CO2 Absorption Research Articles

High-temperature carbon dioxide capture in a porous material with terminal zinc hydride sites.

Carbon capture can mitigate point-source carbon dioxide (CO2) emissions, but hurdles remain that impede the widespread adoption of amine-based technologies. Capturing CO2 at temperatures closer to those of many industrial exhaust streams (>200°C) is of interest, although metal oxide absorbents that operate at these temperatures typically exhibit sluggish CO2 absorption kinetics and instability to cycling. Here, we report a porous metal-organic framework featuring terminal zinc hydride sites that reversibly bind CO2 at temperatures above 200°C-conditions that are unprecedented for intrinsically porous materials. Gas adsorption, structural, spectroscopic, and computational analyses elucidate the rapid, reversible nature of this transformation. Extended cycling and breakthrough analyses reveal that the material is capable of deep carbon capture at low CO2 concentrations and high temperatures relevant to postcombustion capture.

Uncovering the structure and kinematics of the ionized core of M\,2-9 with ALMA

We present interferometric observations at 1 and 3\,mm with the Atacama Large Millimeter Array (ALMA) of the free-free continuum and millimeter(mm)-wavelength recombination line (mRRL) emission of the ionized core (within lsim 130\,au) of the young planetary nebula (PN) candidate M\,2-9. These inner regions are concealed in the vast majority of similar objects. A spectral index for the mm-to-centimeter(cm) continuum of sim 0.9 indicates predominantly free-free emission from an ionized wind, with a minor contribution from warm dust. The mm continuum emission in M\,2-9 reveals an elongated structure along the main symmetry axis of the large-scale bipolar nebula with a C-shaped curvature surrounded by a broad-waisted component. This structure is consistent with an ionized, bent jet and a perpendicular compact dusty disk. The presence of a compact equatorial disk (of radius sim 50\,au) is also supported by redshifted CO and absorption profiles observed from the base of the receding northern lobe against the compact background continuum. The redshift observed in the CO absorption profiles likely signifies gas infall movements from the disk toward a central source. The mRRLs exhibit velocity gradients along the axis, implying systematic expansion in the C-shaped bipolar outflow. The highest expansion velocities (sim 80\ are found in two diagonally opposed compact regions along the axis, referred to as the high-velocity spots or shells (HVSs), indicating either rapid wind acceleration or shocks at radial distances of sim 0 (sim 15-25\,au) from the center. A subtle velocity gradient perpendicular to the lobes is also found, suggesting rotation. Our ALMA observations detect increased brightness and broadness in the mRRLs compared to previously observed profiles, implying variations in wind kinematics and physical conditions on timescales of less than two years, which is in agreement with the extremely short kinematic ages (lsim 0.5-1\,yr) derived from observed velocity gradients in the compact ionized wind. Radiative transfer modeling indicates an average electron temperature of sim 15000\,K and reveals a nonuniform density structure within the ionized wind with electron densities ranging from to 10$^8$\ These results potentially reflect a complex bipolar structure resulting from the interaction of a tenuous companion-launched jet and the dense wind of the primary star.

Comparative study of deterministic and stochastic optimization algorithms applied to the absorption of CO2 by alkanolamine solution

Abstract A model based on simulated annealing approach is used with e-UNIQUAC model as well as two other algorithms to study the absorption of carbon dioxide by monoethanolamine solutions. In this work, we propose to compare the performance (through the knowledge of RMSD values) of two stochastic methods, namely the GA (genetic algorithm) and SA (simulated annealing) methods and a deterministic method that is the simplex method. These methods were applied to the absorption of carbon dioxide by an alkanolamine solution using a chemical equilibrium model and a thermodynamic equilibrium model. The latter is based on the use of the modified-UNIQUAC (UNIQUAC-electrolyte) model instead of e-NRTL model for the liquid phase and a fugacity model for the vapor phase. The chemical equilibrium in this work represents the absorption of CO2 by monoethanolamine solution at different temperatures. Solving the coupled system of material and charge balances gives us the carbon dioxide pressure while taking into account the non-ideality of the system. The three-optimization methods show good agreement with the experimental data with a better performance of the simulated annealing method..

