Method for producing manganese sulfate through low-temperature roasting and water leaching of manganese alloy slag

Abstract

The invention discloses a method for producing manganese sulfate by low-temperature roasting and water leaching of manganese alloy slag, which is characterized by comprising the following steps of: drying, crushing and screening the manganese alloy slag, uniformly mixing the manganese alloy slag with a flux according to a mass ratio of (2.5-4.5): 1, heating to 80 DEG C in a tubular furnace under the protection of inert gas, roasting at constant temperature, heating to 280 DEG C, roasting at constant temperature, heating to 630 DEG C, cooling to the room temperature, cooling to the room temperature, cooling to the room temperature, cooling to the room temperature, cooling to the room temperature, cooling to the room temperature, cooling to the room temperature, cooling to the room temperature, and and after roasting is completed, natural cooling is conducted to the room temperature, deionized water is added, manganese sulfate is leached from a roasted sample at the room temperature, filtering separation is conducted, and high-purity manganese sulfate is obtained after classified purification and impurity removal are conducted on filtrate. According to the method, hydrazine hydrate is added into ammonium sulfate, high-valence manganese in the manganese alloy slag is converted into low-valence manganese under the protection of inert gas, and the extraction rate of manganese in the manganese alloy slag is increased.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metallurgy, and particularly relates to a method for producing manganese sulfate by low-temperature roasting and water leaching of manganese alloy slag. BACKGROUND

[0002] In industrial production, a large amount of manganese slag is generated in the smelting process of manganese alloy. According to statistics, about 3 tons of manganese alloy slag are generated on average for every ton of manganese alloy smelted. If these manganese alloy slags are not reasonably treated, they will pose a serious threat to the environment. At present, most enterprises treat manganese alloy slags by simply stacking them. This method not only occupies a large amount of land resources, increases the land acquisition and site disposal costs of enterprises, but also may cause potential harm to the surrounding environment. Manganese alloy slags contain various heavy metal elements such as manganese, iron, silicon, etc. Long-term stacking may cause these harmful substances to enter surface water and groundwater through rainwater erosion or penetration, polluting water resources. In addition, the accumulation of manganese alloy slags may block river channels, affecting the normal operation of water systems, and even causing damage to the balance of the surrounding ecological system.

[0003] The content of manganese in manganese alloy slag is usually between 5% and 20%. Due to the large production and high treatment cost of manganese alloy slag, its resource utilization and manganese extraction have become the focus of the industry. At present, the technologies for extracting manganese from manganese alloy slag mainly include physical beneficiation method and chemical method. The physical beneficiation method separates manganese-iron particles in manganese alloy slag through magnetic separation, gravity separation, etc. The method is simple in process and low in cost, and is suitable for treating manganese alloy slag with large particle size and high manganese content. However, due to the fine particle size of manganese-iron particles in manganese alloy slag, the enrichment ratio of the physical beneficiation method is limited, and the extraction efficiency is low. The chemical method includes acid leaching method, oxidation-reduction method, electrochemical method, etc. Among them, the acid leaching method reacts acid with manganese alloy slag to dissolve manganese and separate it from other impurities, and then recovers manganese through precipitation or extraction, etc. The acid leaching method can treat fine-grained manganese alloy slag and has high extraction efficiency, and is the most commonly used method for extracting manganese at present, but the cost is high and the treatment of acid-containing filtrate is difficult. SUMMARY

[0004] 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 producing manganese sulfate by low-temperature roasting and water leaching of manganese alloy slag. The yield of recovered manganese is high, the purity is high, and the operation is simple.

[0005] To achieve the above-mentioned first purpose, the present application provides the following technical solution: a flux, characterized by being composed of 92% ammonium sulfate and 8% hydrazine hydrate.

[0006] The second object of the present application is achieved by a method for producing manganese sulfate by low-temperature roasting and water leaching of manganese alloy slag, characterized in that the following steps are performed: the manganese alloy slag is dried and crushed, and then sieved and mixed with the flux in a mass ratio of 2.5-4.5:1, heated to 80℃ at a rate of 5-10℃ / min in a tube furnace under inert gas protection, kept at a constant temperature for 5-10 min, heated to 280℃ at a rate of 15-20℃ / min, kept at a constant temperature for 5-10 min, then heated to 630℃ at a rate of 20-25℃ / min, kept at a constant temperature for 15-20 min, and then naturally cooled to room temperature, deionized water is added to leach manganese sulfate from the roasted sample at room temperature, the filtrate is separated by filtration, and the filtrate is purified by fractional purification to obtain high-purity manganese sulfate.

