US2349094A - Froth flotation - Google Patents

Description

-by froth flotation.

Patented May 16, 1944 FBOTH FLOTATION- Thorbjern Hellmann, Copenhagen, Denmark, assignor to Separation Process Company, Catasauqua, Pa., a corporation of Delaware No Drawing. Application April 4,1941, Serial no. I

386,848. In Great Britain April 10, 1940 3 Claims.

This invention relates to the froth flotation of lime-bearing materials, and it is particularly"applicable to the cleaning of cement raw materials The flotation is brought about by the addition to the flotation pulp of reagents which act as frothing agents and collectin g agents, and usually different reagents are introduced for the two functions. The material that is treated in the flotation cells is often highgrade slurry, and in such a case the amount of lime-bearing concentrate that has to be removed as froth is usuallynot less than 50% of the material fed to the cells and often as much as 75%. It follows that the frothing agents used must have a large frothing capacity. It is, however, very important that the development of froth should not be too violent, since, if it is, a large part of the minerals which should be left in the reject will be carried out of the cells in the concentrate.

It is naturally desirable to use reagents that are as cheap as possible, and this is particularly important because the comparatively low value of the concentrate obtained from lime-bearing materials makes its necessary to use cheap reagents if the process is to be economically practicable. Accordingly, reagents prepared from waste materials, such as those described in the pending application of M. Vogel-Jorgensen, Serial No. 230,342, filed September 16, 1938, may be used with advantage. These reagents are derived from waste products obtained in the refining of vegetable or animal oils, which as a rule are glycerides of mixtures of fatty acids of different molecular weights, ,(some being saturated fatty acids and others unsaturated r oxidised fatty acids) together with unsaponifiable materiads. The reagents described in the said application which has now issued as U. S. Patent No. 2,216,992, under date of October 8, 1940, give surface active ions in water, and comprise the products resulting from'the reaction of the waste products remaining after the distillation of impure fatty acid oils produced in the refining of a member from the group consisting of animal and fixed vegetable oils and fats for the recovery of refined fatty acid, with a strong alkali or a strong mineral acid, or the products resulting from the sulphonation or saponification of such products. They are collecting agents, but they also have so strong a'frothing capacity that the results obtained with them are not entirely satisfactory in the treatment of some raw materials, particularly those that are very finely divided, as the concentrates are not of a high enough grade. There is a particular tendency for froth to be produced too violently when the water obtained from the subsequent dewatering of the concentrate is circulated and used again in the flotation cells: This circulating water generallycontains a certain amount-of the reagents, so

that it is economical to use it again.

According to the present invention, the development of the froth produced by the waste products referred to above or other collecting agents having too strong frothing action is controlled I by using together with them hydrogen-saturated products, and which are also usable in the form of saponified, sulphonated or similar products. Appropriate proportions of the froth controlling agent will vary depending on the frothing properties of the collecting agent and the pulp being treated. In the case of waste product collecting agents-of the above referred to type, 10 to parts of hydrogenated whale oil or beef tallow should be used with every to parts of waste 2:5 oil derivative. In a specific case one part of the froth-controlling reagent was used with every two parts of waste oil derivatives.

The fatty acids of high molecular weight are not suitable for use alone, firstly because a large quantity is required for collecting the lime par-,

ticles, much larger, indeed, than would be expected from-th difference in molecular weight, and still more because a large amount of froth-'- ing agent is required to obtain sufllcient lime in the overflow from the flotation machine. Their poor frothing capacity, however, makes them i capable of reducing the frothing capacity-of the Waste oils described in the pending application Serial No. 230,342 referred to above by the addition of a relatively small proportion of the fatty acids of high molecular weight, so that the mixture is cheap and satisfactory.

When according to the invention reagents derived from products containing hydrogen saturated fatty acids of high molecularweight are .ter and 75% of fatty acids.

stated as suitable froth-controlling reagent to be used together with ordinary reagents having too strong frothing action, it should be understood that the two types of reagents may be added to the pulp before and/or during the fio Often the fatty acids used for floating the lime-bearing minerals are used in the form of water-soluble soap and in this case the fatty acids or the neutral fats or oils are saponified before they are used as flotation reagents. In such .case the two types of reagents: the ordinary collecting reagent and the froth controlling fatty acid reagent, may be mixed before the saponification, the two products saponified together thus giving a mixtureof the desired frothing properties. In other cases a partial saponification is used or fatty acids are emulsified before they are used as flotation reagents, and also in that event the two products may be mixed together before the final preparation of the reagents is carried out.

