US2466671A - Froth flotation of nonmetallic ores with black liquor soap in acid circuit - Google Patents

Description

UNITED STATES PATENT orrica morn non-non or Nomnmimc onus gr BLACK LIQUOR soar in ACID cm-- Elmer William can, our Greenwich, assignor to American Cylnamld York, N. Y.,- a corporation of Maine No Drawing. Application Se'ptember 22, 1945,

sfllal No. 818,052

1 2Claims. (01.209-166) 2 This invention relates to the beneflciation by agent cost." Also, because it gives a very poor froth flotation of the mineral values of various quality of froth it does not readily lend itself to ores. In particular, it relates to a novel reagent cleaning operations and when used on phosphate combination suitable for useinbeneflciating those rock the grade of concentrate obtained is too non-metallic ores which are amenable to flotalimited. On the other hand, a fatty acid alone did tion with anionic promoters of the fatty-acid not prove successfulin any ordinary procedure. soap type and to a method of using such re- Saponifled fatty-acidsinsome cases proved someagents. what more effective. Even with soaps however,

Beneficiation of various ores by froth flotation, consumption was high and the metallurgical retaking advantage of the selective afilnity of varisuits were generally poor. In compromising beous materials for particular mineral constituents tween these factors, it came to b considered nechas come to be common practice. One of the most essary to use with the fatty acid both a saponifycommon procedures in that field is the use of a ing agent, the caustic soda; and a modifying fatty acid, or a soap thereof, as the selective agent, the oil.- This 'was thought necessary in reagent. An excellent illustration of such usage order to insure eflicient distribution and lower th is in the beneficiation of phosphate rock, particufatty-acid consumption,

larly the treatment of rock from the Florida Peb- Having come to be more or less standardized ble Phosphate District. Since most of the probpractice, the art began to seek more economical lems to be overcome are met in this operation, reagents. Principally this led to variations in the the present invention, although not necessarily an nature and amount of the fatty-acid used. Some so limited, will be principally illustrated with rela appear to have greater selectivity, others give tion thereto. This is a P rtic l rly 8 0 i lll equivalent results only when used in. excessive tration since it represents one of the best exquantity, Talloel, a, mixture of fatty and resin amples of large-volume, low-cost operation in acids, was generally found the most economical which even small savings per unit become of ofthe fatty-acid reagents. In some cases, for

marked commercial importance. example in phosphate flotation, it also was found For many years, in this field, the practice has to be one of the most emcient. Likeother fattybeen standardized on a flotation agent combinaacid reagents, however, for best results it was tion comprising an alkali, such as caustic soda; generally considered desirable to use therewith a fatty acid, such as oleic acid or the like; and an 80 a saponifying agent and, in phosphate flotation, unsaponifiable oil such as kerosene or fuel oil. a non-saponifiable oil. The actual process of using these agents may be V Where talloel or a talloel soap can be successvaried. For example, the reagents may be prefully used, a natural inclination is to attempt to combined before being fed to a pulp of the ore or make use of the less expensive, crude, black-liquor they may be fed separately in various sequences 35' soap. In addition to its general availability and or combinations. They may be added to the ore low cost, such material looks particularly attracpulp in a preconditioning operation or during flotive because it is in soap form. It would appear tation. Supplementary conditioning, dispersing therefrom that considerable economy in alkali or depressing agents are also sometimes used. Reconsumption might be effected by its use. gardless of procedure, however, the reagent com- 0 Unfortunately, a direct substitution of black bination normally is comprised of one represenliquor soap for a fatty acid or the talloel of the tative of each of these three classes of materials. prior art, or for soaps of these materials, does not A number of reasons contributed to the develproduce satisfactory results. Such substitution, opment of this practice. A straight oil flotation, particularly in phosphate flotation, does not give useful insome fields, suffered from fairly high reresults which are of suflicient utility to be commercially acceptable. There remained, therefore,

the desirability of using black liquor soap as a substitute for flotation reagent materials in commen use, but no practical method of satisfying the demand.

