Rapid Temperature Swing Adsorption Research Articles

Incorporation of market signals for the optimal design of post combustion carbon capture systems

Recent studies have shown that fossil generators equipped with post-combustion carbon capture (PCC) systems are needed to reduce the cost of deep decarbonization. Such generators need to be flexible and responsive to grid conditions, particularly in a high variable renewable energy (VRE) environment. In this work, we evaluate the net present value (NPV) of retrofitting an existing natural gas combined cycle (NGCC) unit with a flexible PCC system while incorporating market signals from a high VRE grid. We use our industrial partner’s NGCC configuration as representative of existing NGCC units and Svante’s rapid-temperature swing adsorption (TSA) for PCC. Because of its ability to rapidly startup/shutdown and ramp-up/ramp-down, the chosen capture technology is very attractive for load-following operations. For a given set of market signals, we formulate a two-stage stochastic multi-period optimization problem, under the price-taker assumption, to simultaneously optimize the design of the capture system and operation of the entire plant. Rigorous models for the NGCC unit, PCC system, and compression system are developed using commercial process simulators and validated with either plant or vendor data. For computational tractability, we develop surrogate/reduced-order models for use in the optimization problem. The surrogate model for the NGCC plant is constructed by linearizing the rigorous dynamic model at 75% load, while data-driven nonlinear surrogate models for the capture and compression systems are constructed using simulation data from the rigorous models. The optimization problem, formulated as a mixed integer bilinear program, is implemented in the IDAES® integrated platform and solved to global optimality using Gurobi 9.5. Using this formulation, we determine the profitability of retrofitting an existing NGCC unit with the chosen capture system for multiple regions in the U.S. under two scenarios with different carbon prices. The results show that the optimal decision strongly depends on the region and on the carbon price, thereby demonstrating the importance of the inclusion of market signals in the design process.

Rapid temperature swing adsorption using microwave regeneration for carbon capture

The use of microwave heating for the thermal regeneration of a porous carbon adsorbent in adsorptive carbon capture was evaluated. In this Microwave Swing Adsorption (MSA) process, a multimode microwave oven has been used to accelerate the desorption of CO2 after the adsorption of a CO2 / N2 (15/85 v/v) mixture. Starting from a commercial activated carbon (AC) material (MSP-20X), sorbent extrudates were prepared and loaded in a Teflon column. The heating of the sorbent bed inside the microwave (MW) cavity was characterised at different locations. Although the adsorption bed is not heated uniformly due to hot spots in the multimode MW cavity, flowing a purge gas reduces the non-uniform heating during the regeneration step. This study also reports that MSA regeneration achieves extremely fast total desorption (in 56 to 79 s), the quickest regeneration reported up to date in MSA, and very rapid desorption rates allowing swift adsorption–desorption cycles. This fast desorption is associated with the extremely high heating rates achieved (100 to 400 °C/min). We show that the desorption rate is faster when using higher powers at practically identical MW energy inputs. Complete CO2 desorption can be achieved at slightly longer durations when using 2-step MW heating. When comparing the MSA results with a reference TSA process, MSA outperforms TSA, due to the higher heating rates achieved by MSA. During eleven adsorption–desorption cycles, it is evidenced that the MSA process can regenerate the adsorption bed at a high reproducibility. The microporosity of the material remained intact during the MSA, revealing that localised heating and the high heating rates are not damaging the sorbent material.

Modeling of Fixed‐Bed Rapid Temperature Swing Adsorber for Butanol Dehydration

AbstractA fixed‐bed system of rapid temperature swing adsorption (RTSA), which uses a solid absorbent for dehydration of butanol, was studied. The packed bed was simulated using proper partial and algebraic equations which were solved by the central difference method in MATLAB software. The equilibrium relationship and fixed‐bed breakthrough curves were determined experimentally. The value of unknown parameters such as equilibrium constants, liquid film mass transfer coefficient, intraparticle diffusion coefficient, and axial diffusivity were estimated by appropriate equations. The model fitted well to experimental breakthrough data. The results proved that it would be possible to operate a complete RSTA cycle in just a few hours to allow a large quantity of organic solvent dehydrated with reasonable concentration.

