A method for recovering manganese from ferromanganese alloy waste residues

Abstract

The application discloses a method for recovering manganese from manganese-iron alloy waste residues, and recovery is carried out according to the following method: after the manganese-iron alloy waste residues are crushed and dried, the dried manganese-iron alloy waste residues are uniformly mixed with a binary flux according to a mass ratio of 1:1.8-2, complete roasting reaction is carried out, the roasting residue sample is taken out after the temperature is reduced to room temperature, deionized water is added to leach manganese sulfate at room temperature, filtration separation is carried out, and a manganese sulfate crude liquid is obtained; after metal manganese powder, ammonium sulfide and a flocculating agent are further added to the manganese sulfate crude liquid to remove impurities, the pH is adjusted and citric acid is added, filtration separation is carried out, and a purified manganese sulfate liquid is obtained. The recovery rate of manganese can reach more than 99.1%, energy consumption is low, operation is simple, impurity removal is complete, and the obtained product has high quality.

Description

Technical Field

[0001] This invention relates to the field of industrial waste resource utilization, specifically a method for recovering manganese from ferromanganese alloy slag. Background Technology

[0002] In the smelting process of ferromanganese alloys, ferromanganese alloy waste slag is inevitably generated. Its main components include oxides of manganese, iron, silicon, calcium, and magnesium. The manganese content is generally around 5%-20%, and the iron content is relatively high. It also contains certain amounts of silicon dioxide, calcium oxide, and magnesium oxide. Industrially, physical and chemical methods are generally used to recover valuable metals such as manganese and iron from the waste slag, improving resource utilization. However, due to the intertwined components of the ferromanganese alloy waste slag, forming complex mineral phases, the separation and extraction of manganese is quite difficult. The composition of waste slag varies greatly depending on its source and production process, increasing the complexity and difficulty of the recovery process. In particular, the high iron content in the ferromanganese alloy waste slag is a key impurity that needs to be controlled in battery-grade manganese tetroxide. Traditional physical beneficiation and chemical leaching methods for producing the precursor manganese sulfate have excessively high iron content, failing to meet the requirements for bio-battery-grade manganese tetroxide. Therefore, domestic manufacturers generally use it for hazardous waste storage, preparation of building materials, acid soil conditioners, or mine filling, and it has not been well developed and comprehensively utilized. This not only wastes resources, but also easily causes considerable environmental pollution if not handled properly. Summary of the Invention

[0003] To address the aforementioned technical problems, the first objective of this invention is to provide a binary flux, and the second objective is to provide a method for recovering manganese from ferromanganese alloy waste slag, achieving a manganese recovery rate of over 99.1%, with low energy consumption and simple operation.

[0004] To achieve the first objective mentioned above, the present invention is implemented through the following technical solution: a binary flux, characterized in that it is composed of 60% ammonium sulfate and 40% urea.

[0005] The second objective of this invention is achieved as follows: a method for recovering manganese from ferromanganese alloy waste slag, characterized by the following recovery process: the ferromanganese alloy waste slag is crushed and dried; the dried ferromanganese alloy waste slag is mixed evenly with the binary flux at a mass ratio of 1:1.8-2; the mixture is heated to 320°C in a tube furnace at a heating rate of 5-10°C / min and calcined at a constant temperature for 80-90 min; then, the temperature is further increased to 520°C at a heating rate of 5-10°C / min and calcined for another 25-30 min; finally, the temperature is further increased to 620°C at a heating rate of 5-10°C / min and calcined for another 55-60 min; after the reaction is complete, the temperature is allowed to drop to room temperature, the calcined slag sample is removed, deionized water is added to leach manganese sulfate at room temperature, and the mixture is filtered to obtain crude manganese sulfate solution;

[0006] Manganese powder is added to crude manganese sulfate solution, reacts at room temperature, and then separated and filtered to remove heavy metals, yielding a primary purified manganese sulfate solution. Ammonium sulfide is added to the primary purified manganese sulfate solution to further remove heavy metals, and the solution is filtered to obtain a secondary purified manganese sulfate solution. A flocculant is added to remove small amounts of residual aluminum and silicon from the secondary purified manganese sulfate solution, and the solution is filtered to obtain a tertiary purified manganese sulfate solution. Ammonia is added to the tertiary purified manganese sulfate solution to adjust the pH to 6-7, citric acid is added to complex with magnesium ions in the solution, and the solution is filtered and separated to obtain a purified manganese sulfate solution. In the above scheme, the ferromanganese alloy waste slag is crushed to a particle size ≤100μm and dried at 100-110℃.

