high levels of CO 2 capture with advanced chemical solvent-based systems. Such solvents have lower regeneration energy requirements, lower volatility, and lower degradation rates than commercially available amine systems, combined with high CO 2 capture capacity and tolerance to flue gas impurities. Water-lean solvents are particularly promising for CO 2 capture processes, providing significant reductions in energy requirements, corrosion, and solvent losses. Projects include: piperazine solvent with flash regeneration, advanced solvents, heat integration and membrane, CO 2 binding organic liquid solvents, electrochemical regeneration of amine, biphasic solvents for CO 2 absorption, molecular refinement of water-lean solvent, and direct air capture from dilute CO 2 sources, among others. • Sorbent-based post-combustion technologies aim at developing low-cost, durable sorbents that have high selectivity, high CO 2 adsorption capacity, and can withstand multiple regeneration cycles with little to no attrition. Projects include: alkalised alumina solid sorbent, fluidisable solid sorbents, pressure swing adsorption process with novel sorbent, and porous polymer networks, among others. • Membrane-based post-combustion technologies include the development of low-cost, durable membranes that have improved permeability and selectivity, thermal and physical stability, tolerance to contaminants in combustion flue gas, and are integrated into low pressure drop modules. Projects include: sub-ambient temperature membrane, selective membranes for <1% CO 2 sources, and large pilot polymer membrane system, among others. In addition, the researchers are working on novel concepts for large-scale CO 2 capture or compression related subjects. Walton reports nine projects for “Finding ways to remove and store CO 2 directly from the air”. The projects include discovery of novel materials, chemistries and processes for extraction of CO 2 from air, and combined experimental and computational studies on CO 2 capture for sequestration or reuse. “This investment in carbon capture technology research through seven universities and two DOE laboratories will position America as a leader in this growing field, create good-paying jobs, and help make our carbon-free future a reality” (Walton, 2021).
solid adsorbents, and membranes – which all depend upon materials and chemicals and physical processes to separate a targeted gas from a mixture. Although some of today’s technologies for capturing CO 2 may be relatively efficient, all require considerable energy for isolation of the CO 2 due to changes in temperature and/or pressure to drive the separation process. In addition, because of the massive volumes of CO 2 involved, regeneration and reuse of the materials used to capture the CO 2 is required. Carbon capture materials, including aqueous amines, require a large amount of energy to release the captured CO 2 . The additional energy required lowers the overall efficiency of a power plant, resulting in substantially higher overall costs for electricity (50-80% higher) compared with facilities without carbon capture. There is a critical need for next-generation separation concepts that will provide efficient, cost-effective technologies for carbon capture in the future. Carbon capture technologies – advanced multipronged R&D programmes The US Department of Energy (DOE) has adopted a comprehensive, multi-pronged approach for R&D on advanced CO 2 capture technologies for existing fossil power plants and for industry, with the National Energy Technology Laboratory (NETL) as the implementing agency to develop the next generation of CO 2 capture technologies (NETL, 2020). The Carbon Capture Program consists of two core research areas – post- and pre-combustion capture projects with technology readiness levels (TRLs) ranging from conceptual engineering and materials design (i.e., TRL 2) to 25 Megawatt electrical (MWe) equivalent pilot testing (i.e., TRL 5-7) – and are focused on creating technological improvements, providing a step- change in both cost and performance as compared to current state-of-the-art solvent-based capture systems. Post-combustion systems separate CO 2 from nitrogen, the primary constituent of the flue gas. Pre-combustion systems are designed to separate CO 2 and hydrogen from the syngas stream produced by the gasifiers in integrated gasification combined cycle (IGCC) power plants. In both cases, R&D is investigating advanced solvents, sorbents, membranes, hybrid systems, and other novel concepts. Area wise developments are as below: • Post-combustion solvent technologies aim at
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