Method for producing crude zinc oxide and method for treating flue dust

Abstract

To provide a method for manufacturing a crude zinc oxide using steel dust as a raw material which can effectively utilize flue cinder containing zinc and copper produced in a copper refining furnace as a part of a raw material, while avoiding mixing the copper into a reduced iron pellet that is a by-product and is available as an iron source.SOLUTION: A method for manufacturing a crude zinc oxide includes a reducing and roasting step ST21 of reducing and roasting steel dust, and obtaining crude zinc oxide dust, a wet step ST22 of subjecting the crude zinc oxide dust to wet treatment, and obtaining a crude zinc oxide cake, and a drying and heating step ST23 of firing the crude zinc oxide cake, and obtaining a crude zinc oxide sintered mine, wherein the drying and heating step ST23 fires flue cinder produced and collected in a copper refining furnace, together with the crude zinc oxide cake.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing crude zinc oxide from a raw material containing flue dust generated in a copper smelting furnace, and a method for treating flue dust containing zinc and copper generated in a copper smelting furnace. [Background technology]

[0002] The flue gas recovered from the exhaust gas generated in copper smelting furnaces contains not only the copper contained in the copper concentrate, but also large amounts of easily volatile zinc, bismuth, etc. Generally, flue gas generated in the copper smelting process is recycled and processed back into the copper smelting furnace because it contains the metals to be smelted.

[0003] However, since the above-mentioned flue dust contains bismuth, if it is repeatedly fed into a copper smelting furnace, the impurity content of bismuth and other substances in the copper anode obtained in the copper smelting process increases, resulting in a problem of an increase in the impurity content of the electrolytic copper obtained in the subsequent copper refining process (electrolysis process).

[0004] Regarding this problem, Patent Document 1 discloses a method for treating flue dust, which contains a high concentration of lead and is generated and recovered in the smelting of non-ferrous metals, by mixing the flue dust with chlorine-containing steel dust to form mixed pellets and then feeding the pellets into a reducing roasting step in a crude zinc oxide production process, in a manner similar to the conventional method for treating steel dust which includes a reducing roasting step.

[0005] In the production of crude zinc oxide, steel dust is often used as a raw material. Reduced iron pellets, a by-product of the reduction roasting process of the steel dust, are recycled as iron sources by steel manufacturers. However, when the flue gas treated in the reduction roasting process contains copper, a new problem arises: copper is distributed in the reduced iron pellets. This is because copper is one of the impurities that steel manufacturers using reduced iron pellets strictly restrict from being mixed into their iron sources. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-139618 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a method for producing crude zinc oxide using steel dust as a raw material, which can effectively utilize flue dust containing zinc and copper generated in a copper smelting furnace as part of the raw material, while avoiding copper contamination in reduced iron pellets, which are by-products and can be used as an iron source. [Means for solving the problem]

[0008] The present inventors have come up with the idea that the above-mentioned problems can be solved by changing the process in which flue dust, which has conventionally been fed together with steel dust as a primary raw material into a reduction heating step, which is an upstream step in the process of producing crude zinc oxide, is fed directly into a drying heating step, which is a downstream step, as a secondary raw material, and have thus completed the present invention. Specifically, the present invention provides the following.

[0009] (1) A method for producing crude zinc oxide, comprising: a reduction roasting step of reducing and roasting steel dust to obtain crude zinc oxide dust; a wet process of subjecting the crude zinc oxide dust to wet treatment to obtain crude zinc oxide cake; and a dry heating step of calcining the crude zinc oxide cake to obtain crude zinc oxide cinder, wherein in the dry heating step, flue dust generated in a copper smelting furnace and recovered is calcined together with the crude zinc oxide cake.

[0010] According to the method for producing crude zinc oxide described in (1), in the production of crude zinc oxide using steel dust as a raw material, copper-containing flue dust can be effectively used as part of the raw material while avoiding the inclusion of copper in reduced iron pellets, which are by-products and can be used as an iron source. Therefore, when shipping reduced iron pellets to steel manufacturers as an iron source, the possibility of rejecting shipments due to high copper content can be significantly reduced.

[0011] (2) A method for producing crude zinc oxide, comprising: a reduction roasting step of reducing and roasting steel dust to obtain crude zinc oxide dust; a wet process of subjecting the crude zinc oxide dust to wet treatment to obtain crude zinc oxide cake; and a dry heating step of calcining the crude zinc oxide cake to obtain crude zinc oxide cinder, wherein in the dry heating step, flue dust containing zinc and copper, with a copper content of 10% or more, is calcined together with the crude zinc oxide cake.

[0012] According to the method for producing crude zinc oxide (2), even when flue dust containing zinc and copper, especially with a high copper content, is used as a raw material at the site of production of crude zinc oxide, the flue dust containing copper can be effectively used as part of the raw material while avoiding the contamination of reduced iron pellets, which are a by-product and can be used as an iron source.

