CA1289274C - Method of concentration of rebellious oxidized copper ores - Google Patents

Abstract

Abstract A method comprises preparation of a pulp, its sulphidizing and flotation. Sulphidizing of the pulp is carried out with molten sulphur at a temperature of 115-180°C and pressure 1.5-10 atm. in the presence of sodium sulphate or sodium chloride additives.

Description

~289274 The present invention relates to non-ferrous metallurgy, concerns a method of copper recovery and, more specifically, a method of concentration of rebellion oxidized copper ores.

According to mineralogical composition copper ores are divided into the following types: sulphide, mixed (oxide-sulphide) and oxide ores. Concentration of sulphide ores by conventional techniques of flotation is not accompanied with any difficulties. Oxide ând mixed ores are, a rule, complex for concentration.

By flotation of said ores a low-grade concentrate is produced. The degree of Recovery of copper and other associated valuable ore constituents, for example, silver, is not high. This is due to the presence of badly-flotative minerals such ass chrysocolla, cuprite, malachite, broshantite, etc. in oxide ores. However, as sulphide ore resources are being exhausted, concentration of oxidized ores becomes a matter of high practical importance.

Several methods of concentration of oxidized copper ores are known in the art.

US Patent No. 4,200, 455, IPC C22B 15/10 published on 29.04.80 teaches roasting of oxidized copper ore in a reducing medium at a temperature of 500-1000 C in the presence of additive of hydrochloric acid and hydrogen sulphide with subsequent leaching of coppper from theroasted ore with an ammoniacarbonate solution. This method requires high energy consumption for heating the total amount of ore to said temperature.

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rhis ~echnique involves emission OI' dust and togic gases into the atmosphere durin~ roasting, this requiring dust collection and purification of eIiluent ~,ases.
Besides, th~ use of such toxic materials as ammonia and hydrogen sulphide necessitates special safety means to be developed, this making the process more expensive.
According to another process, described in US Patent i~To. 2,989,394. IPC 75-2, published on 2ù.06.1961, oxidized copper ore is mixed with iron sulphides (pyrite and pyrrho-tite) and chlorides oE alkali- and alkali-earth metals.
~hen, the mixture is roasted at a tem era ture OI 500-8ùo~c in a neutral or reduciné; medium ~n the presence of water vapour. 'rhe object o~ such treatment is to con~7ert oxidized copper constituents to sulphides wk~oh are readily reco-vered by ioam ilotation. As the previously mentioned techni-que, this method also involves high energy consumption and is accompanied with toxic gas and dust emission. The extrac-tion oi copper and silver in the concentrate produced by such a method i9 82~ and 7270 respectively.
It i6 kno~n that copper can be recovered irom its oxidized ores through leaching by alkali and acid solu-tions. So, US Patent No 3,985,855, IPC COlG3/00, published on 12.11.1976, te~ches to use a 25Sg solution oi sodium hydroxide as 8 leaching agenb. The process is carried out at a tem~erature oi 60-1()0-C in the presence OI an additi-ve OI a silicate material, taken in an amount of 50-10a%
by mass oi the initial ore.
Then, a copper-containing solution is separated irom the solld phase b~ iiltration. However, this method is ap-" 1289274 plicable only ~or copper extraction. Treatment oi~ oxidizedores containing copper and silver is not eIiicient ior silver extraction since silver compound 9 under such con-ditions are not leached out.
~ he use o~ sodium hydroxide is also undesirable as it is ~ery expensive, toxic and difiicult to handle~
Well kno~n is a method OI bene~ication OI rebellious oxi dized copper ores, which includes leaching OI copp~r with hydrochloric acid, preoipitation of copper Irom its solution, addition Or iron chips or sponge iron into the pulp and ~lotation o~ the metal copper deposition thereby obtained.
~ here are known other methods OI concentratine oxidi-zed ores ~ith the use o~ acids for leaching. According to US Patent No. 4,0008,072 IPC C22B 15/08, published on 15.02.1977, a pulp, obtained by leachin~ oxidized copper ore ~ith sulphuric acid, is treated with ionized sulphides, preierably hydrogen sulphide. The copper sulphides thus obtained are then recovered by flotation.
US Patent No 3,728,43~, IPC GOlG, 3/12, published on 17.04.1973, discloses a method of concentration o~
oxidized and mixed oxide-sulphide ores, wherein leachin~
o~ copper and its precipitation in the iorm o~ sulphides occur simulta~eou~lg. According to this method crushed ore is mixed ~ith l~ater, elementary- sulphur, an acid, and ~ater-soluble sulphites (bisulphites).
!he pulp obtained by such technique is heated.
Leaching copper ~ith its simultaneous sulphidizing is carried out at a temperature oi 25~ C ~or 20 ~inutes.

