Pilot cooling tests conducted for high-copper converter matte ingots at Polar Division of PJSC MMC Norilsk Nickel

This paper describes the test methods that were applied to three ingots of high-copper converter matte with the weight ratio of Cu:Ni ~ 2.3 at Polar Division of PJSC MMC Norilsk Nickel to determine their cooling rate. The obtained results are also discussed. A test heat was done in the converter of the Nadezhdinski Metallurgical Plant, during which the following compositions were closely monitored: that of middlings; that of the finished matte that was discharged at 1,255–1,260 оС and poured in molds at 1,200 and 1,140 оС; and that of metallized matte that was intentionally overheated to 1,285–1,290 оС and poured at 1,200 оС. The cooling time was 82 and 93 hours (for capped ingots). The temperature was monitored with the help of six chromel-alumel thermocouples located at the level of 1,350, 850 and 350 mm from the bottom; three of them in the centre and the other three on a side. The ingots were crushed at the Nickel Plant, and a ~300 kg representative sample with the size of 3 mm was taken from each ingot for flotation tests. Spot samples were taken from the temperature monitoring areas for structural characterization. Based on experimental data, functional dependencies were derived with R2 0.99 that describe the obtained cooling curves. It is shown that due to the use of insulation cap in the structure defining temperature range of 1,150–750 оС, the cooling rate of the ingot top can be considerably decreased (approximately by three times). It is equal to 28–29 оС/h. In the vertically central part of all test ingots — i. e. ~850 mm from the bottom both in the centre and on a side, the cooling rates vary in the range of ~9–10.5 оС/h; in lower monitoring points — i. e. 350 mm from the bottom, they are equal to 24–33 оС/h. The cooling rate of the overheated matte at the top drops to 67 versus 87 оС/h for the uncapped ingot, whereas in the centre and at the bottom it almost remains the same.