Abstract:
An apparatus for the removal of uranium from a body of material is provided. The apparatus has at least one ultrasonic extractor, having a bottom and a top. The at least one ultrasonic extractor is configured to accept solids at the bottom and acid at the top, and has a mixing screw and at least one source of ultrasonic energy. The mixing screw is configured to transport the solids in a direction countercurrent to the acid in the at least one ultrasonic extractor; and the source of ultrasonic energy is configured to impart ultrasonic energy into the solids and the acid, as the solids and the acid traverse the at least one ultrasonic extractor countercurrently.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a division of U.S. patent application Ser. No. 10/883,073, filed Jul. 1, 2004, now U.S. Patent No. X,XXX,XXX, hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a method and device for uranium recovery. More specifically, the present invention provides an apparatus and method for recovering uranium from a body of material using an ultrasonic counter-current screw extractor. 
       BACKGROUND INFORMATION 
       [0003]    Contaminated materials, such as incinerator ash and soils, pose many challenges for the uranium processing industry. At uranium processing sites, incinerator ash and soils may be contaminated with different materials, including heavy metals, uranium, and other radioactive materials. Uranium materials, when present in such solids, may be either uniformly distributed throughout the solids or may be concentrated in discrete sections. Removal of uranium materials from these solids is particularly difficult as, in most instances, a non-uniform distribution of uranium at low concentration levels occurs. Material treatment/separation techniques that use a mechanical separation technique (i.e. classifiers) are not equipped to separate uranium at low concentrations, and, as a consequence, are not of practical use in these instances. Another drawback of mechanical separation classifiers is that these classifiers use large amounts of energy for the amount of materials separated, and are therefore economically unfeasible. 
         [0004]    Current systems used to separate uranium from solids are also expensive due to several other economic factors. The solids that are contaminated must be removed (i.e. excavated), trucked to a treatment site, treated, and then returned to the original excavation site for filling. The multiple handling steps for cleaning the solid material increases both the ultimate energy costs associated with treatment as well as the associated labor costs. Handling of contaminated solids also requires special trucking systems to prevent the solids from contaminating the trucking system and the surrounding environment due to leaks in the trucking system. 
         [0005]    There is therefore a need to provide a method and apparatus that will allow uranium to be separated from a base solid, such as incinerator ash and/or soils, with greater efficiency than current mechanical separation techniques. 
         [0006]    There is a further need to provide an apparatus and method that will allow the uranium to be separated economically from the base solid. 
         [0007]    There is a further need to provide an apparatus that is easily transportable so that contaminated materials may be treated on-site, thereby minimizing handling costs. 
       SUMMARY 
       [0008]    It is therefore an objective of the present invention to provide a method and apparatus that will allow uranium to be separated from a base solid, such as incinerator ash and/or soils, with greater efficiency than current mechanical separation techniques. 
         [0009]    It is also a further objective of the current invention to provide an apparatus and method that will allow the uranium to be separated economically from the base solid. 
         [0010]    It is a still further objective of the current invention to provide an apparatus for treating solids that is easily transportable so that contaminated materials may be treated on-site, thereby minimizing handling costs. 
         [0011]    The objectives of the present invention are achieved as illustrated and described. The invention provides a method to remove uranium from a body of solid material. The invention recites the method steps of providing the body of solid material containing a concentration of uranium, depositing the body of solid material in an ultrasonic extractor, and depositing an amount of acid in the ultrasonic extractor. The method also provides for the steps of heating a jacket of the ultrasonic extractor, transporting the body of solid material in the ultrasonic extractor and the amount of acid, such that the body of solid material and the acid contact each other inside the heated ultrasonic extractor while the ultrasonic extractor provides ultrasonic energy to both the body of solid material and the amount of acid, wherein the amount of acid strips uranium from the body of solid material. The method further provides for collecting the amount of acid and the body of solid material in the ultrasonic extractor in different positions in the ultrasonic extractor, transporting the amount of acid with the stripped uranium to an extraction mixer settler, and settling uranium product from the extraction mixer settler. 
         [0012]    The invention also provides for an apparatus to remove uranium from a body of solid material. The invention provides at least one ultrasonic extractor configured to accept the body of solid material at a bottom and an amount of acid at a top, wherein the at least one ultrasonic extractor is configured in a mixing screw arrangement, the ultrasonic extractor configured with at least one ultrasonic unit to impart ultrasonic energy into the body of solid material and the amount of acid while the body of solid material and the amount of acid traverse the at least one ultrasonic extractor and an acid delivery system configured to deliver the amount of acid to the at least one ultrasonic extractor. The invention also provides for a pump configured to remove the amount of acid that has drained to the bottom of the at least one ultrasonic extractor, a feed tank configured to accept the amount of acid removed by the pump and an extraction mixer settler connected to the feed tank, the extraction mixer settler configured to accept material from the feed tank and separate uranium product from a remainder of the amount of acid. 
