JP2000290735A - Reduction treatment in dry-type refining of raw copper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely and stably raise molten metal temp. at the completion of reduction to not lower than a target lowest molten metal tapping temp. even in the case where the temp. just before starting the reduction is low, by measuring the molten metal temp. just before starting the reduction treatment and adjusting the flowing amount of hydrocarbon and oxygen-containing gas so that the lower the molten metal temp. is, the higher the ratio of the oxygen-containing gas is corresponding to the molten metal temp. SOLUTION: The reduction treatment reduces the oxygen in the molten metal by blowing a hydro-carbon base gas together with an oxygen-containing gas (air) into molten crude copper after oxidizing process. It is desirable that the blowing amount ratio is adjusted so that the molten metal temp. at the completion of the reduction becomes not lower than the target lowest molten metal tapping temp. The target molten metal tapping temp. is a temp. adding the dropping temp. estimated in the interval from a refining furnace to a casting machine to the optimum casting temp. when the molten metal after refining is cast into an anode with the casting machine, and ordinarily, this temp. is usually 1,160-1,180 deg.C and the target lowest molten metal tapping temp. is about 1,160 deg.C. It is unnecessary to heat the molten metal with oil-burner, etc., in the interval of the molten metal tapping after completing the reduction, and thus, the productivity is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dry-refining blister copper, and more particularly, to a reduction treatment step after an oxidation step, in which a hydrocarbon-based gas as a reducing agent is introduced into a blister copper melt together with an oxygen-containing gas such as air. It relates to a method of blowing and reducing.

[0002]

2. Description of the Related Art Generally, various processes are carried out as a smelting process of copper. A typical process is smelting in a flash smelting furnace to form a mat, and further converting the mat into a converter. To obtain blister copper having a copper content of about 98.5%, and further purifying the blister copper to obtain a copper content of 99.3%.
% To about 99.5%, and then cast into the anode and finally electrolytically refined. Among such processes, as a method for purifying blister copper obtained from a converter, generally, a blister copper melt obtained from a converter is received, for example, in a cylindrical horizontal tilting type refining furnace, and in the refining furnace. Dry purification is often performed. As a specific method of the dry refining in this case, an oxidizing step for blowing air into the molten crude copper to mainly remove and oxidize S (desulfurize);
A reducing agent is blown into the molten metal to remove (deoxidize) oxygen present in the blister copper sent from the converter and 0.8 to 1.0% of oxygen absorbed in the molten metal in the oxidation step. And a reducing step for reducing the amount to 0.1 to 0.2% by adding a reducing agent in the latter reducing step. Recently, petroleum liquefied hydrocarbon gas (LPG) has been used as a reducing agent in the latter reducing step.
Is often blown with cracking air.

After the above-described reduction step in the refining furnace, the molten metal is discharged from the refining furnace, guided to a casting machine through a gutter or the like, and cast into an anode for electrolytic refining. Therefore, should the tapping temperature from the refining furnace be as close as possible to the temperature that allows for the temperature drop between the refining furnace and the casting machine (hereinafter referred to as “target tapping temperature”) to the optimal casting temperature in the casting machine? Alternatively, the temperature must be equal to or higher than the allowable minimum casting temperature of the casting machine in view of the amount of temperature drop between the refining furnace and the casting machine (hereinafter referred to as "target minimum tapping temperature"). Here, the target tapping temperature is
Although it varies depending on the length and structure of the gutter from the refining furnace to the casting machine, the degree of heat retention, etc., it is generally 1160 ° C.
In many cases, the temperature is about 1180 ° C., and therefore, the target minimum tapping temperature is usually about 1160 ° C.

[0004]

The temperature of the molten metal immediately before the start of the reduction in the blister copper refining furnace depends on the amount of the molten metal in the furnace, the structure of the furnace,
Alternatively, the temperature of pouring from the converter and the heat retention conditions before the oxidation process,
Although it depends on the treatment conditions of the oxidation step, etc., it is generally 1
It is often about 100 to 1130 ° C. On the other hand, in the reduction step, the temperature of the molten metal rises due to the exothermic reaction accompanying the blowing of the hydrocarbon gas and air, and the temperature rise is generally about 50 ° C. Therefore, the temperature of the molten metal at the end of the reduction is usually about 1160 to 1180 ° C., but actually, the temperature of the molten metal immediately before the start of the reduction is 11 ° C.
If the temperature is as low as around 00 ° C., the temperature of the molten metal at the end of the reduction may be lower than the target minimum tapping temperature of 11 due to variations in the process conditions.
In many cases, the temperature is lower than 60 ° C. and about 1150 ° C.

