Method for extracting tin from tin slag

Abstract

The invention relates to the technical field of valuable metal recovery, in particular to a method for extracting tin from tin slag. The method comprises the following steps: firstly, dry-mixing the tin slag with NaOH and KOH, then carrying out ball milling, then adding sodium nitrate into the mixture in a mass ratio of the tin slag to the sodium nitrate of 1: (0.02-0.03) for multiple times, mixing, reacting at 400-600 DEG C for 1-4 hours, and cooling to room temperature after the reaction is completed, so as to obtain molten slag; the molten slag is crushed into powder, the powder and water are mixed and leached, the mixture reacts for 1-3 h at the temperature of 40-60 DEG C, tin-containing leachate is obtained after solid-liquid separation, and the leaching rate of tin in the tin slag is larger than or equal to 90%. According to the method, sodium hydroxide and sodium nitrate are adopted as a mixed solvent, tin is preferentially converted into soluble sodium stannate, compared with a traditional acid leaching method, the corrosivity is lower, compared with a traditional alkali melting method, the reaction is more sufficient, compared with a pyrogenic smelting method, the energy consumption is reduced by adopting a medium-temperature reaction, the technological process is short, and the efficiency is high.

Description

Technical Field

[0001] This invention relates to the field of valuable metal recycling technology, and specifically to a method for extracting tin from tin slag. Background Technology

[0002] Tin slag is the slag produced during the pyrometallurgical refining of crude lead. It often contains metals such as tin, indium, lead, and antimony. Tin has wide applications in the electronics, battery, chemical, and pharmaceutical industries. With technological advancements, the demand for tin is increasing, while global tin reserves are limited and non-renewable. Therefore, recovering tin from tin slag can effectively alleviate the supply-demand imbalance of metal resources and improve the overall utilization rate of metal resources. While various existing methods for extracting tin exist, they often face problems such as low efficiency, high cost, and complex operation in practical applications. Existing technologies often use wet extraction methods, such as Chinese patent CN110872649A, which uses a chlorination-water leaching-alkali fusion-water leaching-concentration crystallization process to recover tin from tin-containing lead slag to prepare sodium stannate. However, this method is lengthy and costly. Existing technologies also use solid-phase melting methods for extraction. For example, Chinese patent CN101705372B involves heating the temperature to 700-800℃ and adding alkaline oxidants such as sodium nitrate and sodium hydroxide to oxidize and slag for tin recovery. The process is short and simple to operate, but for slag with high tin content, the tin enrichment is obvious, and it is easy to agglomerate. It is also easy to run out of control during the reaction process and the reaction is also easy to be incomplete.

[0003] Therefore, this study aims to develop a method for efficient and low-cost extraction of tin from tin dross. Summary of the Invention

[0004] To address the problems of existing technologies, this invention proposes a method for extracting tin from tin dross, wherein the tin content in the dross is 20wt% to 50wt%, comprising the following steps:

[0005] Step 1: Dry mix the tin dross with NaOH and KOH, then ball mill for 1-2 hours; the mass ratio of tin dross to NaOH and KOH is 1:0.2-0.6:0.05-0.1.

[0006] Step 2: Add sodium nitrate to the mixture of tin dross and NaOH and KOH. The mass ratio of tin dross to sodium nitrate is 1:0.02 to 0.03. After mixing, react at 400 to 600°C for 1 to 4 hours. During the reaction, add the same mass of sodium nitrate at least once. After the reaction is complete, cool to room temperature to obtain molten slag.

[0007] Step 3: Crush the molten slag obtained in Step 2 into powder, mix the powder with water at a liquid-solid ratio of 1 to 4:1 and leach it. React at 40 to 60°C for 1 to 3 hours. After solid-liquid separation, a tin-containing leachate is obtained. The tin leaching rate in the tin slag is ≥93%.

[0008] Furthermore, in step 1, the ball-to-material ratio in the ball milling process is 1:3 to 5, and the rotation speed is 200 to 300 rpm.

[0009] Furthermore, in step 1, the mass ratio of tin dross to NaOH and KOH is 1:0.4:0.05.

[0010] Furthermore, in step 2, the mass ratio of tin dross to all added sodium nitrate is 1:0.04 to 0.1.

[0011] Furthermore, in step 2, the mass ratio of tin dross to all added sodium nitrate is 1:0.06.

[0012] Furthermore, after mixing in step 2, the mixture is reacted at 500°C for 3 hours.

