Estudo da solubilidade e composição da fase sólida do cloreto de cálcio em misturas contendo água e monoetilenoglicol

Abstract

In the oil exploration industry, the formation of hydrates is a problem, especially when associated with gas-producing wells, can cause blocking of pipelines, compromising the safety and operational efficiency. Therefore, the use of thermodynamic inhibitors, of gas hydrates formation like the Monoethyleneglycol (MEG), becomes highly relevant. However, because this glycol have relatively low dielectric constant, when in contact with water, has the effect of reducing the solubility of most salts, increasing the precipitation. Such a process may cause operational problems such as flow interruption of pipelines and valves plunge and immobilization of drill string. The damage by the salts incrustation generates greater energy consumption, reaching a global scale of billions of dollars a year in the oil and gas industry. Then, studies relating to the hydrates inhibition are essential in the production of oil and gas. Moreover, to be injected in the oil well, the glycol returns to the surface containing water and salts, needing so regeneration treatment for your reinjection, where these contaminants are removed. In addition, the study of the salts solubility in water and MEG are essential for optimizing projects and plants for recovery and regeneration of glycol. The calcium chloride (CaCl2) solubility on systems in different MEG concentrations and water is the aim of this work. However, the salt solid-liquid equilibrium this in high concentrations Monoethyleneglycol favors the salting-out effect or reducing the solubility. In addition, there is incorporation of water molecules and MEG (salt-free) to the solid phase of calcium chloride for the equilibrium, which may increase or decrease the solubility. Thus, this work aims to study the precipitation conditions in aqueous systems containing MEG and calcium chloride (CaCl2), assessing the solubility. Also, the solid phase composition of calcium chloride and the amount of water molecules and MEG grouped this salt and how this phase influences the solubility. The methodology used is based on density and conductivity analyses for solubility determination, and Thermogravimetry and titration for the determination of the the solid phase composition in systems containing concentrations of MEG within the interval from 0% to 100%. The temperatures studied 25 ºC and 50 ºC. The behavior identified from the solubility data analysis shows that increasing the concentration of MEG causes a decrease in the salt solubility in the system. The determination of the solid phase composition of the solidliquid equilibrium salt explains the behavior of the curves of solubility and hygroscopic nature of species, showing the amount of water salt- free, and water of crystallization, plus small percentage of MEG.