US2088325A

US2088325A - Flotation process

Info

Publication number: US2088325A
Application number: US62277A
Authority: US
Inventors: Kirby James Emory
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1936-02-04
Filing date: 1936-02-04
Publication date: 1937-07-27
Anticipated expiration: 1954-07-27

Description

Patented July 27, 1937 UNITED STATES FLOTA'I'ION PROCESS James Emory Kirby, Wilmington, Del., asslgnor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application February 4, 1936, Serial No. 62,277

Claims.

This invention relates to a method of concentrating ores and salt mixtures by froth flotation. More particularly it relates to the concentration of ores and salt mixtures containing sodium and potassium chlorides by froth flotation. Still more particularly it relates to the use of water-soluble salts of certain aliphatic amines in a froth flotation process for the separation of potassium chloride of high quality from ores and salt mixtures containing that material in admixture with sodium chloride and other impurities.

A recent development in the domain of ore flotation is that of Lenher as described in his copending patent application, Serial No. 730,551, filed June 14, 1934. In that application, Lenher describes a number of flotation separations which were diflicult or impossible by previously known methods, and in carrying out these separations, Lenher contemplates using a class of reagents which has the long-chain surface-active group in the positive ion. The following are two examples of flotation reagents belonging to the class discovered by Lenher:

C mHsa Cetyl pyridinium bromide C 17H:5NH3 CI Heptadecylamine hydrochloride The present application deals with the use of certain members of this group of new reagents in the flotation of potassium chloride.

This invention has as an object the development of an improved flotation method for the separation of potassium chloride from sodium chloride and other impurities. A further object is the utilization of certain members of the class of collecting agents having the surface-active group in the positive ion in a flotation process for the purification of potassium chloride. Other objects will appear hereinafter.

These objects are accomplished by the use of surface-active reagentschosen from the class of water-soluble salts of normal, primary, aliphatic amines having 6 or more carbon atoms, and preferably 8 to 12 carbon atoms in the aliphatic chain, and water-soluble salts of mono-alkyl substituted guanidines in which the alkyl substituent is a normal, primary, aliphatic radical having 6 or more carbon atoms in a flotation process for the separation of potassium chloride from a pulp comprising finely ground ore or salt mixture containing potassium chloride, and a saturated brine prepared from the ore or salt mixture.

The process of this invention may best be understood by reference to the following examples. It is to be understood that the scope of the invention is in no wise limited to the processes as set forth in these examples.

Example 1 A sample of sylvinite ore was obtained from Carlsbad, New Mexico. This ore is composed of about 40% sylvite (potassium chloride), 57% halite (sodium chloride) and about 3% of ironstained clay intimately associated with the sylvite. Due to the presence of the clay, the sylvite crystals are pink in color and may be readily distinguished from the colorless halite or rock salt crystals. Part of the ore was reduced to minus 40-mesh by means of a Braun disc pulverizer. A saturated brine was prepared from another portion of the ore by agitating it with water at room temperature until no more was dissolved. The resulting brine had a specific gravity at room temperature of 1.233. Eight hundred grams of the ground ore was then further ground for 30 minutes in a l-gallon pebble mill in the presence of 1 liter of the saturated brine and 3 kg. of flint pebbles. This amount of grinding reduced the ore to substantially 100 per cent minus 65-mesh and about 85 per cent minus 100-mesh. The slurry of ground ore and brine was then split into eight portions of about 100 g. each by means of an ordinary type of sample splitter. One of these 100 g. samples was transferred to a small laboratory mechanical agitation flotation cell of the type described by J. F. Gates and L. K. Jacobsen (Engineering and Mining Journal, 119, 19, 771 (1925)). The cell was filled to the pulp level by adding saturated brine. The agitation was started, and then 2 cc. of a 1% aqueous solution of n-octyla-mine hydrochloride added. A pink froth carrying sylvite particles quickly formed and was removed from the cell into a dry beaker. The froth was sufficiently voluminous that its removal from the cell was readily effected without carrying out an excessive amount of the pulp itself. After 4 minutes, the froth had become barren and was dying out, and at this point, flotation was discontinued. The concentrate and tailings were filtered, dried, weighed and analyzed with results as shown in the following table.

Reagent used: n-octylamine hydrochloride,

0.39 lb. per ton.

Potassium chloride in feed, calcd., 40.98%

Example 2 A second charge of ground ore prepared as in Example 1 was floated in the same manner as in the preceding example except that instead of the n-octylamine hydrochloride, 2 cc. of a 1% aqueous solution of n-decylguanidine hydrochloride,

was used as the flotation agent. Again a pink froth, well loaded with sylvite, was produced. After the flotation was complete, the products were filtered and dried as in Example 1. The concentrate weighed 49.3 g. and consisted of potassium chloride of good quality, while the tailings weighed 43.4 g. and were practically barren of potassium chloride. The quantity of reagent used was 0.02 g. or 0.43 pound per ton of feed.

