US2165268A - Flotation of oxide ore minerals - Google Patents

Description

Patented July 11, 1939 UNITED STATES PATENT. creme FLOTATION OF ORE MINERALS Mikael Vogel-Jorgensen,

Frederiksberg, near Copenhagen, Denmark, assignor to Separation Process Company, a corporation of Delaware No Drawing.

Application June 30, 1937, Serial No. 151,203. In Great Britain July 17, 1936 5 Claims.

argillaceous limestones, marls and chalks, to produce concentrates useful in the manufacture of Portland cements, but it will be understood that it is of broader scope.

In general, the invention has to do with the utilization of talloel, a waste product derived from the black liquor soap of the sulphate process for the manufacture of cellulose and paper. Talloel, as referred to herein, is the refined product obtained when the black liquor soap, which floats on the black liquor, has been removed by skimming and is then treated with a mineral acid, usually sulphuric acid, and refined to remove ligneous and other insoluble material, and should not be confused with black liquor soap itself, which contains ligneous matter and other impurities which render it unsatisfactory as a flotation reagent. The talloel is saponified and preferably clarified of any insoluble matter, and may be employed in dilute solutions in water. The phrase saponified talloel throughout the specification and claims is limited to the definition of a'reagent which has been saponifled prior to its addition to the water of a flotation pulp, to distinguish the reagent from talloel possibly at least partially saponifled by soap-forming alkalies present in the'pulp water, Talloel, separately with fuel oil, has been used as a fiotation reagent, but lacks many of the advantageous properties of saponifled talloel and is not its equivalent in either handling or flotation characteristics, but is' similar to the high titre fatty acids in handling characteristics and collccting power, although oi! greater frothing power. The 'saponified talloel has selective collecting qualities for the oxide mineral-grains and also frothing characteristics, both of which may be controlled-or modified to-satisfy the conditions of a specific flotationrgjilp and circuit. The collecting power per unit weight of reagent and material can'be increasgfid by the use of increasing quantities of fatty acids,' preferably saponidied with the talloel, the mixture having lower frothing characteristics than an equivalent weight of saponifled talloel. The frothing characteristlcs may be ubstantially l'gqllgegl by incorporating increasing quantities of fuel oil with the saponified talloel without apparent decrease in collecting power in quantities not exceeding equal proportions by ,weight of fuel oil and raw talloel, low proportions of fuel oil slightly increasing collecting power, but reducing selectivity. By mixing the fuel oil with the raw talloel before the saponifying reagent is added, as will be described more fully hereinafter, the

product is apparently completely soluble in water, or at least forms a clear aqueous dispersion that is stable at all working dilutions and temperatures. Some of the "soluble mineral oils and soluble vegetable oils may be substituted for fuel oil, but are less satisfactory as they are more expensive, many must be emulsified and aqueous dispersions of the mixtures are unstable and make operation erratic.

Among the purposes of the invention are to provide a low cost but highly selective collecting reagent; to extend the practical use of flotation for the economical recovery of oxide ore minerals of low commercial value, and to permit the recovery of useful concentrates from slimy pulps which do not react successfully to froth flotation with the known collectors. Among the advantages of. 'saponified talloel are first, that it can be diluted in water to any convenient degree to make possible light and uniform stage oiling; second. it is completely stable at all working temperatures and is quickly dispersed even in ice water; third, it takes effect quickly and its action ceases quickly, i. e., it is sensitive; fourth, the coating of the oxide mineral grains is light, thereby avoiding heavy flocculation with consequent trapping of fine gangue particles, and fifth, it is highly selective. These advantages extend the practical use of flotation to the. recovery of the valuable content of slimes, such as those described later, which are not amenable to flotation to produce concentrates of commercial grades, with the usual collectors, such as the fatty acids, resin acids, soaps or emulsions, or mixtures thereof. The light coating may readily be at least partially removed by washing, thereby promoting rapid thickening.

Froth flotation processes have been employed successfullyheretofore for the purpose of deriving satisfactory cement raw material mixtures, or lime components thereof, from inferior argillaceous limestones, marls or chalks, containing excessive quantities, or undesirable proportions, oi'one or more of the argillaceous constituents, usually alumina compounds and crystalline silica. It is among the purposes of the invention to reduce the cost of these processes and to extend the practical or economical utility of fiotation to the treatment of materials that cannot be separated readily or practically with the known reagents. The use of cold water is not the least of these economies since not only is the cost of heating the relatively enormous water volumes of a classification, flotation and thickening circuit eliminated but also classification and thickening are not unbalanced by the currents of warm water.