Anesthetic Management of Laparoscopic Surgery on a Pediatric Patient: Case Report

Inguinal hernia is an opening on myofascial oblique muscle and transversal muscle or the failure of Nuck canal or processus vaginalis during the gestation week which allows herniation of intra-abdominal or extraperitoneal organ. A 5-year-old child was diagnosed with a left lateral inguinal hernia. The results of the inguinal ultrasound showed movement and movement of the intestines in the left inguinal area through a defect measuring approximately 2.96 centimeters. The patient was planned to undergo laparoscopic high ligation hernia. Laparoscopic technique in adult commonly applied with special consideration. However, the practice in pediatric patient could be more challenging for anesthesiologist. Although laparoscopic surgery is less invasive it could cause more stress due to the pressure of the intra-abdominal pneumoperitoneum by CO2 that is done during the procedure, which then causes hypercapnea due to the absorption of CO2, the decrease of tidal volume, and the decrease of end-tidal volume. Considering pediatric’s different physiology compared to adult and the risks of laparoscopic surgery, special anesthesia management should be conducted.

Accelerated weathering of construction‐grade limestone for CO2 absorption

AbstractAccelerated weathering of limestone (AWL) process efficiently captures CO2 from point source emissions. However, despite achieving an outstanding capture efficiency of 73.51 %, lab‐grade (LG) limestone with 99.90 % CaCO3 as an absorbent is costly ($2757.70/t), making commercialization of AWL impractical. This work delves into the viability of utilizing construction‐grade (CG) limestone (93.26% purity) for the AWL process facilitated by potable water in an absorption tower for post‐combustion capture. The result shows that CG limestone achieves comparable CO2 capture efficiency of 8.0–74.68% and bicarbonate (Ca(HCO3)2) concentration of 0.63–3.10 mM compared with LG limestone. However, LG limestone has 0.29 mol CO2/mol CaCO3 higher CO2 absorption capacity and a faster absorption rate than CG limestone, indicating a somewhat better CO2 capture performance. Nevertheless, CG limestone offered a more cost‐effective alternative, with a $2735.24 lower cost per ton of CaCO3 and a $2651.63 per ton CO2 lower CO2 capturing cost at the highest carbon capture efficiency (HCCE) condition compared to LG limestone. The kinetic analysis shows that the forward reactions in the AWL process are significantly faster at elevated CO2 concentration, with the mass transfer coefficient affirming that CO2 dissolves faster than CaCO3, in line with prior research. Thus, this work validates that CG limestone‐based AWL achieves comparable CO2 capture performance to that of LG limestone, offering a cost‐efficient alternative. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

Enhancing CO2 uptake by aqueous K2CO3 solutions using H2O2‐derived reactive oxygen species: Novel rate promotion for CCU processes

AbstractThis study introduces a novel approach to promote CO2 absorption by aqueous K2CO3 solutions through the in‐situ generation of reactive oxygen species (ROS) via the alkali activation of H2O2. The superoxide radical anion (O2•‐) is recognized as a major contributor in this process, with its presence confirmed by UV‐Vis (Ultraviolet–visible) spectroscopy through the characteristic diformazan peak formed from the reaction between nitro blue tetrazolium (NBT) and superoxide. CO2 absorption experiments and 13C NMR (Carbon‐13 nuclear magnetic resonance) characterization demonstrate the enhanced efficiency of the promoted solution in both CO2 absorption and the conversion of K2CO3 to KHCO3. Comparative analysis with traditional promoters reveals the superior kinetic performance of the H2O2‐promoted system at room temperature. Notably, our system yields pure KHCO3 without by‐products, making it highly suitable for carbon capture and utilization (CCU) by enabling versatile subsequent transformation processes. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

Real-Time Estimation of CO2 Absorption Capacity Using Ionic Conductivity of Protonated Di-Methyl-Ethanolamine (DMEA) and Electrical Conductivity in Low-Concentration DMEA Aqueous Solutions

The present study investigates the real-time estimation of CO2 absorption capacity (CAC) based on the electrical conductivity (EC) of low-concentration di-methyl-ethanolamine (DMEA) solutions (0.1–0.5 M). CO2 absorption experiments are conducted to measure the variation in CAC and EC during CO2 absorption, revealing a strong correlation between the two properties. The ionic conductivity of DMEAH+ formed during absorption is calculated to be 53.1 S·cm2/(mol·z), which is found to be larger than that of TEAH+ and MDEAH+. This can be attributed to the smaller molar mass and higher ionic mobility of DMEAH+. A significant finding is that the measured EC (ECM) of the DMEA solutions consistently demonstrates a lower value than the theoretically predicted value. This discrepancy is due to the larger ionic size of DMEAH+, which results in a reduction in the real mean ionic activity coefficient. This effect becomes more pronounced with increasing DMEA concentration. Consequently, a higher CAC is required to produce the same change in EC at higher amine concentrations. Based on these findings, an empirical equation is devised to estimate CAC from ECM in solutions of constant DMEA concentration. This equation will be employed as a practical approach for the in situ monitoring of CO2 absorption using DMEA aqueous solution.

