DE2255977B2 - Process for refining metallic copper - Google Patents

Description

The invention relates to a method of refining copper and, more particularly, to refining of copper precipitated from solution. The invention particularly relates to fire refining of metallic copper precipitates.

Cement copper, d. H. Copper deposited on metallic iron from acid process solutions is separated from the solution and can be treated by magnetic separation and / or sieving to extract enriched cement copper. Cement copper, whether it is now enriched or not, has hitherto been viewed as an intermediate product, either recycled into smelting processes becomes or in small amounts to copper electrolytes in electro-refining operalions has been given. However, the use of cement copper as an intermediate product is a burden Smelting or electro-refining capacity with no corresponding benefits.

Metallic powdery copper precipitates can also be obtained by hydrogen reduction of copper-containing solutions at 24.6 kgcm ² and 200.degree. These powders are generally finely divided and contain up to 711 about 0.1 ", 1 sulfur and 0.01" 0 iron.

Also in> <Material! Thandbueh non-ferrous metals, · ... 1940. YOI-Verlag GmbH, Berlin, Ό 1. p. 1 his 3. the fire limitation described north. Here is however, a purge gas treatment at sub-atmospheric pressure and a subsequent process stage under further reduced pressure is not provided. Therefore, the achieved Raffmalionserüchnisse not yet completely satisfied.

It has now been found that cement copper coats through the surface of the iron and that the cement can be pyrorefined in a special two-stage, sub-atmospheric reaction to a complete standstill. When the particle size of the metallic iron used to precipitate the copper can be deoxidized and cast by copper. 5 decreases, the iron content of the cement also decreases. The object of the invention is therefore a method from copper. If coarse metallic iron particles are used for the fire-refining of metallic copper, for the precipitation of copper, then which is up to 5 ⁰ O iron, up to 10 oxygen, until the cement copper can by magnetic Abtrenru 1 ⁰ Zo sulfur and at least one Volatile dilution and / or sieving are treated in order to enrich the impurity, namely arsenic, bismuth, lead, selenium, copper, so that it contains less than say tellurium, tin or zinc, with the me- 3 "o iron and contains more than about 90 ⁰ Zo copper-metallic copper in a free oxygen included- Thus, according to an advantageous Ausführungsden atmosphere melts the iron to comparable of the present invention the cement copper slag and to form a copper bath which encryption initial by magnetic separation and / or contains impurities, the oxygen being treated at least 15 sieves in order to obtain an enriched cement in excess of the sulfur content, copper n.

