US2461875A - Froth flotation of iron ores - Google Patents

Description

Patented Feb. 15, 1949 UNITED STATES PATENT OFFICE Herkenhoff, Stamford, Conn., American Cyanamid Company,

assignors to New York,

N. Y., a corporation of Maine No Drawing. Application February 14, 1944, Serial No. 522,268

Claims.

1 This invention relates to the beneficiation of iron ores by froth flotation.

In the past, iron ores have presented a very serious problem to the ore dressing engineer. There are many collectors, for example, of the fatty acid type which will float iron ore, but the mere flotation is not sufficient. The ore commands so low a price and the requirements for grade are so high that the ordinary froth flotation process with anionic collectors will not give results which are commercially useful.

In our Patents Nos. 2,385,054, September 18, 1945; 2,410,376 and 2,410,377, October 29, 1946, we have described processes in which certain types of promoters containing sulfonic or sulfate groups have been used in conjunction with acid treatment of the iron ore. These applications, of which the present application is a continuation in part, represent three particular groups of promoters which can be used with acid treated iron ore.

According to the present invention we have found that iron ore can be effectively beneficiated by acid treatments under specified conditions with sulfonated promoters obtained by sulfonating the residues from the refining of glyceride oils or fatty acids. These residues are of two general types, the so-called foots, which are products that settle out in the refining of oils by chemical means, and the pitches or still bottoms which are residues from the refining of fatty acids by distillation. These residues are characterized by a definite but relatively low fatty acid content associated with other organic material such as glyceride oils, proteinaceous material, neutral oils, and the like. The distillation residues, in addition, contain many products of partial decomposition such as carbon, cracked glyceride oils and other products. The chemical composition of these residues is not constant and is not completely known as they are a mixture of a large number of impure compounds. The general characteristic, however, is a relatively low fatty acid content, the fatty acid bein much lower than ordinary fatty acids or acid oils and, in many cases, is only a minor constituent, particularly in the case of distillation residues.

When the iron ore is conditioned at high solids, preferably 60-70%, with a strong acid having a dissociation constant greater than 10- in sufficient quantities so that when diluted to froth flotation density without neutralization, a pH of 1.5-5.5 is obtained, the ore can be floated with the sulfonated residues from the refining of glyceride oils and fatty acids to produce concentrates of satisfacory iron content with high recoveries.

The term sulfonated is used in its general sense to describe a product obtained by the chemical reaction of sulfuric acid or other sulfonating agents such as chlorsulfonic acid with the residue. This produces, normally, a mixture of sulfonates and other acid sulfur containing compounds such as sulfonated compounds where double bonds are present. It is not intended to be used in a narrow sense that all of the sulfur containing compounds are true sulfonic acids or salts thereof.

The acid used in the treatment is not critical. Many strong acids which do not have an anion that adversely affects flotation, may be used. Acids weaker than those having a dissociation constant of 10- are not suitable. The amount of acids to be used will vary with dilferent acids and to some extent with different iron ores. In every case suflicient acid must be used to produce enough free hydrogen ions so that on dilution to froth flotation pulp density a pH of from 1.5- 5.5 results. In general, larger amounts of acids produce high grade but a falling 01f in recovery while smaller amounts produce falling oil in grade and sometimes also in recovery. The conditioning itself is at high solids but in practice the acid concentration generally is determined by measurement after dilution to flotation pulp density.

'The pH measurements after dilution are, of

course, definite numerical measures. The dilution from pulp density during conditioning to flotation pulp density without neutralization changes the pH but little and in general raises the pH by about 0.5 to 1.0. The measurement after dilution will, therefore, be used in the present specification and claims because it is the convenient practical method for large scale use. It should be understood that the particular pH of the flotation circuit itself is relatively less important. With some promoters and some ores, it is feasible after conditioning to effect considerable neutralization without serious adverse effects in flotation. It is the acid strength during the conditioning and not in the flotation circuit which appears to be the most important single factor.

While it is an advantage of the present invention that the range of acidity in conditioning is not critical, nevertheless with most promoters and most iron ores we find that the best results are usually obtainable with acid strength which will dilute to flotation pulp density giving a pH from about 2-3. In every case, of course, the ore dressing engineer will choose the amount of acid giving optimum results with the particular reagent combinations and ore with which he is dealing.

The amount of the collector used is not critical and in general will Vary from amounts somewhat less than 1 lb. up to 5 or 6 lbs. per ton of ore. In some cases where the residue is very low grade larger amounts may be necessary up to a maximum of about 10 lbs. The larger amounts are not a serious economic deterrent because of the extremely low price of the residues in normal times, most of them having hardly more than fuel value.

In every case only the optimum amount of collector will be chosen. However, the optimum amount is practically never critical and slight variations do not produce disastrous effects. This is a very real operating advantage because many of the commercially attractive collectors such as petroleum sulfonates and sulfonate residues are of indeterminate nature and vary from batch to batch.

Conditioning at high solids, which is an important feature of the present invention, often presents a problem of distribution of the collector over the ore particles. This is particularly acute where the collector is not readily dispersible in water or on the other hand in certain cases where the collector is very soluble. In such cases an oiling agent may profitably be used as an adjunct. It is an advantage of the present invention that the character and amount of the oiling agent is not critical. Hydrocarbon oils such as fuel oil give excellent results and their low price makes them very attractive in most locations. However, other oils such as glyceride oils, for example, coconut oil, linseed or cottonseed oils, work satisfactorily and certain fatty acids of oily nature may also be used. The amount of oiling, however, depends very largely on the particular collector used and may vary from a small amount up to several pounds per ton. With every reagent combination there is an optimum range of oiling agent. This range is not critical and is not the same with different collectors. In every case, of course, the range for optimum results should be determined with the desired collector, but once determined, no operating difficulties result because the range is broad enough to take care of ordinary fluctuations in operation. The elimination of the necessity for critical control of the operation is an important practical advantage.

The acids which can be used are numerous and, j

the acid must alter the'surface of the iron oxide particles but the nature of the alteration is not susceptible to exact determination. The oiling agents also may perform several functions. It is reasonably assured that one of the main, and, perhaps in most cases, the main function is that of distributing the collector over the iron ore particles. It is probable that in most cases the oiling agent may also beneficially modify the froth. This is directly observed with certain water soluble petroleum sulfonates and may be a factor in many other combinations.

While conditioning at high solids, which is a feature of the present invention, permits using collectors which are not dispersible in water, it is, nevertheless, desirable where possible to use water dispersions. In some cases some of the collectors may be dispersed in hot water, and these dispersions or solutions make the feeding of the reagent much easier and are preferred where the nature of the collector permits the formation of such dispersions.

It is not necessary to use a single type of collector. Mixtures may be profitably employed and in some cases oiling agents are also Weak collectors for iron. Mixture of oil soluble and water soluble petroleum sulfonates are particularly important.

The problem of slime is not greatly different in the process of the present invention than in the general run of flotation processes. Here, as elsewhere, slime is never desirable. However, it is an advantage of the present invention that it is not peculiarly critical as far as slime is concerned and it is possible to operate with undeslimed ore or, which is more important, with ore which has been only partially deslimed, thus permitting more economical desliming procedures. The effect of slime is normal and manifests itself primarily in added consumption of reagent. As many of the reagents are fairly cheap it is sometimes desirable to use relatively economical desliming procedures which do not remove the slime completely and such procedures are permissible by reason of the relative lack of sensitivity of many of the reagents of the present process to the presence of small amounts of slime. More involved desliming procedures, such as those employing a polishing or scrubbing of the ore particle followed by desliming, are not normally necessary although they may be used and do effect some economy of reagent. The extent to which the desliming is to be effected is largely one of economic compromise and the degree of desliming to produce optimum results with minimum costs will be determined in the case of each ore.

The invention will be described in greater detail in conjunction with the following specific example which illustrates typical modifications.

Example A low grade Minnesota iron ore containing about 14.5% Fe was deslimed, conditioned at high solids with sulfuric acid, various sulfonated residues and an unsulfonated mineral oil, dilutecl to froth flotation density and floated. The sulfuric acid used was about 2 lbs. per ton with cottonseed still residues and bottoms and also lauric acid residues, 4.0 lbs/ton with cottonseed pitch, 5.0 lbs/ton with wood oil residues, 3.0 lbs/ton in the remainder of the tests. The cottonseed still residues used in the first test were sulfonated with 50 parts of 95.5% sulfuric acid per parts residues. In the second test, the

vegetable pitch was sulfonated with 67% of the same strength acid. The other materials were treated with 67 parts of chlorosulfonic acid per 100 parts residue. The chlorosulfonic acid was added. directly to the residues in the third to glyceride oils and fatty acids, the amount of collector being suflicient to permit effective flotation, diluting the conditioned pulp to froth flotation density and subjecting it to froth flotation to produce a concentrate relatively rich in iron and a tailing relatively poor in iron.

2. A method of beneficiating oxidized iron ores by froth flotation which comprises conditioning the ore at high solids with a collector and m sulfuric acid, the amount of the acid being sufficient so that on dilution to froth flotation density without neutralization the pulp will have a pH between 1.5 and 5.5, the effective collecting constituent of the collector being a sulfonated residue from the refining of glyceride oils and Conditioning- 0 oncentrate, gigs/{Fay percent, Fe Rough Tailing Sulfonated Product, Type Sulfo- Assay, nated 6 5 Assay Distrib percent pH Product Fe Cottonseed Still Residues 5. 2.83 53.33 82.67 2.81 2.7 Vegetable Pitch 2. 0 4. 0 56. 82 86. 84 1. 73 2. 5 Talloel Bottoms. 4. 0 4. 0 56. 13 82.01 2. 42 2. 5 Coconut Bottoms 2. 0 4. 0 55. 32 87. 37 l. 96 2. 6 Marine PitclL- 2. 0 4. 0 55. 09 90. 44 1. l5 2. 5 Linseed Pitch- 2.0 6.0 58. 89 82.29 2.19 2. 5 Corn Oil Bottoms.. 10.0 4.0 55.90 92. 44 1.27 2.4 Laurie Acid Residues.... 10.0 4. 0 56.92 85. 70 2. 23 2. 5 Vegetable Pitch 2. 0 4. 0 58. 78 80. 54 1.73 2. 5 VRO Residues 2. 0 4. 0 57.45 82. 43 l. 27 2. 6 Cottonseed Residues 2.0 4.0 55. 54 86. 53 1. 59 2.8 Linseed Residues... 2.0 4.0 53.83 72.23 3. 80 2.6 Soya Bean Residues 2. 0 4. 0 57.98 82. 67 l. 48 2. 6 Tallow Residues. 2. 0 4. 0 57. 74 84. 36 1. 38 2. 6 Wood Oil Residues. 10.0 4. 0 54. 40 80. 2, 53 2. 5 Animal Still Residues. 2. 0 4. 0 59. 12 72. 78 3. 11 2. 6 Soft Steaiine Pitch 2. 0 4. 0 57. 45 85.07 1. 27 2. 6 Cottonseed Foots 10. O 4. 0 57. 97 81.35 3.11 2. 3 Fleshing Greaseby-product in glue mfg 2. 0 4. 0 59.35 76. 84 2. 76 2. 6 Dark Cottonseed Distillate 2.0 4. 0 58.09 82.29 2. 30 2. 5 Dark Animal Distillate...- 2. 0 4. 0 57. 51 84. 13 1. 84 2. 5 Linseed Still Residues... 2.0 4. 0 55. 78 77.86 2. 42 2. 6 2. (l 4. 0 58. 32 75. 90 2. 42 2. (i 2. 0 4. 2 58.09 78. 25 3.11 2. 6 5.0 4. 0 54. 52 90. 28 1. 38 2. 4 4. 0 4. 4 56. 70 87. 95 1.50 2. 5 l0. 0 10.0 57. 51 74. 42 2. 88 2. 5 Fatty Acid Pitch. 2. 0 5. 2 57. 63 87. 18 1. 73 2. 5 Cottonseed Pitch. 3.0 4.0 56.92 78.03 2.76 2. 5 Fuel Oil #2 10.0 None No useful promotion. Fuel Oi1#2 4.0 2.0 Barren Froth Only.

The examples describe froth flotation operations as this is the most important field in which the process of the invention can be used. It should be understood, however, that the process is also applicable in the case of some collectors to other wet separation processes involving agglomeration, for example, tabling, belt tabling and film flotation. In tabling operations, in general, more oiling agent should be used than in froth flotation.

In the claims the term oxidized iron ores is used in its commonly accepted meaning to include not only iron oxide ores such as those containing magnetite, hematite, etc., but also hydroxides, carbonates, etc.

We claim:

1. A method of beneficiating oxidized iron ores by froth flotation which comprises conditioning the ore at high solids with a collector and an inorganic acid substance, the anion of which is a constituent of an acid having a dissociation constant of at least 10*", the amount of the acid substance being sufflcient sothat on dilution to froth flotation density without neutralization the pulp will have a pH between 1.5 and 5.5, the efiective collecting constituent of the collector being a sulfonated residue from the refining of fatty acids, the amount of collector being suflicient to permit effective flotation, diluting the 55 3. A method according to claim 1 in which the collector is associated with an unsulfonated oil as an oiling agent.

4. A method according to claim 2 in which the collector is associated with an unsulfonated oil as an oiling agent.

5. A method according to claim 2 in which the collector is a vegetable oil foot.

6. A method according to claim 5 in which the collector is associated with an unsulfonated oil as an oiling agent.

7. A method according to claim 2 in which the collector is a residue from the distillation refining of vegetable fatty acids.

8. A method according to claim 7 in which the collector is associated with an unsulfonated oil as an oiling agent.

9. A method according to claim 2 in which the collector is a residue from the distillation of marine oil fatty acids.

5 10. A method according to claim 9 in which the collector is associated with an unsulfonated oil as an oiling agent.

ROBERT BEN BOOTH. EARL CONRAD HERKENHOFF.

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

Number UNITED STATES PATENTS Name Date Higgins Feb. 8, 1916 Number 8 Name Date Nutter Feb. 8, 1916 Tartaron Jan. 18, 1938 Gillson Mar. 29, 1938 Harris June 7, 1938 Carter Feb. 7, 1939 Trotter June 13, 1939 Patek Oct. 12, 1943 Booth Sept. 18, 1945 Booth Oct. 29, 1946 Booth Oct. 29, 1946