Methyldiethanolamine Research Articles

Determination of mass transfer coefficient of CO2 removal in water-in-oil emulsion

The removal of carbon dioxide is an important process in natural gas purification since its lower down the calorific value of the natural gas. In addition, carbon dioxide also capable of forming corrosion in the pipeline, thus its removal is crucial. Water-in-oil emulsion was proposed in this research since the absorption of carbon dioxide in emulsion would be an effective method to prevent corrosion. However, the absorption capability of the emulsion and the mass transfer coefficient of carbon dioxide during absorption process needs further investigation. The aim of this study is to determine the diffusivity and mass transfer coefficient of carbon dioxide in the emulsion and observed the correlation between mass transfer coefficient and the carbon dioxide absorption values obtained from experiment. In this study, water-in-oil emulsion was prepared by mixing the aqueous phase and organic phase solutions under two different formulation conditions. Firstly, the methyldiethanolamine (MDEA) and 2 amino-2-methyl-1-propanol (AMP) blending was mixed in different alkaline solution; sodium hydroxide (NaOH) solution, potassium hydroxide (KOH) solution and distilled water (H2O) to form aqueous phase solution. Secondly, MDEA was combined with different alkanolamines; dimethylethanolamine (DMEA), diethanolamine (DEA) and triethanolamine (TEA) in KOH solution to form another aqueous phase solution. The synthesized aqueous phase is then mixed with the organic phase consists of kerosene and Span-80 mixtures. Furthermore, viscosity and particle sizes of the emulsions at different emulsion formulations were measured and the diffusivity and mass transfer coefficients of carbon dioxide were calculated. This study showed that, by using suitable emulsion formulation containing MDEA/AMP in KOH solution, the estimated value of diffusivity and mass transfer coefficient of carbon dioxide was 1.0876 × 1010 m2/s and 1.15 × 103 m/s respectively, with viscosity of 261.03 mPa s and particle size of 189.71 nm was achieved. It was found the diffusion coefficient and mass transfer coefficient of carbon dioxide is highly influenced by the characteristics of emulsion such as viscosity and particles sizes.

Carbon dioxide capture, enhanced-oil recovery and storage technology and engineering practice in Jilin Oilfield, NE China

This paper systematically presents the established technologies and field applications with respect to research and engineering practice of CO2 capture, enhanced oil recovery (EOR), and storage technology in Jilin Oilfield, NE China, and depicts the available series of supporting technologies across the industry chain. Through simulation calculation + pilot test + field application, the adaptability of the technology for capturing CO2 with different concentrations in oilfields was confirmed. The low energy-consumption, activated N-methyl diethanolamine (MDEA) decarburization technology based on a new activator was developed, and the operation mode of CO2 gas-phase transportation through trunk pipeline network, supercritical injection at wellhead, and produced gas-liquid separated transportation was established. According to different gas source conditions, liquid, supercritical phase, high-pressure dense phase pressurization technologies and facilities were applied to form the downhole injection processes (e.g. gas-tight tubing and coiled tubing) and supporting anti-corrosion and anti-blocking techniques. In the practice of oil displacement, the oil recovery technologies (e.g. conical water-alternating-gas injection, CO2 foam flooding, and high gas-oil ratio CO2 flooding) and produced fluid processing technologies were developed. Through numerical simulation and field tests, three kinds of CO2 cyclic injection technologies (i.e. direct injection, injection after separation and purification, and hybrid injection) were formed, and a 10×104 m3/d cyclic injection station was constructed to achieve “zero emission” of associated gas. The CO2 storage safety monitoring technology of carbon flux, fluid composition and carbon isotopic composition was formed. The whole-process anti-corrosion technology with anticorrosive agents supplemented by anticorrosive materials was established. An integrated demonstration area of CO2 capture, flooding and storage with high efficiency and low energy-consumption has been built, with a cumulative oil increment of 32×104 t and a CO2 storage volume of 250×104 t.

