US3642464A

US3642464A - Tin ore treating process

Info

Publication number: US3642464A
Application number: US782064A
Authority: US
Inventors: Adrian C Dorenfeld; Fernando Jorge Dick; Strathmore R B Cooke
Original assignee: University of Minnesota
Current assignee: University of Minnesota
Priority date: 1968-12-09
Filing date: 1968-12-09
Publication date: 1972-02-15
Anticipated expiration: 1989-02-15

Abstract

A method of beneficiating crushed and ground tin oxide ores, including concentrates, by first sulfidizing to produce stable tin sulfides SnS2, Sn2S3 and SnS, and then, after initial separation of magnetic iron sulfide constituents, subjecting to progressive and selective flotation to remove the several tin sulfides formed. Flotation is ordinarily first carried out under alkaline conditions and then under conditions of increasing acidity. Nonmagnetic iron sulfide may be removed by flotation under mildly acid conditions and any residual magnetic iron sulfide may be removed by further magnetic separation. When elemental sulfur is used as the sulfidizing agent, as when pyrite is used as the sulfur source, iron oxide minerals in the tin ore or concentrates are preferentially sulfidized to form magnetic and nonmagnetic iron sulfide components. This characteristic enables the iron oxide minerals to be separated from the tin oxide ore by magnetic separation and progressive flotation.

Description

United States Patent I 3,642,464 Dorenield et al. 1 Feb. 15, 1972 [s41 TIN ORE TREATING PROCESS 636,356 4/1950 Great Britain ..74/2

' ..209 167 [72] Inventors: Adrian C. Dorenteld, Brooklyn Center, l059476 2/1967 Great Bmam I Minn.; Fernando Jorge Dick, Oruro, Bolivia, South America; Strathmore R. B. OTHER PUBLICATIONS Cooke, Robbinsdale, Minn. [73] Assignee: The Regents o the University of Mim Chem abstracts,Vo1.66, 1967,P.5484,58030p nesota Mmneapohs Mmn' Primary Examiner-Frank W. Lutter [22] Filed: Dec. 9, 1968 Assistant Examiner-Robert Halper [2]] App] No 782 064 Attorney-Kurd, Braddock & Bartz [57] ABSTRACT [52] US. Cl ..7S/2, 209/ l 1,220%9//l3697, A method of beneficiating crushed and ground tin oxide ores, including concentrates, by first sulfidizing to produce stable g F {3; tin sulfides sns,, sn s nd SnS, and then, after initial separa.

tion of magnetic iron sulfide constituents, subjecting to 75/1 progressive and selective flotation to remove the several tin sulfides formed. Flotation is ordinarily first carried out under [56] References Cited alkaline conditions and then under conditions of increasing U E STATES PATENTS acidity. Nonmagnetic iron sulfide may be removed by flotation under mildly acid conditions and any residual magnetic 1,513,812 11/1924 Henders n t iron sulfide may be removed by further magnetic separation.

1,312,668 8/1919 Bacon When elemental sulfur is used as the sulfidizing agent, as when 2,424,402 7/ 1947 Loane....

----- pyrite is used as the sulfur source, iron oxide minerals in the Mercade tin ore o concentrates are preferentially sulfidized to femmagnetic and nonmagnetic iron sulfide components. This FOREIGN PATENTS 0R APPLICATIONS characteristic enables the iron oxide minerals to be separated 9,508 6/1913 Australia ..209/167 fr m he tin oxide ore by magnetic separation and progressive 26,019 12/1910 Great Britain ....209/ 167 ta 252,414 1 1963 Australia ..75 2

I 18 Claims, 2 Drawing Figures Lea I N DINHSTRQNGLY MAGNETIC MATERIAL REMOVED] SULFIDIZATION MAGNETIC L MAGNETIC SEPARATION CONCENTRATE SULFIDIZED TIN ORE FLOTATION AT HS P-Ensz CONCENTR/Elq snszsn, s;-sns-Fes MIX AND CONDITION FLOTAT'ON AT CONCENTRATE WITH GLUE SPESJ'T 5H5 FLOTATION AT PH2.8 CONCENTRATE L IFLOTATIOII AT HTHlRON suLFIDFT] TIN SULFIDE CONCENTRATE OPTIONAL MAGNETIC SEPARATION SULF'DE IFINAL TIN SULFIDE CONCENTRATEI TIN ORE TREATING PROCESS This invention relates to the treatment of low-grade tin ore including concentrates, hereinafter referred to simply as ores, in order to make them more amenable to flotation methods of concentration, and to the subsequent concentration of those ores by flotation. More particularly, the invention relates to the sulfidization of low-grade tin oxide ores by treatment of the ore with sulfur or sulfur-bearing material in gaseous or vapor form at elevated temperatures in a nonoxidizing or reducing atmosphere and, thereafter, concentrating the resulting sulfides by progressive and selective flotation methods.

