Poly(amide-imide)/Silica Supported PEI Hollow Fiber Sorbents for Postcombustion CO₂ Capture by RTSA

Amine-loaded poly(amide-imide) (PAI)/silica hollow fiber sorbents are created and used in a rapid temperature swing adsorption (RTSA) system for CO₂ capture under simulated postcombustion flue gas conditions. Poly(ethylenimine) (PEI) is infused into the PAI/mesoporous silica hollow fiber sorbents during fiber solvent exchange steps after fiber spinning. A lumen-side barrier layer is also successfully formed on the bore side of PAI/silica hollow fiber sorbents by using a mixture of Neoprene with cross-linking agents in a post-treatment process. The amine loaded fibers are tested in shell-and-tube modules by exposure on the shell side at 1 atm and 35°C to simulated flue gas with an inert tracer (14 mol % CO2, 72 mol % N2, and 14 mol % He, at 100% relative humidity (RH)). The fibers show a breakthrough CO₂ capacity of 0.85 mmol/g-fiber and a pseudoequilibrium CO₂ uptake of 1.19 mmol/g-fiber. When tested in the temperature range of 35-75°C, the PAI/silica/PEI fiber sorbents show a maximum CO₂ capacity at 65°C, owing to a trade-off between thermodynamic and kinetic factors. To overcome mass transfer limitations in rigidified PEI infused in the silica, an alternate PEI infusion method using a glycerol/PEI/methanol mixture is developed, and the CO₂ sorption performance is improved significantly, effectively doubling the functional sorption capacity. Specifically, the glycerol-plasticized sorbents are found to have a breakthrough and equilibrium CO₂ capacity of 1.3 and 2.0 mmol/g of dry fiber sorbent at 35°C, respectively. Thus, this work demonstrates two PAI-based sorbents that are optimized for different sorption conditions with the PAI/silica/PEI sorbents operating effectively at 65°C and the PAI/silica/PEI-glycerol sorbents operating well at 35°C with significantly improved sorption capacity

Post-Spinning Infusion of Poly(ethyleneimine) into Polymer/Silica Hollow Fiber Sorbents for Carbon Dioxide Capture

Amine-loaded hollow fiber sorbents for CO₂ capture from dilute gas streams are created using a novel post-spinning amine-infusion technique. This technique infuses poly(ethyleneimine) (PEI) into cellulose acetate/mesoporous silica hollow fiber sorbents during the solvent exchange steps after dry-jet, wet-quench, non-solvent induced phase separation spinning. A suitable post-spinning infusing solution was found to be 10% PEI in methanol with an infusion time of 4h. After amine infusion, the 51 wt% silica hollow fiber sorbents are demonstrated to have a nitrogen loading of 0.52 mmol/g-fiber and a CO₂ uptake of 1.2 mmol/g-fiber, at equilibrium. Amine-loaded fibers are packaged into a shell-and-tube module and exposed on the shell side to simulated flue gas with an inert tracer (10 mol% CO₂, 80 mol% N₂ and 10 mol% He at 100% relative humidity; 1 atm, 35°C). The fibers are shown to have a breakthrough CO₂ capacity of 0.58 mmol/g-fiber and CO₂ uptake after 20 min of 0.92 mmol/g-fiber (1 atm and 35°C). Under the same conditions, the water uptake was found to be 3.2 mmol/g-fiber. The preparation of amine-containing polymeric hollow fibers and demonstration of their CO₂ adsorption properties is an important step towards realizing new, scalable process configurations for supported amine sorbents relevant to post-combustion CO₂ capture

Evaluation of CO₂ Adsorption Dynamics of Polymer/Silica Supported Poly(ethylenimine) Hollow Fiber Sorbents in Rapid Temperature Swing Adsorption

