US 2890795 A
Description (OCR text may contain errors)
, June 16, 1959 R. DERING 2,890,795
METALLURGICAL PROCESSING OF URANIUM ORES Filed Jan. 31, 1955 RAW ORE I cRusHING wETTING AGENT CONDITIONING REAGENT v ATTR'T'ON (COAL TAR cREosoTE COLLECTOR) PREDOMINANTLY CARBONACEOUS FROTH CONCENTRATE FROTHING REAGENT F'RST FLOTAT'ON (PINE DERIVATIVE) TAILINGS SANDS scouRIN SLIMES AND ABRADING CLASSIFIED MINUS I MESH I THICKENING I SIZING FIRST METALLIC RESURFACING SALTS -40 -60 -80 BO-IOO I I M MESH I MESH MESH ESH SECOND FACTIVATING RESURFACING REAGENTS GRAVITY GRAVITY GRAVITY GRAVITY OONCEN- CONCEN- CONCEN- CONCEN- FLOTATION FLOTATION REAGENTS- TRATION TRATION TRATION TRATION I v I REJECTS I I 20o GRINDING MESH I FLOAT CONCENTRATES CONCENTRATES I T w (A FINAL (A FINAL PRODUCT) M PRODUCT) (FINAL MILL TAILINGS) INVENTOR.
- RDGER DERI METALLURGICAL PROCESSING OF URANIUlVI ORES Roger Dering, Salt Lake City, Utah Application January 31, 1955, Serial No. 485,215
. 8 Claims. (Cl. 209-12) This invention relates to the metallurgical processing of uranium ores for the concentration or beneficiation of the uranium values contained thereby.
The invention is concerned with all types of uranium ores, and with the obtaining of a maximum recovery of uranium values from the raw ore.
' All known uranium ores are oxidized in character. While there are a variety of metallurgical processes applicable to such ores, for the extraction of their uranium content, none have proven entirely satisfactory. While major portions of the uranium minerals are generally recovered by such processes, by far too great a percentage of the total values are lost when considered from the standpoint of modern metallurgical expectations. Furthermore, too much gangue content is subjected to processing thereby introducing'complications.
Pitchblende and uraninite are presently recognized as the primary ores of uranium, but because of different chemical and physical action occurring in nature, ap proximately ninety difierent oxidation products of these two primary minerals have been identified by authorities in this field.
In working with many diiferent types of uranium ores, I have found that practically all are of a highly complex nature, containing, in themselves, mineral components exhibiting many difierent phases of oxidation. This makes for processing difiiculties, and undoubtedly explains why existing processes are not more efficient in the recovery of the uranium content.
A principal purpose of the present invention is to provide a processing procedure applicable to run-of-the-mine uranium ores of all types, and designed to effect a maximum recovery of uranium values, regardless of how they may exist in the ore.
My new procedure is somewhat analogous to selective flotation, in that the diiferent components of any given ore are treated selectively for the recovery of their respective values, without interfering with, and, in fact, enhancing over-all recovery.
Thus, I pass the ore through a series of successive processing steps, each designed to accomplish a beneficial result with respect to either actual recovery of a portion of the uranium values or to furthering the condition of the ore toward that end. Certain of these steps have precedents in existing processes, but I am aware of no existing process utilizing, or of any recognition by the art of what can be accomplished by, the combination of processing steps here disclosed applied sequentially to any given ore of uranium.
.The present procedure is particularly advantageous in that it is capable of large-scale application in practice, without the necessity of precise control by technically trained operators.
The accompanying drawing illustrates a flow sheet representing a typical processing circuit pursuant to the invention.
" "Referring now to the drawing:
United States Patent As indicated in the flow sheet, the first step involves size reduction of the ore as mined.
While size reduction is a universal practice in the metal lurgical art, the manner in which it is carried out is of particular importance in the processing of uranium ores.