~. . ~ . . . . - ~

Then the pulp is cooled and delivered to flotation. RecoverY
of copper in flotation concentrate provided by this method is 75-85%.

The use of acid leaching for treatment of oxidized copper ores of high calcium content and magnium carbonates is not expedient as it results in high consumption of the acid which reacts with said carbonates and thereby is irretrievably lost There are also other disadvantage in using acids; as they are highly corrosive the problem of protecting equipment against destructive action of acids raises and the environment is polluted with dump waste product, flotation tailings and acid-containing waste water.

All the hereinbefore-mentioned prior art methods of concentration of ores fail to provide for the most efficient recovery of copper and accociated valuable components from them. Besides, some of these methods involve high energy consumption and environment pollution, other demand utilization of acids and alkalis which are harmful for the working personnel and bring about additional difficulties caused by separation of solid and liquid phases and neutralization of waste products.

The object of the present invention is to provide such a method of concentration of rebellious oxidized copper ores, which would provide for the most efficient recovery of copper in concentrate with simultaneous recovery of silver from said ores, decrease environment pollution and simplify the process.

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The object oi the present invention is accomplished by the development of a method of concentration oi rebel-lious oxidized copper ores, ~hich comprises preparation o~ a pulp, sulphidizing the pulp obtained b~ elementary sulphur, ilotation oi the pulp to produce a sulphide con-centrate, the a¢cording to the invention bein~ characteri-zed in that sulphidizing o~ the pulp is carried out ~ith molten sulphur.
~ he method o~ the invention permits increasing copper recovery in the concentrate up to 92.6~. Besides, the method permits extracting silver in the same process with a high recovery oi up to 9~.2~. Further more, the method o~ the invention permits considerable reduction o~ harmful emis-sions i~to the environment. The method oi the invention also permits simpliiication of the production process through obviation o~ the ore leaching stage and the stage o~ converting copper irom the ore into a solution.
It is e~pedient ~or sulphidizing a pulp to use a mass ratio oi elementar~ sulphur to oxidized copper equal to 0!2-1.551. Such a quantity is suificient ~or an e~iicient sulphidisation reaction. It is preierable to carry out pulp sulphidizing at a temperature irom 115 to 180C and pres~ure irom 1.5 to 1V atm. Under su¢h conditions sulphur melts and eiiicie~tly reacts with oxidized copper in the ore as well as ~Lth ~ther valuable associated compone~ts, ior exa~ple, silver.
It is advisable to sulphidize pulp in the presence of sodium sulphate or a mineral containing sodium sulphate, ior example, mirabilite. This promotes an additional in-crease o~ copper recovery up to 98.6~. It is desirable to maintain a mass ratio o~ sodium sulphate or mirabilite to elementary sulphur corresponding to 3-7 parts by mass of sodium sulphate bein~ ~aken ~or one part by mass of elemen-tary sulphur.
Besides said additions o~ sodium sulphate and mira-bilite, pulp can be sulphidized in the presence of sodium chloride or a calcium chlo~ide taken in a mass ratio to sulphur equal to 0.7-3:1. The additions oi said meterials oan increase copper recovery by 2-5~ and that o~ silver by 3-7~
Ait~r sulphidizing the pulp is treated by ilotation to obtain a sulphi~e concentrate ~rom ~hich copper, silver and other valuable components are extracted by metallurgical treatment.
It is advisable to return a part of sulphide concent-rate in the amount o~ 1.5-3.0'~ by mass as related to the initial oxidized ore back to the preparation stage. This promotes a decrease in the consumption o~ elementary sulphur used ~or sulphidizin3 by as much as 1.5-3 times.
These and other advantages oi the invention will be more apparent ~rom a detailed description oi the method.
An--oxidized complex copper ore i9 crushed to 0.74 mm size. Then a rraction containin~ said size in the amount oi 5Q-1~Q~ is soreened, mixed with water and a pulp is prepared ~ith a ratio o~ solid and liquid phase~ (S:L) equal to 1:0.5-3Ø

