US2146163A - Ore concentration by flotation - Google Patents

Description

Patented Feb. 7, v1939 ORE CONCENTRATION BY FLOTATION John Ross Tuttle, Summit, N. J., assignorto General Chemical Company, New` York, N. Y., a corporation of New York Application September 29, 1937, Serial No. 166,303

8 Claims.

This invention relates to notation or mineral collecting agents and to the separation of minerals and the concentration of ores by flotation 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 forvseparation of minerals and concentration of ores carried out with the utilization of such sulfur bearing voils as 4flotation or mineral collecting agents..

The principal objects of the invention are'directed to improvements in the separation of minerals and the concentration of `ores by flotation processes and to the provision of sulfur bearing oils for this purpose. lIt is a further aim of the invention to provide sulfur bearing notation or lmineral collecting oils having a relatively high sulfur content substantialy all of which sulfur is in strong chemical combination. It is a iuras sulfur dioxide, carbon dioxide, nitrogen and uncondensable hydrocarbons. Y

According to the present invention, it has been discovered that when sludge material, resulting from` treatment with.sulfuric acid of relatively light hydrocarbon oil distillates containing substantial quantities of sulfur compounds, is dissociated preferably by destructive decomposition by heating to form a hot gas mixture containing hydrocarbon vapors and the gas mixture is cooled, for example to about normal temperature, an oily condensate is obtained which is a sulfur bearing oil possessing properties rendering the oil esspecially suited foruse as otation or mineral collecting agents in the separation of minerals and the concentration of ores by notation processes. The oils so produced are light colored, light bodied, stable oils, high in sulfur in strong chemical combination, and do not become turbid or deposit free sulfur on standing. y

A further appreciation of the objects and advantages of the invention may be had from a consideration of thel following description oi the oils constituting the improved notation or mineral collecting agents, of flotation processes involving 1 utilization of the improved notation or mineral collecting agents, and of methods for making the improved flotation ,or mineral .collecting agents. They accompanying drawing illustrates diagrammatically apparatus by which the improved otation or mineral collecting oils may be made.

Referring to the drawing, I 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 lexample a xed shell provided with suitable mechanism such as a screw conveyor, not shown, to facilitate discharge of coke. A rotary retort may 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 sludge is continuously discharged. Header I4 empties into air-lock I through which coke may 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-con-Y trolled 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 atmospheric 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 2I throughl apipe 22 having a liquid seal.

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

Separator 2l 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 hydrocarbon oils of the condensate rise to the top of the mass in the separator, and may be withdrawn continuously or intermittently through pipe 25 discharging into a collecting tank 2,6. Water settling to the bottom of the separator may be drawn off 'through pipe 21, controlled by valve 28,

and discharged to Waste or otherwise disposed of.

The still 30, of any approved construction, may be externally heated by hot combustion gases generated in brickwork setting 3|. Raw condensate from collecting tank 26 is run into the still through pipe 38, controlled by valve 39. Vapors generated in the still flow through line 4I to a condenser 43, the condensate of which drains through pipes 45 and 46, into receivers 50 and 5I.

The improved notation oilsof 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 flotation or mineral collecting agents, acid sludges which may be employed are those resulting from sulfuric acid treatment of light distillate oils obtained from petroleum crudes containing sulfur. The .acid sludges employed in making theflotation or mineral collecting oils ofthe present invention are preferably sludges resulting from treatment with sulfuric acid of light hydrocarbon oil distillates such as gasoline and kerosene, containing not less than about 0.15% sulfur, although distillates containing less sulfur may be employed if desired. Illustrative examplesof distillate oils from which sludges are produced of a character suitable' for use in the present invention are straight-run gasoline distillates containing about 0.15% sulfur or more, and cracked distillate averaging 0.25 to 0.30% sulfur or more.

Sludge material of the type indicated and which may have for example a titratable acidity of 40% to 60% expressed as HzSO4 is Acontinuously fed into kiln Il from supply tank i1. 'l'.'he burners in furnace Il) are adjusted to maintain within the kiln 'tempertures desirably not in excess of about 750 F., as above this temperature thev sulfur oils constituting the notation 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 thekiln.

