Aqueous Solutions Of Monoethanolamine Research Articles

Measurement of the reaction enthalpy of CO2 in aqueous solutions with thermographic and gravimetric methods

In this work, a new concept for the approximate determination of the reaction enthalpy of the reaction between CO2 and monoethanolamine (MEA) in aqueous solution was developed. For this purpose, a CO2 gas stream was flowed into aqueous MEA solutions with different concentrations of 1 wt%, 2.5 wt% and 7.5 wt%. The weight difference ∆T, which is based on the increase in CO2 bound by the MEA over time, was documented using a thermographic camera. The mass difference ∆m, which is also based on the increase in CO2 bound by the MEA over time, was determined using a balance. By determining ∆T and ∆m, an approximate calculation of the reaction enthalpy is possible. The deviation from the values from the data known from the literature was less than 5% in all experiments.

Modeling H2S solubility in aqueous MDEA, MEA and DEA solutions by the electrolyte SRK-CPA EOS

In this study, an electrolyte cubic plus association equation of state (e-CPA EOS) has been proposed to predict the vapor–liquid equilibrium of (H2S) in aqueous solutions of monoethanolamine (MEA), diethanolamine (DEA), and methyldiethanolamine (MDEA). This EOS is composed of repulsive forces, short-range interactions, short-range ionic interactions, association term, long-range ionic interactions, and Born term. The Soave– Redlich– Kwong EOS is used as a non-electrolyte part. A new iterative procedure based on the Jacobi method is introduced to obtain the compositions of all species in the liquid phase. The genetic algorithm (GA) is used to find the optimal values of binary interaction coefficients between molecules and ions. Compared with experimental data, the e-CPA EOS model successfully describes the vapor–liquid equilibrium of H2S in the aqueous solutions of MEA, DEA, and MDEA. The average absolute deviations for 313 data of MEA-H2S-H2O, 156 data of DEA-H2S-H2O, and 145 data of MDEA-H2S-H2O systems were obtained as 8.20 %, 8.04 %, and 9.41 %, respectively. In addition, for some similar cases, the capability of the e-CPA EOS was compared with the Clegg–Pitzer, N-Wilson-NRF, e-NRTL, and e-CTS models. The results indicated that the e-CPA EOS has less error than the four other models.

The Reaction of CO2 absorption in MEA(monoethanolamine) aqueous Solution: A Theoretical Study on the Effect of Neighboring Molecules

Objectives : CO<sub>2</sub> is one of the greenhouse gases that cause the global warming. Alkanolamine aqueous solutions are frequently used as a chemical absorption solvent for post combustion capture process. The reaction of CO<sub>2</sub> and MEA(monoethanolamine) was studied by theoretical analysis to describe the effect of neighboring molecules.Methods : The reaction of CO<sub>2</sub> absorption in MEA aqueous solution was investigated using DFT (density functional theory) method. The 14 reaction models were designed according to the arrangement of reactant and neighboring molecules.Results and Discussion : The structures of reactant, TS (transition state) and product were analyzed in perspective of the geometry, thermodynamics and kinetics. The neighboring molecules stabilized the structures of reactant complex due to increasing intermolecular interaction (hydrogen bond) between reactants and these molecules. The structures of reactant complex were change to the arrangement that MEA can easily react with CO<sub>2</sub> . However, the neighboring molecules would slightly affect the reaction pathway of the structures of TS and product. The activation energy and TS structure were differed according to the type of hydrogen atom transfer, not the effect of neighboring molecules. The neighboring molecules seems to work slightly in the aspect of chemical kinetics of the reaction between CO<sub>2</sub> and MEA in aqueous solution.

Estimation of the Amount of CO2 Chemically Absorbed in Real Time by Measuring the Electrical Conductivity Variation of Monoethanol-Amine Aqueous Solutions

Estimation of the Amount of CO₂ Chemically Absorbed in Real Time by Measuring the Electrical Conductivity Variation of Monoethanol-Amine Aqueous Solutions

Investigation of CO2 Absorption Rate in Gas/Liquid Membrane Contactors with Inserting 3D Printing Mini-Channel Turbulence Promoters.

