An environmentally friendly crude tin pyrometallurgical refining process

Abstract

The invention discloses an environmentally friendly crude tin pyrometallurgical refining process, wherein crude tin A is first smelted and condensed to remove iron to obtain crude tin B; crude tin B is then subjected to vacuum distillation treatment to remove arsenic, lead, bismuth, antimony, cadmium, zinc and silver elements to obtain crude tin C; crude tin C is then sulfurized to remove copper to obtain refined tin; sulfur slag produced by sulfurization and copper removal is distilled to obtain stannous sulfide and copper sulfide products. The process realizes environmentally friendly refining of crude tin, can realize efficient purification of tin in crude tin materials, comprehensive utilization of metals such as lead, antimony and bismuth, and harmless separation of arsenic, reduces the refining cost per ton of tin, reduces solid waste emissions, realizes the productization of tin and impurity elements in tin refining sulfur slag through innovative and improved process flow, and realizes efficient and high-value utilization of elements in the tin refining process.

Description

Technical Field

[0001] The invention relates to the technical field of pyrometallurgical refining, and in particular to an environmentally friendly pyrometallurgical refining process for crude tin. Background Art

[0002] There are more than 20 kinds of tin minerals discovered in the world, including chlorides, sulfides, sulfates, silicates, borates, tantalates, niobates and natural tin alloys. It is generally recognized at home and abroad that the only truly valuable tin mineral is cassiterite (SnO 2 ), so far, tin produced from cassiterite and its variants accounts for more than 99% of the world's total production, so reduction smelting naturally becomes the main method of tin smelting. In recent years, due to the decrease in the grade of raw ore year by year, the easy-to-select ore has gradually decreased. In order to improve resource utilization, the rich slag sulfide volatilization method has been widely used at home and abroad to replace the rich slag reduction smelting.

[0003] There are currently three main tin smelting methods:

[0004] (1) Two-stage smelting method: This method is suitable for processing high-grade tin concentrate with low iron content (Sn60% or more);

[0005] (2) Reduction smelting-sulfurization volatilization method: This method is suitable for processing tin concentrates with high iron content (Fe20-30%) and medium tin content (Sn40-50%);

[0006] (3) Sulfidation volatilization-reduction smelting method: This method is suitable for processing low-grade (less than 30% Sn) tin concentrate and (3-10% Sn) tin medium ore.

[0007] The crude tin produced by reduction smelting contains many impurities, common impurities include iron, copper, arsenic, antimony, lead, bismuth, etc. In order to achieve the 3N grade of refined tin required by industry, it needs to be purified and refined.

[0008] At present, the output of refined tin obtained through fire refining accounts for more than 90% of the world's total output. The main purpose of fire refining of tin is to remove impurity elements such as iron, copper, arsenic, antimony, lead, and bismuth. In Chinese patent CN102492861A, a method for fire refining of crude tin is disclosed, which uses smelting and condensation methods to remove iron and arsenic; sulfur is added to remove copper; vacuum distillation is used to remove lead, bismuth, arsenic, and antimony, and aluminum is added to remove antimony and arsenic. Finally, the residual aluminum is removed to obtain refined tin. This method will produce a large amount of iron-arsenic slag, tin refining sulfur slag and aluminum slag during the operation. In addition, the aluminum slag containing Sb and As produced in the process of adding aluminum to remove arsenic and antimony is easy to produce highly toxic AsH 3Gases bring huge safety hazards, and aluminum slag carries a large amount of tin, which directly affects the direct recovery rate of tin and reduces the economic benefits of the enterprise. A large amount of tin, copper and other valuable metals are accumulated in the traditional sulfur slag. How to deal with sulfur slag has always been an urgent problem to be solved in the production of various tin smelters. At present, sulfur slag mainly has roasting-leaching process, electrolysis process, flotation process, fuming furnace volatilization and other treatment methods to recover the valuable elements in it, so that the tin element in it can become a raw material for tin refining again. The sulfur element generally generates SO in the recovery process. 2 Then carry out environmental protection treatment or acid production. The current pyrometallurgical process has problems such as high treatment cost and serious pollution. Summary of the invention

[0009] In view of the above problems, the inventors have provided an environmentally friendly crude tin pyrometallurgical refining process, which reduces the refining cost per ton of tin and reduces solid waste emissions, and achieves high-efficiency and high-value utilization of tin refining sulfur slag with low investment.