Calibration experiments for dual-comb IPDA XCO2 measurements using a variable pressure absorption cell

Measuring XCO2, the column-averaged dry-air mixing ratio of CO2 in the atmosphere, is essential for monitoring climate change and guiding mitigation efforts. Integrated Path Differential Absorption (IPDA) is a highly effective XCO2 measurement solution for space-borne lidar. However, the limited number of wavelengths limits its capabilities. IPDA, enhanced with Electro-Optical Frequency Comb (EOFC) technology, offers a robust solution. This study validates IPDA measurements using both asymmetric and symmetric Electro-Optic Dual-Comb Spectroscopy (EO-DCS) systems at 1572 nm. This indoor experimental system does not operate in a true lidar mode, but focuses on IPDA measurements of XCO2 through a transmission-style cell. We achieved atmospheric spectral transmittance by a variable pressure CO2 absorption cell, correlating pressures from 425 to 470 mb to XCO2 of 386.81–447.08 ppm. The XCO2 measurements of asymmetric/symmetric systems both exhibit excellent linearity. Their linear fittings yielded the Root Mean Square Error (RMSE) as low as 0.198/0.064 ppm, and the Mean Absolute Percentage Errors (MAPE) was as low as 0.0386%/0.0140%. This level of measurement performance has never been demonstrated in other works. Accuracy was assessed by comparing IPDA results with a pressure gauge, and precision was confirmed through repetitive measurements (1000 times over 10 min) and Allan variance analysis. Notably, our system operates effectively without frequency stabilization, showing tolerance to laser frequency drift—a significant advantage for IPDA applications. The entire experiment was conducted in a comparison between asymmetric and symmetric systems, especially in the analysis of absorption line residuals. We discuss the error transfer from phase to spectral transmittance and its implications and explained why the residuals in the asymmetric system were larger. These results underscore the superior performance of EO-DCS IPDA in measuring XCO2 and its promising potential for applications. To our knowledge, this is the only DCS IPDA calibration demonstration to date.

Dual-channel infrared OPO lidar optical system for remote sensing of greenhouse gases in the atmosphere: Design and characteristics

Current global warming and climate change under the greenhouse effect call for a thorough understanding of the spatial distribution of greenhouse gases in different atmospheric layers. Lidar systems are the most effective for remote greenhouse gas monitoring. We design a two-channel infrared OPO lidar optical system for remote DIAL/DOAS sensing of carbon dioxide and water vapor in the atmosphere. In this work, optimal geometric parameters of the transceiving channel of the lidar optical system are chosen, a need to focus laser radiation at a distance of 1 km from an observation point is demonstrated, and numerical simulations confirm the possibility of detecting lidar signals ranging from 10−7 to 10−10 W in the informative spectral range 4800–5100 cm−1 (1960–2083 nm). Laboratory experiments with the main components of the lidar system with experimentally confirmed parameters, which simulate atmospheric measurements of CO2 absorption at a calibrated sensing wavelength of 2005 nm (4987 cm−1) (pressure of 1 atm; CO2 concentration corresponding to the midlatitude summer background atmosphere) in the informative spectral range of the lidar system, enable selecting a pair of wavelengths with resonant absorption of the target gas near 2005 nm to study the background state of the atmosphere in the surface layer. Efficiency of the lidar optical system is confirmed by in situ test experiments, where backscattering signals from a topographic target with an albedo of ∼0.15 spaced 168 m apart from an observer are recorded at 60 mV when operating along a horizontal atmospheric path. The lidar system we design can be used in measuring complexes at carbon test sites. It can also be used for atmospheric monitoring in industrial centers, at background measuring stations, and in swamp areas.

