CO2 Absorption Rate Research Articles

Physiology of the forage cactus cultivate Opuntia stricta (Haw.) Haw under different irrigation frequencies in the Semiarid

The objective of this work was to evaluate the physiological variables of the cultivar Opuntia stricta (Haw.) Haw in the first cycle and in the regrowth, under different frequencies of drip irrigation, cultivated in the Agreste da Paraíba mesoregion. Therefore, a randomized block design was used, with 2 treatments (irrigation frequencies) and 4 replications (blocks), with each treatment repeated 3 times within the block (triplicate) totaling 24 experimental plots. For physiological variables, data were evaluated by analysis of variance (ANOVA) and means compared by t test at 5% probability using SAS ® (2002). The present study shows that the stress of environmental conditions had a greater impact on the frequency of irrigation every 28 days, since the forage cactus irrigated every 7 days had the highest internal concentration of CO2; CO2 absorption rate; instant efficiency in water use; intrinsic efficiency of water use; instantaneous carboxylation efficiency, both in the first cycle and in the regrowth period. Respiratory rate and stomatal conductance did not differ between irrigation frequencies for both cycles, showing the good adaptation of the cultivar to the semiarid region.

Toward economical application of carbon capture and utilization technology with near-zero carbon emission

Carbon capture and utilization technology has been studied for its practical ability to reduce CO2 emissions and enable economical chemical production. The main challenge of this technology is that a large amount of thermal energy must be provided to supply high-purity CO2 and purify the product. Herein, we propose a new concept called reaction swing absorption, which produces synthesis gas (syngas) with net-zero CO2 emission through direct electrochemical CO2 reduction in a newly proposed amine solution, triethylamine. Experimental investigations show high CO2 absorption rates (>84%) of triethylamine from low CO2 concentrated flue gas. In addition, the CO Faradaic efficiency in a triethylamine supplied membrane electrode assembly electrolyzer is approximately 30% (@−200 mA cm−2), twice higher than those in conventional alkanolamine solvents. Based on the experimental results and rigorous process modeling, we reveal that reaction swing absorption produces high pressure syngas at a reasonable cost with negligible CO2 emissions. This system provides a fundamental solution for the CO2 crossover and low system stability of electrochemical CO2 reduction.

Highly Cyclic Stability and Absorbent Activity of Carbide Slag Doped with MgO and ZnO for Thermochemical Energy Storage.

Carbide slag is a solid waste with a high content of reactive CaO, which can be used as an active material for the chemical absorption of CO2 and calcium looping. Calcium looping of CaO-based absorbents is one of the most promising methods of thermochemical energy storage. However, the sintering of pores and a reduction in the CO2 diffusion rates as the carbonization/calcination cyclic reaction progresses have posed challenges to the practical application of CaO-based absorbents. This study proposes a method for alleviating the sintering of the pore structure by improving the activity and cycling stability of such absorbents by doping carbide slag with MgO and ZnO powders. Results showed that the raw material ratio, reaction temperature, and reaction time have a considerable influence on the CO2 absorption rate. Furthermore, the specific surface area and pore volume of the absorbents increased with increasing ZnO and MgO doping levels in the carbide slag. Thus, the problems of sintering and clogging of pores in CaO-based absorbents were effectively alleviated, and the MgO and ZnO-doped absorbents CMZ85 and CMZ90 maintained 41-42% CO2 absorption after 10 cycles. These results confirmed that the cyclic stability and absorbent activity improved significantly with the MgO and ZnO doping of carbide slag for the calcium looping process.

Chemical Absorption of CO2 Enhanced by Solutions of Alkali Hydroxides and Alkoxides at Room Temperature

