Abstract

One of the main difficulties in the operation of trough and runners at Arcelor Mittal Tubarão (AMT) Blast-furnace no.02, which is limited by two tap holes, is the reduced amount of time available for repair procedures. The consequence is that the castable installation in main troughs must often be performed during hot conditions. The most critical issue which must be addressed is that the installed castable could easily detach from the base material during the early stage of operation.  This could result in exposing the previously oxidized base material to molten iron and corrosive slag attack. When events like this happen, emergency repairs must be executed, resulting in increased refractory unit consumption and an unplanned shutdown of unit operation.  Highly oxidation resistant materials were demanded in order to avoid a decline in the efficiency of the furnace operation and increase refractory unit consumption.  This would achieve a reliable campaign without any risks, and also reduce the number of hours spent in trough repairs. Considering these targets, Nippon Crucible Co. and Saint-Gobain HPR Brazil have developed a high-performance Al2O3-SiC-C composition based on an entirely novel anti-oxidation technology. Oxidizing reactions could be attenuated by using a special deffloculant in combination with carbon black addition. As a result, the water required for castable installation was significantly reduced in addition to reducing its open porosity values. The new material was tested  on one of the main troughs at AMT BF no.02, resulting in a 50% improvement of  campaign life in terms of passing pig iron when compared with the regular castable. An analysis of this life improvement showed successful results for the material after 250 days of campaign. We determined that the main reason for such successful results was that the deterioration caused by the oxidation was significantly less and that this change made on the high cohesive structure of the base material was maintained for a long time. The attained results allowed Arcelor Mittal Tubarão to achieve longer trough campaigns, and avoid any unplanned stoppages with zero breakdown risks.