without a separate copper (I) -oxyd-phase overall leather any metallic copper precipitate is formed and the slag from the copper bath to about 5 ° / o iron, up to about 1 ⁰ Zo sulfur, up separated, the is characterized in that to about 10 ⁰ O oxygen, up to about 0.1 ⁰ Zo arsenic, a cleaning or flushing gas, the free acid 20 up to about 0.1 ⁰ O bismuth, up to about 0, 1 ⁰ Zo lead, up to ftoff can contain, through the copper bath, to about 0.01 ° o selenium, up to about 0.01 ⁰ zo tellurium, up to about 0.1 ° 0 tin and holds up to about 0.1 «0 zinc below 0.01 at until the sulfur content holds less, according to the method of the present invention, passing through the cleaning invention can be treated ^{as 0.001 0 zo.} As already to the Aus-Ibzw. Purging gas is terminated, the pressure is brought above the copper pressure, the cement-copper bath can advantageously be lowered to less than 0.002 atm in order to volatilize the copper-enriched impurities by magnetic separation and sieving. Such an enriched Zeferbath is deoxidized and the copper is poured. Mement copper can contain up to about 3 ° 0 iron, up to about Thus metallic copper, which contains up to about 1% sulfur, up to about 10 ° .o oxygen, up to 5 ° Ό iron, up to about 10 ° Zo oxygen, until /_; about 30 about 0.1 ⁰ O arsenic, up to about 0.1 ° 0 bismuth, up to I ⁰ Ii sulfur and at least one volatile impurities about 0.1% lead, up to about 0.01% selenium, up to cleaning, such as arsenic, bismuth, lead, selenium, tellurium, about 0.01 ° 0 tellurium, up to about 0.1 ⁰ zo tin and up to tin and zinc, contain up to 0.1% zinc after any preliminary. Copper powder that has been melted processing treatment in a free oxygen by hydrogen precipitation from process solutions containing atmosphere to 35 and the up to 0.5 ° 0 sulfur to slag the iron, and a copper bath to 0.01% iron and arsenic. Bismuth, lead, selenium. Tellurium, which contains sulfur and oxygen, with tin and zinc containing the oxygen content at least in excess within the specified ranges, can likewise be treated by the process in which the sulfur content is present, without a separate present invention being treated. Herein copper (l) oxide phase and at least one additional 4 ° are compositions of the solid and liquid volatile impurities from the group arsenic, wis- phases expressed on a weight basis, if nothing dares. Lead, selenium. Tellurium, tin and zinc is formed. other is indicated. Gaseous composition- After removing the slag on the copper bath, tongues are expressed on a volume basis,
If a cleaning gas is passed through the copper bath, which If the metallic copper precipitate can contain more free oxygen, while 45 contains more than about 2% oxygen, then the Zedas bath is kept at subatmospheric pressures below cement copper during the melting with a wa 0.001 atmosphere Treated to the sulfur reducing agent in order to reduce the oxygen content rapidly to less than about 0.001 ⁰ O to reduce the formation of an immiscible low. At this point, the single-phase copper (I) oxide phase contains to avoid which copper bath is at least 0.1% acidic diff. The highly corrosive passage of the cleaning gas through the refractory furnace components is ended, and the sulfur content of the copper bath is reduced to less slag in order to reduce copper losses to the iron-containing bath. The copper ^{precipitate, when it has been depressed about 0.001 0} O, and the bath, whether or not it is enriched, is advantageously subjected to subatmospheric pressures of less than about 0.0002 atmospheres with a carbon reducing agent to mix with To carry out refining the amount of carbonaceous reef by at least reducing an impurity such as arsenic with the iron and sulfur content. Bismuth. Lead. Selenium, the copper deposit is related. Tellurium. Tin and zinc are volatilized from the bath, so that the final oxygen content of the copper bath is then deoxidized. Before pouring, at least in excess, after melting, the copper bath can be treated, if it has a sulfur content of 60 cl and is less than one The carbon-containing Reduk-Wic has already been expressed, can be either liquid or solid. The cement copper is made up by filling copper from the amount of acidic solutions on metallic iron added to the metallic copper precipitate If the iron used as the precipitating agent depends on the iron and oxygen content of the copper, it may be lumpy or massive , that this

carbonaceous reducing agents, the sulfur, and the iron are effective to give a sulked copper with an oxygen content of below about 1.5 ⁰ zo. In most cases the amount of carbonaceous reducing agent added to the copper precipitate will be between about 0.5 and 5% based on the weight of the cement copper to ensure that the oxygen content of the molten copper is below about

Contains oxygen, is passed through the bath to reduce the sulfur content of the bath to less than about 0.001 »/ Ό advantageously less than about 0.0005 ^u ι ,. to humiliate. The desulphurisation takes place very quickly at sub-atmospheric pressures, but the speed of the desulphurisation is surprisingly increased by passing a cleaning gas through the melt, while the melt is contained at sub-atmospheric pressures.

1.5 per cent lying ». The oxygen content can naturally be io th. It can be assumed that the B! Tigregulated are by, in an atmosphere, the inert gas flowing through the melt; is melted, which compared to the copper (l) - overcome the high energies, which are lost to it is reducing. Are high to form sulfur dioxide bubble germs Copper deposits generally have one

and a big difference in chemical potential

considerable proportion of particles finer than 15 tial between the sulfur dioxide in the bubbles and

-0.044 mm and which can cause dust formation and metal loss when heated. Finely distributed copper precipitates can also introduce material handling problems and the meltdown process less effective when induction furnaces are used. It is therefore advantageous to use agglomerates the mixture of the copper precipitates and the carbonaceous reducing agent by conventional ones Procedure to form. The mixture of copper

the sulfur dioxide, which is dissolved in the bath, which results in violent stirring; follows to decrease concentration gradients z, i in dom bath. The cleaning gas used is nitrogen, Ar-20 gon. Air, carbon dioxide and / or oxygen are used. In most cases flow velocities of about 0.028 to 0.566 m ^:: i k 929 cm ^{ä of} the bath surface area are used; about the cleaning and stirring effect of the gas . '■. Precipitation and the carbonaceous reduction can be realized, while the outlay on equipment becomes small-scale according to the known combination.