It is, therefore, the principal object of the present invention to develop a process in the practice of which black liquor soap can be utilized to produce an effective and acceptable beneficiation of non-metallic ores. In particular, it is one of the principal objects of the invention to devise a process whereby black liquor soap can be effectively used to reduce the acid-insoluble content of phosphate concentrates.

Surprisingly, the desired object of the invention can be easily and simply accomplished by the exercise of a practice which is exactly contrary to that taught bythe prior art. According to the present invention, it has been found that the desirable results are accomplished, not by using the black liquor soap in conjunction with an alkali, but by carrying out the operation in a circuit to which a strong acid has been added. This is particularly surprising since, as noted above, effective results in an anionic flotation of ores such as pebble phosphate were previously considered possible only on the presence of excess alkali.

On the contrary, in the practice of the present invention, the optimum results in phosphate flotation are obtained when the tailing water has a pH less than 6.9.

In this respect it should be noted that an ore pulp frequently may appear to have an-alkaline pH whereas the tailing watermay be distinctly acid. Whether this is dueto the alkaline reaction of black liquor soap or to some pulp pretreatment or to the presence of other reagents, however, may

be uncertain. An instance of this may be found for example in phosphate floatation. The pulp even after being conditioned "with the other reagent or reagents in the presence of the acid may have an apparent pH of 7.0 to 7.5, yet the pH of the rougher tailing water willbe only 6.5-6.7. Where there is a discrepancy between the apparent pH of the ore pulp and that of the tailing water, the latter shouldv be the chosen control since the removal of much or all of the solids content therefrom enables a more accurate reading to be taken.

It is for asimilar reason that the beneficial effect of adding extra acid in the present process may not always Foe immediately observable. For example, a particular mill may be using process water which naturally, or because of prior use, has an inherent pH less than 6.9. In such cases addition of more acid, to a phosphate flotation for example, will not produce a particularly marked improvement in grade over that obtained when using black liquor soap'without added acid. Nevertheless, the improvement over the prior practice, in which excess alkali would have been added without realizing the advantage in the acid water, is very real.

The present invention is in no way concerned with the practice of refining talloel in which crude black liquor soap is acidified to free the talloel. The amount of acid used in the process of the present invention is but a fraction of that needed to neutralize the total alkali content of the black liquor soap. In fact, the presence of free acid in the flotation circuit of the present invention is possible only because neutralization of the black liquor soap is very slow. Flotation is completed after the pH change takes place but before the acid is exhausted: In addition, if a large excess of acid, i. e., sumcient to liberate the talloel content, is used, the catalytic effect of the acid on selectivity during flotation is not obtained. The benefit of the free acid on the selectivity of the black liquor soap is not observed at a pH less The distinguishing characteristics of the present invention therefore may be summarized as:

(1) the benefication of non-metallic ores, particularly phosphate ores containing an excessive content of silica-bearing gangue; (2) by producing a froth concentrate high in mineral values; (3) in an anionic flotation; (4) using black liquor soap as the collector; (5) in the presence of suflicient acid to activate the selective tendency of the collector, but insufficient to neutralize the black liquor soap; normally enough to produce a tailing water-pH of from about 4.0-6.7; and (6) completing the flotation before the acid is consumed in neutralizing the alkali content of the black liquor soap.

I The present invention will be more fully illustrated in connection with the following examples which are meant to be illustrative only and not by way of limitation. All parts are by weight unless otherwise noted. In tabulating the results, the following abbreviations are used: B. P. L.- bone phosphate of lime (Caa(P0i)2); B. L. S. or B. L. Soap-black liquor soap; Insolacid insoluble gangue.

Example 1 A sample of Florida pebble phosphate ore, assaying about 43.4% B. P. L. and 43.5% Insol, was prepared for flotation by reducing the size sufliciently for flotation feed; pulping with water, to about 22% solids; polishing in a Fagergren flotation machine with the air shut off for 6 minutes; and completely desliming by conventional hydraulic procedures. This sample was then divided into a number of portions which were separately conditioned at about 70% solids with various amounts of black liquor soap, diluted to about 20% solids and floated in Fagergren flotation machines under standard conditions, including a rougher float followed by 3 cleaner floats. The procedural steps and metallurgical results appear in the following table. The first test is a blank with no acid, followed by three tests in which the acid was added to the flotation cell and then by three tests in which varying amounts of acid were added during conditioning.

