The regeneration of waste foundry sand and residue stabilization using coal refuse

The processes for recycling waste foundry sand are divided between regeneration and beneficial reuse, and the potential for regeneration is higher than that of reuse. In this study, two processes for the recycling and residue stabilization of waste foundry sands were considered. One is the dry mechanical process for recycling, and the other is the stabilization process for powdered residue. The dry mechanical process of regeneration consists of crushing, grinding, separation, and classification. To stabilize the residues that were generated through the regeneration process, powdered residues were pelletized by a high-shear pelletizer, and the surfaces of the pellets were subsequently coated with coal refuse powders that contained sodium silicate as a binder. Coated pellets were sintered by a self-propagating combustion method. The refractory index of the recycled sands, as measured by the Seger cone method, was over -34, and their SiO2 contents of 94% was similar to that of green sand. The general conclusion that coal refuse and sodium silicate stabilize heavy metals better than other processes may lead to the development of a cost-effective solution for stabilizing heavy metals in residues. (C) 2011 Elsevier B.V. All rights reserved.