Operating method of a copper smelting converter

Abstract

To provide a method for operating a copper smelting converter capable of continuously and stably treating secondary raw materials such as copper, copper slag, and gold and silver slag even when the conditions in the converter are changed.SOLUTION: The method for operating a copper smelting converter completes a batch of operation by repeating a plurality of times, as a first slag-making step and a subsequent slag-making step, a slag-making step of oxidizing a raw material containing a matte charged together with a flux to produce a white copper and a converter slag and then extracting only the converter slag, wherein after obtaining a theoretical flux addition amount based on an amount of Fe contained in the material to be charged and the SiO2 content of the flux in each of the forming processes, the theoretical flux addition amount is multiplied by a correction factor based on the amount of Fe and SiO2 remaining in the furnace at the start of each forming process to obtain an actual flux addition amount, such that a mass-based target Fe / SiO2 ratio of the converter slag produced in each of the plurality of can-making steps is higher in the subsequent slab-making step than in the first can-making step.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an operation method of a converter used in copper smelting.

Background Art

[0002] The copper smelting method using copper sulfide ore as a raw material consists of a previous dry smelting process (also referred to as a smelting process) and a subsequent wet smelting process (also referred to as an electrolysis process). In the previous dry smelting process, by separating components other than copper from copper concentrate with a copper grade of about 20 to 30%, a refined anode concentrated to a copper grade of 99% is finally produced. In the subsequent wet smelting process, the produced refined anode is electrolytically smelted to produce electrolytic copper with a copper grade of 99.99% as the final product.

[0003] In the above dry smelting process, in order to efficiently concentrate copper while suppressing copper loss, treatment is carried out step by step using multiple types of furnaces. Specifically, first, in a smelting furnace typified by a self-smelting furnace, copper concentrate is charged together with oxygen and air to cause an oxidation reaction, so that most of the iron contained in the copper concentrate is separated as calamine (also referred to as slag) together with silica to which an appropriate amount of iron is separately added, and matte with a copper grade of about 60 to 65% is produced. Next, the matte withdrawn from the above smelting furnace is charged into a converter, and air is blown in from the tuyere to cause an oxidation reaction as above to separate calamine (also referred to as converter slag), and finally, blister copper with a copper grade of about 98% is produced. Finally, the blister copper withdrawn from the above converter is charged into a refining furnace, and oxygen is removed by reduction to produce refined blister copper with a copper grade of 99%. The refined anode is produced by casting this refined blister copper.

[0004] In both the smelting furnace and the converter described above, the matte and slag are separated into layers due to the difference in specific gravity. Therefore, the operating conditions are adjusted as appropriate to prevent the copper content of the matte from being mixed into the slag by dissolution or suspension and being lost. For example, Patent Document 1 discloses a technique in which the molar ratio of T.Fe (total iron content) to SiO2 in the slag produced in a self-smelting furnace (T.Fe / SiO2 molar ratio) is set to 1.0 to 1.5, preferably 1.1 to 1.4, the Al2O3 content is set to 4 to 8 wt%, preferably 5 to 7 wt%, and the viscosity is set to 300 mPa·s or less.

[0005] Patent Document 1 discloses a technique in which slag produced in a self-smelting furnace is sampled, its constituent components are quantitatively analyzed, and its viscosity is measured at 1250°C. A regression equation is calculated using the obtained quantitative values ​​of the constituent components, the T.Fe / SiO2 molar ratio obtained from the quantitative values, and the viscosity value. The weight ratio of the constituent components of the solvent is then determined using this regression equation, and a solvent with constituent components corresponding to this weight ratio is introduced into the furnace. It is stated that by adjusting the composition of the slag in this way, the viscosity can be maintained at the optimal level, and thus the Cu content of the slag can be reduced. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2002-146448 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The converter used in copper concentrate production consists of a horizontally elongated furnace with a roughly cylindrical container supported horizontally so as to be rotatable. By rotating this around a central axis, matte can be charged in and slag and crude copper discharged from the furnace opening on its side. For this reason, the processing in the converter is carried out in batches. Furthermore, the processing in the converter from receiving matte from the smelting furnace to producing crude copper is carried out in two stages: a barrel-making stage in which converter slag and white wax are produced from the matte and separated into layers, and a copper-making stage in which sulfur is separated from the white wax obtained in the barrel-making stage to produce crude copper.

[0008] Specifically, in the first stage of copper production (also called the copper production process), for example, matte with a copper content of 60 to 65% received from a self-smelting furnace and silica, mainly composed of SiO2, called flux, are charged into the converter. Then, air is blown in from the tuyeres to oxidize the matte. This produces Fe-SiO2 converter slag and white wax with a copper content of about 70 to 80% that contains almost no Fe. By tilting the converter, this converter slag is removed from the furnace opening. In the next stage of copper production (also called the copper production process), the white wax remaining in the converter is again oxidized by blowing air in from the tuyeres to produce crude copper. The obtained crude copper is poured from the furnace opening into a ladle by tilting the converter and transferred to the subsequent refining furnace.

[0009] Incidentally, during the copper smelting stage described above, in addition to the molten mat (hereinafter sometimes referred to as "molten slag") extracted from the aforementioned self-smelting furnace, solid mat (hereinafter sometimes referred to as "solid slag"), and secondary raw materials such as scrap copper with a copper content of about 95%, and copper slag and gold / silver slag with a copper content of about 10 to 60% and containing a large amount of precious metals are generally fed into the converter for processing. Furthermore, the amount of flux added to the converter during the copper smelting stage is determined so that the composition of the converter slag reaches a predetermined SiO2 grade. By adjusting the composition of the converter slag in this way, its properties can be indirectly stabilized, and thus it becomes possible to stably process the aforementioned scrap copper and secondary raw materials such as copper slag and gold / silver slag, leading to increased copper production.

[0010] However, the properties of the converter slag produced in the converter (also referred to as the furnace conditions) could fluctuate due to variations in the composition of the raw materials. As a result, the properties of the converter slag produced in the copper-making process could negatively affect the subsequent copper-making process or the operation of the next batch. For example, if the viscosity of the converter slag was higher than usual, it became difficult to properly extract the converter slag from the furnace opening towards the ladle even when the converter was tilted, and some of it would remain in the furnace. In this case, the liquid level of the molten metal in the furnace would be higher than usual, which could reduce the amount of air blown in from the tuyeres, thus decreasing operational efficiency, or the amount of residual converter slag could reduce the furnace space available for the mat to be received in the next process.

[0011] As described above, in order to restore the deteriorated internal conditions of a converter, the input of secondary raw materials such as scrap copper, copper slag, and gold and silver slag, which act as heat-absorbing substances in the furnace, is sometimes temporarily withheld. However, this method results in a loss of opportunity in processing secondary raw materials and leads to a decrease in copper smelting production. This invention has been made in view of the above-mentioned problems of copper smelting converters, and aims to provide an operating method for a copper smelting converter that can continuously and stably process secondary raw materials such as scrap copper, copper slag, and gold and silver slag even when the internal conditions of the converter fluctuate. [Means for solving the problem]

[0012] To achieve the above objective, the converter operation method of the present invention is a copper smelting converter operation method in which the operation of one batch is completed by repeating a barrel-making process multiple times as a first barrel-making process and subsequent barrel-making processes, in which raw materials including mat charged together with flux are oxidized to produce white wax and converter slag, and then only the converter slag is extracted, and then a copper-making process is performed in which the white wax remaining in the furnace is oxidized to produce crude copper, wherein the operation of one batch is completed by performing a copper-making process, wherein the target Fe / SiO2 ratio by mass basis of the converter slag produced in each of the multiple barrel-making processes is higher in the subsequent barrel-making processes than in the first barrel-making process, after determining the theoretical flux addition amount based on the amount of Fe contained in the raw materials charged in each barrel-making process and the SiO2 grade of the flux, and then multiplying the theoretical flux addition amount by a correction coefficient based on the amount of Fe and SiO2 remaining in the furnace at the start of each barrel-making process. [Effects of the Invention]

[0013] According to the present invention, even if the conditions inside the converter furnace fluctuate, it becomes possible to continuously and stably process secondary raw materials such as scrap copper, copper slag, and gold and silver slag. [Brief explanation of the drawing]

[0014] [Figure 1] This is a flow chart of multiple copper smelting converters that are subject to the operating method of a copper smelting converter according to an embodiment of the present invention. [Figure 2] Figure 1 shows a specific example of an operating schedule for batch operations using multiple copper smelting converters. [Figure 3] Figure 1 shows a block flow diagram of a single batch operation in each copper smelting converter. [Modes for carrying out the invention]

[0015] The following describes in detail the operating method of a copper smelting converter according to an embodiment of the present invention. This operating method of a copper smelting converter according to an embodiment of the present invention can be suitably applied when, for example, as shown in Figure 1, the mat extracted from the self-smelting furnace 1 into the ladle 2 is charged into two of the three converters 3A to 3C and operated in batches with time differences between them. In this case, the remaining converter is a spare, but batch operation of the converters is not limited to this, and one or more converters may be operated in batches with time differences between them without providing a spare.

[0016] As described above, when the two converters are operated in batches with a time difference between them, designated as Furnace 1 3A and Furnace 2 3B, the operation is carried out according to an operating schedule such as that shown in Figure 2. Since each of Furnace 1 3A and Furnace 2 3B repeats batch processing in basically the same way, except that the processing is carried out with a time difference, the following explanation will take the case of operating the nth batch in Furnace 1 3A as a representative example. Specifically, in the first slag-making process S1, a predetermined amount of mat extracted from the self-melting furnace 1 and a predetermined amount of flux prepared separately are charged into Furnace 1 3A, and then air supplied from the blower 4 or oxygen-enriched air (hereinafter simply referred to as air, etc.) is blown in through the tuyeres. This oxidizes the mat and produces white slag and converter slag (karami).

[0017] After the generation of the white wax and converter slag as described above, the supply of air and other resources by blower 4 is switched from furnace 1 3A to furnace 2 3B, and furnace 1 3A is tilted to extract only the converter slag by overflow and receive it in a ladle. At this time, care is taken to ensure that the white wax does not mix with the converter slag and is extracted, so that all the white wax remains in furnace 1 3A. This completes the first wax production phase S1. By switching the supply of air and other resources by blower 4 to furnace 2 3B, the second copper production process B2 of the mth batch begins in furnace 2 3B.

[0018] Next, in the second smelting process S2, a predetermined amount of matte withdrawn from the self-smelting furnace 1 again and a predetermined amount of flux prepared separately are charged into the No. 1 furnace 3A, and the supply destination of air or the like by the blower 4 is switched from the No. 2 furnace 3B to the No. 1 furnace 3A, and air or the like is blown in from the tuyere. Thereby, the matte is oxidized to produce white slag and converter slag. After the production of the above-mentioned white slag and converter slag, the supply of air or the like from the tuyere by the blower 4 is temporarily stopped, and while paying attention to prevent the white slag from mixing into the converter slag and being withdrawn as in the above, the No. 1 furnace 3A is tilted to extract only the converter slag by overflow and receive it in the ladle, and all the white slag is left in the No. 1 furnace 3A. Thereby, the second smelting period S2 ends.

[0019] Next, in the first copper-smelting process B1, the supply of air or the like to the No. 1 furnace 3A by the blower 4 is restarted, and the white slag in the No. 1 furnace 3A is oxidized over a predetermined time to produce blister copper halfway. After the above-mentioned predetermined time has elapsed, the first copper-smelting process B1 ends by switching the supply destination of air or the like by the blower 4 from the No. 1 furnace 3A to the No. 2 furnace 3B. In this way, by switching the supply destination of air or the like by the blower 4 to the No. 2 furnace 3B, the first smelting process S1 of the (m + 1)-th batch, which is the next batch, starts in the No. 2 furnace 3B.

[0020] Finally, in the second copper-smelting process B2, the supply destination of air or the like by the blower 4 is switched from the No. 2 furnace 3B where the first smelting process S1 has ended to the No. 1 furnace 3A, and the white slag in the No. 1 furnace 3A is oxidized over a predetermined time in the same manner as in the first copper-smelting process B1 to produce blister copper. After this predetermined time has elapsed, the second copper-smelting process B2 ends by switching the supply destination of air or the like from the blower 4 from the No. 1 furnace 3A to the No. 2 furnace 3B. Thereafter, the No. 1 furnace 3A is tilted to extract the blister copper in the furnace by overflow and recover it in the ladle. Thereby, the operation of the n-th batch in the No. 1 furnace 3A ends.

