US3258330A

US3258330A - Pyrometallurgical refining process for copper

Info

Publication number: US3258330A
Application number: US218434A
Authority: US
Inventors: Ito Toshio
Original assignee: Nippon Mining Co Ltd
Current assignee: Eneos Corp
Priority date: 1961-09-27
Filing date: 1962-08-21
Publication date: 1966-06-28
Anticipated expiration: 1983-06-28
Also published as: BE622116A; DE1161034B

Description

United States Patent O 8 Claims. (in. 75-75 The present invention relates to a pyrometallurgical refining process for copper.

An object of the present invention is to provide an improved process for refining copper, which can economically be effected with a high reaction efiiciency.

Another object of the present invention is to provide a new process for refining copper, wherein the maximum result in the heating, oxidation and reduction can be fully achieved solely through the feeding of fuel blended with air containing oxygen in various densities (hereinafter referred to as air).

A further object of the present invention is to provide a new process wherein copper can be refined by appropriately adjusting the ratio of fuel to air respectively for each stage of heating, oxidation and reduction without the aid of any other additional fuel.

Other objects, features and advantages of the present invention will be apparent from the following description.

The conventional pyrometallurigical process for copper refining includes the stages of anode refining into refined blister, followed by electrolytic refining into copper cathode, and subsequent melting and casting into wire bars. Similar processes are also widely practised in the treating and refining of copper scrap.

These conventional processes generally comprise melting copper charge, heating in a reverberatory or any other type of suitable furnace, and removing impurities container in the said charge by oxidation with air, and finally reducing Cu O.

Oxidation is effected by means of air being blown onto the surface of molten mass or into the molten mass, causing to separate Pb, Zn, S, As, Sb, Ni, Co, Mn, Bi and Fe contained in the molten mass from the molten copper. The volatile impurities are carried away in the waste gas, whilst those remaining in the slag floating on the surface of molten copper are skimmed out of the furnace. The molten copper remaining in the furnace is fully or almost saturated with Cu O. When the said molten copper is reduced with a reducing agent to remove oxygen, the refining of copper will then be completed. The thus-refined copper is then cast in casting moulds to the desired form. The reducing operation as herein set forth is the so-called poling wherein green wood is considered as the most suitable as a reducing agent. Since the suitability of green wood referred to above depends on its water content, size and shape, its availability and cost offers an economic problem.

In all hitherto known refining processes, since fuels are generally burnt on the surface of molten mass, a considerable amount of heat dissipates in the course of the oxidation and poling operations. Furthermore, during the reduction of the large amount of Cu O which is formed during oxidation, the reaction between green wood and Cu O is carried out only on the surface of molten mass, and because of evaporation of the moisture in the green wood with the progress of time, stirring action in the course of said reaction tends to decrease. Thus, the reducing action takes a long period of time.

In view of the increasing scarcity of the suitable green wood, the above-mentioned conventional processes are exposed to the difiiculty in ensuring economic maintenanoe of heat efiiciency as well as reaction efliciency. The present invention is to provide an improved refining process which entirely overcomes these above-mentioned defects and disadvantages.

The characteristic feature of the present invention lies in that the best results can be achieved in each stage of heating, oxidation and reduction by merely feeding fuel blended with air.

The fuel used in the present invention may be liquid fuels such as heavy oil and light oil, or pulverized carbonaceous material including solid fuels such as coal, coke, charcoal, saw-dust and the like.

In general, these fuels, having a wide range of choice, are easily and cheaply available on the market. They are more economical than green wood normally used.

Of the above-mentioned fuels, these in the powdered form are mixed with air in the desired ratio and blown beneath the surface of the molten mass, by means of a combined mixing and feeding apparatus such as variable speed feeder with injector. On the other hand, of the said fuels, liquid fuels are similarly blown into the molten mass in atomized form by such means as an injection feeder.

The refining reaction takes place in two stages, namely the oxidation and the reduction of the molten copper. In the oxidation stage, selective oxidation is effected at optimum temperature by utilizing the lower oxidizing tendency of copper than other impurities, while in the reducing stage, deoxidation is carried out at optimum temperature by a close contact of a reducing agent with oxygen in molten copper, and it is to be noted that optimum temperature is also required in subsequent casting operation.

After further research and numerous experiments, taking into consideration the special features of the refining processes described above, it has been determined that better results can be achieved by appropriately regulating the mixing ratio of fuel to air respectively in each stage of heating, oxidation and reduction. In this case, the oxygen ratio, namely the ratio of the actually supplied amount of oxygen (b) to the theoretical amount of oxygen (a) necessary for combustion, that is, b/aXlOO (percent), within the ranges of approximately to 130% during heating, within the range of approximately to 200% during oxidation and within the range of approximately 20 to 100% during reduction, in order to effectively accomplish the respective objects.

To summarize, according to the present invention, the desired refining can be advantageously and economically carried out by merely adjusting the above-mentioned oxygen ratio within the rang-e of 20 to 200%, without the aid of the additional or supplemental fuel such as heavy oil, as in the case of conventional known processes. Furthermore, because of its simple and inexpensive operation, the process of the present invention is superior to any of the conventional processes.

Moreover, the fuel used in this process may be one or a mixture of two or more kinds of fuels. Further, a different kind of fuel may respectively be used for each stage of oxidation, reduction and heating, or instead thereof, the oxygen density in the air may sometimes be varied with the kind of fuel used.

In the present invention, since all kinds of fuels, for which the oxygen ratio has appropriately been adjusted, are always blown into the bath of molten copper, the heat efficiency is remarkably improved. Thus, no supplemental heating is necessary in the present process due to the improved heat efliciency, although in the usual processes additional or supplemental heating fuel is required. Furthermore, in the oxidation stage in the process of the present invention, due to the low partial presshould respectively be adjusted sure of oxygen in the combustion gas, impurities may etfectively be separated and eliminated to a desired extent by oxidation without any excessive increase of oxygen in the molten copper. Also in the reduction stage, the reac- Example 2 In a manner similar to that in Example 1, blister copper was refined with pulverized charcoal.

After the first charging of molten copper from contion can rapidly be effected by a close contact of Cu O 5 in molten copper with reducing material, because violent the g Was treated in the P y Stage for stirring takes place throughout the said stage. In this 25 Inihunder the blowing conditions Where the Char case, the reaction velocity is accelerated by the regulated e031 feeding rate was kg/Ihihand the Oxygen atio temperature conducive towards chemical reaction with f; and ill the next Stage for 35 under blowing said temperature maintained by fuel combustion taking 10 eohdltiehs Where the Charcoal feeding rate was place within molten mass. On-the other hand, there is and the Oxygen ratio 30 t0 After the a further advantage in that the molten copper is pro Second charging of molten PP from e0hVeIter, the tected from reoxidation with unburnt carbonaceous matecharge was first treated for 45 under eohditlehs i l floating on i f where the charcoal feeding rate was 0.8 kg./min. and Kinds of copper material to which the present inventhe y e ratio 140%, and in the next Stage of 35 milk tion are applicable, include blister copper or electrolytic Under blowing Conditions Where the Charcoal feedihg fate copper and/ or scrap copper and the like. Particularly, W35 kgJITll'hthe Oxygen ratio 30 t0 After this process is most effective in anode refining when the Second charging of molten PP from Converter, lt copper i li d fr convertel; the charge was first treated for 45 min. under the con- The above-mentioned features of this invention will ditiohs Where the C031 feeding rate was kgJmmand b apparent f h f ll i examples, the oxygen ratio 140% and in the next stage for 2 hours Th invention i further d ib d i h foll i under the conditions where the charcoal feeding rate examples which are illustrative but not limitative thereof. was kg/ Ini11- and the Oxygen ratio 30 t0 The charcoal used was as follows. Example 1 Type of charcoal Shiro-Zumr (whitlsh charcoal). Approximately 20 metric tons of molten copper (con- Size 5 mfish taming 0.02% and O 0.0%) from converter were p i t analyses; charged in a 40 metric ton cylindrical anode furnace, and c l ifi value 920 cal/kg slag floated on the surface of molten mass was skimmed 3 Volatile matter 5% off, and then pulverized coal was blown into the molten 0 Fixed carbon 4 Copper at the rate of 0.8 kg./min. and the oxygen ratio Ash maintained at 150%. Moisture 10 7% After min. blowing, a sample of the molten copper S lf (103%. was taken out for analysis. As the S content was found below 0.01%, the coal feeding rate was readjusted to 1.4 35 Analyses of original charge and finished refined prodkg./min. and the oxygen ratio to 90 to 100%, under uct showed as follows. which conditions pulverized coal was blown into the molten copper for one hour. P t

