Isobaric Vapor–Liquid Equilibrium Measurements and Modeling of Water + Monoethylene Glycol + NaCl Mixtures

Abstract

Vapor−liquid equilibrium (VLE) data for aqueous systems in the presence of electrolytes have many industrial applications. VLE data for water + monoethylene glycol (MEG) mixtures in the presence of sodium chloride at low pressures are important to describe the effects of composition, temperature, and pressure on a MEG (gas hydrate inhibitor) regeneration unit. A modified version of the Othmer ebulliometer was applied to measure reliable VLE data for water + MEG + NaCl at 101.325, 65, and 35 kPa. Binary systems (water + MEG and MEG + NaCl) were also experimentally studied. Vapor pressures for water and MEG were determined and compared with the selected literature data via Antoine correlation. The electrolyte nonrandom twoliquid and universal quasi-chemical activity coefficient models were successfully parameterized to describe the VLE behavior for water + MEG + NaCl systems. Thermodynamic consistence of the data sets was also checked. Interaction parameter estimation followed a systematic strategy: (1) water−MEG, (2) water−NaCl, and finally (3) MEG−NaCl with the experimental data of MEG + NaCl and ternary data. MEG + NaCl solutions presented an inverted colligative property, that is, the addition of salt decreases the boiling point. VLE data indicated that water separation is less efficient due to the addition of salt. The parameterized models allow an evaluation of the MEG regeneration process as a function of temperature, pressure, and composition.

Density and Electrical Conductivity for Aqueous Mixtures of Monoethylene Glycol and Sodium Chloride: Experimental Data and Data-Driven Modeling for Composition Determination

“…The whole density database is available in Table S1. In total, 509 data points are gathered to provide the desired correlation, regarding Table S1 and the values at 298.15 K Figures – show excess volume and density data at T = 298.15–358.15 K for the studied binary systems: water + MEG at whole concentration range and solvent + NaCl up to near saturation, respectively.…”

“…MEG and water purities were corroborated by vapor pressure measurements . The humidity of MEG and NaCl was monitored using Karl Fischer titration (Mettler Toledo, model DL39).…”

“…MEG and water purities were corroborated by vapor pressure measurements. 26 The humidity of MEG and NaCl was monitored using Karl Fischer titration (Mettler Toledo, model DL39). This control has been performed continuously due to the hygroscopic nature of the compounds.…”

“…Density experimental data were also collected from the literature − for the water + NaCl pair, aiming the estimation of parameters. For the MEG + NaCl mixture, values reported previously at 298.15 K and in this work (Table S1) were considered. For both binary solutions, a linear dependence of the apparent molal volume was properly obtained as a function of the square root of the salt molality, as expected. − The extrapolation for zero molality provides the values of ρ φ3,1 ∞ and ρ φ3,2 ∞ , using the definition ( V  1/ρ) and the conversion from molar density to mass density.…”

“…Thus, in total 15 parameters were adjusted: 5 for each binary data set (water + NaCl and MEG + NaCl) and 5 for the ternary one. In total, 248 data points (this work and previously reported 26 ) were considered for the model parametrization. The objective function based on the relative deviation for electrical conductivity was applied.…”