MDEA Concentration Research Articles

Kinetics of CO2 absorption in N-Methyldiethanolamine solution promoted by potassium sarcosine

Potassium sarcosine (KSar) shows promise as an effective co-promoter of N-methyldiethanolamine (MDEA), a tertiary amine known for its high CO2 absorption capacity but relatively slow kinetics. This study investigated the CO2 absorption kinetics in a KSar + MDEA + H2O solution using the pressure-decay technique in a stirred cell reactor. The experiments were performed at temperatures ranging from 303.15 K to 333.15 K, with varying concentrations of KSar (ranging from 3% to 15% by weight), while keeping the MDEA concentration constant at 20% by weight. Furthermore, the study involved assessing the physicochemical and mass transfer properties and comparing them to those of a solution containing MDEA (30 wt%) + H2O solution. Properties like density, viscosity, Henry's constant (HN2O), and the physical mass-transfer coefficient of the liquid phase (kl) were measured and applied to analyze CO2 absorption kinetics. The overall reaction rate constant (kOV) was assessed using both termolecular and zwitterion mechanisms within a pseudo-first-order reaction regime. Additionally, kOV was estimated via correlated Arrhenius power law expression of the individual rate contributions of CO2−MDEA, CO2–H2O, and CO2−KSar. The calculated kOV values were found to closely match the experimental data, with absolute average relative deviations (AARD) of 4.53% and 3.03% for the termolecular and zwitterion models, respectively. The experimental results clearly showed that the rate of CO2 absorption, represented by kOV, can be significantly enhanced by adding a small amount of KSar into the MDEA + H2O solution.

Designing back propagation neural network to predict CO2 mass transfer enhancement factor of TiO2-MEA/MDEA blended amine nanofluids

This study presented a novel methodology to predict the CO2 absorption enhancement performance of TiO2-Monoethanolamine/Methyl diethanolamine (MEA/MDEA) blended amine nanofluids using back propagation neural network (BPNN) model in artificial neural networks. The absorption enhancement factor of TiO2-MEA/MDEA nanofluid were determined experimentally by a two-step method with various nanoparticle solid contents (0.4–1.4 ​g/L). The results showed that the enhancement factor was firstly increased and then decreased with the rising nanoparticle solid content, and the extreme point appeared at 0.6 ​g/L. Based on the experimental data, a relevant empirical formula and a back propagation neural network (BPNN) model were used to estimate the enhancement factor of nanofluid and both exhibited good applicability. Additionally, an optimization model incorporating genetic algorithm, particle swarm algorithm and adaptive learning rate (C-BPNN) was also proposed to estimate the enhancement factor. Compared with the empirical formula and BPNN, C-BPNN exhibited a higher prediction accuracy (all data R2 ​= ​0.9966) and a faster prediction rate. The weight analysis of key parameters (nanoparticle solid content, concentration of MEA and MDEA) showed that the relative importance of nanoparticle solid content was foremost (42.63%) in the absorption enhancement process. All these results indicate that the neural network can provide a guiding role for the research in the field of nanofluid transfer.

Enhancement of mass transfer performance by nanoparticles during the CO2 absorption with MDEA solution in a randomly packed tower

AbstractIn this study, the mass transfer enhancement by nanoparticles during CO2 absorption process with MDEA solution in a randomly packed tower was investigated. The mass transfer performance of MDEA solution with and without nanoparticles were quantified and analyzed in terms of the volumetric overall mass transfer coefficient (KGav). An enhancement factor (E), defined as the ratio of KGav with and without nanoparticles, was further introduced to evaluate the enhancement effect of the addition of nanoparticles. The effects of TiO2 nanoparticle concentration, MDEA concentration, liquid flow rate, liquid temperature, inert gas flow rate, and CO2 loading on KGav and E were systematically studied in the packed tower. It is found that the maximum value of E can reach 1.37, when the nanoparticle concentration is 0.09wt%, the liquid flow rate is 21.22 m3/m2·h, the liquid temperature is 27°C, the MDEA concentration is 30%, the gas flow rate is 7.58 kmol/m2·h and the CO2 loading is 0.2 mol CO2/mol MDEA. Usually, the KGav of the MDEA nanofluids can be increased by 10–37% in a randomly packed tower compared to that of the MDEA solution, which is consistent with the results from the bubbling reactors. However, when the CO2 loading of absorption exceeds 50%, E becomes less than 1.0, which means that high CO2 loading inhibits the enhancement effect of nanoparticles. In order to predict the mass transfer performance of MDEA nanofluid, a formula correlating E and various dimensionless operating parameters (i.e. , , and ) is proposed and fitted with an average absolute deviation of 14%. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd.

