Methyldiethanolamine Research Articles

Simulation of Natural Gas Treatment for Acid Gas Removal Using the Ternary Blend of MDEA, AEEA, and NMP

Natural gas (NG) requires treatment to eliminate sulphur compounds and acid gases, including carbon dioxide (CO2) and hydrogen sulphide (H2S), to ensure that it meets the sale and transportation specifications. Depending on the region the gas is obtained from, the concentrations of acid gases could reach up to 90%. Different technologies are available to capture CO2 and H2S from NG and absorb them with chemical or physical solvents; occasionally, a mixture of physical and chemical solvents is employed to achieve the desired results. Nonetheless, chemical absorption is the most reliable and utilised technology worldwide. Unfortunately, the high energy demand for solvent regeneration in stripping columns presents an obstacle. Consequently, the present study proposes a novel, ternary-hybrid mixture of N-methyl diethanolamine (MDEA), amino ethyl ethanol amine (AEEA), and N-methyl 2-pyrrolidone (NMP) to overcome the issue and reduce the reboiler duty. The study employed high levels of CO2 (45%) and H2S (1%) as the base case, while the simulation was performed with the Aspen HYSYS® V12.1 software to evaluate different parameters that affect the reboiler duty in the acid gas removal unit (AGRU). The simulation was first validated, and the parameters recorded errors below 5%. As the temperature increased from 35 °C to 70 °C, the molar flow of the CO2 and H2S in sweet gas also rose. Nevertheless, the pressure demonstrated an opposite trend, where elevating the pressure from 1000 kPa to 8000 kPa diminished the molar flow of acid gases in the sweet gas. Furthermore, a lower flow rate was required to achieve the desired specification of sweet gas using a ternary-hybrid blend, due to the presence of a higher physical solvent concentration in the hybrid solvent, thus necessitating 64.2% and 76.8%, respectively, less reboiler energy than the MDEA and MDEA + AEEA.

Evaluation of adsorption efficiency of activated carbon functionalized with methyl diethanolamine in carbon dioxide gas

Background: Adsorption is a process in which some of the components in the fluid phase, are selectively transferred to the surface of the porous solid particles in the filled bed, which is called the adsorbent. The aim of this study was to examine the adsorption effectiveness of CO2 by activated carbon functionalized with methyl diethanolamine (MDEA), as well as the effects of adsorption temperature, the total pressure of adsorption, and mass of adsorbent. Methods: Activated carbon was first produced using the desired biomasses and suitable activated carbon was chosen. The activated carbon was then functionalized with MDEA amination method. The crystal structure of adsorbents was studied using X-ray diffraction (XRD) methods. In addition, the porosity, specific surface area and structure of prepared activated carbon were measured using BET techniques. Finally, the morphology and strength of the functional groups were measured using Field emission scanning electron microscopy (FESEM) and Fourier-transform infrared spectroscopy (FTIR) analyses. Results: The findings of the FESEM and BET analyses for functionalized activated carbon revealed that the specific surface area of the adsorbent increased throughout the chemical and physical modification process, resulting in a BET amount of 725/84 m2 /g. The results showed that the selectivity of the functionalized activated carbon is greater than that of the non-functionalized adsorbent. Conclusion: The adsorption capacity of functionalized activated carbon was 3.98 mmol CO2 g-1 sorbent, compared to 2.587 mmol CO2 g-1 sorbent in the non-functionalized carbon, indicating a 35% improvement in the efficiency of the functionalized sample. According to the findings of the desorption experiments, functionalized carbon shows a 25% decrease in CO2 adsorption efficiency after 20 desorption steps.