[0007] In the above scheme, the manganese alloy slag is dried at 100-110℃, and the dried manganese alloy slag is crushed to a particle size of ≤75μm. The crushed manganese alloy slag is sieved through a 200-mesh sieve.

[0008] In the above scheme, the inert gas is nitrogen, and the flow rate is 1.0-2.0L / min.

[0009] In the above scheme, the amount of deionized water added is 8-12 times the mass of the manganese alloy slag, and the leaching time is 50-70 min.

[0010] In the above scheme, the step of fractional purification of the filtrate to remove impurities is as follows: manganese powder is added to the filtrate, and the mixture is reacted at room temperature, and then filtered; ammonium sulfide is added to the filtrate, and the mixture is reacted at room temperature, and then filtered, a flocculating agent is added to the filtrate, and the mixture is precipitated and filtered; ammonia water is added to the filtrate to adjust the pH to 6-7, and citric acid is added, and the mixture is reacted at room temperature, and then filtered to obtain a purified solution.

[0011] In the above scheme, the amount of manganese powder added is 2‰-3‰ of the mass of the manganese alloy slag; the amount of ammonium sulfide added is 1‰-2‰ of the mass of the manganese alloy slag; the flocculating agent is polyacrylamide, and the amount added is 1‰-2‰ of the mass of the manganese alloy slag; and the amount of citric acid added is 1.5‰-2‰.

[0012] The addition of manganese powder reduces the trace amounts of metal ions such as lead, iron, cobalt, nickel, copper, and zinc remaining in the crude manganese sulfate solution (filtrate) to metal, and the metal ions are separated by filtration; the addition of ammonium sulfide further removes the trace amounts of metal ions remaining in the filtrate; the addition of polyacrylamide to the filtrate removes the trace amounts of aluminum and silicon remaining in the filtrate; and the addition of citric acid to the filtrate allows the trace amounts of magnesium ions remaining in the solution to be complexed with the citric acid, and the magnesium ions are removed in the subsequent ammonium bicarbonate precipitation process.

[0013] The mixed flux of ammonium sulfate and hydrazine hydrate is used in the present application. Hydrazine hydrate starts to decompose obviously at 50℃ or above. The decomposition rate increases rapidly with the increase of temperature. When the temperature exceeds 110℃, the decomposition is violent and explosive. Therefore, the initial temperature of the present application is controlled at 80℃. At this temperature, hydrazine hydrate is decomposed to release NH3, H2 and N2 under the protection of inert gas. H2 has reducing property and can reduce a small amount of high-valence manganese in the manganese alloy slag into divalent manganese. At the same time, a large amount of gas generated flows in the roasting material, which reduces the mass transfer and heat transfer resistance in the roasting process. Then the temperature is increased, and hydrazine hydrate is gradually decomposed. When the temperature increases to 280℃, ammonium sulfate starts to decompose to generate a large amount of ammonia and ammonium bisulfate. Ammonium bisulfate continues to decompose to generate ammonia and sulfuric acid vapor, so that the manganese in the manganese alloy slag starts to be sulfated to generate water-soluble manganese sulfate. Other metal elements in the manganese alloy slag also undergo sulfation reaction to generate corresponding sulfates. When the temperature is continuously increased to 630℃, iron sulfate and nickel sulfate start to decompose. Iron sulfate can be almost completely decomposed to generate iron oxide, and nickel sulfate can be partially decomposed into nickel oxide, while manganese sulfate does not decompose and stably exists in the roasting material. After roasting is completed, the temperature is cooled to room temperature, and deionized water is used for complete leaching. Calcium sulfate, barium sulfate, lead sulfate and part of the metal oxides formed by decomposition are retained in the leaching residue, so that a large amount of impurity elements are separated from manganese sulfate in the roasting stage.

[0014] Advantages:

[0015] (1) The present application converts high-valence manganese in the manganese alloy slag into low-valence manganese by adding hydrazine hydrate in ammonium sulfate under the protection of inert gas, thereby improving the extraction rate of manganese in the manganese alloy slag.

[0016] (2) The present application realizes energy saving and consumption reduction by low-temperature roasting and water leaching treatment of the manganese alloy slag, and prolongs the service life of the equipment.

[0017] (3) Compared with the prior art of single ammonium sulfate roasting and leaching, the present application not only reduces the consumption of ammonium sulfate by several times, but also increases the leaching rate of manganese in the manganese alloy slag from 85% to 98.9% or above. The recovery rate is 98.5% or above. DETAILED DESCRIPTION

[0018] The present application will be further described below in combination with examples.

[0019] Example 1

[0020] The manganese alloy slag is taken from a smelting plant in Chongqing, and the main chemical composition is: manganese 10.2%, magnesium 3.6%, iron 2.8%, aluminum 6.5%, calcium 25.7%, silicon 17.2%, and trace amounts of heavy metal elements such as zinc, copper, nickel, and lead. The manganese alloy slag is coarsely crushed and dried at a temperature of 100-110°C to a constant weight, and then further crushed to a particle size of ≤75μm and sieved through a 200-mesh sieve to obtain a manganese alloy slag sample. 100g of the sample and 30g of a mixed flux (mass ratio of 92% ammonium sulfate and 8% hydrazine hydrate) are accurately weighed and mixed uniformly, and then roasted in a tube furnace under protection of nitrogen gas at a flow rate of 1.8L / min. The roasting program is as follows: temperature is raised to 80°C at a rate of 5°C / min, and then held at this temperature for 10min; temperature is raised to 280°C at a rate of 20°C / min, and then held at this temperature for 8min; temperature is then raised to 630°C at a rate of 25°C / min, and then held at this temperature for 20min; after roasting is completed, the sample is naturally cooled to room temperature; 1000g of deionized water is added at room temperature and leached for 60min; the crude manganese sulfate solution is obtained by filtration separation; 0.28g of metallic manganese powder is added to the crude manganese sulfate solution, and the mixture is reacted at room temperature for 30min; the mixture is filtered, and 0.15g of ammonium sulfide is added to the filtrate, which is reacted at room temperature for 15min; the mixture is filtered, and 0.2g of flocculating agent polyacrylamide is added to the filtrate, which is reacted for 30min; the mixture is precipitated and filtered; ammonia water is added to the filtrate to adjust the pH value to 6.5, and 0.15g of citric acid is added to the mixture, which is reacted at room temperature; the purified solution is obtained by filtration separation. The leaching rate of manganese in the manganese alloy slag is 99.12%, and the manganese sulfate is converted into manganese carbonate by adding ammonium bicarbonate; the mixture is washed with deionized water for 3 times, and then calcined at a high temperature of 940°C to obtain trimanganese tetraoxide; the trimanganese tetraoxide is crushed or sand-ground, washed with deionized water for 3 times, and then dried to obtain high-purity trimanganese tetraoxide. The recovery rate of manganese in the low-grade rhodochrosite is 98.92%, and the purity of the trimanganese tetraoxide is 99.79%.

[0021] Example 2

[0022] The manganese alloy slag is taken from a smelting plant in Chongqing, and the main chemical composition is: manganese 10.2%, magnesium 3.6%, iron 2.8%, aluminum 6.5%, calcium 25.7%, silicon 17.2%, and trace amounts of heavy metal elements such as zinc, copper, nickel, and lead. The manganese alloy slag is coarsely crushed and dried at a temperature of 100-110°C to a constant weight, and then further crushed to a particle size of ≤75μm and sieved through a 100-mesh sieve to obtain a manganese alloy slag sample. 100g of the sample and 40g of a mixed flux (mass ratio of 92% ammonium sulfate and 8% hydrazine hydrate) are accurately weighed and mixed uniformly, and then roasted in a tube furnace under protection of nitrogen gas at a flow rate of 2L / min. The roasting program is as follows: temperature is raised to 80°C at a rate of 10°C / min, and then held at this temperature for 10min; temperature is raised to 280°C at a rate of 15°C / min, and then held at this temperature for 10min; temperature is then raised to 630°C at a rate of 20°C / min, and then held at this temperature for 15min; after roasting is completed, the sample is naturally cooled to room temperature, 1200g of deionized water is added and soaked at room temperature for 50min, and then filtered to obtain a crude manganese sulfate solution. 0.3g of metallic manganese powder is added to the crude manganese sulfate solution, and the mixture is reacted at room temperature for 30min, filtered, and then 0.1g of ammonium sulfide is added to the filtrate, which is reacted at room temperature for 15min, filtered, and then 0.2g of a flocculating agent, polyacrylamide, is added to the filtrate, which is reacted for 30min, precipitated, and filtered. Ammonia water is added to the filtrate to adjust the pH value to 6.7, and then 0.2g of citric acid is added, and the mixture is reacted at room temperature, filtered, and then a purified solution is obtained. The leaching rate of manganese in the manganese alloy slag is 98.90%, and the manganese sulfate is converted into manganese carbonate by adding ammonium bicarbonate, washed with deionized water for 5 times, calcined at a high temperature of 940°C to obtain trimanganese tetraoxide, and then crushed or sand-milled, washed with deionized water for 5 times, and dried to obtain high-purity trimanganese tetraoxide. The recovery rate of manganese in the low-grade rhodochrosite is 98.65%, and the purity of the trimanganese tetraoxide is 99.76%.

