Phase Change Absorption Research Articles

Experimental and theoretical investigation of a novel multi-amino-functionalized ionic phase change absorbent for highly efficient CO2 capture

Experimental and theoretical investigation of a novel multi-amino-functionalized ionic phase change absorbent for highly efficient CO2 capture

Study on the thermo-mechanical properties of adaptive thermal control anchoring materials in high-geothermal tunnels

The heat conduction of the rock in high-geothermal tunnels can damage the grout during the initial hardening process, which directly affects the effectiveness of the anchoring support of the surrounding rock. This paper proposed the incorporation of phase change materials in grout to provide the new modified grouting material with the ability to control temperature by exploiting the phase change absorption and exothermic properties of the material. The changes in thermomechanical parameters of anchoring grout containing microencapsulated phase change material (m-PCM) under high geothermal environment were investigated. The influences of m-PCM content on the temperature control effect and mechanical properties of modified grout under different high geothermal environments were explored through macro-mechanical, micro-structural, and thermo-physical property tests on the specimens. The results indicated that m-PCM can effectively control the early hydration temperature of the grout in a high temperature environment, which can slow down the rate of change of the hydration temperature and reduce the peak temperature. The temperature control performance of modified grouts improved as the phase-change content increased, but the mechanical properties showed a significant decline after the initial increase. The results of the scanning electron microscope (SEM) analysis indicated that the high curing temperature had a negative impact on the internal structural integrity of the grout. The addition of a small amount of m-PCM reduced the fractal dimension and irregularity of the pore space in the grouting material, ultimately improving the strength of the grout body. The addition of a certain amount of m-PCM could significantly reduce the thermal conductivity of the grout, with the thermal conductivity of the specimens decreasing as the temperature increased. These study results provided valuable experimental data and theoretical support for the design of cement-based grouting materials in high-geothermal tunnels.

Investigation of CO2 Rapid Phase Change Absorbent System Based on Amino Acid Salts and Ether Solvents

Investigation of CO₂ Rapid Phase Change Absorbent System Based on Amino Acid Salts and Ether Solvents

A novel ionic liquids phase change absorption system for carbon dioxide capture and utilization

In order to achieve low cost, and reduce energy consumption during regeneration, a novel ionic liquid phase change absorbent composed of tetraethylenepentamine [TEPA] imidazole [Im] and diethylene glycol dimethyl ether (DGME) and water was designed for CO2 capture applications. The absorbent [TEPAH][Im]+DM+H2O can achieves a CO2 absorption capacity of 2.08 mol CO2/mol ILs, the rich phase volume accounts for 15.6 vol%, and the mass fraction of CO2 is 99 %, this greatly reduces the regenerative volume of the absorption system, showing the potential of energy saving and emission reduction. After five absorption–desorption cycles, the regeneration efficiency of the system remained above 96 %. The CO2 capture mechanism was analyzed using both 13C NMR spectroscopy and density functional theory (DFT) calculations to elucidate its underlying processes. The cation [TEPAH]+ and the anion [Im]- each undergo a reaction with CO2 to produce carbamate, followed by hydrolysis of carbon dioxide to yield carbonate. The absorption system’s phase transition behavior primarily arises from variations in CO2 product solubility across solvents. Moreover, the ionic liquid facilitated the conversion of CO2 into quinazoline-2,4 (1H, 3H)-dione with a remarkable yield of 98 %. Even after five cycles, the ILs maintained substantial catalytic activity.

A Novel Phase Change Absorbent for CO2 Capture with Low Viscosity and Effective Absorption–Desorption Properties