As described above, when the temperature at the end of the reduction is lower than the target minimum tapping temperature, if the low-temperature molten metal is directly discharged from the refining furnace to the casting machine, the viscosity of the molten metal in the gutter or the casting machine is increased. In some cases, clogging of molten metal occurs in a gutter or a casting machine due to rising or partial solidification of the molten metal. Therefore, generally, the temperature at the end of the reduction is measured, and if the temperature does not reach the target minimum tapping temperature, the fuel oil is heated by burning the heavy oil burner after the reduction is completed, and the temperature of the molten metal is raised to the target minimum tapping temperature or more. Is being raised.

[0006] However, when the molten metal is heated by the heavy oil burner after the completion of the reduction as described above, it takes a long time to heat the molten metal, and there is a problem that productivity is impaired. For example, 350
In the case of a cylindrical horizontal tilting type refining furnace that holds tons of molten metal, it takes about one hour to heat the molten metal to raise the temperature of the molten metal to 10 ° C. by the heavy oil burner, which hinders productivity. Would. By the way, 35 blister copper
One cycle of the operation in the refining furnace with 0 tons, if heating by the heavy oil burner is not performed after the reduction is completed,
Generally, it is about 6 hours (1.5 hours of reduction + 4.5 hours of casting), and it is apparent that heating for 1 hour to raise the temperature of the molten metal by 10 ° C. has a significant effect on productivity. Further, performing the heating for a long time by the heavy oil burner after the completion of the reduction in this manner also increases the energy cost. Furthermore, as described above, if the time of one cycle in the refining furnace is prolonged due to heating by the heavy oil burner after the completion of the reduction, the processing step in the upstream converter and the like is affected, and the production plan is disturbed. Not only that, it is necessary to keep the molten metal warm even in the upstream process, which may further increase the energy cost.

[0007] The present invention has been made in view of the above circumstances, and even if the molten metal temperature immediately before the start of the reduction is low, the molten metal temperature at the end of the reduction is reliably and stably maintained at a target minimum molten metal discharge temperature. Therefore, it is not necessary to heat the molten metal by a heavy oil burner or the like after the completion of the reduction, and it is an object to prevent a decrease in productivity and an increase in energy cost.

[0008]

SUMMARY OF THE INVENTION The present inventors have found that the ratio (flow rate ratio) of a hydrocarbon-based gas and an oxygen-containing gas such as air blown into a blister copper melt for a reduction process is reduced during the reduction process. As a result of further research focusing on affecting the degree of temperature rise, the molten metal temperature immediately before the start of reduction was measured, and the flow rate ratio between the hydrocarbon-based gas and oxygen-containing gas blown into the molten copper was measured. The present inventors have found that, by changing the temperature of the molten metal immediately before the start of the reduction, the temperature of the molten metal at the end of the reduction can be stably ensured to be equal to or higher than the target minimum temperature of the molten metal.

Specifically, in the invention of claim 1, in the dry refining of blister copper, a reduction treatment for reducing oxygen in the molten copper by blowing a hydrocarbon-based gas together with an oxygen-containing gas into the molten copper after the oxidation step. In the method, the temperature of the molten metal immediately before the start of the reduction treatment is measured, and the flow rate ratio between the hydrocarbon-based gas and the oxygen-containing gas blown into the molten metal according to the molten metal temperature is determined. It is characterized in that it is adjusted to be higher.

According to a second aspect of the present invention, there is provided the method for reducing treatment in dry refining of blister copper according to the first aspect, wherein the hydrocarbon-based gas and the oxygen-containing gas are mixed so that the molten metal temperature at the end of the reduction is equal to or higher than a target minimum tapping temperature. It is characterized in that the flow ratio with the gas is adjusted.

Further, according to a third aspect of the present invention, in the method for reducing a blister copper according to the first aspect of the present invention, the flow rate ratio is changed during the reducing process.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the entire process of purifying blister copper in a refining furnace including the reduction treatment method of the present invention will be described.

