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Dr. Colin Scholes
Department of Chemical and Biomolecular Engineering, University of Melbourne, Parkville, VIC 3010, Australia

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0 Contactors
0 Gas Separation
0 Helium
0 carbon dioxide
0 Polymeric

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Journal article
Published: 17 January 2021 in Separation and Purification Technology
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The potential of membrane technology for Xenon (Xe) and Krypton (Kr) separation is evaluated at sub-ambient temperatures (-30 °C to 20 °C) by simulating two- and three-stage membrane processes. Unlike conventional membrane simulations, a rigorous approach of modelling is employed to capture the non-ideal behavior of Xe and Kr at the sub-ambient temperatures and permeability changes due to the Joule-Thomson effect. A selectivity target of ≥99 mol% in Xe and Kr purity is used, based on the activation energy of permeation. Results show the membrane processes require moderate Xe/Kr selectivity, achievable with current membranes, and reasonable pressure ratios of 5–15 to produce high purity Xe and Kr at the sub-ambient temperatures. The energy demand of the three-stage membrane process is determined and compared to that of conventional cryogenic distillation. The comparison shows significantly lower energy demand for the membrane process.

ACS Style

Ehsan Soroodan Miandoab; Seyed Hesam Mousavi; Sandra E. Kentish; Colin A. Scholes. Xenon and Krypton separation by membranes at sub-ambient temperatures and its comparison with cryogenic distillation. Separation and Purification Technology 2021, 262, 118349 .

AMA Style

Ehsan Soroodan Miandoab, Seyed Hesam Mousavi, Sandra E. Kentish, Colin A. Scholes. Xenon and Krypton separation by membranes at sub-ambient temperatures and its comparison with cryogenic distillation. Separation and Purification Technology. 2021; 262 ():118349.

Chicago/Turabian Style

Ehsan Soroodan Miandoab; Seyed Hesam Mousavi; Sandra E. Kentish; Colin A. Scholes. 2021. "Xenon and Krypton separation by membranes at sub-ambient temperatures and its comparison with cryogenic distillation." Separation and Purification Technology 262, no. : 118349.

Review article
Published: 17 December 2020 in ACS Sustainable Chemistry & Engineering
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CO2 emissions from industrial processes and their adverse implications on the climate is of major concern. Carbon capture and storage (CCS), especially using chemical-absorption-based processes, has been regarded as one of the most realistic pathways to curtail global warming and climate change. However, the energy-intensive nature of CO2 capture and therefore its expensive cost of operation has been regarded as the main barrier halting its widespread implementation among the portfolio of low-carbon energy technologies currently available. Recently, catalytic solvent regeneration has drawn significant attention as a new class of technology for energy-efficient CO2 capture with great potential for large-scale implementation. In this review, recent progress and developments associated with catalyst-aided solvent regeneration for low-temperature energy-efficient CO2 desorption is presented. A detailed discussion of heterogeneous acid–base catalyst is undertaken and the specific privileges, drawbacks, and challenges of each catalyst identified and commented upon. In keeping with the latest investigations, the promotion mechanism of catalytic CO2 desorption and the role of Lewis acids, Brønsted acids, and basic active sites are scrutinized. The performance of solid acid–base catalysts in different primary and blended amine solutions associated with their physicochemical properties is also reviewed. Finally, the status of catalytic solvent regeneration for post-combustion CO2 capture is comprehensively analyzed and a clear pathway for future research investigations is provided.

ACS Style

Masood S. Alivand; Omid Mazaheri; Yue Wu; Geoffrey W. Stevens; Colin A. Scholes; Kathryn A. Mumford. Catalytic Solvent Regeneration for Energy-Efficient CO2 Capture. ACS Sustainable Chemistry & Engineering 2020, 8, 18755 -18788.

AMA Style

Masood S. Alivand, Omid Mazaheri, Yue Wu, Geoffrey W. Stevens, Colin A. Scholes, Kathryn A. Mumford. Catalytic Solvent Regeneration for Energy-Efficient CO2 Capture. ACS Sustainable Chemistry & Engineering. 2020; 8 (51):18755-18788.

Chicago/Turabian Style

Masood S. Alivand; Omid Mazaheri; Yue Wu; Geoffrey W. Stevens; Colin A. Scholes; Kathryn A. Mumford. 2020. "Catalytic Solvent Regeneration for Energy-Efficient CO2 Capture." ACS Sustainable Chemistry & Engineering 8, no. 51: 18755-18788.

