Optimization and modeling of the performance of polydimethylsiloxane for pervaporation of ethanol−water mixture

Response surface methodology was used to optimize the performance of pervaporation of ethanol aqueous solution using polydimethylsiloxane hollow-fiber membrane. The effects of four operating conditions, that is, the feed temperature (30–50°C), the feed flow rate (10–50 L/h), ethanol concentration (5–20 wt%), and the vacuum pressure (10–50 KPa) on the membrane selectivity and the total flux of permeation were investigated with response surface methodology. The results showed that a quadratic model was suggested for both selectivity and total flux showing a high accuracy with R² = 0.9999 and 0.9995, respectively. The developed models indicated a significant effect of the four studied factors on both selectivity and total flux with some significant interactions between these factors. The optimum selectivity was 15.56, achieved for a feed temperature of 30°C, feed flow rate of 10 L/h, ethanol concentration of 15 wt%, and a permeate pressure of 10.74 KPa whereas the optimum total flux was 1833.66 g/m².h was observed for at a feed temperature of 50°C, a feed flow rate of 50 L/h, ethanol concentration of 15 wt%, and a permeate pressure of 49.38 KPa.     

Ionic liquid effects on mass transfer efficiency in extractive distillation of water–ethanol mixtures

The relatively high viscosities of ionic liquids could reduce the mass transfer efficiency of the extractive distillation process. The rate-based model was adopted to analyze this phenomenon since it predicted the performance of an extractive distillation pilot plant using ionic liquids as solvent. For the water–ethanol separation, three ionic liquids: 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium acetate and 1-ethyl-3-methylimidazolium dicyanamide and the organic solvent ethylene glycol were used for the analysis. Simulations were conducted for sieve trays and Mellapak^® 250Y. The results indicate that relatively high viscosities affect the mass transfer efficiency. However, the improvements in relative volatilities obtained from the ionic liquids help to overcome this effect. However, with high solvent viscosities (>65 mPa s at T = 353.15 K) it was not possible to overcome the reductions. Additionally, at higher distillate rates high relative volatilities yielded negative effects on mass transfer efficiency because of a decrease in vapor velocity.     

Steady-state operation analysis of an ideal heat integrated distillation column

A systematic approach for the steady-state operation analysis of chemical processes is pro-posed.The method affords the possibility of taking operation resilience into consideration during thestage of process design.It may serve the designer as an efficient means for the initial screening ofalternative design schemes.An ideal heat integrated distillation column(HIDiC),without any reboileror condenser attached,is studied throughout this work.It has been found that among the various va-riables concerned with the ideal HIDiC,feed thermal condition appears to be the only factor exertingsignificant influences on the interaction between the top and the bottom control loops.Maximuminteraction is expected when the feed thermal condition approaches 0.5.Total number of stages andheat transfer rate are essential to the system ability of disturbance rejection.Therefore,more stagesand higher heat transfer rate ought to be preferred.But,too many stages and higher heat transfer ratemay increase the load of the compres     

Separation of ethyl acetate–isooctane mixture by heteroazeotropic batch distillation

This paper studies the separation of an ethyl acetate–isooctane mixture by heterogeneous azeotropic distillation in a batch rectifying column. An initial list of 60 candidates was studied but only methanol and acetonitrile were obtained as potential heterogeneous entrainers. These entrainers form a low boiling heterogeneous azeotrope with isooctane. Experimental verification of the miscibility gap with isooctane was performed at 25 °C for each entrainer giving a smaller region for methanol than for acetonitrile. Feasibility of the heterogeneous azeotropic batch distillation was carried out experimentally in a laboratory batch distillation column having 44 theoretical equilibrium stages and using a high reflux ratio. Several distillate fractions were taken as a function of the temperature at the top of the column. For both methanol and acetonitrile, the main fraction was defined by the condensed vapor providing a liquid–liquid split of the isooctane/entrainer heteroazeotrope into the decanter. Ethyl acetate impurity was detected in both decanted phases, but in much lower amount when using acetonitrile as entrainer. The process with acetonitrile also resulted in a shorter operating time and higher purity and recovery yield of isooctane as the main distillate product. Pure ethyl acetate remained into the boiler at the end of each process.     

Design,optimization and controllability of an alternative process based on extractive distillation for an ethane–carbon dioxide mixture

Alternative configurations based on cryogenic extractive distillation were proposed and simulated by using Aspen Plus 7.0^® coupled to a multi-objective stochastic optimization procedure (differential evolution, DE). The evaluation of the performances of the proposed configurations was focused on the ethane–carbon dioxide azeotrope separation considering different liquefied hydrocarbon fractions as entrainers. The design alternatives were compared to the conventional chemical absorption system.The proposed sequences were simultaneously Pareto optimized by minimizing the total annual cost (TAC) and maximizing the acid gas removal. Complementary studies regarding the theoretical control properties, the thermodynamic efficiency and the greenhouse gases generation were conducted for several representative operating conditions obtained from the Pareto optimized fronts. The proposed cryogenic extractive distillation sequences realized the higher carbon dioxide removal together with the lower TAC compared to the conventional chemical absorption system.     

