Method for extracting manganese from soft manganese ore by ammonium sulfate composite molten salt reduction roasting

Abstract

The application discloses a method for extracting manganese from soft manganese ore by ammonium sulfate composite molten salt reduction roasting, which comprises the following steps: drying and crushing the soft manganese ore, screening, mixing the screened soft manganese ore with flux, uniformly mixing, heating to 200 DEG C in a tube furnace under inert gas protection, constant temperature roasting, heating to 280 DEG C, constant temperature roasting, then heating to 605 DEG C, constant temperature roasting, naturally cooling to room temperature after roasting, taking out the roasting slag sample, adding deionized water to leach manganese sulfate at room temperature, filtering and separating, obtaining manganese sulfate crude liquid and leaching residue, grading and purifying the manganese sulfate crude liquid to remove impurities, converting the manganese sulfate into manganese carbonate by adopting a carbonate precipitation method, high-temperature calcination, and obtaining solid-state trimanganese tetraoxide. The method realizes efficient sulfation of MnO2 under inert gas protection by using a pyrogenic flux, forms soluble MnSO4, realizes water leaching of manganese from the roasting slag, and realizes a technical breakthrough in efficient extraction of manganese from the soft manganese ore.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, specifically to a method for extracting manganese from pyrolusite by reduction roasting with ammonium sulfate composite molten salt. Background Technology

[0002] Pyrolusite, a high-manganese mineral with strong oxidizing properties, occupies an irreplaceable core position in the modern industrial system. It is not only a key raw material supporting the new energy battery revolution and providing a core guarantee for improving the energy density of power batteries, but also an indispensable source of alloying elements in high-end steel smelting, significantly enhancing the strength, toughness, and corrosion resistance of steel. Simultaneously, in the field of environmental technology, pyrolusite, due to its strong oxidizing properties, plays a vital role in wastewater treatment, exhaust gas purification, and soil remediation, serving as a cornerstone mineral for promoting green industrial development.

[0003] my country's manganese resources are mainly composed of pyrolusite, but these resources generally suffer from high processing difficulty and high mining costs. On the one hand, pyrolusite has a dense mineral structure, with manganese existing stably in the form of high-valence oxides, making efficient leaching difficult using conventional methods. On the other hand, domestic pyrolusite resources are scattered, with a high proportion of low-grade ore. How to improve the utilization rate of pyrolusite and reduce overall production costs under existing resource conditions has become a key issue for the sustainable development of my country's manganese industry.

[0004] Currently, the technological routes for extracting manganese from pyrolusite in China are showing a diversified development trend, mainly including the two-ore reduction leaching method, SO2 gas reduction method, pre-reduction method, direct acid leaching method, and ferrous sulfate reduction leaching method. The two-ore reduction leaching method achieves manganese reduction leaching by synergistic reaction between pyrolusite and sulfur-containing minerals, which has advantages in comprehensive resource utilization. The SO2 gas reduction method utilizes the reducing properties of gas to react directly with manganese ore, resulting in a relatively fast reaction rate. The pre-reduction method lowers the valence state of manganese through pretreatment, creating favorable conditions for subsequent leaching. The direct acid leaching method is relatively simple and has low cost in processing specific minerals. The ferrous sulfate reduction leaching method, due to the high availability of reducing agents, is widely used in small and medium-sized production. These technological routes each have their own focus on cost control and resource utilization efficiency, providing diversified options for processing different types of pyrolusite.

[0005] However, these extraction methods still face numerous challenges in actual production. Technically, some processes suffer from unstable leaching rates and demanding reaction conditions, requiring further parameter optimization to improve stability. Environmentally, the waste acid and residue generated by liquid-phase reactions, as well as potential tail gas pollution during gas reduction, place higher demands on pollution control technologies. Economically, high reagent consumption and energy costs put some processes at a disadvantage in market competition. Facing these challenges, breakthroughs in the core technologies for efficient extraction of pyrolusite and the construction of a complete industrial chain recycling system can not only significantly enhance my country's manganese resource self-sufficiency and reduce dependence on imports, but also promote the green and efficient transformation of the manganese industry. This is of vital strategic significance for ensuring my country's manganese resource security and supporting the development of new energy and high-end manufacturing industries. Summary of the Invention

[0006] To address the aforementioned technical problems, the first objective of this invention is to provide a flux, and the second objective is to provide a method for extracting manganese from pyrolusite by reducing roasting with ammonium sulfate composite molten salt. This method utilizes a pyrometallurgical flux to efficiently sulfatize MnO2 under inert gas protection to form soluble MnSO4, thereby achieving water leaching extraction of manganese from roasting slag and realizing a technological breakthrough in the efficient extraction of manganese from pyrolusite.