Then the blowing was stopped once for receiving anmen other supply of molten copper from the converter. Ap- Cu Pb S 0 Others Total proximately 20 metric tons of molten copper (containing S 0.02% and O 0.6%) werecharged in the said anode Charge 9M5 018 0.018 M4 bal 100 furnace. After slag being skimmed 01f, pulv-enzed coal Product 99,38 0,14 M04 010 bal 100 was blown into the molten copper for 20min. under the conditions where the coal feeding rate was 0.8 kg./min. and the oxygen ratio 150%. Example 3 c 0 a fig'g g fi igg i 1& 5 5 5 3352? 23 1; In a manner similar to that in Example 1, blister copper conditions the blowing was continued for 2.5 hours. A convmter was refined by blowmg mlxture of portion of molten copper was taken out and analysed verized coal and fine powdered charcoal mto molten cop- Since the result thereof was found to be satisfactory, After the first chargmg 9 molten copper from the blowing was stopped and the refined copper cast into verter the charge was fi m the first Stage for 0 moulds. ulfnigr the vtilowirg C(fndltlOlS wahlerell ienfuell feedlfi g rate o e mix ure 0 pu venze co an r e c arcoa in e The pulvenzed coal used was as follows' mixing ratio 'by weight of 50:50, was 0.8 kg./min. and the Type of coal Washed pulverized coal. oxygen ratio 140%, and in the next stage of 40 min. under Size -150 mesh. the conditions where the fuel feeding rate was 1.5 kg./min. Proximate analyses: and oxygen ratio 30%. After the second charging of Calorific value 7,910 cal./ kg. molten copper from converter, the charge was treated first Volatile matter 36.5%. for 45 min. under the conditions where the fuel feeding Fixed carbon 56.0%. rate was 0.8 kg./min. and oxygen ratio 140% and then for Ash 5.9%. 2.5 hours under the conditions where the fuel feeding Moisture 1.6%. rate was 2.5 kg./ min. and oxygen ratio 30 to 32%. Sulfur 0.4%, Fuels used Were the same as in Example 1 and Exam- I ple 2 respectively. Analyses of Oflglhal charge and finlshed refined P On the other hand, analyses of original charge and finuct showed as follows: ished refined product showed as follows.

Percent Percent Cu Pb S 0 Others Total Cu Pb S 0 Others Total Charge 98.73 0.13 0. 019 0. e0 bal 100 Charge 98.89 0.16 0.020 0.61 bal 100 Product 99.40 0.12 0. 007 0.10 bal 100 Product 99.35 0.15 0. 008 0.10 bal 100 Example 4 53 metric tons of electrolytic copper were charged into a 5 5 metric ton reverberatory furnace and melted by burning heavy oil. Scum was skimmed out, and then pulverized charcoal was blown into the molten copper under the conditions where the fuel feeding rate was 2.5 kg./min. and the oxygen ratio 30 to 33%. After blowing for 1.5 hours, a portion of melt was taken out and analysed. As the result was judged as satisfactory, the blowing was stopped and the finished product cast in the usual manner into wire bars.

