Method and apparatus for decontaminating molten metal compositions

Abstract

A method and apparatus for decontaminating molten metal compositions. A molten metal composition (typically containing elemental lead or a lead alloy) is initially provided which also includes various inorganic contaminants. The composition is placed in contact with a specialized decontamination member which actively allows diffusion of the contaminants therein. As a result, the contaminants are removed from the molten metal composition. Contaminants of particular interest in lead-based molten metal compositions include arsenic, tin, antimony, tellurium, and combinations thereof. A reducing agent is optimally combined with the molten metal composition to prevent oxide formation on the decontamination member. The decontamination member preferably contains iron in the form of an iron alloy (for example, steel). Additional preferred components in the decontamination system include an iron trap for removing iron-containing contaminants from the molten metal composition. As a result, the composition is rapidly and effectively decontaminated.

1 . A method for decontaminating a molten metal composition comprising: 
 providing a supply of a molten metal composition comprising lead therein, said molten metal composition further comprising at least one inorganic contaminant in said composition;    placing said molten metal composition in contact with at least one decontamination member that will allow said inorganic contaminant to diffuse into said decontamination member, said decontamination member comprising iron therein; and    allowing said inorganic contaminant to diffuse into said decontamination member for removal thereof from said molten metal composition.    
     
     
         2 . The method of  claim 1  wherein said molten metal composition is comprised of a material selected from the group consisting of elemental lead, a lead-containing alloy, and combinations thereof.  
     
     
         3 . The method of  claim 2  wherein said lead-containing alloy comprises a lead-bismuth alloy.  
     
     
         4 . The method of  claim 1  wherein said inorganic contaminant is comprised of a material selected from the group consisting of arsenic, tin, antimony, tellurium, and combinations thereof.  
     
     
         5 . The method of  claim 1  wherein said decontamination member is comprised of an iron-containing alloy.  
     
     
         6 . The method of  claim 5  wherein said iron-containing alloy comprises steel.  
     
     
         7 . The method of  claim 1  further comprising maintaining said molten metal composition at a temperature of about 400-600° C. during said placing of said molten metal composition in contact with said decontamination member.  
     
     
         8 . The method of  claim 1  wherein said placing of said molten metal composition in contact with said decontamination member causes at least one iron-containing contaminant to be introduced into said molten metal composition, said method further comprising removing at least some of said iron-containing contaminant from said molten metal composition.  
     
     
         9 . The method of  claim 8  wherein said removing of said iron-containing contaminant from said molten metal composition comprises placing said molten metal composition having said iron-containing contaminant therein within a magnetic field in order to draw said iron-containing contaminant out of said molten metal composition.  
     
     
         10 . A method for decontaminating a molten metal composition comprising: 
 providing a supply of a molten metal composition comprising lead therein, said molten metal composition further comprising at least one inorganic contaminant in said composition;    introducing at least one reducing agent into said molten metal composition;    placing said molten metal composition in contact with at least one decontamination member that will allow said inorganic contaminant to diffuse into said decontamination member, said decontamination member comprising iron therein; and    allowing said inorganic contaminant to diffuse into said decontamination member for removal thereof from said molten metal composition.    
     
     
         11 . The method of  claim 10  wherein said molten metal composition is comprised of a material selected from the group consisting of elemental lead, a lead-containing alloy, and combinations thereof.  
     
     
         12 . The method of  claim 10  wherein said reducing agent is comprised of a material selected from the group consisting of C (s) , H 2(g) , CH 4(g) , C 2 H 2(g) , C 3 H 8(g) , and combinations thereof.  
     
     
         13 . The method of  claim 10  wherein, after said placing of said molten metal composition in contact with said decontamination member, said molten metal composition comprises at least some of said reducing agent therein which remains in an unreacted state, said method further comprising removing at least some of said reducing agent in said unreacted state from said molten metal composition.  
     
     
         14 . The method of  claim 13  wherein said placing of said molten metal composition in contact with said decontamination member causes at least one iron-containing contaminant to be introduced into said molten metal composition, said method further comprising removing at least some of said iron-containing contaminant from said molten metal composition.  
     
     
         15 . A method for decontaminating a molten metal composition comprising: 
 providing a supply of a molten metal composition comprised of a material selected from the group consisting of elemental lead, a lead-bismuth alloy, and combinations thereof, said molten metal composition further comprising at least one inorganic contaminant therein, said inorganic contaminant comprising a material selected from the group consisting of arsenic, tin, antimony, tellurium, and combinations thereof;    introducing at least one reducing agent into said molten metal composition, said reducing agent comprising a material selected from the group consisting of C (s) , H 2(g) , CH 4(g) , C 2 H 2(g) , C 3 H 8(g) , and combinations thereof;    placing said molten metal composition in contact with at least one decontamination member that will allow said inorganic contaminant to diffuse into said decontamination member, said decontamination member being comprised of steel;    allowing said inorganic contaminant to diffuse into said decontamination member for removal thereof from said molten metal composition, said placing of said molten metal composition in contact with said decontamination member further causing at least one iron-containing contaminant to be introduced into said molten metal composition, said molten metal composition further comprising at least some of said reducing agent therein which remains in an unreacted state within said molten metal composition after said placing of said molten metal composition in contact with said decontamination member;    removing at least some of said reducing agent in said unreacted state from said molten metal composition; and    removing at least some of said iron-containing contaminant from said molten metal composition.    
     