Results Reagents Lbs. on Cleaned Concentrate Added to Conditioning 1 pH Test No. R. Tail Assays Dist. I Water 9;, Wt B. L. s. also Insol B. r. L.. Insol B. r. L.

' Added to flotation cell.

grades are obtained with amounts above /6 1b.,

and recovery remains good until lb. is reached, at which point the recovery begins to drop.

froth flotation u'slng 2 .0 lbs/ton of black liquor inthe following Table II.

. Table II A Assay-spodumene Content Acid (Lba/Ton) Taillnl;

' .Water pH Feed Sp. Ro. Tail Cl. Tall 01. Cone.

9;, Sp. Dist. Sp. Dist. sp. not. R0 01.

2 6.16 5 1Z2; 19 92.6 1.1 1.1 2 20.33 10 1 121 14 65.5 0.5 6.7 6.9 1 3.63 10 5.95 on 00.4 .25 0.25 6.8 6.2

Nora: Sp.=Spodumen'e. dist.=% Distribution. While the present invention is primarily con- Example 3 cerned with the use of acid and black liquor soap in the beneflciation of phosphate ores, the invention is not necessarily so-limited. The mineral values of many non-metallic ores are commonly concentrated by an anionic flotation using fatty acid soap reagents. In general, these types of operations may be adapted to the substitution of black liquor soap for the more expensive reagents in common use if the acid treatment of the present invention is joined therewith. In order to demon- A low grade fluorspar ore was treated by grinding for 15 minutes at about 67% solids in a rod mill after which the pulp was diluted to about 4 22% solids and conditioned for 5 minutes with strate this feature, the following examples are given for purposes of illustration.

Example 2 1 lb./ton of sodium silicate and 1 lb./ton of quebracho. Where acid was used in the rougher float it was added during this conditioning operation. The conditioned pulp was transferred to a flotation machine and given a 6 minute rougher float in which the black liquor soap was stage-added. The rougher, concentrate in the second and third tests was conditioned for 1 minute withthe sulfuric acid and given a 2 minute cleaner flotation. The cleaner concentrate was conditioned for 1 minute with additional black liquor soap and in i the second and third tests with sulfuric acid. and

given a 2 minute cleaner flotation. The reagents used and representative metallurgical results are shown in the following Table 111. It will be noted that the use of acid throughout the process results in an extremely high grade concentrate in a field in which grade is primarily important.

Table III Concentrate Rte Feed AS88178 Assays R0. Float 01. Float Bocl. Float Wt.

9506!: 930600; %CBF: %Ca00i B. L. S. H1804 B. L. 8. H1804 B. L. S. H1804 I claim:

1.111 the beneflclation of non-metallic ores by froth flotation, using at least one rougher and one cleaner stage, to recover the mineral values in a high grade concentrate, the improvement which comprises subjecting an aqueous pulp of the .ore to iroth flotation at least the rougher" float being carried out in the presence of an effective amount of black liquor soap as the principal collector and a suflicient amount of free strong acid to produce a pH of from not more than 6.7 or less than about 4.0 in the tailing water, but insufllcient to neutralize appreciable amounts of-the alkali content of the black liquor soap during the period of operation. i

2. In the beneflciation of phosphate ores to recover the mineral values in a high grade concentrate, the. improvement which comprises subjectin: an aqueous pulp oi the ore to froth flotation in the presence of an eflective amount of black liquor-soap as the principal collector and a s m- 8 clent amount of free strong acid to produce a pH of not more than 6.7 or less than about 4.0 in the tailing water but insufliclent to neutralize appreciable amounts of the alkali content of the black liquor soap during the period of operation.

ELMER WILLIAM GIESEKE.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED s'ra'ms PATENTS OTHER REFERENCES Soap Flotation by Coghill in Milling Methods, 1934, pa es 452, 462, 463, 464,