AbstractThis article presents the study of CO2 capture through aqueous solutions with high basicity conditions. Systematic experiments were conducted to assess the performance of alcohols mixed with aqueous alkaline hydroxides for carbon dioxide capture. Alcohols can work as a catalyst in the capture of CO2 providing greater basicity, a lower surface tension, and an amphiphilic character in the polar aqueous solvent/ (nonpolar CO2 and N2) gas mixture interface, and a lower temperature of solvent regeneration. The results showed that short‐chain alcohols, such as methanol and ethanol, and alkaline metals of greater molar mass (i. e., K compared to Na) can produce greater basicity and a higher CO2 absorption rate in the mixtures than conventional aqueous solutions such as ammonia or monoethanolamine in the same concentration. DFT calculations of electronic and thermodynamic properties for CO2 absorption reactions were carried out to analyze the nucleophilic trend of the short‐chain alkoxides studied. The volumetric proportion between water and alcohol, as well as the concentration of alkaline hydroxide, influences the rate of CO2 absorption, the temperature of regeneration and volatility of the solvent, and the formation of precipitates. CO2 absorption rates greater than 90 % v/v and solvent regeneration temperatures of approximately 78 °C were achieved using ethanol, water, and KOH.

Ionic Liquid Mixtures for Direct Air Capture: High CO2 Permeation Driven by Superior CO2 Absorption with Lower Absolute Enthalpy.

This paper reports a series of liquid materials suitable for use as high-performance separation membranes in direct air capture. Upon mixing two ionic liquids (ILs), namely N-(2-aminoethyl)ethanolamine-based IL ([AEEA][X]) and 1-ethyl-3-methylimidazolium acetate ([emim][AcO]), the resulting mixtures with a specific range of their composition showed higher CO2 absorption rates, larger CO2 solubilities, and lower absolute enthalpies of CO2 absorption compared to those of single ILs. NMR spectroscopy of the IL mixture after exposure to 13CO2 allowed elucidation of the chemisorbed species, wherein [AEEA][X] reacts with CO2 to form CO2-[AEEA]+ complexes stabilized by hydrogen bonding with acetate anions. Supported IL membranes composed of [AEEA][X]/[emim][AcO] mixtures were then fabricated, and the membrane with a suitable mixing ratio showed a CO2 permeability of 25,983 Barrer and a CO2/N2 selectivity of 10,059 at 313.2 K and an applied CO2 partial pressure of 40 Pa without water vapor. These values are higher than those reported for known facilitated transport membranes.

Investigating the kinetics of CO2 absorption in aqueous sodium serinate/piperazine solutions: An experimental and mathematical modeling

Aqueous solutions of amino acids are some of the most important alternatives to conventional alkanolamines for gas absorption applications. This study investigates the kinetics of CO2 absorption in sodium serinate solutions and their blend with piperazine. To that end, the kinetic analysis for sodium serinate was performed at 0.5, 1, 2, and 4 kmol/m3 concentration levels. The blended solution was prepared with 1 kmol/m3 of sodium serinate solution as the main component and piperazine in 0.5, 1, and 2 kmol/m3 concentration levels as the additive. The temperature ranged from 293 to 323 K. The density and viscosity of the solutions, gas solubility in the liquid, and physical mass transfer coefficient of the liquid phase were measured directly. The gas diffusion coefficient in the solution was calculated using the modified Stokes-Einstein relation. At constant concentration, the CO2 absorption rate increased by increasing temperature, while at a constant temperature, the rate directly correlated with concentration up to an optimum level. Beyond the optimum concentration, an increase in concentration decreased the rate. Here, a rate equation for the absorption of CO2 in sodium serinate/piperazine solutions was developed. It can be concluded that aqueous solution of sodium serinate can be used as a CO2 absorbent. Moreover, adding piperazine to the aqueous solution of sodium serinate can improve the CO2 absorption efficiency.

CO2 absorption performance of ChCl-MEA deep eutectic solvent in microchannel

Deep eutectic solvent (DES) has been a new type of absorbent for CO2 capture due to the advantages of environmental friendliness, simple synthesis and excellent selectivity. A series of choline chloride (ChCl)-monoethanolamine (MEA) deep eutectic solvents with various water contents were prepared. The effects of gas-liquid flow rate, molar ratio of ChCl-MEA, water content and temperature on CO2 absorption performance and mass transfer were investigated. The addition of an appropriate amount of water can effectively reduce the viscosity of DES and improve its CO2 capture ability. The results show that the CO2 absorption efficiency, absorption rate, loading and mass transfer coefficient of ChCl-MEA deep eutectic solvent are optimal when the water content is 70 wt% for the DES with the molar ratio of ChCl and MEA 1:6. When the water content exceeds 70 wt%, the hydrogen bond network of DES would be destroyed, and its CO2 capture ability would be weakened. According to the Arrhenius equation, the reaction activation energy of CO2 absorption is as low as 7.54 kJ·mol−1 when the water content is 70 wt% in DES with the molar ratio of ChCl and MEA 1:6. This study can provide technical support for the application of deep eutectic solvents in CO2 capture.

