Immersion heater for molten metal

Abstract

The invention relates to a device for heating molten metal by the use of a heater that can be immersed into the molten metal. This immersion heater includes an outer cover formed of one or more materials resistant to the molten metal in which the immersion heater is to be used, and a heating element inside of the outer cover, where the heating element is protected from contacting the molten metal.

Claims

1. A device comprising: a vessel for containing molten metal, the vessel having a length, a width, a top surface, a first chamber and a second chamber, and an inlet in the first chamber in fluid communication with the vessel; a plurality of immersion heaters being rectangular and positioned in line across the width of the vessel, each of the plurality of immersion heaters comprising an outer cover of material resistant to molten metal and a heating element inside of the outer cover, the heating element connectable to an energy source, the outer cover comprised of a material formulated to be resistant to the molten metal, wherein the outer cover protects the heating element from contacting the molten metal when the immersion heater is positioned in the molten metal; and wherein the plurality of immersion heaters divides the vessel into the first chamber and the second chamber.

2. The device of claim 1, wherein the energy source of each heating element is a source of electricity.

3. The device of claim 1, wherein each heating element is one or more wire coils.

4. The device of claim 1, wherein each outer cover is comprised of one or more of graphite and ceramic.

5. The device of 1, wherein each outer cover is molded over each heating element.

6. The device of claim 1, wherein each outer cover has a cavity and the heating element corresponding to each outer cover is positioned in the cavity.

7. The device of claim 1, wherein the vessel has a top surface and further comprises one or more insulated covers to cover a portion of the top surface of the vessel.

8. The device of claim 7, wherein at least one of the one or more of the insulated covers has (a) a first position, wherein it is attached to the vessel and covers a portion of the top surface of the vessel, and (b) a second position, wherein it is attached to the vessel and does not cover a portion of the top surface of the vessel.

9. The device of claim 7, wherein the vessel comprises a plurality of insulated covers.

10. The device of claim 1 that further includes a plurality of degassers, wherein each of the plurality of degassers is positioned in the vessel.

11. The device of claim 1, wherein molten metal flows from the first chamber to the second chamber during use.

12. The device of claim 1 that further comprises an outlet in the second chamber in fluid communication with the vessel.

13. The device of claim 1, wherein each of the plurality of immersion heaters has a bottom surface that is positioned above a bottom surface of the vessel.

14. The device of claim 1, wherein each outer cover is comprised of a refractory material.

15. The device of claim 1 that further includes a superstructure at the top of the vessel and each of the plurality of immersion heaters is suspended from the superstructure.

16. The device of claim 15, wherein the superstructure includes a metal bar and at least one bolt extends from the metal bar into each outer cover.

17. The device of claim 1, wherein each outer cover is comprised of one or more of the group consisting of graphite and ceramic.

18. The device of claim 1, wherein each of the plurality of immersion heaters is connected to a control that controls the temperature of each of the immersion heaters.

19. The device of claim 1, wherein each of the plurality of immersion heaters includes a silicon controlled rectifier power controller to help prevent each immersion heater from overheating.

20. The device of claim 10, wherein each of the plurality of rotary degassers has a shaft that extends into the molten metal, and the shaft of each rotary degasser is the same distance from the plurality of immersion heaters.

21. The device of claim 1 that further includes a first baffle inside of the vessel, downstream of the inlet and upstream of the plurality of immersion heaters, the first baffle for directing molten metal entering the vessel downward.

22. The device of claim 21 that further includes a second baffle inside of the vessel and an outlet in the vessel, the second baffle downstream of the first baffle, downstream of the plurality of immersion heaters and upstream of the outlet, the second baffle for helping to prevent molten metal at the surface of the molten metal contained within the vessel from exiting the outlet.

23. The device of claim 1 that further includes a molten metal pump inside of the vessel.

24. The device of claim 1 that includes a first molten metal pump in the first chamber and a second molten metal pump in the second chamber.

25. The device of claim 23 wherein the molten metal pump is one of a circulation pump and a gas-release pump.

26. A device comprising: a vessel for containing molten metal, the vessel having a length, a width, a top surface, a first chamber and a second chamber, and an inlet in the first chamber in fluid communication with the vessel; a plurality of immersion heaters, wherein each of the plurality of immersion heaters in line across the width of the vessel, each of the plurality of immersion heaters comprising an outer cover of material resistant to molten metal and a heating element inside of the outer cover, the heating element connectable to an energy source, the outer cover comprised of a material formulated to be resistant to the molten metal, wherein the outer cover protects the heating element from contacting the molten metal when the immersion heater is positioned in the molten metal; wherein the plurality of immersion heaters divides the vessel into the first chamber and the second chamber; and a plurality of degassers, wherein each of the plurality of degassers is positioned in the vessel.

