A zinc extraction rotary kiln process

Abstract

This invention discloses a rotary kiln process for zinc extraction, belonging to the field of metallurgical and mineral processing technology. The process includes: S1, mixing high-zinc raw materials with coke at a specific mass ratio to form a mixture, wherein the Zn content in the mixture is 10%–15% and the C content is 20%–30%; S2, wetting the mixture and granulating it to obtain a high-zinc mixture with a particle size of 10mm–15mm, which is then fed to a high-temperature reduction zone at a temperature of 1100℃–1250℃ for 2–3 hours; S3, wetting low-zinc raw materials and granulating them to obtain a low-zinc mixture with a particle size of 3mm–8mm, wherein the Zn content in the low-zinc mixture is 2%–5%; S4, injecting the low-zinc mixture into the high-zinc mixture, where it is mixed with the high-zinc mixture and reduced and roasted to obtain reduction slag and flue gas. This device utilizes a high-zinc raw material rotary kiln and a material injection device to achieve efficient recovery of low-zinc materials. The cooled kiln slag can be used as a raw material for building materials or steel plants. The flue gas discharged from the rotary kiln enters the flue gas dust removal system to obtain zinc oxide dust.

Description

Technical Field

[0001] This invention belongs to the field of metallurgy and mineral processing technology, specifically a rotary kiln process for zinc extraction. Background Technology

[0002] The rotary kiln process for zinc extraction is used to treat zinc-containing dust. Zinc-containing dust and a reducing agent are batched, mixed, granulated, and then fed into the rotary kiln. Reduction treatment is carried out in a high-temperature atmosphere of 1000-1300℃. The metal oxides in the material react with the reducing agent, and the reduced zinc, along with other volatile metals, enters the flue gas and undergoes secondary oxidation, separating from the kiln slag. The rotary kiln process has a high zinc removal rate, generally exceeding 90%, and is widely used due to its advantages such as low investment and simple operation, with processing capacities ranging from tens of thousands to hundreds of thousands of tons. However, current rotary kiln processes for zinc extraction are mostly used to process dust materials with high zinc content. Directly processing low-zinc materials is not economically efficient; therefore, it is necessary to find economically feasible methods to recover valuable metals from low-zinc materials. Summary of the Invention

[0003] The purpose of this invention is to propose a zinc extraction rotary kiln process to solve the problems mentioned in the prior art.

[0004] A rotary kiln process for zinc extraction is provided, comprising:

[0005] S1. Mix high-zinc raw materials and coke in a certain mass ratio to form a mixture, wherein the Zn content in the mixture is 10% to 15% and the C content is 20% to 30%;

[0006] S2. After wetting the mixture, granulate it to obtain a high-zinc mixture. The high-zinc mixture is then conveyed to the high-temperature reduction zone of the rotary kiln. The temperature of the high-temperature reduction zone is 1100℃~1250℃, and the reduction time is 2h~3h.

[0007] S3. After wetting the low-zinc raw material, granulate it to obtain a low-zinc mixture. The Zn content in the low-zinc mixture is 2% to 5%.

[0008] S4. During the high-temperature reduction of the high-zinc mixture, a low-zinc mixture is injected into the high-temperature reduction zone by an injection device at the kiln head. After the low-zinc mixture and the high-zinc mixture are mixed, reduced, and calcined, reduction slag and flue gas are obtained. The reduction slag is discharged and cooled, while the flue gas is discharged into a flue gas dust removal system to obtain zinc oxide dust.

[0009] As a further aspect of the present invention: the particle size of the high-zinc mixture in S2 is 10mm to 15mm.

[0010] As a further aspect of the present invention: the particle size of the low-zinc mixture in S3 is 3mm to 8mm.

[0011] As a further aspect of the present invention, the mass ratio of the low-zinc mixture to the high-zinc mixture injected into the high-temperature reduction zone is maintained at 1:5 to 20.

[0012] As a further aspect of the present invention: the injection device in step S4 is a high-pressure air gun, and the low-zinc mixture is injected into the high-temperature reduction zone by the high-pressure gas generated by the high-pressure air gun.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] This invention utilizes a rotary kiln to co-process low-zinc raw materials with high-zinc raw materials. The low-zinc mixture and the high-zinc mixture are mixed and reduced in the high-temperature reduction zone of the rotary kiln. The cooled kiln slag can be used as a raw material for building materials or steel plants. The flue gas discharged from the rotary kiln enters a flue gas dust removal system to obtain zinc oxide dust, and the purified flue gas is discharged into the atmosphere. This device achieves efficient recovery of low-zinc materials and extraction of valuable metals by utilizing a high-zinc raw material rotary kiln and a material injection device. Attached Figure Description