The art is crowded with various proposals for effecting the flotation and separation of nonsulfide ores by first superficially converting the metallic nonsulfide minerals in aqueous suspension into sulfides and then subjecting the sulfidized ores to flotation methods of concentration. These prior processes where directed at the recovery of tin have not found acceptance by the mining industry for various reasons, because they have been too expensive or result in low-grade products or produce low yields or otherwise are not economically and practically feasible.

As our civilization advances and sources of high-grade ores become depleted, it becomes necessary to be able to treat ore bodies of ever-decreasing quality. In the constant search for economically and practically feasible methods of treating lowgrade ores, it is useful to study and reevaluate past failures with the objective of modifying and improving them in order to produce new, useful and valuable methods of ore treatment and recovery. I

It is the particular object of this invention to provide a process for the separation and recovery of oxide tin (cassiterite) ores by first crushing the ore, followed by magnetic separation of conventional magnetic materials, and exposing the nonmagnetic ore to the effects of sulfur or sulfurbearing material in gaseous or vapor form in a nonoxidizing or reducing atmosphere at elevated temperatures, removing magnetic iron compounds by magnetic separation, and then separating the resulting tin sulfides by progressive and selective flotation procedures. 7

Other objects of the invention will become apparent as the description proceeds.

. To the accomplishment of the foregoing and related ends, this invention then comprises the features hereinafter fully described and particularly pointed outin the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed.

The invention is illustrated by the accompanying drawings which show in schematic flow sheet form the steps by which the beneficiation processes are carried out.

Flotation has long been recognized as an effective and economical procedure for concentrating natural sulfide ores. However, most nonsulfide metallic ores are not readily amenable to concentration by flotation. Tin sulfides rarely occur in nature. The most common tin mineral in the tin ores is cassiterite, a tin dioxide. It is not amenable to sulfide mineral flotation without prior treatment. The present invention resides in the development of a simple, effective and economical method of sulfidization using sulfur or sulfur-bearing material in gaseous or vapor form in a nonoxidizing or reducing atmosphere, followed by magnetic separation of magnetic constituents and progressive and selective flotation.

The ore is crushed or ground before sulfidization although the particle size is not critical, except that the tin mineral should be sufficiently liberated so as to be exposed to the sulfurgas reactions. The ores are desirably crushed. to one-eighth inch particles or less and preferably are crushed to about 20- mesh size (about one thirty-second of an inch). Sulfidization proceeds somewhat more rapidly with smaller ore particles, and for this reason, somewhat smaller particle. sizes are preferred.

The essence of the sulfidization step of the present invention is treatment of the ore with sulfur or sulfur-bearing material in gaseous or vapor form in a nonoxidizing or reducing atmosphere. The sulfur gas may be generated by heating elemental sulfur above its boiling point or by heating a sulfurcontaining compound high enough to cause it to decompose enough to yield gaseous sulfur. Sulfur-containing sources acceptable for this process include iron pyrite, marcasite, hydrogen sulfide, and the like. Certain minerals associated with cassiterite contain sulfur in the form of iron pyrites or other metal sulfides or other decomposable sulfur compounds as impurities. When this occurs, some or all of the sulfur already present may be yielded when heated for use in the sul fidization step as gaseous sulfur.

Because the sulfur should be maintained in gaseous form, the sulfidization s'tep must be carried out at elevated temperatures. In the case where relatively pure sulfur is used as the source of sulfur gas, the temperature must be near or above the boiling point of sulfur (445 C.). in the case of iron pyrite, temperatures of the order of about 720 C. are necessary to decompose the sulfide andliberate half of the sulfur in the pyrite as gas. In the case where hydrogen sulfide is used as the source of sulfur, and because hydrogen sulfide is a gas at the operating conditions, conversion of tin oxide to tin sulfide can be accomplished over a broader range of temperatures. Where lower temperatures are employed, the time required is longer for conversion of the tin oxide to a sulfide form.

