A process for separating lead and silver

Abstract

The application provides a method for separating lead and silver, and belongs to the technical field of nonferrous metallurgy. The method is carried out by using a solid-liquid separator, the solid-liquid separator comprises a tank body and a screw rod in the tank body, the inclination angle of the tank body is 8-15 DEG, and the method comprises the following steps: flowing lead-silver alloy melt into the solid-liquid separator, and then condensing and dissolving under the action of the screw rod, discharging high-silver lead at the bottom of the tank body, removing silver-lead alloy generated at the top of the tank body after condensing and dissolving for at least 2 hours, and starting to produce low-silver lead; the interval time of adjacent two times of discharging high-silver lead is 20-30 min, starting from the time when the flowing starts; and the rotating speed of the screw rod is 3-10 r / min. The lead condensed out is transported to the high-temperature section by the screw rod to be dissolved and purified, so that low-silver lead is obtained; and the melt flows back to the low-temperature section by gravity to increase the purity of condensed silver, so that high-silver lead is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nonferrous metallurgy, in particular to a method for separating lead and silver. BACKGROUND

[0002] The silver ore in China has low grade and cannot be extracted alone, so it is usually combined with lead smelting system. In the lead smelting system, silver will enter the crude lead, and in the refining of the crude lead, silver as impurities will be separated from lead.

[0003] The condensation-melting method is widely used in the removal of lead, bismuth and other impurities in crude tin. The electric heating continuous crystallization machine developed in China in 1975 is a process for removing lead and bismuth in crude tin by using this method. However, since it was put into operation, it has only been used for removing lead and bismuth in the refining of crude tin, and the separation of lead and silver has not been realized. SUMMARY

[0004] The purpose of the present application is to provide a method for separating lead and silver. The method of the present application realizes the separation of lead and silver by using condensation-melting.

[0005] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0006] The present application provides a method for separating lead and silver, which is carried out by using a solid-liquid separator, wherein the solid-liquid separator comprises a tank body and a screw in the tank body; the inclination angle of the tank body is 8-15°;

[0007] The method comprises the following steps:

[0008] After the lead-silver alloy melt flows into the solid-liquid separator, condensation-melting is carried out under the action of the screw, and high-silver lead is discharged at the bottom of the tank body; after condensation-melting for at least 2 h, silver-lead alloy produced at the top of the tank body is removed, and low-silver lead starts to be produced;

[0009] The interval time between adjacent two times of discharging high-silver lead is 20-30 min, starting from the time when the flowing starts;

[0010] The rotation speed of the screw is 3-10 r / min.

[0011] Preferably, the content of silver in the lead-silver alloy is 0.02-1.2 wt%.

[0012] Preferably, the surface of the screw is coated with a silicone coating.

[0013] Preferably, the content of silver in the low-silver lead is less than 0.008 wt%, and the content of silver in the high-silver lead is 0.2-1.8 wt%.

[0014] Preferably, the melting temperature for obtaining the lead-silver alloy melt is 330-360℃;

[0015] The temperature of the groove body increases in the range of 305-333 DEG C along the extension direction from low to high.

[0016] Preferably, the temperature difference between two adjacent groove bodies is greater than or equal to 0.1 DEG C.

[0017] The width of the groove body at each temperature is independently 0.16-1 m along the extension direction of the groove body.

[0018] Preferably, the groove body is open.

[0019] The inflow is performed at the position of the groove body at the second temperature from low to high.

[0020] Preferably, the conveying capacity of the screw is 20-100 kg / h.

[0021] Preferably, the length of the groove body is 0.5-6 m.

[0022] Preferably, the method further comprises: remelting and condensation-melting the silver-lead alloy produced in the last 2 h.

