Discussion on the design of high purity electrolytic manganese production process

Electrolytic manganese production of stainless steel, alloy steel and high-strength copper, aluminum, ferrous alloys important raw materials. In recent years, with the rapid development of steel industry and the aluminum industry, the amount of manganese greatly increases the amount of high-quality high-purity manganese is to accelerate growth. Although the production capacity of ordinary electrolytic manganese in China's electrolytic manganese industry has reached 15×10 ⁴ t/a, it can fully meet the needs of ordinary iron in the steel industry and aluminum industry. However, high-quality high-purity electrolytic manganese has no domestic manufacturers. Some enterprises have to spend a lot of foreign exchange to import high-quality high-purity electrolytic manganese in order to adjust the product structure. In the international market, high-quality high-purity electrolytic manganese products have been diversified, including flakes, granules, powders, dehydrogenation grades, low-oxygen grades, nitriding grades, etc., with manganese content of over 99.9%, while China can only The production of sheet-like ordinary electrolytic manganese with a manganese content of about 99.7%, for which the production of high-quality high-purity electrolytic manganese in China is imperative.

First, the process is determined

After many years of development and improvement, the traditional electrolytic manganese production process has now formed a relatively mature process: manganese carbonate ore grinding-manganese ore fine powder leaching-tank vulcanization-electrolytic cell electrolysis-manual passivation, washing, drying-product stripping -package. The process solution purification process uses one-stage vulcanization-one-stage activated carbon smoking; the electrolysis process uses SeO ₂ as an electrolytic additive, so there are problems of incomplete vulcanization and high impurity content, and the content of impurity selenium is greatly increased, and the purity of electrolytic manganese metal is lowered. The idea of ​​determining the high-purity electrolytic manganese production process is to solve a series of factors affecting the production of high-purity electrolytic manganese in the solution purification and electrolysis process on the basis of the traditional electrolytic manganese production process.

The raw manganese ore produced by high-purity electrolytic manganese has a manganese content of about 21.68%. The amount of solution in the whole system of manganese smelting is large. Compared with other industries, especially the wet non-ferrous metallurgy industry, there are disadvantages such as high labor intensity, poor working environment and low mechanization. With the development and improvement of hydrometallurgical process technology, the continuous leaching process has been widely used in the hydrometallurgical and chemical industries. Changing the intermittent leaching process of manganese carbonate ore powder into continuous leaching process has the characteristics of large equipment production capacity, labor saving, good working conditions, easy production process automation, stable leaching slurry, etc. It is more suitable for large-scale production of high-purity electrolytic manganese. And it is suitable to indirectly heat the anolyte with steam to avoid volume expansion of the solution and ensure leaching temperature and recovery rate.

The solution purification process adopts a three-stage purification and three-stage filtration purification process to replace the traditional one-stage vulcanization and one-stage activated carbon adsorption process, and is more suitable for the complete removal of impurities in the solution. The vulcanization operation is carried out in a stirred tank, and the second stage vulcanization is used to prolong the residence time of the vulcanized liquid in the tank, to ensure sufficient vulcanization reaction, to ensure the quality of the electrolyte, and to provide a qualified solution for producing high-purity electrolytic manganese.

In the electrolysis process in the traditional electrolytic manganese production process, the excessive use of selenium dioxide as an additive causes the amount of selenium in the product to be too high, generally about 0.08%, thereby reducing the purity of manganese, and its manganese content is only 99.7%. about. High-purity electrolytic manganese has strict requirements on impurities, and the selenium content is required to be less than 0.05%. How to reduce the content of selenium, the relevant information describes a number of methods: (1) reduce the amount of selenium dioxide additive, using selenium dioxide and another new additive to form a mixed additive; (2) using new auxiliary additives, supporting several Auxiliary additives, etc. Most auxiliary additives are less effective and have more side effects. Simply reducing the amount of additive selenium dioxide affects current efficiency and reduces production. Too much reduction in the amount of selenium dioxide, electrolysis is not normal, shelling, and severely dissolved. The use of a selenium dioxide mixed additive has the disadvantage that its ratio is difficult to accurately control in actual operation. At present, the successful verification of the use of sulfur dioxide as a new additive at home and abroad is reasonable and feasible for the production of high-purity electrolytic manganese.

The production of large-scale high-purity electrolytic manganese, the loading of the cathode plate and the passivation and washing work are very large. In order to reduce the labor intensity of the operators and improve the equipment level of the electrolytic metal manganese industry, the process should be manually supplemented with mechanical plates, and the passivation, washing and drying automated production lines replace the traditional manual operations.

Second, the process

The production process of high-purity electrolytic manganese metal, on the basis of the traditional electrolytic manganese production process, some processes are improved, and the process flow is shown in FIG.

Figure 1 High-purity electrolytic manganese production process

(1) crushing and grinding

The rhombohedral ore is fed from the plate feeder by the jaw-type feeder, coarsely crushed to 100mm by the jaw crusher, into the fine crusher jaw crusher to less than 40mm, and then enters the vertical mill, and the upper end is provided with a classifier for material. Grading, qualified powder below 0.147mm is introduced into the cyclone by the induced draft fan, 90% of the product is captured by the cyclone, and the remaining 10% of the fine material is captured by the bag filter, and the product enters the silo bin. Grinding products. The exhaust gas from the bag filter is evacuated from the chimney by the induced draft fan, and the exhaust gas concentration of the exhaust gas is less than 120 mg/m ³ , which can meet environmental protection requirements.

(2) Leaching and filtration

The leaching process includes three processes of continuous acidic leaching, oxidation, and neutralization of manganese carbonate ore powder.