A refining furnace, for example, a refining furnace of a cylindrical horizontal tilting type, is preheated and kept warm by a heavy oil burner in advance. Then, the blister copper melt discharged from the converter in the preceding process is received into the refining furnace via a ladle or the like. Even at the time of receiving, the inside of the refining furnace is heated by the heavy oil burner. Here, it is needless to say that the blister copper melt for two or more converters may be sequentially received in the refining furnace. In addition, generally, the period of receiving the blister copper melt from the converter to the refining furnace,
Alternatively, even during a standby period between receptions, the blister copper melt in the refining furnace is heated and kept warm by the heavy oil burner.

After the predetermined amount of the molten copper from the converter is received in the refining furnace as described above, an oxidation step for oxidizing and removing S in the molten metal from the molten metal is performed. This oxidation step is generally performed by blowing a gaseous oxidant such as air from a tuyere below the surface of the molten metal in the refining furnace, but is not particularly limited in the present invention. Prior to the oxidizing step, it is usual to perform a "scratching" to scrape an oxide such as iron oxide floating on the molten metal, that is, a so-called "tangling". In addition, during the oxidation process after "scratching", the fuel oil burner is generally burned to keep the temperature warm,
It is usual to keep the melt warm.

After the completion of the oxidation step as described above, a reduction step is performed. This reduction step is for removing (deoxidizing) oxygen present in the blister copper sent from the converter and oxygen absorbed in the molten metal in the oxidation step.
This is carried out by blowing hydrocarbon-based gas into the molten metal in the refining furnace together with the oxygen-containing gas from the tuyere below the surface of the molten metal.
Here, a typical example of the hydrocarbon-based gas is a gas obtained by vaporizing a petroleum-based liquefied hydrocarbon gas (LPG) containing butane (C ₄ H ₁₀ ) as a main component. It is general to use LPG, but it is not limited to LPG, and it goes without saying that natural gas or the like may be used. Air is a typical oxygen-containing gas, but other oxygen-enriched air or any gas containing a large amount of oxygen (of course, it is necessary that components other than oxygen do not adversely affect the molten copper). ) May be used.

In the reduction step, an oxygen-containing gas (hereinafter, referred to as "air" as a representative example) partially burns a hydrocarbon-based gas to produce CO, H ₂ , C _m H _n (m ≦ 4; n). ≤
10) to accelerate the deoxidation rate. When air is blown into the molten metal, oxygen in the blown air is converted into a hydrocarbon-based gas (for example, C ₄ H ₁₀ )
Reacts with.

C ₄ H ₁₀ + O ₂ → CO + H ₂ + C _m H
_n (m ≦ 4; n ≦ 10)

By this reaction, CO, H ₂ , C _m H
_n (m ≦ 4; n ≦ 10) contributes to the reduction and removal of oxygen in the molten metal. The above reaction is a partial combustion reaction, and the calorific value increases as the amount of oxygen increases, and the amount of rise in the temperature of the molten metal during the reduction treatment increases. Thus, in the present invention, the temperature of the molten metal is measured immediately before the start of the reduction step (before the start of the injection of the hydrocarbon gas and the air) after the end of the oxidation step, and the injection of the hydrocarbon gas and the air is performed in accordance with the temperature of the molten metal. Adjust the flow ratio. Specifically, when the temperature of the molten metal before the start of reduction is low, the ratio of air is increased to increase the amount of temperature rise during the reduction process. Conversely, when the temperature of the molten metal before the start of reduction is high, By lowering the ratio, the amount of temperature rise during the reduction process is suppressed, and thereby, the molten metal temperature at the end of the reduction process is controlled so as to approach the target tapping temperature. Alternatively, control is performed so that the temperature of the molten metal at the end of the reduction process is equal to or higher than the target minimum tapping temperature. The target tapping temperature is, as described above, the temperature obtained by adding the temperature drop expected between the refining furnace and the casting machine to the optimal casting temperature when the molten metal after the casting is cast into the anode in the casting machine. It is usually about 1160 to 1180 ° C., and the target minimum tapping temperature is a temperature obtained by adding a temperature drop expected between a refining furnace and a casting machine to an allowable minimum casting temperature in the casting machine, Therefore, it is generally about 1160 ° C.

