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1999, Separation and Purification Technology
https://doi.org/10.1016/S1383-5866(98)00117-8…
13 pages
1 file
The effect of membrane distillation process parameters on ethanol-water separation has been investigated using a comprehensive mathematical model. Three mass transfer solutions are considered in the model, namely: the exact solution of the Stefan-Maxwell equations developed by Krishna and Standart; the approximate solution of the Stefan-Maxwell equations suggested by Krishna and Wesselingh; and the binary Fickian solution. Temperature and concentration variation along the flow and diffusion paths are accounted for in the model. Though the exact and approximate solutions of the Stefan-Maxwell equations are coincident with each other, some differences are noticed between them and the Fickian-based solution. The difference between the three mass transfer-based solutions, as well as the process performance under several process parameters, are discussed.
2014
The growing demand for energy and expected oil depletion have dramatically increased the fuel prices all over the world. Consequently, research and development are motivated to look-up other alternatives and discoveries to recover the shortage and maintain the fuel prices at lower rates. Ethanol is considered to be one of the fossil fuel alternatives which can be produced from renewable resources(Biomass) such as molasses (byproduct of cane sugar industry) . molasses can be fermented then separated from water using the pervaporation membrane technology .The aim of this study is to model and simulate the permeable evaporation (pervaporation) membrane unit for the separation ethanol-water mixture at different operating conditions. The investigation of the permeable evaporation (pervaporation) model has been conducted by altering the mixture inlet temperature and concentration step wise. Due to the model complexity, simulation of the process has been conducted on a computer program tha...
Chemical Engineering Journal, 1999
A multicomponent mass transfer model based on the Stefan–Maxwell formalism is developed to predict membrane distillation performance in separating azeotropic mixtures. The developed model accounts for all coupling interactions between the diffusing species as well as for temperature and concentration polarization effects. The model is validated with previously published experimental data of propionic acid/water azeotropic mixture. The model predicts the effect of the process relevant parameters very well.
CT y F - Ciencia, Tecnologia y Futuro
En este trabajo se planteó un modelo matemático para la transferencia de masa y energía durante la etapa de separación de etanol utilizando destilación con membranas al vacío. Este modelo es uno de los pocos propuestos para el estudio de la separación de etanol por destilación con membranas al vacío; solo Soni, Abildskov, Jonsson y Gani (2008) han propuesto un modelo de mayor complejidad que el del presente estudio. El modelo matemático fue validado utilizando cuatro casos de estudio reportados en la literatura. El modelo permite predecir satisfactoriamente los resultados experimentales para condiciones de operación que se encuentren entre 20 - 70ºC, con 0.25 - 5% p/p de etanol en la alimentación, presiones de 2000 - 6000 Pa y Reynolds entre 50 y 2700. Este modelo permitió realizar el análisis de la influencia de parámetros de operación y de diferentes tipos de membranas sobre variables de respuesta como flux de etanol, flux de agua y fracción de etanol en el permeado, utilizando la...
Membranes
The vacuum membrane distillation (VMD) process was applied to separate ethanol from a simulated ethanol–water solution using a commercial polytetrafluoroethylene (PTFE) membrane. The presence of ethanol in the ethanol–water solution with a 2 wt.% ethanol concentration at a temperature above 40 °C during the MD process may result in membrane failure due to an increase in the chance of the PTFE membrane wetting at high temperatures. Therefore, the operating temperature in this study was not higher than 35 °C, with an initial ethanol concentration up to 10 wt.%. This work focuses on optimizing the VMD operating parameters using the Taguchi technique based on an analysis of variance (ANOVA). It was found that the feed temperature was the most-affected parameter, leading to a significant increase in the permeation flux of the PTFE membrane. Our results also showed that the permeate flux was reported at about 24.145 kg/m2·h, with a separation factor of 8.6 of the permeate under the operat...
IAEME PUBLICATION, 2024
Fermentation of biomass is a well known technique used to produce the ethanol that can be used as an energy source to fulfill the energy demand of the rapidly expanding population and fuel demand of the transportation sector. Continuous ethanol separation from the fermentation broths can enhance the efficiency of the fermentation process. Membrane distillation in combination with the fermentation process may be the effective technique for ethanol separation. Membrane distillation is a separation process in which liquid mixture is vaporized by providing heat and vapour molecules are transferred through the microporous membrane. The required driving force for the Membrane distillation is vapour pressure difference across the microporous membrane which is induced by the temperature difference. Membrane distillation is commercialized for various applications such as desalination, wastewater treatment and in the food industry. This process is also applicable for various fields like Crystallization, treatment of dye effluents, Arsenic removal from aqueous solution and contaminated groundwater, Recovery of aroma compounds, Separation of azeotropic mixture. This review emphasized on various Membrane distillation configurations, membranes used in membrane distillation, their characteristics and performance parameters for ethanol separation from fermentation broth.
