FACULTY OF TECHNOLOGY

An effective classification system for the grinding circuit is a critical prerequisite to controlling circulating load, excessive generation of fines, and ultimately, stable flotation performance. This thesis investigated the effect of injecting water at the apex of a hydrocyclone (Cyclowash, CW) on hydrocyclone classification in the industrial autogenous (AG) grinding circuit at the Boliden Kevitsa Mine. Two plant-scale sampling campaigns were executed under normal operating conditions, one with the conventional hydrocyclone and one with the test cyclone equipped with the CW system. Feed, overflow, and underflow samples were collected and analyzed to measure particle size distribution (PSD), pulp density, and partition values. Mineralogical compositions were analyzed using X-ray diffraction (XRD). Three types of ores were tested to determine the effect of ore type on CW performance. Results showed that the CW's effectiveness on classification performance significantly depends on ore type and wash-water flow rate, revealing a negligible to slightly negative effect on classification efficiency under stable conditions, yet indicating increases in fine sulphide mineral content in the overflow for certain ore types. This study provides essential industrial benchmarks for CW application in AG grinding circuits and highlights important optimization factors.