Example 3 The process of Examples 1 and 2 was repeated using 5 cc. of a 1% aqueous solution of n-dodecylamine hydrochloride as flotation agent. Flotation proceeded very satisfactorily, a froth loaded with pink sylvite particles being produced. The concentrate, consisting of good quality potassium chloride, weighed 46.3 g., and the tailings, predominantly sodium chloride, weighed 52.7 g. The amount of reagent used was 1.01 pound per ton of ore.

Example 4 performed to show that the filtrates recovered from a flotation carried out as in Example 1 may be used in subsequent flotations, instead of fresh brine, utilizing the flotation reagent contained therein to decrease the amount of fresh reagent necessary. A flotation was carried out as in Example 1 except that 3 cc. of 1% aqueous solution of It-octylamine hydrochloride was added instead of 2 cc. as in Example 1. This flotation was termed the first flotation". The products of the first flotation were filtered and dried and the filtrates preserved. A second charge of ground ore was now washed into the cell using the filtrates from the first flotation to aid in the transfer and to fill the cell to the pulp level. One cubic centimeter of the n-octylamine hydrochloride sufilced to give a good yield of potassium chloride flotation concentrate. This second flotation was called the first recirculation". A second recirculation" was carried out like the first recirculation, using a third charge of ore, filtrates from the first recirculation as pulp brine, and 1 cc. of 1% n-octylamine hydrochloride solution. Again, a satisfactory froth and yield of concentrate were produced. The results are summarized in the following table.

This experiment was The results of Example 4 indicate that in commercial operation recirculation of concentrate and tailing liquors could be practiced with a saving in reagent cost and without detriment to the results obtained.

Example 5 A sample of a crude crystallized mixture of sodium chloride and potassium chloride was obtained from the Bonneville district of western Utah. This salt mixture had been prepared from a brine obtained from a natural salt deposit. The potassium chloride content of the deposit as it occurs in the Bonneville district is only a few per cent, the bulk of the deposit consisting of sodium chloride, together with small amounts of soluble salts, e. g., magnesium chloride. The brine had been partially evaporated to allow a large amount of sodium chloride to crystallize out. The mother liquid had then been evaporated further to yield a mixture of salts containing about 24% potassium chloride. This salt mixture was used in a flotation test similar to those described in the preceding examples.

One kilogram of the crude salt mixture was suspended in one liter of a brine saturated with potassium and sodium chlorides and ground in a pebble mill until substantially all of the particles were finer than -mesh. The slurry of ground salts and brine was then split into eight portions, and one of these portions subjected to a flotation test in the miniature flotation cell described in Example 1. One cubic centimeter of a 1% solution of octylamine hydrochloride was added to the charge in the flotation cell, whereupon a well loaded froth quickly formed and carried over the lip of the cell into a dry beaker. The froth quickly broke in the receiver, and the floated salt particles quickly settled out. Flotation was complete in 4 minutes. The concentrate and tailings were filtered out on a Buchner funnel, dried at C. in an oven, weighed and analyzed for their potassium chloride content. The results of the experiment are summarized in the following table:

In carrying out the process of purifying potassium chloride as exemplified above, numerous reagents other than the three cited above will give satisfactory results. Among them, the following may be mentioned:

n-Hexylamine hydrochloride, n-Heptylamine hydrochloride, n-Nonylamine hydrochloride, n-Decylamine hydrochloride, n-Undecylamine hydrochloride, n-Tetradecylamine hydrochloride, n-Hexadecylamine hydrochloride, n-Octadecylamine hydrochloride, n-Octylamine hydrobromide, n-Octylamine nitrate, n-Octylamine acetate, n-Octylguanidine hydrochloride. and n-Dodecylguanidine hydrochloride.

All of these reagents possess a straight chain at least 6 carbon atoms in length in the positive ion of the molecule. It has been found that the presence of a straight carbon chain of the specified length is essential to impart collecting power for potassium chloride to the flotation agent. Thus, it has been shown that salts of aliphatic amines, e. g., n-amylamine hydrochloride, tri-n-butylamine hydrochloride, and the hydrochloride of the branched chain amine, approximately CQHIQNHZ, boiling from ISO-190 C., prepared from a higher alcohol obtained in the catalytic synthesis of methanol from carbon monoxide and hydrogen will not produce satisfactory flotation of potassium chloride under the conditions of the above cited examples. Likewise, salts of amines in which the amino nitrogen either forms a part of a heterocyclic nucleus, e. g., pyridine hydrochloride, dodecyl pyridinium chloride, and cetyl pyridinium bromide, or is attached to an aryl or aralkyl nucleus, e. g., p-toluidine hydrochloride, alpha-naphthylamine hydrochloride, and benzylamine hydrochloride will not produce satisfactory flotation of potassium chloride under the conditions exemplified herein.