It has been known that the sulfidization of tin oxide (cassiterite) produces three stable tin sulfides: SnS Sn S and SnS. It is our discovery that these three sulfides have different flotation characteristics, and that the SnS is the preferred form. It has been found that the critical upper temperature limit for the production of the SnS is about 600 C. Above this temperature the production of Sn S and SnS predominates. lf sulfidization of the ore is carried out at higher temperatures so that Sn S and SnS are produced, our process teaches that the product can then be soaked in a sulfur vapor atmosphere at a lower temperature to produce the preferred outermost coating of SnS The sulfidization reaction is carried out in the presence of a nonoxidizing or reducing atmosphere. Suitable nonoxidizing or reducing atmospheres, such as hydrogen, methane, carbon monoxide and natural gas, or inert or neutral gases, such as nitrogen or the like, may be used. The sulfidized ore is cooled in a nonoxidizing or reducing atmosphere or otherwise cooled in such a manner as to avoid reoxidation.

In this process sulfidization is a function of the amount of sulfur gas present, the period the material is exposed to the gas, and the operating temperature. The quantity of sulfur gas present need only be that amount which permits the formation of a sulfide surface coating on the ore particles so that the material will act as a sulfide in the flotation step; any additional sulfur in the gas will not harm the reaction nor will it add any significant benefit. With respect to treatment times, good conversion and subsequent flotation recovery rates have resulted in treatments ranging from about 5 minutes to about 1 hour; a typical treatment time is about 10 to 20 minutes. With respect to temperature, conversion of the tin oxides to sulfides begins at about 200 C. with the process operating to best advantage in the range from about 400 to about 600 C.

The sulfides produced as a result of the sulfidization step are first subjected to magnetic separation treatment to remove magnetic constituents, principally magnetic iron sulfide, and thereafter they are concentrated by flotation procedures.

Flotation procedures for the concentration of sulfide minerals are well known. Briefly, the flotation method of separation depends upon selective or preferential floating of one or more materials from other materials with which it, or they, are associated. Ore is usually mixed with water in the proportion of about 1 part by weight of ore to 4 or 5 parts by weight of water. Small amounts, about 0.1 to 5 pounds per ton of ore, of desired reagents are added to the pulp, each having a specific function and referred to as collectors, frothers, pH

modifiers, depressants, and activators. Collecting agents react preferentially with the surfaces of sulfide minerals in such a manner that when gas bubbles come into contact with these coated minerals, these minerals either stick to the bubbles or tend to do so. The noncoated mineral particles do not adhere to the gas bubbles. The usual gas employed to make bubbles is air. Compounds used to produce particular types of froths (called frothers) are also added to the gulps. Besides collectors and frothers, other chemicals are used to control collector reactions with particular sulfides or froth reactions or reactions among the minerals themselves. There is voluminous literature, both in patents and technical periodicals, which lists innumerable variants and combinations of chemicals.

Typical collectors are potassium or sodium alkyl xanthates and other sulfliydryl types of collectors. Potassium amyl xanthate is a common collecting agent. Another common collecting agent is marketed under the trade name Aerofloat, a thio phosphate organic. The general structural formula is:

no SH(orM) in which R is an alkyl or aryl radical and M an alkali metal or ammonium ion. Typical frothing agents are crude cresylic acid, higher alcohols, such as amyl alcohols, steam distilled pine oil and the like. Typical pH modifiers are soda ash, sodium hydroxide, lime, sulfuric acid and the like. Typical depressants are alkali cyanides, starches, sulfites of various types, zinc sulfate, chromates and the like. Typical dispersants are sodium silicates, lignin sulfates and the like. Activators are metal ions added to alter the surfaces ofa sulfide mineral. This altered surface in turn may then be coated by a collector.

After the ore, properly ground, is in suspension in water and the reagents added for flotation, gas bubbles are made by machines well known in the art in such a way that a froth phase forms on the surface of the agitate ore pulp. The froth containing the gas bubbles, which tend to preferentially stick to or otherwise sort out the sulfide minerals preferentially, generally contains the sulfide minerals of interest.

According to the present invention, sulfidization followed by certain concentration steps, results in ores that have been concentrated from 2 to times their original metal content with recoveries, in some tests in excess of 90 percent. Because the several stable tin sulfides formed during sulfidization and contained in the aqueous pulp have different flotation characteristics, progressive and selective flotation is necessary for maximum recovery. The table appearing below sets forth the qualitative flotation characteristics of tin sulfides.