Predictive modeling of CO2 capture efficiency using piperazine solutions: a comparative study of white-box algorithms

The urgency to mitigate carbon dioxide (CO2) emissions and combat climate change has spurred the development of effective CO2 capture technologies. One of the industry’s most well-known CO2 collection processes is CO2 absorption utilizing amine solvents. However, designing a successful amine scrubbing system in power plants requires precise prediction of CO2 absorption in aqueous amine solutions under various operating circumstances. Using aqueous piperazine (PZ) solutions for chemical absorption is promising due to the favorable reactivity of PZ with CO2. In this study, a comprehensive evaluation of PZ solution performance in CO2 capturing, employing the white-box algorithms, namely, Genetic Programming (GP), Gene Expression Programming (GEP), and Group Method of Data Handling (GMDH), was performed. Through extensive experimentation and data analysis, several correlations were developed with high and acceptable R2 values, such as 0.933 for GP, 0.949 for GEP, and 0.889 for GMDH, which shows high accuracy and reliability in predicting the CO2 capture efficiency of PZ solutions under varying operating conditions. The results of sensitivity analysis revealed that CO2 partial pressure increased CO2 absorption, while PZ concentration and temperature had negative and decreasing effects. These insights provide essential guidance for optimizing process conditions to enhance the CO2 capture efficiency. Finally, the leverage method was used to assess the reliability of both experimental and predicted data from white-box algorithms. This analysis identified potential outliers and validated the accuracy of the model’s predictions, enhancing the credibility of developed correlations and demonstrating the robustness of the approach.

Sustainable Solutions in Gas Separation: Exploring the Potential of Deep Eutectic Solvents

In the face of escalating environmental concerns, particularly related to greenhouse gas emissions, this study delves into the potential of Deep Eutectic Solvents (DESs) as a sustainable alternative in gas separation technologies. Focusing on the significant emissions of CO2, SO2, and H2S from industrial processes, this work reviews the application of DESs for their capture and separation. We investigate the physical properties of DESs, such as solubility and viscosity, which are crucial for their efficacy as sorbents. This review includes a comprehensive analysis of various DES formulations, exploring their roles in CO2 absorption, SO2 removal, and the separation of other gases like H2S. Additionally, we extend our examination to the applicability of DESs in the oil and gas industry, highlighting their effectiveness in removing sulfur and nitrogen impurities, and their potential in the extraction of organic constituents. The study reveals that DESs, characterized by their biodegradability and environmental sustainability, offer promising performance in gas separation, aligning with the principles of green chemistry. However, challenges such as high viscosity and the need for further understanding of their solubility dynamics under different conditions are addressed. This work underscores the importance of DESs as novel sorbents for gas purification and sets a foundation for future research aimed at enhancing their application on a broader industrial scale.

Characteristics of Carbon Fluxes and Their Environmental Control in Chenhu Wetland, China

Carbon dioxide (CO2) flux measurements were conducted throughout the year 2022 utilizing the eddy covariance technique in this study to investigate the characteristics of carbon fluxes and their influencing factors in the Chenhu wetland, a representative subtropical lake-marsh wetland located in the middle reaches of the Yangtze River in China. The results revealed that the mean daily variation of CO2 flux during the growing season exhibited a U-shaped pattern, with measurements ranging from −12.42 to 4.28 μmolCO2·m−2·s−1. The Chenhu wetland ecosystem functions as a carbon sink throughout the growing season, subsequently transitioning to a carbon source during the non-growing season, as evidenced by observations made in 2022. The annual CO2 absorption was quantified at 21.20 molCO2·m−2, a figure that is lower than those documented for specific subtropical lake wetlands, such as Dongting Lake and Poyang Lake. However, this measurement aligns closely with the average net ecosystem exchange (NEE) reported for wetlands across Asia. The correlation between daytime CO2 flux and photosynthetically active radiation (PAR) can be accurately represented through rectangular hyperbola equations throughout the growing season. Vapor pressure deficit (VPD) acts as a constraining factor for daytime NEE, with an optimal range established between 0.5 and 1.5 kPa. Furthermore, air temperature (Ta), relative humidity (RH), and vapor pressure difference (VPD) are recognized as the principal determinants affecting NEE during the nocturnal period. The association between Ta and NEE during the non-growing season conforms to the van’t Hoff model, suggesting that NEE increases in response to elevated Ta during this timeframe.

