Method for preparing manganese sulfate from sulfur-free low-grade rhodochrosite

Abstract

The invention discloses a method for preparing manganese sulfate from sulfur-free low-grade rhodochrosite. The method comprises the following steps: by taking low-grade rhodochrosite as a raw material, grinding and pretreating the low-grade rhodochrosite, mixing the low-grade rhodochrosite with water, adding acetic acid, fully stirring, heating and leaching, and carrying out solid-liquid separation after the reaction is finished, so as to obtain a liquid-phase manganese acetate mother solution and solid-phase sulfur-free manganese slag; sulfuric acid is added into the manganese acetate mother liquor, heating and reduced pressure distillation are conducted, acetic acid is vaporized and then condensed and recycled for ore leaching, and manganese sulfate is crystallized and separated out in the heating process to serve as a product. Sulfuric acid is not in direct contact with manganese ore, the manganese slag does not contain sulfur, resource utilization is facilitated, and the treatment cost of the manganese slag can be remarkably reduced; and residual acid in the slag can be neutralized by lime water to stably exist, so that the risk of secondary pollution is avoided. The concentration of the acetic acid is not high, cyclic utilization is achieved in the method, the production cost is reduced through recycling of the acetic acid, the resource utilization rate is further increased, and the method is particularly suitable for the manganese extraction process of low-grade rhodochrosite.

Description

Technical Field

[0001] The invention relates to a technology for extracting manganese mineral resources, and in particular to a method for preparing manganese sulfate from low-grade rhodochrosite ore with sulfur-free slag, and belongs to the field of metallurgy and mineral processing. Background Art

[0002] With the vigorous development of the new energy storage industry, the demand for manganese is growing. Against the background of the gradual reduction of high-grade manganese ore resources, the development of low-grade rhodochrosite has become particularly urgent. At present, the leaching methods of manganese ore mainly include direct acid leaching, sulfur dioxide leaching, microbial method and pre-roasting leaching. The main problem faced by the direct acid leaching method and the sulfur dioxide leaching method is the treatment of sulfur-containing manganese slag. The sulfur content in these slags is between 5wt% and 18wt%, which is difficult to be used as building materials and gypsum raw materials. It can only be used as cement admixture for small-scale consumption. The microbial leaching method has high requirements for environmental conditions and is still in the laboratory stage and has not yet been applied in industry. The pre-roasting leaching method can not only enhance the activation effect, but also remove certain volatile substances and cause phase change of effective components. In the development and utilization of low-grade manganese ore, the two main problems faced are the disposal and resource utilization of manganese slag and the cost of sulfuric acid leaching caused by the low grade of ore. The sulfur content of manganese slag produced by the traditional sulfuric acid leaching method is between 5% and 18%, which does not meet the requirements of direct utilization in the cement industry (sulfur content <3% or sulfur content >30%). It needs to be roasted and desulfurized before it can be used in cement production, which leads to a significant increase in costs. At the same time, due to the low grade of the ore, the concentration of manganese sulfate obtained by sulfuric acid leaching is too low, and the cost of subsequent purification and crystallization is also increased accordingly.

[0003] Under this industry situation, domestic manganese enterprises are faced with a difficult choice: although the production cost of imported high-grade manganese ore is low, the production of ore sources cannot be stably guaranteed; while the comprehensive cost of mining and utilizing domestic poor ore remains high, making it difficult to make a profit. Therefore, the development of low-grade rhodochrosite ore using new technologies with low development costs and light slag burden is an era demand for the development of the new energy industry. Summary of the invention

[0004] In view of the problems of disposal and resource utilization of manganese slag in the current development of low-grade rhodochrosite and the cost problem of sulfuric acid leaching caused by too low ore grade, the present invention provides a method for preparing manganese sulfate from low-grade rhodochrosite with sulfur-free slag.

[0005] The technical solution adopted by the present invention is specifically as follows: A method for preparing manganese sulfate from low-grade rhodochrosite ore containing no sulfur in the slag comprises the following steps: S1. Using low-grade rhodochrosite as raw material, adding acetic acid solution after pretreatment, fully stirring and performing leaching reaction under heating conditions, utilizing the characteristics of acetic acid solution that easily reacts with manganese salts and manganese oxides to generate manganese acetate solution, performing solid-liquid separation after the reaction is completed, and separating the liquid phase manganese acetate mother liquor and the solid phase sulfur-free manganese slag; S2. According to the principle of strong acid to weak acid and taking advantage of the easy volatility of acetic acid, sulfuric acid is added to the manganese acetate mother liquor obtained in step S1 to react so as to regenerate acetic acid and simultaneously generate manganese sulfate solution. The acetic acid is vaporized, condensed, recovered and recycled for the leaching process. Manganese sulfate is crystallized and precipitated during the heating process as the final product.

