A method for enriching tellurium and silver from low-grade soda ash using waste heat from crude lead impurity removal.

Abstract

This invention relates to a method for enriching tellurium and silver from low-grade soda ash residue using the residual heat from crude lead impurity removal. The method includes the following steps: S1. Removing copper and tin from the molten lead; S2. Adding the soda ash residue to the molten lead containing the copper- and tin-removed residue in a specific ratio, heating and stirring to dissolve the tellurium and silver in the soda ash residue into the molten lead, and removing the surface slag; S3. Cooling the resulting tellurium- and silver-rich molten lead, adding industrial salt and sodium hydroxide in a specific ratio, and stirring a second time to enrich the tellurium in the slag and allow the silver to enter the molten lead. This invention improves upon traditional pyrometallurgical processes, enriching the tellurium content in the low-grade soda ash residue to over 25%, which is beneficial for further comprehensive tellurium recovery. The silver, after entering the molten lead, can be further recovered through the lead anode electrolysis process. This method has a short process flow, high comprehensive metal recovery rate, and low production cost, and has significant theoretical and practical value.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal smelting technology, specifically relating to a method for enriching tellurium and silver from low-grade soda ash using the residual heat from impurity removal of crude lead. Background Technology

[0002] Currently, most lead anode slime is processed using a pyrometallurgical process: "anode slime reduction smelting – precious lead oxidation refining – silver electrolysis – gold electrolysis." In the later stages of oxidation refining, valuable metals such as tellurium, bismuth, and copper in the lead anode slime are enriched in the soda ash. Simultaneously, the precious lead blowing process also introduces a certain amount of silver into the soda ash. This soda ash contains approximately 0.3-2% silver and 0.3-8% tellurium. Due to the mixed nature and low grade of these metals, directly using it in wet leaching for tellurium recovery results in low tellurium leaching rates, consumes large amounts of leaching agent, and makes silver recovery extremely difficult, leading to resource waste and excessively high production costs. Therefore, exploring a process that can efficiently and cost-effectively enrich tellurium and silver in low-grade soda ash has significant theoretical and practical value. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a method for enriching tellurium and silver from low-grade soda ash using the residual heat from crude lead impurity removal.

[0004] The specific technical solution is as follows: a method for enriching tellurium and silver from low-grade soda ash using the residual heat from crude lead impurity removal, including the following steps:

[0005] S1. Crude lead is put into a lead melting pot, heated and melted to obtain molten lead liquid, and copper and tin are removed from the molten lead liquid;

[0006] S2. Add the soda residue to the molten lead liquid that has been decoaled and detined in proportion, heat it up to completely melt the soda residue, put it into a mixer for the first stirring, so that the tellurium and silver in the soda residue can be melted into the lead liquid, remove the waste residue on the surface, and obtain molten lead liquid rich in tellurium and silver.

[0007] S3. After cooling the obtained tellurium-rich and silver-rich molten lead liquid, add industrial salt and sodium hydroxide in proportion, and stir a second time to allow the tellurium in the lead liquid to enter the scum, forming tellurium-rich scum. The scum is skimmed off every hour, and the tellurium content in the lead liquid and scum is tested. Stirring is stopped when the tellurium content in the lead liquid can no longer be reduced, and the tellurium-rich scum is skimmed off. At this point, the tellurium is enriched in the scum and can be wet leaching. The silver is enriched in the lead liquid and can be further enriched in the anode mud during the electrolysis process of the lead anode.

[0008] Furthermore, in step S1, the lead content in the lead solution is greater than 70%, the copper content is less than 0.8%, and the tin content is less than 0.2%.

[0009] Furthermore, the tellurium content in the soda ash described in step S2 is 0.3%-8%, and the silver content is greater than 0.01%.

[0010] Furthermore, the ratio of soda residue to lead liquid in step S2 is 1:5-20.

[0011] Furthermore, in step S2, the temperature at which the soda slag melts in the lead liquid is 700-900℃, and the duration of the first stirring is 1-5 hours; in step S3, the temperature of the tellurium-rich and silver-rich molten lead liquid is reduced to 500-750℃.

