Electrolyte Nonrandom Two-liquid Research Articles

New Process for Na2CO3 Production from Na2SO4 Based on Modeling the Na2SO4-(NH4)2SO4-MEA-MEG-H2O System.

Alternative means for soda ash (Na2CO3) production from sodium sulfate (Na2SO4) are needed due to the intensive consumption of energy in the conventional Mirabilite-Solvay process (MSP). We demonstrate a new process to produce soda ash using sodium sulfate as a feed material. The new process relies on the antisolvent crystallization of unreacted Na2SO4 to separate it from soluble (NH4)2SO4 in a mixed monoethanolamine (MEA) and monoethylene glycol (MEG) solution. To develop the process, the solubilities of Na2SO4 and (NH4)2SO4 solids in aqueous mixed MEA-MEG solutions were first measured and then modeled using regressed paired-ion interactions from the electrolyte nonrandom two-liquid (E-NRTL) model. Anhydrous dense soda ash with a bulk density of up to 1146 kg/m3 was obtained when the concentrated Na2SO4 brines reacted with CO2 and NH3.

Thermodynamic study of imidazolium halide ionic liquid–water binary systems using excess Gibbs free energy models

In this work, the excess Gibbs free energy models, i.e., non-random two-liquid (NRTL) model and electrolyte NRTL model, including the original one and those with new strategies (association or hydration), were used to describe the macroscopic properties and interpret the microstructure of ionic liquid (IL) - H2O binary systems, clarifying the role of IL association and ion hydration in model development. To provide systematic data for model development, the enthalpy of mixing of three imidazolium-based IL-H2O systems containing the same cation but different sizes of anions, i.e., Cl−, Br−, and I−, were measured. The models were developed and evaluated based on the newly measured data and the osmotic coefficient from the literature. The results reveal that the model reflecting the intrinsic mechanism of dissociation and hydration gives the best modeling results; and the ionic strength and the degree of IL dissociation as a function of water content can be predicted using the newly established model. The study clarifies the significance of IL association and anion hydration in model development and quantitatively demonstrates how water content influences the microstructure and real species in IL-H2O systems.

Rate-based modeling and energy optimization of acid gas removal from natural gas stream using various amine solutions

Reduction in energy consumption of industrial plants is always an essential need due to high cost, CO2 emissions and global warming caused by energy supply from fossil fuels for boilers and electricity consumers. Iran has been struggling to compensate the lack of gas supply for domestic and industrial demands in winter within the past decade despite of having large natural gas resources. One of the most economical methods to decrease energy requirements in hydrocarbon plants is process improvement and revamping by changing existing solvents. There are already 44 identical acid gas removal units under operation in the South Pars Gas Complex (located in Iran) with the same feed composition. The gas-sweetening unit in the Phase 12, operating with the solution of 45.5 wt% methyldiethanolamine (MDEA), was modeled by Aspen Plus for acid gas removal (CO2 and H2S) as a rate-based model with the application of electrolyte non–random two–liquid (E-NRTL) activity model and Peng–Robinson equation of state in addition to the actual characteristics of the absorber and regenerator, and the operational conditions of the gas and liquid streams. After validation of the model by the real data from the plant, the incumbent amine solution was replaced with five proposed amine solutions – one single and four blended amine mixtures – in the same mass concentration to select the most efficient alternative from the aspects of outlet acid gas concentration, H2S content in the treated flash gas, required total power, reboiler power supply, and regeneration heat duty. The simulation results revealed that H2S was sharply absorbed on the top of the column, while CO2 was smoothly removed from the gas phase to the MDEA and blended solutions along the absorber and it occurred at the bottom of the column for the DEA solution. The blended amine solution of 1.5 wt% sulfolane + 44 wt% MDEA (Sulfinol-M) has shown to be the most appropriate option instead of the solution of MDEA compared to other suggested absorbents, with several advantages such as higher selectivity of H2S over CO2, low temperature bulge, highest H2S loading, and outlet sweet gas flow rate while required total power, reboiler power supply, and regeneration heat duty were reduced by 21.19%, 21.26%, and 23.54% respectively. The operational conditions of the unit with the application of the Sulfinol-M solution were optimized to achieve three specifications (constraints) and the minimum required total power (objective function) through a sensitivity analysis and optimization using a genetic algorithm to assure the reliability of values for three independent parameters, namely, amine solution temperature, amine solution flow rate, and gas temperature. The optimum limits and values of these parameters were 47–50 °C, 220 – 240 ton/h, and 34 °C respectively.