     
         16 . An apparatus for decontaminating a molten metal composition comprising: 
 a supply of a molten metal composition comprising lead therein, said molten metal composition further comprising at least one inorganic contaminant in said composition; and    a containment vessel in fluid communication with said supply of said molten metal composition so that said molten metal composition can enter into said containment vessel, said containment vessel comprising: 
 at least one decontamination member therein that will allow said inorganic contaminant to diffuse into said decontamination member when said molten metal composition comes in contact with said decontamination member so that said contaminant can be removed from said molten metal composition, said decontamination member comprising iron therein; and  
 at least one outlet port in said containment vessel for passage of said molten metal composition out of said containment vessel after said composition comes in contact with said decontamination member.  
   
     
     
         17 . The apparatus of  claim 16  further comprising at least one heater which is used to provide heat to said molten metal composition.  
     
     
         18 . The apparatus of  claim 16  wherein said molten metal composition is comprised of a material selected from the group consisting of elemental lead, a lead-containing alloy, and combinations thereof.  
     
     
         19 . The apparatus of  claim 18  wherein said lead-containing alloy comprises a lead-bismuth alloy.  
     
     
         20 . The apparatus of  claim 16  wherein said inorganic contaminant is comprised of a material selected from the group consisting of arsenic, tin, antimony, tellurium, and combinations thereof.  
     
     
         21 . The apparatus of  claim 16  wherein said containment vessel is produced from a composition which comprises zirconium therein.  
     
     
         22 . The apparatus of  claim 16  further comprising at least one iron trap which receives said molten metal composition after contact thereof with said decontamination member.  
     
     
         23 . The apparatus of  claim 22  wherein said iron trap comprises at least one magnet.  
     
     
         24 . An apparatus for decontaminating a molten metal composition comprising: 
 a supply of a molten metal composition comprising lead therein, said molten metal composition further comprising at least one inorganic contaminant in said composition;    a supply of at least one reducing agent which is in fluid communication with said supply of said molten metal composition so that said reducing agent can be introduced into said molten metal composition; and    a containment vessel in fluid communication with said supply of said molten metal composition so that said molten metal composition can enter into said containment vessel, said containment vessel comprising: 
 at least one decontamination member therein that will allow said inorganic contaminant to diffuse into said decontamination member when said molten metal composition comes in contact with said decontamination member so that said contaminant can be removed from said molten metal composition, said decontamination member comprising iron therein; and  
 at least one outlet port in said containment vessel for passage of said molten metal composition out of said containment vessel after said composition comes in contact with said decontamination member.  
   
     
     
         25 . The apparatus of  claim 24  wherein said containment vessel further comprises at least one additional outlet port therein for passage of unreacted quantities of said reducing agent out of said containment vessel.  
     
     
         26 . The apparatus of  claim 25  further comprising at least one iron trap which receives said molten metal composition after contact thereof with said decontamination member.  
     
     
         27 . An apparatus for decontaminating a molten metal composition comprising: 
 a supply of a molten metal composition comprised of a material selected from the group consisting of elemental lead, a lead-bismuth alloy, and combinations thereof, said molten metal composition further comprising at least one inorganic contaminant therein, said inorganic contaminant comprising a material selected from the group consisting of arsenic, tin, antimony, tellurium, and combinations thereof;    a supply of at least one reducing agent which is in fluid communication with said supply of said molten metal composition so that said reducing agent can be introduced into said molten metal composition, said reducing agent comprising a material selected from the group consisting of C (s) , H 2(g) , CH 4(g) , C 2 H 2(g) , C 3 H 8(g) , and combinations thereof;    a containment vessel in fluid communication with said supply of said molten metal composition so that said molten metal composition can enter into said containment vessel, said containment vessel comprising: 
 at least one decontamination member therein that will allow said inorganic contaminant to diffuse into said decontamination member when said molten metal composition comes in contact with said decontamination member so that said contaminant can be removed from said molten metal composition, said decontamination member being comprised of steel;  
 at least one outlet port in said containment vessel for passage of said molten metal composition out of said containment vessel after said composition comes in contact with said decontamination member; and  
 at least one additional outlet port in said containment vessel for passage of unreacted quantities of said reducing agent out of said containment vessel; and  
   at least one iron trap which receives said molten metal composition after contact thereof with said decontamination member, said iron trap comprising at least one magnet.    
     
     
         28 . The apparatus of  claim 27  further comprising at least one heater which is used to provide heat to said molten metal composition.  
     
     
         29 . The apparatus of  claim 27  wherein said containment vessel is produced from a composition which comprises zirconium therein.