Evaluation of the performance of a constructal mixer with the iodide–iodate reaction system

A novel fluidic mixer, which takes advantage of impingement mixing and is designed according to the constructal approach, is evaluated by the Villermaux/Dushman method. The effects of different configurations (including the structure of the fluid collector and the diameter of the nozzles on the fluid injector) on the mixing performance (i.e. the segregation index and the energy dissipation rate) are determined. The segregation index is smaller, or in other words the degree of mixing is better, when a branch type fluid collector or smaller nozzles are used, however, at the cost of higher energy dissipation rate. When the flow rate is sufficiently high, mixing caused by the impingement of streams is almost complete, rendering the mixing in the branched channels unnecessary. As a result, if very high degree of mixing is pursued, the collector with a simple empty space should be used in the mixer to reduce energy consumption.     

Ionic liquids as entrainer in extractive distillation for effectively separating 1-propanol–water azeotropic mixture

Economically separating 1-propanol(NPA) from water is an emergent issue for producing pharmaceutical intermediates such as n-propyl acetate, n-propylamine and so on. In this work, fourionic liquids(ILs) 1-ethyl-3-methylimidazolium thiocyanate([EMIM][SCN]), 1-butyl-3-methylimidazolium tetrafluoroborate([BMIM][BF₄]), 1,3-dimethylimidazolium methylsulfate([MMIM][MS]), 1,3-dimethylimidazolium dimethylphosphate([MMIM][DMP]) were introduced as potential entrainers for separating NPA–water a...     

Physiochemical insight into the solution behavior of cationic gemini surfactant in water and ethanol–water systems

Surfactants in water and both alcohol-water mixed solutions are used extensively in a host of industrial applications. This work presents the solution behavior and micellar transition of a cationic gemini surfactant (GS): N,N′-dihexadecyl-N,N,N′,N′-tetramethyl-N,N′-ethanediyl-diammonium dibromide (16-2-16) in water and mixed water-ethanol media. Phase behavior for 16-2-16 in the ethanol–water system was investigated at ambient temperature. The rheological data obtained for these systems at varying alcohol concentrations showed that the system viscosity (η) decreased with as the ethanol concentration increased. Small-angle neutron scattering (SANS) was used to probe the structural details of the cationic micelles as a function of ethanol concentration and temperature. The scattering data inferred a structural transition from unilamellar vesicles (ULV) through rod-like micelles to ellipsoidal micelles occurs that is dependent on the solvent composition and temperature indicating the behavior of ethanol molecules as a cosolvent in the process of micelle breaking. The plausible physicochemical interactions in the 16-2-16-ethanol mixed system were further investigated using a computational simulation study employing density functional theory (DFT)/B3LYP (Gauss View 5.0.9) utilizing a 3-21G basis set.     

Design and control of a middle-vessel batch distillation for separating DMC–EMC–DEC mixture

In this paper, the mixture of dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate was separated by middle-vessel batch distillation with feeding in middle-vessel and process control characteristics were researched. The steady state simulation results in Aspen Plus were exported to Aspen Dynamics. Then control effect of liquid level control with HighSelector, composition control (structure1, structure2) and temperature control (proportional action, proportional integration action) were proposed. Composition control structure 2 and temperature control with PI action were investigated to achieve a good control effect.     

Thermodynamic parameters of amitriptyline hydrochloride–additives at cloud point: effects of the ethanol–water mixed media

Abstract

Addition of organic solvents is known to change the properties of amphiphiles through modification of bulk phase. Amitriptyline hydrochloride (AMT) is a tricyclic amphiphilic drug which is usually used as an antidepressant. In drug delivery, the cloud point (CP) of the drug is an important parameter. This article discusses the effects of ethanol–water (EtOH–WR) compositions on the energetic parameters, such as changes in Gibbs energy of clouding (Δ_sG⁰), enthalpy of clouding (Δ_sH⁰), and entropy of clouding (TΔ_sS⁰) of AMT-additive systems. Monovalent alkali halide salts, cationic conventional surfactants, and gemini surfactants were used as additives in the EtOH–WR mixed media whose compositions were varied between 0 and 15% (w/w). The Δ_sG⁰ values are positive for all the additives and the values decrease with the rise in mole fractions of the additives. The Δ_sH⁰ and TΔ_sS⁰ were noted to be positive except for KF in 15% EtOH–WR mixed media.     