The qualified ore powder conveyed by the manganese ore powder preparation process is fed into the leaching tank quantitatively by the electronic weighing belt conveyor, and the anolyte and concentrated sulfuric acid are added in a certain proportion to control the leaching temperature of about 85 ° C, and the liquid-solid ratio is 8 ～. 10:1, starting acid 100 g / L, final acid pH 3.0 ~ 3.5, time 4h. After leaching, the slurry is oxidized to the oxidation tank, and MnO ₂ ore powder is added for oxidation for about 1 hour to oxidize Fe ²⁺ in the solution to Fe ³⁺ . After oxidation, the solution is neutralized to a neutralization tank, and the pH of the final acid is controlled to be 6.5 to 7.0, and then pumped to a chamber filter press for pressure filtration. The filter slag contains 25% to 30% water and is sent to the slag yard. The filtrate enters the purification process.

(3) Purification, electrolysis, passivation, washing and drying

The purification operation is divided into two stages of vulcanization, one stage of activated carbon adsorption, and three stages of filtration. A vulcanization is carried out in a vulcanization tank. SDD solution is added to the vulcanization tank 20 to 30 times of Ni+Co in the solution. After vulcanization, the solution passes through a vulcanization and sedimentation tank to enter a vulcanization filter press, and the filtrate is re-vulcanized and the filter residue is transported to the slag. field. Add appropriate amount of SDD or vulcanizing agent to the secondary vulcanization, and the liquid enters the secondary vulcanization filter press through the secondary vulcanization and sedimentation tank. The filtrate flows into the static sedimentation tank and is allowed to stand for 16 to 24 hours to further remove Ca and Mg from the solution. , Fe, Al, Zn, Si and other impurities; filter residue sent to the slag yard. After the clarification, the liquid passes through three purification tanks, and the activated carbon and the filter aid adsorb the extremely fine particles in the solution, and then are separated by pressure filtration, and the filtrate is sent to the electrolysis process, and the filter slag is sent to the slag field.

During electrolysis, the bath temperature is controlled at about 40 °C, the average cathode current density is 400 A/m ² , the cell voltage is 4.6 to 4.8 V, and the same pole pitch is 79 to 81 mm. An appropriate amount of SO ₂ is added as an additive, and part of the ammonia water is added as necessary to adjust the pH of the cathode region.

After the electrolysis cycle is completed, the crane is taken out by the crane to take out the trough, and the cathode plate is passivated, and then placed on the direct moving line for cold and hot water washing and drying operation. The discharged wastewater is sent to a wastewater treatment station for treatment, and the dried cathode plate is artificially stripped of manganese.

Third, technical indicators

The high-purity electrolytic manganese production process has higher purity and less slag content than the electrolytic manganese metal production process produced by the conventional electrolytic manganese production process. At present, the advanced level of electrolytic manganese metal in domestic manganese industry: 99.8% manganese content, selenium amount ≤0.06%; high-purity electrolytic manganese production process electrolytic manganese metal quality: manganese content ≥99.9%, selenium amount ≤0.02%, product quality reached At the international advanced level, the total manganese recovery rate can reach 75%, which is 5% higher than the traditional electrolytic manganese production process. The main technical indicators are as follows:

Manganese leaching rate /% > 93

Leaching slag rate /% 70

Leaching process recovery rate /% 87 .41

Purification rate /% 92.12

Purification solution containing manganese / g · L ^-1 36

The anolyte contains 钰/g·L ^-1 16

Electrolytic straight yield /% 93.6

Total manganese recovery /% 75

Fourth, the problem discussion

There are wastewater treatment problems in the high-purity electrolytic manganese production process, which mainly comes from electrolytic cell cooling water, filter press cleaning water, passivation and plate cleaning water, and workshop floor cleaning water. Cooling water manganese enterprises generally use straight-line mode to enter the river; filter press washing filter water is filtered and reused by microporous ceramic bricks; passivation and washing wastewater contains a large amount of water-soluble manganese, suspended solids, total chromium and hexavalent Chrome and so on. Due to the large amount of water, high concentration of pollutants and difficulty in treatment, the domestic electrolytic manganese production wastewater treatment generally uses sodium thiosulfate to reduce hexavalent chromium to trivalent chromium, and then add soluble carbonate to make manganese ions in the wastewater. The carbonate ions combine to form a manganese carbonate precipitate, and the trivalent chromium ions are separated from the hydroxide formed by the hydrolysis of the carbonate to form a hydroxide precipitate. Or adding soluble alkali, the manganese ions, trivalent chromium ions and hydroxide ions in the wastewater are combined to form manganese hydroxide and chromium hydroxide precipitates and separated. Since the electrolytic passivation sewage contains 5-10 mg/L of chromium, and the sewage of the washed cathode plate does not contain chromium, it is not suitable to adopt a mixed treatment method. If the treatment of chromium-containing sewage alone, in addition to chromium and then combined with the washing of the cathode sewage (including NH ₃ -N50 ~ 700mg / L, Mn ²⁺ 640 ~ 5210 mg / L) in addition to ammonia nitrogen and manganese, then appropriate Reduce the amount of solution treated and reduce the difficulty of wastewater treatment. The ferrous sulfate-lime method for removing chromium is used, and the process of demineralizing and adding chlorine for removing ammonia is used. The process for removing manganese by lime is more suitable for sewage treatment in high-purity electrolytic manganese production, and the effluent treated by the process contains chromium. The amount of manganese and ammonia nitrogen is lower than the Integrated Wastewater Discharge Standard.

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