US2145848A - Ore concentration by flotation - Google Patents

Description

ORE CONCENTRATION BY FLOTATION Filed Sept. 29, v1939?' B Tt ATTO R N EY Patented Feb. 7,

ORE. CONCENTRATION BY FLOTATION Be'rnard M. Garter, Montclair, N. J., assignor to General Chemical Company, New York, N. Y., a

corporation` of New York Application september 29, 1933:, serial No. 166,304l

6 Claimsl This invention relates to flotation or mineral collecting agents and to separation of minerals and concentration of ores byflotation processes. The invention is more particularly directed to flotation or mineral collecting agents comprising sulfur bearing oils derived from sludges formed in oil refining processes in which sulfuric acid is employed, and is also particularly directed to processes forV separation-of minerals and concentration of ores carried out with utilization of such sulfurfbearing oils as flotation or'mineral collecting agents.

The principal objects of the invention are directed to improvements in separation of minerals and concentration of ores by flotation processes and to provision of markedly effective sulfur bearing oils for this purpose. It is a further vaim of the invention to provide relatively concentrated and/or purified sulfur bearing flotation or mineral collecting oils having a high sulfur content substantially all of which sulfur isv in chemical combination. It is a furthehr object of the invention to provide sulfur bearing flotation or mineral collecting oils which are stable, and

por yand condensable hydrocarbon vapors, and` gases'such as sulfur dioxide, carbon dioxide, ni-

trogen and uncondensable hydrocarbons.

When sludge material, resulting from treaty ment with sulfuric acid of relatively'light hydrocarbon oil distillates containing substantial quantities of sulfur compounds, is dissociated preferably by destructive decomposition by heating to 40 densate is obtained which is a sulfur bearing oil. A sulfur oilof this type is of such nature 4,5- that it maybe treated, for example with sulfuric acid, in such a Way as to 'effect a selective separation of a large portion of certain sulfur flotation vo r mineral collecting agent constituents from other4 sulfur and non-sulfurv constituents. In accordance with the present invention it has been found that sulfur bearing oils containing said' certain sulfur constituents'and resulting from such sulfuric acid treatment possess properties rendering these oils especially suited for use as flotation or mineral collecting agents in the separation of minerals and the concen- .tration of ores by flotation processes. I'he oils so produced are stable, as a general rule higher in 60V sulfur than the initial oily condensate, and do do not deposit sulfur vor become less effective on' form a hot gas mixture containing hydrocarbon vapors and the gas mixture is cooled, for example to about normal temperature, an oily connot deposit free sulfur or become less effective on standing.

' A further appreciation of the objects and advantages of the invention maybe had from a consideration of the following description of the oils constituting the improved flotation or mineral collecting agents, of `flotation processes involving utilization of the improved flotation or making the improved flotation or mineral collecting agents. .The accompanying drawing illusmineral collecting agents. and f methods fortrated diagrammatically apparatus by which the v improved flotation or mineral collecting oils may be made.

Referring to the drawing, I 0 indicates the combustion chamber of a .furnace adapted to burn coal, coke, oil, natural gas or other fuel. Mounted in chamber I0 is a decomposing kiln or retort II of any desirable construction, for example afixed shell provided with suitable mechanism such as a screw conveyor, not-shown, to facilitate discharge of coke. A rotary retortmay also be employed if desired. Preferably an externally heated kiln adapted to substantially exclude admission of air is used. One end of kiln II communicates with a gas outlet I3, and the opposite end projects into a header ,I4 into which the solid residue of the decomposition of the acid sludgeis continuously discharged. Header I4 `empties into air-lock I5 through which cokemay be discharged Without admitting air to the kiln. Acid sludges, constituting sources of the flotation or mineral collecting oils of the invention,` are run into the kiln from supply tank I1 through a. valve-controlled pipe I8. Gas outlet I3 is connected to the lower end of a cooler or condenser 20 of any suitable construction, either air or Water cooled, and operated so as to reduce the temperature of the gas stream to substantially normal to condense the bulk of the water vapor and a major portion of condensable hydrocarbons contained in the gas. Condensate from the cooler drains into a separator .or collecting tank 2Ir through a pipe 22 having a liquid seal.

