| 摘要 |
PURPOSE:To eliminate replenishment of new sand by allowing reconditioned sand to contact with flowing air mixing prescribed time, and converting CaO on the surface 8 the sand to CaCo3, in the process of fluidizing classification removal of fine grains in the sand. CONSTITUTION:The sands containing CaO in their superficial layer recovered in the shaking-out stage are once stored in the recovery hopper 1, and then sent to a calcination oven 2 at a constant flow rate, where coal powder contained in the sand and resin film on the surface are burnt. Calcination, after being cooled, is sent to the superficial layer removing device 3 in which mechanical impacts using the centrifugal force is applied to deposit of binder such as bentonite stuck on the surface of sands as a result of calcination to grind the surface of sands and remove the deposit material. Then, the sand is introduced in the fluidization classification device 4 where the sand comes in contact with the flowing air containing more than 0.5%, preferably 2-3% Co2 for 5min or more. Fine powder classified is collected by the dust collector 5, and reconditioned sand is stored in the hopper 6. CaO on the surface of the sand is changed into CaCO3 being an inert compound against resins, giving reconditioned sand capable of forming casting molds stronger than normally reconditioned sand.
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