Journal article
Published: 27 August 2020 in Journal of Membrane Science
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Blending is a strategy to improve the permselectivity of gas separation membranes by combining the advantages of two or more polymers. The blending of polymers results in miscible or immiscible morphologies, which have distinctly different properties and performance benefits. Perfluoropolymers, specifically Teflon AF1600 and Hyflon AD60, have unique chemical properties that make them attractive as membranes for natural gas sweetening. Here, blended membranes of these two perfluoropolymers are generated, with miscible and immiscible morphologies achieved by varying the evaporation rate of the solvent. This ability to achieve two different blended morphologies is associated with the different solvability of the two perfluoropolymers in the solvent, not the miscibility of the polymers with each other. The miscible blended membranes had higher density than the pure polymers and CO2 sorption is bounded by that observed for pure Teflon AF1600 and Hyflon AD60 membranes, while CH4 sorption is depressed in the miscible blended membranes. Correspondingly, the CO2/CH4 selectivity of the miscible blended membranes was improved relative to the two pure polymer membranes. In contrast, the immiscible blended membranes had lower density and a more open morphology, especially the Teflon AF1600 discrete domains. This increased CO2 and CH4 permeability, compared to the pure polymer membranes, with comparable CO2/CH4 selectivity. To model the resulting performance, blended membrane mixing theories were applied; standard approximations based on the permeability of the pure polymer membranes and more rigorous modelling based on dual-sorption theory of the blended membranes sorption and diffusivity. The standard approximation models were unable to correlate with the experimental data for these blended membranes, while the dual-sorption based model was significantly more accurate. Therefore, to predict permselectivity of blended membranes performance it is more appropriate to employ the rigorous dual-sorption model.

ACS Style

Colin A. Scholes. Blended perfluoropolymer membranes for carbon dioxide separation by miscible and immiscible morphologies. Journal of Membrane Science 2020, 618, 118675 .

AMA Style

Colin A. Scholes. Blended perfluoropolymer membranes for carbon dioxide separation by miscible and immiscible morphologies. Journal of Membrane Science. 2020; 618 ():118675.

Chicago/Turabian Style

Colin A. Scholes. 2020. "Blended perfluoropolymer membranes for carbon dioxide separation by miscible and immiscible morphologies." Journal of Membrane Science 618, no. : 118675.

Journal article
Published: 20 August 2020 in Journal of Membrane Science
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A mathematical model of membrane performance is developed that incorporates fugacity-dependent permeabilities, competitive sorption, penetrant blocking and plasticization effects. The model also accounts for non-isothermal operation and includes real gas behavior and concentration polarization. Importantly, the model simultaneously considers plasticization caused by water vapor (H2O) and carbon dioxide (CO2). A simulation of biogas (composed of methane (CH4), CO2 and H2O) upgrading is performed using the new model and compared to models that use constant and pure gas permeability. Relative to these simplified models, the new model predicts differences up to 2% and 18% in CH4 recovery at low feed flowrates and the difference in CO2 removal can be as significant as 50%. Furthermore, simulations with and without water vapor in the feed give predictions that are 4.5%–34% different. The differences are attributed to the changes in fugacity-dependent permeabilities, particularly the sensitivity of these permeabilities to feed composition. An analysis indicates that the contributions of competitive sorption and penetrant blocking/plasticization to these differences is 19% and 32% in terms of CH4 recovery and CO2 removal, respectively. The remaining differences are due to real gas behavior, while concentration polarization has a negligible impact under the chosen conditions.

ACS Style

Ehsan Soroodan Miandoab; Sandra E. Kentish; Colin A. Scholes. Modelling competitive sorption and plasticization of glassy polymeric membranes used in biogas upgrading. Journal of Membrane Science 2020, 617, 118643 .

AMA Style

Ehsan Soroodan Miandoab, Sandra E. Kentish, Colin A. Scholes. Modelling competitive sorption and plasticization of glassy polymeric membranes used in biogas upgrading. Journal of Membrane Science. 2020; 617 ():118643.

Chicago/Turabian Style

Ehsan Soroodan Miandoab; Sandra E. Kentish; Colin A. Scholes. 2020. "Modelling competitive sorption and plasticization of glassy polymeric membranes used in biogas upgrading." Journal of Membrane Science 617, no. : 118643.

Journal article
Published: 23 May 2020 in Separation and Purification Technology
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Membrane gas-solvent contactors are a viable approach for the absorption of carbon dioxide (CO2) into solvents, such as potassium glycinate, compared to traditional solvent absorption. The hollow fibre membrane design does have limitations, as the presence of the membrane adds extra resistance to mass transfer compared to traditional solvent absorption. To reduce the impact of this extra resistance it is necessary to increase mass transfer in the solvent and gas phase boundary layers. This investigation aimed to increase mass transfer in the gas phase boundary layer of a membrane contactor process by applying oscillating gas flow conditions. For an asymmetric polydimethylsiloxane membrane contactor undergoing oscillating gas flow conditions, an average increase of 19% in overall mass transfer coefficient (KG) compared to non-oscillating gas flow was observed, for 15 wt% potassium glycinate solvent. The oscillating frequency of the gas phase had only a minor impact on performance, above 2 Hz, implying that oscillation of the gas phase was important for mixing, not the rate of the oscillation. Alternatively, KG approximately doubled in value as a function of increased oscillating amplitude. This was due to the resulting pressure wave producing localized increases in the partial pressure driving force for mass transfer across the membrane. For the membrane contactors studied, mass transfer correlations, in terms of Sherwood number, were proposed for the oscillating and non-oscillating flow conditions and fitted to the experimental data. This outcome highlighted the importance of inducing mixing within the gas phase to maximise mass transfer in membrane contactors.

