Abstract:
A method of separating metal particulates from a slurry of original constituents of liquid metal and metal particulates and salt particulates is disclosed. The metal and salt particulates are concentrated by removing at least some of the liquid metal, and then, liquid metal or a liquid of the original salt constituent or a mixture thereof is passed through the particulates at a temperature greater than the melting point of the original salt constituent to further concentrate the metal particulates. The metal particulates are then separated from the remaining original constituents or a mixture of the salt constituent. Density differences between the liquid metal and salt are also used to facilitate separation.

Description:
RELATED APPLICATIONS  
       [0001]     This application, pursuant to 37 C.F.R. 1.78(c), claims priority based on provisional application Ser. No. 60/408,932, filed Sep. 7, 2002, U.S. Provisional Application Ser. No. 60/408,925, filed Sep. 7, 2002 and U.S. Provisional Application Ser. No. 60/408,933, filed Sep. 7, 2002 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     This invention relates to the separation of unwanted constituents from a slurry produced during operation of the Armstrong Process and method to produce a product as disclosed in U.S. Pat. Nos. 5,779,761, 5,958,106 and 6,409,797 patents, the disclosures of which are herein incorporated by reference. As indicated in the above-identified and incorporated patents, the continuous process there disclosed, produces, for instance, titanium or a titanium alloy by the reduction of titanium tetrachloride with excess sodium. The product stream that exits the reactor is a slurry of liquid metal, salt particles or powder and titanium metal or metal alloy as particulates or powder. It should be understood that this invention relates to any material which can be made according to the Armstrong Process. When the slurry produced by the Armstrong Process is filtered, a gel or gel-like material is formed of the metal powder or particulates, the salt powder or particulates and the excess liquid reducing metal. This slurry has to be treated to separate the unwanted constituents, such as excess liquid metal, salt particulates from the desired end product which is the metal particulates or powder.  
       SUMMARY OF THE INVENTION  
       [0003]     In developing the Armstrong Process with respect to titanium and its alloys, it has been found that the method of producing the slurry above referenced is very rapid and separation of the product from the slurry is the most difficult aspect in engineering of the continuous process. The description will be in terms of the exothermic reduction of titanium tetrachloride with sodium to produce titanium particles, sodium chloride particles and excess sodium; however, this is not to be construed as a limitation of the invention but for convenience, only.  
         [0004]     Accordingly, it is an object of the present invention to provide a method for separating metal powder or particulates from a slurry of liquid metal and metal powder or particulates and salt powder or particulates.  
         [0005]     Yet another object of the present invention is to provide a method of separating metal particulates from a slurry of the type set forth in which one of the unwanted constituents is used to separate both constituents from the slurry.  
         [0006]     A still further object of the present invention is to provide a method of separating metal particulates from a slurry of original constituents of liquid metal and metal particulates and salt particulates, comprising concentrating the metal and salt particulates by removing at least some of the liquid metal, passing the liquid metal or a liquid of the original salt constituent or a mixture thereof at a temperature greater than the melting point of the original salt constituent or mixture thereof through the concentrated metal and the particulates to further concentrate the metal particulates, and thereafter separating the metal particulates from the remaining original constituents or a mixture of the salt constituent.  
         [0007]     A final object of the present invention is to provide a method of separating metal particulates from a slurry of original constituents of liquid metal and metal particulates and salt particulates, comprising introducing the slurry of original constituents into a vessel having a liquid salt therein wherein layers form due to density differences with the liquid metal being the lightest and the metal particulates being the heaviest increasing the concentration of the metal particulates toward the bottom of the vessel, removing liquid metal from the vessel, separating the concentrated metal particulates with some liquid salt from the vessel, filtering the salt from the metal particulates, and thereafter cooling and water washing the salt from the metal particulates.  
         [0008]     Additional advantage, objects and novel feature of the invention will become apparent to those skilled in the art upon examination of the following and by practice of the invention.  
