Behavior of self-reducing pellets (SRP) for the use in a low height blast furnace

One way to decrease the reducing agent rate in a blast furnace (BF) is the lowering of thermal reserve zone (TRZ) temperature by using highly reactive materials such as self-reducing pellets (SRP). The lower strength requirement of raw materials for small BFs allows the charging of SRP. In the scope of the current study, the behavior of SRP under the TRZ simulated conditions has been investigated. Coal, charcoal and coke breeze were used as embedded reducing agents. The reduction experiments have been performed under different iso- and non-isothermal scenarios. A Tammann furnace laboratory rig and a simultaneous Thermogravimetric/Differential Thermal Analysis (TG/DTA) experimental set were used for investigations. Mass loss during reduction, reduction degree, metallization degree, volume change, reaction heat flow and the starting temperature of the Boudouard reaction were examined. The results from experiments with TRZ condition show that embedded reducing agents, especially charcoal, promote iron oxide reduction in pellets. The isothermal reduction kinetics model of SRP considering the reduction reactions, Boudouard reaction, devolatilization and gas exchange was developed in order to estimate the kinetic parameters. The crushing strengths of SRPs after both methods of hardening, fire-hardening and cement-bonded curing, and the reduction of cement-bonded SRP after curing have been investigated as well.