EFFECT OF FLUXES ON SLAG FORMATION IN A BLAST FURNACE BY TOP CHARGING AND TUYERE INJECTION

Synopsis: Based on a proposal for injecting fluxes into the blast furnace via tuyeres an evaluation of the influence of fluxes top-charged or tuyere-injected into a blast furnace has been done. The interaction between the slag formers and pellets in the lower part of the shaft and in the cohesive zone of the blast furnace was studied. Chemical analyses, melting point measurements and morphological studies were carried out on samples from previous laboratory softening and melting tests as well as on samples from the LKAB pilot blast furnace at MEFOS. The slag formation mechanism in the blast furnace is discussed. The results show that interaction between olivine pellet and BOF slag may cause variations in slag composition and slag properties at different levels in the blast furnace as well as at different radial positions. The results indicate that the deteriorated melting properties of fluxed pellets by adding BOF slag are caused by formation of a high basicity slag. The negative effect on slag formation caused by top charged fluxes might be avoided by injection of fluxes through the tuyeres.