Thegases uncondensed in cooler 20, containing principally sulfur dioxide, are discharged through gas line 23, and may be used as desired, for example inthe manufacture of sulfuric acid by the contact process.

Separator 2| may be a-tank or vat large enough to permit continuous gravity separation of water 'and oil contained in the condensate discharged from condenser 20. The sulfur bearing hydrocarbonroils of the condensate rise to the top of the mass in the separator, and may be withdrawn continuously or intermittently through pipe discharging into a. collecting tank 26. Water settling to the bottom of the separator may be drawn off through pipe 2l, controlled generated in brickwork setting 3|. nRaw condensatefrom collecting tank 26 is run into the still"through pipe` 38, controlled by valve 39.

' A. Vapors generated in the still flow through line 4| HAto a condenser 43, the condensate of which drains illrrough pipes 45 and 46, into receivers 50 and The improved flotation oils of the invention may be'made in apparatus such as illustrated in the drawing and described above by operating substantially as follows.

In producing the improved otation or mineral collecting agents, acid sludges which may be employed arethose resulting from sulfuric acid treatment of light distillate oils obtained from petroleum crudes containing sulfur. The acid sludges employed in making thelotation or mineral collecting oils of the present invention are preferably sludges 'resulting from treatment with s'ulfuric'acid of light hydrocarbon oil distillates such as gasolne and kerosene, containing not less than about 0.15% sulfur, although distillates containing less sulfur may be employed if desired. Illustrative examples of distillate oils from which sludges are produced of a character suitable for use in the present invention are straight-run gasolene distillates containing about 0.15% sulfur or more, and cracked distillate aver-y aging 0.25 to 0.30% sulfur or more.

Sludge material of the type indicated and which may have for example a titratable acidity 0f 40% to 60% expressed as HzSO4 is continuously fed into kiln Il from supply tank I'I. The burners in furnace I0 are adjusted to maintain within the kiln temperatures desirably not in excess of about 750 F., as above this temperature the sulfur oils constituting the basis of the flotation or mineral collecting agents of the present invention tend to be decomposed. The preferred temperatures are about 250 F. at the sludge inlet end, and about 500 F. to 600 F. at the coke outlet end of the kiln.

The sludge, gradually passed through the retort, is relatively gradually heated through the preferred temperature range and is decomposed by the action of heat, and the free and/or combined sulfuric acid of the sludge is reduced to sulfur dioxide by the hydrogen of the hydrocarbons and/or by the carbonaceous matter contained in the sludge. The sludge material thus dissociated, as by the destructive distillation method indicated, with production of water vapor, and hydrocarbon vapors and sulfur compounds are formed. Residual coke is continuously discharged from the kiln through air-lock I5. The major part ofthe sulfur oils appear to have been evolved by the time the sludge has reached a temperature of 350 400 F.

'I'he gas resulting from the decomposition of the sludge contains principally water vapor and sulfur dioxide, substantial amounts of condensable hydrocarbons and sulfur compounds and smaller quantities of uncondensable hydrocarbons and gases such as carbon dioxide, carbon monoxide, and nitrogen. For example, one representative sludge having a titratable acidity of -about 50% expressed as H2SO4 yielded on devstantially normal temperatures.

the weight of the sludge, the balance of the retort gas comprising sulfur dioxide, carbon dioxide,

carbon monoxide, nitrogen and uncondensable hydrocarbons and Water vapor. As previously noted, according to the preferred Way for making the sulfur bearing oils, decomposition of sludges is effected in the kiln substantially in the absence of oxygen and in the absence of other extraneous gases. When so operating, the volume of gas formed of lessened and loss of sulfur oil by volatilization is decreased.

The hot gaseous and Vaporous products of decomposition of the sludge are discharged from the kiln and passed through conduit i3 into condenser 20 in which the gases are cooled to sub- Cooling may be accomplished by circulating through the condenser in indirect heat exchange relation with the retort gas mixture any suitable cooling liquid or gas. In place of the condenser illustrated in the drawing, a vertical tower having a spray head at the top for introduction of water may be employed. In such cases, the retort gas mixture is introduced into the bottom of the tower and ii'ows upwardly. intimately contacting and mingling with the downwardly directed spray of water fed in at the top of the tower. The amount of cooling water introduced is so controlled as to cool the exit gases leaving the top of the tower to about normal atmospheric temperatures.

