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Amine emissions from a post-combustion CO 2 capture process can lead to solvent loss and serious environmental issues. The emission characteristics of amine mixtures and influencing factors are seldom reported. This work comprehensively investigated emissions of AMP (2-amino-2-methyl-1-propanol)/MEA (monoethanolamine) from a 3.6 Nm 3 /h flue gas CO 2 capture platform. The condensation nuclei in flue gas dominated the generation of amine aerosols and resulted in a heavy total amine loss of over 1400 mg/Nm 3 , which is equivalent to 5.88 kg/t CO 2 captured under the high nuclei concentration scenario. Inside the absorber, a higher CO 2 concentration and lower lean solvent CO 2 loading can significantly promote the growth of aerosols due to the intensive reaction of CO 2 absorption. The maximum amine emissions were observed at 8-12 vol % CO 2 . The flue gas temperature and liquid/gas ratio had insignificant effects on aerosol emissions, while amine emissions after the absorber increased 340-500% as the lean solvent temperature increased from 30 to 50 °C. A synergistic control strategy of nuclei pretreatment, operating optimization, and water scrubbing can effectively reduce amine emissions to 4.0 mg/Nm 3 MEA and 8.3 mg/Nm 3 AMP.

Aqueous sarcosine salts are fast carbon dioxide (CO(2)) absorbents suitable for use in postcombustion CO(2) capture in coal-fired power plants. We have developed a detailed reaction scheme including all the reactions in the sarcosine-CO(2)-water system. All unknown rate and equilibrium constants were obtained by global data fitting. We investigated the temperature-dependent rate and equilibrium constants of the reaction between aqueous CO(2) and sarcosine using stopped-flow spectrophotometry, by following the pH changes over the wavelength range 400-700 nm via coupling to pH indicators. The corresponding rate and equilibrium constants ranged from 15.0 to 45.0 °C and were analyzed in terms of Arrhenius, Eyring, and van't Hoff relationships. The rate constant for the reaction between CO(2) and sarcosine to form the carbamate at 25.0 °C is 18.6(6) × 10(3) M(-1) s(-1), which is very high for an acyclic amine; its activation enthalpy is 59(1) kJ mol(-1) and the entropy is 33(4) J mol(-1) K(-1). In addition, we investigated the slow reaction between bicarbonate and sarcosine using (1)H nuclear magnetic resonance spectroscopy and report the corresponding rate and equilibrium constants at 25.0 °C. This rate constant is 5.9 × 10(-3) M(-1) s(-1).

Chemical absorbents with low-energy requirements have become the primary focus of the research on CO2 capture from flue gas in power plants. To verify the absorption performance of the NICE absorbent developed by the National Institute of Clean-and-Low-Carbon Energy in China, a performance optimization test was conducted in Zhejiang University's pilot-scale platform, and the effects of the liquid–gas ratio, regeneration pressure, rich liquid fractional flow, and interstage cooling on the absorption performance and regeneration energy consumption were investigated. The results showed that in the CO2 pilot test, the optimized minimum regeneration energy consumption was 2.85 GJ/t CO2, and the corresponding process parameters were as follows: a liquid–gas ratio of 1.82 L/m3, regeneration pressure of 191 kPa, an interstage cooling temperature of 40 °C, and a rich liquid fractional flow ratio of 0.18. This study preliminarily verified the low-energy consumption performance of the NICE absorbent and showed its good potential for industrial applications. Additionally, the NICE absorbent showed promise for capital and operating cost savings because of its low liquid–gas ratio. [ABSTRACT FROM AUTHOR]

The industrial application of emerging water‐lean solvents to CO2 capture from flue gas is challenged by their high viscosity. In this work, we report a novel water‐lean CO2 solvent which possesses lower viscosity and higher CO2 cyclic capacity than other water‐lean solvents reported in the literature. The new solvent consists of N, N‐dimethyl‐1, 2‐ethanediamine (DMEDA), physical cosolvent N‐methyl‐2‐pyrrolidone (NMP) and up to 15% water (named ENH). We evaluated the effect of the solvent composition on the viscosity, CO2 cyclic capacity and regeneration energy of ENH and compared it with the reference monoethanolamine (MEA) based solvents. It was found that ENH containing 5% H2O (ENH‐5%H2O) with a CO2 loading of 0.767 mol CO2·mol amine–1 had a viscosity of 7.603 mPa·S at 40 ˚C, which was comparable with that of traditional blended amines. Excellent cyclic capacity performance was also observed, with ENH‐5% H2O showing a 140% improvement compared to aqueous MEA. Regeneration energy of ENH‐5% H2O was estimated to be 2.418 GJ·tCO2–1 which is 36% lower than the 30 wt. % aqueous MEA solvent. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Highlights • Novel type of biphasic solvent with low costs and high cyclic capacity is proposed. • DEEA-AEEA solvent shows regeneration energy as low as 2.58 GJ/tCO 2. • Phase split time as short as minutes enables fast phase separation. • Driving and resistance forces dominating the phase split dynamics are analyzed. • CO 2 reactions and phase split mechanism are revealed by NMR analysis. Abstract Using biphasic solvents for carbon dioxide (CO 2) capture is regarded as a promising technology to drastically reduce the regeneration energy. However, this technology hasn't been put into commercial application due to lack of the biphasic solvents with high stabilities and low costs. To overcome this challenge, we developed a novel type of biphasic solvent based on alkanolamine-alkanolamine blends, i.e., aqueous blends of 2-(diethylamino)-ethanol (DEEA, 50 wt%) and monoethanolamine (MEA, 25 wt%) or 2-((2-aminoethyl) amino) ethanol (AEEA, 25 wt%). The aqueous DEEA-AEEA solvent demonstrated a cyclic capacity as high as 0.64 mol CO 2 /mol which is significantly higher than those of 30 wt% MEA and other reported biphasic solvents. In addition, a phase split time as short as a few minutes is obtained. The phase split dynamics were analyzed to investigate the effects of CO 2 loading, temperature, gas flow rate and height-to-diameter ratio. Quantitative 13C NMR analysis was then performed to reveal the reaction and phase split mechanism of CO 2 absorption in the DEEA-AEEA solvent. It indicated that the reaction of AEEA with CO 2 dominated at the beginning of CO 2 absorption and the products are formed as carbamates. Then, DEEA began reacting with CO 2 to yield bicarbonate and carbonate. The phase split mechanism indicated that the reaction products of carbamates and HCO 3 −/CO 3 2− migrated to the lower phase while DEEA and unreacted AEEA migrated to the upper phase. Finally, the cyclic tests were repeated and the energy consumption was evaluated. The regeneration energy of the biphasic solvent, without process optimizations, is 2.58 GJ/tCO 2 , which is 32% lower than that of the traditional 30 wt% MEA solvent. [ABSTRACT FROM AUTHOR]