Excessive carbon dioxide (CO2) emissions can lead to environmental problems, and the use of phase change absorbents for CO2 capture has received much attention due to their excellent absorption and desorption properties. Herein, a novel liquid–liquid phase change absorbent consisting of N‐aminoethylpiperazine (AEP), diethylene glycol dimethyl ether (DEGDME), and H2O is utilized. Under the optimal absorption conditions, the absorption capacity is 1.23 mol CO2·mol−1 amine. The rich‐phase viscosity of the AEP/DEGDME/H2O solution is only 6.2 mPa s−1, and the rich phase‐to‐volume ratio is 52.7%, which is suitable for industrial applications. After five cycles of absorption–desorption experiments, the cyclic capacity reaches 0.62 mol CO2·mol−1 amine. However, it should be noted that this leads to an increase in the viscosity of the solution with time. The 13C Nuclear Magnetic Resonance characterization is used to analyze the material distribution and phase separation mechanism, and it is found that during the absorption process, the carbamate and carbonate products generated by the reaction of the amino group in the AEP with CO2 are mainly located in the rich phase, while the DEGDME and H2O mainly remain in the lean phase. In the desorption process, most of the absorbed products are decomposed, and the regeneration efficiency is 66.8%. Through the regeneration energy consumption experiment, when the regeneration efficiency is 56%–67%, the total regeneration energy consumption is 2.71–2.89 GJ t−1 CO2, which is 0.91–1.09 GJ t−1 CO2 lower than that of the regeneration efficiency of 30 wt% MEA solution at 63%, which indicates that this absorbent has certain energy‐saving advantages.

Highly Efficient Nonaqueous Phase Change Absorbent for H2S Absorption with Low Energy Consumption

Highly Efficient Nonaqueous Phase Change Absorbent for H₂S Absorption with Low Energy Consumption

Research progress of small molecule carbon dioxide capture agent

At present, the excessive emission of carbon dioxide has threatened people 's living environment and future development. More and more countries have begun to pay attention to carbon emission reduction. China has set the dual-carbon strategic goal of “carbon dioxide content reaches its peak” and “carbon neutrality”. According to the research on carbon dioxide capture technology by many scholars at home and abroad, it is found that the use of chemical absorbents to capture carbon dioxide is a relatively low cost, less technical difficulty, and can be widely put into industrial production. In this paper, several common chemical absorbents such as hot potassium alkali method, organic amine absorption method, amino acid salt, ionic liquid and phase change absorbent are reviewed. Through the research of various kinds of absorbents by researchers from various countries, their reaction principle, performance advantages and disadvantages, research status are introduced, and the future development direction of carbon dioxide negative emission technology is analyzed.

CO2 absorption by diethylenetriamine-based phase change absorbents: Phase change mechanism and absorption performance

CO2 phase change absorbents (CPCAs) have garnered significant attention for their potential to reduce energy consumption. However, suitable phase change agent is suffering from the selection among a wide range of organic solvents. In order to explore the phase separation mechanism and minimize screening efforts of CPCAs, the phase separation behaviors of the diethylenetriamine (DETA)-based absorbents constituted with different organic solvents were investigated, and the interaction energies revealed that the ion–dipole interaction is the dominant role in CO2-riched absorbents. The intensification of the self-aggregation of organic solvents by the ion-water interaction, was proposed as the main reason for the differences in the phase separation behavior in different DETA-based absorbents. Based on the relative ET(30) and relative dielectric constant of the organic solvent, a phase separation diagram can be drawn to predict the phase change behaviors of DETA absorbents. Among the DETA-based CPCAs, DETA + DMF + H2O absorbents showed the largest CO2-rich phase loading, and the optimized DETA + DMF + H2O CPCA exhibited 200 % of the CO2 cyclic loading compared to 30 wt% MEA aqueous solution.

Regulating the absorption and solid regeneration performance of a novel anhydrous solid–liquid phase change absorbent for carbon capture

The solid–liquid biphasic solvent has great energy-saving potential, but its absorption rate and solid regeneration performance need to be improved. In this study, a new solid–liquid biphasic solvent was proposed using 1,3-diaminopropane (DAP) as the main absorbent, 2-amino-2-methyl-1-propanol (AMP) and piperazine (PZ) as the absorption enhancer, and n-propanol (NPA) as the organic diluent and regeneration promoter. AMP and PZ could boost the CO2 absorption and thus shorten the absorption saturation time from 120 min to 80 and 60 min, and further reduce the regeneration energy to 1.30 and 1.35 GJ·t−1 CO2 as well. They were much lower than the reported biphasic absorbents and only 34.2 % and 35.6 % of the 3.80 GJ·t−1 CO2 produced by 5 M MEA. Moreover, adding a small amount of NPA to the lower phase could significantly increase the desorption efficiency to 84.5 %, whereas no CO2 was desorbed without the help of NPA. Experimental and theoretical analysis indicated that during CO2 absorption, the DAP-NPA system absorbed CO2 to produce DAPCOO- and protonated DAP. Adding AMP or PZ to the system enhanced product coupling by replacing DAPCOO- with a small amount of AMPCOO- or PZCOO-, thereby accelerating the reaction. Furthermore, during regeneration, NPA would weaken the hydrogen bonding between the products and promote the CO2 desorption and the regeneration of solid products. This work developed a promising solid–liquid biphasic solvent with good comprehensive performance.

