US3615361A - Fire refining of copper - Google Patents

Abstract

A process is disclosed for fire-refining copper sulfide having a copper to nickel ratio of more than about 7:3, which process comprises maintaining a molten bath of copper sulfide in a turbulent state to volatilize at least about 50 percent of at least one impurity from the group consisting of bismuth, lead, tin and zinc, then surface blowing the turbulent bath of copper sulfide with a free-oxygen-containing gas to convert a minor portion of the copper sulfide to an immiscible metal phase in which at least one element from the group consisting of antimony, arsenic, bismuth, lead, tin and the precious metals is concentrated. After removing the immiscible metal phase the turbulent supernatant bath of copper sulfide is converted to liquid copper which is substantially saturated with oxygen by surface blowing with free oxygen-containing gas. At least one impurity from the group consisting of lead, selenium, sulfur, tellurium and tin are volatilized from the molten copper and the molten copper is thereafter treated with a reducing gas to lower the oxygen content to at least about 0.1 percent.

Description

United States Patent 72] Inventors Paul E. Queneau [54] FIRE REFINING OF COPPER 24 Claims, No Drawings [52] US. Cl 75/73, 75/82, 75/93 [51] Int. Cl ..C22bl5/06, C22b 23/06 [50] Field of Search 75/72, 1, 76, 83, 93

[56] References Cited UNITED STATES PATENTS 1,922,301 8/1933 Kekich 75/75 2,790,713 4/1957 Kenworthy 75/82 2,944,883 7/1960 Queneau 75/82 X 3,004,846 10/1961 Queneau 75/82 X 3,069,254 12/1962 Queneau 75/82 3,321,300 5/1967 Worner 75/93 X 3,516,818 6/1970 ONeill..... 75/74 X 1,817,935 8/1931 Stout 75/76 2,758,022 B/1956 Jordon 75/76 OTHER REFERENCES Buch, I v E., The Mufulia Smelter, Northern Rhodesia in AIME Transactions, 1949, 182: p. 137 and 138.

Primary Examiner-L. Dewayne Rutledge Assistant Examiner-Joseph E. Legru Att0rneyMaurice L. Pinel ABSTRACT: A process is disclosed for fire-refining copper sulfide having a copper to nickel ratio of more than about 7:3, which process comprises maintaining a molten bath of copper sulfide in a turbulent state to volatilize at least about 50 percent of at least one impurity from the group consisting of bismuth, lead, tin and zinc, then surface blowing the turbulent bath of copper sulfide with a free-oxygen-containing gas to convert a minor portion of the copper sulfide to an immiscible metal phase in which at least one element from the group consisting of antimony, arsenic, bismuth, lead, tin and the precious metals is concentrated. After removing the immiscible metal phase the turbulent supernatant bath ofcopper sulfide is converted to liquid copper which is substantially saturated with oxygen by surface blowing with free oxygen-containing gas. At least one impurity from the group consisting of lead, selenium, sulfur, tellurium and tin are volatilized from the molten copper and the molten copper is thereafter treated with a reducing gas to lower the oxygen content to at least about 0.1 percent.

FIRE REFllNllNG 01F COPPER The present invention relates to the fire refining of cupriferous materials to produce high-grade copper, and more particularly to an integrated process for treating copper sulfide which may contain nickel.

Production of refined copper from cupriferous. sulfidic materials requires a number of complex treatments involving high capital expenditures. Most of the virgin copper produced in the world is obtained by smelting copper sulfides in reverberatory or electric furnaces, converting the resulting matte to blister copper in sideblown Peirce-Smith type converters, partially refining the blister copper by crude redox operations in an anode furnace, casting the furnace product into metal anodes, subjecting the anodes to electrolysis for final refining, melting the cathodes and casting the copper into shapes for market. Fire refining of blister copper is also employed, which practice involves an extension of anode furnace refining practice as a substitute for electrolysis.

in addition to iron, sulfur and precious metals, containing furnace feed may contain significant amounts of nickel originating in the ore or in scrap additions. Other common impurities which must be lowered to acceptable levels include antimony, arsenic, bismuth, lead, selenium, tellurium, tin and zinc. Prior art pyrometallurgical processes for eliminating such impurities from the final copper product are either inadequately effective or inefiicient.

It has now been discovered that cupriferous materials can be refined pyrometallurgically to produce high grade copper while recovering valuable impurities by means of an economic, integrated process.

It is an object of the invention to provide a process for pyrometallurgical production of high-quality copper from cupriferous materials and for separate recovery of precious metals associated therewith.

Another object of the invention is to provide an integrated process for recovering high-grade copper and nickel from copper sulfide containing nickel by a combination of pyrometallurgical and vapometallurgical techniques.

the copper- Generally speaking, the present invention contemplates establishing a turbulent bath containing copper sulfide and having a copper to nickel ratio of more than about 7:3, maintaining the bath in a turbulent state without forming a metal phase to volatilize more than about 50 percent of at least one impurity selected from the group consisting of bismuth, lead, tin and zinc, then surface blowing the turbulent bath with a free-oxygen-containing gas to convert a controlled minor portion of the copper sulfide to an immiscible metal phase in which at least one element from the group consisting of antimony, arsenic, bismuth, lead, tin and the precious metals is concentrated, removing the immiscible metal phase, then surface blowing the turbulent supernatant bath of copper sulfide with a free-oxygen-containing gas to convert copper sulfide to liquid copper, to substantially saturate the liquid copper with oxygen and to oxidize and volatilize at least one impurity selected from the group consisting of lead, selenium, sulfur, tellurium and tin and thereafter treating the liquid copper with an atmosphere reducing to cuprous oxide to lower the oxygen content to less than about 0.1 percent.

