A method for recovering manganese from low-grade manganese carbonate ores at low temperatures

Abstract

This invention discloses a method for low-temperature manganese recovery from low-grade manganese carbonate ore. The method involves crushing, grinding, and drying the low-grade manganese carbonate ore. The dried ore is then mixed evenly with a ternary flux and heated to 120°C in a tube furnace at a rate of 5-10°C / min. After constant-temperature roasting for 55-65 minutes, the temperature is further increased to 280°C at a rate of 5-10°C / min, and roasted for another 25-35 minutes. Finally, the temperature is increased again at a rate of 8-12°C / min. The temperature is rapidly increased to 500℃, and roasting continues for 55-65 minutes. After the reaction is complete, the temperature is allowed to drop to room temperature. The roasted residue sample is then removed, and deionized water is added to leach manganese sulfate at room temperature. The residue is then filtered and separated to obtain crude manganese sulfate solution and leaching residue. This process of sulfatating metal oxides in low-grade manganese carbonate ore is more efficient than existing sulfatation technologies, accelerating the extraction of manganese from low-grade manganese carbonate ore to produce high-purity manganese tetroxide. At the same time, it solves the problems of resource waste and environmental pollution caused by low-grade manganese carbonate ore.

Description

Technical Field

[0001] This invention relates to the field of industrial waste resource utilization, specifically a method for low-temperature recovery of manganese from low-grade manganese carbonate ore. Background Technology

[0002] Low-grade manganese carbonate ore refers to manganese ore with a manganese content below the industrial mining standard. The definition varies slightly in some regions due to differences in resource endowment. As an important potential manganese resource, low-grade manganese carbonate ore is often extracted using the roasting-acid leaching process, a common chemical method. This method involves mixing the ore with additives, roasting it at high temperatures to convert the metals into soluble metal salts, and then leaching with an acid solution to obtain the corresponding salt solution. However, the forms of manganese in low-grade ore are complex, including manganese trioxide or manganese dioxide in addition to manganese carbonate. The ammonium salt roasting-acid leaching process for recovering manganese from low-grade manganese carbonate ore containing multiple manganese valence states requires high roasting temperatures, and acid leaching is costly and environmentally unfriendly. Continuous breakthroughs are needed in cost reduction, recovery rate improvement, and environmentally friendly technologies to promote the sustainable utilization of manganese resources. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention aims to provide a method for low-temperature manganese recovery from low-grade manganese carbonate ore. Utilizing a ternary mixed flux to sulfatate the metal oxides in the low-grade manganese carbonate ore achieves higher sulfatation efficiency than existing technologies, accelerating the extraction of manganese from low-grade manganese carbonate ore to produce high-purity manganese tetroxide. Simultaneously, it solves the resource waste and environmental pollution problems associated with low-grade manganese carbonate ore.

[0004] To achieve the above objectives, the present invention is implemented through the following technical solution: a ternary flux, characterized in that it is composed of 60% ammonium sulfate, 20% thiourea and 20% urea.

[0005] A method for low-temperature recovery of manganese from low-grade manganese carbonate ore, characterized by: crushing, mixing, grinding, and drying the low-grade manganese carbonate ore; mixing the dried low-grade manganese carbonate ore with the ternary flux; heating the mixture to 120°C in a tube furnace at a heating rate of 5-10°C / min; roasting at a constant temperature for 55-65 min; then heating the mixture to 280°C at a heating rate of 5-10°C / min; roasting for another 25-35 min; then heating the mixture to 500°C at a heating rate of 8-12°C / min; roasting for another 55-65 min; after the reaction is complete, allowing the temperature to drop to room temperature; removing the roasted residue sample; adding deionized water; leaching manganese sulfate at room temperature; filtering and separating to obtain crude manganese sulfate solution and leaching residue;

[0006] Manganese powder was added to crude manganese sulfate solution, and the mixture was reacted at room temperature before separation and filtration to remove heavy metal ions, 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 mixture 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 mixture was filtered to obtain a tertiary purified manganese sulfate solution. The pH of the tertiary purified manganese sulfate solution was adjusted to 6-7, and citric acid was added to complex with magnesium ions in the solution. After filtration and separation, a quaternary purified manganese sulfate solution was obtained. Ammonium bicarbonate was added to the quaternary purified manganese sulfate solution, and the reaction yielded manganese carbonate precipitate. The precipitate was filtered to obtain manganese carbonate and ammonium sulfate solution. The manganese carbonate precipitate was washed with water and then calcined to obtain manganese tetroxide.