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 is 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 of the flotation or mineral collecting oils of theinvention appears to have been evolved by the time the sludge has reached a temperature drocarbon gases and water vapor.

'Ihe gas resulting from the decomposition of the sludge contains principally water vapor and sulfur dioxide, substantial amounts of condensable hydrocarbons vand 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 decomposition by destructive distillation about 28% residual coke and a retort gas which after cooling to about normal temperatures, produced about 6%v condensable oils, about 35% water, based on the weight of the sludge, the balance of the retort gas comprising sulfur dioxide, carbon dioxide, l

carbon monoxide, nitrogen, uncondensable hy- As previously noted, according to the preferred way for making the sulfur bearing oils' of the invention, decomposition of sludges is effected in the kiln substantially in the absence of oxygen and in the absence ofother extraneous gases. When so operating. the volume of gas formed is lessened an -loss of 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 substantially normal temperatures. Cooling may be accomplished by circulating through the condenser in indirect heat exchange relation with the retort gas mixture any suitable cooling liquid 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, containingvarying proportions of water and liquid hydrocarbons'and sulfur compounds, is drained through pipe 22 into separator 2|. In the latter, the oils rise to the top of the liquid mass inthe tank, and'may be intermittently or continuously withdrawn through pipe 25 into tank 26 for collecting what may be termed a raw condensate or initial sulfur oil. The 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 characteristics 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 sulfurie acid treatment of -a straight-run gasoline yielded an oil condensate of 12% by volume of the sludge, the `condensate analyzing 14.8% sulfur. A cracked distillate sludge yielded by Volume of oil condensate having a sulfur content of 7.5%. AIn 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 analyt-v ing 20.8% sulfur.

According to the invention, it has been found Ithat oils produced are sulfur bearing oils havemployed directly as flotation or mineral collecting agents in notation processes. However, the oil in this state contains appreciable quantities of foreign matter, such as coke dust and tars,

which under some circumstances may be desirably removed. Further,v the oil collecting in tank 26 comprises several low and high boiling fractions.- The raw condensate of tank 26, the raw condensate of tank 26 with foreign matter such as' coke dust and tars removed, a light fraction of the raw condensate or a heavy fraction of the raw condensate may be suited for flotation of different y marked action as flotation or mineral collecting agents in ore concentration, in general theyexhibit insulcient frothing qualities and thereforel may be employed to best advantage in conjunction With any suitable or well-known frothing agent, e. g. pine oil, cresylic acid, coal tar acids, terpineol, turpentine, etc.4 They may be also sometimes used to advantage in conjunction with other flotation agents. y

lThe process of the present invention can be carried out in any suitable apparatus, for example, those of the pneumatic type such as the Mc- Intosh cell, or those where the air is incorporated with the pulp by agitation, such as the Fahrenwald or Denver apparatus, or the like.

It is of advantage in some cases, as with certain copper ores, to subject the ore pulp to the action of an amount of alkali sufficient to give it an alkaline reaction before subjecting it to flotation with the aid of the flotation agents of the present invention. The alkaliA may be caustic `alkali such as caustic soda, or an alkaline salt such as soda ash, or it may be calcium oxide or hydrate. The flotation 'agents may be added to the ball or equivalent mill during grinding of the ore, to the conditioner, or to the flotation cell.

In the differential separation of various minerals, such as zinc blende from associated minv erals, the presence of an alkali metal cyanide, or of copper sulfate or other salts, is sometimes advanta'geous. y

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

This invention may be illustrated by the following speciflc examples:

Example 1 Oil A .08# per net ton of ore treated Ore subjected to preferentiall flotation in mechanical machines to recover Pb and Zn. The Water used in the entire operation, i. e. in grinding and in flotation, was new water, i. e. water that did not contain flotation agents previously used in the flotation process. Reagents used to float Pb and Zn-A Lead float Zinc float Cresylic acid.- .10# Oil A .20# Pine oi1,.--` .04# C11SO4.5H2O 2.0 Oil A.l .04# Na 2CO3 3.0

Pine oil .04# pH 8.7 9.2 l Temp--. 19 C. 19 C.

