Vapor-liquid Equilibrium Of CO2 Research Articles

Vapor-liquid equilibrium experiment and prediction of excess property of new working pair CO2-[BMP][Tf2N] in absorption refrigeration system: Expérience d'équilibre vapeur-liquide et prédiction de la propriété excédentaire de la nouvelle paire de travail CO2-[BMP][Tf2N] dans un système de réfrigération à absorption

Solubility of CO2 in ionic liquids (ILs) is of great importance in absorption refrigeration system as new working pairs. Vapor-liquid equilibrium (VLE) of CO2 in [BMP][Tf2N] (1-butyl-1-methyl-pyrrolidine bis(trifluoromethylsulfonyl)imide) is carried out experimentally using the experiment system at temperature range 303.15 K-363.15 K. The experimental results show that the solubility of CO2 in [BMP][Tf2N] can reach up to 0.1235–0.5324 (molar fraction) within temperature range 283.15∼363.15 K and pressure range of 0.2∼5 MPa. The solubility of CO2 in [BMP][Tf2N] increases with increase of temperature and pressure. The VLE data of CO2-[BMP][Tf2N] binary system is correlated with two models (SRK equation of state +WS mixing rule +UNIFAC activity coefficient model and PR equation of state +WS mixing rule +UNIFAC activity coefficient model). The excess Gibbs free energy (GE), excess enthalpy (HE) and excess entropy (SE) of the system are obtained and the interaction parameters kij is regressed based on the VLE of CO2-[BMP][Tf2N] binary system. The variation trend of GE, HE and SE are obtained with temperature, pressure and molar fraction of CO2. The calculation results show that the accuracy of SRK equation of state is slightly higher than that of PR equation of state in CO2-[BMP][Tf2N] binary system. The accuracy of SRK equation of state and PR equation of state decreases with increase of temperature and pressure.

Stimulation of CO2 solubility in reversible ionic liquids activated by novel 1-(2-aminoethyl piperazine) and bis (3-aminopropyl) amine

The quest of energy efficient post combustion CO2 capture through an integrated process approach leads to the development of various novel solvents which can yield the necessary outputs. In line with this, the current work explores the experimental and simulation analysis of vapor liquid equilibrium of CO2 in novel aqueous 3-aminoproyl triethoxysilane (TESA) solvent blends enhanced by amine activators. Specific amine activators, viz. 1-(2-aminoethyl) piperazine (AEP) and bis (3-aminopropyl) amine (APA) were considered. The experiments were carried out over the temperature range of (303.2–323.2) K and pressure of (4–350) kPa. In order to realize the effect of activator, AEP/ APA concentration was gradually increased from 0.5 to 1.0 mol/kg with a total solvent concentration of ≈3 mol/kg. Along with this, qualitative 13C NMR and FTIR analysis were also performed to assess the proposed reaction scheme. The experimental vapour liquid equilibrium data (VLE) were correlated by modified Kent-Eisenberg equilibrium model considering gas phase non-ideality as well as non-rigorous statistical non-linear model. The equilibrium constants associated to deprotonation of protonated TESA, AEP and APA as well as carbamate formation reactions of these amines with CO2 are function of solvent concentration, temperature and CO2 partial pressure. These are regressed to fit the experimental VLE data. The modified KE model is further prolonged to estimate the concentration profiles of various molecular and ionic species involved in the reactive system.

Simulation on vapor-liquid equilibrium of CO2-[emim][Tf2N] in flow state and depressurization of its refrigeration cycle based on Aspen Plus

To investigate the depressurization mechanism of the CO 2 vapor compression refrigeration cycle with an ionic liquid loop, a vapor-liquid equilibrium (VLE) model of CO 2 -[emim][Tf 2 N] in the flow state was established based on Aspen Plus, and the prediction of VLE in the supercritical state was carried out. Furthermore, the effects of CO 2 inlet pressure, absorber temperature, CO 2 inlet mole fraction and CO 2 inlet flow rate on the depressurization amplitude of absorber were analyzed through the absorption-desorption process simulation. The results showed that with the increase of CO 2 inlet pressure in the supercritical state, the depressurization amplitude increased but its growth rate slowed down, which indicated that the effect of pressure as a driving term of mass transfer decreased in the supercritical state. The depressurization amplitude decreased with the increase of absorber temperature, and decreased rapidly with the increase of CO 2 inlet mole fraction. In this sense, adding an auxiliary desorber at the absorber inlet is beneficial to the system depressurization. Due to the limited absorption capacity of quantitative [emim][Tf 2 N] in the absorber, with the continuous increase of CO 2 inlet flow rate, the depressurization amplitude first dropped sharply, then flattened, and later dropped rapidly. Because the CO 2 flow rate in an actual system is proportional to the system cooling capacity, the proper mass flow ratio of CO 2 -[emim][Tf 2 N] should be selected to reconcile the cooling capacity and depressurization amplitude.

