The shop's recent average of 3.5 relines per year equals 70,000 lost tons. At Algoma, a lance blows nitrogen in the furnace after tapping the molten steel. The blown nitrogen coats the refractories with the liquid slag. Operators direct the slag by moving the lance and altering the rate of nitrogen blow through the lance. If the slag contains too much oxygen, it might be too thin for effective slag splashing.
Operators add dolomite to thin slag, which acts to thicken slag.
Ideal slag for splashing should include oxygen at 400-900 ppm. If slag is too thick or thin, the lance height or blow rate can be adjusted to better move the slag. The BOF shop gets nitrogen from a Praxair oxygen-enrichment facility added to the No. 7 blast furnace in 1996. The oxygen plant liquefies air and separates liquid oxygen from liquid nitrogen. Managers decided to use the nitrogen by-product for slag splashing.