[0007] In the above scheme: during leaching, the amount of deionized water added is 8-12 times the mass of the ferromanganese alloy waste residue, and the leaching time is 50-70 minutes.

[0008] In the above scheme: the amount of manganese powder added is 2‰-3‰ of the mass of the ferromanganese alloy waste slag; the amount of ammonium sulfide added is 1‰-2‰ of the mass of the electrolytic furnace ferromanganese slag.

[0009] In the above scheme: the flocculant is polyacrylamide, and the amount added is 1‰-2‰ of the mass of the manganese-iron alloy waste slag.

[0010] The manganese in ferromanganese alloy waste slag is typically MnO due to the high-temperature reducing environment. However, due to differences in the source of the waste slag, smelting process, and environmental exposure, a small amount of high-valence manganese (trivalent and tetravalent) still remains. To improve the manganese recovery rate, the high-valence manganese must be reduced to low-valence manganese. Meanwhile, battery-grade manganese tetroxide has strict limits on the amount of impurity iron. Therefore, the key to extracting manganese from ferromanganese alloy waste slag to produce battery-grade manganese tetroxide is the efficient reduction of high-valence manganese oxides and the efficient separation of impurity iron.

[0011] In a binary flux, ammonium sulfate has a melting point of 280℃, and urea has a melting point of 133℃. Their eutectic point is 60℃, meaning that the melting point of ferromanganese alloy slag is 220℃ lower than that using ammonium sulfate alone as a flux (current common technology). This indicates that ammonium sulfate begins to flow at a low temperature of 60℃, reducing the mass and heat transfer resistance in the reaction process of the ferromanganese alloy slag. Correspondingly, the decomposition temperature of ammonium sulfate and urea decreases. At low temperatures (60℃-180℃), large amounts of ammonia, ammonium bisulfate, and carbon dioxide are generated, while ammonium bisulfate continues to decompose to form sulfuric acid and ammonia (220℃-280℃). This causes the valuable metals in the ferromanganese alloy slag, including manganese, iron, nickel, and cobalt, to undergo sulfation. The large amount of reducing ammonia generated can reduce the high-valence manganese in the ferroalloy slag to low-valence manganese, promoting the formation of manganese sulfate. When the temperature continues to rise above 320℃, the decomposition of sulfuric acid to form sulfur trioxide accelerates, thus slowing down the sulfation reaction process. Therefore, this invention patent controls the first-stage roasting temperature to 320℃. However, existing methods use only ammonium sulfate for roasting at 380℃. Since ammonium sulfate completely decomposes into various gases at 350℃, this complete decomposition slows down the sulfation reaction process. Therefore, existing technologies require increasing the amount of ammonium sulfate (the ratio of ammonium sulfate to manganese slag is as high as 15:1) to compensate for the decomposition loss.

[0012] Because the roasting temperature in the first stage is relatively low, it is difficult to completely reduce the high-valent manganese in the ferromanganese alloy slag to divalent manganese. In the second stage, by maintaining the roasting temperature at 520℃ for 30 minutes, under this high-temperature condition, the high-valent manganese is reduced to divalent manganese by ammonia gas, thereby continuing the sulfation reaction of manganese to produce manganese sulfate.