Hollow fiber-based rapid temperature swing adsorption process for carbon capture from coal-fired power plants

Post-combustion carbon capture is one of the feasible methods to reduce emission of carbon dioxide (CO2) from coal-fired power plants. The biggest challenge in this technology is reduction of energy consumption. This work proposes a hollow fiber based rapid temperature swing adsorption (RTSA) method for capturing CO2 from typical coal-fired power plants. The proposed RTSA approach can shorten the operating time and using low-grade energy for regeneration of adsorption elements. In this study, the tank-in-series model is used to simulate the RTSA process including adsorption and desorption periods. A dual-column operating procedure is then used to treat the flue gas continuously from the coal-fired power plants. Main operating variables including inlet gas volume flow rate (0.1–0.2 m3/s), abandon time (0–10 s), desorption temperature (80–120 °C) on key performance factors such as discharge gas purity, capture ratio of CO2, and energy consumption per unit CO2, etc. are investigated for reducing the energy consumption. This study found that the inlet gas volume flow rate will significantly affect the capture ratio, where smaller gas volume flow rate would be beneficial to increase capture ratio. The abandon time obviously affects the purity of the captured CO2, where the longer abandon time leads to higher purity. Desorption temperature affects both the capture ratio and purity of captured CO2. The higher the desorption temperature, the greater the purity and capture ratio. For one typical basic unit with dual-column hollow fiber-based RTSA, the study found that when the inlet gas volume flow rate is 0.12 m3/s, the desorption waiting time is 7 s, and the desorption temperature is 120 °C, both the CO2 purity and capture ratio can exceed 90%. With considering the possibility of using steam in a low-pressure turbine as a source of heat required for Dual column vacuum RTSA (DC-vRTSA), the impact on the efficiency and stream data of typical coal-fired power plants are calculated. DC-vRTSA at 120 °C, 100 °C and 80 °C will reduce the efficiency of coal-fired power plants by 8.2%, 6%, and 3.4%, respectively.

A new honeycomb carbon monolith for CO2 capture by rapid temperature swing adsorption using steam regeneration

A rapid process for CO2 capture is of key importance for the economic feasibility of the process in industry, consequently short adsorption/desorption cycles are crucial. With this aim in mind, a carbon based honeycomb monolith was evaluated for CO2 capture in a thermal swing adsorption process at short contact times. The effect of (1) regeneration time, (2) presence of water vapor during adsorption and desorption and (3) regeneration method (steam versus hot air) on CO2 adsorption was studied. The monolith was characterized in terms of porosity and CO2, N2, and H2O isotherms. Cyclic adsorption/desorption experiments were performed using different synthetic gas mixtures with concentrations of CO2 ranging between 6 and 15 vol%. The effect of water vapor in the synthetic gas mixture on adsorption capacity was limited but increases with relative humidity. Steam of 120 °C was used to heat the monolith and desorb CO2. Advantages of steam usage are the facile separation of steam and concentrated CO2 and the low (waste) heating energy cost of steam. It was demonstrated that the steam allows very fast heating and cooling of the monolith. However, the presence of residual condensation water after the cooling step reduces the cyclic adsorption capacity, requiring an additional drying step with hot or cold air.

Optimization of Carbon Dioxide Capture Using Sorbent-Loaded Hollow-Fiber Modules

The performance of sorbent-loaded hollow-fiber modules to capture carbon dioxide from the exhaust stream of a thermal power plant is analyzed. The hollow-fiber modules undergo a Rapid Temperature Swing Adsorption (RTSA) process to capture carbon dioxide. A detailed heat and mass transfer model is developed to simulate the performance of the fiber module. The thermal wave technique for heat recovery is incorporated to reduce the thermal energy consumption and reduce operating costs. A parametric study of six key operating parameters is presented, and tradeoffs in performance metrics with variations in operating parameters are discussed. The proposed process compares favorably with other adsorption-based carbon capture technologies.

Impact of operating parameters on CO2 capture using carbon monolith by Electrical Swing Adsorption technology (ESA)

Electrical Swing Adsorption (ESA) technology is an interesting option for rapid temperature swing adsorption to capture CO2 due to its highly efficient and rapid regeneration with the Joule effect. Electric current, electrification time and N2 purge rate have strong effects on ESA processing performance. In this study, these operating parameters were investigated experimentally and theoretically, for their effect on CO2 product purity, recovery, harvest time and energy consumption. For a feed stream of 15% CO2 balanced with N2 using a MAST© carbon monolith, CO2 purity and energy consumption significantly increased as electric current and electrification time increased; CO2 recovery increased as N2 purge rate increased; these three factors all impacted on CO2 productivity positively, that is, productivity increased with increase of each of electric current, electrification time and N2 purge rate. The optimal conditions obtained for CO2 capture using MAST© monolith in this study are electric current of 12A, electrification time of 80s and N2 purge rate of 600ml/min (0.088m/s). Under such optimal condition, a CO2 purity of 52%, and a recovery of 76% was achieved with an energy consumption of 5.64MJ/kg.CO2.