` Rougher cells Pb Zn Fc Percent Percent Percent Heads contained--. 4.0 9.' 4.1 Pb conc. contained. 63.8

Zn conc. contained.. l. 0 Tails contained 0.05

^ Pb conc. contained 72.

' Example 2 Flotation oil used: Oil'B-composite oil collected as a single fraction from condenser 43 and stabilized with 20% NaOH solution and 30% HzSOi as described.

lOre used: a lead-zinc-iron-sulde ore containing Pb 4.7%, Zn 7.75%, Fe 3.44%. Ore initially ground in ball mill with following reagents:

vOil B 0.104# per net ton of ore treated NacN .3o ZnSO4.7I-I2O 1.0 #1

Ore subjected to preferential flotation in mechanical machines to recover Pb and Zn. New water was used in the entire operation. Reagents used to float Pb and Zn- Lead float Zinc float Cresylic acid--- .10 #at Oil B .21# Pine oil .02 #1 CuSO4.5H2O 2.0 #r Oil B .022# NazCO: 3.0 f Pine oil .04#

pH v8.9 Temp 18 C.

Percent Percent 4. 7 7. 75

Heads contained 3 Zn conc. contained 2.8 u Tails contained 0.03

Overall recovery of total Pb and Zn of initial ore- Lead- 91.2% in Pb conc. 8.3% in Zn conc. 0.50% in tails Zinc- 1.6% in Pb conc. 93.6% in Zn conc. 4.8% in tails.

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 relatvely 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 sulfldes, 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 vheat at temperatures not more than vabout 750 F. to break up the sludge under conditions to form a hot gas mixture containing sulfur bearing oil vapors, and cooling the gas mixture to form an oily condensate boiling at temperatures less than about 650,F.

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 lighttillation operation may be carried out in any suitable still, preferably one provided with equipment for collecting separate fractions of distillate. From the above, 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 range, and another fraction having a higher boiling point range. Distillation may be effected for example by external heating of still 30.. If desired, distillation of the crude condensate may also be accomplished at temperatures lower than those hereinafter mentionedby introducing live steam directly into the oil body while externally heating the same. Distillation may also be effectedfthough possibly less desirably, by super-V heated live steam, using steam'at slightly above atmospheric pressurev and heated to say 225250 F. before introduction into the oil. Vacuum distillation may be employed if desired.

Still maybe operated to produce a first cut including all the oils distilling over at temperatures up to about 350 F. at normal pressure. Vapors. generated within this temperature range are liqueed inv condenser 43, and are run into receiver 50. This relatively low boiling fraction may for example constitute approximately 20% by weight of the raw 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 lfrom about 350 F. up to about 650 F. Vapors formed are condensed in cooler43, and may be recovered in receiver 5I. This high boiling fraction may comprise for eX- ample (iO-66% by weight of the raw condensate introduced into still 30. Approximately 10% by weightof 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 originalraw condensate may be lost inthe distillation operation as uncondensable .vapors and gases. The low boiling cut recoveredl in receiver` 50 contains a slightly higher percentagel of sulfur than the higher boiling fraction collected 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 H28, .the condensate collected corresponds in a general way with the condensate collected in tank` 26 except that foreign matter, such as coke-dust and tars, have been removed.

Any of the foregoing oils may be used as flotation or mineral collecting agents, directly as collected in tank 26 or as collected as a single frac-` tion from condenser 43, or as collected in re- Aceivers 50 or 5|. The oils, however, apparently contain substances .such as pyridines and mer captans which impart to the oils undesirable odors and which tend to render the oils somewhat unstable on standing. Accordingly, itis preferred to further treat the 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-l employing caustic alkali, as is preferred, the oil may be agitated with a 20% caustic soda solution at temperatures of about 190 F. untilreaction appears complete. The reaction products are allowed to settle, and are withdrawn. The oil may then be washed with water to remove traces 'of alkali, andbrightened as by blowing with air.

The oils may also be stabilized by treating with sulfuric acid, say about equal volume, and washed with water and alkali to remove traces of acid.l It is preferred to use acid of concentration not in excess of about 60% H2SO4, since acid of this or less'concentration does not appear to ment 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 equalvolume of dilute sulfuric acid, for example 30% HnSOi. The nal oil products may be washed 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, the resulting oil may be stabilized asf described.

