JPS59197531A - Vacuum purification of blister copper - Google Patents

Abstract

PURPOSE:To volatilize and remove impurities in blister copper in good efficiency, in a process for preparing an anode plate for copper electrolysis, by applying vacuum treatment to molten blister copper issued from a converter. CONSTITUTION:Blister copper issued from a converter is received in a ladle 1 and the leg L of a vacuum furnace 3 having a DH type sucking part suspended and supported in a freely up-and-down movable manner by a crane is immersed in the blister copper bath issued from the converter. When the vacuum furnace 3 is reduced in pressure, molten copper rises to a predetermined height determined by pressure difference and pressure head in the vacuum furnace 3 to be exposed in vacuo. During this time, impurities such as As, Sb, Si or Pb present in the blister copper bath are volatilized and removed. After a predetermined time is elapsed, the vacuum furnace 3 is raised to return the molten copper therein to the laddle 1. This procedure is repeated several times at every min and the whole blister copper bath in the ladle 1 is subjected to vacuum treatment to volatlize and remove impurities. By using this process, an anode plate for copper electrolysis is prepared.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a process for processing blister copper for the purpose of volatilizing and removing impurities such as molten blister copper, Sb, Bi, and Pb present in the blister copper by vacuum treating the molten blister copper for converter. It relates to vacuum purification methods.

In copper smelting, copper concentrate basically goes through the following steps: smelting in a flash furnace, wrought copper in a converter, and refining in a refining furnace to become refined blister copper, which is used as an anode for electrolysis. Removal of impurities has not always been achieved satisfactorily. Particularly when there are many impurities in the raw material, the amount of impurities remaining after purification becomes unacceptably high. Therefore, in the prior art, it was necessary to carry out fairly strict raw material management to prevent the amount of impurities from becoming too large, by taking measures such as mixing and diluting raw materials with many impurities with raw materials with few impurities.

The refining furnace, which plays the final role in the smelting process, was originally built primarily to reduce the gasified components in the blister copper extracted from the converter, namely sulfur and oxygen, and in particular to reduce oxygen. As, Sb, Bi,
It is not suitable for removing heavy metal impurities such as Pb. In order to improve the removal rate of these impurities, a method has also been proposed in which a calcium compound or a sodium compound is added in a converter or refining furnace to remove the impurities as lime slag or soda slag. However, the problem with this method is how closely contact can be made between the additives and the molten steel, and generally a high removal rate cannot be expected.In addition, the separation of the produced slag and the molten steel is poor, resulting in a score of 59. there were.

Impurities such as As, Sb, Bi, and Pb have a serious negative effect on the subsequent electrolytic process, so it is not only necessary to reduce them as much as possible, but also to actively remove them to improve the impurity tolerance of the smelter. There is a strong desire to establish the ability to use large amounts of ore with many impurities by increasing its capacity.

While searching for a method to effectively remove the above-mentioned impurities from bath-molten blister copper for converters, the present inventors discovered that the above-mentioned impurities could be removed extremely efficiently by applying a vacuum refining process to the molten blister copper. I discovered that it can be done.

By the way, vacuum melting or vacuum casting of pure silver or silver alloys has been practiced for a long time. These are mainly used to reduce or prevent impurities such as oxygen, sulfur, and hydrogen in molten metal, and to bring out better properties of the metal. This is in a different category from the present invention, which performs vacuum treatment in preparation for the process.

Next, Japanese Patent Application Laid-Open No. 49-26116 discloses a method for removing impurities from copper matte by volatilization using a vacuum. However, between matte and blister copper, matte is sulfide and generally has a copper grade of less than 78% and contains a large amount of impurities, while blister copper has a copper grade of 97%.
This is the above, and the two cannot be discussed in the same way regarding vacuum processing. In addition, in order to supply copper@electrode plates of controlled quality to electrolytic plants, it is necessary to establish a means for removing impurities from the blister copper itself for converters before the manufacturing process of copper electrolytic anode plates. Comparing matte and blister copper, blister copper has fewer impurities, but the impurities are inactive, and the effects of vacuum treatment on matte cannot be predicted at all from the effects of vacuum treatment on blister copper. In this way, the vacuum treatment of matte and the vacuum treatment of blister copper for converters also belong to different categories.

