Behavior of SO2 in the process of flue gas circulation sintering (FGCS) for iron ores

Abstract

In order to reduce SO2 emission in the iron sintering process, the flue gas circulation sintering (FGCS) process has been recommended and put into practice. In this process, flue gas containing low SO2 concentration is recirculated to the sintering process, achieving the concentration of SO2 content in the off-gas, which is favorable for current flue gas desulphurization processes. In this study, SO2 behavior in different sintering zones was investigated under the simulated experimental conditions. In the moisture condensation zone and sinter mixture zone, SO2 of recirculated flue gas is absorbed by the moisture and slaked lime of sinter mixture; in the drying and preheating zone, part of SO2 in circulating flue gas is absorbed by dry slaked lime in sinter mixture under low temperature conditions, and SO2 is generated by oxidization of sulfides and re-released by decomposition of sulphurous acid; in the hot zone, SO2 in circulated gas is partially absorbed by the molten phases, newly crystallized minerals such as calcium ferrite and dissociative CaO; in sinter zone, part of SO2 is absorbed by residual CaO in sinter under the condition of humid circulated flue gas, which results in unfavorable increase of residual S in the up layer sinter. © 2014 ISIJ.