[0010] The present invention provides an environmentally friendly crude tin pyrometallurgical refining process, comprising:

[0011] Step 1: First, the crude tin A is melted and condensed to remove iron, and crude tin B and iron slag are obtained; the iron slag can be returned and mixed with the crude tin A before smelting again.

[0012] Step 2: The crude tin B is then subjected to vacuum distillation to remove low-boiling impurities such as arsenic, lead, bismuth, antimony, cadmium, zinc, and silver elements, so that it meets the GB / T 728-2020Sn99.90A refined tin standard to obtain crude tin C and lead-antimony alloy.

[0013] Step 3: Then, the crude tin C is subjected to a conventional sulfur addition and copper removal operation to make the copper element meet the GB / T728-2020Sn99.90A refined tin standard to obtain refined tin and tin refined sulfur slag; in the tin refined sulfur slag, Pb≤0.05%, Bi≤0.05%, Sb≤0.05%, Cd≤0.001%, As≤0.01%, the Cu content is 5-30%, the Sn content is 40-85%, and the rest is S element.

[0014] Furthermore, the crude tin A in step 1 has an arsenic content of less than 3%, a copper content of less than 2% (wherein the ratio of copper to tin is less than 1:20), and a nickel content of less than 0.005%.

[0015] Furthermore, the iron content in crude tin B is less than 0.007%.

[0016] Further in step 2, the conditions of vacuum distillation are:

[0017] The pressure in the furnace is 1-20 Pa, and the distillation temperature is 1000-1800°C.

[0018] Furthermore, if the tin content in the lead-antimony alloy produced in step 2 is ≥ 0.5%, the lead-antimony alloy is returned for multiple vacuum distillations until the tin content is < 0.5%, in order to improve the recovery rate of tin.

[0019] Furthermore, in the crude tin C, except for copper, other elements meet the national GB / T 728-2020Sn99.90A refined tin standard.

[0020] Furthermore, the process also includes:

[0021] Step 4: After the tin refined sulfur slag is sulfurized, vacuum distillation is performed for separation. During sulfurization, a sulfurizing agent is added according to 1.0 to 1.2 times the mole fraction of the sulfurizing agent required for the non-sulfided tin and copper elements in the sulfur slag to become sulfurized, and the sulfurization temperature is 200 to 900°C for oxygen-free deep sulfurization. The sulfurization conditions can refer to Chinese patents CN107619936B and CN113502397A.

[0022] After sulfurization, the sulfur slag is vacuum distilled to separate the SnS product with a purity of ≥99% and the CuS with a purity of >99%. The conditions for vacuum distillation are: the pressure in the furnace is 1-500Pa, and the distillation temperature is 1000-1500℃. The output is CuS or Cu 2 S and stannous sulfide products. The vacuum distillation conditions refer to Chinese patent CN107522223A.

[0023] The chemical composition of GB / T 728-2020Sn99.90 is as follows:

[0024]

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) Different from the traditional process sequence, the process is shorter, and Sn and impurity elements can be commercialized and utilized at a high value.

[0027] (2) Almost no waste slag is produced in the whole process. The iron slag can be returned to smelting to recover the tin in the iron slag, while the sulfur slag can be used to produce CuS or Cu 2 S and stannous sulfide products.

[0028] (3) The elements other than Cu in crude tin are distilled to the refined tin standard through vacuum distillation. There is no step of adding aluminum to remove As and Sb in the traditional process, and no aluminum slag hazardous waste is generated in the traditional antimony removal process.

[0029] (4) The removal of Cu is carried out after the removal of impurity elements such as Pb, Sb, and Bi. This solves the problem that copper must be removed before As and Sb are removed in traditional processes, making it possible to directly utilize copper slag in a high-value manner.