• Novel alkanolamine-based biphasic solvent with low regeneration energy and viscosity is proposed for CO 2 capture. • Tertiary amine 3-(dimethylamino)propan-1-ol(3DMA1P) is firstly introduced to decrease regeneration energy. • Phase separation mechanism is revealed by NMR and LogP analysis. • Molecular dynamics simulation is applied to study liquid structure and monitor the phase separation process. Biphasic solvents for CO 2 capture have received significant attention due to their potential for energy conservation. However, traditional biphasic solvents result in highly viscous CO 2 rich-phases and high amine losses. To overcome these drawbacks, we have developed a novel alkanolamine-based biphasic solvent by blending 2-(methylamino) ethanol (MAE), 3-(dimethylamino)propan-1-ol (3DMA1P), diethylene glycol dimethyl ether (DGM), and water. The aqueous MAE/3DMA1P/DGM solvent showed a cyclic capacity of 0.45 mol CO 2 /mol amine, which is 1.8 times that of monoethanolamine (MEA), and a desorption rate and regeneration efficiency twice those of MEA. The viscosity of the biphasic solvents can be reduced to 13.12 mPa⋅s at 313 K, which is lower than that of reported biphasic solvents. The evaluated regeneration energy was 2.33 GJ/ton CO 2. Cation chromatography measurements revealed the tendency of MAE to accumulate in the CO 2 -rich phase with increasing CO 2 absorption loading. Quantitative 13C NMR analyses were performed to investigate the species distribution in both phases, and DGM was found to be the major component of the CO 2 -lean phase. Different solubilities of the MAE molecules and MAE carbamate in DGM resulted in phase separation. Molecular dynamics (MD) simulations on the CO 2 -unloaded and CO 2 -loaded solutions verified the phase separation mechanism. MAE molecules tended to cluster, and the interactions between MAE and DGM dropped significantly, with increasing DGM concentration. [ABSTRACT FROM AUTHOR]

Amino acid salts are promising absorptions for CO 2 capture. This work investigated six common potassium amino acid solutions: L-proline, sarcosine, glycine, β- alanine, taurine, and L- threonine solutions using wetted-wall column at 313 K and atmospheric pressure (1 bar). We found potassium L-proline solution has significant mass transfer properties similar to 30 wt% MEA. The influence of total pressure in wetted-wall column on CO 2 absorption rate in potassium L-prolinate solutions is determined. It is found that elevated total pressure has positive effect on CO 2 absorption rate. The CO 2 absorption flux increases approximately by 40% from 1 bar to 3 bar when CO 2 inlet concentration is 10%. What's more, the gas side mass transfer coefficient is found not only dependent on the hydrodynamic conditions of wetted-wall column, but also the total pressure in the apparatus. The analytical relations between the hydrodynamic conditions of the column and k g in wetted-wall column at different pressures are got in this work, and the gas mass transfer coefficient k g is found decreases by 86% from 1 bar to 3 bar. [ABSTRACT FROM AUTHOR]

A crucial problem for the promising absorbent aqueous ammonia (NH 3 ) is the low CO 2 absorption rate and high ammonia volatile loss rate. This work investigated the effect of potential promoters for CO 2 absorption into aqueous ammonia solutions on a wetted wall column. Monoethanolamine, sarcosinate, taurinate, glycinate, piperazine and 1-methyl piperazine were introduced to NH 3 solutions as promoters. We found sarcosinate, piperazine and 1-methyl piperazine could increase the mass transfer coefficient of CO 2 into the ammonia-based solutions significantly. We further undertook a detailed mass transfer study of CO 2 into ammonia based blended solutions to investigate the effects of temperature and additive concentration. Besides, a novel ammonia separation method from low concentration ammonia solution by membrane vacuum regeneration was developed which could recover more than 80% of ammonia gas from low concentration ammonia. [ABSTRACT FROM AUTHOR]

In order to investigate the mechanism of membrane wetting in the membrane absorption process at elevated temperature, the commercial polypropylene (PP) hollow fiber membrane was used to simulate the absorption exposure conditions by immersing the membrane into different absorbents at 60°C up to 40 days. Three absorbents which are 30wt% of aqueous monoethanolamine (MEA), 2-amino-2-hydroxymethyl-1,3-propanediol (THAM) and potassium sarcosinate (KSar) were selected to investigate the interaction between absorbents and membrane. Several characterization methods including X ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FE-SEM), atomic force microscope (AFM), mercury intrusion porosimetry (MIP) and contact angle measurement were used to study the changes of membrane properties. The results showed that the pore size, porosity and surface roughness of membrane increased after immersion. XPS demonstrated that absorbent molecules diffuse into the polymer matrix resulting in the swelling of membrane. Membrane deformation is dependent on the surface tension of the absorbent. KSar with a high surface tension caused less deformation of membrane than other absorbents. The change of membrane resistances as a function of operating time was also examined by continuous testing of membrane modules for a prolonged period under membrane absorption conditions at 60°C. It is found that transmembrane pressure has significantly increased the membrane resistance. KSar has a less tendency of increasing membrane resistance than MEA and THAM, but this advantage is not as significant as that at lower temperature. [ABSTRACT FROM AUTHOR]