Elucidation of Operating Parameters Influencing the Ultrasonic-Assisted Absorption of Bulk CO2 Using Unpromoted and Promoted Methyldiethanolamine

Various acid gas sweetening processes can be used to separate CO2 from natural gas. As one of the most matured and widely utilized gas sweetening processes, absorption has been continuously improved to meet the stringent separation requirement. Ultrasonic irradiation has recently been introduced as an alternative technique to intensify the absorption process. Nevertheless, further studies are still needed to mature this new technique, particularly using slow kinetic absorbents possessing high inherent CO2 absorption capacity. Moreover, performing experimental studies using blended solvents in the high-frequency ultrasonic-assisted absorption system has also introduced a new idea in this field. This experimental study presents the CO2 absorption into aqueous solutions of methyldiethanolamine (MDEA) and piperazine (PZ)-promoted MDEA in an ultrasonic-assisted batch reactor. The influences of various operating parameters on CO2 absorption performance were evaluated in both promoted and unpromoted conditions. The parameters of the experiments included ultrasonic power at a frequency of 1.7 MHz, absorbent concentration, temperature, and CO2 partial pressure. Based on the results, ultrasonic power was found to be the most critical factor influencing the CO2 absorption rate. Moreover, the potential of the high-frequency ultrasonic-assisted CO2 absorption reactor was further elucidated via comparison with the conventional stirring and silent conditions under identical operating conditions. The highest CO2 absorption rate was achieved at an ultrasonic power of 12.36 W, a temperature of 70 °C, a CO2 partial pressure of 10 bar, an absorbent concentration of 50 wt %, and a promoter concentration of 5 wt %. In addition, the CO2 absorption rate in the high-frequency ultrasonic-assisted reactor using the MDEA absorbent was 28 and 52 times higher compared to stirring and silent conditions, respectively. The CO2 absorption rate enhancement was approximately 17 and 54 times higher for the PZ-MDEA.

Vapor-liquid equilibrium of carbon dioxide solubility in a deep eutectic solvent (choline chloride: MDEA) and a mixture of DES with piperazine-experimental study and modeling

In recent decays, many investigators have carried out the CO2 absorption in ionic liquids, but these green solvents are expensive and hard to prepare. In recent years, researchers have introduced deep eutectic (DES) solvents composed of a hydrogen bond donor and a hydrogen bond acceptor. DES melting point is usually lower than the ideal solution of its constituents' components and is in the liquid phase at room temperature. In this work, we have measured CO2 solubility in a deep eutectic solvent composed of choline chloride and methyldiethanolamine (MDEA) in a molar ratio of 1–6. We carried out experiments at 323.15, 333.15, and 343.15 K within the 1–50 bar pressure range. Besides, we added piperazine (Pz) as a physical solvent at 5, 10, and 15 wt% to the DES. Based on the obtained results, we observed enhancing pressure and reducing temperature led to increasing CO2 absorption. Also, increasing piperazine caused to intensify the CO2 absorption in the mixture of the DES + Pz system. Finally, we used a thermodynamic approach for the computation of the vapor–liquid equilibria of the present systems. We applied the Peng-Robinson (PR) equation of state to calculate the gas fugacity coefficient in the vapor phase. The non-random two-liquid (NRTL) activity coefficient model was used to compute the non-ideality of the liquid mixture. The modeling results were in very good agreement with the experimental data.

Power and Hydrogen Co-Production in Flexible “Powdrogen” Plants

Abstract This study investigates the potential of “Powdrogen” plants for blue hydrogen and decarbonized electric power production, conceived to operate flexibly depending on the electricity price and to increase the capacity factor of the hydrogen production and CO2 separation units. The hydrogen production is based on fired tubular reforming or autothermal reforming technologies with precombustion CO2 capture by a methyl diethanolamine (MDEA) process. The power island is based on a combined cycle with an H2-fired gas turbine and a triple pressure reheat heat recovery steam generator (HRSG). The analysis considers three main plant operating modes: hydrogen mode (reformer at full load with hydrogen export and combined cycle off) and power mode (reformer at full load with all hydrogen burned in the combined cycle), plus an intermediate polygeneration mode, producing both hydrogen and electricity. The possibility of integrating the HRSG and the reformer heat recovery process to feed a single steam turbine has been explored to allow keeping the steam turbine hot also in hydrogen operating mode. The economic analysis investigates the competitivity of the plant for different operating hours in hydrogen and power modes. Results suggest that these plants are likely to be a viable way to produce flexibly low-carbon hydrogen and electricity following the market demand.