During cooling of the retort gas mixture in the condenser 20, substantially all of the water vapor and the major portion of the condensable hydrocarbon vapors and sulfur compounds are condensed out of the gas stream. The condensate of cooler 20, containing varying proportions of water and liquid hydrocarbons and sulfur cornpounds., is drained through pipe 22 into separator 2l. In the latter, the oils' rise to the top of the liquid mass in the tank, and may be intermittently or continuously withdrawn through pipe 25 into tank 26 for collecting what may be termed a raw condensate. T he water settling to the bottom of the separator 2| may be discharged from the system through pipe 21.

The oil collecting in tank 26 is an oil containing generally from about 3 to about 22% sulfur, apparently in strong chemical combination. It will be understood the sulfur content of this condensate may vary considerably in accordance with the Icharacteristics of the initial crude oils and of the acid sludges produced on treatment of the hydrocarbon oil distillates with sulfuric acid. For example, an acid sludge formed through sulfuric acid treatment of a straight-run Agasolene yielded an oil condensate of 12% by volume of the sludge, the condensate Ianalyzing 14.8% sulfur. A cracked distillate sludge yielded 10% by volume of oil condensate having a sulfur content of 7.5%. In another instance, a cracked distillate averaging about .25 to .30% sulfur produced on treatment with sulfuric acid a sludge which, on treatment in accordance with the present method, yielded 10.8% by volume of oil condensate analyzing 20.8% sulfur. For convenience in the following discussion, crude sulfur bearing oilsl of the kind just described are referred to herein as initial sulfur oils.

Initial sulfur oils of the type described apparently contain sulfur constituents and nonsulfur constituents and are of such nature that they may be treated, for example with sulfuric acid, in such a way as to bring about a selective separation of l certain sulfur constituents from other sulfur and non-sulfur constituents. Such separation treatment, in most instances results in production of oils having substantiallyhigher sulfur content than the initial sulfur oils and containing all or almost all of the said certain sulfur constituents of the initial sulfur oils. 'The high sulfur oils resulting from such treatment for convenience may be termed refined oils, or

purified or concentrated or extracted oils. In accordance with the present invention, it has been found that these refined oils, or purified or concentrated or extracted high sulfur oils possess properties making such oils especially suited f removed. Separation of foreign matter from the initial oil may be effected by distilling the initiall oil`producing a coke or asphalt-like still residue and distillate or .condensate which may be termed; an unstabilized distillate oil. If desired, the separation treatment referred to may be applied to the oil an undesirable odor and may tend to render the refined product oil unstable. Hence, according to the more satisfactory procedure for making the refined flotation oils of the invention, it is preferred to (l) remove from the initial sulfur oil of tank 26 .the foreign. matteras coke and tars as by distillation; (2) simultaneously fractionate the initial o-il during the distillation operation (since different fractions, e. g. a light fraction'or, a heavy fraction, may besuited for ilotation'of different types o'f ores); (3) stabilize the fractions (to removemercaptans, pyridines, etc.); and then treat the stabilized oils or if desired the oils in unstabilized condition to produce theerefined' or purified or concentrated or extractedhigh sulfur notation oils.

Removal of -foreign matter from the raw condensateA of tank 26 and splitting of the condensate into two or more fractions may be done by distillation. For this purpose, oilsfrom tank 26 are run into still SILthrough line 38, l The distillation operation may be carried out in any suitable still, preferably one provided with equipment for collecting separate fractions of distillate. It will "be understood distillation of the raw condensate is principally for two purposes, first, to remove coke and tars from the oil, and second to produce preferably two fractions,'one having a relatively low boiling point range, andv another having a Y distillation may also ybe effected, though possibly less desirably, by superheated live steam, using steam at slightly above atmospheric pressure and heated to say 225-250" F.-before introduction into the oil. Vacuum distillation may be employed if desired.

