Phase Change Absorption Research Articles

A novel phase change absorbent with ionic liquid as promoter for low energy-consuming CO2 capture

Phase change absorbents had great potential to achieve low energy-consuming CO2 capture. In this work, a novel four-component phase change absorbent system, N,N-diethylethanolamine (DEEA)/N-(2-aminoethyl) ethanolamine (AEEA)/1-butyl-3-methyl imidazolium tetrafluoroborate ([Bmim][BF4])/H2O blends, was designed. AEEA and DEEA were used as the main absorption component and the phase separation component, respectively. As one of the most conventional ionic liquids, [Bmim][BF4] was introduced as a promoter to improve the phase separation capability and the absorption/desorption performance. The species distribution was determined by 13C NMR analysis, and it was found that [Bmim][BF4] was located in the lower phase. Quantum chemical calculations unveiled that the main reason for phase separation was the difference in polarity and hydrogen bond interactions. The introduction of the [Bmim][BF4] not only promoted CO2 absorption through chemical and physical intensification effects but also enhanced the desorption rate through hydrogen bond formation. Moreover, the [Bmim][BF4] addition significantly reduced regeneration energy consumption due to its lower heat capacity and less water evaporation. The energy consumption of this absorbent could be reduced to 2.06 GJ∙t−1 CO2, which was 45.8% less than 30 wt% MEA.

Development of phase-change absorbent for hydrogen chloride with hydrogen and chlorine generation by electrolysis

To reduce the energy consumption of regeneration for HCl absorption, and to recover HCl to high-value products, a sustainable phase-change system was constructed with N-methyldiethanolamine (MDEA) and polyethylene glycol dimethyl ether (NHD) in this paper. The MDEA/NHD phase change absorbent for HCl absorption is optimized by the ternary phase diagram and phase behavior of MDEA/NHD/HCl system. The results demonstrate that the biphasic system can be constructed with the mass fraction of HCl less than 28% and NHD component in the range of 23.0% ∼ 95.3%. Because of the higher stability of protonated MDEA·HCl than that of NHD·HCl, HCl molecules are mainly enriched in MDEA phase containing the volume ratio of less than 1/3 and partition coefficient over 100 at the neutral point. Therefore, only MDEA phase needs to be recycled, which results in reducing the circulation of regeneration by approximately 68%. Moreover, concentrated HCl in anhydrous MDEA phase could further prevent the side reaction of OER and improve the Faradaic efficiency toward HER and CER to reach 98.5% and 90.5% at 55 °C, respectively. And the energy consumption of regeneration is reduced to 0.37 GJ/t(absorbed HCl) in MDEA/NHD biphasic absorbent compared with that of 2.3 GJ/tCO2 by DMX™ phase change absorption for CO2. By enhancing the conductivity and decreasing the viscosity of MDEA phase, introducing water in MDEA/NHD/HCl solution within 5% could significantly promote the current density and maintain high Faradaic efficiency toward HER and CER as 89.0% and 86.8%, respectively. Therefore, it is a promising technology to be applied in industry.

Evaluation of the rapid phase change absorbents based on potassium glycinate for CO2 capture

Phase-change process is deemed as an energy-saving approach for CO2 capture, however, the low phase change rate of the current absorbents leads to low separation efficiency, difficult operation and solvent loss. Herein, a novel rapid phase change absorbent composed of ether solvent (SA) and potassium glycinate (GlyK) aqueous solution was developed, and the phase-change behavior, phase separation mechanism, and the energy consumption were investigated. Results showed that the GlyK-30SA absorbent exhibited the highest CO2 capacity of 0.64 molCO2/molGlyK, the liquid-liquid phase separation within 2 min and more than 91% CO2 enrichment in the lower phase. The mechanism of the split phase and regeneration was explored by 13C NMR. More significantly, the absorbent also showed excellent cycling stability and a 30% reduction in energy consumption compared to the 3 M MEA system. It provided a new possibility for the development of stable and energy-saving amino acid salts phase change absorbents.

Experimental Analysis of Reaction Heat of CO2 Absorption of Phase Change Absorber AEP-DPA at Low Partial Pressure

The reaction heat of CO2 absorption by organic amines is directly related to the regenerative heat consumption of absorbers. Therefore, it is necessary to study and determine the heat of absorption reaction and heat of regeneration reaction of CO2 capture solvent before its industrial validation and application. According to the law of thermodynamics, a computer model of the heat of absorption reaction and desorption reaction is established and verified. The heat of reaction of the AEP-DPA phase transition absorption system was studied under different ratios, absorption temperatures, reaction concentrations and reaction pressures. The heat of reaction increases with concentration and decreases with pressure. The reaction heat of the AEP-DPA phase transition absorption system and MEA were compared. The optimum reaction conditions were as follows: AEP-DPA ratio 6:4, absorption temperature 40 °C. The reduction rate of absorption heat and regenerative heat of the AEP-DPA phase change absorption system is more than 35% and 31%, respectively.