• A new carbon capture solvent named HNC-5 was developed with lower heat consumption and lower solvent consumption. • The continuous operation results of the 120,000-ton/year CO 2 capture unit show that heat duty of regeneration of HNC-5 is about 2.8GJ/tCO 2. • The cost per ton of CO 2 captured is reduced by about 63 CNY due to lower heat penalty and lower solvent consumption. Post-combustion CO 2 capture for coal-fired power plants is an important technical option to mitigate greenhouse gas emission from coal-based power generation. CO 2 capture based on chemical absorption is currently the dominant technology for large-scale capture unit. The main obstacle of commercial application is the high cost and high energy consumption, innovation of new absorption solvent is one of the keys to the performance improvement. Based on the characteristics of flue gas, combined with the analysis and comparison of potential amine components, the formula of blended amines are developed, which is further screened by true-heat flux calorimetric test combined with vapor-liquid equilibrium test, HNC-5 is selected through the lab test, because of its lower heat of absorption and higher capture performance. The test on a 1000 t/a CO 2 capture pilot plant under real flue gas conditions shows that the performance index of HNC-5 is consistent with the lab test results. The CO 2 capture ratio is higher than 90%, and the heat consumption during regeneration is reduced by about 20% compared with MEA. The continuous operation results of the 120,000-ton/year CO 2 capture unit show that heat duty of regeneration of HNC-5 is about 2.8GJ/tCO 2 , the cost per ton of CO 2 captured is reduced by about 63 CNY, the usage life is longer, helping improve the system availability and reliability. [ABSTRACT FROM AUTHOR]

• A shortcut was built to evaluate water balance and amine emission in CO 2 capture. • Simple water wash enables to reduce MEA emission to a level below 5 mg/m3. • 2nd stage water wash reduces moderate volatile amine (AMP) emission below 1 mg/m3. • Acid wash may be favored for highly volatile amine like DEEA-biphasic solvent. CO 2 capture using amine-based solvent is now available for large scale deployment. Water balance and amine emission are drawing more and more attention as they have significant impacts on operation stability, economic cost and environmental pollution. However, experimentally investigating a new amine solvent in a demonstration test platform is time-consuming and costly. In this paper, a shortcut method was developed based on volatility data of a solvent to evaluate water balance and amine emission in CO 2 capture system. Water balance can be achieved by employing a simple water wash after absorber and regulating water wash temperature according to flue gas temperature, CO 2 concentration, and CO 2 removal efficiency. Simple water wash reduces monoethanolamine (MEA) emission from absorber (215–425 mg/m3) to a level below 5 mg/m3. With constant water wash temperature, increasing absorber temperature condenses more water which is beneficial for reducing amine emission. Variable amines and configurations are also evaluated. Simple water wash is not efficient for those volatile solvents such as 40% 2-amino-2-methyl-1-propanol (AMP), piperazine (PZ)/1-(2-Hydroxyethyl)piperidine (HEPD), MEA/N-methylpyrrolidone (NMP) water-lean solvent, and 2-(diethylamino)ethanol (DEEA)/2-((2-aminoethyl) amino) ethanol (AEEA) biphasic solvent as their amine emissions after simple water wash are still higher than 100 mg/m3. For those solvents with moderate volatility, such as 30%MEA and 30–40%AMP, a second water wash is effective to reduce amine emission below 1 mg/m3. While for those highly volatile solvents, such as PZ/HEPD and DEEA blended biphasic solvents, acid wash for further amine emission reduction may be more competitive in view of capital cost and operation cost. [ABSTRACT FROM AUTHOR]

Promoted aqueous ammonia is a potentialsolvent for CO2separation processes. In this work, weinvestigated the effect of temperature, sarcosinate concentration,and CO2loading on the mass transfer coefficients of CO2absorption in a sarcosinate-promoted aqueous ammonia solutionon a wetted-wall column. We further investigated the kinetics of thereaction between CO2and a blended NH3/sarcosinateabsorbent using stopped-flow spectrophotometric techniques, followingthe pH changes via coupling to pH indicators. Our study revealed thatthe mass transfer coefficient for CO2absorption in a 3M ammonia + 1.5 M sarcosinate blended solution at 288 K is close tothat in 5 M monoethanolamine absorbent at 313 K. We did not observeany synergistic or catalytic effects between NH3and sarcosinatein the blended solution; the mechanism of the reaction of CO2with the NH3/sarcosinate mixture is the simple combinationof the individual reactions of NH3and sarcosinate withCO2. [ABSTRACT FROM AUTHOR]

Abstract: A novel membrane vacuum regeneration (MVR) technology was developed to achieve lower regeneration energy demand for CO2 absorption process. Sixteen different amine-based absorbents including primary, secondary, tertiary amines, polyamines, diamines, and sterically hindered amines were analyzed by combined absorption–desorption screening experiments for selecting the most effective absorbents for CO2 membrane vacuum regeneration (MVR) technology. The CO2 absorption experiments were conducted in a hollow fiber membrane contactor (HFMC) at 25°C and 12.5kPa CO2 partial pressure. The CO2 rich solvent was regenerated at 75°C and 20kPa regeneration pressure by using the MVR technology. The chain length, number of functional groups, side chain, and number of hydroxyl groups of amines were investigated to get a better understanding on the effects of the structure in the MVR process. The results show that the tertiary amines have greater regeneration performances than the primary amines, but the CO2 absorption rates of the tertiary amines are worse than the primary amines. For the polyamines, the absorption performance of polyamines can be improved by increasing the number of amine groups while the MVR performance of the polyamines can be reduced. Steric hindered amines exhibited greater MVR performances. In addition, amines with steric hindrance effect caused by the substitution of hydroxyl group or methyl group to amine group in structure has also shown good performance in the MVR process for CO2 desorption. The overall performance of amine-based absorbents was also investigated by an absorption–desorption characters analysis. It shows triethylenetetramine (TETA) and N-methyldiethanolamine (MDEA) have great average CO2 absorption rates and relatively high cyclic capacities per mole absorbent, and ethylenediamine (EDA) is considered to be the promising absorbent as cyclic capacity in mol CO2/kg absorbent. Diethanolamine (DEA) and 2-Amino-2-methyl-1-propanol (AMP) are found to have the best overall performances in terms of CO2 absorption rate at lean loading and cyclic capacity in mol CO2/mol absorbent. In terms of overall performance, MDEA is mostly recommended for using in MVR process. Sweeping steam can significantly improve MVR performance in most selected absorbents except AMP and 2-amino-2-hydroxymethyl-1,3- propanediol (THAM) absorbents which present the potential to reduce the regeneration energy demand by operating without sweeping steam. The study also finds that MVR shows better regeneration performance as compared to traditional thermal regeneration process at the same regeneration temperature. [Copyright &y& Elsevier]