[0013] Furthermore, in step 3, the liquid-to-solid ratio is 3:1, the water immersion temperature is 50℃, and the water immersion time is 3 hours.

[0014] This invention uses sodium hydroxide, potassium hydroxide, and sodium nitrate as a mixed solvent, which preferentially converts tin into soluble sodium stannate, while impurities such as copper and iron form insoluble oxides. This allows for efficient separation of tin from impurities during the second stage of water immersion. Ball milling mechanically activates and breaks down Sn-Pb agglomerates, generating a nano-scale SnO2 / NaOH composite layer, which is more conducive to subsequent complete reactions. Furthermore, the addition of a small amount of potassium hydroxide lowers the melting point, facilitating the formation of a liquid phase and preventing the agglomeration of peripheral tin after reaction, thus reducing incomplete reactions. It also lowers the reaction temperature and reduces energy consumption. Simultaneously, the addition of sodium nitrate in multiple stages avoids localized excessive concentrations that could lead to explosive reactions and improves the utilization rate of the oxidant, thus enhancing the completeness of the reaction.

[0015] This technical solution uses a molten salt system of sodium hydroxide and sodium nitrate, which is less corrosive than the traditional acid leaching method. The waste gas is mainly alkaline flue gas, which is easier to treat. The use of medium-temperature reaction reduces energy consumption compared to pyrometallurgical smelting, and the alkali fusion-water leaching process is shorter and more efficient.

[0016] This technical solution has wide adaptability to raw materials and has a good separation and extraction effect on tin in various forms. It is especially suitable for tin slag with high tin content, and the tin recovery rate can reach more than 93%. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is further described in detail below through specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0018] Example 1

[0019] Tin slag is the slag produced during the pyrometallurgical refining of crude lead. The tin content in tin slag is 28.5%, existing in the form of SnO2, SnO, and metallic Sn.

[0020] Step 1: Mix 200g of tin dross with 80g of NaOH and 10g of KOH, then ball mill for 1 hour. The ball-to-material ratio during ball milling is 1:5, and the rotation speed is 300 rpm.

[0021] Step 2: Add 6g of sodium nitrate to the mixture of tin dross, NaOH, and KOH. After mixing, react at 500℃ for 3 hours. Add 6g of sodium nitrate once during the reaction. After the reaction is complete, cool to room temperature to obtain molten slag.

[0022] Step 3: Crush the molten slag obtained in Step 2 into powder, mix the powder with water at a liquid-solid ratio of 3:1 and leach, react at 50°C for 3 hours, and filter to obtain tin-containing leachate. The tin leaching rate in the tin slag is 94.8%.

[0023] Example 2

[0024] Tin slag is the slag produced during the pyrometallurgical refining of crude lead. The tin content in tin slag is 40.1%, existing in the form of SnO2, SnO, and metallic Sn.

[0025] Step 1: Mix 200g of tin dross with 120g of NaOH and 12g of KOH, then ball mill for 1 hour. The ball-to-material ratio during ball milling is 1:3, and the rotation speed is 200 rpm.

[0026] Step 2: Add 5g of sodium nitrate to the mixture of tin dross, NaOH, and KOH. After mixing, react at 400℃ for 4 hours. During the reaction, add 5g of sodium nitrate in three batches. After the reaction is complete, cool to room temperature to obtain molten slag.

[0027] Step 3: Crush the molten slag obtained in Step 2 into powder, mix the powder with water at a liquid-solid ratio of 4:1 and leach, react at 40°C for 2 hours, and filter to obtain tin-containing leachate. The tin leaching rate in the tin slag is 96%.

[0028] Example 3

[0029] Tin slag is the slag produced during the pyrometallurgical refining of crude lead. The tin content in tin slag is 32.5%, existing in the form of SnO2, SnO, and metallic Sn.

[0030] Step 1: Mix 200g of tin dross with 40g of NaOH and 10g of KOH, then ball mill for 2 hours. The ball-to-material ratio during ball milling is 1:4, and the rotation speed is 150rpm.

[0031] Step 2: Add 4g of sodium nitrate to the mixture of tin dross, NaOH, and KOH. After mixing, react at 600℃ for 1 hour. Add 4g of sodium nitrate during the reaction. After the reaction is complete, cool to room temperature to obtain molten slag.

