Gas CO2 Capture Research Articles

Study of gas reservoir of the volume of geological formations adjacent to the sources of gas emissions in Azerbaijan

Although there are numerous measures towards reduction of charges to the atmosphere (increase of energy efficiency, nuclear energy, wind and solar energy, transition to the new types of energy etc.), the method of CO2 gas capture and storage in the geological formations (in depleted oil-gas formations and under the deep layers of seawater) with highly favorable conditions in Azerbaijan is considered the most environmental and cost effective (significant part of costs is realized due to the involving mining equipment and idle wells into the process) one. Corresponding geological formations in Azerbaijan and their gas reservoirs have been studied via specifying geological formations for storage of accumulated CO2 gases in underground formations (undergorund gas storages). The research surveys are based on the global experience, actual production capacities, new projects, state-of-the-art technologies and the equipment for CO2 gathering as well.

Large-scale preparation of multilayer composite membranes for post-combustion CO2 capture

Membrane technology is a promising strategy in flue gas CO2 capture. Recently, many high-performance multilayer composite membranes for CO2/N2 separation were successfully developed in the laboratory. However, the detailed scaling-up processes were rarely discussed due to the lack of mature technology and equipment that specially designed for the proven advanced membrane materials. This study investigated the large-scale production of the defect-free thin multilayer composite membrane for flue gas CO2 capture. A novel coating machine with double blades and surface cross-linking unit was designed, and the industrial scale multilayer composite membranes were prepared by running the coating machine twice. The coating solution stability of intermediate layer solution was prolonged to more than 72 h. The key technologic parameters including web speed and the concentration of cross-linking unit were analyzed. The continuously prepared multilayer composite membrane shows high and stable CO2/N2 performance and great potential in the application of flue gas CO2 capture.

Development of facile synthesized mesoporous carbon composite adsorbent for efficient CO2 capture

Amine-functionalized adsorbents show broad application prospects in the field of flue gas CO2 capture. However, the development of support materials with excellent CO2 capture performance and facile synthesis method is still a challenge. In this work, mesoporous carbon (MC) with the ultra large pore volume of 3.1 cm3/g is synthesized by direct carbonization of the mixture of adipic acid and zinc powder without further chemical/physical activation process. The synthesized MC was then impregnated with tetraethylenepent amine (TEPA) to prepare the adsorbent. The formed ultra large pore volume and abundant mesopores structure could promote adsorption active site dispersion, thereby improving CO2 adsorption performance. As a result, the MC support loaded with 80 wt% TEPA exhibits a large CO2 capture amount of 5.3 mmol/g at 75 ℃ with 15 vol%CO2. In addition, the carbon dioxide adsorption capacity is only 8.1 % less than that of the fresh adsorbent after 10 adsorption cycles, indicating that this adsorbent has excellent cycling stability. Noted that the synthesis of MC significantly improves the CO2 adsorption performance while simplifying the support material preparation process. Thus, it is believed that the MC material is promising adsorbent support for highly efficient CO2 capture.

Feasibility of a Mineral Carbonation Technique Using Iron-Silicate Mining Waste by Direct Flue Gas CO2 Capture and Cation Complexation Using 2,2′-Bipyridine

Mineral carbonation is gaining increasing attention for its ability to sequester CO2. The main challenge is doing it economically and energy-efficiently. Recently, many studies have focused on the aqueous reaction of carbon dioxide with the alkaline earth minerals such as serpentine, Mg-rich olivine and wollastonite. Nevertheless, Fe-rich olivines have been poorly studied because of their high energy demand, which make them unfeasible for industrial implementation. This article describes the feasibility of an indirect mineral carbonation process using silicic, Fe-rich mining waste with direct flue gas CO2 via iron complexation using 2,2′-bipyridine. The overall process was performed in three main steps: leaching, iron complexation, and aqueous mineral carbonation reactions. The preferential parameters resulted in a recirculation scenario, where 38% of Fe cations were leached, complexed, and reacted under mild conditions. CO2 uptake of 57.3% was achieved, obtaining a Fe-rich carbonate. These results are promising for the application of mineral carbonation to reduce CO2 emissions. Furthermore, the greenhouse gas balance had a global vision of the overall reaction’s feasibility. The results showed a positive balance in CO2 removal, with an estimated 130 kg CO2/ton of residue. Although an exhaustive study should be done, the new and innovative mineral carbonation CO2 sequestration approach in this study is promising.

Aerosol Emissions of Amine-Based CO2 Absorption System: Effects of Condensation Nuclei and Operating Conditions.

Amine emissions from a post-combustion CO2 capture process can lead to solvent loss and serious environmental issues. The emission characteristics of amine mixtures and influencing factors are seldom reported. This work comprehensively investigated emissions of AMP (2-amino-2-methyl-1-propanol)/MEA (monoethanolamine) from a 3.6 Nm3/h flue gas CO2 capture platform. The condensation nuclei in flue gas dominated the generation of amine aerosols and resulted in a heavy total amine loss of over 1400 mg/Nm3, which is equivalent to 5.88 kg/t CO2 captured under the high nuclei concentration scenario. Inside the absorber, a higher CO2 concentration and lower lean solvent CO2 loading can significantly promote the growth of aerosols due to the intensive reaction of CO2 absorption. The maximum amine emissions were observed at 8-12 vol % CO2. The flue gas temperature and liquid/gas ratio had insignificant effects on aerosol emissions, while amine emissions after the absorber increased 340-500% as the lean solvent temperature increased from 30 to 50 °C. A synergistic control strategy of nuclei pretreatment, operating optimization, and water scrubbing can effectively reduce amine emissions to 4.0 mg/Nm3 MEA and 8.3 mg/Nm3 AMP.

Combination of Silica Gel and Surfactin Promoting Methane Hydrate Formation

Abstract Recently, gas hydrates based technologies have been exploited for few novel applications such as storage and transpiration of natural gas, gas mixtures separation, CO2 capture, and seawater desalination. Most of these applications are currently facing a challenge of low rate of gas hydrate formation. Chemical additives like surfactants can play a role of a good kinetic promoter for gas hydrate formation. The present study reports the application of biosurfactant for enhancing gas hydrate formation. Biosurfactant was produced by Bacillus subtilis strain A21. These types of microbes show their presence in the real gas hydrate sites also. The surfactin was characterized using many sophisticated techniques, conforming the formation of surfactin. It was used in the presence of fixed bed media of silica gel, and it was observed that surfactin in the presence of silica gel increased the consumption of moles of methane as well as reduced the induction time also as well as the conversion was also increased up to 27.9% for 390 min for 1000 ppm surfactin hence indicating it to be a clean and novel promoter of methane hydrate formation in combination with silica gel which can replace its synthetic counterparts which have environmental concerns.

Nitrogen-Doped Porous Graphene-like Carbon Nanosheets as Efficient Oxygen Reduction Reaction Catalysts under Alkaline and Acidic Conditions

Electrocatalysts are vulnerable to be influenced during the oxygen reduction reaction (ORR) process on the cathodes of direct methanol fuel cells, mainly by the reaction products and air-containing traces of acidic gas carbon dioxide (CO₂), leading to low activity and durability. Herein, an ORR catalyst was derived from furfural, nitrogen carbide (g-C₃N₄), and calcium chloride (CaCl₂) via a dual-template method, resulting in two-dimensional graphene-like carbon nanosheets with a micro–mesoporous architecture, large Brunauer–Emmett–Teller surface areas (748 m²/g), an ultrahigh pyridinic nitrogen-doping level (13.6 wt %), and high degree of graphitization. The as-synthesized sample shows high ORR performance and robust durability in both alkaline and acidic electrolytes undergoing a gas mixture of O₂ and CO₂ (95:5), demonstrating a strong tolerance of CO₂ during the ORR process. Besides, the as-prepared material also exhibits competitive properties in the selective capture of CO₂ gas versus N₂. Thus, this work provides a facile route of preparing high-performance bifunctional carbonaceous materials in both ORR and CO₂ gas capture.

Solvothermal growth of Mg-MOF-74 films on carboxylic functionalized silicon substrate using acrylic acid

The fabrication of metal-organic framework (MOF) films on solid substrates is challenging due to poor wettability and lack of sufficient reactive functional groups on the surface, which prevents the stable attachment and growth of MOF films. For this reason, many studies have been conducted to directly grow MOF films on solid substrates such as metals, metal oxides and ceramics using polymer or functional groups. In this work, silicon (100) substrates were functionalized with carboxylic functional groups using a mixture of acrylic acid and hydrofluoric acid through hydrosilylation process. Mg-MOF-74 films formed on silicon substrates by 24 hours of solvothermal synthesis exhibited high surface areas (965 m2/g) and high CO2 gas capture behavior (186 cm3/g). This approach allowed the direct growth of Mg-MOF-74 films on silicon substrates by solvothermal synthesis. Further, this work provides a concept for the surface treatment to form sufficient reactive functional groups based on carboxylic acid on silicon substrates.

Enhanced Hydrate-Based Geological CO2 Capture and Sequestration as a Mitigation Strategy to Address Climate Change

Geological sequestration of CO2-rich gas as a CO2 capture and storage technique has a lower technical and cost barrier compared to industrial scale-up. In this study, we have proposed CO2 capture and storage via hydrate in geological formation within the hydrate stability zone as a novel technique to contribute to global warming mitigation strategies, including carbon capture, utilization, and storage (CCUS) and to prevent vast methane release into the atmosphere caused by hydrate melting. We have attempted to enhance total gas uptake and CO2 capture efficiency in hydrate in the presence of kinetic promoters while using diluted CO2 gas (CO2-N2 mixture). Experiments are performed using unfrozen sands within hydrate stability zone condition and in the presence of low dosage surfactant and amino acids. Hydrate formation parameters, including sub-cooling temperature, induction time, total gas uptake, and split fraction, are calculated during the single-step formation and dissociation process. The effect of sands with varying particle sizes (160–630 µm, 1400–5000 µm), low dosage promoter (500–3000 ppm) and CO2 concentration in feed gas (20–30 mol%) on formation kinetic parameters was investigated. Enhanced formation kinetics are observed in the presence of surfactant (1000–3000 ppm) and hydrophobic amino acids (3000 ppm) at 120 bar and 1 ℃ experimental conditions. We report induction time in the range of 7–170 min and CO2 split fraction (0.60–0.90) in hydrate for 120 bar initial injection pressure. CO2 split fraction can be enhanced by reducing sand particle size or increasing the CO2 mol% in incoming feed gas at given injection pressure. This study also reports that formation kinetics in a porous medium are influenced by hydrate morphology. Hydrate morphology influences gas and water migration within sediments and controls pore space or particle surface correlation with the formation kinetics within coarse sediments. This investigation demonstrates the potential application of bio-friendly amino acids as promoters to enhance CO2 capture and storage within hydrate. Sufficient contact time at gas-liquid interface and higher CO2 separation efficiency is recorded in the presence of amino acids. The findings of this study could be useful in exploring the promoter-driven pore habitat of CO2-rich hydrates in sediments to address climate change.

Field trial of hollow fiber modules of hybrid facilitated transport membranes for flue gas CO2 capture in cement industry

Alarming increase in global CO2 emissions warrants acceleration of CO2 capture technologies. In this work, testing of pre-pilot scale membrane modules containing hybrid facilitated transport membranes in hollow fiber configuration is reported. The tests were carried out using real flue gas from a slipstream in the Colacem cement plant located in Gubbio, Italy. With the fabricated modules, CO2 flux of up to 750 NL m−2h−1 with a CO2 permeate purity ranging from 50 to 55 vol% was recorded. All pre-pilot membrane modules showed increased CO2 permeance in industrial testing (1.5 to 1.9x higher) compared to laboratory evaluation owing to the reliable water profile and high temperature of the flue gas from the chimney. Influence of operating parameters (e.g., pressures in the feed and permeate) were studied. Long-term testing showed no obvious reduction in permeation performance. Furthermore, the membranes with mobile carriers when exposed to the feed gas containing SOx and NOx exhibited good resistance to performance deterioration despite high concentrations of acidic impurities. Simulation studies based on validated experimental performance under industrial conditions reveal the high potential of the fabricated membranes as an efficient separation unit capable of achieving industrial capture rate and CO2 purity requirements using a relatively low membrane area.

Multi-objective optimization of post combustion CO2 capture using methyldiethanolamine (MDEA) and piperazine (PZ) bi-solvent

Global warming is becoming a critical issue in 21st century which is mainly due to the growing rate of greenhouse gas emissions. This is mostly due to the large amount of CO2 emission from power generation activity using fossil fuels. One of the main methods of fighting global warming and reducing CO2 emission into atmosphere is to perform carbon capture, sequestration and utilization. Carbon capture can be performed through different ways, in which post combustion CO2 capture (PCC) has been developed and both economic and technically wise is in state of art. One of the disadvantages of PCC is its high efficiency penalty due to energy consumption in the reboiler for solvent regeneration. Many efforts have been done to reduce the consumption of energy in the reboiler via different strategies including process parameters optimization, solvent development and novel process configuration. This investigation used different blends of PZ and MDEA as solvent and process parameters optimization via evolutionary algorithm and multi-objective optimization. The optimization was performed on a conventional process flow diagram. CO2 capture efficiency and reboiler heat duty were used as the objective functions and main decision variables are solvent flowrate and MDEA/PZ concentration. Flue gas CO2 capture of 90, 91, 92, 93, and 94% corresponded to regeneration energy consumption of 2.68, 2.71, 2.72, 2.75, and 2.76 Eregen/tCO2; respectively. These optimized values showed a higher energy efficiency compared to MEA and MDEA/PZ in conventional process configuration.

CO2 geological storage: Critical insights on plume dynamics and storage efficiency during long-term injection and post-injection periods

In the quest for net-zero greenhouse gas emission, CO2 capture and storage technologies play a prominent role. Estimates suggest a potential of sequestering up to several thousand metric gigatons of CO2. However, some of the main challenges in its development are an assessment of reservoir-specific storage capacities due to variabilities and heterogeneities in the underlying properties (structure, formations, facies, petrophysics, reservoir architecture, and others) and understanding the migration of CO2 in the subsurface.This article critically investigates CO2 plume characteristics and determines the evolving contributions of different trapping mechanisms during a 100-year injection and 200-year post-injection periods. CO2 can reside in various forms in saline aquifers. To account for these, we characterized CO2 plumes in multiple ways based on dissolved CO2 in the aqueous phase, free phase CO2, pH change, and finally, change in solid-phase saturation (due to precipitation and dissolution of salts and calcite). Based on how we define the plumes, the sizes, and the shapes of the plumes differ. Emphasis is on the characterization of the plume, its evolution, and the contributing trapping mechanisms. Additionally, we ascertain the impact of various uncertain variables, including heterogeneity and anisotropy in geological formation properties, reservoir-brine composition, and molecular diffusion on CO2 plume dynamics and storage via statistical Design of Experiments.Simulation results indicate that lateral propagation of the CO2 plume is much larger than vertical dispersion typically attributed to the presence of flow baffles and vertical stratification. The ratio of average lateral to vertical propagation ranged between 7 and 44. In general, various geometries and growth patterns evolved for the CO2 plume and are strongly influenced by the total amount of CO2 injected and the permeability directional anisotropies. On average, for all case scenarios investigated, free phase CO2 is the dominant trapping mechanism (in terms of the amount of CO2 stored) during the injection period, storing up to 60% of the CO2 injected. Both residual (20%) and solubility (16%) trapping storage ratios exhibited higher storage with time than structural trapping (10%). Effectively little mineral trapping transpires during the 100-year injection period. Another important observation is the fact that facies-dependency on saturation functions appears to have a substantial effect on different trapping mechanisms. Shale-dominant facies manifests more residual trapping than other facies.

The interaction nature between hollow silica-based porous ionic liquids and CO2: A DFT study

Carbon dioxide (CO2) is one of the main factors leading to the greenhouse effect, so the capture of CO2 gas is currently a hot spot of research. Hollow silica-based porous ionic liquids (HS-liquids) are porous liquids containing cavities that are not only fluid but also have a high specific surface area and were used for the capture of CO2. However, the mechanism of CO2 absorption by HS-liquids has not been studied. In this work, the mechanism of CO2 absorption by HS-liquids was systematic studied by density functional theory (DFT). First, five possible models for absorbing CO2 in HS-liquids were constructed and optimized. The interaction energies between HS-liquids and CO2 at different sites were obtained. Moreover, the effects of HS-liquids with different degrees of polymerization of polyethylene glycol and different alkyl chain lengths on CO2 absorption were also investigated. Results show that the strongest absorption site locates near the polyethylene glycol unit. Then, the electrostatic potential (ESP) and reduced density gradient (RDG) methods were employed to further understand the interaction nature between them. The results show that hydrogen bonding dominates the weak interaction between the HS-liquid and CO2.

Techno‐economic assessment on the fuel flexibility of a commercial scale combined cycle gas turbine integrated with a CO 2 capture plant

