Sonic method and apparatus for heap leaching
SPECIFICATION 
     This invention relates to the leaching of metal from ore and more particularly to a method and apparatus which utilizes sonic energy to implement this end result. The leaching or extraction of metal from ore as is well known in the art involves the utilization of a leachant solution in which the metal salt in the ore is dissolved. The metalic material contained in the leaching solution is then separated from the solution to obtain the desired end product. It has been found that leaching action can be greatly enhanced by applying sonic energy to the ore material while it is being penetrated by the leaching solution such as described in my U.S. Pat. Nos. 3,525,606 and 4,566,800. This end result can be achieved with the ore and leachant contained in a tank into which a bar or tube member is inserted, this bar or tube member being sonically driven by means of an orbiting mass oscillator. While these prior art methods and apparatus have been found to be quite efficient in enhancing the leaching action, the processing in a tank limits the quantity of ore that can be processed at a time. The method and apparatus of the present invention is an improvement over that of my aforementioned prior art patents in that it enables the leaching of large volumes of mined ore which are spread out over an area on the ground (typically an acre or more). 
     In carrying out the present invention a liquid impervious covering with may be in the form of a plastic membrane or a concrete floor is first installed over the area to be employed for carrying out the leaching process. The ore material is then heaped onto this covering in the shape of a mound. The mound of ore material is then wetted with the leaching solution either by forming a crater in the top of the mound into which the solution is poured and allowed to ooze through the ore material, or by employing a sprinkler system surrounding the mound to wet the ore with the leachant. With the ore material wetted with the leachant, sonic energy is applied to such material by means of a tube or bar member which is lowered into the mound from a crane and sonically driven by means of an orbiting mass oscillator, preferably at a frequency which effects resonance standing wave vibration of the bar or tube member. The sonically excited bar or tube member is successively placed in different portions of the mound until the entire mound of ore material has been stirred and fluidized to effect thorough mixing with the leachant. 
     It is therefore an object of this invention to facilitate the leaching of large volumes of mined ore material. 
     It is a further object of this invention to provide a method and apparatus employing sonic energy to enhance the leaching of a large mount of ore material heaped on the ground. 
    
    
     Other objects of the invention will become apparent as the description proceeds in connection with the accompanying drawings of which: 
     FIG. 1 is schematic illustration of a first embodiment of the invention; 
     FIG. 1A is a cross sectional view taken along the plane indicated by plane 1A--1A in FIG. 1; and 
     FIG. 2 is a side elevational view of a second embodiment of the invention. 
    
    
     Referring now to FIGS. 1 and 1A, the first embodiment of the invention is illustrated. The first embodiment employs a sonic excitation device generally similar to that described in connection with FIG. 4 of my U.S. Pat. No. 4,566,800 the disclosure of which is incorporated herein by reference. 
     An area of ground 21 which may be about an acre is covered with a liquid impervious covering 20 which may be in the form of a plastic membrane or a concrete base, a catchment gutter 37 being formed around this covering. A mound of mined metal ore material 22 is heaped onto the covering 20, a crater 23 being formed in the top of this mound. A leaching solution is poured into the crater 23 to form a lake 24, the leaching solution being permitted to peneterate and thoroughly wet the ore material. A sonic drive device 27 which is suspended from a crane on cables 17 is lowered into the ore material 22 so that it penetrates to near the bottom of the mound. Sonic drive device 27 has an elongated elastic tube member 12 which may be of steel which is sonically driven by means of an orbiting mass oscillator 19 in a lateral mode of vibration as described in my aforementioned U.S. Pat. No. 4,566,800, preferably at a resonant frequency as to fluidize the ore material and thoroughly mix the leachant therewith. After the sonic energy has been applied to one area of the mound, sonic device 27 is withdrawn from that section and installed in another section, this operation being repeated successively until the entire mound has been sonically simulated. Also the sonic drive device 27 can be moved sidewise in the mound while it is being sonically excited. 
     Tube member 12 has an inlet pipe 12a through which additional leaching solution can be fed to the ore material if need be to accelerate the penetration of the leachant. The sonic drive device 27 may be of the type described in connection with FIG. 4 of my aforementioned U.S. Pat. No. 4,566,800, utilizing an open lattice structure 30 formed in housing 31 by means of slats 30a with an orbiting mass oscillator 19 mounted in the housing, this oscillator being rotatably driven by motor 14. Tube member 12 which is sonically driven by oscillator 19 is centered within the housing by means of resilient posts 25 which are attached to and extend inwardly from the lattice structure 30. As in the device of my U.S. Pat. No. 4,566,800, the surface of tube member 12 is coated with a resilient material 12b. 
     Referring now to FIG. 2, a second embodiment of the invention is shown. In this second embodiment, rather than forming a crater in the top of the mound of ore material 22, the leaching solution is rather mixed with the ore by means of sprinklers 36 which surround the mound. In this embodiment, a pipe member 12 having a pluality of radial protuberances in the form of circular flanges 38 extending therefrom is employed to transfer the sonic energy to the ore material. Pipe member 12 as for the previous embodiment has an inlet 12a for adding additional leachant if this be required. Pipe member 12 is supported from and attached to an orbiting mass oscillator 19 which is rotatably driven by a pair of motors 39. The entire structure is supported by a crane by means of cables 17 as in the previous embodiment and is utilized in the same fashion as described in connection with the previous embodiment in providing sonic energy to various portions of the mound of ore material. The oscillator 19 and motor drive 39 may be of the type described in my U.S. Pat. No. 3,291,227 which is incorporated herein by reference for the portion of the disclosure relating thereto. Oscillator 19 is driven at a frequency such as to set up longitudinal resonance standing wave vibration of pipe member 30 as indicated by graph lines 45. 
     The apparatus and method of the invention thus enables the large scale leaching of mineral ore material employing sonic energy to enhance the leaching process. 
     While the invention has been described and illustrated in detail, it is to be clearly understood that this is intended by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the invention being limited only by the terms of the following claims: