Production of pre-reduced sinter based on sensible heat updraft of sinter

Utilization of pre-reduction burden in the blast furnace ironmaking process is an important measure for realizing low-carbon operation. In this paper, a new process for the production of pre-reduced sinter based on sensible heat updraft of sinter was put forward. The effects of sinter temperature and reducing gas composition in the pre-reduction cooling section on metallization rate and sieve size distribution of pre-reduction sinter were studied. The results showed that the metallization rate and proportion of 10–12.5 mm particle size of pre-reduction sinter increase with the increase of sinter temperature. When the sintering temperature was 950 °C and the reducing gas was the mixture of H2 and CO, the metallization rate of the pre-reduced sinter was up to 35.5%. When the sintering temperature was lower than 750 °C, the carbon deposition reaction between H2 and CO reduces the proportion of 10–12.5 mm particle size of the pre-reduced sinter significantly. The metallurgical properties of pre-reduced sinter with different roasting systems under hydrogen-rich smelting in blast furnace were studied. The results showed that compared to the traditional sinter, the reduction degradation index, reducibility index, and softening-melting properties of pre-reduced sinter were improved, and the permeability and maximum differential pressure of the stock column were reduced, which was beneficial to the improvement of blast furnace production efficiency. Based on the comprehensive effects of sinter temperature and reducing gas composition on the metallization rate, sieve size distribution, and metallurgical properties of pre-reduced sinter, the quality of the pre-reduced sinter was better when the sintering temperature was higher than 750 °C and the reducing gas was a mixture of H2 and CO. In addition, the new process could organically combine sinter sensible heat utilization, flue gas circulation, and denitrification to form a complete technological process, which had a good development prospect.