[0021] In the operation schedule shown in FIG. 2, the matte-making process in each of the No. 1 furnace 3A and the No. 2 furnace 3B was carried out in two steps of S1 and S2. However, the number of matte-making processes is not limited to the above two times, and it may be three or more times. Also, the number of copper-making processes is not limited to the above two times of B1 and B2, and it may be once or three or more times.

[0022] In the operation method of the copper smelting converter according to the above-described embodiment of the present invention, the target Fe / SiO2 ratio based on the mass standard of the converter slag generated in each of the above-mentioned multiple matte-making processes is higher in the subsequent matte-making processes than in the first matte-making process. After obtaining the theoretical flux addition amount based on the amount of Fe contained in the raw materials charged in each matte-making process and the SiO2 grade of the flux, the actual flux addition amount is obtained by multiplying the theoretical flux addition amount by a correction coefficient based on the amount of Fe and the amount of SiO2 remaining in the furnace at the start of each matte-making process.

[0023] That is, in the copper smelting converter in which the oxidation reaction shown in the following formula 1 occurs, the material balance shown in FIG. 3 occurs in each of the above-described first matte-making process S1, second matte-making process S2, first copper-making process B1, and second copper-making process B2. [Formula 1] 2(Cu2S·FeS)+SiO2+5O2 →4Cu+2FeO·SiO2+4SO2

[0024] Therefore, as shown in the following formula 2, if the amount of Fe in the charged raw materials and the SiO2 grade in the flux are known, the theoretical flux addition amount required to make the target Fe / SiO2 ratio in the subsequent matte-making processes higher than the target Fe / SiO2 ratio in the first matte-making process can be obtained by material balance calculation.

[0025] [Formula 2] (Theoretical flux addition amount)= (Amount of Fe in raw materials)÷(Target Fe / SiO2 ratio)÷(SiO2 grade of flux)

[0026] As described above, the target Fe / SiO2 ratio of the mass standard of the converter slag generated in each of the multiple smelting processes is set to be higher in the subsequent smelting processes than in the first smelting process. That is, in the case of Fig. 3, when the target Fe / SiO2 ratio of the converter slag generated in the first smelting process S1 is r1 and the target Fe / SiO2 ratio of the converter slag generated in the second smelting process S2 is r2, r1 < r2. The reason is that at the start of the first smelting process S1, the state in the converter after the copper smelting process of the previous batch operation is maintained, so there is almost no SiO2 present. Also, the raw materials such as matte fed into the converter contain almost no SiO2, or even if they do, the amount of SiO2 can be roughly grasped from the analysis values. In contrast, when the subsequent second smelting process S2 and the third smelting process S3 and later are further carried out, in these processes, SiO2 that remains in the furnace without being extracted at the end of the previous smelting process is carried over.

[0027] For example, when the converter is tilted to extract the converter slag after the end of the first smelting process S1, the converter slag is separated into layers above the white slag, so initially only the upper-layer converter slag can be extracted. However, when most of the extraction of the converter slag is completed, the white slag on the lower layer side of the converter slag is likely to be extracted from the converter along with the converter slag. When the white slag is extracted along with the converter slag in this way, the Cu grade of the converter slag becomes extremely high and it results in copper loss. To avoid this, although a part of the converter slag remains in the furnace and is carried over to the second smelting process S2, the extraction of the converter slag is terminated at the timing when it is confirmed that the white slag is mixed into the converter slag to be extracted from the converter.

[0028] Thus, when the second barrel making process S2 and the third barrel making process S3 and beyond are performed, converter slag containing unreacted SiO2 is carried over from the previous process, and this amount is taken into consideration in the mass balance calculation. The target Fe / SiO2 ratio of the converter slag extracted in the first barrel making process S1 should be determined by referring to past operating data, etc., so that the properties of the converter slag can be made to be such that the copper content of the converter slag is minimized. Similarly, the target Fe / SiO2 ratio of the converter slag extracted in the second barrel making process S2 and subsequent barrel making processes should also be determined considering the properties of the converter slag that can be made to be such that the copper content of the converter slag is minimized, as well as considering the shape of the furnace opening and the size of the converter, which affect the amount of converter slag remaining when the converter slag is extracted in the previous barrel making process.

