Exploring Distillation-Pervaporation Hybrid Process in a Single Column Using Hollow ﬁber Pervaporation Composite Membranes As Structured Packing

Materials Express

Exploring distillation-pervaporation hybrid process in a single column using hollow ﬁber pervaporation composite membranes as structured packing

Liwei Zhuang, Qingyuan Cao, Fei Liang, Yichao Hu, Weite Su, Xin Wen, Xiao-Hua Ma∗, and Zhen-Liang Xu State Key Laboratory of Chemical Engineering, School of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China

ABSTRACT Article This study developed a novel strategy for azeotrope separation such as ethanol-water binary system. Distillation-pervaporation hybridIP: 192.168.39.211 process was On: employed Fri, 01 Oct by 2021 using 04:07:40 hollow fiber pervaporation composite Copyright: American Scientific Publishers membranes as structured packing in a singleDelivered hybrid by column Ingenta rather than using pervaporation as an externally connected unit of the distillation column. The separating limitation of azeotrope challenged in conventional distillation could be readily overcome by continually removing water from the hybrid system via pervaporation. The competition between distillation and pervaporation has been found to be cause of unexpected concentration distribution in the hybrid column. The mass flux of mixture decreased with time whereas the selectivity of water to ethanol first increased then decreased with time. Analysis of this system illustrated that the increase in heating power and membrane area shortened time for obtaining certain content of ethanol in the mixture. However, faster decline in mass flux occurred due to an increase in the removal rate of water. With respect to its simplicity, efficiency and broad applicability, this hybrid process is expected to provide a benchmark for the enhancement of distillation-pervaporation process by hollow fiber membrane packing. Keywords: Pervaporation, Distillation, Hybrid Column, Hollow Fiber Structured Packing, Azeotrope Separation.

1. INTRODUCTION powerful weapon in combating global warming and a key Process integration is now a widely accepted technique for technology to realize green processes. designing sustainable and green chemical processes [1]. Currently, distillation and related operations are still the It refers to “complex technologies that replace large, most commonly employed separation processes, involved expensive, energy-intensive equipment or processes with in more than 95% of industrial applications in the chemical smaller, less costly, more efficient plants, or plants that industries [4, 5]. However, the separation of a large number combine multiple operations into a single apparatus or into of industrial solvent mixtures containing azeotropes which fewer devices” [2], to make the factory layout more com- cannot be separated through traditional distillation due to pact and reasonable, with lower unit consumption, less the identical composition in liquid and vapour phases. waste and byproducts, and eventually to improve produc- In addition, distillation is an energy intensive technology, tion efficiency, reduce production cost, improve security which is a considerable source of pollutants and green- and reduce environmental pollution [3]. It is therefore a house gases or a high consumption of auxiliary agents such as entrainer [6, 7]. Therefore, a drastic development in the field of azeotrope separation is of great significance and ∗Author to whom correspondence should be addressed. extremely urgent [8].

