A desulfurization smelting process for high-sulfur tin concentrates

Abstract

The present application relates to the technical field of mineral processing, and particularly relates to a desulfurization smelting process for high-sulfur tin concentrate, comprising the following steps: ore pretreatment, tin ore is crushed, ground and screened to obtain ore powder; bacteria cultivation and inoculation, bacteria suitable for high-sulfur environment are selected and inoculated into a small-scale cultivation tank and cultivated in a sterile environment; leaching reaction, the pretreated ore powder is mixed with water, bacterial culture solution is added to prepare ore slurry, and the ore slurry is leached; solution treatment and tin recovery, tin metal is recovered after solid-liquid separation of the ore slurry, and waste liquid is treated.The present application provides a desulfurization smelting process for high-sulfur tin concentrate, effectively solves the problems of environmental pollution and high cost existing in the traditional smelting process through the bacterial leaching method, bacteria can grow and reproduce quickly in a high-sulfur environment, so that the desulfurization efficiency is improved, the process operation is simple, low in cost and friendly to the environment, and the tin recovery rate can be significantly improved.

Description

Technical Field

[0001] This invention relates to the field of mineral processing technology, and in particular to a desulfurization smelting process for high-sulfur tin concentrate. Background Technology

[0002] With the continuous growth of industrial demand, the mining and utilization of high-sulfur tin concentrate has become an important issue in the mining industry. However, the high sulfur content in high-sulfur tin concentrate makes it difficult for traditional smelting processes to effectively remove these sulfur elements, which directly affects the purity and quality of tin metal.

[0003] Currently, commonly used desulfurization processes for high-sulfur tin concentrate mainly include pyrometallurgical smelting and hydrometallurgical smelting. However, pyrometallurgical smelting generates a large amount of sulfur dioxide gas, which not only pollutes the environment but also poses a threat to the health of operators; although hydrometallurgical smelting can partially remove sulfur, its process is complex, costly, and its processing efficiency is not ideal.

[0004] Therefore, there is a need for a new and efficient desulfurization smelting industry that is easy to operate, low in cost, and environmentally friendly. Summary of the Invention

[0005] The main objective of this invention is to provide a desulfurization smelting process for high-sulfur tin concentrate, aiming to solve the problems of environmental unfriendliness and high cost in the existing desulfurization process for high-sulfur tin concentrate.

[0006] To achieve the above objectives, this invention proposes a desulfurization smelting process for high-sulfur tin concentrate, which includes the following steps:

[0007] Ore pretreatment involves crushing, grinding, and sieving the tin ore to obtain ore powder;

[0008] Bacterial culture and inoculation: Select bacteria suitable for high-sulfur environments, inoculate them into small-scale culture tanks, and culture them under aseptic conditions;

[0009] Leaching reaction involves mixing pretreated mineral powder with water, adding bacterial culture medium to prepare mineral slurry, and then leaching the mineral slurry.

[0010] Solution treatment and tin recovery: The slurry is separated into solid and liquid components to recover tin metal and treat the waste liquid.

[0011] Furthermore, the steps of culturing and inoculating bacteria, specifically selecting bacteria suitable for high-sulfur environments, inoculating them into small-scale culture tanks, and culturing them under aseptic conditions, include:

[0012] Strain culture involves initially culturing bacterial strains suitable for high-sulfur environments in a small-scale culture medium to ensure the activity and purity of the strains.

[0013] Culture medium preparation involves configuring a culture medium containing nitrogen source, phosphorus source, and trace elements, and then sterilizing the culture medium at high temperature to eliminate contaminating bacteria.

[0014] Bacterial inoculation involves inoculating the bacterial strain into a sterilized culture medium under aseptic conditions.

[0015] Bacterial culture involves using thermostats to stably control the temperature within the culture medium and controlling the pH value of the culture medium using acid or alkali solutions.

[0016] Bacterial concentration monitoring involves regularly sampling the culture medium to test the bacterial concentration and ensure it reaches 10⁻⁶. 7 ~10 9 per ml.

[0017] Furthermore, the ore pretreatment, which involves crushing, grinding, and sieving the tin ore to obtain ore powder, includes the following steps:

[0018] Tin ore is fed to a jaw crusher for primary crushing, which breaks the ore into ore particles with a diameter of 50-100 mm.

[0019] The ore particles after primary crushing are sent to a cone crusher for secondary crushing, which crushes the ore particles to a diameter of 10-20mm.

