US2695101A - Frothing agents for the flotation of ores and coal - Google Patents

Description

United States Patent FROTHIN G AGENTS FOR THE FLOTATION OF ORES AND COAL Robert B. Booth and John M. Dobson, Stamford, Conn., assignors to American Cyanamitl Company, New York, N. Y., a corporation of Maine No Drawing. Application December 10, 1952, Serial No. 325,226

4 Claims. (Cl. 209166) This invention relates to an improved process for beneficiating ores, coal and the like and more particularly is concerned with the use of new frothing agents in the froth flotation of such minerals.

Frothing agents are compounds having structural formulas that are characterized by the presence of two constituents having opposite properties. One part of the molecule is polar and the other part is non-polar, that is, one part repels water, while the other is water avid.

It is generally recognized that effective frothers should have only one polar group. For example, Gaudin in his text Flotation reports that Taggart, Taylor and Ince in Experiments with Flotation Reagents A. I. M. M. E. Tech. Pub. 204 states that all good frothers, with very few exceptions, contain one polar group and one only, preferably a group containing oxygen in the hydroxy (OH) or other group. Typical compounds that have been Widely used as frothing agents are amyl alcohol, hexyl alcohol, cresol, terpineol, xyleonol, etc., all of which, it is to be noted, contain only one hydroxy group.

In accordance with the present invention it has now been found that dihydroxy compounds such as the various polypropylene glycols are remarkably effective frothers. This is particularly surprising in view of the fact that the art teaches that only the monohydroxy compounds are good frothers. The polypropylene glycols of the present invention are effective producers of a strong froth possessing the physical properties required for supporting the mineral particles.

It is an advantage of the present invention that these new frothers produce an equivalent or greater quantity of froth with a materially smaller quantity of frothing agent as compared to the standard frothers such as pine oil, cresylic acids and certain alcohols and hence are markedly superior to these standard frothers in specific frothing power.

Moreover, although it has been proposed to use the lower alkyl mono-ethers of propylene glycol and polypropylene glycol as frothers, which are also monohydroxy compounds, tests have shown that it requires at least one third more of these compounds to produce an equivalent concentrate in the case of many ores and coal, as it does with the polypropylene glycols of the present invention. Hence, the compounds of the present invention are remarkably superior in specific frothing power to the lower alkyl monoethers of propylene and polypropylene glycol. Likewise, in the case of many ores the new frothers of this invention have been found to produce a lower content of acid-insoluble gangue as compared either to the standard frothers or to the compounds mentioned above.

The compounds of the present invention are polyglycols and are prepared according to methods known to the art such as by reacting propylene oxide with propylene glycol according to the equation HOCaHsOH+nC3HeO+ HOCHz CHCHaOCHz) IZCHCHaOI-I wherein n represents the number of mols of propylene oxide used and wherein in the final product n averages 2 to 34. The greater the value of n, the longer is the average chain length of the polypropylene glycol produced. The polypropylene glycols contemplated herein thus include such compounds as the di-, tri-, tetra-, penta-, hexaand higher propylene glycols. The pure compounds as 2,695,101 Patented Nov. 23, 1954 "ice such are useful in the present invention although the reaction mixtures or mixed fractions are usually more desirable as they are usually less costly.

The polypropylene glycols useful in the present invention are perhaps best defined in terms of their molecular Weights. The average molecular weights of these compounds range from about to about 2100. While both the lower molecular weight and the higher molecular weight polypropylene glycols are useful in the present invention, it has been found that optimum results are secured with the more median molecular weight range compounds, that is, those polypropylene glycols having molecular weights of from about 400 to about 1100 as in this range not only do such compounds possess good frothing characteristics but the cost is usually somewhat lower than in the case of the higher molecular weight compounds.

It is also within the scope of the present invention to use the polypropylene glycols in conjunction with standard frothers. Furthermore, the polypropylene glycol frothers herein described may be stabilized by, extended by, and used in combination with various hydrocarbon oils such as kerosene, fuel oils, and the like and this frequently effects a reduction in the amount of actual frothing agent that need be used but without sacrificing the excellent frothing properties possessed by the polypropylene glycols.

It is also to be understood that since the polypropylene glycols of the present invention function solely as frothers and are not effective as mineral collectors, a suitable promoter for the minerals must be used in the froth flotation process. Suitable promoters such as xanthates, dithiophosphates, hydrocarbon oils, naphthenic acids, fatty acids, resin acids and mixtures thereof, the alkali soaps of such acids and their mixtures, cationic agents such as the long chain amines and amine derivatives may be used.

