A method for recovering tin and copper from dust

Abstract

The application discloses a tin-copper soot recovery method, which comprises the following steps: step P1, tin-copper soot cleaning, ball milling the tin-copper soot in pure water and performing a filtering and drying procedure to obtain tin-copper soot powder; step P2, carbon powder mixing, mixing the tin-copper soot powder obtained after the drying in step P1; step P3, stirring and heating, stirring and heating the mixture of the carbon powder and the tin-copper soot powder obtained in step P2 at a preset temperature in an acidic atmosphere; step P4, sieving, sieving the mixture obtained in step P3, wherein the main component of the powder falling through the sieve is a copper powder mixture, and the main component of the powder obtained on the sieve is carbon powder and a mixture of carbon powder and tin dioxide; and step P5, high-temperature roasting, performing high-temperature roasting on the carbon powder and the mixture of carbon powder and tin dioxide in step P4 in an air or oxygen atmosphere to generate tin dioxide powder; and high-purity nanoscale tin dioxide particles can be obtained.

Description

Technical Field

[0001] This invention relates to the field of flue dust recovery, and more particularly to methods for recovering tin and copper flue dust. Background Technology

[0002] Smelting processes frequently generate flue dust containing a large amount of usable metals, making metal recovery from flue dust a crucial aspect of industry. Copper processing, in particular, produces substantial amounts of copper flue dust. Different processes and applications yield flue dust with varying copper content. For tin-copper flue dust with high tin content, chemical recovery methods are generally employed, such as acid treatment to separate acid-soluble metals like tin from acid-insoluble copper. However, due to the complex metal composition of tin-copper flue dust, including lead and zinc, this chemical method cannot yield high-purity single metals. Electrochemical electroplating is another method for metal recovery, but it involves complex equipment and high energy consumption. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a method for recovering tin-copper fume, which includes the following steps: Step P1, washing tin-copper fume.

[0004] The tin-copper fume is ball-milled in pure water and then filtered and dried to obtain tin-copper fume powder. Ball milling can break up agglomerated particles, shorten the subsequent reaction time, and improve the tin recovery rate. The filtration process can remove some water-soluble organic or inorganic impurities.

[0005] Step P2, toner mixing

[0006] The tin-copper soot powder obtained after drying the carbon powder in step P1 is mixed; the mixing in step P2 is to prepare for the stirring and heating in step P3, and the purpose is to improve the mixing degree of tin-copper soot powder and carbon powder in the early stage of heating, thereby improving the efficiency of step P3.

[0007] Step P3: Stirring and heating

[0008] The mixture of carbon powder obtained in step P2 and tin-copper fume powder is stirred and heated at a preset temperature under an acidic atmosphere. The preset temperature is higher than the melting point of metallic tin but lower than the melting points of other metals in the tin-copper fume. At this preset temperature, the reaction process operates as follows: after heating in an acidic atmosphere, the oxide film on the surface of tin metal and the oxide film on the surface of tin alloy in the fume breaks down. Simultaneously, the oxygen content is very low in the acidic atmosphere, allowing the molten tin in the fume to contact the carbon powder in elemental form. (At this time, the acidic atmosphere acts similarly to a flux, but due to the absence of a surfactant, its ability to reduce the surface tension of the molten tin on the carbon powder is weak, but it can still allow the molten tin to contact the carbon powder without causing it to agglomerate on the carbon powder surface. The presence of carbon powder also...) (To prevent molten tin from self-agglomerating), as the acidic atmosphere disappears, oxygen begins to contact the molten tin, causing the edges of the molten tin in contact with the toner to oxidize and form tin oxide. The resulting tin oxide solidifies on the toner surface. Due to the absence of the acidic atmosphere, the surface tension of the molten tin on the toner surface increases, causing the molten tin on the toner surface to tend to shrink and agglomerate. This shrinkage and agglomeration occurs simultaneously with the solidification process of the molten tin on the toner surface, ultimately forming a large number of fine tin dioxide particles solidified on the toner surface. Further research by the inventors revealed that as the toner volume decreases, the tin dioxide particles solidified on the toner surface also become correspondingly finer and more uniform. If the toner particle size reaches the micrometer or nanometer level, most of the tin dioxide particles solidified on the toner surface will also become nanoparticles. The stirring function serves two purposes: firstly, it ensures more thorough contact between the tin and the toner, allowing a large amount of molten tin to adhere to the toner surface; secondly, it prevents excessive self-agglomeration of the molten tin.