27. The device of claim 26, wherein the energy source of each heating element is a source of electricity.

28. The device of claim 26, wherein each heating element is one or more wire coils.

29. The device of claim 26, wherein each outer cover is comprised of one or more of graphite and ceramic.

30. The device of 26, wherein each outer cover is molded over each heating element.

31. The device of claim 26, wherein each outer cover has a cavity and the heating element corresponding to each outer cover is positioned in the cavity.

32. The device of claim 26, wherein the vessel has a top surface and further comprises one or more insulated covers to cover a portion of the top surface of the vessel.

33. The device of claim 32, wherein at least one of the one or more of the insulated covers has (a) a first position, wherein it is attached to the vessel and covers a portion of the top surface of the vessel, and (b) a second position, wherein it is attached to the vessel and does not cover a portion of the top surface of the vessel.

34. The device of claim 32, wherein the vessel comprises a plurality of insulated covers.

35. The device of claim 26, wherein molten metal flows from the first chamber to the second chamber during use.

36. The device of claim 26 that further comprises an outlet in the second chamber in fluid communication with the vessel.

37. The device of claim 26, wherein each of the plurality of immersion heaters has a bottom surface that is positioned above a bottom surface of the vessel.

38. The device of claim 26, wherein each outer cover is comprised of a refractory material.

39. The device of claim 26 that further includes a superstructure at the top of the vessel and each of the plurality of immersion heaters is suspended from the superstructure.

40. The device of claim 31, wherein the superstructure includes a metal bar and at least one bolt extends from the metal bar into each outer cover.

41. The device of claim 26, wherein each outer cover is comprised of one or more of the group consisting of graphite and ceramic.

42. The device of claim 26, wherein each of the plurality of immersion heaters is connected to a control that controls the temperature of each of the immersion heaters.

43. The device of claim 26, wherein each of the plurality of immersion heaters includes a silicon controlled rectifier power controller to help prevent each immersion heater from overheating.

44. The device of claim 26, wherein each of the plurality of rotary degassers has a shaft that extends into the molten metal, and the shaft of each rotary degasser is the same distance from the plurality of immersion heaters.

45. The device of claim 26 that further includes a first baffle inside of the vessel, downstream of the inlet and upstream of the plurality of immersion heaters, the first baffle for directing molten metal entering the vessel downward.

46. The device of claim 45 that further includes a second baffle inside of the vessel and an outlet in the vessel, the second baffle downstream of the first baffle, downstream of the plurality of immersion heaters and upstream of the outlet, the second baffle for helping to prevent molten metal at the surface of the molten metal contained within the vessel from exiting the outlet.

47. The device of claim 26 that further includes a molten metal pump inside of the vessel.

48. The device of claim 26 that includes a first molten metal pump in the first chamber and a second molten metal pump in the second chamber.

49. The device of claim 47, wherein the molten metal pump is one of a circulation pump and a gas-release pump.

50. A device comprising: a vessel for containing molten metal, the vessel having a length, a width, a top surface, a first chamber and a second chamber, and an inlet in the first chamber in fluid communication with the vessel; a plurality of immersion heaters positioned in line across the width of the vessel, each of the plurality of immersion heaters comprising an outer cover of material resistant to molten metal and a heating element inside of the outer cover, the heating element connectable to an energy source, the outer cover comprised of a material formulated to be resistant to the molten metal, wherein the outer cover protects the heating element from contacting the molten metal when the immersion heater is positioned in the molten metal; wherein the plurality of immersion heaters divides the vessel into the first chamber and the second chamber; and a first baffle inside of the vessel, downstream of the inlet and upstream of the plurality of immersion heaters, the first baffle for directing molten metal entering the vessel downward.

51. The device of claim 50, wherein the energy source of each heating element is a source of electricity.

52. The device of claim 50, wherein each heating element is one or more wire coils.

53. The device of claim 50, wherein each outer cover is comprised of one or more of graphite and ceramic.

54. The device of 50, wherein each outer cover is molded over each heating element.

55. The device of claim 50, wherein each outer cover has a cavity and the heating element corresponding to each outer cover is positioned in the cavity.

56. The device of claim 50, wherein the vessel has a top surface and further comprises one or more insulated covers to cover a portion of the top surface of the vessel.

57. The device of claim 56, wherein at least one of the one or more of the insulated covers has (a) a first position, wherein it is attached to the vessel and covers a portion of the top surface of the vessel, and (b) a second position, wherein it is attached to the vessel and does not cover a portion of the top surface of the vessel.