Experimental and e-NRTL model predicted VLE of CO2 in aqueous solutions of 2-((2-aminoethyl)-amino)-ethanol and speciation study

Recently, 2-((2-Aminoethyl) amino) ethanol (AEEA), containing a primary and a secondary amino group, is focused as a new solvent for post-combustion CO2 absorption. In this work, vapour-liquid equilibrium (VLE) of CO2 absorption in the aqueous AEEA is studied over a wide temperature range of 303.15–343.15 K and pressure up to 243 kPa in the amine concentration range of 0.51–4.11 mol AEEA.kg−1 water using a stirred cell thermostatic setup. A rigorous thermodynamically consistent model based on Electrolyte Non-Random Two-Liquid (ENRTL) theory is developed using Aspen V9.0 to correlate and predict the vapour liquid equilibrium of CO2 in aqueous AEEA solutions. The model predicted CO2 solubility showing 28% of average absolute deviation (AAD) from experimental data. The model predicted pair parameters, binary interaction parameters, equilibrium constant, dielectric constant, pure component physical properties and coefficients of extended Antoine vapour pressure correlation are presented in this study. Equilibrium liquid phase speciation for all solvents is predicted using ENRTL-model. The ENRTL model is also used to predict the heat of reactions for the individual equilibrium reactions as function of temperature and the heat of absorption of CO2 in aqueous AEEA solutions as a function of CO2 loading.

A Comparative Performance of New Materials for Carbon Dioxide Removal in Absorption Process

Nowadays, the problems of climate change and global warming become more serious on environmental concern due to the higher amount of carbon dioxide in the atmosphere. Basically the main sources of carbon dioxide come from anthropogenic activities such as power generation, industries and so on. Currently, the effective technology to remove CO2 from these sources is absorption especially chemical absorption. Also, the chemicals used are one of the key parameters for effective CO2 removal. The widely used amine solutions are monoethanolamine (MEA) and diethanolamine (DEA). Nevertheless, they also have disadvantages such as low capacity, corrosion and high heat of regeneration thus making carbon capture technology more expensive. Therefore, many novel materials have been developed to improve the efficiency and compensate the disadvantages of some amines. Consequently, the objective of this work is to investigate the vapor-liquid equilibrium of CO2 in novel materials of 2-(methylamino) ethanol or 2-MAE and 3-Amino-1-Propanol or 3-AP at the temperature from 40 °C to 80 °C and CO2 partial pressures ranging from 5 to 100 kPa. The solubility results of CO2 in novel materials are compared with those of aqueous solution of MEA and DEA. For cyclic capacity, the results present that novel materials provide higher performance than that of MEA with less cost. This means that novel materials can save more energy and cost for solution regeneration and making it more economically viable.

Experimental measurement and Kent-Eisenberg modelling of CO2 solubility in aqueous mixture of 2-amino-2-methyl-1-propanol and hexamethylenediamine

In this work, vapour-liquid equilibrium of CO2 in aqueous mixture of 2-amino-2-methyl-1-propanol (AMP) and hexamethylenediamine (HMDA) is studied in the temperature and pressure range of 303.15–333.15 K and 1–100 kPa respectively. Concentration of the aqueous solutions used are (5mass% HMDA+25mass% AMP), (10 mass% HMDA+20 mass% AMP), (15mass% HMDA +15mass% AMP) and (20 mass% HMDA+10 mass% AMP). Density of aqueous amine solution is also measured in the same range of temperature and concentration. Redlich-Kister equation for excess molar volume is used to model density of the mixed solvent system. To correlate experimental CO2 solubility data, Kent and Eisenberg thermodynamic model is used. Equilibrium constants of bicarbamate formation reaction of HMDA and deprotonation reaction of AMP are regressed to fit experimental data with the model expression. Kent and Eisenberg model is found to predict the CO2 solubility in aqueous (HMDA + AMP) with good accuracy (AAD: 7.2%).