[0023] The present application provides a method for separating lead and silver, comprising the following steps: the solid-liquid separator comprises a groove body and a screw in the groove body; the inclination angle of the groove body is 8-15 DEG; the method comprises the following steps: condensation-melting of the lead-silver alloy melt under the action of the screw after the inflow of the lead-silver alloy melt into the solid-liquid separator, discharging high-silver lead at the bottom of the groove body; removing the silver-lead alloy produced at the top of the groove body after condensation-melting for at least 2 h, and starting to produce low-silver lead; the interval time between two adjacent discharges is 20-30 min, starting from the time when the inflow starts; and the rotating speed of the screw is 3-10 r / min. In the low-temperature section, the lead in the melt is condensed, the lead condensed out is transported to the high-temperature section by the screw for purification, the rotating speed of the screw is controlled to make the condensation complete, the time interval of discharging is controlled to avoid the high-silver lead being brought to the top of the groove body by the screw, thereby obtaining low-silver lead; the liquid produced by condensation returns to the low-temperature section by gravity to continue condensation, the lead produced is continuously transported to the high-temperature section for condensation, the purity of silver in the residual melt is increased, and the rotating speed of the screw and the inclination angle of the groove body are controlled to make the return flow speed appropriate, thereby avoiding the silver being brought into the lead, and obtaining high-silver lead.

[0024] The method of the present application is a physical separation method, does not introduce new impurities, is simple in form, does not produce waste gas and waste liquid in the treatment process, only produces a small amount of oxidation slag, has a good working environment, and is safe and controllable in process;

[0025] The method of the present application has less equipment investment, short production cycle, low energy consumption, and high enrichment of silver in high-silver lead, thereby reducing the production cost for subsequent silver recovery.

[0026] The method can directly treat lead-silver alloy containing 0.04-1.2% silver, and can obtain high-silver lead containing 0.2-1.8% silver, low-silver lead containing less than 0.008% silver, and high silver direct recovery rate. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Mechanism diagram for separating lead and silver according to the present application;

[0028] Figure 2 Solid-liquid separator used in examples and comparative examples. DETAILED DESCRIPTION

[0029] The present application provides a method for separating lead and silver, which is carried out by using a solid-liquid separator, wherein the solid-liquid separator comprises a tank body and a screw in the tank body; the inclination angle of the tank body is 8-15°.

[0030] The method comprises the following steps:

[0031] After the lead-silver alloy melt is flowed into the solid-liquid separator, the condensation-dissolution is carried out under the action of the screw, and the high-silver lead is discharged at the bottom of the tank body; after the condensation-dissolution for at least 2h, the silver-lead alloy produced at the top of the tank body is removed, and the low-silver lead is started to be produced.

[0032] The interval time between two adjacent discharges of the high-silver lead is 20-30min, starting from the time when the flowing is started.

[0033] The rotation speed of the screw is 3-10r / min.

[0034] In the present application, the content of silver in the lead-silver alloy is preferably 0.02-1.2wt%, more preferably 0.2-0.8wt%, and further preferably 0.4-0.6wt%. In the present application, the melting temperature for obtaining the lead-silver alloy melt is 330-360℃.

[0035] In the present application, the solid-liquid separator comprises a tank body and a screw in the tank body, and the tank body is preferably open. In the present application, the length of the screw is preferably the same as the length of the tank body; the conveying capacity of the screw is preferably 20-100kg / h, more preferably 40-80kg / h, and further preferably 50-60kg / h.

[0036] In the present application, the inclination angle of the groove is 8-15°, preferably 10-12°. The inclination angle of the present application is conducive to the reflux of the melt to the low-temperature zone for further condensation. In the present application, the temperature of the groove preferably increases in the direction from low to high, and the temperature of the groove is preferably in the range of 305-333℃; the difference between the temperatures of two adjacent grooves is preferably ≥0.1℃, more preferably 4-9℃, and further preferably 5-8℃; the decrease in temperature causes the lead in the melt to condense and precipitate crystals, but part of the lead-silver alloy is entrained and encapsulates the lead. Because the melting point of the alloy is lower than that of pure lead, the encapsulated lead-silver alloy will melt and reflux to the low-temperature zone of the groove as the temperature rises, while the crystallized lead does not melt because it does not reach the melting point temperature, thus realizing liquid-solid separation, so that the lead is separated from the silver at the top of the groove.

[0037] In the present application, the length of the groove is preferably 0.5-6m, more preferably 2-5m, and further preferably 3-4m; the width of the groove at each temperature is preferably independently 0.16-1m, more preferably 0.2-0.8m, and further preferably 0.4-0.6m, in the direction of the groove. In the present application, the inflow is preferably performed at the groove position at the second temperature from low to high.

[0038] In the present application, the surface of the screw is preferably coated with a silicone coating. The silicone coating can prevent the lead from adhering to the screw. In the present application, the rotation speed of the screw is preferably 3-10r / min, and more preferably 4-6r / min.

[0039] In the present application, the interval time between two adjacent times of discharging high-silver lead is 20-30min, and preferably 24-28min, starting from the time when the inflow starts. In the present application, the weight of the high-silver lead discharged at a time is preferably 0.58-1.12wt% of the total amount of the melt, and more preferably 0.6-0.8wt%. In the present application, the same amount of melt as the high-silver lead discharged is preferably supplemented into the liquid outlet after the discharge.

[0040] In the present application, the method preferably further comprises: removing the silver-lead alloy produced in the 2h before condensation-melting and then remelting and condensation-melting. The removal is preferably continuous removal starting from the time when the melt inflow starts, and the present application further preferably comprises supplementing the same amount of melt as the silver-lead alloy removed.

[0041] In the present application, the content of silver in the low-silver lead is preferably less than 0.008wt%, and the content of silver in the high-silver lead is preferably 0.2-1.8wt%.

[0042] The mechanism of lead and silver in the present application is as shown in Figure 1 .

[0043] The method for separating lead and silver provided by the present application will be described in detail below in combination with examples, but they should not be understood as limiting the protection scope of the present application.

[0044] The solid-liquid separator used in the examples and comparative examples is shown in Figure 2 .

[0045] Example 1

[0046] The solid-liquid separator has a length of 1 m, a width of 0.22 m, a depth of 0.16 m, and a screw conveying capacity of 55 kg / h. The slope of the solid-liquid separator is adjusted to 10°, and the screw rotating speed is adjusted to 4 r / min. The temperature of the solid-liquid separator tank is set as follows: the first section is 305 ℃, the second section is 310 ℃, the third section is 315 ℃, the fourth section is 320 ℃, the fifth section is 325 ℃, and the sixth section is 333 ℃. Along the extension direction of the tank, the width of each section with an increasing temperature is independently 0.16 m.

[0047] 500 kg of lead-silver alloy containing 0.027 wt% of silver is melted in a melting pot at 350 ℃ and kept until the end of the operation. After a period of time, the temperature of the solid-liquid separator tank is raised to the set value, the melting pot switch is opened to release the liquid, and the lead-silver alloy melt flows into the position corresponding to the third temperature section of the solid-liquid separator. After natural cooling, the crystals start to be produced. The liquid is released every 25 min (the mass is 0.82 wt% of the mass of the melt), and high-silver lead is obtained. The crystals produced in the first 2 hours are put back into the melting pot for remelting. After 2 hours, qualified low-silver lead is produced. The chemical compositions of the raw material and the products are shown in Table 1.

[0048] Example 2

[0049] The solid-liquid separator has a length of 1 m, a width of 0.22 m, a depth of 0.16 m, and a screw conveying capacity of 51 kg / h. The slope of the solid-liquid separator is adjusted to 11°, and the screw rotating speed is adjusted to 5 r / min. The temperature of the solid-liquid separator tank is set as follows: the first section is 305 ℃, the second section is 312 ℃, the third section is 316 ℃, the fourth section is 320 ℃, the fifth section is 326 ℃, and the sixth section is 333 ℃. Along the extension direction of the tank, the width of each section with an increasing temperature is independently 0.16 m.

