Modification of amine collector for low temperature flotation of potash

Abstract

The most common potash ore in Canada is sylvinite which consists of mainly halite (NaCl) and sylvite (KCl) with addition of trace amounts of insoluble materials such as clay and silt. KCl is loosely referred to as potash or sylvite and NaCl as salt or halite. The potash (KCl) is separated from NaCl for the production of fertilizer for agricultural use and other industrial applications. KCl is separated from NaCl mainly by a flotation process. The most common collector (flotation reagent) used in the flotation process are long chain aliphatic amines. Temperature variations have adverse effect on the physical, chemical and physicochemical properties of amine dispersion, viscosity of the brine solution, dissolution and adsorption of the amine as well as the wettability of the potash particles. The froth flotation process is efficient when temperatures are within the range of 20oC-32oC. Inefficiency of the flotation process occurs when temperature of the saturated brine falls below 15oC because of the inability of amine collectors to disperse well in highly viscous brines. The primary purpose of this study was to select organic additives that can improve the rate of dispersion of the collector emulsion and enhance recovery of KCl from lower temperature (10-15oC) brine solutions. The secondary goal was to determine the optimum particle size of potash required for low temperature flotation. Particle size distributions of amine precipitates were determined using a Malvern Mastersizer S Long Bench Particle Size Analyzer. Dispersion experiments were performed and optical (OM) and scanning electron microscopy techniques (SEM) were used to determine the effect of selected additives on dispersion of amine particles in saturated brine solutions. Based on results from the dispersion tests, the most effective additive, polyglycol ether (PGE) was selected and mixed with dodecyl amine-hydrochloride to form a modified amine collector. Flotation experiments were carried out in saturated brines at lower temperatures (10- 15oC) and higher temperatures (24-28oC) to determine the effect of the presence of additives on flotation recovery. Urea was added to the brine solution to determine its impact on recovery. Flotation with the modified collector led to 12% increase in flotation recovery at 10-15oC. The flotation recovery further increased by 1.9% when urea was added to the saturated brine prior to flotation. It was discovered that the modified collector functioned as a collector and as frother and additional frother was not required for the flotation process. The optimum particle size of potash required for improved flotation with the modified collector was 180-335µm.