ACS Style

Elaheh Hosseini; Ehsan Soroodan Miandoab; Geoffrey W. Stevens; Colin A. Scholes. Absorption of CO2 from flue gas under oscillating gas flow conditions in gas-solvent hollow fibre membrane contactors. Separation and Purification Technology 2020, 249, 117151 .

AMA Style

Elaheh Hosseini, Ehsan Soroodan Miandoab, Geoffrey W. Stevens, Colin A. Scholes. Absorption of CO2 from flue gas under oscillating gas flow conditions in gas-solvent hollow fibre membrane contactors. Separation and Purification Technology. 2020; 249 ():117151.

Chicago/Turabian Style

Elaheh Hosseini; Ehsan Soroodan Miandoab; Geoffrey W. Stevens; Colin A. Scholes. 2020. "Absorption of CO2 from flue gas under oscillating gas flow conditions in gas-solvent hollow fibre membrane contactors." Separation and Purification Technology 249, no. : 117151.

Journal article
Published: 07 January 2020 in Chemical Engineering Journal
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Hydrogen cyanide is an important feedstock in many chemical industries, synthesized from natural gas and ammonia. To recovery unreacted ammonia and purify the hydrogen cyanide from water and hydrogen, additional chemical separation processes are required. The conventional approach is to undertake these separations through solvent absorption; but gas separation membranes are a competitive alternative. This investigation examines the potential for membrane gas separation to replace solvent absorption in hydrogen cyanide processing. Importantly, the HCN permeability through a range of common polymeric membranes were measured and resulting HCN selectivity reported. Rubbery polymeric membranes’ permeability strongly correlated with condensability of the gases, and therefore in HCN processing the order of permeability was H2O > H2 ≈ HCN > N2. In contrast, glassy polymeric membranes’ permeability correlated with kinetic diameter of the gases, and permeability order was H2O > H2 > HCN ≈ N2. The presence of N2 in the gas stream however presented a challenge, as the similar permeability between N2 and HCN meant that separation of these two gases was difficult. A facilitated transport mechanism was developed based on metal chlorides within both glassy and rubbery polymeric membranes. The complexation between the hydrogen cyanide and the metal ion increased the concentration of HCN within the polymeric membrane and facilitated the permeation of HCN. Zinc chloride demonstrated a clear increase in HCN permeability and improved HCN/N2 selectivity for the two membranes studied. This improvement was further enhanced by the presence of water vapour, which augmented the complexation between HCN and the metal ion, achieving an order of magnitude increase in selectivity. Hence, this investigation demonstrated the potential for membrane gas separation to compete in hydrogen cyanide processing.

ACS Style

Colin A. Scholes. Hydrogen cyanide recovery by membrane gas separation. Chemical Engineering Journal 2020, 386, 124049 .

AMA Style

Colin A. Scholes. Hydrogen cyanide recovery by membrane gas separation. Chemical Engineering Journal. 2020; 386 ():124049.

Chicago/Turabian Style

Colin A. Scholes. 2020. "Hydrogen cyanide recovery by membrane gas separation." Chemical Engineering Journal 386, no. : 124049.

Journal article
Published: 23 December 2019 in Separation and Purification Technology
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Membrane gas-solvent contactors are a hybrid technology of solvent absorption with membrane separation that achieves efficient and compact carbon dioxide capture. Here, we report on a successful pilot plant trial of membrane contactor technology undertaking post-combustion carbon dioxide capture from flue gas generated by an Australian black coal fired power station. The pilot plant utilised membrane contactors to undertake CO2 absorption into 30 wt% monoethanolamine (MEA) and the subsequent solvent regeneration stage to produce a pure CO2 product. The pilot plant trials identified a commercially available non-porous poly dimethylsiloxane composite hollow fiber membrane as the most suitable for both CO2 absorption and solvent regeneration. The overall mass transfer coefficient for CO2 absorption across the membrane into the solvent was comparable to laboratory results, enabling a recovery of >90% CO2 from the flue gas. Over time the mass transfer coefficient decreased because of both solvent dilution and some MEA loss, which reduced the enhancement the reaction provides to mass transfer in the solvent boundary layer. The overall mass transfer of CO2 from the solvent into the steam sweep during solvent regeneration was greater than that observed in the laboratory for the same temperature. The energy demand of the pilot plant was higher than for conventional CO2 capture technology, given the pilot nature of the process, lack of energy integration and thermal losses from uninsulated membrane modules. Accounting for these factors, the energy duty of the membrane contactor process was evaluated to be less than 4.2 MJ/kg of CO2 captured. Critically, the pilot plant demonstrated the viability of membrane contactor technology for post-combustion carbon capture on an industrial scale.

