JPS6141972B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for purifying copper-containing matte to remove impurities from the matte, namely one or more of lead, arsenic, bismuth, zinc, antimony and cadmium. Removing trace amounts of lead and the aforementioned impurities from copper or copper-nickel mats is a difficult and expensive task. When treating nickel, a particularly effective method of removing impurities such as lead is based on the ease with which such impurities can be chlorinated. Therefore, when molten nickel pine is treated with a chlorinating agent, such as chlorine gas, impurities are either volatilized from the vessel or extracted into the solvent phase, such as molten sodium chloride, that comes into contact with the molten pine, depending on the process used. Chloride is formed. This technique has been very successful for nickel mats and is described, for example, in commonly assigned US Pat. No. 3,802,870. The sulfur content of pine has been shown to be critical when attempting to remove arsenic from nickel pine;
As described in commonly assigned US Pat. No. 3,938,989, a sulfur content of about 28% or more is required to achieve adequate arsenic removal. (Unless otherwise specified, all percentages in the text are percentages by weight). Chlorination techniques are applied to nickel pine containing small amounts of copper as impurities, making it possible to remove copper as well as other impurities. However, if one attempts to remove other impurities without chlorinating the majority of the copper in the mat, this technique can be used to treat matt containing significant amounts of copper, i.e. copper matt or 10% or more copper. It was never even applied to the nickel pine containing it. The inventor has discovered that the main reason why the methods used for nickel mat cannot be applied to copper mat is the high solubility of chlorides in copper mat. As a result, chlorination of the molten copper mat produces an unacceptably large amount of copper chloride in the melt without effective impurity removal. Further processing of the melt produces excess chloride fumes. Furthermore, the sulfur levels found necessary to remove arsenic from nickel pine cannot be achieved under practical conditions in copper pine. The inventors have discovered that a modified chlorination technique can be successfully applied to purify pine containing substantial amounts of copper. Additionally, the inventors have surprisingly found that high sulfur contents of 28% or more are not necessary to remove arsenic from such pine through the practice of the present invention. Therefore, the present invention provides a method for removing at least one impurity selected from the group consisting of lead, arsenic, bismuth, zinc, antimony, and cadmium from copper-containing pine containing at least 10% copper. A method for purifying copper-containing matte without chlorinating significant amounts of copper is provided, the method comprising the steps of: (i) forming a molten bath of matte at a temperature of at least 800°C; (ii) introducing into the bath a chlorinating agent selected from the group consisting of copper chloride and a gas stream containing free chlorine; (iii) chlorine necessary to stoichiometrically combine with the impurities to be removed; ceasing the introduction of the chlorinating agent after the predetermined amount has been introduced, which is at least sufficient to provide the chlorinating agent; and (iv) thereafter purging the bath with a gas stream containing an inert gas for at least 10 minutes. In practice, the refining process can be carried out in the same converter vessel in which the matte is produced, so long as the converter vessel is fitted with suitable fume handling and slubbing equipment. However, it is preferred to use a separate chlorination vessel, such as a ladle equipped with a tightly fitting lid. The chlorinating agent can be introduced into the hot bath through a lance that passes through the lid of the container. The lid shall be provided with suitable holes to allow waste gas containing impurities chloride to exit the vessel and be transferred to a wet scrapper for removal and recovery of chloride products and unreacted chlorine. When chlorine gas is used as the chlorinating agent (which is preferred), the chlorine gas can be injected into the bath of molten matte alone or with a carrier gas. The carrier gas serves the useful purpose of providing additional agitation to the bath. Nitrogen is suitably used as carrier gas. Air can be used as a cheap alternative to nitrogen, but the oxygen present in the air tends to oxidize some of the copper itself or the nickel or iron present in the mat. This may be acceptable or even desirable if the iron content of the pine is significant and the iron oxide floats to the bath surface as a scum and can then be removed. Instead of using chlorine gas, solid chlorinating agents including cuprous chloride can be used. It can be stirred into the molten mat or poured into the bottom of the bath. Another effective measure consists in providing a layer of molten salt which covers the surface of the molten mat and which acts as a solvent to collect at least a portion of the chloride products that form. The chloride product not only contains some portion of the impurity chloride, but also some chloride of base metals, and it is necessary to treat the salt to recover the chloride from the salt from which it was collected. Will. The salt used must be appropriate for the temperatures involved. The purification method is preferably carried out on pine at 900-1200°C. At such temperatures,
