JP3217675B2 - Copper smelting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for the dry smelting of copper, and more particularly to a method for the dry smelting of copper in a flash smelting furnace with an improved method of adding a carbonaceous material.

[0002] In a copper smelting operation, Fe
Part of the steel is subjected to peroxidation and magnetite (Fe ₃
O ₄ ) is produced. This Fe ₃ O ₄ is deposited as a coating layer on the furnace bottom and the furnace wall and serves as a protective layer for the furnace refractory. On the other hand, when the amount of Fe ₃ O ₄ generated is large, the coating layer becomes excessively thick and the furnace internal volume becomes large. At the same time, tapping holes in slag and mats are eventually filled, making tapping difficult. Furthermore, a semi-solid phase, a so-called “intermediate layer”, is formed between the slag layer and the mat layer in the furnace to inhibit the separation of the slag and the mat, and the slag is suspended in the slag by increasing its viscosity significantly. And causes various troubles such as an increase in the amount of Cu lost. For this reason, Fe
It is important to keep ₃ O ₄ low for efficient and stable operation of copper smelting.

[0003]

2. Description of the Related Art In copper smelting furnace smelting, coke fine coke or coke fine powder and pulverized coal are co-melted with heavy oil together with copper concentrate in order to lower the copper content in discharged slag and reduce fuel cost. It is known to blow into a furnace (JP-A-5
8-222241). According to the description in this publication,
In the flash smelting furnace, the metallurgical reaction is rapid, and because of the oxidizing atmosphere, a large amount of magnetite (Fe ₃ O ₄ ), which is a peroxide of iron, is generated, and the unburned coke powder that covers the surface of the slag containing it Reacts with magnetite to reduce magnetite, and the copper quality in slag decreases. Further, according to the above-mentioned Japanese Patent Application Laid-Open No. 58-221241, as a preferred method, the addition of coke breeze in the reaction tower of the flash smelting furnace should be such that unburned powder coke uniformly covers the entire surface of the solution in the setter. Preferable; coke and pulverized coal have a mesh size of 16 mesh (1 mm) to 325 mesh (44 μm) because coke and pulverized coal have a reduced magnetite reduction rate.
m) that the particle size distribution is good; that the carbonaceous material has a high volatile content.

At the Sagaseki smelter to which the present applicant belongs, coke breeze having the following particle size distribution is used in a flash smelting furnace, the magnetite in the slag becomes 2 to 4%, and the unburned powder floating on the slag surface. We considered that coke reduced a part of magnetite ("Non-ferrous smelting and energy saving" Research Committee on Non-ferrous smelting technology and energy, use of coke breeze in flash furnace, Japan Mining Association Showa) 1960 (1985).

[0005]

[Table 1] Types of coke breeze ABC 10mm over 0000 grains 5-10mm 66 5 degrees 3-5mm 45 9 minutes 1-3mm 16 25 21 cloth 0.15-1mm 42 50 55 (%) 0.15mm under 32 14 10 total 100 100 100 C. 85 85 85 minutes Volatile content 1 1 2 (%) Ash content etc. 14 14 13 Calorific value (kcal / kg) 6,800 6,800 7,000

As described above, in the copper smelting operation using a flash furnace, in order to prevent the above-mentioned trouble due to excessive production of Fe ₃ O ₄ , coal such as coke breeze, pulverized coke and pulverized coal is used in a reaction tower. At present, charging a material as a reducing agent for Fe ₃ O ₄ is widely performed.

That is, conventionally, heavy oil, coke breeze, pulverized coal, etc. are added and burned as auxiliary fuel for heat compensation in the reaction tower of the flash smelting furnace. A portion of the fuel enters the solution below the reaction tower and becomes Fe ₃ O ₄
Coke and pulverized coal are added to the reaction tower as an effective means for reducing Fe ₃ O ₄ in addition to the purpose of heat compensation in order to reduce the amount of Fe.

[0008]

In the dry smelting method of copper in a flash smelting furnace by adding a carbon material, if the method of adding the carbon material is inappropriate and excessive reduction occurs, the coating layer of the furnace refractory disappears. The refractory material becomes severely damaged, causing molten metal to leak from the furnace, and a metal phase is formed in the furnace and penetrates the joints of the bottom furnace bricks to raise the bricks, and the impurities are distributed to the metal phase and are transferred to the slag phase. The distribution is reduced, and unburned carbonaceous materials fly to the exhaust heat boiler and burn in the boiler, causing various adverse effects such as significantly impairing the operation of the boiler.

