Abstract
ABSTRACT Improper disposal of sand used in molding processes after casting increases logistical costs and environmental impact because of the presence of the phenolic resin in its composition. The regeneration process of waste foundry phenolic sand (WFPS) aims to recycle this material. As mechanical regeneration methods are not efficient to guarantee 100% cleaning of the sand grains and their use again in the molding process, this work investigated the efficiency of a method of thermal regeneration of this type of residue that can be employed as a complementary procedure. A laboratory-scale fluidized bed reactor was designed and built to regenerate WFPS that was previously treated by a mechanical method. The methodology used to design and construct the fluidized bed prototype is described, as well as the characterization of the residual, the standard clean sand and the regenerated sand. The results of the thermal regeneration in the fluidized bed were very satisfactory with respect to the regeneration efficiency. For the nine process conditions tested, loss on ignition values were reduced when compared to standard clean sand. This study presents the advantages of a combination of two processes, mechanical and thermal regeneration, which allows to reduce the time and eventual temperature of resin removal due to the partial removal of the resin layer or its weakening during the mechanical regeneration process. Of the nine process conditions tested, six had loss on ignition values below the CSS. Thus, the thermal regeneration in the fluidized bed results was quite satisfactory in relation to the regeneration efficiency.
Highlights
Requirements of environmental laws have forced foundries to increase the costs associated with the disposal of molding sands in specialized landfills
Research has investigated waste foundry phenolic sand (WFPS) as partial replacement of fine aggregate in concrete. These findings suggest that WFPS may be effectively utilized as a partial replacement of fine aggregates in making concrete of considerable quality, with no adverse effects in terms of mechanical, environmental, and micro-structural impacts [8-9]
Laboratory studies that looked into physical, geotechnical, and leaching properties of flowable fills consisting of WFPS, cement, and fly ash mixed to different water contents were performed by Deng and Tikalsky (2008) [10]
Summary
Requirements of environmental laws have forced foundries to increase the costs associated with the disposal of molding sands in specialized landfills. Waste foundry phenolic sand (WFPS) consists of uniformly sized, high-quality silica sand or lake sand that is bonded to form molds for ferrous (iron and steel) and nonferrous (copper, aluminum, brass) metal castings. This silica sand is coated with a thin film of burnt carbon, residual binder (bentonite, and sea coal, or organic resins by chemically bonding like in the present work). Thermomechanical methods to regenerate foundry sands have been investigated in the effort to mitigate the effects of environmental degradation as much as possible, improve conservation of sand extraction sites, considering in-house recycling as the best solution for valuation of a waste according to the cleaner production concepts [11,12]. The results showed that the major challenge remains the cost investment required to implement reclamation foundries units, mainly the small ones
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