Desenvolvimento de modelo matemático do fluxo de líquidos no cadinho do alto-forno

Abstract

Molten iron and slag flow play a critical role in the blast furnace lower zone, transporting mass and energy, whilst impairing and redistributing gas flow. In turn, molten iron and slag undergo physical and chemical changes, and are redistributed radially while it is descent to the hearth. At the blast furnace operation is common fluctuation, accompanying the cycles of iron and slag leak. The liquids accumulation into the hearth and its influence on the descent of the load is the main cause of thatfluctuation. It is possible to observe that there is an increase in the blow pressure during the period among twice leaks, and the pressure decrease only along the tapping. Using the conservation flux and energy equation, the liquids flow inside the blast furnace can be characterised. It is strongly influenced by the radial variation in void fraction entering the furnace, gas flow in the vicinity of the raceway and the furnace profile. The slag flow is more sensitive to operating conditions than molten iron. In this paper, it was made an discussion about the liquid movement inside the hearth of Usiminas Blast-Funace 3. This study included a mathematical model development using a balance of forces that allows to evaluate the dead man's flotation, based on the characteristics of the blast furnace and in its operational conditions. Also, with new calculation routines, that result is used then to feed the mathematical model of liquids flow, previously developed. The results indicate that the drainage behaviour and residual iron and slag volume are affected by the conditions inside the hearth; the determination of the dead manfluctuation is linked to the variation of the blow and top pressure. In addition, the weight of the burden in the blast furnace have a great influence too; the movement of the liquid inside a hearth is very influenced by the situation of the dead man's flotation; the homogeneous variation of the coke granulometry has no strongly influence in thedistribution of the liquids, ether in the residence time. However, the particle size distribution of the coke along the radio inside the hearth has strong influence in the liquid flow lines, and consequently, in its retention.