Method for melting solid metal

Abstract

A scrap melting system and method includes a vessel that is configured to retain molten metal and a raised surface about the level of molten metal in the vessel. Solid metal is placed on the raised surface and molten metal from the vessel is moved upward from the vessel and across the raised surface to melt at least some of the solid metal. The molten metal is preferably raised from the vessel to the raised surface by a molten metal pumping device or system. The molten metal moves from the raised surface and into a vessel or launder.

Claims

1. A method for melting solid aluminum utilizing a system that comprises: (a) a vessel having a first chamber, a second chamber, and a raised surface; (b) a molten metal pump in the vessel; (c) a first dividing wall between the first chamber and second chamber, the first dividing wall having a first height, and an opening that is beneath the height; and (d) a second dividing wall between the second chamber and the raised surface, the second dividing wall having a second height that is less than the first height; wherein the method comprises the following steps: (e) placing solid aluminum on the raised surface; and (f) operating the pump to move molten metal through the opening in the first dividing wall, so that the molten metal exceeds the second height and flows across the raised surface until at least some of the solid aluminum is melted into melted aluminum.

2. The method of claim 1, wherein the system further comprises a grate on the raised surface, and the method further comprises the step of a melt comprising at least most of the molten metal and melted aluminum passing through the grate.

3. The method of claim 1 that further includes the step of moving the molten metal from the raised surface and into a launder.

4. The method of claim 1 that further includes the step of moving the molten metal from the raised surface and into a third chamber.

5. The method of claim 1 that further includes the step of stopping the flow of molten metal across the raised surface after at least some of the solid aluminum on the raised surface is melted.

6. The method of claim 1 that further includes the step of removing unmelted pieces of metal from the raised surface.

7. The method of claim 5 that further includes the step of removing unmelted pieces of metal from the raised surface after stopping the flow of molten metal across the raised surface.

8. The method of claim 4 that further includes the step of pumping the molten metal in the third chamber.

9. The method of claim 4 that further includes the step of degassing the molten metal in the third chamber.

10. The method of claim 1 that further includes the step of moving the molten metal from the raised surface and into a third chamber.

11. The method of claim 1 that further includes the step of stopping the flow of molten metal across the raised surface after at least some of the solid aluminum on the surface is melted.

12. The method of claim 1 that further includes the step of removing unmelted pieces of metal from the raised surface.

13. The method of claim 1, wherein the pumping is not continuous.

14. The method of claim 1, wherein the pumping is performed by a transfer pump.

15. The method of claim 1, wherein the pumping is performed by a circulation pump.

16. The method of claim 1, wherein the pumping is performed by a gas-release pump.

17. The method of claim 1, wherein the dividing wall has an opening to permit molten metal to be pumped from the first chamber through the opening and into the second chamber.

18. The method of claim 17, wherein the pump has a pump base and a discharge, and the dividing wall has an opening to permit molten metal to be pumped from the first chamber through the opening and into the second chamber, the discharge being aligned with the opening so that at least some of the molten metal exiting the discharge passes through the opening.

19. The method of claim 1, wherein the pumping is performed at a speed, and the speed is variable.

20. The method of claim 1, wherein the pumping is performed at a speed, and the speed is constant.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a cross-sectional side view of a system according to this disclosure for melting solid metal on a raised surface.

(2) FIG. 1A is a cross-sectional side view of a system according to this disclosure for melting solid metal on a raised surface and that includes one or more side walls.

(3) FIG. 2 is the system of FIG. 1 showing the level of molten metal in the furnace being increased.

(4) FIG. 2A shows the system of FIG. 1 with side walls on the raised surface that help contain the molten metal.

(5) FIG. 2B shows the system of FIGS. 1 and 2 and displays how heights H1 and H2 are determined.

(6) FIG. 3 is a top, partial cross-sectional view of the system of FIG. 2A.

(7) FIG. 3A is a partial, cross-sectional side view of a system according to this disclosure.

(8) FIG. 4 is a partial, cross-sectional side view of a system according to this disclosure that is utilized to fill a ladle.