[0020] The ore particles after secondary crushing were further ground into fine powder with a diameter of 75-150 μm using a ball mill;

[0021] The fine powder of ore after grinding is sent to a vibrating screen for screening.

[0022] Furthermore, the leaching reaction involves mixing the pretreated mineral powder with water, adding bacterial culture medium to prepare a slurry, and the step of leaching the slurry includes:

[0023] The pretreated fine ore powder is mixed with water at a solid-liquid ratio of 1:3 to 1:5 to form a slurry.

[0024] Add the cultured thiobacillus oxidans to the slurry at a ratio of 5-10% of the slurry volume;

[0025] Use a high-efficiency mixer to thoroughly mix the slurry with the bacteria, ensuring that the bacteria are evenly distributed;

[0026] Maintain environmental stability of the slurry and bacterial mixture, and circulate the slurry periodically during the leaching reaction.

[0027] Furthermore, the step of maintaining environmental stability of the slurry-bacterial mixture and periodically circulating the slurry during the leaching reaction also includes:

[0028] pH control involves adding acid or alkali to maintain the pH of the mixture of mineral slurry and bacteria between 1.5 and 2.5.

[0029] Oxygen regulation is achieved through aeration devices and oxygen supply equipment to ensure a sufficient oxygen supply in the slurry.

[0030] The reaction time is controlled to maintain the leaching reaction time at 7–30 days, and the slurry is circulated regularly.

[0031] Furthermore, the solution treatment and tin recovery steps, which involve solid-liquid separation of the slurry to recover tin metal and treatment of the waste liquid, further include:

[0032] Solid-liquid separation: using a solid-liquid separation device to separate the solids and liquids of the leached slurry;

[0033] Washing involves rinsing the solid residue after solid-liquid separation with clean water.

[0034] Tin recovery involves recovering tin metal through chemical precipitation, electrolytic recovery, or solvent extraction.

[0035] Waste liquid treatment involves neutralization, sedimentation, and filtration.

[0036] Furthermore, the bacteria suitable for high-sulfur environments are at least one of thiobacillus oxidans and thiobacillus.

[0037] This invention provides a desulfurization smelting process for high-sulfur tin concentrate. The bacterial leaching method effectively solves the environmental pollution and high cost problems existing in the traditional smelting process. The bacteria can grow and reproduce rapidly in a high-sulfur environment, thereby improving the desulfurization efficiency. The process proposed in this invention is simple to operate, low in cost and environmentally friendly, and can significantly improve the tin recovery rate. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0039] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0040] Furthermore, the use of terms such as "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.

[0041] The desulfurization process involved in this invention employs bacterial leaching, which utilizes specific sulfur-oxidizing bacteria to oxidize sulfides in the ore, converting them into soluble sulfates, thereby achieving desulfurization. These bacteria release acidic substances through metabolic processes, promoting the dissolution and oxidation of sulfides.

[0042] In this invention, the constant temperature device for initial culture controls the culture temperature at 28–32°C and the culture is carried out in a sterile environment. The culture medium formula includes: 0.4 g / L (NH4)2SO4, 0.1 g / L K2HPO4, 0.5 g / L MgSo4·7H2O, 0.01 g / L CaCl2, and the pH value is adjusted to 2.0.

[0043] In detail, during bacterial inoculation, the initially cultured bacterial strain is inoculated into the sterilized culture medium at a ratio of 5-10% using a sterile pipette or inoculation loop, ensuring uniform bacterial distribution and avoiding bacterial aggregation. The acid solution used during bacterial culture is dilute sulfuric acid, and the alkali solution is sodium hydroxide solution, ensuring uniform distribution of bacteria and nutrients. Furthermore, the gas flow rate needs to be controlled at 0.2-0.5 vvm (volume of gas / volume of liquid / minute), and samples should be taken every 24 hours to monitor bacterial growth. Bacterial concentration is detected using microscopic counting or a densitometer (OD600), ensuring the bacterial concentration reaches 10-1. 7 ~10 9 per ml.

[0044] During bacterial inoculation, the cultured bacteria are inoculated into the slurry at a rate of 5-10% of the slurry volume. The slurry is then placed in a mixing device and continuously stirred to ensure that the bacteria are evenly distributed in the slurry. The stirring time is 30-60 minutes to ensure that the ore and bacteria are in full contact.