Life cycle assessment of methanol production and conversion into various chemical intermediates and products

Transportation sector, particularly road transport, together with the industrial expansion stand out as key factors behind the unprecedented CO2 levels, hence the need for green fuel alternatives and sustainable technologies. The present investigation evaluates methanol (MeOH) production via direct CO2 hydrogenation, and conversion into valuable derivatives: i) formalin, ii) dimethyl ether (DME), iii) methyl tert-butyl ether (MTBE), and iv) biodiesel through modelling and simulation, as well as environmental assessment. Hydrogen is produced by water electrolysis considering three different energy scenarios: i) EU grid mix; ii) wind power; iii) hydro power. The amount of CO2 needed is obtained from cement manufacturing through a chemical scrubbing process using Methyl-Di-Ethanol-Amine (MDEA). The environmental analysis is carried out following the Life Cycle Assessment (LCA) methodology using GaBi software, and ReCiPe as impact assessment method. The key performance indexes, main product purity (>99%) and energy requirements (i.e., 1.72 MWe/t, and 5.89 MWe/t respectively) point towards alkali biodiesel, and MTBE production as the most promising MeOH conversion routes. The environmental analysis highlights that MeOH production and conversion towards alkali biodiesel process displays the lowest impact score for each energy scenario. The second-best conversion route is MTBE when using the grid mix energy scenario, and formalin when wind or hydro power is considered.

A novel molecular structure-based model for prediction of CO2 equilibrium absorption in blended imidazolium-based ionic liquids

• A comprehensive dataset including 4397 data points of CO 2 equilibrium solubility in imidazolium-based ionic liquids was acquired. • Various blended of imidazolium-based ILs were characterized based on their molecular frameworks. • Three machine learning predictive models were proposed to predict CO 2 solubility. • The simple but effective FFNN model gives reliable predictions, as compared with RBFNN and SVM algorithms. The present study highlights a comprehensive database including 4397 data points of CO 2 equilibrium solubility measurements in the 43 different imidazolium-based ionic liquids (ILs) over a broad range of pressures and absorption temperatures. The relation between the equilibrium CO 2 solubility and the molecular structure of the imidazolium-based ILs mixed with different kinds of solvents, including Diethanolamine (DEA), Methyl diethanolamine (MDEA), Diisopropylamine (DIPA), Amionomethyl propanol (AMP), and the equilibrium absorption pressure and the temperature has been accurately correlated. According to this database, a novel chemoinformatics-based descriptor model with a large number of 26 input data of structural information of all involved cation and anions and experimental conditions has been extracted. Three different machine learning methods, namely feed-forward neural network (FFNN), radial-based function neural network (RBFNN), and support vector machine (SVM), are employed to develop the derived descriptor-based model. The results of the three machine learning methods demonstrate that the prediction performance of the suggested models is quite reliable. Comparing the results indicate that the FFNN with corresponding values of RMSE = 0.071, R 2 = 0.952, and MAPE = 0.544 is the best paradigm to predict the CO 2 equilibrium solubility in imidazolium-based ILs.

Absorption of carbon dioxide in mixture of N-Methyl-2-Pyrrolidone and six different chemical solvents

Today, the emission of carbon dioxide (CO2) has increased sharply as a result of world industrialization and an increase in energy demand. Therefore, finding an economic way to reduce CO2 emissions has been considered a crucial subject for industries. In this research, the mixture of n-methyl-2-pyrrolidone (NMP) and six various chemical solvents of monoethanolamine (MEA), methyldiethanolamine (MDEA), potassium carbonate (K2CO3), potassium glycinate (KGly), potassium argininate (KArg), and triethylenetetramine (TETA) is applied in a semi-continuous bubble column reactor system at pressure 1 bar and room temperature. Based on the result, the addition of the NMP to water causes the absorption capacity to increase. But, it has a negative effect on the absorption capacity of chemical absorbents so that the order of absorption is aqueous solvent (water 95 wt% + chemical compound 5 wt%) > semi-aqueous solvent (water 45 wt% + NMP 50 wt% + chemical compound 5 wt%) > non-aqueous solvent (NMP 95 wt% + chemical compound 5 wt%), respectively. TETA with 637 and 538% absorption enhancement among aqueous and semi-aqueous solvents, respectively, and MEA with 572% absorption increment compared to water among non-aqueous solvents have shown the best absorption capacity. Also, KArg has the highest CO2 loading (mole CO2/mole chemical), therefore, KArg is a promising solvent to use in CO2 absorption. Further, due to the inability of the bubble column to tolerate high pressures, the effect of pressure (2, 5, 10 and 30 bar) on MDEA solutions has been investigated in a high-pressure batch system at temperature 298 K. It has been observed that an increase in pressure strongly affects the performance of non-aqueous solvents. So, the non-aqueous solvents are more effective when the partial pressure of CO2 is high.