Rapid temperature swing adsorption (RTSA) using polymer/silica supported amine hollow fiber sorbents is a new post combustion CO₂ capture methodology that facilitates CO₂ adsorption under nearly isothermal conditions with improved energy efficiency via heat integration. In this work, the dynamic CO₂ adsorption characteristics of polymer/silica supported poly(ethylenimine) hollow fiber sorbents (CA-S-PEI-PI) are evaluated in a bench scale RTSA system. Non-isothermal fibers have breakthrough and pseudo-equilibrium CO₂ capacities of 0.67 mmol/g and 1.03 mmol/g at 35°C, respectively, under humid simulated flue gas conditions (100% R.H.). Prolonged exposure of the fiber sorbents to water vapor enabled the breakthrough and pseudo-equilibrium CO₂ capacities to increase by 60% and 43%, respectively. Upon the removal of the heat of adsorption by flowing cooling water in the bores of the fiber sorbents, there is a substantial increase in the CO₂ breakthrough capacity, reaching 1.16 mmol/g using simulated humid flue gases. The breakthrough capacity is found to increase 5% upon increasing the adsorption temperature from 35°C to at 45°C, suggesting improved mass transfer in the fiber sorbent at the higher temperature. The CO₂ adsorption and desorption rates are shown to be very rapid, with CO₂ breakthrough occurring in less than 72s and the majority of the adsorbed CO₂ desorbing in 5 min. Extensive cycling studies demonstrate that the CA-S-PEI-PI sorbents have good dynamic swing capacities, stabilizing over 60 cycles. A newly developed rechargeable post-spinning amine infusion technique provides the feasibility of recovering the CO₂ adsorption performance of deactivated CA-S-PEI-PI fiber modules, by allowing for straightforward re-infusion of PEI into the deactivated sorbents. Amine-incorporated hollow fiber sorbents have good potential for practical use as scalable, adsorbing heat-exchangers

Optimization and Technoeconomic Analysis of Rapid Temperature Swing Adsorption Process for Carbon Capture from Coal-Fired Power Plant

Greenhouse gas emissions from coal-fired power plants are expected to increase over the next 20 years as international demand for energy continues to grow. A rapid temperature swing adsorption (RTSA) process employing polymeric hollow fiber contactors loaded with sorbent particles has been demonstrated experimentally as a novel and efficient process for postcombustion CO₂ capture. One of the advantages of the process is the rapid heat and mass transfer enabled by the hollow fibers. This feature can achieve efficient heat integration by recycling spent hot and cold water. In this chapter, a dynamic optimization strategy was employed to find the optimal operating conditions of a hollow fiber RTSA process. In the optimization problem, dynamic heat integration is performed to minimize the utility cost for hot and cold water while maintaining sufficient CO₂ throughput. The optimal operation was evaluated by a detailed technoeconomic analysis for a plant capacity of 550 MW

Aminosilane-Grafted Polymer/Silica Hollow Fiber Adsorbents for CO₂ Capture from Flue Gas

Amine/silica/polymer composite hollow fiber adsorbents are produced using a novel reactive post-spinning infusion technique, and the obtained fibers are shown to capture CO₂ from simulated flue gas. The post-spinning infusion technique allows for functionalization of polymer/silica hollow fibers with different types of amines during the solvent exchange step after fiber spinning. The post-spinning infusion of 3-aminopropyltrimethoxysilane (APS) into mesoporous silica/cellulose acetate hollow fibers is demonstrated here, and the materials are compared with hollow fibers infused with poly(ethyleneimine) (PEI). This approach results in silica/polymer composite fibers with good amine distribution and accessibility, as well as adequate porosity retained within the fibers to facilitate rapid mass transfer and adsorption kinetics. The CO₂ adsorption capacities for the APS-infused hollow fibers are shown to be comparable to those of amine powders with similar amine loadings. In contrast, fibers that are spun with presynthesized, amine-loaded mesoporous silica powders show negligible CO₂ uptake and low amine loadings because of loss of amines from the silica materials during the fiber spinning process. Aminosilica powders are shown to be more hydrophilic than the corresponding amine containing composite hollow fibers, the bare polymer as well as silica support. Both the PEI-infused and APS-infused fibers demonstrate reduced CO₂ adsorption upon elevating the temperature from 35 to 80°C, in accordance with thermodynamics, whereas PEI-infused powders show increased CO₂ uptake over that temperature range because of competing diffusional and thermodynamic effects. The CO₂ adsorption kinetics as probed via TGA show that the APS-infused hollow fiber adsorbents have more rapid uptake kinetics than their aminosilica powder analogues. The adsorption performance of the functionalized hollow fibers is also assessed in CO₂ breakthrough experiments. The breakthrough results show a sharp CO₂ front for APS-grafted fibers, indicating fast kinetics with comparable pseudo-equilibrium capacities to the CO₂ equilibrium capacities measured via thermogravimetric analysis (TGA). The results indicate the post-spinning infusion method provides a new platform for synthesizing composite polymer/silica/amine fibers that may facilitate the ultimate scale-up of practical fiber adsorbents for flue gas CO₂ capture applications

CO₂ Sorption Performance of Composite Polymer/Aminosilica Hollow Fiber Sorbents: An Experimental and Modeling Study

