US2249569A - Treatment of clay by flotation - Google Patents

Description

Patented July 15, 1941 Donald S. Phelps, Harvard, Masa, assignor to 'Edgar Brothers Company, Metuchen, N. .L, a

corporation of New Jersey No Drawing. Application my 29, 1940, Serial No. uazsa 6 Claims.

This invention relates to the treatment of clay by flotation. In recent times some effort has been made to eliminate impurities from crude clays by flotation treatments, and thus it has.

been proposed, for example, to separate impurities simply by oiling and floating them; but such treatment appears to have been insumciently suc-, cessful' for any practical commercial use. Eflorts have also been made to treat clay by froth flotation, but so far as has been ascertained, such efforts have been unsatisfactory in attempting to separate the impurities by elevating them in the froth, and'have been in any practical sense equally unsuccessful in attempting to carry up clay in the froth free of undesired particles.

For instance, oiling or like water-repelling agents clay,-of one of the very impurities which are ordinarily undesired in important uses of clay such as for paper coating. It is'accordingly an important object of present invention to provide new and improved procedures and reagents for the treatment of clay to improve its quality, and biilticlllaiiy for the refinement of clay by flotat on.

The invention is particularly directed to the treatment of clay by froth flotation for elevation in the froth, and consequent concentration, of hydrated aluminum silicate, that is to say, actual clay material; so that, for instance, the clay may thus be separated from contaminating impurities ordinarily found with it,ex'amples of such impurities being mica, sand, ilmenite, tourmaline, particles of iron compounds, and clay particles substantially, contaminated with compounds of iron or titanium. To these ends, it has now been discovered that sulflte waste liquor, viz., waste liquor from the manufacture of paper, pulp by the sulflte process, is a remarkably effective frothflotatlon agent for clay, and more specifically, that .it' has, in addition to frothing characterlstics a peculiar aptitude for carrying up clay in the froth while rejecting contaminating impurimarkably high recovery of pure clay, with simultaneous accumulation of the contaminating impurities in the tailings. That is to say, the sulflte waste liquor is found to have a specific clayselecting power, and the strong tendency is,either for the impurities to fail to get into the froth at all, or only to be carried in the froth by entanglement rather than by selective action,-as

evidenced by the concentration of the impurities in the taillngs.

Although tests of the invention have been made with clays of various stages of refinement. and in each case success has been obtained in improving the quality of the clay, the invention ties such as mentioned hereinabove. This action of su lflte waste liquor, and its peculiar 'aiflnity for kaolin in a froth, are evidencedby the fact that the bubbles of the froth are generally milky 60 with clay (and clay alone) throughout their areas, and by the results of numerous tests wherei in upon froth flotation treatment of a crude clay slip containing sulfite waste liquor a froth conmay conveniently be illustrated by examples relating to the treatment of crude .clay as mined and as containing impurities of the character described above. The crude clay, coming from the mine, is conveniently introduced in a blunger, for instance of the usual type employed to make crude clay slip, and a slip or pulp is thus obtained, containing, say from 3% to 35% of solids. Although the sulfite waste liquor may be otherwise introduced, for example by incorpor'ating it in-the water prior to its mixture with the clay in the blunger, the material may be readily introduced in the prepared clay slip. Thorough permeation of the reagent in the slip having been obtained, the latter is fed to a suitable froth flotation apparatus for-produ'ction of a froth which is collected for recover of the improved clay.

Althoughother types of froth flotation cells may be employed, it appears preferable to utilize direct aeration by blowing air or other gas into the pulp. Thus, for example, good results have been had with the Callow type of froth flotation cell, wherein the aeration is directly obtained by blowing air through, and subdividing it with, a fine canvas screen beneath the pulp column. Especially advantageous operation has been achieved with a cell providing both direct aeration'and self-agitation, and comprising a series of ducts extending down into a. central pulp chamber for blowing air into the pulp, and ad- Jacent frothing chambers to which the agitated and aerated pulp passes and in which a rising froth column, height, is produced to pass over into suitable collecting launders. It will be understood that in such cells the central chamber is preferably separated from the frothing chamber by depending baiiies extending down into and slightly centrate has been obtained consisting of a rethe vigorousiniection f iriflle pulp is not only advantageously of substantial By way of specific example, an untreated white clay from a mine at'McIntyre, Wilkinson County, Georgia, was subjected to the following procedure: The clay was blunged with water to produce a slip containing about 25% solids, and

