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.

SO₂ Absorption in the Sinter Bed during the Sintering Process

“…Moreover, the moisture content of sinter mixture could increases the SO 2 absorption. 2,9) And the SO 2 behavior could be described as generated, In order to analyse the influence of sinter bed on the SO 2 , the sulphur distribution in the sintering process is studied, which indicates that the sulphur enrichment mainly at the preheating layer and drying layer during sintering process. At the wet layer, the sulphur content only is a slightly higher than the sinter mixture where the SO 2 dissolve in the moisture.…”

Desulfurization of Iron Ores: Processes and Challenges

“…The first problem with thermal decomposition process is evolution of environmental polluting gases (SO x ) during the iron ore sintering process or in iron or steel plants. In the iron ore sintering process, more than 90% sulfur in raw materials releases and enters into flue gases in the form of SO2 in the drying, preheating, and hot zone …”

“…Dry FGD process or furnace desulfurization process is characterized by dry waste products that are generally easier to dispose of than wet waste or byproducts from wet FGD processes . Usually limestone to be used for desulfurization, causing the following reaction to remove SO2 furnace temperature of 760–860 °C: …”

Effect of CO and CO2 Content in Suction Gas on Sintering Process for Iron Ores

“…The sintering indexes were deteriorated when the O 2 content in the suction gas was less than 18 vol%. 2,3) So the O 2 content in the tests was maintained at 18 vol%. The suction gas compositions of the sintering tests are shown in Table 1.…”

“…3) Some of the previous works 2,4,5) showed the effect of suction gas components (O2, CO, humidity) only on the quality and property of the sinter ores, however, the underlying reasons for the changing rule of the sintering indexes were not determined. This note will add them several findings obtained thereafter to clarify the influence of CO and CO2 content in suction gas.…”