In carrying out the process of this invention, any of the well-known types of froth flotation cells such as the minerals separation sub-aeration type, the Callow cell, the MacIntosh cell, etc., may be used. The ratio of pulp solids to brine may vary from about 1:1 to about 1:6. The pulp temperature may vary from about 50 F. to about F. or even higher without materially affecting the results. The amount of reagent will vary somewhat for different ores and different types of water supply. In some cases it may be as low as 0.05 pound per ton of ore, while in others, it may be as great as 2-3 pounds per ton or even greater. Usually 0.2-1.0 pound per-ton will suflice. The fineness of grinding depends, as in all flotation processes, on the size of the individual grains present in the material being treated. As in all flotation processes, the various constituents must be "liberated in the grinding operation. With some ores, grinding to 50-mesh will suflice, while with others it is necessary to grind to ISO-mesh, 200-mesh, or even finer. The process can be applied only to ores in which the potassium chloride occurs as such.

One of the uses of this invention is that set forth in Examples 1 to 4; namely, the recovery of potassium chloride of high quality from natural ores containing it. The ability of the flotation reagents to select or "collect the potassium chloride while rejecting the sodium chloride is very remarkable. Another use of the invention is the recovery of potassium chloride from salt mixtures obtained by evaporating to dryness, brines obtained from salt wells as illustrated in Example 5. The process is successful with salt mixtures of this kind only when they have been crystallized under such conditions that the potassium chloride can be set free from the sodium chloride, magnesium chloride, and other contaminants by grinding.

Resort may be had to such modification and variations as fall within the spirit and scope of the appended claims.

I claim:

1. A process for separating potassium chloride from a pulp containing the same which comprises subjecting said pulp to a froth flotation process employing an agent of the class of water-soluble salts of normal, primary, aliphatic amines having 6 or more carbon atoms in the aliphatic chain and preferably 8 to 12 carbon atoms in the aliphatic chain, and water-soluble salts of mono-alkyl substituted guanidines in which the alkyl substituent is a normal, primary, aliphatic radical having 6 or more carbon atoms.

2. A process for separating potassium chloride from a mixture of potassium chloride, sodium chloride, and other impurities which comprises subjecting a pulp of said mixture in its'saturated brine to a froth flotation process employing an agent of the class of water-soluble salts of normal, primary, aliphatic amines having 6 or more carbon atoms in the aliphatic chain and preferably 8 to 12 carbon atoms in the aliphatic chain, and water-soluble salts of mono-alkyl substituted guanidines in which the alkyl substituent is a normal, primary, aliphatic radical having 6 or more carbon atoms.

3. A process for separating potassium chloride from a mixture of potassium chloride, sodium chloride, and other impurities which comprises subjecting a pulp of said mixture in its saturated brine to a froth flotation process employing an agent of the class of water-soluble salts of normal, primary, alkyl amines having from 6 to 18 carbon atoms in the alkyl group, and water-soluble salts of mono-alkyl substituted guanidines in which the alkyl substituent is a normal, primary, aliphatic radical having from 6 to 18 carbon atoms.

4. A process for separating potassium chloride from a mixture of potassium chloride, sodium chloride, and other impurities which comprises subjecting a pulp of said mixture in its saturated brine to a froth flotation treatment wherein a hydrochloride of a normal, primary aliphatic amine containing at least 8 and not more than 12 carbon atoms in the aliphatic chain is employed as a flotation agent,

5. A process as set forth in claim 4 wherein the mixture being treated is sylvinite ore.

6. A process as set forth in claim 4 wherein the mixture being treated is obtained by the evaporating of salt brine.

7. A process as set forth in claim 4 wherein the hydrochloride of an aliphatic amine which is employed as a flotation agent is n-octylamirie hydrochloride.

8. A process as set forth in claim 4 wherein the hydrochloride of an aliphatic amine which is employed as a flotation agent is 'n-dodecylamine hydrochloride.

9. A process for separating potassium chloride from a mixture of potassium chloride, sodium chloride, and other impurities which comprises subjecting a wulp of said mixture in its saturated brine to a froth flotation treatment wherein a hydrochloride of a mono-alkyl guanidine in which the alkyl substituent is a normal, primary, aliphatic radical having at least 8 and not more than 12 carbon atoms in the aliphatic chain is employed as a flotation agent.

10. A process as set forth in claim 9 wherein the hydrochloride of a mono-aikyl guanidine which is employed as a flotation agent is n-decylguanidine hydrochloride.

' JAMES EMORY KIRBY.