The Effect of MDEA/AMP and Span-80 in Water-in-Oil (W/O) Emulsion for Carbon Dioxide Absorption

Emulsion liquid membrane (ELM) has been widely studied as an alternative method for amine absorption technology in the removal of acid gases such as carbon dioxide (CO2) and hydrogen sulphide (H2S). However, searching for stable ELM formulation with an enhanced CO2 absorption remains as challenge. Therefore, in this study, the aqueous solution containing a mixture of methyl diethanolamine (MDEA) and 2-amino-2-methyl-1-propanol (AMP) in sodium hydroxide (NaOH) solution was introduced as a dispersed phase, kerosene as continuous phase and Span-80 acts as a surfactant for the formation of water-in-oil (W/O) emulsion. In this study, the dispersed phase consists of 8% v/v MDEA and 4% v/v AMP and the continuous phase which contains 6% v/v Span-80 produced a stable emulsion and exhibited 65.2% of CO2 removal. This study indicates that the introduction of blended amine able to produce stable emulsion with an enhanced CO2 removal.

АБСОРБЦИОННАЯ ОЧИСТКА ГАЗОВ ПРОИЗВОДСТВЕННЫХ КОТЕЛЬНЫХ ДЛЯ СНИЖЕНИЯ АНТРОПОГЕННОЙ НАГРУЗКИ НА АТМОСФЕРУ

Reducing the impact of emissions of pollutants, including carbon dioxide, formed during the combustion of fossil fuels, can be carried out with the use of technologies of capture, disposal and burial. The absorption of CO2 after combustion is mainly used in operating boiler units – sources of emissions, where various solvent -absorbers are used for the chemisorption of carbon dioxide. The urgency of solving the problem of carbon dioxide capture from natural gas combustion products of industrial boilers is shown. A method of carbon dioxide capture by chemical absorption using solutions of methyldiethanolamine (MDEA) is proposed on the example of a production boiler house of JSC Altayvagon. Flue gases containing CO2 are supplied to the carbon dioxide workshop of the enterprise for cleaning, followed by the utilization of carbon dioxide, which is used at Altaivagon JSC for welding operations. The proposed chemosorbent MDEA of domestic production in comparison with the imported analogue currently used at the enterprise has certain advantages, which will reduce the circulation of the absorbent solution, use the chemosorbent more fully, reduce energy consumption; due to the low corrosion activity of the absorbent used and the absence of tar formation, the costs of maintenance and repair of equipment will decrease. Due to the use of domestic MDEA instead of imported analogues, as well as due to a longer service life of the absorbent without reducing its characteristics and adding fresh absorbent during operation, significant savings on the purchase of the absorbent will occur. Capturing emissions of pollutants from flue gases will solve the issues of both resource conservation and reduction of anthropogenic load on the environment. In addition, carbon dioxide capture will contribute to achieving carbon neutrality of the enterprise.

Performance of nitrogenous polybutylene succinate/polylactic acid materials and their degradation effects on physiological indicators of lettuce

Nitrogenous polybutylene succinate (N-PBS) was synthesized herein by melt polycondensation with a 10% molar content of the third monomer, N-methyldiethanolamine (N-MDEA). The chemical structure of the synthesized N-PBS was characterized, and its crystallinity and relative molecular mass were tested. Then the N-PBS was modified by blending with polylactic acid (PLA) in different proportions, and the crystal morphology, thermodynamic properties, water contact angle, degradation properties, and plant nutritional properties of the resulting composites were studied. The results confirmed that the N-PBS copolymer was successfully synthesized. Polarizing microscope (POM)and differential scanning calorimetry tests revealed defects in the crystallization of the N-PBS in the composite, while the crystallinity also declined. Thermogravimetry tests revealed an overall enhancement of the thermal properties of the composite, with mass loss occurring above 300 °C. When the N-PBS content is 60%, the overall mechanical properties of the composites are optimal. The water contact angle of the N-PBS was also lower than that of the PLA, indicating higher hydrophilicity in the N-PBS than the PLA. The composite degraded in the soil supernatant for six months, reaching a degradation rate of up to 40%, and grooves and holes on the surface of the material were observed clearly by scanning electron microscopy. By identifying the components in the degradation solution, it was found that most of the small nitrogen-containing molecules were oligomers of succinic acid, butanediol, and N-MDEA. With the degradation of N-PBS in the composites, nitrogen was released, facilitating lettuce growth.

