Leaching dicalcium silicates from iron ore sinter to remove phosphorus andother contaminants

Although dicalcium silicates can constitute up to 10vol % of many modern he matite/goethite iron ore sinters, traditional mineralogical investigations of such sinters have largely overlooked this phase and focused on the more abundant iron oxides and ferrites. However, dicalcium silicates have a rang e of properties that make them unique in sinter parageneses. These properti es may contribute significantly to hulk sinter properties and also make dic alcium silicates potentially exploitable in novel upgrading processes. Anal yses on a pot grate test sinter have shown that phosphorous land possibly o ther elements including potassium and chromium) was heavily concentrated in the dicalcium silicates. A series of etch tests have demonstrated that dic alcium silicates can be selectively removed from the surface of polished si nter samples using weak acids. In addition, bulk leaching trials showed tha t the phase can also be removed from powdered and coarser (-5 mm) sinter in mild acids. These leaches resulted in a >90 % reduction in phosphorous wit h a 7 % improvement in iron grade for the powdered material and a 70 % redu ction in phosphorous with a 5 % improvement In Iron grade for the coarser m aterial. Two novel processes are proposed to exploit the leachability of co ntaminated dicalcium silicates from sinter: one being a potential route to a high-grade iron product, the other being a return fines washing circuit.