Three-component 1,1,3,3-tetramethylguanidine based CO2-binding organic liquids: Statistical solvent design and thermodynamic modeling of CO2 solubility by LJ-Global TPT2 EoS

In this study, three-component CO2-binding organic liquids (CO2BOLs) are introduced for high pressure CO2 absorption. The non-aqueous, green solvents consist of a superbase (1,1,3,3-tetramethylguanidine (TMG)), a tertiary alkanolamine (Dimethylethanolamine (DMEA), Diethylethanolamine (DEEA) and N-methyldiethanolamine (MDEA)) and an alcohol (MeOH, n-BuOH, sec‑BuOH, tert‑BuOH and 1-HexOH). The best combination of solvent components was determined to be the TMG/DMEA/n-BuOH BOL (molar ration:1/1/1) based on both CO2 loading (αeq= 0.431 mol CO2/mol solvent) and absorption rate (αR= 0.225 mol CO2/mol solvent within 20 min) by implementing screening experiments. The mixture design approach was applied for the design of experiments, modeling and investigating the effect of components’ proportion on αeq and αR at the constant temperature of 35.0 °C and initial CO2 pressure of 25.0 bar. The highest αeq (0.573 mol CO2/mol BOL) and αR (0.362 mol CO2/mol solvent) were obtained using TMG/n-butanol (1/1) and DMEA BOLs, respectively. The CO2 solubility data in the two-component BOLs: TMG/n-BuOH, TMG/DMEA and DMEA/n-BuOH as well as the three-component TMG/DMEA/n-BuOH BOL were gathered at 25.0, 35.0 and 45.0 °C and the pressures up to 35.0 bar using equimolar solvent mixtures. The LJ-Global TPT2 EoS was used in the simultaneous VLE and chemical equilibrium calculation algorithm for the thermodynamic modeling of CO2 solubility in the BOLs. The AAD% in the modeling of TMG/n-BuOH, TMG/DMEA, DMEA/n-BuOH and TMG/DMEA/n-BuOH BOLs were calculated to be 11.5%, 12.4%, 10.5 and 12.9%, respectively. The enthalpies of CO2 absorption in BOLs and the speciation of the system components were predicted from reaction equilibrium constants and using LJ-Global TPT2 EoS.

Experimental investigations of CO2 absorption and catalyst-aided CO2 desorption performance of several different amines blending with a promoter

This research presented the new experimental results of the absorption and desorption performance of various single and blended solvents in terms of initial CO2 absorption rate, initial desorption rate for blank solvents and solvents with the aid of HZSM-5 catalyst, and equilibrium CO2 solubility. MEA and PZ are two promoters used to facilitate several individual aqueous single solvents including BEA, AMP, BDEA, and MDEA. In order to check the altered performance of absorption and desorption, the solvents were specified at 2.5 M. The initial desorption rate was evaluated by varying the temperature, weight of the solid catalyst, and initial rich CO2 loading. The experimental results were then taken to compare with the obtained data of the benchmark solution (2.5 M MEA). The comparison results revealed that all the selected blank solvent blends can provide better absorption and desorption performance than the blank benchmark solution. The results also indicated that the performance of catalyst-aided CO2 desorption could be strongly affected by the rich loading and operating temperature. Meaning that the activation of proton donation by HZSM-5 was patently affected by the above two conditions, which eventually affect the CO2 separation from the rich solvent.

Experimental Study on the Modular Vertical Greening Shading in Summer.

