Abstract:
A method of producing concentrates of colemanite and probertite from mixed low grade ore which involves desliming at different particle sizes for colemanite and probertite recovery.

Description:
This invention relates to a process for recovering concentrates of colemanite and probertite from mixed low grade core. 
     In one of its more specific aspects, this invention relates to the recovery of colemanite and probertite, by differential flotation, from a mixed crude ore, in the form of high grade borate concentrates. 
     The existance of crude ores containing colemanite and probertite is well known. While the colemanite and probertite are important from the standpoint of their B 2  O 3  values, processes for recovering these minerals as individual high grade concentrates from mixed crude ore have not been particularly effective. This invention provides a method of doing so. 
     STATEMENT OF THE INVENTION 
     According to the invention, there is provided a method of producing concentrates of colemanite and probertite from mixed low grade crude ore which comprises crushing and grinding the ore to 35 mesh maximum, desliming the ground ore at about 10 microns, and recovering a combined fraction, separating the combined fraction to a colemanite-rich concentrate and a probertite-rich concentrate, desliming the probertite-rich concentrate at about 14 to about 20 microns and individually floating the probertite-rich concentrate and the colemanite-rich concentrate to produce a probertite concentrate and a colemanite concentrate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The attached drawing is a schematic flow diagram of the process. 
    
    
     DETAILED DESCRIPTION 
     The method of this invention is applicable to any colemanite-containing and probertite-containing ore. It is particularly applicable to a mixed crude ore. 
     Referrring to the attached drawing, the crude ore is subjected to a size reduction step 1 to reduce the ore to about 35 mesh, maximum. Any suitable size reduction process can be employed. Preferably, a plurality of steps will be employed, the first being impact crushing and the second being wet ball milling, the combination being sufficient to attain the desired particle sizes. 
     The ground crude ore 2 is then introduced into a conventional desliming process 3. Any desliming process suitable for efficient removal of micron slimes, including hydrocycloning or elutration, can be employed. The desliming is conducted at approximately 10 microns and the slime 4 is withdrawn and a recovered fraction 5 is routed to flotation step 6. 
     Any suitable flotation process can be employed. Preferably, this flotation step, which separates a colemanite-rich fraction 17 and a probertite-rich fraction 18 will be followed by 3 cleaner stages step 19. Conventional collecting agents are introduced into the charge at the rougher flotation step 6. 
     Any suitable collecting agent can be employed. Such agents usually are anionic petroleum sulfonates, such as American Cyanamid&#39;s Aero Promoters 801, 825 and 845, these being employed individually, or in combination, in an amount of about 2.3 pounds per ton of crude ore. 
     From the colemanite flotation 19, a colemanite concentrate 7 is recovered. 
     The rougher and cleaner tailing products 18 and 8 from the colemanite circuit are combined and subjected to desliming at 14 to 20 microns. The deslimed material 12 is then conditioned with about 0.8 pounds of the above-mentioned collecting agents per ton of crude ore. 
     The deslimed and conditioned material is routed to flotation step 13. Any suitable flotation process 13 can be employed. Preferably, this flotation step which recovers the probertite-rich fraction will consist of one rougher stage and 3 cleaner stages. The rougher tailings 14 are discharged as final reject while the cleaner cell underflow products 15 can be recirculated as middlings, the probertite concentrate being recovered as product stream 16. 
     Each of the concentrates can be reclaimed in any suitable manner, including filtering and drying. 
     EXAMPLE I 
     The following example demonstrates the benefits of carrying out this invention according to the method previously described. 
     A differential flotation process, as described above, was carried out to separate colemanite and probertite. 
     The feed was a mixed crude ore comprising colemanite and probertite in approximately a 3 to 1 mixture by weight with a boron grade of approximately 20% B 2  O 3 . The natural pH of the ore pulp was 8.9. 
     American Cyanamid&#39;s Aero Promotors 801 and 825 were employed in a 1 to 3 weight ratio as the collecting reagent, 2.3 pounds of the mixture per ton of crude ore being employed in the colemanite rougher flotation stage and 0.8 pound of the mixture per ton of crude ore being employed in the probertite rougher flotation stage. Results were as follows, when desliming the crushed ore at about 10 microns and the probertite-rich fraction at about 20 microns. 
     
         ______________________________________                               % B.sub.2 O.sub.3Product    % Wgt   % B.sub.2 O.sub.3                         % Na  Dist.______________________________________Colemanite 27.37   42.2       0.26  59.32ConcentrateProbertite 12.16   35.6       2.75  22.23ConcentrateMiddlings  10.30   10.2       1.21  5.37Tailings   17.51   3.3        0.54  2.97Combined Slimes      32.67   6.0        0.70  10.11Total (Feed)      100.00  19.47      0.85  100.00______________________________________ 
    
     The above data demonstrate the efficiency of the process in concentrating the B 2  O 3  values in the colemanite and probertite concentrates. 
     EXAMPLE II 
     The process described above was carried out on colemanite ore and probertite ore with the following results: 
     
         ______________________________________          Flotation ResultsTest Nominal Particle                Conc. Grade                           Boron RecoveryNo.  Size of Slime Removed                (% B.sub.2 O.sub.3)                           (% B.sub.2 O.sub.3 Units)______________________________________A - Colemanite Ore5A   (No desliming)  No separation5    10 microns      41.2       76.367   14 microns      43.0       75.6B - Probertite Ore38   (No desliming)  No separation 3   10 microns      No separation47   14 microns      36.89      46.848   17 microns      37.99      49.762   20 microns      37.10      62.9______________________________________ 
    
     These data demonstrate that slime removal at 10 microns is preferred for colemanite flotation and that recovery of probertite requires a more intensive desliming, that is, material in the size range of 10 to 20 microns, nominal, must also be removed in order for the flotation process to yield an acceptable boron recovery. 
     It will be evident from the foregoing that various modifications can be made to the method of this invention. Such, however, are within the scope of the invention.