(158e) Material Screening and Process Optimization for Cost-Effective Adsorption-Based CO2 Capture

Elecrticity generation in power plants account for more than 73% of the total stationary CO₂ emissions in the United States [1]. 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 [2].

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 [11] 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 [11]. 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: