Method For CO2 Capture Research Articles

Kinetics studies of CO2 hydrate formation in the presence of l-methionine coupled with multi-walled carbon nanotubes

In recent years, gas hydrate technology has been considered to be a promising method for CO2 capture and transport. Nevertheless, the development of the gas hydrate technology is hindered by the slow hydrate formation. In this work, the effects of concentration, initial pressure and gas-liquid ratio on the CO2 hydrate formation kinetics in the compound system of environmentally friendly additive l-methionine (L-met) coupled with low-dose multi-walled carbon nanotubes (MWCNTs) were investigated for the first time. The results showed that L-met coupled with MWCNTs could effectively promote the CO2 hydrate formation, and the promotion effect was related to the MWCNTs concentration. At 4.0 MPa, compared to the 0.1250 wt% L-met single system, the compound system with the MWCNTs concentration of 0.0270 wt%∼0.0720 wt% increased the CO2 gas consumption (Gsum) by an average of 6.37 %, and the induction time (tin) of CO2 hydrate formation were shortened by an average of 36.03 %. The optimal concentration of MWCNTs was 0.0450 wt%. Meanwhile, the increase of the pressure and gas-liquid ratio could effectively accelerate the kinetics of CO2 hydrate formation. The promotion effect of the pressure increasing was better than that of the gas-liquid ratio increasing. The pressure increasing could result in the maximum increase of 39.75 %, 122.83 %, and 69.85 % in Gsum, initial gas consumption rate (N10), and the gas to hydrate conversion (GTH), respectively; and the highest reduction of tin was 83.72 %. Furthermore, the hydrate morphological observations revealed that CO2 hydrate initially nucleated in the inner of L-met solution, and the hydrate particles in the compound system of L-met coupled with the MWCNTs were porous snowflakes. The wall climbing effect induced by capillary forces was further explained, and the presence of L-met enhanced the mass transfer capacity of CO2 hydrates. The practical use of fast hydrate formation technology for CO2 capture and sequestration has been facilitated by this work.

CO2 capture using gas-lift pumps operating under two-phase flow conditions

CO2 capture through dissolution in water offers environmental benefits and industry applications. However, current studies mostly focus on CO2 extraction into solvents, overlooking its direct solubility in water. Alternatively, gas-lift pumps may hold significant potential for capturing and storing CO2 in water; but this ability remains unexplored. Therefore, this study experimentally delves into the CO2 capture capacity and hydraulic performance of a dual injection gas-lift pump with a 25.4 mm riser diameter. Operating at a constant submergence ratio of 70 %, the pump is fed with simulated flue gas with flow rates within 5–30 LPM at volumetric CO2 concentrations of 10 %, 15 %, and 25 %, and temperatures of 22 °C (isothermal operation) and 110 °C (non-isothermal operation). Two-phase flow hydrodynamics is also evaluated using high-speed imaging in conjunction with time-series void fraction measurements. Within the riser pipe, three distinct two-phase flow patterns — slug, intermittent, and churn flows — are identified. The results reveal that under both isothermal and non-isothermal operations and across all volumetric CO2 concentration levels, churn flow demonstrates superior mass transfer coefficient and lifted liquid flow rate, while slug flow achieves minimum energy consumption per ton of captured CO2, highest CO2 capture degree, and maximum lifting efficiency. Also, the highest degrees of sensitivity to inlet gas flow rate for volumetric mass transfer coefficient, delivered liquid flow rate, and void fraction were observed in slug flow regime. Both gas temperature and volumetric CO2 concentration positively impacted the mass transfer performance. However, the pump showed remarkably higher lifting efficiencies under isothermal operation conditions. Moreover, compared to four established CO2 capture methods (absorption, adsorption, cryogenic distillation, and membrane diffusion), the gas-lift pump exhibits moderately lower energy consumption, at 38-266 kWh/tonCO2, but with lower CO2 capture degree of 2.3 % to 6.7 %.

CO2 capture from flue gases in a temperature swing moving bed

This paper presents a test stand for the capture of CO2 from flue gases arising due to firing pulverised hard coal. The stand, financed from the 2014–2021 Norway Grants, is installed at a Polish power plant. The innovation of the proposed CO2 capture method, developed by the Norwegian partner in the project (SINTEF Industry), lies in the use of activated carbon in the process of temperature swing adsorption in a moving bed. The paper also presents preliminary results of numerical simulations performed using the General PROcess Modelling System (gPROMS) software. The simulations concerned the operation of a supercritical power unit combined with a system for capturing CO2 from flue gases. Transient operation of the system was analysed, assuming rapid changes in the power unit load. Special attention was paid to the CO2 capture process energy consumption at an increase in load by 5% of the power unit nominal capacity in 30 s. It is found that the proposed CO2 capture method “keeps up” with such rapid load changes at the method energy consumption smaller than 2 MJ/kg CO2.

A CFD study on the start-up hydrodynamics of fluid catalytic cracking regenerator integrated with chemical looping combustion

ABSTRACT The integration of chemical looping combustion with fluid catalytic cracking (CLC-FCC) is an innovative concept that serves as a cost-effective method for CO2 capture in refineries. This approach has the potential to reduce refinery CO2 emissions by 25–35%, offering a promising solution. As in the conventional FCC unit, it is common for CLC-FCC regenerators to be exposed to an on-off process while they are being maintained and cleaned. The novelty of this research lies in its specific focus on a less-explored phase (start-up) of CLC-FCC regenerators, the application of advanced CFD modeling, and the comprehensive analysis of operational parameters that influence the system’s performance. To validate the CFD simulations of the different drag models for solid-gas granular, bed density profiles under steady-state conditions, collected from industrial processes, were used. For the flow period based on the start-up process of the drag models, the fluidization gas inlet geometry of the regenerator, flow regime (laminar and turbulent), and superficial gas velocity were comprehensively investigated to reveal their effects on hydrodynamic characteristics. The results show that Gidaspow and Syamlal-O’Brien drag models of the solid-gas multiphase granular flow exhibited a better fit with industrial data. The Syamlal-O’Brien and Gidaspow models closely align with industrial data under steady-state conditions, displaying similar bed densities in the dense phase region (230–310 kg/m3 for Syamlal-O’Brien and 235–300 kg/m3 for Gidaspow). During the initial stage (less than 0.2 seconds), both laminar and turbulent models yield comparable bed density profiles, approximately 510 kg/m3 in the dense phase. However, as the process progresses, the dense phase density decreases to about 250–350 kg/m3 at around 0.5 seconds, with laminar flow models showing a slightly better fit with industrial data. Notably, at 0.5 seconds of fluidization time, inlet geometries having better gas distribution achieve a highly diluted phase with bed densities of 10–20 kg/m3. Reaching a steady state, the bed density decreases from around 400 kg/m3 to 260–300 kg/m3, expanding into a higher section of the regenerator where it aligns well with industrial data. The increase in superficial gas velocity would result in the clarification of the difference and well mixing of the solid-gas multiphase flow.

New porous amine-functionalized biochar-based desiccated coconut waste as efficient CO2 adsorbents.

Climate change caused by the greenhouse gases CO2 remains a topic of global concern. To mitigate the excessive levels of anthrophonic CO2 in the atmosphere, CO2capture methods have been developed and among these, adsorption is an especially promising method. This paper presents a series of amine functionalized biochar obtained from desiccated coconut waste (amine-biochar@DCW) for use as CO2 adsorbent. They are ethylenediamine-functionalized biochar@DCW (EDA-biochar@DCW), diethylenetriamine-functionalized biochar@DCW (DETA-biochar@DCW), triethylenetetramine-functionalized biochar@DCW (TETA-biochar@DCW), tetraethylenepentamine-functionalized biochar@DCW (TEPA-biochar@DCW), and pentaethylenehexamine-functionalized biochar@DCW (PEHA-biochar@DCW). The adsorbents were obtained through amine functionalization of biochar and they are characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, Brunauer-Emmett-Teller (BET), and thermogravimetric analysis (TGA). The CO2 adsorption study was conducted isothermally and using a thermogravimetric analyzer. From the results of the characterization analyses, a series of amine-biochar@DCW adsorbents had larger specific surface area in the range of 16.2 m2/g-37.1 m2/g as compare to surface area of pristine DCW (1.34 m2/g). Furthermore, the results showed an increase in C and N contents as well as the appearance of NH stretching, NH bending, CN stretching, and CN bending, suggesting the presence of amine on the surface of biochar@DCW. The CO2adsorption experiment shows that among the amine modified biochar adsorbents, TETA-biochar@DCW has the highest CO2adsorption capacity (61.78mg/g) when using a mass ratio (m:m) of biochar@DCW:TETA (1:2). The adsorption kinetics on the TETA-biochar@DCWwas best fitted by the pseudo-second model (R2 = 0.9998), suggesting the adsorption process occurs through chemisorption. Additionally, TETA-biochar@DCW was found to have high selectivity toward CO2 gas and good reusability even after five CO2adsorption-desorption cycles. The results demonstrate the potential of novel CO2 adsorbents based on amine functionalized on desiccated coconut waste biochar.

Membrane Separation Technology in Direct Air Capture.

Direct air capture (DAC) is an emerging negative CO2 emission technology that aims to introduce a feasible method for CO2 capture from the atmosphere. Unlike carbon capture from point sources, which deals with flue gas at high CO2 concentrations, carbon capture directly from the atmosphere has proved difficult due to the low CO2 concentration in ambient air. Current DAC technologies mainly consider sorbent-based systems; however, membrane technology can be considered a promising DAC approach since it provides several advantages, e.g., lower energy and operational costs, less environmental footprint, and more potential for small-scale ubiquitous installations. Several recent advancements in validating the feasibility of highly permeable gas separation membrane fabrication and system design show that membrane-based direct air capture (m-DAC) could be a complementary approach to sorbent-based DAC, e.g., as part of a hybrid system design that incorporates other DAC technologies (e.g., solvent or sorbent-based DAC). In this article, the ongoing research and DAC application attempts via membrane separation have been reviewed. The reported membrane materials that could potentially be used for m-DAC are summarized. In addition, the future direction of m-DAC development is discussed, which could provide perspective and encourage new researchers' further work in the field of m-DAC.

Fabrication of CaO pellets via polyvinyl alcohol (PVA) method for efficient CO2 capture and solar energy storage

Calcium looping (CaL) exhibits great prospects for both thermochemical energy storage and CO2 capture. The granulation of CaO into spherical pellets is a crucial step for its practical application. In this study, a PVA solution was utilized as a binder to prepare CaO spherical pellets. Two different methods including the direct method and indirect method assisted with PVA solution were employed to produce CaO pellets. The experimental results indicated that the carbonation conversion of the sorbents from the indirect method was significantly superior to those from the direct method. For energy storage, CaO pellets decomposed from calcium hydroxide using indirect method exhibited satisfying energy storage density, starting with 3200 kJ/kg at the 1st cycles and ending with a high level of ∼2400 kJ/kg over 10 cycles. In the CO2 capture performance test, CaO spheres prepared with calcium citrate as a precursor showed promising CO2 capture performance at around 700 °C. In addition, the effects of carbonation temperature on the energy storage and CO2 capture performance were also studied. It was indicated that CaO pellets exhibited better cyclic energy storage performance at 750 and 800 °C, and that performed best when carbonated at 700 °C for cyclic CO2 capture. Besides, the pellets also demonstrated good mechanical properties such as satisfactory long-term anti-attrition ability, further supporting the practical viability of CaO pellets for both thermochemical energy storage and CO2 capture applications.

Study on biochar and silicon co-production technology of rice husk based on the new ammonia CO2 capture method and its comprehensive benefits

Biomass energy coupling with CO2 capture-utilization-storage (BECCUS) technology has been confirmed essential for achieving net-zero CO2 emissions. A new co-generation technology for producing porous biochar and nano silica from rice husk, with KOH and K2CO3 as silica solubilizers, based on the new ammonia-based CO2 capture method is innovatively proposed, whose energy value-economic analysis model is established, and its comprehensive benefits are further investigated. The results of the energy value analysis show that the BECCU technology is environmentally friendly, especially when the reaction reagent is K2CO3, the environmental loading rate is reduced from 1.19 to 0.19, and the sustainability index is increased from 1.40 to 5.32. The economic evaluation results show that it leads to a higher Net Present Value (NPV) and Internal Rate Return (IRR) of the system with solid profitability and self-solvency. While when KOH is selected as the reaction reagent, the NPV increases from 34,253,700 RMB to 119,637,600 RMB, the IRR increases from 40.84% to 59.70%, and its profitability and self-solvency reach the optimum. It provides new ideas for the utilization of biomass energy in low-carbon and multi-production, accompanied by the large-scale consumption and informed utilization of ammonia-based CO2 capture products.

Preparation of hierarchically porous carbon ash composite material from fine slag of coal gasification and ash slag of biomass combustion for CO2 capture

With the spread and development of industrialization, CO2 emissions are increasing dramatically, posing a serious threat to the global ecosystem. Based on coal gasification fine slag (CGFS) pore structure characteristics, CGFS was used to prepare carbon-ash composite hierarchically porous material by chemical activation and hydrothermal methods for CO2 capture. It would achieve comprehensive and high value utilization of CGFS. In addition, the biomass combustion ash slag (BCA) is rich in alkali and metal elements, there are extremely important influence on CGFS pore formation. Therefore, the alkali and potassium sources were extracted in leaching experiments for CGFS-based porous materials preparation. It was found that the prepared porous material had a large specific surface area (1270 m2/g), a graded porous structure and excellent CO2 adsorption capacity (4.06 mol/kg at 0 °C), while the pores of the BCA-impregnated porous material were further developed with a larger specific surface area (1406 m2/g) and more functional groups on porous material surface. All these results indicate the relevance between using BCA impregnates and material performance enhancement. Furthermore, the CGFS-based graded porous composite porous materials have great potential for repurposing in practical and industrial CO2 adsorption applications.

Performance evaluation on CO2 fixation with chlorine gas production based on direct electrolysis of seawater

CO2 fixation from seawater is an effective way to mitigate climate change and has gained widespread attention in recent years. However, the existing research mostly involves stoichiometric bases and bipolar membrane electrodialysis methods, and the performance of direct seawater electrolysis for CO2 fixation is presented with limited studies and rare research data. The performance evaluation on CO2 fixation based on the technology of direct seawater electrolysis is presented in this paper. Energy consumption, decalcification rate, and calcium carbonate production rate are employed as performance indexes to assess the feasibility of CO2 fixation through direct electrolysis of seawater. The simulation method is adopted in this paper, with validation based on data from experiment. As a result, the minimum energy consumption for per amount of calcium carbonate deposited ranges from 557.82 to 730.06 kJ/mol CaCO3 at the seawater flow rate range of 0.01–0.1 L/s, which has an advantage over other electrochemical CO2 capture method. Additionally, the decalcification rate and calcium carbonate production rate can reach a maximum of 100% and 0.36 mmol/s respectively. The conclusions presented in this paper can serve as a valuable guide for conducting large-scale evaluations or application analyses.