The Recycling of Lithium from LiFePO4 Batteries into Li2CO3 and Its Use as a CO2 Absorber in Hydrogen Purification

The growing adoption of lithium iron phosphate (LiFePO4) batteries in electric vehicles (EVs) and renewable energy systems has intensified the need for sustainable management at the end of their life cycle. This study introduces an innovative method for recycling lithium from spent LiFePO4 batteries and repurposing the recovered lithium carbonate (Li2CO3) as a carbon dioxide (CO2) absorber. The recycling process involves dismantling battery packs, separating active materials, and chemically treating the cathode to extract lithium ions, which produces Li2CO3. The efficiency of lithium recovery is influenced by factors such as leaching temperature, acid concentration, and reaction time. Once recovered, Li2CO3 can be utilized for CO2 capture in hydrogen purification processes, reacting with CO2 to form lithium bicarbonate (LiHCO3). This reaction, which is highly effective in aqueous solutions, can be applied in industrial settings to mitigate greenhouse gas emissions. The LiHCO3 can then be thermally decomposed to regenerate Li2CO3, creating a cyclic and sustainable use of the material. This dual-purpose process not only addresses the environmental impact of LiFePO4 battery disposal but also contributes to CO2 reduction, aligning with global climate goals. Utilizing recycled Li2CO3 decreases the demand for virgin lithium extraction, supporting a circular economy. Furthermore, integrating Li2CO3-based CO2 capture systems into existing industrial infrastructure provides a scalable and cost-effective solution for lowering carbon footprints while securing a continuous supply of lithium for future battery production. Future research should focus on optimizing lithium recovery methods, improving the efficiency of CO2 capture, and exploring synergies with other waste management and carbon capture technologies. This comprehensive strategy underscores the potential of lithium recycling to address both resource conservation and environmental protection challenges.

Estimating the Greenhouse Gas Emission Potential Due to Construction Work on the 225 kV Segou - Bamako High Voltage BI-Ternal Electric Line in Mali in The Context of Climate Change

The aim of this study is to assess the carbon emissions resulting from the construction of the power line linking Bamako to Ségou. It focuses on direct emissions, more specifically those linked to the degradation and desctruction of the vegetation cover in the project right-of-way. To collect the data, surveys were set up on the project right-of-way, through which 3302 trees were inventoried in situ at the three sites. Circumference was measured at 1.30 m from the ground surface. Allometric equations for direct biomass estimation were used as a predictor o f tree diameter. Emission factors were then used to estimate the potential greenhouse gas emissions resulting from tree felling during power line construction. The standard error associated with the carbon fraction in dry biomass was calculated. In the Ségou, Koulikoro and Dioïla project areas, there are a number of plant species that provide local populations with various ecosystem services, including micro-climate regulation through carbon sequestration or absorption of atmospheric CO2. The implementation of the project will undoubtedly result in the felling of these trees. This felling will generate emissions of 22.11 t.eqCO2/ha in Ségou, 16.56 t.eqCO2/ha in Koulikoro and 15.43 t.eqCO2/ha in Dioïla. Across Ségou, Koulikoro and Dioïla, the trees in the project right-of-way represent a reservoir of 34.04 t/ha of above-ground woody biomass. This biomass represents a carbon stock of around 16.58 t.C/ha. This carbon stock will be transformed into a carbon source with emissions of 60.78 t.eqCO2/ha if the trees in the power line right-of-way are systematically felled. Mitigation measures are therefore urgently needed, with compensatory reforestation areas planted with species with high carbon sequestration potential.

One-pot synthesis of copper phthalocyanine polymer: An efficient CO2 fixation catalyst

The chemical transformation of CO2 into high-value-added products is not only favourable to environmental preservation, but also promising for economy. Developing novel and practical catalysts play a critical role in facilitating conversion of CO2 and the synthesis of high value-added chemicals. Herein, we present the fabrication of biphenyl-typed copper phthalocyanine polymer (BPh-CuPc) from 4,4’-bis(3,4-dicyanophenoxy)biphenyl via a one-pot synthesis procedure, and application of it as a promising catalyst for CO2 conversion into cyclocarbonate. FTIR, XPS, UV–vis, TGA and SEM measurements confirm the successful fabrication of BPh-CuPc. Attributing to the existence of copper ions which can act as a Lewis acid to activate epoxide, and phthalocyanine rings that is positive for CO2 absorption, within the chemical framework of BPh-CuPc, it exhibits excellent catalytic activity for CO2 conversion into cyclic carbonates under mild conditions when combined with tetrabutylammonium iodide (TBAI). As a result, a 98 % yield and 99 % selectivity are obtained for the BPh-CuPc/TBAI system in CO2/propylene oxide conversion under condition of 90 °C, 8 h and 2.0 MPa. The obtained high yield and selectivity, as well as remarkable stability and versatility, validate the promising application of BPh-CuPc as a CO2 conversion catalyst. SynopsisAttributing to the existence of copper ions and phthalocyanine rings within the chemical framework, BPh-CuPc exhibits excellent catalytic activity for CO2 conversion into cyclic carbonates under mild conditions.