A Coupling Calculation Method of Desorption Energy Distribution Applied to CO2 Capture by Chemical Absorption

The pursuit of low-energy-consumption CO2 capture technology has promoted the renewal and iteration of absorbents for chemical absorption. In order to evaluate the regeneration energy consumption of absorbents and obtain the distribution of energy consumption, a coupling method combining rigorous energy balance and simple estimation is proposed in this study. The data regarding energy balance and material balance from process simulation are transformed into the model parameters required in the simple estimation model. Regenerative energy consumption and distribution are determined by the empirical estimation formula. Two CO2 capture processes of an MEA aqueous solution and MEA–n-propanol aqueous solution (phase-change absorbent) were used to verify the feasibility and applicability of the coupling method. The effects of n-propanol concentration, CO2 loading in the lean solution, and temperature on energy consumption were discussed. The results show that the energy consumption of 30 wt% MEA aqueous solution is the lowest at 3.92 GJ·t−1-CO2 when CO2 load in the lean solution is 0.2 mol CO2·mol−1-MEA, and the reaction heat Qrec, sensible heat Qsen, and latent heat Qlatent were 1.97 GJ·t−1-CO2, 1.09 GJ·t−1-CO2, and 0.86 GJ·t−1-CO2, respectively. The lowest energy consumption of the phase-change absorbent with CO2 loading of 0.35 mol CO2·mol−1-MEA in the lean solution is 2.32 GJ·t−1-CO2. Qrec, Qsen, and Qlatent were 1.9 GJ·t−1-CO2, 0.29 GJ·t−1-CO2, and 0.14 GJ·t−1-CO2, respectively. This study provides a simple and meaningful method for accurately assessing absorber performance and process improvement, which can accelerate the development of economically viable, absorption-based CO2 capture processes.

Experimental study on CO2 capture by MEA/n-butanol/H2O phase change absorbent.

Monoethanolamines (MEAs) are widely used for CO2 capture, but their regeneration energy consumption is very high. CO2 Phase change absorbents (CPCAs) can be converted into CO2-rich and CO2-lean phases after absorbing CO2, and the regeneration energy consumption can be reduced because only the CO2-rich phase is thermally desorbed. In this paper, a novel CPCA with the composition "MEA/n-butanol/H2O (MNBH)" is proposed. Compared with the reported MEA phase change absorbent, the MNBH absorbent has higher CO2 absorption capacity, smaller absorbent viscosity and CO2-rich phase volume. The MNBH absorbent has the highest CO2 absorption capacity of 2.5227 mol CO2 per mol amine at a mass ratio of 3 : 4 : 3. The CO2 desorption efficiency reaches 89.96% at 120 °C, and the CO2 regeneration energy consumption is 2.6 GJ tCO2-1, which is about 35% lower than that of the 30 wt% MEA absorbent. When the mass ratio of MNBH absorbent was 3 : 6 : 1, the CO2 recycling capacity was 4.1918 mol CO2 L-1, which is 76% higher than that of the conventional 30 wt% MEA absorbent. The phase change absorbent developed in this paper can reduce the desorbent volume by about 50% and has good absorption performance for CO2 in flue gas.