Biogas upgrading with various single and blended amines solutions: Capacities and kinetics

Biogas is an important renewable energy and biogas upgrading which separate CH4/CO2 to increase the heating value of biogas is necessary for its utilization. Amine scrubbing is a promising biogas upgrading technology. In this study, we applied various single and blended amines solutions for biogas upgrading and reconsidered the evaluation method by comparing the equilibrium CO2 absorption capacity (qe) and optimal CO2 absorption capacity under 90 vol% or 95 vol% pure CH4 requirement (q90%CH4, q95%CH4). Three apparent kinetic models and Fourier-transform infrared spectroscopy (FT-IR) were applied to study the kinetics. The results showed that, compared with the qe, the new indicator q90%CH4 and q95%CH4 could better reveal the difference and improvements between various amines solutions and be more accordance with the real situation of biogas upgrading. The q90%CH4 increased from 0.15 to 0.82–1.70 mol/kg after adding other amines with methyldiethanolamine (MDEA), but qe was almost the same. For kinetics, the fitting results of Avrami model are the best among the three models. FT-IR analysis before and after absorption showed CO2 formed different groups with different amine molecules. This study provided a new perspective and method on evaluation of amine scrubbing for biogas upgrading, contributing to future research and industrial application.

The pressure effects on the Amine-Based DES performance in NG Sweetening: Insights from molecular dynamics simulation

Deep eutectic solvents (DESs) have gained considerable attentions as novel green solvents in the natural gas (NG) sweetening processes Using molecular dynamics simulations, the performance of an amine-based DES composed of a 6: 1 M ratio of methyl diethanolamine (MDEA) and choline chloride (ChCl) for NG sweetening process is investigated. To this end, the effect of pressure on the performance of amine-based DESs for sweetening of the NG, and the penetration of acid gasses from the NG to the DES are examined. The results of the H2S and CO2 solubility in the DES phase demonstrate that H2S and CO2 solubilities are proportional to the pressure, and the maximum values of 0.225 and 0.04 are obtained for H2S and CO2 solubilities, respectively, at 2 MPa and 310 K. Additionally, calculations of the solubility selectivity parameter at various pressures reveal monotonic behaviors for the solubility selectivity of H2S over CH4. The solubility selectivity of H2S over CH4 has a larger value, by a factor of 10 to 20, than the solubility selectivity of CO2 over CH4 at pressure range from 0.1 MPa to 2 MPa. It can be concluded that the MDEA-based DES used here, have higher efficiency for H2S separation, and greater selectivity towards CO2 and CH4 compared to aqueous MDEA-solvent. The structural and dynamical analyses are computed to assist interpreting of the observed behavior at the molecular level. Moreover, diffusion coefficient of H2S (102 Å2/n) and CO2 (302.3 Å2/ns) in MDEA-based DES at 2 MPa and 310 K have the lowest values among all the considered pressures. Our findings indicate that MDEA-based DES can compete with the conventional amine solvents in the NG sweetening processes.

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.

Low-Viscosity Nonaqueous Sulfolane–Amine–Methanol Solvent Blend for Reversible CO2 Capture

In this work, the absorption–desorption performance of CO2 in six new solvent blends of amine (diisopropylamine (DPA), 2-amino-2-methyl-1-propanol (AMP), methyldiethanolamine (MDEA), diethanolamine (DEA), diisopropanolamine (DIPA), and ethanolamine (MEA)), sulfolane, and methanol has been monitored using ATR-FTIR spectroscopy. Additionally, NMR-based species confirmation and solvent viscosity analysis were done for DPA solvent samples. The identified CO2 capture products are monomethyl carbonate (MMC), carbamate, carbonate, and bicarbonate anions in different ratios. The DPA solvent formed MMC entirely with 0.88 molCO2/molamine capture capacity, 0.48 molCO2/molamine cyclic capacity, and 3.28 mPa·s CO2-loaded solvent viscosity. MEA, DEA, DIPA, and MDEA were shown to produce a low or a negligible amount of MMC while AMP occupied an intermediate position.