Still 30 may be operated to produce a first cut including all the oils dstilling over at temperatures up to about 350 F. at normal pressure. Vapors generated within this temperature range are liqueiiedin condenser 43, and are run into receiver 50. This relatively low boiling fraction may, for example, constitute approximately 20% by weight of the raw initial sulfur oil condensate fed into still 30. When removal of these low boiling fractions from the oil in still 30 is substantially complete, the temperature is raised to distill over oils having boiling points ranging \from about 350 F. up to about 650 F. Vapors formed are condensed in cooler 43, and may be recovered in receiver 5|. This high boiling fraction may comprise for example 60-66% by weight of the raw condensate introduced into still 30. Approximately by Weight of the original raw condensate withdrawn from tank 26 may remain as a coke or asphalt residue in the still, and around 5-10% by weight of the original raw condensate may be lost in the distillation operation as uncondens'ed vapors and gases. The lowl boiling cut recovered in receiver 50 contains a slightly higher percentage of sulfur than,l the higher boiling fraction collecting in receiver 5I. If desired, all of the vapors evolved in still 30 may be condensed and collected in a single receiver instead of in two receivers as 50 and 5|. In this situation, while there is some decomposition with liberation of HzS, the condensate collected corresponds in a general way with the condensate collected in tank 2liv except vthat foreign matter, such as coke-dust and tars, has been removed.

As indicated above. the hereinafter described sulfur constituent separation treatment -may be applied directly to the raw -condensate collecting `in tank 26, or the fractions collecting in receivers 50 and 5i, or tothe condensate collecting in a single receiver used in place of receivers 50 and 5|. The oils, however, apparently contain substances such as pyridines and mercaptans which impart to the oils undesirable odors and which tend to render the oils somewhat unstable on standing. Accordingly. it is preferred to further treat vthe oils to stabilize the same and remove odors. This may be accomplished by treating the oils with a solution of caustic soda or sulfuric acid or both. When employing caustic alkali, as is preferred, tl i oil may be agitated with a 20% caustic soda solution at temperatures of about `190 F. until reaction appears complete. The reaction products are allowed to settle, and are withdrawn. The oil may thenbe washed with water to remove vtraces of alkali, and brightened as by blowing with air.v

The oils may also be stabilized Py treating with relatively low concentration su furic acid, say about equal volume, separating reaction producis, and washing the oils withwater and alkali to remove traces of acid. For this-stabilization treatment, it is preferred to use aci"d of concentration not in excess of about H2804, since acid of this or lessconcentration, while suitable for removing odor-imparting substances, does not appear t'o have appreciable eifectvon the desired sulfur compounds which should be left in the oils at this stage and recovered by the subsequent sulfur constituent separation treatment. If desired, the oils may be stabilized by using acid of greater concentration, say up to about 93.2%.

H3804 (66 B.) in which case the amount lof v50% by volume of total acid used.

stronger acid should not desirably exceed '7% by volume of the oil treated.

Treatment of the oils with either caustic alkali or sulfuric acid notably improves the odor and increases the stability of the oils. In some instances, it is desirable to subject to the oils to treatment with both caustic alkali and sulfuric acid. In this case, after subjecting the oils to the caustic soda treatment noted above, and removing the alkali extract, the oils are washed with Water to remove the alkali, and then treated with one or more Washes of equal volume of dilute sulfuric acid, for example 30% H2804. oil products may bewashed With water to remove traces of acid, and then brightened by blowing with air, or other methods.

In the case where the foreign matter is removed from the condensate of tank 26, as by distillation and collection of all the distillate in a single receiver, theA resulting oil may be stabilized as described. L

The oils stabilized, for example as mentioned above, are sulfur bearing mineral oils, light bodied, and have a relatively high sulfur content, substantially all of which is in strong chemical combination. It appears substantial amounts of thecontained sulfur is present as alkyl suldes and possibly also some disulfides and other sulfur bearing compounds. The sulfur content of the oils at this stage may vary from about 3 to about 22%, and on standing the oils do not become turbid or deposit sulfur. The oils area light straw color. The specific gravity of a representative oil is about 0.98. The viscosity 32 to 34 Saybolt at 100 F.

The Aoils in unstabilized and stabilizer condition appear to `comprise mixtures of sulfur constituents especially adapted for use as flotation or mineral collecting agents, and other less valuable sulfur and non-sulfur constituents. The ultimate refined oils, used in accordance With the invention as flotation or mineral collecting agents, are obtained by selectively separating the sought for sulfur constituents from other sulfur and non# sulfur constituents. This separation may be effected for example by treatment of unstabilized or stabilized oils with relatively strong sulfuric acid which does not appear to react to any great extent with the non-sulfur constituents but which does appear to have the property of dissolving or combining with the sought for sulfur constituents and forming an acid sludge containing such sulfur. constituents. The sought for sulfur constituents may thus be separated from the other sulfur and non-sulfur constituents.

