Cold-bond agglomeration of reactive pyrrhotite tailings for backfill using low cost binders: Gypsum β-hemihydrate and cement

The Cold-Bond Tailings Agglomeration (CBTA) technique was first presented by Amaratunga and Annor (1989) for agglomeration of the fine fraction of tailings, allowing total utilization of tailings as backfill and other products. The main objective of the CBTA technique is to reduce or eliminate the surface impoundment of tailings. Surface disposal of reactive pyrrhotite tailings with high iron sulphide composition, which are commonly produced in Sudbury mining operations will lead to oxidation in the presence of air and water resulting in Acid Mine Drainage (AMD). Therefore, for environmental and economic reasons, surface impoundment of pyrrhotite tailings should be avoided. TA process has also been proven effective in controlling AMD using alkaline additives such as Portland cement, fly ash and bactericides. The removal of industrial S02 by the Flue Gas Desulphurization (FGD) process produces gypsum β-hemihydrate (CaS0412H20) its a waste by-product, which may also be used as a non-alkaline binder. This paper will outline the investigation of the agglomeration of fine reactive pyrrhotite tailings for backfill employing Portland cement and gypsum β-hemihydrate as low cost binders. The study showed that the development of an optimum cold-bonded pyrrhotite tailings pellet with Portland cement and Gypsum β-hemihydrate as binder depends on the fracture load of the cured pellet, availability and cost of Gypsum β-hemihydrate.