Bismuth refining lead removal method and bismuth refining lead removal device

Abstract

The invention relates to the technical field of bismuth refining, and discloses a method for removing lead in bismuth refining, which comprises the following steps: introducing chlorine gas into a bismuth solution in a molten state to enable impurity lead in the bismuth solution to generate lead chloride, and separating the lead chloride from the bismuth solution; in the process of introducing chlorine, air or inert gas is intermittently introduced to stir the bismuth liquid, the interval time is 4-8 h, the continuous introduction time of the air or inert gas is 0.5 h, and the introduction pressure is 2-3 Mpa. The invention further discloses a lead removal device for bismuth refining, and the lead removal device is used for implementing the method. According to the method, lead in the bismuth liquid can be removed, the reaction time can be shortened, the reaction rate can be increased, and the content of lead in the bismuth liquid can be reduced to 10 ppm.

Description

Technical Field

[0001] This application relates to the field of bismuth refining technology, specifically to a method and apparatus for removing lead in bismuth refining. Background Technology

[0002] Bismuth, as an important rare dispersed metal, is widely used in medicine, electronic solder, nuclear radiation shielding materials, high-temperature superconducting materials and cosmetics due to its low melting point, high density, non-toxicity and unique semiconductor properties. With the development of high-end manufacturing, especially the surge in demand for electronic-grade high-purity bismuth, it is necessary to remove impurities, particularly lead, from bismuth as much as possible. However, bismuth and lead are highly similar in elemental properties and physicochemical behavior, and easily form solid solutions in mineral symbiotic systems and during smelting. Currently, the commonly used bismuth refining and impurity removal methods are mainly pyrometallurgical processes. During the bismuth refining and impurity removal process, lead is a stubborn impurity, and the mainstream lead removal method is chlorination. This method can remove most of the lead within 24 to 48 hours, leaving about 100 ppm of lead, which generally requires 3 to 5 days to remove. During these 3 days, chlorine will react with the main metal bismuth to generate bismuth oxychloride ash, resulting in smelting waste. The chlorination lead removal process is relatively mature, but the reaction diffusion effect is poor, and it is inconvenient to introduce mechanical stirring because of its high corrosiveness. The part of the mechanical stirring that comes into contact with the bismuth liquid is easily damaged, resulting in the reaction rate not being able to be improved.

[0003] In the prior art, Chinese patent CN115354172A discloses a method for improving the direct recovery rate of the tellurium removal process in the refining of high tellurium crude bismuth. High-tellurium crude bismuth is added to a bismuth pot and heated to completely melt. Chlorine gas is then introduced into the resulting high-tellurium crude bismuth solution to remove lead. The introduction of chlorine gas is stopped when the lead content is ≤0.001%. The resulting solution is pumped into the next bismuth pot, surface slag is removed, and then the solution is heated and compressed air is introduced for oxidation and impurity removal. Solid caustic soda is added in batches to the resulting solution after oxidation and impurity removal, and slag is skimmed off using a strainer while stirring. The addition of solid caustic soda is stopped when no slag forms on the surface. The refining process is complete when the tellurium content in the bismuth is <0.0003%. This method removes lead impurities from the bismuth solution using chlorine gas. After the lead impurity content is reduced to 0.01%, the reaction requires a long time to reduce the lead impurity content from 0.01% to below 0.001%. Prolonged chlorine gas introduction may also cause a reaction between chlorine gas and metallic bismuth, leading to a decrease in yield.

[0004] Therefore, the technical problem to be solved in this case is: how to shorten the reaction time for lead removal and increase the yield of bismuth.

[0005] Application content

[0006] To address the aforementioned technical problems, this application provides a method and apparatus for removing lead in bismuth refining. The method involves melting bismuth, which contains lead impurities. Chlorine gas is introduced to react with the lead impurities, generating lead chloride slag that floats on the surface of the bismuth liquid. The lead chloride slag is then separated from the bismuth liquid. Over a period of time, the lead impurities are consumed to a certain level. At this point, intermittently introducing air or inert gas to stir the bismuth liquid can increase the reaction rate between the lead impurities and chlorine, reducing the lead impurity content in the bismuth liquid to below 10 ppm. This shortens the reaction time required to reduce the lead impurity content in the bismuth liquid to 10 ppm.

[0007] The technical solution of this application is:

[0008] A method for refining bismuth and removing lead involves introducing chlorine gas into molten bismuth to generate lead chloride from impurities in the bismuth liquid and then separating the lead chloride from the bismuth liquid. During the chlorine gas introduction process, air or an inert gas is introduced intermittently to stir the bismuth liquid. The interval between the introductions is 4 to 8 hours, and the continuous introduction time of the air or inert gas is 0.5 hours. The introduction pressure is 2 to 3 MPa. Alternatively, the interval can be 4 hours, 6 hours, or 8 hours. The introduction pressure can be 2 MPa, 2.5 MPa, or 3 MPa.

[0009] In practical applications, bismuth is melted to form bismuth liquid. The bismuth liquid contains impurities, the main component of which is lead. When chlorine gas is introduced into the bismuth liquid, it can react with the lead impurities to form lead chloride. In order to increase the reaction rate, air or inert gas is introduced to agitate and stir the bismuth liquid. In the process of removing lead, we found that the reaction rate is higher when air or inert gas is introduced intermittently to agitate and stir the bismuth liquid than when air or inert gas is continuously introduced to agitate the bismuth liquid.

[0010] Preferably, in the initial state, the chlorine gas introduction rate is 1~2 m³ / h until the impurity lead content drops to 100~120 ppm. More preferably, the chlorine gas introduction rate can be selected as 1 m³ / h, 1.5 m³ / h, or 2 m³ / h until the impurity lead content drops to 100 ppm, 110 ppm, or 120 ppm, and then the chlorine gas introduction rate is reduced to 0.5~1 m³ / h. More preferably, the chlorine gas introduction rate can be selected as 0.5 m³ / h, 0.7 m³ / h, or 0.9 m³ / h, while air or inert gas is introduced intermittently. The reaction time is 24~48 h. More preferably, the reaction time can be selected as 24 h, 36 h, or 48 h.

[0011] Initially, the chlorine gas flow rate is 1 m³ / h to 2 m³ / h. A higher flow rate increases the reaction rate between chlorine and lead, allowing lead to react more quickly until the lead content reaches 100 ppm. Typically, the reaction takes 48 hours, reducing the lead content to approximately 100 ppm, completing the initial lead removal. Then, the chlorine flow rate is reduced. It's important to note that this reduction is necessary to avoid excess chlorine overflow and waste once the lead content reaches 100 ppm. However, when the initial flow rate is 1 m³ / h, the flow rate can remain constant or be reduced throughout the process. When the lead content in the bismuth solution decreases to 100 ppm, stirring the solution with air or inert gas increases the reaction rate between chlorine and lead. We found that intermittently introducing air or inert gas resulted in a higher reaction rate than continuous introduction.

[0012] Preferably, the gas introduced is air.

[0013] Introducing air can effectively agitate and stir the bismuth liquid, and it is low in cost.

[0014] Preferably, the gas introduced intermittently is an inert gas.

[0015] Introducing an inert gas can prevent the inert gas from reacting with bismuth and thus stabilize the stirred bismuth solution.

[0016] Preferably, the interval is 6 to 8 hours; more preferably, the interval can be 6 hours, 7 hours, or 8 hours.

[0017] Adjusting the interval to 6-8 hours results in a faster reaction rate, reducing the lead content of the bismuth solution to below 10 ppm in a shorter time.

[0018] Preferably, the 9 impurity lead is returned to the bismuth solution, which consumes bismuth and reduces the yield of bismuth refining.

[0019] A lead removal apparatus for bismuth refining, used to implement the above-mentioned lead removal method for bismuth refining, includes a pot body, a chlorine gas pipe, and a vent pipe. The pot body is used to load molten bismuth, the chlorine gas pipe is used to pass chlorine gas into the molten bismuth, and the vent pipe is used to pass air or an inert gas.

[0020] Preferably, there are multiple chlorine gas pipes.

[0021] Preferably, the chlorine gas tube is inserted into the bismuth liquid to a depth of 400-600 mm; more preferably, the chlorine gas tube can be inserted into the bismuth liquid to a depth of 400 mm, 500 mm, or 600 mm.

[0022] Preferably, the vent tube is inserted into the bismuth liquid to a depth of 600-800 mm; more preferably, the vent tube can be inserted into the bismuth liquid to a depth of 600 mm, 700 mm, or 800 mm.

