Method for extracting manganese from low-grade rhodochrosite

Abstract

The invention discloses a method for extracting manganese from low-grade rhodochrosite, which comprises the following steps: drying, crushing and screening the low-grade rhodochrosite, uniformly mixing with a flux, heating to 165 DEG C in a tubular furnace under the protection of inert gas, roasting at constant temperature, heating to 245 DEG C, roasting at constant temperature, then heating to 620 DEG C, roasting at constant temperature, and naturally cooling to room temperature after roasting, and adding deionized water, leaching manganese sulfate from the roasted sample at room temperature, filtering and separating, carrying out graded purification and impurity removal on the filtrate, adding ammonium bicarbonate to convert the manganese sulfate into manganese carbonate, filtering, washing with deionized water, and carrying out high-temperature calcination to obtain the manganous-manganic oxide. According to the method, a pyrogenic process flux is utilized to form a reducing atmosphere under the protection of inert gas, a manganese source in the low-grade rhodochrosite is fully utilized, high-valence manganese in the low-grade rhodochrosite is reduced into + 2-valence low-valence manganese, the low-valence manganese is utilized to carry out sulfation reaction, and formed soluble MnSO4 is soaked in deionized water, so that manganese is efficiently extracted from the low-grade rhodochrosite.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of comprehensive utilization of low-grade minerals, and particularly relates to a method for extracting manganese from low-grade rhodochrosite. BACKGROUND

[0002] Manganese ore is an important mineral resource in China. The metallic manganese produced from manganese ore is widely used in the fields of metallurgy, chemical industry, light industry, and electronic material. China is rich in manganese resources, which are mainly stored in the form of rhodochrosite. However, most of the rhodochrosite in China has a low grade, and the main mineral MnCO3 is associated with a large amount of other minerals. In addition, due to the complexity of the formation of manganese deposits in nature, some manganese ores obtained by mining contain high-valence manganese. Therefore, it is more beneficial to the leaching of manganese in manganese ore to reduce the high-valence manganese to low-valence manganese by reduction. Since manganese is easily soluble in acid, the main process for extracting manganese from rhodochrosite in China at present is the wet process supplemented by the fire process. The acid leaching method is the most widely used, among which the roasting-acid leaching method is commonly used. The rhodochrosite is first decomposed into manganese oxide by low-temperature roasting, and then acid leaching is performed to improve the leaching rate. The fire process is suitable for high-grade rhodochrosite. The manganese carbonate is converted into manganese monoxide by reduction roasting, and then manganese-iron alloy is obtained by smelting in a blast furnace or an electric furnace. In addition, there is an ammonia leaching method. The manganese is leached by using an ammonia water-ammonium carbonate solution to generate a soluble complex, and a manganese compound is obtained by precipitation after purification. These methods have advantages in cost and resource utilization, but still face challenges in technical optimization, pollution control, and economy in actual production. It is of great importance to break through the efficient leaching technology of manganese in low-grade rhodochrosite and build a green recycling system to ensure the safety of manganese resources in China. SUMMARY

[0003] In order to solve the above technical problems, the first purpose of the present application is to provide a flux, and the second purpose is to provide a method for extracting manganese from low-grade rhodochrosite. The flux is used to form a reducing atmosphere under the protection of inert gas by the fire process, so as to fully utilize the manganese source in low-grade rhodochrosite, reduce the high-valence manganese in low-grade rhodochrosite to low-valence manganese (+2), and perform a sulfuric acidization reaction by using the low-valence manganese. The formed soluble MnSO4 is leached by deionized water, so as to realize the efficient extraction of manganese from low-grade rhodochrosite.

[0004] In order to achieve the above first purpose, the present application provides the following technical scheme: a flux, characterized in that it is composed of 78% ammonium sulfate and 22% oxalic acid.

[0005] The second object of the present application is achieved in that a method for extracting manganese from low-grade rhodochrosite is characterized in that the extraction is carried out in the following way: the low-grade rhodochrosite is dried and crushed, screened, and then mixed uniformly with the flux, heated to 165℃ at a speed of 15-20℃ / min in a tube furnace under the protection of inert gas, constant temperature roasting for 5-10 min, heated to 245℃ at a speed of 10-15℃ / min, constant temperature roasting for 5-10 min, then heated to 620℃ at a speed of 20-25℃ / min, constant temperature roasting for 10-20 min, after roasting is completed, natural cooling to room temperature, adding deionized water to leach manganese sulfate from the roasted sample at room temperature, filtering and separating, after the filtrate is purified and impurities are removed, adding ammonium bicarbonate to convert the manganese sulfate into manganese carbonate, filtering and washing with deionized water, high-temperature calcination, obtaining trimanganese tetroxide, crushing or sand grinding the trimanganese tetroxide, washing with deionized water, drying to obtain high-purity trimanganese tetroxide.