It is my purpose to crush the raw ore to a size suitable for metallurgical processing, while preserving so far as possible the silica grains in their original size, thereby minimizing the quantity of secondary slimes of both metalliferous and silicious character which owe their origin to this necessary size reduction stage. It can be readily appreciated that there are various ways of producing the results desired in this stage and that much must be left to those skilled in the metallurgical art, who may be supervising application of this process in any given instance in practice, to select that particular way,- which, in their judgment, is best suited for the particular ore concerned. I have found that, in most instances, satisfactory results are had by utilizing a reduction crusher for reducing preliminarily crushed, raw ore to a size which ordinarily does not exceed nor go below 20 mesh, it being realized that a considerable quantity of the raw ore will inevitably disintegrate into extremely fine particle sizes productive of dust and slime in subsequent stages of the process.
The preliminary crushing of the raw ore may be accomplished by a conventional jaw crusher. The reduction crushing is preferably accomplished by a conventional reduction crusher of cone type, although a set of rolls may also be used.
All crushing is preferably accomplished by the application of moisture or some other wetting agentto the ore for preventing dust loss.
The ore, as so reduced in size, is passed to an attrition stage for removing relatively loose surface occurrences of uranium minerals from the ore particles. An attrition mill, conveniently a rubber-lined, tube mill equipped with grinding media of smaller than normal size and of fewer than normal number, is preferably employed in this stage to accomplish the scouring. A rubber or other non-metallic lining has been found to be a most desirable thing, in that it eliminates the usual spalling off of iron particles from ferrous liners conventionally employed in such mills, thereby avoiding undue consumption of flotation reagents and serious reduction in selectivity in later stages of this process.
This attrition stage is open-circuit in character. No oversize is returned to the attrition mill. For the purpose of the immediately subsequent stage, a coal tar creosote collector, such as Barrett No. 4, is introduced into the attrition mill in super-normal quantity, e.g. one to two pounds per ton of crude ore, either initially with the ore particles or during the scouring procedure. The duration of this attrition and conditioning stage will depend upon the particular ore concerned, as will be apparent to those skilled in the art.
Discharge from the attrition mill is run directly to the next stage of the process, which involves flotation for the removal of any carbonaceous materials that might be present. In practically all instances, more or less of one or another or several uranium-bearing, carbonaceous materials, such as asphaltite, will occur naturally in the ore. Whether or not the occurrence is recognized in any particular instance, I have found such carbonaceous materials to be responsible for many difliculties in the metallurgical processing of uranium ores, and removal thereof to be imperative'for maximum recovery proper by this stage of my process may beandadvanta geously are passed to auxiliary processing for the recovery of the uranium contained therein. The nature of that auxiliary processing forms no. part of the present invention, and may be of any suitable character.
Utilizing the flotation collector reagent above-specified, together with a suitable frother reagent, preferably a pine derivative containing pinenes and terpineols, such as the proprietary product Solvenol" marketed by Hercules Powder Co., the carbonaceous materials are floated off from the ore proper as a froth concentrate, which may be. easily processed for the recovery of its uranium content.
The actual flotation may be of conventional character, and may be carried out in any of the currently popular flotation machines. The tailings containing the ore proper are passed to the next stage of my process, which involves abrasive scouring of the ore particles for the removal therefrom of surface films of uranium-bearing material.
In contradistinction to the previously mentioned attrition stage, where a rubber-lined tube mill is preferably employed, the abrasive scouring of the considerably cleaner silica particles fed to this stage of the process as a metallurgical pulp is preferably accomplished by a Dutch Cone or modification thereof. While a Dutch Cone is commonly employed for classification or thickening purposes, I know of no other instance Where it has been employed as an abrasive scouring agency.
The constituents of the removed surface films are conveniently separated from the larger sand particles by removal through the slimes-discharge opening of the Cone. Thus, the Dutch Cone enables an effective sandsslime separation to be made coincidentally with the abrasive scouring procedure.
In the subsequent processing, the slimes are treated separately from the sands.
As indicated by the flow sheet, the slimes obtained from the abrasive scouring action of the Dutch Cone are thickened by the use of any suitable thickening device, for example, a Centriclone, Dutch Cone, or a gravity thickener.
The sands, on the other hand, are classified into several size groups, for gravity concentration in a subsequent processing stage. Such size classification is conveniently accomplished by successive screening of the sands to obtain separate groups containing sand particles within respectively different size ranges, for example, first, a size range between 20 and 40 mesh, second, a size range between 40 and 60 mesh, third, a size range between 60 and 80 mesh, and fourth, a size range between 80 and 100 mesh, all material passing through a 100 mesh screen being preferably passed to thickening and further slime treatment alongwith the slime obtained from the Dutch Cone scouring stage.