Pre-combustion CO2 capture using amine-based absorption process for blue H2 production from steam methane reformer

A novel pre-combustion CO2 capture process using methyl diethanolamine with piperazine (MDEA/PZ) was investigated for the production of blue H2 from a steam methane reformer (SMR). A sensitivity analysis was performed at various operating parameters (such as MDEA or PZ concentration, flash drum pressure, CO2 loading in a lean-amine solvent, and CO2 removal efficiency) using a validated rate-based model. The energy consumption to capture CO2 from SMR gas at 21 bar was evaluated, including the compression energy (up to 30 bar) for the dehydration of captured CO2. For 90% and 95% CO2 removal efficiency, reboiler duties were 1.318 GJ/tonCO2 and 1.364 GJ/tonCO2, and CO2 compression works were 11.673 kW/molCO2 and 11.615 kW/molCO2. The results indicated more than 40% lower reboiler duty than the energy consumption of conventional CO2 capture processes in post-combustion. Subsequently, artificial neural network model (ANN)-based optimization using the differential evolution method was performed. The developed ANN-based optimization suggested the possibility of additional 0.3 % reduction in the equivalent work at a low computational cost. The results indicated that the developed pre-combustion CO2 capture for a SMR was highly competitive in industrial applications. Moreover, the H2 mixture produced at 21 bar is beneficial for a H2 recovery unit because of no need for additional compression energy. Therefore, the MDEA/PZ-based absorption process can effectively contribute to centralized or semi-central blue H2 production from a SMR. This study provides a guideline for the feasible optimization and control of the CO2 absorption process at high feed pressures.

CO2 absorption/desorption rates in aqueous DEEA/MDEA and sulfolane-contained hybrid solutions: effects of physical properties and reaction rate.

The rates of CO2 absorption into fresh and regenerated aqueous solutions of N,N-diethylethanolamine (DEEA), N-methyldiethanolamine (MDEA), and their mixture with sulfolane are investigated in a batch stirred cell reactor. The data are obtained in the temperature range of 293.15-313.15K, pressures up to 800kPa, and different concentrations of alkanolamines and sulfolane. The diffusion coefficients and Henry's law constants for all the solutions are obtained. The absorption rate of DEEA solutions increased by increasing component concentrations and pressure, but the effects of temperature on the absorption rates of hybrid and aqueous DEEA solutions are different. Comparison of absorption rates in aqueous and hybrid solutions under the same conditions can determine the role of sulfolane as the physical solvent. It has been found that sulfolane acts as an effective absorption activator in the hybrid DEEA solutions. However, in the MDEA solutions, in all experimental conditions except for high pressure ([Formula: see text] 400kPa) and certain MDEA concentration (20 wt%), sulfolane has a negative effect on the absorption rate. The absorption rates of regenerated aqueous DEEA solutions are in the range of 50.5-87.7% of fresh ones, while these values for the hybrid DEEA solution are in the range of 75-90.5%. These values for the aqueous and hybrid MDEA solutions are almost equal. Based on the values of Hatta number and enhancement factor, the CO2 absorption regime in the DEEA solutions is determined as the fast second-order reaction. The absorption rate can be interpreted considering the tradeoff between kinetics and thermodynamics of CO2 absorption in the aqueous and hybrid DEEA/MDEA solutions. The desorption rates in hybrid DEEA/MDEA solutions are higher than those in aqueous solutions.