Experimental study of the mass transfer behavior of carbon dioxide absorption into ternary phase change solution in a packed tower

Phase change absorbents for CO 2 are of great interest because they are expected to greatly reduce the heat energy consumption during the regeneration process. Compared with other phase change absorbents, monoethanolamine (MEA)-sulfolane-water is inexpensive and has a fast absorption rate. It is one of the most promising solvents for large-scale industrial applications. Therefore, this study investigates the mass transfer performance of this phase change system in the process of CO 2 absorption in a packed tower. By comparing the phase change absorbent and the ordinary absorbent, it is concluded that the use of MEA/sulfolane phase change absorbent has significantly improved mass transfer efficiency compared to a single MEA absorbent at the same concentration. In the 4 mol⋅L −1 MEA/5 mol⋅L −1 sulfolane system, the CO 2 loading of the upper liquid phase after phase separation is almost zero, while the volume of the lower liquid phase sent to the desorption operation is about half of the total volume of the absorbent, which greatly reduces the energy consumption. This study also investigates the influence of operating parameters such as lean CO 2 loading, gas and liquid flow rates, CO 2 partial pressure, and temperature on the volumetric mass transfer coefficient ( K G a V ). The research shows that K G a V increases with increasing liquid flow rate and decreases with the increase of lean CO 2 loading and CO 2 partial pressure, while the inert gas flow rate and temperature have little effect on K G a V . In addition, based on the principle of phase change absorption, a predictive equation for the K G a V of MEA-sulfolane in the packed tower was established. The K G a V obtained from the experiment is consistent with the model prediction, and the absolute average deviation (AAD) is 7.8%.

The quasi-activity coefficients of non-electrolytes in aqueous solution with organic ions and its application on the phase splitting behaviors prediction for CO2 absorption

CO 2 capture with a low energy consumption is of important application significance for reducing CO 2 emission. The phase-change absorbent developed in recent years shows its potential for low-energy CO 2 capture. The unclear phase-splitting rule hinders the efficient development of CO 2 phase-change absorbents. To predict phase-splitting behaviors of mono/poly-amine-organic solvent–water system with various concentrations, a quasi-activity coefficient was developed based on Debye & McAulay equation and some Density function theory descriptors. Six models based on Debye & McAulay equation were developed with different ion radius, descriptors or poly-amine-CO 2 products. The phase-splitting boundary was drawn on the model with the best predictability. This quasi-activity coefficient would provide guidance for the phase-splitting systems development, especially for polyamines.

New insight and evaluation of secondary Amine/N-butanol biphasic solutions for CO2 Capture: Equilibrium Solubility, phase separation Behavior, absorption Rate, desorption Rate, energy consumption and ion species

• MAE + n-butanol + H 2 O system for CO 2 capture was first proposed. • The phase change mechanism and energy consumption of the system were investigated. • The influence of temperature on absorption capacity was explored. • The developed biphasic absorbent has excellent energy saving advantages. Effective phase-change solvent system, n-methyl-2-hydroxyethylamine (MAE) + water-insoluble alcohol + H 2 O, was developed for CO 2 capture. First, a preliminary screening of several alcohols was carried out and showed that the MAE/n-butanol/water system had the potential to become an excellent phase change absorbent. Then, through phase change experiment, absorption experiment, desorption experiment, and theoretical energy consumption analysis, the MAE:n-butanol:water ratio of 3:4:3 possessed the most impressive CO 2 capture performance. Theoretical calculation of CO 2 desorption energy consumption showed that in comparison with 30 wt% monoethanolamine (MEA), 50% of reboiler heat duty can be reduced in case of the 3:4:3 system. In addition, equilibrium phase diagram of the three components showed that concentration of n-butanol significantly affected the phase separation. The two-phase species distribution after phase separation was determined using Nuclear magnetic resonance spectroscopy (NMR). This work also shows that temperature has influence on absorption and desorption performance. Finally, the absorbent stability test during absorption–desorption process confirmed that MAE/n-butanol/water absorbent had a great potential for capturing CO 2 .

