The impact of water salinity and its interaction with flotation reagents on the quality of coal flotation products

Abstract

Coal preparation plants are increasingly turning to alternative sources of water to reduce their consumption of fresh water, including recycled water. Some of these sources can vary greatly in inorganic electrolyte content. In this study, standard flotation tests were conducted with varying water chemistry. The concentrations of collector, frother and salt, which reflect the water quality, were varied to study the main effect of the reagents with water of varying purity as well as their interactions. The concentration of frother was clearly the most influencing factor for the yield, water recovery and ash. However, it was found that ionic content (or water quality) also had a profound effect. In particular, a higher concentration of salt tended to produce flotation products with a higher ash content. Thus, as regulation of coal preparation plants becomes more stringent and water of varying quality such as process water is used in flotation, the quality of the coal concentrates deteriorate. Thus, the environmentally beneficial practice of recycling water can lead to increased air pollution and waste generation due to an inferior product.