An increase in the productivity of ore-thermal furnaces (OTFs) for smelting oxidized nickel ores to ferronickel is limited by the intensive wear of the sidewall lining at the slag–ferronickel interface. An increase in the resistance of furnace sidewalls is possible in several ways, for example, by using cooling. A new explosion-proof cooling system — water-air cooling — was developed by the Furnace Department of the LGI and tested on matte melts.