Each size group of sands is passed individually and separately to gravity concentration, preferably! heavy media separation utilizing media selected from the range of approximately 2.00 specific gravity to approximately 3.20 specific gravity, as may be found appropriate depending. upon the nature of the ore. This stage of my process is believed to represent, in itself, a novel and useful metallurgical procedure, inasmuch as it involves the new concept of providing a classified feed for gravity separation, which has the advantage of far greater selectivity and over-all efficiency of dififerential action. Heavy media separation has heretofore been employed for its sorting action preliminary to conventional concentrating procedures. In contradistinction to this customary application of the heavy media technique, I here utilize, it to. effect a primary concentrating action with respect to the ore sands of each of the size groups fed thereto.
I much prefer this heavy media treatment for this gravityconcentration stage of my process, but may emplo'y gravity tabling as an alternative and'usually less efficient treatment.
The concentrates resulting from these several gravity concentrations are ordinarily predominantly uraniumvanadium minerals and coarser sizes of primary uranium minerals, such as pitchblende and uraninite. These concentrates, considered collectively, represent final recovery product of my process.
The rejects resulting from the several gravity concentrations are passed to a grinding mill, such as a Silex or porcelain lined tube mill (for the same reason as aforespecified for the rubber-lined tube mill), and are ground to a fineness of approximately 200 mesh for the purpose of releasing any occluded uranium minerals. The finely ground pulp discharge from such mill usually requires thickening. This is conveniently accomplished in common with the slime drawn from the slime-discharge opening of the Dutch Cone, as indicated by the flow sheet.
The thickened slimes are passed to a first resurfacing stage, where they are conditioned with a reagent capable of applying a monomolecular film having metallic characteristics on the surfaces of those of the particles as are sub-metallic in character, i.e predominantly uranium minerals. The reagent is preferably lead nitrate or lead acetate, but in some cases some other heavy metal salt, eg of copper, mercury, or manganese, may be preferred by those skilled in the art, depending upon particular characteristics of the ore and the nature of the subsequent treatment stages.
Following this first resurfacing stage, the conditioned slimes are passed to a second resurfacing stage, where they are conditioned with activating reagents for a subsequent flotation stage which may and usually will be of orthodox character, for example, conventional sulfide flotation utilizing well known flotation reagents applicable thereto. In such instances, the main activating agent could be sodium sulfide or one of its analogues. Methods of activating are well known and need not be gone into further here.
The so-conditioned slimes are then passed to flotation,-
where the float concentrates obtained represent a final product. The tailings represent the final mill tailings of the process, and will ordinarily be passed to waste.
Thus, my process results in the obtaining of, first, a
predominantly carbonaceous froth concentrate containing uranium values, which may be further processed irrany suitable manner for extraction of such uranium values, second, a gravity concentrate product containing uranium and in some cases vanadium values, and, third, a float concentrate containing uranium values. The tailings from the final flotation stage of the process constitute the only waste.
Whereas this process has been illustrated and described with respect toa particular preferred application thereof in practice, it should be realized that the invention is not limited to the specific procedures set forth, and that such procedures may be varied by those skilled in the art within the scope of the claims which here follow.