In addition, there are several reports on vacuum refining of crude steel on a laboratory scale, but it is generally concluded that the removal rate of As and sb is low and that vacuum refining of blister copper is not appropriate. There are significant differences between such crucible tests and those carried out on an industrial scale in terms of equipment, amount handled, etc. (This fact is presumed to have led to a conclusion that is contradictory to the present invention.The present invention Despite the existence of such reports, these authors dared to attempt vacuum treatment of blister copper on an industrial scale, and were successful.

Finally, vacuum refining technology has been used in steel smelting for more than 10 years, and in recent years, the DH method or wall method has become established as the superior vacuum refining method. However, the purpose of vacuum refining in steel smelting is to reduce impurities such as carbon, oxygen, nitrogen, and hydrogen in steel, and as in the case of the present invention, the purpose of vacuum refining is to remove heavy metal impurities. is fundamentally different. In addition, in the case of iron plates, the product from the vacuum refining process is a steel ingot that is subjected to processing such as rolling, and the product from the blister vacuum refining process is a copper electrolytic anode plate. Their positions in the process are also completely different.

Thus, there is no prior art or peripheral technology that suggests the industrialization of vacuum refining of blister copper for converters. Under these circumstances, as mentioned above, the present invention is the first in the industry to tackle industrial vacuum refining of blister copper for converters, and has succeeded in its industrialization. It pioneered a more efficient and effective converter-vacuum processing equipment process, and its industrial significance is significant.

Briefly stated, the present invention provides vacuum purification of blister copper, characterized in that impurities in the blister copper are volatilized and removed by vacuum treating molten blister copper for a converter in the process of manufacturing an anode plate for copper electrolysis. This method can be carried out advantageously by using a vacuum furnace with a DH type suction, especially for blister copper stored in a tilting furnace.

Furthermore, the deoxidizing treatment can be carried out more efficiently by providing a wall in the tilting furnace.

The present invention will be specifically explained below.

As mentioned above, the converter crude copper produced in the converter still contains a considerable amount of impurities, sulfur, and acid rock. Impurities vary depending on operating conditions and raw material conditions, but include 0.03-0.08% Bi, 0.03-0.08% Bi,
04% Sb, 0.2-0.3% As.

0.015-0.030%pb, 0.001-0.00
2% Zn is a typical example. Sulfur is 0.601~0.02%
Oxygen is contained in an amount of about 0.50 to 0.60%.

If the proportion of ore with many impurities is high, the amount of impurities can further increase.

According to the conventional method, blister copper for converters is processed in a tilting type refining furnace, where sulfur and impurities are removed by blowing air through the tuyere or adding additives if necessary, and then the oxides floating on the surface are removed from the furnace. A scraping operation was carried out to remove it, and then it was reduced, that is, deoxidized, using a reducing agent such as ammonia. However, this method cannot sufficiently remove impurities, and the present invention attempts to remove the impurities by vacuum treatment.

The blister copper for converters is transferred to a ladle, holding furnace, heating furnace, tilting furnace, etc., and then subjected to vacuum treatment. The production temperature of blister copper for converters is 1100-1200°C, and if necessary, it may be heated to a temperature of up to 1350°C before vacuum application. Since the temperature of the molten copper decreases during vacuum treatment, it is preferable to raise the temperature for the converter or to perform preheating.