Liquid–Liquid Equilibria of the System Nitric Acid + Phosphoric Acid + Calcium Nitrate + Water + Tri-n-Octylamine at 298.15 K

Liquid–liquid equilibrium (LLE) data of the system nitric acid + phosphoric acid + calcium nitrate + water + tri-n-octylamine (TOA) were measured at 298.15 K and atmospheric pressure. The distribution coefficients of nitric acid, phosphoric acid, calcium nitrate, and water and the separation factors of nitric acid against phosphoric acid, nitric acid against calcium nitrate, and nitric acid against the water were calculated. Based on these data, the capability and selectivity of TOA for extracting nitric acid in this system were evaluated. The experimental results were used to obtain binary interaction parameters and pair parameters as correlated by the electrolyte non-random two-liquid (eNRTL) model. The eNRTL model was shown to be suitable for predicting the LLE data of this system, with a root-mean-square deviation of just 1.17%.

Modeling and experimental measurement of NaBr solubility in water, methanol, ethanol, 1-propanol, and its mixtures at different temperatures

This work reports experimental data of NaBr solubility measured in water, methanol, 1-propanol, and mixed solvents water + ethanol, 1-propanol + methanol, and water + 1-propanol + methanol solvents at temperatures ranging from 283.15 K to 343.15 K. The effect of temperature on the solid–liquid-liquid equilibrium of the ternary system water + 1-propanol + NaBr was also studied, and it was found that the increase in temperature caused an increase in the immiscibility region of the system. The new solubility and phase equilibrium data measured in this work, as well as experimental information from the literature, were used to estimate the interaction parameters of the e-NRTL model, which combines the original Electrolyte Nonrandom Two-Liquid (NRTL) with a Pitzer–Debye–Huckel expression to consider the long-range interactions. Although the model overestimated the size of the liquid-liquid equilibrium regions for the water + 1-propanol + NaBr system, it adequately fit all the experimental solubility data.

Effect of choline chloride based deep eutectic solvents on the aqueous solubility of 4-hydroxycoumarin drug: Measurement and correlation

This work aims to improve the aqueous solubility of 4-hydroxycoumarin (4H-coumarin) as one of the lowest soluble derivatives of coumarin, by using deep eutectic solvents (DESs). The applied DESs are composed of choline chloride (ChCl) as a hydrogen bond acceptor (HBA) and ethylene glycol (EG), urea (U), or glycerol (GLY) as hydrogen bond donors (HBD). The shake-flask method was used to determine the experimental solubility of 4H-coumarin at T = (298.15 to 313.15) K. The results demonstrate that 4H-coumarin solubility was increased noticebly at higher DES concentration and temperature. Moreover, in the presence of ChCl/EG, the 4H-coumarin solubility was more than 250 times higher than that in pure water. The experimental solubility data were fitted to the Wilson, electrolyte Non-Random Two-Liquid (e-NRTL), and UNIQUAC activity coefficient models, which shows that the Wilson model has the best correlation performance for aqueous solutions containing ChCl/EG, ChCl/GLY and ChCl/U with 0.05, 0.07 and 0.22 of ARD%, respectively. The Gibbs and van't Hoff equations to estimate the dissolution apparent thermodynamic quantities including enthalpy, Gibbs free energy, and entropy. The results indicate that 4H-coumarin dissolution processes in the investigated systems are endothermic. Quantum mechanical Density functional theory (DFT) method has also been implemented to discover the nature of the interactions in the studied DES/4H-coumarin complexes at the B3LYP-D3(BJ)/6-311g(d,p) level of theory. The DFT calculations confirm that the formations of the DESs and DES/4H-coumarin complexes are spontaneous, and the most dominant interactions are hydrogen-bonding of Cl from ChCl as electron donor and H of the other components as electron acceptor.