[0007] In the above scheme, the mass ratio of low-grade manganese carbonate ore to ternary flux is 1:1.5-1.8.

[0008] In the above scheme: low-grade manganese carbonate ore is crushed into particles with a diameter ≤80μm and dried at 100-110℃.

[0009] In the above scheme: during leaching, the amount of deionized water added is 8-12 times the mass of manganese carbonate ore, and the leaching time is 50-70 minutes.

[0010] In the above scheme: the amount of metallic manganese powder added is 2-3‰ of the mass of low-grade manganese carbonate ore; the amount of ammonium sulfide added is 1-2‰ of the mass of low-grade manganese carbonate ore.

[0011] In the above scheme: the flocculant is polyacrylamide, and the amount added is 1-2‰ of the mass of low-grade manganese carbonate ore.

[0012] The valence state distribution of manganese in low-grade manganese carbonate ore is quite complex, containing not only manganese carbonate but also manganese trioxide or manganese dioxide. To achieve efficient recovery of manganese from low-grade manganese carbonate ore, it is necessary to ensure efficient reduction of manganese trioxide or manganese dioxide and efficient sulfation of manganese monoxide. Simultaneously, the sulfation process must be used to initially separate a large number of impurity elements.

[0013] The mixed flux used in this invention has a melting point of 280℃ for ammonium sulfate, 180℃ for thiourea, and 133℃ for urea. The eutectic point of these three is 70℃, meaning that the low-grade manganese carbonate ore and the ternary mixed flux begin to flow and decompose at a low temperature of 70℃, reducing the mass and heat transfer resistance during the reaction process. Simultaneously, the lower decomposition temperature of the mixed flux (around 120℃) generates large amounts of ammonia, ammonium bisulfate, cyanamide, hydrogen sulfide, and isocyanate. The continued decomposition of ammonium bisulfate produces ammonia and sulfuric acid vapor, initiating a sulfation reaction. The generation of reducing substances such as hydrogen sulfide reduces high-valence manganese to low-valence manganese, improving manganese recovery efficiency. To prevent the gradual decomposition of sulfuric acid into sulfur trioxide from accelerating and to slow down the sulfation reaction, this invention controls the secondary roasting temperature at 280°C, lower than the temperature at which ammonium sulfate completely decomposes into various gases (350°C). Under these low-temperature reaction conditions, the decomposition loss of ammonium sulfate can be effectively reduced. The main products of thiourea are sulfur dioxide, ammonia, and nitrogen, while the main products of urea are ammonia, carbon dioxide, and water. Sulfur dioxide, in conjunction with hydrogen sulfide, further reacts manganese dioxide into low-valence manganese, accelerating the sulfation process of manganese oxide by generating sulfur dioxide. The formation of nitrogen and carbon dioxide helps to slow down the rapid decomposition of ammonium sulfate into sulfur trioxide, strengthens the sulfation reaction process, and plays a protective role. This invention controls the calcination temperature to 500℃ for three stages. At this temperature, the sulfation products of some metallic impurities begin to decompose and form metal oxides, especially iron impurities. At this temperature, ferric sulfate almost completely decomposes to form iron oxide, while manganese sulfate does not decompose, facilitating subsequent water leaching. Simultaneously, the reducing atmosphere created under this high-temperature ammonia atmosphere keeps manganese in a low valence state, preventing secondary oxidation reactions between manganese and oxygen in the air, thereby improving manganese recovery efficiency. The resulting calcined residue is leached with deionized water at room temperature to remove manganese sulfate. Then, impurities are further removed by adding metallic manganese powder, ammonium sulfide, flocculants, citric acid, etc., to obtain a high-purity manganese sulfate purified solution. This achieves the goal of manganese recovery. The obtained manganese sulfate purified solution can be further reacted to form manganese carbonate, which is then calcined to produce high-purity manganese tetroxide. The obtained manganese tetroxide is battery-grade manganese tetroxide.