As described in JP-A-58-221241 and the above-mentioned technical report from the smelter to which the present applicant belongs, if unburned powder coke is present enough to cover the slag surface. By excessively staying on the solution, the equilibrium oxygen partial pressure is extremely lowered, and a strong reducing atmosphere is formed in the furnace. In such a strongly reducing atmosphere, troubles such as erosion of the refractory due to disappearance of the furnace refractory coating layer, elevation of the furnace bottom brick due to generation of a metal phase, and reduction in the removal rate of impurities to slag often occur. In addition, a large amount of unburned carbon material is carried over to the boiler, which may cause after-burning in the exhaust heat boiler.

Accordingly, the present invention requires the unburned carbon material to obtain the effect of reducing Fe ₃ O ₄ by the carbon material such as coke breeze added in the flash smelting furnace reaction tower. By overcoming the trade-off phenomena of causing the above troubles when a large amount of steel stays in the furnace, to provide a copper dry smelting method capable of obtaining a good reduction effect and eliminating the above troubles in various copper melting and melting operations. Aim.

A method according to the present invention for achieving the above object is as follows.
In a method of dry-smelting copper by adding a carbon material to a reaction tower of a white-melting furnace, the carbon material has a particle size of under 100 μm of 65% by weight or more based on the entire carbon material, and 100 μm to 44 μm. Particle size is 25% by weight based on the carbon material (hereinafter, referred to as
Percentages representing particle size are by weight unless otherwise specified) and have a fixed carbon content of 80% by weight
( Hereinafter, the fixed carbon content is% by weight ) is a dry smelting method in which the carbon material is unburned and dust-collected carbon generated during burning of petroleum coke by a burner. This is a dry smelting method for copper as powder (so-called PC carbon).

Hereinafter, the configuration of the present invention will be described in detail. Hereinafter, an example of coke breeze as a carbon material will be mainly described, but it should be understood that this description also applies to other carbon materials. The present inventors have reported that the reduction of Fe ₃ O _{4 in} slag by unburned powder coke is carried out by (a) as previously considered, powder coke floating and remaining on the slag bath surface reduces the oxygen partial pressure in the furnace and strongly reduces it. Reduction by forming an atmosphere,
And (b) clarified by focusing on the fact that there are two mechanisms of catalytic reduction while the coke breeze invading the slag floats on the slag bath surface.

It has been found that which one of the two reduction reaction mechanisms (a) and (b) is activated is greatly affected by the particle size of the carbonaceous material such as powdered causk. That is, since the carbon material coarser than about 100 μm has a large particle size of the unburned portion, the catalytic reduction speed according to (b) is small and (a) is mainly used. On the other hand, when the particle size of the coke breeze is refined and specified in the range of the present invention, (b) is activated as described in detail below.

The present invention is characterized in that the particle size of the coke breeze is made finer than before, as described above.
The result of considering combustion in the reaction tower when the particles are made into fine particles will be described. The burning rate of the carbonaceous material added in the reaction tower is affected by the atmospheric oxygen partial pressure in the reaction tower, the particle temperature, the gas flow rate, and the like. FIG. 1 shows an example in which the change in these factors in the reaction tower is predicted by a calculation model (flash furnace model). The oxygen partial pressure in the reaction tower is determined by the amount of spontaneous copper concentrate charged together with the carbonaceous material. Since the amount is overwhelmingly large, it can be seen that the amount is dominated by this combustion and drops sharply toward the lower part of the reaction tower. In the figure, PO ₂ is the oxygen partial pressure, Up / Ug is the particle / gas flow rate (m / sec), Tp is the particle temperature (K), and tp is the particle falling time (sec). Thus, combustion behavior in the reaction tower of three types of coke breeze having a particle size distribution shown in FIG. 2 was examined. In FIG. 2, the particle size distribution of each coke breeze is as follows.