[0030] (5) The sulfur slag produced after adding sulfur to remove copper has a low impurity content. After sulfurization and vacuum distillation, SnS products with a purity of ≥99% and CuS with a purity of >99% are produced, which can be directly used for high value.

[0031] (6) The sulfur element added in the impurity removal process is fully utilized to realize the commercialization of sulfur and tin elements in the sulfur slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a process flow chart of crude tin pyrorefining in Example 1. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0034] Example 1

[0035] (1) Crude tin A having the following components: Sn 83.450%, Pb 7.21%, Sb 6.15%, Bi 0.29%, As 0.357%, Cu 1.960%, and Fe 0.261% is subjected to a melting and condensation process to remove iron, thereby obtaining crude tin B having an iron content of 0.0015%.

[0036] (2) The crude tin B obtained in step (1) is subjected to vacuum distillation in a vacuum distillation furnace at a pressure of 20 Pa and a distillation temperature of 1000-1400° C. to remove low-boiling impurities such as As, Pb, Bi, Sb, Cd and Zn, thereby obtaining crude tin C (As 0.0025%; Pb 0.0085%; Bi 0.0040%; Sb 0.004%; Cd 0.0001%; ​​Zn 0.001%) and a Pb-Sb-Bi alloy (containing Sn 0.15%).

[0037] (3) The crude tin C obtained in step (2) is subjected to a sulfur addition and copper removal operation to make the copper content in the tin 0.0063%, and the obtained refined tin meets the refined tin standard of GB / T 728-2020Sn99.90AA, as well as tin refining sulfur slag.

[0038] (4) adding sulfur to the tin refined sulfur slag obtained in step (3) at a molar fraction of 1.0 times the molar fraction of the sulfurizing agent required to convert the non-sulfided tin and copper in the tin refined sulfur slag (mass percentage: Sn 69.20%, Cu 19.26%) into a sulfided state, and sulfurizing the slag at 700° C. The sulfidation product is vacuum distilled at a furnace pressure of 100 Pa and a distillation temperature of 1000° C. to obtain SnS (containing Sn 78.67%) and CuS.

[0039] The components of each stage are shown in Table 1:

[0040] Table 1

[0041]

[0042] Example 2

[0043] (1) 20 tons of crude tin with the composition of Sn 94.87%, Pb 1.25%, Sb 2.24%, Bi 0.065%, As 0.275%, Cu 0.750% and Fe 0.273% were subjected to smelting and condensation to remove iron, thereby obtaining crude tin B with an iron content of 0.0022%.

[0044] (2) The crude tin B obtained in step (1) is subjected to vacuum distillation in a vacuum distillation furnace at a pressure of 10 Pa and a distillation temperature of 1400-1600° C. to remove low-boiling impurities As, Pb, Bi, Sb, Cd and Zn, thereby obtaining crude tin C (As 0.0017%; Pb 0.0087%; Bi 0.0039%; Sb 0.009%; Cd 0.0001; Zn 0.0008) and a Pb-Sb-Bi alloy (containing Sn 0.23%).

[0045] (3) The crude tin C obtained in step (2) is subjected to a sulfur addition and copper removal operation to make the copper content in the tin 0.0055%, and the obtained refined tin meets the refined tin standard of GB / T 728-2020Sn99.90AA, as well as tin refining sulfur slag.

[0046] (4) adding sulfur to the tin refined sulfur slag obtained in step (3) at a molar fraction of 1.0 times the molar fraction of the sulfurizing agent required to convert the non-sulfided tin and copper in the tin refined sulfur slag (mass percentage: Sn74.70%, Cu14.96%) into the sulfided state, and sulfurizing at 900°C. The sulfidation product is vacuum distilled at a furnace pressure of 50 Pa and a distillation temperature of 1300°C to obtain SnS (containing Sn78.33%) and CuS.