Common salts such as sodium chloride or potassium chloride are unsuitable as they exhibit too high a vapor pressure, and salts such as barium chloride, calcium chloride or calcium fluoride or certain mixtures thereof must be resorted to. When using such a salt cover, not all of the chloride that forms is captured. This is because some, for example metalloid chlorides, will still escape from the salt cover due to the high vapor pressure. Regardless of whether the chlorinating agent used is gaseous or solid, or whether a salt cover is used, the chlorination step should be followed by a purge step of at least 10 minutes, preferably 20 to 60 minutes. Required. Purging can be done with inert gas alone,
Or, if some degree of base metal oxidation can be tolerated,
The purge gas can economically be air.
The purge period must be sufficient to drive off any residual chlorine dissolved in the refined matte. After purging, the pine should not contain more than about 0.1% chlorine if unhealthy fumes are to be avoided during subsequent handling of the pine. The refining process works best on pine with an iron content of no more than about 5%. Of course, this can easily be ensured by treating the impure mat with air in the presence of a siliceous flux in the necessary conventional converter. The sulfur content of the pine to be refined is also important to the success of the process. There is no need to resort to sulfur contents of 28% or more as is done in the case of nickel pine refining, but arsenic and bismuth removal ensures that the sulfur content combines with all base metals (copper, nickel, cobalt and iron) in the pine. It proceeds most effectively when there is at least enough to correspond to the stoichiometric amount. Preferably, the sulfur content of the initial pine is at least 1.05 times the stoichiometric amount. If adjustments are necessary to ensure this, elemental sulfur may be stirred into the molten matte to be refined or the sulfur vapor may be stirred into the sulfur vapor using graphite lances or tuyeres, such as in a conventional Pierce Smith converter. Alternatively, sulfur-containing gas can be injected into the melt. Let me explain an example. Example 1 A nickel-copper mat containing 28% copper, 48% nickel, 0.56% iron, 0.62% cobalt, 0.061% lead and 21.7% sulfur was used to demonstrate lead removal by the method of the present invention. Approximately 5 kg of this pine was induction heated in an aluminum crucible and chlorinated at 1020-1090°C.
Chlorination was carried out by blowing chlorine gas through a lance immersed in the pine bath at a rate of 21/hour. After 40 minutes of blowing, corresponding to the introduction of an amount of chlorine corresponding to 0.8% of the pine weight, a small sample was taken for analysis. Matsuto is 0.031% lead and
It was found to contain 0.54% chlorine and severe fumes were experienced when it was poured. Immediately after chlorination, nitrogen gas was introduced at a flow rate of 30/h from the same lance used for chlorine. After a 30 minute nitrogen purge, another sample was poured out and analyzed. In this case no fumes are experienced and only a few
It contained only 0.013% lead and 0.04% chlorine. The same tests aimed at high purification showed that the purge period should be chosen according to the degree of chlorination. Therefore, using a chlorine addition of 1.0% by weight of the pine, the lead content of the pine decreased to 0.018% by the time the chlorine flow was stopped. then 60/
Nitrogen purge for 45 minutes at a flow rate of h resulted in a final mat containing 0.007% lead and 0.12% chlorine.
The chlorine level was higher than desired and resulted in a light fume when the pine was poured. Purging similarly chlorinated pine at a nitrogen flow rate of 90/h for 1 hour resulted in a fume-free pine with an analysis of 0.005% lead and 0.06% chlorine. Example 2 A pair of comparative tests A and B were conducted using the same mats as in Example 1. As before, Matsuto's
A 3.34Kg sample was induction heated to 1020-1089℃ in an aluminum crucible. The crucible had a diameter of 9.4 cm, and the crucible depth was about 17 cm. In this case, separate lances were used to inject the chlorine and nitrogen, each lance consisting of a 6 mm inner diameter tube with discharge at a point approximately 16 cm below the melt surface. For the purposes of Test A, a method similar to Example 1 was used, in which chlorine was first injected;
After stopping the chlorine flow, nitrogen was injected from the other lance.
For Test B, a modified method was employed in which nitrogen was injected throughout the process, including the chlornitridation cycle. Table 1 below shows the pine composition analyzed at various stages of chlorination and purging. A comparison of the 10 minute results for tests A and B shows that nitrogen injection after, as well as during, chlorine injection is advantageous for the degree of purification and indeed for the degree of chlorine retention in the pine. Example 3 To prove that the method is effective on an industrial scale, larger scale tests were carried out on batches of approximately 2 tons of pine. The mats were injected through a chlorine-soaked graphite lance into a ladle fitted with a tight-fitting lid. The waste gas was discharged to an alkaline scrapper to clean the gas. The pine used in these tests was 32% Cu, 44
%Ni, 0.63%Co, 0.83%Fe, 22%S and 0.049
It had an analytical value of %Pb. Two typical tests (C
The results of and D) are shown in Table 2.