~2892~4 Then elementary sulphur is added to the pulp thus ob-tained in the amount corresponding to the mass ratio of sulphur to oxidized copper equal to 0.2-1.5:1, that is for 1 part by mass oi o~idized copper 0.2-1.5 part by mass o~ sulphur should be taken. Then, according to the invention, the pulp is sulphidized with molten sulphur.
One o~ simple and available ways of keepiny sulphur in the molten state is heating the pulp to a temperature ~ithin the range ~rom 115 to 180-C in an air-tight vessel, ior example in an autoolave. During heating the pulp to said temperature the pressure in the vessel inareases to a value within the range oi rrom 1.5 to 10 atm. Under such conditions sulphidizin~ is carried out for 2~-120 minutes. At said temperature the elementary sulphur melts and reacts with oxidized copper and silver compounds being in a solid phase. The process results in the highest yield Or copper and silver sulphides, so that their recovery in ilotation is increased up to 90~ and more.
It is desirable to periorm sulphidizing at a tempera-ture oi 115-180-C becau~e a temperature lower than 115C
would not be suiiicient ior melting the sulphur and the reaction oi the copper ~ith the sulphur would not be ei-~icient, whereas a temperature over 180-C does not in-crease the yield of copper and silver sulphides but results in extra energy consumption.
Said quantit~ oi sulphus uaed ior sulphidizing is so deiined because a ~uantity oi le~s than 0,2 part b~
mass is not enough to convert all copper ~rom the ore into sulphides, whereas a quantity over said upper limit, i.e.
1.5 part by mass, does not increase sulphide yield, but results in unreasonably high sulphur consumption.
~ he duration of sulphidizinæ as stated above is 20-120 minutes. This duration is so deiined -because during a period shorter than 20 minutes sulphides are not obtained with a high yield whereas sulphidizing for a period longer than 120 minutes does not increase the sulphide yield but prolongs the process, and this is not desirable.
Thus, according to the invention, sulphidiziLg of the pulp is carried out with elementary sulphur at a temperature of an ore pulp oi 115-180-C, wherein sulphur is in molten state and copper is in the solid phase but not in dissolved state as in the methods kno~n in the art.
The prior art methods envisage obligatory leaching oi ore with an acid or an alkali to convert copper to a solution and only aiter that copper in its dissolved state i9 subaected to sulphidizing.
In the present method sulphides are produced through the reaction of molten sulphur directly with copper present in the solid phase but not in solution. Such a way of pulp sulphidizing permits one to obtain an unexpected e~iect oi a higher copper sulphide yield. This, in its turn, iavourably tells on copper ~ulphide recovery in ilota-tion concentrate, which has considerably increased to 9 and even more. Beside~, there is also another unexpected eiiect, that-is, high recovery oi silver-, while in the _9 _ methods known in the prior art, silver reoovery was rather low or silver was not recovered at all.
The method oi the inventio~ of concentration o~ oxidi-zed copper ores rules out the operation of leaching copper from ore and thereby simplifies the production process.
A~ter sulDhidizin~, the pulp ¢ontaining copper and silver sulphides is cooled to an ambient temperature (1~-30-C) and subJected to ~oam flotation, which i9 ac-complished with the utilization of a conventional col-lector reagent (butyl xanthate) and a ~rothing reagent (a mixture o~ mono- and dihydric alcohols oi the thioran and dioxane alcohols). Recovery of copper in ilotation concentrate amounts to 92.6~. We have ~ound that by the prese~t method a suiiiciently ~ull recover of silver is obtained, amounting to 9~
~ uring flotation there is not necessity to use rea-gents regulatin~ pH-medium, what simpliries the ilotation process. ~his is due to the ract that the pulp a~ter sulphi-dizing has a pH36-7 what corresponds to the value required ior eiiicient ~lotation and thereiore the use o~ additional reagen-ts-regulators o~ the medium pH is not necessary.
It is advisable to sulphidize the pulp in the presence o~ sodium sulphate or a- mineral containing sodium sulphate, ior example~ mirabilite, ~hose composition is Na2S04 10 ~ 0.
Said additive permits a ~urther 4-6~ increase in the reaovery oi copper and silver.
It is advisable to keep the mass ratio Or sodium sulphate or miraoilite to elementary sulphur such that ,, 12~39;~74 ~or 1 part by mass o~ elementary sulphur 3-7 parts by mass of sodium sulphate would be taken. Said additive improves the eificienc~ of the reaction oi copper and silver with elementary sulphur and thereby promotes ior increasing the copper- and silver sulphide yield. When sodium sulphate or mirabilite (on conversion to sodium sulphate) is added in an amount oi less than 3 parts by mass, additional yield of said sulphide~ does not occur, 90 that its addition in an amount oi more than 7 parts by mass does not ~urther increase said sulphide yield.
Sulphidizing the pulp may be carried out in the presence oi sodium or calcium chlorides. The addition oi said chlorides also permits further increase in the reco-very oi copper and silver sulphide~. ~he advisable consump-tion oi said materials is irom 0.7 to 3 parts by mass per part by ma~s oi elementary sulphur.
I~ sodium or calcium chlorides are added in an amount less than 0.7 part by mass an sdditional increase oi sulphi-de recovery doe 9 not occur.
Addition oi said chlorides in an amount oi more than 3 parts by mass does not iurther increase sulphide recovery but only unreasonably enlarges the consumption o~ said agents. Introduction oi sodium chloride into the pulp increases copper and silver recovery by 5-7% each and introduction oi calcium chloride increases same by 2-3~.
It is preierable to use sodium chloride irom said mate-rials due to its availability, lo~ cost and ei~icient action o~ the process.