[0015] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0016] Figure 1 This is a flowchart of the zinc extraction rotary kiln process. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, and not all embodiments. The components of the embodiments of the invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0018] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0019] Please see Figure 1 As shown, in this embodiment of the invention, it specifically includes:

[0020] High-zinc raw materials and coke are mixed in a specific mass ratio to form a mixture with a Zn content of 10%–15% and a C content of 20%–30%. The mixture is then moistened and granulated to obtain a high-zinc mixture with a particle size of 10mm–15mm. This high-zinc mixture is conveyed via belt to the high-temperature reduction zone of a rotary kiln, where the kiln temperature is controlled at 1100℃–1250℃, and the reduction time in the rotary kiln is 2h–3h. Low-zinc raw materials are also moistened and granulated to obtain a low-zinc mixture with a particle size of 3mm–8mm and a Zn content of 2%–5%. During the high-zinc mixture's high-temperature reduction, the low-zinc mixture is injected into the high-temperature reduction zone through an injection device at the kiln head. The low-zinc mixture is then mixed with the high-zinc mixture for reduction and calcination. After roasting, the reducing slag, with a temperature of 800℃~1000℃, is discharged from the rotary kiln outlet and enters the cooling system. The cooled slag can be used as building materials or as a raw material for steelmaking. The Zn content in the slag is <1%. The flue gas discharged from the rotary kiln inlet enters the flue gas dust removal system. The bag filter obtains zinc oxide dust, in which the ZnO content is >50%. The purified flue gas is then discharged into the atmosphere.

[0021] The purpose of granulating high-zinc and low-zinc raw materials is to increase the contact area between the raw materials and the environment, and to thoroughly mix them to improve the reaction rate. Coke in the high-zinc mixture creates a reducing atmosphere to reduce the Zn in the high-zinc mixture. This process uses the excess reducing atmosphere in the rotary kiln to reduce the low-zinc mixture, simultaneously processing both high-zinc and low-zinc raw materials, separating volatile metals, effectively enriching and extracting zinc, improving the rotary kiln's processing efficiency, and expanding production capacity. Furthermore, it reduces carbon addition, utilizing coke in the high-zinc mixture to create a reducing atmosphere while simultaneously reducing low-zinc materials, thus saving energy.

[0022] The low-zinc mixture has a particle size of 3mm to 8mm. The particle size is adjusted according to the zinc content of the low-zinc raw materials to ensure sufficient contact between the zinc in the mixture and the surrounding high-temperature environment and reducing gases during the reduction roasting process. The high-zinc mixture has a particle size of 10mm to 15mm, with a particle size ratio of 1:1.25 to 5 between low and high zinc mixtures. Furthermore, the mass ratio of the low-zinc mixture to the high-zinc mixture injected into the high-temperature reduction zone is maintained at 1:5 to 20. This particle size and mass ratio ensures that the low-zinc mixture is evenly distributed within the high-zinc mixture, better dispersed in the gaps between the high-zinc mixtures, and does not encroach on the space of the high-zinc mixtures. This allows both the high-zinc and low-zinc mixtures to undergo normal reduction reactions, thereby improving zinc extraction efficiency.

[0023] In step S4, the injection device is a high-pressure air gun. The low-zinc mixture is injected into the high-temperature reduction zone by the high-pressure gas generated by the air gun. The injection device is connected to both a blower and the low-zinc mixture inlet. The injection device can adjust the air pressure, thereby adjusting the injection distance. The air pressure adjustment system of the injection device can also adapt to different low-zinc mixture conditions, adjusting according to different particle sizes and masses to ensure that the low-zinc mixture is evenly distributed on the high-temperature reduction zone.

[0024] Example 1

[0025] High-zinc raw materials are mixed with coke, resulting in a Zn content of 14.5% and a C content of 30%. After being moistened with water in a disc granulator, the mixture yields a high-zinc mixture with a particle size of 15 mm. Low-zinc raw materials, containing 4% Zn, are also moistened with water in a disc granulator to obtain low-zinc mixture spherical particles with a particle size of 3 mm. The high-zinc mixture is then conveyed via belt to the tail of a rotary kiln for feeding. The high-temperature reduction zone temperature is controlled at 1250℃, and the material is reduced in the kiln for 2 hours. A low-zinc mixture is injected into the high-zinc mixture rotary kiln's high-zinc mixture ...

[0026] Example 2

[0027] High-zinc raw materials are mixed with coke, with a Zn content of 10% and a C content of 20%. After being moistened with water in a disc granulator, the mixture yields a high-zinc mixture with a particle size of 13 mm. Low-zinc raw materials contain 3% Zn, and after being moistened with water in a disc granulator, low-zinc mixture spherical particles with a particle size of 6 mm are obtained. The high-zinc mixture is then conveyed by belt to the tail of a rotary kiln for feeding. The kiln temperature in the high-temperature reduction zone is controlled at 1150℃, and the material is reduced in the kiln for 3 hours. A low-zinc mixture is injected into the high-zinc mixture rotary kiln's high-zinc mixture ...

