Gypsum Scaling in Bulk Neutralization Circuits

Hydrometallurgical water treatment circuits experience substantial scaling due to the neutralization of sulphuric acid and precipitation of dissolved metals with slaked lime slurry. Operationally disruptive counter-measures, such as mechanical and chemical cleaning, are often required to remove scale and restore capacity to process equipment. The composition of scale formed in the Key Lake Bulk Neutralization circuits was characterized using X-Ray Powder Diffraction, Raman Spectroscopy, Scanning Electron Microscopy, and Energy Dispersive X-Ray Spectroscopy. The impact of hydrodynamics, and degree of super-saturation on the propensity for scale formation was evaluated using rotating cylindrical coupons to measure the induction period and specific scaling rate under conditions typical of Bulk Neutralization circuits located in Northern Saskatchewan