after passing the slip through-sand-cone separators to remove coarse material such as coarse sand, gravel and the like, sulfite waste liquor was incorporated'in the proportion of about 25 pounds per ton of dry clay. In this run the sulflte waste liquor was one obtained from a pulp mill in Maine, and was derived from sulfite treatment of a blend of northern spruce and northern hemlock; it appearing from other tests that sulflte liquor from these woods has preferable qualities for the purposes of the present invention; The liquor had been somewhat evaporated, to have a specific gravity of about 1.28, i. e., so as to weigh about pounds per gallon.

After thorough mixing to obtain full permeation of the liquor in. the crude clay suspension,- such permeation being apparently desirable to attain the optimum intimate action on the clay in the flotation treatment,the resulting slip or pulp was fed to a flotation apparatus comprising four cells of the combined agitation and aeration type described hereinabove. The apparatus was conveniently so arranged as to feed the froth concentrate from each cell (except the last) to the feed end of the next one in the series, and it was found desirable to break down the froth in each such transfer, for instance by running each froth to a corresponding storage tank and pumping the resulting refined pulp from the bottom of the tank to feed the next cell. The froth from cell No. was collected, for recovery therefrom of a highly refined clay; and the cells were connected in a closed circuit at the tails ends, so that the only tailings came from No. 1 cell.

That is, the tailings of the fourth cell were re-' turned into the feed of the third, those of the third into the feed of the second, and those of the second into the feed of the first, whereby the final concentrate consisted of the collected froth of the fourth cell and the final tailings were taken from the end of cell No. 1. Operation was had at the rate of about one ton of original clay feed (dry weight of clay) per hour, and with an air pressure in the aeration ducts, of about one pound per square inch.

Upon operation of this system, clay bearing froth was collected as described at each cell and the final froth concentrate (from cell No. 4) was found to provide a very satisfactory recovery or high quality kaolin, and to be entirely free from any appreciable content of sand, mica, ilmenite or other contaminating particles, such as hard clay particles and heavily iron-stained particles.

The solids content of the concentrate and the one 31-hour run of the procedure of the example I described above; the impurities were conveniently determined on the basis of the content, by weight,

of particles larger than about 25 microns, such particles substantially constituting the impurities.

Solids Impurities Yield Percent Percent Percent 25 25 a; 2.0 n 92s A further run of about 20 hours under substantially the same conditions resulted as follows:

Solids Impurities Yield Percent Percent 25 It will be understood that multiple flotation treatment is not necessary in all cases for efficient separation of the clay from its contaminating particles; demands of the industry vary and as a consequence the degree of purity required varies so that in some cases a single cell is ample to yield a product of the desired quality.

As further examples of the invention, using other apparatus, the following test runs were made: One thousand grams of untreated clay, of the character described above, were permitted to soak for two or three hours and introduced to a froth flotation cell of the Callow type, with a total of three kilograms of water. Seven cc. of

sulfite waste liquor were added in dilute solution as flotation progressed; operation of the cell being initiated with the first introduction of the reagent and the resulting froth collected as a concentrate. Flotation was very rapid, and the concentrate yielded a refined clay of good color, substantially free of impurities. The solids in the concentrate, comprising purified kaolin, weighed 567.5 grams, whereas the solids in the tailing weighed 398 grams. As indicated, the sulflte waste liquor was employed in the proportion of about eighteen pounds per ton of clay.

In another run 1000 grams of the crude clay were similarly pulped and introduced to the Callow cell with a total of three liters of water. 12.5 cc. of the sulfite waste liquor was added, conveniently in a l to 10 solution, and at the rate of about 3 cc. at a time over a period of /z hour during which the cell was operated. The froth was collected, and when broken down it appeared that the resulting concentrate contained about 20% solids, constituting purified kaolin having a very good color and free of contaminating particles, including not only the simpler impurities but also the larger clay particles contaminated with iron or the like. The solids in the concentrate weighed 727.5 grams, and those in the tailing 239 grams. The reagent was used in the proportion of about 32 pounds per ton of clay.