The CO2 absorption by Monoethanolamine (MEA) solutions as chemical absorption was conducted in the membrane gas absorption module with inserting 3D mini-channel turbulence promoters of the present work. A mathematical modeling of CO2 absorption flux was analyzed by using the chemical absorption theory based on mass-transfer resistances in series. The membrane absorption module with embedding 3D mini-channel turbulence promoters in the current study indicated that the CO2 absorption rate improvement is achieved due to the diminishing concentration polarization effect nearby the membrane surfaces. A simplified regression equation of the average Sherwood number was correlated to express the enhanced mass-transfer coefficient of the CO2 absorption. The experimental results and theoretical predictions showed that the absorption flux improvement was significantly improved with implementing 3D mini-channel turbulence promoters. The experimental results of CO2 absorption fluxes were performed in good agreement with the theoretical predictions in aqueous MEA solutions. A further absorption flux enhancement up to 30.56% was accomplished as compared to the results in the previous work, which the module was inserted the promoter without mini channels. The influences of the MEA absorbent flow rates and inlet CO2 concentrations on the absorption flux and absorption flux improvement are also illustrated under both concurrent- and countercurrent-flow operations.

Energy-efficient carbon dioxide capture using piperazine (PZ) activated EMEA+DEEA water lean solvent: Performance and mechanism

Water vapor contained in industrial waste gas will be accumulated in non-aqueous amine solvents when used for CO2 capture and subsequently affect capture efficiency. While Piperazine (PZ) could be considered as an activator of the solution. Hence the effect of different contents of water and PZ added into the non-aqueous amine solvents on the CO2 capture performance has been investigated. 13C NMR has been used to identify the compounds present in aqueous CO2-rich amine solvents to characterize the mechanism of reactions. The energy consumption using 2-(ethylamino)ethanol (EMEA) water-lean amine solvent and aqueous monoethanolamine (MEA) solution was tested and compared on lab-scale, and further a comprehensive evaluation in a bench-scale pilot plant has been performed; It was found that the regeneration efficiency of the solution was reduced by approximately 10% when the water content was 10 wt%. The addition of PZ can recover the regeneration efficiency of the solvent to 94.2%. And its energy consumption was reduced by about 45% compared to the aqueous MEA solution in a 72-hour continuous absorption-desorption experiment. The results demonstrated that the aqueous PZ solution could improve the regeneration efficiency by involving in the proton transfer process. This work has proven that the blend of water-lean amine solvent and PZ is a novel, energy-efficient absorbent for CO2 capture.

Integration of solid acid catalyst and ceramic membrane to boost amine-based CO2 desorption

Amine-based absorption has matured into an established technology for CO2 capture from fossil fuel power plants. However, high energy consumption for CO2 desorption remains a challenge. Herein, we report a promising integration of a solid acid catalyst (i.e., HZSM-5) filled into a vapor permeable-liquid impermeable tubular α-Al2O3 ceramic membrane for boosting CO2 desorption from aqueous monoethanolamine (MEA) solution. Experiments were conducted to investigate the effects of catalyst weight, temperature, pressure, liquid flow rate and CO2 loading on CO2 desorption rate and energy consumption. Furthermore, 60 runs of cyclic tests were carried out to assess the stable CO2 desorption rate and the thermal and chemical stability of both the HZSM-5 catalyst and the α-Al2O3 membrane. The experiment results demonstrated that the HZSM-5 filled α-Al2O3 ceramic membrane contactor exhibited high CO2 desorption performance and long-term stability. It is anticipated that integration of solid acid catalyst with porous ceramic membrane holds great promise in practical application to boost the CO2 desorption rate and reduce the energy requirement.

