BED FILTER GRID PLATE

BACKGROUND

[0001] This invention pertains to an improvement for bed filters in use in wrought aluminum casting applications, and specifically to the support of the bed, i.e., a bed filter grid plate. The overall concept of the invention is to replace an array of cast grid plates in a bed filter with 6-8-10 grit bonded particle filter media plates. ■ The current grid plate being used is constructed from a cast refractory material such as Armorkast 65 Al, and current filter media being utilized is tabular alumina."

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] FIG. 1 is a plan view of a current bed filter vessel;

[0003] FIG.2 is a cross-sectional view taken along line A-A of FIG. 1 , showing a side view;

[0004] FIG. 3 is a top view of a plate;

[0005] FIG. 4 is a side view of the plate;

[0006] FIG. 5 is a side view of the plate.

DETAILED DESCRIPTION

[0007] This invention pertains to a Bed Filter Grid Plate. FIG. 1 illustrates a plan view of a current bed filter vessel. FIG. 2 shows a side view of a cross-section consisting of a series of plates that are further illustrated in FIGS. 3-5. The plates shown in FIG. 3 are all monolithic/solid cast alumina compositions. The slots shown are open holes. Additional views of the plates are shown in FIGS. 4 and 5. The purpose of the present invention is to replace the array of slotted grid plates used as supports for the bed with an array of bonded particle filter media grid plates as illustrated in FIG. 3.

FIGS. 1-5 illustrate one example of a bed filter, but it is to be understood that any other similar type of bed filter may be used and we are not limiting the present development to what has been described here.

[0008] The bonded particle media is made of discrete particle of silicon carbide or aluminum oxide grains and an aluminum-alloy resistant binder system. The bonded particle filter is less porous than other filter materials and contains a greater number of tortuous, interconnected pathways. Therefore, there are many more chances to capture inclusions as the molten aluminum flows through the filter. In addition, the binder system actually has a "fly paper" effect in holding on to inclusions, even with repeated usage.

[0009] Bonded particle filtration is a proven and efficient means for removing oxides from molten aluminum and its alloys. By filtering oxide inclusions and intermetallic sludge, hard spots caused in machining are eliminated, and the full range of alloy properties are improved. Specifically, bonded particle filtration improves fluidity, castability, machinability, yield, and productivity, which will increase profitability. In the present application, two other properties of bonded particle filter media are important. The specific nature of the binder system employed to bond the silicon carbide or alumina grains is chemically resistant to attack by most aluminum alloys; therefore, the media resists degradation through long-term exposure. As bed filter systems are designed to process several million pounds before replacement, such chemical resistance is necessary.

[0010] Furthermore, the bonded particle filter media exhibits sufficient strength at molten aluminum operating temperatures, such that a series of plates, properly supported by "ribs" in the floor of the bed filter vessel, will sufficiently support the weight of the tabular alumina and molten aluminum during operation. The bonded particle filter is also corrosion-resistant to molten aluminum over long time periods and thermally conductive.

[0011] Many advantages are anticipated from using the bonded particle media, such as a faster heat-up rate (using silicon carbide), enhanced filtration (since the bonded media serves as a filter as well), and potentially lower cost is anticipated, especially with the replacement of one or more layers of the tabular alumina currently used in the bottom of the bed, and extended bed life (through filtration of the bonded media). In addition, reduced labor in rebuilding the bed layering is anticipated by using the bonded media in place of one or more existing bed layers with tabular alumina. The bonded media serves as a better "buffer" against "channeling" since the bonded media grid plate is "rigid" and has much lower porosity than the current refractory grid plate with holes. "Channeling" is the phenomena whereby the loose layering of the non-bonded tabular alumina "shifts" with metal flow or external disturbance and creates preferential flow paths for the molten aluminum to by-pass steady filtration through the bed. By potentially using several layers of bonded media as the filter bed, with positive filtration as cited in the foregoing, less metal volume may need to be employed in the bed and a smaller vessel size (footprint) may result. Moreover, additional filter media results in extended metal flow capacity capability.

[0012] The exemplary embodiment has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the exemplary embodiment be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.