[0023] One of the above-mentioned technical solutions in this application has at least one of the following advantages or beneficial effects:

[0024] This application involves melting bismuth, which contains lead impurities. Chlorine gas is introduced to react with the lead impurities, generating lead chloride slag that floats on the surface of the bismuth solution. The lead chloride slag is then separated from the bismuth solution. Over a period of time, the lead impurities are consumed to a certain level. At this point, the reaction rate between the lead impurities and chlorine gas in the bismuth solution can be increased by intermittently introducing air or inert gas to stir the bismuth solution, thereby reducing the lead impurity content in the bismuth solution to below 10 ppm. This shortens the reaction time required to reduce the lead impurity content in the bismuth solution to 10 ppm. Attached Figure Description

[0025] Figure 1 This is a perspective view of Embodiment 1 of this application;

[0026] Figure 2 This is a front view of Embodiment 1 of this application;

[0027] Figure 3 This is a side view of Embodiment 1 of this application;

[0028] Figure 4 This is a top view of Embodiment 1 of this application.

[0029] The reference numerals for each of the attached figures are as follows: 1. Bismuth pot; 2. Chlorine gas pipe; 3. Vent pipe. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] Example 1

[0032] Please see Figures 1-4 A lead removal apparatus for bismuth refining, used to implement the above-mentioned lead removal method for bismuth refining, includes a pot body, a chlorine gas pipe, and a vent pipe. The pot body is used to load molten bismuth, the chlorine gas pipe is used to introduce chlorine gas into the molten bismuth, and the vent pipe is used for air or an inert gas.

[0033] In practice, molten bismuth (hereinafter referred to as molten bismuth) is loaded into a pot. At this time, the molten bismuth contains impurities, the main component of which is lead. Chlorine gas is introduced into the molten bismuth through a chlorine gas pipe, causing the lead impurities in the molten bismuth to react with the chlorine gas to form lead chloride, thereby refining and removing impurities from the molten bismuth. During the impurity removal process, most of the lead can react within 24 to 48 hours, but about 100 ppm of impurity lead will remain. This 100 ppm of lead needs at least another 72 hours to remove impurities. However, during these 72 hours, chlorine gas may also react with bismuth to form bismuth oxychloride fumes, resulting in waste. To increase the reaction rate, stirring can be introduced. If mechanical stirring is used, the components of the mechanical stirring mechanism are easily corroded due to the strong corrosiveness of the entire lead removal process. Mechanical corrosion not only introduces new impurities but also damages the components, making it inconvenient to use mechanical stirring to increase the reaction rate. Therefore, the reaction rate is increased by introducing gas for stirring. Air or inert gas is introduced through a vent pipe to accelerate the reaction rate between lead and chlorine in the bismuth solution, thereby increasing the reaction rate and shortening the refining and impurity removal reaction time. However, in the lead removal process, we found that the reaction rate is higher when air or inert gas is introduced intermittently than when air or inert gas is introduced continuously.

[0034] Preferably, there are multiple chlorine gas pipes.

[0035] In this embodiment, there are six chlorine gas pipes, but in practice there can be more. The specific number can be adjusted according to the actual situation. Chlorine gas is transported to the bismuth liquid through the six chlorine gas pipes, and all six chlorine gas pipes are located in the bismuth pot and inserted into the bismuth liquid. In this way, chlorine gas can be introduced into all parts of the bismuth liquid, so that the lead in the bismuth liquid can react more evenly with the chlorine gas.

[0036] Preferably, the chlorine gas tube is inserted into the bismuth liquid to a depth of 400-600 mm, but not including 600 mm.

[0037] In this embodiment, the deeper the chlorine gas tube is inserted into the bismuth liquid, the more complete the chlorine gas reaction.

[0038] Preferably, the vent tube is inserted into the bismuth liquid to a depth of 600~800mm.

[0039] In this embodiment, the depth of the vent pipe needs to be greater than the depth of the chlorine pipe. This is because if the depth of the vent pipe is shallower than the chlorine pipe after air or inert gas is introduced, it will lead to insufficient stirring. It should be noted that, in order to avoid the influence of the air or inert gas introduced through the vent pipe on the chlorine pipe, the outlet of the vent pipe should be as far away from the chlorine pipe as possible to prevent the bubbles generated by the gas and inert gas from touching the chlorine pipe, which could cause instability or even breakage of the chlorine pipe. It should also be noted that neither the outlet of the chlorine pipe nor the outlet of the vent pipe should contact the bottom of the bismuth pot. The depth of the bismuth pot can be selected as 1000~2000mm.