Reduction of energy consumption in post-combustion carbon capture process via amine-functionalized metal-organic frameworks

In this study, CO2 capture performance of ethylenediamine-functionalized Mg-MOF-74 (EDMOF-74) suspended in 30 wt% monoethanolamine (MEA) aqueous solution is analyzed. A CO2 absorption experiment was performed in a bubble column reactor based on EDMOF-74 concentrations of 0.005, 0.01, 0.05, and 0.1 wt% for different ethylenediamine loadings. It shows that EDMOF-74/30 wt% MEA mixtures improve CO2 absorption performance by a maximum of 7.18 % as compared with the base fluid. Subsequent experiment based on large-volume feed gas reveals a less volatile CO2 absorption rate. By adding EDMOF-74 to the 30 wt% MEA aqueous solution in a cyclic CO2 absorption experiment to evaluate its industrial application, an increase in durability is indicated, which implies a reduction in energy consumption during CO2 regeneration. A feasibility study on the reduction of CO2 regeneration energy was investigated in terms of the results of cyclic experiment and the facility status of Boryeong power plant. The CO2 regeneration energy can be reduced by 13.64 %, which corresponds to a decrease of 484,233 MWht/year for 1 unit of the Boryeong power plant. The abovementioned approach is expected to compensate for the disadvantages of MEA in the industrial CO2 capture process, i.e., low CO2 capacity and high CO2 regeneration energy input.

Predicting overall mass transfer coefficients of CO2 capture into monoethanolamine in spray columns with hybrid machine learning

In order to avoid the catastrophic effects of global warming, we need to reduce CO2 emissions. Currently, the most mature technology to reduce large industrial CO2 emissions is the absorption of CO2 into aqueous monoethanolamine (MEA) solutions. The process is mostly studied in packed columns, for which many correlations have been offered to predict overall mass transfer coefficients (KGa). Spray columns are less prone to corrosion and were shown to enhance KGa. However, to the best of our knowledge, there are no models to predict KGa in spray columns. Hybrid modelling tools, a combination of machine learning techniques and first-principle information, showed remarkable capabilities in modelling complex systems. In this work, we applied hybrid modelling techniques benchmarking performances of four regressors: Ridge regression, decision tree regressor (DTr), support vector machine regressor (SVMr) and fully connected artificial neural network (ANN). We compared the performances of these modelling techniques with a model developed using the Buckingham Π-theorem, which is the most used state of the art technique to model KGa based on dimensionless numbers. SVMr and DTr showed higher accuracies among the trained models on the test set. SVMr can predict KGa within 6.4% error on the test set, whereas the Buckingham modelling approach resulted in 83 % error. The use of machine learning techniques resulted in predictive models with higher accuracies compared to the Buckingham Π-theorem. Predicting KGa with a higher accuracy allows more control over operational parameters and better column designs.

Structural Features of Monoethanolamine Aqueous Solutions with Various Compositions: A Combined Experimental and Theoretical Study Using Vibrational Spectroscopy.

In this work, we studied aqueous solutions of monoethanolamine (MEA), which are widely used to remove CO2 from flue and oil gases. This study combined experimental and theoretical methods of vibrational spectroscopy, using high-temperature infrared spectroscopy, quantum-chemical calculations of theoretical vibrational spectra, and structural electronic and energy characteristics of model structures. MEA has a propensity to form associations between various compositions and structures with water molecules, as well as those composed solely of water molecules. The structural and energy characteristics of such associates were analyzed in terms of their ability to interact and retain carbon dioxide. The influence of elevated temperatures and concentration of aqueous MEA solution on change in the structure of associates has also been investigated. An analysis of theoretical and experimental vibrational spectra allowed us to examine the IR spectra of MEA solutions, and identify the bands responsible for the formation of associates that would sorb CO2 well, but would delay its desorption from the solution.

