In situ ore leaching using freeze barriers

Abstract

A method is provided herein for performing a leaching process on a substrate ( 113 ). In accordance with the method, a freeze wall ( 115 ) is created which isolates a portion ( 117 ) of a substrate, and the isolated portion of the substrate is subjected to a leaching process.

1 . A method for performing a leaching process on a substrate, comprising:
 creating a freeze wall which isolates a portion of the substrate; and   subjecting the isolated portion of the substrate to the leaching process.   
     
     
         2 . The method of  claim 1 , wherein creating a freeze barrier comprises:
 creating a plurality of holes in the substrate; and   circulating a working fluid through said plurality of holes such that said working fluid absorbs heat from the substrate.   
     
     
         3 . The method of  claim 2 , further comprising:
 extracting the heat from the working fluid by passing the working fluid through a heat exchanger.   
     
     
         4 . The method of  claim 3 , further comprising:
 recirculating the working fluid through said plurality of holes after the working fluid is passed through the heat exchanger.   
     
     
         5 . The method of  claim 2 , further comprising:
 after the working fluid absorbs heat from the substrate, venting the heated working fluid to the atmosphere.   
     
     
         6 . The method of  claim 5 , wherein the working fluid comprises a material selected from the group consisting of nitrogen and carbon dioxide. 
     
     
         7 . The method of  claim 5 , wherein the working fluid undergoes a phase transition from a liquid to a gas when it absorbs heat from the substrate. 
     
     
         8 . The method of  claim 2 , wherein the working fluid is circulated through the plurality of holes in series. 
     
     
         9 . The method of  claim 2 , wherein the working fluid is circulated through the plurality of holes in parallel. 
     
     
         10 . The method of  claim 2 , wherein the working fluid is a brine. 
     
     
         11 . The method of  claim 10 , wherein the working fluid comprises calcium chloride. 
     
     
         12 . The method of  claim 2 , wherein the working fluid is selected from the group consisting of nitrogen, ammonia and carbon dioxide. 
     
     
         13 . The method of  claim 12  wherein, after the freeze wall is created, maintaining the freeze wall with a device selected from the group consisting of thermosyphons and heat pipes. 
     
     
         14 . The method of  claim 1 , wherein the freeze wall consists of at least one essentially vertical wall and at least one essentially horizontal wall. 
     
     
         15 . The method of  claim 1 , further comprising:
 subjecting the isolated portion of the substrate to a remediation process after the leaching process; and   removing a portion of the freeze wall after the remediation process.   
     
     
         16 . The method of  claim 15 , wherein the remediation process comprises treating the isolated portion of the substrate with an alkaline solution. 
     
     
         17 . The method of  claim 1 , further comprising:
 subjecting the isolated portion of the substrate to a remediation process after the leaching process; and   removing the entire freeze wall after the remediation process.   
     
     
         18 . A method for performing a leaching process on a substrate, comprising:
 performing the method of  claim 1  on a first portion of a substrate; and   performing the method of  claim 1  on a second portion of the substrate which is adjacent to the first portion of the substrate;   
       wherein a portion of the freeze wall used to isolate the first portion of the substrate is reused to isolate the second portion of the substrate. 
     
     
         19 . The method of  claim 1 , wherein the leaching process comprises treating the isolated portion with a metal leaching solution. 
     
     
         20 . The method of  claim 19 , wherein the metal is selected from the group consisting of nickel, gold, copper, uranium and zinc. 
     
     
         21 . The method of  claim 19 , wherein the metal is nickel. 
     
     
         22 . The method of  claim 1 , wherein the leaching process comprises treating the isolated portion with an acidic leaching solution. 
     
     
         23 . The method of  claim 1 , wherein the leaching process comprises treating the isolated portion with a biological leaching solution. 
     
     
         24 . The method of  claim 1 , wherein the leaching process comprises treating the isolated portion with a bacterial leaching solution. 
     
     
         25 . The method of  claim 1 , wherein said freeze wall hydrodynamically isolates a portion of the substrate. 
     
     
         26 . A method for extracting nickel from a porous substrate containing a nickel bearing ore, comprising:
 creating a freeze wall in the substrate such that a portion of the substrate is hydrodynamically isolated from the rest of the substrate; and   treating the isolated portion of the substrate with an acidic leaching solution which dissolves a portion of the nickel content in the substrate.   
     
     
         27 . A mining construct, comprising:
 an ore bearing substrate;   a freeze wall which hydrodynamically isolates a portion of the substrate; and   a leaching solution disposed in the isolated portion of the substrate.   
     
     
         28 . The mining construct of  claim 27 , further comprising:
 a heat exchange system adapted to maintain said freeze wall.   
     
     
         29 . The mining construct of  claim 28 , wherein said heat exchange system comprises a thermosyphon. 
     
     
         30 . The mining construct of  claim 28 , wherein said heat exchange system comprises a heat pipe. 
     
     
         31 . The mining construct of  claim 28 , wherein said heat exchange system comprises a plurality of downpipes and a plurality of freeze pipes. 
     
     
         32 . The mining construct of  claim 31 , wherein said heat exchange system comprises a working fluid, and wherein said working fluid is a brine. 
     
     
         33 . The mining construct of  claim 32 , wherein said brine comprises calcium chloride. 
     
     
         34 . The mining construct of  claim 31 , wherein said heat exchange system comprises a working fluid, and wherein said working fluid is selected from the group consisting of nitrogen, ammonia and carbon dioxide. 
     
     
         35 . The mining construct of  claim 31 , wherein said heat exchange system comprises a working fluid, and wherein the working fluid undergoes a phase transition from a liquid to a gas when it absorbs heat from the substrate. 
     
     
         36 . The mining construct of  claim 31 , wherein the working fluid is circulated through the plurality of downpipes in series. 
     
     
         37 . The mining construct of  claim 31 , wherein the working fluid is circulated through the plurality of downpipes in parallel. 
     
     
         38 . The mining construct of  claim 27 , wherein the freeze wall consists of at least one essentially vertical wall and at least one essentially horizontal wall. 
     
     
         39 . The mining construct of  claim 27 , wherein the leaching solution is a metal leaching solution. 
     
     
         40 . The mining construct of  claim 39 , wherein the metal is selected from the group consisting of nickel, gold, copper, uranium and zinc. 
     
     
         41 . The mining construct of  claim 39 , wherein the metal is nickel. 
     
     
         42 . The mining construct of  claim 27 , wherein the leaching solution is an acidic leaching solution. 
     
     
         43 . The mining construct of  claim 27 , wherein the leaching solution is a biological leaching solution. 
     
     
         44 . The mining construct of  claim 43 , wherein the leaching solution is a bacterial leaching solution.