[0012] Furthermore, the industrial salt addition ratio mentioned in step S3 is the ratio of industrial salt to lead solution, specifically 1:150-600.

[0013] Furthermore, the sodium hydroxide addition ratio in step S3 is the ratio of sodium hydroxide to tellurium content in the soda ash, specifically 1:0.9-4.

[0014] The beneficial effects of this invention are as follows: This invention improves upon the traditional pyrometallurgical process by adding soda ash to high-temperature molten lead solution after copper and tin removal, along with industrial salt and sodium hydroxide, and stirring. This process enriches tellurium in the scum, achieving a tellurium content of over 25% in the low-grade soda ash and a direct tellurium recovery rate of over 98%. Silver enters the lead solution and can be further recovered during the lead anode electrolysis process without increasing silver recovery costs. This invention fully utilizes the high heat after impurity removal from crude lead to enrich and recover tellurium and silver from low-grade soda ash, increasing the sustainability of metal recovery, reducing production costs, and featuring a short process flow, high overall metal recovery rate, and high tellurium grade product. It can provide more competitive high-grade tellurium-containing materials for tellurium wet leaching, possessing significant theoretical and practical value. Implementation

[0015] To make the technical problems and solutions solved by the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention. Example

[0016] The soda slag produced by the pyrometallurgical refining process for extracting precious metals from the anode mud after lead electrolysis by a company in Guangxi has the following main components: 3.15% tellurium, 1.26% silver, 35.34% lead, and 18.89% antimony.

[0017] This experiment was conducted in a lead melting pot capable of holding 50 tons of molten lead. 35 tons of crude lead were added to the pot and melted to obtain molten lead. After removing copper and tin, the molten lead reached a temperature of 600℃ and a composition of 0.0023% tellurium, 0.133% silver, 85.44% lead, and 8.67% antimony. Three tons of the aforementioned soda ash were added to this molten lead, raising the temperature to 800℃. After the soda ash melted, the mixture was stirred in a mixer for 2 hours. Surface waste was removed, yielding tellurium- and silver-rich lead molten lead with a composition of 0.26% tellurium and 0.24% silver. The temperature of this tellurium- and silver-rich lead molten lead was lowered to 650℃, and 100 kg of industrial salt and 100 kg of sodium hydroxide were added. The mixture was stirred for a total of 5 hours, and 360 kg of tellurium-rich slag was obtained. Tests revealed that the tellurium-rich slag contained 25.14% tellurium, 0.06% silver, and 8.42% lead, while the lead solution contained 0.003% tellurium, 0.24% silver, and 85.47% lead.

[0018] Under the conditions of this embodiment, the recovery rate of tellurium in soda residue = 360kg * 25.14% / (3000kg * 3.15%) = 95.8%. Example

[0019] The soda slag produced by the pyrometallurgical refining process for extracting precious metals from the anode mud after lead electrolysis by a company in Guangxi has the following main components: 7.68% tellurium, 2.11% silver, 32.63% lead, and 17.24% antimony.

[0020] This experiment was conducted in a lead melting pot capable of holding 50 tons of molten lead. 35 tons of crude lead were added to the pot and melted to obtain molten lead. After removing copper and tin, the molten lead reached a temperature of 630℃ and a composition of 0.0019% tellurium, 0.126% silver, 84.73% lead, and 9.13% antimony. Three tons of the aforementioned soda ash were added to this molten lead, raising the temperature to 750℃. After the soda ash melted, the mixture was stirred in a mixer for 1.5 hours. Surface waste was removed, yielding tellurium- and silver-rich lead molten lead with a composition of 0.65% tellurium and 0.31% silver. The temperature of this tellurium- and silver-rich lead molten lead was lowered to 700℃, and 100 kg of industrial salt and 350 kg of sodium hydroxide were added. The mixture was stirred for a total of 6 hours, yielding 690 kg of tellurium-rich slag. Tests revealed that the tellurium-rich slag contained 32.36% tellurium, 0.07% silver, and 7.13% lead, while the lead solution contained 0.002% tellurium, 0.305% silver, and 84.62% lead.