Transport properties of mixtures of acid gases with aqueous monoethanolamine solutions: A molecular dynamics study

We investigated the effect of temperature and monoethanolamine (MEA) concentration on the self-diffusivity of acid gases, CO2 , and H2S in aqueous MEA solutions. For this purpose, we computed densities of pure MEA and 30 wt% MEA/water solutions while scaling the LJ energy (ϵ) parameter and point charges of MEA. Results show that with a scaling factor of 0.80 applied to the point charges of MEA, computed densities agree well with the experimental ones from literature. This was tested by computing viscosities and the self-diffusivity of pure MEA and 30 wt% MEA/water solutions and comparing these with experiments. We showed that the scaling factor of 0.80 also works well for predicting transport properties of MEA/water solutions. Finally, we computed self-diffusivities of infinitely diluted CO2 and H2S for temperatures ranging from 293–353 K and MEA concentrations of 10–50 wt%. Our results show that the self-diffusivity of both acid gases depends significantly on the temperature and MEA concentration in the solution. The results of this study will contribute to the development of more efficient acid gas treatment processes.

Use of copper carbonate as corrosion inhibitor for carbon steel in post combustion carbon capture

The realisation of post-combustion CO2 capture (PCCC) at industrial scale remains limited; one challenge is the concerns around capital costs and another concern is corrosion of the system itself. Corrosion resistance and mitigation against the amine solvent monoethanolamine (MEA) was studied, using the inhibitor copper (II) carbonate basic (CC). Carbon steel (C1018) was tested in CO2 loaded, 5M aqueous MEA solution, alone and in the presence of CC, to assess the corrosivity of the solution. Immersion testing used mass loss, Fe and Cu ion concentration in solution via ICP-MS, imaging (SEM) and analytical techniques (XRD and EDX) to investigate the effect of corrosion. Generally, the use of CC improved C1018 corrosion resistance relative to C1018 alone. Even at low concentrations (0.9 mM), CC was effective in inhibiting corrosion against CO2 loaded MEA, as the observed corrosion rate was effectively zero and no dissolved Fe was detected in solution. There was no evidence of copper surface adsorption. To clarify the solution chemistry resulting in corrosion inhibition, the local chemical environment of Fe and Cu were probed by Cu and Fe K-edge X-ray Absorption Spectroscopy, respectively. The Cu K- edge HERFD-XANES spectra reveal that a Cu2+ amine complex forms, critical to understanding the structure which is promoting significant corrosion inhibition.

Thermochemical model for evaluating CO2 regeneration energy for amine absorbents

We present a thermochemical model for evaluating CO2 regeneration energies for aqueous solutions of monoethanolamine (MEA), diethanolamine (DEA), 2-amino-2-methyl-1-propanol (AMP), and 2-(isopropylamino)ethanol (IPAE). The regeneration heat consists of the reaction heat, the sensible heat, and the vaporization heat. We calculated the reaction heat using a thermochemical model. We calculated the concentrations of all chemical species present in the CO2 absorption state at 40 °C and the CO2 release state at 120 °C. We calculated the reaction heat by summing enthalpies of associated reactions and reacted molar quantities derived from the concentration changes between the absorption and release states. For sterically hindered amines AMP and IPAE, the contribution of the protonation reaction to the reaction heat is large, whereas the contributions of protonation and carbamate hydrolysis are large for MEA and DEA. In the regeneration heat, the sensible heat is much larger than the reaction and vaporization heats.

Impact of Solvent on the Thermal Stability of Amines.

Water-lean solvents have been proposed as a possible alternative to aqueous amine systems in postcombustion carbon capture. There is however little data available on how amine degradation is affected by different solvents. This study presents new insights on the effect of solvent on thermal degradation of alkanolamines from laboratory-scale degradation experiments. Replacing the water in aqueous monoethanolamine (MEA) solutions with organic diluents resulted in varying thermal degradation rates. Overall, all tested organic diluents (triethylene glycol, diethylene glycol, mono ethylene glycol, tetrahydrofurfuryl alcohol, N-formyl morpholine/water, and N-methyl-2-pyrrolidone) resulted in higher thermal degradation rates for loaded MEA. None of the proposed parameters, such as acid-base behavior, polarity, or relative permittivities, stood out as single contributing factors for the variation in degradation rates. The typical degradation compounds observed for an aqueous MEA solvent were also observed for MEA in various concentrations and with various organic diluents.