(9) FIG. 5 is a partial, cross-sectional side view of an alternate embodiment of the present disclosure.

(10) FIG. 6 is a partial cross-sectional, side view of an embodiment of this disclosure.

(11) FIG. 7 is a top, partial cross-sectional view of the embodiment of FIG. 6 with a pump.

(12) FIG. 8 is a partial side, cross-sectional view of the system of FIG. 6.

(13) FIG. 9 is a partial perspective, side view of a system according to this disclosure.

(14) FIG. 10 is a cross-sectional, side view of an embodiment of this disclosure that further includes a launder.

(15) FIG. 11 is a cross-sectional, side view of an embodiment of this disclosure that further includes an additional vessel or chamber.

(16) FIG. 12 is a side, cross-sectional view of an alternate system of this disclosure that includes an additional vessel or chamber that has a molten metal pump.

(17) FIG. 13 is a side, cross-sectional view of an alternate system of this disclosure that includes an additional vessel or chamber that has a rotary degasser.

DETAILED DESCRIPTION

(18) Turning now to the Figures, where the purpose is to describe preferred embodiments of the invention and not to limit same, FIGS. 1-3A show a system 10 for moving molten metal M onto a raised surface 20 in order to melt solid metal, such as aluminum scrap. System 10 includes a furnace 1 that can retain molten metal M, which includes a holding furnace 1A, a vessel 12, a raised surface 20, and a pump 22. System 10 preferably has a vessel 12, a dividing wall 14 to separate vessel 12 into at least a first chamber 16 and a second chamber 18, and a device or structure, which may be pump 22, for generating a stream of molten metal from first chamber 16 into second chamber 18.

(19) Using heating elements (not shown in the figures), furnace 1 is raised to a temperature sufficient to maintain the metal therein (usually aluminum or zinc) in a molten state. The level of molten metal M in holding furnace 1A and in at least part of vessel 12 changes as metal is added or removed to furnace 1A, as can be seen in FIGS. 2 and 11.

(20) For explanation, furnace 1 includes a furnace wall 2 having an archway 3. Archway 3 allows molten metal M to flow into vessel 12 from holding furnace 1A. In this embodiment, furnace 1A and vessel 12 are in fluid communication, so when the level of molten metal in furnace 1A rises, the level also rises in at least part of vessel 12. It most preferably rises and falls in first chamber 16, described below, as the level of molten metal rises or falls in furnace 1A. This can be seen in FIGS. 2 and 11.

(21) Dividing wall 14 separates vessel 12 into at least two chambers, a pump well (or first chamber) 16 and a skim well (or second chamber) 18, and any suitable structure for this purpose may be used as dividing wall 14. As shown in this embodiment, dividing wall 14 has an opening 14A and an optional overflow spillway 14B (best seen in FIG. 3), which is a notch or cut out in the upper edge of dividing wall 14. Overflow spillway 14B is any structure suitable to allow molten metal to flow from second chamber 18, past dividing wall 14, and into first chamber 16 and, if used, overflow spillway 14B may be positioned at any suitable location on wall 14. The purpose of optional overflow spillway 14B is to prevent molten metal from overflowing the second chamber 18, or a launder in communication with second chamber 18 (if a launder is used with the invention), by allowing molten metal in second chamber 18 to flow back into first chamber 16. Optional overflow spillway 14B would not be utilized during normal operation of system 10 and is to be used as a safeguard if the level of molten metal in second chamber 18 improperly rises to too high a level.

(22) At least part of dividing wall 14 has a height H1 (best seen in FIG. 2A), which is the height at which, if exceeded by molten metal in second chamber 18, molten metal flows past the portion of dividing wall 14 at height H1 and back into first chamber 16. In the embodiment shown in FIGS. 1-3A, overflow spillway 14B has a height H1 and the rest of dividing wall 14 has a height greater than H1. Alternatively, dividing wall 14 may not have an overflow spillway, in which case all of dividing wall 14 could have a height H1, or dividing wall 14 may have an opening with a lower edge positioned at height H1, in which case molten metal could flow through the opening if the level of molten metal in second chamber 18 exceeded H1. H1 should exceed the highest level of molten metal in first chamber 16 during normal operation.