Polymers, 2020
High energy demand, competitive fuel prices and the need for environmentally friendly processes have led to the constant development of the alcohol industry. Pervaporation is seen as a separation process, with low energy consumption, which has a high potential for application in the fermentation and dehydration of ethanol. This work presents the experimental ethanol recovery by pervaporation and the semi-empirical model of partial fluxes. Total permeate fluxes between 15.6–68.6 mol m−2 h−1 (289–1565 g m−2 h−1), separation factor between 3.4–6.4 and ethanol molar fraction between 16–171 mM (4–35 wt%) were obtained using ethanol feed concentrations between 4–37 mM (1–9 wt%), temperature between 34–50 ∘C and commercial polydimethylsiloxane (PDMS) membrane. From the experimental data a semi-empirical model describing the behavior of partial-permeate fluxes was developed considering the effect of both the temperature and the composition of the feed, and the behavior of the apparent activ...
Brazilian Journal of Chemical Engineering, 2008
The aim of this work is to simulate and analyze an extractive distillation process for azeotropic ethanol dehydration with ethylene glycol and calcium chloride mixture as entrainer. The work was developed with Aspen Plus® simulator version 11.1. Calculation of the activity coefficients employed to describe vapor liquid equilibrium of ethanol -water -ethylene glycol -calcium chloride system was done with the NRTL-E equation and they were validated with experimental data. The dehydration process used two columns: the main extractive column and the recovery column. The solvent to feed molar ratio S/F=0.3, molar reflux ratio RR=0.35, number of theoretical stages Ns=18, feed stage Sf=12, feed solvent stage SS=3, and feed solvent temperature TS=80 ºC, were determined to obtain a distillate with at least 99.5 % mole of ethanol. A substantial reduction in the energy consumption, compared with the conventional processes, was predicted by using ethylene glycol and calcium chloride as entrainer.
Egyptian Journal of Chemistry, 2023
This work presents an investigation into the efficiency of ethanol separation from water using vacuum membrane distillation (VMD). The study explores the influence of variables such as feed flow rate, initial ethanol concentration, and temperature on the performance of the distillation process. The polyvinylidene fluoride (PVDF) membrane was utilized due to its desirable properties such as high thermal stability, chemical resistance, and excellent mechanical properties. The results showed that the feed temperature had the greatest impact on the permeation flux. The permeate flux and ethanol flux increased with increasing initial ethanol concentration, while the separation factor decreased. Increasing the feed flow rate also resulted in increased permeate flux, ethanol flux, and separation factor. The study provides valuable insights into the optimization of the VMD process for efficient ethanol-water separation. The findings could potentially contribute to the development of more sustainable and efficient separation processes in the industry.
Chemosphere, 2019
Four commercially available hydrophobic membranes (0.22 μm / 0.45 μm PVDF, 0.1 μm PP, and 0.22 μm PTFE) in direct contact membrane distillation (DCMD) apparatus were investigated in terms of the effect of fouling on the membrane distillation (MD) mass transfer coefficient and the dominant mode of mass transport phenomenon under different conditions (temperature, membrane material, flow regime, and membrane pore size). Accordingly, results confirmed that the fouling layer affects the mass transport resistance directly by resisting mass transport and indirectly by decreasing the heat transfer mechanism. In addition to the surface fouling layer, in MD, a significant quantity of particles was found to accumulate in the membrane pores. It was also observed that the contribution of Poiseuille flow to the entire mass transport phenomenon is significant at higher temperatures for larger pore size membranes. This highlights the need for careful consideration of the Poiseuille flow in the modeling and simulation of the MD mass transport process. It can be concluded that the flow rate does not affect the Poiseuille flow and cannot directly influence the entire mass transfer. Besides, this study provides systematic insight into how to develop a strategy to select the appropriate operating feed/permeate temperature fitting for our water demand and environmental conditions.
Separation and Purification Technology, 2015
Membrane distillation is a technique aimed at separating non-volatile components such as salts from aqueous feed streams. Mathematical modelling of a complex process like membrane distillation allows building further insight needed for effective analysis and optimization of the system, possibly leading to a breakthrough of the technology. Several models have been proposed in the literature for the heat and mass transport in the water channels of the module as well as inside the porous membranes. This article provides a critical review of these models and discusses the pros and cons of the different models to guide the reader into selecting the most suitable simulation approach. Moreover, research gaps in the literature are listed to indicate what is currently missing from a modelling as well as experimental data collection perspective. Areas for further research are suggested.
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