[0014] The present invention has the following beneficial effects:

[0015] (1) This invention utilizes the low eutectic point to reduce the initial roasting temperature of low-grade manganese carbonate ore to 120°C and the maximum roasting temperature to 500°C, which greatly reduces energy consumption and extends the service life of the equipment.

[0016] (2) The present invention utilizes molten salt + water leaching to remove impurities, and the recovery rate of manganese extracted from manganese carbonate ore can reach more than 99.2%.

[0017] (3) The present invention utilizes a mixed flux to sulfatate metal oxides, which is more efficient than the existing sulfatation technology, accelerates the process of extracting manganese from low-grade manganese carbonate ore to produce high-purity manganese tetroxide, and solves the problems of resource waste and environmental pollution caused by low-grade manganese carbonate ore. 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 low-grade manganese carbonate ore sample is as follows: manganese 13.5%, iron 5.9%, magnesium 4.0%, aluminum (calculated as alumina) 3.8%, calcium (calcium oxide) 14.4%, silicon (calculated as silicon dioxide) 12.8%, and heavy metal elements such as zinc, copper, nickel, and lead are in trace amounts.

[0021] The low-grade manganese carbonate ore is crushed and mixed evenly, then crushed to a particle size of ≤80μm and dried at 100-110℃ to constant weight.

[0022] Accurately weigh 100g of crushed low-grade manganese carbonate ore and 150g of mixed flux (composed of 60% ammonium sulfate, 20% thiourea, and 20% urea by mass). Mix thoroughly and then perform gradient roasting in a tube furnace. First, heat to 120℃ at a rate of 5℃ / min and roast at this temperature for 60min. Then, continue heating to 280℃ at a rate of 5℃ / min and roast for another 30min. Finally, continue heating to 500℃ at a rate of 10℃ / min and roast for another 60min. After the reaction is complete, allow the temperature to drop to room temperature, remove the roasted residue sample, add 1L of deionized water, and leach manganese sulfate at a constant room temperature. After leaching for 60min, filter to obtain crude manganese sulfate solution. At room temperature, 2‰ metallic manganese powder was added to crude manganese sulfate solution. After reacting at room temperature for 30 minutes, the solution was separated and filtered to remove heavy metals such as zinc, nickel, and cobalt, yielding a primary purified manganese sulfate solution. 2‰ ammonium sulfide was added to the primary purified manganese sulfate solution, and the reaction further removed heavy metals. After filtration, a secondary purified manganese sulfate solution was obtained. 1‰ polyacrylamide was added to the secondary purified manganese sulfate solution to remove trace amounts of residual aluminum and silicon. After filtration, a tertiary purified manganese sulfate solution was obtained. Ammonia was added to the tertiary purified manganese sulfate solution to adjust the pH to 6.5, and 21g of citric acid was added to complex with magnesium ions in the solution. After filtration and separation, a quaternary purified manganese sulfate solution was obtained. Excess ammonium bicarbonate (5% excess based on the molar excess of manganese in the manganese carbonate ore) was added to the quaternary purified manganese sulfate solution to obtain manganese carbonate precipitate. Manganese carbonate precipitate was washed five times with deionized water and then calcined at 890℃ using a suspension low-temperature instantaneous calcination system (ZL201110100752.1) to decompose and obtain solid manganese tetroxide. The solid manganese tetroxide was then pulverized or sand-milled, washed with deionized water, and dried to obtain high-purity manganese tetroxide. The manganese recovery rate reached 99.2%.