【table】

【table】

【table】

TABLE EXAMPLE 4 Continuous introduction of chlorine and nitrogen was used as in Example 1 in two tests E and F on the same pine except that the sulfur content was much higher in the pine of test F. In each case, chlorine was added until an amount equivalent to 3% of the mat weight had been introduced, followed by a nitrogen purge for 30 minutes using a flow rate of 12/h. Mat analysis is shown in Table 3, initially, after chlorination, and after purging. From these results it will be seen that the most significant difference between the two tests is in arsenic removal, which progresses satisfactorily in Test F, while no arsenic is removed from the low sulfur pine in Test E.

[Table] Example 5 28%Cu, 48%Ni, 0.036%Pb, 0.38%Fe and
Copper mats containing 21.7% S were used in tests where purification was carried out under a molten salt layer. The method used reached 10% of the pine weight and 75% calcium chloride and 25%
% copper chloride. The matte and molten salt were combined and the two phases were purged by injecting nitrogen into the matte phase at 60/h. Analysis of pine as a function of purge time is shown in Table 4. The results show that satisfactory purification is achieved after 15-30 minutes of purging and that the purging reduces the matte and surface salt impurity levels.

【table】

[Table] Example 6 When using a thin phase containing CuCl for purification,
It has been found that this salt can be used many times in the purification of new pine. 0.058 with the same composition as the previous example
Purified pine containing %Pb. Matsuto's 400
7 g batches were first mixed with 20% CuCl and 80% CaCl ₂
Using the same 60 g batch of salt mixture containing
Purified at 1000℃. Each batch of mats was purified for 15 minutes with a 1/min _N2 purge. The results are shown in Table 5.

[Table] Example 7 The above example demonstrated the effectiveness of the present method on nickel-containing copper sulfide materials. This example shows that the method is equally applicable to nickel-free copper sulfide. Copper sulfide melt containing Pb and As in 3% _Cl2
Chlorine was bubbled into the mat for 20.6 minutes and chlorinated at 1170℃. The pine was then purged with nitrogen equal to 1.5% of the pine. The results obtained are shown below:

Table This example again shows that purging is essential to obtain low impurity levels. Although the invention has been particularly described with reference to preferred embodiments, various modifications may be made in the details of those embodiments without departing from the scope of the invention as defined by the appended claims.

Claims (1)

[Claims] 1. Copper-containing pine containing at least 10% copper by removing at least one impurity selected from the group consisting of lead, arsenic, bismuth, zinc, antimony, and cadmium. A method for refining comprising: (i) forming a molten bath of pine at a temperature of at least 800°C; (ii) introducing into the bath a chlorinating agent selected from the group consisting of copper chloride and a gas stream containing free chlorine; (iii) ) ceasing the introduction of the chlorinating agent after a predetermined amount has been introduced that is at least sufficient to provide the necessary chlorine to stoichiometrically combine with the impurities to be removed; and (iv) thereafter. A method as described above, characterized in that it comprises the step of purging the bath with a gas stream containing an inert gas for at least 10 minutes. 2. The pine composition, if required, before the introduction of the chlorinating agent, is such that the sulfur content is at least equal to 1.05 times the stoichiometric amount required to combine all of the copper as well as the iron, nickel and cobalt present in the pine. Claim 1 adjusted so that
The method described in section. 3 Matsutto is chlorinating and purging 800~
A method according to claim 1, wherein the temperature is maintained at 1200°C. 4. The method of claim 1, wherein an inert gas-containing gas stream is bubbled into the bath during both the chlorination and purging operations. 5. The method of claim 1, wherein the bath of molten mat is maintained under a layer of molten salt comprising barium chloride, calcium chloride, calcium fluoride or mixtures thereof. 6. The method of claim 1, wherein the pine contains iron and the chlorinating agent comprises a gas mixture of chlorine and air. 7. The method of claim 6, wherein the inert gas-containing gas stream comprises air.