ACS Style

Colin A. Scholes; Sandra E. Kentish; Abdul Qader. Membrane gas-solvent contactor pilot plant trials for post-combustion CO2 capture. Separation and Purification Technology 2019, 237, 116470 .

AMA Style

Colin A. Scholes, Sandra E. Kentish, Abdul Qader. Membrane gas-solvent contactor pilot plant trials for post-combustion CO2 capture. Separation and Purification Technology. 2019; 237 ():116470.

Chicago/Turabian Style

Colin A. Scholes; Sandra E. Kentish; Abdul Qader. 2019. "Membrane gas-solvent contactor pilot plant trials for post-combustion CO2 capture." Separation and Purification Technology 237, no. : 116470.

Articles
Published: 23 November 2019 in Australian Journal of Multi-Disciplinary Engineering
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Helium is a non-renewable resource that is obtained from natural gas. The recent increase in the wholesale price of He has focused attention on exploiting low grade reservoirs. Cryogenic liquefaction for He recovery becomes increasing energy intensive as the feed He concentration decreases. Hence, alternative separation technologies are required and membrane gas separation has potential. Here, membranes are simulated for the recovery of He for a range of feed gas compositions. A cellulose acetate membrane is the focus, with simulations indicating that for a feed with less than 3 mol% He, a three-membrane stage cascade process is viable. The energy duty of the process increased with reduced He concentration, but this increase in energy duty is less than that observed for cryogenic liquefaction and below a feed concentration of 2.5 mol% He, the membrane process is energy competitive. Hence, membrane gas separation has potential for He recovery from natural gas.

ACS Style

Colin A. Scholes. Potential for helium recovery and purification in Australia through membrane gas separation. Australian Journal of Multi-Disciplinary Engineering 2019, 16, 13 -19.

AMA Style

Colin A. Scholes. Potential for helium recovery and purification in Australia through membrane gas separation. Australian Journal of Multi-Disciplinary Engineering. 2019; 16 (1):13-19.

Chicago/Turabian Style

Colin A. Scholes. 2019. "Potential for helium recovery and purification in Australia through membrane gas separation." Australian Journal of Multi-Disciplinary Engineering 16, no. 1: 13-19.

Review article
Published: 07 November 2019 in Frontiers of Chemical Science and Engineering
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Membrane technology holds great potential in gas separation applications, especially carbon dioxide capture from industrial processes. To achieve this potential, the outputs from global research endeavours into membrane technologies must be trialled in industrial processes, which requires membrane-based pilot plants. These pilot plants are critical to the commercialization of membrane technology, be it as gas separation membranes or membrane gas-solvent contactors, as failure at the pilot plant level may delay the development of the technology for decades. Here, the author reports on his experience of operating membrane-based pilot plants for gas separation and contactor configurations as part of three industrial carbon capture initiatives: the Mulgrave project, H3 project and Vales Point project. Specifically, the challenges of developing and operating membrane pilot plants are presented, as well as the key learnings on how to successfully manage membrane pilot plants to achieve desired performance outcomes. The purpose is to assist membrane technologists in the carbon capture field to achieve successful outcomes for their technology innovations.

ACS Style

Colin A. Scholes. Pilot plants of membrane technology in industry: Challenges and key learnings. Frontiers of Chemical Science and Engineering 2019, 14, 305 -316.

AMA Style

Colin A. Scholes. Pilot plants of membrane technology in industry: Challenges and key learnings. Frontiers of Chemical Science and Engineering. 2019; 14 (3):305-316.

Chicago/Turabian Style

Colin A. Scholes. 2019. "Pilot plants of membrane technology in industry: Challenges and key learnings." Frontiers of Chemical Science and Engineering 14, no. 3: 305-316.

Journal article
Published: 13 September 2019 in Journal of Membrane Science
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Some membrane gas separation applications operate at high temperature and pressure. However, the majority of membrane gas separation models employ simplifying assumptions which are not realistic under these conditions. In this study, a rigorous model is developed for polymeric hollow-fibre membrane modules incorporating non-isothermal separation (the Joule-Thomson effect), real gas behavior and concentration polarization. The model also accounts for temperature-dependent permeability, friction-based pressure loss on both feed and permeate sides and variable physical and transport properties. The rigorous model is applied for pre-combustion CO2 capture, i.e. CO2/H2 separation, and compared with a simplistic model for various polymeric membranes through changing temperature-independent activation energy of permeation and pre-exponential factor. Two types of H2- and CO2-selective membranes are then chosen for further analysis. As feed conditions change, the deviation between the rigorous and simplistic models ranges approximately from 2 to 12% for stage-cut and 2–20% for the permeate composition. The difference is mostly because of real gas behavior at low stage-cuts, while the Joule-Thomson effect adds to this behavior at high stage-cuts (≥40%) resulting in the greater deviation. The influence of concentration polarization, however, is found negligible even at high stage-cuts.