[0009] Step P4, sieving

[0010] The mixture obtained in step P3 is sieved. The powder that passes through is mainly a mixture of copper powder, while the powder obtained on the sieve is mainly carbon powder and a mixture of carbon powder and tin dioxide. The sieve size in this process is between the particle size of the carbon powder and the particle size of the tin-copper soot powder obtained in step P1.

[0011] Step P5, High-temperature roasting

[0012] The carbon powder and the mixture of carbon powder and tin dioxide described in step P4 are calcined at high temperature in air or oxygen atmosphere to produce tin dioxide powder. The high temperature of calcination exceeds the ignition point of carbon powder but is lower than the melting point of tin dioxide. This allows the carbon powder to be burned off during the calcination process to generate carbon dioxide, leaving high-purity tin dioxide powder.

[0013] The mesh size used in step P4 is between the carbon powder particle size and the tin-copper soot powder particle size obtained in step P1.

[0014] The median particle size of the tin-copper ash powder obtained by ball milling in step P1 is less than 10 μm, and the median particle size of the carbon powder is greater than 50 μm.

[0015] The toner includes at least one of carbon fiber, carbon nanotubes, and graphite.

[0016] The mixing process in step P2 is carried out using a powder mixer in a fume hood because the metal powder in the carbon powder and soot is difficult to dissolve when the particles are small, which can easily cause respiratory diseases.

[0017] The preset temperature in step P3 is higher than the melting point of metallic tin, but lower than the melting point of other metals in the tin-copper fumigation powder. The metal composition and content in the tin-copper fumigation powder can be determined by X-ray fluorescence spectroscopy. Other metals in the tin-copper fumigation powder are defined as having a mass percentage content higher than 1% in the overall tin-copper fumigation powder.

[0018] The preset temperature range is between 250°C and 280°C. Since the melting point of lead is 327°C and the melting point of tin is 232°C, and the melting point of micro-nano powders will decrease accordingly, the preset temperature cannot be higher than 280°C, otherwise the lead will melt and affect the purity of tin dioxide.

[0019] In addition to the heating process, step P3 also includes a heat preservation and cooling process, which is carried out in an air or oxygen atmosphere. Specifically, hydrogen chloride gas is introduced during the heating process of P3, and when the temperature rises to the preset temperature, the supply of hydrogen chloride gas is stopped and replaced with the supply of air or oxygen.

[0020] The acidic atmosphere in step P3 can be achieved by premixing tin tetrachloride pentahydrate in step P2. Since tin tetrachloride pentahydrate generates hydrogen chloride gas during heating and tin dioxide is eventually generated during preheating, it will not interfere with the final tin dioxide.

[0021] In step P5, the high-temperature calcination temperature exceeds the ignition point of the carbon powder but is lower than the melting point of tin dioxide.

[0022] The advantages of the method disclosed in this invention are as follows: This application utilizes the low melting point of tin in tin-copper flue dust and draws on the principle of welding process. By high-temperature calcination in an acidic atmosphere, the tin in the flue dust is fixed in carbon powder as tin dioxide. Since there is no surfactant in the high-temperature calcination process and the carbon powder is in the micron range, nano-sized tin dioxide can be obtained. Furthermore, by ball milling in the early stage to reduce the particle size of the flue dust to be smaller than the screen size, but the carbon powder size is larger than the screen size, the carbon powder containing tin dioxide can be left on the screen through a simple sieving method. Then, by calcination in the presence of oxygen, high-purity nano-sized tin dioxide can be obtained. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0024] Figure 1 This is a schematic diagram of the main process of this application.

[0025] Figure 2 This is the XRD pattern of the high-purity tin dioxide particles obtained by the preparation method of this application.

[0026] Figure 3 This is a transmission electron microscope (TEM) image and elemental mapping of a mixture of tin dioxide and carbon nanotubes obtained after sieving in step P4 according to the first embodiment of this application.