Modeling the effect of piperazine on CO2 loading in MDEA/PZ mixture

The equilibrium of CO2 solubility and species concentration data for the absorption of CO2 in the aqueous solutions of Methyl-di-ethanolamine (MDEA), Piperazine (PZ) and their mixture (MDEA+PZ) were analyzed using Matlab software. A thermodynamic model was developed to predict the vapor liquid equilibrium of CO2 in aqueous mixtures of MDEA/PZ. The electrolyte-nonrandom two-liquid (e-NRTL) model was used to build the vapor-liquid equilibrium model, which defines equilibrium behavior of the solution. This model was applied to correlate the species concentration in the solutions of MDEA, PZ and their mixtures using default interaction parameters reported in the literature. It was observed that this model gave a good estimation of CO2 loadings over a wide range of operating conditions for both single and mixed amine solutions. The model has been used to estimate the species concentrations and CO2 solubility in aqueous DEA/PZ [1]. The application of this model is new to this system, i.e. of CO2-MDEA-PZ-H2O. In this work, the model was further extended to predict the effect of piperazine on CO2 loading for carbonated aqueous solutions of MDEA/PZ systems. The addition of PZ to MDEA as an activator increased the solubility of CO2 under low and high range of CO2 partial pressures and temperatures. The species concentrations, activity coefficients, and pH of the CO2 loaded solutions were studied, and the model predicts amine volatility as well. The model was validated using the experimental data generated from our previous work and data available in the open literature. The results of the current model are in an acceptable degree of agreement with the experimental data of CO2 solubility reported in previous work for this system.

Effect of piperazine on solubility of carbon dioxide using aqueous diethanolamnie

Experimental results of vapor–liquid equilibrium of this study for CO2 capture in solutions of activated diethanolamine (DEA) are presented at temperatures ranging from 313.15 to 353.15 K. Piperazine (PZ), which is used as an activator in this study, its concentration ranged from 0.01 to 0.1 M. Total alkalinity of the solution was kept 2 M. The partial pressure of CO2 varied from 0.01 to 100 kPa. A thermodynamic model is developed to predict the vapor liquid equilibrium of CO2 in aqueous mixtures of DEA/PZ. For CO2+H2O + DEA + PZ system, the e-NRTL model is used to develop the VLE model, which defines equilibrium behavior of the solution. Model is validated using data generated from this work as well as data available in literature. Results of the current model are in an acceptable degree of agreement with the experimental data of CO2 solubility of this work as well as of those stated in literature. The species concentration, activity coefficients, pH of the CO2 loaded solutions, and the model predicts amine volatility. Addition of PZ to DEA, as an activator, has increased the solubility of CO2 under a specific range of CO2 partial pressure.

VLE of CO2 in aqueous sodium glycinate solution – New data and modeling using Kent–Eisenberg model

Vapor–liquid equilibrium (VLE) of CO2 in aqueous sodium glycinate solution (SG) is studied in this work. Equilibrium solubility data is measured experimentally in 5–25mass% aqueous sodium glycinate solution at 313.15, 323.15 and 333.15K, over the CO2 partial pressure range of 2–600kPa. Density and viscosity of aqueous sodium glycinate are also measured at same temperature range. From the experimental results it is seen that aqueous solution of SG has good CO2 loading (mole of CO2 absorbed per mole of amine) potential. Experimental VLE data is then correlated using the Kent–Eisenberg model and carbamate hydrolysis equilibrium constant and amine deprotonation equilibrium constant are regressed. Average absolute deviation between experimental and model predicted results is found to be 7.13%.

Vapor–liquid equilibrium of CO2 in NH3–CO2–SO2–H2O system

Vapor–liquid equilibrium (VLE) of CO2 in CO2 and SO2 loaded aqueous ammonia (NH3–CO2–SO2–H2O system) was investigated in this study. The effect of SO2 loading (mol SO2/mol NH3 in solvent) on VLE of CO2 was measured in the range of 0.1–0.3mol SO2/mol NH3 in 2.5–7.5wt.% aqueous ammonia at 20°C, 40°C and 60°C, using a Fourier transform infrared (FT-IR) gas analysis method with a pressure determination stirred tank apparatus. The equilibrium vapor pressures of CO2 in the aqueous ammonia with no SO2 content were compared with experimental data in the public domain. The electrolyte NRTL model was carried out to predict the VLE data using Aspen Plus. The comparison between experimental results and model predictions showed good agreement. The total equilibrium pressure, NH3 equilibrium partial pressure and liquid speciation in the NH3–CO2–SO2–H2O system were calculated and analyzed. It was found that the total equilibrium pressure decrease slightly at lower CO2 loading (mol CO2/mol NH3), but increase sharply at higher CO2 loading with SO2 loading. The NH3 equilibrium partial pressure, and the NH3 and NH2COO− molar concentrations decrease with SO2 loading. However, the NH4+ and HCO3− molar concentrations increase with SO2 loading. Further CO2 equilibrium partial pressure analysis shows that the driving force and solvent capacity of CO2 absorption decrease with SO2 loading, while the desorption capacity and driving force of CO2 at high temperature significantly increases with SO2 loading, which has the potential to reduce the regeneration energy of CO2.

