Method for removing copper ash in a short furnace smelting

Abstract

This invention provides a method for removing copper ash in short-kiln smelting, belonging to the field of non-ferrous metal smelting. The method provided by this invention enriches the copper element in the copper ash into matte as much as possible, thereby maximizing the copper recovery rate. The smelting process of this invention includes three stages: oxidation, reduction, and slag refining. In the oxidation stage, only copper ash is added, without any auxiliary materials; in the reduction stage, the auxiliary materials are pig iron filings and anthracite; in the slag refining stage, no auxiliary materials are added; the oxidation and reduction stages mainly release low-copper and low-lead materials, minimizing lead content in the furnace; the slag refining stage releases high-copper, low-lead matte and low-copper, low-lead tailings. This invention achieves copper enrichment and improves copper recovery rate by adjusting the existing smelting mode and feedstock without using a new smelting furnace, using a smaller amount of auxiliary materials, resulting in better smelting economic benefits.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal smelting. Background Technology

[0002] Copper removal ash is a black, fine powder produced during the copper removal process in crude lead refining. It has a relatively high copper content, reaching around 2%, with other main components including lead, sulfur, and iron. As a common byproduct of lead recycling companies, copper removal ash accounts for a small percentage of total output. Because its effectiveness in recovering copper on its own is poor, it is generally mixed directly with alloy slag during smelting, resulting in most of the copper ending up in the tailings and being wasted. Summary of the Invention

[0003] The purpose of this invention is to overcome the above-mentioned shortcomings of the prior art and to provide a method for removing copper ash in short kiln smelting, which concentrates the copper element in the copper ash into matte as much as possible, thereby maximizing the copper recovery rate.

[0004] To achieve the above objectives, the technical solution of the present invention is: a method for removing copper ash in short kiln smelting, the smelting process comprising the following stages:

[0005] Oxidation stage: Copper removal ash is added to the short kiln, the weight of which is M, in t; the short kiln door is closed and the furnace is ignited; after smelting for a period of time while maintaining a certain natural gas combustion power and oxygen-fuel ratio, the smelting is stopped, and a lead discharge hole with a diameter of 20mm to 40mm is made at the discharge port to discharge lead, and lead is oxidized and discharged; after the lead discharge is completed, the lead discharge hole is plugged, and the oxidation stage ends.

[0006] Reduction stage: Open the furnace door and add pig iron scraps with a weight of A%×M and anthracite coal with a weight of B%×M; close the furnace door and maintain a certain natural gas combustion power and oxygen-fuel ratio for smelting. Stop smelting when the short kiln rotation current reaches the minimum value and is maintained for 30±5 minutes. Make a lead discharge hole with a diameter of 20mm~40mm at the discharge port to discharge lead and release the reduced lead. After the lead discharge is completed, plug the lead discharge hole, and the reduction stage ends.

[0007] Slag refining stage: After maintaining a certain natural gas combustion power and oxygen-fuel ratio for a period of time, smelting is stopped. A lead discharge hole with a diameter of 20mm to 40mm is drilled at the discharge port to discharge lead, slag, lead and matte are discharged. After the discharge is completed, a slag discharge hole with a diameter of 100mm to 200mm is drilled on the basis of the lead discharge hole to discharge the tailings. After the slag discharge is completed, the slag discharge hole is plugged. The smelting stage of one cycle is completed.

[0008] After smelting, once the matte on the surface of the lead slag has solidified, it is removed and stored separately.

[0009] The copper-removing ash has the following Cu content: Cu%, Pb content: Pb%, Fe content: Fe%, and S content: S; the excess ratio of the pig iron scrap is a; and A% = (S% / 32 - Fe% / 56) * 56 * a%;

[0010] The excess ratio a% of the pig iron scrap is determined based on the elemental iron content of the pig iron scrap.

[0011] Elemental iron content ≥85%, a% is taken as 100%;

[0012] 80% ≤ elemental iron content < 85%, a% is taken as 115% ± 2%;

[0013] 70% ≤ elemental iron content < 80%, a% is taken as 120% ± 2%;

[0014] 60%≤Elemental iron content<70%, a% is taken as 130%±2%.

[0015] The copper-removing ash has the following Cu content: Cu%, Pb content: Pb%, Fe content: Fe%, and S content: S; the anthracite has the following fixed carbon content: C, and the anthracite has the following excess ratio: b%.