The effects of counter ion on CO2 capture performance of amino acid salt solutions for direct air capture applications

Direct CO2 capture from the atmosphere has received growing attention driven by the imperative of achieving global net-zero emission targets. Amino acid salt solutions are promising candidates for liquid-based direct air capture processes. Utilised as a neutralized salt by reacting initially with hydroxides, it has been speculated that their performance may vary with the type of counter ion present in the solution. This work investigates the influence of counter ions, potassium, sodium, and lithium, of amino acid salt solutions on the physical properties, the CO2 absorption capacities, and the CO2 absorption kinetics under atmospheric CO2 concentration levels. The potassium-containing amino acid solutions exhibited significantly lower viscosities and mildly elevated densities compared to sodium- and lithium-containing ones. At 25 °C, the potassium-prolinate solution demonstrated the highest viscosity (8.5 mPa⋅s), whereas K-glycinate exhibited the lowest viscosity (2.5 mPa⋅s). Additionally, potassium-based solutions consistently displayed the highest CO2 mass transfer coefficients, followed by sodium- and lithium-containing ones. The CO2 mass transfer coefficient was highest for potassium-prolinate (2.99 mmol m−2⋅s−1⋅kPa−1) with the lowest rate observed for potassium-β-alaninate (1.68 mmol m−2⋅s−1⋅kPa−1). Interestingly, the type of counter ion had minimal impact on the CO2 absorption capacity, with potassium-based solutions exhibiting only a slightly elevated capacity compared to sodium- and lithium-based solutions. Specifically, potassium-lysinate displayed the highest CO2 absorption capacity (0.7 mol CO2 /mol amine), while potassium-β-alaninate showed the lowest (0.65 mol CO2/mol amine). It should be noted that all lithium-based solutions of all amino acids formed precipitates during CO2 absorption. From a practical and operational perspective, these findings suggest that the potassium salt solution of amino acids would be the optimal choice for direct air capture applications due to their enhanced solubility and CO2 mass transfer rates compared to the corresponding sodium and lithium counter ion salt solutions.

Performance of a novel waste heat-powered ionic liquid-based CO2 capture and liquefaction system for large-scale shipping

In this work, we proposed a novel CO2 capture and liquefaction system for large-scale shipping using ionic liquid as capture solvent. By utilizing the waste heat of the exhaust gas and jacket cooling water from the ship’s engine as well as the residual pressure energy of the N2-O2 mixture from the CO2 absorption and desorption process, the system’s net energy consumption has been significantly reduced. We established the thermodynamic model of the system and investigated the effect of 10 primary system operational parameters on system performance with 3 different ionic liquids as CO2 capture solvent. The results demonstrated that the system with [DEME][TF2N] as the CO2 capture solvent had the best system performance. In addition, we performed a multi-parameter optimization of the system using simulated annealing algorithm with net energy consumption as the optimization objective and the minimal net energy consumption is 0.467 GJ/tCO2. Compared to the CO2 capture system that do not utilize waste heat and residual pressure energy, the net energy consumption was reduced by 57.29 % under optimal operational conditions which proves that the novel system significantly reduces the energy consumption of the CO2 capture and liquefaction process.