ACS Style

Ehsan Soroodan Miandoab; Sandra E. Kentish; Colin A. Scholes. Non-ideal modelling of polymeric hollow-fibre membrane systems: Pre-combustion CO2 capture case study. Journal of Membrane Science 2019, 595, 117470 .

AMA Style

Ehsan Soroodan Miandoab, Sandra E. Kentish, Colin A. Scholes. Non-ideal modelling of polymeric hollow-fibre membrane systems: Pre-combustion CO2 capture case study. Journal of Membrane Science. 2019; 595 ():117470.

Chicago/Turabian Style

Ehsan Soroodan Miandoab; Sandra E. Kentish; Colin A. Scholes. 2019. "Non-ideal modelling of polymeric hollow-fibre membrane systems: Pre-combustion CO2 capture case study." Journal of Membrane Science 595, no. : 117470.

Research article
Published: 19 June 2019 in Journal of Chemical Education
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Indigenous Australians are significantly underrepresented in chemistry based professions, which arises from their low participation in physical science subjects in secondary and tertiary education. This is a multifaceted issue with a number of identified solutions, one of which is to link chemistry with aspects of Indigenous culture. Here, four modules are presented that examine traditional Indigenous Australian practices in detail through a chemistry perspective. These modules assist students to better identify with chemistry principles and therefore encourage further inquiry. The first module is based on toxin removal from plant seeds through water solubility; the second is based on the medicinal properties of the tea tree, which results from isomers of organic compounds. The third module presents color hues of ochre pigments, which are dependent on inorganic chemistry, and the fourth module utilizes plant resin adhesive properties, which are based on glass transition temperatures. These modules have been assessed with Indigenous and non-Indigenous students, who demonstrated increased interest in chemistry. There is also encouraging evidence that these modules have assisted students in taking up additional chemistry subjects.

ACS Style

Colin A. Scholes. Educational Modules for Increasing Indigenous Australian Students’ Involvement in Chemistry. Journal of Chemical Education 2019, 96, 1914 -1921.

AMA Style

Colin A. Scholes. Educational Modules for Increasing Indigenous Australian Students’ Involvement in Chemistry. Journal of Chemical Education. 2019; 96 (9):1914-1921.

Chicago/Turabian Style

Colin A. Scholes. 2019. "Educational Modules for Increasing Indigenous Australian Students’ Involvement in Chemistry." Journal of Chemical Education 96, no. 9: 1914-1921.

Journal article
Published: 30 May 2019 in Separation and Purification Technology
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Membrane gas-solvent contactors are a viable hybrid technology approach to undertake efficient carbon dioxide capture. Current state-of-the-art membrane contactors are limited by the solvent boundary layer, which represents the major resistance to CO2 mass transfer. Here, oscillating solvent flow conditions were applied to membrane contactors to enhance the transfer of CO2 from the gas to the solvent phase. The membranes consisted of composite poly dimethyl siloxane hollow fibres and the solvent was potassium glycinate solution. The effect of oscillating solvent amplitude and frequency resulted in 20% increase in CO2 flux across the contactor system as well as an improvement in the overall mass transfer coefficient, compared to the non-oscillating system. Increasing both amplitude and frequency improved mass transfer, but with diminishing effect as the solvent flowrate increased. Hence, oscillating solvent flow conditions improved mass transfer only over a range of solvent flowrate. Describing the oscillation through a modified Reynolds number enabled a mass transfer correlation to be determined for this membrane contactor system. This correlation demonstrated that enhanced mass transfer was associated with the significant increase in the Reynolds Number of the oscillating system.

ACS Style

Elaheh Hosseini; Geoffrey W. Stevens; Colin A. Scholes. Membrane gas-solvent contactors undergoing oscillating solvent flow for enhanced carbon dioxide capture. Separation and Purification Technology 2019, 227, 115653 .

AMA Style

Elaheh Hosseini, Geoffrey W. Stevens, Colin A. Scholes. Membrane gas-solvent contactors undergoing oscillating solvent flow for enhanced carbon dioxide capture. Separation and Purification Technology. 2019; 227 ():115653.

Chicago/Turabian Style

Elaheh Hosseini; Geoffrey W. Stevens; Colin A. Scholes. 2019. "Membrane gas-solvent contactors undergoing oscillating solvent flow for enhanced carbon dioxide capture." Separation and Purification Technology 227, no. : 115653.