[0015]

[Table 2] 100 μm under 100 μm to 44 μm coke fine 1 78% 63% coke fine 2 49% 41% coke fine 37 % 5%

Table 3 shows the results of predicting the combustion rates of the three types of coke breeze having different particle size distributions shown in FIG. 2 in the reaction tower based on the behavior of various factors shown in FIG. The particle size of the carbon material particles after combustion can be calculated by the following equation. _{r = r o - (Mc /} ρc) × kt × C (O 2) × θ r: post-combustion of the carbonaceous material particle radius (m) r _o: initial radius of carbonaceous material particles (m) Mc: Molecular weight of carbon 0 .012 kg / mol ρc: density of carbon material particles 1,000 kg / m ³ kt: overall reaction rate constant (m / hr) C (O ₂ ): oxygen concentration (mol / Nm ³ ) θ: reaction time (hr) Reaction rate constant (kt) is based on Refining Chemical Engineering Exercise (Edited by Washigan, January 15, 1974, published by Yokendo, 1st edition), 2nd edition
It was determined by the calculation method of pages 5 to 31, especially pages 28 to 31. This calculation method is for estimating the burning rate of carbon particles in the sintering process. It is a single carbon particle, the initial outer diameter is retained by the ash layer, and the diffusion resistance in the ash layer is negligible (ie, gas barrier film). Although only the internal diffusion resistance and the chemical reaction resistance are considered), these assumptions are considered to be actually valid in the estimation of carbon particle combustion in the flash smelting furnace. The formula of the particle size (r) is based on the above-mentioned smelting chemical engineering practice page 30.

[0017]

Table 3 Result of predicting combustion rate of coke breeze in the reaction tower (unit:%) Calculation value of combustion rate in the reaction tower Measured value coke breeze 1 74 55-80 coke breeze 59 40-67 coke breeze 3 17 10 30

Table 3 also shows the measured and calculated values of the burnup rate obtained from the carbon analysis values of the falling objects in the reactor taken from the sampling holes installed at the lowermost end of the side wall of the reactor. Both of them are in good agreement with each other, indicating that the coarser the particle size distribution of the added coke powder, the lower the combustion rate and the higher the unburned content. As described above, the calculated value obtained by the model and the measured value were in good agreement with each other. Next, the particle size distribution of coke unburned in the reaction tower and remaining in the furnace was considered by the calculation model.

FIG. 3 and FIG. 4 show the cumulative weight ratio of unburned powder coke and the weight ratio by particle size of the three types of coke flour at the lowermost end of the reaction tower predicted by this calculation model, respectively.

In FIG. 3, comparing the particle diameters with a cumulative weight percentage of 50%, in the case of coke breeze 1 before combustion (FIG. 2) and after (FIG. In the case of coke breeze 2, 100 μm becomes 70 μm similarly, but 500 μm
The particle size distribution hardly changes in the coke breeze powder 3 having a coarse particle size of m.

In terms of the weight ratio by particle size shown in FIG. 4, the proportion of fine particles of 40 μm or less after combustion is about 55% in the case of coke breeze 1 ′ and 2% in the case of coke breeze 2 ′.
It is expected that the ratio of coarse particles of 300 μm or more in the coke breeze 3 ′ will be 70% or more.

As described with reference to FIGS. 3 and 4, when fine coke powder having a certain particle size or less is burned in the reaction tower, the ratio of the fine powder becomes higher, and as described below, the proportion of magnetite is reduced. The reduction rate can be increased.

That is, slag that has been adjusted and melted so that the content of Fe ₃ O ₄ has a constant value has been sieved in advance, and the coke breeze has been adjusted so that the particle size distribution is 1 ′ and 2 ′ in FIG. FIG. 5 shows the results of an investigation of the effect of the coke breeze particle size on the reduction rate of Fe ₃ O ₄ by the crucible test. As shown in FIG. 5, the fine particle size such as coke fine 1 ′ is compared with the fine particle size of coke fine 2 ′ in Fe ₃ O.
It can be seen that the reduction rate of ₄ is remarkably fast.

