Solutions Of N-methyldiethanolamine Research Articles

Preparation of “dry water”-type liquid marbles with enhanced mechanical stability and CO2 capture performance

Liquid marbles(LMs) are formed by encapsulating liquid with hydrophobic particles showed potential application in capturing CO2. However, conventional LMs are mostly millimeter scale and easily deformed by extrusion. This study aimed to enhance the mechanical stability by controlling the particle size to prepare “dry water” type LMs (DWLMs). The N-methyldiethanolamine (MDEA) solution was used as the core in constructing DWLMs, and SiO2/graphene(GPE) was used as the shell material. The incorporation of GPE can endow DWLMs with photothermal conversion properties, with a particle size distribution around 100 ∼ 250 μm occupying the largest volume fraction. These DWLMs exhibited good flow ability and mechanical stability. Moreover, the effects of MDEA concentration, and content of SiO2/ GPE on the preparation of DWLMs were investigated. Under an illumination intensity of 1 × 106 Lux, the temperature of DWLMs reached above 95 °C. Subsequently, the absorption performance was examined by a fixed-bed absorption tower, and it was found that decreasing the droplet size can increase the gas–liquid mass transfer area to reduce the mass transfer resistance. The height of the fixed bed constructed by DWLMs was higher than 7 cm, and the bottom particles can still maintain stability without agglomeration and blocking the supporting mesh. The breakthrough point (t0.5 and t0.95) of large-DWLMs (L-DWLMs) were greater than that of tiny-DWLMs (T-DWLMs). The absorption kinetics have validated that chemisorption is the primary mode of CO2 absorption. In desorption process, the results showed that the desorption of CO2 was realized by photothermic desorption, and the desorbed DWLMs were regenerated and recycled, which could prevent the corrosion of the device as well as utilize the energy provided by the sunlight.

Continuous biomethanation of flue gas-carbon dioxide using bio-integrated carbon capture and utilization

Biomethanation of carbon dioxide (CO2) from flue gas is a potential enabler of the green transition, particularly when integrated with the power-to-gas chain. However, challenges arise in achieving synthetic natural gas quality when utilizing CO2 from diluted carbon sources, and the high costs of CO2 separation using amine-based solutions make large-scale implementation unfeasible. We propose an innovative continuous biomethanation system that integrates carbon capture and CO2 stripping through microbial utilization, eliminating expenses with the stripper. Stable continuous biomethane production (83–92 % methane purity) was achieved from flue gas-CO2 using a biocompatible aqueous n-methyldiethanolamine (MDEA) solution (50 mmol/L) under mesophilic and hydrogen-limiting conditions. MDEA was found to be recalcitrant to biodegradation and could be reused after regeneration. Demonstrating the microbial ability to simultaneously strip and convert the captured CO2 and regenerate MDEA provides a new pathway for valorization of flue gas CO2.

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.

Multi-stage solvent circulation absorption enhancement: System optimization for energy-saving CO2 capture

One of the major barriers in industrial applications of solvent-based CO2 capture is the significant energy consumption required for absorbent regeneration. In this study, a novel multi-stage circulation (MSC) CO2 absorption process was proposed, which implemented independent regulation of each stage, resulting in enhanced CO2 capture performance and reduction of CO2 regeneration duty. The MSC absorber was designed with four stages from bottom to top, each serving distinct functions, including CO2 enrichment, CO2 main absorption, CO2 capture efficiency enhancement and aerosol capture. Simulation of the MSC process achieved a rich ethanolamine (MEA) solvent CO2 loading of 0.512–0.570 mol CO2/mol amine, which was 8.1 %–9.9 % higher than typical process. The effects of test duration, amine solution flow rates, reaction temperatures and inlet CO2 concentrations on CO2 absorption performance were studied using the MSC experimental platform. The CO2 regeneration duty reduced by over 13.2 % of the MSC process compared to a typical process using 25 wt% MEA solution and by over 22.9 % using piperazine (PZ)/N-methyldiethanolamine (MDEA) solution. Furthermore, the utilization of NH3/K2CO3 solution achieved an energy consumption reduction of over 41.7 %, resulting in a CO2 regeneration duty as low as 2.02 GJ/t CO2 (1.84 GJ/t CO2, subtracting the heat loss). Meanwhile, potential strategies for optimizing parameters of MSC process were proposed to address the complex and volatile conditions.