[0016] The value of B% is calculated as follows: B% = (Pb% / 207 - (S% / 32 - Cu% / 64 - Fe% / 56)) * 12 * b% / C.

[0017] The fixed carbon content of the anthracite is 77% ≤ C% < 84%, and the excess ratio b% of the anthracite is 110% ± 2%.

[0018] During the oxidation stage, the natural gas combustion power is (55-62)×M, in kW;

[0019] In the reduction stage, the natural gas combustion power is (59-65)×M, in kW; in the slag refining stage, the natural gas combustion power is (65-73)×M, in kW.

[0020] In the oxidation stage, the oxygen-fuel ratio is 2.8–3.1; in the reduction stage, the oxygen-fuel ratio is 1.9–2.2; and in the slag refining stage, the oxygen-fuel ratio is 2.2–2.5.

[0021] In the oxidation stage, the smelting time is (1.8~2.2)×M, in min; in the reduction stage, the smelting time is determined by maintaining the short kiln rotation current at its minimum value for 30±5 min; in the slag refining stage, the smelting time is (2.9~3.2)×M, in min.

[0022] Preferably, 27 ≤ M ≤ 32.

[0023] A short kiln, also known as a rotary kiln, primarily radiates heat to the furnace wall via a spray gun, and then transfers the heat to the material through rotation. The inventors discovered that because there is no high-speed gas directly acting on the material within a short kiln, it can be used to process powdery materials. In the recycling of waste lead-acid batteries, short kilns can be used to process various alloy slag ash, such as dry slag, copper removal ash, and alkali ash. Further research revealed the following problems with using short kilns for copper removal ash smelting: 1) Copper has a high affinity for sulfur. Copper removal in crude lead utilizes this principle, using a high-sulfur copper removal agent to transfer copper into the copper removal ash. During direct smelting, most of the copper enters the matte layer, resulting in low copper content in lead and poor direct copper recovery; 2) In related smelting methods, the separation of tailings and matte is ineffective, failing to completely separate them. This leads to the matte being diluted by the low-copper-content tailings, resulting in a lower copper content and affecting the selling price. To address these issues, this invention proposes a method for removing copper ash in short-kiln smelting. The smelting process comprises three stages: oxidation, reduction, and slag refining. In the oxidation stage, only copper ash is added, without any auxiliary materials. In the reduction stage, pig iron filings and anthracite are added as auxiliary materials. No auxiliary materials are added in the slag refining stage. The oxidation and reduction stages primarily release low-copper and low-lead content, minimizing lead levels in the furnace. The slag refining stage releases high-copper, low-lead matte and low-copper, low-lead tailings. Compared to existing technologies, this invention achieves copper enrichment without requiring a new smelting furnace. By adjusting the existing smelting mode and feedstock, it uses a smaller amount of auxiliary materials, improving copper yield and resulting in better economic benefits. This method has good potential for widespread application. Detailed Implementation

[0024] The following is a clear and complete description of a method for removing copper ash in short-kiln smelting proposed in this invention. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0025] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0026] Unless otherwise specified, the test methods or experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are obtained from conventional commercial sources or prepared by conventional methods.

[0027] A method for removing copper ash in short-kiln smelting:

[0028] Oxidation Stage: Add copper-removing ash (weight M) to the short kiln. The amount of copper-removing ash per furnace should be based on the kiln's capacity, and should be added until the material level reaches the bottom of the kiln's feed inlet. Ignite. Maintain a certain natural gas combustion power and oxygen-fuel ratio for a period of time, then stop smelting. Drill small holes (approximately 20mm-40mm in diameter) to release lead, allowing oxidation to occur. After lead release, plug the small holes; the oxidation stage is complete.

[0029] Reduction Stage: Open the short kiln door and add pig iron scraps (weight A%×M) and anthracite coal (weight B%×M) according to the calculated auxiliary material ratio. Close the kiln door and maintain a certain natural gas combustion power and oxygen-fuel ratio for smelting. Smelting is stopped after the short kiln rotation current reaches its minimum value and is maintained for half an hour, typically taking 80-110 minutes. After smelting, drill a small hole (approximately 20-40mm in diameter) to release the reduced lead. After releasing the lead, plug the small hole; the reduction stage is now complete.

[0030] The proportion A% of pig iron scrap is calculated as follows:

[0031] First, the Cu content (Cu%), Pb content (Pb%), Fe content (Fe%), and S content (S) of the copper-free ash were determined; and the excess ratio (a%) of the pig iron scrap was confirmed based on the elemental iron content.