[0027] Figure 4 This is a scanning electron microscope (SEM) image of the mixture of tin dioxide and carbon nanotubes obtained after sieving in step P4 according to the first embodiment of this application. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to specific embodiments. The terms "low-immersion" or "secondary low-immersion" in the present invention have the same meaning, as do "precision filtration solution" or "precision filtration solution". Unless otherwise specified in the following embodiments, the ratios between the components are mass ratios.

[0029] To address the problems existing in the prior art, this invention provides a method for recovering tin-copper fume.

[0030] The method described in this application applies to flue dust where the tin content is higher than 20%. If the tin content is lower than 20%, it has no recycling value. Common tin-copper flue dust typically contains more than 40% copper and more than 30% tin, and also contains other metals such as lead and zinc.

[0031] The method includes the following steps: Step P1, cleaning tin-copper fumes.

[0032] The tin-copper fume is ball-milled in pure water and then filtered and dried to obtain tin-copper fume powder. Ball milling can break up agglomerated particles, shorten the subsequent reaction time, and improve the tin recovery rate. The filtration process can remove some water-soluble organic or inorganic impurities.

[0033] Step P2, toner mixing

[0034] The tin-copper soot powder obtained after drying the carbon powder in step P1 is mixed; the mixing in step P2 is to prepare for the stirring and heating in step P3, and the purpose is to improve the mixing degree of tin-copper soot powder and carbon powder in the early stage of heating, thereby improving the efficiency of step P3.

[0035] Step P3: Stirring and heating

[0036] The mixture of carbon powder obtained in step P2 and tin-copper fume powder is stirred and heated at a preset temperature under an acidic atmosphere. The preset temperature is higher than the melting point of metallic tin but lower than the melting points of other metals in the tin-copper fume. At this preset temperature, the reaction process operates as follows: after heating in an acidic atmosphere, the oxide film on the surface of tin metal and the oxide film on the surface of tin alloy in the fume breaks down. Simultaneously, the oxygen content is very low in the acidic atmosphere, allowing the molten tin in the fume to contact the carbon powder in elemental form. (At this time, the acidic atmosphere acts similarly to a flux, but due to the absence of a surfactant, its ability to reduce the surface tension of the molten tin on the carbon powder is weak, but it can still allow the molten tin to contact the carbon powder without causing it to agglomerate on the carbon powder surface. The presence of carbon powder also...) (To prevent molten tin from self-agglomerating), as the acidic atmosphere disappears, oxygen begins to contact the molten tin, causing the edges of the molten tin in contact with the toner to oxidize and form tin oxide. The resulting tin oxide solidifies on the toner surface. Due to the absence of the acidic atmosphere, the surface tension of the molten tin on the toner surface increases, causing the molten tin on the toner surface to tend to shrink and agglomerate. This shrinkage and agglomeration occurs simultaneously with the solidification process of the molten tin on the toner surface, ultimately forming a large number of fine tin dioxide particles solidified on the toner surface. Further research by the inventors revealed that as the toner volume decreases, the tin dioxide particles solidified on the toner surface also become correspondingly finer and more uniform. If the toner particle size reaches the micrometer or nanometer level, most of the tin dioxide particles solidified on the toner surface will also become nanoparticles. The stirring function serves two purposes: firstly, it ensures more thorough contact between the tin and the toner, allowing a large amount of molten tin to adhere to the toner surface; secondly, it prevents excessive self-agglomeration of the molten tin.

[0037] Step P4, sieving

[0038] The mixture obtained in step P3 is sieved. The powder that passes through is mainly a mixture of copper powder, while the powder obtained on the sieve is mainly carbon powder and a mixture of carbon powder and tin dioxide. The sieve size in this process is between the particle size of the carbon powder and the particle size of the tin-copper soot powder obtained in step P1.

[0039] Step P5, High-temperature roasting

[0040] The carbon powder and the mixture of carbon powder and tin dioxide described in step P4 are calcined at high temperature in air or oxygen atmosphere to produce tin dioxide powder. The high temperature of calcination exceeds the ignition point of carbon powder but is lower than the melting point of tin dioxide. This allows the carbon powder to be burned off during the calcination process to generate carbon dioxide, leaving high-purity tin dioxide powder.

[0041] The mesh size used in step P4 is between the carbon powder particle size and the tin-copper soot powder particle size obtained in step P1.

[0042] The median particle size of the tin-copper ash powder obtained by ball milling in step P1 is less than 10 μm, and the median particle size of the carbon powder is greater than 50 μm.