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Pervaporation is a membrane separation process in side of the hollow fibers without direct contact. The mass which a certain component of liquid mixture preferentially transfer is merely driven by the concentration gradient permeates through a dense membrane/porous ceramic without the presence of two-phase mixing. Thanks to the membrane and evaporates downstream [9]. The selectiv- operation, the hydrodynamic problems such as flooding, ity of pervaporation is governed by the transport rate of loading, weeping, foaming that are frequently found in the molecules through the membrane due to the differ- conventional devices disappear, presenting good chemi- ence in solubility and diffusivity among the components cal/thermal stability and high separation efficiency. Ma and rather than relative volatility. It is therefore one of the most coworkers employed a new process [32]. They used hol- potential technologies for azeotropic separations and the low fiber membrane as structured packing in a distillation like [10–12]. In addition, pervaporation is considered as column, in which, both vapour and liquid flow on the feed an energy saving process for separation [13–15]. side of the hollow fiber membranes. The mass transfer then Distillation integrated with pervaporation can potentially takes place on the feed side of the membranes with mixing exploit and improve the performance that both technology of the two phases. Compared with conventional packing will achieve separately, while overcoming the disadvan- such as Raschig ring, Berl saddle, Mellapark (250Y) and tages of both [10, 16]. The first reported work regarding so on, a better performance is observed and the height of a distillation column integrated with membranes for per- transfer unit can be reduced to 3.6 cm (with current vapour vaporation or vapour permeation in the same column can velocity 39.4 cm/s) and also can be operated above the be seen in the patent by Fontalvo et al. [17]. A series of flooding line. further studies have been conducted, which significantly Better separating performance could be expected promote the understanding and application of distillation- through hybrid distillation and pervaporation together pervaporation hybrid system [5, 16, 18–22]. A traditional since the azeotrope limitation could be broken by pervapo- distillation-pervaporation hybrid system is comprised of ration. In addition, there is no need for inter-stage heating a distillation column and an externally connected perva- because the energy required for pervaporation is supplied poration module, either removing a specific component by the condensation of the vapour, and the hybrid pro- from a side stream of the distillation column or used cess provides a convenient geometry since it is relatively as a final treatment stage [12,IP: 16]. 192.168.39.211 However, a tempera- On: Fri, 01compact Oct 2021 and 04:07:40 allows good vapour and liquid distributions. ture drop along the membrane existsCopyright: as the components American ScientificTherefore, Publishers in the present work, hollow fiber pervapora- permeate and evaporate through the membrane,Delivered which by Ingentation composite membranes with a dense separation layer leads to the demand for the inter-stage heat exchangers on the outside surface were used as structured packing to between the consecutive pervaporation modules where the combine distillation and pervaporation together in a single Article retentate flows between stages in liquid phase [13, 23]. column. The performances of the pervaporation-distillation Fontalvo et al. found that a retentate stream composed hybrid process were analyzed and it was expected that of liquid and vapour could cause significant decrease in this analysis would provide guidance for the research on requirements of membrane area (about 20–40%) and no distillation-pervaporation hybrid process. inter-stage heat exchangers would be needed [24, 25]. This special operation of liquid-vapour feed enables the 2. EXPERIMENTAL DETAILS reduction in capital cost and mitigation of the effects 2.1. Materials and Hollow Fiber Pervaporation of concentration/temperature polarization. Meanwhile, the Membrane Fabrication vapour phase has intensified the heat and mass transfer by All the reagents were purchased from Sinopharm Group supplying heat through condensation and promoting two- Co. Ltd., Shanghai, China, and used without further purifi- phase instability. Therefore, a proper configuration for a cation. Deionized water was used throughout the work. distillation-pervaporation hybrid system will be of great The hollow fiber pervaporation membranes could be importance. purchased from Sulzer or any other supplier, whereas To this end, a novel coupling method was employed the ones used in the current work were home-made and in the present work: hollow fiber membranes were used reported previously [33]. Firstly, polyacrylonitrile (PAN) as structured packing as well as the pervaporation mem- hollow fiber ultrafiltration membranes were fabricated via branes to combine distillation and pervaporation processes nonsolvent induced phase inversion (mass fraction ratio: together in a single column. In feed side of membrane, PAN/polyvinylpyrrolidone/dimethylacetamide = 15/4/81). vapour and liquid flow in counter-current mode as the two Secondly, PAN hollow fiber membranes were coated by phases in distillation, and in the permeate side, the per- 8.0 wt% polyvinyl alcohol aqueous solution for 30 sec- meate is collected to achieve the pervaporation process. onds and hanged vertically singly to dry at room temper- Cussler et al. [26–28], and many other researchers [29–31], ature. Thirdly, the coated PAN hollow fiber membranes have adopted hollow fiber membranes as structured pack- were crosslinked by glutaraldehyde crosslinking solution = ing in membrane contactors. In their operation system, the (mass fraction ratio: glutaraldehyde/HCl/acetone/H2O vapour and liquid flow separately in the feed or permeate 4/1/45/50) for 30 minutes. The hollow fiber pervaporation