[0029] As shown in Equation 3 below, the actual amount of flux to be added can be determined by multiplying this theoretical amount of flux by a correction factor that takes into account the amount of Fe and SiO2 remaining in the furnace at the start of the molten metal process. [Formula 3] (Actual flux addition amount) = (Theoretical flux addition amount) × Correction factor

[0030] As mentioned above, the above correction coefficient is used because, at the start of the first copper-making process S1, there is almost no SiO2 remaining in the converter, and the raw materials such as mat charged into the converter also contain almost no SiO2. Furthermore, even if some SiO2 is present, the amount can be largely determined from the analytical values. In addition, the amount of Fe contained in the mat charged into the converter can also be largely determined from its analytical values. For this reason, the stoichiometric relationship of Equation 2 above can be adopted almost as is in the first copper-making process S1. However, for example, at the end of the copper-making process of the previous batch, a certain amount of Fe-containing composite oxide may remain in the furnace on a regular basis, albeit in small quantities. Therefore, if necessary, a slight correction may be made to the correction coefficient within the range of 0.9 to 1.1, taking this residue into consideration.

[0031] On the other hand, when performing the second barrel making process S2 and subsequent barrel making processes, as mentioned above, the amount of flux added is adjusted in those processes so that the target Fe / SiO2 ratio of the converter slag is greater than that of the previous process, taking into account the unreacted SiO2 carried over from the converter slag. However, if flux is added based on this target Fe / SiO2 ratio, the Fe / SiO2 ratio of the converter slag actually becomes smaller than the target. That is, for example, in the second barrel making process S2, although the amount of flux added is controlled to reduce the target Fe / SiO2 ratio of the converter slag so that it is greater than that of the first barrel making process S1, taking into account the SiO2 carried over from the first barrel making process S1, this amount of flux added is still too much. For this reason, further adjustment with a correction factor is necessary. Specifically, this correction factor is preferably between 0.5 and 0.8.

[0032] The mass of the mat charged into the converter, as well as the mass of the converter slag and crude copper separately extracted from the converter, can be measured by a weighing scale equipped on the crane that suspends the ladle that receives them. Furthermore, the composition of the converter slag produced in the first barrel-making process S1 and the second barrel-making process S2 can be determined by sampling the converter slag in the process of being discharged into the ladle and performing X-ray fluorescence analysis. The amount of Fe contained in the mat and the SiO2 grade of the flux can also be determined by X-ray fluorescence analysis. Almost all of the iron in the mat charged into the converter is oxidized and distributed to the converter slag. Also, almost all of the copper contained in the mat charged into the converter becomes sulfide Cu2S (white copper).

[0033] In the copper smelting converter operation method of the embodiment of the present invention, the target Fe / SiO2 ratio of the converter slag is preferably 1.8 or more and 2.8 or less. This makes it possible to produce converter slag with properties that minimize the copper content of the converter slag, as described above. If this value is less than 1.8, although the copper content of the converter slag can be reduced, it is undesirable because it requires a large amount of flux to be added. Conversely, if this value exceeds 2.8, SiO2 becomes insufficient, increasing the viscosity of the converter slag, and consequently increasing the copper content of the converter slag, which is undesirable. In particular, the target Fe / SiO2 ratio of the converter slag in the first smelting process S1 is preferably 1.8 or more and 2.3 or less, and the target Fe / SiO2 ratio of the converter slag in the second smelting process S2 and later is preferably 2.3 or more and 2.8 or less.

[0034] In the copper smelting converter operation method of the embodiment of the present invention, it is preferable that the amount of matte charged from the preceding smelting furnace to the converter is 150 tons or more and 300 tons or less per batch operation. If the amount of matte charged is less than 150 tons, the influence of converter slag containing unreacted SiO2 and Fe-containing composite oxides carried over to the second smelting process and beyond becomes relatively large, making it difficult to apply the operation method of the embodiment of the present invention. Conversely, if the amount of matte charged exceeds 300 tons, the influence of converter slag containing unreacted SiO2 and Fe-containing composite oxides carried over to the second smelting process and beyond becomes relatively small, thus reducing the significance of applying the operation method of the embodiment of the present invention. [Examples]

