US3424186A

US3424186A - Circulating device

Info

Publication number: US3424186A
Application number: US581896A
Authority: US
Inventors: Robert J Sparks
Original assignee: Individual
Current assignee: Individual
Priority date: 1966-09-26
Filing date: 1966-09-26
Publication date: 1969-01-28
Anticipated expiration: 1986-01-28

Description

Jan. 28,1969 R. J. SPARKS 3,424,185

CIRCULATING DEVICE Filed Sept. 26. 1966 Sheet of 4 INVENTOR. ROBERT J. SPARKS J/pwmd wm ATTORNEY Jan. 28, 1969 R. .1. SPARKS CIRCULATING DEVICE INVENTO ROBERT J. SPAR R Q ATTORNEY BY Juana! 1; WWW

I v I United States Patent 3,424,186 CIRCULATING DEVICE Robert J. Sparks, 7250 Brecksville Road, Independence, Ohio 44131 Filed Sept. 26, 1966, Ser. No. 581,896 US. Cl. 137205 Claims Int. Cl. F04f 3/00; C21c 7/00 ABSTRACT OF THE DISCLOSURE The combination of a vessel and a device for circulating molten material from one place to another within the vessel, characterized by a hollow chamber, a partition separating an inlet port and outlet port formed in the walls of the chamber and a vacuum of pressure source for transporting molten material from a submerged strata in the vessel, through the inlet port, over the partition, through the outlet port to discharge into a submerged strata in the vessel.

This invention relates generally to the art of materials handling and more particularly to a device for circulating molten materials.

In general terms, one aspect of the invention relates to a device of the type described, comprising a wall generatrix defining a hollow chamber; an inlet port and an outlet port located in said wall generatrix; partition means located within said hollow chamber, and cooperating with said wall generatrix to provide an indirect path of communication between said inlet and outlet ports and to block direct communication between said ports; and means for changing the pressure within said hollow chamber, whereby molten material entering said chamber from said inlet port is caused to travel said indirect path of communication to said outlet port in response to a change in pressure.

Also in general terms, another aspect of the invention relates to a device of the type described comprising a wall generatrix defining a hollow chamber; means for changing the pressure within said hollow chamber; inlet means for ingress of molten material to said chamber, and outlet means for egress of molten material from said chamber; said inlet means comprising a valve seat, and a normally seated inlet valve operative to be unseated in response to a pressure change within said hollow chamber; and said outlet means comprising a valve seat, and a normally seated outlet valve operative to be unseated in response to a pressure change within said hollow chamber, said inlet and outlet valves being responsive to directionally different unseating pressure changes.

The device of this invention will find utility in the handling of diverse types of molten materials such as resins, glass, salts, metals, and even comestibles such as chocolate and fats. The invention finds particular utility in the handling of molten metals. For purposes of illustrating a specific utility and without limiting the scope of the invention, an example will be made of the device as applicable to a secondary aluminum smelting operation. From this example, other applications of the device will readily suggest themselves to those skilled in the art.

Secondary aluminum smelting involves charging scrap aluminum to a melting furnace, rendering the scrap molten, chemically and/or physically removing undesired impurities, adding alloying materials as required, and 'then casting ingots or otherwise forming products from the resulting melt.

Reverberatory furnaces with external charging wells are conventionally used in secondary aluminum smelting operations. The charging wells have ports or doors which communicate with the furnace proper. Scrap is charged to the external well and melted with heat conducted by molten metal flowing from the furnace proper, through the communicating ports or doors, into the external charging well.

The transfer of heat from molten metal to scrap is presently assisted by agitating the contents of the external charging well with a long rake; an inefficient and uneconomical procedure at best. As the scrap charge breaks up and begins to melt, it is pushed with a rake through a communicating port or door into the furnace proper for further heating.

Thus, according to present day practice, circulation and heat transfer is facilitated by manual raking. This practice has a number of disadvantages. First, because raking is inefficient, the metal in the furnace must be substantially overheated so that when it reaches the external charging well it will still be hot enough to melt the scrap charge. This overheating increases fuel costs and increases the undesirable conversion of metal to oxide, reducing the yield of desired product.

Second, raking necessarily breaks the protective oxide film or skim which forms on molten aluminum and tends to inhibit further oxidation. This exposes more aluminum to the atmosphere, increasing oxide formation,

Third, circulating by raking is an ineffective way of dispersing alloying ingredients in the melt. This results in a product having a nonuniform composition.