As described above, by adjusting the ratio between the hydrocarbon-based gas and air blown into the molten metal in accordance with the temperature of the molten metal before the start of the reduction in the reduction step, the temperature of the molten metal at the end of the reduction can be adjusted to a predetermined temperature ( (The target hot water temperature or the target minimum hot water temperature or more), so that it is not necessary to heat the molten metal by a heavy oil burner or the like after the reduction is completed.

In the above, specific means for measuring the temperature of the molten metal before the start of the reduction is arbitrary, and may be performed using, for example, a consumable thermocouple. Adjustment of the flow rate ratio between the hydrocarbon-based gas and air in accordance with the measured molten metal temperature before the start of the reduction may be manually adjusted by an operator based on the molten metal temperature measurement result, or may be predetermined. The adjustment may be made automatically based on a table or a relational expression.

Further, the ratio of the flow rate of the hydrocarbon-based gas to the air may be constant during the entire reduction step or may be changed during the reduction step. When changing the blow flow rate ratio in the middle of the reduction step, generally, from the start of the reduction to the middle, the reduction of the oxygen in the molten metal is emphasized and the flow rate ratio of the hydrocarbon-based gas / air is increased (therefore, the hydrocarbon-based gas It is preferable that the flow rate ratio is reduced (the air ratio is increased) from the middle of the reduction period to the end of the reduction with emphasis on the temperature rise of the molten metal. Of course, in some cases, the flow ratio may be changed in three or more stages during the reduction step.

Since the hydrocarbon-based gas is originally blown to reduce oxygen in the molten metal, the amount of air blown together with the hydrocarbon-based gas depends on the complete combustion of the hydrocarbon-based gas and the CO ₂ and CO _2. It must be lower than the theoretical air combustion amount of the hydrocarbon-based gas so that only H ₂ O is not generated. Specifically, the blown air amount is the theoretical air combustion amount. It is desirable to set the ratio to be in the range of about 5 to 30%. Therefore, when determining the flow rate of the hydrocarbon-based gas and the air in accordance with the molten metal temperature before the start of the reduction, the components of the hydrocarbon-based gas It is desirable to determine the amount of air blown in the range of 5 to 30% of the theoretical amount of air combustion depending on the composition.

[0023]

EXAMPLE A blister copper material having a Cu purity of about 98.5% was prepared in the following manner using a 400-ton cylindrical horizontal tilting type refining furnace.
Purification of 0 tons was performed. That is, after receiving 180 tons of the blister copper melt from the first converter from the converter in the refining furnace which was previously kept warm by the combustion of the heavy oil burner, 180 tons of the second blister copper melt from the converter was received. The amount of blister becomes 350 tons by scraping and reduction described later. here,
The amount of fuel oil burned by the fuel oil burner before receiving the first furnace at the time of heat insulation was 150 l / hr, the amount of fuel oil burned by heating the fuel oil burner at the time of receiving the first furnace was 200 l / hr, and 1
The fuel oil burning amount of the heavy oil burner heating between the furnace and the second furnace and at the time of receiving the second furnace was 300 l / hr. After receiving the second blister copper melt from the converter as described above,
After the entanglement, air is supplied from the tuyere below the surface of the bath at a flow rate of 800 Nm ³ / hr for 0.5 to
I blew it for 2.0 hours. After the oxidation step, as a reduction step, a gas (LPG) obtained by vaporizing a petroleum-based liquefied hydrocarbon gas containing butane as a main component and air were blown from a tuyere below the surface of the molten metal. Immediately after the end of the oxidation step, that is, before the start of the reduction, the temperature of the molten metal is measured with a consumable thermocouple, and the LPG injection flow rate and the air injection flow rate are determined as shown in Table 1 according to the molten metal temperature. Was carried out for 1.5 hours. Then, the temperature of the molten metal at the end of the reduction step was measured by a consumable thermocouple. In Table 1, in each example of the molten metal temperature before the start of the reduction of 1125 ° C. to 1115 ° C., LP
The G flow rate was changed to change the LPG / air flow ratio. On the other hand, in each of the examples in which the temperature of the molten metal before the start of reduction was 1110 ° C. to 1100 ° C., the LPG flow rate was constant, and thus the LPG / air flow rate ratio was constant.