[0007] To achieve the aforementioned first objective, the present invention provides the following technical solution: a flux, characterized in that it is composed of 65% ammonium sulfate and 35% ammonium oxalate.

[0008] The second objective of this invention is achieved as follows: a method for extracting manganese from pyrolusite by reduction roasting with ammonium sulfate composite molten salt, characterized by the following steps: pyrolusite is dried, pulverized, and sieved, then mixed uniformly with the flux at a mass ratio of 1.5–2.5:1. Under inert gas protection, the mixture is heated to 200°C at a rate of 15–20°C / min in a tube furnace, roasted at a constant temperature for 5–10 min, then heated to 280°C at a rate of 10–15°C / min, roasted at a constant temperature for 5–10 min, then heated to 605°C at a rate of 20–25°C / min, roasted at a constant temperature for 10–20 min, and after roasting, naturally cooled to room temperature. The roasting residue sample is taken out, and deionized water is added to leach manganese sulfate at room temperature. The mixture is filtered and separated to obtain crude manganese sulfate solution and leaching residue. The crude manganese sulfate solution is purified by fractionation to remove impurities, and manganese sulfate is converted to manganese carbonate by carbonate precipitation. The manganese is then calcined at high temperature to obtain solid manganese tetroxide.

[0009] In the above scheme: the pyrolusite is dried at 100-110℃, and the dried pyrolusite is crushed into particles with a diameter ≤75μm.

[0010] In the above scheme: the inert gas is nitrogen, and the flow rate is 1.5 to 2.5 L / min.

[0011] In the above scheme: the amount of deionized water added is 8 to 12 times the mass of pyrolusite, and the leaching time is 50 to 70 minutes.

[0012] In the above scheme, the steps for graded purification and impurity removal of crude manganese sulfate solution are as follows: Add metallic manganese powder to the crude manganese sulfate solution, 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 solution. Adding metallic manganese powder reduces residual trace metal ions such as lead, iron, cobalt, nickel, copper, and zinc in the crude manganese sulfate solution to metals, which are then separated by filtration; adding ammonium sulfide to the filtrate further removes residual trace metal ions; adding polyacrylamide to the filtrate removes residual aluminum and silicon; adding citric acid to the filtrate allows residual magnesium ions in the solution to combine with the citric acid, which is then removed during the subsequent ammonium bicarbonate precipitation process.

[0013] The amount of manganese powder added is 2‰ to 3‰ of the mass of pyrolusite powder; the amount of ammonium sulfide added is 1‰ to 2‰ of the mass of pyrolusite powder. The flocculant is polyacrylamide, and the amount added is 1‰ to 2‰ of the mass of pyrolusite powder. The amount of citric acid added is 1.5‰ to 2‰.

[0014] In this invention, ammonium oxalate in the ammonium sulfate composite flux begins to lose its water of crystallization at 70-100℃, gradually transforming into anhydrous ammonium oxalate. When the temperature rises to 160℃, the anhydrous ammonium oxalate begins to decompose and release gases, the products being NH3, CO, N2, and CO2. When the temperature reaches 200℃, the decomposition of anhydrous ammonium oxalate intensifies, and the gaseous products gradually increase. Among them, the CO and NH3 generated, which have reducing properties, gradually reduce MnO2 in pyrolusite to low-valence manganese (+2 valence). This invention controls the initial reaction temperature at 200℃. Ammonium sulfate decomposes at 280℃ to produce a large amount of ammonia and ammonium bisulfate. Ammonium bisulfate continues to decompose to produce ammonia and sulfuric acid vapor, thereby causing sulfation reactions of various metal elements in pyrolusite, including manganese. It is worth noting that at excessively high temperatures (320℃), the rate at which sulfuric acid gradually decomposes to form sulfur trioxide accelerates, slowing down the sulfation reaction process. To enhance the sulfation reaction process, this invention controls the intermediate sulfation reaction temperature at 280℃. When the reaction temperature reaches 605℃, some other metal sulfates (ferric sulfate, nickel sulfate, etc.) begin to decompose to form water-insoluble oxides, while manganese sulfate, calcium sulfate, lead sulfate, and barium sulfate remain stable. Calcium sulfate, lead sulfate, and barium sulfate are insoluble in water, while manganese sulfate is soluble. Therefore, this invention controls the later-stage roasting temperature to 605℃. Leaching manganese sulfate with deionized water removes most of the metallic impurities during the roasting stage, providing a good foundation for further impurity removal to prepare high-purity manganese sulfate. Further impurity removal ultimately yields high-purity manganese tetroxide.