CO<sub>2</sub> Absorption in a 5M Aqueous Solution of 2-(Diethylamino)Ethanol

Currently, climate change and global warming are the main issues on environmental concern due to the higher amount of carbon dioxide in the atmosphere. The main sources of carbon dioxide are energy-related activities such as power generation. Now, the effective technology to remove CO2 from these sources is absorption especially with amine solution. The commercially used amine solutions are monoethanolamine (MEA) and methyldiethanolamine (MDEA). Nevertheless, they also have disadvantages such as low capacity, corrosion and high energy requirement. Therefore, many new solvents have been developed to improve efficiency for CO2 capture. Therefore, the objective of this work is to measure the vapor-liquid equilibrium of CO2 in a 5M aqueous solution of 2-(Diethylamino) ethanol (DEAE) as a novel solution at the temperature from 30 °C to 80 °C and CO2 partial pressures ranging from 5 to 100 kPa. The solubility results of CO2 in DEAE solution are compared with those of aqueous solution of MEA. For cyclic capacity, the results present that DEAE provides higher performance which is up to 861% higher than that of MEA. This means that DEAE can save more energy and cost for solution regeneration.

Amine blends using concentrated piperazine

Blends using concentrated (25 35wt %) piperazine (PZ) were characterized as solvents for CO2 capture at typical coal flue gas conditions. The new blends are 6 m PZ/2 m hexamethylenediamine (HMDA), 6 m PZ/2 m diaminobutane (DAB), 6 m PZ/2 m bis(aminoethyl)ether (BAE), 5 m PZ/2 m aminoethylpiperazine (AEP), and 5 m PZ/2.3 m 2-amino 2-methyl-propanol (AMP). The CO2 absorption rate of the blends was measured using a wetted wall column (WWC). The CO2 vapor liquid equilibrium was measured at 20–160°C. Amine vapor pressure measurements are reported to show potential volatility at practical conditions. The rate of thermal degradation was measured from 135 to 175°C. Oxidative degradation was measured in two semi-batch experiments with different O2 rate at absorber conditions. Advanced parameters are introduced to demonstrate the overall rate and energy performance of the solvents in a real process. The performance of 7 m MEA, 8 m PZ, and six other competitive PZ blends are evaluated based on previous results and presented as basis of comparison.All of the PZ blends have better solubility window than 8 m PZ, with no precipitation at rich loading. The absorption rate of the concentrated PZ blends is similar to that of 8 m PZ and 1.5 2 times higher than 7 m MEA; the solvent capacity is about 20% lower than 8 m PZ and 15% higher than 7 m MEA. Among all of the PZ blends, 5 m PZ/5 m MDEA has the best combination of rate and capacity. Blends using HMDA, AEP, BAE, AMP, and MEA have a high heat of CO2 absorption. Blends using MEA, MDEA, and AMP are not thermally stable, while other blends have good thermal stability. The combination of high Habs and thermal stability leads to good overall energy performance, which is observed for 6 m PZ/2 m HMDA, 6 m PZ/2 m BAE and 5 m PZ/2 m AEP. AMP has relatively high volatility, whereas BAE and AEP are expected to have low volatilities. The only drawback of 6 m PZ/2 m BAE is its high oxidation rate. 6 m PZ/2 m HMDA and 6 m PZ/2 m DAB have good oxidative stability.PZ blends using low viscosity amines will have high absorption rate, and tertiary and hindered amines will contribute to high capacity. Amines with high pKa will improve the blend Habs. For thermal stability, alkanolamines should not be used together with PZ. Highly viscous blends such as 6 m PZ/2 m HMDA are expected to have 10–20% higher cost associated with cross-exchanger design and operation than solvents with low viscosity.

Thermodynamic Behavior of the CO2 + NO2/N2O4 Mixture: A Monte Carlo Simulation Study

The thermodynamic behavior of the carbon dioxide + nitrogen dioxide (CO2 + NO2) mixture was investigated using a Monte Carlo molecular simulation approach. This system is a particularly challenging one because nitrogen dioxide exists as a mixture of monomers (NO2) and dimers (N2O4) under certain pressure and temperature conditions. The chemical equilibrium between N2O4 and 2NO2 and the vapor-liquid equilibrium of CO2 + NO2/N2O4 mixtures were simulated using simultaneously the reaction ensemble and the Gibbs ensemble Monte Carlo (RxMC and GEMC) methods. Rigid all atoms molecular potentials bearing point charges were proposed to model both NO2 and N2O4 species. Liquid-vapor coexistence properties of the reacting NO2/N2O4 system were first investigated. The calculated vapor pressures and coexisting densities were compared to experimental values, leading to an average deviation of 10% for vapor pressures and 6% for liquid densities. The critical region was also addressed successfully using the subcritical Monte Carlo simulation results and some appropriate scaling laws. Predictions of CO2 + NO2/N2O4 phase diagrams at 300, 313, and 330 K were then proposed. Derivative properties calculations were also performed in the reaction ensemble at constant pressure and temperature for both NO2/N2O4 and CO2 + NO2/N2O4 systems. The calculated heat capacities show a maximum in the temperature range where N2O4 dissociation occurs, in agreement with available experimental data.