Abstract: In order to give a better understanding for the selection of suitable absorbents for the novel membrane vacuum regeneration technology (MVR) which has the potential to reduce CO2 energy requirement by utilizing the waste heat or low-grade energy, an experimental study to determine the relationships between chemical structure and vacuum regeneration behavior of CO2 absorbents at 70°C and 10kPa was performed. Eleven typical absorbents with different functional groups in their chemical structures were investigated in terms of vacuum regeneration efficiencies. Results showed that the regeneration efficiency decreased with an increase of number of activated hydrogen atom in amine group and decreased with the number of hydroxyl group. Especially, more attention should be paid to these alkanolamines with one hydrogen atom in amine group and two or more hydroxyl groups in the structures due to their better comprehensive performance in regeneration, absorbent loss and CO2 absorption aspects. Increasing the carbon chain length and amine groups in the absorbent structure contributed to the improvement of regeneration performance and reduction of absorbent volatile loss. These absorbents with a four carbon chain length bonded at amine group might be more attractive to MVR. Furthermore, polyamines were superior to monoamines in terms of higher regeneration efficiencies and lower absorbent losses. Additionally, the individual effects of the potassium carboxylate group and hydroxymethylene group were also compared in this study. Results showed that amino acid salts were more appropriate for MVR due to their advanced regeneration performance, negligible absorbent losses and higher surface tensions. In this study, the regeneration performance of the same absorbents was also investigated by using the conventional heating regeneration method at 75°C and ambient pressure (HRM). It could be found that although longer regeneration time and relatively higher regeneration temperature were given for HRM, it was still inferior to MVR in terms of its lower regeneration efficiency. [Copyright &y& Elsevier]

Abstract: Aiming to achieve lower regeneration energy consumption and less absorbent loss, membrane vacuum regeneration technology was developed as the novel regeneration technology for CO2 enrichment in the chemical absorption process. In this study, monoethanolamine (MEA) was selected as absorbent and polypropylene (PP) hollow fiber membrane contactors were used to test the regeneration performance. Two different operating modes, solution flowing in tube side (mode A) and in shell side (mode B) of membrane module were compared by investigating mass transfer individual resistances and the influences of key operating parameters on CO2 desorption flux for both modes. The experimental results showed that mode A was superior to mode B, and liquid side resistance was dominant in overall mass transfer resistance for both modes when membrane was gas-filled. By optimizing the operating condition, better regeneration performance could be achieved to CO2 desorption flux 2.2×10−4 mol/m2 s and lower total equivalent work compared to thermal regeneration. In addition, amine loss problem, MEA concentration variation after regeneration and pressure drop on liquid side were also discussed, it showed MEA loss could be limited at 0.5g MEA/kg CO2 in Mode A. However, after the long-term running of membrane vacuum regeneration, it was also supposed that risk of membrane wetting will be increased due to the increase of membrane pore size. [Copyright &y& Elsevier]

Abstract: Absorption characteristics of CO2 into aqueous ammonia are the key factors to achieve simultaneous removal of pollutants from coal-fired flue gas by ammonia scrubbing. An experimental study with asemi-continuous flow reactor was conducted to investigate the CO2 absorption characteristic of aqueous ammonia solutions. Pure CO2 was chosen in order to avoid the effect by the other gas components in this paper. The effect on solution CO2 loading and CO2 absorption capacity, which is caused by ammonia concentration, CO2 inlet velocity and temperature, has been given. Furthermore, the effect on absorption characteristic and slippery characteristics of ammonia caused by additives is also covered. The experiment results show that, with increase of ammonia concentration, the solution CO2 loading increases while the CO2 absorption capacity decreases. Both the above two parameters decrease with the increase of CO2 inlet velocity, but the total reaction rate acts reversely. When the temperature reaches 15 °C or 35 °C, the absorption characteristic can reach the extreme points. Adding AMP into ammonia can enhance the absorption of CO2, and control the slippery of ammonia in the absorption process. What’ s more, 3% is a better choice for addition concentration. [Copyright &y& Elsevier]

Abstract: The novel regeneration process by using membrane vacuum technology was put forward to reduce the regeneration energy consumption in the chemical absorption process for CO2 separation from flue gas. The rich MEA solution was flowed in the lumen of the hydrophobic PP hollow fiber membrane contactors, and the shell side was maintained at a reduced pressure by a vacuum pump. In addition, the additional low temperature steam whose temperature is the same to rich MEA solution was also provided to act as the sweep gas to improve the regeneration performance and to prevent the water loss of the lean solution. Results showed that this membrane vacuum regeneration process can regenerate rich MEA solution to reach a relatively better regeneration performance and can effectively utilize the low temperature energy or waste heat in the power plants. [Copyright &y& Elsevier]

Abstract: The novel regeneration concept by using reduced thickness and vacuum technology was put forward in this paper to solve the higher regeneration energy consumption in the chemical absorption process for CO2 separation from flue gas. A 120-mm I.D. vessel was precisely designed to regenerate the CO2-rich solution, and the change of the thickness of thin-layer solutions was simulated by controlling the volume of rich solution added into the vessel. The experimental results show that vacuum regeneration may be viable if the CO2-rich solution can be easily partitioned into the continuous single thin-layer solutions with an appropriate thickness. The great decrease of thin-layer solution thickness and regeneration pressure, and the increase of liquid temperature can improve the regeneration performance considerably. In addition, it is worthy to determine the optimum initial CO2 loading of rich solution, regeneration time and absorbent concentration due to the contradiction between the CO2 loading of lean solution and regeneration energy consumption per kg of CO2. Finally, the simple comparison between vacuum and heating regeneration methods shows that the novel regeneration method may have the potential to reduce the regeneration energy requirement. [Copyright &y& Elsevier]