A low energy-consuming phase change absorbent of MAE/DGM/H2O for CO2 capture

The concept of phase change absorbents has been widely studied as a novel and low-energy consumption option for CO2 capture. This work screened diethylene glycol dimethyl ether (DGM) from 17 physical solvent species as a better phase change accelerator for absorbents of 2-(methylamino)ethanol (MAE)-physical solvent-H2O. Then, the optimized mass ratio of 30:49:21 for MAE-DGM-H2O solution was investigated with phase change behaviors, CO2 absorption–desorption performance, cyclic capacity, and energy consumption. The experimental results showed that the cyclic CO2 capacity reached 1.32 mol/L and the CO2-rich phase made up only 50.4 % of the total volume for the 30 wt%MAE-49 wt%DGM-21 wt%H2O, as well as its regenerative energy consumption was 40 % lower than that of 30 wt% monoethanolamine (MEA) solution. Also, the viscosity and surface tension gap of the CO2-rich phase and CO2-lean phase for the optimized absorbent were studied. It was observed that those gaps increase with the increasing mass ratio of DGM. In addition, the possible phase change mechanism was proposed by using the dipole moment values of components calculated by Gaussian (B3LYP/6-31G) coupled with 13C NMR spectra.

A functionalized ionic liquid phase change absorbent ([DETAH][Py]-DEDM-water) for reversible carbon dioxide capture

Phase change absorbent can effectively reduce energy consumption in the process of CO2 capture. In the present work, a series of CO2-capturing phase change absorbents consisting of diethyltriamine pyrazole ([DETAH][Py])-solvent–water have been studied. Among them, [DETAH][Py]-diethylene glycol dimethyl ether (DEDM)-water present good absorption and phase change performance. The experimental results showed that under the conditions of 303.15 K, C[DETAH][Py] = 1 mol/L, VDEDM:water = 4:6, the CO2 absorption reached 1.515 mol CO2/mol IL, and the regeneration efficiency remained 90.75 % at 403.15 K. In addition, the absorption mechanism was explored based on FT-IR and 13C NMR. [DETAH][Py] captured CO2 to generate carbamate, which was then partially hydrolyzed to HCO3−/CO32−. In order to further explain the phase change mechanism, as to absorbed products, the difference of solvation free energy (ΔGsol) between water phase and DEDM phase was calculated by DFT. The results showed that the solubility of products in water is different from the solubility of DEDM, and most of products will dissolve in water, where the organic phase undergoes self-aggregation and is extruded out of the aqueous phase due to salting-out effect, causing phase change.

Mass transfer and reaction mechanism of CO2 capture into a novel amino acid ionic liquid phase-change absorbent

In order to overcome high heat duty and poor regeneration efficiency of existing chemical absorbent, a novel aqueous amino acid ionic liquids (AAILs) phase change absorbent with tetraethylenepentamine (TEPA) as cation, L-proline (L-Pro) as anion and N-propanol (NPA) as phase separator was proposed in this study. [TEPAH][Pro]/NPA/H2O owned the maximum absorption loading of 2.01 mol CO2·mol absorbent−1, and the rich phase viscosity was only 8.06 mPa·s. Moreover, its desorption efficiency was 84.4% while the 5th cyclic loading kept above 1.61 mol CO2·mol absorbent−1. With the presence of NPA, the rich phase only accounted for 41% of the total volume while it contained 99.3% of CO2 products. The heat duty was only 2.39 GJ·t CO2-1, which was 37% lower than that of 30 wt% ethanolamine (MEA) aqueous solution. Meanwhile, the reaction mechanism and product distribution were revealed by 13C NMR and the mass transfer kinetics was investigated using the wetted wall column. The products in the rich phase mainly consisted of carbamate, hydrogen carbonate, propyl carbonate and water while the main component of the lean phase was NPA. The reaction followed a fast pseudo-first order reaction. At 313.15 K, the rate constant of fresh absorbent was 51346 s−1, which showed a decreasing trend with the increase of absorption loading at 313.15 K. The second order reaction rate was calculated by: k2 = 9.88 × 109exp(-3591.2/T), where the reaction activation energy was only 29.86 kJ·mol−1.