Molecular simulations for improved process modeling of an acid gas removal unit

Reliable process modeling and simulation is required to optimize the design and performance of acid gas removal units, which play a key role in the H2S and CO2 removal from natural gas, and in the CO2 capture from flue gasses. Many physico-chemical properties that are key input parameters to the process models are obtained from time-consuming and sometimes dangerous experimental campaigns (H2S) or are not (easily) accessible experimentally and are currently estimated. In this work, we investigated which of these properties could quickly and reliably be obtained using molecular simulations, to improve the accuracy of the process models and to reduce the need for long or difficult experiments. The absorption properties of H2S, CO2, and CH4 in aqueous MethylDiEthanolAmine (MDEA) were computed using a combination of forcefield-based molecular dynamics, Monte Carlo methods, and quantum mechanical approaches. The results are compared to experimental data and/or currently used estimates in the AspenPlus process model. It was found that the key properties which might reliably and relatively easily be obtained by molecular simulations are physical: density, phase behavior, Henry coefficients, diffusion coefficients, viscosity, and surface tension. Quantum mechanical calculations based on the widely used density functional theory are instrumental in exploring reaction mechanisms and in determining the structure of transition states, but obtaining accurate free energies of reactions remains a challenge, especially when energy differences of less than 1 kJ mol−1 are necessary for quantitative predictions. Such an accuracy can only be reached if the solvent effects, which are detrimental, are correctly included in the model [1].

An investigation on simultaneous freshwater production and CO2 capture using flue gas of a power plant

AbstractThis paper presents an investigation on simultaneous freshwater production and CO2 capture using the flue gases of a 500 MWe coal‐fired power plant. Generally, a fan/cooler is used to reduce the temperature of flue gas before flowing into the absorber column of a CO2 capture unit. It has been replaced with a heat exchanger in this study. Seawater and flue gas were passed through the heat exchanger to raise the temperature of seawater and reduce the temperature of flue gas. The high‐temperature seawater was subsequently fed into a membrane distillation (MD) unit for freshwater production. The cold flue gas was directed to the CO2 capture unit. The heat exchanger and CO2 capture unit were modeled with Aspen Plus software. Whereas MATLAB software was used to develop and solve the MD mathematical model software for freshwater production. The seawater flow rate was varied from 4000 L/min to 7000 L/min in the heat exchanger. As a result, the flue gas (flow rate 781.6 t/h) and the outlet seawater temperatures were reduced from 27.498 to 22.360°C and 73.384 to 52.670°C, respectively. However, higher inlet seawater temperature in the MD unit produced more freshwater. An increase in inlet seawater feed temperature in the MD unit from 52.670 to 73.384°C increased the freshwater production from 211,956.5 to 299,244 L/day. Furthermore, the CO2 capture process has been analyzed by varying the methyldiethanolamine (MDEA) and piperazine (PZ) concentrations in weight% (45 and 5, 40 and 10, 35 and 15, and 30 and 20, respectively). It was observed that the energy requirement reduced from 3.55 to 3.26 MJ/kg CO2 by increasing the PZ content from 5 to 20 wt.%. At 15 and 20 wt.% of PZ content in the blended solution of MDEA/PZ, the energy required to regenerate the solvent was 3.31 and 3.26 MJ/kg CO2, respectively. PZ emissions from the absorber were also increased with the raising of PZ content in the blended solution. The energy requirement was not much higher at 15 wt.% than 20 wt.%. Therefore, MDEA/PZ solution (15/35 wt.%) was considered an optimal concentration. The reboiler duty was reduced up to 3.25 MJ/kg CO2 at 15/35 wt.% concentration with stripper pressure of 2.3 bar. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd.