[0032] A% = (S% / 32 - Fe% / 56) * 56 * a%;

[0033] The proportion of anthracite in the batching process, B%, is calculated as follows:

[0034] The fixed carbon content (C%) of anthracite was determined; and the excess ratio (b%) of anthracite was confirmed based on its usage.

[0035] B%=(Pb% / 207- (S% / 32-Cu% / 64-Fe% / 56))*12*b% / C%.

[0036] Slag Refining Stage: After maintaining a certain natural gas combustion power and oxygen-fuel ratio for a period of time, smelting is stopped. Small holes are drilled for lead discharge, releasing the slag and producing lead and matte. After the lead and matte have been discharged, larger holes (approximately 100mm-200mm in diameter) are drilled to discharge the tailings. Since matte has a lower density and solidifies faster than molten lead, it can be directly scooped from the surface of the molten lead and collected after cooling. The large holes are then plugged after slag discharge. One smelting cycle is now complete.

[0037] After smelting, once the matte on the surface of the lead slag has solidified, it is removed and stored separately.

[0038] The following will describe in detail the method for removing copper ash from short kiln smelting provided by the present invention using several specific implementation methods. The following examples all use short kilns with a copper ash feed rate of 28t to 32t as examples. Example 1

[0039] Confirmation of raw and auxiliary materials:

[0040] Raw material ash content (excluding copper):

[0041] element Cu Pb Fe S content / % 1.67% 77.50% 6.28% 8.22%

[0042] Auxiliary materials: Pig iron scraps contain 74.10% elemental iron, and the excess ratio of pig iron scraps is confirmed to be 120%; Anthracite has a fixed carbon content of 81.4%, and the excess ratio is 110%.

[0043] Oxidation stage: 28.47t of copper-removing ash is added to the short kiln and ignited. The natural gas combustion power is 1700kW and the oxygen-fuel ratio is 3.0. After smelting for 60 minutes, smelting is stopped, and a small hole is drilled for lead release to oxidize and release lead. After lead release is completed, the small hole is plugged, and the oxidation stage ends.

[0044] Reduction Stage: Open the short kiln door, add 2.77t of pig iron scrap and 1.18t of anthracite, close the door, adjust the natural gas combustion power to 1800kW and the oxygen-fuel ratio to 2.0, and stop smelting after the short kiln rotation current reaches its minimum value and is maintained for half an hour. The actual smelting time was 90 minutes. Drill a small hole to release lead, releasing the reduced lead. After the lead release is complete, plug the small hole, and the reduction stage ends.

[0045] Slag refining stage: Adjust the natural gas combustion power to 2100kW and the oxygen-fuel ratio to 2.3. After smelting for 90 minutes, stop smelting, drill a small hole for lead discharge, and discharge the slag to produce lead and matte. After discharge, drill a large hole to discharge the tailings slag, and then plug the large hole.

[0046] After smelting, once the copper matte on the surface of the lead slag has solidified, it is removed and stored separately. The data from weighing and testing of each product are shown in Table 1.

[0047] Based on data analysis and calculation, the lead recovery rate in this smelting cycle was 98.36%, and the copper recovery rate (the proportion of copper in matte to the total copper input) was 92.51%. The complete smelting cycle described in this example has now ended. Example 2

[0048] Confirmation of raw and auxiliary materials:

[0049] Raw material ash content (excluding copper):

[0050] element Cu Pb Fe S content / % 1.14% 80.07% 4.93% 9.15%

[0051] Auxiliary materials: The elemental iron content of pig iron scrap is 83.2%, and the excess ratio of pig iron scrap is confirmed to be 115%; the fixed carbon content of anthracite is 80.3%, and the excess ratio is 110%.

[0052] Oxidation stage: 30.43t of copper-removing ash is added to the short kiln and ignited. The natural gas combustion power is 1700kW and the oxygen-fuel ratio is 3.0. After smelting for 60 minutes, smelting is stopped, and a small hole is drilled for lead release to oxidize and release lead. After lead release is completed, the small hole is plugged, and the oxidation stage ends.

[0053] Reduction Stage: Open the short kiln door, add 3.88t of pig iron scrap and 1.03t of anthracite, close the door, adjust the natural gas combustion power to 1800kW and the oxygen-fuel ratio to 2.0, and stop smelting after the short kiln rotation current reaches its minimum value and is maintained for half an hour. The actual smelting time was 95 minutes. Drill a small hole to perform lead release, releasing the reduced lead. After lead release is complete, plug the small hole, ending the reduction stage.

