Gravity Furnace Charger Helps Foundries Remelt Scrap at 96-98% Yield.

A simplified device for the introduction of flowable metal scrap into a molten bath of like or similar material has been developed by Premelt Systems, Inc., Kalamazoo, Michigan, to operate in conjunction with its furnace charger cover. The proposed use of this device is for introducing sized metal scrap on a continuous or semi-continuous basis below the surface of the molten bath through a hole in the furnace cover, while maximizing metal yield to between 96-98%.

This device can be used in both the ferrous and nonferrous metals industries and can deliver finely divided metal chips, shavings and screened/shredded scrap such as that which might come from a whole castings.

There have been more than 24 installations of this device, melting over 375 million lb of aluminum/yr, representing a metal savings of over 20 million lb/yr that otherwise would have been destroyed with conventional melting practices. It also represents a savings of at least $0.15/lb for every pound of scrap generated within foundries using the device.

In the process, the floating metal scrap is submerged below the surface of the melt bath where the high-temperature molten metal and the absence of oxygen results in a rapid change of state from solid to liquid form with a minimum melt loss. The furnace charger conduit permits accumulation of a sufficient quantity of scrap material contained above the surface of the molten metal so that when the weight balance between the column of scrap material and the specific gravity of the molten metal is overcome, the column of scrap metal automatically submerges itself further into the bath.

Initial trials have indicated that between 40-75% of molten metal weight/cu ft is required to continually submerge the column of scrap into the molten metal. This method of submerged scrap charging also provides effective scrap preheating from the bath.

To provide the most desirable conditions for scrap melting, an inert gas supply is added to the column of scrap metal near the molten metal surface to displace the free oxygen contained in void areas of the scrap with a non-oxidizing cover gas. The refractory-lined bottom surface of the furnace charger provides an air seal so that the gas can supply a positive pressure inside the conduit that causes the flow of oxygen-laden air and gas to exit from the top of the conduit. A conventional dust-collecting device is connected to an air vent at the top of the conduit to dispose of any dust or effluent generated in the charging process.

Two separate controls handle the melt rate and level of the furnace charger conduit with cover. The charger is constructed from steel or stainless steel, depending on the temperature zone.