[0006] In the above scheme: the low-grade rhodochrosite is dried at 100-110℃.

[0007] In the above scheme: the low-grade rhodochrosite after drying is crushed to a particle size of ≤75μm. Screening through a 200-mesh screen.

[0008] In the above scheme: the mass ratio of the rhodochrosite powder to the flux is 2-3:1.

[0009] In the above scheme: the inert gas is nitrogen, and the flow rate is 1.5-2.5L / min. Nitrogen is low in cost and relatively common.

[0010] In the above scheme: the amount of deionized water added is 8-12 times the mass of the low-grade rhodochrosite, and the leaching time is 50-70min.

[0011] In the above scheme: the step of purifying and removing impurities from the filtrate is: adding manganese powder to the filtrate, reacting at room temperature, and filtering; adding ammonium sulfide to the filtrate, reacting at room temperature, and filtering, adding a flocculating agent to the filtrate, precipitating and filtering; adding ammonia water to the filtrate to adjust the pH value to 6-7, adding citric acid, reacting at room temperature, and filtering to obtain a purified solution. The trace amounts of metal ions such as lead, iron, cobalt, nickel, copper, and zinc remaining in the manganese sulfate crude liquid are reduced to metals by adding manganese powder, and the metal ions are separated by filtering; the remaining trace amounts of metal ions are further removed by adding ammonium sulfide to the filtrate; aluminum and silicon remaining in the filtrate are removed by adding polyacrylamide; magnesium ions remaining in the solution are removed in the subsequent ammonium bicarbonate precipitation process by adding citric acid to complex with the magnesium ions.

[0012] The adding amount of the metal manganese powder is 2‰-3‰ of the low-grade rhodochrosite powder; the adding amount of the ammonium sulfide is 1‰-2‰ of the mass of the low-grade rhodochrosite powder. The flocculating agent is polyacrylamide, and the adding amount is 1‰-2‰ of the mass of the low-grade rhodochrosite powder. The adding amount of the citric acid is 1.5‰-2‰.

[0013] The mixed flux of the ammonium sulfate and the oxalic acid in the application has a eutectic mixture with a lower melting point than the melting point of the ammonium sulfate and the oxalic acid. The oxalic acid decomposes at a temperature much lower than its theoretical melting point, and the ammonium sulfate also decomposes in advance when it is close to its melting point. When the temperature is raised to 165℃, the oxalic acid decomposes to release gas, and the products are CO, N2 and CO2, wherein the CO has a reducing property and can reduce a small amount of high-valence manganese in the low-grade rhodochrosite to +2 valence manganese, and the flow of a large amount of gas in the low-grade rhodochrosite improves the mass and heat transfer efficiency. When the temperature is raised to 245℃, the ammonium sulfate starts to decompose to produce a large amount of ammonia and ammonium bisulfate, and the ammonium bisulfate continues to decompose to produce ammonia and sulfuric acid vapor, so that the manganese in the low-grade rhodochrosite starts to sulfate. Due to the effect of the oxalic acid in the early stage, the high-valence manganese in the low-grade rhodochrosite also exists in +2 valence, so that all the manganese in the low-grade rhodochrosite participates in the sulfation reaction to generate manganese sulfate, and the reaction behaviors of other metals in the low-grade rhodochrosite are similar to those of manganese, forming metal sulfates. When the temperature is raised to 620℃, part of the metal sulfates starts to decompose, especially the decomposition temperature of the iron sulfate is low, and almost all of the iron sulfate can be decomposed to generate iron oxide, and at this temperature, the manganese sulfate still exists stably. Since the manganese sulfate is easily soluble in water, the manganese sulfate in the sample after the roasting at 620℃ can be completely leached by using deionized water, and the impurity elements exist in the leaching residue in the form of insoluble substances such as iron oxide, nickel oxide, calcium sulfate, barium sulfate and lead sulfate, so that the separation of a large amount of impurity elements and the manganese sulfate is realized in the roasting stage.

[0014] Advantages:

[0015] (1) The application strengthens the reducing atmosphere by inert gas protection roasting, greatly reduces the consumption of the ammonium sulfate complex flux, and realizes the complete conversion of a small amount of high-valence manganese in the low-grade rhodochrosite into low-valence manganese.

[0016] (2) The low-temperature roasting process combined with the water leaching treatment to extract manganese prolongs the service life of the equipment while reducing the energy consumption, and belongs to a green and environmental protection process.