On treatment of raw condensate or any of the fractions mentioned, in stabilized or unstabilized condition, with acid as in tank or vat 55, there is formed a sludge which contains at least `the major portion and in most cases substantially all of the desired sulfur constituents of the oil. A preferred procedure for carrying out the sulfur constituent separation treatment is as follows: The particular oil being handled is treated with sulfuric acid of concentration preferably from about to about 93.2% H2SO4 in two equal dumps, each dump of acid representing about The first dump of acid is added with agitation to the initial sulfur oil in tank or vat 55. If heat of reaction is severe, the reaction mass may be cooled, since the temperature should preferably not exceed about F. 'Ihe acid is added to the oil gradually say over a period 'of about 15 minis low, about utes or more. 'I'he reaction mass is allowed to"` The nal settle for say 30 minutes or more, after which time the acid sludge formed is withdrawn from tank 55 by gravity' through line 51 and fed into hydrolyzer 58. The acid insoluble oil from the first dump remaining in tank 55 is treated with a second dump of acid (about 50% by volume of the total acid used) in the same manner as with the first dump, allowed to settle, and the acid sludge withdrawn through line 51 and added to the sludge already in hydrolyzer 58 from the first dump. If desired, all of the acid used to treat the oil may be added thereto in one dump, although it is preferred to employ two or more dumps since this procedure brings about more `complete extraction of sulfur constituents from the oil. 'I'he sludge in hydrolyzer 58 is treated with about twice the volume'of water and is hydrolyzed, resulting in breaking up of the sludge and a separation of the sulfur oil constituents extracted out of the stabilized or unstabilized oil from the acid which was used to effect this extraction of sulfur constituents from the stabilized or unstabilized oil. During hydrolysis, the temperaturev is preferably not permitted to exceed about F. The oil formed on hydrolysis of the sludge is generally lighter than the acid which settles and forms a layer of acid in the bottom of the hydrolyzer. After settling, the acid is drawn off through line 59, and the oil discharged through pipe 60 is preferably given a light wash for example with vcaustic alkali,I or several washes withwater to neutralize traces of acid which may remain in the oil on account of imperfect separation of oil and acid in the hydroylzer. The oil may be brightened by ltering. Oils recovered in this Way are the oils referred to herein as the refined oils, or purified or concentrated or extracted oils.

The sulfuric acid used to eiect extraction of the sulfur inhibitor constituents should be of strength desirably not less than about 70% H2SO4, although it is preferred to use stronger acids. Satisfactory extraction may be obtained by utilizing 93.2% acid (66 B.) although indications are that acid of around 85% strength is more selective than the 93.2% acid. The amount of acid used to bring about separation -of sought for sulfur constituents from other sulthan stronger acids of the order of 93%.y -As to the total amountof acid used in the separation operation, it is preferred to vemploy acid in amount corresponding to not less lthan about one volume of acid to one volume of refined sulfur oil, since experience indicates about such amount of acid is desired to dissolve or extract the sought for sulfur constituents from the initial stabilized or unstabilized oil. That is, for any given volume of the refined high sulfur oil recovered, preferably not less than about an equal volume of acid was used in one or more dumps to treat the stabilized or unstabilized oil to bring about separation of the sulfur constituents from the non-sulfur constituents. In practice, the amount of acid needed may be determined by taking a sample of the oil and adding thereto successive small amounts of acid until on further addition of sulfuric acid to the sample, further solution or dissolving of the oil ceases.v

On hydrolysis of theacid sludges produced by vio . takes place.