The present invention overcomes these and other disadvantages in the existing practice for circulating aluminum. Specifically, the inventive device is capable of circulating molten metal with much greater efiiciency and thus overheating of the melt can be kept to a minimum. Further, the device withdraws molten metal from beneath the oxide film and returns it to a level beneath the oxide film, wherein the oxide film remains substantially undisturbed thus minimizing oxide formation. Still further, the device provides sufficient agitation of the molten metal to uniformly distribute alloying ingredients.

Other advantages will become apparent from the following detailed description of the invention and the accompanying drawings in which:

FIG. 1 is a perspective view with parts cut away showing the inventive device installed in the external charging well of a reverberatory furnace;

FIG. 2, is a section of an embodiment of the invention, showing the device at rest;

FIG. 3 is a section of the embodiment of FIG. 2, but showing the device during intake;

FIG. 4 is a section of the embodiment of FIG. 2, but showing the device during discharge;

FIG. 5 is a section of another embodiment of the invention, showing the device at rest;

FIG. 6 is a section of the embodiment of FIG. 5, but showing the device during intake;

FIG. 7 is a section of the embodiment of FIG. 5, but showing the device during discharge;

FIG. 8 is a section of a modification of the embodiment shown in FIG. 5;

FIG. 9 is a section of yet another embodiment of the invention, showing the device at rest;

FIG. 10 is a section modification of the embodiment shown in FIG. 2;

FIG. 11 is a section of a modification of the embodiment shown in FIG. 4; and

FIG. 12 is a section of a modification of the embodiment shown in FIG. 3.

Referring now to the drawings, FIG. 1 shows a reverberatory furnace designated generally as 10 in which is installed one embodiment of a circulating device, designated generally as 11. The furnace comprises a heating chamber 12 and an external charging well 13, separated 3 by a common wall 14, having communicating

ports

15 and 16.

Heating chamber 12 comprises radiant heating means 17, most conventionally gas fired, a stack 18 for removing gases and fumes, and a door 19 for cleaning the furnace and charging an initial heel (a term defined presently). Means for removing molten metal from the chamber is provided by tap-hole 19a.

The circulating device 11 comprises a wall generatrix 20, defining a hollow chamber, an inlet port, which in the preferred arrangement shown corresponds to port 16 in common wall 14 separating the heating chamber from the external charging well; an outlet port 21; a partition 22 interposed between inlet port 16 and outlet port 21; and vacuum producing means 23 communicating with the interior of the hollow chamber defined by wall generatrix 20.

Partition 22 extends upwardly from the bottom of the hollow chamber, resting on the floor of external charging well 13, with the width of the partition conforming to the walls of the hollow chamber. Thus the partition blocks direct communication between inlet port 16 and outlet port 21. But since partition 22 is shorter in height than the hollow chamber it does provide an indirect path of communication between the inlet and outlet ports as will presently be explained in greater detail.

Vacuum means per se forms no part of the present invention and therefore has not been shown in detail. Various commercially available types of vacuum producing mechanisms can be used in the practice of the invention. Vacuum pumps and air ejectors are two such types.

FIGS. 2, 3 and 4 show one embodiment of the circulating device at various times in its operating cycle. In FIG. 2, the device is at rest and it will be seen that the level of molten metal 24 is the same outside as it is inside the hollow chamber. Air ejector 23a is at rest.

FIG. 3 shows the circulating device toward the end of its intake stroke. During intake, compressed air from a source not shown passes horizontally through the air ejector from nozzle 25. In accordance with the well known venturi principle, this creates a partial vacuum in upstanding tube 26. Air resting on the molten metal within the hollow chamber is drawn up into tube 26 and out exhaust port 27 of the air eject-or. Molten metal from outside the hollow chamber rushes into the chamber through

ports

16 and 21 to fill the void left by the exiting air. The pull of vacuum is continued until the level of molten metal within the chamber rises above partition 22.

In the embodiment illustrated inlet port 16 is shown to be larger than outlet port 21. This means more metal will enter the hollow chamber from port 16 than from port 21, producing a net flow of metal toward outlet port 21. This is desirable and even preferred in some instances but not essential to the operativeness of the device. Even where both ports are substantially the same size, the mere raising and lowering of a body of molten metal will serve to improve heat transfer in the system.