Experimental Study on the Kinetics of the Natural Gas Hydration Process with a NiMnGa Micro-/Nanofluid in a Static Suspension System

Natural gas is a resource-rich clean energy source, and natural gas hydration technology is a promising method for natural gas storage and transportation at present. To realize the rapid generation of hydrates with a high gas storage capacity, in this paper NiMnGa micro/nanoparticles (NMGs) with different mass fractions (0.1 wt%, 1 wt%, 2 wt%) were prepared with 0.05 wt% sodium dodecyl sulfate (SDS) and 1 wt% L-tryptophan to form static suspension solutions of gellan gum, and the methane hydration separation kinetics experiments were carried out under the condition of 6.2 MPa for the SDS-NMG-SNG (SNG) and L-tryptophan-NMG-LNG (LNG) systems. The results showed that the induction time of the systems with NMG micro-/nanoparticles was shortened to different degrees and the gas consumption rate was increased. The best effect was achieved in the SNG system with 1 wt% NMG, and the induction time was shortened by 73.6% compared with the SDS-gellan system (SG). The gas consumption rate of the system with L-tryptophan was better than that of the system with SDS, and the best effect was achieved in the system with 2 wt% NMG. The system with 2 wt% NMG had the best effect, and the problem of foam decomposition did not occur. The analysis concluded that NMG has strong mass transfer and phase-change heat absorption properties, which can significantly improve the kinetics of the natural gas hydrate generation process; L-tryptophan can weaken the diffusion resistance of methane molecules in the suspended static solution, further enhancing the mass transfer of the hydrate generation process. These findings will provide new perspectives regarding the application of phase-change micro-/nanoparticles in methane hydrate generation under static conditions.

Development of Phase-Change Absorbent for Hydrogen Chloride with Hydrogen and Chlorine Generation by Electrolysis

Development of Phase-Change Absorbent for Hydrogen Chloride with Hydrogen and Chlorine Generation by Electrolysis

Absorption performance and reaction mechanism study on a novel anhydrous phase change absorbent for CO2 capture

• A novel phase change absorbent was proposed for CO 2 capture with low energy consumption. • Ethanol promoted phase change behavior and increased CO 2 loading. • Reaction of CO 2 capture with [N 1111 ][Gly]/ethanol was a three-step reaction. • Intramolecular hydrogen bonds affected products’ solubility, causing phase change. Carbon capture and utilization technologies are urged more than ever due to the excessive emissions of CO 2 that could lead to serious environmental problems. Phase change absorbents are quite competitive in reducing the energy consumption of carbon capture. In this work, tetramethylammonium glycinate ([N 1111 ][Gly]), an efficient absorbent, was dissolved in ethanol and 1-propanol, respectively, to absorb CO 2 . After CO 2 absorption, the saturated solution separated into two phases. CO 2 was enriched in the lower phase, so that only the CO 2 -rich phase needed to be regenerated and the energy consumption of regeneration could be thus reduced. Under the optimal conditions, the CO 2 loading of fresh absorbents could reach 0.85 mol CO 2 /mol IL. On the basis of the 13 C NMR analysis and quantum chemical calculation, a three-step reaction mechanism of CO 2 capture with [N 1111 ][Gly]/ethanol was proposed. CO 2 reacted with [N 1111 ][Gly] to form carbamate, which was similar to the two-step Zwitterionic mechanism of MEA with CO 2 . Then the formed carbamate could react with ethanol to form ethyl carbonate and [N 1111 ][Gly], which resulted in higher CO 2 loading. Moreover, hydrogen bond characteristics were analysed to clarify the phase change mechanism. The number and bonding energy of intramolecular hydrogen bonds were increased after capturing CO 2 , leading to the formation of precipitation.

An indirect CO2 utilization for the crystallization control of CaCO3 using alkylcarbonate

Carbon mineralization into calcium carbonate (CaCO3) has been widely studied as a promising CO2 resource utilization pathway. In this work, CO2 was fixed to alkylcarbonate through phase change absorption in polyethylene glycol 200 (PEG) plus ethanediamine (EDA) system at ambient conditions. This alkylcarbonate was identified by FTIR and 13C cross-polarization magic-angle spinning (CP-MAS) NMR spectra. It was used as both CO32− source and crystal modifier to induce crystallization of CaCO3 particles. The CaCO3 microsphere with uniform morphology and vaterite crystal phase was acquired by adjusting quality of alkylcarbonate, concentration of Ca2+ concentration, and crystallization period without any additives. Furthermore, a plausible self-assembly formation mechanism toward inducing crystallization of vaterite CaCO3 microsphere also was proposed. This synthesis strategy is environmentally friendly and offers an alternative strategy for indirect utilization of CO2.

A Water-Heat-Force Coupled Framework for the Preparation of Soils for Application in Frozen Soil Model Test

The freezing of soil containing a liquid is a complex transient heat conduction problem involving phase change and release or absorption of latent heat. Existing efforts have essentially focused on theoretical research and nu... | Find, read and cite all the research you need on Tech Science Press

Efficient SO2 Capture by 2-(Diethylamino)ethanol/Hexadecane Phase Separation Absorbent

Removal of sulfur dioxide (SO2) from flue gas by developing a highly efficient phase-change absorption solution is an effective way to tackle increasingly serious air pollution problems. In this st...