In yet another test wherein 1000 grams of the crude clay were pulped in about three liters of water, the sulfite waste liquor was added in the proportion of about 30.8 pounds per ton of clay, i. e., about 12 cc. of the liquor being used in the test. The pulp and reagent were treated in the Callow cell for twenty minutes and the resulting froth concentrate was then re-floated, in the Callow cell, twice. The rougher concentrate, i. e., that resulting from the first flotation, weighed 3.6 kilograms wet,--i. e., contained about 16% solids. The final concentrate from the two cleanings was a very hlgh quality kaolin, lacking any appreciable content of contaminating impurities; indeed the No. 2 middling, while of somewhat lower quality, revealed a. substantial absence of impurities. The solids recovery is indicated by the following table:

Although the foregoing tests were all. made with clay fresh from the mine, the procedure is.

effective for treatment of other clay compositions, for example, for recovery of clay in tailing resulting from sedimentation, centrifuging or other fractionating operation on clay. It will also now be understood thatwthe procedure is susceptible of considerable variation as to thesolids content of t e clay pulp used, the nature of the froth flotation apparatus, the number of cells utilized, the amount of air employed for frothing, the quantity of the reagent, and other factors, all as may be readily determined by simple tests in the light of the foregoing description and examples, and depending on the nature of thegiven clay under treatment and the specific results. desired from the flotation. For instance, it has been found in tests of the character described above, that the sulflte waste liquor (having the stated specific gravity of about 1.28) may be included in the clay slip for very efficient froth flotation results, in amounts ranging from about 15 to' about 35 pounds per' ton of clay; it being noted that the toughness of the froth and consequently its clay-elevating power, tend to increase somewhat with the amount of the reagent, and yet without undesirable efiect of carrying over impurities even at proportions of 30-35 pounds of liquor per ton. I

The exact action of the suliite waste liquor is not fully understood, except that it not only has advantageous frothing characteristics but also has a peculiar selectivity for clay, as explained above. It is my belief that the clay-selecting action stems at least partly from the lignin material in the waste liquor, which is reported to be present in a sulfonic form, say a lignosulfonate. Although the exact chemical constitution of sulflte waste liquor is not known, it appears that other components have some bearing, including the presence of fat or fatty material, probably in the form of fatty acid soap, which contributes to the frothing characteristics in the clay pulp undergoing treatment. On the other hand, soaps alone, although efficient frothing agents, do not appear to produce worth while results in treatment of clay by froth flotation, especially for separation of impurities of the type described above.

It is to be understood that other sulfltewaste liquors, or concentrates or extracts thereof, may be used in many cases. Examples of other products generally classifiable as sulflte waste liquor are the materials commercially available under the trade names, respectively, of Super- Spruce and Spruce Extract," which are solid products understood to be derived by evaporating down the actual waste liquor from sulfite pulp mills.

It will be understood that the-invention is not limited to the specific procedures hereinabove described, but may be carried out in other ways without departure from itsspirit, asdefined by the following claims.

I claim: 7

1. In the treatment of clay material, the steps comprising establishing a clay pulp containing sulfite waste liquor and blowing air into the pulp to produce a clay-selecting froth.

2. A method of purifying clay, comprising establishing a clay pulp containing sulflte waste liquor, aerating the pulp to produce a rising, clay-lifting, froth column selectively favoring the elevation of clay particles therein rather than contaminating particles, andcollecting the froth for recovery of purified clay.

3. A method of treating clay material, comprising establishing a clay pulp and subjecting the pulp to froth flotation treatment in the presence of sulflte waste liquor for promoting the elevation of clay in froth.

4. A'method of treating clay material, comprising establishing a clay pulp, and subjecting the pulp to froth flotation treatment in the presence of sulflte waste liquor, by directly aerating and agitating the pulp, to produce a clay-bearing froth. I

5.-A method of separating clay from contaminating particles of mica, sand, ilmenite and iron compounds, comprising subjecting the clay to froth flotation treatment, including direct aeration of a pulp of the clay, in the presence of sulflte waste liquor.

6. A method of separting clay from particlgs