This paper firstly evaluated the CO2 absorption performance of a membrane gas absorption system (MAS) and chemical absorption system (CAS) using the overall mass transfer coefficient (K G a V) as a basis for comparison. MAS selected microporous polypropylene (PP) hollow fiber membrane contactors to capture CO2 from the simulated flue gas while CAS used a randomly packed column containing stainless Pall packing. Aqueous monoethanolamine (MEA) solution was adopted in both absorbers. Experimental results show that if the fresh membranes were tested, MAS has the higher K G a V values than that of CAS. However, when all the membrane pores were completely wetted or 50% pores were plugged, CAS inversely performs better than MAS in terms of K G a V values. In addition, the economic performance of MAS and CAS was also estimated. Results indicate that if the real operational time of membrane module is reduced to less than the critical value affected by the membrane price, the CO2 captured cost of MAS is inversely higher than that of CAS. Therefore, the current well-accepted statement that MAS is superior to CAS in any case may be somewhat arbitrary unless membrane pore-wetting and pore-plugging problems, how to reduce the membrane price and how to prolong the membrane lifetime can be solved perfectly in the future. [Copyright &y& Elsevier]

• Aerosol emissions and vapor emissions of 2 million tons per year CO2 capture plant were evaluated respectively. • A fitting formula for aerosol emission is proposed. • Three control methods were compared on the premise of water balance. • Drain-off water of the water wash is good for the emission control in dry bed. Solvent emissions is a serious problem in the industrialization of the amine scrubbing process. To design pollutant control equipment for a 2 million tons/year CO 2 capture plant, a bench and a pilot facility were tested to investigate the aerosol emissions. And three Aspen models were built to study vapor emission and design emissions control measurement. The emissions assessment showed the treated flue gas after the absorber was about to discharge 1078 mg/Nm3 aerosol-type solvent and 1055 mg/Nm3 vapor-type solvent. The experimental results of particle size distribution indicated that improving the growth of the submicron droplets before the water wash and demister was the key to control aerosol emissions. Three control methods were compared by simulation, the best control measure was the combination of dry bed and water wash section, and the drain-out water is feed to the top of the dry bed. Considering the economy and control efficiency, the packing height of the water wash section is 2.5 m, and the scrubbing flow rate is 5000 Nm3/h. The extra cooling for the dry bed is not necessary and uneconomic. Under this countermeasure, the vapor emissions solvent is as low as 1.27 mg/Nm3 without additional freshwater for the water wash section. [ABSTRACT FROM AUTHOR]

• The public investigations are carried out in the feasibility study work of 2 million tons/year flue gas CO 2 capture, transmission, flooding and storage project of Shengli Coal-fired Power Plant, which is the world's largest proposed flue gas CO 2 capture, utilization and storage project CO 2 capture projects. • The survey results show that the public acceptance of carbon capture utilization and storage (CCUS) project is very high. • Effective publicity methods of CCUS are discussed in this study, including display board publicity, face-to-face dialogue, model exhibition, short film screening, etc., to help people of different cultural levels quickly understand CCUS technology and improve the public acceptance of CCUS project. This study introduces the survey on the public acceptance of the 2 million tons/year CO 2 capture, transportation, oil displacement and storage project of Sinopec Shengli Oilfield. The survey results show that the public acceptance of carbon capture utilization and storage (CCUS) project is very high. At the same time, the survey found that the higher the level of education, the higher the level of understanding of CO 2 capture, transportation, oil displacement and storage technology, but the more opposed to the scenario assumption that "CO 2 transmission pipeline and storage site are near their own residential area". The result of low education level is just the opposite. It is speculated that the main reason for this phenomenon is that there is no risk case in large-scale CCUS project, and the degree of risk of CCUS technology is still in the stage of research and demonstration. According to the research conclusions, the study puts forward some measures for public publicity of CCUS, including display board publicity, face-to-face dialogue, model exhibition, short film screening, etc., to help people of different cultural levels quickly understand CCUS technology and improve the public acceptance of CCUS project. [ABSTRACT FROM AUTHOR]

• The world's largest carbon capture projects from flue gas of coal power plants of Shengli oilfield 2 million tons/year of flue gas CO 2 capture project is introduced. • The blend amine absorbent performance, chemical absorption process, energy-saving method, and the layout area of engineering were interpreted. The health, safety, and environmental affect was analyzed and economic analysis was also carried out. The conclusion showed that the project has technical and economic feasibility. It is a comprehensive introduction of large-scale CO 2 capture process and parameters. • The energy consumption level of regeneration reaches the leading level of flue gas CO 2 capture demonstration project. New energy-saving process of "interstage cooling + MVR heat pump + desorption heat energy recovery" is applied, and comprehensive regeneration energy consumption is less than 2.2 GJ/tCO 2. • The level of total energy consumption is advanced in the world. The study showed that the total energy consumption per unit product is 121.4 kg (standard coal equivalent (SCE))/tCO 2 , which reduces the net CO 2 emission by 1.3687 million tons per year. The world's largest 2 million tons/year CO 2 capture project from flue gas of coal power plants for EOR at Shengli oilfield of China was introduced. The blend amine absorbent performance, chemical absorption process, energy-saving method, and the layout area of engineering were interpreted. The health, safety, and environmental affect was analyzed and economic analysis was also carried out. The conclusion showed that the project has technical and economic feasibility. The study showed that the total energy consumption per unit product is 121.4 kg (standard coal equivalent (SCE))/tCO 2 , and the comprehensive regeneration energy consumption of the project is less than 2.2GJ/tCO 2. The total investment of the project is 1329.4 million CNY; the after-tax internal rate of return reaches 8% when the ex-factory price of CO 2 is 301.84 CNY /t(excluding tax). [ABSTRACT FROM AUTHOR]