Experimental and Thermodynamic Investigation on CO2 Absorption in Aqueous MEA Solutions

The vapor-liquid equilibrium (VLE) of CO2 in a reactive solvent is essential for the proper simulation and design of CO2 absorption processes. This work presents a systematic investigation on CO2 absorption in various aqueous monoethanolamine (MEA) solutions. CO2 solubility in MEA was measured at 298, 313, 333, and 353 K with CO2 partial pressure ranging from 34.5 to 78.0 kPa. A modified Kent-Eisenberg model was developed based on the measured solubility data, showing good predictions over the liquid phase speciation for the CO2-H2O-MEA system. We presented a new analysis based on the first-order difference curve of distribution profiles of the species. Based on the main reactions that occurred, the CO2 absorption process was demonstrated to be divided into four regions with increasing CO2 loading from 0 to 1. Accordingly, kinetic study was proposed to be conducted in the first region, whereas measuring of mass transfer in the first three regions. The findings in this work extend the existing knowledge of CO2 absorption process in terms of speciation and can provide important guidance for further study of the process characteristics using aqueous amine absorbents.

Perstraction of Heat-Stable Salts from Aqueous Alkanolamine Solutions

Amine absorption processes designed to remove acid gases from gas streams generally face a major challenge of solvent degradation. This degradation leads to the formation of heat-stable salts (HSS), corrosive agents that irreversibly bind free alkanolamine. The present study proposes, for the first time, a method for HSS perstraction using a liquid–liquid membrane contactor that allows HSS to transfer through porous membranes from the solvent into a hydrophobic extractant represented by a methyltrioctylammonium solution in 1-octanol. The perstraction provides selective extraction of HSS anions without direct mixing of liquid phases or the formation of stable emulsions of the solvent and the extractant. For this purpose, a number of industrial and laboratory porous membrane samples fabricated from polyvinylidene fluoride, polypropylene, and polysulfone were investigated. Their chemical and morphological stability, surface properties, and transport properties were tested under prolonged (>600 h) contact with a model solvent (an aqueous monoethanolamine solution) and with the components of the selective extractant. The feasibility of HSS perstraction was demonstrated using the formic acid (as an HSS model) extraction from the model solvent. The most promising results were obtained for a system with a polyvinylidene fluoride membrane: up to 50% of formic acid was extracted over 18 h.

Nanostructured AlOOH – A promising catalyst to reduce energy consumption for amine-based CO2 capture

In order to alleviate the intensive energy demand of amine-based post-combustion carbon capture technology, metal oxyhydroxide AlOOH of nanoscale was synthesized through the hydrothermal method and applied to accelerate the CO2 desorption rate and reduce the regeneration heat duty of aqueous monoethanolamine (MEA) solution for the first time. Results showed that the use of AlOOH could accelerate the desorption rate by up to 560% and increase the desorption amount by 251%. By comparing the performance between AlOOH and Al2O3, it can be found that the presence of extra hydroxyl groups is 20.6% more efficient in catalyzing CO2 desorption. According to a simplified heat transfer model created in this work, AlOOH could reduce the heat duty by 17% with only 0.1 wt% loading, which exhibited the highest performance cost ratio among related literature. In addition, the cyclic stability of AlOOH was confirmed through various characterization methods, including XRD, FT-IR, SEM, and N2 adsorption–desorption. More importantly, a possible catalytic mechanism of AlOOH was discussed and proved where it could change reaction pathways in different CO2 loading regions. This work reveals a promising research direction towards cost-efficient and high-performance metal oxyhydroxide catalysts in the catalytic amine regeneration field to approach the net-zero carbon emission goal.