58. The device of claim 56, wherein the vessel comprises a plurality of insulated covers.

59. The device of claim 50, wherein molten metal flows from the first chamber to the second chamber during use.

60. The device of claim 50 that further comprises an outlet in the second chamber and in fluid communication with the vessel.

61. The device of claim 50, wherein each of the plurality of immersion heaters has a bottom surface that is positioned above a bottom surface of the vessel.

62. The device of claim 50, wherein each outer cover is comprised of a refractory material.

63. The device of claim 50 that further includes a superstructure at the top of the vessel and each of the plurality of immersion heaters is suspended from the superstructure.

64. The device of claim 63, wherein the superstructure includes a metal bar and at least one bolt extends from the metal bar into each outer cover.

65. The device of claim 50, wherein each outer cover is comprised of one or more of the group consisting of graphite and ceramic.

66. The device of claim 50, wherein each of the plurality of immersion heaters is connected to a control that controls the temperature of each of the immersion heaters.

67. The device of claim 50, wherein each of the plurality of immersion heaters includes a silicon controlled rectifier power controller to help prevent each immersion heater from overheating.

68. The device of claim 50 that further includes a second baffle inside of the vessel and an outlet in the vessel, the second baffle downstream of the first baffle, downstream of the plurality of immersion heaters and upstream of the outlet, the second baffle for helping to prevent molten metal at the surface of the molten metal contained within the vessel from exiting the outlet.

69. The device of claim 50 that further includes a molten metal pump inside of the vessel.

70. The device of claim 50 that includes a first molten metal pump in the first chamber and a second molten metal pump in the second chamber.

71. The device of claim 69, wherein the molten metal pump is one of a circulation pump and a gas-release pump.

72. A device comprising: a vessel for containing molten metal, the vessel having a length, a width, a top surface, a first chamber and a second chamber, and an inlet in the first chamber in fluid communication with the vessel; a plurality of immersion heaters positioned in line across the width of the vessel, each of the plurality of immersion heaters comprising an outer cover of material resistant to molten metal and a heating element inside of the outer cover, the heating element connectable to an energy source, the outer cover comprised of a material formulated to be resistant to the molten metal, wherein the outer cover protects the heating element from contacting the molten metal when the immersion heater is positioned in the molten metal; wherein the plurality of immersion heaters divides the vessel into the first chamber and the second chamber; and a molten metal pump positioned inside of the vessel.

73. The device of claim 72, wherein the energy source of each heating element is a source of electricity.

74. The device of claim 72, wherein each heating element is one or more wire coils.

75. The device of claim 72, wherein each outer cover is comprised of one or more of graphite and ceramic.

76. The device of 72, wherein each outer cover is molded over each heating element.

77. The device of claim 72, wherein each outer cover has a cavity and the heating element corresponding to each outer cover is positioned in the cavity.

78. The device of claim 72, wherein the vessel has a top surface and further comprises one or more insulated covers to cover a portion of the top surface of the vessel.

79. The device of claim 78, wherein at least one of the one or more of the insulated covers has (a) a first position, wherein it is attached to the vessel and covers a portion of the top surface of the vessel, and (b) a second position, wherein it is attached to the vessel and does not cover a portion of the top surface of the vessel.

80. The device of claim 78, wherein the vessel comprises a plurality of insulated covers.

81. The device of claim 72, wherein molten metal flows from the first chamber to the second chamber during use.

82. The device of claim 72 that further comprises an outlet in the second chamber in fluid communication with the vessel.

83. The device of claim 72, wherein each of the plurality of immersion heaters has a bottom surface that is positioned above a bottom surface of the vessel.

84. The device of claim 72, wherein the outer cover is comprised of a refractory material.

85. The device of claim 72 that further includes a superstructure at the top of the vessel and each of the plurality of immersion heaters is suspended from the superstructure.

86. The device of claim 85, wherein the superstructure includes a metal bar and at least one bolt extends from the metal bar into each outer cover.

87. The device of claim 72, wherein each outer cover is comprised of one or more of the group consisting of graphite and ceramic.

88. The device of claim 72, wherein each of the plurality of immersion heaters is connected to a control that controls the temperature of each of the immersion heaters.

89. The device of claim 72, wherein each of the plurality of immersion heaters includes a silicon controlled rectifier power controller to help prevent each immersion heater from overheating.