Mathematical modeling of rapid temperature swing adsorption; the role of influencing parameters

Abstract CO 2 capture from power plant emissions has posed a great challenge in recent decades. The key factor to respond to such a challenge is to develop a separation process consuming less energy, but producing high purity and recovery compared to the available commercial technologies such as amine absorption. Adsorption process is one of the promising leads to achieve this goal. However, it suffers from the large time period required for the regeneration step. One remedy to overcome this problem is employing Rapid Temperature Swing Adsorption (RTSA). In this study, a two dimensional mathematical model of a RTSA process was developed. A sensitivity analysis was also carried out to determine how different transport parameters and simplifying assumptions influence the calculated breakthrough curve. It was concluded that the external and inter-particle mass transfer resistances were negligible. Also, the effects of the key operating variables such as water velocity in the adsorption and desorption steps (0.01–1 m/s), gas velocity (0.5–5 m/s), adsorption time period (40–200 s), adsorption temperature (5–40 °C), desorption temperature (80–120 °C), and hollow fiber thickness (80–680 µm) on RTSA performance were investigated. The RTSA performance was analyzed in terms of recovery, purity, productivity, the amount of separated pure carbon dioxide in 24 h, and specific energy consumption. The following conclusions were drawn for the base-case scenario: (1) the best thickness of the hollow fiber is 260 µm in which purity, recovery, and the amount of separated pure CO 2 are at the maximum values (2) a decrease in adsorption step period time tends to an increase in the productivity and recovery, e.g. the productivity and recovery decrease by half if the adsorption step continues after reaching breakthrough time up to fully saturation state, (3) increasing the gas velocity leads to increasing the productivity and decreasing the recovery with the appropriate value of 2.7 m/s, (4) the water velocity in the adsorption and desorption steps were selected 0.4 m/s, and (5) higher adsorption temperature and desorption temperature resulting in less specific energy consumption.

Carbon Dioxide Capture Using Sorbent-Loaded Hollow-Fiber Modules with Integrated Heat Recovery

A model of a rapid temperature swing adsorption CO2 capture module using sorbent-loaded hollow fibers is presented. The system incorporates an integrated heat recovery technique using a thermal wave to reduce the external thermal input and operational energy costs of the capture facility. The model includes a detailed heat and mass transport model for the sorbent-loaded fibers to address accurately the rapid radial kinetics of the adsorption process. The local heating and cooling of the sorbent possible with the use of coupling fluid in the bore of the fibers significantly reduces the time required for each adsorbing and desorbing phase. Results for a representative operating condition indicate that a capture facility based on the sorbent-loaded hollow fibers can achieve significantly higher sorbent productivities (∼1400%) than that of other thermally driven capture technologies with moderate energy consumption (∼5.9 MJ kg–1). The very fast cycle times (∼100 s) achievable with this adsorption process enab...

Poly(amide-imide)/silica supported PEI hollow fiber sorbents for postcombustion CO(2) 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.

Dynamic CO2 adsorption performance of internally cooled silica‐supported poly(ethylenimine) hollow fiber sorbents

The dynamic adsorption behavior of CO2 under both nonisothermal and nearly isothermal conditions in silica supported poly(ethylenimine) (PEI) hollow fiber sorbents (Torlon®‐S‐PEI) is investigated in a rapid temperature swing adsorption (RTSA) process. A maximum CO2 breakthrough capacity of 1.33 mmol/g‐fiber (2.66 mmol/g‐silica) is observed when the fibers are actively cooled by flowing cooling water in the fiber bores. Under dry CO2 adsorption conditions, heat released from the CO2‐amine interaction increases the CO2 breakthrough capacity by reducing the severity of the diffusion resistance in the supported PEI. This internal resistance can also be alleviated by prehydrating the fiber sorbent with a humid N2 feed. The CO2 breakthrough capacity of prehydrated fibers is adversely affected by the release of the adsorption enthalpy (unlike the dry fibers); however, active cooling of the fiber results in a constant CO2 breakthrough capacity even at high CO2 delivery rates (i.e., high adsorption enthalpy delivery rates). In full RTSA cycles, a purity of 50% CO2 is achieved and the adsorption enthalpy recovery rate can reach ∼72%. Studies on the cyclic stability of uncooled fiber sorbents in the presence of SO2 and NO contaminants indicate that exposure to NO at 200 ppm over 120 cycles does not lead to a significant degradation of the sorbents, but SO2 exposure at a similar high concentration of 200 ppm causes 60% loss in CO2 breakthrough capacity after 120 cycles. A simple amine reinfusion technique is successfully demonstrated to recover the adsorption capacity in poisoned fiber sorbents after deactivation by exposure to impurities such SO2. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3878–3887, 2014

