Mechanical and flow properties of residue from dry desulfurization of iron ore sinter plant off-gas

In off-gas desulfurization in sinter plants, dry systems consisting of a sorption process for the separation of sulfur dioxide and a fabric filter for final dedusting are normally used. As a rule, hydrated lime is the base sorbent although sodium bicarbonate can be an alternative. Mechanical and flow properties of the residues produced are relevant for the design of handling and storage facilities for these materials. In this study the mechanical and flow properties of residues from three dry off-gas desulfurization systems were investigated. The particle size and the density of all three residues were very similar, but all other parameters measured differed depending on the sorbent used. Bulk density of the residues from lime-based desulfurization was higher and the flowability was better. This has to be taken into account when a change of the desulfurization reagent from Ca(OH)2 to NaHCO3 is considered. Generally, the flowability of the residues was poor at low consolidation stress and improved at higher stress, whereas the effective angles of internal friction and the wall friction angles decreased. Results produced by three flowability indicators (angle of repose, Hausner ratio, Carr's compressibility) overestimated the flowability of the residues considerably compared to the shear test results. Therefore, shear tests are strongly recommended for a reliable characterization of the flowability of such residues.