the sulfuric acid treatment of stabilized or unstabilized oils generally 85'-90% as much oil is recovered as was removed from the stabilized or unstabilized oils on treatment with sulfuric acid, and the reiined oils recovered on hydrolysis are as a rule considerably higher in sulfur content than the unextracted stabilized or unstabilized oils. For example, on treating a heavy 1 about 19%. In another instance, on treating an I unstabilized heavy fraction,'boiling approximately within the range 35o-650 F. and containing about 2.8%V sulfur, with about one volume of 93.2% sulfuric acid,l the sulfur content of the unreacted oil after separation of the acid sludge formed was about 0.6%, and the sulfurA content of the refined extracted oil obtained on hydrolysis was about 8.9%. On treating an unstabilized light oil fraction, bdilingat temperatures less than about 350 Rand containing'about 18% sulfur,

with about one volume of 93.2% sulfuric acid,

the sulfur content of the unreacted oil after separation of the acid sludge formed was about 5.3% and the sulfur-content of the refined extracted oil obtained on hydrolysis of the acid sludge was about 23%.

.Instead of decomposing the acid sludge by heating asA describedv in connection -with the drawing, the original acid .sludge` may be subi jected to 4hydrolysis as by steaming with live steam,`for say an,hour, luntil separation of weak acid (sludge acid) and an upper` acid tar layer The weak acidV may bedrawn olf and the resulting acid tar or sludge material decomposed by heating as in av retort II. The

oily distillate may be taken in two or more cuts,

if desired, although it is preferred vto collect the oily distillate .'as in a tank 26. Duringsteaming Voi the acid sludge a lightcolored distillate may be recovered in a suitable condenser. This distillate and the' condensate collected in tank 26 may be separatelytreated as already describedto produce high sulfur reiined oils, ormay be combined and then so treated.

In accordance with the invention, refined high sulfur oils obtained as described above may be used to marked advantage as notation or mineral collecting agents for thel separation loi' minerals or the concentration of ores by flotation processes carried 4out generally in ',.accordance with the known practices. =l

While the j agents of the present invention are effective as notation or mineral collecting agents in ore concentration, in general they exhibit insuflicient frothing qualities and therefore'may be employed to best advantagein conjunction with any suitable or well-known frothing agent, e. -g. pine o il, cresylic acid, othercoal tar acids, terpineol, turpentine, etc.,

The process of thepresent invention can be carried out in any suitable apparatus, for example, those of the pneumatic type such-as the `McIntosh cell, or those where the air is incorporated with the pulp by agitation such as the Fahrenwald or Denver apparatus, or the like. The flotation agentsmay be added to the ball 'remp. \1s. of

. Zn conc. contained- "Tails coutained.1.f,-.--

or 4equivalent mill during grinding of the ore, to the conditioner, or to the notation cell.

It is of advantage insome cases, as with certain copper or lead-zinc ores, to subject the ore pulp to the action of an amount of alkali sufficient to give it an alkaline reaction before subject'ing it to flotation with the aid of the flotation agents of the present invention. AThe alkali may be caustic alkali such as caustic soda, or an alkaline salt such as soda ash, or it may be calcium oxide or hydrate.

In the differential separation of various minerals, such as lead and zinc of a lead-zinc ore', depressants and promoters known in the art such as alkali metal cyanide, zinc sulfate, copper sulfate or other salts may be used to advantage.

Diiferent fractions of the refined high sulfur oils, suchas the light and heavy fractions mentioned above may be used to advantage in treatment of dierent ores.

'I'he amount of flotation or mineral collectingv oils required to be -used in any given flotation process will vary, depending partly on the character and composition of the ore, partly whether any of the water employed is reused in the process, partly on the character of the sludge material from which the oils are derived, and partly on other conditions encountered in practice.

Thisinvention may be illustrated by the following .speciilc examples:

' AExample 1 Flotation oil used: Oil A-light fraction, stabilized with NaOH solution and 30% H2804, `66" B. 4H2804 treated, and hydrolyzed as described. e

Oreused: lead-zinc-iron-suliide ore containing Pb 1.52%, Zn 11.3%, Fe 4.8%.l

Ore initially ground in ball-mill with reagents:

NaCN 0.30# per net ton of ore treated ZnSO4.7HzO 1.0# Ninco; 0.2#

- 'Cresylic acid- 0.06#

.Pine oil. .04#

18 C.l l

following Roughsr cells Heads contained.-. Pb conc. contained- Overall recovery of total Pb and Zn of initial Lead- 90.8% in Pb conc. 4.3% in Zn conc.

0.8%"in Pb conc. 92.5% in Zn conc. i 615%'intails Example 2 regents:

NaCN 0.30# per net ton of ore treated ZnSO4.7H2O 1.0# NazCO3 2.0#

Cresylic acid- 0.05#

Ore subjected to preferential notation in mechanical machines to recover Pb and Zn. New water was used in the entire opertion.

Y Reagents used to float Pb and Zn- Overall recovery of total Pb and Zn of initial ore- Lead- 93.0% in Pb conc. 2.5% in Zn conc. 4.5% in tails Zinc- 1.4% in Pb conc. 95.7% in Zn conc. 3.0% in tails Example 3 Flotation oil used: Oil C--combined condensate collected in a single receiver used in place of receivers 50 and 5|, 66 B. HzSOl treated and hydrolyzed as described.

Ore used: lead-zinc-iron-sulde ore containing Pb 3.9%, Zn 8.85%, Fe 3.98%.

Ore subjected to preferential fiotation in mechanical machines to recover Pb and Zn. New water was used in the entireoperation.

Reagents used (in pounds per net ton of ore treated) to float Pb and Zn- Lead float Zinc float NaCN 0.4# OilC 0.198# Cresylic acid 0.10# CuSO4.5H2O- 3.0# NazCO3 1.00# NazCOa 310# Oil C 0.11# ZnSO4.7H2O... 1.5# Pine oil 0.04# pH 9.1 9.3 Temp 19 C 19 C.

Rougher cells Pb Zn Fe v Per cent Per cem Per cent Heads contained 3. 9 8.85 3.98 Ph conc. contained 64. 5 5. 0 Zn conc. contained 0.90 51.0 v'Iails contained 0.03 0. 40

Recovery of 95.7% of total lead in lead concentrates.

Recovery of 93.4% of total zinc'in zinc concentrates. f

I claim:

1. The improvement in the concentration of minerals by flotation which comprises subjecting mineral in the form of a pulp to a froth flotation operation in the presence of a relativelylightbodied, light-colored, low Viscosity sulfur oil boiling at temperatures less than about 650 F., stable with respect to sulfur deposition, substantially free of free sulfur, containing alkyl suldes, having a sulfur content not less than about 3% and formed by dissociating sludge material, resulting from sulfuric acid treatment of hydrocarbon oils obtained from sulfur containing crudes, with aid of heat at temperatures not more than about '750 F. to break up the sludge under conditions to form a hot gas mixture containing water and sulfur bearing oil vapors, cooling the mixture tov form a condensate comprising water and oil, separating Water from oil, treating the oil with sulfuric acid of concentration not less than about 70% HzSO4 and in quantity sucient to effect extraction of sulfur bearing oil constituents from said oil, separating the resulting sludge reaction product from said oil, subjecting said resulting sludge to hydrolysis to separate sulfur oil and acid, and recovering sulfur oil from the reaction product resulting from said hydrolysis.

2. The improvement in the concentration of minerals by flotation which comprises subjecting mineral in the form of a-pulp to a froth flotation operation in the presence of a relatively lightbodied, light-colored, low viscosityvsulfur oil boiling at temperatures less than about 650 F., stable with respect to sulfur deposition, substantially free of free sulfur, containing alkyl suli'ldes, having a sulfur content not less than about 3% and formed by dissociating sludge material, resulting from sulfuric acid treatment of hydrocarbon oils obtained from sulfur containing'crudes, with aid of heat at temperatures not more than about 750 F. to break up the sludge under conditions to form a hot gas mixture containing water and sulfur bearing oil vapors, cooling the-mixture to form a condensate comprising water and oil, separating water from oil, distilling the oil, recovering as condensate oil boiling at temperatures less than about 650 F., treating the oil with sulfuric acid of concentration not less than about 70%'H2SO4 and in quantity sufficient to effect extraction of sulfur bearing oil constituents from said oil, separating the resulting sludge reaction product from said oil, subjecting said resulting sludge to hydrolysis to separate sulfur oil and/.'55

acd,'and recovering sulfur oil from the reaction" product resulting from said hydrolysis.