New Chemical Weapons Destruction Technologies as the Key to Successful Completion of Chemical Weapons Disarmament Process

The fulfillment of international obligations of the Russian Federation under the Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on Their Destruction required the development and the creation of safe innovative industrial technologies and facilities for the destruction of chemical weapons. The purpose of this work is to give brief characteristics of the technologies for the destruction of chemical weapons developed and commercially implemented at various facilities. The destruction of chemical weapons was carried out at seven facilities specially designed and built for this purpose. These facilities were located in six regions of the country. The choice of technologies for the destruction (utilization) of chemical weapons was carried out on a competitive basis in the period from 1992 to 1995.The priority was given to the so-called two-stage technology. At the first stage, the toxic chemicals were extracted from the munitions or the containers and detoxified chemically in «soft» controlled conditions. Then the empty munitions were degassed. At the second stage, thermal neutralization or bituminization of the reaction masses was carried out with their subsequent burial. The two-stage technology for the destruction of mustard and mustard-lewisite mixtures was based on the interaction of toxic chemicals with an 80 ± 5% aqueous solution of monoethanolamine, which was supplied into the reactor at a temperature of 60–80 °C in the ratio toxic chemical: degassing formulation - 1:1.2 according to mass. The detoxification process was considered completed if the content of toxic chemicals in the reaction mass did not exceed 3,2×10 -3 %. To destroy lewisite, a «short scheme» in a jet-type reactor was implemented. The mixing of the initial reagents, lewisite and 20% alkali solution, was carried out using a nozzle of a special design, where lewisite was swirled with a special device (swirler) and supplied into the reactor. The first stage of the destruction of V-gases was carried out in munitions cases. The munitions were considered as chemical reactors. The process of detoxification of V-gases was considered completed when the residual content of toxic chemicals was at the level of 5×10 -4 %, and the reaction mass was delivered for thermal neutralization (second stage). In total, 39966,588 tons of toxic chemicals were destroyed. The whole number of destroyed containers with agents and chemical munitions amounted to 4,158,456 units. On September 27, 2017, the last chemical weapon was destroyed at the Kizner chemical weapons destruction facility, thus completing the process of complete destruction of chemical weapons stockpiles in the Russian Federation.

Unveiling the internal pressure polytherms for ethylene glycol and monoethanolamine in aqueous solutions: A modeling approach

The Buckingham's function is proposed as a valid tool to approximate the polytherms Pi, i.e., the internal pressure of aqueous solutions of ethylene glycol and monoethanolamine in a wide temperature range (278.15–333.15 K) using physically understandable realistic model. It is shown that the proposed modeling function approximates the temperature dependences of Pi for a great majority of aqueous solutions under scrutiny with an error of less than 3 %. In situations where the adequacy of basic Buckingham model is less significant, the use of a modified Buckingham function is suggested.

Studies on advanced configurations of post-combustion CO2 capture process applied to cement plant flue gases

This study used ProMax® 5.0 process simulator to develop three innovative configurations for cement plant flue gases specifically. A detailed evaluation of three innovative configurations was presented, and the advanced technical and economic benefits of the three innovative configurations were compared with the conventional configuration. The simulation consisted of three cases of flue gas compositions. The major case was simulated based on the published design parameters from an existing cement plant in Quebec, Canada. The other two cases of flue gas compositions were two assumptions for higher CO2 content of the cement plant flue gases, including 20 vol.% CO2 and 28.6 vol.% CO2. This research provided a comparison of the solvent regeneration energy using a single aqueous Monoethanolamine (MEA) solution and the solution activated with 1-(2-Aminoethyl)piperazine (AEP). The evaluations showed that the innovative configurations were able to reduce regeneration energy up to 22% and solvent demand up to 10%. The savings towards variable CO2 content of the flue gases were also discovered.