~289274 It is advisable to return a portion o~ the sulphide concentrate thus produced to the initial pulp in an amount o~ 1.5-3.0~ to the total mass o~ the ore treated.
Such an approach permits one to reduce sulphur consumption without deterioratin3 sulphidization and flotation results.
~his is provided by the iact that unreacted sulphur re-maining in the concentrate in the rorm of Yine particles can participate in the sulphidization reaction along with sulphur introduced into the initial pulp. Said am~unt o~
sulphide concentrate returned to the stage o~ pulp prepa-ration i9 determined b~ the presence o~ unreacted sulphur therein. An the amount oi reused concentrate less than 1.5 by mass does not provide ~or signi~icant decrease oi sulphur consumption, whereas its amount o~ more than 3 by mass ~hile providi~g ~or its additional savin~ in-creases the volume oi materials, which is not desirable.
~ hus, return of the sulphide concentrate in said amounts to the stage of ore pulp preparation permits 1.5-~times reduction o~ elementary su~phur consumption, re~ulting in it 9 saving.
The preierred embodiment of the present invention is described below.
A rebellious oxidized copper ore is crushed to the particle sizeles~ than 0.74 mm in an amount o~ 7~. The crushed ore is mixed with water in a mass ratio o~ solid and liquid phases S:L.1:0.5, then elementary sulphur is introduced into the obtained pulp in a mass ratio to the oxidized copper equal to 0.5:1 and then sodium sulphate `- ~289~74 is added therein in a ratio of 7 parts by mass to 1 part by mass of elementary sulfur. Then the pulp is charged into an air-tight tank, for example, an autoclave, and heated. The process is carried out at temperature of 160 c and pressure of 6 atm. Under such conditions the sulphur melts and efficiently reacts with oxidized copper ore and associated valuable components. The products of the sulphidization reaction, viz., copper and silver, are recovered by foam flotation. To this end, after sulphidizing the pulp having pH=6.4 is cooled to 25 C, then a collector (butzl exanthate), a frothing reagent (a mixture of mono- and dihydric thioran and dioxane alcohols) are introduced therein and the pulp is subjected to flotation.

A part of the concentrate produced in the amount of 1.5~ by mass related to the ore quantity is returned back to the stage of the initial pulp preparation and sulphidizing of new portions of the ore is carried out in the presence of this concentrate.

Copper recovery from the ore is 98.6%, that of silver is 975~.

The method of the invention has commercial advantages over the methods known in the art.