Foam and Antifoam Behavior of PDMS in MDEA-PZ Solution in the Presence of Different Degradation Products for CO2 Absorption Process

Absorption is one of the most established techniques to capture CO2 from natural gas and post-combustion processes. Nevertheless, the absorption process frequently suffers from various operational issues, including foaming. The main objective of the current work is to elucidate the effect of degradation product on the foaming behavior in methyldiethanolamine (MDEA) and piperazine (PZ) solution and evaluate the antifoaming performance of polydimethylsiloxane (PDMS) antifoam. The foaming behavior was investigated based on types of degradation product, temperature, and gas flow rate. The presence of glycine, heptanoic acid, hexadecane, and bicine in MDEA-PZ solution cause significant foaming. The presence of hexadecane produced the highest amount of foam, followed by heptanoic acid, glycine and lastly bicine. It was found that increasing the gas flow rate increases foaming tendency and foam stability. Furthermore, increasing temperature increases foaming tendency, but reduces foam stability. Moreover, PDMS antifoam was able to reduce foam formation in the presence of different degradation products and at various temperatures and gas flow rates. It was found that PDMS antifoam works best in the presence of hexadecane with the highest average foam height reduction of 19%. Hence, this work will demonstrate the cause of foaming and the importance of antifoam in reducing its effect.

Diamine based hybrid-slurry system for carbon capture

Hybrid adsorption-absorption slurry systems are very attractive for CO2 capture, given their ability to simultaneously lower regeneration energy and increase absorption rate and uptake, because of enhanced mass and heat transfer mechanisms. In this work, novel hybrid slurries were formulated from the dispersion of 1 wt.% of solid adsorbents in a water-lean solvent of 30 wt.% of Tetramethyl-1,3-diaminopropane (TMPDA) + 10 wt.% Ethanol (EtOH) for CO2 capture. Different solid particles were suspended in the water-lean solvent such as activated carbon, ion-exchanged zeolite Y (Mg-Y), and polyethyleneimine doped silicas (PEI-SG and PEI-MCM-41). The CO2 uptake of the solid and fluid components of the slurries was confirmed by pH, density, and Fourier transform infrared analysis. The neat water lean solvent reduced the absorption energy by 16 % and slightly increased the CO2 uptake by 0.6 % compared to the aqueous TMPDA solvent. Additionally, the hybrid slurries exhibited further reductions in absorption energy of 10 – 30 % compared to the benchmark TMPDA-based solvents. The PEI-MCM-41-based slurry presented the highest CO2 uptake of 0.33 g CO2.g−1 and lowest regeneration energy of 2261.30 kJ.kg−1 among the studied systems. Additionally, the hybrid slurry exhibited a 21 % reduction in CO2 uptake compared to the benchmark 30 wt.% aqueous monoethanolamine (MEA) and similar capacity to aqueous methyl diethanolamine (MDEA), however, resulting in a far higher reduction in absorption enthalpy of 56 %, and 29 % compared to aqueous MEA and MDEA, respectively. The results obtained here encourage further development and optimization of hybrid slurry systems as potential efficient systems for CO2 capture.

Gas absorption in reactive solutions: Adapted instrumentation of a stirred cell for kinetic study and application to CO2/amine systems

The elimination of impurities from natural gas (water, CO2, H2S, mercaptans) is an obligation: in Europe, a max. of 20 mg/Sm3 in total sulfur (at 15°C and 1 atm) is allowed, as well as 2.5 vol% in CO2. It maximizes the calorific value of delivered gas and limits chemical risks (corrosion, toxicity) associated with this transition fuel to cleaner energy sources. Acid gas separation is commonly performed by reactive gas-liquid absorption. Raw gas and absorptive solution are brought into counter current contact in an absorber at 40-80°C and 30-80 bar. Then the acid-gas loaded solvent is sent to a stripper where acid gas desorption from the solvent takes place at T between 105 and 140°C and P ≤ 2.5 bar. The solvent is an aqueous base (e.g., amine) solution. A good solvent has a high reactivity with the dissolved gas during absorption and a low regeneration energy, hence the advantage of mixtures of two amines. Here we study an aqueous solution of a small amount of piperazine (PZ) added to methyldiethanolamine (MDEA). PZ reacts faster with CO2 than MDEA, and the major reaction product with CO2 is the hydrogen carbonate ion HCO3-, which lowers the solvent regeneration duty. This work aims at characterising the kinetics of the absorption of CO2 in an aqueous solution of MDEA-PZ. Indeed, no consensus has been found on the reaction mechanism of CO2 in this amine mixture; the synergies between MDEA and PZ observed in the literature remain poorly explained. However, its knowledge is essential to optimize solvent formulation and industrial unit design.

