Method of and apparatus for conveying molten metals while providing heat thereto

Abstract

The invention relates to a method of and apparatus for providing heat to a molten metal flowing through metal-conveying apparatus. The apparatus includes a molten metal-conveying channel, an enclosure for receiving and circulating combustion gases while preventing entry of the gases into said channel, a heat-conductive body of material separating at least part of the channel from the enclosure; and a combustion device for generating combustion gases and delivering the gases to the enclosure. Heat from the combustion gases is used to heat molten metal held in the channel, while preventing contact between the combustion gases and the molten metal. The body of material may be a trough used to form the channel, a tube for conveying the molten metal, or a tube acting as the enclosure, or the like.

1 . A molten metal-conveying apparatus, comprising:
 a molten metal-conveying channel;   an enclosure for receiving and circulating combustion gases while preventing entry of said gases into said channel;   a heat-conductive body of material separating at least part of said channel from said enclosure; and   a combustion device for generating combustion gases and delivering said gases to said enclosure;   whereby, in use, heat from said combustion gases is transferred to molten metal in said channel through said body of heat conductive material.   
     
     
         2 . The apparatus of  claim 1 , wherein said material has a thermal conductivity in a range of 2.5 to 200 W/mK. 
     
     
         3 . The apparatus of  claim 1 , wherein said material has a thermal conductivity in a range of 5 to 80 W/mK. 
     
     
         4 . The apparatus of  claim 1 , wherein said material has a thermal conductivity of 7 to 25 W/mK. 
     
     
         5 . The apparatus of  claim 1 , wherein said material comprises a refractory metal compound. 
     
     
         6 . The apparatus of  claim 5 , wherein said refractory metal compound is selected from the group consisting of silicon carbide, boron nitride and silicon nitride. 
     
     
         7 . The apparatus of  claim 5 , wherein said material comprises at least 65% by weight of silicon carbide. 
     
     
         8 . The apparatus of  claim 1 , wherein said material is a metal having a coating of a substance, at least on a metal-contacting surface of the material, that is resistant to attack by said molten metal. 
     
     
         9 . The apparatus of  claim 8 , wherein said metal is cast iron. 
     
     
         10 . The apparatus of  claim 8 , wherein the substance is boron nitride. 
     
     
         11 . The apparatus of  claim 1 , wherein said channel is defined by an open-topped trough section and said enclosure encircles an outer surface of said trough section. 
     
     
         12 . The apparatus of  claim 1 , wherein channel is defined by at least one tube adapted to convey molten metal therethrough, said body of material forms walls of said at least one tube, and said enclosure fully surrounding said at least one tube. 
     
     
         13 . The apparatus of  claim 1 , wherein said body of material forms a hollow tubular element suspended in said channel, and said hollow tubular element acts as said enclosure defining said enclosed space within said element. 
     
     
         14 . A molten metal-conveying trough apparatus, comprising:
 a molten metal conveying trough section having an upper end and an outer surface extending around the trough section from said upper end;   an enclosure at least partially enclosing said outer surface of the trough section, said enclosure containing at least one enclosed chamber adjacent to said outer surface;   an entrance into the chamber, or an entrance into each chamber when more than one, through which hot combustion gases can be introduced into the or each chamber; and   an exit from the chamber, or each chamber when more than one, through which said hot combustion gases can be removed from the chamber, or each chamber when more than one, after flowing through the or each chamber, thereby transferring heat to the trough section through said outer surface.   
     
     
         15 . The apparatus of  claim 14 , wherein said enclosure encloses substantially all of said outer surface of the trough section. 
     
     
         16 . The apparatus of  claim 14 , further comprising at least one generator of a stream of hot combustion gases, one said generator being positioned at said entrance of the or each chamber. 
     
     
         17 . The apparatus of  claim 16 , wherein said at least one generator introduces said stream of hot combustion gases into the or each chamber generally horizontally beneath said trough section. 
     
     
         18 . The apparatus of  claim 14 , wherein said trough section is made of a heat-conductive refractory material. 
     
     
         19 . The apparatus of  claim 14 , wherein the heat-conductive refractory material comprise silicon carbide. 
     
     
         20 . The apparatus of  claim 14 , having at least two said chambers arranged one following another in a longitudinal direction of said trough section. 
     
     
         21 . The apparatus of  claim 14 , wherein the or each chamber comprises at least two compartments interconnected together at a distance from said inlet and said outlet and positioned to confine said stream of hot combustion gases to flow along an extended path adjacent to said outer wall of said trough section. 
     
     
         22 . The apparatus of  claim 14 , wherein the chamber, or each chamber when more than one, has an inner volume in use receiving said hot combustion gases, and said outer surface of said trough section is directly exposed to said inner volume. 
     
     
         23 . The apparatus of  claim 14 , further comprising at least two thermocouples, one positioned to measure temperatures of molten metal when present in said trough section, and another positioned to measure temperatures in said chamber, or at least one of said chambers when more than one. 
     
     
         24 . The apparatus of  claim 14 , further comprising a heat-insulating cover positioned over said upper end of said trough section. 
     
     
         25 . A method of providing heat to a molten metal flowing through metal-conveying apparatus provided with at least one channel for conveying said molten metal, an enclosure for receiving and circulating combustion gases and a heat-conductive body of material separating at least part of said channel from said enclosure, said method comprising:
 conveying molten metal through said channel;   generating combustion gases;   causing said combustion gases to enter and circulate through said enclosure while confining said combustion gases to prevent said gases entering said channel.   
     
     
         26 . A method of heating a section of a molten metal conveying trough having an upper end and an outer surface extending around the trough section from said upper end, which comprises:
 generating at least one moving stream of hot combustion gases; and   directing said at least one stream of hot combustion gases to flow through at least one enclosed volume surrounding at least part of said outer surface of said molten metal conveying trough section, thereby exposing said at least a part of said outer surface of said trough section to said hot combustion gases and enabling heat to transfer into said trough section through said outer surface.   
     
     
         27 . The method of  claim 26 , wherein said at least one enclosed volume surrounds substantially all of said outer surface of said trough section. 
     
     
         28 . The method of  claim 27 , wherein said at least one stream is directed to flow in an extended path adjacent to said outer surface of said trough section. 
     
     
         29 . The method of  claim 28 , wherein said at least one stream is directed to flow in an extended winding path. 
     
     
         30 . The method of  claim 26 , wherein said stream of hot combustion gases is generated by burning fuel in a stream of combustion air. 
     
     
         31 . The method of  claim 26 , wherein said at least one stream of gases is directed to flow initially beneath said trough section. 
     
     
         32 . The method of  claim 26 , wherein at least two streams of said hot combustion gases are generated and each is directed to flow through a different enclosed volume, each volume being arranged one after another in a longitudinal direction of said trough section.