In many of the materials of the types described, the component minerals are naturally so fine, or must be reduced to such fineness to free the mineral bonds, that the resulting pulp is a slime, or the proportion of slime is so large that it may not be wasted. In addition to the finely divided calcite, the slimes almost always include a wide variety of clay minerals, micaceous matter and crystalline silica, which tend to flocculate naturally in a flotation pulp, many of the mineral particles being colloidal or having colloidal behavior. The low commercial value of Portland cement, precludes the use of dispersing reagents prior to the introduction of the usual collectors, and dispersers are not always effective in view of the variety of classes of mineral compounds. The usual fatty and resin acids are ineffective as their relatively highly collecting power and poor selectivity produces heavy flocculation and consequent trapping of the fine gangue minerals. Further, these reagents cannot be uni- -formly and quickly dispersed in coldwater, some of them dispersing slowly if at all.

Solutions of the fatty or resin acids, or mixtures thereof, in mineral oils likewise cause overoiling, the heavy flocculation producing low-grade concentrates, and are almost as difiicult to disperse in the pulp. The usual soaps produce lowgrade concentrates but their principal disadvantage is their exceptionally poor selectivity. Emulsions of fatty and resin acids may be dispersed readily but produce matted froths of lower grade than saponified talloel, the froths being diificult to break down, aggravating difficulties in thickening, forming excessive and heavy scum on the thickeners and more dilute thickener underfiow.

The reagent is prepared by saponifying the refined talloel with the customary reagents such as caustic soda, potash or ammonium hydroxide. Between 10 and 14% of caustic soda on the weight of the talloel, or the equivalent of another saponifying reagent, may be required depending upon the acid value of the available talloel. Incomplete saponification results in a mixture comparable to an unstable fatty acid emulsion with respect to its handling characteristics, but is more selective in flotation. Saponification is accelerated by slow boiling and stirring the mixture, satisfactory results being had when the lumps have disappeared, but it is preferable to add the causticuntil the mixture is alkaline within' a range between pH 9 and 9.5, particularly for calcite concentration. Any insoluble matter canbe removed by allowing the mixture to settle for several days, when the supernatant liqfuidomay'be drawn off. .At least partial dilution withsuwater "accelerates clarification. The reagent may less conveniently be clarified by filtration. To obtain'a maximum uniformity in dispersing the'reagei'it in the pulp and to permit closely controlled light stage oiling, the reagent referably'used'in 5% to 20% dilution in waterfalthough 'ot'herjdilutions may be employed, the finer pulps-responding more satisfactorily to the more dilute solutions. The use of saponified talloel has no marked effect on the alkalinity of pulps of the types described, which remain in. the normal range between pH 7.6 and 7.8, the alkalinity of limestone pulps being naturally buffered by dissolved carbon dioxide.

When the pulp does not contain excessive quantities of the finer slimes, the collecting power can be increased and the frothing characteristics reduced and controlled, whereby flotation is more rapid, by the use of increasing quantities of fuel oil. By reducing the frothing characteristics, frothing reagents may be employed to control the balance of stage oiling circuits. saponified talloel is insoluble in fuel oil, but if prior to saponification, in the manner described above, the fuel oil is mixed with the raw talloel and the caustic is added afterward, the composition is apparently completely soluble in water or is possibly a clear aqueous disperson stable and capable of dilution to any degree at any working temperature. An excess of caustic soda is required. For talloel requiring 12% caustic soda for complete saponification, a mixture of equal parts of talloel and fuel oil by weight requires a total of 20% caustic on the weight of the mixture to produce a clear or stable solution. It is to be understood that the best results are obtained by proportioning the relative quantities of fuel oil with relation to the fineness of the slimes, partial desliming or increasing grain sizes permitting satisfactory use of increasing quantities. Increasing proportions of fuel oil increase the collecting power, but decrease the selectivity, and no appreciable loss in collecting power is apparent when the proportion of fuel oil does not exceed that of the talloel, but beyond this proportion collecting power drops rapidly. Frothing characteristics, desirable with fine pulp but undesirable with coarse, particularly in stage oiling circuits, decrease as the proportion of fuel oil is increased. While the use of saponified mixtures of talloel and fuel oil is included within the broad scope of the invention, this specific improvement is not claimed herein, as saponified talloel and fuel oil mixtures, which are miscible with water, are the invention of Robert C. Ried and are described and claimed in his co-pending application, Serial No. 163,307, filed September 10, 1937.