Previous studies have shown that vertical greening has a significant cooling and energy-saving effect, most of which are applied to opaque walls. However, windows are the critical factor contributing to the indoor thermal environment. This study developed a modular vertical greening shading device (MVGSD), and introduces its detailed structure: water supply mode, plant selection, and substrate preparation. To investigate the thermal performance of MVGSD, a structural model test was carried out. The results show that MVGSD has a noticeable effect on indoor temperature. Specifically, the greatest indoor temperature can be reduced by 4 °C and effectively low the concentration of CO2 (The CO2 absorption rate is 53.1%). In addition, the characteristics of the louver shading and MVGSD were compared, and it was found that the indoor temperature by using MVGSD is 2.6 °C lower than the louver. It is also worth mentioning that indoor humidity is improved by MVGSD, which has a beneficial effect on the thermal comfort of human beings.

Effects of Solubilizer and Magnetic Field during Crystallization Induction of Ammonium Bicarbonate in New Ammonia-Based Carbon Capture Process

As a chemical absorption method, the new ammonia carbon capture technology can capture CO2. Adding ethanol to ammonia can reduce the escape of ammonia to a certain extent and increase the absorption rate of CO2. The dissolution and crystallization of ethanol can realize the crystallization of ammonium bicarbonate and generate solid products. The induction of the crystallization process is influenced by many parameters, such as solution temperature, supersaturation, and solvating precipitant content. The basic nucleation theory is related to the critical size of nucleation. Accurate measurement of the induction period and investigating relevant factors can help to assess the nucleation kinetics. The effects of solubilizer content, temperature, and magnetic field on the induction period of the crystallization process of ammonium bicarbonate in the ethanol–H2O binary solvent mixture and determining the growth mechanism of the crystal surface by solid–liquid surface tension and surface entropy factor are investigated. The results indicate that under the same conditions of mixed solution temperature, the crystallization induction period becomes significantly longer, the solid–liquid surface tension increases, and the nucleation barrier becomes more significant and less likely to form nuclei as the content of solvating precipitants in the components increases. At the same solubilizer content, there is an inverse relationship between the solution temperature and the induction period, and the solid–liquid surface tension decreases. The magnetic field can significantly reduce the induction period of the solvate crystallization process. This gap tends to decrease with an increase in supersaturation; the shortening reduces from 96.9% to 84.0%. This decreasing trend becomes more and more evident with the rise of solvent content in the solution. The variation of surface entropy factor under the present experimental conditions ranges from 0.752 to 1.499. The growth mode of ammonium bicarbonate in the ethanol–H2O binary solvent mixture can be judged by the surface entropy factor as continuous growth.

Investigating the Performance of Ethanolamine and Benzylamine Blends as Promising Sorbents for Postcombustion CO2 Capture through 13C NMR Speciation and Heat of CO2 Absorption Analysis

Aiming at formulating efficient sorbents for carbon capture and separation (CCS) processes, in this work, we evaluated the CO2 capture performance of aqueous blends of two primary amines, namely, ethanolamine (MEA), the benchmark for any capture process, combined with benzylamine (BZA), which has intriguing characteristics for industrial use, such as low corrosivity and good resistance to thermal and oxidative degradation. The CO2 loading, the CO2 absorption rate, and the CO2 heat of absorption were determined at 313 K for three different formulations of aqueous BZA/MEA blends, all with the same overall amine concentration (6 M) but with different amine molar ratios (1/2, 1/1, 2/1) by treating a gas mixture containing 15% CO2 (by volume) mimicking a fossil-derived flue gas. Furthermore, through an accurate 13C NMR study, the species present in solution during the CO2 absorption process were identified and quantified to understand the capture mechanism and to evaluate the interactions of the two primary amines when present together in different molar ratios. As a result, the three tested blends show similar high CO2 absorption rates, and their final loading values decrease in the order BZA/MEA 1/2 > BZA/MEA 1/1 > BZA/MEA 2/1, suggesting that a greater relative amount of MEA in the blend is advantageous to achieve a relatively higher CO2 loading. The 13C NMR analysis confirmed that the greater alkalinity of MEA leads to a greater formation of bicarbonate in solution and consequently higher loading. Finally, the CO2 absorption heat of all tested mixtures, measured using a high-precision microcalorimeter, was found to be comparable, if not even higher, to that of each individual amine.