Low-Energy-Consumption CO2 Capture by Liquid–Solid Phase Change Absorption Using Water-Lean Blends of Amino Acid Salts and 2-Alkoxyethanols

Solvent regeneration for the conventional aqueous amine-based CO2 capture is very energy intensive. Development of phase-changing absorbents is an attractive solution for low energy consumption. In...

Liquid-liquid phase-change absorption of hydrogen sulfide by superbase 1,8-diazabicyclo[5.4.0]undec-7-ene and its chemical regeneration

Here, we developed a novel absorbent for the sustainable capture of hydrogen sulfide (H2S), which is the blend of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-triethylene glycol dimethyl ether (TEGDME)-H2O. The results indicated that the gravimetric absorption capacity was 0.174 g H2S/g lower phase at 101.3 kPa and 15 °C, which was 1.3 times higher than that of widely used aqueous methyldiethanolamine (MDEA) solution under the similar condition. In addition, TEGDME was mainly remained in the upper phase, while H2S, H2O, and DBU were mainly concentrated in the lower phase. Moreover, only around 44 wt% of the total absorbent needed to be delivered to the stripper for desorption, and other portion of absorbent was directly sent to the absorption tower. Most importantly, this absorption system was demonstrated to be a benign medium for absorbent regeneration through the liquid-phase Claus process. Our results suggested that this DBU-TEGDME-H2O blend was promising for the sustainable H2S capture and conversion in industrial applications.

Correction to Development of SO2 Phase Change Absorption: Viscosity Change and Component Distribution Rules

Correction to Development of SO₂ Phase Change Absorption: Viscosity Change and Component Distribution Rules

Development of SO2 Phase Change Absorption: Viscosity Change and Component Distribution Rules

As phase change absorption of CO2 could drastically reduce energy consumption, a liquid–liquid phase change absorption process of SO2 was developed in the present work using N,N-dimethylethanolamin...

Liquid-solid phase-change absorption of SO2 with tertiary diamines in long-chain alkane

Phase-change absorption was considered to be a new promising strategy for capture of acid gas since only the rich-phase needed to be disposed and the lean-phase could be reused directly. In the present work, liquid-solid phase-change absorption of SO2 with a series of tertiary diamines as absorbent was investigated. Long-chain alkane was found to be the best one among the tested solvents. Among the investigated diamines, tetramethylhexanediamine has the highest SO2 molar absorption capacity of ~2.6 mol/mol. The SO2 absorption products of diamines were demonstrated to be pyrosulfites based on the FTIR and elemental analysis. Among them, the single crystal of dimethylpiperazine pyrosulfite was obtained through recrystallization. These results indicated that the absorption mechanism of tertiary diamines is different from that of primary and secondary diamines. The effect of absorption conditions such as concentration of absorbent, temperature and partial pressure on the capacity was also investigated. The variation tendency of diamines in liquid along with SO2 loading indicated that the absorbed SO2 would force diamines to be separated from liquid phase completely. TG analysis indicated that the initial decomposition temperature sequence of absorption products is C10H26N2S2O5 > C7H20N2S2O5 > C6H16N2S2O5·H2O > C6H18N2S2O5.

Phase-Change Reversible Absorption of Hydrogen Sulfide by the Superbase 1,5-Diazabicyclo[4.3.0]non-5-ene in Organic Solvents

Phase-change absorption has shown a promising application prospect for acid gas capture because only the gas-rich phase needs to be transported to the stripper for recovery, which could drastically...

Novel SO2 Phase-Change Absorbent: Mixture of N,N-Dimethylaniline and Liquid Paraffin

In order to avoid the high energy consumption in SO2 capture with aqueous amine absorbents, a liquid–liquid SO2 phase-change absorbent (SPCA) was developed in the present work using N,N-dimethylaniline (DMA) as absorbent, and high-boiling liquid paraffin was used as solvent to adjust the boiling point of the solution. The homogeneous solution would form two immiscible liquid phases after SO2 bubbling, only the SO2-rich phase needed to be desorbed, which could effectively reduce the energy consumption. Different from the liquid–solid phase-change absorbents developed in our previous work, the liquid–liquid phase-change absorbent avoid their shortcomings such as difficulties in separation of absorption products. The absorption product of SPCA was proved to be a charge-transfer complex DMA·SO2 by NMR and FTIR characterization, and the phase-change mechanism was attributed to the polarity variation between DMA and DMA·SO2. The viscosities of SPCAs was lower than 11.65 mPa·s, and the viscosity of SO2-rich phas...