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Fig. 1. Schematic diagram of the hybrid process using hollow fiber pervaporation composite membranes as structured packing. composite membranes were finally obtained after drying with the same shell structure. There were 3 fiber bundles and used as structured packing. with different number of fibers as the inserted units for Article The break strength, elongation at break and Young’s each parallel test. The fibers were evenly packed to offer modulus of these hollow fibers (universalIP: 192.168.39.211 testing machine, On: Fri, 01uniform Oct 2021 transport 04:07:40 condition for each fiber. The gaps among QJ210A, China) were 10.4 ± 1MPa,4.27Copyright:± American0.1% and Scientific Publishers Delivered by Ingentathe upper end of the hybrid column and the hollow fibers 351±7 MPa, respectively, indicating excellent mechanical were potted with epoxy resin. Whilst at the bottom end of properties. The initial water contact angle (JC2000D, Pow- the hollow fibers, each end of the hollow fiber was potted erEach, China) was 65 (hydrophilic if contact angle is with epoxy resin. During the experiment, 100 g 85.0 wt% below 90 ), confirming that water would be preferentially ethanol aqueous was added to the reboiler, which was permeated through the membrane. heated with an oil bath. The vapour entered the hybrid column from the bottom and flowed upwards along the 2.2. Distillation-Pervaporation Hybrid Process outside surface of the hollow fiber membranes. The vapour The main part of the hybrid process was an integrated leaving the top of the column was condensed and refluxed distillation-pervaporation hybrid column, as shown in downward along the outside surface of the hollow fiber Figure 1. A designed number of hollow fiber pervaporation membranes. Countercurrent contact between the vapour composite membranes were vertically packed in the hybrid and liquid was achieved. Meanwhile, pressure of 2.0 kPa column, i.e., 10, 15, 20 fibers in columns 1, 2, 3, respec- was applied on the upper end of the permeate side of tively. The tests were conducted in 3 separated columns hollow fiber membranes to allow water/ethanol evaporation and permeation through the hollow fiber membranes. Table I. Parameters of integrated distillation-pervaporation hybrid The permeate stream was removed and collected into the column. cold trap, while the vapour and liquid kept countercurrent Column type Column 1 Column 2 Column 3 contact on the outside separation layer of the membrane to allow both the pervaporation and distillation processes Column diameter (ds , cm) 1.90 1.90 1.90 Column cross section (cm2) 2.84 2.84 2.84 to be carried out at the same time within the same col-

Fiber inner diameter (di , cm) 0.115 0.115 0.115 umn. The parameters of each hybrid column were shown d Fiber outer diameter ( 0, cm) 0.180 0.180 0.180 in Table I. The hybrid column was run at total reﬂux to Number of ﬁbers (n)101520simplify the process analysis. Effective length (l,cm)∗ 19.0 19.0 19.0 Effective membrane area (A,10−2m2) 1.07 1.61 2.15 Area per volume (a,m2/m3) 281 422 563 3. ANALYSIS AND CALCULATION Module void fraction () 0.910 0.865 0.820 Packing factor (a/3,m−1) 373 652 1021 Samples were taken simultaneously from two sources: the distillate reservoir and the liquid discharged from the ∗ Notes: Length of mass transfer, total length was 25.0 cm. column bottom. The samples were measured with Gas