90. The device of claim 72 that further includes (a) a first baffle inside of the vessel, downstream of the inlet and upstream of the plurality of immersion heaters, the first baffle for directing molten metal entering the vessel downward, and (b) a second baffle inside of the vessel and an outlet in the vessel, the second baffle downstream of the first baffle, downstream of the plurality of immersion heaters and upstream of the outlet, the second baffle for helping to prevent molten metal at the surface of the molten metal contained within the vessel from exiting the outlet.

91. The device of claim 72, wherein the molten metal pump is in the first chamber.

92. The device of claim 91 that further includes a second molten metal pump in the second chamber.

93. The device of claim 72, wherein the molten metal pump is one of a circulation pump and a gas-release pump.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a perspective view of one embodiment of the invention.

(2) FIG. 2 is a side cut away view of the embodiment depicted in FIG. 1, illustrating, among other things, a flow of gas in the molten metal and immersion heater 300.

(3) FIG. 3 is a side cut away view of the embodiment depicted in FIGS. 1 and 2, illustrating a flow of molten metal.

(4) FIG. 4 is a side cut away view of the embodiment depicted in FIGS. 1, 2, and 3 illustrating both a flow of molten and a flow of gas.

(5) FIG. 5A is a perspective view of another embodiment of the invention depicting exemplary lifting mechanisms.

(6) FIG. 5B is a side view of the embodiment depicted in FIG. 5A in the up, or lifted, position.

(7) FIG. 6 depicts a side cut away view of an immersion heating element housed within a vessel according to one embodiment of the invention.

(8) FIG. 7 is side cut away view of one embodiment of the invention depicting the heat radiating from an immersion heating element.

(9) FIG. 8 is a perspective view of one embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(10) Reference will now be made to the present exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. FIGS. 1 and 2 depict a system 10 according to the invention. The system 10 includes a vessel 1 for holding molten metal, having a lower wall 2 and side walls 3. The vessel 1 can be any suitable size, shape, and configuration.

(11) The system 10 as shown includes one or more rotary degassers 50, each of which include a shaft 100 and an impeller 200. Shaft 100, impeller 200, and each of the impellers used in the practice of the invention, are preferably made of graphite impregnated with oxidation-resistant solution, although any material capable of being used in a molten metal bath, such as ceramic, could be used. Oxidation and erosion treatments for graphite parts are practiced commercially, and graphite so treated can be obtained from sources known to those skilled in the art.

(12) If a rotary degasser is used with the invention, it may be any suitable type and exemplary rotary degassers are described in some of the documents already incorporated herein by reference.

(13) The exemplary system 10 depicted in FIGS. 1 and 2 includes a pair of degassers 50 separated by an immersion heater 300. An immersion heater according to the invention has an outer cover 360 and one or more heating elements 370 (hereafter, heating element) positioned within the outer cover 360. The outer cover 360 is comprised of heat-resistant material, such as refractory material (for example, ceramic or graphite) selected so that it can be placed into molten aluminum, molten zinc or other molten metals so that the material is suitable for the environment in which the invention will be used. The outer cover 360 has a cavity that retains the heating element 370, or the outer cover 360 can be formed around the heating element 370 (in a casting process, molding process or other suitable process) so that the outer cover 360 protects the heating element 370 and prevents it from contacting the molten metal when the immersion heater 300 is positioned in the molten metal. This enables heat to be applied directly from the heating element 370 through the outer cover 360 to virtually any portion of the molten metal bath, based on the shape and position of the immersion heater 300. Due to the heat generated by the heating element 370, the portion of the outer cover 360 that is in contact with the molten metal (which as shown are sides 360A and the ends of outer cover 360) can reach temperatures of, for example, 500 F.-1500 F., 500 F.-1200 F. or 500 F.-900 F., or any other suitable temperature depending upon the heating element, outer cover and type of molten metal.

(14) The immersion heater 300 of the present invention is inserted into the molten metal and heats it directly, and is thus considerably more efficient than conventional molten metal heating systems, including those that heat the air above the molten metal.

(15) The immersion heater 300 is preferably suspended and retained in place by a superstructure 380. Superstructure 380 as shown is a steel bar with bolts 382 that connect to the outer cover 360, but any suitable method or structure can be used to position an immersion heater 300 in a vessel.

(16) As shown, the immersion heater 300 divides vessel 1 into two chambers (213 and 214). Here, each chamber defines a separate degassing zone and each chamber includes a degasser 20. The immersion heater 300 heats the molten metal in both chambers (213 and 214) within the vessel 1. A degassing system of the present invention may include any number of immersion heaters 300 of any suitable shape or size and any number of degassers 20. Any or all of the functions of each degasser 20, such as the speed of each impeller 200, may be independently controlled.