Experimental study and modified modeling on effect of SO2 on CO2 absorption using amine solution

Understanding the competitive mechanism in absorption process between SO2 and CO2 is essential for simultaneous absorption of SO2 and CO2. In this study, the effect of SO2 on CO2 absorption using amine solution was studied experimentally and theoretically. The CO2 absorption rates in MEA/MMEA/MDEA solutions were determined using wetted wall column. Results showed that the reduction of flue gas temperature was beneficial for CO2 absorption at the typical coal-fired flue gas CO2 concentration. On this basis, the effect of SO2 on CO2 absorption performance was studied. Firstly, the overall CO2 mass transfer coefficient decreased under exposure to SO2. Secondly, in the presence of SO2, pH variation of amine solution increased. In addition, the saturated CO2 capacity largely decreased when SO2 was continuously bubbled into the solution. Furthermore, the quantum chemical calculation showed that CO2 had little effect on the absorption performance of SO2 whereas SO2 greatly weakened the interaction between CO2 and amines. The overall CO2 mass transfer coefficient was modified considering the effect of SO2. The competitive absorption factor, χ, was introduced to modify the CO2 liquid phase diffusion coefficients. The average deviation of overall CO2 mass transfer coefficient narrowed to 1.76 % (0.5 mol/L MEA), 1.13 % (1.0 mol/L MEA), 1.88 % (1.0 mol/L MMEA) and 1.43 % (1.0 mol/L MDEA) respectively, which agreed well with the experimental results.

Effects of hydroxyethyl group on monoethanolamine (MEA) derivatives for biomethane from biogas upgrading

Upgrading of biogas to produce biomethane is an essential way to increase the calorific value of biogas by separating CH4 and CO2 to satisfy the global renewable energy demand. In this study, the efficiency of carbon dioxide (CO2) trapping in aqueous monoethanolamine (MEA), diglycolamine (DGA), diethanolamine (DEA), and triethanolamine (TEA) solution during biogas upgrading for biomethane was determined. Effects of hydroxyethyl groups on MEA derivatives were investigated in terms of biogas upgrading and regeneration, CO2 desorption heat, initial CO2 absorption rate and CO2/CH4 selectivity. The duration of upgraded biogas meeting certain European Union (EU) application standards for methane purity during upgrading was reduced by 70, 78 and 200 mins for DGA, DEA and TEA respectively compared to MEA due to the partial substitution of H-bonds by hydroxyethyl groups, and the absorption rate was also reduced, whereas TEA was not suitable for biogas upgrading as it was inefficient for biogas upgrading effect and absorption rate. The calculated results from the Gibbs-Helmholtz equation showed that MEA had the largest CO2 desorption heat (82.47 kJ/mol CO2) and the other MEA derivatives had lower desorption heat than MEA, indicating that MEA consumes more energy in the desorption process. As for the equilibrium partial pressure, all amine solutions absorbed less than 0.4% of the total volume of CH4 and had a high CO2/CH4 selectivity.

Simple energy-efficient electrochemically-driven CO2 scrubbing for biogas upgrading

The conversion of biogas to biomethane represents an attractive solution to replace fossil gas with a renewable gas. However, removal of such a large percentage of CO2 from a fuel gas comes at a significant energy cost using the conventional CO2 capture technologies and hence has led to an opportunity to develop an alternative technique for large-scale carbon capture. Results of the current study suggest that employing an anion exchange membrane (AEM)-based alkaline water electrolyser for CO2 removal from gas mixtures offers an energy-efficient strategy for the capture and removal of CO2 from biogas. After capturing CO2 in an aqueous absorption column, the resulting bicarbonate solution was fed through the cathode of an AEM-based electrolyser. Although the CO2 absorption rate increased from about 300 to 900 mol m−3 h−1 when the pH was elevated from 9 to 13, the system's energy requirement was lowest at pH = 9. The economic assessment shows that the electrochemical work requirement for CO2 removal from biogas using the AEM-based alkaline electrolyser ranges between 0.25 and 0.92 kWh/kg CO2 at optimum conditions (pH = 9). This could potentially reduce the energy input for CO2 removal by about 50% compared to commercially available biogas upgrading technologies.

