Mechanical and thermal methods for reclamation of waste foundry sand

Abstract

Binder material (e.g. bentonite, polymeric resins) is used for producing molds and cores in foundries. It deactivates upon exposure to the high temperature (~1400°C) of molten metal. As a result, these binders form either loosely or strongly bound deposits on the surface of sand grains, leaving them unsuitable for further use. Disposal of Waste Foundry Sand (WFS) remains to be one of the significant challenges faced by foundry industry nowadays. In order to remove these deposits from WFS, we have studied and compared two types of methods namely, mechanical and thermal reclamation. The WFS samples after being reclaimed either mechanically or thermally or by combination of both, are compared using various tests. These tests include determination of loosely bound and strongly bound clay content, compressive strength, Grain Fineness Number (GFN), Loss on Ignition (LOI), Acid Demand Value (ADV), Particle size distribution and optical microscopy. We have used the aforementioned tests to characterize the quality of foundry sand and the suitability of reclaimed sand for use in mold and core production in foundries. The results showed that neither of these treatments is sufficient to completely remove the deposits from sand grains. However, solely mechanically reclaimed sand is suitable for the mold production after maintaining 8% active clay and 10% loosely bound clay in the reclaimed sand, respectively.