(17) FIG. 6 depicts a side view of one embodiment of an immersion heater 300. In this embodiment, heater 300 includes three separate heating structures 311, 312, 313 that are approximately equally spaced apart. Heating structures 311, 312, 313 may be made from any suitable material and may be any suitable size, shape, and configuration, as previously described. While the heater 300 may be configured to provide any suitable amount of heat, the heater in the present exemplary embodiment can produce about 30 kW of heat. An immersion heater 300 of the present invention may include any number of individual heating elements.

(18) The temperature of each heating structure 311, 312, 313, may be independently controlled or controlled as a group in any suitable manner. In one exemplary embodiment, each element is controlled by a full-proportioning silicon controlled rectifier (SCR) power controller, which can help prevent the heating element 300 from overheating, resulting in a longer service life. While the heater 300 may be formed from any suitable materials, in the present exemplary embodiment each heating structure comprises a graphite or silicon carbide outer cover 360 in which the individual heating elements are positioned. The shaded arrows in FIG. 7 illustrate how the heating element 300 of the present invention can provide heat to the molten metal within the vessel 1, including both chambers 213, 214 simultaneously.

(19) In one embodiment the heating elements 311, 312, 313 may be controlled by an optional control system. This control system may be operated and controlled by a user and/or software. The heating elements 311, 312, 313 may be individually controlled. The system 10 may also include one or more temperature sensors which directly or indirectly measure the temperature of the molten metal and/or components of the system 10. The measured temperatures may be used with the computerized control system to achieve a desired temperature of the molten metal. Also, these measured temperatures may be used to diagnose potential problems with the components of the system 10.

(20) A degassing pattern provided by the rotor 200 according to one embodiment of the invention is depicted by the shaded arrows in FIG. 2. In this example, the rotor 200 of each degasser circulates the molten metal while dispersing gas (depicted in the drawings as bubbles) into the molten metal. In this manner, the molten metal in each chamber (213, 214) is mixed with the gas.

(21) Additionally, the system 10 may include one or more dividers 235 to help redirect the flow of gas mixed with molten metal. Dividers 235 may be of any suitable size and be made out of any suitable material for use in the molten metal bath. In the preferred embodiment, the dividers 235 are made from refractory materials such as graphite and/or ceramic. The dividers 235, vessel 1, and immersion heater 300 may be sized, shaped, and configured in any desired manner to achieve a desired flow pattern of the molten metal and/or gas.

(22) Although any suitable flow pattern may be implemented in the present invention, the shaded arrows in FIG. 3 depict one preferred flow pattern of molten metal through vessel 1. Molten metal is introduced to vessel 1 through inlet 280. Inlet 280 is in fluid communication with outlet 290. The arrows of FIG. 3 depict one flow pattern on molten metal from the inlet 280 through the vessel 1 to the outlet 290. This metal flow pattern helps to thoroughly disperse gas into the molten metal passing through the system 10. The shaded arrows in FIG. 4 depict the combined flow pattern of the molten metal and the degassing patterns of FIGS. 2 and 3. The darker arrows represent the degassing pattern, while the lighter arrows represent the metal flow pattern.

(23) FIGS. 5A and 5B illustrate another view of the present invention wherein each degasser 20 is coupled to a removable cover 350 that can be independently positioned onto, or removed from, the vessel 1. A cover 350 operating in conjunction with the present invention may be any suitable size, shape, and configuration, and may be formed from any suitable material(s). In the present embodiment, each cover 350 is encased in steel and insulated to help retain heat. Also, the cover 350 at least partially maintains an inert gas environment when it is in position on the vessel 1.

(24) In this exemplary embodiment, in its first position, each cover 350 is positioned to help retain gas and heat. Weirs (not shown) at the inlet 280 and outlet 290 likewise help retain gas and heat within the vessel 1.

(25) Each cover 350 may be independently moved from a first position on the top surface of vessel 1 (i.e., the cover 350 in the background of FIG. 5A) to a second position removed from the vessel 1 (i.e., the cover 350 in the foreground of FIG. 5A). Cover 350 may be manually positioned or removed, but the present exemplary embodiment utilizes a lifting mechanism 510. The lifting mechanism 510 may include any suitable system, structure, or device to manipulate the cover 350. Through use of the removable cover 350 and the lifting mechanism 510, components of the system 10, such as the heating element 300, shaft 100 and rotor 200 may be easily accessed, replaced and/or cleaned. In one embodiment, the lifting mechanism 510 includes a gear-driven 4-bar linkage.

(26) Having thus described some embodiments of the invention, other variations and embodiments that do not depart from the spirit of the invention 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 result.