[0050] 500 kg of lead-silver alloy containing 0.081 wt% of silver is melted in a melting pot at 339 ℃ and kept until the end of the operation. After a period of time, the temperature of the solid-liquid separator tank is raised to the set value, the melting pot switch is opened to release the liquid, and the lead-silver alloy melt flows into the position corresponding to the third temperature section of the solid-liquid separator. After natural cooling, the crystals start to be produced. The liquid is released every 20 min (the mass is 0.58 wt% of the mass of the melt), and high-silver lead is obtained. The crystals produced in the first 2 hours are put back into the melting pot for remelting. After 2 hours, qualified low-silver lead is produced. The chemical compositions of the raw material and the products are shown in Table 1.

[0051] Example 3

[0052] The solid-liquid separator has a length of 1 m, a width of 0.22 m, and a depth of 0.16 m, and the screw conveying capacity is 68 kg / h. The slope of the solid-liquid separator is adjusted to 8°, and the screw rotating speed is adjusted to 8 r / min. The temperatures of the solid-liquid separator tank are set as follows: the first section is 305°C, the second section is 311°C, the third section is 318°C, the fourth section is 322°C, the fifth section is 327°C, and the sixth section is 333°C. Along the extension direction of the tank, the width of each part of the tank with an increasing temperature is independently 0.16 m.

[0053] 500 kg of lead-silver alloy containing 0.32 wt% of silver is melted in a melting pot at 330°C and kept until the end of the operation. After a period of time, the temperature of the solid-liquid separator tank is raised to the set value, the melting pot switch is opened to pour the liquid, and the lead-silver alloy melt flows into the corresponding position of the third temperature section of the solid-liquid separator. After natural cooling, the crystals start to be produced. The liquid is poured every 30 min (the mass is 1.12 wt% of the mass of the melt). High-silver lead is obtained. The crystals produced in the first two hours are put back into the melting pot for remelting. After two hours, qualified low-silver lead is produced. The chemical compositions of the raw material and the product are shown in Table 1.

[0054] Example 4

[0055] The solid-liquid separator has a length of 1 m, a width of 0.22 m, and a depth of 0.16 m, and the screw conveying capacity is 63 kg / h. The slope of the solid-liquid separator is adjusted to 12°, and the screw rotating speed is adjusted to 7 r / min. The temperatures of the solid-liquid separator tank are set as follows: the first section is 305°C, the second section is 314°C, the third section is 319°C, the fourth section is 323°C, the fifth section is 326°C, and the sixth section is 333°C. Along the extension direction of the tank, the width of each part of the tank with an increasing temperature is independently 0.16 m.

[0056] 500 kg of lead-silver alloy containing 0.86 wt% of silver is melted in a melting pot at 340°C and kept until the end of the operation. After a period of time, the temperature of the solid-liquid separator tank is raised to the set value, the melting pot switch is opened to pour the liquid, and the lead-silver alloy melt flows into the corresponding position of the third temperature section of the solid-liquid separator. After natural cooling, the crystals start to be produced. The liquid is poured every 28 min (the mass is 0.86 wt% of the mass of the melt). High-silver lead is obtained. The crystals produced in the first two hours are put back into the melting pot for remelting. After two hours, qualified low-silver lead is produced. The chemical compositions of the raw material and the product are shown in Table 1.

[0057] Table 1 Chemical compositions of raw materials and products

[0058] Example 1 Example 2 Example 3 Example 4 Raw material (Ag / wt%) 0.027 0.081 0.32 0.86 Low silver lead (Ag / wt%) 0.0036 0.0015 0.0041 0.0067 High silver lead (Ag / wt%) 0.38 0.57 0.79 1.45

[0059] As can be seen from Table 1, the application can separate silver from lead-silver alloy by controlling process parameters such as temperature, rotation speed, slope, time, etc., and the separation efficiency is high, and the silver content in low-silver lead can meet the requirements in GBT 469-2013.