[0043] The toner includes at least one of carbon fiber, carbon nanotubes, and graphite.

[0044] The mixing process in step P2 is carried out using a powder mixer in a fume hood because the metal powder in the carbon powder and soot is difficult to dissolve when the particles are small, which can easily cause respiratory diseases.

[0045] The preset temperature in step P3 is higher than the melting point of metallic tin, but lower than the melting point of other metals in the tin-copper fumigation powder. The metal composition and content in the tin-copper fumigation powder can be determined by X-ray fluorescence spectroscopy. Other metals in the tin-copper fumigation powder are defined as having a mass percentage content higher than 1% in the overall tin-copper fumigation powder.

[0046] The preset temperature range is between 250°C and 280°C. Since the melting point of lead is 327°C and the melting point of tin is 232°C, and the melting point of micro-nano powders will decrease accordingly, the preset temperature cannot be higher than 280°C, otherwise the lead will melt and affect the purity of tin dioxide.

[0047] In addition to the heating process, step P3 also includes a heat preservation and cooling process, which is carried out in an air or oxygen atmosphere. Specifically, hydrogen chloride gas is introduced during the heating process of P3, and when the temperature rises to the preset temperature, the supply of hydrogen chloride gas is stopped and replaced with the supply of air or oxygen.

[0048] The acidic atmosphere in step P3 can be achieved by premixing tin tetrachloride pentahydrate in step P2. Since tin tetrachloride pentahydrate generates hydrogen chloride gas during heating and tin dioxide is eventually generated during preheating, it will not interfere with the final tin dioxide.

[0049] In step P5, the high-temperature calcination temperature exceeds the ignition point of the carbon powder but is lower than the melting point of tin dioxide.

[0050] The high-purity tin dioxide particles obtained in this application were subjected to XRD testing, such as... Figure 1 As shown, the obtained product is high-purity tin dioxide particles.

[0051] To further illustrate this application, the following preferred embodiments are disclosed: Example 1

[0052] The main metal contents of tin-copper flue dust are: copper 40%, tin 30%, lead 10%, and zinc 8%.

[0053] The median particle size of the tin-copper fumigant obtained after ball milling and drying in step P1 is 8 micrometers.

[0054] The carbon powder used in step P2 is multi-walled carbon nanotubes, with a diameter of about 10-20 nanometers and a length of more than 50 micrometers.

[0055] In step P3, hydrogen chloride gas is introduced beforehand. After reaching the preset temperature of 250°C, heating and hydrogen chloride gas supply are stopped, and air supply is turned on. At the same time, the heat preservation process is started. After heat preservation for 5 minutes, the cooling process is started. Air supply is continued during the cooling process.

[0056] The sieve aperture used in step P4 is 20 micrometers;

[0057] Figure 3 This is a transmission electron microscope (TEM) image and elemental mapping of a mixture of tin dioxide and carbon nanotubes obtained after sieving in step P4 according to the first embodiment of this application. The left image clearly shows the nanoscale tin dioxide adhering to the surface of the carbon nanotubes. The right image shows the elemental energy scanning (mapping) results from the TEM, which shows that the particles on the surface of the carbon nanotubes contain tin. The presence of copper is because the TEM sample was prepared on a wire mesh.

[0058] Figure 4 This is a scanning electron microscope (SEM) image of the mixture of tin dioxide and carbon nanotubes obtained after sieving in step P4 according to the first embodiment of this application. The image clearly shows a relatively uniform layer of nano-sized tin dioxide adhering to the surface of the carbon nanotubes.

[0059] The reason for using carbon nanotubes for TEM and SEM is that, on the one hand, TEM and SEM have good imaging effects on conductive samples, while tin dioxide is not a conductive material, and carbon nanotubes are conductive; on the other hand, using carbon nanotubes also allows us to see the distribution and particle size of tin dioxide on the surface of the carbon nanotubes, thus providing a reference direction for adjusting other steps of the method in this application.

[0060] The high-temperature roasting temperature in step P5 is 800-1000 degrees Celsius. Example 2

[0061] The difference between Example 2 and Example 1 is as follows:

[0062] The carbon powder used in step P2 is multi-walled carbon nanotubes, with a diameter of about 10-20 nanometers and a length of more than 50 micrometers.