Copper mattes or copper sulfide concentrates which contain significant amounts of iron, nickel, cobalt, lead, bismuth, tin, arsenic, antimony, selenium, tellurium, zinc and the precious metals can be treated by the process of the present invention. Cupriferous scrap to which sufficient sulfur has been added to combine with all the copper contained therein can also betreated in accordance with the present invention. It is to be noted that the term precious metals, as used herein, refers to the platinum group metals and gold. When the feed material contains substantial amounts of iron as iron sulfide, the iron is initially oxidized to iron oxide which is removed. The nickel content in the sulfide feed material must be controlled so that the copper to nickel ratio is more than about 7:3 to insure production of the immiscible liquid metal phase for the concentration of precious metals present and of impurities. Advantageously, the copper to nickel ratio in the cupriferous material is controlled at a level greater than about 10: 1 since at ratios of copper to nickel of greater than about 10:] arsenic, in addition to bismuth, lead, tin and zinc, can be volatilized from both the sulfide phase and the metal phase and the concentration of precious metals in the immiscible metalphase is remarkably more effective. Furthermore, at copper to nickel ratios of greater than about 10:], arsenic is more readily oxidized and volatilized from the liquid copper bath. Thus, control of the copper to nickel ratio at such levels provides more effective arsenic elimination and more effective concentration of the precious metals in the immiscible metal phase. When treating sulfide mineral concentrates or metallurgical crudes thereof which have a copper to nickel ratio of less than about 10:1, such material can be treated to produce asulfur deficient matte, i.e., sulfur in amounts insufficient to form sulfides by combination with all of the nickel and copper. The matte of controlled sulfur content can then be slow cooled to provide a solidified mass of three readily separable phases-a precious-metals-containing magnetic fraction which is about 5 percent to 15 percent of the solidified mass, a nickel sulfide fraction of low copper content and a copper sulfide fraction with a nickel content such that the copper to nickel ratio is greater than about 10:1, e.g., 15:1. This process for separation of nickel sulfide from copper sulfide isdescribed in Canadian Pat. Nos. 452,861 and 452,862. The precious-metals-containing magnetic fraction is ad vantageously melted, treated with. a free-oxygen-containing gas to lower the sulfur content to between about 0.5 percent and 4 percent and the iron content to less thanabout 3 percent, granulated by drastic quenching to uniformly distribute the remaining sulfur throughout the granules and then treated with carbon monoxide at elevated pressure, advantageously below about atmospheres, to carbonylate and remove substantially all of the nickel as nickel carbonyl, as described in U.S. Pat. No. 1,067,638, leaving a residue containing copper, sulfur and the precious metals which can be treated by leaching to remove copper, sulfur and other contaminants from the precious metals. Advantageously, the sulfur deficien cy of the matte is slight and is controlled so that only a nickel sulfide phase containing the precious metals and a copper sulfide phase are produced upon slow cooling. For example, the sulfur deficiency is controlled to produce less than about 2 percent metallics, e.g., about 0.5 percent to 1 percent metallics. The nickel sulfide phase is then treated in a manner similar to that described for the precious metals magnetic fraction in order to concentrate the precious metals and to produce nickel carbonyl. When the slow-cooled matte contains unimportant amounts of precious metals, the nickel sulfide fraction can advantageously be blown to nickel metal as described in Canadian Pat. No. 655,210. The copper sulfide fraction, with a copper to nickel ratio greater than about 10:1, can be treated in accordance with the process of the present invention.

An advantageous feature of the present invention is maintenance of a turbulent copper sulfide bath while avoiding formation of a metal phase to maximize the volatilization of impurities from the liquid copper sulfide. Although some of the impurities are volatile as sulfides at conventional smelting and converting temperatures, the bath should be held at temperatures above 1,300 C., more than about 1,400 C., in order to increase the rate and the extent of impurity volatilization. The results shown in Table l, which were obtained by surface blowing copper mattes with air at temperatures of 1,200 and 1,340C. and with nitrogen containing less than about 1 percent oxygen at a temperature of 1,500" C. for one hour, confirm that higher temperatures are more effective in volatilizing impurities such as bismuth and lead from the matte. This comparison must take into consideration the loss of weight of the matte being treated. The effectiveness of higher smelting and converting temperatures is confirmed by the results in table 11 from which it is readily seen that surface blowing with air at higher temperatures gives a remarkable decrease in the level of impuriadvantageously at temperatures of ties commonly present in smelter feed. It is important during this phase of the treatment to avoid formation of a metal phase since such a phase tends to preferentially dissolve the impurities, which dissolution sharply lowers impurity volatilization efficiency. Advantageously, this part of the process is conducted in a top-blown rotary converter, e.g., a Kaldo converter, equipped with a burner, which converter provides great flexibility in operation by provision of gaseous atmospheres of optimum oxidizing potential, independent control of bath temperature and independent mechanical generation of a turbulent bath for excellent gas-liquid-solid contact. The absence of submerged tuyeres in such converters allows them to be operated at high temperatures unattainable in the standard converters of the nonferrous industry. When the sulfide bath is a low-grade matte, some of the impurities can be volatilized during the oxidation and slagging of iron. However, when the sulfide bath is a high-grade matte, impurities such as arsenic, bismuth, lead, tin and zinc are advantageously volatilized by maintaining the copper-containing sulfide bath in a turbulent state by either pneumatic or mechanical means and without forming a metal phase by maintaining high temperature, neutral or only slightly oxidizing atmospheres above the turbulent bath. For example, surface blowing a partially converted matte at 1,340 C. with nitrogen containing less than about 1 percent oxygen, by volume, was effective in lowering the lead, arsenic and bismuth contents as shown in table Ill. The results in table lll also confirm that superior results are obtained by volatilizing impurities from the matte at temperatures above 1,400 C. The test conducted at 1,500 C. employed surface blowing with air for the first 10 minutes, then surface blowing with nitrogen containing less than about 1 percent oxygen, by volume, for the remainder of the test. It is readily apparent from the results in table 111 that temperatures above 1,400" C. are effective in increasing the rate and extent of impurity elimination from the matte phase. The latter embodiment is advantageously conducted in a top blown converter with the burner being operated to maintain both high bath temperature and an atmosphere substantially neutral to copper sulfide, i.e., neither oxidizing nor reducing to copper sulfide. Advantageously, the atmosphere above the sulfide bath is controlled to have an oxidizing-reducing potential equivalent to a value between about 10 1 and 10 for the ratio of (CO)(SO )%(CO wherein the values of CO, 50 and CO are their respective partial pressures. Both the rate and extent of impurity volatilization from the matte can advantageously be improved by subjecting the matte, after iron removal, to a subatmospheric pressure treatment. The matte is advantageously transferred to a separate vessel wherein it is maintained in a turbulent state and at high temperatures, e.g., above l,400 C., and the pressure in the vessel is lowered to less than about 10 atmosphere.