         [0013]    The invention also provides an apparatus for separating uranium from a mass of material. The apparatus provides a combustible waste feed system, a combustion chamber connected to the combustible waste feed system, the combustion chamber configured to combust waste from the waste feed system and a fuel source, a feed tank, a first ultrasonic counter-current screw extractor, a second ultrasonic counter-current screw extractor connected to the first ultrasonic counter-current screw extractor and a third ultrasonic counter-current screw extractor connected to the second ultrasonic counter-current screw extractor. The apparatus also includes a pump connected to the first ultrasonic counter-current screw extractor, the pump configured to remove an amount of acid from the first ultrasonic counter-current screw extractor, and provide the amount of acid to the feed tank, an acid delivery system configured to add the amount of acid to the third ultrasonic counter-current screw extractor, and remove accumulated acid at a bottom of the third ultrasonic counter-current screw extractor, and transport the accumulated acid to a top of the second ultrasonic counter-current screw extractor, and transport accumulated acid at a bottom of the second ultrasonic counter-current screw extractor, and transport the accumulated acid at the bottom of the second ultrasonic counter-current screw extractor to a top of the first ultrasonic counter-current screw extractor and an extraction mixer settler connected to the feed tank, the extraction mixer settler configured to treat material received from the feed tank in an aqueous phase and an organic phase. The apparatus moreover provides a raffinate treatment system connected to the extraction mixer settler, the raffinate treatment system configured to treat raffinate waste from the extraction mixer settler, an organic phase reconditioning system connected to the extraction mixer settler, the organic phase reconditioning system configured to regenerate an organic phase arrangement of the extraction mixer settler, a process off-gas scrubber connected to the feed tank and the extraction mixer settler, the process off-gas scrubber configured to process off-gas for release, a neutralization system, and a dissolver off-gas scrubber connected to the third ultrasonic counter-current screw extractor, the dissolver off-gas scrubber configured with an outlet to the process off-gas scrubber and the neutralization system, the neutralization system configured to neutralize materials obtained from the dissolver off-gas scrubber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0014]      FIG. 1  is a schematic representation of an arrangement using an ultrasonic counter-current screw extractor for uranium recovery from solid materials; and 
           [0015]      FIG. 2  is an expanded view of the ultrasonic counter-current screw extractor for uranium recovery illustrated in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION  
       [0016]    Referring to  FIG. 1 , an arrangement  10  using an ultrasonic counter-current screw extractor for uranium recovery is illustrated. The arrangement  10  is used to treat solids, such as incinerator ash and/or soils that are contaminated with uranium. In the arrangement, a combustible waste feed  12  feeds into a combustion chamber  14  of an incinerator for ultimate disposition. The combustion chamber  14  may be fed with an input of natural gas  18 , or other combustible power source such as oil as a non-limiting example. Gaseous components resulting from the combustion process in the combustion chamber  14  are released from the combustion chamber  14  by an off-gas outlet  16  that, as illustrated, releases the gaseous components generated in the combustion chamber  14  to the atmosphere. Although not illustrated, further processing steps may occur for the off-gas exiting the combustion chamber in order to reduce the ultimate amount of pollutants discharged to the atmosphere. Such treatment steps may be, for example, selective non-catalytic reduction, urea injection as non-limiting treatments available. 
         [0017]    The resulting solid uranium containing component derived from the combustion process in the combustion chamber  14  is a uranium bearing ash  20  as the volatile and combustible materials have been removed in the combustion chamber  14  by the combustion process. The concentration of the uranium in the ash exiting the combustion chamber  14  may vary according to the amount of uranium concentration originally added to the combustion chamber  14 . The combustible waste feed  12 , for example, may contain a greater or lesser uranium component, and as a result, the resulting ash may have a varying concentration of uranium. 