Thermodynamic analysis of H2O − 3-aminopropyl tributyl phosphonium glycinate as a working pair for absorption refrigeration system

In this paper, A hydrophilic dual amino-functionalized ionic liquid 3-aminopropyl tributyl phosphonium glycinate ([aP4443][Gly]) with high thermal stability was used as absorbent and the refrigerant was water for the absorption refrigeration system (ARS). The heat capacities of the system were estimated by the differential scanning calorimetry (DSC) with various water mass fractions (w1) (0.004 to 0.6993) and temperatures (285 K to 365 K), and a polynomial equation on temperature and mass fraction of ionic liquid (w2) was associated. Between the experimental and estimated values, the average relative deviation (ARD) was 0.66%. The vapor–liquid equilibrium (VLE) data of the H2O–[aP4443][Gly] binary mixture was correlated using the electrolyte nonrandom two-liquid (eNRTL) model, and the binary mixture's excess thermodynamic properties were simulated. The first and second laws of thermodynamics were used to simulate the performance of a single-effect ARS with a solution heat exchanger (SHE). The ARS simulation results show that the coefficient of performance (COP) of the system with H2O–[aP4443][Gly] as the working pair is higher than that of the conventional working pair NH3-H2O but slightly lower than that of H2O-LiBr. Furthermore, the effect of generator temperature (Tg) on ARS is investigated; simulation results show that the ARS of the novel working pair has a higher COP value at higher generator temperature, indicating that H2O–[aP4443][Gly] has the potential to be a new type of absorption refrigeration working pair.

Linear relationships for modeling CO2 absorption in aqueous alkanolamine solutions in a thermodynamically consistent way

AbstractA thermodynamically consistent model for the carbon dioxide (CO2) absorption in aqueous alkanolamine system is of great importance in the research and development of a CO2 capture process. To facilitate the development of thermodynamic models, linear Gibbs free energy, enthalpy, and heat capacity relationships using well‐known amines as reference are used to correlate the standard reference state properties of ionic species with those of molecular species in the electrolyte system, which has been approved to provide a reliable and consistent way to estimate required parameters when there is minimal or no appropriate experimental data available. The proposed relationships have been applied to the development of an electrolyte nonrandom two liquid (NRTL) activity coefficient model for CO2 absorption in aqueous 1‐amino‐2‐propanol (A2P) solution, as an example to demonstration the methodology. With limited vapor–liquid equilibrium data and other thermodynamic properties, the parameters in the electrolyte NRTL model are identified with good accuracy.

Thermodynamic modeling of calcium carbonate scale precipitation: aqueous Na+-Ca2+-Cl–-HCO3–-CO32–-CO2 system

To allow for accurate calculations of calcium carbonate scaling in highly saline produced waters, we present a comprehensive thermodynamic model based on the electrolyte nonrandom two-liquid (eNRTL) activity coefficient equation for the aqueous Na+-Ca2+-Cl–-HCO3–-CO32–-CO2 system. The eNRTL binary interaction parameters for the H2O:(Na+-CO32–) pair, the H2O:(Na+-HCO3–) pair, the (Na+-Cl–):(Na+-CO32–) pair, and the (Na+-Cl–):(Na+-HCO3–) pair are identified in this work via the regression of thermodynamic, calorimetric, and phase equilibria experimental data. The binary interaction parameters associated with the H2O:(Na+-Cl–) pair, the CO2:(Na+-Cl–) pair, the H2O:(Ca2+-Cl–) pair, and the (Na+-Cl–):(Ca2+-Cl–) pair are retrieved from the literature. The remaining binary interaction parameters are retrieved from Aspen Plus or set to zero. In addition, the solubility product constants are identified for Na2CO3•10H2O(s), Na2CO3•7H2O(s), Na2CO3•H2O(s), Na2CO3•NaHCO3•2H2O(s), Na2CO3•3NaHCO3(s), and CaCO3(s) via regression of solubility data. The model is capable of accurately calculating all phase equilibria and calorimetric properties at temperatures up to 473.15 K and salt concentrations up to saturation.