Modeling and simulation of an enzymatic reactive absorption process in the internal zone of a rotating packed bed apparatus

A kinetic model of carbon dioxide absorption within an internal of a rotating packed bed (RPB) apparatus was developed using experimental data. Kinetics of the chemical reaction between carbon dioxide and aqueous solution of N-methyldiethanolamine with and without carbonic anhydrase additive were determined in a flat phase contact surface batch stirred reactor and implemented into the model. Overall pressure drop and absorption efficiency within a metal foam internal were modeled and compared with experimental measurements. The model's predictions of CO2 absorption and pressure drop fit mostly within 20% error range. Validated model served as a tool for further absorption process simulations and sensitivity analysis.

Catalytic ozonation of N-methyldiethanolamine over mixed oxides derived from Mg/Fe-LDH.

The aim of this study was to evaluate the efficiency of catalytic ozonation to increase the degradation of aqueous N-methyldiethanolamine (MDEA) solutions, using two lamellar double hydroxides, namely MgxFe-LDH with x = Mg/Fe = 2, 3, were synthesized by the simple and rapid co-precipitation method. Then, the obtained materials were calcined at 400 °C for 6 h. The calcined products were respectively designated as HTcMg2Fe and HTcMg3Fe, and characterized by powder X-ray diffraction (XRD), N2 physisorption (BET), Fourier transform infrared spectra (FT-IR), and scanning electron microscopy (SEM). The powders produced were used in the ozonation reaction to remove MDEA from aqueous solutions. Experimental results showed that the highest MDEA removal efficiency is in the catalytic ozonation process. Under the optimal conditions for heterogeneous catalytic ozonation of MDEA: initial concentration of 4 Wt% MDEA, 30 °C, catalyst mass of 30 mg/100 ml solution, and contact time of 60 min. The results showed the highest percentage of COD removal, which was up to 80.76% for HTcMg2Fe higher than that of HTcMg3Fe 80.36%.

Metal Oxides Enhance the Absorption Performance of N-Methyldiethanolamine Solution during the Carbon Dioxide Capture Process.

Fly ash from coal-fired power plants can enter chemical absorbents along with flue gas. Silica and metal oxides are the main components of fly ash. To explore the effect of the metal oxides on absorbents, we analyzed the integrated CO2 absorption-desorption process using N-methyldiethanolamine (MDEA) as the standard and an amine absorbent after adding different metal oxides. The effects of each metal oxide on CO2 capture by the MDEA solution, including CO2 reaction heat, absorption rate, cyclic loading, and carbonation rate, were assessed. It was found that supplementation with appropriate calcium oxide and magnesium oxide proportions accelerates the CO2 absorption rate and shortens the saturation time of the MDEA solution by 9%-17%. Magnesium oxide and calcium oxide were precipitated as carbonates during absorption. The CO2 reaction heat of the MDEA solution increased by 95% after adding magnesium oxide, thereby significantly increasing the energy consumption of the desorption process. On the basis of the experimental studies, the increase in CO2 absorption rate by MDEA after adding MgO and CaO may be mediated through two different mechanisms.

Utilization of an innovative sono-microreactor for CO2 stripping from aqueous methyldiethanolamine solution

In the present study, a novel designed ultrasound-equipped microchannel reactor has been used to improve the CO2 desorption process from aqueous N-methyldiethanolamine (MDEA) solutions. CO2 desorption rate for a microreactor without ultrasound irradiation was compared with an ultrasound-equipped one at various temperatures, flow rates, and ultrasound powers. The results revealed that ultrasound vibrations could facilitate CO2 desorption and cause a significant increase in the rate of that through generation of cavitation bubbles and turbulence. Evaluation of energy and mass transfer characteristics was performed; 37.8% energy saving and 144.2% increase in mass transfer coefficient was obtained using ultrasound at its maximum power compared to microreactor without ultrasound irradiation. Also, comparisons between the designed sono-microreactor and conventional methods for CO2 desorption were performed in terms of desorption energy consumption and mass transfer coefficient, indicating 40.9% energy saving compared to 30 wt% MEA benchmark process and 160 times increase in mass transfer coefficient. Due to its high performance in terms of energy saving and mass transfer enhancement compared to the conventional method, the newly designed sono-microreactor can be introduced as a highly efficient technique for solvent regeneration.