(23) Second chamber 18 has a portion 18A, which has a height H2, wherein H2 is less than H1 (as can be best seen in FIG. 2A) so during normal operation molten metal pumped into second chamber 18 flows past wall 18A and out of second chamber 18 rather than flowing back over dividing wall 14 and into first chamber 16.

(24) Dividing wall 14 may also have an opening 14A that is located at a depth such that opening 14A is submerged within the molten metal during normal usage, and opening 14A is preferably near or at the bottom of dividing wall 14. Opening 14A preferably has an area of between 6 in..sup.2 and 24 in..sup.2, but could be any suitable size. Further, dividing wall 14 need not have an opening if a transfer pump were used to transfer molten metal from first chamber 16, over the top of wall 14, and into second chamber 18 as described below.

(25) Dividing wall 14 may also include more than one opening between first chamber 16 and second chamber 18 and opening 14A (or the more than one opening) could be positioned at any suitable location(s) in dividing wall 14 and be of any size(s) or shape(s) to enable molten metal to pass from first chamber 16 into second chamber 18.

(26) Molten metal pump 22 may be any device or structure capable of pumping or otherwise conveying molten metal, and may be a transfer, circulation or gas-release pump. Pump 22 is preferably a circulation pump (most preferred) or gas-release pump that generates a flow of molten metal from first chamber 16 to second chamber 18 through opening 14A. Pump 22 generally includes a motor 24 surrounded by a cooling shroud 26, a superstructure 28, support posts 30 and a base 32. Some pumps that may be used with the invention are shown in U.S. Pat. Nos. 5,203,681, 6,123,523 and 6,354,964 to Cooper, and pending U.S. application Ser. No. 10/773,101 to Cooper. Molten metal pump 22 can be a constant speed pump, but is most preferably a variable speed pump. Its speed can be varied depending on the amount of molten metal in a structure such as a ladle or launder, as discussed below.

(27) Utilizing system 10, as pump 22 pumps molten metal from first chamber 16 into second chamber 18, the level of molten metal in chamber 18 rises. When a pump with a discharge submerged in the molten metal bath, such as circulation pump or gas-release pump is utilized, there is essentially no turbulence or splashing during this process, which reduces the formation of dross and reduces safety hazards. The flow of molten metal is smooth and generally at an even flow rate.

(28) A system according to this disclosure could also include one or more pumps in addition to pump 22, in which case the additional pump(s) may circulate molten metal within first chamber 16 and/or second chamber 18, or from chamber 16 to chamber 18, and/or may release gas into the molten metal first in first chamber 16 or second chamber 18. For example, first chamber 16 could include pump 22 and a second pump, such as a circulation pump or gas-release pump, to circulate and/or release gas into molten metal M.

(29) If pump 22 is a circulation pump or gas-release pump, it is at least partially received in opening 14A in order to at least partially block opening 14A in order to maintain a relatively stable level of molten metal in second chamber 18 during normal operation and to allow the level in second chamber 18 to rise independently of the level in first chamber 16. Utilizing this system the movement of molten metal from one chamber to another and from the second chamber into a launder does not involve raising molten metal above the molten metal surface. As previously mentioned this alleviates problems with blockage forming (because of the molten metal cooling and solidifying), and with turbulence and splashing, which can cause dross formation and safety problems. As shown, part of base 32 (preferably the discharge portion of the base) is received in opening 14A. Further, pump 22 may communicate with another structure, such as a metal-transfer conduit, that leads to and is received partially or fully in opening 14A. Although it is preferred that the pump base, or communicating structure such as a metal-transfer conduit, be received in opening 14A, all that is necessary for the invention to function is that the operation of the pump increases and maintains the level of molten metal in second chamber 18 so that the molten metal ultimately moves out of chamber 18 and into another structure. For example, the base of pump 22 may be positioned so that its discharge is not received in opening 14A, but is close enough to opening 14A that the operation of the pump raises the level of molten metal in second chamber 18 independent of the level in chamber 16 and causes molten metal to move out of second chamber 18 and into another structure. A sealant, such as cement (which is known to those skilled in the art), may be used to seal base 32 into opening 14A, although it is preferred that a sealant not be used.

