Cyclic Use of Ladle Furnace Refining Slag for Desulfurization

Industrial experiments were carried out to study the cyclic use of ladle furnace refining slag on desulfurization. Sampling of refining slag and steel were undertaken simultaneously at roughly equal intervals of time. The desulfurization capacity remained almost unchanged in the recycling slag compared with the primary slag. The amount of lime added was gradually increased each time when the slag was reused. As a result, the basicity increased, and therefore the sulfide capacity (Cs) increased. Cs reached a maximum when the lime added was 816 kg. The effect of sulfur enrichment on desulfurization reaction in ladle furnace slag-recycled process could be partially offset mainly by two aspects: the amount of slag increased with increases in the number of times recycled slag reused and in the quantity of lime added, which could directly reduce the mass fraction of sulfur in the recycled slag; on the other hand, during the process of transport, casting, and pouring recycled slag into next ladle, a part of CaS in the recycled slag has opportunity to be oxidized by air. Based on such favorable conditions for desulfurization, a final desulfurization ratio of up to 82.6 % was obtained, and the end-point sulfur content can be reduced to about 40 ppm.