• The FTIR method is effective for measuring amine volatility. • 2-(diethylamino)-ethanol (DEEA) is too volatile to be a practical solvent alternative. • DEEA volatility increases with CO 2 loading. Amine volatility may be a critical problem with biphasic solvent for CO 2 capture such as the blend of 2-(diethylamino)-ethanol (DEEA) and 2-((2-aminoethyl) amino) ethanol (AEEA). The Henry's law constant (H am) of DEEA and AEEA in water at 40 and 50 °C was measured using a hot gas FTIR. DEEA is 20–30 times more volatile than monoethanolamine (MEA) while AEEA is nearly non-volatile. At lean loading, the amine volatility is 327 ppm in 12 m DEEA and 1.1 ppm in 2.5 m AEEA at 40 °C. The NRTL model shows good consistency with the DEEA-H 2 O data for amine and water activity coefficients. Amine volatility in 12 m DEEA with 0 to 0.4 mol CO 2 /mol DEEA and in 2.5 m AEEA with 0 to 0.9 mol CO 2 /mol AEEA at 40 and 50 °C was also measured. DEEA partial pressure (P DEEA) increases with CO 2 loading even though there is less free DEEA in the loaded solutions. The ionic reaction products of DEEA and CO 2 increase the ionic strength and DEEA activity coefficient. The effect of ionic strength on the DEEA activity coefficient was confirmed with data for 12 m DEEA-H 2 O-KNO 3 and 12 m DEEA-H 2 O-H 2 SO 4. AEEA partial pressure (P AEEA) decreases with CO 2 loading as AEEA is converted by the reaction with CO 2 to other non-volatile species. [ABSTRACT FROM AUTHOR]

[Display omitted] • Using alkanolamine to regulate the viscosity of biphasic solvents is proposed. • A novel polyamine-based biphasic solvent with low costs is developed. • The phase split mechanism is investigated by NMR analysis. • A molecular-scale understanding of the viscosity regulation mechanism is revealed. Biphasic solvent has attracted widespread attention in CO 2 chemical absorption technology due to its significant potential for reducing capture energy consumption. However, the high viscosity of CO 2 -rich phase after phase split could lead to issues such as high flow resistance, low heat transfer efficiency, and phase separation instability in application. To address these limitations, a strategy of using alkanolamine as a viscosity regulator for biphasic solvents was proposed. Diethanolamine(DEA), an alkanolamine regulator, was introduced to a system of polyamine/amide absorbent, and then a novel biphasic solvent of diethylenetriamine (DETA)/diethanolamine(DEA)/N, N-Dimethylacetamide(DMAC)/water(H 2 O) was developed. The viscosity of the CO 2 -rich phase solvent was reduced to 19.02 mPa⋅s, a significant decrease compared to the solution without DEA regulation. The novel solvent exhibited a high cyclic capacity of 2.08 mol/kg, which was 43.4 % higher than that of the solution without DEA, and a desorption rate twice as high as 30 wt% monoethanolamine(MEA). Quantitative 13C Nuclear Magnetic Resonance (NMR) and Molecular Dynamics (MD) simulations revealed the phase split and viscosity regulation mechanisms. It was proved that DETA species, especially carbamates, tend to self-aggregate with each other due to intermolecular hydrogen bonding with the CO 2 loading increases, which leads to phase split and high viscosity of the saturated solution. Through DEA regulation, the protonation of carbamates and the generation of HCO 3 –/CO 3 2– were promoted, which weakened the self-aggregation of carbamates species, decreasing the viscosity and the regeneration energy of saturated CO 2 -rich phase solution. The regeneration energy reached 2.19 GJ/ton CO 2 , which exhibited a 42.4 % reduction compared with that of 30 wt% MEA. [ABSTRACT FROM AUTHOR]

• Water-lean EMEA was tested in a pilot with 280 m3/h flue gas for 100 operating hours. • Water-lean EMEA achieved 90% CO 2 removal and regeneration energy of 2.2 GJ/tCO 2. • Measured ΔT for lean/rich exchanger increases with viscosity in a power function relation. • Water-lean EMEA has a volatile amine emission higher than 110 mg/m3. Water-lean solvent for post-combustion CO 2 capture is promising to significantly reduce regeneration energy. It hasn't been put into commercial application due to unsolved challenges including water balance issue, increased viscosity, and high volatility. Even though numerous water-lean solvents were developed in laboratory, rare of them were tested in pilot scale. Water-lean solvent of 2-(ethylamino) ethanol (EMEA) dissolving into 1-methyl-2-pyrrolidinone (NMP) and water was tested in a CO 2 capture pilot with flue gas rate of 280 m3/h. Effects of liquid/gas ratio and reboiler steam rate on CO 2 removal efficiency, regeneration energy, lean/rich heat exchanger performance, and volatile amine emission were investigated. Water-lean EMEA achieved CO 2 removal efficiency greater than 90 % and the lowest regeneration energy of 2.3 GJ/tCO 2 , which is 43 % lower than that of 5 M MEA. Water-lean EMEA showed significantly reduced latent heat, greater CO 2 capacity, and lower reaction heat (secondary amino) than aqueous MEA and amine blends. It was found that water-lean EMEA regeneration in stripper had extremely lower lean loading (0.1–0.5 mol CO 2 /L) than aqueous MEA and amine blends, which enables a faster CO 2 absorption rate in absorber and a greater CO 2 capacity, but also causes larger volatile amine emission. Volatile amine emission after water wash was 110–380 mg/m3. 13C NMR spectrum suggested amine carbamate dominated CO 2 absorption products. Due to that increased viscosity decreases heat transfer coefficient (h), lean/rich heat exchanger temperature difference (Δ T) for water-lean EMEA (6.5–7.5℃) was greater than MEA (3.5-5℃) and amine blends (5-6℃), yet smaller than biphasic solvent (8-9℃). A negative power (-0.614) function relation between h and viscosity was fitted and can be further used to normalize sensible heat. [ABSTRACT FROM AUTHOR]