The invention will be described in greater detail in conjunction with the following specific examples in which the parts are by weight unless otherwise specified.

Example 1 A zinc ore containing sphalarite and assaying 2.85% Zn was ground to about minus 65 mesh, conditioned with 0.5 lb./ ton copper sulfate, and 0.10 lb./ton of technical grade sodium diethyldithiophosphate. Varying quantities of frothing agents were used in a series of separate tests on this ore. Mixed amyl alcohols were used as frothing agents in the first test for comparison with the polypropylene glycol frothers. The following results were obtained.

The above data clearly show that less of the polypropylene glycol frothers were required than the amyl alcohol frothers.

Example 2 A second zinc ore containing sphalarite and assaying 7.1% Zn was treated as in Example 1 with 0.6 lb./ton copper sulfate, 0.11 lb./ton of technical grade sodium diisopropyldithiophosphate. Three separate flotation tests were conducted on this ore using as frothing agents 0.4 lb./ ton mixed amyl alcohols in the first test, 0.2 lb./ton pine oil in the second test, and 0.1 lb./ ton of a polypropylene glycol of molecular weight 400-450 in the third test. Zinc recoveries and concentrate assays were as follows:

Concentrate, Percent Zn Frother Recov. Assay 0.4 lb./ton Mixed Amyl Alcohols 94. 57 34. 53 0.2 lb./ton Pine Oil 04. 58 33.17 0.1 lb./tn Polypropylene Glycol (mol. wt.=400

As in the preceding example, the above results indicate the superiority in frothing power of the polypropylene glycol frother over that of the conventional fI'OthlIllZ agents.

Example 3 Pennsylvania anthracite coal fines were conditioned with 2.0 lb./ton of fuel oil and varying quantities of frother and then floated in a Fagergren flotation machine. From a flotation feed containing about 24.0% ash the following recoveries of low ash coal were obtained Frother Used Coal Concentrate Percent Approx. Percent Type Mol. Wt. 19/ mm Weight s Pine Oi] 0. 80. 1 l4. 3 Methyl Amy] Alcohol O. 5 76. 4 14.0 300 0.27 85. 5 14. 2 425 0. 08 83. 6 14. 3 550 0.11 84.2 14.2 1, 025 0. 14 82. 6 14. 3 2, 025 0. 27 80. 5 13. 9

The above results indicate that the polypropylene glycol frothers were required in considerably less quantity than standard frothers such as pine oil and methyl amyl alcohol to give equal or better coal concentrates.

Example 4 Samples of bituminous coal fines containing 25.5% ash were floated with 1.0 lb./ton fuel oil and varying quantities of polypropylene glycol frothers as given in the following table, which also summarizes the recoveries of coal obtained and the ash contents of the coal concentrates. In the first test a technical grade heptanol, commonly used as a frother in coal flotation operations, was used for purposes of comparison.

As in the foregoing examples, lower amounts of the polypropylene glycols were required and lower ash contents were obtained when these frothers were used.

Example 5 A polypropylene glycol in the molecular weight range of 400-450 was compared with the methyl ether of tripropylene glycol (a frother in the class of the lower alkyl ethers of polypropylene glycols which is preferred in practice) in a flotation test on a second sample of Pennsylvania anthracite coal fines. The flotation testing procedure employed in Example 1 was used ing results.

with the follow- Coal Concentrate Frother Used Percent Percent Weight Ash b./ton Polypropylene Glycol 0.08 1 82. 0.126 lb./ton Methyl Ether of Tripropylene Glycol.

Example 6 A comparison also was made with the frother of the preceding example and with pine oil on a Tennessee sulfide zinc ore (3.0% Zn) which was ground to about minus mesh, conditioned with frother and with 0.5 lb./ton copper sulfate, and 0.10 lb./ton technical grade sodium diisopropyldithiophosphate as promoter. Zinc recoveries and grades of concentrate were as follows:

Concentrate, Percent Z11 Frother Used Recov. Assay 1b./ton Pine 01] lb./ton Polypropylene Glycol lb./ton Methyl Ether of Tripropylene Glycol..