Alcohol regulated phase change absorbent for efficient carbon dioxide capture: Mechanism and energy consumption

Phase change absorbents based on amine chemical absorption for CO2 capture exhibit energy-saving potential, but generally suffer from difficulties in CO2 regeneration. Alcohol, characterized as a protic reagent with a low dielectric constant, can provide free protons to the rich phase of the absorbent, thereby facilitating CO2 regeneration. In this investigation, N-aminoethylpiperazine (AEP)/sulfolane/H2O was employed as the liquid-liquid phase change absorbent, with alcohol serving as the regulator. First, appropriate ion pair models were constructed to simulate the solvent effect of the CO2 products in different alcohol solutions. The results demonstrated that these ion pair products reached the maximum solvation-free energy (ΔEsolvation) in the rich phase containing ethanol (EtOH). Desorption experiment results validated that the inclusion of EtOH led to a maximum regeneration rate of 0.00763 mol/min, thus confirming EtOH's suitability as the preferred regulator. Quantum chemical calculations and 13C NMR characterization were performed, revealing that the addition of EtOH resulted in the partial conversion of AEP-carbamate (AEPCOO−) into a new product known as ethyl carbonate (C2H5OCOO−), which enhanced the regeneration reactivity. In addition, the decomposition paths of different CO2 products were simulated visually, and every reaction's activation energy (ΔEact) was calculated. Remarkably, the ΔEact for the decomposition of C2H5OCOO− (9.465 kJ/mol) was lower than that of the AEPCOO− (26.163 kJ/mol), implying that CO2 was more likely to be released. Finally, the regeneration energy consumption of the alcohol-regulated absorbent was estimated to be only 1.92 GJ/ton CO2, which had excellent energy-saving potential.

Effect of water on CO2 absorption by a novel anhydrous biphasic absorbent: Phase change behavior, absorption performance, reaction heat, and absorption mechanism

The ionic liquids (ILs)-based biphasic absorbents are viewed as promising substitutes for CO2 capture due to their remarkable CO2 absorption performance, excellent stability and low energy requirement for regeneration. Further decreasing the regeneration heat requirement can be achieved by utilizing ILs-based anhydrous biphasic absorbents, whose solid CO2-rich phase contained small volume and low specific heat capacity. Given the high hygroscopicity of ILs and the water present in the flue gas, comprehending the effect of water is crucial for post-combustion carbon capture using ILs-based anhydrous biphasic absorbents. In this work, the effect of water on CO2 absorption by an anhydrous biphasic absorbent, tetramethylammonium glycinate ([N1111][Gly])/ethanol, was studied. The experimental results demonstrated that the CO2 loading and absorption rate were decreased in the presence of water, but the CO2 desorption efficiency was enhanced. Besides, the presence of water slightly reduced the reaction heat of CO2 absorption by [N1111][Gly]/ethanol to 69.48 kJ/mol CO2, which was 20% lower than that of monoethanolamine (MEA) absorbent. Furthermore, the 13C NMR results indicated that the primary CO2-product was bicarbonate in the presence of water rather than carbamate. There were three possible pathways for bicarbonate generation: zwitterion hydrolysis, carbamate hydrolysis, and base-catalyzed CO2 hydration. Water and ethanol competed to react with carbamate. When a large amount of water was present (≥70 wt%), the reaction of ethanol with the carbamate hardly occurred.

The formation of high CO2 loading solid phase from 1,4-butanediamine/ethylene glycol biphasic solvent: Phase-changing behavior and mechanism

Liquid-solid phase change absorption has been considered a promising strategy for CO2 capture. To achieve efficient and economic CO2 capture in industrial-scale applications, it is essential to understand the phase-change behaviors and mechanisms of the biphasic system. In this study, a blend of 1, 4-Butanediamine (BDA) and ethylene glycol (EG) was developed as a biphasic solvent that can form a high CO2 loading solid phase product (BESP) after absorption. The total solvent loading reached 0.9039 mol·mol−1, with 90.74% of the loading enriched in the solid phase, which only accounts for 51.01% of the total solvent mass. Based on the 13C NMR analysis and quantum chemical calculations, the reaction and phase change mechanism of CO2 capture was proposed. The BDA/EG system absorbs CO2 to generate carbamate species, protonated amines and alkyl-carbonates, which combine each other through hydrogen bonding or electrostatic attraction. The self-aggregation of zwitterions and the high polarity of the absorption products are considered to be the main reasons for the phase change. Alkyl-carbonate species are believed to co-precipitate through organic gelation via van der Waals force with the carbamate or protonated amine. Moreover, the viscosity, turbidity, solid-phase mass, and particle size distribution changes also demonstrate the growth and aggregation of particles during absorption. BESP, identified as a coupling product of carbamate and alkyl-carbonate ([2BDAH+COO-]·[EG‐OCO2-]), decomposes at a peak temperature of 127.4 °C. The calorimetric method determined regeneration heat to be approximately 3.17 GJ·ton-1 CO2, indicating its potential for alternative uses rather than direct heat regeneration. Such a biphasic solvent may provide unique solutions for industries to reduce CO2 emissions.