[0035] Using a dry copper smelting plant as shown in Figure 1, the operating method of the embodiment of the present invention involved charging matte produced in a self-smelting furnace into three converters and producing crude copper through batch operation with time differences between them. In each converter, processing was carried out according to the block flow shown in Figure 3, consisting of a first slag-making process S1 and a second slag-making process S2 for generating converter slag, and a first copper-making process B1 and a second copper-making process B2 for generating crude copper. In each converter, the amount of matte charged into the converter in the first slag-making process S1 was 140 to 170 tons, and the amount of matte charged into the converter in the second slag-making process S2 was 60 to 90 tons.

[0036] Using equations 2 and 3 above, the theoretical amount of flux to be added was determined based on the amount of Fe contained in the mat charged in each barrel-making process and the SiO2 grade of the flux, so that the target Fe / SiO2 ratio on a mass basis for the converter slag produced in the first barrel-making process S1 was 1.8 or more and 2.3 or less, and the target Fe / SiO2 ratio on a mass basis for the converter slag produced in the second barrel-making process S2 was 2.3 or more and 2.8 or less. Then, the actual amount of flux to be added was determined by multiplying the theoretical amount of flux to be added by a correction factor based on the amount of Fe and SiO2 remaining in the furnace at the start of each barrel-making process. Specifically, the correction factor for the first barrel-making process S1 was set to 0.9 or more and 1.1 or less, and the correction factor for the second barrel-making process S2 was set to 0.5 or more and 0.8 or less.

[0037] As a comparative example, instead of using the above formulas 2 and 3, the amount of flux added was determined so that the SiO2 grade of the converter slag in each of the first and second molding processes S1 and S2 would reach a predetermined target value. In the same manner as in the above example, the mat produced in the self-smelting furnace was charged into three converters and crude copper was produced by batch operation with time differences between them.

[0038] As a result, the operating method according to the above-described embodiment of the present invention made it possible to stabilize the composition of the converter slag compared to the conventional method. The amount of secondary raw materials processed in the converter, consisting of copper slag, gold and silver slag, and repeated materials in the system such as boiler flue ash discharged from the waste heat boiler into which the converter's exhaust gas is introduced, was 5.9 tons per batch operation on average in the comparative example from April 2018 to March 2020, compared to 8.4 tons per batch operation on average in the embodiment from April 2020 to March 2021. This represents an increase of 2.5 tons, meaning that the amount of secondary raw materials processed was increased by approximately 40%. [Explanation of Symbols]

[0039] 1 Flash-melting furnace 2 ladles 3A~3C Converter 4. Blower

Claims

1. A method for operating a copper smelting converter, comprising: first, a barrel-making process in which raw materials including matte charged together with flux are oxidized to produce white wax and converter slag, and then only the converter slag is extracted; this process is repeated multiple times as the first barrel-making process and subsequent barrel-making processes; and then, a copper-making process is performed in which the white wax remaining in the furnace is oxidized to produce crude copper, thereby completing the operation of one batch. Target Fe / SiO2 by mass of the converter slag produced in each of the aforementioned multiple barrel-making processes ２ The ratio is such that the ratio is higher in the subsequent bottle-making process than in the first bottle-making process, and the amount of Fe contained in the raw materials charged in each bottle-making process and the amount of SiO in the flux are adjusted accordingly. ２ After determining the theoretical flux addition amount based on the grade, the amount of Fe and SiO remaining in the furnace at the start of each of the aforementioned kiln-making processes is determined. ２ A method for operating a copper smelting converter, characterized by determining the actual flux addition amount by multiplying the theoretical flux addition amount by a correction coefficient based on the quantity.

2. The aforementioned target Fe / SiO ２ The method for operating a copper smelting converter according to claim 1, characterized in that the ratio is 1.8 or more and 2.8 or less.

3. The method for operating a copper smelting converter according to claim 1 or 2, characterized in that the amount of mat charged per batch is 150 tons or more and 300 tons or less.

4. A method for operating a copper smelting converter according to claim 1 or 2, characterized in that the correction coefficient for the first barrel making process is 0.9 or more and 1.1 or less, and the correction coefficient for the subsequent barrel making process is 0.5 or more and 0.8 or less.

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