In the embodiment illustrated partition 22 is shown to be closer to port 16 than to port 21. This provides additional room on the outlet side of the partition to accommodate the larger volume of molten metal flowing in that direction. Again, this feature is desirable since it increases the efliciency of the device, but it is not essential to its operativeness.

At some predetermined heat of metal Within the hollow chamber, compressed air to nozzle 25 is shut off. This can be a manual operation but is preferably automatically timed. At this point, atmospheric pressure is instantaneously restored to the air pocket in the hollow chamber (FIG. 4.), and the head of metal in the chamber falls under its own weight. The metal flows through

ports

16 and 21, but principally through the latter since more metal was stored on the port 21 side of partition 22.

Referring again to FIG. 1, the device just described will provide a flow of molten metal from outlet port 21 into external charging well 13 where it will contact and assist the melting of fresh scrap charged to the well. Molten metal is fed to the hollow chamber principally from heating chamber 12, through inlet port 16. This molten metal has a high sensible heat which is transferred in part to the molten metal and fresh scrap located in external charging well 13. As the scrap begins to melt, the flow currents established by the circulating device cause the melting scrap to move in the direction of port 15, where it passes into heating chamber 12 for further heating.

Once a reverberatory furnace is placed in service it will always contain at least a minimum level of metal. Even after the furnace is tapped, a residual amount of molten metal, referred to in the trade as a heel is left in the furnace to facilitate the melting of the next charge of scrap. The inlet and outlet ports of the circulating device are preferably positioned at levels below any level of molten metal the furnace normally contains. Since the level of the heel of metal is the lowest level of molten metal the furnace normally contains, it follows that the ports are desirably positioned below the heel level. This permits the circulating device to operate continually,

even immediately after the furnace has been tapped. In this manner the melting of a new charge of scrap begins promptly upon its being fed to the external charging well. Implicit in this discussion is the fact that the circulating device will not operate if portions of

ports

16 and 21 are exposed above the level of molten metal in the furnace. Should this happen it would be necessary to add metal to the furnace, in the form of scrap, ingot or a melt, until the ports are completely submerged in molten metal.

FIGS. 5, 6, and 7 show another embodiment of circulating device at various points in its operating cycle. In this embodiment the previously used partition has been omitted and the inlet and outlet ports of the hollow chamber have been augmented with positive one way valving means.

As seen in FIG. 5 which shows the device at rest, inlet port 16 is provided with a valve seat 28, and a normally seated valve 29. Similarly, outlet port 21 is provided with a valve seat 30 and a normally seated valve 31. In these arrangements the valves are more dense than the molten metal. Accordingly gravity urges them down the inclined planes of their respective valve seats and into sealing engagement with the respective ports.

FIG. 6 shows the circulating device toward the end of its intake stroke. During intake, compressed air from a source not shown passes horizontally through air ejector 23a from nozzle 25. As previously discussed, this reduces the pressure on the molten metal within the hollow chamber, causing molten metal from outside the chamber to rush in and equalize the internal and external pressure.

The force of the molten metal of inlet port 16 overcomes the gravitational pull seating inlet valve 29, causing the valve to ride up the inclined plane of valve seat 28 and out of sealing engagement with inlet port 16. The arrangement of outlet valve 31 is such that it remains seated when the pressure within the hollow chamber is reduced. In fact, the pull of vacuum on the interior of the hollow chamber produces a force on outlet valve 31 which is directionally the same as the gravitational force urging the valve into sealing engagement with outlet port 21. Consequently, all of the metal introduced into the hollow chamber during the intake stroke, enters by way of inlet port 16.

FIG. 7 shows the circulating device at the beginning of its discharge stroke. This state is achieved by shutting off the compressed air to nozzle 25 of air ejector 23a. This instantaneously restores atmospheric pressure to the interior of the hollow chamber, and the head of molten metal therein begins to fall under its own weight. The force of metal at outlet port 21 overcomes the gravitational pull seating outlet valve 31, causing the valve to ride up the inclined plane of valve seat 30 and out of sealing engagement with outlet port 21. The arrangement of inlet valve 29 is such that it returns to a seated position when the interior of the hollow chamber is released to atmospheric pressure. Consequently the head of molten metal released from the hollow chamber discharges through outlet port 21.