TABLE I Qualitative Flotation Characteristics ofTin Sulfides lhiophosphate organic amyl xanthate Alkaline Acid Alkaline Acid SnS poor oor poor good Sn,S poor poor poor good SnS good good poor good In order to produce a tin concentrate which is acceptable to tin smelters, it is necessary that the tin concentrate contain as little iron as possible. The upper limit of iron is dependent upon the smelters ability to accept that type of ore. The smelters blend these high-iron with low-iron ores. Such low-iron ores are in short supply. When the other iron minerals are sulfidized, along with the tin-containing mineral, magnetic and nonmagnetic iron sulfides are formed. The magnetic iron sulfide, although not readily floatable, reacts in the aqueous pulp to form a significant concentration of iron ions. It has been discovered that iron ions depress tin sulfides during flotation. Therefore it is important to remove the magnetic iron sulfides prior to the tin sulfide flotation. This can be accomplished by conventional magnetic separators. The nonmagnetic iron sulfides float readily, and therefore float with the tin sulfides using xanthate in the acid pH range. These nonmagnetic iron sulfides are eliminated by a flotation step consisting of adding glue to a tin sulfide iron sulfide concentrate causing the tin sulfide to be depressed and allowing the iron sulfide to enter the froth phase, forming an iron sulfide concentrate which is either in whole or in part discarded or recycled through sulfidization or flotation or both, depending upon its tin content.

The process of beneficiating tin oxide ores according to the present invention, as illustrated in the flow sheet, proceeds generally as follows: The crude tin ore is crushed and ground and then sulfidized. Where sufficient magnetite is present, it is separated by magnetic means. sulfidization is carried out in the presence of sulfur in gaseous form under completely nonoxidizing or reducing atmospheric conditions at an elevated temperature, preferably no greater than 600 C. The sulfidized tin ore is cooled under nonoxidizing or reducing atmospheric conditions and then subjected to magnetic separation to remove any magnetic iron sulfide which may be present.

When the objective is to float tin sulfides, the sulfidized tin ore, after magnetic separation, is subjected to a first flotation treatment under alkaline conditions between about pH 7.5 to 9, preferably at about pH 8, using a thiophosphate organic as the promoter. Cyanide may be added to depress the iron minerals. The first tin concentrate, which is removed as froth, contains predominantly SnS The pulp from the first flotation treatment is then acidified to between about pH 4.5 to 5.5, preferably about pH 5, and conditioned with a xanthate. This second tin concentrate, which is removed as froth, contains most of the iron sulfide remaining in the ore along with the balance of the SnS and some Sn S and SnS. The pulp is then acidified further to between about pH 2 and 3.5, preferably about pH 2.8 for optimum recovery, and conditioned with xanthate. The froth making up this third tin concentrate contains the balance of the Sn S and SnS.

The second tin concentrate from flotation at about pH 5 is then mixed with the magnetic concentrate from the magnetic separation step and conditioned with glue. Flotation is carried out at between about pH 4.5 and 5.5, preferably about pH 5. The iron sulfide separates in the froth, leaving a tin sulfide concentrate in the pulp. Because magnetic iron sulfides do not float as well as the nonmagnetic, any residual magnetic iron sulfide remaining in this tin concentrate is extracted by further magnetic concentration. The product of this optional further magnetic concentration, if rich enough in tin, is recycled for retreatment. Otherwise, it is discarded along with the iron sulfide collected in the froth from the preceding flotation treatment. The several tin concentrates are then joined to produce a final product for smelting.

When the objective is to float iron sulfides from tin sulfides as a first step and where elemental sulfur is used as the sulfidizing agent, then xanthates are used as the promoter. The flotation is conducted in either a slightly alkaline pulp or slightly acid pulp to encourage the iron sulfides to float. Glue is added to depress any of the tin sulfides that were formed during sulfidization.

The invention is further illustrated by the following examples.

EXAMPLE I Hematite Z+270Mesl1 8.0

Ottawa Sand l50+200 Mesh 40.0 A medium-grade tln concentrate produced from Catav1 tin ore (Bolivia) by gravity concentration was sulfidized with H S gas in a fluid bed at 580-600 C. for 90 minutes. The concentrate then assayed: Sn-9.0l%, Fe (tomb-23.09%; S-l1.50%; and Fe (soluble in HCl )8.35%.

