Reagents For Beneficiating Ores

Abstract

Flotation concentration of sylvite from sylvinite or other potassium chloride ores in a brine of the ore, particularly effective where brine carrier is dirty or at high temperature. Small amounts of silicone polymers are introduced as auxiliary agents in conjunction with primary aliphatic amines and aliphatic and/or aromatic oils as collectors reducing total reagent requirement with resulting cost reduction and substantial improvement in flotation efficiency.

Description

This invention relates to the beneficiation or concentration of the sylvite content of sylvinite ores by a flotation procedure and has particular reference to the use of certain auxiliary reagents introduced in a minor quantity with the regular collector reagents now used commercially in the treatment of such ores.

The present invention is especially concerned with decreasing total reagent cost and improving the recovery of the valuable minerals in processes where it is desired to float coarse mineral particles and other difficult to float minerals through more effective use of the regular flotation reagents for such treatments. The minerals to be beneficiated must exist naturally in a floatable size or they have to be reduced to a size that will permit the required mineral beneficiation by the particular reagents and processing equipment employed.

In many cases, it is desirable to separate the valuable mineral constituents at maximum possible size so as to reduce grinding and processing costs and also to retain the mineral in coarse sizes as a more desirable product by market requirements. In general, the cost of flotation reagents increases as the size of the mineral being floated is increased due to the larger amounts of reagents required per unit weight of mineral.

In other instances, the minerals may not be completely physically separated from each other at coarse sizes. These particles, known as "true Middlings" are normally more difficult to separate by flotation than the completely liberated minerals. The use of the increased amount of reagents required to float the large particles and middlings often reduces selectivity in the beneficiation process and results in carrying larger amounts of an undesired constituent with the valuable mineral being concentrated than would occur if the treatment were performed on finer sized material using lesser amounts of reagent per weight of material. Depressant reagents may be used in addition to collector reagents to reduce the concentration of such constituents with the primary reagentized mineral being floated.

According to the present invention, it has been discovered that the use of extremely small amounts of polymers, known under the trade name of silicones, introduced as auxiliary reagents give a greatly improved flotation performance with a reduction in cost and total reagent consumption where conventional collectors, secondary collectors and froth modifying flotation reagents are used. As used herein, the terms silicone polymer or silicone are intended to include those synthesized organosiloxane fluids that are characterized by unusually low surface tension values ranging from about 15-30 dynes per centimeter. These organosiloxane-polymers not only include the normal commercially available fluids or emulsions of the fluids consisting generally of dimethyl silicone, phenyl silicone, methyl-phenyl silicones, methyl hydrogen silicone and the like, but those siloxanes that may include ethyl, propyl, butyl and other organic side groups as well as anions such as chlorine and fluorine.

Although these silicones may have extreme variation in the length of the polymer chain and in viscosity from less than 1 to over 100,000 centistokes at 25.degree. C., they are characterized by their unique performance where high surface activity and great spreading power is necessary. Such materials are often described as "wetting agents" which promote the spreading of the liquid over the surface of the solid by reducing the contact angle of the liquid on the solids to zero.

The present invention has been found particularly applicable to a flotation process where it is desirable to obtain a thin, tightly adherent reagent film on mineral particles and thereby improve the floatability of the filmed particles.

It is an object of our invention to provide an improved auxiliary reagent for recovery of sylvite particles in the range of -4 +20 mesh from sylvinite ores when the auxiliary reagent is used in addition to the normal collectors and other secondary collecting and froth modifying reagents of such a flotation treatment.

Another object of the invention is to provide an improved flotation process employing mineral collectors and other collecting and froth modifying reagents so as to attain maximum recovery of the valuable constituents of the ore with a minimum cost of the total reagents required in the treatment.

Still another object of this invention is to provide an improved recovery of minerals where an aliphatic amine or salts thereof are employed as the primary collector reagent along with aliphatic and/or aromatic hydrocarbon oil collectors in the flotation of the valuable constituent into the froth or where the undesirable mineral impurities are floated and discarded leaving the valuable mineral to be recovered from the flotation cell residue.

In investigating the uses of such auxiliary reagents, it has been found that silicones are efficient when used in small amounts as the auxiliary reagent in conjunction with primary aliphatic amine collectors and/or aliphatic and/or aromatic oils, and it is believed that it has wide application in commercial processes employing such selective collectors. The silicones not only act as auxiliary wetting agents in assisting filming of mineral particles with the collectors, but may also be incorportated into the actual collector film and increase the floatability of the mineral through the known effect of silicones ability to increase the angle of contact between a drop of water and a silicone coated surface. This results in improving the necessary hydrophobic characteristics of the reagentized film on the surface of the mineral.