From the above examination results, the reduction of Fe ₃ O _{4 in} the slag by the unburned powder coke is caused by the catalytic reduction (b) while the coke fine entering the slag floats on the slag bath surface as described above. There are two mechanisms of reduction (a) by reducing the oxygen partial pressure in the furnace and forming a strong reducing atmosphere by the coke breeze floating and staying on the slag bath surface, thereby reducing the particle size of the unburned coke. The former mechanism (b) is prepared by adding a carbon material having a particle size distribution as shown in FIG.
By increasing the reduction ratio of slag, even if the amount is reduced, the fine unburned matter generated causes Fe ₃ O ₄ in the slag to be reduced.
And the amount of unburned matter generated is small and there is almost no unburned powder remaining on the slag bath surface in the setter.Therefore, problems caused by excessive reduction as described above and troubles in the exhaust heat boiler Has been found that can be eliminated. By deceiving, the present inventors carried out test operations shown in Examples and Comparative Examples, which will be described in detail later, in an actual furnace to confirm this, and could actually confirm the effects thereof.

In the present invention, the particle size was adjusted so that 65% or more, preferably 70% or more of the carbon material was under 100 μm. More preferably, 100 μm under is 8
0% or more. Further, when the particle size distribution of 100 μm to 44 μm is less than 25%, the number of ultrafine particles of less than 44 μm increases, which is burned in the reaction tower and no unburned matter remains. And More preferably, 100 μm to 44 μm is 40% or more.

Next, regarding the composition of the carbonaceous material, an example of the analysis value (%) of the commercially available coke breeze is shown in the following table.

[0027]

[Table 4] Fixed carbon Total sulfur Volatile ash Fine powder coke (product of Company A) 87.9 0.55 1.7 10.5 Coke powder (product of Company B) 93.8 1.06 1.8 4.4 Pulverized coal (C company product) 47.2 2.36 42.7 9.0

As described above, carbon in carbonaceous materials such as coke breeze and pulverized coal is composed of fixed carbon and carbon in volatile components. The latter has high flammability and is almost completely burned in the process of falling down the reaction tower. Since it does not remain unburned, it is effective as a fuel but is not suitable as a reducing agent. That is, it is preferable that the carbon material as the reducing agent added in the reaction tower has a high fixed carbon content and a low volatile content. In particular, if the concentration of copper concentrate, that is, the productivity, is increased by increasing the oxygen concentration of the air blown into the flash furnace, the amount of auxiliary fuel required will decrease. If charcoal is used, the amount of unburned carbon required for reduction will be drastically reduced, and a situation will be reached in which little reduction effect can be obtained. For example, in the case of pulverized coal containing about 40% each of a volatile component and fixed carbon and having a particle size of about 90 μm or less, it is almost completely burned in the reaction tower, and almost no unburned components required for reduction remain. From this viewpoint, when comparing coke breeze and pulverized coal, the volatile matter of the former is generally 1 to 5
% While the fixed carbon is as high as about 80-95%,
The latter contains 30-40% volatiles and the fixed carbon is 40-7
Since it is as low as 0%, it is necessary that the reducing agent contains 80% or more of fixed carbon. It is more preferably at least 90%.

As a means for adding the carbonaceous material, the main charge such as copper concentrate and a solvent may be added and mixed in advance and charged from a concentrate burner, or a dedicated burner may be installed at the top of the reaction tower. May be charged. As the flash smelting furnace, various furnaces such as a parakeet type flash smelting furnace can be used in addition to the auto-kump type furnace shown in FIG. If the copper concentrate also contains enough sulfur to allow flash smelting and contains mainly copper as a valuable metal,
Various raw materials can be used.

[0030]

Under normal operating conditions of the flash smelting furnace, it is calculated by calculation that coke breeze having a particle size of about 250 μm or less is carried over to the boiler. In contrast, the unburned powder coke is considered to be liable to carry over as the particle size becomes smaller, but actually the opposite result was obtained.
After investigating the cause, the following interesting phenomenon was found.

FIGS. 6 to 9 show optical microscope photographs (magnifications) of sections cut and polished by embedding a fallen object in the reaction tower taken from a sampling hole installed at the lowermost end of the side wall of the reaction tower into a resin during the operation test of the example. 200 times). These photographs show that many of the unburned fine coke breeze particles collide with the molten copper concentrate particles melted by the heat of reaction and are captured. That is, the unburned powder coke collides with and is trapped by the molten copper concentrate particles with a high probability, and is not carried over. Further, the unburned coke passes through the slag liquid surface, settles in the liquid, and then comes into contact with the coke breeze and Fe ₃ O ₄ during floating.