5 A sample of the mineral mixture (300 parts by weight) with the addition of 6 parts by weight of coke was sulfidized in a fluid bed vertical reaction tube by heating at 7l0-740 C. for The Ore sepalrated magneucan! The tallmgs from 90 minutes in a stream of nitrogen. The use of coke was an atthe magnetlc concentratlon were then floated at about pertempt to reduce the cassiterite to o and then sulfidize the cent solids at a pH of 7.7-8.1 (the pH varied during flotation) l0 s o with the Sulfur released from pyrite Although the bed for 5 minutes w1th 3.2 mg. of Aerofloat per liter of water in the was barely moving, a definite segregation by weight was pulp. Dowfroth was used as the frother, as needed. A tin froth served in the bed during the heating period. The fohowihg is concentratfer rich f Snszv resulted the assay of a sample of the product:

After this flotation, the pH of the pulp was adjusted with H 80, to 4.9 and enough potassium amyl xanthate added to l 5 make a concentration of 2.4 mgJl. H O. Frother was added as 2" needed. A pyritic-tin sulfide concentrate was made. The tin Fe (Total) sulfides were SnS Sn S and SnS. Time for flotation was 5 Fe (sol HCI) 25.66%;and i Sn (sol HCl) 0.35%.

The last flotation step was to adjust the tailings pulp of the 20 above step, with H SO.,, to pH 2.7. Then enough potassium The assay of this sample when compared to the assay of a samamyl xanthate was added to give a concentration of 18 mg /1 ple of the same mineral mixture sulfidized with hydrogen sul- Frother was added as needed. Time for flotation was 5 fide at 580 to 600 C. shows that the percent of acid soluble minutes. The concentrate contained SnS as the predominant n n indication of the amount of reacted is somewhat tin mineral. 2 5 lower in the sample in which sulfldization of cassiterite was at- The results were as follows. tempted by the sulfur release from pyrite.

TABLE II Separation of tin from medium grade concentrate sulphldlzed at 580-600 C.

Aero- Percent Sn Percent Fe KAX, float, Percent Step pH mgJl. mg./1. Product wt. Assay Recovery Assay Recovery 7. 09 2.77 2.04 61.93 19.0 12.92 49.30 66.20 14. 37 8.0 35.26 2.04 7.50 44.94 68.7 9.68 21.36 21. 58 8.02 3.3 35. 05 0. 73 2. 68 0. 65 1. 0 100.0 9.62 23.09 Combined tin concentrate. 22.6 37.2 87.78 11.6 11.3

No'm.KAX=p0tass1um amylxanthate. Aerofloat=thlophosphate collector.

EXAMPLE II A 60 part by weight sample of the heated mineral mixture was separated dry into magnetic and nonmagnetic portions. The nonmagnetic portion was floated at a pH value of about 5.0. The collector was 3.5 mg./l. potassium amyl xanthate (3.0 to 4.0 mg./l.). This low concentration was used in order to float the remaining iron sulfides. Any tin sulfides remaining (Sn s and SnS) could then be floated at a pH of about 2.8 with high xa lthate concentration-18 mg./l. 16 to 20 mg./l.

To show the separation of essentially nonmagnetic iron sulfides from tin sulfides, in another flotation test on sulfidized tin ores, the following product was obtained in the second step of flotation, at pH 5, under conditions shown in the previous 45 test: Sn-25.6 percent; Fe16.8 percent.

This concentrate was conditioned 5 minutes with 18 mg./ 1. (in water) potassium amyl xanthate at pH 5 with mg./1. glue (Darling Co., Chicago, Black Stripe Glue). Dowfroth was The s ns are 5 9 added as a frother, as needed. Flotation time used was 5 minutes, but flotation was very rapid, and probably less time would have sufficed. The results were: Assay Recovery G ade Reco ery Product Wt Sn Fe Sn 7: Fe

Mag. Conc. 27.9 3.21 57.42 11.1 57.0 Iron Concentrate (Froth) Sn 17.23% 23% Frmh 1 (PH 51)) H1) 373 5451 45 215 Iron Concentrate (Froth) Fe 45.73% 98% Froh 2 (PH 18) [L7 13'72 45 2 5 g UD9 1F l7 P f Bl V 30-37% 77% Residual Pulp 49.4 9.35 1.45 57.7 2.6 Cmwemme (PulP) Fe 031% 2% Feed (calc.) 2.05 27.99 100.0 100.0 Heads (calculated) Sn 25.6% Heads (calculated) Fe 16.8%