[0013] (3) The method for producing crude zinc oxide according to (1), wherein the copper smelting furnace is a copper smelting converter.

[0014] According to the method for producing crude zinc oxide (3), in the method for producing crude zinc oxide described in (1), lead, zinc, and bismuth can be recovered more efficiently by using flue gases that are generated in a copper smelting converter and contain large amounts of lead, zinc, bismuth, etc., and that volatilize and scatter from the molten metal and have a relatively low boiling point.

[0015] (4) A method for producing crude zinc oxide according to any one of (1) to (3), wherein the flue dust has a lead content of 12% or more and a zinc content of 4% or more.

[0016] According to the method for producing crude zinc oxide (4), in the method for producing crude zinc oxide described in any one of (1) to (3), by using flue dust containing the target metals, zinc, copper, and lead, in high concentrations, zinc, copper, and lead can be recovered more efficiently.

[0017] (5) A flue ash processing method for processing flue ash generated and recovered from a copper smelting furnace, the flue ash having a lead content of 12% or more, in which the flue ash is used as a secondary raw material to be input into a drying and heating step in a crude zinc oxide production process.

[0018] According to the flue dust processing method (5), flue dust generated in a copper smelting furnace and containing a high concentration of lead can be effectively utilized in the production of crude zinc oxide using steel dust as a raw material, while preventing copper from being mixed into reduced iron pellets, which are a by-product and can be used as an iron source. This significantly reduces the possibility that reduced iron pellets will be rejected due to their high copper content when shipped as an iron source to steel manufacturers. Furthermore, because the flue dust is processed in a dry heating process, there is no need to go through upstream processes such as a reduction roasting process and a wet process. This reduction in processes reduces the cost of flue dust processing. [Effects of the Invention]

[0019] According to the present invention, in the production of crude zinc oxide using steel dust as a raw material, copper-containing flue dust can be effectively used as part of the raw material while avoiding copper contamination in reduced iron pellets, which are by-products and can be used as an iron source. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a flow chart showing the flow of a method for producing crude zinc oxide of the present invention using flue dust generated in copper smelting as a secondary raw material. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings, in which: Figure 1 is a flow chart showing the process for producing crude zinc oxide according to the present invention, in which flue gas generated in copper smelting is used as part of the raw material;

[0022] <Method of manufacturing crude zinc oxide> The method for producing crude zinc oxide of the present invention is a process that uses zinc-containing steel dust generated from blast furnaces, electric furnaces, etc. in the steel industry as raw material, and removes impurities from the raw material to produce crude zinc oxide with a zinc content of approximately 65%, which can be used as a raw material for zinc products.

[0023] The method for producing crude zinc oxide of the present invention is a process for carrying out the conventionally known crude zinc oxide production process P2, the basic flow of which is shown in Figure 1. In the method for producing crude zinc oxide of the present invention, the basic flow of steps is the same as in the conventional method shown in Figure 1.

[0024] However, the method for producing crude zinc oxide of the present invention is a process with a new feature different from conventional methods in that flue dust containing at least zinc and copper (also referred to in this specification as "zinc-copper-containing flue dust"), such as flue dust generated in a copper smelting furnace and recovered in a copper smelting process P1, is directly introduced as part of a secondary raw material into a drying and heating step ST23, which is a step downstream of a crude zinc oxide production process P2, as shown in FIG.

[0025] The present invention is an excellent method for producing crude zinc oxide in that it recovers zinc at a high recovery rate while avoiding the contamination of reduced iron pellets, which are by-products and can be used as an iron source, by feeding "zinc- and copper-containing flue dust" generated in copper smelting into the drying and heating step ST23 in the crude zinc oxide production process P2, and thereby enables the flue dust to be effectively used as a secondary raw material.

[0026] Furthermore, the present invention is also an excellent method for treating flue dust, in that it can treat "zinc- and copper-containing flue dust" generated in copper smelting at low cost using existing facilities, without the need for new capital investment in rotary kilns or other equipment used in the existing crude zinc oxide manufacturing process.

[0027] <Copper smelting process P1> The copper smelting process P1, which serves as the source of the "zinc-copper-containing flue dust" used as the secondary raw material in the method for producing crude zinc oxide of the present invention, is a process for obtaining blister copper with a copper content of approximately 98% from copper concentrate, and ultimately obtaining electrolytic copper. In this copper smelting process P1, copper concentrate, which is the raw material for copper smelting, is generally first processed in a flash furnace to separate it into matte with a copper content of approximately 60% and slag. The matte obtained here is then sent to the converter process, where it is refined into blister copper with a copper content of approximately 98%. This is then refined into blister copper with a copper content of approximately 99% in the subsequent refining furnace, and cast as anodes for processing in the subsequent refining process. In the refining process, electrolytic copper is obtained from these anodes.