1. It permits to efficiently solve the problem of processing rebellious oxidized copper ores and surpasses in its technical and economic characteristics all the known method intended for the purpose 2. The important advantage of the present invention is an increased copper recovery. If ores contain silver, gold and platinum, these metal can be adequately recovered as well.

3. The present invention simplifies the concentration process due to obviation of leaching, which usually involves .

~89274 additional problems associated with separation of solid and liquid phases , protection of the equipment against corrosive action of acids, subsequent recovery or neutralizing of the leaching agent, etc.

4. The present invention promotes environment pollution control. The implementation of the method is not accompanied with the gas emission, and waste product (flotation tailings, waste water) do not contain acids and alkalis, and, therefore, do not create additional ecological problems.

5. The present invention can be readily used in commercial production as it does not require any special equipment. The method may be successfully used in any heated air-tight vessel, for example in an autoclave.

6. The copper-sulphide concentrate produced by this method can be efficiently processed in the copper-smelting production by the same method which is usually used for the concentrate recovered from the sulphide ores If a concentration plant is located close to a copper-smelting plant, the possibility of obtaining high economic profits is apparent.

7. The subject invention may be efficiently used for processing of copper plant intermediate and waste products, containing oxidized copper compounds: dust, cinder, slimes, etc.

lZ89274 To make the present invention more apparent, illustra-tive exa~ples o~ the embodiment oi the method ~or concent-ration oi oxidized copper ores are gi~en below.
Example 1 ~ hd initial oxidized rebellious copper ore cont~ned 1.2,~
copper and 1~.4 ~ per ton of silver, includi~g 0.93~ copper present in the com~osition oi oxidized minerals (chrysocol-las, malachites, broshantites) and 0.39% copper in the ~orm oi sulphides. Sai~ ore was crushed ~o particle size o~
less than 0.74 mm (7~0 of particles). ~he ground ore was mixed with ~ater in a mass ratio S:L equal to 1 :1.5.
Elementary sulphur was added to the pulp thus produced in the mass r2tio to the oxidized copper oi 0.2-1.5:1.
rhe pulp was charged into a~ autoclave o~ 1 litre capacity, equipped with a mixer, and heated to 1~0C.
As the temperature increased the pressure in the autocla~e also increased and amounted to 6 atm. ~he pulp lasted sulphidizing 60 minutes. Under said conditions the sulphur melted and reacted with the o~idized copper irom the ore.
Thereby copper sulphides, mainly covellite, as ~ell as sil~er sulphides were produced.
Then the pulp, which by the end oi the sulphidizing process had pH.6-7, ~as cooled to 25-C and directed to ~lotation. In ilotation butyl xanthate was used as a collector and a mi~ture oi mono- and dih~dric thioran and dio~ane alcohols was used as a irothing rea~ent.
The characteristics o~ copper and silver recovery in concentrate depending on the quantit~ oi sulphur used are shown in Table 1.

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Table 1 . .
Amount of elementary sulphur, kg O.2 05 0.751 1~5 Copper recovery in concentrate, ~ 74 9 84.3 91-5 91.7 91.8 Silver recovery in concentrate, ~ 72.~ 82.7 90.09~.1 9~.2 .
~xample 2 The same ore as in Example 1 was used. The ~rocess ~as carried out as described in Example 1, exceDt that pulp sulphidizin, ~as accomplished with temperature varyin~
vithin the interval oi 115-18~C and pressure within the ran~e oi 1.5-10 atm. Sulphur was added in the amount o~ 0.75 kg per kg o~ the oxidized copper ore. The carac-teristics oi copper and silver recovery in concentrate are shown in Table 2.
rable 2 :
Temperature o~
sulphidizin~,-C 115 14~ 160 180 Pressure in autoclave~ atm. 1.5 4 6 10 Copper recovery in concentrate,~ 81.5 87.2 91-5 ~2.6 .. . . ... . _ . .
Silver recovery in concentrate,~ 80.8 86.0 90.0 9~.1 Example ~
~ he ore and conditions o~ concentration were -the same as in Example 1, except that so~ium sulphate was introduced in the pulp in a mass ratio to elementary sulphur equal to 3-7:1, or natural mineral (mirabilite) oi the compo-sition Na2S04-10H20 was adiied therein in the amount as con-verted to sodium sulphate and related to sulphur, according to the same ratio 3-7:1. Elementary sulphur in this case was added in the amount accordin~ ~o the ratio ~.2:1.
The data characterizin~ recovery o~ copper in flotation concentrate within said alteration range of sodium sulphate or mirabilite consumption are shown in ~able 3.
~able 3 .
Sodium .sulphite consumption in sulphidizing, kg 3:I 5 I 7 I
-Copper reco~ery in concentrate, when sodium sulphate was used, ~ 92.I 97.5 98.6 _ . .
Gopper recovery in concentrate, .~hen natural mineral (mira-bilite) was use,~0 91-3 96-3 '7-5 Exa~ple 4 The method of ore concrentration was the same as in Example 1, except that sodium chloride was added to the pulp in the amount of 0.7:3.0 kg per kg o~.the sulphur charged. Sulphur aonsumption in this case was 0.75 k3/kg.
The data o~tained are shown ln Table 4.