(30) A system according to this disclosure could also be operated with a transfer pump, although a pump with a submerged discharge, such as a circulation pump or gas-release pump, is preferred since either would be less likely to create turbulence and dross in second chamber 18, and neither raises the molten metal above the surface of the molten metal bath nor has the other drawbacks associated with transfer pumps that have previously been described. If a transfer pump were used to move molten metal from first chamber 16, over dividing wall 14, and into second chamber 18, there would be no need for opening 14A in dividing wall 14, although an opening could still be provided and used in conjunction with an additional circulation or gas-release pump. As previously described, regardless of what type of pump is used to move molten metal from first chamber 16 to second chamber 18, molten metal would ultimately move out of chamber 18 and into a structure, such as ladle 52 or launder 20, when the level of molten metal in second chamber 18 exceeds H2.

(31) Once pump 22 is turned off, the respective levels of molten metal level in chambers 16 and 18 essentially equalize. Alternatively, the speed of pump 22 could be reduced to a relatively low speed to keep the level of molten metal in second chamber 18 relatively constant but not exceed height H2. To move molten metal onto raised surface 20, pump 22 is simply turned on again and operated as described above.

(32) A system for melting scrap according to this disclosure includes a molten metal pump and a raised surface 20 on which solid metal S, such as scrap aluminum, can be positioned, wherein molten metal is flowed onto and across the raised surface 20 in order to melt at least some of the solid metal S. As described above, the pump 22 generates a flow of molten metal M from first chamber 16 into second chamber 18. When the level of molten metal M in second chamber 18 exceeds H2, the molten metal moves out of second chamber 18 and onto the raised surface 20 to melt scrap placed on surface 20. The level of molten metal M in the second chamber 18 rises until it flows onto raised surface 20, and flows along the raised surface 20 until it melts at least some of the solid metal S on the raised surface 20 melts. The amount of molten metal flowed across raised surface 20 can be varied based on any suitable factor, such as based on the amount of solid metal S on raised surface 20.

(33) The raised surface 20 has a first side 20A adjacent the second chamber 18 and a second side 20B. Raised surface 20 can be the upper surface of a refractory block 23, which may be inside or outside of vessel 1. A refractory grate 75 is preferably positioned at, or just before or just after, second side 20B. The refractory grate 75 acts as a filter that blocks pieces of unmelted metal, such as pieces of iron or steel, from being mixed with the molten metal M and moving off of raised surface 20. Any suitable filter could be used for this purpose.

(34) Preferably, before or after the melt moves off the raised surface 20 it is filtered to remove at least some solid particles. The filtering can be done by grate 75. Solid particles, such as iron or steel, that remain on the raised surface 20 are removed, such as by using a steel arm that is lowered onto the raised surface 20 and pulled across the raised surface 20 to remove the solid particles. The method of adding solid metal S and melting it can then be repeated.

(35) The raised surface 20 may also include one or more side walls 29 (as shown, for example, in FIG. 1A) that help retain molten metal on the raised surface.

(36) The molten metal M could pass from the raised surface 20 into another vessel or chamber 2000, or move into a launder 31 (as shown in FIG. 10) or any suitable structure.

(37) Furthermore, molten metal can be moved across the raised surface 20 in any suitable manner, such as by using pumping and transfer devices incorporated by reference herein. The specific system described herein using a dividing wall, however, is most preferred because the flow of molten metal can be carefully controlled and spread over a large area, in order to cover the width of the raised surface 20 or a large portion of the width of the raised surface 20.

