Metallurgical apparatus – Means for melting or vaporizing metal or treating liquefied... – Means to melt and separate metal from mass of diverse...
Reexamination Certificate
2000-09-01
2002-10-15
Kastler, Scott (Department: 1742)
Metallurgical apparatus
Means for melting or vaporizing metal or treating liquefied...
Means to melt and separate metal from mass of diverse...
C266S227000, C266S275000
Reexamination Certificate
active
06464929
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a system for processing dross which forms on a molten metal bath during melting and holding in a furnace and more particularly to a system for reclaiming metal entrapped in the dross.
BACKGROUND OF THE INVENTION
Various techniques have been developed for reclaiming metals from drosses to reduce metal losses associated with melting and holding molten metal in a furnace. One technique has been to transport the dross to a site remote from the furnace site for processing. A second technique processes the dross at the furnace site. These techniques frequently employ a reaction vessel where the dross is stirred or agitated to promote separation of the metal entrapped therein. During processing, the entrapped metal forms a pool of molten metal at the bottom of the reaction vessel. The molten metal is then drained from the bottom of the reaction vessel into a collection vessel, and the spent dross is dumped from the reaction vessel.
U.S. Pat. No. 3,198,505 illustrates an apparatus used for remote processing of the dross. This apparatus includes a frame to which a motor-driven stirrer is mounted. A drum is employed as a reaction vessel for containing the dross. The reaction vessel is designed to be transported by forklift from the furnace site, where the dross is loaded into the reaction vessel, to a remote site where the frame is located. A movable platform is provided to raise the drum so as to immerse the stirrer into the dross in the drum. A recovery tray resides below the platform to collect the drained metal. This apparatus requires dedicated space, making it impractical for use where free space to accommodate the apparatus is not available. The remote processing of the dross also introduces temperature losses during transport of the dross and can complicate the effective processing of the dross.
U.S. Pat. No. 4,121,810 illustrates an in situ apparatus which can be effectively used for processing larger volumes of dross. The '810 patent discloses a container with a motorized stirrer which extends through the bottom of the container. The container is mounted on a wheeled carriage to allow positioning it near a furnace for loading dross, thus avoiding the need for a dedicated space. Trunnions are provided to allow pivoting the container to dump the remaining dross after the metal has been drained. A frusto-conical shield in the bottom of the container protects the bearing of the stirrer drive shaft from the dross and the molten metal. The drive shaft is driven via a chain by a motor, which is apparently mounted to the side of the container to allow the container to be tipped without disengaging the drive mechanism. The requirements of shielding the drive bearing and mounting the motor to the container complicate the structure of the container, and make replacement of such a container impractical. While the system of the '810 patent is mobile, it is complex, making it difficult to maintain, and makes the elimination of the spent dross difficult.
U.S. patent application Ser. No. 09/233,564, now issued as U.S. Pat. No. 6,136,262, the inventor has disclosed and claimed an apparatus suitable for in situ processing which provides a mobile apparatus with reduced complexity; however, such does not provide for automated stirring, which effectively limits the quantity of dross that can be conveniently processed since it relies on the operator stirring the dross. Furthermore, the effectiveness of such apparatus is dependent on the skills of the operator. Also, for larger volumes of dross, the operator is required to stir the dross for a substantial time and may choose to foreshorten the cycle since, while stirring, the operator is working in close proximity to the hot dross and is exposed to fumes which are generated as the dross reacts with exothermic compounds and fluxes employed to enhance the recovery of the entrapped metal.
Thus, there is a need for a dross processing system which avoids the disadvantages of the devices discussed above and which is simple to operate, requires minimum maintenance, and yet provides a high recovery rate.
SUMMARY OF THE INVENTION
The present invention is for an in situ dross processing system for reclaiming entrapped metal from a dross. The in situ dross processing system of the present invention reclaims entrapped metal from the dross which develops while melting metal and holding the molten metal in a furnace. The system of the present invention has been found to have particular utility in processing the dross associated with molten aluminum alloys.
In an elementary form, the dross processing system has a substantially vertical support and means for positioning the support in close proximity to the furnace. The substantially vertical support terminates in an upper support region and a lower support region. In one embodiment, the means for positioning the support is a bracket affixed to the furnace and engaging the lower support region, while in another embodiment a stand is attached to the lower support region and serves to position the substantially vertical support in close proximity to the furnace. The stand can be designed to either anchor the substantially vertical support with respect to the furnace or can be mounted on wheels to facilitate the movement of the dross processing system to and from a position in close proximity to the furnace.
A reaction vessel is provided, into which the dross is loaded and processed to extract molten metal entrapped therein and separate it therefrom, by allowing the molten metal to settle to the bottom of the reaction vessel. The reaction vessel preferably has a substantially vertical sidewall, terminating in an upper rim and a lower rim, and a bottom member attached to the lower rim so as to form a concave surface when viewed from the sidewall. Some limited degree of draft is preferred in the substantially vertical sidewall to better facilitate dumping the contents of the reaction vessel. Furthermore, having draft in the substantially vertical sidewall, in combination with the bottom member having a concave surface promotes relief of the resulting stress field from thermal expansion by axial symmetric strains and prevents local buckling even when the reaction vessel is fabricated of relatively thin stock.
A port is located in the bottom of the reaction vessel and is preferably formed by a cylindrical sleeve passing through the bottom member. The port is configured to be sealingly engaged by a port plug, which is preferably fabricated from a refractory fiber material such as an alumino silicate that is packed into the port to seal the port and avoid run-out of the molten metal collected in the bottom of the reaction vessel. It is further preferred that a removable plug support plate be positioned below the sleeve and maintained in position by a plate support rack attached to the bottom of the reaction vessel. The plug support plate provides additional support to the plug to withstand the pressure from the head of recovered metal which collects in the bottom of the reaction vessel. It is further preferred that the plate support rack have two substantially horizontal members which attach to the reaction vessel and on which the support a plate slidably rests. In a preferred embodiment, the two substantially horizontal members are formed as U-shaped plate support bars on which the plug support plate rests.
The dross processing system may be configured such that the reaction vessel can reside over the furnace for loading the dross. In such cases, it is preferred that the reaction vessel be fabricated of metal sheet stock. For processing dross from aluminum alloys, a low alloy stainless steel such as
304
stainless steel has been found adequate for forming the metal reaction vessel. For ease in fabrication, it is preferred that the reaction vessel be fabricated from a multiple part assembly having a substantially vertical sidewall, which can be readily formed from metal sheet stock, to which a bottom member is attached. The bottom member can be readily form
Kastler Scott
Q. C. Designs, Inc.
Semprebon Jeffrey E.
Weins Michael J.
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