TABLE I Temper- Perccnt ature, M Sample C. Cu S Fe Bi Pb HeatL 1,500 48 25 20.5 0.05 116 After 1 hour 1,500 21. 5 0. 026 0 058 Head 1, 340 42 25. 9 28 0. 11 0. 13 After 1 hour 1,340 53. 5 24 10. 5 0.07 0.11 H 1,200 41.9 26 28.3 0.11 0.13 After 1 hour 1,200 57. 4 23. 7 14. 7 0. 11 0. 14

1 Not analyzed.

TABLE II Temper- Percent ature,

Sample 0, Cu Se Fe As Bi Pb Head 1,340 42 0.1 28. 5 0.11 0.11 0. 13 Blister 1, 340 0. 003 0. 03 0. 44 0. 002 Head 1, 200 41. 9 0.104 28. 3 0.11 0.11 0.13 Blister. 1,200 0.02 0.07 0.18 0. 006

l Contained about 26% sulfur. 2 Balance includes small amounts of iron, sulfur and oxygen. 3 Not analyzed.

TABLE III Temper- Percent ature, M Sample C. Fe Pb As Bi Partially converted matte 1, 340 10 0. 092 0. 012 0. 05 After blowing:

hour 1, 340 18 0. 083 0. 013 0. 03 1 hour 1, 340 15 0. 064 0. 012 0. 01 2 hour 1, 340 10 0. 054 0. 011 0. 01 Head 1, 500 20. 5 0. 096 0. 09 0. 075 Alter blow hour. 1, 500 21. 5 0. 072 0. 05 0. 035 1 hour. 1, 500 21. 5 0. 058 0. 04 0. 026 1% hours. 1, 500 21. 0 0. 054 0. 035 0. 01 2 hours- 1,500 20. 5 0. 053 0. 031 0. 01 solidified sample 17. 5 0. 048 0. 027 0. 01

After the copper-containing sulfide feed has been melted, iron present has been oxidized by blowing and removed and substantial amounts of impurities such as arsenic, bismuth, lead, tin and zinc have been volatilized, the turbulent sulfide bath is surface blown with free-oxygen-containing gas, such as air, oxygen-enriched air of commercial oxygen, to convert a controlled portion of the sulfide bath into a metal phase to collect substantially all the precious metals and substantial portions of other impurities remaining in the bath. Advantageously, the metallized portion of the bath is controlled within the limits of about 5 percent to about 15 percent of the sulfide phase, by weight, to insure collection of the precious metals and concentration of substantial portions of other impurities. It will be noted here that a highly desirable combination exists between the elimination of the impurities from the matte by volatilization and the subsequent collection of impurities and precious metals in the immiscible molten metal phase. Since more than about 50 percent of at least one impurity from the group consisting of arsenic, bismuth, lead, tin and zinc is removed by volatilization from the sulfide phase, a smaller amount of the immiscible metal phase can be formed and later tapped to remove remaining impurities and, therefore, the latter step is economically advantageous. Greater and lesser amounts of the metal phase can be employed but greater amounts, unless warranted by the precious metal content, result in a less economical process while lesser amounts result in substantially lower collection of the precious metals and the impurities. in order to confirm the effectiveness of a metal phase in concentrating impurities, a test, the results of which are shown in table IV, was conducted on a copper matte which was surface blown with air at l,340 C. to produce a metal phase which was about 10 percent, by weight, of the matte phase. The results in table lV show that concentrations of impurities in the metal phase are at minimum five times greater than in the matte phase and even 10 times or more. It will also be noted from table N that antimony, which is particularly difficult to eliminate by volatilization from the sulfide phase or by subsequent oxidation and volatilization from the metal phase, is highly concentrated and collected in the metal phase. Thus, substantial amounts of antimony can be eliminated at this point in the process without employing special slagging techniques at later processing stages. Strong agitation of the sulfide bath to insure efiective interphase liquid-liquid contact and resulting washing of the sulfide phase by the metal phase is important at this point to collect precious metals and other impurities in the metal phase. The metal is then allowed to settle into a liquid bottom and is removed for treatment, e.g., cast into anodes and treated electrolytically to recover the copper and the precious metals.

It has been found that the embodiments of volatilizing impurities from the sulfide phase and of concentrating the precious metals and impurities are dependent on the copper to nickel ratios in the sulfide material being treated and that for the greatest efficiency of both embodiments the copper to nickel ratio should be morethan about :1. Although applicants do not wish to be bound by any particular theory, it is believed that increasing amounts of nickel in the sulfide phase lower the chemical activities of the precious metals and impurities in the sulfide phase. Whatever the explanation for the adverse effects of excessive amounts of nickel in the sulfide phase, tests have shown that it is advantageous to control the copper to nickel ratio to a value of more than about 10:]. Thus, a copper matte containing 42 percent copper, 28.5 percent iron, 25.9 percent sulfur, 0.11 percent arsenic and the balance essentially silica was surface blown with air at a temperature of 1,340 C. for 1 hour to lower the sulfur content to 24 percent, the iron content to 19.5 percent and the arsenic content to 0.035 percent. In a similar manner, a matte containing 29.4 percent copper, 13.9 percent nickel, 27.6 percent iron, 26 percent sulfur, 0.103 percent arsenic and the balance essentially silica was surface blown with air at a temperature of l,340 C. for about 100 minutes to lower the iron content to l 1 percent, the sulfur content to 24.5 percent and the arsenic content to about 0.088 percent. Thus, it is seen from the first test that the proportion of arsenic in the matte was lowered by more than two-thirds when no nickel was present while in the second test with a copper to nickel ratio of 2.1:] the proportion of arsenic in the matte was lowered by less than about percent. In addition to lowering the efficiency of arsenic volatilization from the matte, excessive amounts of nickel in the matte also lower the efficiency of precious metal concentration in the immiscible metal phase. For example, in two tests in which the copper to nickel ratios were 13:1 and 5:1 the overall distribution of precious metals in the metal phase was as follows:

TABLE V Percentage of Total Precious Metals in Metal Phase Cu2Ni 1' of Pd of Pt it of Au The results in table 1V confirm the importance of controlling the copper to nickel ratio to have a value of more than about 10:1.