Multi-dimensional assessment for the novel carbon capture process integrated the low-temperature adsorption and desorption

The heat-integrated solid adsorbent process exhibits the potential to become an energy-saving method for CO2 capture. Here, a super thermal integrated process (STILT) for CO2 capture is proposed based on our experimental data. The novel process strengthened the process of internal thermal integration and significantly improved the total energy efficiency. This study further takes the commercial MEA process as the benchmark for the multi-dimensional assessment (considering the techno-economic-environment). When CO2 products are compressed to 110 bar, the energy efficiency of the STILT process and MEA process is 53.45 % and 48.8 %, and the energy consumption is 1.5 MJ/kgCO2 and 3.41 MJ/kgCO2. Without CO2 compression, the energy efficiencies of the STILT process and MEA process are 55.3% and 50.61%. The energy consumptions are 0.82 MJ/kgCO2 and 2.63 MJ/kgCO2. Due to the combination of internal thermal integration and enhanced CO2 circulation capacity, the capture costs of the STILT process are 25.8–34.94 €·t−1 CO2, which significantly outweigh the MEA process (43.3–55.07 €·t−1 CO2). This exhibits the superior techno-economic-environment advantages of the STILT process. This study harbors tremendous referential significance for the design and scale-up of the industrial CO2 capture process.

A review on different methods of CO2 capture, separation and utilization

A review on different methods of CO2 capture, separation and utilization

Investigation on the performance of EDA-based blended solvents for electrochemically mediated CO2 capture

EDA-Cu based electrochemically mediated CO2 capture method was developed as a promising technology to substitute the conventional amine-based CO2 capture, especially in industries without available steam source. However, the highly corrosive and poor Cu cycling performance seriously obstruct its large-scale application. In this work, traditional primary amine, secondary amine and tertiary amine (MEA, DEA and TEA) are chosen to blend with EDA to alleviate the problems of EDA. Electrochemical measurements, corrosiveness comparison, CO2 absorption and desorption performance were conducted to investigate the advance performance of proposed blended solvents comprehensively. The corrosion potential in all the mixtures is significantly higher than that in sole EDA solution, which illustrates that the corrosiveness of proposed mixed solvents to Cu electrode is weaker. Besides, the Cu cycling performance is greatly improved and the energy consumption is significantly reduced by using blended solvents. Overall, 50/50 EDA/MEA mixed solution with high CO2 capacity and fast absorption rate is suggested to be a substitute for traditional EDA solvent. The CO2 desorption energy consumption of 50/50 EDA/MEA mixed solution decreases 14% than that of EDA solution at a current density of 0.01 A/cm2. Meanwhile, the copper cycling performance is also improved in 50/50 EDA/MEA mixed solution as the cathode Faraday efficiency (CFE) increased from 43% (EDA) to 53% (50/50 EDA/MEA). Results show that the proposed mixed amine solvents lead to the successful circumvention of highly corrosive and poor Cu cycling performance in the electrochemically mediated CO2 capture system, which will contribute to the exploration of efficient blended solvents for EMAR CO2 capture process and promote its industrial application.

CO2 capture by microporous carbon based on Brazil nut shells.

The increase in burning, deforestation, and the exorbitant use of fossil fuels have contributed to the increase in carbon dioxide emissions; this gas is responsible for the intensification of the greenhouse effect and radical climate changes. In this way, it becomes necessary to find alternatives to reduce its emission. Porous carbon materials synthesized from lignocellulosic waste can be employed in technologies for capture and utilization of CO2 due to the advantages such as selectivity, low-cost synthesis, high surface area and pore volume, and thermal and chemical stability. Considering the availability of Brazil nut biomass residues in the Amazon region, this article proposes to synthesize activated carbon from the lignocellulosic residue using physical and chemical activation methods for CO2 capture. The analysis of N2 adsorption-desorption isotherms proves the predominance of a microporous structure when using the two synthesis methods described here. In physical activation, the surface area was 912 m2/g, while, in chemical activation, it was 1421 to 2730 m2/g. The sample treated via the chemical method (BS6-K1) showed better performance in CO2 adsorption, with adsorption results of 3.8 and 6mmol/g of CO2 at 25 ℃ and 0°C, respectively, at 101kPa. CO2 adsorption capacity is due to the high volume of ultramicropores. It is believed that the microporous carbon material synthesized from Brazil nut residues is an alternative precursor for carbon materials used as CO2 capture.