ballungsxerfahren? \ i pellets or by the manufacturer, if the copper is not enough SauciMoü

deformed into briquettes using conventional pressing processes. contains that the sulfur as sulfur dioxide climi-notwithstanding the way in which the mixture is renated and that after desulphurisation ei, Cement copper and the carbon-containing Keduk oxygen content between about 0.1 and 1.5 "n propionant is agglomerated, if the agglomeration is, then additional oxygen has to be added to the bath rate a particle size with a minimum size of be added. This can be done by going into the at least about π 1 mm and advantageously at least by bath by means of a lance of air or oxygen Have about 20 mm to direct the problems or by removing oxidized copper powder dust formation, handling of the material and 35 bath.

of a less effective melting \. The copper precipitate, whether it is agglomerating is or not, is; uifgesehmolzen. a copper bath and a slag floating on it

Desulfurization is advantageously carried out at sub-atmospheric pressures of less than about 0.01 at and advantageously carried out at pressures between about 0.001 and 0.0002 at. Within

form, which contains Fiscnoxyd. Desulfurization proceeds around a rapid desulfurization of this area

to enable removal of iron oxide slag and in order to facilitate the subsequent removal of the impurities, the mixture is made of cement-copper and the carbonaceous reducing agent

technically justifiable speeds without placing too high demands on the vacuum equipment be asked. At higher subatmospheric pressures, the desulphurisation rate is

to a temperature of at least about 1200 C. 45 with sulfur contents below about 0.001

Advantage ^{: it is} probably heated to a temperature between about 1250 and 1400 C. At temperatures in the above range, the molten copper is sufficiently fluid that that formed in the copper

technically not interesting, while the usage line from lower pressures the use of koui complex and expensive, high-capacity facilities to cope with such low pressures.

Iron oxide quickly rises to the surface of the bath, which is especially the case in this case

rises where the iron oxide is removed as a solid slag will. An effective and essentially complete removal of the iron oxide slag before the Bath is an advantageous embodiment of the

wiire. when cleaning with an inert gas.

When the sulfur switch to the preselected values, e.g. B. to less than about 0.001'Vn or so to less than about 0.0005 "0.

lying invention, since the e-nfi.Tiuing of the iron 55 then the passage of R; cleaning gas is

oxide slag the subsequent atmospheric pressure desulfurization and lubrication treatments are facilitated. Higher temperatures are «! same to you effective to the kinetic conditions of the subsequent desulfurization and other Raffinierungsreaktiop.cn to vcnu-ssem.

After the iron content of the docking bath up less than about 0.01 ° /,> has been lowered and the Iron oxide slag is coiled away from the bail.

the bath is about 65 ming under atmospheric pressure. like arsenic, bismuth, lead, selenium. Tellurium, tin below about 0.01 atmospheres 'beneficial'. is volatilized. The copper melt will between about 0.001 and 0.0002 atmospheres 1: 11- during this stage mechanically or inductively in

ends and the Endraffinierung / for lowering the (ehaltcs \ on at least one impurity, such as arsenic bismuth, lead, selenium, tellurium, tin and zinc, is started. The oxygen content of the bath is iul / wipe "set u about 0.1 and 1.5 and Κ.ιηι1οι · is subjected to a subatmospheric pressure of less than about 0.0002 at., Advantageously less than about (1,000! At.

subjugated. while a Reinieirii'.siias. the free

Switch turbulence to avoid the volatility of the

to facilitate the above-mentioned impurities. Although a violent turbulence also from the passage an inert gas could be achieved through the melt, it has been shown that the lower sub-atmospheric pressures obtainable in the absence of an inert gas are more effective to remove the aforementioned impurities than the overall effects of the inert gas, that flows through the melt. This refining operation is effective in order to reduce the content of Arsenic, bismuth, lead, tin and zinc to be reduced to less than about 0.001 per cent, while the contents of Selenium and tellurium can be reduced by at least half.