[0023] Example 2

[0024] The main chemical composition of the low-grade manganese carbonate ore sample is as follows: manganese 17.5%, iron 5.2%, magnesium 4.9%, aluminum (calculated as alumina) 7.8%, calcium (calcium oxide) 10.3%, silicon (calculated as silicon dioxide) 23.6%, and heavy metal elements such as zinc, copper, nickel, and lead are in trace amounts.

[0025] The low-grade manganese carbonate ore is crushed and mixed evenly, then crushed to a particle size of ≤80μm and dried at 100-110℃ to constant weight.

[0026] 100g of crushed low-grade manganese carbonate ore and 180g of mixed flux (composed of 60% ammonium sulfate, 20% thiourea, and 20% urea by mass) were accurately weighed and mixed evenly in a tube furnace for gradient roasting. First, the temperature was increased to 120℃ at a rate of 10℃ / min and roasted at this temperature for 65min. Then, the temperature was increased to 280℃ at a rate of 10℃ / min and roasted for another 35min. Finally, the temperature was increased to 500℃ at a rate of 12℃ / min and roasted for another 65min. After the reaction was complete, the temperature was allowed to drop to room temperature. The roasted residue sample was removed, and 1.2L of deionized water was added to leach manganese sulfate at a constant room temperature. After leaching for 70min, the mixture was filtered to obtain crude manganese sulfate solution. At room temperature, 3‰ metallic manganese powder was added to crude manganese sulfate solution. After reacting at room temperature for 30 minutes, 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 for further reaction to remove heavy metals. After filtration, a secondary purified manganese sulfate solution was obtained. 2‰ polyacrylamide was added to the secondary purified manganese sulfate solution to remove trace amounts of residual aluminum and silicon. After filtration, a tertiary purified manganese sulfate solution was obtained. Ammonia was added to the tertiary purified manganese sulfate solution to adjust the pH to 7. 26g of citric acid was added to complex with magnesium ions in the solution. After filtration and separation, a quaternary purified manganese sulfate solution was obtained. Excess ammonium bicarbonate (5% excess based on the molar excess of manganese in the manganese carbonate ore) was added to the quaternary purified manganese sulfate solution to obtain manganese carbonate precipitate. Manganese carbonate precipitate was washed five times with deionized water and then calcined at 890℃ using a suspension low-temperature instantaneous calcination system (ZL201110100752.1) to decompose and obtain solid manganese tetroxide. The solid manganese tetroxide was then pulverized or sand-milled, washed with deionized water, and dried to obtain high-purity manganese tetroxide. The manganese recovery rate reached 99.5%.

[0027] Example 3

[0028] The main chemical composition of the low-grade manganese carbonate ore sample is as follows: manganese 14.6%, iron 7.1%, magnesium 5.6%, aluminum (calculated as alumina) 6.9%, calcium (calcium oxide) 12.8%, silicon (calculated as silicon dioxide) 20.7%, and heavy metal elements such as zinc, copper, nickel, and lead are in trace amounts.

[0029] The low-grade manganese carbonate ore is crushed and mixed evenly, then crushed to a particle size of ≤80μm and dried at 100-110℃ to constant weight.