Hierarchically Porous SIFSIX‐3‐Ni/PAN Composite Beads for Carbon Dioxide Adsorption

AbstractThe increase in CO2 concentration in the atmosphere has led to global warming, which draws great attention all over the world. Adsorption is considered as an effective method for CO2 capture and stabilizing the increasing CO2 concentration. Metal–organic frameworks (MOFs) are promising materials for carbon capture. However, the direct use of MOF powders may lead to issues such as high pressure drop, pipe clogging, and handling difficulties in applications. Herein, a phase inversion strategy is reported to prepare SIFSIX‐3‐Ni@PAN composite beads. The prepared composites exhibit hierarchically porous structure with uniform MOF distribution inside the materials and good mechanical stability. The MOF content can be well controlled and composites with up to 70% loading are prepared. Finally, the obtained materials possess high CO2 capture capacity, even at low CO2 concentrations (1.19 mmol g−1 at 0.01 bar and 298 K).

Analysis of CO2 capture process from flue-gases in combined cycle gas turbine power plant using post-combustion capture technology

Combined cycle gas turbine power plants (CCGTs) are a combined cycle consisting of a gas turbine and a steam turbine to generate electricity. Sometimes CCGTs incorporate cogeneration to produce both heat and power. After the gas fuel combustion in the gas turbine combustion chamber, the flue gases are passed through the Heat Recovery Steam Generator (HRSG) to extract heat and generate additional electrical power using the steam turbine. The CCGT technology is recognized for its highest efficiency of 58% in electricity production among the power production technology. A highly efficient CCGT power plant with 60% efficiency produces even 2.5 times less CO2 than a modern coal power plant with an efficiency of 45% because of the use of gas fuel and electrical efficiency. The CO2 emission can be reduced further when the post-combustion CO2 capture methods are applied. To perform CO2 capture and to reduce the CO2 emission from power plants, the CO2 mass fraction in flue gas is the crucial parameter for the operation of the Post-combustion Carbon Capture and Storage (PCCS) technology. The PCCS technology uses solvents, which is the aqueous solution of amine that reacts with flue gas and absorbs the CO2, which is treated and separated later. The paper presents the results of the energy analysis of a post-combustion carbon capture process when integrated with a combined cycle gas power plant. The study considered two different gas fuels such as methane and syngas. Syngas composition was determined from the sewage sludge gasification process and can be treated as zero-emission CO2 gas fuel. When the flue gas produced from the syngas is used in PCCS at more than 50% of load conditions, the negative CO2 emission level in large-scale CCGT power plants can be reached. The paper presents the results of mass and energy balance analysis of HRSG of a CCGT integrated with PCCS to perform CO2 capture. The analysis of HRSG using flue gases from methane and syngas is performed by calculating the enthalpy of flue gas, rate of heat exchange, and temperature distribution of each component of HRSG. The comparison of the result shows slight differences due to the different composition and flow rates of flue gases. The flue gas at the outlet of two HRSG is used in the PCCS at different load conditions. An aqueous solution of 30 wt% Monoethanolamine (MEA) with rich loading of 0.5 mol-CO2/mol-MEA and a mixture of 16 wt% 2-amino-2-methyl-1-propanol (AMP) – 14 wt% Piperazine (PZ) with rich loading of 0.62 and 0.86 mol-CO2/mol-amine respectively are used in the PCCS. Due to the reboiler duty of amines, the steam consumed by the PCCS for AMP-PZ regeneration is less compared to MEA. Depending upon the flue gas and solvent used in the PCCS, the power consumed by the PCCS from CCGT power plant is measured from 9.6% to 11.6%. For the given operating condition of the CCGT and PCCS at more than 50% load condition, the negative CO2 emission level can be achieved.