[0040] Example 2

[0041] A method for lead removal in bismuth refining employs the lead removal apparatus of Example 1. Initially, the chlorine gas flow rate is 2 m³ / h. When the lead content drops to 100 ppm, the chlorine gas flow rate is reduced to 1 m³ / h. Simultaneously, air is introduced every 8 hours. The reaction time is 24 hours, and the duration of each air introduction is 0.5 hours. The pressure of the introduced gas is 3 MPa. During the entire refining and lead removal process, the generated lead chloride slag is removed. The chlorine gas pipe is inserted into the bismuth liquid to a depth of 600 mm, and the air pipe is inserted into the bismuth liquid to a depth of 700 mm.

[0042] Example 3

[0043] This embodiment 3 is basically the same as embodiment 2, except that:

[0044] Initially, the chlorine gas flow rate was 1.5 m³ / h. When the impurity lead content dropped to 110 ppm, the chlorine gas flow rate was reduced to 0.7 m³ / h. At the same time, air was introduced every 6 hours at a gas pressure of 2.5 MPa, and the reaction time was 36 h.

[0045] Example 4

[0046] This embodiment 4 is basically the same as embodiment 2, except that:

[0047] Initially, the chlorine gas flow rate was 1 m³ / h. When the impurity lead content dropped to 100 ppm, the chlorine gas flow rate was reduced to 0.5 m³ / h. At the same time, air was introduced every 4 hours at a gas pressure of 2 MPa, and the reaction time was 48 h.

[0048] Example 5

[0049] This embodiment 5 is basically the same as embodiment 4, except that:

[0050] The introduced air was replaced with nitrogen.

[0051] Comparative Example 1

[0052] Comparative Example 1 is basically the same as Example 2, except that:

[0053] The interval is 2 hours.

[0054] Comparative Example 2

[0055] Comparative Example 2 is basically the same as Example 2, except that:

[0056] The interval is 10 hours.

[0057] Comparative Example 3

[0058] Comparative Example 3 is basically the same as Example 2, except that:

[0059] When the lead content of impurities is reduced to 90 ppm, the intermittently introduced gas is replaced with chlorine gas.

[0060] To further demonstrate the advantages of the present invention, Examples 2-5 and Comparative Examples 1-3 were used to remove lead from molten bismuth. It should be noted that the total mass of bismuth liquid in each example and each comparative example was 20 tons. The mass of bismuth in the initial state, the mass of lead in the initial state, the total reaction time, the mass of bismuth after impurity removal, and the mass of lead after impurity removal in each example and each comparative example are shown in Table 1.

[0061] Table 1. Detailed breakdown of total reaction times for each embodiment and comparative example.

[0062] Mass of bismuth in its initial state / T Mass of lead in its initial state / T Total reaction time / h Yield after impurity removal Quality of lead after impurity removal Example 2 20 1.25 80 87.62% 10ppm Example 3 20 1.4 85 84.32% 10ppm Example 4 20 1 88 86.32% 10ppm Example 5 20 1.1 73 86.23% 10ppm Comparative Example 1 20 1.3 77 84.11% 10ppm Comparative Example 2 20 0.9 117 83.33% 10ppm Comparative Example 3 20 1.14 73 83.59% 10ppm

[0063] Results analysis:

[0064] 1. Based on Examples 2 and 3, it can be seen that when the content of impurity lead drops to 110 ppm and air is introduced, the yield decreases. We speculate that this is because the reaction efficiency of impurity lead only drops sharply after 100 ppm. Therefore, introducing air and stirring at 110 ppm will cause chlorine and the main metal bismuth to react, resulting in a decrease in yield.

