Research on the Preparation of Sinter for COREX Reduction Process by Varying Basicity and MgO Content

Abstract

Sinter has been introduced into the composite burden of the COREX ironmaking process in China to lower the material cost, but the proportion is limited due to its poor low-temperature reduction degradation performance in the shaft furnace. This work dealt with the preparation of sinter for the COREX process by varying the MgO content and basicity. Their effects on the sintering and reduction properties under reducing condition simulating COREX shaft furnace were investigated, and the changes in the mineralogy of sinter with different MgO content and basicity were explored. The results showed that increasing MgO content affected the sinter strength and solid fuel consumption but restrained reduction degradation of sinter in the shaft furnace. In the basicity range of 0.8–2.6, the strength, RDI+6.3 and RDI+3.15 of sinter all presented a V-shaped curve and the minimum value occurred at a basicity of approximately 1.6. By comprehensive consideration, sinter with 2.35%+ MgO and 2.2+ basicity for COREX process was proposed and verified in industrial tests. Sinter with higher MgO content contained less SFCA and hematite, while glass and SFCA were dominant in the binding phase in sinter with low basicity (0.8) and high basicity (2.6) respectively and were associated with the relatively higher sinter strength. The changes in the mineralogy of sinter determined the variations of RDI of sinter with different MgO content and basicity, by affecting the sinter strength and the probable reduction of inner stress.