Journal article
Published: 25 May 2019 in International Journal of Greenhouse Gas Control
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Membrane gas-solvent contactors are potentially more efficient at undertaking solvent regeneration in carbon capture applications compared to traditional desorber columns. This potential is investigated here through modelling of two experimentally reported membrane contactors based on Teflon AF1600 and polydimethylsiloxane active layers, by a simple approximate model and a one-dimensional mass transfer model. The respective membrane contactors could be operated at temperatures below that corresponding to the vaporisation of the solvent, due to the separation of the solvent and gas phase by the membrane. This required a steam sweep operating under vacuum conditions. The calculated module length for the Teflon AF1600 membrane varied between 8.9–70.2 m with decreasing regeneration temperature. This increase in required length was due to reductions in overall mass transfer coefficient and mass transfer driving force as temperature is lowered. It was determined that at 110 °C a PDMS contactor of length 1.1 m was required to regenerate the solvent, achievable with commercial modules. A comparison of the equipment volume footprint, known as process intensification, revealed that both the Teflon AF1600 and PDMS membranes required a lower volume than a standard packed column when operating at temperatures above 90 °C. Temperatures higher than 95 °C also designated the transition above which membrane contactors have a lower energy duty than the corresponding solvent column approach. This energy duty is a trade-off between the reduction in latent heat required to produce CO2 and regenerate the solvent at lower temperatures, countered by the work duty of the vacuum pump needed to operate the steam sweep at pressures below atmospheric. The investigation demonstrated that membrane contactors are a viable alternative technology for solvent regeneration.

ACS Style

Colin A. Scholes. Membrane contactors modelled for process intensification post combustion solvent regeneration. International Journal of Greenhouse Gas Control 2019, 87, 203 -210.

AMA Style

Colin A. Scholes. Membrane contactors modelled for process intensification post combustion solvent regeneration. International Journal of Greenhouse Gas Control. 2019; 87 ():203-210.

Chicago/Turabian Style

Colin A. Scholes. 2019. "Membrane contactors modelled for process intensification post combustion solvent regeneration." International Journal of Greenhouse Gas Control 87, no. : 203-210.

Journal article
Published: 18 March 2019 in Membranes
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Polymers of intrinsic microporosity (PIMs) are a promising membrane material for gas separation, because of their high free volume and micro-cavity size distribution. This is countered by PIMs-based membranes being highly susceptible to physical aging, which dramatically reduces their permselectivity over extended periods of time. Supercritical carbon dioxide is known to plasticize and partially solubilise polymers, altering the underlying membrane morphology, and hence impacting the gas separation properties. This investigation reports on the change in PIM-1 membranes after being exposed to supercritical CO2 for two- and eight-hour intervals, followed by two depressurization protocols, a rapid depressurization and a slow depressurization. The exposure times enables the impact contact time with supercritical CO2 has on the membrane morphology to be investigated, as well as the subsequent depressurization event. The density of the post supercritical CO2 exposed membranes, irrespective of exposure time and depressurization, were greater than the untreated membrane. This indicated that supercritical CO2 had solubilised the polymer chain, enabling PIM-1 to rearrange and contract the free volume micro-cavities present. As a consequence, the permeabilities of He, CH4, O2 and CO2 were all reduced for the supercritical CO2-treated membranes compared to the original membrane, while N2 permeability remained unchanged. Importantly, the physical aging properties of the supercritical CO2-treated membranes altered, with only minor reductions in N2, CH4 and O2 permeabilities observed over extended periods of time. In contrast, He and CO2 permeabilities experienced similar physical aging in the supercritical treated membranes to that of the original membrane. This was interpreted as the supercritical CO2 treatment enabling micro-cavity contraction to favour the smaller CO2 molecule, due to size exclusion of the larger N2, CH4 and O2 molecules. Therefore, physical aging of the treated membranes only had minor impact on N2, CH4 and O2 permeability; while the smaller He and CO2 gases experience greater permeability loss. This result implies that supercritical CO2 exposure has potential to limit physical aging performance loss in PIM-1 based membranes for O2/N2 separation.

ACS Style

Colin A. Scholes; Shinji Kanehashi. Polymer of Intrinsic Microporosity (PIM-1) Membranes Treated with Supercritical CO2. Membranes 2019, 9, 41 .

AMA Style

Colin A. Scholes, Shinji Kanehashi. Polymer of Intrinsic Microporosity (PIM-1) Membranes Treated with Supercritical CO2. Membranes. 2019; 9 (3):41.

Chicago/Turabian Style

Colin A. Scholes; Shinji Kanehashi. 2019. "Polymer of Intrinsic Microporosity (PIM-1) Membranes Treated with Supercritical CO2." Membranes 9, no. 3: 41.