Regarding the vacuum treatment equipment itself, many vacuum degassing methods have been established in the iron rust industry, and these techniques can be implemented here either as they are or with modifications. The following vacuum processing methods can be used: (a) A ladle or other container containing molten steel is placed in a vacuum chamber,
This measures the volatilization of impurities from the surface of the hot water, but since processing capacity is limited, it is preferable to use mechanical stirring such as electromagnetic induction stirring or tilting of the grapple as much as possible.

(b) Droplet method: After placing a ladle in a vacuum chamber in advance and reducing the pressure by evacuating the vacuum chamber, the converter blister copper stored in the intermediate ladle installed at the top of the vacuum chamber is This is a method in which molten steel is poured out while being scattered as droplets, and utilizes the phenomenon that when molten steel enters a vacuum chamber, impurities dissolved in the molten steel droplets separate from the molten steel due to a sudden pressure drop. Blister copper is poured into the intermediate ladle using a receiving ladle that receives the blister copper from the converter.

Further efficiency can be achieved by disposing in the vacuum chamber, in place of the ladle, an anode mold that is moved intermittently into and out of the vacuum chamber in an appropriate sealed manner.

(→ Vacuum suction method This method is known as a positive type vacuum furnace in the Qin world.
This is a method using the DH method, which was developed by Tmund H6rder and is called the DH method by its acronym.

The DH type vacuum furnace is equipped with a single suction and descending pipe (leg) at the bottom of the vacuum chamber, and the upper vacuum chamber and lower ladle are moved up and down relative to each other in a predetermined cycle, and the molten steel in the ladle is removed. The process is repeated by sucking up the material into a vacuum chamber, vacuum-processing it within the vacuum chamber, and then returning it to the ladle. The molten steel that ascends through the suction pipe and is vacuum-treated in the vacuum chamber is returned to the ladle where it is vigorously stirred and mixed uniformly with the untreated molten steel, gradually increasing the vacuum treatment effect.

2) Circulation method Using a vacuum furnace equipped with suction and discharge pipes (legs), these pipes are immersed in molten steel in a ladle or furnace, and from the suction pipe to the discharge pipe via the vacuum furnace. This process vacuum-processes molten steel by creating a circulating molten steel flow. In the steel industry, a continuous degassing method called the dish method (co-developed by Ruhrstah 1 and Daneraus) is widely used, in which an inert gas such as argon is blown into a suction pipe, and the principle of an air lift pump is used. Vacuum treatment of molten steel is possible by a modified method of this method (described later).

Vacuum treatment is performed at a temperature of molten blister copper = 11'O0~1350
C. and a degree of vacuum of 0.01-10 wiHg. By vacuum treatment according to the invention,
As and Sb are conventionally difficult to remove.

Bi and Pb are removed very effectively. During the vacuum treatment, not only the impurities mentioned above but also elements that are easily gasified such as sulfur and oxygen are simultaneously removed. When oxygen and sulfur cannot be sufficiently degassed by vacuum treatment, the blister copper after vacuum treatment may be transferred to a tilting furnace for degassing.

The drawings illustrate preferred embodiments of the invention.

FIG. 1 shows the implementation of vacuum pumping. The blister copper for the converter is stored in the ladle 1, and the blister copper of the vacuum furnace 3 is placed in the blister bath.
i L is immersed. An induction furnace may be used instead of a ladle. The vacuum furnace 3 is lowered by a crane or the like, or is supported so as to be vertically movable by a hydraulic lifting device (not shown). It is preferable to install an electric current in the vacuum furnace to prevent the formation of adhered substances due to dust and metal.

When vacuum processing molten steel, the vacuum furnace is depressurized, the vacuum furnace is lowered, and the suction tube is immersed deeply in the blister copper bath.The molten steel rises into the vacuum furnace to a predetermined height determined by the pressure difference and the head, and is then released under vacuum. exposed to

When the vacuum furnace is raised after being maintained in this state for a predetermined period of time, the molten steel in the vacuum furnace returns to the ladle and mixes with the blister copper in the ladle. By repeating this process several times per minute, the entire blister copper in the ladle can be vacuum treated. The blister copper thus subjected to the vacuum treatment is subsequently transferred to a tilting furnace where it is deoxidized by blowing in a reducing gas.