[Display omitted] • The ILs biphasic absorbent [TEPAH][CPL]/EG/DGDE was developed for CO 2 capture. • Phase separation was due to polarity change of the absorbent after CO 2 absorption. • The regeneration energy consumption is 51% lower than that of 30 wt% MEA solution. • The absorbent showed obvious low-corrosive advantage since the absence of H+. To achieve low regeneration energy consumption and low corrosion, a novel ILs nonaqueous biphasic absorbents composed of Tetraethylenepentamine (TEPA) Caprolactam (CPL), Ethylene glycol (EG), and Diethylene glycol dimethyl ether (DGDE) have been proposed for CO 2 capture. The maximum CO 2 loading of the optimal absorbent ([TEPAH][CPL]/EG/DGDE) could reach 1.88 mol·mol−1, with 40 % of the saturated phase volume containing 98 % of the mass percentage of CO 2 products. Furthermore, the regeneration energy consumption was only 1.88 GJ·t−1 CO 2 , approximately 51 % lower than that of 30 wt% monoethanolamine (MEA) aqueous solution. 13C NMR analysis has shown that the amino group on the cation [TEPAH]+ reacted with CO 2 to form CO 2 products-carbamate, and the anion [CPL]- assisted the proton transfer during the reaction. Combined with the results from quantum chemical calculation, the phase separation behavior of the absorbent was mainly due to the polarity difference between the CO 2 products and the solvent. Additonally, [TEPAH][CPL]/EG/DGDE was non-corrosive to 20# carbon steel before and after CO 2 absorption, and exhibited superior stability than MEA aqueous solution. [ABSTRACT FROM AUTHOR]

[Display omitted] • The novel in-situ gas sampling provides 2D spatial maps of gas product compositions. • The CO 2 conversion drops significantly in the afterglow due to recombination. • Dissociation dominates in the plasma, while recombination prevails in the afterglow. • Afterglow quenching considerably increases the CO 2 conversion and energy efficiency. Warm plasma offers a promising route for CO 2 splitting into valuable CO, yet recombination reactions of CO with oxygen, forming again CO 2 , have recently emerged as critical limitation. This study combines experiments and fluid dynamics + chemical kinetics modelling to comprehensively analyse the recombination reactions upon CO 2 splitting in an atmospheric plasmatron. We introduce an innovative in-situ gas sampling technique, enabling 2D spatial mapping of gas product compositions and temperatures, experimentally confirming for the first time the substantial limiting effect of CO recombination reactions in the afterglow region. Our results show that the CO mole fraction at a 5 L/min flow rate drops significantly from 11.9 % at a vertical distance of z = 20 mm in the afterglow region to 8.6 % at z = 40 mm. We constructed a comprehensive 2D model that allows for spatial reaction rates analysis incorporating crucial reactions, and we validated it to kinetically elucidate this phenomenon. C O 2 + M ⇌ O + C O + M and C O 2 + O ⇌ C O + O 2 are the dominant reactions, with the forward reactions prevailing in the plasma region and the backward reactions becoming prominent in the afterglow region. These results allow us to propose an afterglow quenching strategy for performance enhancement, which is further demonstrated through a meticulously developed plasmatron reactor with two-stage cooling. Our approach substantially increases the CO 2 conversion (e.g., from 6.6 % to 19.5 % at 3 L/min flow rate) and energy efficiency (from 13.5 % to 28.5 %, again at 3 L/min) and significantly shortens the startup time (from ∼ 150 s to 25 s). Our study underscores the critical role of inhibiting recombination reactions in plasma-based CO 2 conversion and offers new avenues for performance enhancement. [ABSTRACT FROM AUTHOR]

• MnO x /HZ is proposed as an efficient catalytic packing for CO 2 desorption. • Visualization method can quantify the CO 2 desorption rate per unit surface area of packing. • The E a of CO 2 desorption with MnO x /HZ can be reduced by 58.6%. • The catalytic performance of MnO x /HZ declines due to the blockage of micropores by reaction product. The high energy consumption in the CO 2 desorption process is one of the main issues of the chemical absorption method. To address this issue, a MnO x modified HZSM-5 catalyst (MnO x /HZ) was prepared by impregnation method and used as catalytic packing to improve the CO 2 desorption rate in the monoethanolamine (MEA) solution. Since the catalytic effects mainly work around the catalytic packing, a visualization method, which can measure the CO 2 desorption rate per unit surface area (v C O 2 / a r e a ) of a single packing, is proposed to avoid some uncertain effects occurring as the conventional bubbling method is used. The results showed that the v C O 2 / a r e a of the MnO x /HZ catalytic packing is 10.06 μmol·cm−2·s−1 at 80 °C, which is 1.78 times of that of HZSM-5 and 15 to 60 times of that of commercial packings. Actually, the MnO x /HZ has more Brønsted and Lewis acid sites than HZSM-5 according to the pyridine adsorption infrared spectroscopy (Py-IR) characterization. As a result, the apparent activation energy (E a) of the CO 2 desorption reaction with the addition of MnO x /HZ can be reduced by 58.6% and 18% compared with the addition of ceramic saddle ring packing and HZSM-5, respectively. However, the catalytic performance of MnO x /HZ packings degrades gradually due to the blockage of micropores by the reaction product, that needs to be settled in the future. [ABSTRACT FROM AUTHOR]

Using an inert, immiscible organic component as the purging gas is an innovative technology in the CO 2 stripping process. It allows stripping at a lower temperature and overcomes the inherent problem of high energy consumption in steam-based CO 2 stripping processes. This work focused on developing a novel, direct non-aqueous gas stripping process and exploiting its potential for energy saving through experiments. An elaborate pre-screening of carrier gases was conducted through hydrocarbon, alcohols, aldehydes, ketones, and their isomers, etc. Pentane, hexane, and cyclohexane were selected as the carrier candidates for their good immiscibility with water/amine, low vaporization energy, mild condensation conditions, and low toxicity. The effects of carrier gas category, carrier gas flow rate, and rich solvent feeding temperature on the stripping performance were investigated. Pentane was found to be the superior carrier gas due to its low heat of vaporization, high regeneration rate, and low energy requirement. A unique phenomenon of water evaporation from the solvent was discovered in the organic gas stripping process, providing a promising approach to break the gas-liquid interface for enhanced diffusion kinetics. The feasibility of low temperature CO 2 stripping was analyzed by varying the rich solvent feeding temperature (70–100 °C). With pentane as the stripping gas, it was interesting to find an optimum rich-feed temperature lower than 90 °C, indicating great potential for a reduction in the overall energy requirement. Under the optimal conditions, the energy consumption during CO 2 regeneration, using pentane as the carrier gas, was 2.38 GJ/t CO 2 , 38.8% lower than that of the conventional stripping process. Furthermore, parasitic issues, such as water loss and solvent loss, were discussed. An improved direct non-aqueous gas stripping process with two-stage compression was used to tackle the carrier gas recovery problem. The simulation results show that more than 98% of the carrier gas can be recovered through preliminary separation approaches. [ABSTRACT FROM AUTHOR]