EXAMPLE I The results show that little concentration of tin has been accomplished but that 97.4 percent of the iron has been To demons rate the separation of tin from iron using pyrite separated. The tailings were carefully inspected under the as a sulfur source, a mixture of minerals, comprising highmicroscope. This inspection showed that the cassiterite in the g a cassltel'lte, pyrl hematite, n wa quartz sand was tailings was, in the main, unreacted, or at best very little prepared in the weight proportion similar to a cassiterite table 1. W

concentrate obtained from Catavi, Bolivia. This proportion The test was repeated using additional amounts of pyrite. was as follows: 5

Thirty-eight parts by weight of pyrite were added for each parts by weight of themineral mixture. The mixture, after Mineral Size heating at 7 l0-740 C. for 90 minutes was sampled and the analysis was:

Cussilcritc 200+270 Mesh 15.0 Pyrite +270 Mesh 37.0 75 Sn (1018i) 7.59%;

S 24.18%; Fe (total) 31.75%; Fe (sol HCl) 25.63%; and Sn (sol HCl 0.38%.

Magnetic and flotation test procedures were followed with this sample, similar to those described in the preceding test. The results are summarized as follows:

The results show that there was little concentration of tin but that 94.5 percent of the iron has been separated. The material in the residual pulp was observed under the microscope and, again, there were large amounts of unreacted cassiterite. The separation results shown indicate that most of the hematite and pyrite have reacted enough to become magnetic.

These tests indicate the possibility of upgrading hematitecassiterite concentrates by sulfiziding with elemental sulfur (either as elemental sulfur or derived from pyrite) and, or, hydrogen sulfide, and to form the least amount of sulfidized cassiterite. Most of the iron is recovered by magnetic separation, and the pyrite iron sulfide by flotation into the froth phase. Any sulfidized cassiterite tending to float into the froth is depressed by glue. The remainder, in the pulp, is the low iron cassiterite concentrate.

While it is well known that metal ions such as copper, lead, silver and mercury activate various sulfide minerals it is not too well known nor practiced that certain metal ions depress various minerals. 1n the course of the work leading to the present invention, it was found that manganese, iron and nickel ions in particular depress tin sulfide. In particular, the following tests were performed.

EXAMPLE IV A tin concentrate from Potosi, Bolivia was mixed with Ottawa quartz sand. The total was mixed in the proportions of parts by weight of Potosi concentrate with 40 parts by weight of sand for each flotation test. The Potosi concentrate contained about 40 percent tin. The ores were sulfidized with H 8 for 1 hour in a horizontal quartz tube, static bed. The sulfidized mixture was then floated with distilled water in the usual manner.

The base comparison of whether the metal ions are of value or a hindrance is a test repeated many times which yielded the following typical results:

pH 8.8 with Na CO Tin recovery 54.8 percent Concentrate grade 6.85 percent This test is indicative of what can be expected when the sulfidized material is floated immediately after sulfidization without any further treatment prior to flotation nor any addition of metal ions.

lf copper sulfate is added to the extent of 1 lb. per ton of ore, the following results have been obtained:

Tin recovery 81.0 percent Concentrate grade 13.5 percent tin With lead ions added in the form of lead acetate, 1 lb. per ton of ore, at a pH of 9, a tin recovery of 77 percent and a tin concentrate grade of 8.0 percent was obtained.

With manganese added in the form of manganese chloride at 1 lb. per ton of ore, at a pH of8.5 a recovery of 18.8 percent tin and a tin concentrate grade of 8.25 percent tin was obtained.

With ferrous chloride added to the extent of 1 lb. per ton of ore at a pH of 8.5, a recovery of 9.8 percent tin with a concentrate grade of 9.85 percent tin, was obtained.

The addition of nickel sulfate in place of iron chloride, to the extent of 1 lb. per ton ore yielded a tin recovery of 8.3 percent and a concentrate grade of 10.0 percent. The pH in this case was 6.2. Similarly using ferrous chloride at a pH of 6.7, the tin recovery was 16.5 percent with a concentrate grade of 15.5 percent.

The addition of antimony chloride to the extent of 1 lb. per ton of ore gave a recovery of 32.5 percent with a concentrate grade of 10.0 percent and a pH of 8.5. At a pH of 6.2 the antimony chloride addition gave a recovery of 19.5 percent and a concentrate grade of 17.2 percent.

For manganese chloride the change from a pH of 8.5 to 6.1 gave a tin recovery of 6.0 percent with a concentrate grade of 8.4 percent Sn.

The change of cobalt nitrate from a pH of 8.8 to a pH of 6.2 yielded a tin recovery of 10.4 percent and a concentrate grade of 14.0 percent.