[0032] Step 3: Crush the molten slag obtained in Step 2 into powder, mix the powder with water at a liquid-solid ratio of 1:1 and leach, react at 60°C for 1 hour, and filter to obtain tin-containing leachate. The tin leaching rate in the tin slag is 93%.

[0033] Comparative Example 1

[0034] Tin slag is the slag produced during the pyrometallurgical refining of crude lead. The tin content in tin slag is 28.5%, existing in the form of SnO2, SnO, and metallic Sn.

[0035] Step 1: Mix 200g of tin dross with 80g of NaOH, then ball mill for 1 hour. The ball-to-material ratio during ball milling is 1:5, and the rotation speed is 300 rpm.

[0036] Step 2: Add 12g of sodium nitrate to the mixture of tin dross and NaOH, mix and react at 500℃ for 3 hours. After the reaction is complete, cool to room temperature to obtain molten slag.

[0037] Step 3: Crush the molten slag obtained in Step 2 into powder, mix the powder with water at a liquid-solid ratio of 3:1 and leach, react at 50°C for 3 hours, and filter to obtain tin-containing leachate. The tin leaching rate in the tin slag is 91%.

[0038] Comparative Example 2

[0039] Tin slag is the slag produced during the pyrometallurgical refining of crude lead. The tin content in tin slag is 28.5%, existing in the form of SnO2, SnO, and metallic Sn.

[0040] Step 1: Mix 200g of tin dross with 80g of NaOH and 12g of sodium nitrate, and react at 500℃ for 3 hours. After the reaction is complete, cool to room temperature to obtain molten dross.

[0041] Step 2: Crush the molten slag obtained in Step 1 into powder, mix the powder with water at a liquid-solid ratio of 3:1 and leach, react at 50°C for 3 hours, and filter to obtain tin-containing leachate. The tin leaching rate in the tin slag is 90.2%.

[0042] The foregoing descriptions have outlined some exemplary embodiments of the present invention. It is understood that these embodiments are merely illustrative and do not constitute a limitation on the scope of protection of the present invention. Features in these embodiments can be rearranged in suitable ways, and the resulting solutions remain within the scope of protection claimed by the present invention. All other embodiments obtained by those skilled in the art based on the foregoing embodiments without inventive effort, i.e., all modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, fall within the scope of protection claimed by the present invention.

Claims

1. A process for the extraction of tin from tin residues having a tin content of 20 to 50 wt%, characterized in that, The method comprises the following steps: Step 1: tin slag is first dry-mixed with NaOH and KOH, and then ball-milled for 1-2 hours; the mass ratio of tin slag to NaOH and KOH is 1:0.2-0.6:0.05-0.1; Step 2: sodium nitrate is added to the mixture of tin slag and NaOH and KOH, the mass ratio of tin slag to sodium nitrate is 1:0.02-0.03, after mixing, the mixture is reacted at 400-600 DEG C for 1-4 hours, at least once the same amount of sodium nitrate is added during the reaction, after the reaction is completed, the mixture is cooled to room temperature, and a molten slag is obtained; Step 3: the molten slag obtained in step 2 is crushed into powder, the powder is mixed with water according to a liquid-solid ratio of 1-4:1, and leaching is carried out at 40-60 DEG C for 1-3 hours, after solid-liquid separation, a tin-containing leaching solution is obtained, and the leaching rate of tin in the tin slag is greater than or equal to 93%.

2. A process for the extraction of tin from tin residue as claimed in claim 1 wherein, In the ball-milling process in step 1, the ball-to-material ratio is 1:3-5, and the rotation speed is 200-300 rpm.

3. A process for the extraction of tin from tin residue as claimed in claim 1 wherein, In step 1, the mass ratio of tin slag to NaOH and KOH is 1:0.4:0.

05.

4. A process for the extraction of tin from tin dross as claimed in claim 1 wherein, In step 2, the mass ratio of tin slag to all added sodium nitrate is 1:0.04-0.

1.

5. A process for the extraction of tin from tin residue as claimed in claim 4 wherein, In step 2, the mass ratio of tin slag to all added sodium nitrate is 1:0.

06.

6. A process for the extraction of tin from tin residue as claimed in claim 1 wherein, In step 2, after mixing, the mixture is reacted at 500 DEG C for 3 hours.

7. A process for the extraction of tin from tin residue as claimed in claim 1 wherein, In step 3, the liquid-solid ratio is 3:1, the water leaching temperature is 50 DEG C, and the water leaching time is 3 hours.