The partially purified copper sulfide remaining in the converter, e.g., a Kaldo or LD converter, is maintained in a state of turbulence, by mechanical or pneumatic means, as top blowing with a free-oxygen-containing gas such as air, commercial oxygen or oxygen-enriched air is resumed. Surface blowing is continued to convert the partially purified copper sulfide to copper and to substantially saturate the copper with cuprous oxide, e.g., an oxygen content of between about 0.5 percent and 1.5 percent. During this stage of the blowing operation, the surface of the turbulent liquid bath is kept reasonably clear of slag in order to assure efficient gas-liquid contact and the bath is maintained at a temperature between about l,l00 and l,500 C. The introduction of the aforementioned amounts of oxygen is effective in oxidizing the impurities remaining in the liquid copper bath and in volatilizing more than about 50 percent of at least one volatile oxide of elements such as arsenic, lead, selenium, sulfur, tellurium and tin. Advantageously, the oxidation and volatilization of the impurities is conducted at temperatures above l,300 C. in order to insure more rapid and complete elimination of the impurities. The oxygen contained in the copper bath is also effective in oxidizing substantially all of the nickel in the bath. Nickel removal is advantageously conducted at low temperatures, e.g., about l,l00 C., because at higher temperatures nickel removal is less efficient. Although the nickel content can be lowered to below 0.5 percent without a flux at a temperature of about l,l00 C., the nickel content can be further lowered by employing an acidic flux such as silica. When an acidic flux is employed, the nickel content in the copper bath can be lowered to about 0.1 percent,

After such purification, the copper-containing bath is then brought to the proper pitch and cast. Advantageously, the purified liquid copper-containing bath containing up to about 1.5 percent oxygen is treated with an atmosphere reducing to cuprous oxide to lower the oxygen content to less than about 0.1 percent. In bringing the molten copper-containing bath to the proper pitch, the bath is held at a temperature of about 1,100 to about l,200 C. while maintaining the atmosphere above the bath to have a reducing potential equivalent to a COzCO ratio of at least one part of CO for each 1,000 parts of CO For kinetic reasons, it is advantageous to employ atmospheres having reducing potentials equivalent to COzCO ratios of at least about 1:50, e.g., about 1:10. To facilitate lowering of the oxygen content in the second reaction vessel, a turbulent bath is also employed therein in order to assure intimate gas-liquid contact. Alternatively, the oxygen content of the copper bath can be lowered during the subatmospheric pressure treatment described hereinafter by passing reducing gases having the aforedescribed reducing potentials through the copper bath. When the oxygen content has been lowered to predetermined levels, the copper-containing bath is cast into commercial shapes such as wire bars or cast into anodes for further purification.

If it is desired to continuously cast the copper-containing bath or if a product substantially free of gas is desired, the copper-containing bath is advantageously subjected to a subatmospheric pressure treatment to degas the bath. The copper-containing bath is introduced to a vacuum chamber which is maintained at a pressure of less than about 10 atmosphere. The subatmospheric pressure treatment will be more efficient if the copper-containing bath is maintained in constant state of circulation or turbulence by well-known means, e.g., electromechanical. In addition to the degassing effect, the subatmospheric pressure treatment has the further advantage of further lowering the level of impurities such as sulfur, arsenic, bismuth, lead, selenium, sulfur, tellurium, tin and zinc by volatilization. The effectiveness of the subatmospheric pressure treatment in lowering the level of the various impurities is partly dependent on the oxygen content of the liquid copper. For example, the lead content can be lowered in the absence of oxygen but the elimination of sulfur and arsenic is facilitated by the presence of sufficient oxygen as cuprous oxide to form the volatile oxides of the respective impurities. In order to insure elimination of sulfur and/or arsenic, the copper-containing bath with oxygen contents up to about 1.5 percent can be directly transferred to the vacuum chamber without deoxidation; and after these impurities have been lowered to acceptable levels, reducing gases having a reducing potential equivalent to COzCO ratios of at least one part of CO for each 1,000 parts ofCO are then passed through the liquid copper. Although the subatmospheric pressure treatment is effective in lowering the impurity levels at conventionally employed temperatures for casting copper, it has been found particularly advantageous to subject the copper bath to the subatmospheric pressure treatment at temperatures of at least about 1,200 C. Even bismuth, which is considered difficult or impossible to eliminate by conventional pyrometallurgical techniques, can be readily removed by the subatmospheric pressure treatment. In a test, a sample of copper containing 20 parts per million (ppm) bismuth was heated to about l,l50 C. for 45 minutes at a final vacuum of 14 microns and the bismuth content was lowered to less than 1 ppm. The results in table Vl further confirm the effectiveness of the subatmospheric pressure treatment in lowering the impurity levels. The results shown in table Vl were obtained by subjecting molten copper containing about 0.3 percent oxygen to a subatmospheric pressure of 0.4x 1 0 atmosphere for 1 /2 hours at a temperature of 1,260 C. It is quite evident from the results in table Vl that the subatmospheric pressure treatment is highly effective in removing lead, arsenic and bismuth.

n.d.= not detected For the purpose of giving those skilled in the art a better appreciation of the advantages of this invention, the following illustrative example is given:

