Reduction and Degradation Behaviour of Sinter under Simulated Vertical Probe Trial Condition

Ferrous burden encounters several low temperature isotherms during descent in the blast furnace. Low temperature degradation of ferrous burden becomes critical particularly in the temperature region of 450–650°C. The low temperature degradation, mainly of sinter, results in generation of fines, which affect gas permeability in the stack region. A severe reduction degradation of sinter hampers permeability causing imbalance in reduction degree in the radial and circumferential direction and disturbs the furnace heat level-all detrimental to stability of furnace operation. Experimental studies were carried out with the following conditions: Temperature: 550, 650, 900 and 1000°C; soaking time: 30, 60 and 90 min, and Gas composition corresponding to Softening-melting test condition (CO - 40% and N2 - 60%) and Vertical Probe trial condition (ηCO - 40% and ηCO - 30%). Degradation takes place both at low temperature (550 and 650°C) and high temperature (900 and 1000°C) reduction of sinter simulated under Vertical Probe trial condition. Reducibility was appreciably lower for all tests carried out under simulated Vertical Probe trial condition compared with the results obtained using Softening-melting test condition. Results clearly showed that for minimizing sinter degradation and improving reduction degree in the blast furnace, low temperature holding zone has to be avoided and high temperature holding zone has to be minimized. This can be achieved by increasing sinter reduction degree by adjusting sinter chemistry and burden distribution in blast furnace.