The copper bath after refining contains between about 0.1 and 1.5% oxygen and it is advantageously deoxidized before casting. At least partial deoxidation can be effected by passing a reducing gas such as hydrogen, carbon monoxide, and natural gas or propane through the copper bath. Passing a reducing gas through the copper bath works fairly well, but it has surprisingly been found that when the oxygen level approaches about 0.05%, a solid reducing agent such as solid carbon or coke is kinetically more effective than the oxygen level to humiliate. Therefore, the copper bath becomes either during the whole. Desoxydationsbehandlung or during the latter stages of the same, that is, when the oxygen content of the bath decreases to about 0.05 ° '' or less, where a solid reducing agent to the oxygen content to approximately 0.01 ° / o, voiteilhafterweise about 0.005 ⁰ Zo, to humiliate. If oxygen-free copper is desired, the copper melt can, if necessary, be completely deoxidized by adding phosphorus. The deoxidation treatment with solid carbon is advantageously carried out at sub-atmospheric pressures of less than about 0.01 at. Ζ. B. between about 0.005 and 0.0005 at. During deoxidation, the bath is kept in a turbulent state by purging with a non-oxidizing gas, ie an inert or reducing gas. Inert gases such as nitrogen or argon are advantageously used as purge gases to reduce the problems associated with dissolved hydrogen at low oxygen levels. In the case of deoxidation at subatmospheric pressures, flow rates of the cleaning gas between approximately 0.028 and 0.56 mVh per 929 cm ^{2 of} the bath surface are used in order to produce the required turbulence without the demands on the vacuum devices becoming too high. When deoxidizing at ambient pressures, a wide range of purge gas flow rates can be used as long as the copper bath is adequately agitated. After deoxidation, the copper melt is poured into commercially available molds.

The copper bath is desulfurized, refined and deoxidized at temperatures of at least about 1200 ⁰ C and vorteilh to ensure after at temperatures between about 1250 and 1400 ⁰ C to produce a fast and essentially complete desulfurization, refining and deoxidation. The various operations can be carried out in any furnace, but it has been found to be advantageous to use induction furnaces in order to take advantage of the stirring effect of these furnaces. The induction furnaces have the further advantage that they completely eliminate the possibility of contamination of the copper by combustion products of the fuel. Another advantage of induction furnaces is that they can easily be provided with the appropriate vacuum equipment,
ίο The invention is explained in the examples.

B e i s ρ ie 1 1

Cement copper, which came from the precipitation of copper from sulphate leaching solutions on crushed, tinned tin cans and which contained 0.7% / o sulfur, 6% oxygen, 1.2% iron, 0.029% arsenic, 0.038% lead, 0.0023% selenium , 0.0007 "' ₅ tellurium and smaller amounts of calcium oxide, silicon dioxide and aluminum oxide, was melted in an induction furnace with access to air. The furnace used was provided with a vacuum unit. This was done to remove the iron, calcium oxide, silicon dioxide and aluminum oxide slagging and forming a copper bath containing 0.01 vol iron, 0.30 vol sulfur and 49.4 vol oxygen. The surface of the bath was deslagged, and the pressure m of the vacuum unit was then reduced to 0.0003 at. while passing nitrogen at a rate of 0.425 mVh / 929 cm ² of the surface of the bath was passed through the bath to lower the sulfur content to 0.0005 ⁰ Zo. the rinsing of the bath with nitrogen was then stopped, and d The pressure in the furnace was decreased to 0.0001 atm to further refine the bath. During this stage of the refining operation the arsenic, lead. Selenium, tellurium to 0.01% , to less than 0.002, 0.001 brw. 0.0003 ⁰ O decreased. Was then added to the bath zn carbon and the bath again purged with nitrogen at a flow rate of 0.340 cm ^3/929 cm ² of the surface of the bath per hour to the oxygen content of the bath at 0.02 ° to lower / o. Then the bath was poured.

Example 2

This example confirms that molten copper is desulfurized more rapidly by simultaneous inert gas purging and vacuum treatment than by vacuum treatment alone, even when pressures of ^{1 to} ₁₀ or less are used in the inert gas purging. Two copper baths, one containing 1.2% oxygen and 120 ppm sulfur and the other 0.95% oxygen and 100 ppm sulfur, were formed by heating cement-copper to 1260 ° C. The bath, which initially contained 120 ppm sulfur, was simultaneously subjected to subatmospheric pressures and a nitrogen purge at a rate of about 0.425 ms / 929 cm ^{2 of} bath surface per hour. An equilibrium pressure between about 200 and 250μ quickly developed across the Bac, and the sulfur content was reduced to less than 1 ppm ei in about 1 hour. Table IA shows the sulfur content and the pressure over the bath at various times. The copper bath, which contained 100 ppm of sulfur, was subjected to such sub- atmospheric pressures between about 15 and 32 μ , what

409517/31

the moisture content of the bath was measured at various intervals. The results are shown in Table IB. Without the nitrogen purge, it took almost 2 hours. to lower the sulfur content to 1 ppm, especially at pressures of less than ¹ Z _{10 of} the pressures. used in nitrogen purification was the case.