Effects of Alkyl Groups on Monoethanolamine Derivatives for Biomethane from Biogas Upgrading

Amine scrubbing is one of the key technologies for biogas upgrading to biomethane, which can be used to increase the calorific value of biomethane by separating out CO2 to meet the global demand for renewable energy. In this paper, several monoethanolamine (MEA) derivatives with alkyl groups as variables are screened as sorbents for the biogas upgrading process. The effect of alkyl groups on the efficiency of biogas upgrading, the effectiveness of sorbent regeneration, and the selectivity of CO2/CH4 during biogas upgrading are investigated. The analysis of biogas upgrading experiments with different MEA derivatives shows that methyl and butyl are more favorable for improving CO2 absorption and meeting the biogas upgrading effect of methane purity for a long period of time applicable in some countries, and ethyl is more conducive to the regeneration efficiency of amines. The results of the CO2 desorption heat calculations show that the CO2 desorption heat of ethyl monoethanolamine (EMEA) (66.67 kJ/mol CO2), formed by replacing a hydrogen near the nitrogen with an ethyl group, is significantly lower than those of methyl monoethanolamine (MMEA) (73.04 kJ/mol CO2) and butyl monoethanolamine (BMEA) (73.27 kJ/mol CO2), formed by replacing a hydrogen near the nitrogen with a methyl group and a butyl group, respectively. The CO2 desorption heats were significantly lower than those of MEA (82.12 kJ/mol CO2), suggesting that ethyl can significantly reduce the CO2 desorption heat of the amine compared to other alkyl groups. In the CO2/CH4 selectivity experiments, BMEA showed the fastest initial CO2 absorption rate of 0.83%/s, while dimethyl monoethanolamine (DMMEA) showed the lowest initial CO2 absorption rate of 0.16%/s. All amine solutions showed less than 1% absorption of CH4 and had high CO2/CH4 selectivity.

실내조명에 따른 무궁화 ‘백단심’의 경관구성요소별 특징 및 도입방안

This study was conducted to find an efficient introduction plan by examining the landscape characteristics of each indoor light source in order to introduce Mugunghwa, which has high symbolism as a national flower, into the indoor space. As an experimental plant, Hibiscus syriacus 'Paektanshim known to have relatively strong shadow tolerance characteristics among Mugunghwa varieties, was selected, and experiments were conducted at four types of light sources, including fluorescent lamp, LED lamp, three wave lamp, and optical fiber, and at 500, 750, 1500, and 2,500lux for seven months. Leaf length, leaf width, plant height, number of leaves, number of fallen leaves, joint internode length, and chlorophyll were investigated as landscape measurements of plants. Photosynthesis rate(Pn), CO2 absorption rate(CO2), intercellular CO2 concentration(Ci), atmospheric CO2 concentration(Ca), pore conductivity(Cs), and increasing amount(Tr) were measured as physiological factors of plants. In addition, stomatal density was observed to confirm whether photosynthesis rate was well performed, and the blooming rate of each light source and the color difference meter were used to investigate. The experimental results and introduction plans are as follows. First, among the landscape components of plants, the number of leaves showed a statistically significant difference in all light sources. The number of leaves affects the width of the tree's crown and tree shapes along leaf length and leaf width, and the higher the luminosity, the more leaved, and the most leaved under fiber optics 1,500lux. The higher the luminosity, the larger the size of the leaf length and leaf width. Second, Mugunghwa has unique leaves, but its flowers are beautiful and symbolic, so it is preferred, but Hibiscus syriacus 'Paektanshim blooms from August to October. Looking at the optical conditions of each light source for the purpose of viewing flowers, it was identified as 750lux to 2,500lux for fluorescent lamp, 1,500lux to 2,500lux for LED lamp, 750lux to 2,500lux for three wave lamp, and 1,500lux to 2,500lux for fiber optics. The most effective light source and light intensity were found to be 1,500lux and 2,500lux of optical fibers. Third, the freshness of the leaves can also be measured by the amount of photosynthesis rate and the stomatal characteristics of the leaves, and the higher the luminous intensity, the higher the photosynthesis rate. The stomatal frequency by light source was 7 to 28, and the largest stomatal frequency was found in 1,500 lux of LED lights and 1,500 lux of optical fiber. Fourth, as a result of color difference analysis, the flower color was closer to light green than pink and showed a color close to blue. The value of L* was found to be very bright as it showed a value of 90 or more. Finally, considering the growth condition, growth volume, and flowering rate, it is judged that the optimal light source of the Hibiscus syriacus 'Paektanshim is 1,500lux of optical fiber. However, it is necessary to improve the utilization value and utilization area of the national flower Mugunghwa by identifying the appropriate light source and appropriate light intensity for more Mugunghwa varieties in the future and adding experiments on the flowering rate by age.