[0006] Furthermore, in step S1, the pretreatment is grinding and / or roasting, and the rhodochrosite is pretreated by roasting after being ground into powder, which can further improve the leaching rate of manganese.

[0007] Furthermore, the calcination is carried out in a rotary atmosphere furnace, the calcination temperature is 500-700° C., and the calcination time is 1.5-3 hours.

[0008] Furthermore, in step S1, the leaching reaction is carried out in a closed jacketed stirred tank, the heating temperature is 40-60°C, and the heating time is 5-6h.

[0009] Further, in step S1, the liquid-solid mass ratio of the acetic acid solution to rhodochrosite is 2.0-3.0, the mass fraction of the acetic acid solution is 30%-50%, and the molar ratio of acetic acid to manganese in rhodochrosite is 10-15.

[0010] Furthermore, in step S2, the molar ratio of the added sulfuric acid to the acetate ion is 0.5-0.6.

[0011] Furthermore, in step S2, the sulfuric acid is concentrated sulfuric acid.

[0012] Furthermore, in step S2, the reaction is carried out in an evaporator, and the pH is controlled to be lower than 2 during the evaporation process.

[0013] Furthermore, the evaporator is a reduced pressure evaporator, the vacuum degree is -0.1~0.05MPa, the evaporation temperature is 50℃~60℃, and the evaporation time is 0.5~2 hours.

[0014] Furthermore, in step S2, the device used for condensation recovery is a spray tower.

[0015] The beneficial effects of the present invention are: The present invention achieves the purpose of efficiently extracting manganese sulfate from low-grade rhodochrosite through the interaction between acetic acid and manganese sulfate. In the present invention, sulfuric acid does not directly contact the manganese ore, and the manganese slag does not contain sulfur, which is conducive to resource utilization and can significantly reduce the disposal cost of manganese slag; the residual acid in the slag can be neutralized by lime water to achieve stable existence, avoiding the risk of secondary pollution. Acetic acid is recycled in the present invention, and the recycling of acetic acid reduces the production cost and improves the resource utilization rate, so that the method of the present invention is particularly suitable for the manganese extraction process of low-grade rhodochrosite. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0017] The present invention is further described in detail below with reference to specific embodiments, but the present invention is not limited thereto. Example 1

[0018] Take 1 kg of low-grade rhodochrosite powder (manganese content is 9.6wt%), place it in a rotary atmosphere furnace, and calcine it at 600℃ for 2 hours without oxygen to obtain 0.92 kg of roasted ore. The roasted ore is slurried with 2L of acetic acid solution (the mass fraction of acetic acid solution is 50%), placed in a closed reactor, fully stirred and leached at 50℃ for 6 hours. After the reaction is completed, it is separated by filter pressing to obtain 1.92 L of manganese acetate mother liquor and 0.95 kg of sulfur-free manganese slag. According to the sulfur meter, the sulfur content in the sulfur-free manganese slag is less than 0.1wt%. The manganese acetate mother liquor is transferred to a reduced pressure evaporator, and 0.55L of concentrated sulfuric acid (the molar ratio of sulfuric acid to acetate is 0.6) is slowly added. The pH of the system is controlled to be lower than 2, the vacuum degree is maintained at -0.1 kPa, the evaporation temperature is set to 60℃, and the evaporation time is 1 hour. After the evaporation is completed, manganese sulfate powder is obtained, and acetic acid and water vapor are condensed and captured at the same time. The recovery amount is 1.89 L, and the mass fraction of acetic acid is 49%. It was determined that the purity of manganese sulfate powder was 79.4% and the manganese leaching rate was 95.1%. Example 2

[0019] The acetic acid prepared in Example 1 was supplemented with acetic acid and water to make the mass fraction of acetic acid reach 50%, and the liquid was replenished to 2L to serve as the leaching agent in Example 2.