Reactive absorption of carbon dioxide in aqueous n-methyldiethanoloamine solutions catalysed with carbonic anhydrase in a rotating packed bed (RPB)

Studies on absorption of carbon dioxide in the rotating packed bed (RPB) were performed with two different types of metal foam packing, and two types of liquid absorbents: 30 wt.% solutions of N-methyldiethanolamine in water, with and without the addition of 0.2 wt.% of carbonic anhydrase. Different rotation speeds, gas flow rates and liquid flow rates were investigated. Results were evaluated using normalized interphase molar flow. Increased rotation speeds and phase flow rates positively affected the interphase mole flow of CO2, but high gas and liquid flow rates limited the operating window due to flooding. The addition of anhydrase significantly increased the absorption efficiency, but also narrowed the operating window. The addition of carbonic anhydrase resulted in an increase in the degree of absorption 2–5-fold for the analogous gas and liquid flow rates, compared to the amine without the biocatalyst. The highest normalized mole flow of 66.3 kmol h−1m−3 was observed for NC1116 packing with the solvent containing anhydrase, while the highest normalized mole flow for solvent without catalyst was 26.2 kmol h−1m−3. The results were compared with analogous absorption processes in a packed column and showed up to 50-fold higher mass transfer efficiency.

Numerical simulation of galvanic corrosion and sacrificial anode protection of U-tube Material of kettle reboiler in N-Methyldiethanolamine solution

Numerical simulation of galvanic corrosion and sacrificial anode protection of U-tube Material of kettle reboiler in N-Methyldiethanolamine solution

Thermodynamic modeling of CO2 solubility into an aqueous solution of N-methyldiethanolamine using EoS/GE approach and different Alpha-functions

Carbon dioxide is among the most crucial impurity in natural gas and must be removed from the gas before any use to avoid environmental damage and problem. The CO2 absorption with the alkanolamine process is widely used for this purpose. This study has been dedicated to modeling the aqueous CO2+ N-methyldiethanolamine (MDEA) system's vapor-liquid equilibrium within the temperature range 297.7-413.15 K and gas loading in the range of 0.000249-1.507 CO2 mole/MDEA mole. In combination with the Wong-Sandler mixing rule and the NRTL activity coefficient model, the Peng-Robinson equation of state has been applied as an EOS/GE approach for modeling of vapor-liquid equilibrium of the CO2-MDEA-H2O system. For improving the performance of the model, five alpha,α, functions have been considered for the Peng-Robinson equation of state.Moreover, ions in the aqueous phase have been accounted for by contributions of the short-range, long-range interactions and the Born term in the Wong-Sandler mixing rule through the Peng-Robinson equation of state. Initially, the binary interactions of the CO2+H2O and MDEA+H2O systems are optimized. Using 283 experimental data of carbon dioxide solubility in the MDEA solution, one can calculate the other binary, and energy interaction parameters by applying simultaneous chemical and phase equilibrium computations. Consequently, to achieve the present modeling's predictability, the obtained parameters were used to predict the other 313 point data's phase equilibrium. The present model results showed that a good agreement is obtained between the calculated and experimental data. The Coquelet and Chapoy (C&C) and Twu alpha, α, functions present more accurate results than the others.

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.

Droplet Characteristics of Rotating Packed Bed in H2S Absorption: A Computational Fluid Dynamics Analysis

Rotating packed bed (RPB) has been demonstrated as a significant and emerging technology to be applied in natural gas desulfurization. However, droplet characteristics and principle in H2S selective absorption with N-methyldiethanolamine (MDEA) solution have seldom been fully investigated by experimental method. Therefore, a 3D Eulerian–Lagrangian approach has been established to investigate the droplet characteristics. The discrete phase model (DPM) is implemented to track the behavior of droplets, meanwhile the collision model and breakup model are employed to describe the coalescence and breakup of droplets. The simulation results indicate that rotating speed and radial position have a dominant impact on droplet velocity, average residence time and average diameter rather than initial droplet velocity. A short residence time of 0.039–0.085 s is credited in this study for faster mass transfer and reaction rate in RPB. The average droplet diameter decreases when the initial droplet velocity and rotating speed enhances. Restriction of minimum droplet diameter for it to be broken and an appropriate rotating speed have also been elaborated. Additional correlations on droplet velocity and diameter have been obtained mainly considering the rotating speed and radial position in RPB. This proposed formula leads to a much better understanding of droplet characteristics in RPB.