[0028] Example 3

[0029] High-zinc raw materials are mixed with coke, resulting in a Zn content of 12% and a C content of 25%. After being moistened with water in a disc granulator, the mixture yields a high-zinc mixture with a particle size of 15 mm. Low-zinc raw materials, containing 2.5% Zn, are also moistened with water in a disc granulator to obtain low-zinc mixture spherical particles with a particle size of 3 mm. The high-zinc mixture is then conveyed via belt to the tail of a rotary kiln for feeding. The kiln temperature in the high-temperature reduction zone is controlled at 1200℃, and the material residence time in the kiln is 2 hours. Low-zinc material is injected into the high-temperature reduction zone of the high-zinc material rotary kiln via compressed air from the injection device at the kiln head. The mass ratio of low-zinc material to high-zinc material is 1:10. After the low-zinc mixture and high-zinc mixture are mixed, roasted, and reduced, the reduction slag at a temperature of 800℃~1000℃ is discharged from the discharge end of the rotary kiln and enters the cooling system. The cooled kiln slag can be used as a raw material for building materials or steel plants, and the Zn content in the slag is 0.4%. The flue gas discharged from the feed end of the rotary kiln enters the flue gas dust removal system. As the flue gas velocity decreases, the dust settles and accumulates under gravity, resulting in zinc oxide dust with a ZnO content of 58%. The purified flue gas is then discharged into the atmosphere.

[0030] Example 4

[0031] High-zinc raw materials are mixed with coke, resulting in a Zn content of 12% and a C content of 25%. After being moistened with water in a disc granulator, the mixture yields a high-zinc mixture with a particle size of 10 mm. Low-zinc raw materials contain 2.5% Zn, and after being moistened with water in a disc granulator, spherical low-zinc mixture particles with a particle size of 8 mm are obtained. The high-zinc mixture is then conveyed via belt to the tail of a rotary kiln for feeding. The kiln temperature in the high-temperature reduction zone is controlled at 1200℃, and the material residence time in the kiln is 2 hours. Low-zinc material is injected into the high-temperature reduction zone of the high-zinc rotary kiln via compressed air from the injection device at the kiln head. The mass ratio of low-zinc material to high-zinc material is 1:20. After the low-zinc mixture and high-zinc mixture are mixed, roasted, and reduced, the reduction slag at a temperature of 800℃~1000℃ is discharged from the rotary kiln outlet and enters the cooling system. The cooled kiln slag can be used as a raw material for building materials or steel plants, and the Zn content in the slag is 0.6%. The flue gas discharged from the rotary kiln inlet enters the flue gas dust removal system. As the flue gas velocity decreases, the dust settles and accumulates under gravity, resulting in zinc oxide dust with a ZnO content of 51%. The purified flue gas is then discharged into the atmosphere.

[0032] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A rotary kiln process for zinc extraction, characterized in that, include: S1. Mix high-zinc raw materials and coke in a certain mass ratio to form a mixture, wherein the Zn content in the mixture is 10% to 15% and the C content is 20% to 30%; S2. After wetting the mixture, granulate it to obtain a high-zinc mixture. The high-zinc mixture is then conveyed to the high-temperature reduction zone of the rotary kiln. The temperature of the high-temperature reduction zone is 1100℃~1250℃, and the reduction time is 2h~3h. S3. After wetting the low-zinc raw material, granulate it to obtain a low-zinc mixture. The Zn content in the low-zinc mixture is 2% to 5%. S4. During the high-temperature reduction of the high-zinc mixture, the low-zinc mixture is injected into the high-temperature reduction zone by the injection device at the kiln head of the rotary kiln. After the low-zinc mixture and the high-zinc mixture are mixed, reduced and roasted, reduction slag and flue gas are obtained. After the reduction slag is discharged, it is cooled and the flue gas is discharged into the flue gas dust removal system to remove dust and obtain zinc oxide dust.

2. The zinc extraction rotary kiln process according to claim 1, characterized in that, The high-zinc mixture in S2 has a particle size of 10mm to 15mm.

3. The zinc extraction rotary kiln process according to claim 1, characterized in that, The particle size of the low-zinc mixture in S3 is 3mm to 8mm.

4. The zinc extraction rotary kiln process according to claim 1, characterized in that, The mass ratio of low-zinc mixture to high-zinc mixture injected into the high-temperature reduction zone is maintained at 1:5 to 20.

5. The zinc extraction rotary kiln process according to claim 1, characterized in that, The injection device in step S4 is a high-pressure air gun, through which the low-zinc mixture is injected into the high-temperature reduction zone by the high-pressure gas generated by the high-pressure air gun.

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