Study on heterogeneous catalytic wet air oxidation process of high concentration MDEA-containing wastewater

High concentration N-methyldiethanolamine (MDEA)-containing wastewater with strong alkaline, high chemical oxygen demand (COD), and toxic organics, cannot be directly treated by biochemical process. In this paper, effect of operation parameters (temperature, reaction pressure and residence time) on removal ratio of COD and MDEA was investigated by catalytic wet air oxidation (CWAO) over commercial activated carbon (AC). The degradation pathway of MDEA in the CWAO was proposed. The results showed that the concentration of MDEA, COD, total organic carbon (TOC), and total nitrogen (TN) were 18.92, 61.2, 21.34 and 5.65 g·L−1, respectively. The contribution rate of MDEA concentration to COD in the wastewater reached up to 89.8%. The removal ratio of MDEA and COD exceeded 98% and ∼90% at temperature of 230 °C, reaction pressure of 5.0 MPa and residence time of 90 min for 168 h continuous running, respectively. The surface carboxylic acid groups of AC played a key role in the formation of hydroxyl radicals (·OH), due to the O2 was adsorbed by the carboxyl groups on the surface of AC to form ·OH, and the ·OH then attacked the CN bond of the MDEA to generate other intermediate products, and then these intermediate products was further oxidized to NH4+, CO2 and H2O. This work provides a promising pretreatment technology of high concentration MDEA-containing wastewater.

Electrolyte solution of MDEA–PZ–TMS for CO2 absorption; response surface methodology and equilibrium modeling

This research aims to study the performance of MDEA–PZ–TMS​ blends solution in CO 2 reactive absorption via a stirrer reactor. Two modeling approaches of the response surface methodology (RSM) and equilibrium modeling using the modified Pitzer model were employed to predict process behavior at the equilibrium state. Five independent variables of temperature, pressure, MDEA, PZ, and TMS concentrations were considered in the ranges of 20–75 °C, 2–8 bar, and 1–5wt%, respectively. Based on the RSM modeling, both CO 2 loading and absorption percentage were simultaneously maximized with the degree of importance of 1 and 5, respectively, at operating conditions of 3.5 bar, 32.5 °C, 2wt% TMS, 4wt% MDEA, and 4wt% PZ concentrations. In the equilibrium modeling, the equilibrium CO 2 loading was predicted with an average relative error of 4.85% for all empirical data. The present modeling can be applied to various CO 2 absorption processes using different electrolyte solutions. • The CO 2 reactive absorption process is examined by MDEA-PZ-TMS blends solution. • The process is modeled by response surface methodology and equilibrium modeling. • Pressure, temperature, MDEA, PZ, and TMS concentrations are optimized by RSM. • Equilibrium modeling error is less than 5% makes suitable for different solvents. • The concentrations of all existing species in the electrolyte system are predicted.

Cost-Effective Nanoporous Hypercross-linked Polymers Could Drastically Promote the CO2 Absorption Rate in Amine-Based Solvents, Improving Energy-Efficient CO2 Capture

Energy-efficient solvents with favorable thermodynamic properties that offer significantly low regeneration energy to the state-of-the-art CO2 capture technologies are typically limited by slow reactivity with CO2. To compensate for low absorption rates, herein, we report that the nonporous hypercross-linked polymeric (HCP) networks as rate promoters are capable of drastically accelerating CO2 absorption in N-methyldiethanolamine (MDEA) sorbents. It is a new topic toward the application of HCPs. Two HCPs were synthesized from cost-effective monomers: polystyrene (HCP-S) and benzene (HCP-B), and then the novel slurry solvents were prepared by suspending HCP-S and HCP-B in MDEA solutions. Benefiting from the inherent properties, HCP-S and HCP-B increased the overall rates of CO2 absorption in the MDEA solution by 253 and 130%, respectively, compared to the blank MDEA. The effect of temperature and amine concentration on the promoting performance of HCP-B was investigated. HCP-B promotes CO2 sorption in the whole temperature range from 25 to 80 °C, and at 2 to 4 molar concentrations of MDEA. The promoting effect of HCP-B was also observed in the DEA solvent, demonstrating that it is not unique to MDEA. Moreover, 13C NMR analysis was used to confirm the promoting effect of the network on CO2 sorption, and a possible mechanism was investigated.