An experimental/computational study of steric hindrance effects on CO2 absorption in (non)aqueous amine solutions

AbstractThe reaction kinetics and molecular mechanisms of CO2 absorption using nonaqueous and aqueous monoethanolamine (MEA)/methyldiethanolamine (MDEA)/2‐amino‐2‐methy‐1‐propanol (AMP) solutions were analyzed by the stopped‐flow technique and ab initio molecular dynamics (AIMD) simulations. Pseudo first‐order rate constants (k0) of reactions between CO2 and amines were measured. A kinetic model was proposed to correlate the k0 to the amine concentration, and was proved to perform well for predicting the relationship between k0 and the amine concentration. The experimental results showed that AMP/MDEA only took part in the deprotonation of MEA‐zwitterion in nonaqueous MEA + AMP/MEA + MDEA solutions. In aqueous solutions, AMP can also react with CO2 through base‐catalyzed hydration mechanism beside the zwitterion mechanism. Molecular mechanisms of CO2 absorption were also explored by AIMD simulations coupled with metadynamics sampling. The predicted free‐energy barriers of key elementary reactions verified the kinetic model and demonstrated the different molecular mechanisms for the reaction between CO2 and AMP.

Modeling the solubility of carbon dioxide in the MDEA + AEEA aqueous solution using the SAFT-HR equation of state and extended UNIQUAC model

In this study, a thermodynamic model has been used to determine the solubility of carbon dioxide in an aqueous solution which is the combination of methyldiethanolamine (MDEA) and aminoethylethanolamine (AEEA). The physical equilibriums have been considered between the liquid and vapor phases and chemical equilibrium in the liquid phase. The SAFT-HR equation of state has been used to specify the fugacity coefficients of the components in the vapor phase. The liquid phase is considered as an electrolyte solution besides; the extended UNIQUAC has been applied to figure out the activity coefficients. The bubble point calculation has been used in this research. This method includes two main loops. Calculations related to chemical equilibrium are performed in the interior loop and the ones associated with phase equilibrium are done in the exterior loop. The solubility of carbon dioxide has been predicted by the optimized parameters of the model in the temperature range of 308.2–368.2 K. It has been calculated that the absolute average relative deviations of the model are 16.65, 19.33, 28.91 and 19.99 in the calculation of partial pressure of carbon dioxide in various loadings at the temperatures of 308.2, 328.2, 343.2 and 368.2 K.

Treatment of methyldiethanolamine wastewater using subcritical and supercritical water oxidation: parameters study, process optimization and degradation mechanism.

In this examination, sub/supercritical water oxidation (SCWO) in a batch reactor was employed to degrade methyldiethanolamine (MDEA). To do so, the impact of different operating parameters including temperature (300-500°C), time (0-100s), initial MDEA concentration (1000-4000ppm), oxidant coefficient (0.7-2), and pH (7.3-9.5) on MDEA degradation was separately and together investigated. Subsequently, the response surface method (RSM) was applied to optimize the operating condition of MDEA degradation. Based on the obtained results, a maximum amount of 97.4% MDEA degradation was achieved at the initial MDEA concentration of 1095ppm in optimal condition (i.e., oxidant coefficient: 1.913, temperature: 472°C and residence time: about 17s). Furthermore, according to the HPLC analysis, there was a negligible amounts of formic acid (CH2O2) and nitrous acid (HNO2) in the solution at the end of MDEA removal experiment. Eventually, the mechanism of MDEA degradation was acquired using molecular dynamics simulation (MDS), which had an acceptable coordination with the experimental results. In this way, the MDS results revealed that the presence of CH2O2 and HNO2 compounds in the products was related to the degradation of MDEA and their production as by-products during the SCWO experiments.

