Numerical simulation of the moving bed furnace for reduction and melting of oxidized iron-scrap briquette containing coke breeze

Briquettes of oxidized iron-scrap containing coke breeze are attracting much attention as a new raw material for ironmaking from the viewpoints of energy saving, recycling and environmental protection. The reduction and melting of the oxidized iron-scrap briquettes in a moving bed reactor has been proposed for hot metal production. The aim of this study is to investigate the reduction and melting behavior of the briquette in the reduction-melting furnace. For this purpose, a total mathematical model of the reduction-melting furnace has been developed considering the rates of briquette reduction, iron melting and carburization to molten iron. The model was applied to the reduction-melting furnace, of which inner shape is a cylinder of 1 m in inner diameter, 4.5 m in effective height and the tuyere opening is 10% of the cross-sectional area of the furnace. Computations were performed under the conditions of air flow rate of 1.7 kg/s, air preheating 673K and coke ratio of 350 kg/thm. The numerical simulation describes flow of three phases (gas, solid and liquid), chemical reactions and phase changes; specifically, the distributions of temperature of the three-phase, gas concentration, reduction degree and carbon content of molten iron in the furnace. From the calculated distribution of temperature and melting ratio, it was proven that the briquette could be melted with preheated air blowing at 673K. The reduction degree distribution showed that sufficient carbon content of coke breeze in the briquette is necessary in order to obtain higher reduction degree.