Data Analysis for Electrolyte Systems: A Method Illustrated on Alkali Halides in Water

In the recent years, the need to improve the thermodynamic models, particularly making them more precise and predictable for complex systems, has increased [Hendriks, E. Industrial Requirements for Thermodynamics and Transport Properties. Ind. Eng. Chem. Res. 2010, 49, 11131 11141 and Kontogeorgis, G. Industrial Requirements for Thermodynamic and Transport Properties. Ind. Eng. Chem. Res. 2021, 60, 4987 5013]. The complexity of electrolyte systems is due to the strong interactions between ions, the hydration forces that take place during salt dissociation, and the physical forces at high concentrations of solute. Consequently, the existing thermodynamic electrolyte models show some limitations and are far from being completely optimized for industrial simulations. Thermodynamics based on electrolyte mixtures and mixed solvents requires further development and research [Poling, B. E. The Properties of Gases and Liquids, 5th ed.; McGraw-Hill Education, 2001].The EleTher Joint Industrial Project (JIP) aims at promoting research in this field. A practical workflow is under development where the first stage consists in analyzing the data. The present work is part of this larger scope and presents a strategy to analyze the internal and external consistency of experimental data for electrolyte mixtures. The focus is on alkali halide salts in water. Internal consistency allows testing the quality of data by confronting them to each other and using the thermodynamic relationships between these data. For that purpose, the data are confronted with a model that was initially optimized and the deviations are analyzed. For this purpose, the electrolyte non-random two-liquid (eNRTL) thermodynamic model was selected. Some deviations are attributed to the model inadequacy (high temperature or high molalities). Others are to be attributed to data inconsistencies. On the other hand, the objective of external consistency is to evaluate the consistency between different systems of the same family. The Bromley model is used for this purpose, as it contains a single adjustable parameter. Investigating the trend of this parameter with type of compound or with temperature may provide valuable information regarding the underlying physics, in addition to identifying outliers.

Assessment of carbon dioxide separation by amine solutions using electrolyte non-random two-liquid and Peng-Robinson models: Carbon dioxide absorption efficiency

A high pressure carbon dioxide (CO2) absorption from a specific gas in a conventional column has been evaluated by the Aspen HYSYS simulator using a wide range of single absorbents and blended solutions to estimate the outlet CO2 concentration, absorption efficiency and CO2 loading to choose the most proper solution in terms of CO2 capture for environmental concerns. The property package (Acid Gas-Chemical Solvent) which is compatible with all applied solutions for the simulation in this study, estimates the properties based on an electrolyte non-random two-liquid (E- NRTL) model for electrolyte thermodynamics and Peng-Robinson equation of state for the vapor and liquid hydrocarbon phases. Among all the investigated single amines as well as blended solutions, piperazine (PZ) and the mixture of piperazine and monoethanolamine (MEA) have been found as the most effective absorbents respectively for CO2 absorption with high reactivity based on the simulated operational conditions.

Modeling aqueous multivalent polyelectrolytes systems with polyelectrolyte NRTL model

Thermodynamic modeling of aqueous polyelectrolyte systems is of great interest in many industrial applications and biological systems. Recently a Polyelectrolyte Nonrandom Two-Liquid activity coefficient model was proposed for aqueous monovalent polyelectrolyte systems. Integrating Manning’s counterion condensation theory, Pitzer-Debye-Hückel theory, and electrolyte Nonrandom Two-Liquid theory, the model accounts for the solution nonideality derived from long-range electrostatic polyion-ion and ion-ion interactions as well as short-range van der Waals molecule–molecule, molecule-ion, and ion-ion interactions. This work extends the model for aqueous multivalent polyelectrolyte systems and shows satisfactory agreement between the model results and the available literature data on thermodynamic properties of varieties of multivalent polyelectrolyte systems.

Effect of CaCl2 and ZnCl2 salts on isobaric vapor-liquid equilibrium in separation of the azeotropic mixture of ethanol + water

Present work analyzes potential of calcium chloride (CaCl2) and zinc chloride (ZaCl2) salts as entrainer for breaking the minimum boiling azeotrope of ethanol and water. Isobaric vapor-liquid equilibrium (VLE) data for the binary systems of water + ethanol and ternary system of water + ethanol + calcium chloride, and water + ethanol + zinc chloride were measured at a constant pressure of 94.5 kPa. The effect of salts on the relative volatility of ethanol to water as well as on the vapor phase mole fractions of ethanol were also studied experimentally. From the experimental results, it is observed that with addition of salts, the azeotropic point of the ethanol and water system can be eliminated. Salting out effects in case of calcium chloride was more than that zinc chloride salt. The results obtained in this work showed that calcium chloride could be a better choice for separation of the water + ethanol azeotrope. Electrolyte nonrandom two-liquid (eNRTL) model was used to correlate the experimental VLE data. The model prediction with the regressed parameters was found in well agreement with the experimental data. The experimental data obtained in this work was found thermodynamically consistent using van Ness test.