3. The improvement in the concentration of minerals by flotation which comprises subjecting mineral in the form of a pulp to a froth flotation operation in the presence of a relatively lightbodied, light-colored, low viscosity sulfur oil boiling at temperaturesless than about 650 F., stable with respect to sulfur deposition. substantially free of free sulfur, containing'alkyl suldes, having a sulfur content not less than about 3% and formed by dissociating sludge material, resulting from sulfuric acid treatment of hydrocarbon oils obtained from sulfur containing crudes, with aid of heat at temperatures not more than about '750 F. to break up the sludge under conditions to form a hot gas mixture containing water and sulfur bearing oil vapors, cooling the mixture to form a condensate comprising water and oil, separating water from oil, distilling the oil, re-

covering as condensate oil boiling at temperatures less than about 650 F., stabilizing the oil, treating the oil with sulfuric acid of concentration. not less than about r% H2804 and in quantity suiiicient to eiect extraction of sulfur bearing oil constituents from said oil, separating the yresulting sludge reaction product from said oil, subjecting said resulting sludge to hydrolysis to separate sulfur oil and acid, and recovering sulfur oil from the reaction product resulting from said hydrolysis. v g

4. The improvement in the concentration of minerals by notation which comprises subjecting mineral in the form of a pulp to a froth flotation operation in the presence of a relatively lightbodied, light-colored, low viscosity sulfur oil boiling at temperatures less than about 650 F., stable with respect to sulfur deposition, 'substantially' free of free sulfur, containing alkyl sulfides, having a. sulfur' content not less than about 3% and formed by dissociating sludge materiahresulting from sulfuric acid treatment of hydrocarbon distillate oils containing not less than about 0.15%

, sulfur, with aid of heat at temperatures not more than about 750 F. to break up the sludge under conditions to form a hot gas mixture containing Water and sulfur bearing oil vapors, cooling the mixture to form a condensate comprising Water and oil, separating Water from oil, treating the `oil with sulfuric acid of concentration not less thanl about '70% HzSOiand in quantity sufficient to effect extraction of sulfur bearing oil constituents from said oil, separating the resulting sludge reaction product from said oil, subjecting said resulting sludge to hydrolysis to separate sulfur oil and acid, and recovering sulfur oil from the reaction product resulting from said hydrolysis.

5. The improvement in the concentration of minerals by flotation which comprises subjecting mineral in the form of a pulp to a froth flotation operation in the presence of a relatively lightbodied, light-colored, low viscosity sulfur voil boiling at temperatures not more than about 350 F.,

stable with respect to sulfur deposition, substantially free offree sulfur, containingalkyl sulfdes,

having a sulfur content not less than about 3% and formed by dissociating sludge material, resulting from sulfuric acid treatment of hydroabout 350 F., treating the fraction with sulfuric acid of concentration not less than about '70% H2SO4 and in quantity sufficient to effect extraction of sulfur bearing oil constituents from said fraction, separating the resulting sludge reaction product from said fraction, subjecting said resulting sludge to hydrolysis to separate sulfur oil and acid, and recovering ,sulfur oil from the reaction product resulting from said hydrolysis.

6. The improvement in the concentration of minerals by flotation which comprises subjecting mineral in the form of a pulp to a froth flotation operation in the presence of a relatively lightbodied, light-colored, low viscosity sulfur oil boiling substantially Within the range 350 F. to

. 650 F., stable with respect to sulfur deposition,

substantially free of free sulfur, containingalkyl sulfides, having a sulfur content not less than about 3% and. formed by dissociating sludge material, resulting from sulfuric acid treatment of hydrocarbon distillate oils'obtained from sulfur containing crudes, with aid of heat at tempera- -tures not more than about 750 F. to breakup the sludge under conditions to form a hot vgas mixture containing water and sulfur bearing oil vapors, cooling the mixture to form a condensate comprising water and oil, separating water from oil, distilling the oil,'recovering'as condensate a fraction boiling substantially within the range 350 F. to 650 F., treating the fraction with sulfuric acid of concentration not less than about 70% H2804 and in quantity sufiicient to effect extraction of sulfur bearing oil constituents from said fraction, separating 'the resulting sludge reaction product from said fraction, subjecting said resulting sludge'to hydrolysis to separate sulfur oil and acid, and recovering sulfur oil from theI reaction product resulting from said hydrolysis.

BERNARD M. CARTER.

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