1. A process for the concentration of uranium values from ores containing same, comprising subjecting the raw ore to size-reduction operations while preserving: component sand particles largely in their original condition and while preventing the occurrence of dust; passing the said ore, as so reduced in size, to an attri tion mixing operation, and dislodging relatively loose materials from said sand particles by said attrition mixing operation; passing the so-treated ore to a flotation op.- cration, and conducting said flotation operation in the presence of collector and frother reagents specific to carbonaceous material, whereby a float concentrate of predominantly carbonaceous material is obtained; passing; the tailings from said flotation operation to an abrading operation, and scouring tenacious encrustations from the surfaces of the sand particles by said abrading opera-- tion; segregating the slimesof'th'e so-treated ore and separating them from the sands thereof; passing said slimes to a thickening operation; passing the said sands to a sizing operation, and establishing by said sizing operation a plurality of individual groups of sands of successively decreasing size ranges, respectively; passing said individual groups of sands of respectively differing size ranges to respective gravity concentration operations, and deriving concentrates from said operations; passing the rejects from the said individual gravity concentration operations to a grinding operation, and grinding said rejects, in common, to slime condition; passing the siime from the said grinding operation to a thickening operation; passing the thickened slime from said operation and the thickened slime from the said sand-slime segregation operation to a resurfacing operation, and applying a quasi-metallic coating to the surfaces of sub-metallic components of said slimes by conditioning said slimes with at least one metallic salt suitable for the purpose; passing said conditioned slimes to a second resurfacing operation, and activating the said coated particles for a subsequent flotation operation by further conditioning said conditioned slimes with an activating reagent suitable for the purpose; and passing the said further conditioned slimes to a flotation operation, and utilizing collector and frother reagents specific to the surface coatings of said activated particles for recovering a uraniumcontaining float concentrate from said flotation operation.
2. A process as set forth in claim 1, wherein the abrading operation on the tailings from the first-named flotation operation is carried out by passing said tailings through a Dutch Cone type of apparatus.
3. A process as set forth in claim 2, wherein the slimes from the abrading operation are separated from the sands by withdrawal from the said apparatus through the slimes-discharge opening thereof.
4. A process as set forth in claim 1, wherein the respective gravity concentration operations are heavy media in charcter.
5. A process as set forth in claim 1, wherein the attrition mixing operation on the size-reduced ore and the grinding operation on the rejects from the respective gravity concentration operations are carried out in mills having non-ferrous linings.
6. A process as set forth in claim 1 wherein the sizereduction operations are such as to reduce the raw ore to a size of approximately 20 mesh with a minimum of slime-forming fines; wherein the size classification operation on the sands resulting from the abrading operation is such as to separate said sands into respective groups of range between approximately 20 and 40 mesh, of range between approximately 40 and 60 mesh, of range between approximately 60 and 80 mesh, and of range between approximately 80 and 100 mesh, respectively; and wherein all material from the said sands which is minus 100 mesh is passed to the slime thickening operation for subsequent treatment together with the slime from the grinding operation.
7. A process as set forth in claim 1, wherein the ore materials subjected to the attrition mixing operation are conditioned for the carbonaceous flotation operation with a coal tar creosote collector reagent, and said flotation operation is conducted in the presence of a pine derivative frothing reagent.
8. A process for the concentration of uranium values from ores containing same, comprising subjecting the raw ore to size-reduction operations while preserving component sand particles largely in their original condition and while preventing the occurrence of dust; passing the said ores, as so reduced in size, to an attrition mixing operation, and dislodging relatively loose materials from said sand particles by said attrition mixing operation; passing the so-treated ore to an abrading operation, and scouring tenacious encrustations from the surfaces of the sand particles by said abrading operation; segregating the slimes of the so-treated ore and separating them from the sands thereof; passing said slimes to a thickening operation; passing the said sands to a sizing operation, and establishing by said sizing operation a plurality of individual groups of sands of successively decreasing size ranges, respectively; passing said individual groups of sand of respectively differing size ranges to respective gravity concentration operations, and deriving concentrates from said operations; passing the rejects from the said individual gravity concentration operations to a grinding operation, and grinding said rejects, in common, to slime condition; passing the slime from the said grinding operation to a thickening operation; passing the thickened slime from said operation and the thickened slime from the said sand-slime segregation operation to a resurfacing operation, and applying a quasi-metallic coating to the surfaces of sub-metallic components of said slimes by conditioning said slimes with at least one metallic salt suitable for the purpose; passing said conditioned slimes to a second resurfacing operation, and activating the said coated particles for a subsequent flotation operation by further conditioning said conditioned slimes with an activating reagent suitable for the purpose; and passing the said further conditioned slimes to a flotation operation, and utilizing collector and frother reagents specific to the surface coatings of said activated particles for recovering a uranium-containing float concentrate from said flotation operation.
References Cited in the file of this patent UNITED STATES PATENTS Maust Sept. 28, 1954 Krijgsman Feb. 8, 1955 Handbook of Mineral Dressing, Taggart, 1945, John Wiley and Sons, section 8, page 8-01.