[0045] In this invention, primary crushing typically uses a jaw crusher or gyratory crusher to break large pieces of raw ore into smaller fragments, usually 50-100 mm in diameter. After primary crushing, cone crushers or impact crushers are used to further reduce the ore particles to 10-20 mm. Finally, vibrating screens or rotary screens are used to screen the ore particles according to their size, ensuring that most particles are within the 10-20 mm diameter range. Any ore particles exceeding this range are returned to the secondary crushing equipment for further crushing.

[0046] In detail, limiting ore particles to 10-20mm helps improve grinding efficiency and increase the surface area for leaching reactions, which is conducive to sufficient contact between bacteria and ore, enhancing leaching efficiency and effect. It also helps subsequent separation and purification processes, improving the overall stability and efficiency of the process.

[0047] In order to further improve the efficiency and effect of the leaching reaction, this invention has refined the control of key parameters such as temperature, pH value, aeration and stirring during the bacterial leaching process, and introduced periodic reaction and circulation flow technology.

[0048] In detail, in this invention, ore particles and water are mixed at a solid-liquid ratio of 1:3 to 1:5 to form a slurry, which is then transferred to a leaching tank. At the same time, a constant temperature device is used to control the temperature of the leaching tank at 30 to 35°C. This temperature range is the most suitable range for the growth and activity of *Thiobacillus oxidans*. A temperature sensor can also be installed to monitor the temperature in the leaching tank in real time, ensuring that the temperature fluctuates within ±1°C, so as not to affect the growth of bacteria.

[0049] This invention can also control the pH value between 1.8 and 2.2 by adding dilute sulfuric acid or sodium hydroxide solution, ensuring a stable acid-base environment for bacterial growth. It can also use high-efficiency aeration equipment to introduce oxygen into the slurry, ensuring sufficient oxygen concentration. During the leaching reaction, a mechanical stirring device can be used to stir the slurry at a speed of 150-250 revolutions per minute, and a liquid pump can be used to draw the slurry from the bottom of the leaching tank and then return it from the top, forming a circulating flow, which enhances the uniformity of the slurry and the contact efficiency of bacteria.

[0050] In detail, in this invention, a filter press or centrifuge is used to perform solid-liquid separation on the leached slurry to obtain a tin-containing solution and solid residue. After solid-liquid separation, the solid residue is washed with clean water to further recover the residual tin-containing solution. The obtained tin-containing solution is then used to recover tin metal through chemical precipitation, electrolytic recovery, or solvent extraction. The waste liquid generated in the process is treated by neutralization, sedimentation, and filtration.

[0051] In this invention, the tin-containing solution obtained after the leaching reaction is recovered by electrolysis. The tin-containing solution is placed in an electrolytic cell, and a chloride electrolyte (such as potassium chloride, sodium chloride, etc.) is added. Then, an electric current is applied to the mixture. During the electrolysis process, the anode loses electrons to generate chlorine gas, and the cathode absorbs electrons to reduce tin ions to metallic tin, thereby achieving efficient reduction of tin ions to metallic tin.

[0052] The present invention has the following application embodiments:

[0053] Example 1:

[0054] 1. Ore pretreatment: crush the high-sulfur tin concentrate to below 75μm;

[0055] 2. Cultivate and inoculate bacteria using *Thiobacillus oxidans*, and incubate at 30°C for 5 days;

[0056] 3. Leaching reaction: Add bacterial culture medium to the slurry at 10% of the total volume of the slurry and control the pH value at 2.0. The leaching reaction lasts for 20 days.

[0057] 4. Solution treatment and tin recovery: Pour the tin-containing solution into a sodium chloride electrolytic cell and stir thoroughly. Then, pass an electric current through the solution to obtain metallic tin.

[0058] Example 2:

[0059] 1. Ore pretreatment: crush the high-sulfur tin concentrate to below 100μm;

[0060] 2. Cultivate and inoculate bacteria using *Thiobacillus oxidans*, and incubate at 28°C for 7 days;

[0061] 3. Leaching reaction: Add bacterial culture medium to the slurry at 7% of the total volume of the slurry and control the pH value at 1.8. The leaching reaction lasts for 25 days.

[0062] 4. Solution treatment and tin recovery: Pour the tin-containing solution into a sodium chloride electrolytic cell and stir thoroughly. Then, pass an electric current through the solution to obtain metallic tin.