Reduction of waste disposed to the environment through recycling of unused methyldiethanolamine

A 30% aqueous solution of waste methyldiethanolamine (MDEA) can be regenerated, reused in gas treatment, and its residue can be used as a secondary raw material in another area of production. (HOCH2CH2)2NСH3 is separated from water by a 30% aqueous vacuum-extraction method. MDEA and its destroyed part remain in the column. In laboratory conditions, it was shown that the degree of purification from destruction products by this method is from 60 to 78%. The analysis of the research results showed that the parameters of the main operational properties (density, viscosity, surface tension, foaming) of purified amine were significantly improved.

Study of pathways to reduce the energy consumption of the CO2 capture process by absorption-regeneration

Several industrial sectors, such as for example cement manufacturers and lime producers, produce so-called “unavoidable” CO2 emissions because these ones are intrinsically linked to the industrial process itself (decarbonation of calcium carbonate). In order to reduce these emissions, it is necessary to implement a Carbon Capture, Utilization and/or Storage (CCUS) process chain, whose step of capture, although already technologically mature (especially the absorption-regeneration process using amine(s)-based solvents), leads to very high energy consumption. Three pathways to reduce this consumption have been investigated (experimentally and/or through the development of Aspen PlusTM simulations), namely: (i) upstream of the process thanks to the increase of the flue gas CO2 content (by partial oxy-combustion and/or flue gas recirculation), (ii) within the process (using more efficient and innovative mixtures of solvents such as demixing solutions), and (iii) at the configurational level by using advanced configurations in the capture process. It emerged that the use of a demixing process such as the mixture composed of diethylethanolamine (DEEA) and methylamino-propylamine (MAPA), or the implementation of an advanced process configuration (InterCooling Absorber + Rich Vapor Compression + Rich Solvent Splitting and Preheating, with methyldiethanolamine (MDEA) + piperazine (PZ) as a solvent) are the most energy reducing pathways for the absorption-regeneration process, i.e. more than 40% in comparison with a conventional process using monoethanolamine (MEA). Moreover, from an economical point of view, and compared to a basic configuration with MEA, the demixing technology has the advantage of being able to achieve such energy performance with a more limited investment (CAPEX) (+1.6%) than with advanced process configurations (+8.8%).

Bi-objective optimization of post-combustion CO2 capture using methyldiethanolamine

Process simulation and analyzes based on multiple evaluation indexes are crucial for accelerating the practical use of the post-combustion CO2 capture process. This study presents a bi-objective optimization of the post-combustion CO2 absorption process using methyldiethanolamine (MDEA) via machine-learning and genetic algorithm to evaluate CO2 emissions from the absorption process using life cycle assessment and cost from operating and capital expenditures. An initial dataset was generated by changing eight design variables, and machine-learning models were built using random forest classifier and Gaussian process regression. Pareto solutions were predicted using a genetic algorithm (NSGA-II) with the constraints of purity, recovery, and temperature, and were verified via process simulation. Verified data were added to the dataset, and model building, prediction, and verification were repeated. Eventually, 56 Pareto solutions were obtained after 11 iterations. In the final Pareto solutions, CO2 emissions increased from 0.56 to 0.6 t-CO2/t-CO2 with a decrease in cost from 74 to 66 USD/t-CO2. The trends and composition of each objective variable were examined, and the optimal structure of the equipment and operation conditions was clarified. The approach of bi-objective optimization in this study is promising for evaluating the CO2 capture process and individual processes of carbon capture, utilization, and storage.