[0030] 100g of crushed low-grade manganese carbonate ore and 160g of mixed flux (composed of 60% ammonium sulfate, 20% thiourea, and 20% urea by mass) were accurately weighed and mixed evenly in a tube furnace for gradient roasting. First, the temperature was increased to 120℃ at a rate of 6℃ / min and roasted at this temperature for 55 min. Then, the temperature was increased to 280℃ at a rate of 6℃ / min and roasted for another 25 min. Finally, the temperature was increased to 500℃ at a rate of 8℃ / min and roasted for another 55 min. After the reaction was complete, the temperature was allowed to drop to room temperature. The roasted residue sample was removed, and 0.8L of deionized water was added to leach manganese sulfate at a constant room temperature. After leaching for 50 min, the mixture was filtered to obtain crude manganese sulfate solution. At room temperature, 2‰ metallic manganese powder was added to crude manganese sulfate solution. After reacting at room temperature for 30 minutes, the solution was separated and filtered to remove heavy metals such as zinc, nickel, and cobalt, yielding a primary purified manganese sulfate solution. 2‰ ammonium sulfide was added to the primary purified manganese sulfate solution for further reaction to remove heavy metals. After filtration, a secondary purified manganese sulfate solution was obtained. 1‰ polyacrylamide was added to the secondary purified manganese sulfate solution to remove trace amounts of residual aluminum and silicon. After filtration, a tertiary purified manganese sulfate solution was obtained. Ammonia was added to the tertiary purified manganese sulfate solution to adjust the pH to 6.3. 30g of citric acid was added to complex with magnesium ions in the solution. After filtration and separation, a quaternary purified manganese sulfate solution was obtained. An excess of ammonium bicarbonate (5% excess based on the molar excess of manganese in the manganese carbonate ore) was added to the quaternary purified manganese sulfate solution to obtain manganese carbonate precipitate. Manganese carbonate precipitate was washed five times with deionized water and then calcined at 890℃ using a suspension low-temperature instantaneous calcination system (ZL201110100752.1) to decompose and obtain solid manganese tetroxide. The solid manganese tetroxide was then pulverized or sand-milled, washed with deionized water, and dried to obtain high-purity manganese tetroxide. The manganese recovery rate reached 99.2%.

[0031] 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 low-temperature recovery of manganese from low-grade manganese carbonate ore, characterized in that: Low-grade manganese carbonate ore is crushed, mixed, ground evenly, and dried. The dried low-grade manganese carbonate ore is then mixed evenly with a ternary flux, which consists of 60% ammonium sulfate, 20% thiourea, and 20% urea. The mixture is heated to 120°C in a tube furnace at a heating rate of 5-10°C / min and roasted at a constant temperature for 55-65 min. Then, the temperature is increased to 280°C at a heating rate of 5-10°C / min and roasted for another 25-35 min. Finally, the temperature is increased to 500°C at a heating rate of 8-12°C / min and roasted for another 55-65 min. After the reaction is complete, the temperature is allowed to drop to room temperature. The roasted residue sample is then removed, and deionized water is added to leach manganese sulfate at room temperature. The mixture is then filtered to separate the manganese sulfate crude solution and the leaching residue. Manganese powder was added to crude manganese sulfate solution, and the mixture was reacted at room temperature before separation and filtration to remove heavy metal ions, 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 mixture 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 mixture was filtered to obtain a tertiary purified manganese sulfate solution. The pH of the tertiary purified manganese sulfate solution was adjusted to 6-7, and citric acid was added to complex with magnesium ions in the solution. After filtration and separation, a quaternary purified manganese sulfate solution was obtained. Ammonium bicarbonate was added to the quaternary purified manganese sulfate solution, and the reaction yielded manganese carbonate precipitate. The precipitate was filtered to obtain manganese carbonate and ammonium sulfate solution. The manganese carbonate precipitate was washed with water and then calcined to obtain manganese tetroxide. The mass ratio of low-grade manganese carbonate ore to ternary flux was 1:1.5-1.

8.

2. The method for low-temperature recovery of manganese from low-grade manganese carbonate ore according to claim 1, characterized in that: Low-grade manganese carbonate ore is crushed to a particle size ≤80μm and dried at 100-110℃.

3. The method for low-temperature recovery of manganese from low-grade manganese carbonate ore according to claim 2, characterized in that: During leaching, the amount of deionized water added is 8-12 times the mass of manganese carbonate ore, and the leaching time is 50-70 minutes.

4. The method for low-temperature recovery of manganese from low-grade manganese carbonate ore according to claim 3, characterized in that: The amount of metallic manganese powder added is 2-3‰ of the mass of low-grade manganese carbonate ore; the amount of ammonium sulfide added is 1-2‰ of the mass of low-grade manganese carbonate ore.

5. The method for low-temperature recovery of manganese from low-grade manganese carbonate ore according to claim 4, characterized in that: The flocculant is polyacrylamide, and the amount added is 1-2‰ of the mass of low-grade manganese carbonate ore.