US2689649A - Concentration of sylvite ores - Google Patents

Description

Patented Sept. 21, 1954 CONCENTRATION OF SYLVITE ORES George E. Atwood, Carlsbad, N. Mex., assignor to International Minerals & Chemical Corporation, a, corporation of New York No Drawing. Continuat cation Serial No. 696, This application M 8 Claims.

This invention relates to the concentration of sylvite ores and is of particular value in connection with the separation of sylvite from ores of the sylvinite type, for example such ores as are found in the Carlsbad district of New Mexico, U. S. A. The invention has been successfully employed in the concentration of the sylvinite ores produced from that part of the Carlsbad field which is mined by International Minerals and Chemical Corporation.

The typical analysis of such ore is as follows:

Per cent Sylvite (KCl) 31 Halite (NaCl) 65 Other constituent or impurities consisting of silicates, sulphates, etc 4 This invention is of particular value in con.- nection with processes of the general type dis.- closed in the Tartaron, Cole and Duke Patent No. 2,288,497. Said patent describes a process which comprises suspending comminuted sylvinite ore in a circulating saturated brine formed by dis solving the soluble constituents of the ore in water and then floating the particles of sylvite in the brine by means of a suitable collector agent while permitting the particles of halite to settle. The type of process to which this invention relates i thus distinguished from that type of process disclosed in the Weinig Patent No. 2,222,331, issued November 19, 1940, in which the halite is floated and the sylvite is settled.

In processes of this general character, it had been the general practice to grind the ore to a rather fine mesh, for example, in a good many cases, to a degree of fineness where at least 9.0% of the ore would pass through a sieve of about 40 mesh. Flotation of the. valuable constituents of an ore of such degree of fineness is not too difficult a problem, and various types of collector agents for efiecting such flotation can be used. However, a concentrate in which the particles are of extremely fine size is not easily handled. There is more caking in storage in the shipping container than in the case of particles of relatively larger size, andin general it maybe said that a fertilizer ingredient in the form of fine powder is not as desirable as a material which occurs in the form of relatively large crystals. Furthermore, the expense of fine grinding is rather considerable and adds materially to the cost of the final product.

It may be stated as a general propositionthat the flotation of ore consisting of relatively large particles is attended with considerably more ion of abandoned appli- 933, September 18, 1946. ay 15, 1952, Serial No.

difiiculty than in a case where the particles are of relatively smaller dimensions. Furthermore, there are so many problems and so many variables in a flotation plant that it is an extremely difficult matter sometimes to determine just what is the trouble with the system when a falling off in the recovery or purity of product is observed, and sometimes because of the character of the operation a falling off in recovery or quality is not noticed until after the condition causing the poor result has disappeared and perhaps totally different conditions have developed in connection with other variables in the system. Thus, it wili be seen that there are three factors involved in the cure of a bad result:

First, the bed result must be observed at the precise time when the system is producing a bad result.

Second, the conditions existing at the time of the bad result must be accurately and promptly ascertained.

Third, which one or two or more of the variable conditions are responsible for the bad result, and how should these variables be adjusted in order to obtain an optimum result.

I have discovered that in the concentrating of sylvinite ore to obtain a relatively coarse concentrate, for example, one in which the particles of sylvite are of such size that 50% of the material will be retained on a 40 mesh sieve, an overthe-year orannual loss in recovery or quality of product, or both, is caused by a variation in the temperature of the circulating brine. In some cases, when the temperature rises to say, 40 (3.,

wh h. it s m times does the Carl bad district.

the recovery often falls .01? very much as compared with the recovery under apparently. the same condition at a brine temperature of 25 C., whereas, in the cold winter weather when the brine temperature may be as low as 10 C., the percentage of recovery is often found to be much lower than it was at 25 C., brine temperature. Apparently, with all other conditions equal, there seems to be an optimum temperature for the best recovery. This would suggest that steps should be taken to maintain the temperature of the brine at the optimum temperature. But, unfortunately, the capital expense and the operating expense for maintaining a constant brine temperature is prohibitive at a place like Carlsbad, New Mexico, where the air temperature may range from I.) F., in the winter to as high as F., in the middle of summer, and where a large part of the system equipment is located out 3 of doors or is subject to out-door weather conditions.

I have found that in the treatment of an ore such as has been described and of coarse particle size the best average results have been obtained with a collector agent selected from the class of primary aliphatic amines and their acid addition salts, preferably the acetates or hydrochlorides. The chain length apparently should be predominantly equivalent to about C18. Compounds with a greater chain length, e. g., C20, and a higher melting point may be used but are not generally available, while compounds with a shorter chain, e. g., C14 and a lower melting point do not appear to work so well except at much lower brine temperatures. A typical analysis of asatisfactory collector is:

Double Bonds Percent Compound I have made the surprising discovery that with collector agents of an average chain length within the range between C16 and C20, which appear to give fair results with fine particle size pulp, and give inferior average results with coarser pulp, the results can be materially improved by varying the degree of unsaturation (average number of double bonds in the chain) in accordance with variations in the brine temperature. The higher the temperature of brine, the lower should be the degree of unsaturation, i. e., the average number of double bonds in the chain should be reduced.

The reduction in unsaturation of iodine value can be accomplished by selection of the various fatty acids or combinations of same from which the amine or amines are made, or by a hydrogenation step. In general, working under the conditions and with the materials indicated, it is found to be satisfactory to operate with a saturation range extending between an iodine value of about 150, which is roughly equivalent to about one and one-half double bonds in the chain, down to an iodine value or double bond equivalent of about 0. This range will accommodate brine temperatures between about C., and 40 C. With lower temperatures than 10 C., a reagent with a somewhat higher double bond equivalent or iodine value or a reagent with a somewhat shorter average chain length than C18 is indicated, although complete data in respect of actual test runs at temperatures lower than 10 C., are not yet available.

The effect of varying amounts of unsaturation when using a collector reagent having a chain of approximately C18 is shown by the following actual flotation tests.

The particle size of feed material (sylvinite ore) was as follows:

Per cent Particle size larger than 20 mesh i- 8.35 Particle size larger than 35 mesh 44.80 Particle size larger than 80 mesh 80.53 Particle size less than 80 mesh 19.47

The collector used had a chemical analysis sub stantially the same as that stated previously. The only variables in the various tests were the temperatures and degree of unsaturation or number of double bonds. About .35 pound of the 4 amine collector was used for each ton of feed, and in addition thereof, the amount of corn starch added was about 1.25 pounds per ton of feed. The general proces was substantially as set forth in the Tartaron, et al. Patent No. 2,288,497, previously referred to. The starch is added to the closed system preferably at a high point ahead of the stage where the primary collecting agent is introduced into the system. It is preferably used in the form of a dispersion in brine made by boiling 3% of dry starch in about 97% of brine. About 0.20 pound of pine oil per ton of feed is added to the system at any convenient point before the pulp reaches the flotation cells. The pulp fed to the cells contains 30% of solids by weight.

The results at various temperatures in a single flotation operation when using a collector of the same average chain length (about C18) but having different degrees of saturation are shown in the following table:

Saturation Double Pulp Temp. g i I2 Value Feed Tails Cone. Recovery alent A collector agent consisting of a single compound could be used if its degree of saturation and its chain length happened to fit the conditions existing. However, since the saturation of individual compounds cannot differ by less than one double bond, it is usually convenient to use combinations of different compounds in order to obtain the average saturation and chain length required. Further tests at an intermediate temperature of 18 C. indicate that an optimum recovery was obtained when the double bond equivalent was about 1.0 with an iodine value of approximately 90. The recovered material when cleaned and re-cleaned according to improved flotation procedure was of high purity, containing more than 61% K20 equivalent. ,7

When employing the described collector agent for the flotation of relatively coarse material of the kind referred to, I have found that there is considerable economy effected in consumption of reagent, because it is possible to obtain a satisfactory flotation effect by the use of considerably less collector agent. Since these collector agents are fairly expensive, any saving in this respect will be reflected in the cost of production of concentrate I have also discovered that it is possible to effect a further increase in recovery or to employ a still coarser feed than indicated, or to accomplish both of these desirable results, if there be present in the brine system in addition to the amine collector a minute quantity, preferably not more than about 50 parts per million, of a metallic salt which is soluble in the brine. I have found that these results can be obtained by the use of an amount of such salt which will maintain in the brine a concentration equivalent to about 10 parts by weight of salt to 1,000,000 part by weight of brine. The particular salts with which I have had best results are the brine-soluble salts of lead or other metals such as bismuth or silver. The acetates, chlorides, etc., of these metals, which are brine soluble, may be employed.

This application is a continuation of application Serial No. 696,933, filed September 13, 1946, and now abandoned.

I claim:

1. In a process for separating sylvite from sylvinite ore by first pulping the comminuted ore in an aqueous brine saturated with respect to the ore under the conditions obtaining, and then floating ofi sylvite by subjecting the pulp to-a flotation step involving the use of a collecting agent containing a mixture of alkyl and alkenyl amine components selected from the group consisting of primary aliphatic amines containing long straight chain hydrocarbon groups and their Water soluble acid addition salts where the flotation step is carried out over a period of time during which the temperature of the flotation pulp changes, the improvement comprising maintaining the flotation efliciency of the collecting agent by first selecting an amine mixture which has been found to give optimum results at one temperature and then changing the relative amount of the alkyl and alkenyl components of the amine mixture in accordance with changes of temperature of the flotation pulp so as to reduce the iodine number in accordance with an increase in temperature and increase the iodine number in accordance with a decrease in temperature.