Techno-economic analyses of Sulfinol-based absorber-stripper configurations for improving the energy consumption of natural gas sweetening process

This work presents a two-step method to reduce the energy consumption (in terms of the reboiler duty) of a natural gas sweetening process via a physical-chemical solvent mixture (Step 1) followed by a techno-economic analysis of 15 different absorber-stripper configurations (Step 2). Initially, an amine-based sweetening process using a H2S-free sour gas was simulated on Aspen HYSYS and the simulation results were validated against real plant data. In Step 1, different ratios of Sulfinol-M and Sulfinol-D based sweetening process were simulated and the superior physical-chemical solvent mixture that provides the lowest reboiler duty while meeting the sweet gas CO2 product concentration specification (i.e., less than 2 mol.%) is the Sulfinol-M solvent that contains 38 wt.% methyl diethanolamine (MDEA), 40 wt.% Sulfolane, and 22 wt.% water. This Sulfinol-M based model is then optimized via a parametric analysis to further improve its performance in terms of the reboiler duty prior to Step 2. The optimized Sulfinol-M based model achieved 65% saving in the reboiler duty while fulfilling the CO2 concentration specification in product gas relative to the base case. In Step 2, four main absorber-stripper configurations, namely absorber intercooling (AI), lean amine stream split flow (LASSF), rich amine stream split flow (RASSF), and mechanical vapor recompression (MVR) along with their 11 possible combinations were simulated in an attempt to decrease the energy consumption of the process and hence, ranked based on their total cost of production (TCOP). The results revealed that the integration of LASSF + RASSF provides the best option as it achieved the lowest TCOP of $4.60 M while fulfilling the CO2 concentration in product gas and contributed to 6.39% savings in the reboiler duty compared to the optimized conventional Sulfinol-M based model.

Intensification of CO2 absorption and desorption by metal/non-metal oxide nanoparticles in bubble columns.

In this study, four different metal/non-metal oxide nanoparticles including CuO, Fe3O4, ZnO, and SiO2 were employed to improve CO2 absorption and desorption in methyl diethanolamine (MDEA)-based nanofluid. CO2 absorption experiment with various nanofluids was done in a bubble column reactor at ambient temperature. Also, CO2 stripping experiments for all nanofluids were done at 60 and 70°C. The influence of nanoparticles type, nanoparticle concentration, and the stability of nanoparticles were studied on both CO2 absorption and stripping. The obtained results revealed that Fe3O4 nanoparticles at 0.01 wt.% concentration had the best influence on CO2 absorption and it improved the CO2 loading up to 36%. Also, CO2 stripping experiments for all nanofluids were done at 60 and 70°C. The desorption experiments illustrated that metal oxide nanoparticles can be more efficient in improving CO2 desorption. In CO2 desorption, the CuO nanoparticles at 0.05 wt.% had higher efficiency, and enhanced CO2 concentration at outlet gas phase up to 44.2 vol.% at 70°C. Finally, as an indication, the chemical stability of Fe3O4 NPs under optimum operational conditions was studied using XRD analysis and the result showed that the proposed operational condition did not have any negative effect on the chemical nature of Fe3O4 NPs.

Vapor–Liquid Equilibrium Measurements for Aqueous Mixtures of NH3+ MDEA + CO2and KOH + MDEA