[0063] Example 3:

[0064] 1. Ore pretreatment: crush the high-sulfur tin concentrate to below 150μm;

[0065] 2. Cultivate and inoculate bacteria using *Thiobacillus oxidans*, and incubate at 32°C for 6 days;

[0066] 3. Leaching reaction: Add bacterial culture medium to the slurry at 5% of the total volume of the slurry and control the pH value at 2.2. The leaching reaction lasts for 30 days.

[0067] 4. Solution treatment and tin recovery: Tin metal is recovered by electrolysis. The tin-containing solution is poured into a sodium chloride electrolytic cell and thoroughly stirred and mixed. An electric current is then passed through to obtain metallic tin.

[0068] Comparative Example 1:

[0069] 1. Ore pretreatment: crush the high-sulfur tin concentrate to below 100μm;

[0070] 2. Tin concentrate reduction smelting: The crushed ore is mixed with coal and coke and then fed into an Osmette furnace and heated to 232°C to reduce the tin oxides in the tin concentrate to crude tin.

[0071] 3. Pyrometallurgical refining of crude tin: The crude tin is heated in multiple stages from 232℃ to 596℃ to separate the tin from most of the metal impurities in the crude tin, resulting in liquid refined tin containing a small amount of metal impurities.

[0072] 4. Cooling the liquid tin produces crystalline suspensions of Fe-As solid compounds, copper sulfide, and other impurity metals. These crystalline suspensions float on the liquid tin as dross. Adding sawdust promotes the coagulation and floating of the impurity metal grains. The dross is then removed.

[0073] 5. Repeatedly add sawdust and skim off the slag until no more slag is produced. Cool the liquid tin to obtain refined tin.

[0074] Comparative Example 2:

[0075] 1. Ore pretreatment: The high-sulfur tin concentrate is crushed through multi-stage crushing, filtration and screening to reduce the high-sulfur tin concentrate to below 100μm.

[0076] 2. The crushed ore particles were sent to a 3 mol / L dilute hydrochloric acid solution for leaching reaction. The leaching time was 3 hours and the temperature was 70℃ to obtain an acid leaching solution containing tin.

[0077] 3. The acid leachate and solid residue are separated by filtration to obtain a clear acid leachate;

[0078] 4. Tin metal is recovered by electrolysis. The tin-containing acid leaching solution is poured into a sodium chloride electrolytic cell and thoroughly mixed. Then, electricity is passed into the sodium chloride electrolytic cell, and tin ions are reduced to metallic tin at the cathode and deposited to obtain metallic tin.

[0079] Comparative Example 1 employed pyrometallurgical smelting, a traditional method, while Comparative Example 2 employed hydrometallurgical smelting. In Comparative Example 1, pyrometallurgical smelting involved heating tin ore at high temperatures to melt the tin, then reducing the tin to obtain metallic tin. The main process included roasting, reduction, and refining. Roasting oxidized sulfides in the tin ore to oxides, increasing the ore's grade. Reduction then reduced the tin oxides to metallic tin, and finally refining removed impurities from the metallic tin to obtain pure tin. In Comparative Example 2, hydrometallurgical smelting involved dissolving the tin in the tin ore using chemical solvents, then precipitating the tin through a chemical reaction to obtain metallic tin.

[0080] Tin recovery rate and tin purity testing experiments:

[0081] Materials from Examples 1-3 and Control Examples 1-2 were used as samples for tin recovery rate and tin purity testing. The specific experimental steps are as follows:

[0082] (I) Tin recovery rate test

[0083] step:

[0084] S1. Weigh 1g of tin metal;

[0085] S2. Dissolve tin metal in 10 ml of 1 mol / L dilute hydrochloric acid and stir until the tin metal is completely dissolved;

[0086] S3. Adjust the volume of the dissolved sample solution to 100 ml;

[0087] S4. The concentration of tin in the solution (mg / L) was determined using inductively coupled plasma mass spectrometry (ICP-MS).

[0088] S5. Based on the measured tin concentration, calculate the actual total amount of tin and convert it to the tin recovery rate. The formula for calculating the tin recovery rate is (actual total amount of tin / theoretical total amount of tin) * 100%.

[0089] (II) Tin Purity Test

[0090] step:

[0091] S1. Weigh 1g of tin metal;

[0092] S2. Dissolve tin metal in 10 ml of 1 mol / L dilute hydrochloric acid and stir until the tin metal is completely dissolved;

[0093] S3. Adjust the volume of the dissolved sample solution to 100 ml;

[0094] S4. Use inductively coupled plasma mass spectrometry (ICP-MS) to determine the concentration (mg / L) of tin and other impurity metals in the solution;

[0095] S5. Calculate the tin purity according to the purity formula, where tin purity = (tin concentration / total metal concentration) * 100%.