FIG. 2 shows a method of carrying out the same treatment as described above in the vacuum furnace 3 while the blister copper for a converter is housed in the tilting converter 11. In this case, the vacuum-treated blister copper is deoxidized by removing LPG steam, air, NU8+inert gas, or other gas from the tuyere 5 of the tilting furnace after removing the vacuum furnace. According to this method, the vacuum treatment and the degassing treatment can be performed in the same furnace, which is efficient.

In the case of vacuum refining of blister copper, unlike that of steel, a relatively large amount of heavy metal impurities is removed by volatilization, so it is necessary to install a dust removal device 10 that removes these impurities by washing, filtration, etc. There is. The vacuum furnace is connected to the dust removal device and the vacuum system by a universal joint to allow vertical movement of the vacuum furnace.

By appropriately selecting vacuum conditions and stirring conditions, impurity removal and degassing can be performed simultaneously during vacuum processing.
Separate degassing treatment using a tilting furnace or the like can be made unnecessary, and the current refining furnace process can also be eliminated.

In this way, the present invention can remove As, which has been difficult to remove in the past.

This is a successful industrialization of the removal of impurities such as Sb, Bi, and Pb, and its significance is extremely significant.

Example 1 After heating 1 ton of converter high-melting blister copper to 1300°C, it was placed in a ladle and subjected to vacuum treatment using a vacuum furnace having a DH type suction tube. The internal pressure of the vacuum furnace was reduced to 0.05 mxHg, and the treatment was carried out for 40 minutes. The vacuum furnace is operated by a crane at a rate of 2 times per minute.
It was moved up and down at a rate of ~4 times.

The results are shown in the table below. Thereafter, it was transferred to a tilting furnace and deoxidized by gas injection, resulting in a carbon concentration of 0.
The deoxidation rate decreased to 16%, resulting in a deoxidation rate of 72.4%.

Through the above treatment, 881 steel of a quality that could be cast as an electrolytic anode was obtained. Incidentally, the blister copper for the converter used as the test material was processed using the current refining furnace method, and the molten crude copper from the converter shown in the table below is 6? 'J1 ton was received in a ladle, and the furnace pressure was reduced to 0.5 rnvJg using a vacuum furnace having a DH type suction part, and vacuum treatment was performed for 15 minutes. As a result, the values shown in the table below were obtained. After the vacuum treatment, it was transferred to a tilting furnace and deoxidized by gas injection. By performing the above treatment, the oxygen in blister copper is reduced to 0.15
% and a deoxidation rate of 75% was obtained, and the quality of the anode is as follows. In this treatment, the treatment time was set to 15 minutes to see the effect of vacuum treatment in a short time, but even with this, sb and As
could be removed by 28% and 43%, respectively. By increasing the treatment time, it is possible to remove impurities to the same level as in Example 1.

[Brief explanation of the drawing]

1 and 2 are schematic diagrams of preferred embodiments of equipment for practicing the present invention. 1: Ladle (or induction furnace) 3: Nitrogen furnace L: Suction pipe 5: Tuyere 10: Dust removal device 11: Inclination furnace Fig. 1

Claims (1)

[Scope of Claims] 1) A method for vacuum refining blister copper, characterized in that in the step of manufacturing an anode plate for copper electrolysis, molten blister copper for a converter is vacuum-treated to volatilize and remove impurities in the blister copper. 2) The method according to claim 1, wherein the vacuum treatment is performed using a vacuum furnace having a DH type suction section. 3) The method according to claim 2, wherein the vacuum treatment is carried out on blister copper stored in a tilting furnace using a vacuum furnace having a DH type suction section. 4) The method according to claim 3, wherein the tilting furnace is provided with a lining.