[0013] To achieve the separation of manganese and iron in the ferromanganese alloy slag during the roasting process, a gradient heating method was adopted. Roasting was carried out at 620℃ in the third stage. At this temperature, ferric sulfate completely decomposes to form ferric oxide, nickel sulfate partially decomposes to form nickel oxide, while manganese sulfate does not decompose. Therefore, at this selective temperature, ferric sulfate completely decomposes to form water-insoluble ferric oxide. Water leaching achieves complete or partial separation of manganese sulfate from metallic impurities such as ferric oxide and nickel oxide. The main components of the leaching residue are calcium sulfate, ferric oxide, and nickel oxide. The leachate is further treated with manganese powder, ammonium sulfide, and flocculants to remove impurities, ultimately yielding a high-purity manganese sulfate solution. The obtained manganese sulfate solution can be reacted with excess ammonium bicarbonate to form manganese carbonate, which is then calcined to produce manganese tetroxide, used as a raw material for battery and soft magnetic material production.

[0014] Beneficial effects:

[0015] (1) The present invention uses molten salt + water leaching to remove impurities, and the recovery rate of manganese extracted from ferromanganese alloy waste can reach more than 99.1%.

[0016] (2) Compared with the prior art, the present invention removes impurities more thoroughly. The manganese sulfate obtained by the present invention reacts to form manganese carbonate and is then calcined to obtain manganese tetroxide iron with a content far less than 10 ppm, which can be used as a raw material for preparing high-end battery cathode materials.

[0017] (3) The present invention utilizes a mixed flux to sulfate metal oxides. Due to the appearance of the eutectic point, the decomposition temperature is reduced and the sulfation efficiency is higher, which accelerates the process of producing battery-grade manganese tetroxide from ferromanganese alloy slag. At the same time, it solves the problems of resource waste and environmental pollution caused by ferromanganese alloy slag. Detailed Implementation

[0018] The present invention will be further described below with reference to embodiments.

[0019] Example 1

[0020] The main chemical composition of the ferromanganese alloy waste slag sample is as follows: manganese 19.1%, magnesium 4.3%, iron 1.8%, aluminum 4.8%, calcium 15.7%, silicon 18.6%, with trace amounts of heavy metals such as zinc, copper, nickel, and lead. The ferromanganese alloy waste slag was crushed and mixed evenly, with a particle size ≤100 μm, and dried to constant weight at 100-110℃. 100 g of ferromanganese alloy waste slag and 180 g of binary flux (60% ammonium sulfate and 40% urea by mass) were accurately weighed and mixed evenly, then subjected to gradient calcination in a tube furnace. First, the temperature was increased to 320℃ at a rate of 10℃ / min and calcined at this temperature for 90 min; then, the temperature was increased to 520℃ at a rate of 10℃ / min and calcined for another 30 min; finally, the temperature was increased to 620℃ at a rate of 10℃ / min and calcined for another 60 min. After the reaction was complete and the temperature was lowered to room temperature, the roasted residue sample was removed. 1 L of deionized water was added to leach manganese sulfate at a constant room temperature. After leaching for 60 min, the solution was filtered to obtain crude manganese sulfate solution. The leaching residue was reserved for other uses. At room temperature, based on the heavy metal ion content in the crude manganese sulfate solution, 2‰ manganese powder was added. After reacting at room temperature for 30 min, the solution was separated and filtered to remove heavy metals such as zinc, nickel, and cobalt, yielding a primary purified manganese sulfate solution. 1‰ ammonium sulfide was added to the primary purified manganese sulfate solution to further remove heavy metals, yielding a secondary purified manganese sulfate solution. 1‰ polyacrylamide was added to remove small amounts of residual aluminum and silicon from the secondary purified manganese sulfate solution, and the solution was filtered to obtain a tertiary purified manganese sulfate solution. Ammonia was added to the tertiary purified manganese sulfate solution to adjust the pH to 6.8, and 23 g of citric acid was added to complex with magnesium ions in the solution. After filtration and separation, the purified manganese sulfate solution was obtained. Excess ammonium bicarbonate (5% excess based on the molar amount of manganese) was added to the manganese sulfate purification solution. After reaction, the mixture was filtered to obtain manganese carbonate precipitate and ammonium sulfate solution. The ammonium sulfate solution was evaporated and crystallized for recycling. The manganese carbonate precipitate was washed 5 times with deionized water and calcined at 850℃ using a suspension low-temperature instantaneous calcination system (ZL 201110100752.1) to decompose and obtain solid manganese tetroxide. The solid manganese tetroxide was crushed or sand-milled, washed with deionized water, and dried to obtain battery-grade manganese tetroxide.