         [0009]     The invention consists of certain novel features and a combination of parts hereinafter fully described, illustrated in the accompanying drawings, and particularly pointed out in the appended claims, it being understood that various changes in the details may be made without departing from the spirit, or sacrificing any of the advantages of the present invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     For the purpose of facilitating an understanding of the invention, there is illustrated in the accompanying drawings a preferred embodiment thereof, from an inspection of which, when considered in connection with the following description, the invention, its construction and operation, and many of its advantages should be readily understood and appreciated.  
         [0011]      FIG. 1  is a schematic illustration of a first embodiment of the invention;  
         [0012]      FIG. 2  is a schematic illustration of another embodiment of the present invention; and  
         [0013]      FIG. 3  is a schematic illustration of another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0014]     Referring now to the drawings and more particularly to  FIG. 1 , there is shown a separation system  10  in which a vessel  15  has a generally cylindrical portion  16  with a dome shaped top  17  and a frustoconical shaped bottom  18  and exit pipe  19  extending from the bottom of the vessel  15 . A reactor  20  of the type disclosed in the above-referenced patents has a outer liquid metal or sodium tube  21  and an inner halide vapor or titanium tetrachloride tube  22 . A liquid metal or sodium supply tank  25  feeds sodium to the sodium or other liquid metal to the reactor  20  and a halide boiler  26  feeds the appropriate halide vapor to the reactor  20 , all as previously described.  
         [0015]     Internally of the vessel  15  is a downwardly sloping baffle  28  having a distal end  28   a  extending at a more acute angle and generally opposite to a sodium or liquid metal outlet  29 . The liquid metal outlet  29  is in fluid communication with a metal or sodium pump  31  which leads to a heat exchanger  33  having a fluid inlet  34  and a fluid outlet  35 . A liquid metal make-up line  37  is in communication with the supply tank or reservoir  25 . A vent line  38  is provided in the tank or reservoir  25 , as is well known in the engineering art.  
         [0016]     A valve  40  with an actuator  41  is positioned in the exit  19  of the vessel  15  which is in communication with two exit lines  42  and  43 , each of which being provided with a valve such as a valve  44  illustrated in line  42 .  
         [0017]     A filter assembly  45  includes a container  46  and a sloping filtered plate  47  for a purpose hereinafter set forth. A passivating gas inlet  50  has a valve  51  intermediate the source of passivating gas (not shown) and the container  46 . A vacuum drying line  52  exits the container  46  and is provided with a valve  53 . A slurry outlet line  56  at the bottom of the container  46  is provided with a valve  57  and a salt outlet line  61  is provided with a valve  62 . Finally, a water wash inlet pipe  66  is provided with a valve  57 .  
         [0018]     The separation system  10  operates in following manner wherein material such as a metal or metal alloy is produced in the reactor  20  by the method previously described in the aforementioned and incorporated Armstrong patents. By way of illustration only, titanium or a titanium alloy may be made by the reduction of titanium tetrachloride vapor or a plurality of halide vapors for an alloy by an alkali or alkaline earth metal such as sodium or magnesium. Alloys are easily made with the Armstrong Process by mixing the halide vapors in the appropriate quantities and reducing them in the exact same manner as hereinbefore described. In any event, using a large excess of the reducing metal to control the reaction produces a slurry of excess reducing metal, such as sodium, the metal particulates such as titanium and another reaction product such as salt particles, sodium chloride. The slurry leaving the reactor  20  may be at a variety of temperatures controlled, in one instance, by the amount of excess reducing metal present.  
         [0019]     In an actual example, the slurry may typically have up to about 10% by weight particulates, and the particulates may be salt having diameters on average of from about 10 to about 50 microns and titanium having diameters on average in the range of from about 0.1 micron to about 500 microns, the titanium particulates or powder may be more likely to be in the range of from about 1-10 microns and the agglomerated ligaments (lumps) of the titanium in the range of between about 50 and about 1000 microns. This combination of liquid metal, salt particulates and titanium particulates leave the nozzle  20  and enter the vessel  15 . The salt in the vessel  15  is indicated to be at a level of which may be arbitrarily chosen so long as it is below the sodium outlet  29 . The salt may be the reaction product salt, for instance sodium chloride, or a salt mixture which has a melting point lower than the reaction product salt. Although the salt may be as stated any salt, preferably the salt is the product of reaction or a mixture thereof, for instance an eutectic such as the calcium chloride-sodium chloride eutectic which melts at about 600° C.  