A distinct advantage of the embodiment shown in FIGS. 5, 6 and 7 is efficiency. The use of valving permits the positive, directional movement of more metal per cycle than the embodiment shown in FIGS. 1-4. However this more eflicient arrangement includes moving parts submerged in molten metal, which will require maintenance and replacement from time to time.

FIG. 8 shows a modification of the embodiment of FIGS. 5-7. In this modification the

valves

29a and 31a are less dense than the molten metal. Accordingly these valves are maintained in a normally seated configuration by the force of buoyancy urging them up the inclined planes of their respective valve seats 28a and 30a and into sealing engagement with the respective inlet and outlet ports. In all other respects, the operation of this modification is identical to that described in connection with FIGS. 5-7.

FIG. 9 shows a further embodiment combining certain of the features of the two embodiments described above. In FIG. 9, partition 22 is retained and only outlet port 21 is augmented with a valve seat 30 and a normally seated valve 31. The etficiency of this one valve embodiment will be better than the valveless arrangement of FIGS. l-4, but not quite as high as the double-valved arrangement of FIGS. 5-8.

The positive valving of outlet port 21 in FIG. 9 ensures that all of the molten metal admitted to the hollow chamber on intake, enters through inlet port 16. However, only that portion of the molten metal which passes over partition 22 will be discharged through outlet port 21; the remainder of the molten metal will fall back and be discharged through inlet port .16.

The valves shown in FIGS. 5-9 may take various configurations, such as rods, balls, wedges, etc. Similarly, the configuration of the valve seat can be varied to include more positive guide means such as grooves or tracks for seating the valve, as well as restraining means to limit the distance the valve can move out of seating engagement with a port. Other variations of this type will readily suggest themselves to those skilled in the art.

The composition of the valves will vary with the nature of the molten material they contact, and with the selection between valves more dense and less dense than the molten material. For instance, for use with molten aluminum, a less dense valve of graphite may be used, and as a more dense valve, graphite with a steel core will be satisfactory. For contacting with molten zinc, graphite can be used as a less dense valve and stainless steel as a more dense valve.

The invention alSO contemplates the use of an over pressure as well as vacuum to effect the change from atmospheric pressure necessary to operate the circulating device. FIGS. -12 show such an embodiment at various points in its operating cycle.

FIG. 10 shows the circulating device at rest and it will be noted that the air ejector has been replaced by pair of valves, each connected by piping to tube 26 which communicates with the interior of the hollow chamber defined by Wall generatrix 20. Valve 32 is connected to a source of pressurized fluid not shown. The fluid may be a liquid or a gas. Preferably, the fluid is inert with respect to the molten metal so that it neither contaminates nor reacts with the melt. In handling molten metals, gaseous nitrogen or argon are preferred fluids.

It will also be noted that in this embodiment that the equilibrium level of molten metal substantially fills the hollow chamber and is higher than the top of partition 22. Discharging of metal from the hollow chamber is accomplished by closing valve 33 and opening valve 32 to admit pressurized fluid through tube 26 into the interior of the hollow chamber.

FIG. 11 shows the device during its discharge stroke. Due to the fact that partition 22 is located closer to inlet port 16 than to outlet port 21, a larger amount of metal will discharge through outlet port 21, producing a net flow of metal in that direction. At the end of the discharge stroke, valve 32 is closed and valve 33 is opened to exhaust pressurized fluid from the hollow chamber.

As the over pressure within the hollow chamber is relieved, molten metal from outside the chamber rushes in (FIG. 12) to fill the chamber to an equilibrium level. Due to the fact that inlet port 16 is larger than outlet port 21, a greater amount of metal will enter the hollow chamber from the inlet port than from the outlet port. This will produce a net flow of metal over partition 22 from the inlet side to the outlet side.

It will be obvious to those skilled in the art that the over pressure principle can be readily applied to the single and double valved embodiments of FIGS. 5-9.

The materials of construction of wall generatrix 20 and partition 22 can vary widely, depending on the nature of the molten material to be circulated. As a rule of thumb, those portions of the wall generatrix and the partition which come in contact with the molten material can be constructed of the same material as is the vessel used to contain the melt. In the case of handling molten metals, fire brick and castable refractories can be used to fabricate at least those portions of the wall generatrix and partition contacted by the melt. In the cases of handling resins and comestibles, stainless steel and glass lined construction materials are suitable.