EXAMPLE I A turbulent bath of copper matte, the composition of which is given in table Vll, was established and surface blown with oxygen for 1% hours at l,340 C. and then a sample was taken for analysis. Surface blowing of the turbulent bath with oxygen was then discontinued and was replaced by surface blowing with nitrogen containing less than about 1 percent oxygen for 2 hours at l,340 C. after which a sample was taken for analysis. Surface blowing of the turbulent bath with oxygen at l,340 C. was resumed for 1 hour to produce a metal phase which, along with a sample of matte, was removed and analyzed. After 70 minutes of surface blowing with oxygen at 1,340 C. another metal phase was produced and was again removed along with a sample of the matte for analysis. The remaining matte was converted to blister copper and saturated with oxygen after blowing with oxygen for 80 minutes. After taking two samples for analysis, the blister copper was subjected to a subatmospheric pressure of less than about 1O atmosphere at 1,500 C. The results of the chemical analyses at different stages of the process are reported in table Vll together with an analysis of commercially produced cathode copper for comparative purposes. The results in table Vll confirm that copper produced in accordance with the process of the present invention is comparable with electrolytic copper. In addition to the results listed in table VII, the tellurium content, which was 0.l percent in the head sample, was lowered to less than 0.01 percent after the vacuum treatment whereas a similar vacuum treatment at l,260 C. only lowered the tellurium content to 0.05 percent. Also, one of the blister copper samples contained 0.3 percent selenium; and after the vacuum treatment at 1,500 C., the selenium content was lowered to less than about 0.002 percent.

lence can be induced by pneumatic or electromagnetic means. The efficiency of volatilizing impurities from the matte is greatly increased by a turbulent bath since the turbulence constantly exposes fresh surfaces from which volatilization occurs. The use of a rotary furnace during the converting operation is advantageous since the rotating furnace avoids the establishment of localized areas of lower temperature where magnetite and other accretions can build up and eventually lower the capacity of the converter. Furthermore, the turbulence induced by a rotary converter provides a rapid approach to equilibrium conditions by rapid decrease of concentration gradients and, thus, for instance, the problem of slag foaming is minimized. The turbulence mechanically induced by a rotary furnace also provides excellent liquid-liquid contact between the impure copper sulfide phase and the controlled metal portion, which contact greatly increases the amount and rate of concentration of impurities in the controlled metal portion. The highly efficient gas-liquid contact realized by conducting the process in a top blown furnace provides greater control of the production of the controlled metal portion, the converting of the partially purified copper sulfide and the subsequent oxidation of the remaining impurities in the coppercontaining bath. A rotary furnace permits required tempera ture control including efficient heat exchange between the liquid bath and the furnace wall refractory. The furnace is equipped with a lance for delivering freeoxygen-containing gas to the'surface of the turbulent bath and with a burner for supplying heat to, and for controlling the atmosphere above, the turbulent bath. The burner gases serve the additional function of continually flowing over the surface of the turbulent bath thereby flushing residual gases and lowering the partial pressures of volatile impurities whereby volatilization efficiency is increased.

Top blowing by directing a stream of free-oxygen-containing gas on the surface of the agitated bath is another advantageous feature of the present invention. When a free-oxygen-containing gas is directed to the surface of a molten copper-containing sulfide bath, liquid copper is formed in the vicinity of impingement of the free-oxygcn-containing gas and by gravitational forces descends through the molten sulfide phase which provides even greater liquid-liquid contact between the liquid sulfide phase and the liquid copper to further increase the effectiveness of the concentration of impurities in the liquid copper. it is to be further noted that the surface blowing permits the use of commercial oxygen or oxygen-enriched air during the converting operation whereby the offgases are rich in sulfur dioxide which facilitates sulfur recovery. Surface blowing is also characterized by a high oxygen activity which in combination with independent agitation by mechanical means and independent temperature control provides procedures responsive to accurate regulation of TABLE VII Percent- Weight Tempera- (grams) ture, 0. Fe Pb As Bi S 1, 340 1.17 2 0.007 0.012 Metal 1, 340 0. 01 2 0. 003 0. 03 Blow 02.80 minutes 1,340 0.03 2 0. 0006 1 0.005 1, 340 0.02 0.0013 0.0001 2 0. 005 0. 005 Vacuum 1, 500 0. 01 0. 001 0.001 0. 0001 0. 001 0. 0001 0. 002 1,500 0. 01 0. 001 0. 001 0. 0001 0. 001 0. 0001 0. 002 Cathode copper t t 0.0005 0. 0001 0.0001 0. 0003 0.0001 0. 0001 0. 0005 Not analyzed. 2 Speetrographically estimated.

A turbulent bath is one of the advantageous features of the process variables.

present invention and is achieved advantageously by the mechanically induced agitation of a rotary furnace of the Kaldo type because the rotary furnace provides agitation independent of any other function. Although the mechanically induced agitation of a rotary furnace is preferred, the turbu- It will be observed that the present invention contemplates, in an advantageous embodiment, establishing a turbulent bath containing copper sulfide and having a copper to nickel ratio of more than about 10:1, maintaining the bath in a turbulent state without forming a metal phase to volatilize more than about 50 percent of at least one impurity selected from the group consisting of arsenic, bismuth, lead, tin and zinc, then surface blowing the turbulent bath with a free-oxygen-containing gas to convert a controlled minor portion of the copper sulfide to an immiscible metal phase in which at least one element from the group consisting of antimony, arsenic, bismuth, lead, tin and the precious metals is concentrated, removing the immiscible metal phase, then surface blowing the turbulent supernatant bath of copper sulfide with a free-oxygencontaining gas to convert copper sulfide to a turbulent bath of liquid copper, to substantially saturate the liquid copper with oxygen and to oxidize and volatilize at least one impurity selected from the group consisting of arsenic, lead, selenium, sulfur, tellurium and tin and thereafter treating the liquid copper with an atmosphere reducing to cuprous oxide to lower the oxygen content to less than about O. l percent.

It is to be noted that all solid and liquid composition given herein are taken on a weight basis and that all gaseous compositions are given on a volumetric basis.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Thus, the process in accordance with the present invention, particularly the use of a turbulent bath, can be employed for the treatment of plumbiferous materials, e.g. mineral concentrates, to yield directly fire-refined lead. Such modifications and variations are considered to be within the purview and scope of the invention and appended claims.