The pulverized charcoal used was similar to that in Example 2. Analyses of the wire bar obtained were as follows.

Example 5 54 metric tons of electrolytic copper were charged into a 55 metric ton reverberatory furnace and melted by burning heavy oil. Scum was skimmed out. Then, saw-dust was blown into the molten mass under the conditions where the fuel feeding rate was approximately 5 kg./ min. and the oxygen ratio 27 to 30%. A portion of melt was taken out and analysed after blowing for 80 min. As the result was found satisfactory, the blowing was stopped and the finished product cast in the usual manner into wire bars.

Analysis of the saw-dust used was as follows.

Proximate analyses:

Calorific value ca1./kg. 4,510 Moisture (wet base) percent 30.1 Ash do 0.7 Volatile matter do 56.2 Fixed carbon do 43.1

Elementary analyses: Percent S 0.05 H 6.27

Analyses of wire bar obtained were as follows.

Percent Cu 99.97 Fe 0.0005 Ni 0.0003 Pb 0.0008 S 0.0010 Sb 0.0002 As 0.0002 Sn 0.0001 0 0.024

Others bal. Total 100 Example 6 Into a 60 metric ton reverberatory anode furnace, 58 metric tons of blister copper (containing S 0.027% and O 0.38%) were charged in a molten state. Then, after skimming 01f slag floating on the surface of molten copper, light oil was blown into the molten mass, under the conditions where the oil feeding rate was 1 liter/min. and the oxygen ratio 140%. After blowing for 45 min., a

Calorific value cal./kg. 11,500 Specific gravity 0.82 Sulfur percent 0.20

The analyses of original charge and finished product were as follows:

Percent Cu Pb S 0 Others Total Charge 98. 0. 15 0. 018 0. 68 bal Product 99. 34 0. 14 0. 005 0. 10 bal 100 What is claimed is:

1. A pyrometallurgical refining process for copper, wherein a molten bath of unrefined copper is subjected to consecutive stages of heating, oxidation and reduction, said process comprising the steps of blowing directly into the bath of unrefined copper a mixture of oxygen and a fuel selected from the group consisting of liquid oil and solid carbonaceous material while heating the bath, adjusting the volume of oxygen in the mixture to an oxygen-fuel ratio capable of oxidizing the copper, continuing the blowing of the adjusted mixture directly into the copper bath until the oxidation is completed, adjusting the volume of oxygen in the mixture to an oxygen-fuel ratio capable of reducing the copper, and then continuing the blowing of the adjusted mixture directly into the copper bath until the reduction is completed.

2. A process in accordance with claim 1, wherein the unrefined copper is selected from the group consisting of blister copper, electrolytic copper and scrap copper.

3. A process in accordance with claim 1, wherein the unrefined copper consists of a mixture of two different substances selected from the group consisting of blister copper, electrolytic copper and scrap copper.

4. A process in accordance with claim 1, wherein said fuel consists of a mixture of liquid oil and solid carbonaceous material.

5. A pyrometallurgical refining process for copper, wherein a molten bath of unrefined copper is subjected to consecutive stages of heating, oxidation and reduction, said process comprising the steps of blowing directly into the bath of unrefined copper a mixture of oxygen and a fuel selected from the group consisting of liquid oil and solid carbonaceous material while heating the bath, the oxygen b/a ratio ranging between 80 and 130, adjusting the oxygen b/a ratio to one ranging between 100 and 200, continuing the blowing of the adjusted mixture directly into the copper bath until the oxidation is completed, adjusting the oxygen b/a ratio to one ranging between 20 and 100, and then continuing the blowing of the adjusted mixture directly into the copper bath until the reduction is completed, said oxygen b/a ratio being one hundred times the ratio of the actually supplied amount of oxygen to the theoretical amount of oxygen necessary for combustion.