[0017] (3) Compared with the prior art, the application improves the sulfation efficiency of manganese in the roasting stage, and the recovery rate of manganese in the low-grade rhodochrosite is more than 98.50%. DETAILED DESCRIPTION

[0018] The application will be further described in connection with the following examples.

[0019] Example 1

[0020] Low-grade bixbyite manganese ore was taken from a smelting plant in Guizhou (containing 18.6% Mn), the bixbyite manganese ore was dried at 105±5℃, crushed to a particle size of ≤75 μm, and sieved through a 200 mesh screen to obtain a bixbyite manganese ore sample. 100 g of the sample was mixed uniformly with 40 g of a composite flux composed of 78% ammonium sulfate and 22% oxalic acid, and was subjected to fractional roasting in a tube furnace under nitrogen protection at a nitrogen flow rate of 1.8 L / min. First, the temperature was raised to 165℃ at a rate of 15℃ / min, and constant temperature roasting was performed for 10 min; then, the temperature was raised to 245℃ at a rate of 10℃ / min, and constant temperature roasting was performed for 8 min; finally, the temperature was raised to 620℃ at a rate of 25℃ / min, and constant temperature roasting was performed for 15 min. After roasting was completed, the sample was allowed to cool to room temperature naturally, and was removed. 1 L of deionized water was added to the sample at room temperature for leaching for 55 min, and filtration was performed. 0.2 g of metallic manganese powder was added to the crude manganese sulfate solution at room temperature for reaction for 30 min, and filtration was performed. 0.15 g of ammonium sulfide was added to the filtrate at room temperature for reaction for 15 min, and filtration was performed. 0.1 g of flocculant polyacrylamide was added to the filtrate for reaction for 30 min, and precipitation and filtration were performed. Ammonia water was added to the filtrate to adjust the pH value to 6.8, 0.2 g of citric acid was added to the filtrate at room temperature for reaction, and filtration was performed to obtain a purified solution. Ammonium bicarbonate was added to convert the manganese sulfate to manganese carbonate, the solution was washed with deionized water 3 times, and calcination was performed at 936℃ to obtain trimanganese tetroxide. After crushing or sand milling, the trimanganese tetroxide was washed with deionized water 3 times, dried, and high-purity trimanganese tetroxide was obtained. The recovery rate of manganese in the low-grade bixbyite manganese ore was 98.67%, and the purity of the trimanganese tetroxide was 99.86%.

[0021] Example 2

[0022] Low-grade rhodochrosite was taken from a smelting plant in Guizhou (Mn content 18.6%), and the rhodochrosite was dried at 105°C, crushed, and sieved to a particle size of 75 μm or less, 200 mesh. 100 g of the sample was mixed with 33.3 g of a composite flux composed of 78% ammonium sulfate and 22% oxalic acid, and the mixture was uniformly mixed under nitrogen protection in a tube furnace. The nitrogen flow rate was 1.5 L / min. First, the temperature was raised to 165°C at a rate of 20°C / min, and the sample was held at this temperature for 5 min. Then, the temperature was raised to 245°C at a rate of 15°C / min, and the sample was held at this temperature for 10 min. Finally, the temperature was raised to 620°C at a rate of 20°C / min, and the sample was held at this temperature for 20 min. After the roasting was completed, the sample was allowed to cool to room temperature, and 1.2 L of deionized water was added to the sample at room temperature and allowed to stand for 50 min. The sample was then filtered. 0.3 g of metallic manganese powder was added to the crude manganese sulfate solution, and the mixture was allowed to react at room temperature for 30 min. The mixture was then filtered, and 0.1 g of ammonium sulfide was added to the filtrate, and the mixture was allowed to react at room temperature for 15 min. The mixture was then filtered, and 0.2 g of the flocculating agent polyacrylamide was added to the filtrate, and the mixture was allowed to react for 30 min. The mixture was then precipitated and filtered. Ammonia water was added to the filtrate to adjust the pH to 6.5, and 0.15 g of citric acid was added to the mixture, and the mixture was allowed to react at room temperature. The mixture was then filtered to obtain a purified solution. Ammonium bicarbonate was added to convert the manganese sulfate to manganese carbonate, and the mixture was washed with deionized water three times. The mixture was then calcined at 936°C to obtain trivalent manganese tetroxide. The trivalent manganese tetroxide was crushed or sand-milled, washed with deionized water three times, and dried to obtain high-purity trivalent manganese tetroxide. The recovery rate of manganese from the low-grade rhodochrosite was 98.96%, and the purity of the trivalent manganese tetroxide was 99.75%.