[0063] In step P3, an acidic atmosphere is provided by mixing tin tetrachloride pentahydrate. Specifically, tin tetrachloride pentahydrate is pre-mixed in step P2, or added at the beginning of heating in step P3. The amount of tin tetrachloride pentahydrate added accounts for 0.1%-1% of the tin-copper fumigation powder. After heating, since the amount of tin tetrachloride pentahydrate is relatively small, it will decompose completely during the heating process. Therefore, there is no need to supply air or oxygen in the subsequent heat preservation and cooling stages. It is only necessary to keep the temperature and cool down in an open environment. At the same time, stirring is continuously carried out during the heat preservation and cooling process.

[0064] The sieve aperture used in step P4 is 20 micrometers;

[0065] The high-temperature roasting temperature in step P5 is 800-1000 degrees Celsius.

[0066] The advantages of the method disclosed in this invention are as follows: This application utilizes the low melting point of tin in tin-copper flue dust and draws on the principle of welding process. By high-temperature calcination in an acidic atmosphere, the tin in the flue dust is fixed in carbon powder as tin dioxide. Since there is no surfactant in the high-temperature calcination process and the carbon powder is in the micron range, nano-sized tin dioxide can be obtained. Furthermore, by ball milling in the early stage to reduce the particle size of the flue dust to be smaller than the screen size, but the carbon powder size is larger than the screen size, the carbon powder containing tin dioxide can be left on the screen through a simple sieving method. Then, by calcination in the presence of oxygen, high-purity nano-sized tin dioxide can be obtained.

Claims

1. A method for recovering tin-copper fume, characterized in that, The method includes the following steps: Step P1: Tin-copper fume cleaning The tin-copper flue dust is ball-milled in pure water and then filtered and dried to obtain tin-copper flue dust powder. Step P2, toner mixing Mix the tin-copper soot powder obtained after drying the carbon powder in step P1; Step P3: Stirring and heating The mixture of the carbon powder obtained in step P2 and the tin-copper soot powder is stirred and heated at a preset temperature in an acidic atmosphere. The preset temperature in step P3 is higher than the melting point of metallic tin, but lower than the melting points of other metals in the tin-copper ash powder. In addition to the heating process, step P3 also includes a heat preservation and cooling process, which is carried out in an air or oxygen atmosphere; Step P4, sieving The mixture obtained in step P3 is sieved. The powder that passes through is mainly a mixture of copper powder, while the powder obtained on the sieve is mainly carbon powder and a mixture of carbon powder and tin dioxide. Step P5, High-temperature roasting The carbon powder and the mixture of carbon powder and tin dioxide described in step P4 are calcined at high temperature in an air or oxygen atmosphere to produce tin dioxide powder.

2. The method for recovering tin-copper fume ash according to claim 1, characterized in that, The mesh size used in step P4 is between the carbon powder particle size and the tin-copper soot powder particle size obtained in step P1.

3. The method for recovering tin-copper fume ash according to claim 2, characterized in that, The median particle size of the tin-copper ash powder obtained by ball milling in step P1 is less than 10 μm, and the median particle size of the carbon powder is greater than 50 μm.

4. The method for recovering tin-copper fume according to claim 3, characterized in that, The toner includes at least one of carbon fiber, carbon nanotubes, and graphite.

5. The method for recovering tin-copper fume ash according to claim 4, characterized in that, The mixing process in step P2 is carried out using a powder mixer.

6. The method for recovering tin-copper fume according to claim 3, characterized in that, The metal composition and content in the tin-copper flue powder can be determined by X-ray fluorescence spectroscopy. Other metals in the tin-copper flue powder are defined as having a mass percentage content higher than 1% in the total tin-copper flue powder.

7. The method for recovering tin-copper fume ash according to claim 6, characterized in that, The preset temperature range is between 250°C and 280°C.

8. The method for recovering tin-copper fume ash according to claim 7, characterized in that, The acidic atmosphere in step P3 can be achieved by premixing tin tetrachloride pentahydrate in step P2.

9. A method for recovering tin-copper fume ash according to claim 8, characterized in that, In step P5, the high-temperature calcination temperature exceeds the ignition point of the carbon powder but is lower than the melting point of tin dioxide.

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