Analysis of Operating Conditions of Shaft Furnace for Reduction of Iron-Ore Pellet by Using a Mathematical Model

Abstract

A mathematical model having the multi-interface model for the reduction of single pellet is employed for the theoretical analysis of the commercial operating conditions of shaft furnace and the following results are obtained.
(1) The required bed height for the reduction is linear to the productivity of iron per cross sectional area of furnace under the same composition and utilization of reducing gas.
(2) The temperature of injection reducing gas greatly affects the required bed height. Under the each operating condition, the critical temperature exists and it correlates to the equilibrium point from Fe₃O₄ to FeO reduction by hydrogen on the operational line chart of oxygen exchange in shaft furnace.
(3) The reduction by the gas contained carbon-monoxide is more effective than that by only hydrogen because of the magnitude of the reaction heat.
(4) Being below 10%, the H₂O and CO₂ in reducing gas do not bring a large shortcoming on the process.
(5) The increasing of gas pressure until about 5 atm has a marked effect to the reduction rate and the productivity becomes larger, the higher the pressure goes, then the shaft furnace having the pressure over several atmospheres is desirable.