Packed column modelling and experimental evaluation for CO2 absorption using MDEA solution at high pressure and high CO2 concentrations

N-Methyl-diethanolamine (MDEA) is a potential solvent to capture CO2 at high-pressure and high CO2 concentration conditions due to its high CO2-loading capacity and the pressure-driven nature of CO2-MDEA reaction equilibrium. However, no studies have been reported on packed column modelling and experimental evaluation of CO2 absorption process using MDEA solvent for high pressure and high CO2 concentration conditions. Therefore, this study presents the experimental evaluation and modelling of CO2 absorption in the packed column using the MDEA solution at these extreme conditions. The effects of amine concentrations (0.83–3 M), liquid flowrates (3.61–5.42 m3/m2h) and feed CO2 concentrations (35–45%) have been studied on the CO2 removal efficiency at 40 bar total pressure and 1.8 kg/h gas flowrate. Highest CO2 removal efficiency is found to be 61.7% for 35% CO2 at 5.42 m3/m2h and 2 M MDEA solution. Further, a rate-based model is developed by accounting for sequential chemical reactions and associated mass transfer resistances occurring at low (<1 molCO2/molMDEA) and high CO2 (>1 molCO2/molMDEA) loadings. The developed model has been successfully validated with the experimental data. In a parity plot of CO2 concentration profiles along the column height, R2 is found to be 0.97. Further the model is applied to forecast CO2 absorption performance over the extended process conditions. It is found that 98.2% CO2 removal efficiency can be achieved for 40% CO2 at the conditions of 333.15 K temperature, 4 M MDEA concentration, and 5.42 m3/m2h liquid flowrates.

Application of ePC_SAFT-MB EoS in prediction of VLE for CO2+MDEA+H2O ternary and H2O+MDEA+CO2-CH4 quaternary mixtures

The present study aims to implement an electrolyte EoS developed in our previous work [A. Raeispour Shirazi, M. N. Lotfollahi, Fluid Phase Equilib., 502 (2019) 112289] to model the vapor-liquid equilibria (VLE) of CO2 solubility in aqueous N-methyldiethanolamine (MDEA) solution (CO2+MDEA+H2O ternary mixture) as well as H2O+MDEA+CO2-CH4 quaternary mixture. The proposed electrolyte PC-SAFT+MSA+Born equation of state ((ePC_SAFT-MB) consists of PC-SAFT equation of state, the mean spherical approximation (MSA) term and the Born term. First, an appropriate association scheme for water is specified via performing VLE calculations for H2O-CO2 binary mixture and without any adjustment in binary interaction parameter (BIP). By determining the proper association scheme for water (4C), the BIPs of H2O-CO2, MDEA-CH4 and CH4-H2O binary mixtures are adjusted with binary VLE experimental data. In what follows, the nonelectrolyte PC-SAFT EoS is applied considering the obtained BIPs to predict 162 selected data points of bubble pressure for H2O-MDEA-CO2 ternary system in a wide range of temperature (298-413 K), MDEA concentration (18.7-48.8 wt.%) and CO2 loading (0.0001-1.5). The average absolute relative deviation (AAD%) for the calculation results is obtained 25.9%. In order to consider the ions interactions in the solution and to improve the precision of calculations, Born and MSA contributions are added to PC-SAFT EoS. By adjusting two BIPs (kMDEAH+−−CO2and kMDEAH+−HCO3−) and without any readjustment of other BIPs, the AAD% is obtained 15.3%. Finally, the obtained BIPs between the molecular and ionic species for proposed ePC_SAFT-MB EoS are employed to predict the VLE of H2O-MDEA-CO2-CH4 quaternary mixture without any readjustment in BIPs. For this case, the AAD% of 28.05% indicates the reliability of proposed ePC_SAFT-MB EoS for the prediction of H2O-MDEA-CO2-CH4 quaternary VLE results.

High CO2 absorption in new amine based-transition-temperature mixtures (deep eutectic analogues) and reporting thermal stability, viscosity and surface tension: Response surface methodology (RSM)

To study CO2 capture potential, three types of transition-temperature mixtures (TTMs) were prepared by mixing ethyltriphenylphosphonium bromide (MTPPB) as a hydrogen bond acceptor (HBA) and n-methyl diethanolamine (MDEA) as a hydrogen bond donor (HBD) in different molar ratios (1:7, 1:10 and 1:16). Fourier transform infrared spectroscopy (FT-IR) results showed that TTMs have almost similar spectra to their HBD (MDEA) with different levels of transmittance and exhibit similar behavior. From the experimental results, it was found that the thermal stability, viscosity and surface tension of TTMs decreased as the concentration of MDEA in the mixture increased. According to response surface methodology (RSM) models and analysis of variance (ANOVA), temperature and molar ratio had a great effect on the viscosity and surface tension of TTMs. Finally, it was found that CO2 solubility in TTMs (at 303.15 K at pressure up to 1.35 MPa) was enhanced as the MDEA quantity increased in the mixture up to 1:10 mol ratio. However, by increasing MDEA concentration to 16:1 mol ratio, there was a decreasing trend in the CO2 solubility data. Also, all TTMs, particularly TTM containing 10:1 mol MDEA (MTPPB-MDEA 1:10) exhibited an equilibrium loading capacity approaching 1 mol CO2 per mole solvent at high pressure, revealing their high potential for CO2 capture. A comparison showed that the CO2 solubility in the studied solvents was higher than that of existing deep eutectic solvents (DESs) and other TTMs as well as several ionic liquids (ILs) to date. To the best of our knowledge, this is the first study to report the CO2 solubility in phosphonium-base TTMs containing MDEA.