Post‐combustion carbon capture is a valuable technology, capable of being deployed to meet global CO2 emissions targets. The technology is mature and can be retrofitted easily with existing carbon emitting energy generation sources, such as natural gas combined cycles. This study investigates the effect of operating a natural gas combined cycle plant coupled with carbon capture and storage while using varying fuel compositions, with a strong focus on the influence of the CO2 concentration in the fuel. The novelty of this study lies in exploring the technical and economic performance of the integrated system, whilst operating with different fuel compositions. The study reports the design of a natural gas combined cycle gas turbine and CO2 capture plant (with 30 wt% monoethanolamine), which were modelled using the gCCS process modelling application. The fuel compositions analysed were varied, with focus on the CO2 content increasing from 1% to 5%, 7.5% and 10%. The operation of the CO2 capture plant is also investigated with focus on the CO2 capture efficiency, specific reboiler duty and the flooding point. The economic analysis highlights the effect of the varying fuel compositions on the cost of electricity as well as the cost of CO2 avoided. The study revealed that increased CO2 concentrations in the fuel cause a decrease in the efficiency of the natural gas combined cycle gas turbine; however, rising the CO2 concentration and flowrate of the flue gas improves the operation of the capture plant at the risk of an increase in the flooding velocity in the column. The economic analysis shows a slight increase in cost of electricity for fuels with higher CO2 contents; however, the results also show a reduction in the cost of CO2 avoided by larger margins.

Spray-Drying Synthesis of MOFs, COFs, and Related Composites.

ConspectusMetal-organic frameworks (MOFs) and covalent organic frameworks (COFs) are among the most attractive porous materials today. They exhibit outstanding porosity for countless applications such as gas storage, CO2 capture, gas separation, sensing, drug delivery, and catalysis. Moreover, researchers have recently begun to combine MOFs or COFs with other functional materials to obtain composites that boast the respective strengths, and mitigate the respective weaknesses, of each component, enabling enhanced performance in many of the aforementioned applications. Accordingly, development of methods for fabrication of MOFs, COFs, and related composites is important for facilitating adoption of these materials in industry. One promising synthetic technique is spray-drying, which is already well-integrated in manufacturing processes for diverse sectors. It enables rapid, continuous and scalable production of dry microspherical powders in a single step, leading to lower fabrication costs and shorter production times compared to traditional methods.In this Account, we outline our ongoing work on spray-drying synthesis of crystalline porous MOFs, COFs, and related composites. Versatile and tunable, spray-drying can be adapted to perform reactions involving coordination and covalent chemistry for the synthesis of micrometer spherical beads/superstructures of MOFs and COFs. Likewise, MOF- and COF-based composites can be synthesized using similar conditions as those for pure MOFs or COFs, through the simple introduction of additional functional materials into the feed precursor solution or colloid. Interestingly, spray-drying can also be done in water, thus providing the basis for its use as a scalable green method for industrial fabrication of these materials. To date, spray-drying has already been scaled up for pilot production (kilogram scale) of MOFs.

CO2 capture with room temperature ionic liquids; coupled absorption/desorption and single module absorption in membrane contactor

A membrane gas CO2 capture setup, based on the concept of single module absorption and single cycle coupled absorption/desorption, was developed in this work. Ionic liquids (ILs) 1-ethyl-3-methylimidazolium methylsulfate ([emim][MS]) and 1-ethyl-3-methylimidazolium dicyanamide ([emim][DCA]) were used as absorbents. The CO2 absorption rate decreased initially and reached to a nearly constant value achieving pseudo steady state. Coupled absorption/desorption revealed very high performance by retaining 82% and 66% absorption efficiency, for [emim][MS] and [emim][DCA], respectively, even after 70 min of operation. Mass transfer coefficients of the coupled absorption/desorption at pseudo steady state were 9 and 5 folds higher than single module absorption, for [emim][MS] and [emim][DCA], respectively. Parametric analysis for the membrane absorber outlet concentration and optimization of the parameters to achieve zero concentration at the membrane stripper outlet were studied in simulations. As a conclusion, coupled absorption/desorption in combination with ILs, can be considered very suitable for continuous post-combustion carbon capture.

Bis(phenyl)fluorene-based polymer of intrinsic microporosity/functionalized multi-walled carbon nanotubes mixed matrix membranes for enhanced CO2 separation performance

