Acoustic-Cavitation-Assisted chemical removal of gypsum Scale: Mechanisms and process intensification.

Abstract

Calcium sulfate (gypsum) scale removal is a major operational issue concerning oil production facilities, as the deposits damage equipment and their removal causes prolonged downtime. Therefore, investigating process intensification techniques is pivotal for reducing scale removal time. This study focuses on the application of acoustic cavitation to the dissolution of gypsum, using two different types of dissolvers: potassium carbonate, a converter, and tetrasodium EDTA, a chelating agent. Compared with soaking at ambient temperature, ultrasound-assisted treatment increased gypsum removal 8.5-fold with potassium carbonate and 56-fold with tetrasodium EDTA. Silent experiments following the same temperature profile showed that heating accounts for much of this gain, with cavitation providing a further 1.6-fold and 2.9-fold increase, respectively. Electron microscopy indicated different mechanisms. Potassium carbonate converts gypsum layer by layer under silent conditions, whereas ultrasound produced deep cavities beyond the surface layer, consistent with localized cavitation-induced penetration. With tetrasodium EDTA, surface morphology was unchanged, suggesting that enhanced mass transfer dominates. These bench-scale findings support acoustic cavitation as a process intensification tool for scale removal, warranting further studies on field applicability.