Carburization, Melting and Dripping of Iron through Coke Bed

Coke bed in the blast furnace allows gas distribution through the furnace for heating the charged burden materials effectively. In the cohesive zone, slag and metal start to melt and flow down through the dripping zone to the hearth. As the melt formation becomes slower at the cohesive zone, gas permeability becomes worse, and the heat exchange efficiency decreases. Consequently, the formation of molten slag and molten iron should be enhanced for better energy efficiency of the blast furnace. On the other hand, in order to decrease carbon dioxide gas emission from the blast furnace, hydrogen can be considered as an alternative reducing agent. As the hydrogen concentration increases in the blast furnace operation, the reduction of iron oxide can be accelerated from the solid state. Once iron oxide is fully reduced by hydrogen gas, the slag melting can be merely determined by the slag chemistry of gangue and flux materials. Consequently, the carburization of reduced iron by coke plays an important role in the melts formation. Carburization and melting behavior of solid iron by solid carbon have been studied by many researchers. Murakami et al.1) investigated the reaction between solid iron and solid graphite at high temperatures using a confocal laser scanning microscopy (CLSM). Kim et al.2) reported that the carburization rate of solid iron could be increased by placing wustite near the iron due to the Marangoni flow. Ohno et al.3) showed that the initial carburization rate could be slightly increased by lowering the degree of crystallization. In our previous works, it was proved that the carbon diffusion in liquid iron is the rate-determining step.4) However, Carburization, Melting and Dripping of Iron through Coke Bed