煤灰及各种矿物质对SO2排放特性的影响

It has been clarified that SO2 emission during coal combustion is the main source of acid rain， and the level of SO2 in flue gas determines the erodibility of equipments. Sulfur emission form coal during combustion is determined by fuel properties and combustion conditions. The reaction mechanism of fuel sulfur conversion to oxide and the influence of different factors are still remained unclear. In this paper， combustion of six coals with carbon contents of 77％～93% (daf) and the corresponding demineralized samples has been studied in a thermogravimetric analyzer with heating rate of 20 ℃/min to examine the effect of coal rank， demineralization and inherent mineral species on SO2 emissions. For Fushun coal demineralized by HCl， Si is the main remaining mineral species with content of 3.4% (db)， so the effect of Si on devolatilization can be examined. AlCl3， Fe(C5H5)， Ca(OH)2， KOH， MgCl2， NaOH and TiO2 were used as the catalyst precursors. The results show that the concentration of SO2 in flue gas is associated with the sulfur content in coal， whereas there is no clear relation between them. That demineralization increases the SO2 emission， which indicates that inherent mineral species play a major role during combustion. Si， Al， Mg， Na， K， Ca， Fe and Ti， which are the main species in the ash of Fushun coal， are added into the demineralized coal sample by suitable method with different catalysts precursors. In the minerals， some species decrease the SO2 emission with the sequence of MgNa≈K>Ca>Mg>Ti. Si and Al are found to be inert during coal combustion. The mechanism of influence of different catalysts on the combustion is also discussed.