Research On The Formation Of TiCN And Regulation Mechanism In Blast Furnace Process Treating Vanadic Titanomagnetite

The utilization of vanadium-bearing titanomagnetite in blast furnace processremained as a worldwide problem until the1970s in the last century. It was found thatthe main problems occurred during the process were all somehow related to a highmelting point phase which was produced from over-reduced titanium oxide. That is theTiCxNy. These problems include slag foaming, large viscosity of slag, difficulty ofiron-slag separation and low efficient desulfuration. As a solution, certain amount ofcommon iron ores was added to the raw materials to relieve those problems to someextent. However, this approach became a limitation for the multipurpose utilization ofthe vanadium-bearing titanomagnetite. Moreover, with the increase of common ironores’ price, the production cost of the process is getting higher. Therefore, it is a criticalpoint to restrain the formation of Ti（CN） in blast furnace.In this paper, the thermodynamic conditions for the carbothermic reduction of TiO₂and the meltdown properties of the slag in blast furnace were discussed with thesoftware of FACTSage. The results were in agreement with the former published worksand were verified with experiments. In addition, the iron-slag reaction and coke-slagreaction, which were considered as the two main routes for the formation of TiCxNy inblast furnace, were calculated respectively. The potential control methods to prevent theformation of TiCxNy in blast furnace process were proposed based on the calculatedresults.The results of thermodynamic calculation indicate that when TiCxNy wasproduced in slag-coke reaction, it is likely to occur in the softening zone whichcorresponds to the experimental result of blast furnace dissection. For another, under thecurrent condition of raw material in Panzhihua Steel Ltd. China, the formation ofTiCxNy would theoretically begin at about1280℃. The restriction of formation ofTiCxNy in blast furnace could be achieved by increasing the systematic pressure oroxygen enrichment. Another approach is to adjust the slag composition by decreasingthe content of titanium dioxide and alumina in the slag or increasing the slag basicityand the content of magnesium oxide in the slag. However, the decrease of titaniumdioxide content in the slag was not appreciated.In the experimental study, the composition of TiCxNy produced in the slag-ironreaction was recognized as TiC_0.67N_0.33and the content of TiC_0.67N_0.33would increase with the increasing of temperature. These obeservations match the results calculatedwith Factsage very well. The potential measures to prevent TiCxNy from beingproduced in the slag-iron reaction were similar with those in the slag-coke reaction. Itwas found that the lower down of nitrogen partial pressure could efficiently prevent theformation of TiCxNy. Furthermore, the prevention means could also be either increasingthe slag basicity and the content of magnesium oxide or decreasing the content ofalumina in the slag.