[0028] The above-mentioned flash furnace, converter, and refining furnace each generate flue dust with different compositions and properties. The flue dust generated in a flash furnace is a flash smelting process, which includes carryover of concentrates and other materials. Because the copper content is high, it is preferable to repeatedly process the flue dust in a flash furnace. Furthermore, the amount of flue dust generated in a refining furnace is very small. In contrast, the flue dust generated in a converter is a bath smelting process, which contains large amounts of lead, zinc, bismuth, and other elements with relatively low boiling points that volatilize and scatter from the molten metal. Therefore, in the method for producing crude zinc oxide of the present invention, it is particularly preferable that the "zinc- and copper-containing flue dust" used as part of the raw material (or the "zinc- and copper-containing flue dust" to be treated by the flue dust treatment method of the present invention) be flue dust with a high content of lead and zinc obtained from a converter, among the various flue dusts described above. Alternatively, in the method for producing crude zinc oxide of the present invention, flue dust having an increased content of lead and zinc, which is obtained by repeatedly treating flue dust generated in a converter in a copper smelting process (also referred to as a "copper smelting converter" in this specification) within the copper smelting process, can also be used.

[0029] Furthermore, the method for producing crude zinc oxide of the present invention exhibits significant advantages over conventional techniques when the "zinc- and copper-containing flue dust" used as part of the raw material (or the "zinc- and copper-containing flue dust" to be treated by the flue dust treatment method of the present invention) contains zinc and copper, with the copper content being 10% or more. Conventionally, when flue dust with such a high copper content was used, there was a risk that the copper component would be mixed into reduced iron pellets, preventing them from being recycled as an iron source. However, according to the present invention, which avoids flue dust treatment in upstream processes and instead focuses flue dust treatment downstream, after the drying and heating process, such a risk can be completely avoided.

[0030] Furthermore, in the crude zinc oxide production method or flue ash treatment method of the present invention, the above-mentioned "zinc- and copper-containing flue ash" preferably has a lead content of 12% or more and a zinc content of 4% or more. Even if flue ash containing a high concentration of lead is repeatedly treated at copper smelting sites, it will volatilize again, significantly increasing the amount of material circulating within the process. However, by feeding such "zinc- and copper-containing flue ash" with a high lead content into the production and treatment methods of the present invention, lead, zinc, and copper can be recovered more efficiently in the crude zinc oxide production process and the subsequent lead and zinc production process.

[0031] <Crude zinc oxide manufacturing process P2> The crude zinc oxide production process P2 is a process in which a reduction roasting step ST21, a wet step ST22, and a dry heating step ST23 are sequentially performed, as will be described in detail below.

[0032] [Reduction roasting process ST21] In the reduction roasting step ST21, primary raw materials such as steel dust are roasted in a reducing atmosphere at an appropriate temperature and residence time to reduce and volatilize zinc, lead, and other components, which are then reoxidized to obtain crude zinc oxide dust. Also, in this step, iron is recovered as solid reduced iron pellets. A rotary kiln is preferably used as the reduction roasting furnace for this step.

[0033] [Wet process ST22] The wet process ST22 is a process for obtaining a dehydrated cake of crude zinc oxide (also referred to as "crude zinc oxide cake" in this specification) by further removing remaining impurities such as chlorine and fluorine from the crude zinc oxide dust that has been reoxidized through the reducing roasting process ST21 and contains zinc oxide and lead oxide. The wet process ST22 can be performed using a conventionally known method.

[0034] [Drying and heating process ST23] The dry heating step ST23 is a step in which the crude zinc oxide cake that has been subjected to the wet step ST22 is calcined to obtain crude zinc oxide cinder. This step allows for the production of crude zinc oxide cinder (also referred to as "crude zinc oxide cinder" in this specification) with a zinc content of about 65%.

[0035] The drying and heating step ST23 uses a rotary kiln, and the raw material, crude zinc oxide cake, and other secondary raw materials are charged into the charging end of the rotary kiln. A burner is provided at the discharge end of the rotary kiln, and the raw materials in the rotary kiln are dried, heated, and fired by this burner, and crude zinc oxide cinder is obtained at the discharge end, which has been fired to about 800 to 900°C.

[0036] In the method for producing crude zinc oxide of the present invention, the above-mentioned copper-containing flue dust used as part of the raw materials is input as part of the secondary raw materials in this drying and heating step ST23.

[0037] Furthermore, when treating flue dust, the grade of copper, tin, and bismuth contained in the flue dust is predicted from the impurity balance in the resulting crude zinc oxide, and the amount of flue dust to be treated is determined so that it falls within the process standard, assuming that it will be recovered in the copper removal process of the lead-zinc smelting, which is established as a process further downstream from the crude zinc oxide manufacturing process.In addition, the crude zinc oxide obtained in the drying and heating process ST23 is also analyzed at regular intervals to confirm that it falls within the above standard.