Journal article
Published: 04 September 2018 in Journal of Membrane Science
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Supercritical carbon dioxide (sc-CO2) will plasticize and partially solubilise polymeric membranes, resulting in alteration to the polymer morphology, impacting the gas separation properties. Here, cellulose triacetate (CTA) and polyimides, Matrimid and 6FDA-TMPDA membranes were exposed to supercritical CO2 for 2 and 8 h, followed by two depressurization protocols; a rapid depressurization of 12 MPa/min and a slow depressurization of 0.17 MPa/min. The resulting impact on He, N2, CH4 and CO2 permeability as well as the corresponding selectivities were then quantified. Matrimid membranes undergo substantial plasticization in the presence of sc-CO2 resulting in significant increases in permeability and loss of selectivity, irrespective of the sc-CO2 exposure protocol. CTA and 6FDA-TMPDA membranes experience competing phenomenon under supercritical conditions, both demonstrate limited CO2 plasticization which is offset by sc-CO2 partly solubilising the polymers, enabling rearrangement to a more compact morphology. The depressurization protocol strongly impacted the underlying morphology for these two membranes. Rapid depressurization resulted in a higher fractional free volume and greater gas permeability, which is attributed to the sudden expansion of CO2 sorbed in the polymer opening up the morphology. Slower depressurization resulted in a lower fractional free volume and decreased gas permeabilities, because the CO2 gradually desorbs, leaving behind a more dense morphology. The resulting decrease in permeability also corresponded with a significant increase in selectivity. For both CTA and 6FDA-TMPDA membranes the sc-CO2 treatment improved the gas permselectivity relative to the original state. Therefore, exposure to sc-CO2 presents an advantageous process to improve the performance of common polymeric membranes for gas separation.

ACS Style

Colin A. Scholes; Shinji Kanehashi. Polymeric membrane gas separation performance improvements through supercritical CO2 treatment. Journal of Membrane Science 2018, 566, 239 -248.

AMA Style

Colin A. Scholes, Shinji Kanehashi. Polymeric membrane gas separation performance improvements through supercritical CO2 treatment. Journal of Membrane Science. 2018; 566 ():239-248.

Chicago/Turabian Style

Colin A. Scholes; Shinji Kanehashi. 2018. "Polymeric membrane gas separation performance improvements through supercritical CO2 treatment." Journal of Membrane Science 566, no. : 239-248.

Journal article
Published: 21 May 2018 in Applied Sciences
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Membranes that are resistant to water vapor permeation have potential in natural gas sweetening by reducing the need for pretreatment. The perfluorinated polymer Teflon AF1600 has proven resistance to water vapor, which is adapted here in the form of composite membranes consisting of a Teflon AF1600 protective layer on membranes of the polyimide 4,4′-(hexafluoroisopropylidene) diphthalic anhydride 2,3,5,6-tetramethyl-1,4-phenylenediamine (6FDA-TMPDA) as well as Polymer of Intrinsic Micro-porosity (PIM-1). The permeability of CO2 and CH4 through the composite membranes was shown to be a function of the respective permeabilities of the individual polymer layers, with the Teflon AF1600 layer providing the majority of the resistance to mass transfer. Upon exposure to water, the composite membranes had reduced water permeation of 7–13% compared to pure membranes of 6FDA-TMPDA and PIM-1, because of the water resistance of the Teflon AF1600 layer. It was observed that water permeated as clusters through the composite structure. Under CO2-CH4 mixed gas conditions, 6FDA-TMPDA layer permselectivity performance was reduced and became comparable to Teflon AF1600, while the PIM-1 layer retained much of its high permselectivity performance. Importantly, at water activities below 0.2 the PIM-1 composite membrane achieved higher permeability for CO2 compared to water.

ACS Style

Colin A. Scholes. Water Resistant Composite Membranes for Carbon Dioxide Separation from Methane. Applied Sciences 2018, 8, 829 .

AMA Style

Colin A. Scholes. Water Resistant Composite Membranes for Carbon Dioxide Separation from Methane. Applied Sciences. 2018; 8 (5):829.

Chicago/Turabian Style

Colin A. Scholes. 2018. "Water Resistant Composite Membranes for Carbon Dioxide Separation from Methane." Applied Sciences 8, no. 5: 829.