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chromatograph (Techcomp, GC7890, China) installed with column top after 8 h when the ethanol-water azeotropic a thermal conductivity detector (TCD) and a GDX-102 concentration was broken. This unexpected phenomenon packed column. may result from the competition between the distillation The pervaporation performance was tested as detailed in and pervaporation. In conventional distillation, the light Ref. [34]. The pressure was kept at 2.0 kPa via a vacuum component (ethanol) concentrates in the gas phase and the pump. The temperature of the ethanol aqueous solution heavy component (water) concentrates in the liquid phase was 50 C. Permeation flux (J ,g·m−2 ·h−1) and selectivity due to their difference in volatility. This process results (ij ) of hollow fiber pervaporation composite membrane in a higher concentration of ethanol in the upper region were defined as follows [35–37]. than the one in the lower region of the distillation column. m However, a higher concentration of water corresponds to J = A × t (1) a higher partial pressure of water in the feed side, which will cause a higher rate of water pervaporation in the bot- where m is the total amount of permeate liquid (g); A is tom than the one in the top of the distillation column. 2 the effective area of the membrane for pervaporation (m ); Therefore, a higher concentration of ethanol in the bottom t is the duration (h). than the one in the top was realized, presenting a reverse G G ethanol concentration distribution to the conventional one. = P /P (2) ij i j This special competition between processes, i.e., perva- G G poration and distillation, in such hybrid system deserves where Pi and Pj represent the permeability of component G G attention as it is essential to the design and optimization i or j. Pi (Pj ) has the expression as follows. of hybrid systems. P G = J Figure 2(b) presents the total amount of collected per- i i p − p (3) i0 i meate and the accumulative ethanol content, both as a function of time. The total amount of permeate increased p p where i0 (Pa) and i (Pa) are partial pressures of compo- from 2.64 g at t = 1 h to 15.03 g at t = 12hwithagrad- i nent on either side of the membrane, is the thickness of ually decreasing rate of accumulation. The accumulative membrane (m), J (mol·m−2 ·h−1) is the molar flux of com- i IP: 192.168.39.211 On: Fri, 01ethanol Oct 2021 content 04:07:40 in the permeate increased with time. The i J · −2 · −1 ponent , which differs from the massCopyright: flux ( ,g Americanm h ) Scientificchanges Publishers of the two aforementioned parameters resulted in Eq. (1). Delivered by Ingentain the time dependence of mass flux and selectivity of water to ethanol, as shown in Figure 2(c). The mass flux 4. RESULTS AND DISCUSSION decreased from 164 g/(m2 · h) to 15 g/(m2 · h) during t = Article 4.1. Effect of Pervaporation on Distillation- 1 h to 12 h, whereas the selectivity first increased then Pervaporation Hybrid Process decreased with a maximum of 525.5 at t = 9h. Figure 2(a) shows the ethanol content in three regions: In the initial stage, the gas and liquid mixture with bottom and top in the feed side and the permeate side, high water content in the hybrid column, kept contact with demonstrating the effect of pervaporation on distillation- the liquid film on the pervaporation composite membrane. pervaporation hybrid process with hollow fiber pervapo- A large amount of mixture was removed by pervaporation, 2 ration composite membranes as structured packing. When resulting in high mass flux [up to 164 g/(m · h)]. At t = using hollow fiber pervaporation composite membrane as 1 h, the molar flux ratio of water to ethanol was approxi- structured packing without pervaporation, ethanol contents mately 35.6 to 1 [18.49 mol/(m2 ·h) and 0.24 mol/(m2 ·h)]. kept constant, 84.9 wt% in column top and 78.7 wt% in As the hybrid process progressed, the content of water in column bottom, and reached a steady state due to total the hybrid column decreased due to the relatively higher reflux. However, this steady state was not observed in the removal rate of water than the one of ethanol. Since the hybrid process. As shown in Figure 2(a), both ethanol con- membranes are more permeable to water as indicated by tents in column top and bottom increased with operating the selectivity, the decrease in water content of the mix- time until it finally exceeded the ethanol azeotropic con- ture could result in the decline of mass flux by decreas- centration of 95.6 wt% [shown in dashed line in Fig. 2(a)] ing the partial pressure of water in the feed side. As the at 8 h because water was selectively removed by perva- dynamic change in the content of mixture caused the time- poration. Ethanol content was finally up to 96.0 wt% in dependence of partial pressure distribution between the column top and 97.7 wt% in column bottom at 12 h. two components, the molar flux ratio of water to ethanol The results showed that in the distillation-pervaporation gradually decreased into 4.9 to 1 [0.548 mol/(m2 · h) and hybrid column the ethanol-water azeotropic concentration 0.113 mol/(m2 · h)]. Therefore, the accumulative ethanol could be broken and that ethanol concentrations greater content in the total amount of permeate increased with than 96.0 wt% were achievable, which agreed well with time. those reported in literatures [5, 16, 21]. The ethanol con- The experimental results presented in Figure 2 have centration in column bottom was even higher than that in been analyzed and the mechanisms behind them have been

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(a) (b)

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Fig. 2. Effect of pervaporation on distillation-pervaporation hybrid process with hollow fiber pervaporation membranes as structured packing, (a) ethanol content in feed side and permeate side; (b) total amount of collected permeate and accumulative ethanol content in the permeate; (c) flux and selectivity (water to ethanol) of pervaporation membrane unit in the hybrid system. Column 2 was used, which contained 15 hollow fiber pervaporation composite membranes with 19.0 cm in effective length, as shown in Figure 1. The operating conditions were as follows: Feedstock was 100 g ethanol aqueous solution (85 wt.%), oil bath temperature was set at 105 C and pressure in the permeate side of hollow fiber membranes was kept at 2.0 kPa through a vacuum pump. Total reflux was kept in the experiment. discussed, except for the phenomenon regarding the turn- of ethanol near the membrane surface. The increase in the ing point of selectivity. Similar phenomenon happened in driving force of ethanol was reflected by the reduction of the study by Baker et al. [37], which described the removal the membrane selectivity of water to ethanol. of ethanol from the water/ethanol mixture (ethanol 0.5– 16 wt%) by pervaporation with membranes more perme- 4.2. Effect of Oil Bath Temperature on able to ethanol. In their study, ethanol/water selectivity Pervaporation-Distillation Hybrid Column first decreased then increased with a minimum of approx- Figure 3 shows the effect of oil bath temperature on imately 1.4. We attempt to explain this phenomenon in pervaporation-distillation hybrid process with hollow fiber present study by describing the process in a micro level. membranes as structured packing. The bath temperature is Initially, the increase in the ethanol content of feedstock an indication of the heating power supplied in the reboiler, caused a higher mass transfer resistance to ethanol in within which the water/ethanol evaporate due to the heat- the boundary layer of feed side. Although the selectivity of water to ethanol is an intrinsic property of the ing by oil bath. The gas mixture from the reboiler keeps pervaporation membrane, it appeared to increase due to supplying heat in the entire system. Therefore, the main the underlying effect of boundary layer resistance. As the effect of oil bath temperature was associated with the rate ethanol content of feedstock increased, another effect on of heat supplied to the hybrid system. Higher oil bath the selectivity became dominant, which was the increase in temperature corresponded to higher flow rates of upward the real partial pressure of ethanol due to the accumulation gas and downward liquid. Every elementary process in the