         [0020]     The entire system  10  then may be operated at a lower temperature. For instance, sodium chloride melts at about 850° C. so if the salt in the vessel  15  is sodium chloride, then the vessel  15  must be operated above the melting point thereof, but as the eutectic melts at 600° C., this reduces the operating temperature. In any event, irrespective of what salt is present at the level  30  in the vessel  15 , the liquid metal will float due to density differences and be extracted through the outlet  29  by means of the sodium or liquid metal pump  31 . A heat exchanger  33  having suitable inlet and outlet lines  34 ,  35  serves to reduce the temperature of the sodium out from the 600° in the vessel  15  (by way of example only) so that the recycled sodium enters the reactor  20  at a preselected temperature (for instance about 400° C.). The baffle  28  and  28   a  prevents particulates entering the vessel  15  from the reactor  20  from being sucked into the sodium outlet  29 .  
         [0021]     As particulates settle in the lower portion  18  of the vessel  15 , the particulate concentration is increased due to the removal of sodium through the line  29 . Upon actuation of the valve  40 , concentrated slurry will drain through the outlet or exit  19  through line  42  into the filter assembly  45 . In the filter assembly  45 , which is maintained by temperatures sufficient to keep the molten salt in a liquid phase, metal particles collect on the filter plate  37  while salt passing through the filter plate exits through line  61  to be returned, for instance, to an electrolytic cell (not shown). The valve  62  opens the line  61  to permit the salt to drain while valve  57  is closed to prevent material from exiting the filter assembly  45 . After a sufficient filter cake has been built up, the valve  62  is closed, the valve  44  is closed and the vacuum drying line  53  is opened after the filter cake has cooled to less than about 100° C. so that the passivating gas which may be argon and a small percentage of oxygen may be introduced into the container  46  by actuation of the valve  51 . After the filter cake which may be principally titanium powder with some salt is passivated, then the valve  51  is closed and the water wash valve  67  opened thereby allowing water to enter into the container  46  which both dissolves salt and moves the filter cake through line  56  to a finish wash and classification, it being understood that valve  67  will be opened prior to the water wash. The salt coming out of the filter assembly  45  through line  61  can be recirculated to the vessel  15  as indicated by the line  61   a.    
         [0022]     As seen therefore, the separation system  10  depends on the difference in gravity between the unwanted liquid metal constituent of the slurry and the salt and metal particulates produced during the reaction of the dried vapor and the reducing metal. Although this separation system  10  is a batch system, it can be rapidly cycled from one filter assembly  45  to other filter assemblies as needed through a simple valve distribution system, as is well known in the art.  
         [0023]     Although the above example was illustrated with sodium and titanium tetrachloride, it should be understood that any material made by the Armstrong Process may be separated in the aforesaid manner.  
         [0024]      FIG. 2  shows an alternate embodiment separation system  80  in which a vessel  85  is similar to the vessel  15  and has a cylindrical portion  86 , a dome top  87  and a frustoconical bottom  88  having an exit  89  extending therefrom. A reactor  90  of the same type as hereinbefore described is in communication with the vessel  85  and has a halide inlet  91  and a reducing metal inlet  92 . A slurry outlet  93  which is in communication with the top  87  of the vessel  85 . The filter  95  is any suitable filter, well known in the art, but preferably, for purposes of illustration only, is a “wedge screen filter” of a size to pass up to 125 micron particles. The material that flows through the filter  95  exits the vessel  85  through an output line  96  and flows into a gravity separator  97 . The gravity separator  97  is frustoconical in shape and has an outlet  99  through which the heavier of the materials flows, in this particular case sodium chloride. An outlet  98  takes the lighter of the material, in this case sodium and recycles same through appropriate filters and other mechanisms, not shown, to the reactor  90 . In this embodiment, the vessel  85  is maintained at an elevated temperature of about 850° C. with either internal or external heaters, as is well known in the art, in order that the salt in this case, sodium chloride, is liquid or molten. The molten sodium in large excess displaces the sodium chloride around the particulates and therefore the sodium and the salt flows through the filter plate  95  into the gravity separator  97  and is recycled as previously described. After a suitable filter cake is built up on the filter plate  95 , the valves are closed and the filter cake is thereafter removed for further processing. The advantage of the embodiment disclosed herein is that one of the unwanted constituents, that is the sodium liquid metal is used to displace the other unwanted constituent which in this case is the molten salt. Suitable heat exchangers are required to reduce the temperature of the exiting sodium in line  98  before it is recycled and to heat and maintain the temperature of the salt in the molten state in both the vessel  85  and in the vessel  97 .  
         [0025]     Referring now to  FIG. 3 , there is another embodiment of the present invention illustrated as the separation system  100 . The separation system  100  is provided with similar equipment as illustrated in embodiments  10  and  80 . In the system  100 , there is a vessel  105  having a cylindrical portion  106 , a dome shaped top portion  107  and a frustoconical shaped bottom portion  108  having an exit  109  at the bottom thereof. A reactor  110  of the type described in the previously described for practicing the Armstrong process has, as for example only, a titanium tetrachloride inlet  111  and a sodium inlet  112  which serves to produce the reaction previously described with the outlet  113  carrying the slurry produced from the reaction.  
         [0026]     A gravity separator  117  is frustoconical in shape and has an outlet  118  for the lighter weight liquid metal such as sodium and a bottom outlet  119  through which the heavier unwanted constituent, in the present case sodium chloride, exits. Suitable valves are provided between the exit line  116  and the gravity separator  117  as indicated by the valve  121  and a valve  122  is in the exit line  116  between the vessel  105  and the sodium inlet  112 . Another valve  123  is intermediate the vessel  105  and the sodium chloride outlet from the gravity separator  117  and finally a valve  124  is intermediate the reactor  110  and the vessel  105 .  
         [0027]     In the present system  100 , the filter plate  115  collects the metal particulates as the salt which is molten and at a suitable temperature such as greater than the melting points, such as 850° C. for sodium chloride flows through the filter plate  115  carrying with it excess molten sodium which is displaced from the filter cake as it builds on the filter  115 . The combination of liquid sodium and liquid salt flows out of the vessel  105 . Closing valve  122  and opening the valve  121  results in the material being moved by a suitable pump (not shown) to the gravity separator  117 . In the gravity separator  117 , the liquid metal sodium floats and the liquid salt forms the heavier layer at the bottom of the separator  117  and is separated as indicated with the sodium being drawn off at the top of the separator through line  118  to be recycled (after cooling if required) to the sodium inlet to the reactor  110 . The salt is recycled through valve  123  to the vessel  105 . The reactor  110  can be isolated from the system by the valve  124  so that after a predetermined amount of time, the reactor can be disconnected from the system and shunted to a different separation module while liquid salt is used to displace liquid sodium present in the vessel  105  and in the titanium particulates forming the cake on the filter  115 .  
         [0028]     Although the separation systems disclosed herein are batch operations, the valving is such that continuous separations can occur while the reactor is running. A simple system of two or more of the separation systems  10 ,  80  or  100  permits a reactor continuously to produce the product of the Armstrong reaction.  
         [0029]     Although described herein with reference to titanium and sodium, any alkali metal or alkaline earth metal or various combinations thereof may be used as the reductant metal. Any halide may be useful or any combinations of halides may be useful as the vapor which is injected into the liquid metal to cause the exothermic reaction to occur. For reasons of economics, sodium or magnesium are preferred with sodium being mostly preferred. For other reasons, titanium tetrachloride along with the chlorides of vanadium and aluminum are also preferred in order to make titanium powder or various titanium alloys, the titanium 6:4 alloy being the most preferred titanium alloy presently in use. The 6:4 titanium alloy is 6% aluminum and 4% vanadium with the remainder titanium, as is well known in the art.  
         [0030]     While there has been disclosed what is considered to be the preferred embodiment of the present intention, it is understood that various changes in the details may be made without departing from the spirit, or sacrificing any of the advantages of the present invention.