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Table 4 . _ _ . .. _ . .. _ . . . . _ Sodium chloride cons~mption in sulphidizin~, kg 0.7 1.5 3-_ _ . . _ . _ Copper re cove ry in concentrate, ~ 95.6 97.1 97.8 Silver recovery in concentrate, ~0 94.1 96.6 -~6.8 . _ _ _ . _ .
3xample 5 The ore used and the conditions of concentration were the same as described in Example 4 -~ith ~he onl~ difference that instead of sodium chloride be~ore sulphidizing calcium chloride was added to the pulp in an amount oi 0.7-3.0kg per kg of the sulphur charged.
~ he data obtained are sho~n in Table 5.
rable 5 ~ _ _ .
Calcium chloride consumption in sulphidizing, kg 0.7 1.5 ~.0 _.~ . _ _ . .
Copper recovery in concentrate, % ~2.7 94-5 94-7 Silver recovery in concentrate,~ 92.1 92.8 9~.0 Example 6 The initial ore contained 1.22%.aopper including copper in the ~orm oi o~idized minerals (chrysocollas, malachites, azurites) in the amount oi 1.1~. The ore was .

concentrated u~der the conditions described in Example 1 with S:L-1:0.5 and the quantity of sul?hur added was equal to 0.75:L. Copper recovery in the concentrate .Jas 85.0~. A portion of copper-sulphide concentrate in the amount of 1.5-3.57~ to the mass of the initial ore ~as returned back ior the preparation oi a new portion of the pulp. In this case the amount o~ sulphur used eor sulphidizin3 ~as decreased, as this reduction was balanced ~ith sulphur present in the concentrate. rhe data charac-terizing the ore concentration with sulphur consumption of O.2:l dependinæ on the quantit~ o~ recovered concentrate used ln sulphidiæin~ are shown in ~able 7 r~ble 6 ~mount of recovered concentrate, % by mass 1-5 2.5 3 _ . _ Copper recovery in concentrate, ~o 74'7 36.5 89.8 . .

Claims (8)

1. A method of concentration of rebellious oxidized copper ores, comprising preparation of a pulp, sulphidizing the pulp with molten sulphur, flotation of the pulp, to obtain a copper-sulphide concentrate.

2. A method as claimed in Claim 1, in which pulp sulphidizing is carried out with a mass ratio of sulphur to oxidized copper equal to 0.2-1.5:1.

3. A method as claimed in Claim 1, in which pulp sulphi-dizing is carried out at a temperature of 115-180°C.

4. A method as claimed in Claim 1, in which pulp sulphidizing is carried out at a pressure within the range of 1.5 to 10 atm.

5. A method as claimed in Claim 1, in which pulp sulphidizing is carried out in the presence of an additive selected from the group consisting of sodium sulphate, natural mineral mirabilite, sodium chloride, calcium chloride.

6. A method as claimed in Claim 5, in which the mass ratio of sodium sulphate to sulphur is 3-7:1.

7. A method as claimed in Claim 5, in which the mass ratio of sodium chloride or calcium chloride to sulphur is 0.7-3:1.

8. A method as claimed in Claim 1, in which a portion of the concentrate obtained in an amount of 1.5-3% to the weight of the initial oxidized ore is used for the preparation of the initial pulp.