[0015] Beneficial effects:

[0016] (1) The present invention strengthens the reducing atmosphere by using inert gas to protect the roasting process, which greatly reduces the consumption of ammonium sulfate composite flux and improves the reduction efficiency of high-valence manganese to low-valence manganese.

[0017] (2) The low-temperature roasting process proposed in this invention, combined with water immersion treatment to extract manganese, reduces energy consumption and extends the service life of the equipment, which is a green and environmentally friendly process.

[0018] (3) The present invention completes the removal of a large number of impurities in manganese sulfate during the roasting stage, especially solving the problem of removing impurity iron, and reducing the pressure of subsequent manganese sulfate purification and impurity removal.

[0019] (4) Compared with the prior art, the present invention improves the sulfation efficiency in the roasting stage, so that the recovery rate of manganese in pyrolusite is above 98.59%. Detailed Implementation

[0020] The present invention will be further described below with reference to embodiments.

[0021] Example 1

[0022] The pyrolusite ore (containing 52.64% MnO2) was obtained from a smelter in Guizhou Province. The pyrolusite ore was dried at 105±5℃, pulverized, and sieved to a particle size ≤75μm (200 mesh sieve) to obtain a pyrolusite sample. 100g of the sample was mixed evenly with 62g of a composite flux consisting of 65% ammonium sulfate and 35% ammonium oxalate. The mixture was then subjected to staged roasting in a tube furnace under nitrogen protection at a nitrogen flow rate of 2.2L / min. The first stage roasting involved heating to 200℃ at a rate of 20℃ / min and maintaining that temperature for 10min; the second stage roasting involved heating to 280℃ at a rate of 10℃ / min and maintaining that temperature for 8min; and the third stage roasting involved heating to 605℃ at a rate of 25℃ / min and maintaining that temperature for 15min. After roasting, the mixture was allowed to cool naturally to room temperature. The roasted residue sample was then removed, and 1L of deionized water was added for leaching at room temperature for 60min. The residue was then filtered to obtain crude manganese sulfate solution and leaching residue. Add 0.3g 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 0.1g of flocculant polyacrylamide to the filtrate, react for 30min, precipitate, filter; add ammonia water to the filtrate to adjust the pH to 6.3, add 0.2g of citric acid, react at room temperature, filter and separate to obtain the purified solution.

[0023] Manganese sulfate was converted to manganese carbonate by adding ammonium bicarbonate via carbonate precipitation. The manganese was washed five times with deionized water and then calcined at 965℃ to obtain solid manganese tetroxide. After crushing or sand milling, it was washed three times with deionized water and dried to obtain high-purity manganese tetroxide. The manganese recovery rate in pyrolusite was 98.59%, and the purity of manganese tetroxide was 99.77%.

[0024] Example 2

[0025] The pyrolusite ore (containing 60.16% MnO2) was obtained from a smelter in Guizhou Province. The pyrolusite ore was dried at 105℃, pulverized, and sieved to a particle size ≤75μm (passing through a 200-mesh sieve) to obtain a pyrolusite sample. 100g of the sample was mixed evenly with 67g of a composite flux consisting of 65% ammonium sulfate and 35% ammonium oxalate. The mixture was then subjected to staged roasting in a tube furnace under nitrogen protection at a nitrogen flow rate of 2.5L / min. The first stage roasting involved heating to 200℃ at a rate of 15℃ / min and maintaining that temperature for 5min; the second stage roasting involved heating to 280℃ at a rate of 15℃ / min and maintaining that temperature for 10min; and the third stage roasting involved heating to 605℃ at a rate of 20℃ / min and maintaining that temperature for 20min. After roasting, the mixture was allowed to cool naturally to room temperature. The roasted residue sample was then removed, and 1.2L of deionized water was added for leaching at room temperature for 50min. The residue was then filtered to obtain crude manganese sulfate solution and leaching residue. Add 0.28g of metallic manganese powder to the crude manganese sulfate solution, react at room temperature for 30min, filter, add 0.16g of ammonium sulfide to the filtrate, react at room temperature for 15min, filter, add 0.12g of flocculant polyacrylamide to the filtrate, react for 30min, precipitate, filter; add ammonia water to the filtrate to adjust the pH to 6.7, add 0.16g of citric acid, react at room temperature, filter and separate to obtain the purified solution.