[0096] Table 1. Tin recovery rate and tin purity test data

[0097]

[0098] Experimental conclusion:

[0099] Based on the experimental data from the above three sets of embodiments and two sets of comparative embodiments, it can be seen that the bacterial leaching method used in this invention for desulfurizing high-sulfur tin concentrate has a high tin recovery rate and purity, and can also reduce energy consumption and environmental pollution, proving the effectiveness and feasibility of the bacterial leaching method in the desulfurization and smelting process of high-sulfur tin concentrate.

[0100] In combination with all the above embodiments, the present invention provides a desulfurization smelting process for high-sulfur tin concentrate, which effectively solves the environmental pollution and high cost problems existing in traditional pyrometallurgical and hydrometallurgical processes through bacterial leaching. In this invention, through bacterial culture and inoculation technology, bacteria can grow and reproduce rapidly in a high-sulfur environment, thereby improving desulfurization efficiency. By controlling temperature, pH value, and aeration rate, bacterial activity is maximized, and the sulfur removal rate is significantly improved. Furthermore, this process is simple to operate, low in cost, and environmentally friendly, and can significantly improve the tin recovery rate to over 85%, showing good industrial application prospects and economic benefits.

[0101] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A desulfurization smelting process for high-sulfur tin concentrate, characterized in that, Includes the following steps: Ore pretreatment involves crushing, grinding, and sieving the tin ore to obtain ore powder; Bacterial culture and inoculation: Initial culture of bacteria suitable for high-sulfur environments is performed in a small-scale culture medium to ensure the activity and purity of the strain. Culture medium preparation: A culture medium containing nitrogen, phosphorus, and trace elements is prepared and sterilized at high temperature to eliminate contaminants. Bacterial inoculation: Under aseptic conditions, the strain is inoculated into the sterilized culture medium. Bacterial culture: The temperature of the culture medium is stably controlled using a thermostat, and the pH is controlled by acid or alkali solutions. Bacterial concentration monitoring: Samples are periodically taken from the culture medium to test the bacterial concentration, ensuring that the bacterial concentration reaches 10⁻⁶. 7 ~10 9 pcs / ml; The leaching reaction involves mixing pretreated fine ore powder with water at a solid-liquid ratio of 1:3 to 1:5 to form a slurry. Cultured *Thiobacillus oxidans* is added to the slurry at a ratio of 5-10% of its volume. A high-efficiency agitator is used to thoroughly mix the slurry and bacteria, ensuring uniform bacterial distribution. The environment of the slurry-bacterial mixture is maintained stable, and the slurry is circulated periodically during the leaching reaction. pH is controlled by adding acid or alkali to maintain the pH of the slurry-bacterial mixture between 1.5 and 2.

5. Oxygen levels are controlled using aeration devices and oxygen supply equipment to ensure sufficient oxygen supply to the slurry. The reaction time is controlled, maintaining the leaching reaction for 7-30 days, with periodic slurry circulation. Solution treatment and tin recovery: After solid-liquid separation of the slurry, tin metal is recovered from the tin-containing slurry by electrolysis, and the waste liquid is treated.

2. The desulfurization smelting process for high-sulfur tin concentrate as described in claim 1, characterized in that, The ore pretreatment process, which involves crushing, grinding, and sieving the tin ore to obtain ore powder, includes the following steps: Tin ore is fed to a jaw crusher for primary crushing, which breaks the ore into ore particles with a diameter of 50~100mm. The ore particles after primary crushing are sent to a cone crusher for secondary crushing, which crushes the ore particles to a diameter of 10~20mm. The ore particles after secondary crushing are further ground into fine powder with a diameter of 75~150μm using a ball mill; The fine powder of ore after grinding is sent to a vibrating screen for screening.

3. The desulfurization smelting process for high-sulfur tin concentrate as described in claim 2, characterized in that, The solution treatment and tin recovery process involves separating the slurry into solid and liquid components and then recovering tin metal from the tin-containing slurry via electrolysis. The waste liquid treatment step also includes: Solid-liquid separation: using a solid-liquid separation device to separate the solids and liquids of the leached slurry; Washing involves rinsing the solid residue after solid-liquid separation with clean water. Tin recycling involves recovering tin metal through electrolysis. Waste liquid treatment involves neutralization, sedimentation, and filtration.

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