The oils stabilized, for example as mentioned labove are sulfur bearing mineral oils, light bodied, possessing a characteristic odor, and have a high sulfur content, substantially all of which is in strong chemical combination. It appears substantial amounts of the contained sulfur Ais present as alkyl sulfldes and possibly also some disuldes, and other sulfur bearing compounds. The sulfur contentvaries from about 3 to about .22%. The oils on standing do not become turbid or deposit sulfur. The oils of the invention are a light straw color. The specic gravity of a representative oil is about 0.98. 'I'he viscosity is low, about 32 to 35i `Saybolt at 100 F.-

Instead of decomposing the acid sludge by heating as described in connection with the drawing, the original acid sludge may be subjected to hydrolysis as by steaming with live steam, for say an hour, until separation of weak acid (sludge acid) and an upper acid tar layer takes place. The weak acid may be drawn oi and the resulting acid tar or sludge material decomposed by heating as in a retort Il. The oily distillate may be taken in two or' more cuts if desired, although it is preferred tocollect the oily distillate as in tank 261 During steaming of the acid'sludge a light colored distillate may be recovered in a suitable condenser. This distillate andthe condensate collected in tank 26 m'ay be separately treated as already described to produce high sulfur oils,

or may be combined and then so treated.

In accordance with the invention, the sulfur bearing oils described, comprising the raw condensate of tank 26, the raw condensate of tank l26 distilled toremove foreign matter such as tars and coke, or either of the fractions recovered in receivers 50 and 5I, may be used in stabilized or unstabilized condition as flotation or mineral collecting agents, for the separation of minerals or 'the concentration of oresby flotation processes carried out generally in accordance with thev known practices. While the agents ofthe present invention show" of heat at temperatures not more than about 750 F. to break upthe sludge under conditions to form a hot gas mixture containing water and sulfur bearing oil vapors, cooling the gas mixture to form a condensate comprising Water and oil, separating Water from oil, distilling the oil, and recovering as condensate oil boiling at temperatures less than about 650 F.

3. The improvement in the concentration of 4minerals by notation which comprises subjecting mineral in the form of a pulp to a froth flotation yoperation 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 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 gas 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 l about 650 F., and stabilizing the oil.

4. The' improvement in the concentration of l 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 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 l formed by dlssociating sludge material, resulting 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 sulfur bearing oil vapors, and cooling the gas mixture to form an oily condensate boiling at temper- 'atures less than about 650 F.

5. The improvement in the concentration of minerals by flotation which comprises subjecting l mineral in the form of a pulp to a froth notation than about '750 F. to break up the sludge under conditions to form a hot gas mixture containing water andsulfur bearing oil vapors, cooling the gas mixture to form a condensate comprising Water and oil, separating Water from oil, distilling the oil, and recovering as condensate oil boiling at temperatures less than about 650 F.

6. 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 suldes, having a sulfur content not less than about 3% and formed by dissociating sludge material, resulting 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 gas '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., and treating the oil with caustic alkali to stabilize the same.

7. 'Ihe improvement in the concentration of minerals by notation which comprises subjecting mineral in theform of a pulp to a froth flotation operation in the presence of a relatively lightbodied, light-colored, low visc-osity sulfur oil boiling at temperatures not more than about 350 F., stable with respect to sulfur deposition, sub-stantially free of free sulfur, containing alkyl suldes, having a sulfur content no less than about 3% and formed by dissoclating sludge material, resulting fr-om sulfuric acid treatment of hydrocarbon distillate 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 gas mixture to form a condensate comprising water and oil, separating water from oil, distilling the oil, and recovering as condensate a fraction boiling at temperatures not more than about 350 F.

8. The improvement in the concentration of minerals by flotation which comprises subjecting mineral in the form of a pulp to a froth notation 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, containing alkyl sulfides, having a su-lfur 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 attempera-` tures 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 gas mixture to form a condensate comprising water and oil, separating Water from oil, distilling the oil, and recovering as condensate a fractionl boiling substantially Within the range 350 F. to 650 F.

JOHN ROSS TUITLE.

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