Amine blends have been extensively studied as advanced solvents modification for CO 2 absorption. Due to the lack of knowledge on mechanism of amines interaction, reaction in blends was traditionally regarded as parallel reactions between CO 2 and different amines. In this work, the kinetics of CO 2 reaction with blends of two promising diamines, piperazine (PZ), N-(2-aminoethyl) ethanolamine (AEEA), were studied in a wetted wall column. The reaction rate constants of single amine were derived from kinetic data based on the zwitterion and termolecular mechanism for PZ and AEEA, respectively. It is interesting to find that the overall reaction rate of the blend is 12.0–28.1% lower than the calculated value through parallel reaction mechanism, which indicates the strong interaction between PZ and AEEA. A ‘zwitterion bridge’ reaction pathway was proposed as the microscopic mechanism of the interaction in the blend. Based on the kinetic models and experimental data, the interaction that PZ can promote the reaction in amines blend by transferring CO 2 to AEEA through the PZ-CO 2 intermediate was revealed. Besides, the interaction was proved to be a fast reaction with the reaction rate of same magnitude compared with the zwitterion hydrolysis reaction. The mechanisms of interaction between the two amines are further investigated through density functional theory (DFT). Results of simulation, in terms of activation energy and molecular geometry deformation, indicate that the PZ prefers a direct reaction with CO 2 rather than the reaction with the AEEA-CO 2 intermediate. [ABSTRACT FROM AUTHOR]

This study proposes a novel method for simultaneously dealing with the waste carbide slag (WCS) and CO 2 mitigation. In addition, the ultrafine vaterite CaCO 3 with high economic value was produced under mild conditions of 25 °C and 0.1 MPa. Ammonium sulfate ((NH 4) 2 SO 4) was employed to efficiently extract calcium from WCS into the solid phase calcium sulfate dehydrate (CaSO 4 ·2H 2 O). Subsequently, it was subjected to "dropwise carbonation" leading to the formation of a calcium carbonate with controllable particle size between 100 nm–1 μm through multiple crystalline phase transformations. The results showed that nano-sized CaCO 3 with nearly 90% purity and whiteness was prepared at 25 °C, CO 2 -500 mL/min, and NH 4 +/Ca2+ = 2.4 conditions. Results of TG and FTIR analyses confirmed that CaCO 3 polymorphs with vaterite and metastable were formed. Based on the calcium conversion ratio of the entire process, treatment with 1 ton of WSC captured ∼0.5 tons of CO 2 and yields about 1.15 tons of nano-sized CaCO 3 per each cycle operation. This study provides a valuable method for identifying potential application for scale preparation of vaterite nanoparticles from low cost but abundant calcium resource such as WCS and gypsum. [Display omitted] • Simultaneously deal with the waste carbide slag (WCS) and CO 2 mitigation. • A stepwise mild method for preparation of nano-sized CaCO 3 from WCS based on CO 2 mineralization is proposed. • Multiple crystal phase transformations of calcium component contribute to control vaterite particle size. • Treatment of 1 ton of WSC captures ∼0.5 tons of CO 2 and yields about 1.15 tons of nano-sized CaCO 3. [ABSTRACT FROM AUTHOR]

• Eight diamines and two cosolvents are screened for use in water-lean solutions. • DMEDA- and DMPDA-based water-lean solutions are developed for CO 2 capture. • A diamine-based water-lean solution using NMP as a cosolvent shows comparable viscosity with aqueous MEA. • A 140% improvement in cyclic capacity is achieved in ENH-5% H 2 O compared with that of aqueous MEA. • Diamine water-lean solutions have high sensitivity to the CO 2 partial pressure. In an effort to reduce energy penalties, a range of advanced water-lean solutions blended from one of 8 diamines, an organic solvent diluent and water, were screened. The diamines N,N -dimethyl-1,3-propanediamine and N,N -dimethyl-1,2-ethanediamine with one primary and one tertiary amino group remain homogenous during CO 2 uptake with the addition of cosolvents (1-methyl-2-pyrrolidinone or sulfolane) and are further investigated for absorption and desorption performance compared with their corresponding aqueous solutions. Water-lean solutions with different water concentrations are tested to explain the impact of water content on the solution performance. Physical properties such as density and viscosity are also measured for a versatile evaluation. The results show that diamine water-lean solutions obtain low viscosity, preferable cyclic capacities and rapid absorption and desorption rates. ENH-5% H 2 O (mass ratio DMEDA: NMP: H 2 O = 3:6.5:0.5) shows the most competitive advantages with comparable viscosity (1.49 mPa∙S at 313 K) to aqueous MEA-H 2 O and a 140% improvement in cyclic capacity. Four-fold higher desorption rate is gained ESH-5%H 2 O (mass ratio DMEDA: SFL: H 2 O = 3:6.5:0.5) compared with MEA-H 2 O. Considerable reduction in energy penalties is expected to be achieved in diamine water-lean solutions. In addition, the equilibrium solubility of diamine water-lean solutions also shows potential for industrial application due to their sensitivity to CO 2 partial pressure in contrast with aqueous solutions. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the experimental results of CaO sorption enhanced anaerobic gasification of biomass in a self-design bubbling fluidized bed reactor, aiming to investigate the influences of operation variables such as CaO to carbon mole ratio (CaO/C), H2O to carbon mole ratio (H2O/C) and reaction temperature (T) on hydrogen (H2) production. Results showed that, over the ranges examined in this study (CaO/C: 0–2; H2O/C: 1.2–2.18, T: 489–740°C), the increase of CaO/C, H2O/C and T were all favorable for promoting the H2 production. The investigated operation variables presented different influences on the H2 production under fluidized bed conditions from those obtained in thermodynamic equilibrium analysis or fixed bed experiments. The comparison with previous studies on fluidized bed biomass gasification reveals that this method has the advantage of being capable to produce a syngas with high H2 concentration and low CO2 concentration. [Copyright &y& Elsevier]