Electrochemically Mediated Amine Regeneration-CO2 mineralization: Mechanism and influencing factors

High energy consumption due to the thermal amine regeneration is one of the key issues hindering its large-scale applications. Amine regeneration by electrochemical is a promising technology, which can reduce energy consumption by up to 40% for amine regeneration. However, there are still some problems during the utilization and storage of captured CO2. In response to the current problems, this study introduces an innovative approach termed Electrochemically Mediated Amine Regeneration-CO2 Mineralization (EMAR-M), which innovatively synergizes in-situ regeneration of CO2-rich amine with CO2 mineralization through an electrochemical method. Electrochemical analysis was utilized to examine the anodic and cathodic reactions of EMAR-M, incorporating findings from XRD and CO32- concentration analysis, the reaction pathways and mechanisms of EMAR-M were elucidated. The results suggested that the reaction of EMAR-M followed the order of electrochemically mediated metal ion release, in-situ metal-amine coordination desorption, directed migration of CO32- and mineralization of CO2. The analysis of influence factors identified that the types of amines, electrolytes and metal electrodes significantly influence the EMAR-M. Compared with DEA and TEA, MEA has good CO2 absorption and electrochemical regeneration properties, which is advantageous for EMAR-M. Although electrolytes such as NaCl, Na2SO4, and KCl did not significantly affect the CO2 absorption of the amine absorbent, NaCl can promote the redox reaction at the metal electrode, which also favors EMAR-M. Cu electrodes also favor EMAR-M due to its swift cathodic/anodic reaction rates. Compared to other technologies, EMAR-M can reduce energy consumption by up to 58% for CCUS. The utilization of calcium-based solid wastes such as calcium carbide slag for synergistic CO2 mineralization can further reduce the operating costs of the technology as well as enable green applications of solid wastes.

Screening and evaluation of phase change absorbents by molecular polarity index: Experimental and quantum chemical calculation studies

Phase change absorbents have recently received increasing attention due to their potential to reduce the energy penalty of CO2 capture. However, its complex composition makes the prediction of phase separation performance difficult. Phase separation behavior and phase separation rate have been investigated for the amine-aqueous 5.0 M amine blends by experimental and quantum chemical calculations (including MPI, hydrogen bonds and Gibbs free energy). The different phase behaviors upon CO2 absorption were discussed and well explained by the polarity change of components and the reaction products. A defined MPI value of tertiary amines was recommended to predict the immiscible type (MPI > 10.55 Kcal/mol), phase separation type (9.00 Kcal/mol < MPI < 10.08 Kcal/mol), and miscible type (MPI < 6.74 Kcal/mol). The electron density at the critical point of hydrogen bonds and interaction region indicators were employed to visually evaluate the influence of intramolecular and intermolecular hydrogen bonds on phase separation behaviors. The results show that the presence of excessive hydrogen bonds decreased the phase separation capacity. Furthermore, the relationship between the MPI, the Gibbs free energy of the proton transfer process and the phase separation time were explored. The increase of MPI caused by the tertiary amines can enhance the stability of the final product, delay the appearance of the phase separation peak and reach a maximum phase separation time of 230 min. Therefore, this study is significant for the screening and evaluation of efficient phase change absorbents with good potential for industrial applications in CO2 capture.

A study of nano-micro-bubble process for CO2 absorption in water for biogas upgrading application

The work proposed a novel micro-bubble system using swirling jet flow method for improving the physical absorption of CO2 in water. The effects of operating conditions; e.g. gas flow rate (from 500 to 2000 mL/min), inlet pressure (2 and 3.5 bar) and inlet CO2 concentration (from 5 to 60% v/v in CO2/N2 gas mixture) on the physical absorption of CO2 were studied. It was found that the CO2 absorption system reached to steady state after 30 minutes with the outlet CO2 concentrations of 2.9% and 8.8% at 40% and 60% of inlet CO2 concentrations, respectively. These outlet CO2 concentrations demonstrated the standard of bio-methane for replacing natural gas in vehicle use, from which less than 10% CO2 is required. Moreover, the increase of gas flow rate resulted in increase of outlet CO2 concentration. The rising of inlet pressure from 2 to 3.5 bars let to reduction of the outlet CO2 concentration together with enhancing the dissolved CO2 concentration in water from 49.1 to 51.7 mg/L at gas flow rate of 2000 mL/min and 60% of inlet CO2 concentration. The highest efficiency of CO2 removal was 98.41% under gas flow rate at 500 mL/min with 60% of inlet CO2 concentration. Under the optimized conditions, this system was tested with real biogas as raw material containing mainly 57.7% of CH4 and 40.3% of CO2 which achieved to remove the 95.1% of CO2 removal and no significant loss of CH4. This highlight demonstrated the potential application of this technology for biogas upgrading or purification further.