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(a) (b)

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Fig. 3. Effect of oil bath temperature on pervaporation-distillation hybrid process with hollow fiber membranes as structured packing, (a) ethanol content in the column top; (b) ethanol content in the column bottom; (c) flux of pervaporation; (d) water content in the permeate liquid. Column 2 was used, which contained 15 hollow fiber pervaporation composite membranes with 19.0 cm in effective length, as shown in Figure 1. The operating conditions were as follows: Feedstock was 100 g ethanol aqueous solution (85 wt.%), oil bath temperature was set at 105 C and pressure in the permeate side of hollow fiber membranes was kept at 2.0 kPa through a vacuum pump. Total reflux was kept in the experiment.

hybrid system was accelerated due to the increase in heat- In the proceeding of the hybrid process, the mass fluxes ing power. all decreased with time regardless of the difference in oil As shown in Figures 3(a), (b) and (d), increasing the oil bath temperatures, as shown in Figure 3(c). The mecha- bath temperature reduced the time to obtain certain ethanol nism of the decline in mass flux with time was analyzed content in mixture. For example, nearly 2 h has been saved and discussed in previous section of this paper. However, at 115 C than 105 C to achieve the ethanol content of attention should be paid to the difference in the mass 91 wt% in the column bottom, as shown in Figure 3(b). fluxes among different oil bath temperatures. Initially, the This is because the process in the hybrid system is a higher the oil bath temperature was, the higher the mass mass/heat transfer coupled process. The improvement in flux was. A turning point emerged at t = 4hwhenthe the heat transfer rate has accelerated the evaporation in mass flux at 115 C dropped below the ones at 105 or the reboiler and liquid film adhering to the membrane, 110 C. 2 Hours later, a second turning point showed resulting in the double intensification of the distillation and up when the mass flux at 110 C became lower than pervaporation. Although the change in heating power has the one at 105 C. It indicates that the widely accepted altered the rate of process, the phenomenon of ethanol con- fouling behavior in water filtration is also applicable to tent in the bottom being higher than the one in the top has the distillation-pervaporation or pervaporation in another also been found at 110 and 115 C due to pre-described form. In water filtration with foulants accumulated on the process competition in such hybrid systems. membrane surface, higher flux will cause faster decline

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(a) (b)