[0021] Example 2

[0022] The main chemical composition of the ferromanganese alloy waste slag sample is as follows: manganese 19.1%, magnesium 4.3%, iron 1.8%, aluminum 4.8%, calcium 15.7%, silicon 18.6%, with trace amounts of heavy metals such as zinc, copper, nickel, and lead. The ferromanganese alloy waste slag was crushed and mixed evenly, with a particle size ≤100 μm, and dried to constant weight at 100-110℃. 100 g of ferromanganese alloy waste slag and 200 g of binary flux (60% ammonium sulfate and 40% urea by mass) were accurately weighed and mixed evenly, then subjected to gradient calcination in a tube furnace. First, the temperature was increased to 320℃ at a rate of 5℃ / min and calcined at this temperature for 80 min; then, the temperature was increased to 520℃ at a rate of 5℃ / min and calcined for another 25 min; finally, the temperature was increased to 620℃ at a rate of 5℃ / min and calcined for another 55 min. After the reaction was complete and the temperature was lowered to room temperature, the calcined residue sample was removed. 1.2 L of deionized water was added to leach manganese sulfate at a constant room temperature. After leaching for 70 min, the solution was filtered to obtain crude manganese sulfate solution. The leaching residue was reserved for other uses. At room temperature, based on the heavy metal ion content in the crude manganese sulfate solution, 3‰ manganese powder was added. After reacting at room temperature for 30 min, the solution was separated and filtered to remove heavy metals such as zinc, nickel, and cobalt, yielding a primary purified manganese sulfate solution. 1‰ ammonium sulfide was added to the primary purified manganese sulfate solution to further remove heavy metals, yielding a secondary purified manganese sulfate solution. 1‰ polyacrylamide was added to remove small amounts of residual aluminum and silicon from the secondary purified manganese sulfate solution, and the solution was filtered to obtain a tertiary purified manganese sulfate solution. Ammonia was added to the tertiary purified manganese sulfate solution to adjust the pH to 6, and 23 g of citric acid was added to complex with magnesium ions in the solution. After filtration and separation, the purified manganese sulfate solution was obtained. Excess ammonium bicarbonate (5% excess based on the molar amount of manganese) was added to the manganese sulfate purification solution, and the reaction was carried out. After filtration, manganese carbonate precipitate and ammonium sulfate solution were obtained. The ammonium sulfate solution was evaporated and crystallized and then recycled. The manganese carbonate precipitate was washed 5 times with deionized water and calcined at 850°C using a suspension low-temperature instantaneous calcination system (ZL 201110100752.1) to decompose and obtain solid manganese tetroxide. The solid manganese tetroxide was crushed or sand-milled, washed with deionized water, and dried to obtain battery-grade manganese tetroxide.