Research article
Published: 06 March 2018 in Industrial & Engineering Chemistry Research
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Helium recovery and purification from a natural gas process is increasingly being investigated globally to address rising market demand, as traditional helium sources become depleted. Here, process simulations of two types of inorganic membranes were undertaken in Aspen HYSYS to investigate the possibility of recovering and purifying helium from the Nitrogen Rejection Unit (NRU) offgas close to the NRU’s operating temperature. The two membranes were a cobalt-silica membrane that has He/N2 selectivity through molecular sieving and a zeolite membrane that has N2/He selectivity at low temperatures, because of surface diffusion. Both membranes were able to achieve the desired He recovery and purification through a three-membrane-stage process, and for a feed of 4% He, the cobalt-silica membrane could achieve the same separation performance through a two-membrane-stage process above 340 K, because of increasing selectivity with temperature. In contrast, the zeolite membrane could not operate above 220 K, because of the loss of the surface diffusion mechanism. The difference in permeance of the two membranes significantly affected the membrane area, with the cobalt-silica membrane requiring three orders of magnitude more area than the zeolite membrane to recover and purify the same amount of helium. However, the zeolite membrane’s selectivity for N2 meant that the vast majority of the NRU offgas passed through the membrane into the permeate streams. Hence, to ensure a high helium recovery, the permeate streams from the second and third membrane stages must be recycled, resulting in permeate gas throughputs that are orders of magnitude higher than the cobalt-silica membrane process. This placed significant recompression duty on the zeolite membrane process, compared to the cobalt-silica process, and, as such, the zeolite membrane’s power duty for helium separation was at least five times greater than that of the cobalt-silica membrane. Hence, there is a tradeoff between the two inorganic membranes for helium recovery and purification, based on required membrane area and power demand.

ACS Style

Colin A. Scholes. Helium Recovery through Inorganic Membranes Incorporated with a Nitrogen Rejection Unit. Industrial & Engineering Chemistry Research 2018, 57, 3792 -3799.

AMA Style

Colin A. Scholes. Helium Recovery through Inorganic Membranes Incorporated with a Nitrogen Rejection Unit. Industrial & Engineering Chemistry Research. 2018; 57 (10):3792-3799.

Chicago/Turabian Style

Colin A. Scholes. 2018. "Helium Recovery through Inorganic Membranes Incorporated with a Nitrogen Rejection Unit." Industrial & Engineering Chemistry Research 57, no. 10: 3792-3799.

Correction
Published: 30 August 2017 in Industrial & Engineering Chemistry Research
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ACS Style

Colin A. Scholes; Ujjal Kumar Gosh; Minh T. Ho. Correction for “The Economics of Helium Separation and Purification by Gas Separation Membranes”. Industrial & Engineering Chemistry Research 2017, 56, 10214 -10214.

AMA Style

Colin A. Scholes, Ujjal Kumar Gosh, Minh T. Ho. Correction for “The Economics of Helium Separation and Purification by Gas Separation Membranes”. Industrial & Engineering Chemistry Research. 2017; 56 (36):10214-10214.

Chicago/Turabian Style

Colin A. Scholes; Ujjal Kumar Gosh; Minh T. Ho. 2017. "Correction for “The Economics of Helium Separation and Purification by Gas Separation Membranes”." Industrial & Engineering Chemistry Research 56, no. 36: 10214-10214.

Research article
Published: 19 April 2017 in Industrial & Engineering Chemistry Research
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ACS Style

Colin A. Scholes; Ujjal Kumar Gosh; Minh Ho. The Economics of Helium Separation and Purification by Gas Separation Membranes. Industrial & Engineering Chemistry Research 2017, 56, 5014 -5020.

AMA Style

Colin A. Scholes, Ujjal Kumar Gosh, Minh Ho. The Economics of Helium Separation and Purification by Gas Separation Membranes. Industrial & Engineering Chemistry Research. 2017; 56 (17):5014-5020.

Chicago/Turabian Style

Colin A. Scholes; Ujjal Kumar Gosh; Minh Ho. 2017. "The Economics of Helium Separation and Purification by Gas Separation Membranes." Industrial & Engineering Chemistry Research 56, no. 17: 5014-5020.

Review
Published: 17 February 2017 in Membranes
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Membrane gas separation has potential for the recovery and purification of helium, because the majority of membranes have selectivity for helium. This review reports on the current state of the research and patent literature for membranes undertaking helium separation. This includes direct recovery from natural gas, as an ancillary stage in natural gas processing, as well as niche applications where helium recycling has potential. A review of the available polymeric and inorganic membranes for helium separation is provided. Commercial gas separation membranes in comparable gas industries are discussed in terms of their potential in helium separation. Also presented are the various membrane process designs patented for the recovery and purification of helium from various sources, as these demonstrate that it is viable to separate helium through currently available polymeric membranes. This review places a particular focus on those processes where membranes are combined in series with another separation technology, commonly pressure swing adsorption. These combined processes have the most potential for membranes to produce a high purity helium product. The review demonstrates that membrane gas separation is technically feasible for helium recovery and purification, though membranes are currently only applied in niche applications focused on reusing helium rather than separation from natural sources.

ACS Style

Colin A. Scholes; Ujjal K. Ghosh. Review of Membranes for Helium Separation and Purification. Membranes 2017, 7, 9 .

AMA Style

Colin A. Scholes, Ujjal K. Ghosh. Review of Membranes for Helium Separation and Purification. Membranes. 2017; 7 (1):9.

Chicago/Turabian Style

Colin A. Scholes; Ujjal K. Ghosh. 2017. "Review of Membranes for Helium Separation and Purification." Membranes 7, no. 1: 9.