This incorporation into the mineral coating is effective and complete as the silicones are soluble in common aliphatic and aromatic oil solvents. The effect of the silicones when used in relatively large amounts along with an aliphatic amine collector, but in the absence of aliphatic or hydrocarbon oils has previously been disclosed in U.S. Pat. No. 2,934,208. The present invention is based on the discovery that the addition of small amounts of the silicones have a beneficial effect on flotation when the primary and secondary collectors have been used inadvertently in amounts greater than desirable for normal effective ore beneficiation. It has been shown that an excess of the collecting reagents under some flotation conditions decreases the speed of mineral separation, but we have discovered that the silicone additions in small amounts in these cases increases the speed of flotation.

The practice of the invention will be described as applied to the concentration or beneficiation of sylvite from sylvinite ores, but it will be understood that it is equally effective in concentrating potassium chloride from other potash-bearing ores. The tests which were made and the results which are set forth herein were confined to flotation of sylvite (potassium chloride) from a sylvinite ore of the Carlsbad, N.M. area.

It is well known that sylvite can be recovered from a pulp of sylvinite ore in a saturated solution of the soluble constituents of the ore through the use of various mechanical flotation devices by using as a collector an aliphatic amine or a mixture of these amines containing a straight chain hydrocarbon group, preferably saturated, but not necessarily so, the salts of such amine resulting from their complete reaction with water soluble acids, or a mixture of amine and the amine salts. The amines or amine salts normally employed usually contain 10-18 carbon atoms in the chain, but other amines containing as many as 22 carbon atom chains would be suitable for the present practice. These amine reagents may contain small amounts of secondary and tertiary aliphatic amines or their salts, such as are commonly found in commercial products. For example, the amine collector may be a hydrogenated tallow amine manufactured by Armour Industrial Chemical Company under the trade name of "Armeen HT" and consisting approximately of 60% octadecyl amine, 30% hexadecylamine, 5% dodecyl and tetradecyl amine and 5% unsaturated secondary and tertiary amines.

In the flotation of coarse sylvinite ores with particles present as large as 6-8 mesh, and sometimes even larger, it is desirable to use a secondary collector along with the primary amine collector to increase the hydrophobic character of the reagent-filmed sylvite particles and thereby improve its floatability. One such group of reagents is the silicone fluids as disclosed in U.S. Pat. No. 2,934,208. Historically, crude oils, diesel oils, so-called "gas oils" and other various fractions resulting from the distillation of petroleum and coal have been used as secondary collectors, due to their effectiveness and relatively low cost as compared with the substantially pure components that may be extracted from these commercially available products.

In the tests reported hereinafter for the recovery of sylvite, the amine collector consisted of a 2% water emulsion of Armeen HT in which 35% of the amine was converted into amine acetate by the addition of acetic acid. A fractionated oil residue from local petroleum refineries was used as a secondary collector in all tests.

Samples of several previously dry crushed sylvinite ores were combined into one blended composite ore batch which was then sized into the following screen fractions: -4, +6; -6, +8; -8, +10; -10, +14; -14, +20; and -20. The -20 mesh ore was discarded. The ore for each individual test was prepared by an actual weight portion of each of the remaining blended ore fractions into 106 gram samples of the following size distribution:

Mesh Size % by Weight __________________________________________________________________________ -4, +6 8.3 -6, +8 25.2 -8, +10 31.3 -10, +14 26.8 -14, +20 8.4 __________________________________________________________________________

Each ore sample taken for test was pulped with 70 ml. of saturated KCl-NaCl brine and scrubbed in a cylindrical vessel having a mechanically driven four-bladed turbine-type agitator to release slimes associated with the ore. The scrubbed ore was diluted with saturated KCl-NaCl to a 35 percent pulp density and decanted to a 70 percent pulp density on two occasions so as to remove the major portion of clay and actual ore slimes. The final ore pulp was then drained on a 35 mesh screen prior to being conditioned for 11/2 minutes with the designated reagents of each test. The reagentized ore was then introduced into a laboratory vertical type brine jet cell patterned after the commercial flotation machines disclosed in U.S. Pat. No. 2,999,595 and floated until absence of mineral in the float product was attained.

The following test data which are self-explanatory show the results obtained by the above procedure using an ore containing about 33 percent potassium chloride. The rate of addition of reagents is measured in pounds of reagent per ton of total ore scrubbed and the percent KCl in the tailings and percent KCl recovered is based on the percent potassium chloride in the ore pulp after desliming. --------------------------------------------------------------------------- TABLE

I Amine Rate--0.3 Lb./Ton Oil Rate--1.8 Lb./Ton Auxiliary Reagent Rougher KCl Rate Tailing Recovered Auxiliary Silicone Reagent Lb./Ton % KCl % __________________________________________________________________________ None 0 7.0 85.5 Emulsion 0.0005 3.8 92.5 Emulsion 0.01 3.2 93.5 Emulsion 0.04 2.6 95.0 Fluid (100 Centistoke Viscosity) at 25.degree. C. 0.0045 3.8 92.2 Fluid (100 Centistoke Viscosity) at 25.degree. C. 0.0009 3.3 93.0 Fluid (100 Centistoke Viscosity) at 25.degree. C. 0.018 2.9 94.4 Fluid (350 Centistoke Viscosity) at 25.degree. C. 0.0045 4.4 91.0 Fluid (350 Centistoke Viscosity) at 25.degree. C. 0.009 3.3 93.4 Fluid (350 Centistoke Viscosity) at 25.degree. C. 0.018 2.8 94.7 --------------------------------------------------------------------------- --------------------------------------------------------------------------- table