A Comprehensive Review of CO2 Capture and Separation Methods

A Comprehensive Review of CO2 Capture and Separation Methods

Amino acid promoted single-step carbon dioxide capture and mineralization integrated with polymer-mediated crystallization of carbonates

Integrated CO2 capture and mineralization is a promising technology for cutting CO2 emissions and associated environmental impacts. Two major challenges in CO2 mineralization in aqueous media are (1) the lack of green and energy-efficient processes and (2) limited applications of the produced carbonates. Here, we present a very efficient, environmentally friendly, and convenient integrated CO2 capture and mineralization method to produce functional calcium carbonate (CaCO3) particles. We use a gas diffuser reaction setup to bubble CO2 in liquid media containing reagents such as amino acid as CO2 absorption promotor, water-soluble polymers as crystal growth modifiers, and Ca2+ ions. Different concentrations of amino acid L-arginine with a fixed CO2 bubbling rate were investigated for Ca2+ conversion. At the optimized conditions, more than 90% Ca2+ was converted to CaCO3 within 5 min of CO2 bubbling at a nominal rate. Additionally, functional carbonates that could be used as dye, heavy metals adsorbents, and functional composite fillers are produced using crystal growth modifiers. The method is simple, efficient, eco-friendly, and could be used for CO2/Ca2+-rich industrial waste valorization.

Synthesis of highly porous N-doped hollow carbon nanospheres with a combined soft template-chemical activation method for CO2 capture

In the present study, N-doped hollow carbon nanospheres (NHCNs) were synthesized with a combined soft template-chemical activation method. Spherical hollow hydrochar was prepared from glucose with the assistance of dual soft templates, and was then chemically activated with KHCO3 and urea to produce the NHCNs. Effects of urea addition and activation temperature on the NHCNs’ physicochemical properties were revealed. The NHCNs were endowed with rich N-doping and developed porosity. The sample activated at 800 °C (NHCN2800) showed an impressive specific surface area of 3234 m2/g. The proposed method could also be extended to the synthesis of N, S co-doped hollow carbon nanospheres. We then investigated CO2 adsorption performances of the NHCNs. At 25 °C and 1 bar, the best CO2 uptake of the NHCNs was 4.36 mmol/g; at 20 bar, it increased to a record high level of 23.62 mmol/g. Correlations between textural characteristics/N-doping and CO2 adsorption at 1/20 bar were analyzed and discussed. The current study indicated that the obtained NHCNs had great potential for applications in both pre- and post-combustion CO2 capture.

Direct Air Carbon Capture and Recovery Utilizing Alkaline Solution Circulation

Direct air capture (DAC) represents a promising technology for mitigating climate change by extracting CO2 from the atmosphere. This study introduces a novel application for effective CO2 capture from dispersed emission sources, integrated with a liquid electrolysis system to improve capture cycle efficiency. By focusing on distributed sources, the DAC application overcomes the constraints of traditional stationary CO2 capture methods. It employs a thin-layer moving bed spray and air convection to capture CO2 in lean liquid, which converts into rich trap liquid when the carbonate concentration exceeds a certain threshold. Electrolysis is then used to recover the lean liquid. This design allows for quick, energy-efficient CO2 absorption even under low partial pressure conditions (462 ppm). The technology is designed to facilitate significant CO2 capture while concurrently generating high-purity hydrogen and collecting carbon dioxide. By reusing the capture liquid, an integrated capture and desorption process is realized. In a test with 1 M KOH as a lean trap solution and a wind speed of 9 m/s, a rich trap solution was obtained after 13 h, lowering the CO2 concentration at the outlet by 97 ppm compared to the input air, demonstrating the device’s effectiveness.