect of this Soret enrichment effect would lead to an over-estimate by a factor of ca. 2.5. Under such “compressed gas” conditions, designers of partial condensation separation processes employing cooler-condensers can use the present formulation to account for all systematic departures from a familiar but degenerate limiting case: y 1 , e = p 1 , sat ( T dp ) / p , no longer valid. The present theory, leading instead to Eqs. (1) and (7) can also form the basis of an experimental method to extract high pressure Soret coefficient information from solid surface dew-point measurements in dilute undersaturated compressed gas systems of known vapor mole fraction, provided the system vapor/liquid equilibrium properties are well understood, and T mp , 1 T dp ≪ T c , 1 .

The batch extractive distillation is compared with the hybrid process ( absorption + distillation ) by feasibility studies and rigorous simulation. A new method is presented for the assessment of feasibility of the hybrid batch extractive distillation. The limiting values of the operational parameters are determined. Calculations are presented for the separation of the minimum boiling azeotropic mixtures of acetone–methanol and ethanol–water by the application of water and ethylene glycol as heavy solvents, respectively.

Ionic liquids (ILs) are promising new solvents, e.g. for catalysis and separation processes. Currently, ILs are produced in batch reactors at comparatively high prices. So improved and continuous reactors are probably provitable. Reaction engineering aspects of the exothermic IL-synthesis are exemplarily discussed for ethylmethylimidazole ethylsulfate ([EMIM][EtSO4]), formed by liquid phase alkylation of methylimidazole with diethylsulfate. Simulations based on the experimentally determined kinetic data show that an adiabatic loop reactor with an external heat exchange is the best choice, e.g. compared to expensive multi-tubular reactors, which are cooled intensively to avoid a runaway. The unfavourable dilution of the reactants in the loop reactor is outbalanced by the higher inlet temperature, which leads to a higher mean reaction rate (compared to multi-tubular reactors) and a much smaller reactor without exceeding the maximum temperature of 100 ◦ C (coloration of IL; long-term thermal stability). In addition, the design and operation of a loop reactor is straightforward and less complex. Compared to batch reactors, the hold-up is by a factor of 1000 lower, which is particularly advantageous for toxic reactants (here diethylsulfate). The results are beyond synthesis of [EMIM][EtSO4] instructive for other ILs, and probably also for other exothermic reactions with a temperature limit. 2006 Elsevier Ltd. All rights reserved.

The aim of this paper is to define the conditions controlling the fragmentation process within the atomization of a suspension. Correlations for the droplet diameter of a suspension spray generated by a twin-fluid nozzle have been derived. Two separate regimes in suspension atomization have been identified with respect to the solid particle size. The atomized droplets from suspensions containing relatively fine solid particles are suspension droplets (containing liquid and solid particles). In this case a correlation for the drop size distribution in the spray of a twin-fluid nozzle has been deduced. Droplet size measurements in the suspension spray with varying solid particle sizes showed that when the suspended solid particle size exceeds a critical value, solid particles and liquid will be more and more separated. This effect is indicated by a bimodal size distribution in the suspension spray. It is shown that complete solid–liquid separation in the suspension spray may be achieved, where the pure liquid drops are significantly smaller than the separated solid particles. The critical process conditions where the solid–liquid separation process is found will be derived. Depending on the operating conditions of the atomizer, the resulting pure liquid droplet size is equal or less than the hydraulic diameter.

International audience; To design cyclic separation processes by adsorption, such as pressure swing adsorption (PSA) processes, one has to simulate the start-up time in order to determine the cyclic steady state (CSS), which can be very time-consuming. A fast way to estimate the CSS reached by a PSA process is proposed by Suzuki (1985)—assuming equivalency between the PSA system and a continuous countercurrent flow system (CCF). The CCF model is improved in the present paper, taking into account the gaseous phase located in a column when the system switches from a constant pressure step to another step. By performing a parametric study, the limits of the CCF model are tested. It is shown that this model can quantitatively predict the purities and recoveries obtained at CSS for kinetically controlled separation by comparison with a detailed model of PSA. It is also shown that the CCF model can also give a good approximation of the dynamic behavior of the PSA process. Finally, the simulation of dry air separation is proposed.