[0023] Example 3

[0024] The low-grade rhodochrosite is taken from a smelting plant in Guizhou (containing Mn 18.6%), the rhodochrosite is dried at 105℃, crushed to a particle size of ≤75μm, screened by a 200 mesh sieve, and a rhodochrosite sample is obtained. 100g of the sample is mixed with 50g of a composite flux composed of 78% ammonium sulfate and 22% oxalic acid, and the mixture is uniformly mixed under nitrogen protection in a tube furnace, and the nitrogen flow rate is 2.5L / min. First, the temperature is raised to 165℃ at a rate of 15℃ / min, and the temperature is kept constant for 10min; then, the temperature is raised to 245℃ at a rate of 10℃ / min, and the temperature is kept constant for 8min; finally, the temperature is raised to 620℃ at a rate of 25℃ / min, and the temperature is kept constant for 10min. After the roasting is completed, the roasting sample is naturally cooled to room temperature, 0.8L of deionized water is added to the roasting sample at room temperature for leaching for 70min, and a crude manganese sulfate solution is obtained by filtration separation. 0.3g of metallic manganese powder is added to the crude manganese sulfate solution at room temperature for reaction for 30min, filtration is performed, 0.1g of ammonium sulfide is added to the filtrate at room temperature for reaction for 15min, filtration is performed, 0.2g of a flocculating agent polyacrylamide is added to the filtrate at room temperature for reaction for 30min, and precipitation and filtration are performed; ammonia water is added to the filtrate to adjust the pH value to 6.6, 0.15g of citric acid is added to the filtrate at room temperature for reaction, and filtration separation is performed to obtain a purified solution. Ammonium bicarbonate is added to convert the manganese sulfate into manganese carbonate, the manganese carbonate is washed with deionized water for 3 times, calcination is performed at a high temperature of 936℃ to obtain trimanganese tetroxide, the trimanganese tetroxide is crushed or sand ground, washed with deionized water for 3 times, and dried to obtain high-purity trimanganese tetroxide. The recovery rate of manganese in the low-grade rhodochrosite is 99.06%, and the purity of the trimanganese tetroxide is 99.82%.

[0025] The present application is not limited to the above-mentioned embodiments, and those skilled in the art can understand that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and purposes of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. A flux, characterized in that: It consists of 78% ammonium sulfate and 22% oxalic acid.

2. A method for extracting manganese from low-grade rhodochrosite, characterized in that, Extraction was performed as follows: Low-grade rhodochrosite was dried, pulverized, and sieved, then mixed evenly with the flux described in claim 1. Under inert gas protection, the mixture was heated to 165°C at a rate of 15–20°C / min in a tube furnace and roasted at a constant temperature for 5–10 min. The temperature was then increased to 245°C at a rate of 10–15°C / min and roasted at a constant temperature for 5–10 min. After roasting, the temperature was increased to 620°C at a rate of 20–25°C / min and roasted at a constant temperature for 10–20 min. After roasting, the mixture was naturally cooled to room temperature. Deionized water was added to leach manganese sulfate from the roasted sample at room temperature. The mixture was filtered and separated. The filtrate was purified by graded purification to remove impurities. Ammonium bicarbonate was added to convert manganese sulfate into manganese carbonate. The mixture was filtered, washed with deionized water, and calcined at high temperature to obtain manganese tetroxide. The manganese tetroxide was pulverized or sand-milled, washed with deionized water, and dried to obtain high-purity manganese tetroxide.

3. The method for extracting manganese from low-grade rhodochrosite according to claim 2, characterized in that: Low-grade rhodochrosite is dried at 100–110°C.

4. The method for extracting manganese from low-grade rhodochrosite according to claim 3, characterized in that: The dried low-grade rhodochrosite is crushed into particles with a diameter ≤75μm.

5. The method for extracting manganese from low-grade rhodochrosite according to any one of claims 2-4, characterized in that: The mass ratio of rhodochrosite powder to flux is 2 to 3:

1.

6. The method for extracting manganese from low-grade rhodochrosite according to claim 5, characterized in that: The inert gas is nitrogen, and the flow rate is 1.5–2.5 L / min.

7. The method for extracting manganese from low-grade rhodochrosite according to claim 6, characterized in that: The amount of deionized water added is 8 to 12 times the mass of low-grade rhodochrosite, and the leaching time is 50 to 70 minutes.

8. The method for extracting manganese from low-grade rhodochrosite according to claim 7, characterized in that: The steps for filtrate classification, purification, and impurity removal are as follows: add manganese powder to the filtrate, react at room temperature, and filter; add ammonium sulfide to the filtrate, react at room temperature, and filter; add flocculant to the filtrate, precipitate, and filter; add ammonia water to the filtrate to adjust the pH to 6-7, add citric acid, react at room temperature, and filter to obtain the purified liquid.