CO2 Reactive Absorption into an Aqueous Blended MDEA and TMS Solution: Experimental and Modeling

In this research, the significant environmental process of CO2 capture is investigated into an aqueous blended MDEA + TMS solution using a stirrer reactor experimentally and numerically. The experiments were designed based on the response surface methodology (RSM) under operating conditions of a pressure range of 2–8 bar, a temperature range of 20–70 °C, MDEA, and TMS concentration range of 10–20 wt%. The results indicated that by enhancing the initial pressure from 3.5 to 8 bar, the equilibrium CO2 loading increases by 17.8%. Based on RSM and central composite design method, the maximum values of CO2 loading and absorption percentages were 0.308% and 72.73%, respectively, at appropriate conditions of the temperature of 32.5 °C, the pressure of 3.5 bar, and MDEA and TMS concentrations of 12.5 wt%. A new relation for CO2 loading was correlated with a correlation coefficient of 0.994, as a function of studied independent variables.

Comparative kinetics of homogeneous reaction of CO2 and unloaded/loaded amine using stopped-flow technique: A case study of MDEA solution

The stopped-flow technique was applied for the investigation of kinetics of CO2 absorption into loaded MDEA solution over the range of MDEA concentration of 0.4 to 1.0 kmol/m3, CO2 loading of 0.14 to 0.17 mol CO2/mol amine and the temperature of 293 to 308 K. The kinetics of unloaded MDEA was also investigated for the comparison and a huge difference of results which should be equal theoretically was indicated between loaded and unloaded systems. Then, the effect of CO2 loading on the kinetics was studied. As the loading increases, there is a turning point around loading of 0.10, below which the overall reaction constant decreases strongly. It was found that contribution of hydroxyl is a crucial to overall reaction rate constant and cannot be ignored and the influence of reverse reaction of MDEA and CO2 can be ignored. The kinetics of loaded system obtained in this work was modified and interpreted well by the base-catalyzed mechanism with AARD of 6.29% and compares favorably with literature using gas-liquid apparatus. The kinetics of unloaded system in this work is approximately twice as that of literature and loaded system. This work provided literature review and interpretation of MDEA-CO2-H2O and is hopeful to shed light on kinetic study of CO2 absorption in tertiary amine using stopped-flow apparatus.

Modeling H2S solubility in aqueous N-methyldiethanolamine solution using a new ePC_SAFT-MB equation of state

Perturbed chain statistical associating fluid theory (PC-SAFT) equation of state (EoS), mean spherical approximation (MSA) term and Born term are combined and proposed as a new electrolyte equation of state (ePC_SAFT-MB EoS) to model the solubility of H2S in aqueous N-methyldiethanolamine (MDEA) solutions in a wide range of temperature, pressure, MDEA concentration, and H2S loading. In order to find the best association schemes (2B, 3B and 4C) for H2O, MDEA and H2S in PC-SAFT EoS, different association schemes are considered for each one of the components in the wide range of temperature and pure parameters are determined. The binary interaction parameters (BIP) for H2O + H2S and MDEA + H2O binary systems are adjusted in the VLE calculation for different association schemes. The best result with minimum average absolute relative deviation percent (AAD%) of 2.21 and 2.72 are obtained with considering the 4C, 4C and 3B association schemes for MDEA, water and H2S, respectively. By using the obtained BIPs, 277 data points of the bubble pressure for H2O + MDEA + H2S system are predicted by PC-SAFT EoS with the AAD% of 25.5. To improve the accuracy of PC-SAFT EoS, the Born and MSA terms are added to PC-SAFT EoS. The BIPs between the ion-ion and molecules-ions are adjusted by the bubble pressure calculation algorithm using 277 experimental data points. Very good results with the AAD% of 18.6 are obtained by adjusting the binary parameters (MDEAH+−MDEA,MDEAH+−H2O,MDEAH+–H2S and MDEAH+−HS−) in H2O + MDEA + H2S ternary system. Finally, to investigate the predictive ability of the proposed ePC_SAFT-MB EoS, it is employed to model the selected 44 solubility data points of H2O + MDEA + H2S system without further adjustment for model parameters. The value of AADs% is obtained about 30.0 for the H2 S partial pressure, which shows the predictive ability of the proposed model.

