Acoplamento reativo-hidrodinâmico na dissolução de incrustações de sulfato de bário: desenvolvimento de sistema dinâmico em escoamento

Abstract

The dissolution of mineral scale in industrial systems is traditionally evaluated through batch experiments, in which the solid is immersed in a dissolving solution and removal is monitored over time by ex situ analyses, with periodic quantification of the dissolved concentration or residual mass. In this approach, results are typically expressed as final removal efficiency or percentage dissolution after a given contact time. Although useful for preliminary comparison of formulations, such metrics fail to capture the complexity of the coupling between chemical and hydrodynamic phenomena under realistic flow conditions. In this work, a novel methodology was developed for investigating the dissolution of barium sulfate (BaSO4) under flow conditions. The experimental arrangement consists of a column filled with a structure of 316 stainless steel spheres interspersed with BaSO4, forming a reactive packed bed that simulates a solid obstruction. The controlled injection of a dissolving solution (DTPA or EDTA) through this bed promotes progressive dissolution of the solid while the obstruction structure evolves throughout the experiment. This process is monitored in an integrated manner using in situ techniques, including infrared spectroscopy for quantification of the dissolved species and hydrodynamic analysis based on continuous differential pressure measurements and estimation of bed permeability. This configuration enables the acquisition of temporal concentration profiles, instantaneous dissolution rates, and the hydrodynamic evolution of the system over time. The methodology allowed the identification of distinct behavioral regimes associated with distributed bed dissolution and the formation of preferential flow paths, highlighting the determining role of hydrodynamics in overall dissolution efficiency. It was observed that, at higher temperatures, although complexation is thermodynamically favored, the more rapid formation of preferential flow paths reduces effective solution-solid contact, limiting the progression of BaSO4 removal. At lower temperatures, in contrast, channeling develops more slowly, promoting more homogeneous permeation of the dissolving solution through the bed. This hydrodynamic behavior compensates for the intrinsically lower chemical efficiency and may result in total dissolution values comparable to those obtained under more thermodynamically favorable conditions. These results demonstrate that dissolution configurations achieving equivalent total dissolution may exhibit significantly different spatial and dynamic dissolution distributions, as reflected in the hydrodynamic and kinetic measurements obtained under continuous flow conditions. Additionally, a phenomenological model based on physical principles was proposed to quantitatively describe the coupling between chemical dissolution and permeability evolution, incorporating the effects of preferential flow path formation into a dissolving efficiency metric. The methodology was validated according to widely adopted metrological performance criteria, demonstrating its repeatability, sensitivity, and applicability. The results establish a more realistic and discriminating approach for the evaluation and selection of dissolving agents under continuous flow conditions, bridging laboratory-scale experimentation and real-world scale removal scenarios.