In pulps in which the finer slimes are not abundant, substantially increased collecting power is desirable to decrease the pulp dilutions and the flotation time, to limit the amount of flotation equipment necessary. This is accomplished by incorporating, as a part of the reagent, quantities of fatty acids, increasing quantities giving favorable results as the relative coarseness of the mineral grains increases. The increasing additions of the fatty acids likewise reduce the frothing characteristics, but to a lesser degree than fuel oils, but also make it possible to add quantities of the common frothing agents, such as cresylic acid or alcohol' frother identified hereinafter,-a feature of especial utility in'stage oiling circuits as it provides for accurate control of each stage. Conversely, with an appropriate pulp and a stage oiling circuit, a low proportion of fatty acid results in excessive frothingin the first stages and too little frothing in the later stages.

The fatty acid and talloel are first mixed, then saponified and clarified in the manner described above. The saponified mixture is completely soluble and may be used in any convenient dilution, formng an excellent collector 'in cold water, in which the selective effect of the saponified talloel is marked in relatively coarse pulp, and provided the proportion of fatty acid does not exceed that of the talloel. Further, excesses of some fatty acids, above an equal proportion, and particularly fish oil fatty acid, usually produce an unstable and lumpy mixture instead of a clear solution.

For a better understanding of the invention eference is made to the following examples. To interpret the results properly, it should be borne in mind that, in a Portland cement raw material of concentrate sufilciently high that only a part of the cement raw materials need be treated and the concentrates mixed with the remainder, a

natural material or both.

First example To illustrate the concentration of calcite from a fine slime, for purposes of cement manufacture, by the use of saponified talloel, the material treated'was an argillaceous marl. Natural mineral particle sizes were so fine that extreme grindrecovery being 90% ing was required to free the constituents to a degree that a useful grade of concentrate could be obtained. The marl was ground in closed circuit, the classified product, forming the flotation pulp, being substantially all minus 325 mesh sieve and about minus 10 microns.

The calcium carbonate content was 68.5%, by titration. The pulp dilution was 15% on a dry solids basis. A 10% solution in water of saponifled talloel was used in the rougher concen-- tration and produced a concentrate of 77.6% calcium carbonate, the calcium carbonate weight Reagent consumption was 1.54 pounds of saponified talloel a tonof dry solids and the flotation time was 8 minutes.

The same material with oleic acid and with cresylic acid, as a frother, produced a concentrate of 74% calcium carbonate, approximately 2% below the necessary cement raw material composition. The reagent consumption was higher, 4.4 pounds of oleic acid being required, and the flotation time was increased to 10 minutes.

Second example To illustrate a so-called pulp, and the use of saponified mixture of talloel and fuel oil, in which the fuel oil was employed principally to reduce frothing, for control in a stage oiling circuit, the material used as the flotation feed wasa metamorphosed micaceouslimes'tone, deficient in calcite and excessive in alumina and silica. It was-normal tube'mill slurry 'of regular cement mill operation. The calcium carbonate content was 64%. The objective was to raise 'the concentrate to cementrawf-material composition, namely about 76% calcium carbonate. The physical analysis was as follows:

3.2% plus 100 mesh 20.5% minus 100 plus 200 mesh 18.9% minus 200 plus 325 mesh 57.4% minus 325 mesh 25.0% minus 10 microns The reagent used was a saponified mixture of 60% refined talloel and 40% fuel oil, saponified with 20% NaOH on the weight of the mixture and diluted to 3% solution in water for convenience in handling and accuracy of control.

' The pulp in the first rougher cell was diluted to 18% dry solids in cold water. The grade of the concentrate of the first rougher cell was 76% calcium carbonate, the total weight recovery was 72.6%, the calcium carbonate recovery was 86.2%,

without cleaning or skimming. Flotation time was 5.25 minutes. R eagent consumption was 0.856 pound of the saponified mixture and 0.0594 pound of alcohol frother comprising a mixture of branched and straight chain aliphatic monohydric alcohols boiling between about 152 C. and about 162 C. obtainable along with methanol *fby the catalytic hydrogenization of carbon oxides.