A novel method for recovering the oil phase from aqueous emulsions has been developed. The method applies a low-intensity, resonant ultrasonic field within a rectangular chamber, which is optionally filled with a highly porous medium. Oil droplets dispersed in water have negative acoustic contrast factor and thus are driven to the pressure antinodes of the standing wave field under the influence of acoustic radiation forces. Subsequent coalescence and/or wetting onto the internal surfaces of the chamber occur. Three types of porous media (an unconsolidated bed of 3-mm glass beads, aluminum mesh or reticulated polyester mesh) having pore sizes two to three orders of magnitude larger than droplets being collected were used. The oil collection was found to be sensitive to the natural affinity between the oil and the porous medium as well as its porosity. Of the three media studied, the polyester mesh was found to be the best in terms of the percentage oil collection while the bed of glass beads performed the poorest. The oil collection was found to be highly sensitive to the residence time of the emulsion in both the porous medium and acoustic field. Oil collection also showed expected trends with applied electrical power, but it was not found to be strongly dependent on the internal surface area of the mesh for the range of feed concentration tested. These experiments enable a preliminary understanding about the mechanisms underlying the separation process.

A batch reactive membrane separation process is analysed and compared with a batch reactive distillation process by means of residue curve maps. In both processes, the chemical reaction takes place (quasi-) homogeneously in the liquid bulk phase and vapour–liquid equilibrium is assumed to be established. Additionally, in the reactive membrane separation process, selective vapour phase permeation through a membrane is incorporated. A model is formulated which describes the autonomous dynamic behaviour of reactive membrane separation at non-reactive and reactive conditions when vacuum is applied on the permeate side. The kinetic effect of the chemical reaction is characterized by the Damkohler number Da, while the kinetic effect of multicomponent mass transfer through the membrane is characterized by the matrix of effective mass transfer coefficients. The process model is used to elucidate the effect of selective mass transfer on the singular points of reactive membrane separation for non-reactive conditions (Da=0), for kinetically controlled reaction (0

A general framework for analyzing and understanding the dynamics of reactive separation processes is developed. The theory is based on the assumption of simultaneous phase and reaction equilibrium. It makes use of transformed concentration variables, which were first introduced by Doherty and co-workers for the steady state design of reactive distillation processes (Proc. Roy. Soc. London A 413 (1987a) 459). It is shown that these transformed variables can be directly generalized to the dynamic problem considered here. Further, they can also be applied to other reactive separation processes like fixed bed as well as countercurrent chromatographic reactors, for example. They provide profound insight into the dynamic behavior of these processes and reveal bounds of feasible operation caused by reactive azeotropy. It is shown that reactive azeotropy, which is a well-known phenomenon in reactive distillation (Proc. Roy. Soc. London A 413 (1987b) 443) may also rise under very similar conditions in other reactive separation processes like chromatographic reactors for example.

Recently, different strategies for improving simulated moving bed (SMB) chromatographic separation processes have been proposed, including a modulation of the feed flow (PREP, 15th International Symposium, Exhibit & Workshops on Preparative/Process Chromatography Ion Exchange, Adsorption/Desorption Processes & Related Separation Techniques, Lecture 201, Washington, DC, USA, pp. 53–54.) and the feed concentration (Chemical Engineering Technology 25(12) 1151) during the tacts. In this contribution these two different strategies are applied to a benchmark problem and are compared with each other. Physical explanations of the improvements obtained compared with the conventional operation mode are given in terms of moving concentration fronts. Practical aspects for the implementation of the different strategies are also discussed.

A model for a semi-batch flotation separation process has been developed, based on available microprocess probabilities, and compared to experimental data obtained using a WEMCO laboratory flotation cell. In general, the model predicts the correct experimental trends. In many cases, the model also predicts removal efficiency very well. Parametric studies reveal that the model predictions are sensitive to a stability parameter, the turbulent energy density in the flotation cell, the contact angle between the solid particle and fluid, and the ratio of initial-to-critical film thickness.

An integrated process system model has been developed for coupled separation operations involving two independent solvent circulation loops. This flow scheme is characterized by lower strippant (energy) consumption compared to the single loop configuration. The character of the relation between the strippant and solvent throughputs satisfying a given purification ratio has been analysed. Interesting characteristics of this flow structure concerning the effect of design and operating parameters such as the total number of stages, the ratio of the separation capacities, and the solvent circulation rates in the two loops on the system behaviour are uncovered. A systematic approach to the design optimization of single and twin loop flow structures is presented.

Experimental investigations on top vented vessel blowdown of pressurized CO2 with dissolved nitrogen are presented. During the processes pressure, axial temperature profile, axial void profile and mass were measured. The release process provokes a separation of the two components. This separation process can be investigated quantitatively by calculating phase equilibria for the measured pressure and temperatures. A one-dimensional simulation model based on mass and energy balances and a drift flux model is developed which predicts well the pressure and temperature transients and the mass flow rate.