[0065] 2. Based on Examples 2, 4, and 5, it can be seen that when the interval between air introductions is shortened from 8 hours to 4 hours, Example 4 initially contains only 1 ton of lead, while Example 2 initially contains 1.25 tons of lead. However, the total reaction time increases. The only difference between Examples 4 and 5 is the gas introduced: Example 4 introduces air, while Example 5 introduces the inert gas nitrogen. However, the total reaction time of Example 5 is shortened. Therefore, we speculate that during the intermittent air introduction process, chlorine may diffuse into the gas cavity formed by the air, that is, diffuse into the bubbles, causing some chlorine to be carried away. Therefore, shortening the interval between air introductions leads to the removal of more chlorine, resulting in an increase in the total reaction time. When nitrogen is used instead of nitrogen, due to the inert nature of nitrogen, it is not easy to remove chlorine. Therefore, the total reaction time is similar to that of Example 2, but the cost of inert gas is higher.

[0066] 3. Based on Example 2 and Comparative Example 1, it can be seen that when the interval between air introduction is shortened from 8 hours to 2 hours, although the total reaction time is shortened, the yield decreases significantly. We speculate that because the interval is shorter, the air stirring frequency is higher, which makes it easier for chlorine to react with the main metal bismuth, thus leading to a decrease in yield.

[0067] 4. As can be seen from Example 2 and Comparative Example 2, when the interval between air introduction is extended from 8h to 10h, the total reaction time is extended due to the longer stirring interval and the lower stirring frequency. Furthermore, the yield also decreases because the longer interval between air introduction makes it easier for chlorine to react with the main metal bismuth.

[0068] 5. As can be seen from Example 2 and Comparative Example 3, when the content of impurity lead is reduced to 90 ppm and gas is introduced for stirring, the chlorine gas may react with the main metal bismuth during the process of reducing the impurity lead from 100 ppm to 90 ppm, resulting in a decrease in yield.

[0069] In summary, we speculate that when stirring a bismuth solution with a lead content of 100 ppm by introducing gas, the preferred interval for introducing gas is 4 to 8 hours. If the interval is too short, chlorine may react more readily with the main metal bismuth, leading to a decrease in yield. If the interval is too long, it will not only prolong the reaction time but also make chlorine react more readily with the main metal bismuth, resulting in poor impurity removal. Therefore, 4 hours or 8 hours is more preferable, as can be seen from the above analysis. However, inert gas is preferred over air, but inert gas is more expensive than air, which does not meet the actual production requirements.

[0070] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A process for the removal of lead from bismuth refining, characterized in that, The chlorine gas is introduced into the molten bismuth liquid to generate lead chloride from the impurity lead in the bismuth liquid, and the lead chloride is separated from the bismuth liquid; during the introduction of the chlorine gas, air or inert gas is introduced intermittently to stir the bismuth liquid, the interval time is 4-8 hours, the air or inert gas is introduced continuously for 0.5 hour, and the introduction pressure is 2-3 MPa.

2. The method of bismuth refining deleading according to claim 1, characterized in that, In the initial state, the introduction rate of the chlorine gas is 1-2 m3 / h until the content of the impurity lead is reduced to 100-120 ppm, and then the introduction rate of the chlorine gas is reduced to 0.5-1 m3 / h, and the air or inert gas is introduced intermittently, and the reaction time is 24-48 hours.

3. The method of bismuth refining deleading according to claim 1, characterized by, The intermittently introduced gas is air.

4. The method of bismuth refining deleading according to claim 1, characterized in that, The intermittently introduced gas is inert gas.

5. The method of bismuth refining deleading according to claim 1, characterized in that, The interval time is 6-8 hours.

6. The method of bismuth refining deleading according to claim 1, characterized by, The method for separating the lead chloride from the bismuth liquid is to fish out the slag generated on the surface of the bismuth liquid.

7. A lead removal device for bismuth refining, for carrying out the method for lead removal in bismuth refining according to any one of claims 1 to 6, characterized in that The device comprises a pot body, a chlorine gas pipe and a gas pipe, the pot body is used to load the molten bismuth, the chlorine gas pipe is used to introduce the chlorine gas into the molten bismuth, and the gas pipe is used to introduce the air or inert gas.

8. The lead removal device for bismuth refining according to claim 7, characterized in that, The number of the chlorine gas pipes is multiple.

9. The bismuth refining lead removal device according to claim 7, characterized in that, The depth of the chlorine gas pipe inserted into the bismuth liquid is 400-600 mm, but not including 600 mm.

10. The bismuth refining lead removal device according to claim 7, characterized in that, The depth of the gas pipe inserted into the bismuth liquid is 600-800 mm.

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