Nickel sulfate at 1 lb. per ton of ore and a pH of 8.5 gave a recovery of 22.7 percent and a concentrate grade of 20.5 percent.

From this it can be seen that the presence of various ions can be deleterious to tin sulfide flotation. 1n particular, ferrous ion is extremely deleterious and it is precisely this ion that is present, after sulfidizing of tin ores, to the detriment of subsequent flotation.

We claim:

1. A method of beneficiating crushed and ground tin oxide ores containing iron which method comprises:

A. sulfidizing the ore by heating at elevated temperatures in the presence of a source of sulfur to produce stable tin sulfides: SnS- Sn S and SnS,

B. subjecting the sulfidized ore to magnetic separation to remove magnetic iron sulfide, and

C. subjecting the sulfidized ore from which magnetic iron sulfide has been removed to progressive and selective flotation to recover a first flotation concentrate containing predominantly SnS a second flotation concentrate containing the balance of SnS along with Sn S and SnS and a third flotation concentrate containing Sn S and SnS.

2. A method according to claim 1 further characterized in that sulfidization is carried out in the presence of reactive sulfur vapor in the absence of air at a temperature below about 600 C. to convert tin oxide predominantly to SnS 3. A method according to claim 1 further characterized in that the sulfidized ore from which magnetic iron sulfide has been removed is subjected to flotation first under alkaline conditions and then under acid conditions.

4. A method according to claim 3 further characterized in that said sulfidized ore is pulped and subjected to a first flotation treatment under alkaline conditions, between about pH 7.5 to 9 to separate a first concentrate which is predominantly SnS 5. A method according to claim 4 further characterized in that said pulped ore is conditioned with a thiophosphate organic flotation promoter.

6. A method according to claim 1 further characterized in that sulfidization is carried out in the presence of sulfur vapor in the absence of air at a temperature above about 600 C. to convert tin oxide predominantly to Sn S and SnS and thereafter the Sn S and SnS are soaked in sulfur vapor below about 600 C. to convert the same predominantly to SnS 7. A method according to claim 6 further characterized in that sulfidization is carried out by heating pyrite in the absence of air at a temperature above about 700 C. to preferentially sulfidize iron oxide in the ore.

8. A method according to claim 7 further characterized in that the sulfidized ore from which iron sulfide has been removed is subjected to flotation treatment under acid conditions between about pH 4.5 to 5.5 to float remaining iron sulfide.

9. A method according to claim 8 further characterized in that flotation of sulfidized tin oxide is depressed by the addition of glue.

10. A method according to claim 8 further characterized in that the pulp from said flotation is acidified to between about pH 2 and 3.5 to separate a concentrate which is predominantly Sn S and SnS.

11. A method according to claim 8 further characterized in that flotation of sulfidized tin oxide is depressed by the addition of metallic ions selected from the group consisting of iron, nickel, cobalt, antimony and manganese.

12 A method of beneficiating crushed and ground tin oxide ores containing iron which method comprises:

A. sulfidizing the ore by heating at elevated temperatures in the presence of a source of sulfur,

C. subjecting the sulfidized ore from which magnetic iron sulfide has been removed to progressive and selective flotation first under alkaline conditions and then under acid conditions,

1. said sulfidized ore being pulped and subjected to a first flotation treatment under alkaline conditions, between about pH 7.5 to 9 to separate a first concentrate which is predominantly SnS- and 2. the pulp from said first flotation being acidified to between about 4.5 to 5.5 and subjected to a second flotation treatment to separate a second concentrate of SnS Sn S and SnS.

13. A method according to claim 12 further characterized in that the pulp from said second flotation is further acidified to between about pH 2 and 3.5 and subjected to a third flotation treatment to separate a third concentrate which is predominantly sn s and SnS.

14. A method according to claim 12 further characterized in-that said second concentrate is pulped, conditioned with glue and subjected to a further flotation treatment at between about pH 4.5 to 5.5 to separate contaminating iron sulfide in the froth.

15. A method according to claim 14 further characterized in that the iron sulfide from the initial magnetic separation is pulped with said second concentrate before conditioning.

16. A method according to claim 14 further characterized in that the tin sulfide concentrate from said further flotation treatment is mixed with said first and third concentrates to produce a final concentrate of tin sulfides.

17. A method according to claim 14 further characterized in that the tin sulfide concentrate from said further flotation treatment is subjected to further magnetic separation to remove any residual magnetic iron sulfide.