[0038] Furthermore, if the flue dust described above is introduced into the dry heating step in its original form, it will be carried over together with dust generated in the conveying equipment and the exhaust gas from the rotary kiln, and will adhere to the perforated plates of the flue and scrubber connected to the rotary kiln, causing blockage. To avoid this, it is preferable to granulate the flue dust into pellets in advance, or to mix and process it in advance in a loader with raw materials such as sediment (with a moisture content of 20% to 50%) other than the dehydrated cake to be treated in the dry heating step. [Example]

[0039] EXAMPLES The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0040] [Example] A trial run for zinc oxide production was conducted using the flow chart shown in Figure 1. The flue dust used as part of the secondary raw material was flue dust generated in a converter at a copper smelting plant and recovered. The composition of this flue dust is shown in Table 1 below. In the drying and heating process, 1 ton / day of the flue dust and 170 ton / day of crude zinc oxide cake were dried and heated at temperatures between 800 and 900°C to obtain crude zinc oxide cinder. The copper content of the crude zinc oxide cinder was 0.21%, the tin content was 0.09%, and the bismuth content was 0.10%, and it was shipped as a raw material for lead-zinc smelting. The copper, tin, and bismuth were separated and recovered in the copper removal process of the lead-zinc smelting process that follows the production of crude zinc oxide. In the reduction roasting process, 200 t / day of steel dust was reduced and roasted at a temperature of 1100°C to 1200°C to obtain crude zinc oxide dust containing zinc oxide and reduced iron pellets, which were shipped as iron sources to steel manufacturers.

[0041] [Table 1]

[0042] [Comparative Example] Test operation was carried out under the same conditions as in the Example, except that the above flue dust was fed into the reduction roasting process together with raw materials such as steel dust, as in the conventional process. In the reduction roasting process, 1 ton / day of the above flue dust and 200 t / day of steel dust were reduction roasted at temperatures of 1100°C to 1200°C to obtain crude zinc oxide dust containing zinc oxide and reduced iron pellets. The reduced iron pellets had a copper content of 0.46%, a tin content of 0.053%, and a bismuth content of 0.092%, and were not shipped as an iron source to steel manufacturers.

[0043] According to the method for producing crude zinc oxide of the present invention, the cost required for treating flue dust containing zinc and copper generated in copper smelting can be significantly reduced by utilizing existing processes and facilities. Furthermore, since the adverse effects of copper on the existing process can be prevented, it is possible to maintain the quality of reduced iron pellets in the existing operation of producing crude zinc oxide, and further, it is possible to recover zinc, copper, and lead contained in the flue dust at a high recovery rate. [Explanation of symbols]

[0044] P1 Copper smelting process P2 Crude zinc oxide manufacturing process ST21 Reduction roasting process ST22 Wet process ST23 Drying and heating process

Claims

1. a reduction roasting step of reducing and roasting the steel dust to obtain crude zinc oxide dust; a wet process for wet treating the crude zinc oxide dust to obtain a crude zinc oxide cake; a dry heating step of calcining the crude zinc oxide cake to obtain crude zinc oxide cinder; A method for producing crude zinc oxide, comprising: In the drying and heating step, flue dust, which is generated in a copper smelting furnace and recovered, contains zinc, lead, and copper, and has a lead content of 12% or more, a zinc content of 4% or more, and a copper content of 10% or more, is calcined together with the crude zinc oxide cake. Method for producing crude zinc oxide.

2. In the drying and heating step, flue dust generated in a copper smelting furnace and recovered, containing zinc, lead and copper, with a lead content of 14% or more, a zinc content of 5.6% or more and a copper content of 18% or more, is calcined together with the crude zinc oxide cake. The method for producing crude zinc oxide according to claim 1.

3. The copper smelting furnace is a copper smelting converter. The method for producing crude zinc oxide according to claim 1.

4. 1. A flue ash treatment method for subjecting flue ash generated in a copper smelting furnace and recovered, the flue ash having a lead content of 12% or more, a zinc content of 4% or more, and a copper content of 10% or more, to a process for producing crude zinc oxide, comprising: The process for producing crude zinc oxide comprises a reduction roasting step of reducing and roasting iron and steel dust to obtain crude zinc oxide dust, a wet process of subjecting the crude zinc oxide dust to wet treatment to obtain crude zinc oxide cake, and a dry heating step of calcining the crude zinc oxide cake to obtain crude zinc oxide cinder, The flue ash treatment method uses the flue ash as a secondary raw material to be input into the drying and heating step in the process for producing crude zinc oxide.

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