Isothermal vapor–liquid equilibrium measurements were performed for aqueous solutions containing N-methyl diethanolamine (MDEA), MDEA + ammonia (NH3), MDEA + potassium hydroxide (KOH), MDEA + carbon dioxide (CO2), NH3 + CO2, and MDEA + NH3 + CO2. The experiments were carried out between 310 and 390 K and 0.07 and 34 bar using a static synthetic apparatus. Overall, 202 data points are reported in terms of total volume, total number of moles, temperature, and pressure. The experimental results for MDEA(aq), NH3(aq) + CO2(aq), and MDEA(aq) + CO2(aq) are in good agreement with the calculations done using the Extended UNIQUAC model within the studied range. The data presented in this work are also comparable to previously published measurements. This work reports for the first time VLE measurements for aqueous mixtures of MDEA + NH3 and MDEA + KOH. These data suggest that the interactions between MDEA(aq) and NH3(aq) or K+(aq) ions have a minor effect on the equilibrium pressures. Consequently, other physical properties are needed to describe the thermodynamic state of these systems, such as heat capacity, heat of dilution, and other phase equilibrium measurements. The isothermal VLE measurements for solutions containing NH3(aq) showed a pressure minimum that was confirmed by model estimates and by other works done in similar conditions. As a consequence, it is not possible to estimate the partial pressure of CO2 based on the difference between the pressure at equilibrium conditions and the partial pressure of the lean solvent. This paper demonstrates that this common approach to determining the partial pressure of gases may introduce a bias in these values. The dissolution of CO2 into MDEA(aq) + NH3(aq) mixtures changes the speciation of the system, leading to an increase in the concentration of their protonated species (MDEAH+(aq) and NH4+(aq), respectively). For this reason, the interaction between these charged species must be determined in order to perform reliable phase equilibrium calculations. Ultimately, the measurements reported in this work can be used for thermodynamic modeling of CO2 capture solvents to ensure accurate results in process simulation.

Simultaneous desulfurization and denitrification of flue gas enabled by hydrojet cyclone

Boiler flue gas in the chemical industry contains SO2 and nitrogen oxides (NOx). These flue gases not only pollute the environment, but also seriously endanger human health. In this work, we studied the process of jet atomization and swirl enhancement. Then we constructed a miniaturized hydrojet cyclone. After that, we proposed a new type of flue gas purification technology to achieve integrated and efficient desulfurization and denitrification. All studies were based on combining the liquid jet field with the three-dimensional swirl field to increase the mass transfer area of the gas and liquid phases. The industrial sideline test results showed that the gas purification efficiency increased with the increase of inlet velocity and absorption liquid flow rate, Efficiency is always above 80%. Increasing the concentration of activator could significantly improve the desulfurization efficiency by 27%. Increasing the concentration of oxidant was beneficial to denitrification, and the maximum denitrification efficiency of methyldiethanolamine (MDEA) was 98.2%. Overall, this technology can not only help enterprises save maintenance and treatment costs, but also protect the environment by avoiding the harm caused by flue gas pollution.

Experimental Study of the Influence of Different Load Changes in Inlet Gas and Solvent Flow Rate on CO2 Absorption in a Sieve Tray Column.

An experimental study was conducted in a sieve tray column. This study used a simulated flue gas consisting of 30% CO2 and 70%. A 10% mass fraction of methyl diethanolamine (MDEA) aqueous solution was used as a solvent. Three ramp-up tests were performed to investigate the effect of different load changes in inlet gas and solvent flow rate on CO2 absorption. The rate of change in gas flow rate was 0.1 Nm3/h/s, and the rate of change in MDEA aqueous solution was about 0.7 NL/h/s. It was found that different load changes in inlet gas and solvent flow rate significantly affect the CO2 volume fraction at the outlet during the transient state. The CO2 volume fraction reaches a peak value during the transient state. The effect of different load changes in inlet gas and solvent flow rate on the hydrodynamic properties of the sieve tray were also investigated. The authors studied the correlation between the performance of the absorber column for CO2 capture during the transient state and the hydrodynamic properties of the sieve tray. In addition, this paper presents an experimental investigation of the bubble-liquid interaction as a contributor to entropy generation on a sieve tray in the absorption column used for CO2 absorption during the transient state of different load changes.

Interrogating the chemical mechanism for carbon dioxide (CO2) reactivity in aqueous tertiary amine solutions: Can a simple parallel hydration reaction mechanism work?

