Effect of coating structure of granulated quasi-fuel particles in iron ore sintering

To reduce greenhouse gas emissions, biomass fuels are used to gradually replace fossil fuels in the sintering process. Unfortunately, the sinter quality will deteriorate sharply due to too fast combustion rate when using biomass fuels. To address this problem, pregranulation proved to be an effective method. In this study, the pilot-scale sinter pot tests were carried out to study the effect of coating structure of granulated quasi-fuel particles on the granulation properties, flame front propagation in sintering, sinter indexes, sinter mineralogy, and pore structure. The experimental results show that when substituting coke with biomass char, the average size of the granules decreased whereas bed voidage increased due to the irregular shape and lower apparent density of granules. Pregranulation can reduce the flame front speed and increase the maximum bed temperature, thereby alleviating the deterioration of sinter quality and sinter yield. By pregranulating biomass char and 2% magnetite concentrate, the tumbler strength, sinter yield, and productivity can be increased from 44.9% to 55.0%, from 41.9% to 49.3%, and from 28.54 to 31.10 t/m(2)/d, respectively. The microscopic observation results show that substituting coke with biomass char for sintering decreased the content of calcium ferrite in sinter and increased sinter porosity. On the contrary, pregranulating increased calcium ferrite content in sinter and decreased sinter porosity, and thus sinter quality was improved.