[0021] Under the conditions of this embodiment, the recovery rate of tellurium in soda ash = 690kg * 32.36% / (3000kg * 7.68%) = 96.9%. Example

[0022] The soda slag produced by the pyrometallurgical refining process for extracting precious metals from the anode mud after lead electrolysis by a company in Guangxi has the following main components: 6.64% tellurium, 1.37% silver, 33.34% lead, and 15.89% antimony.

[0023] The experiment was conducted in a lead melting pot capable of holding 50 tons of molten lead. 35 tons of crude lead were added to the pot and melted to obtain molten lead. After removing copper and tin, the molten lead reached a temperature of 580℃ and a composition of 0.0009% tellurium, 0.164% silver, 84.14% lead, and 8.36% antimony. Three tons of the aforementioned soda ash were added to this molten lead, raising the temperature to 700℃. After the soda ash melted, the mixture was stirred in a mixer for 2.5 hours. Surface waste was removed, yielding tellurium- and silver-rich lead molten lead with a composition of 0.56% tellurium and 0.28% silver. The temperature of this tellurium- and silver-rich lead molten lead was lowered to 650℃, and 150 kg of industrial salt and 400 kg of sodium hydroxide were added. The mixture was stirred for a total of 5 hours, yielding 683 kg of tellurium-rich slag. Tests revealed that the tellurium-rich slag contained 28.25% tellurium, 0.03% silver, and 9.21% lead, while the lead solution contained 0.001% tellurium, 0.28% silver, and 84.15% lead.

[0024] Under the conditions of this embodiment, the recovery rate of tellurium in soda residue = 683kg * 28.25% / (3000kg * 6.64%) = 96.9%.

[0025] The present invention has been described in detail above through specific and preferred embodiments. However, those skilled in the art should understand that the present invention is not limited to the embodiments described above. Any modifications, equivalent substitutions, 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 enriching tellurium and silver from low-grade soda ash residue using waste heat from crude lead impurity removal, characterized in that, Includes the following steps: S1. Crude lead is put into a lead melting pot, heated and melted to obtain molten lead liquid, and copper and tin are removed from the molten lead liquid; S2. Add soda ash with a tellurium content of 0.3%-8% and a silver content of more than 0.01% to molten lead in a ratio of 1:5-20, to the molten lead that has been decoaled and detined. Heat the soda ash to completely melt it, then put it into a mixer for the first stirring to dissolve the tellurium and silver in the soda ash into the molten lead. Remove the surface waste to obtain molten lead rich in tellurium and silver. S3. After cooling the obtained tellurium-rich and silver-rich molten lead liquid, add industrial salt and sodium hydroxide in proportion, and stir a second time to allow the tellurium in the lead liquid to enter the scum, forming tellurium-rich scum. The scum is skimmed off every hour, and the tellurium content in the lead liquid and scum is tested. Stirring is stopped when the tellurium content in the lead liquid can no longer be reduced, and the tellurium-rich scum is skimmed off. At this point, the tellurium is enriched in the scum and can be wet leaching. The silver is enriched in the lead liquid and can be further enriched in the anode mud during the electrolysis process of the lead anode. In step S2, the temperature at which the soda slag melts in the lead liquid is 700-900℃, and the duration of the first stirring is 1-5 hours; in step S3, the temperature of the tellurium-rich and silver-rich molten lead liquid is reduced to 500-750℃.

2. The method for enriching tellurium and silver from low-grade soda ash residue using waste heat from crude lead impurity removal according to claim 1, characterized in that, The lead solution described in step S1 contains more than 70% lead, less than 0.8% copper, and less than 0.2% tin.

3. The method for enriching tellurium and silver from low-grade soda ash residue using waste heat from crude lead impurity removal according to claim 1, characterized in that, The industrial salt addition ratio mentioned in step S3 is the ratio of industrial salt to lead solution, specifically 1:150-600.

4. The method for enriching tellurium and silver from low-grade soda ash residue using waste heat from crude lead impurity removal according to claim 1, characterized in that, The sodium hydroxide addition ratio mentioned in step S3 is the ratio of sodium hydroxide to tellurium content in soda ash, specifically 1:0.9-4.