We claim:

1. A method for recovering copper from cupriferous materials which comprises establishing a bath containing copper sulfide and having a copper to nickel ratio of more than about 7:3, maintaining said bath containing copper sulfide in a turbulent state without forming a metal phase to volatilize more than about 50 percent of at least one impurity selected from the group consisting of bismuth, lead, tin and zinc, then surface blowing the turbulent bath containing copper sulfide with a free-oxygen-containing gas to convert a controlled minor portion of the copper sulfide to an immiscible metal phase in which at least one element from the group consisting of antimony, arsenic, bismuth, lead, tin and the precious metals is concentrated, removing the immiscible metal phase, then surface blowing the turbulent supernatant copper sulfide with a free-oxygen-containing gas to convert copper sulfide to liquid copper, to substantially saturate the liquid copper with oxygen and to oxidize and volatilize at least one impurity from the group consisting of lead, selenium, sulfur, tellurium and tin and then treating the liquid copper with an atmosphere reducing to cuprous oxide to lower the oxygen content to less than about O.l percent.

2. A method for recovering copper from cupriferous materials which comprises establishing a bath containing copper sulfide and having a copper to nickel ratio of more than about 10:1, maintaining said bath containing copper sulfide in a turbulent state without forming a metal phase to volatilize more than about 50 percent of at least one impurity selected from the group consisting of arsenic, bismuth, lead, tin and zinc, then surface blowing the turbulent bath containing copper sulfide with a free-oxygen'containing gas to convert a controlled minor portion of the copper sulfide to an immiscible metal phase in which at least one element from the group consisting of antimony, arsenic, bismuth, lead, tin and the precious metals is concentrated, removing the immiscible metal phase, then surface blowing the turbulent supernatant bath of copper sulfide with a free-oxygen-containing gas to convert copper sulfide to liquid copper, to substantially saturate the liquid copper with oxygen and to oxidize and volatilize at least one impurity from the group consisting of arsenic, lead, selenium, sulfur, tellurium and tin and then treating the liquid copper with an atmosphere reducing to cuprous oxide to lower the oxygen content to less than about 0.1 percent.

comprises establishing a turbulent bath of a sulfide material containing nickel, copper and the precious metals with the copper to nickel ratio being less than about 10:1, directing a stream of a free-oxygen-containing gas upon the surface of the turbulent bath to produce a sulfur-deficient matte, slowly cooling the sulfur-deficient matte to produce a solidified mass of readily separable crystals of nickel sulfide and copper sulfide having a copper to nickel ratio greater than about l'0:l and a magnetic metallic fraction in which the preciousmetals are concentrated, comminuting the solidified mass, magnetically separating the metallic fraction, separating the nickel sulfide and copper sulfide by flotation, melting and then surface blowing the separated metallic fraction with a free-oxygen-containing gas to produce a molten nickel bath containing about 0.5 percent to about 4 percent sulfur and less than about 3 percent iron, drastically quenching the nickel bath to form nickel granules with sulfur uniformly distributed, carbonylating the nickel granules at elevated pressures to produce nickel carbonyl and a precious metal concentrate, fire refining the separated nickel sulfide by surface blowing a turbulent bath thereof with a free-oxygen-containing gas, establishing a bath of the separated copper sulfide, maintaining said bath containing copper sulfide in a turbulent state without forming a metal phase to volatilize more than about 50 percent of at least one impurity selected from the group consisting of arsenic, bismuth, lead, tin and zinc, then surface blowing the turbulent bath containing copper sulfide with a free-oxygen-containing gas to convert a controlled portion of the copper sulfide to an immiscible metal phase in which at least one element from the group consisting of antimony, arsenic, bismuth, lead, tin and the precious metals is concentrated, removing the. immiscible metal phase, then surface blowing the turbulent supernatant bath of copper sulfide with a free-oxygen-containing gas to convert copper sulfide to liquid copper, to substantially saturate the liquid copper with oxygen and to oxidize and volatilize at least one impurity from the group consisting of arsenic, lead, selenium, sulfur, tellurium and tin and then treating the liquid copper with an atmospherp reducing to cuprous oxide to lower the oxygen content to less than about 0.1 percent.

4. A process for recovering copper, nickel and precious metals from nickeland copper-containing materials which comprises establishing a turbulent molten bath of a sulfide material, directing a stream of a free-oxygen-containing gas upon the surface of the turbulent bath to produce a sulfur deficient matte, slowly cooling the sulfur deficient matte to produce a solidified mass of readily separable crystals of nickel sulfide which contains precious metals and copper sulfide crystals having a copper to nickel ratio greater than about 10:1, comminuting the solidified mass, separating the nickel sulfide and copper sulfide phases in the comminuted mass by flotation, melting and then surface blowing the nickel sulfide phase to produce a nickel bath containing about 0.5 percent to about t percent sulfur and less than about 3 percent iron, drastically quenching the nickel bath to form nickel granules with sulfur uniformly distributed, carbonylating the nickel granules at elevated pressures to produce nickel carbonyl and a precious metal concentrate, establishing a turbulent bath of the separated copper sulfide, maintaining said bath containing copper sulfide in -a turbulent state without forming a metal phase to volatilize more than about 5 0 percent of at least one impurity selected from the group consisting of arsenic, bismuth, lead, tin and zinc, then surface blowing the turbulent bath containing copper sulfide with a free-oxygen-containing gas to convert a controlled portion of the copper sulfide to an immiscible metal phase in which at least one element from the group consisting of antimony, arsenic, bismuth, lead, tin and the precious metals is concentrated, removing the immiscible metal phase, then surface blowing the supernatant turbulent bath of. copper sulfide with a free-oxygen-containing gas to convert copper sulfide to liquid copper, to substantially saturate the liquid copper with oxygen and to oxidize and volatilize at least one impurity from the group consisting of arsenic, lead, selenium, sulfur, tellurium and tin and then treating the liquid copper with an atmosphere reducing to cuprous oxide to lower the oxygen content to less than about 0.1 percent.

5. A process as described in claim 2 wherein the impurities are volatilized from the bath containing copper sulfide at a temperature above 1,300 C.

6. A process as described in claim 2 wherein the impurities are volatilized from the bath containing copper sulfide at a temperature of more than 1,400 C.

