Ajuste de parâmetros termodinâmicos de sistemas contendo água, monoetilenoglicol e cloreto de sódio em baixas pressões

Abstract

In oil and gas production, monoethylene glycol (MEG) is used as an inhibitor of hydrate formation by decreasing the amount of free water in the system. Hydrates are crystalline solids that cause pipeline blockages and are generated due to the presence of light hydrocarbons that form crystals in the presence of water. Knowledge of the liquid-vapor equilibrium of aqueous systems with MEG and salt is fundamental for the optimization of the design and operation of the separation plants of the MEG regeneration unit. In this perspective, the present work aims at adjusting the parameters of the thermodynamic model NRTL of the experimental data of liquid-vapor equilibrium (VLE) determined by Moura-Neto (2020) for the systems - binary (Water + MEG) and ternary (Water + MEG + NaCl) - in different mass ratios and at pressures of 350, 650 and 1013mBar. The modeling of these systems was performed in EXCEL software with the help of the thermodynamic supplement XSEOS and the computational tool solver, present in the software, through the gamma-phi approach. From the results obtained, the parameters fitted to the NRTL model for both the binary and ternary systems proved to be adequate to describe the behavior of the solutions, presenting as mean absolute and relative mean absolute deviation of the equilibrium temperature, respectively, 𝛥T_E = 1.10 ºc or 1.14% for the binary system, and 𝛥T_E = 1.16 ºc or 1.24% for the ternary system. Analyzing the excess properties, the H2O + MEG system shows practically ideal behavior, but for the H2O + MEG + NaCl system, the addition of sodium chloride increased the non-ideality of the system. Furthermore, for both systems the lower the pressure to which the system is subjected the greater the deviation from ideality.