         [0018]    Commercial uranium bearing solids  22  may be added separately or blended with the uranium ash  20  exiting the combustion chamber  14 , thereby producing a uranium bearing solid  24  that may be separated into a uranium component and a non-uranium bearing component. The solid form of the material may be discrete particles of material, such as fine powder or uranium bearing solids. The uranium bearing solid  24  may be fed into a first unit  26 A of an ultrasonic counter-current screw extractor for uranium recovery  26 . The uranium bearing solid  24  may be placed in a bottom of an ultrasonic unit  26 A that is configured to accept solid materials, and transport these materials from the bottom of the unit  26 A to the top of the unit  26 A. As illustrated, the ultrasonic units  26  A,B,C may be mixer screw arrangements  26  that provide a height change of the solids entering the bottom of the units  26  A,B,C. At the top of the ultrasonic units  26 A,B,C, acid may be added to the unit  26 A,B,C to allow the uranium to be accurately separated from the non-uranium solids in the uranium bearing solid  24 . As illustrated, three individual ultrasonic units  26 A,B,C may be used in series to separate uranium from the remainder of the solids  24 . Each ultrasonic unit  26 A,B,C may have a separate pump  34  that places an acid in a top of the ultrasonic unit  26 A,B,C. The acid added may be, for example, a nitric acid, as a non-limiting example, for stripping the uranium content from the solids  24 . The acid addition to each ultrasonic unit  26 A,B,C may be from the discharge of any previous ultrasonic unit, thereby minimizing the amount of nitric acid used as well as providing a superior uranium separation capability. The addition of acid to each ultrasonic unit may be staged such that low concentration uranium solids contact acid that is more concentrated so that uranium may be removed with a greater efficiency. Additionally, acid that is not as concentrated (i.e. acid that has been used in a previous step or uranium stripping) may be combined with greater uranium bearing solids. In this manner, an optimal acid concentration is maintained in contact with the solids  24  throughout processing, thereby allowing minimal acid use while maximizing uranium stripping capability. The number of ultrasonic units may vary in order to optimize uranium recovery. The equipment may also be sized to ensure criticality safety, relying upon safe geometry. 
         [0019]    Each of the ultrasonic units  26  may be configured to have a jacket (i.e. an outer covering) that heats the unit  26  and the materials placed in the interior of the ultrasonic unit  26 . The heating of the jacket and the interior placed materials may be accomplished through electric heating or through creation of a steam jacket. Other heating mechanisms may be used, and the heating types are to be considered illustrative and non-limiting. 
         [0020]    In the example embodiment illustrated, a first ultrasonic unit  26 A accepts a combination of enriched uranium ash and commercial uranium bearing solids  24 . This combination of solids  24  is added to the bottom of the first ultrasonic unit  26 A, and subsequently heated by the jacket as the solids traverse up the first ultrasonic unit  26 A. The material placed in the bottom of the ultrasonic unit  26 A is combined with nitric acid added by pump  40 , wherein the nitric acid enters the top of the ultrasonic unit  26 A, and flows down the unit  26 A. The nitric acid added by the pump  40  is obtained from a second ultrasonic unit  26 B preceding the first ultrasonic unit  26 A. 
         [0021]    The material exiting the first ultrasonic unit  26 A enters an ultrasonic discharge  40  that transports the material from the first ultrasonic unit  26 A to a second ultrasonic unit  26 B. The material transported by the ultrasonic discharge  40  enters the bottom of the second ultrasonic unit  26 B, and transfers up through the second ultrasonic unit  26 B. The material is again heated by a jacket of unit  26 B. Simultaneous to the transfer of the material from the first ultrasonic unit  26 A to the second ultrasonic unit  26 B, nitric acid obtained from a third ultrasonic unit  26 C is pumped to the top of the second ultrasonic unit  26 B. The solids entering the second ultrasonic unit  26 B contact the nitric acid from the third ultrasonic unit  26 C within the heated interior of the second ultrasonic unit  26 B. The solids from the second ultrasonic unit  26 B exit the top of the second ultrasonic unit  26 B, and enter the bottom of the third ultrasonic unit  26 C. A nitric acid solution is added to the top of the third ultrasonic unit  26 C. As the solids entering the bottom of the third ultrasonic unit  26 C traverse up the third ultrasonic unit  26 C, they contact the added nitric acid solution traversing down the third ultrasonic unit  26 C. The solid material exiting the third ultrasonic unit  30  may be disposed of as solid waste  30 . 
         [0022]    The nitric acid exiting the first ultrasonic unit  26 A may be gathered by a pump  32 , and sent to a feed tank  86  that collects the gathered nitric acid from the ultrasonic counter-current screw extractors  26 A,B,C. The feed tank  86  may be any size tank to accept the total flow of nitric acid transferred from the ultrasonic units  26 A,B,C. The feed tank  86  has two outlets, a first outlet for gaseous material and a second outlet for aqueous material. The first outlet for gaseous material exits the feed tank  86 , and goes to a process off-gas scrubber  48 . The second outlet for aqueous material  88  goes to an extraction mixer settler  78  that has both an aqueous phase and organic phase component. The aqueous phase component has an outlet for raffinate waste  80  that proceeds to a raffinate treatment system  82 . An outlet for the raffinate treatment system may proceed to a building sump  62 , for example, or another storage facility. The building sump  62  may then empty into a waste tank  62  for disposal. The organic phase of the extraction mixer settler  78  may have an outlet  74  that enters an organic phase reconditioning system  68 . The organic phase reconditioning system  68  may also have an inlet for nitric acid  70  to aid in the reconditioning. The organic phase reconditioning system  68  may also have a return line  72  allowing organic phase constituents to be returned to the extraction mixer settler  78 . Clean uranium product  76  may be recovered from the extraction mixer settler  78  after treatment of the organic phase components. The organic phase reconditioning system  68  may have an outlet for an acid wash  66  that also enters the building sump  62 . 
