Melting furnace or installation of melting furnaces for melting back metal chips(Fig. 1, ZPF GmbH)
In the past, foundries made large investments in chipping castings reworking. This was and still is a reaction especially to car manufacturer requirements that castings ought to be delivered as much elaborated as possible. For this reason, the chip amount in some foundries reached levels where in-house recycling is the more economic alternative to selling the chips to external recycling companies and/or secondary smelters.
In general, the aggregate is for melting chips is regarded by foundries mainly under the aspect of metal yield since the financial bonus of an increased metal yield drastically reduces the amortisation period of the machine. Main factors for metal yield are alloys as well as form and characteristics of the chips. The more fines in the chip charge and the smaller the chip thickness, the lower the chip yield. A sophisticated system of melting chips comprises the analysis of these critical chip characteristics.
For melting chip back in the melting furnace, a chip conditioning machine has to be integrated which provide for chips as dry as possible. Humid chips do not only reduce the metal yield, the also case a heavy smoke emission and soot formation so the developing exhaust gasses have to be cleaned.
The gas-fired ovens are holding ovens, which are equipped with a chip bag (Fig. 2 and 3, ZPF GmbH).
The aluminumchips are transported by a chip processing plant into the chip bag, immediately drawn under the bath surface and conveyed with an agitator into the holdingbath.
These furnaces are designed exactly for the process of chip melting and have the advantage that they build small, relative to the power density. A large shaft construction, as in the case of combined smelting furnaces, is eliminated. A visualization shows Fig. 4 (ZPF GmbH).
The ZPF chip melting furnaces are emptied by tilting the entire furnace.
In the aluminum foundries, ZPF chip melting furnaces with a melting capacity of 0.5 to / h and 1 to / h have proven successful.