H2S solubility enhancement using ethylene diamine functionalized carbon nanotubes and the aqueous solution of N-methyldiethanolamine

Carbon Nanotubes (CNTs) were functionalized using Ethylene Diamine (EDA). To study surface morphology, identify the functional group and crystallography structure, the EDA-functionalized CNT was characterized using FESEM, FT-IR, and XRD, respectively. Synthesized EDA-CNTs were dispersed in 40 wt% MDEA solution and the stability of EDA-CNTs nanoparticles was assessed through zeta potential technique. While the pressure increased up to 8 bar, the solubility of H2S gas was then investigated in the nanofluid composed of 0.1 wt% EDA-CNTs and 40 wt% MDEA solution at 30, 45, and 60 °C. The results revealed that the solubility of the H2S gas could be enhanced to up to 13.65% when the 40 wt% MDEA solution was amended by 0.1 wt% EDA-CNTs nanoparticles.

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.

Study of Various Aqueous and Non-Aqueous Amine Blends for Hydrogen Sulfide Removal from Natural Gas

Various novel amine solutions both in aqueous and non-aqueous [monoethylene glycol (MEG)/triethylene glycol(TEG)] forms have been studied for hydrogen sulfide (H2S) absorption. The study was conducted in a custom build experimental setup at temperatures relevant to subsea operation conditions and atmospheric pressure. Liquid phase absorbed H2S, and amine concentrations were measured analytically to calculate H2S loading (mole of H2S/mole of amine). Maximum achieved H2S loadings as the function of pKa, gas partial pressure, temperature and amine concentration are presented. Effects of solvent type on absorbed H2S have also been discussed. Several new solvents showed higher H2S loading as compared to aqueous N-Methyldiethanolamine (MDEA) solution which is the current industrial benchmark compound for selective H2S removal in natural gas sweetening process.

Volumetric and viscometric properties of ternary solution of (N-methyldiethanolamine + monoethanolamine + ethanol)

The densities and viscosities of binary solutions of (N-methyldiethanolamine + ethanol), (monoethanolamine + ethanol) and (N-methyldiethanolamine + monoethanolamine) as well as ternary solution of (N-methyldiethanolamine + monoethanolamine + ethanol) were measured at T = 293.15 K, 303.15 K, 313.15 K, 323.15 K. The volumetric and viscometric properties, such as the excess molar volume VE, the partial molar volumeV¯, the partial molar volume at infinite dilution V¯∞ and the viscosity deviation Δη, were calculated from the experimental densities and viscosities. The excess molar volumes and viscosity deviations of binary and ternary solutions were correlated by the Redlich-Kister equation and the Cibulka’s equation, respectively. The intermolecular interactions in binary and ternary solutions were analysed.

Corrosion study of carbon steel in CO2 loaded solution of N-methyldiethanolamine and l-arginine mixtures

This study presents an electrochemical corrosion investigation of carbon steel in blends of methyldiethanolamine (MDEA) and arginine (ARG) at different molar concentrations and solvent proportions. The effects of three main parameters which are CO2 partial pressure, solution temperature and MDEA/ARG proportions ratio were studied. The selected temperatures range varied from 293 to 323K and the CO2 partial pressure was in the range of 49–98kPa. The results showed that the corrosion rate increased with increased CO2 partial pressure and solution temperature. However, when ARG was added to MDEA, it was found that ARG acts as an inhibitor, the higher ARG fraction in the mixture, the more inhibition effect was observed. SEM, XRD, and XPS techniques were used to characterize the corroded surfaces; analysis of the corrosion products of the specimen surface confirmed the formation of FeCO3 protective layer.

Mass-Transfer Characteristics of CO2 Absorption into Aqueous Solutions of N-Methyldiethanolamine + Diethanolamine in a T-Junction Microchannel

The mass-transfer process of CO2 absorption into aqueous solution of N-methyldiethanolamine (MDEA) + diethanolamine (DEA) in a T-shaped microchannel was studied using a high-speed camera. The effec...

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.