However, when the amount of unburned powder increases due to coarse particles outside the scope of the present invention, the probability of collision between the coke breeze and the copper particles decreases, and the amount of after-burn that is carried over by the boiler relatively increases. I do.

Furthermore, in addition to the above-mentioned phenomena, it was found that As and Sb in the mat migrated favorably into the slag, and there was no extreme reduction in the distribution ratio to the slag due to excessive reduction.

[0034]

【Example】

Example 1 Coke powder 4 (so-called PC carbon) having a particle size distribution shown in FIG. 10 was inserted into a flash furnace reactor shown in FIG. 11 through a concentrate burner at a weight addition rate of 0.9%. In the figure, 1 is a concentrate burner, 2 is a reaction tower, 3 is a settler, 4 is an uptake, 5 is a slag, and 6 is a mat.

As a result of the test operation, the following results were confirmed. First, Fe ₃ O ₄ content of the slag, which is an index showing the reduction effect is 3-6%, the intermediate layer is not formed, and Cu quality of the slag was 0.60%. The values of the distribution coefficient between the slag of As and Sb and the mat were 0.5 and 1, respectively. Here, the distribution coefficient is As distribution ratio = (As) _slag / [As] _matte Sb distribution ratio = (Sb) _slag / [Sb] _matte for each element expressed in weight%.

The charging of the raw materials was interrupted during the operation test, and immediately after that, the carbon (Fe) ₃ O ₄ content (unit:%) in the slag collected from the bath surface in the settler immediately below the reaction tower was measured. Are shown in Table 5.

[0037]

Table 5 Slag sampling location Settler section immediately below C Fe ₃ O ₄ reaction tower 0.14 4.60 Gutter at slag hole outlet 0.02 4.19

In Table 5, the slag immediately below the reaction tower contains unburned powder coke corresponding to a carbon content of 0.14%, and Fe ₃ O ₄ in the slag has already been reduced to the 4% level. It was confirmed that.

As a result of observation in the furnace, almost no unburned powder coke floating and staying on the bath surface in the setter was recognized. There was no occurrence of afterburn trouble in the boiler, which is an indicator of the quality of operation. In addition, although the coating layer of the settler refractory was considerably thinner as compared with the case of Comparative Example 2, it was confirmed that the state of uniformly covering the entire surface of the refractory was maintained.

Comparative Example 1 Coke powder having a particle size indicated by coke powder 5 in FIG. 10 was added to a charge of copper concentrate, a solvent and the like at a weight ratio of 1.5 to 2.3%, and a concentrate burner was added. Through a flash smelting furnace.
As a result of the test operation, the slag Fe ₂ O ₄ content was 2 to 5%.
However, although there was no intermediate layer, there was no intermediate layer, but the coating layer of the refractory was extremely thin, and some bricks were exposed and came into direct contact with the solution. The distribution coefficients between the slag and the mat of As and Sb were about 0.25 and 0.5, respectively. This value is approximately one-fourth when no carbon material is added.
And the slag transfer rates of these elements decreased. Furthermore, the unburned portion carried over was afterburned in the boiler, which significantly impeded the dust removal operation. As a result of stopping the charging of raw materials and inspecting the furnace interior,
It was observed that a large amount of unburned coke floated and stayed on the bath surface in the settler.

Comparative Example 2 The weight addition rate of coke breeze having the same particle size as that of Comparative Example 1 (coke breeze 5 in FIG. 10) was reduced to 0.9%, and the coke breeze was loaded into a flash furnace reactor through a concentrate burner. Entered. Compared to the case of Comparative Example 1, the slag Fe ₃ O ₄ content increased to 7 to 10%, and the thickness of the intermediate layer became 100 to 200 mm between the slag and the mat. The slag Cu quality (slag loss) was increased by about 0.05%. on the other hand,
The settler refractory became covered with the coating layer over the entire surface, and the values of the distribution coefficient between the slag / mat of As and Sb were about 0.5 and 1, respectively, which was doubled from the case of Comparative Example 1. Although the afterburn trouble of the unburned coke boiler in the boiler almost disappeared, the trouble in the boiler still occurred when the coarse coke having the particle size of the coke fine 5 in FIG. 10 was used on the right side. In addition, as a result of observing the inside of the furnace, the amount of unburned coke floating and staying on the bath surface in the setter was considerably smaller than that in Comparative Example 1, and no state of covering the entire surface was observed. The test results of Example 1 and Comparative Examples 1 and 2 are shown in Table 6 in comparison.