7. A process as described in claim 2 wherein the molten bath containing copper sulfide is a low-grade matte and the impurities are volatilized while surface blowing the turbulent bath with a free-oxygen-containing gas.

8. A process as described in claim 2 wherein the copper sulfide-containing bath is a high-grade matte and the impurities are volatilized by controlling the atmosphere above the turbulent bath to be substantially neutral to copper sulfide.

9. A process as described in claim 8 wherein the atmosphere above the bath is controlled to have an oxidizing-reducing potential equivalent to a value between about 10 and 10 for the ratio (CO)(SO,)%(CO,) wherein the values of CO, S and CO are the respective partial pressures.

10. A process as described in claim 3 wherein impurities are volatilized from the copper sulfide-containing bath by maintaining the atmosphere above the turbulent bath to be substantially neutral to copper sulfide.

11. A process as described in claim wherein the atmosphere above the bath is controlled to have an oxidizingreducing potential equivalent to a value between about 10 and 10 for the ratio (CO)(SO,)%(CO wherein the values of CO, S0 and C0: are the respective partial pressures.

12. A process as described in claim 2 wherein the immiscible metal phase is from about 5 percent to about percent, by weight, of the molten copper sulfide.

13. A process as described wherein more than about 50 percent of at least one impurity from the group consisting of arsenic, lead, selenium, sulfur, tellurium and tin is volatilized from the liquid copper bath substantially saturated with oxygen.

14. A process as described in claim 2 wherein the liquid bath of copper substantially saturated with oxygen is treated with an atmosphere having a reducing potential equivalent to a CO:CO, ratio of at least about 1:1000 to lower the oxygen content to less than about 0.1 percent.

15. A process as described in claim 14 wherein the atmosphere has a reducing potential equivalent to a CO:CO, ratio of at least about 1:5

16.'A process as described in claim 2 wherein the liquid copper containing less than about 0.1 percent oxygen is degassed and further purified by a subatmospheric pressure treatment.

17. A process as described in claim 16 wherein after degassing the liquid copper is continuously cast.

18. A process as described in claim 2 wherein the liquid copper substantially saturated with oxygen is subjected to a subatmospheric preaure treatment to further lower the level of at least one impurity selected from the group consisting of arsenic, bismuth, lead, selenium, sulfur, tellurium, tin and zinc before treating the liquidcopper with an atmosphere reducing to cuprous oxide.

19. A process as described in claim 18 wherein an atmosphere reducing to cuprous oxide is passed through the liquid copper during the subatmospheric pressure treatment to lower the oxygen content in the molten copper to less than about 0.1 percent.

20. A process as described in claim 18 wherein the subatmospheric pressure is less than about 10' atmosphere.

21. A process as described in claim 2 wherein the steps of volatilization of impurities from the copper sulfide-containing bath, the production of the controlled amount of immiscible molten metal phase and the converting of the copper sulfide to a molten bath of copger are conducted in a rotary furnace.

22. A process as escribed in claim 2 wherein the step of volatilization of impurities from the copper sulfide-containing bath is conducted at subatmospheric pressures of less than about 10" atmosphere.

23. A process as described in claim 3 wherein the precious metal concentrate from the carbonylation treatment is leached to further concentrate the precious metals by removing copper, sulfur and other contaminants.

24. A process as described in claim 3 wherein the elevated pressure during carbonylation is less than about 100 atmospheres.

Claims (23)