Evaluation of anti-fouling performance for ion-rod water treater with automatic dynamic simulator of fouling

IntroductionFouling is a layer of solid deposit on thesurface of heat exchanger in contact with liquidcontaining adhering components. According toSteinhagen’s research, more than 90% of heatexchangers have some kind of fouling…     

Anodization of n and p-GaAs in ethylene glycol–water–tartaric acid mixture

This paper describes the pulsed constant current anodization of n+ and p+-GaAs in ethylene glycol–water–tartaric acid (AGW) mixture, up to 17mAcm–2. A 0.26m thick film is obtained for a final voltage of 135V at 4.3mAcm–2 pulsed current density. Cyclic voltammetry showed that the initial growth of a monolayer anodic oxide can be described by a charge transfer with uncompensated cell resistance model. The relationship between peak current, peak voltage and scan rate has been verified for this process, based on the above model.     

Methyl acetate–methanol mixture separation by extractive distillation: Economic aspects

Methyl acetate is considered low toxicity volatile solvent produced either as a by-product during methanol carbonylation or via acetic acid esterification with methanol. In both cases, pure methyl acetate has to be isolated from the reaction mixture. Simulation of methyl acetate separation from its mixture with methanol by extraction distillation was carried out in ASPEN + software. In total three case studies were assumed using two different extraction solvents and two solvent regeneration strategies. In case A, novel extraction solvent 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid, was considered. Raw material separation was achieved in an extraction distillation column while the solvent regeneration was accomplished in a second distillation column in this case. In case study B, the same extraction solvent was used; however, its regeneration was carried out in a single-effect evaporator. Dimethyl sulfoxide was the second extraction solvent selected. Its use in methyl acetate-methanol separation is presented in case study C. As high purity of dimethyl sulfoxide was required for the methyl acetate-methanol azeotrope breaking, its regeneration was carried out in the second distillation column only. To simulate the ternary methyl acetate–methanol–extraction solvent mixtures separation, vapor–liquid equilibrium was predicted based on the NRTL equation. Further, unknown properties of the considered ionic liquid and variation of these properties with temperature were predicted and introduced into the ASPEN + components properties database. Based on these data, optimum operation parameters of the respective separation equipment were established. In all case studies, the same condition had to be fulfilled, namely minimum methyl acetate content in the distillate from the extraction distillation column of 99.5mol-%. Results of simulations using the respective optimum operation parameters were employed in the economic evaluation of the three separation unit designs studied. It was found that the least energy-demanding design corresponds to the case study B in terms of both capital as well as operation expenses.

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Effects of the air–steam mixture on the permeability of damaged concrete

Massive concrete structures such as the containments of nuclear power plant must maintain their tightness at any circumstances to prevent the escape of radioactive fission products into the environment. In the event of an accident like a Loss of Coolant Accident (LOCA), the concrete wall is submitted to both hydric and mechanical loadings. A new experimental device reproducing these extreme conditions (water vapor transfer, 140 °C and 5 bars) is developed in the GeM Laboratory to determine the effect of the saturation degree, the mechanical loading and the flowing fluid type on the concrete transfer properties. The experimental tests show that the previous parameters significantly affect the concrete permeability and the gas leakage rate. Their evolution as a function of the mechanical loading is characterized by two phases that are directly related to concrete microstructure and crack development.     

On the dynamics of distillation processes—VI. batch distillation

We have developed a simple model which explains the behavior of azeotropic batch distillations. The model is in agreement with known experimental results and explains features of the distillation process which have previously been considered anomalous. The model can be used to design batch distillation processes operating at either infinite or finite reflux ratios.     

Separation of water–isotopes mixture in continuous-flow thermal diffusion columns for recovery of deuterium

The present study deals with the estimation of deuterium recovery from the separation of water–isotopes mixture (H₂O–HDO–D₂O) by continuous-flow thermal diffusion. First, the equations for predicting the degrees of separation for each component in H₂O–HDO–D₂O system were derived by following the same procedure performed in the previous work. The recovery of deuterium (D) was then estimated from the degrees of separation of HDO and D₂O and confirmed with the experimental results.     

Selective conversion of dihydroxyacetone–ethanol mixture into ethyl lactate over amphoteric ZrO2–TiO2 catalyst

The conversion of dihydroxyacetone in ethanol solution into ethyl lactate over several acidic and amphoteric oxides at 100–160 °C was studied. The formation of ethyl lactate with 80–90% selectivity was observed on amphoteric ZrO₂–TiO₂ oxide whereas hemiacetal and acetal of pyruval were the main products obtained over the acidic ZrO₂–SiO₂ catalyst and Amberlyst 15. Amphoteric ZrO₂–3TiO₂ oxide provides 89% yield of ethyl lactate at 140 °C and 1.0 MPa under the feed rate of 4 mmol C₃H₆O₃/g_cat/h.