Operational Limits in Processes with Water, Salt, and Short-Chain Alcohol Mixtures as Aqueous Two-Phase Systems and Problems in Its Simulation

The low critical solution temperature (LCST) and minimum salt concentration that cause phase splitting in water and short-chain alcohol mixtures were determined experimentally. The short-chain alcohols, which are completely miscible with water (methanol, ethanol, 1-propanol, 2-propanol, and tert-butanol) and most of the common salts (those with Na+, K+, Ca2+, and NH4+ cations and Cl–, SO42–, CO32–, and NO3– anions), were studied. Experimentally determined data increased future development opportunities of column sequences and process design using aqueous two-phase systems (ATPSs) by establishing alcohols, some salts, and their operational limits. An example using these systems in phase transition extraction (PTE) separation processes was proposed and discussed. Finally, the use of different thermodynamic models, such as the extended UNIQUAC for electrolytes and the electrolyte nonrandom two-liquid (NRTL) model, for equilibrium calculations and the LCSTs necessary for simulation of these extraction processes with ATPS systems were analyzed.

Measurement of vapour-liquid equilibrium and e-NRTL model development of CO2 absorption in aqueous dipropylenetriamine.

Vapour-liquid equilibrium (VLE) of CO2 in aqueous dipropylenetriamine (DPTA) is investigated experimentally using a stirred equilibrium cell setup. Equilibrium solubility of CO2 is measured in the temperature and pressure range of (313-333) K and (1-100) kPa respectively. Composition of aqueous DPTA solvent used for the absorption study is in the range of (5-15) mass%. Experimental data shows higher CO2 loading capacity of this solvent compared to conventional solvents like monoethanolamine (MEA), 2-amino-2-methyl-1-propanol (AMP), and N-methyldiethanolamine (MDEA) as well as recently developed polyamine solvents like aminoethylethanolamine (AEEA), piperazine (PZ), and hexamethylenediamine (HMDA). Experimental VLE data is then correlated using the electrolyte non-random two-liquid (e-NRTL) theory which is an activity coefficient-based model for the electrolyte system. Data regression system (DRS) in Aspen Plus® (V8.8) is employed to fit the e-NRTL model equation with the experimental data by regressing the model parameters. Model-predicted data is found to be in good agreement with the experimental VLE data with an average absolute deviation of 22.3%. Performance of aqueous DPTA solvent is also analysed by predicting solvent capacity, equilibrium liquid-phase speciation, and heat of CO2 absorption using the newly developed e-NRTL model for the investigated system.

Thermodynamic Modeling of Aqueous LiCl, LiBr, LiI, and LiNO3 Solutions

Thermodynamic models are essential to facilitate the advancement of process design, optimization, and operation of electrolyte systems. In this work, a comprehensive thermodynamic framework based on the Electrolyte Nonrandom Two-Liquid model is developed to calculate phase equilibria behavior and salt solubility of aqueous LiCl, LiBr, LiI, and LiNO3 solutions. The model describes the non-ideality of the electrolyte solutions by using two binary interaction parameters for each molecule-electrolyte pair in the system. Each binary interaction parameter is further expressed with up to three temperature coefficients which are regressed from experimental data. To take into account the hydration of lithium ion, two separate chemistries for the dissociation of lithium salts are investigated. In the first case, the lithium ion is considered as a bare ion, Li+, while in the second case hydration of the lithium ion from Li+ to Li(H2O)+ is considered. The calculated thermodynamic properties compare adequately with the experimental data for both sets of chemistries for concentrations up to saturation and temperatures from 273.15 K up to 623.15 K. Moderate to significant improvements are observed with the incorporation of the hydration chemistry for aqueous LiCl, LiBr, and LiI solutions when compared to the non-hydrated lithium ion model results.