[0054] Slag refining stage: Adjust the natural gas combustion power to 2100kW and the oxygen-fuel ratio to 2.3. After smelting for 90 minutes, stop smelting, drill a small hole for lead discharge, and discharge the slag to produce lead and matte. After discharge, drill a large hole to discharge the tailings slag, and then plug the large hole.

[0055] After smelting, once the copper matte on the surface of the lead slag has solidified, it is removed and stored separately. The data from weighing and testing of each product are shown in Table 1.

[0056] Based on data analysis and calculation, the lead recovery rate in this smelting cycle was 98.47%, and the copper recovery rate (the proportion of copper in matte to the total copper input) was 84.15%. The complete smelting cycle described in this example has now ended. Example 3

[0057] Confirmation of raw and auxiliary materials:

[0058] Raw material ash content (excluding copper):

[0059] element Cu Pb Fe S content / % 2.01% 74.96% 7.70% 9.47%

[0060] Auxiliary materials: Pig iron scraps contain 67.40% elemental iron, with an excess ratio of 130%; Anthracite has a fixed carbon content of 83.2%, with an excess ratio of 110%.

[0061] Oxidation stage: 29.93t of copper-removing ash is added to the short kiln and ignited. The natural gas combustion power is 1700kW and the oxygen-fuel ratio is 3.0. After smelting for 60 minutes, smelting is stopped, and a small hole is drilled for lead release to oxidize and release lead. After lead release is completed, the small hole is plugged, and the oxidation stage ends.

[0062] Reduction Stage: Open the short kiln door, add 3.45t of pig iron scrap and 1.12t of anthracite, close the door, adjust the natural gas combustion power to 1800kW and the oxygen-fuel ratio to 2.0, and stop smelting after the short kiln rotation current reaches its minimum value and is maintained for half an hour. The actual smelting time was 90 minutes. Drill a small hole to release lead, releasing the reduced lead. After the lead release is complete, plug the small hole, and the reduction stage ends.

[0063] Slag refining stage: Adjust the natural gas combustion power to 2100kW and the oxygen-fuel ratio to 2.3. After smelting for 90 minutes, stop smelting, drill a small hole for lead discharge, and discharge the slag to produce lead and matte. After discharge, drill a large hole to discharge the tailings slag, and then plug the large hole.

[0064] After smelting, once the copper matte on the surface of the lead slag has solidified, it is removed and stored separately. The data from weighing and testing of each product are shown in Table 1.

[0065] Based on data analysis and calculation, the lead recovery rate in this smelting cycle was 97.97%, and the copper recovery rate (the proportion of copper in matte to the total copper input) was 92.77%. The complete smelting cycle described in this example has now ended. Example 4

[0066] Confirmation of raw and auxiliary materials:

[0067] Raw material ash content (excluding copper):

[0068] element Cu Pb Fe S content / % 1.39% 72.68% 8.40% 9.71%

[0069] Auxiliary materials: Pig iron scraps contain 77.00% elemental iron, with an excess ratio of 120%; Anthracite has a fixed carbon content of 77.8%, with an excess ratio of 110%.

[0070] Oxidation stage: 29.16t of copper-removing ash is added to the short kiln and ignited. The natural gas combustion power is 1700kW and the oxygen-fuel ratio is 3.0. After smelting for 60 minutes, smelting is stopped, and a small hole is drilled for lead release to oxidize and release lead. After lead release is completed, the small hole is plugged, and the oxidation stage ends.

[0071] Reduction Stage: Open the short kiln door, add 3.01t of pig iron scrap and 1.09t of anthracite, close the door, adjust the natural gas combustion power to 1800kW and the oxygen-fuel ratio to 2.0, and stop smelting after the short kiln rotation current reaches its minimum value and is maintained for half an hour. The actual smelting time was 100 minutes. Drill a small hole to perform lead release, releasing the reduced lead. After lead release is complete, plug the small hole, ending the reduction stage.

[0072] Slag refining stage: Adjust the natural gas combustion power to 2100kW and the oxygen-fuel ratio to 2.3. After smelting for 90 minutes, stop smelting, drill a small hole for lead discharge, and discharge the slag to produce lead and matte. After discharge, drill a large hole to discharge the tailings slag, and then plug the large hole.

