Guidelines for techno-economic analysis of adsorption processes

Techno-economic analyses (TEAs) of CO2 capture technologies have risen in popularity, due to growing interest in meeting CO2 emissions reduction targets. Adsorption processes are one of the technologies proposed for CO2 capture, and although difficult, standardisation of TEAs for adsorption should be attempted. The reason is that TEAs are often referred to as input data to other forms of modelling, to guide policy, and act as summaries for those unfamiliar with adsorption processes. Herein, we discuss the aspects that should be considered when conducting TEAs for CO2 adsorption processes, we present the implications of choices made at the TEA stage and offer guidance on best practice. Overall, our aim is to make TEAs of adsorption processes more widely accessible to the adsorption community, and also more generally to communities engaged in the evaluation of CCS technologies

Regeneration performance of metal–organic frameworks

Notions about the reception of print fiction as well as new media texts have a strong tendency to fall back upon the dichotomy between naïve and critical reading. It is presupposed that reception will be characterized by either the one or the other. We will try to critique this dichotomy on the basis of the hypothesis that media cultural change brings with it new and hybrid textual forms, ways of reading, and patterns of reception which not lend themselves to description in simple terms of naïve or critical. We make a case for the necessity of transgressing the dominant assumptions of transactional reception theory within literary studies and instead move in the direction of what we call creative reading and media-reflexivity

Polyrotaxane-based thin film composite membranes for enhanced nanofiltration performance

© 2020 An urgent need exists for the development of advanced water purification technologies to meet the increasing global demand being placed on freshwater resources. Membrane-based separation technologies for size-selective contaminant removal represent a promising approach to achieve this goal. Here, a novel thin film composite nanofiltration membrane is prepared via interfacial polymerization of α-cyclodextrin on a commercially available polyacrylonitrile substrate. Subsequent in-situ inclusion complexation of alkyne-functionalized poly(ethylene glycol) (PEG) is then used to tune the polyrotaxane-based pores for size-dependent filtration. The resultant membrane shows excellent size-selective rejection rates for organic dye (e.g. rhodamine B, >99%) as well as heavy-metal ions (e.g. Co(II), >90%), while crucially maintaining high water permeance (e.g. H2O: 7.1 L h−1 m−2 bar−1). The facile and straightforward synthetic approach to the fabrication of polyrotaxane nanofiltration membranes, combined with their strong nanofiltration separation performance, holds significant promise for membrane-based water purification applications

Electroreduction of CO2/CO to C2 products: process modeling, downstream separation, system integration, and economic analysis.

Direct electrochemical reduction of CO2 to C2 products such as ethylene is more efficient in alkaline media, but it suffers from parasitic loss of reactants due to (bi)carbonate formation. A two-step process where the CO2 is first electrochemically reduced to CO and subsequently converted to desired C2 products has the potential to overcome the limitations posed by direct CO2 electroreduction. In this study, we investigated the technical and economic feasibility of the direct and indirect CO2 conversion routes to C2 products. For the indirect route, CO2 to CO conversion in a high temperature solid oxide electrolysis cell (SOEC) or a low temperature electrolyzer has been considered. The product distribution, conversion, selectivities, current densities, and cell potentials are different for both CO2 conversion routes, which affects the downstream processing and the economics. A detailed process design and techno-economic analysis of both CO2 conversion pathways are presented, which includes CO2 capture, CO2 (and CO) conversion, CO2 (and CO) recycling, and product separation. Our economic analysis shows that both conversion routes are not profitable under the base case scenario, but the economics can be improved significantly by reducing the cell voltage, the capital cost of the electrolyzers, and the electricity price. For both routes, a cell voltage of 2.5 V, a capital cost of $10,000/m2, and an electricity price of <$20/MWh will yield a positive net present value and payback times of less than 15 years. Overall, the high temperature (SOEC-based) two-step conversion process has a greater potential for scale-up than the direct electrochemical conversion route. Strategies for integrating the electrochemical CO2/CO conversion process into the existing gas and oil infrastructure are outlined. Current barriers for industrialization of CO2 electrolyzers and possible solutions are discussed as well

Two-dimensional nanosheet-based gas separation membranes

Two-dimensional (2D) materials of nanosized thickness are emerging building blocks for designing membranes with superior performance (i.e. high gas permeation flux and selectivity), as a result of their unique nanostructures. In this review, we discuss the recent breakthroughs in the synthesis of 2D nanosheets and the preparation of 2D nanosheet-based gas separation membranes, focusing on the synthetic methods for preparing 2D nanosheets (covering inorganics, hybrids, carbons and organics), the structural properties of 2D nanosheets, the fabrication methods of 2D nanosheet-based membranes, and their performance in gas separation. The current technical limitations and future research directions in this field are also discussed

A comparison of multicomponent electrosorption in capacitive deionization and membrane capacitive deionization

In this study, the desalination performance of Capacitive Deionization (CDI) and Membrane Capacitive Deionization (MCDI) was studied for a wide range of salt compositions. The comprehensive data collection for monovalent and divalent ions used in this work enabled us to understand better the competitive electrosorption of these ions both with and without ion-exchange membranes (IEMs). As expected, MCDI showed an enhanced salt adsorption and charge efficiency in comparison with CDI. However, the different electrosorption behavior of the former reveals that ion transport through the IEMs is a significant rate-controlling step in the desalination process. A sharper desorption peak is observed for divalent ions in MCDI, which can be attributed to a portion of these ions being temporarily stored within the IEMs, thus they are the first to leave the cell upon discharge. In addition to salt concentration, we monitored the pH of the effluent stream in CDI and MCDI and discuss the potential causes of these fluctuations. The dramatic pH change over one adsorption and desorption cycle in CDI (pH range of 3.5-10.5) can be problematic in a feed water containing components prone to scaling. The pH change, however, was much more limited in the case of MCDI for all salts

Recent progress on fabrication methods of polymeric thin film gas separation membranes for CO<inf>2</inf> capture

© 2018 Elsevier B.V. Membrane technology has been recognized as an attractive and environment-friendly technology for carbon capture due to its low expense (capital and operating), ease of operation as well as low energy consumption. Traditionally, the membrane materials are cast into dense membranes with a thickness of 50–150 µm and their gas separation properties are evaluated by the trade-off between permeability and selectivity. However, permeance (gas flux), rather than permeability, is more emphasized recently because the increase of the real gas flux through a membrane without the loss of selectivity has been recognized to be more important in industrial scenarios. The permeance is inversely proportional to the membrane thickness, and thus the thin film membranes with sub-micro scale selective layers as part of a composite membrane has drawn particular interests. In thin film membranes, the membrane fabrication technique as well as the membrane configuration design are more important than the membrane materials. However, the recent progress on membrane fabrication techniques, especially the bottom-up approaches for composite membranes, have not been fully reviewed and compared. This review focuses on the recent progress in fabrication techniques and approaches of the thin film (sub-micron) polymeric membranes for CO2 capture, the state-of-art performance of those membranes will be summarized, and future direction of thin film composite membrane will be discussed

MOF Scaffold for a High-Performance Mixed-Matrix Membrane.

A novel composite membrane consisting of an interconnected MOF scaffold coated with cross-linked poly(ethylene glycol) (PEG) has been developed. As a result of its unique structure, the membrane shows an exceptional 18-fold permeability enhancement as compared to pristine PEG membranes, without compromising the selectivity. This performance is unattainable with current mixed-matrix membranes (MMMs). Our optimized membrane has a permeability of 2700 Barrer with a CO2 /N2 selectivity of 35, which surpasses the latest Robeson upper bound