Monitoring of Calcium and Strontium Carbonate Precipitation in H2O + MEG Mixtures Using an NIR Technique

Carbonate precipitation control is important in separation processes such as those involving the monoethylene glycol (MEG) regeneration process in natural gas production plants as glycol reduces the solubility of these salts. The use of sensors that allow continuous monitoring of the precipitation of inorganic salts in aqueous solutions contributes to optimizing the parameters commonly found in these processes. This work proposes the study of calcium and strontium carbonate salt precipitation in H2O + MEG mixtures using near-infrared spectroscopy (NIR) as a monitoring technique. Precipitated salts were obtained from the mixture of solutions at different ionic concentrations (anions and cations), in the absence and presence of MEG (0 or 40 wt %) at 60 °C. The information obtained by the NIR technique was correlated with the data provided by the focused beam reflectance measurement (FBRM) technique, and an algorithm combining principal component analysis (PCA) and artificial neural networks (ANN) was employed to describe the precipitation kinetics of carbonates in the solutions. The results showed that increasing the ionic strength and MEG concentration favors the reduction of the number and size of the calcium carbonate crystals. For solutions containing MEG, the kinetics of crystal growth are reduced. The addition of NaCl increases the ionic strength of the system and affects ion complexation, resulting in a decreased particle size distribution and reduced particle formation. The PCA-ANN model effectively described salt particle growth and precipitation kinetics, demonstrating strong correlations (above 0.90) and low error rates (0.55 for the growth kinetic model and 100 particles for the formation kinetic model), accurately predicting particle formation and growth dynamics. The proposed methodology for the study and monitoring of salt precipitation using NIR techniques proved to be efficient in determining the amount and size of precipitated particles in solutions containing water and MEG under different experimental conditions. This methodology contributes to efficient management by monitoring and controlling the parameters involved in the precipitation and deposition of existing salts in petroleum exploration and production systems.