Abstract:A mathematical model for ore reduction mainly by H2 in shaft furnace was established by a set of conservation equations of materials and heat, and other constraint conditions. All consumptions and productions could be calculated if the composition of N2, the value of V(CO)/V(H2), the metallization ratio of DRI, the temperature of input gas, etc. were given. It shows that the input gas can be reduced from 1650 N·3 for H2 reduction to 1200 N·m3 by CO addition. When the volume ration of CO to H2 V(CO)/V(H2)was 0.6, the energy utilization ratio of shaft furnace was maximum without N2 addition; when V(CO)/V(H2)=0.3, the optimum composition of N2 was 11%; when V(CO)/V(H2)=0, the optimum composition of N2 was 25%. The N2 addition may result in H2 consumption, but could not reduce the total input gas. The simulation will provide reference to process design, operation and energy saving.