Research and design experience of a 150 kt/a CO2 capture and purification project in the Shaanxi Guohua Jinjie power plant

There was little research and demonstration experience in large flue gas carbon projects in China. 150 kt/a flue gas CO2 capture project in the Guohua Jinjie power plant, which is the largest-scale flue gas carbon capture project in China, effectively solved this technical bottleneck. The performance of the used compound amine absorbent, phase change absorbent, and the ionic liquid was described, and the compatibility of performance was considered in the project; new energy-saving processes integrated mechanical vapor recompression heat pump, interstage cooling, and split flow desorption. The plane layout of the project was put forward, and the utility consumption of the capture system was analyzed. The paper explained the health, safety, and environmental protection instructions, presented test category tables, and developed energy consumption and economic analyses. The results showed that the renewable energy consumption per unit product was 2.32 GJ/t CO2, the loss of absorbent was less than or equal to 1.0 kg/t CO2, and the total investment (excluding tax) of the project was 13.8398 million yuan. When the CO2 sales price (excluding tax) was 203.43 Yuan/t, the yield was 0 %, and when the CO2 sales price (excluding tax) was 260.949 Yuan/t, the yield was 8 %. The feasibility study research conclusions indicated that the project was technically and economically feasible.

MXene/d-Mannitol aerogel phase change material composites for medium-temperature energy storage and solar-thermal conversion

Accelerate the development of medium-temperature phase change materials (PCMs) with high enthalpy of phase change and light absorption capability is very important for medium-temperature energy storage and solar thermal utilization. However, low energy conversion capacity and easy leakage limit the practical application of PCMs. To improve these properties of materials, a MXene/DM aerogel composite phase change material was prepared by self-assembly followed by freeze-drying of d-mannitol (DM) and MXene nanosheets using a simple solution blending method. The MXene/DM containing 20 wt% MXene has a high enthalpy (Hm) of phase change (202.7 J/g) with phase change temperature (Tm) of 153.3 °C, and still has good shape stability at 170 °C without leakage. In addition, MXene/DM has strong absorption ability in UV–Vis-NIR regions, with significant solar-thermal conversion efficiency of 88.1 %. The results indicate that the MXene/DM aerogel have comprehensive performance and have promising applications in medium-temperature thermal storage and photothermal conversion.

A CO2-controllable phase change absorbent solvent used to waste recycling of dining lampblack

Dining lampblack as a source of atmospheric pollution, urban residents had to spend a lot of economic costs all year round to solve its impact. However, traditional treatment methods often carry the risk of secondary pollution. The use of phase change absorption solvent (PCAS) controlled by CO2 can effectively absorb the oily components in dining lampblack, and smoothly avoid the generation of secondary pollutants and squandering of resources. The reversibility of PCASs under CO2 control was explained by pH changes and macroscopic visualizations. The absorption effects of favorable absorbents and PCASs on dining lampblack were compared and analyzed. The fatty acid (FA) in the oil absorption mixture was desorbed by interacting with D230. The results of GC/MS analysis on the oil components separated by desorption showed that the desorption of PCASs was effective for these refractory oil components. FAs can be enriched and applied to the subsequent dining lampblack treatment link to realize the waste recycling. In addition, the absorption and desorption of oily components by PCASs were combined with the CO2-controlled phase transformation of PCASs itself to achieve the absorption circulation of treating dining lampblack by using PCASs.