The dynamic CO₂ sorption performance of polymer/silica supported polyethylenimine hollow fiber sorbents (CA-S-PEI), focusing on heat and mass transport effects, is investigated experimentally and computationally during sorption of CO₂ from simulated, dry flue gases. The effect of the nonisothermality on the sorption performance is investigated by varying the module materials of construction. The heat effects are minimized by using a heat conductive module case with a diameter of 0.25 in., and, accordingly, the breakthrough capacities are increased by 30% over a similar module constructed from less conductive components, thereby improving fiber sorbents utilization efficiency. The sorption kinetics in CA-S-PEI hollow fiber sorbents are investigated in terms of flow rates, module packing fraction, module length, and silica particle size. A mathematical model developed previously is successfully utilized to predict various contributions to the overall mass transfer resistance. In fiber sorbents where the amine loading is high, such as those employed here, the sorption process is found to be controlled by intraparticle mass transfer resistances. Unlike fiber sorbents based on physisorbents, the external gas diffusion resistance has minimal effects on the breakthrough capacities, as evidenced with the negligible effects of the module packing fraction on the sorption capacities. Sorption capacities are found to increase with the fiber module length as a result of self-sharpening effects. The increase of particle size increases the mass transfer resistance of the fiber sorbents as illustrated by the more diffuse CO₂ breakthrough fronts in fiber modules containing bigger silica particles. The capacities in fiber sorbents with the largest silica particles exhibit the lowest sorption capacity, as expected

CO₂ Sorption Performance of Composite Polymer/Aminosilica Hollow Fiber Sorbents: An Experimental and Modeling Study

The dynamic CO₂ sorption performance of polymer/silica supported polyethylenimine hollow fiber sorbents (CA-S-PEI), focusing on heat and mass transport effects, is investigated experimentally and computationally during sorption of CO₂ from simulated, dry flue gases. The effect of the nonisothermality on the sorption performance is investigated by varying the module materials of construction. The heat effects are minimized by using a heat conductive module case with a diameter of 0.25 in., and, accordingly, the breakthrough capacities are increased by 30% over a similar module constructed from less conductive components, thereby improving fiber sorbents utilization efficiency. The sorption kinetics in CA-S-PEI hollow fiber sorbents are investigated in terms of flow rates, module packing fraction, module length, and silica particle size. A mathematical model developed previously is successfully utilized to predict various contributions to the overall mass transfer resistance. In fiber sorbents where the amine loading is high, such as those employed here, the sorption process is found to be controlled by intraparticle mass transfer resistances. Unlike fiber sorbents based on physisorbents, the external gas diffusion resistance has minimal effects on the breakthrough capacities, as evidenced with the negligible effects of the module packing fraction on the sorption capacities. Sorption capacities are found to increase with the fiber module length as a result of self-sharpening effects. The increase of particle size increases the mass transfer resistance of the fiber sorbents as illustrated by the more diffuse CO₂ breakthrough fronts in fiber modules containing bigger silica particles. The capacities in fiber sorbents with the largest silica particles exhibit the lowest sorption capacity, as expected

Poly(amide-imide)/Silica Supported PEI Hollow Fiber Sorbents for Postcombustion CO 2

Amine-loaded poly(amide-imide) (PAI)/silica hollow fiber sorbents are created and used in a rapid temperature swing adsorption (RTSA) system for CO₂ capture under simulated postcombustion flue gas conditions. Poly(ethylenimine) (PEI) is infused into the PAI/mesoporous silica hollow fiber sorbents during fiber solvent exchange steps after fiber spinning. A lumen-side barrier layer is also successfully formed on the bore side of PAI/silica hollow fiber sorbents by using a mixture of Neoprene with cross-linking agents in a post-treatment process. The amine loaded fibers are tested in shell-and-tube modules by exposure on the shell side at 1 atm and 35°C to simulated flue gas with an inert tracer (14 mol % CO2, 72 mol % N2, and 14 mol % He, at 100% relative humidity (RH)). The fibers show a breakthrough CO₂ capacity of 0.85 mmol/g-fiber and a pseudoequilibrium CO₂ uptake of 1.19 mmol/g-fiber. When tested in the temperature range of 35-75°C, the PAI/silica/PEI fiber sorbents show a maximum CO₂ capacity at 65°C, owing to a trade-off between thermodynamic and kinetic factors. To overcome mass transfer limitations in rigidified PEI infused in the silica, an alternate PEI infusion method using a glycerol/PEI/methanol mixture is developed, and the CO₂ sorption performance is improved significantly, effectively doubling the functional sorption capacity. Specifically, the glycerol-plasticized sorbents are found to have a breakthrough and equilibrium CO₂ capacity of 1.3 and 2.0 mmol/g of dry fiber sorbent at 35°C, respectively. Thus, this work demonstrates two PAI-based sorbents that are optimized for different sorption conditions with the PAI/silica/PEI sorbents operating effectively at 65°C and the PAI/silica/PEI-glycerol sorbents operating well at 35°C with significantly improved sorption capacity