[0020] Take 1 kg of low-grade rhodochrosite powder (manganese content is 9.6wt%), place it in a rotary atmosphere furnace, and calcine it at 600℃ for 2 hours without oxygen to obtain 9.4 kg of roasted ore. The roasted ore and 2L of acetic acid solution (the mass fraction of acetic acid solution is 50%) are placed in a closed reactor, fully stirred and reacted at 50℃ for 6 hours. After the reaction is completed, it is separated by filter pressing to obtain 0.95 L of manganese acetate mother liquor and 0.94 kg of sulfur-free manganese slag. According to the sulfur meter, the sulfur content in the sulfur-free manganese slag is less than 0.1wt%. The manganese acetate mother liquor is transferred to a reduced pressure evaporator, and 0.55L of concentrated sulfuric acid (the molar ratio of sulfuric acid to acetate is 0.6) is slowly added. The pH of the system is controlled to be lower than 2, the vacuum degree is maintained at -0.1 kPa, the evaporation temperature is set to 60℃, and the evaporation time is 1 hour. After the evaporation is completed, manganese sulfate powder is obtained, and acetic acid and water vapor are condensed and captured at the same time. The recovery amount is 1.91 L, and the mass fraction of acetic acid is 48%. It was determined that the purity of manganese sulfate was 77.9% and the manganese leaching rate was 92.7%.

[0021] Example 2 proves that the process proposed by the present invention can effectively recover the acetic acid solution, realize the resource recycling of acetic acid, and has a good manganese leaching effect. Example 3

[0022] This example is a scale-up experiment.

[0023] Take 20kg of low-grade rhodochrosite powder (manganese content is 9.6wt%), place it in a rotary atmosphere furnace, and calcine it at 600℃ for 2 hours without oxygen to obtain 19.1kg of roasted ore. The roasted ore and 40L of acetic acid solution (the mass fraction of acetic acid solution is 50%) are placed in a closed reactor and reacted at 50℃ for 5 hours. After the reaction is completed, 38.3L of manganese acetate mother liquor and 18.5kg of sulfur-free manganese slag are obtained by filtration. According to the sulfur meter, the sulfur content in the sulfur-free manganese slag is less than 0.1wt%. The manganese acetate mother liquor is transferred to a reduced pressure evaporator, and 11L of concentrated sulfuric acid (the molar ratio of sulfuric acid to acetate is 0.6) is slowly added. The pH of the system is controlled to be lower than 2.0, the vacuum degree is maintained at -0.05 MPa, the evaporation temperature is set to 50℃, and the evaporation time is 0.5 hours. After the evaporation is completed, manganese sulfate powder is obtained, and acetic acid and water vapor are condensed and captured at the same time. The recovery amount is 33.5L, and the mass fraction of acetic acid is 57%. It was determined that the purity of manganese sulfate powder was 73.6% and the manganese leaching rate was 94.8%. Example 4

[0024] The acetic acid prepared in Example 3 was supplemented with acetic acid or water to make the mass fraction of acetic acid reach 50%, and the liquid was replenished to 40 L to serve as the leaching agent in Example 4.

[0025] Take 20kg of low-grade rhodochrosite powder (manganese content is 9.6wt%), place it in a rotary atmosphere furnace, and calcine it at 600℃ for 2 hours without oxygen to obtain 19.3kg of roasted ore. The roasted ore and 40L of acetic acid solution (the mass fraction of acetic acid solution is 50%) are placed in a closed reactor and reacted at 50℃ for 5 hours. After the reaction is completed, 37.8L of manganese acetate mother liquor and 18.8kg of sulfur-free manganese slag are obtained by pressure filtration. According to the sulfur meter, the sulfur content in the sulfur-free manganese slag is less than 0.1wt%. The manganese acetate mother liquor is transferred to a reduced pressure evaporator, and 11L of concentrated sulfuric acid (the molar ratio of sulfuric acid to acetate is 0.6) is slowly added. The pH of the system is controlled to be lower than 2.0, the vacuum degree is maintained at 0.0 MPa, the evaporation temperature is set to 60℃, and the evaporation time is 1 hour. After the evaporation is completed, manganese sulfate powder is obtained, and acetic acid and water vapor are condensed and captured at the same time. The recovery amount is 35.2L, and the mass fraction of acetic acid is 53%. It was determined that the purity of manganese sulfate powder was 75.8% and the manganese leaching rate was 92.3%.

[0026] Example 4 proves that the process can still effectively recover the acetic acid solution in the scale-up test, realize the resource recycling of acetic acid, and the manganese leaching effect is good. Comparative Example 1

[0027] The difference between this comparative example and the example is that the rhodochrosite is not pretreated.

[0028] 1 kg of low-grade rhodochrosite powder (manganese content is 9.6wt%) was mixed with 1L of water, acetic acid was added to make the molar ratio of acetic acid to manganese 2:1, placed in a closed reactor, fully stirred and leached at 50°C for 6 hours. After the reaction was completed, 0.96L of manganese acetate mother liquor and 1.10 kg of sulfur-free manganese slag were separated by filter press operation. The sulfur content in the sulfur-free manganese slag was less than 0.1wt% as detected by the sulfur meter. The manganese acetate mother liquor was transferred to a reduced pressure evaporator, and 0.55L of concentrated sulfuric acid (the molar ratio of sulfuric acid to acetate was 0.6) was slowly added. The pH of the system was controlled to be less than 2, the vacuum degree was maintained at -0.1 kPa, the evaporation temperature was set to 60°C, and the evaporation time was 1 hour. After the evaporation was completed, manganese sulfate powder was obtained, and acetic acid and water vapor were condensed and captured at the same time. The recovery amount was 0.89 L, and the mass fraction of acetic acid was 53%. It was determined that the purity of manganese sulfate powder was 33.7%, and the manganese leaching rate was 48.5%.

Claims

1. A method for preparing manganese sulfate from low-grade rhodochrosite ore containing no sulfur in the slag, characterized in that: The steps include: S1. Using low-grade rhodochrosite as raw material, adding acetic acid solution after pretreatment, fully stirring and performing leaching reaction under heating conditions, utilizing the characteristics of acetic acid solution that easily reacts with manganese salts and manganese oxides to generate manganese acetate solution, performing solid-liquid separation after the reaction is completed, and separating the liquid phase manganese acetate mother liquor and the solid phase sulfur-free manganese slag; S2. According to the principle of strong acid to weak acid and taking advantage of the easy volatility of acetic acid, sulfuric acid is added to the manganese acetate mother liquor obtained in step S1 to react so as to regenerate acetic acid and simultaneously generate manganese sulfate solution. The acetic acid is vaporized, condensed, recovered and recycled for the leaching process. Manganese sulfate is crystallized and precipitated during the heating process as the final product.

2. The method for preparing manganese sulfate from low-grade rhodochrosite ore containing no sulfur in slag according to claim 1, characterized in that: In step S1, the pretreatment is grinding and / or roasting.

3. The method for preparing manganese sulfate from low-grade rhodochrosite ore containing no sulfur in slag according to claim 2, characterized in that: The calcination is carried out in a rotary atmosphere furnace at a temperature of 500-700° C. and a calcination time of 1.5-3 hours.

4. The method for preparing manganese sulfate from low-grade rhodochrosite ore containing no sulfur in slag according to claim 1, characterized in that: In step S1, the leaching reaction is carried out in a closed jacketed stirred tank, the heating temperature is 40-60°C, and the heating time is 5-6h.

5. The method for preparing manganese sulfate from low-grade rhodochrosite ore containing no sulfur in slag according to claim 1, characterized in that: In step S1, the liquid-solid mass ratio of the acetic acid solution to rhodochrosite is 2.0-3.0, the mass fraction of the acetic acid solution is 30%-50%, and the molar ratio of acetic acid to manganese in rhodochrosite is 10-15.

6. The method for preparing manganese sulfate from low-grade rhodochrosite ore containing no sulfur in slag according to claim 1, characterized in that: In step S2, the molar ratio of the added sulfuric acid to the acetate is 0.5-0.

6.

7. The method for preparing manganese sulfate from low-grade rhodochrosite ore containing no sulfur in slag according to claim 1, characterized in that: In step S2, the sulfuric acid is concentrated sulfuric acid.

8. The method for preparing manganese sulfate from low-grade rhodochrosite ore containing no sulfur in slag according to claim 1, characterized in that: In step S2, the reaction is carried out in an evaporator, and the pH is controlled to be lower than 2 during the evaporation process.

9. The method for preparing manganese sulfate from low-grade rhodochrosite ore containing no sulfur in slag according to claim 8, characterized in that: The evaporator is a reduced pressure evaporator with a vacuum degree of -0.1 to 0.05 MPa, an evaporation temperature of 50°C to 60°C, and an evaporation time of 0.5 to 2 hours.

10. The method for preparing manganese sulfate from low-grade rhodochrosite ore containing no sulfur in slag according to claim 1, characterized in that: In step S2, the device used for condensation recovery is a spray tower.

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