6. A pyrometallurgical refining process for copper, wherein a molten bath of unrefined copper is subjected to consecutive stages of heating, oxidation and reduction, said process comprising the steps of blowing directly into the bath of unrefined copper a mixture of air and a fuel selected from the group consisting of liquid oil and solid carbonaceous material while heating the bath, the density of oxygen in the air being adjusted in accordance with the type of fuel, further adjusting the volume of oxygen in the air to a mixture ratio capable of oxidizing the copper, continuing the blowing of the adjusted mixture directly'into the copper bath until the oxidation is completed, further adjusting the volume of oxygen in the air to a mixture ratio capable of reducing the copper, and then continuing the blowing of the adjusted mixture directly into the copper bath until the reduction is completed,

7. A pyrometallurgical refining process for copper, wherein a molten bath of unrefined copper is subjected to consecutive stages of heating, oxidation and reduction, said process comprising the steps of blowing directly into the bath of unrefined copper a mixture of oxygen and a fuel selected from the group consisting of liquid oil and solid carbonaceous material while heating the bath, adjusting the volume of oxygen in the mixture to an oxygen-fuel ratio capable of oxidizing the copper, continuing the blowing of the adjusted mixture directly into the copper bath while violently stirring the bath until the oxidation is completed, whereby impurities are effectivelyseparated' and eliminated from the copper, adjusting the volume of oxygen in the mixture to an oxygenfuel ratio capable of reducing the copper, and then continuing the blowing of the adjusted mixture directly into the copper bath until the reduction is completed.-

8. A pyrometallurgical refining process for copper, wherein a molten bath of unrefined copper is subjected to consecutive stages of heating, oxidation and reduction, said process comprising the steps of blowing-directly into the bath of unrefined copper a mixture of oxygen and a fuel selected from the group consisting Of liquid oil and solid carbonaceous material while heating the bath, adjusting the volume of oxygen in the mixture to an oxygen-fuel ratio capable of oxidizing the copper, continuing the blowing of the adjusted rnixture directly into the copper bath until the oxidation is completed, adjusting the volume of oxygen in the mixture to an oxygen-fuel ratio capable of reducing the copper, and then continuing the blowing of the adjusted mixture directly into the copper bath while stirring the bath until the reduction is completed.

References Cited by the Examiner DAVID L. RECK, Primary Examiner.

BENIAMIN' HENKIN, Examiner.

H. W. CUMMINGS, C. N. LOVELL,

Assistant Examiners.

Claims

1. A PYROMETALLURGICAL REFINING PROCESS FOR COPPER WHEREIN A MOLTEN BATH OF UNREFINED COPPER IS SUBJECTED TO CONSECUTIVE STAGES OF HEATING, OXIDATION AND REDUCTION, SAID PROCESS COMPRISING THE STEPS OF BLOWING DIRECTLY INTO THE BATH OF UNREFINED COPPER A MIXTURE OF OXYGEN AND A FUEL SELECTED FROM THE GROUP CONSISTING OF LIQUID OIL AND SOLID CARBONACEOUS MATERIAL WHILE HEATING THE BATH, ADJUSTING THE VOLUME OF OXYGEN IN THE MIXTURE TO AN OXYGEN-FUEL RATIO CAPABLE OF OXIDIZING THE COPPER, CONTINUING THE BLOWING OF THE ADJUSTED MIXTURE DIRECTLY INTO THE COPPER BATH UNTIL THE OXIDATION IS COMPLETED, ADJUSTING THE VOLUME OF OXYGEN IN THE MIXTURE TO AN OXYGEN-FUEL RATIO CAPABLE OF REDUCING THE COPPER, AND THEN CONTINUING THE BLOWING OF THE ADJUSTED MIXTURE DIRECTLY INTO THE COPPER BATH UNTIL THE REDUCTION IS COMPLETED.