[0042]

[Table 6] Example 1 Comparative example 1 Comparative example 2 Test conditions Carbon material type used Coke powder 5 Coke powder 4 Coke powder 4 Carbon material addition rate (%) 0.9 1.5 to 2.3 0.9 Copper grade in mat (%) 60 to 61 60-61 60-61 test results Fe ₃ O ₄ (%) in the slag 3-6 2-5 7-10 partition coefficient between the intermediate layer thickness (mm) None None 100-200 slag and matte as 0.5 0.25 0.5 Sb 1 0.5 1 Copper loss in slag (%) 0.60 0.60 0.65 Refractory coating Uniform coating Refractory uniform coating Partially exposed Large coating thickness burn No impact after-after-after-burn of the boiler there is a burn ho operation inhibition Tondonashi

Example 2 In the method of Example 1, coke breeze (fixed carbon ratio: 8
(1.6%) is shown in FIG. 10, and the following particle size distribution is used, and copper smelting in a flash furnace is performed in the same manner as in Example 1 except that the weight addition rate is 0.9%. Grain size (μm) Cumulative weight ratio (%) +250 100 250/100 90 150/105 79 79 105/70 69 75/44 43 −44 43 (105-44) 26 As a result of smelting, unburned carbonaceous material is melted. However, the amount was remarkably smaller than that of the comparative example, and there was no operational trouble and the same sufficient reducing power as in Example 1 was obtained.

[0044]

As described above, by adding the carbonaceous materials described in the claims in the reaction furnace of the flash smelting furnace, it is possible to prevent operational troubles due to excessive generation of Fe ₃ O _{4 in} the slag. In addition, the amount of Cu contained and lost in the slag is reduced, and at the same time, refractory erosion due to excessive reduction of Fe ₃ O ₄ , reduction of slag removal rate of impurities, and a stable flash furnace without boiler trouble Operation can be achieved.

[Brief description of the drawings]

FIG. 1 is a graph showing an example in which a change in each factor in a reaction tower is predicted by a calculation model.

FIG. 2 is a graph showing the particle size distribution of coke breeze for which a combustion rate was predicted.

FIG. 3 is a graph showing the particle size distribution of unburned coke at the lowermost end of the reaction tower.

FIG. 4 is a graph showing the weight ratio of unburned coke by particle size at the lowermost end of the reaction tower.

FIG. 5 is a graph showing the results of a reduction test of Fe ₃ O ₄ by crucible reduction.

FIG. 6 is an optical microscope photograph (200) of particles falling in a reaction tower.
Times).

FIG. 7 is an optical microscope photograph (200
Times).

FIG. 8 is an optical microscope photograph (200
Times).

FIG. 9 is an optical microscope photograph (200
Times).

FIG. 10 is a graph showing the particle size distribution of coke breeze used in Examples.

FIG. 11 is a view showing specifications of a flash smelting furnace used in an example.

[Explanation of symbols]

 1 Concentrate burner 2 Reaction tower 3 Settler 4 Uptake 5 Slag 6 Mat

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Yoshiaki Suzuki No. 3382, Seki 3, Saganoseki-machi, Sakaseki-cho, North Sea-gun, Oita Pref. A) Japanese Utility Model Hei 5-45065 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) C22B 1/00-61/00

Claims (2)

(57) [Claims] 1. A method for dry smelting copper by adding a carbon material to a reaction tower of a white smelting furnace, wherein the carbon material has a particle size of under 100 μm is 65% by weight or more based on the carbon material, and 10
Particle size of 0 μm to 44 μm is 25% by weight based on the carbonaceous material.
It has the above particle size and the fixed carbon content is 80% by weight .
A dry smelting method for copper characterized by the above. 2. The method for dry smelting copper according to claim 1, wherein said carbon material is unburned and dust-collected carbon powder generated during burner combustion of petroleum coke.