Effect of Blending Ratio and Temperature on CO2 Solubility in Blended Aqueous Solution of Monoethanolamine and 2-Amino-2-methyl-propanol: Experimental and Modeling Study Using the Electrolyte Nonrandom Two-Liquid Model.

This paper reports the newly measured experimental data for CO2 solubility in a blended aqueous solution of monoethanolamine (MEA) and 2-amino-2-methyl-propanol (AMP) at different amine mixing ratios (MEA/AMP/H2O = 9:21:70, 15:15:70, and 21:9:70 wt %) and working temperatures (323.15, 373.15, and 383.15 K). The successive substitution method was used for calculating the mole fractions of all molecules (four molecules) and electrolytes (three cations and four anions) from the equilibrium along with the material and charge balance equations (11 equations). The electrolyte nonrandom two-liquid (e-NRTL) model was used to investigate nonideality in the liquid phase. Using the abovementioned thermodynamic models, the partial pressures of CO2 in the gas phase, mole fractions of all components in the liquid phase, pH variations, heats of absorption, and cyclic capacities of CO2 according to the absorption/desorption temperature and the blending ratio of MEA/AMP were estimated.

Measurement and correlation of coumarin solubility in aqueous solution of acidic deep eutectic solvents based on choline chloride

The solubility of coumarin in three aqueous solutions of acidic deep eutectic solvents (DESs) based on choline chloride (ChCl) as hydrogen bond acceptor (HBA) with some carboxilic acids (propionic acid, lactic acid and acetic acid) as hydrogen bond donors (HBD) have been measured using the shake flask method at T = (298.15 to 313.15) K. According to obtained results, the solubility of coumarin increases with increasing the weight fraction of ChCl/propionic acid more than 100-fold. The experimental solubility data were correlated by electrolyte Nonrandom Two-Liquid (e-NRTL),Wilson and UNIQUAC activity coefficient models. Then, the dissolution thermodynamic properties, enthalpy, Gibbs free energy and entropy were calculated based on Gibbs and van't Hoff equations to investigate the solvation behavior of coumarin in the aqueous DES solutions.

Modeling and validation of carbon dioxide absorption in aqueous solution of piperazine + methyldiethanolamine by PC-SAFT and E-NRTL models in a packed bed pilot plant: Study of kinetics and thermodynamics

A pilot plant with a closed cycle of the absorption/desorption process has been taken into account for the simulation of carbon dioxide (CO2) capture by piperazine (PZ) + methyldiethanolamine (MDEA) solution using Aspen Plus rate-based model with all design and operational parameters such as the hydraulic specifications of absorber and stripper as well as inlet flue gas conditions which are present in a commercial gas-fired burner for heating houses. Metal FLEXIPAC 250Y has been considered as the packing type to apply the model to the proposed correlations on Aspen Plus for calculation of flooding and pressure drop. In order to simulate the process, a new property package has been developed by electrolyte non-random two-liquid (E-NRTL) model and perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state which are used for the calculation of activity and fugacity coefficients respectively. The model has been compared with some experimental data e.g. CO2 absorption efficiency and CO2 loading and demonstrated good agreement with them.

An ion-specific electrolyte non-random two-liquid segment activity coefficient model with improved predictive capabilities for aqueous electrolyte solutions

The accurate prediction of activity coefficients of electrolyte solutions is of great importance for many engineering applications. The electrolyte non-random two-liquid (eNRTL) model is a commonly used semi-empirical activity coefficient model for electrolyte solutions. This work presents a modified version of the eNRTL model, which aims to extend its predictive capabilities. An ion-specific parameterization scheme is developed to replace the conventionally used salt-specific parameterization scheme. Consequently, this new method allows for the prediction of the properties of electrolytes consisting of ions for which optimal ion-specific parameter values have been determined, which is inherently not possible when using salt-specific parameters. In order to capture the features of solvent-ion interactions, a segment-based local composition term is used and experimental activity data of both the salt and the solvent are utilized for parameter fitting. The modified eNRTL model with optimal ion-specific parameters is applied to aqueous electrolyte solutions and shows satisfying prediction performance.