Example 7 Comparative flotation tests on the frothing agents used in Example 6 were made on a sulfide copper ore containing some oxide copper and assaying 0.93% Cu. The ore was ground with 3.35 lb./ton lime and 0.025 lb./ton sodium secondary butyl Xanthate and frothing agents as indicated in the following table which also summarizes the metallurgical results of the rests.

Copper Concentrate, Percent Cu Frother Used Recov. Assay 0.10 lb./ton Pine Oil 0.081b./ton Methyl Ether of Tripropylene GlycoL. 0.06 lbJton Polypropylene Glycol The above data show that lower quantities of the polypropylene glycol frother were required than pine oil or the methyl ether of tripropylene glycol to achieve equal or better metallurgical results.

Example 8 Samples of a lead ore were floated after grinding and conditioning with 0.035 lb./ ton of sodium isopropyl xanthate and varying quantities of frothers as indicated in the following table. Cresylic acid was used in the first test for purposes of comparison. The following metallurgical results were obtained:

Concentrate, Percent Pb Frother Used Rccov. Assay 0.10 1b./ton Cresylic Acid 24 0.081b./ton Polypropylene Glycol (mol. wt.425 op.)

Example 9 A sample of Pennsylvania cement rock, about 86.7% minus 325 mesh and containing 71.1% CaCOa was treated with 1.0 lb./ ton crude calcium lignin sulfonate, 0.62 lb./ ton oleic acid and 0.06 lb./ ton of a polypropylene glycol frother of approximate molecular weight of 400-450 and floated for 7 minutes. The flotation concentrate contained 90.6% of the total carbonate present in the feed and assayed 82.4% CaCOs.

Example 10 A Michigan iron ore containing mainly hematite and quartz was ground to about minus 65 mesh and deslimed.

The deslimed portions of the ore were conditioned at about 70% solids with 2.0 lb./ton sulfuric acid, 1.6 lb./ton heavy fuel oil and 3.0 lb./ ton of a water soluble etroleum sulfonate of the green acid type, diluted to about 20% solids and floated for 3.5 minutes to recover iron. After 2.5 minutes of flotation, 0.045 lb./ ton of a polypropylene glycol of molecular weight of 400-450 was added as auxiliary frothing agent. The resulting iron concentrate was cleaned twice by refloating to produce a final concentrate containing 91.9% of the total iron and assaying 62.1% Fe and 8.9% silica.

Example 11 A quartz sand containing 0.095% FezOs was deslimed and conditioned at high solids with 0.4 lb./ton. H2SO4, 0.6 lb./ ton of a 1:1 mixture of oil-soluble and water soluble petroleum sulfonates. 0.4 lb./ton fuel oil and 0.08 lb./ ton of a polypropylene glycol frother of molecular weight of about 425, and floated at 20% solids to remove the contaminating iron-bearing minerals. The tailing product containing 87.4% of the weight of the feed assayed 0.026% FezOs.

The term ore as used throughout the specification and claims is to be understood to refer to solid crude ores containing a valuable constituent and therefore includes such ores as sulfide, oxide and oxidized ores, metallic and nonmetallic ores, glass sands, feldspars, coal, materials containing soluble salts, etc.

We claim:

1. The method of concentrating ores which comprises subjecting an equeous pulp of said ore to froth flotation in the presence of a collector and in the presence as a frother of a polypropylene glycol having a molecular weight in the range of 140 to 2100.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,370,366 Sayve Mar. 1, 1921 1,970,578 Schoeller Aug. 21, 1934 1,995,915 Burdick Mar. 26, 1935 2,467,369 Bishop Apr. 19, 1949 2,611,485 Tveter Sept. 23, 1952 FOREIGN PATENTS Number Country Date 674,258 Great Britain June 18, 1952 OTHER REFERENCES Journal of Physical Chemistry, vol. XXXVI, January 1932, pp. 132137. (Copy in Scientific Library.)

Journal of the American Oil Chemists Society, vol. 29, pp. 240-243.

Claims (1)

1. THE METHOD OF CONCENTRATING ORES WHICH COMPRISES SUBJECTING AN EQUEOUS PULP OF SAID ORE TO FROTH FLOTATION IN THE PRESENCE OF A COLLECTOR AND IN THE PRESENCE AS A FROTHER OF A POLYPROPYLENE GLYCOL HAVING A MOLECULAR WEIGHT IN THE RANGE OF 140 TO 2100.