AbstractIn this study, the kinetics of CO2 absorption into tertiary amine methyldiethanolamine (MDEA) was studied intensively using both experimental and theoretical approaches. The experimental work measured the kinetics of CO2(aq) react with MDEA over a range of concentrations including dilute (0.5–10.0 mM) and concentrated (0.5–2.5 M) solutions via stopped‐flow spectrophotometric at 25.0°C. The resulting kinetic data has been theoretically evaluated using three chemical reaction mechanism variants including the complete base catalysis mechanism, the simplified base catalysis mechanism, and the parallel CO2 hydration mechanism. Results showed that the simplified base catalysis mechanism in the absence of the kinetic pathways for CO2 via hydroxide and water is insufficient to predict the measured kinetic data while the complete base catalysis mechanism and parallel hydration mechanisms can accurately predict the kinetics of CO2 absorption into MDEA solutions. In particular, the experimental data of reversibility of the hydration reactions at low pH was in poor agreement with the simplified model predicted results. Given the simplicity of the parallel hydration mechanism with no requirement for determination of rate constants of the base catalysis reaction unlike the complete base catalysis mechanism, the parallel hydration mechanism can be considered the simplest and preferred mechanism describing the reaction between tertiary amine MDEA and CO2. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd.

Effect of chelating solubilization via different alkanolamines on the dissolution properties of steel slag

This work aims to investigate the solubilizing ability of alkanolamines on steel slag (SS) and the chelating ability of alkanolamines with metal ions. In this paper, the chelation effect of four alkanolamines, including triethanolamine (TEA), triisopropanolamine (TIPA), diethanol-isopropanolamine (DEIPA), and methyl diethanolamine (MDEA), and metal ions on the dissolution of SS was investigated. The conductivity meter, pH meter, X-ray powder diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES), total organic carbon (TOC) and isothermal calorimetry were used to investigate the solubilizing ability of SS impacted by alkanolamines. Additionally, the conductivity meter and chemical precipitation method (CPM) were used to investigate and explore the chelating ability of alkanolamines interacting with the metal ions. Finally, the nuclear magnetic resonance hydrogen (1HNMR) spectroscopy was adopted to investigate the chelating mechanism between alkanolamines and metal ions. The results showed that the alkanolamines increased the elemental concentrations of [Ca], [Al], [Fe] and [Si] in the liquid phase of SS through chelating and promoted the dissolution of the mineral phase of C3S, C2S and C4AF in SS. Among the different alkanolamines, DEIPA was present in the liquid phase for the longest time and possessed a more sustained ability to chelating metal ions. The result also shows that alkanolamines can chelate the Ca2+, Al3+ and Fe3+ in solution. The chelating ability of tertiary alkanolamines were stronger than the secondary alkanolamine. And the alkanolamine with asymmetric molecular structure have stronger chelating ability than those with symmetric molecular structure. Tertiary alkanolamines form ternary five-ring structure with metal ion through nitrogen and oxygen atoms.

CO2 and H2S absorption in aqueous MDEA with ethylene glycol: Electrolyte NRTL, rate-based process model and pilot plant experimental validation

Acid gas absorption with aqueous amines is an important industrial technology for natural or flue gas treatment. To lower the high energy required for the regeneration process it has previously been proposed to replace a significant part of the water by a physical co-solvent with a lower specific heat. To investigate this idea, as well as the overall impact of adding a physical co-solvent, a detailed process model for CO2 and H2S absorption using an aqueous mixture of N-methyl diethanolamine (MDEA) – ethylene glycol (EG) is developed based on lab-scale experimental measurements of physical, thermodynamic, and kinetic properties. Those experiments indicate that the addition of EG reduces the solubility of the acid gases and that, despite the higher viscosity of the solvent, the impact on the rate of acid gas absorption is minor. Pilot plant tests further confirmed this. The vapor-liquid equilibrium (VLE) experiments were used to regress the thermodynamic electrolyte e-NRTL (Non-Random Two-Liquid) model parameters. In parallel, the kinetic measurements allowed to develop a rate-based model. All models were implemented in a commercial process simulator that was validated with high-pressure absorption–regeneration pilot tests with the solvent composition of 34 wt% MDEA, 44.5 wt% EG and 21.5 wt% H2O and with the raw gas composition of 2.5 mol% H2S and 2.5 mol% CO2. Comparison with aqueous MDEA (50 wt% MDEA, and 50 wt% H2O) shows that a reduction of 25 % in reboiler duty can be obtained when adding EG. Nevertheless, an 80 % increase in solvent flow rate is needed to get a similar acid gas absorption performance, and a higher co-absorption of hydrocarbons is observed.

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.