Analysis of energetics and economics of sub‐ambient hybrid post‐combustion carbon dioxide capture

Abstract

Adsorption of CO 2 from post-combustion flue gas is one of the leading candidates for globally impactful carbon capture systems. This work focused on understanding the opportunities and limitations of sub-ambient CO 2 capture processes utilizing a multistage separation process. A hybrid process design using a combination of pressure-driven separation of CO 2 from flue gas (e.g., adsorption-or membrane-based separation) followed by CO 2 -rich product liquefaction to produce high-purity (>99%) CO 2 at pipeline conditions is considered. The operating pressure of the separation unit is a key cost parameter and also an important process variable that regulates the available heat removal necessary to reach the sub-ambient operating conditions. The economic viability of applying pressure swing adsorption (PSA) processes using fiber sorbent contactors with internal heat management was found to be most influenced by the productivity of the adsorption system, with productivities as high as 0.015 mol CO 2 /kg sorb À1 sec À1 being required to reduce costs of capture below $60/ ton CO 2 captured. This analysis was carried out using a simplified two-bed process, and thus there is opportunity for further cost reduction with exploration of more complex cycle designs. Three exemplar fiber sorbents (MIL-101(Cr), UiO-66, and zeolite 13X) were considered for application in the sub-ambient process of PSA unit.Among the considered sorbents, zeolite 13X fiber composites were found to perform better at ambient temperatures as compared to sub-ambient. MIL-101(Cr) and UiO-66 fiber composites had improved purity, recovery, and productivity at colder temperatures reducing costs of capture as low as $61/ton CO 2 . Future economic improvement could be achieved by reducing the required operating pressure of the PSA unit and pushing the Pareto frontier closer to the final pipeline requirement via a combination of PSA cycle design and material selection.

Cs-RHO Goes from Worst to Best as Water Enhances Equilibrium CO2 Adsorption via Phase Change

“…A promising approach for dealing with rising levels of CO 2 is its sequestration from flue gas. 1 Zeolites are structurally well-defined materials that adsorb CO 2 (such as zeolite LTA, RHO, CHA, KFI, MER, FAU, etc. ), 2−13 while exhibiting excellent thermal, hydrothermal, and mechanical stability, high volumetric-basis CO 2 adsorption capacity, and low cost.…”

“…2,7 While kinetic considerations in an actual adsorption bed unit operation can favor CO 2 over H 2 O under transport control, 13,14,18 eventually, over multiple bed cycles, the adsorbed H 2 O accumulates and compromises CO 2 capacity, requiring its removal. 1 If selective zeolites could be synthesized that function under equilibrated humid conditions, without compromising CO 2 capacity, this would represent a new understanding and potentially new opportunities for practical CO 2 sequestration. Here, in this manuscript, we demonstrate unique cooperativity in adsorption between H 2 O and Cs + , wherein H 2 O facilitates the adsorption of CO 2 on Cs-containing RHO zeolites, leading to unprecedented higher equilibrium CO 2 adsorption capacity on Cs-RHO under humid (5% relative humidity) rather than dry conditions.…”

“…A promising approach for dealing with rising levels of CO 2 is its sequestration from flue gas . Zeolites are structurally well-defined materials that adsorb CO 2 (such as zeolite LTA, RHO, CHA, KFI, MER, FAU, etc.…”

“…The design of zeolites that retain significant equilibrium CO 2 adsorption capacity from humid gas mixtures remains a grand challenge, , which necessitates a deeper understanding of multicomponent CO 2 adsorption under humid conditions. The conventional belief is that humidity results in a significant decrease of the equilibrium CO 2 adsorption capacity of a zeolite, for example, demonstrated by previous studies based on both large-pore and small-pore zeolites alike and justified by the much higher heat of adsorption for H 2 O compared to CO 2 . ,, This has led to proposals for combating this decreased equilibrium CO 2 capacity under humid conditions by employing energy-intensive flue-gas drying. , While kinetic considerations in an actual adsorption bed unit operation can favor CO 2 over H 2 O under transport control, ,, eventually, over multiple bed cycles, the adsorbed H 2 O accumulates and compromises CO 2 capacity, requiring its removal . If selective zeolites could be synthesized that function under equilibrated humid conditions, without compromising CO 2 capacity, this would represent a new understanding and potentially new opportunities for practical CO 2 sequestration.…”

Multi-Level Computational Screening of in Silico Designed MOFs for Efficient SO2 Capture

“…Similar processes have been previously proposed for the flue gas separation. 84 − 87 Also, despite not being investigated in this work, the structural stability upon gas exposure is crucial for sustainable gas separation applications. These stability tests are typically carried out under dry conditions.…”