2. In a process for separating sylvite from sylvinite ore by first pulping the comminuted ore in an aqueous brine saturated with respect to the ore under the conditions obtaining, and then floating oil sylvite by subjecting the pulp to a flotation step involving the use of a collecting agent containing a mixture of alkyl and alkenyl amine components selected from the group consisting of primary aliphatic amines containing long straight chain hydrocarbon groups and their water soluble acid addition salts where the flotation step is carried out over a period of time during which the temperature of the flotation pulp changes within the range between about and about 40 C., the improvement comprising maintaining the flotation efllciency of the collecting agent by first selecting an amine mixture which has been found to give optimum results at one temperature within said temperature range and then changing the relative amount of the alkyl and alkenyl components of the amine mixture in accordance with changes of temperature of the flotation pulp so as to reduce the iodine number in accordance with an increase in temperature and increase the iodine number in accordance with a decrease in temperature within the range between about 10 C. at which temperature the iodine number is about 150 and about 40 C. at which temperature the iodine number is just above zero.

3. A process as in claim 1 wherein the primary aliphatic amines employed have 16 to carbon atoms, inclusive, per molecule.

4. A process as in claim 2 wherein the primary aliphatic amines employed have 16 to 20 carbon atoms, inclusive, per molecule.

5. In a process for separating sylvite from sylvinite ore by first pulping the comminuted ore in an aqueous brine saturated with respect to the ore under the conditions obtaining, and then floating off sylvite by subjecting the pulp to a flotation step involving the use of a collecting agent containing a mixture of alkyl and alkenyl amine components selected from the group consisting of primary aliphatic amines containing long straight chain hydrocarbon groups and their water-soluble addition salts, the improvement comprising maintaining the flotation efliciency of the collecting agent over a period of time during which the temperature of the flotation pulp changes in the range of between about 10 C. and 40 C., by changing the composition of the collecting agent with respect to the relative amount of the alkyl and alkenyl components from one composition having an iodine number just above zero when the pulp has a tempertaure of about 40 C. to a composition having an iodine number of about 45 when the pulphas a temperature of about 25 C. and to a composition having an iodine number of about when the pulp has a temperature of about 10 C.

6. A process as in claim 5 wherein the primary aliphatic amines employed have 16 to 20 carbon atoms, inclusive, per molecule.

7. In a process for separating sylvite from a sylvinite ore by first pulping the comminuted ore in a brine saturated with respect to the ore under the conditions obtaining, and then floating oif sylvite by subjecting the pulp to a flotation step involving the use of a collecting agent containing amine substances selected from the group consisting of primary aliphatic amines containing a straight chain hydrocarbon group having from 16 to 20 carbon atoms inclusive, and their watersoluble acid addition salts, the improvement comprising, employing a collecting agent comprising a mixture of said amines, at least some of the amine constituents of which contain alkenyl, the iodine number of the amine mixture being about 135, with the brine temperature being about 10 C.

8. In a process for separating sylvite from a sylvinite ore by first pulping the comminuted ore in a brine saturated with respect'to the ore under the conditions obtaining, and then floating oif sylvite by subjecting the pulp to a flotation step involving the use of a collecting agent containing amine substances selected from the group consisting of primary aliphatic amines containing a straight chain hydrocarbon group having from 16 to 20- carbon atoms inclusive, and their watersoluble acid addition salts, the improvement comprising, employing a collecting agent comprising a mixture of said amines, at least some of the amine constituents of which contain alkenyl, the iodine number of the amine mixture being about 45, with the brine temperature being about 25 C.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,211,396 Weinig Aug. 13, 1940 23 Cole Dec. 26, 1944

Claims (1)

1. IN A PROCESS FOR SEPARATING SYLVITE FROM SYLVINITE ORE BY FIRST PULPING THE COMMINUTED ORE IN AN AQUEOUS BRINE SATURATED WITH RESPECT TO THE ORE UNDER THE CONDITIONS OBTAINING, AND THEN FLOATING OFF SYLVITE BY SUBJECTING THE PULP TO A FLOTATION STEP INVOLVING THE USE OF A COLLECTING AGENT CONTAINING A MIXTURE OF ALKYL AND ALKENYL AMINE COMPONENTS SELECTED FROM THE GROUP CONSISTING OF PRIMARY ALIPHATIC AMINES CONTAINING LONG STRAIGHT CHAIN HYDROCARBON GROUPS AND THEIR WATER SOLUBLE ACID ADDITION SALTS WHERE THE FLOTATION STEP IS CARRIED OUT OVER A PERIOD OF TIME DURING WHICH THE TEMPERATURE OF THE FLOTATION PULP CHANGES, THE IMPROVEMENT COMPRISING MAINTAINING THE FLOTATION EFFICIENCY OF THE COLLECTING AGENT BY FIRST SELECTING AN AMINE MIXTURE WHICH HAS BEEN FOUND TO GIVE OPTIMUM RESULTS AT ONE TEMPERATURE AND THEN CHANGING THE RELATIVE AMOUNT OF THE ALKYL AND ALKENYL COMPONENTS OF THE AMINE MIXTURE IN ACCORDANCE WITH CHANGES OF TEMPERATURE OF THE FLOTATION PULP SO AS TO REDUCE THE IODINE NUMBER IN ACCORDANCE WITH AN INCREASE IN TEMPERATURE AND INCREASE THE IODINE NUMBER IN ACCORDANCE WITH A DECREASE IN TEMPERATURE.