Injection of slag correction components into the blast furnace

For the injection of slag correction components considering the fluid dynamics of the injected particles is necessary due to reach a maximised residence time in the raceway zone. Based on cold injection model experiments and additional CFD calculations advice for lance positioning for injection trials at voestalpine BF A are worked out. Aim of the injection model calculation was achieving a maximum residence time in the raceway due to inclination of injection lance related to tuyere axis as well as distance between tuyere tip and lance tip. The thermochemical model calculations showed that the elemental distribution especially sulphur showed a non equilibrium state. The equilibrium values are about an order of magnitude higher than the measured values. Based on measured chemical analysis and mass balance data for the slag-hot metal reactions in the hearth a model with an approach to equilibrium factor was build up. The results of that model showed good results in prediction of the sulphur and alkali content of the slag as well as the sulphur content of the hot metal. The results for the also important silicon content of the hot metal showed a greater deviation from the measured values. The injection of tracer material for the slag correction components together with additional reductants (waste plastics) showed a mean residence time of the injected material of about 8 hours. That unexpected result leads to the conclusion that injected material was transported through the raceway zone into the upper shaft deposited there at the burden and transported back into the hearth with burden material. The same behaviour was also observed when MgO-C containing material was injected to raise the MgO contant in the slag.