[0024]

[Table 1]

The operation in the above-described refining furnace is carried out for a total of 78
When the relationship between the molten metal temperature immediately before the start of the reduction and the molten metal temperature at the end of the reduction was examined, the result shown in FIG. 1 was obtained. FIG. 2 shows the amount of change in the temperature of the molten metal during the reduction step ([the temperature of the molten metal after the end of the reduction] − [the temperature of the molten metal at the end of the reduction]), corresponding to the temperature of the molten metal before the start of the reduction.

As is clear from FIGS. 1 and 2, the lower the temperature of the molten metal immediately before the start of the reduction, the greater the amount of rise in the temperature of the molten metal during the reduction period.
Even when the temperature is as low as 0 ° C, the target minimum tapping temperature (generally
It is clear that the temperature of 60 ° C. or more was stably secured. In addition, in the case of any charge, after the reduction was completed, the molten metal was immediately poured out and led to the anode casting machine, where casting was performed.
It was confirmed that clogging of the molten metal in the gutter or the like after tapping did not occur.

For reference, the reduction start in the conventional general method without adjusting the flow ratio of the hydrocarbon-based gas and air in the reduction step according to the molten metal temperature before the reduction is started as in the method of the present invention. The relationship between the temperature of the pre-molten metal and the temperature of the molten metal at the end of the reduction is shown by a two-dot chain line in FIG. In this case, the amount of increase in the temperature of the molten metal during the reduction period is about 50 ° C. on average irrespective of the temperature of the molten metal before the start of the reduction. Therefore, when the temperature of the molten metal before the start of the reduction is as low as 1100 ° C., Is 1150 ° C. on average, and it is clear that the temperature may be lower than 1160 ° C. due to variations in various conditions.

[0028]

According to the reduction treatment method of the present invention for dry refining of crude copper, the temperature of the molten metal immediately before the start of the reduction is measured, and the hydrocarbon-based gas and air, etc., blown into the molten metal in accordance with the temperature of the molten metal are measured. Since the flow rate ratio with the oxygen-containing gas was adjusted so that the lower the temperature of the molten metal, the higher the ratio of the oxygen-containing gas, the lower the temperature of the molten metal immediately before the start of reduction, the greater the rise in the temperature of the molten metal during the reduction process. Therefore, even if the initial molten metal temperature is low, the temperature at the end of the reduction is not less than the target minimum tapping temperature that allows for the temperature drop from the refining furnace to the casting machine in addition to the allowable minimum casting temperature required for anode casting in the subsequent process. Therefore, even if the initial temperature is low, the molten metal is heated by a heavy oil burner, etc., between the end of the reduction and the tapping, so that the temperature of the molten metal can be raised even if the initial temperature is low. This eliminates the necessity to perform the process, and as a result, the productivity can be greatly improved as compared with the conventional case, the energy cost can be reduced, and further, there is no adverse effect on each upstream process. In the actual operation, excellent effects can be obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the temperature of a molten metal immediately before the start of reduction and the temperature of the molten metal at the end of reduction in an embodiment of the present invention.

FIG. 2 is a graph showing an amount of rise in molten metal temperature during a reduction process according to an embodiment of the present invention, corresponding to a molten metal temperature immediately before the start of reduction.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Toshihiro Kameya 3382 No.3, Seki, Saganoseki-cho, North Sea District County, Oita Prefecture F-term in the Saganoseki Smelter & Refinery, Nippon Mining & Metals Co., Ltd. 4K001 AA09 BA23 DA10 GA19 HA11

Claims (3)

[Claims] In a method of dry-refining blister copper, a hydrocarbon-based gas is blown together with an oxygen-containing gas into a molten copper after the oxidation step to reduce oxygen in the molten metal. And the flow rate ratio between the hydrocarbon-based gas and the oxygen-containing gas blown into the melt according to the temperature of the melt is adjusted so that the lower the temperature of the melt, the higher the proportion of the oxygen-containing gas. A reduction treatment in dry purification of blister copper. 2. A reduction treatment method in dry refining of blister copper according to claim 1, wherein the flow rate ratio between the hydrocarbon-based gas and the oxygen-containing gas is adjusted so that the molten metal temperature at the end of the reduction is equal to or higher than a target minimum tapping temperature. The method of reduction treatment in the dry purification of blister copper to be adjusted. 3. The reduction treatment method in dry refining of blister copper according to claim 1, wherein the flow rate ratio is changed during the reduction treatment.