ii amine Rate--0.5 Lb./Ton Oil Rate--3.0 Lb./Ton Auxiliary Reagent Rougher KCl Rate Tailing Recovered Auxiliary Silicone Reagent Lb./Ton % KCl % __________________________________________________________________________ None 0 5.3 89.0 Emulsion 0.005 2.8 94.4 Emulsion 0.01 3.2 93.7 Emulsion 0.02 2.5 95.4 Fluid (100 Centistoke Viscosity) at 25.degree. C. 0.0075 2.4 95.3 Fluid (100 Centistoke Viscosity) at 25.degree. C. 0.015 2.6 94.8 Fluid (100 Centistoke Viscosity) at 25.degree. C. 0.03 1.9 96.1 Fluid (350 Centistoke Viscosity) at 25.degree. C. 0.0075 2.9 94.1 Fluid (350 Centistoke Viscosity) at 25.degree. C. 0.015 2.5 94.9 Fluid (350 Centistoke Viscosity) at 25.degree. C. 0.03 2.3 95.5 ---------------------------------------------------------------------------

as briefly referred to in the preceding description, the practice of the present invention has a high degree of utility in treatment of dirty potash ores and also when the brine temperature is relatively high. Most of the potash refineries in the United States are located in the Carlsbad, N.M. area which has a relatively long summer period so that brine temperatures in the refinery for several months may be near (at least 85.degree. F.) or higher than 100.degree. F. Many flotation procedures which are effective in a lower temperature range become very erratic at such temperatures.

Testing of the present invention has been undertaken on a plant scale basis with one complete flotation section of the refinery converted to the practice of the present invention on a continuous basis over a substantial time period. The following schedule shows the results of representative tests made during that period. The amounts of collector reagent, secondary collectors and the silicone additive are shown quantitatively. The assay of the KCl content of the feed is shown, the concentrate and the tails are shown and percentage recovery at the rougher stage is stated. In this series of tests, Nos. 5 and 6 are comparative, Nos. 9 and 11, Nos. 13 and 14, Nos. 24 and 25 and Nos. 34 and 35 are taken to illustrate significant results of the testing. Tests 5 and 6 were undertaken when the brine system was clean, Nos. 9 and 11 were taken when a low grade ore constituted the refinery feed, Nos. 13 and 14 relate to testing conducted in a (dirty) system containing small amounts of finely divided and dispersed clay and ore slimes, Nos. 24 and 25 relate to similar (dirty) system tests with brine temperature near 100.degree. F., and Nos. 34 and 35 relate to another clean system series of tests, all of which are shown in the following tabulation: ##SPC1##

From the foregoing, it is apparent that the practice of the present invention in a plant refinery scale affords substantial economies with high efficiency under normal operating conditions and also is equally effective when abnormal conditions, such as low grade ore feed, dirty brine, high temperature brine and the like are encountered. Also, as shown in the tests, a variation in quantity of the silicone reagent may be utilized but in general it may be stated that best results are attained when from 0.01 to 0.02 lb. per ton of feed are used.

Claims

We claim:

1. A froth flotation treatment of sylvinite ore for concentration of the sylvite content of the ore, in which such an ore pulp in a flotation size range of about -4 to +20 mesh Tyler before introduction into a flotation stage is subjected to a conditioning treatment for the selective filming of the sylvite content with a collector reagent selected from the group consisting of primary aliphatic amines having mixtures thereof mixed with an aliphatic or aromatic hydrocarbon oil or mixtures thereof, and the conditioned pulp is directed through the flotation stage after filming, the improvement which comprises adding an amount of auxiliary agent to the pulp before or during said conditioning treatment in the range of 0.004-0.10 pounds per ton of ore treated with the temperature of the pulp circulating in the flotation stage at about 85.degree. F. or higher, said auxiliary agent being selected from the group consisting of organopolysiloxane fluids or emulsions.

2. A treatment as defined in claim 1, in which the pulp has a contaminant content giving a dirty appearance.

3. A treatment as defined in claim 1, in which the pulp temperature approximates 100.degree. F.

4. A treatment as defined in claim 1, in which the auxiliary reagent is a silicone fluid.

5. A treatment as defined in claim 1, in which the auxiliary reagent is a silicone emulsion.

6. A treatment as defined in claim 1, in which the collector reagent comprises a mixture of an amine salt, and aliphatic and aromatic oils.

7. A treatment as defined in claim 1, in which the pulp temperature approximates 105.degree. F.

8. A treatment as defined in claim 1, in which the quantity of auxiliary reagent added does not exceed 1.0 percent of the amine collector or 0.2 percent of the total amine and oil collectors.