Simultaneous solubility measurement of (ethyl mercaptan + carbon dioxide) into the aqueous solutions of (N-methyl diethanolamine + sulfolane + water)

Removal of contaminants such as acid gases, i.e. CO2, H2S, and sulfur components is the main step in a natural gas treatment process. In this study, the simultaneous solubility of carbon dioxide and ethyl mercaptan (ETM) in the different mixtures of the chemical and physical solvents are measured using a static high-pressure equilibrium cell at (328.15, 343.15 and 363.15) K within the total pressure range of (65–1235) kPa. The measurements are carried out for the three different blends of sulfolane-N-methyldiethanol amine–water with the mass compositions of (10.0–40.0–50.0) wt.%, (20.0–40.0–40.0) wt.% and (20.0–30.0–50.0) wt.%, respectively. The solubility results are shown as the partial pressures of CO2 and ETM versus the carbon dioxide loading (moles CO2 per total moles of amine) and ETM mole fraction, respectively. The influence of sulfolane concentration is also investigated on the solubility of ethyl mercaptan and CO2 loading separately. Moreover, the influence of MDEA concentration as a chemical solvent is studied on the solubility of CO2 and ethyl mercaptan. By comparing the solubility of carbon dioxide in the same systems with/without the presence of ethyl mercaptan, it was found that the presences of ethyl mercaptan increases the carbon dioxide loading and by enhancing the gas partial pressure both the physical and chemical solubility intensify. Finally, using the Clausius-Clapeyron equation, the enthalpy of heat absorption for CO2 is calculated.

CO2 capture from water-gas shift process plant: Comparative bench-scale pilot plant investigation of MDEA-PZ blend vs novel MDEA activated by 1,5-diamino-2-methylpentane

This research is a bench-scale pilot plant investigation of novel amine solvent blend containing MDEA and 1,5-diamino-2-methylpentane (DA2MP) for CO2 capture from water-gas shift process plant (H2 production). The CO2 concentration used in this study (50 vol.% CO2 with N2 balance) is similar to that of the water-gas shift product gas. The CO2 capture performance of the MDEA-DA2MP blend was compared to the standard 3 kmol/m3 MDEA-0.5 kmol/m3 PZ blend (34.4 wt.% MDEA-5 wt.% PZ). The low concentration of PZ in this study is because of the chemical toxicity of PZ and possible precipitation at medium to high concentration. The MDEA concentration in the MDEA-DA2MP blend was kept constant at 3 kmol/m3 while the DA2MP was varied from 0.5 kmol/m3 (6.75 wt.%) to 1.5 kmol/m3 (20.3 wt.%). The pilot plant analysis was performed at a gas flow rate, amine solution flow rate, and reboiler temperature of 14 SLPM, 50 mL/min, and 120 °C respectively. Pilot plant results revealed that the higher MDEA-DA2MP blend concentration possesses higher CO2 capture efficiency (up to 24%), higher CO2 absorption rate (up to 23.5%) and higher absorber mass transfer coefficient (up to 23.9%) compared to the MDEA-PZ blend. It was also discovered that the high MDEA-DA2MP concentration has lower regeneration energy (up to 25.4%), lower initial amine solution utilized (up to 20.5%), lower desorber mass transfer coefficient (up to 32.5%) compared to the MDEA-PZ blend. However, the optimal amine concentration is the 3 kmol/m3 MDEA-1 kmol/m3 DA2MP blend. Overall results show that the MDEA-DA2MP blend can offer a cost-effective and energy efficient CO2 capture compared to MDEA-PZ.