[0023] Example 3

[0024] The main chemical composition of the ferromanganese alloy waste slag sample is as follows: manganese 19.1%, magnesium 4.3%, iron 1.8%, aluminum 4.8%, calcium 15.7%, silicon 18.6%, with trace amounts of heavy metals such as zinc, copper, nickel, and lead. The ferromanganese alloy waste slag was crushed and mixed evenly, with a particle size ≤100 μm, and dried to constant weight at 100-110℃. 100 g of ferromanganese alloy waste slag and 200 g of binary flux (60% ammonium sulfate and 40% urea by mass) were accurately weighed and mixed evenly, then subjected to gradient calcination in a tube furnace. First, the temperature was increased to 320℃ at a rate of 8℃ / min and calcined at this temperature for 88 min; then, the temperature was increased to 520℃ at a rate of 8℃ / min and calcined for another 28 min; finally, the temperature was increased to 620℃ at a rate of 8℃ / min and calcined for another 57 min. After the reaction was complete and the temperature was lowered to room temperature, the roasted residue sample was removed, and 0.8 L of deionized water was added to leach manganese sulfate at a constant room temperature. After leaching for 70 min, the solution was filtered to obtain crude manganese sulfate solution. The leaching residue was reserved for other uses. Under room temperature conditions, based on the heavy metal ion content in the crude manganese sulfate solution, 2‰ metallic manganese powder was added. After reacting at room temperature for 30 min, the solution was separated and filtered to remove heavy metals such as zinc, nickel, and cobalt, obtaining a primary purified manganese sulfate solution. 2‰ ammonium sulfide was added to the primary purified manganese sulfate solution to further remove heavy metals, obtaining a secondary purified manganese sulfate solution. 2‰ polyacrylamide was added to remove a small amount of residual aluminum and silicon from the secondary purified manganese sulfate solution, and the solution was filtered to obtain a tertiary purified manganese sulfate solution. Ammonia water was added to the tertiary purified manganese sulfate solution to adjust the pH to 7, and 23 g of citric acid was added to complex with magnesium ions in the solution. After filtration and separation, the purified manganese sulfate solution was obtained. Excess ammonium bicarbonate (5% excess based on the molar amount of manganese) was added to the manganese sulfate purification solution, and the reaction was carried out. After filtration, manganese carbonate precipitate and ammonium sulfate solution were obtained. The ammonium sulfate solution was evaporated and crystallized and then recycled. The manganese carbonate precipitate was washed 5 times with deionized water and calcined at 850°C using a suspension low-temperature instantaneous calcination system (ZL 201110100752.1) to decompose and obtain solid manganese tetroxide. The solid manganese tetroxide was crushed or sand-milled, washed with deionized water, and dried to obtain battery-grade manganese tetroxide.

[0025] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for recovering manganese from ferromanganese alloy waste slag, characterized in that, The process consists of the following steps: crushing and drying the ferromanganese alloy waste slag, mixing the dried ferromanganese alloy waste slag with a binary flux at a mass ratio of 1:1.8-2, wherein the binary flux is composed of 60% ammonium sulfate and 40% urea by mass. In a tube furnace, the temperature is increased to 320℃ at a rate of 5-10℃ / min and calcined at a constant temperature for 80-90 min. Then, the temperature is increased to 520℃ at a rate of 5-10℃ / min and calcined for another 25-30 min. Finally, the temperature is increased to 620℃ at a rate of 5-10℃ / min and calcined for another 55-60 min. After the reaction is complete, the temperature is allowed to drop to room temperature. The calcined residue sample is then removed, and deionized water is added to leach manganese sulfate at room temperature. The residue is then filtered to obtain crude manganese sulfate solution. Manganese powder was added to the crude manganese sulfate solution, and after reacting at room temperature, the solution was separated and filtered to remove heavy metals, yielding a primary purified manganese sulfate solution. Ammonium sulfide was added to the primary purified manganese sulfate solution to further remove heavy metals, and the solution was filtered to obtain a secondary purified manganese sulfate solution. A flocculant was added to remove small amounts of residual aluminum and silicon from the secondary purified manganese sulfate solution, and the solution was filtered to obtain a tertiary purified manganese sulfate solution. Ammonia was added to the tertiary purified manganese sulfate solution to adjust the pH to 6-7, and citric acid was added to complex with magnesium ions in the solution. After filtration and separation, the purified manganese sulfate solution was obtained.

2. The method for recovering manganese from ferromanganese alloy waste slag according to claim 1, characterized in that: The ferromanganese alloy waste slag is crushed into particles with a diameter ≤100μm and dried at 100-110℃.

3. The method for recovering manganese from ferromanganese alloy waste slag according to claim 2, characterized in that: During leaching, the amount of deionized water added is 8-12 times the mass of the ferromanganese alloy waste residue, and the leaching time is 50-70 minutes.

4. The method for recovering manganese from ferromanganese alloy waste slag according to claim 3, characterized in that: The flocculant is polyacrylamide, and the amount added is 1‰-2‰ of the mass of the manganese-iron alloy waste slag.