Polymers of intrinsic microporosity (PIM) as one of potential next generation membrane materials for gas separation has attracted great interests due to its ultra-permeable characteristics. Herein, a novel bis(phenyl)fluorene-based PIMs (Cardo-PIM-1) based on 9,9-bis(3,4-dihydroxyphenyl) fluorene (BDPF), 2,3,5,6-tetrafluoroterephthalonitrile (TFTPN) and spirocyclic 5,5′,6,6′-tetrahydroxy-3,3′,3,3′-tetramethylspirobisindane (TTSBI) were prepared vis dibenzodioxane polymerization reaction, and then the functionalized multi-walled carbon nanotubes (f-MWCNTs) were incorporated into Cardo-PIM-1 to fabricate mixed matrix membranes (MMMs) with solution mixing method for CO2 separation. The structure analysis indicated that the MWCNTs were cut into short ropes and the amino groups were incorporated into the nanotubes surface after treated with acid mixtures followed by ethylenediamine modification. FTIR spectroscopy and nuclear magnetic resonance (NMR) measurement confirmed the formation of Cardo-PIM-1 macromolecule. BET and positron annihilation lifetime spectroscopy (PALS) analysis exhibited that Cardo-PIM-1 contained larger pore-size distribution and fractional free volume (FFV), and preferential CO2 adsorption capacity over N2 compared with that of PIM-1. This work investigated the structure of polymer as well as the effect of nanofillers in the gas separation performance. High CO2 permeability of 2.9 × 104 Barrer with a desirable CO2/N2 separation factor of 24.2 was achieved using the MMMs with 7.5 wt% f-MWCNTs loading, which were among the best performance for CO2 separation. The Cardo-PIM-1/f-MWCNTs MMMs will provide a promising alternative in industrial flue gas separation and CO2 capture process.

Data-driven design of metal-organic frameworks for wet flue gas CO2 capture.

Limiting the increase of CO2 in the atmosphere is one of the largest challenges of our generation1. Because carbon capture and storage is one of the few viable technologies that can mitigate current CO2 emissions2, much effort is focused on developing solid adsorbents that can efficiently capture CO2 from flue gases emitted from anthropogenic sources3. One class of materials that has attracted considerable interest in this context is metal-organic frameworks (MOFs), in which the careful combination of organic ligands with metal-ion nodes can, in principle, give rise to innumerable structurally and chemically distinct nanoporous MOFs. However, many MOFs that are optimized for the separation of CO2 from nitrogen4-7 do not perform well when using realistic flue gas that contains water, because water competes with CO2 for the same adsorption sites and thereby causes the materials to lose their selectivity. Although flue gases can be dried, this renders the capture process prohibitively expensive8,9. Here we show that data mining of a computational screening library of over 300,000 MOFs can identify different classes of strong CO2-binding sites-which we term 'adsorbaphores'-that endow MOFs with CO2/N2 selectivity that persists in wet flue gases. We subsequently synthesized two water-stable MOFs containing the most hydrophobic adsorbaphore, and found that their carbon-capture performance is not affected by water and outperforms that of some commercial materials. Testing the performance of these MOFs in an industrial setting and consideration of the full capture process-including the targeted CO2 sink, such as geological storage or serving as a carbon source for the chemical industry-will be necessary to identify the optimal separation material.

CFD investigation of [formula omitted] absorption/desorption by a fluidized bed of micro-encapsulated solvents

Micro-encapsulated solvents (MECS) have been proposed for flue gas CO2 capture. However, relatively little is known about the collective behavior of MECS in fixed or fluidized beds. Therefore, we extended our model for microcapsule CO2 capture (Finn and Galvin, 2018) to a CFD-DEM framework. Temperature and CO2 absorption measurements for microcapsules with catalyzed, aqueous, sodium carbonate solution in a small (order 20 g) bed were used for validation. The influence of inlet gas temperature, relative humidity, and gas flow rate on absorber/regenerator performance was explored. The bed averaged CO2 mass transfer rates were largely insensitive to inlet gas velocity over the time considered. The direction and magnitude of capsule water flux was very sensitive to changes in inlet gas temperature/relative humidity. Precise control of temperature/humidity may be needed if sodium carbonate capsules are to be deployed in fixed/fluidized beds at larger scales.

Flue gas CO2 capture via electrochemically mediated amine regeneration: System design and performance

The electrochemically-mediated amine regeneration (EMAR) process uses electrons to modulate amine capacity to achieve CO2 separation from flue gas as an alternative to the traditional thermal regeneration process for CO2 capture. The EMAR separation scheme is validated in a batch system designed to evaluate efficiency losses. Current and voltage responses of the electrochemical process were analyzed in a flow system operated continuously for up to 50 h. An isothermal EMAR system can achieve separation efficiencies above 80% from a 15% CO2 feed, which is representative of the CO2 composition in a flue gas. This bench scale continuous system can operate at 40–80 kJe/molCO2 with an amine regeneration of between 0.12 and 0.62 molCO2/molamine. The ability to separate CO2 at high electron utilization and moderate electrical energy consumption will prompt future research into optimization of the electrochemical separation unit to obtain long-term and stable operations for flue gas scrubbing.