Material Screening and Process Optimization for Cost-Effective Adsorption-Based CO2 Capture
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Elecrticity generation in power plants account for more than 73% of the total stationary CO2 emissions in the United States . While carbon capture , utilization and storage (CCUS) is an enabling technology to reduce CO2 emissions from power plants , the costs of CO2 capture and compression , which represent 60–70% of the total CCUS cost , are estimated to exceed $58/tonne of CO2 avoided with current technology , leading to about a 63% increase in the levelized electricity cost . Adsorption-based CO2 capture using zeolites and metal-organic frameworks (MOFs) with large internal surfaces are promising technologies to separate CO2 from power plant flue gases. In a typical adsorption process , CO2 is selectively adsorbed onto a solid sorbent while the clean flue gas passes through. The adsorbed CO2 is released or desorbed by lowering the pressure. While pressure swing adsorption (PSA) process shows promise , the cost of PSA-based CO2 capture is still high. We have identified novel materials for cost-effective CO2 capture by combining in silico screening of microporous materials and PSA process optimization for the first time. Our hierarchical computational approach [3-4] efficiently screens large databases of zeolites , based on three dimensional pore characterization [5-6] , shape selectivity [7-10] , size selectivity , and adsorption selectivity. Next , process optimization is introduced to generate a rank-ordered list based on total cost of capture and compression. The purity , recovery , energy penalty and the cost of capture and compression are obtained by a detailed nonlinear algebraic and partial differential equation (NAPDE) model  that describes the PSA process. We not only select the most cost-effective materials , but we also attain the optimal process conditions while satisfying purity , recovery , and other process constraints. The top zeolites can capture and compress CO2 to 150 bar from a mixture of 14% CO2 and 86% N2 at less than $30 per ton of CO2 captured and compressed. This is a significant reduction in cost , compared to the costs of absorption and membrane processes [12-14] , and other adsorption processes which use zeolite 13X . Several zeolites have moderate selectivities , yet they cost-effectively capture CO2 with 90% purity and 90% recovery using a 4-step adsorption process. Our results show that no single materials-centric metric is sufficient to always select optimal materials , since both material and process considerations play a role. A combined atomistic , geometric , and process understanding is necessary to achieve the design specifications for a cost-effective and optimal CO2 capture process. References: . DOE/NETL. Carbon Sequestration Atlas of the United States and Canada , 2012.. Finkenrath , M. I. 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