         [0023]    The third ultrasonic counter-current screw extractor for uranium recovery  26 C may also have an outlet for a dissolver off-gas scrubber  44 . The dissolver off-gas scrubber  44  may have an inlet for water  42  to aid in the scrubbing process. The dissolver off-gas scrubber  44  may have two outlets, a first outlet being a scrubbed off-gas  46  and a second outlet  92  to a neutralization system  54 . The neutralization system  54  may accept flow from the process off-gas scrubber  48  as well as for caustic input  58 . After neutralization of the materials within the system  54 , the system  54  may discharge materials to a building sump  64 , for example. Scrubbed off-gas  50  exiting the process off-gas scrubber  48  may be discharged to the atmosphere. 
         [0024]    By utilizing this system, the nitric acid transferring over the solids  24  progressing through the ultrasonic units  26  accumulates uranium. This accumulation of uranium is then treated by the system, thereby allowing the uranium content of the solids  24  to be extracted. 
         [0025]    Referring to  FIG. 2 , a single ultrasonic counter-current screw extractor (and associated equipment) is illustrated. Ash and uranium solids  200  may be deposited into a hopper  202  of an auger feed system  204 . Although illustrated as an auger feed system, other systems may be used including, but on limited to, mechanical roller and belt-conveyor systems. The auger feed system  204  may have a variable speed motor  206  that allows the feed rate of the system  204  to be varied according to the loading rate of the uranium solids in the hopper  202 . 
         [0026]    The auger feed system  204  deposits the ash and uranium solids into a base of an ultrasonic counter-current screw extractor  206  The ultrasonic counter-current screw extractor  206  may be a screw feed unit, as a non-limiting example. The jacket of the ultrasonic counter-current screw extractor  206  may be heated, for example, by steam or electricity, to encourage greater removal efficiency of uranium from the solids  200 . The ultrasonic counter-current screw extractor  206  may have an off-gas outlet  208  to the atmosphere for ventilation purposes. An acid inlet  210  located at the top of the ultrasonic counter-current screw extractor  206  allows for acid to be delivered to the solids  200  to enhance the uranium removal process. The acid inlet  210  may be sized according to the feed rate of the ash and uranium contaminated solids fed into the ultrasonic counter current screw extractor  206  by the auger feed system  204 . The speed of transfer of the solids  200  through the ultrasonic counter-current screw extractor  206  may be controlled through a variable speed motor  212 . The ultrasonic counter-current screw extractor  206  may have several ultrasonic transmitters, as illustrated in  FIG. 2 , to provide ultrasonic energy to materials traversing the length of the extractor  206 . 
         [0027]    Solids exiting the top of the ultrasonic counter-current screw extractor  206  exit through an extractor outlet  214 . The extractor outlet  214  may pass through a centrifuge or dryer  216 , or may bypass the centrifuge or dryer  216 , and enter a disposal system  240 . 
         [0028]    Nitric acid that has accumulated uranium by passing over the solids  200  transporting through the ultrasonic counter-current screw extractor  206  is transferred by a pump  218  to a filter press system  224 . The liquid contents, leachate, may be recycled to other systems  220 , or may be recovered by further processing  226 . Solid constituents  222  may be removed by the filter press system  224 . 
         [0029]    For all ultrasonic counter-current screw extractors illustrated, the mass transfer of uranium from solid mass to a uranium leachate or uranium product is enhanced by ultrasonic energy impartation, counter-current flow, mixing, and heat. The applicants have found through experimentation that ultrasonic leaching is proven to be more efficient than static leaching, as the mixing energy improves the diffusion rate of uranium into solution. The screw classifier may be equipped with vibrators attached to the bottom of the extractors. The counter-current flow maximizes the uranium concentration gradient by contacting the fresh acid with the lowest uranium solids, and the uranium loaded acid with high uranium bearing solids. The nitric acid flows downward in an opposite direction to the solids, which are propelled upward through the extractor. Solids mixing may be enhanced through small blades attached to the screw of the extractor. 
         [0030]    The current invention provides for separation of uranium from solid materials in an economic manner. The system provided can be transportable such that treatment can occur at the site of contamination. The system also reduces labor and energy costs associated with separation of uranium as compared to mechanical separation techniques. 
         [0031]    In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereunto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and drawings are accordingly to be regarded in an illustrative rather than in a restrictive sense.