Continuous improvement at the Kokkola zinc plant

Since the expansion of the plant in 1974, major efforts have been put into maximizing the production capacity of the existing installation. During the last few years, the roaster has been a bottleneck and optimization of the operation has involved the adoption of fuzzy logic control and modifications in the gas handling equipment. In leach and purification, process control has been automated and developed to assure high recoveries of the valuable metals and low zinc dust consumption at 100% operational availability. The capacity of the electrolysis was increased by almost 10% in connection with an enlargement of the electrode surface area and the current efficiency has also been continuously improved, now standing at 92%. Automation in the casting department, including continuous alloying, has been greatly developed. At present, an expansion of 50 000 tonnes per year zinc is being implemented. This expansion is based on direct leaching of concentrate at atmospheric pressure.