Reaction of FeS with simulated slag and atmosphere

Dependent upon the size and density of coal particles used in gasifiers, the resulting ash may contain significant quantities of FeS. It is desirable to have these ash particles react and dissolve in the slag. The rate and rate-controlling reaction of FeS droplets with simplified reactor gas and slags were determined using a confocal scanning laser microscope (CSLM) and a thermogravimetric analyzer (TGA). The shrinking FeS droplets were found to remain at the slag/gas interface for a period and conformed to a lens shape, and size change was attributed to both the reaction and submersion into the slag. Whereas the exact rate could not be determined using the CSLM, the rate increased with increasing CO₂, decreasing FeO in the slag, and was slow in argon. The change in the rate with experimental values is consistent with the hypothesis that the rate is controlled by mass transfer of the product gases, COS and SO₂, away from the particles. TGA results indicated that the measured rate was consistent with the rate computed from the relevant mass-transfer equations and the experimentally determined mass-transfer coefficient. The results indicate that FeS should react, thereby forming FeO, which dissolves in the gasifier slag in a coal gasifier.