Absorption of Carbon Dioxide into Glycine Activated Methyldiethanolamine (MDEA) Comparing with Diethanolamine (DEA)

It is widely accepted that increasing carbon dioxide (CO2) emissions to our atmosphere is the major contributor to global climate change, which pollutes environment. The chemical absorption using tertiary alkanolamines solution is one of most important method, which have been proposed and studied for the removal of carbon dioxide because the MDEA solvent has low cost, low corrosive tendencies, high stability, low viscosity, low tendency to foam, and low flammability, however it has low reaction rate. Therefore, we added glycine promoter to conventional solvents to increase the rate of the reaction because glycine is a primary amine compound which is reactive. Moreover, glycine has resistance to high temperatures; so, it will not easy to degrade making it not suitable for application in industry. The main purpose of this study was to provide reaction kinetics data of CO2 absorption into glycine promoted methyldiethanolamine (MDEA) by using laboratory scale wetted wall column equipment at the atmospheric pressure by varying temperature from 303.15 to 328.15 and glycine concentration from 1% to 3%, while the carbon dioxide absorption rate was measured by titration of liquid effluent. Based on the result of this study, we observed that by increasing temperature and concentration of glycine, the absorption rate of carbon dioxide in MDEA solution was increase. In addition, the reaction rate constant will be affected by the temperature and the concentration of promoter. The correlation of reaction rate constant (k glycine) was: k glycine = 5.3409E+13exp(-3251.9/T) with the activation energy for glycine promoter is 27.0363kJ/kmol, indicating it a very influencing, compared to diethanolamine (DEA).

Research on oxygen solubility in aqueous amine solvents with common additives used for CO2 chemical absorption

Oxidative degradation in amine based post-combustion carbon capture (PCCC) leads to solvent losses and decreased solvent performance. Oxygen (O2) in the flue gas is dissolved into the aqueous solvent and can reactively degrade the amine component. Advanced aqueous amine solvents are designed to contain additional surfactant and anti-foam additives as well as two types of corrosion inhibitors. These additives contribute to improve the solvent performance while reducing foaming and corrosion of expensive equipment. This work examines the impact of these additives on oxygen solubility (or dissolved oxygen - DO) in various aqueous amines used in PCCC including ethanolamine (MEA), 1-amino-2-propanol (A2P), 2-amino-1-propanol (2A1P), 2-(methylamino)-ethanol (NMEA), 2-(ethylamine)-ethanol (2EAE), diethanolamine (DEA), methyl-diethanolamine (MDEA), dimethylethanolamine (DMEA), piperazine (PZ), 1,2-ethyldiamine (EDA), and 1,6 hexadiamine (HDA). The impact of carbon loading on oxygen solubility with and without these additives was also examined. The surfactant and anti-foam additives had minimal impact on DO for all the solvents investigated. The two anti-corrosion additives had opposite effects in the measured DO, 2- mercaptobenzothiazole (MBT) decreased the DO concentration, and sodium metavanadate showed an increase. These results indicate that several of these common additives can be expected to minimally affect DO related oxidative degradation in these advance amine solvents.

Quantitative measurement of Mono-Ethylene Glycol (MEG) content using low-field Nuclear Magnetic Resonance (NMR)

Extraction of natural gas from remote subsea reservoirs is often accompanied by increased flow assurance risks such as hydrate blockages, which if formed can pose a serious threat to both productivity and safety. Such hydrates can be prevented via injection of monoethylene glycol (MEG) to subsea systems, which is subsequently regenerated via distillation and re-injected. Inaccurate compositional analysis of reclaimed MEG can, however, result in both process inefficiencies and over-use of MEG during re-injection. Limitations in current analytical methods mean that there is demand for the development and optimisation of alternative methods for quantifying MEG within the recycled fluids. Here, benchtop Nuclear Magnetic Resonance (NMR) Spectroscopy is proven to be an accurate and reproducible method of monitoring such MEG composition to within a concentration error of 1 wt% in the presence of a range of impurities at concentrations consistent with those encountered in industry. Binary mixtures of MEG and water, and those with either methyl diethanolamine (MDEA) or acetic acid, provided accurate determination of MEG concentration within this range. The presence of saline water similarly produced concentration errors within 1 wt% with adequate optimisation of the NMR methods used. Industrial applicability as an on-line measurement was demonstrated by accurate MEG concentration determination during continuous flow (0–20 mL min−1). These results demonstrate low-field benchtop NMR spectrometry to be a viable candidate for MEG composition monitoring under typical environments encountered during the recycling of MEG for hydrate inhibition.