Other modifications and changes falling within the spirit and scope of the invention will occur to those skilled in the art. For instance, the circulating device may be located in various positions relative to the confines of any vessel containing molten material. Even in a reverberatory furnace of the type illustrated the device may be wholly positioned within the heating chamber or elsewhere within the external charging well as an independent structure not making use of walls or ports preexisting in the furnace construction. The device may be portable for use in more than one vessel. It is intended that the invention include these and all other such changes and modifications as come within the scope of the following claims.

What I claim is:

1. In combination with a vessel adapted to contain molten material, a device for circulating molten material from one place to another within said vessel comprising: a wall generatrix defining a hollow chamber positioned within said vessel, said wall generatrix having a lower portion extending into said vessel toward the bottom thereof and terminating at a level below any level of molten material the vessel normally contains, said wall generatrix having an upper portion extending above said lower portion and terminating at a level above any level of molten material the vessel normally contains; an inlet port and an outlet port located in said lower portion of said Wall generatrix, both at levels below any level of molten material the vessel normally contains thereby providing submerged paths of travel for molten material leaving and returning to said vessel; partition means located within said hollow chamber, extending upwardly from the bottom of said vessel to a level above the level of said ports, and cooperating with said wall generatrix and the bottom of said vessel to provide an indirect path of communication between said ports; and means for changing the pressure within said hollow chamber, the location of the partition means and the size of the inlet and outlet ports being such that molten material entering said chamber through said inlet port is caused to travel said indirect path of communication to said outlet port in response to a change in pressure.

2. The combination of claim 1 in which said inlet port is larger than said outlet port.

3. The combination of claim 2 in which said partition means is positioned closer to said inlet port than to said outlet port.

4. The combination of claim 3 in which the upward extension of said partition means is to a level below any level of molten material the vessel normally contains, and said pressure changing means includes means for raising the pressure within said hollow chamber above atmospheric pressure.

5. The combination of claim 3 in which the upward extension of said partition means is to a level above any level of molten material the vessel normally contains and said pressure changing means includes means for lowering the pressure within said hollow chamber below atmospheric pressure.

6. In combination with 'a metal melting furnace comprising a vessel divided by separator means into a closed heating chamber and an open charging well, at least two spaced openings in said separator me'ans, operative as passages for molten metal circulating from said heating chamber into said charging well, and thence back into said heating chamber; a device for assisting the circulation of said molten metal comprising; a Wall generatrix defining a hollow chamber positioned within the charging well portion of said vessel, said Wall generatrix having a lower portion extending into said vessel toward the bottom thereof and terminating at a level below any level of molten material the vessel normally contains, said Wall generatrix having an upper portion extending above said lower portion and terminating at a level above any level of molten material the vessel normally contains; an inlet port and an outlet port located in said lower portion of said wall generatrix, both at levels below any level of molten material the vessel normally contains thereby proinviding submerged paths of travel for molten metal leaving and returning to said vessel; partition means located within said hollow chamber, extending upwardly from the bottom of said vessel to a level above the level of said ports, and cooperating with said wall generatrix and the bottom of said vessel to provide an indirect path of communication between said inlet and outlet ports and to block direct communication between said ports; and means for changing the pressure within said hollow chamher, the location of the partition means and the size of the inlet and outlet ports being such that molten metal entering said chamber through said inlet port is caused to travel said indirect path of communication to said outlet port in response to a change in pressure.

7. The device of claim 6 in which said inlet port is larger than said outlet port.

3. The device of claim 7 in which said partition means is positioned closer to said inlet port than to said outlet port.

9. The combination as defined in claim 6 wherein said wall generatrix includes a portion of said separator means and one of the openings in said separator means constituting the inlet port of said hollow chamber.

10. The combination as defined in claim 1 wherein said outlet port is provided with a valve seat and 21 normally seated valve operative to be unseated in response to a pressure change within said hollow chamber.

References Cited UNITED STATES PATENTS 2,400,651 5/1946 Marsh 103235 3,050,794 8/1962 Holz. 3,058,432 10/1962 Lamb 103-235 3,121,103 2/1964 Beard 137-563 X 3,123,015 3/1964 Linklater 103234 3,191,247 6/1965 Holz. 3,320,970 5/1967 McHenry 103234 X ALAN COHAN, Primary Examiner.

US. Cl. X.R.