Evaluation of grinding circuits for iron ore

Abstract

Grinding has become one of the most important unitary operations for producing pellet feed for direct reduction from low-grade ores and small liberation size, such as compact itabirites. The aim of this study was to evaluate and compare two grinding circuits in an industrial iron ore plant, by evaluating the current operation through sampling, industrial data analysis and mass balancing. The flows analyzed were the grinding circuit, flotation throughput and desliming hydrocyclone overflow. In total, two grinding circuits were tested. One circuit had two mills installed in series, with the first mill operating in an open circuit and the second mill, in a reverse closed circuit. The second grinding circuit involved two mills operating in parallel, both in direct closed circuits. The results indicated that the parallel circuit produced 20% less slime than the series circuit, with an additional 4.3% throughput in the flotation feed. No circuit produced particles (> 0.15mm). The parallel circuit spent less 8.3% of energy by not using one of the hydrocyclone batteries.