(38) Although one specific system is disclosed herein for raising molten metal to flow across the raised surface, and suitable system, method, or device may be utilized to move molten metal across the raised surface with little splashing or turbulence, and to evenly control the flow across the entire raised surface on which the solid metal is positioned.

(39) The problems with splashing or turbulence, or a difficult to control molten metal flow, are greatly reduced or eliminated by utilizing this system. Molten metal M can be smoothly flowed across the raised surface 20 and the level of molten metal M raised or lowered as desired to melt the solid metal S on the raised surface 20. As solid metal S is melted and becomes part of the molten (or liquid) metal, this melt (which includes the original molten metal and the melted, former solid metal) flows past the back, or second, side 20B of the raised surface 20. From there the melt may enter any suitable structure, such as a launder 31, another vessel, or another chamber of the same vessel, 2000 in which the molten metal pump and dividing wall are positioned. The melt may be degassed, such as by a rotary degasser, pumped, or demagged, such as by using a gas-release pump that releases chlorine gas into the melt.

(40) As shown in FIG. 10, launder 31 is any structure or device for transferring molten metal from raised surface 20 to one or more structures, such as one or more ladles, molds (such as ingot molds) or other structures in which the molten metal is ultimately cast into a usable form, such as an ingot. Launder 31 may be either an open or enclosed channel, trough or conduit and may be of any suitable dimension or length, such as one to four feet long, or as much as 100 feet long or longer. Launder 31 may be completely horizontal or may slope gently upward or downward. Launder 31 may have one or more taps (not shown), i.e., small openings stopped by removable plugs. Each tap, when unstopped, allows molten metal to flow through the tap into a ladle, ingot mold, or other structure. Launder 31 may additionally or alternatively be serviced by robots or cast machines capable of removing molten metal M from launder 31.

(41) Launder 31 has a first end 31A juxtaposed the second end 20B of raised surface 20 and a second end 31B that is opposite first end 31B. An optional stop may be included in a launder according to the invention. The stop, if used, is preferably juxtaposed the second end 31B of the launder. If launder 31 has a stop, the stop can be opened to allow molten metal to flow past end 31B, or closed to prevent molten metal from flowing past end 31B. The stop preferably has a height H3 greater than height H1 so that if launder 31 becomes too filled with molten metal, the molten metal would back up on raised surface 20, and spill back over dividing wall 14A (over spillway 14B, if used) rather than overflow raised surface 20 and launder 31.

(42) FIG. 4 shows an alternate system 10′ that is in all respects the same as system 10 except that it has a shorter, downward, sloping surface 20′ for retaining solid metal to be melted, a wall 18A′ past which molten metal moves when it exits second chamber 18 and it fills a ladle 52.

(43) FIG. 12 shows an alternate system 10 that is in all respects the same as system 10 except that it includes an optional second pump 1500 in a third chamber, or second vessel, 2000 having a basin 2012.

(44) FIG. 13 shows an alternate system 10A′ that is in all respects the same as system 10 except that it includes an optional rotary degasser 110 in a third chamber, or second vessel, 2000 having a basin 2012.

(45) Some non-limiting examples of this disclosure are as follows:

(46) Example 1: A method for melting solid aluminum utilizing a system that comprises:

(47) a vessel having a first chamber, a second chamber, and a raised surface;

(48) a molten metal pump in the first vessel;

(49) a first dividing wall between the first chamber and second chamber, the first dividing wall having a first height, and an opening that is beneath the height; and

(50) a second dividing wall between the second chamber and a raised surface, the second dividing wall having a second height that is less than the first height;

(51) wherein the method comprises the following steps:

(52) placing solid aluminum on the raised surface; and

(53) operating the pump to move molten metal through the opening in the first dividing wall, so that the molten metal exceeds the second height and flows across the raised surface until at least some of the solid aluminum is melted into melted aluminum.

(54) Example 2: The method of claim 1, wherein the system further comprises a grate at the rear side of the raised surface, and a melt comprising at least most of the molten metal and melted aluminum passes through the grate.