Modeling of rapid temperature swing adsorption using hollow fiber sorbents

The use of novel polymeric hollow fiber contactors loaded with CO2 sorbents has been recently demonstrated experimentally as a new and scalable process configuration for post-combustion CO2 capture. The hollow fiber contactor allows coupling of efficient heat transfer and gas contacting, potentially yielding lower parasitic loads on host power plants compared to traditional contacting strategies using solid sorbents. In this study, a two dimensional mathematical model of a rapid temperature swing adsorption (RTSA) process is developed for the first time to predict polymer-supported amine hollow fiber sorbent performance during post-combustion CO2 capture from flue gas. In particular, this work is focused on developing a single fiber model to simulate a four-step RTSA system accounting for adsorption, heating/desorption, heating/sweeping and cooling steps. The model is validated with experimental breakthrough data obtained from our RTSA system. The sensitivity of the model to parameter values such as gas and water velocity and initial temperatures are evaluated accordingly by considering the effect of these parameters on CO2 concentration and temperature profiles. Furthermore, the CO2 adsorption isotherms obtained experimentally were fitted with the Toth model. In addition, our model was validated against experimental breakthrough profiles. A good agreement was found between experimental and numerical data indicating that our proposed model can describe experimental observation very well. The numerical results obtained from RTSA cycle modeling indicate that under operating conditions considered here, it is possible to achieve high purity and recovery within a cycle time of shorter than 3min. It was also found that there is a trade-off in cycle time, shorter for lower capital cost and longer to enable heat recovery for lower utility costs.

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 0.67mmol/g and 1.03mmol/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 1.16mmol/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 5min. 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.

Hollow fiber adsorbents for CO 2 capture: Kinetic sorption performance

We describe a CO 2 capture platform based on hollow polymeric fibers with sorbent particles embedded in the porous fiber wall for post-combustion CO 2 capture. These fibers are intended for use in a rapid temperature swing adsorption (RTSA) process. The RTSA system utilizes the hollow fiber morphology by flowing cooling water on the bore-side of the fibers during sorption to prevent temperature rise associated with the sorption enthalpy. Steam or hot water is flowed through the bores during desorption to desorb CO 2 rapidly. To minimize material transfer between the bore and the fiber wall, a dense Neoprene ® lumen layer is cast on the bore-side of the fiber wall. In this paper, the key sorption step and associated kinetic resistances for the uncooled fibers are examined and evaluated for this portion of the RTSA process. Chopped fibers in a packed bed, as well as fibers assembled into a parallel flow module, have been tested in a simulated flue gas stream. Kinetic limitations in the hollow fiber modules are largely overcome by increasing the superficial gas velocity and the fiber packing in the module—indicating that film diffusion is the controlling mass transfer limitation in the fiber system. The un-cooled fiber modules lose apparent capacity as superficial velocities are increased, likely indicating non-isothermal operation, whereas the actively-cooled fibers in the packed bed maintain apparent capacity at all flowrates studied.

Hollow Fiber Adsorbents for CO2 Removal from Flue Gas

The nation’s pulverized coal infrastructure is aging, and implementation of current retrofit postcombustion capture methods is extremely expensive. This paper describes a technology based on hollow polymeric fibers with sorbent particles embedded in the porous fiber wall to enable postcombustion CO2 capture via a rapid temperature swing adsorption (RTSA) system. The system takes advantage of the hollow fiber morphology by passing cooling water through the bores during sorption to maximize sorption capacities and steam through the bores during desorption to desorb CO2 efficiently. The thin-walled hollow fibers offer the advantage of rapid heat and mass transport. To avoid mass transfer between the core and the fiber sheath, a dense lumen layer is used on the interior of the fiber wall. This system has advantages over competing technologies. Specifically, the fiber sorbent contactor minimizes flue gas pressure drop across the bed, while maximizing sorption efficiencies via rapid thermal cycles and low regenerative thermal requirements.