Separation of o - and p -chlorobenzoic acids (CBAs) has been investigated by a two-phase process of dissociation extractive crystallization. On the basis of a screening procedure developed from thermodynamic considerations, methanol and piperazine were selected as a solvent and reagent, respectively. The ternary phase equilibrium diagram depicting several isotherms has been constructed for the o -CBA– p -CBA–methanol system. Also included are the corresponding calculated values based on a modified UNIFAC group contribution method and these show good agreement for such a complex system. A series of batch equilibrium precipitation experiments was performed and the proposed thermodynamic model predicted comparable concentrations of all species in the solution phase at equilibrium. Good recovery of o -CBA (in excess of 90%) was achieved in a single stage and very high separation factors (usually approaching infinity) were possible indicating the potential efficacy of the separation technique for this system.

Experiments have been carried out to investigate the use of direct contact cooling techniques for the separation of different organic mixtures by melt suspension crystallization. Air as a gas coolant, water and sodium chloride solution as liquid coolants were used at atmospheric pressure to cool down the melt and generate crystals. The purity of the product was described with the effective distribution coefficient keff. In the system dodecanol–decanol, a gas coolant lead to higher product purities (keff between 0.2 and 0.6) than a liquid coolant (keff about 0.8). For the systems caprolactam/water (with coolant air) and p-xylene/o-xylene (with a 20 mass % sodium chloride solution as coolant) higher purities than in the system dodecanol/decanol could be achieved (keff in the range of 0.2 and lower). Liquid coolants required additional separation steps because of the miscibility between coolant and melt. The influence of the solid–liquid separation (vacuum filtration, pressure filtration, centrifugation) on the product purity was investigated. Although pure crystals may be the result from the crystallization step, a pure product could not be received by filtration or centrifugation. The experiments showed that solid–liquid separation and the system properties itself and not process parameters like superficial velocity of the coolant or residence time of the melt influenced the product purity. The yield could be estimated from an energy balance.

A novel process using a cascade of packed columns to separate submicron particles from gases with high efficiency is presented. The process is based on the enlargement of the submicron particles by heterogeneous condensation. The particle enlargement as well as the collection of the droplets is achieved in the packed columns. Each column of the cascade is trickled with water which is alternately colder or warmer than the gas. The temperature difference between the gas and the water is required to achieve supersaturation of the vapour and correspondingly droplet growth by condensation in each column. The performance of the process is evaluated by experimental investigations. The collection efficiency of a two-stage cascade is determined using different submicron particles, such as residual particles, quartz particles, and paraffin oil droplets. It is shown that high collection efficiencies can be obtained by this separation process, also at high particle number concentrations. Since a new supersaturation is achieved in each column, large droplets are formed which are collected at the packing material of the columns with high efficiency. Correspondingly, submicron particles are separated with high performance by cascading packed columns.

In this paper, a film-model-based description of multicomponent reactive separation is considered and two different approaches to the solution of the reaction–mass transfer problem in the liquid film are studied and compared. The first approach is based on a numerical treatment of the resulting nonlinear boundary value problem. The second approach requires a simplification of the differential transport equation by linearizing its reaction source term, and further, takes advantage of an analytical technique. To realize numerical solution of a complex matrix-form boundary value problem, a special method has been developed and tested. Both approaches have strengths and weaknesses which are analyzed and discussed. For different systems and process conditions, a comparison of simulation results obtained by both methods is carried out.

Integration of reaction and separation has experienced fast progress in this decade because it provides a convenient way of alleviating kinetic and/or thermodynamic constraints usually present in the more traditional sequential configuration (where reaction is followed by separation), which limit the extent of reaction and also the purity of the products obtained thereby. The aim of this work was to quantitatively compare the final recovery of a desired product in an integrated processing unit and in a sequential one, in the case of a unireactant/uniproduct reaction occuring in an (ideal) liquid phase with separation via liquid/vapor equilibrium. The objective function was set as the local temperature which maximizes the recovery of product in the vapor phase leaving the integrated unit or the separator (as appropriate). It was concluded that (i) the optimum temperature looks as a local maximum for the integrated system and as a global maximum for the sequential one, (ii) it strongly depends on the equilibrium constant of the reaction in question and (iii) it assumes lower (and economically feasible) values only in the case of the integrated unit.