Third example To illustrate a so-called "coarse" pulp and the use of a saponified mixture of talloel-and fish oil fatty acid, the material treated was similar to that of the second example, taken from the same quarry but of better grade. It was also normal tube mill slurry, of regular cement mill operation, but somewhat finer. The calcium carbonate content was 72.7%. The physical analysis was as follows:

2.7% plus 100 mesh 20.4% minus 100 plus 200 mesh 16.9% minus 200 plus 325 mesh 60.0% minus 325 mesh 25.0% minus 10 microns The reagent used was prepared from a mixture of equal parts of raw talloel and high titre fish oil fatty acid of 75 to 78% acid value, saponified by 12% NaOH on the total weight of the mixture, clarified as described above, and diluted for accuracy in-control to 3% solution in water. The pulp in the first rougher cell was diluted in cold water to18% dry solids. The objective was to raise the grade of the concentrate so that only a part of the material mixture had to be treated by flotation. The first rougher cell concentrate was 86.7% CaCOa, without skimming and without cleaning, the total weight recovery was 85.5% and the calcium carbonate recovery was 98.7%. The

- weight loss in calcite in the rejects of the first rougher operation was 1.3%. The flotation time in the first rougher cell was 3% minutes. Re-- agent consumption was 0.785 pound a ton of dry .feed. Significantfifeatures of these results are that the fine andthe coarsecalcite grains were collected together, reagent consumption was low,

flotation was rapid and the calcite loss was neglislble.

A check test with a mixure of equal parts of raw talloel and fish oil fatty acid failed to produce a substantial improvement in the grade of the flotation celllfeed, due principally to the failure to obtain dispersion in cold water.

. Fourth example Material substantially similar to the second and third examples in fineness and composition was treated with a saponified mixture of talloel and oleic acid, in the same manner. The feed had a calcium carbonate content of 71.6%. The reagent was a mixture of 60% talloel and 40% oleic acid, saponified with 12% NaOH, on the total weight of the mixture, which was diluted to 3% so ution in water. The calcium carbonate content of the concentrate was 84%, total weight recovery 83.9%, calcium carbonate weight recovery 98.2%, and the reject was 16.1% weight with l a grade of 0.8% calcium carbonate. Reagent consumption was 0.8 pound of the mixture a ton of dry feed. The flotation time was 4 minutes.

In all of the foregoing discussion, the term coarse, as applied to some of the pulps referred to, is relative, and it should be understood that these pulps are slimes, or contain an abundance thereof, within the meaning of the term slimes in the art of flotation. Saponified talloel has a marked tendency to disperse naturally flocculated pulps and satisfactory grades of concentrates can accordingly, be produced without the use of dispersing agents. However, the usual dispersing agents can be used with the present reagent to complete dispersion to improve the grade of the concentrates, but the low commercial value of the concentrates, with which this invention is particularly concerned, ordinarily makes the cost of dispersers prohibitive. Further, and although the invention opens a new field of utility for flotation in the differential separation of slimes, it should also be realized that it is not so limited, but that the selective characteristics and low cost makes the reagent an excellent collector for use in normal de-slimed pulps.

.I claim:

1. 'Ifhe method of concentrating oxide ore min-= erals by froth flotation which comprises intro 'ducing substantially completely pre-saponified completely pre-saponified mixture of acid-refined talloel and a. fatty acid in an aqueous oxide ore mineral pulp and agitating and aerating the pulp in the presence of said saponifled mixture.

3. The method of concentrating calcite by froth flotation from siliceous gangue minerals which comprises introducing a clarified aqueous solution of a pre-saponified acid-refined talloel in an aqueous pulp containing calcite and agitating and aerating the pulp in the presence of said saponified talloel.

4. The method of concentrating calcite by froth flotation from siliceous gangue minerals which comprises introducing a pre-saponifled mixture of acid-refined talloel and a fatty acid in an aqueous pulp containing calcite and agitating and aerting the pulp in the presence of said saponified mixture.

5. The method of concentrating calcite by froth flotation from siliceous gangue minerals in a stage oiling circuit which comprises introducing an aqueous solution of a pre-saponified mixture of acid-refined talloel and a fatty acid in an aqueous pulp containing calcite, agitating and aerating the pulp in the presence of the mixture, and controlling frothing characteristics of the stages by additions of a separate irothing agent.

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