[0026] Manganese sulfate was converted to manganese carbonate by adding ammonium bicarbonate via carbonate precipitation. The manganese was washed four times with deionized water and then calcined at 890℃ to obtain solid manganese tetroxide. After crushing or sand milling, it was washed three times with deionized water and dried to obtain high-purity manganese tetroxide. The manganese recovery rate in pyrolusite was 98.78%, and the purity of manganese tetroxide was 98.85%.

[0027] Example 3

[0028] The pyrolusite ore (containing 49.21% MnO2) was obtained from a smelter in Guizhou Province. The pyrolusite ore was dried at 105℃, pulverized, and sieved to a particle size ≤75μm to obtain a pyrolusite sample. 100g of the sample was mixed evenly with 40g of a composite flux consisting of 65% ammonium sulfate and 35% ammonium oxalate. The mixture was then staged roasted in a tube furnace under nitrogen protection at a nitrogen flow rate of 1.5L / min. The first stage roasting involved heating to 200℃ at a rate of 20℃ / min and maintaining that temperature for 7 min; the second stage roasting involved heating to 280℃ at a rate of 10℃ / min and maintaining that temperature for 5 min; and the third stage roasting involved heating to 605℃ at a rate of 25℃ / min and maintaining that temperature for 13 min. After roasting, the mixture was allowed to cool naturally to room temperature. The roasted residue sample was then removed, and 0.8L of deionized water was added for leaching at room temperature for 70 min. The residue was then filtered to obtain crude manganese sulfate solution and leaching residue. Add 0.3g 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 0.1g of flocculant polyacrylamide to the filtrate, react for 30min, precipitate, filter; add ammonia water to the filtrate to adjust the pH to 6.8, add 0.2g of citric acid, react at room temperature, filter and separate to obtain the purified solution.

[0029] Manganese sulfate was converted to manganese carbonate by adding ammonium bicarbonate via carbonate precipitation. The manganese was washed three times with deionized water and then calcined at 920℃ to obtain solid manganese tetroxide. After crushing or sand milling, it was washed four times with deionized water and dried to obtain high-purity manganese tetroxide. The manganese recovery rate in pyrolusite was 98.61%, and the purity of manganese tetroxide was 99.53%.

[0030] This invention is not limited to the above embodiments. Those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this invention. The scope of this invention is defined by the claims and their equivalents.

Claims

1. A method for extracting manganese from pyrolusite by reduction roasting with ammonium sulfate composite molten salt, characterized in that, Extraction was carried out according to the following steps: Pyrolusite was dried, pulverized, and sieved, then mixed with a flux at a mass ratio of 1.5–2.5:

1. The flux consisted of 65% ammonium sulfate and 35% ammonium oxalate. Under inert gas protection, the temperature was raised to 200°C at a rate of 15–20°C / min in a tube furnace and roasted at a constant temperature for 5–10 min. Then, the temperature was raised to 280°C at a rate of 10–15°C / min and roasted at a constant temperature for 5–10 min. Finally, the temperature was raised to 605°C at a rate of 20–25°C / min and roasted at a constant temperature for 10–20 min. After roasting, the mixture was allowed to cool naturally to room temperature. The roasted residue sample was removed, and deionized water was added to leach manganese sulfate at room temperature. The residue was filtered and separated to obtain crude manganese sulfate solution and leaching residue. The crude manganese sulfate solution was purified by fractionation to remove impurities. The manganese sulfate solution was converted to manganese carbonate by carbonate precipitation and then calcined at high temperature to obtain solid manganese tetroxide.

2. The method for extracting manganese from pyrolusite by reduction roasting with ammonium sulfate composite molten salt according to claim 1, characterized in that: The pyrolusite was dried at 100–110℃, and the dried pyrolusite was crushed into particles with a diameter ≤75 μm.

3. The method for extracting manganese from pyrolusite by reduction roasting with ammonium sulfate composite molten salt according to claim 2, characterized in that: The inert gas is nitrogen, and the flow rate is 1.5–2.5 L / min.

4. The method for extracting manganese from pyrolusite by reduction roasting with ammonium sulfate composite molten salt according to claim 3, characterized in that: The amount of deionized water added is 8 to 12 times the mass of pyrolusite, and the leaching time is 50 to 70 minutes.

5. The method for extracting manganese from pyrolusite by reduction roasting with ammonium sulfate composite molten salt according to claim 4, characterized in that, The steps for grading, purifying, and removing impurities from crude manganese sulfate solution are as follows: add metallic manganese powder to the crude manganese sulfate solution, 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 separate and obtain the purified solution.