[0047] The components of each stage are shown in Table 2:

[0048] Table 2

[0049]

[0050] Example 3

[0051] (1) 50 tons of crude tin with the composition of Sn 71.63%, Pb 24.34%, Sb 2.44%, Bi 0.465%, As 0.524%, Cu 0.100% and Fe 0.202% were subjected to smelting and condensation to remove iron, and crude tin B with an iron content of 0.0013% was obtained.

[0052] (2) The crude tin B obtained in step (1) is subjected to vacuum distillation in a vacuum distillation furnace at a pressure of 1 Pa and a distillation temperature of 1600-1800° C. to remove low-boiling impurities such as As, Pb, Bi, Sb, Cd and Zn, thereby obtaining crude tin C (As 0.0010%; Pb 0.0079%; Bi 0.0052%; Sb 0.007%; Cd 0.0001%; ​​Zn 0.0005%) and a Pb-Sb-Bi alloy (containing Sn 0.41%).

[0053] (3) The crude tin C obtained in step (2) is subjected to a sulfur addition and copper removal operation to make the copper content in the tin 0.0042%, and the obtained refined tin meets the refined tin standard of GB / T 728-2020Sn99.90AA, as well as tin refining sulfur slag.

[0054] (4) adding sulfur to the tin refined sulfur slag obtained in step (3) at a molar fraction of 1.0 times the molar fraction of the sulfurizing agent required to convert the non-sulfided tin and copper in the tin refined sulfur slag (mass percentage: Sn81.56%, Cu5.30%) into the sulfided state, and sulfurizing at 600°C. The sulfidation product is vacuum distilled at a furnace pressure of 100 Pa and a distillation temperature of 1500°C to obtain SnS (containing Sn78.10%) and CuS.

[0055] The components of each stage are shown in Table 3:

[0056] Table 3

[0057]

[0058] The above specific examples are used to illustrate the present invention, which is only used to help understand the present invention and is not intended to limit the present invention. For those skilled in the art, according to the concept of the present invention, some simple deductions, modifications or substitutions can be made.

Claims

1. An environmentally friendly crude tin pyrometallurgical refining process, It is characterized in that include: Step 1: First, the crude tin A is melted, condensed and iron removed to obtain crude tin B and iron slag; Step 2: vacuum distill the crude tin B to remove arsenic, lead, bismuth, antimony, cadmium, zinc and silver elements to obtain crude tin C and lead-antimony alloy; In crude tin C, except for copper, other elements meet the national GB / T 728-2020 Sn99.90A refined tin standard; Step 3: Then, sulfur is added to the crude tin C to remove copper, thereby obtaining refined tin and tin refined sulfur slag; Step 4: Sulfidize the tin refined sulfur slag and separate it by vacuum distillation to obtain SnS products and CuS.

2. The process according to claim 1, It is characterized in that The crude tin A in step 1 has an arsenic content of less than 3%, a copper content of less than 2%, and a nickel content of less than 0.005%, wherein the copper:tin ratio is less than 1:

20.

3. The process according to claim 1, It is characterized in that The iron content in crude tin B is less than 0.007%.

4. The process according to claim 1, It is characterized in that In step 2, the conditions for vacuum distillation are: The pressure in the furnace is 1-20 Pa, and the distillation temperature is 1000-1800°C.

5. The process according to claim 1, It is characterized in that If the tin content in the lead-antimony alloy produced in step 2 is ≥ 0.5%, the lead-antimony alloy is returned and vacuum distilled to recover tin.

6. The process according to claim 1, It is characterized in that The sulfur slag obtained in step 3 has a copper content of 5-30%, a tin content of 40-85%, and the rest is sulfur; When sulfur slag is sulfurized, a sulfurizing agent is added at 1.0 to 1.2 times the molar fraction of the sulfurizing agent required to convert the non-sulfided tin and copper elements in the sulfur slag into the sulfurized state.

7. The process according to claim 1, It is characterized in that The impurity elements in refined tin meet the Sn99.90A standard.

8. The process of claim 1, It is characterized in that SnS purity ≥99%, CuS purity>99%.

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