1. 2. A method for recovering copper from cupriferous materials which comprises establishing a bath containing copper sulfide and having a copper to nickel ratio oF more than about 10:1, maintaining said bath containing copper sulfide in a turbulent state without forming a metal phase to volatilize more than about 50 percent of at least one impurity selected from the group consisting of arsenic, bismuth, lead, tin and zinc, then surface blowing the turbulent bath containing copper sulfide with a free-oxygen-containing gas to convert a controlled minor portion of the copper sulfide to an immiscible metal phase in which at least one element from the group consisting of antimony, arsenic, bismuth, lead, tin and the precious metals is concentrated, removing the immiscible metal phase, then surface blowing the turbulent supernatant bath of copper sulfide with a free-oxygen-containing gas to convert copper sulfide to liquid copper, to substantially saturate the liquid copper with oxygen and to oxidize and volatilize at least one impurity from the group consisting of arsenic, lead, selenium, sulfur, tellurium and tin and then treating the liquid copper with an atmosphere reducing to cuprous oxide to lower the oxygen content to less than about 0.1 percent.
2. 3. A process for recovering copper, nickel and precious metals from nickel and copper-containing materials which comprises establishing a turbulent bath of a sulfide material containing nickel, copper and the precious metals with the copper to nickel ratio being less than about 10:1, directing a stream of a free-oxygen-containing gas upon the surface of the turbulent bath to produce a sulfur-deficient matte, slowly cooling the sulfur-deficient matte to produce a solidified mass of readily separable crystals of nickel sulfide and copper sulfide having a copper to nickel ratio greater than about 10:1 and a magnetic metallic fraction in which the precious metals are concentrated, comminuting the solidified mass, magnetically separating the metallic fraction, separating the nickel sulfide and copper sulfide by flotation, melting and then surface blowing the separated metallic fraction with a free-oxygen-containing gas to produce a molten nickel bath containing about 0.5 percent to about 4 percent sulfur and less than about 3 percent iron, drastically quenching the nickel bath to form nickel granules with sulfur uniformly distributed, carbonylating the nickel granules at elevated pressures to produce nickel carbonyl and a precious metal concentrate, fire refining the separated nickel sulfide by surface blowing a turbulent bath thereof with a free-oxygen-containing gas, establishing a bath of the separated copper sulfide, maintaining said bath containing copper sulfide in a turbulent state without forming a metal phase to volatilize more than about 50 percent of at least one impurity selected from the group consisting of arsenic, bismuth, lead, tin and zinc, then surface blowing the turbulent bath containing copper sulfide with a free-oxygen-containing gas to convert a controlled portion of the copper sulfide to an immiscible metal phase in which at least one element from the group consisting of antimony, arsenic, bismuth, lead, tin and the precious metals is concentrated, removing the immiscible metal phase, then surface blowing the turbulent supernatant bath of copper sulfide with a free-oxygen-containing gas to convert copper sulfide to liquid copper, to substantially saturate the liquid copper with oxygen and to oxidize and volatilize at least one impurity from the group consisting of arsenic, lead, selenium, sulfur, tellurium and tin and then treating the liquid copper with an atmosphere reducing to cuprous oxide to lower the oxygen content to less than about 0.1 percent.
3. 4. A process for recovering copper, nickel and precious metals from nickel- and copper-containing materials which comprises establishing a turbulent molten bath of a sulfide material, directing a stream of a free-oxygen-containing gas upon the surface of the turbulent bath to produce a sulfur deficient matte, slowly cooling the sulfur deficient matte to produCe a solidified mass of readily separable crystals of nickel sulfide which contains precious metals and copper sulfide crystals having a copper to nickel ratio greater than about 10:1, comminuting the solidified mass, separating the nickel sulfide and copper sulfide phases in the comminuted mass by flotation, melting and then surface blowing the nickel sulfide phase to produce a nickel bath containing about 0.5 percent to about 4 percent sulfur and less than about 3 percent iron, drastically quenching the nickel bath to form nickel granules with sulfur uniformly distributed, carbonylating the nickel granules at elevated pressures to produce nickel carbonyl and a precious metal concentrate, establishing a turbulent bath of the separated copper sulfide, maintaining said bath containing copper sulfide in a turbulent state without forming a metal phase to volatilize more than about 50 percent of at least one impurity selected from the group consisting of arsenic, bismuth, lead, tin and zinc, then surface blowing the turbulent bath containing copper sulfide with a free-oxygen-containing gas to convert a controlled portion of the copper sulfide to an immiscible metal phase in which at least one element from the group consisting of antimony, arsenic, bismuth, lead, tin and the precious metals is concentrated, removing the immiscible metal phase, then surface blowing the supernatant turbulent bath of copper sulfide with a free-oxygen-containing gas to convert copper sulfide to liquid copper, to substantially saturate the liquid copper with oxygen and to oxidize and volatilize at least one impurity from the group consisting of arsenic, lead, selenium, sulfur, tellurium and tin and then treating the liquid copper with an atmosphere reducing to cuprous oxide to lower the oxygen content to less than about 0.1 percent.
4. 5. A process as described in claim 2 wherein the impurities are volatilized from the bath containing copper sulfide at a temperature above 1,300* C.
5. 6. A process as described in claim 2 wherein the impurities are volatilized from the bath containing copper sulfide at a temperature of more than 1,400* C.
6. 7. A process as described in claim 2 wherein the molten bath containing copper sulfide is a low-grade matte and the impurities are volatilized while surface blowing the turbulent bath with a free-oxygen-containing gas.
7. 8. A process as described in claim 2 wherein the copper sulfide-containing bath is a high-grade matte and the impurities are volatilized by controlling the atmosphere above the turbulent bath to be substantially neutral to copper sulfide.
8. 9. A process as described in claim 8 wherein the atmosphere above the bath is controlled to have an oxidizing-reducing potential equivalent to a value between about 10 1 and 10 4 for the ratio (CO)(SO2) 1/2 (CO2) 1 wherein the values of CO, SO2 and CO2 are the respective partial pressures.
9. 10. A process as described in claim 3 wherein impurities are volatilized from the copper sulfide-containing bath by maintaining the atmosphere above the turbulent bath to be substantially neutral to copper sulfide.
10. 11. A process as described in claim 10 wherein the atmosphere above the bath is controlled to have an oxidizing-reducing potential equivalent to a value between about 10 1 and 10 4 for the ratio (CO)(SO2) 1/2 (CO2) 1 wherein the values of CO, SO2 and CO2 are the respective partial pressures.
11. 12. A process as described in claim 2 wherein the immiscible metal phase is from about 5 percent to about 15 percent, by weight, of the molten copper sulfide.
12. 13. A process as described wherein more than about 50 percent of at least one impurity from the group consisting of arsenic, lead, selenium, sulfur, tellurium and tin is volatilized from the liquid copper bath substantially saturated With oxygen.
13. 14. A process as described in claim 2 wherein the liquid bath of copper substantially saturated with oxygen is treated with an atmosphere having a reducing potential equivalent to a CO:CO2 ratio of at least about 1:1000 to lower the oxygen content to less than about 0.1 percent.
14. 15. A process as described in claim 14 wherein the atmosphere has a reducing potential equivalent to a CO:CO2 ratio of at least about 1:50.
15. 16. A process as described in claim 2 wherein the liquid copper containing less than about 0.1 percent oxygen is degassed and further purified by a subatmospheric pressure treatment.
16. 17. A process as described in claim 16 wherein after degassing the liquid copper is continuously cast.
17. 18. A process as described in claim 2 wherein the liquid copper substantially saturated with oxygen is subjected to a subatmospheric pressure treatment to further lower the level of at least one impurity selected from the group consisting of arsenic, bismuth, lead, selenium, sulfur, tellurium, tin and zinc before treating the liquid copper with an atmosphere reducing to cuprous oxide.
18. 19. A process as described in claim 18 wherein an atmosphere reducing to cuprous oxide is passed through the liquid copper during the subatmospheric pressure treatment to lower the oxygen content in the molten copper to less than about 0.1 percent.
19. 20. A process as described in claim 18 wherein the subatmospheric pressure is less than about 10 3 atmosphere.
20. 21. A process as described in claim 2 wherein the steps of volatilization of impurities from the copper sulfide-containing bath, the production of the controlled amount of immiscible molten metal phase and the converting of the copper sulfide to a molten bath of copper are conducted in a rotary furnace.
21. 22. A process as described in claim 2 wherein the step of volatilization of impurities from the copper sulfide-containing bath is conducted at subatmospheric pressures of less than about 10 3 atmosphere.
22. 23. A process as described in claim 3 wherein the precious metal concentrate from the carbonylation treatment is leached to further concentrate the precious metals by removing copper, sulfur and other contaminants.
23. 24. A process as described in claim 3 wherein the elevated pressure during carbonylation is less than about 100 atmospheres.