If waste product from the refining of the oils or fats are used as flotation reagents, either as the raw waste products or in a saponified, sulfonated, emulsified or similar state, the two types of raw oils or fats. may be refined together, either during the whole refining or during the latter part of the refining, in which case a waste product is obtained which could be readily used or treated in a suitable way, thus giving a flotation reagent of the desired frothing properties.

The following example will demonstrate the advantage of, using a waste product containing a large amount of high molecular fatty acid together with an ordinary type of waste oil. The test was made at a cement plant using the flotation process. The raw material was a hard limestone containing about 80% CaCO: and amounts of wollastonite, which were excessive to make it useful for the manufacture of cement, for which reason the limestone was cleaned by the flotation process. The raw stone was ground in closed circuit with a gravity type hydraulic classifier to grain sizes below 0.2 m. 'm., and during normal operation at the plant the slurry so produced was fed directly to the flotation cells. A sample of this ground material was taken and most of the water contained in the slurry was removed by filtration. This material was used for the tests. One part of the filtered material was diluted with pure water to give a suspension of 300 g. of solids per litre and another part with the same amount of overflow water from .the

thickener at the plant in which th concentrate from the flotation cells was dewatered.

As collecting reagents were used the following types:

"Reagent A was waste oil of the type men-- tione'din pending application Serial No. 230,342 referred to above.

"Reagent B" was prepared from a waste product containing about 25% of unsaponifiable mat- About 50% of these fatty acids was the high molecular stearic acid, while the remaining part of the fatty acids was lower molecular fatty acids.

. the figures in tests Nos. 2 and 3.

alcohol frother.

The tests were carried out in a Fagergren laboratory flotation cell and the so-called stage oiling method was used, which means that the reagents were added stepwise during the flotation. The results obtained are given in the following During each flotation test was added the same kind of water as was used originally for diluting the filtered slurry.

Comparing the results fromtest No. 1 and test s No. 2 it will be seen that the use of the overflow water from the thickener reduces the amount of collecting reagent considerably; however, the rade of the concentrate produced in test No. 2. where the overflow water was used, is comparatively low due to a too violent development of the froth in the cell. The small amount of 0.02% of the frothing reagent indicated in the table had to be added during the very last part of this test in order to obtain a satisfactorily low grade of reject. In other words the type A reagent when used with overflow water had too strong frothing properties during the first part of test No. 2

and too weak frothing properties during the last part.

Test No. 3, which is carried out with reagent B containing a high amount of fatty acids with high molecular weight, shows that a concentrate with high lime content is obtained, but at the same time a high reagent consumption is required despite the fact that overflow water has been used.

Test No. 4 shows that by using a reagent in accordance with the presentinvention overflow water can be used whereby less reagent is re (wired and, nevertheless, the concentrate is high in 1 me.

The consumption of collecting and frothing agents in test No. 4 is about what could be calculated by proportioning from tests Nos. 2 and 3, but thecleanness of concentrate and reiect is substantially above what could be expected from Comparing test No. 4 with test No. 1 shows a reductionin reagent consumption of 32%, the

cleanness of the concentrate remaining the same and the cleanness of the rejects being improved.

I clilm:

1. In the flotation of lime-bearing minerala; the process of controlling the frothing action of ucts remaining after the distillation of impure I fatty acid oils produced in the refining of a member from the group consisting of animal and fixed vegetable oils and fats for the recovery of refined fatty'acid, with a strong mineral acid. the compounds resulting from the sulphonation As frothing reagent was used a high molecular from the group consisting of animal and fixed vegetable oils and fats for the recovery of refined .tatty acid, with a strong alkali, by using together with them hydrogen-saturated fatty acids 0! high molecular weight containing not less than 16 and not more than 18 carbon atoms.

3. In the flotation of lime-bearing minerals, the process of controlling the frothing action of collecting reagents which in water give surface active ions, and which comprise the products resulting from the reaction of the waste products remaining after the distillation of impure fatty acid oils produced in the refining of a member from the group consisting of animal and fixed vegetable oils and fats for the recovery of refined fatty acid, with a strong alkali, by using together with them saponifled hydrogen-saturated fatty acids of high molecular weight containing not less than 16 and not more than 18 carbon atoms.

THORBJQZRN HEILMANN.