Table IA Table IIA

Zeil, min I pressure, mm Hg j Se. ppm j Te. ppn

Time, min

Pressure, mm Hg

S content. ppm

0
12th
22nd
33
46
63

300 12U 0.24 ' 9 0.25 ! 4th 0.24 0.20 I ι 0.21 1 ^<]

IO

»5 12th

3 j- 46
63

0.24
0.25
0.24
0.20
0.21

19th

15 24

23 24

Table HB

Time, min pressure, mm Hg

Sc-, ppm

Te. ppm

20th

50

80

110

140

0.032
0.025
0.018
0.016
0.015

28 21

11.1

7.6 7.3 5.S

P.7

Table IB

Time, mm! Pressure, mm Hg

S-housing.

O i 300 100

20: 0.032 20

50 0.025 4

80 0.018 3

110 0.016 1

140 j 0.015 1

A comparison of the results in Tables IA and IB shows that the simultaneous use a flush and subatmospheric pressures the speed of the desulfurization greatly increased.

Example 3

Although an inert gas purging greatly improves the desulfurization carried out at spherical pressure, this example confirms that the inert gas purging interferes with the other refining reactions by preventing the attainment of the necessary low pressures. The example further shows that a two-stage subatmospheric pressure treatment is advantageous in obtaining an overall refining operation. Two copper baths, one of which contained 19 ppm selenium and 13 ppm tellurium and the other 29 ppm selenium and 11.5 ppm tellurium, were formed by heating cement-copper to 126 "C. Both baths were oxidized in such a way that the oxygen in amounts of more than I ⁰ O was present. the bath containing 19 ppm selenium, was added m simultaneously with nitrogen at a rate of 0.425 ^3/929 cm ⁸ of the surface of the bath per hour rinsed and μ subjected to a reduced atmospheric pressure between 200 and 250. samples were taken at different intervals and examined for selenium and tellurium content The results are compiled in Table Π A. The bath, which initially contained 29 ppm selenium, was only exposed to subatmospheric pressures between 15 and 32 μ . Here, too, samples were taken periodically and The results are shown in Table Π Β .

The results presented in Tables II A and II B confirm that lower subatmospheric pressures are more effective to remove selenium and copper Refine tellurium, especially tellurium.

Example 4

This example confirms that molten copper is more effectively deoxidized by carbon at subatmospheric pressures with simultaneous inert gas purging than by bubbling hydrogen through molten copper. A copper bath. containing 0.26 ° 0 oxygen was formed. A hydrogen-nitrogen gas mixture. contained the 75 ° 0 hydrogen was bubbled h through the bath at a speed of 0.195 m * what 2.83 m corresponds to ^3/929 ~ cm ^ä the bath surface per "hour. This flow rate ensures a vigorous through agitation of the bath. The oxygen content of the bath was then determined at various intervals.The results are compiled in Table III A. Another bath was formed which contained 0.27 ⁰ O. On the surface of the bath, graphite granulate was placed in a

UU ^ l UUVUV V * ~ v ~ - ₍ ^

Amount of 1% of the bath applied. The bath was subatmospheric pressures of / wipe 400 and 500 u exposed while the bath with stick

fabric was rinsed at a speed of 0.03 m ^s h. which was 0.312 m ^: 1929 cm- equivalent to the bath surface per hour. The stuierstorTgehal of the bath was determined at different intervals. The results obtained are summarized in Table B.

Table ΠΙ Α

Time, min Oxygen content. Weight percent 0 0.26 13th 0.14 22nd 0.066 30th 0.045 40 0.021 50 0.017 60 0.0105

Table IIIB

Time, min Oxygen content, weight percent O 0.27 10 0.13 20th 0.044 30th 0.014 40 0.0068 50 0.0025

The results reported in Tables III A and III B confirm that the deoxidation of copper with carbon at subatmospheric pressures, although kinetically slower liquid-solid reactions take place, at considerably faster rates proceeds than deoxidation with hydrogen, which is viewed as kinetically more reactive will.