18. A method according to claim 17 further characterized in that the iron sulfide from said further magnetic separation is recycled for further sulfidization and flotation treatment.

3 3 a A UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,642 ,464 Dated February 15 1972 Adrian C. Dorenfeld et al It is certified that error appears in the above-identified patentand that said Letters Patent are hereby corrected as shown below:

In the Abstract, line 3, "nd" should be --and--.

Column 3, line 40, "agitate" should be -agitated-.

Column 3 line 64, "good" should appear under the column entitled "Acid".

Column 6, line 16, "26.51%" should be "1 .51%".

Column 7, line 54, "base" should be basic-.

Column 9, line 27, before "4.5" --pH-should be inserted.

Signed and sealed this 27th day of June 1 972.

(email) Atbest:

EDWARD M.FLLZTGEEEH,JR- ROBERT GOTTSGHALK Attesting Officer 7 Commissioner of Patents

Claims

2. A method according to claim 1 further characterized in that sulfidization is carried out in the presence of reactive sulfur vapor in the absence of air at a temperature below about 600* C. to convert tin oxide predominantly to SnS2.
2. the pulp from said first flotation being acidified to between about 4.5 to 5.5 and subjected to a second flotation treatment to separate a second concentrate of SnS2, Sn2S3 and SnS.
3. A method according to claim 1 further characterized in that the sulfidized ore from which magnetic iron sulfide has been removed is subjected to flotation first under alkaline conditions and then under acid conditions.
4. A method according to claim 3 further characterized in that said sulfidized ore is pulped and subjected to a first flotation treatment under alkaline conditions, between about pH 7.5 to 9 to separate a first concentrate which is predominantly SnS2.
5. A method according to claim 4 further characterized in that said pulped ore is conditioned with a thiophosphate organic flotation promoter.
6. A method according to claim 1 further characterized in that sulfidization is carried out in the presence of sulfur vapor in the absence of air at a temperature above about 600* C. to convert tin oxide predominantly to Sn2S3 and SnS and thereafter the Sn2S3 and SnS are soaked in sulfur vapor below about 600* C. to convert the same predominantly to SnS2.
7. A method according to claim 6 further characterized in that sulfidization is carried out by heating pyrite in the absence of air at a temperature above about 700* C. to preferentially sulfidize iron oxide in the ore.
8. A method according to claim 7 further characterized in that the sulfidized ore from which iron sulfide has been removed is subjected to flotation treatment under acid conditions between about pH 4.5 to 5.5 to float remaining iron sulfide.
9. A method according to claim 8 further characterized in that flotation of sulfidized tin oxide is depressed by the addition of glue.
10. A method according to claim 8 further characterized in that the pulp from said flotation is acidified to between about pH 2 and 3.5 to separate a concentrate which is predominantly Sn2S3 and SnS.
11. A method according to claim 8 further characterized in that flotation of sulfidized tin oxide is depressed by the addition of metallic ions selected from the group consisting of iron, nickel, cobalt, antimony and manganese. 12 A method of beneficiating crushed and ground tin oxide ores containing iron which method comprises: A. sulfidizing the ore by heating at elevated temperatures in the presence of a source of sulfur, B. subjecting the sulfidized ore to magnetic separation to remove magnetic iron sulfide, and C. subjecting the sulfidized ore from which magnetic iron sulfide has been removed to progressive and selective flotation first under alkaline conditions and then under acid conditions,
13. A method according to claim 12 further characterized in that the pulp from said second flotation is further acidified to between about pH 2 and 3.5 and subjected to a third flotation treatment to separate a third concentrate which is predominantly Sn2S3 and SnS.
14. A method according to claim 12 further characterized in that said second concentrate is pulped, conditioned with glue and subjected to a further flotation treatment at between about pH 4.5 to 5.5 to separate contaminating iron sulfide in the froth.
15. A method according to claim 14 further characterized in that the iron sulfide from the initial magnetic separation is pulped with said second concentrate before conditioning.
16. A method according to claim 14 further characterized in that the tin sulfide concentrate from said further flotation treatment is mixed with said first and third concentrates to produce a final concentrate of tin sulfides.
17. A method according to claim 14 further characterized in that the tin sulfide concentrate from said further flotation treatment is subjected to further magnetic separation to remove any residual magnetic iron sulfide.
18. A method according to claim 17 further characterized in that the iron sulfide from said further magnetic separation is recycled for further sulfidization and flotation treatment.