Implementation of electrolyte CPA EoS to model solubility of CO2 and CO2 + H2S mixtures in aqueous MDEA solutions

Abstract The electrolyte version of SRK plus association equation of state (eSRK-CPA EoS) was employed to correlate CO2 solubility in MDEA aqueous solutions. The applied model comprises the classic form of CPA EoS including SRK EoS plus Wertheim association term in addition to MSA theory and Born terms so that the two last terms are responsible for the long-range interactions. A reaction-containing bubble pressure computation technique comprising two nested loops was utilized to model the systems. The internal loop, calculates the liquid phase concentrations via reaction, mass and charge balance equation solving, whereas, the vapor phase concentrations will be obtained in the external one. 470 experimental data were used to correlate binary subsystems and the H2O + MDEA + CO2 ternary system. Since, there not exist any binary VLE data for MDEA + CO2 subsystem, two fitting scenarios were applied. At the first scenario, the binary interaction parameter was assumed equal to zero, while, in second approach the parameter was obtained through ternary system correlation. Both scenarios show very good accuracy in that the Absolute Average Deviation percentages (AAD) obtained were 19.12% and 18.85%, respectively. Also, to show the efficiency of the used model, a comparison between our results and those of the best-known models was made. Finally, having model parameters for H2S solubility from our previous work [A. Afsharpour, Petroleum Science and Technology 35 (3) (2017) 292-298], simultaneous solubility of CO2 + H2S mixtures in MDEA solutions was predicted using the eSRK-CPA EoS with no new optimizable parameters. As the results show, the applied model has a good performance for correlation and prediction of acid gas solubility in a wide range of pressures, temperatures, acid gas loadings, and MDEA concentrations.

Modified nonelectrolyte Wilson-NRF: A new model for strong and weak electrolyte solutions

In this work, the nonelectrolyte Wilson-NRF model has been modified and a new model composed of a modified nonelectrolyte Wilson-NRF (m-Wilson-NRF) equation and the Pitzer-Debye-Hückel equation has been used to represent thermodynamics properties of strong and weak electrolyte solutions. In the first attempt, the present model is applied to correlate activity coefficients of various aqueous solutions of salt at 25 °C and 1 bar as strong electrolyte systems. Also, the osmotic coefficients of the binary and ternary electrolyte solutions are well predicted using the present model. In following, as weak electrolyte systems the solubility of acid gases such as CO2 and H2S in aqueous N-methyldiethanolamine (MDEA) solutions have been represented by the new model in a wide range of temperature, MDEA concentration and partial pressures of acid gases. Comparisons between the results of the new model with other electrolyte models confirm the good capability of the new equation for strong and weak electrolyte solutions.

Absorption of carbon dioxide in aqueous MDEA solution coupling dust suppression under atomization

ABSTRACTLarge amounts of CO2 and dust particles coming from power plant flue need to be captured and removed before flue is discharged into the air. In present work, absorption of carbon dioxide in aqueous N-methylidiethanolamine (MDEA) solution coupling dust suppression has been studied in an atomization absorption column, with MDEA concentrations ranging from 0.1 to 0.5mol/L, and with atomization frequencies ranging from 50 to 80 HZ. The obtained experimental results show that absorption rate of CO2 in aqueous MDEA solution can be enhanced when the absorption process couples a dust suppression one under the condition of atomization. The reason for it is attributed to the adsorption of droplets on the solid particles which restrains the amount of entrainment and makes more droplets contact with gas so as to increase effective mass transfer area, thus resulting in the increase of CO2 absorption rate. The range of obtained enhancement factor is from 1.1 to 1.7. Mass transfer enhancement factor increases with the increase of MDEA concentration and atomization frequency at a certain range. Effective mass transfer areas and entrainment ratios suppressed have been calculated based on theoretic research. The results calculated agree with our experimental phenomena, and support the enhancement mass transfer mechanism proposed.

Heat Transfer Characteristics of CO2 Desorption from N‐Methyldiethanolamine Solution in a Microchannel Reactor

AbstractThe heat transfer performance and energy consumption of CO2 desorption from rich N‐methyldiethanolamine (MDEA) solution were determined experimentally in a straight microchannel reactor. Nucleate boiling was found to be the dominant heat transfer mechanism in this experiment. The heat transfer coefficients were strongly dependent on the heat flux. The solution flow rate was the most influential factor on the heat flux, followed by desorption temperature, MDEA concentration, and CO2 loading. In addition, an empirical correlation was proposed to predict the experimental heat transfer coefficients.