[0073] After smelting, once the copper matte on the surface of the lead slag has solidified, it is removed and stored separately. The data from weighing and testing of each product are shown in Table 1.

[0074] Based on data analysis and calculation, the lead recovery rate in this smelting cycle was 97.81%, and the copper recovery rate (the proportion of copper in matte to the total copper input) was 94.98%. The complete smelting cycle described in this example has now ended.

[0075] Table 1

[0076]

[0077] Although the method for removing copper ash from short kiln smelting provided by the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for removing copper ash during short-kiln smelting, characterized in that: The smelting process consists of the following stages: Oxidation stage: Copper removal ash is added to the short kiln, the weight of which is M, in t; the short kiln door is closed and the furnace is ignited; after smelting for a period of time while maintaining a certain natural gas combustion power and oxygen-fuel ratio, the smelting is stopped, and a lead discharge hole with a diameter of 20mm to 40mm is made at the discharge port to discharge lead, and lead is oxidized and discharged; after the lead discharge is completed, the lead discharge hole is plugged, and the oxidation stage ends. Reduction stage: Open the furnace door and add pig iron scraps with a weight of A%×M and anthracite with a weight of B%×M; the Cu content of the copper-removing ash is Cu%, Pb content is Pb%, Fe content is Fe%, and S content is S%; the excess ratio of the pig iron scraps is a%; the... The copper-removing ash has the following properties: Cu%; Pb%; Fe%; S%; and fixed carbon content of the anthracite is C, with an excess ratio of b%. Close the furnace door, maintain a certain natural gas combustion power and oxygen-fuel ratio for smelting, and stop smelting when the short kiln rotation current reaches the minimum value and is maintained for 30±5 minutes. Make a lead discharge hole with a diameter of 20mm to 40mm at the discharge port to discharge lead and reduce the lead. After the lead discharge is completed, plug the lead discharge hole to end the reduction stage. Slag refining stage: After maintaining a certain natural gas combustion power and oxygen-fuel ratio for a period of time, smelting is stopped. A lead discharge hole with a diameter of 20mm to 40mm is drilled at the discharge port to discharge lead and lead matte. After the discharge is completed, a slag discharge hole with a diameter of 100mm to 200mm is drilled on the basis of the lead discharge hole to discharge the tailings. After the slag discharge is completed, the slag discharge hole is plugged. After smelting, once the matte on the surface of the lead slag has solidified, it is removed and stored separately.

2. The method for removing copper ash in short kiln smelting according to claim 1, characterized in that: The excess ratio a% of the pig iron scrap is determined based on the elemental iron content of the pig iron scrap.

3. The method for removing copper ash in short kiln smelting according to claim 2, characterized in that: Elemental iron content ≥85%, a% is taken as 100%; 80% ≤ elemental iron content < 85%, a% is taken as 115% ± 2%; 70% ≤ elemental iron content < 80%, a% is taken as 120% ± 2%; 60%≤Elemental iron content<70%, a% is taken as 130%±2%.

4. The method for removing copper ash in short kiln smelting according to claim 1, characterized in that: The fixed carbon content of the anthracite is 77% ≤ C% < 84%, and the excess ratio b% of the anthracite is 110% ± 2%.

5. The method for removing copper ash in short kiln smelting according to claim 1, characterized in that: During the oxidation stage, the natural gas combustion power is (55-62)×M, in kW; During the reduction stage, the natural gas combustion power is (59-65)×M, in kW; During the slag refining stage, the natural gas combustion power is (65-73)×M, in kW.

6. The method for removing copper ash in short kiln smelting according to claim 1, characterized in that: During the oxidation stage, the oxygen-fuel ratio is 2.8–3.1; During the reduction stage, the oxygen-fuel ratio is 1.9 to 2.2; During the slag refining stage, the oxygen-fuel ratio is 2.2 to 2.

5.

7. The method for removing copper ash in short kiln smelting according to claim 1, characterized in that: During the oxidation stage, the smelting time is (1.8~2.2)×M, in min; During the reduction stage, the smelting time is determined by maintaining the short kiln rotation current at its minimum value for 30±5 minutes until the smelting ends. During the slag refining stage, the smelting time is (2.9~3.2)×M, in minutes.

8. The method for removing copper ash in short kiln smelting according to claim 1, characterized in that: 27≤M≤32。

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