[0060] Comparative Example 1

[0061] The solid-liquid separator has a length of 1 m, a width of 0.22 m, a depth of 0.16 m, and a screw conveying capacity of 31 kg / h. The slope of the solid-liquid separator is adjusted to 3°, and the screw rotation speed is adjusted to 1 r / min. The temperature of the solid-liquid separator tank is set to be 305°C for the first section, 311°C for the second section, 316°C for the third section, 320°C for the fourth section, 323°C for the fifth section, and 325°C for the sixth section in sequence. The width of each part of the tank with an increasing temperature is independently 0.16 m along the extension direction of the tank.

[0062] 500 kg of lead-silver alloy containing 0.081wt% of silver is melted at 330°C in a melting pot and kept until the end of the operation. After a period of time, the temperature of the solid-liquid separator tank is raised to the set value, the melting pot switch is opened to release the liquid, and the lead-silver alloy melt flows into the corresponding position of the third temperature section of the solid-liquid separator. After natural cooling, the crystals start to be produced. The liquid is released every 10 min (0.36wt% of the mass of the melt), and high-silver lead is obtained. The crystals produced in the first 2 hours are returned to the melting pot for remelting. After 2 hours, qualified low-silver lead is produced. The chemical compositions of the raw material and the products are shown in Table 2.

[0063] Comparative Example 2

[0064] The solid-liquid separator has a length of 1 m, a width of 0.22 m, a depth of 0.16 m, and a screw conveying capacity of 82 kg / h. The slope of the solid-liquid separator is adjusted to 4°, and the screw rotation speed is adjusted to 15 r / min. The temperature of the solid-liquid separator tank is set to be 305°C for the first section, 311°C for the second section, 316°C for the third section, 320°C for the fourth section, 323°C for the fifth section, and 326°C for the sixth section in sequence. The width of each part of the tank with an increasing temperature is independently 0.16 m along the extension direction of the tank.

[0065] 500 kg of lead-silver alloy containing 0.081wt% of silver is melted at 330°C in a melting pot and kept until the end of the operation. After a period of time, the temperature of the solid-liquid separator tank is raised to the set value, the melting pot switch is opened to release the liquid, and the lead-silver alloy melt flows into the corresponding position of the third temperature section of the solid-liquid separator. After natural cooling, the crystals start to be produced. The liquid is released every 10 min (0.36wt% of the mass of the melt), and high-silver lead is obtained. The crystals produced in the first 2 hours are returned to the melting pot for remelting. After 2 hours, qualified low-silver lead is produced. The chemical compositions of the raw material and the products are shown in Table 2.

[0066] Comparative Example 3

[0067] The solid-liquid separator has a length of 1 m, a width of 0.22 m, a depth of 0.16 m, and a screw conveying capacity of 22 kg / h. The slope of the screw type solid-liquid separator is adjusted to 3°, and the screw rotating speed is adjusted to 1 r / min. The temperature of the solid-liquid separator tank is set to be 305 ℃ for the first section, 311 ℃ for the second section, 316 ℃ for the third section, 320 ℃ for the fourth section, 323 ℃ for the fifth section, and 325 ℃ for the sixth section. The width of the tank body at each temperature increasing section is independently 0.16 m along the extension direction of the tank body.

[0068] 500 kg of lead-silver alloy containing 0.081 wt% of silver is melted in a melting pot at 330 ℃ and kept until the end of the operation. After a period of time, the temperature of the solid-liquid separator tank is increased to the set value, and the lead-silver alloy melt is allowed to flow into the position corresponding to the third temperature section of the solid-liquid separator from the melting pot switch. After natural cooling, the crystal production is started. The liquid is discharged every 10 min (0.15 wt% of the mass of the melt), and high-silver lead is obtained. The crystals produced in the first two hours are not returned to the melting pot for remelting. The chemical compositions of the raw material and the products are shown in Table 2.

[0069] Comparative Example 4

[0070] The solid-liquid separator has a length of 1 m, a width of 0.22 m, a depth of 0.16 m, and a screw conveying capacity of 43 kg / h. The slope of the screw type solid-liquid separator is adjusted to 11°, and the screw rotating speed is adjusted to 6 r / min. The temperature of the solid-liquid separator tank is set to be 305 ℃ for the first section, 312 ℃ for the second section, 316 ℃ for the third section, 320 ℃ for the fourth section, 326 ℃ for the fifth section, and 333 ℃ for the sixth section. The width of the tank body at each temperature increasing section is independently 0.16 m along the extension direction of the tank body.

[0071] 500 kg of lead-silver alloy containing 0.081 wt% of silver is melted in a melting pot at 330 ℃ and kept until the end of the operation. After a period of time, the temperature of the solid-liquid separator tank is increased to the set value, and the lead-silver alloy melt is allowed to flow into the position corresponding to the third temperature section of the solid-liquid separator from the melting pot switch. After natural cooling, the crystal production is started. The liquid is discharged every 20 min (0.52 wt% of the mass of the melt), and high-silver lead is obtained. The crystals produced in the first two hours are not returned to the melting pot for remelting, and are directly regarded as the tank head product low-silver lead for detection. The chemical compositions of the raw material and the products are shown in Table 2.

[0072] Table 2 Chemical compositions of raw materials and products

[0073] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Raw material (Ag / wt%) 0.081 0.081 0.081 0.081 Low silver lead (Ag / wt%) 0.052 0.063 0.069 0.021 High silver lead (Ag / wt%) 0.19 0.11 0.21 0.39

[0074] The above only describes the preferred embodiments of the present application. It should be noted that, for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which should also be regarded as the protection scope of the present application.

Claims

1. A method of separating lead and silver, characterized by, The solid-liquid separator comprises a tank and a screw in the tank; the tank has an inclination of 8-15°; The method comprises the following steps: The lead-silver alloy melt flows into the solid-liquid separator and is subjected to condensation-dissolution under the action of the screw, and high-silver lead is discharged at the bottom of the tank; after condensation-dissolution for at least 2 h, silver-lead alloy produced at the top of the tank is removed, and low-silver lead is produced; The interval time between two adjacent discharges of high-silver lead is 20-30 min, counted from the start time of the flow-in. The rotation speed of the screw is 3-10 r / min.

2. The method of claim 1, wherein, The content of silver in the lead-silver alloy is 0.02-1.2 wt%.

3. The method according to claim 1 or 2, characterized in that, The surface of the screw is coated with a silicone coating.

4. The method according to claim 1 or 2, characterized in that, The content of silver in the low-silver lead is less than 0.008 wt%, and the content of silver in the high-silver lead is 0.2-1.8 wt%.

5. The method according to claim 1 or 2, characterized in that, The melting temperature of the lead-silver alloy melt is 330-360℃; Along the extension direction of the tank from low to high, the temperature of the tank increases in the range of 305-333℃.

6. The method of claim 5, wherein, The difference between the temperatures of two adjacent tanks is ≥0.1℃. Along the extension direction of the tank, the width of the partial tank at each temperature is independently 0.16-1 m.

7. The method of claim 6, wherein, The tank is open. The flow-in is performed at the position of the tank at the second temperature from low to high.

8. The method of claim 1, wherein, The conveying capacity of the screw is 20-100 kg / h.

9. The method according to claim 1 or 6, characterized in that, The length of the tank is 0.5-6 m.

10. The method of claim 1, wherein, Further comprising: After the silver-lead alloy produced in the 2 h before condensation-dissolution is removed, remelting and condensation-dissolution are performed.

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