Influences of SO2 in the Recirculation Flue Gas on the Iron Ore Sintering Process

The influences of SO2 in the recirculation flue gas on the sintering process are studied through simulating the flue gas recirculation with sinter pot test at room temperature. The results show that, with the increasing concentration of SO2, the SO2 is absorbed by CaO, the surface of CaO particles will generate CaSO4 which affects the formation of binding phase, so the sinter yield and particle size will decrease. The residual sulfur in sinter ore will increase obviously when SO2 concentration is higher than 500 ppm, the residual sulfur of middle sinter ore in 2 000 ppm is 1.54 times higher than that in 500 ppm. Meanwhile, the SO2 peak concentration in flue gas is enriched, which is conductive for the end-of-pipe treatment of SO2. The RI of sinter ore is increased and softening and melting properties become better, because the consumption of CaO affects the formation of calcium ferrite and increases the reduction rate and melting point of sinter ore, another reason is that the decomposition of CaSO4 leads to an increase in the porosity in the sinter, and the higher porosity makes the sinter expose more surface area to the reduced body, and the RI of the sinter increase. Therefore, adding an appropriate amount of SO2 in the sintering process can improve the quality of the sinter, and if the SO2 content is too high, it will affect the formation of the binder phase and reduce the strength and yield of the sinter.