[0023] Example 3

[0024] The manganese alloy slag is taken from a smelting plant in Chongqing, and the main chemical composition is: manganese 10.2%, magnesium 3.6%, iron 2.8%, aluminum 6.5%, calcium 25.7%, silicon 17.2%, and trace amounts of heavy metal elements such as zinc, copper, nickel, and lead. After coarse crushing, the manganese alloy slag is dried to constant weight at a temperature of 110°C, and then further crushed to a particle size of ≤75μm and sieved through a 200-mesh sieve to obtain a manganese alloy slag sample. Accurately weigh 100g of the sample and 22g of a mixed flux (mass ratio of 92% ammonium sulfate and 8% hydrazine hydrate) and mix uniformly, then perform roasting in a tube furnace under nitrogen protection, with a nitrogen flow rate of 2L / min. The roasting program is as follows: heat to 80°C at a rate of 5°C / min, constant temperature roasting for 5min; heat to 280°C at a rate of 20°C / min, constant temperature roasting for 6min, then heat to 630°C at a rate of 25°C / min, constant temperature roasting for 20min, and after roasting is completed, naturally cool to room temperature, add 800g of deionized water and soak at room temperature for 70min, filter to separate to obtain a crude manganese sulfate solution, add 0.2g of metallic manganese powder to the crude manganese sulfate solution, react at room temperature for 30min, filter, add 0.2g of ammonium sulfide to the filtrate, react at room temperature for 15min, filter, add 0.2g of flocculating agent polyacrylamide to the filtrate, react for 30min, precipitate and filter; add ammonia water to the filtrate to adjust the pH value to 7, add 0.15g of citric acid and react at room temperature, filter to separate to obtain a purified solution. The leaching rate of manganese in the manganese alloy slag is 99.15%

[0025] The manganese sulfate is converted into manganese carbonate by adding ammonium bicarbonate, washed with deionized water for 3 times, calcined at a high temperature of 936°C to obtain trimanganese tetraoxide, and after crushing or sand grinding, washed with deionized water for 3 times, and dried to obtain high-purity trimanganese tetraoxide. The recovery rate of manganese in the low-grade rhodochrosite is 99.01%, and the purity of the trimanganese tetraoxide is 99.8%.

[0026] 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 these 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 92% ammonium sulfate and 8% hydrazine hydrate.

2. A method for producing manganese sulfate by low-temperature roasting and water leaching of manganese alloy slag, characterized in that, The following steps were performed: the manganese alloy slag was dried, pulverized, and sieved, then mixed with the flux at a mass ratio of 2.5–4.5:

1. Under inert gas protection, the mixture was heated to 80°C at a rate of 5–10°C / min in a tube furnace and calcined at a constant temperature for 5–10 min. The temperature was then increased to 280°C at a rate of 15–20°C / min and calcined at a constant temperature for 5–10 min. Finally, the temperature was increased to 630°C at a rate of 20–25°C / min and calcined at a constant temperature for 15–20 min. After calcination, the mixture was allowed to cool naturally to room temperature. Deionized water was added, and manganese sulfate was leached from the calcined sample at room temperature. The mixture was filtered and separated. The filtrate was then purified by grade to remove impurities, yielding high-purity manganese sulfate.

3. The method for producing manganese sulfate by low-temperature roasting and water leaching of manganese alloy slag according to claim 2, characterized in that: The manganese alloy slag is dried at 100-110℃, and the dried manganese alloy slag is crushed into particles with a diameter ≤75μm.

4. The method for producing manganese sulfate by low-temperature roasting and water leaching of manganese alloy slag according to claim 3, characterized in that: The inert gas is nitrogen, and the flow rate is 1.0 to 2.0 L / min.

5. The method for producing manganese sulfate by low-temperature roasting and water leaching of manganese alloy slag according to any one of claims 2-4, characterized in that: The amount of deionized water added is 8 to 12 times the mass of the manganese alloy slag, and the leaching time is 50 to 70 minutes.

6. The method for producing manganese sulfate by low-temperature roasting and water leaching of manganese alloy slag according to claim 2, 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.

7. The method for producing manganese sulfate by low-temperature roasting and water leaching of manganese alloy slag according to claim 6, characterized in that: The amount of metallic manganese powder added is 2‰ to 3‰ of the manganese alloy slag; the amount of ammonium sulfide added is 1‰ to 2‰ of the manganese alloy slag by mass. The flocculant is polyacrylamide, and the amount added is 1‰ to 2‰ of the manganese alloy slag by mass. The amount of citric acid added is 1.5‰ to 2‰.