Theoretical and Experimental Studies of CO2 Absorption in Double-Unit Flat-Plate Membrane Contactors.

Theoretical predictions of carbon dioxide absorption flux were analyzed by developing one-dimensional mathematical modeling using the chemical absorption theory based on mass-transfer resistances in series. The CO2 absorption into monoethanolamine (MEA) solutions was treated as chemical absorption, accompanied by a large equilibrium constant. The experimental work of the CO2 absorption flux using MEA solution was conducted in double-unit flat-plate membrane contactors with embedded 3D turbulence promoters under various absorbent flow rates, CO2 feed flow rates, and inlet CO2 concentrations in the gas feed stream for both concurrent and countercurrent flow operations. A more compact double-unit module with embedded 3D turbulence promoters could increase the membrane stability to prevent flow-induced vibration and enhance the CO2 absorption rate by overwhelming the concentration polarization on the membrane surfaces. The measured absorption fluxes with a near pseudo-first-order reaction were in good agreement with the theoretical predictions for the CO2 absorption efficiency in aqueous MEA solutions, which was shown to be substantially larger than the physical absorption in water. By embedding 3D turbulence promoters in the MEA feed channel, the new design accomplishes a considerable CO2 absorption flux compared with an empty channel as well as the single unit module. This demonstrates the value and originality of the present study regarding the technical feasibility. The absorption flux enhancement for the double-unit module with embedded 3D turbulence promoters could provide a maximum relative increase of up to 40% due to the diminution in the concentration polarization effect. The correlated equation of the average Sherwood number was obtained numerically using the fourth Runge–Kutta method in a generalized and simplified expression to calculate the mass transfer coefficient of the CO2 absorption in the double-unit flat-plate membrane contactor with turbulence promoter channels.

Computational screening methodology identifies effective solvents for CO2 capture

Carbon capture and storage technologies are projected to increasingly contribute to cleaner energy transitions by significantly reducing CO2 emissions from fossil fuel-driven power and industrial plants. The industry standard technology for CO2 capture is chemical absorption with aqueous alkanolamines, which are often being mixed with an activator, piperazine, to increase the overall CO2 absorption rate. Inefficiency of the process due to the parasitic energy required for thermal regeneration of the solvent drives the search for new tertiary amines with better kinetics. Improving the efficiency of experimental screening using computational tools is challenging due to the complex nature of chemical absorption. We have developed a novel computational approach that combines kinetic experiments, molecular simulations and machine learning for the in silico screening of hundreds of prospective candidates and identify a class of tertiary amines that absorbs CO2 faster than a typical commercial solvent when mixed with piperazine, which was confirmed experimentally.

Mass transfer and capture of carbon dioxide using amino acids sodium aqueous solution in microchannel

Capture and storage of CO2 are important to restrain the greenhouse effect. The amino acid salt solution as a new type of CO2 absorbent shows good application potential. Besides, microchannel has a unique enhancement to mass transfer, which is conducive to promote CO2 capture. The absorption performance of CO2 into aqueous solutions of sodium salts of l-threonine, l-valine, l-alanine and glycine in the microchannel was investigated. It was found that the CO2 absorption rate of four sodium amino acid aqueous solutions under the same condition follows in the order: ñ (sodium glycinate) > ñ (sodium l-alaninate) > ñ (sodium l-valinate) > ñ (sodium l-threoninate). The sodium glycinate aqueous solution has maximum CO2 absorption ability, thus the mass transfer and capture of CO2 absorbed into the sodium glycinate aqueous solution were studied systematically. The effects of operating conditions including gas flow rate, liquid flow rate, and sodium glycinate concentration on the specific surface area, overall volumetric mass transfer coefficient, overall mass transfer coefficient and absorption fraction of CO2 were explored. Furthermore, a new correlation was proposed to predict the volumetric mass transfer coefficient.