For comparison purposes, a separate deoxidation test was carried out at atmospheric pressure below Use of granular graphite and an inert gas purge performed. After 50 minutes it was the oxygen content of the bath 0.01 "/», which is four times the amount of oxygen in the bath is, which is 50 minutes with carbon and an inert gas purging at subatmospheric pressure deoxy-

had been dated. After 65 minutes the oxygen content had decreased to 0.0032%, which confirms that that an effective deoxidation with granular graphite and an inert gas purging also realized without having to resort to sub-atmospheric pressures.

The invention thus relates to a method for fire-refining metallic copper, which consists of aqueous solutions has been accrued. The invention was made in the context of treatment of cement copper, but the method of the invention can of course also be used for this purpose be, for example, smelting of electrolytically refined or electrolytically recovered Refining copper, which is contaminated with sulfur during smelting operations or which contain troublesome amounts of arsenic, bismuth, lead, selenium, tellurium, tin and zinc.

The invention is not limited to the described embodiments

ao management forms limited. For example, the copper melt, which contains oxygen minerals, which compared to the sulfur shark; are high during the latter stage of desulfurization desulfurized and partially deoxidized at the same time

as be while flushing with a non-oxidizing Gas is continued and an operation can be carried out in the second stage, to remove other contaminants.

Claims (16)

Patent claims: 1. Process for refining metallic copper, which contains up to 50% iron, up to 10 ⁰ O oxygen, up to 1% sulfur and at least one volatile impurity, namely arsenic, bismuth, lead, selenium, tellurium, tin or zinc , wherein the metallic copper is melted in a free oxygen-containing atmosphere to slag the iron and form a copper bath which contains impurities, the oxygen being at least in excess of the sulfur content without a separate copper (I) - oxide phase is formed, and the slag is separated from the copper bath, characterized in that a cleaning or flushing gas, which may contain free oxygen, is passed through the copper bath while the bath is kept below 0.01 atm at subatmospheric pressure, until the sulfur content is less than 0.01) 1 ° 0, the passage of the cleaning or flushing gas is ended, the pressure above the copper bath is reduced to less than 0.002 atm to volatilize the volatile contamination, to deoxidize the copper bath and to pour the copper. 2. The method according to claim 1, characterized in that gc denotes that ir.an as metallic copper Cement copper is used, which either through a sieve or a magnetic separation or enriched by both methods. 3. The method according to claim 1 or 2, characterized in that the copper before the Melting mixed with a carbonaceous reducing agent. 4. The method according to claim 3, characterized in that the copper and the carbon-containing Reducing agent agglomerated with one another before the melt η. 5. The method according to claim 3 or 4, characterized in that the carbon-containing Adding reducing agent in amounts of 0.5 to 5 percent by weight. 6. The method according to any one of claims 3 to 5, characterized in that one is used as the carbon-containing Fuel oil used as reducing agent. 7. The method according to any one of the preceding claims, characterized in that the Copper bath during desulfurization and the evaporation of impurities to 1250 holds up to 1400 ° C. 8. The method according to any one of claims 1 to 7, characterized in that there is nitrogen, argon, air or as the cleaning or flushing gas Uses oxygen. 9. The method according to any one of the preceding claims, characterized in that the Cleaning or flushing gas through the bath at a speed of 0.028 to 0.566 nv'Vh 929 cm * of the bathroom surface leads. 10. The method according to any one of the preceding claims, characterized in that the desulfurization is carried out so that the Κυρ- Ss ferbad ^{contains 0.1 to 1.5 1} Vo of oxygen after the desulfurization. 11. Method according to one of the preceding Claims, characterized in that additional oxygen is added to the bath after the desulfurization added, in order to adjust the oxygen content to 0.1 to 1.5 per cent. 12. The method according to any one of the preceding claims, characterized in that one the copper bath by adding granular carbon and rinsing with a non-oxidizing one Deoxidized gas. 13. The method according to any one of the preceding claims, characterized in that one carries out the deoxidation at sub-atmospheric levels of less than 0.01 atm. 14. The method according to claim 12 or 13, characterized in that the non-oxidizing gas is passed through the copper ^{bath at a speed of 0.028 to 0.566 m: i} / h / 929 cm of the bath surface. 15. The method according to any one of the preceding claims, characterized in that one the copper bath is desulfurized at subatmospheric pressures of less than 0.001 atm. 16. A process for l.ntoxydieren molten copper, characterized in that a copper melt is formed which contains up to 1.5% oxygen, the surface of the melt is covered with granular carbon and the melt is flushed with a non-oxidizing gas to rapidly reduce the oxygen content to less than 0.01 ^v / o .