(55) Example 3: The method of claim 1 that further includes the step of moving the molten metal from the raised surface and into a launder.

(56) Example 4: The method of claim 1 that further includes the step of moving the molten metal from the raised surface and into a third chamber.

(57) Example 5: The method of claim 1 that further includes the step of stopping the flow of molten metal across the raised surface after at least some of the solid aluminum on the surface is melted.

(58) Example 6: The method of claim 1 that further includes the step of removing unmelted pieces of metal from the raises surface.

(59) Example 7: The method of claim 5 that further includes the step of removing unmelted pieces of metal from the raised surface after stopping the flow of molten metal across the raised surface.

(60) Example 8: The method of claim 4 that further includes the step of pumping the molten metal in the third chamber.

(61) Example 9: The method of claim 4 that further includes the step of degassing the molten metal in the third chamber.

(62) Example 10: The method of claim 1 that further includes the step of moving the molten metal from the raised surface and into a third chamber.

(63) Example 11: The method of claim 1 that further includes the step of stopping the flow of molten metal across the raised surface after at least some of the solid aluminum on the surface is melted.

(64) Example 12: The method of claim 1 that further includes the step of removing unmelted pieces of metal from the raises surface.

(65) Example 13: A method of melting metal scrap, Example 1: The method comprising the steps of:

(66) placing solid metal on a raised surface, wherein the surface will not melt at the melting temperature of the solid metal;

(67) moving molten metal across the raised surface in order to melt at least some of the solid metal; and

(68) removing solid pieces that did not melt from the raised surface.

(69) Example 14: The method of claim 13, wherein the solid metal and liquid metal are the same metal.

(70) Example 15: The method of claim 13, wherein the solid metal and liquid metal are both aluminum.

(71) Example 16: The method of claim 13 that further includes the step of not moving molten metal across the raised surface after at least some of the solid metal has been melted.

(72) Example 17: The method of claim 13 that further includes the step of filtering the melt.

(73) Example 18: The method of claim 13 that further includes the step of filtering the melt before it moves off the raised surface.

(74) Example 19: The method of claim 13 that further includes the step of moving the molten metal into either a launder or a vessel after it moves past the raised surface.

(75) Example 20: The method of claim 13 that further includes the step of moving the molten metal into a vessel and pumping the molten metal.

(76) Example 21: The method of claim 13 that further includes the step of moving the molten metal from the raised surface and into a third chamber.

(77) Example 22: The method of claim 13 that further includes the step of stopping the flow of molten metal across the raised surface after at least some of the solid aluminum on the surface is melted.

(78) Example 23: The method of claim 13 that further includes the step of removing unmelted pieces of metal from the raised surface.

(79) Example 24: The method of claim 1 wherein the pumping is not continuous.

(80) Example 25: The method of claim 1 wherein the pumping is performed by a transfer pump.

(81) Example 26: The method of claim 1 wherein the pumping is performed by a circulation pump.

(82) Example 27: The method of claim 1 wherein the pumping is performed by a gas-release pump.

(83) Example 28: The method of claim 1 wherein the dividing wall has an opening to permit molten metal to be pumped from the first chamber through the opening and into the second chamber.

(84) Example 29: The method of example 28, wherein the pump has a pump base and a discharge, and the dividing wall has an opening to permit molten metal to be pumped from the first chamber through the opening and into the second chamber, the discharge being aligned with the opening so that at least some of the molten metal exiting the discharge passes through the opening.

(85) Example 30: The method of claim 1 wherein the pumping is performed at a speed, and the speed is variable.

(86) Example 31: The method of claim 1 wherein the pumping is performed at a speed, and the speed is constant.

(87) Having thus described different embodiments of the invention, other variations and embodiments that do not depart from the spirit thereof will become apparent to those skilled in the art. The scope of the present invention is thus not limited to any particular embodiment, but is instead set forth in the appended claims and the legal equivalents thereof. Unless expressly stated in the written description or claims, the steps of any method recited in the claims may be performed in any order capable of yielding the desired product or result.