Increase of BOF Converter Life by Own Slag Coating

Résumé

This paper presents a method for the improvement of the lining life of the BOF converter by slag coating, under nitrogen pressure. Own slag coating of converter lining is put in practice after steel tapping. Dolomite blocks are used like standard wear converter lining. Nitrogen blowing for own slag coating is carried out by oxygen lance. After steel tapping without slag, the converter is tilt in blowing position and the oxygen lance is let down in the lowest position. The nitrogen is blown under 10-12 barr pressure and 450-500 Nm³/min rate, for 3 minutes. By this slag coating technology the performance of refractories has been improved from about 370 heats per campaign in reference year to about 800 heats per campaign at the end of two years of experiments, and therefore refractory consumption decreased from 5.25 kg/t under 3.00 kg/t and the cost of converter refractories decreased by 0.24 $/t. Another variant for improvement of the BOF converter lining life was the use of magnesia bricks for selective lining areas (trunion rings area and charging mouth). The own slag coating technology has been used also. In the case of this variant, the lining life of converter has been improved to about 800 heats per campaign at the end of two years of experiments and so the refractories consumption decreased under 2.45 kg/t. Because of the higher price of magnesia bricks and of the lower price of dolomite blocks, the cost for converter refractories has decreased only by 0.02$/t.