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Fig. 4. Effect of membrane area on pervaporation-distillation hybrid process with hollow fiber membranes as structured packing, (a) ethanol content in the column top; (b) ethanol content in the column bottom; (c) flux of pervaporation; (d) water content in the permeate liquid. Columns 1–3 with 10, 15 and 20 hollow fiber membranes inside were used, as shown in Figure 1. The operating conditions were as follows: Feedstock was 100 g ethanol aqueous solution (85 wt.%), oil bath temperature was set at 105 C and pressure in the permeate side of hollow fiber membranes was kept at 2.0 kPa through a vacuum pump. Total reflux was kept in the experiment. in flux due to the increase in fouling resistance [38, 39]. promote the understanding of the general membrane-based In the hybrid process in present study, higher mass flux separations. supported by higher heating power will cause faster concentrating of ethanol in the liquid film adhering to the 4.3. Effect of Membrane Area on Pervaporation- membrane, thus resulting in faster decline of mass flux Distillation Hybrid Column since the membrane is more permeable to water. However, Figure 4 displays the effect of membrane area on the increase in two-phase flow rate can affect the perva- pervaporation-distillation hybrid column with hollow poration flux in an opposite way by suppressing the con- fiber membranes as structured packing. All the tests centration polarization with stronger liquid–gas interaction were conducted in the same column. As shown in (instability of two-phase flow). If the two-phase flow rate Figures 4(a), (b) and (d), increasing the membrane area is assumed to increase linearly with the oil bath tempera- reduced the time to obtain certain ethanol content in mixture, the Reynolds number would increase by a maximum ture. In Figure 4(c), pronounced decline in mass flux with of 8–9%. This magnitude of increase in Reynold number time has also been presented with different membrane could be negligible in terms of hydrodynamics. In addi- areas. The phenomenon of ethanol content in the bot- tion, the liquid film adhered to the membrane may hinder tom being higher than the one in the top has also been the effect of multiphase flow instability on the concen- found in the other cases with different membrane areas. tration boundary layer. Therefore, the positive effect of It indicates that the competition between the distillation two-phase flow on the pervaporation appeared ignorable in and pervaporation is an intrinsic character of such hybrid present hybrid system. This enlightening phenomenon will system.

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The mechanisms of the two aforementioned parameters References and Notes (heating power and membrane area) affecting the process 1. Reay, D., Ramshaw, C. and Harvey, A., 2013. Process Intensi- are different since the turning point regarding the rela- fication: Engineering for Efficiency, Sustainability and Flexibility. tive mass flux among different operating conditions didn’t Oxford, Butterworth-Heinemann. 2. Charpentier, J.C., 2005. Process intensification by miniaturization. show up in Figure 4(c). However, as shown in Figure 3(c), Chemical Engineering and Technology, 28(3), pp.255–258. there is also a difference in the rate of flux decline among 3. Foo, D.C. and Tan, R.R., 2016. A review on process integration tech- cases with different membrane area. At t = 1 h, the ratio of niques for carbon emissions and environmental footprint problems. mass fluxes was 263:164:142, which approximately equal Process Safety and Environmental Protection, 103, pp.291–307. 4. Naidu, Y. and Malik, R.K., 2011. A generalized methodology for to the inverse ratio of membrane areas 2:3:4. As the pro- optimal configurations of hybrid distillation-pervaporation processes. cess progressed, the mass fluxes of cases with membrane Chemical Engineering Research and Design, 89(8), pp.1348–1361. − − areas 1.07 × 10 2 m2 and 2.15 × 10 2 m2 at t = 8hwere 5. Haelssig, J.B., Thibault, J. and Tremblay, A.Y., 2011. Numerical 61 g · m−2 · h−1 and 40 g · m−2 · h−1, respectively. It means investigation of membrane dephlegmation: A hybrid pervaporation- that the initial higher mass flux due to the less mem- distillation process for ethanol recovery. Chemical Engineering and Processing: Process Intensification, 50(11–12), pp.1226–1236. brane area will cause faster concentrating of ethanol in 6. Luis, P., Amelio, A., Vreysen, S., Calabro, V. and Van der mixture. Bruggen, B., 2014. 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The decline in pervaporation flux with Characterization, separation performance, and model analysis of time resulted from the increase in ethanol content of the STPP-chitosan/PAN polyelectrolyte complex membranes. Journal of feed side. The selectivity of water to ethanol first increased Applied Polymer Science, 120(2), pp.1017–1026. then decreased during the operation, presenting a maxi- 12. Mahdi, T., Ahmad, A., Nasef, M.M. and Ripin, A., 2015. State-of- mum selectivity of 525.5. The cause of the turning point of the-art technologies for separation of azeotropic mixtures. Separa- tion and Purification Reviews, 44(4), pp.308–330. the selectivity could be the interaction between the mass 13. Gomez, M.T.D.P., Klein, A., Repke, J. and Wozny, G., 2008.Anew transfer resistance in the liquid film and the dynamic evo- energy-integrated pervaporation distillation approach. Desalination, lution of partial pressure distribution. 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Basic principles of a hybrid dis- acknowledge financial support from China Scholarship tillation and pervaporation unit in a single column: An analytic tool. Council (201906745003). Chemical Engineering, 69, pp.565–570.

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Received: 15 January 2020. Accepted: 25 January 2020.

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