Simultaneous reduction roasting-selective oxidation-magnetic separation method for refractory iron-manganese ores

Abstract

This invention provides a method for simultaneous reduction roasting-selective oxidation-magnetic separation of refractory iron-manganese ore, belonging to the field of refractory iron-manganese ore beneficiation technology. The method includes the following steps: (1) feeding and grinding; (2) drying and dispersing; (3) fluidized bed simultaneous reduction roasting; (4) cooling and selective oxidation; and (5) high-efficiency magnetic separation to obtain iron concentrate and manganese concentrate products. The simultaneous reduction roasting process of introducing air first and then H2 during the reduction stage, and the selective oxidation process of introducing air during the cooling stage, enable precise phase control of the simultaneous reduction and cooling oxidation processes of refractory iron-manganese ore. Furthermore, this invention is a green and low-carbon production process for preparing iron and manganese concentrates, which is more efficient, cleaner, and environmentally friendly.

Description

Technical Field

[0001] This invention belongs to the field of beneficiation technology for refractory iron-manganese ore, specifically relating to a method for simultaneous reduction roasting, selective oxidation, and magnetic separation of refractory iron-manganese ore. Background Technology

[0002] Iron and manganese are essential raw materials in industrial production and strategic national reserves. Manganese plays a crucial role in steel production, serving as a key alloying element, desulfurizer, and deoxidizer, with over 90% of its annual production used in the steel industry. The remainder is used in dry-cell batteries, chemical products, and electronic materials, vital to the national economy. Currently, manganese oxide, manganese carbonate, and manganese sulfide ores are the main industrial applications. However, with China's rapid growth in manganese demand, reserves of rich manganese ore (TMn > 35 wt%) are declining sharply. Iron-manganese ore is a low-manganese ore containing both iron and manganese, with iron content typically between 10% and 40%, while manganese content is relatively low, usually between 10% and 20%. Effective utilization of iron-manganese ore can simultaneously yield iron and manganese concentrates, which is significant for alleviating the supply and demand imbalance of iron and manganese resources and achieving efficient and clean resource utilization.

[0003] Iron-manganese ores are characterized by high gangue content and complex ore composition and mineral phase structure, making it difficult to achieve good technical and economic results using traditional beneficiation methods. Currently, manganese ore processing mainly includes conventional beneficiation, chemical beneficiation, carbothermal reduction, and microwave reduction. These methods can improve separation indicators, but they suffer from low beneficiation efficiency, complex process conditions, and significant environmental hazards. Research indicates that a hydrogen-based mineral phase transformation technology based on fluidized bed roasting offers advantages such as uniform heating, high reduction rate, and environmental friendliness. This process utilizes clean energy hydrogen as a reducing agent, reducing weakly magnetic minerals to strongly magnetic minerals through suspension, followed by magnetic separation. The cooling process of the high-temperature roasting products has a significant impact on process indicators. Current industrial cooling methods mainly rely on water-sealed cooling, but this method generates a large amount of dust and has low waste heat recovery efficiency, limiting its application in arid regions. In contrast, air cooling offers advantages in terms of environmental protection and energy conservation. Research has found that when the roasting products of iron-manganese ore are cooled in air, the resulting magnetite (Fe3O4) is oxidized to maghemite (γ-Fe2O3). This process effectively reduces magnetic agglomeration, making the separation of manganese and iron more efficient. Summary of the Invention

[0004] To address the problems existing in the processing of refractory iron-manganese ore, this invention employs a simultaneous reduction roasting technique where air is introduced first and then H2 is introduced during the reduction stage, and a selective oxidation technique where air is introduced during the cooling stage. This enables precise phase control of the dehydration, simultaneous reduction, and cooling oxidation processes of refractory iron-manganese ore.

[0005] This invention provides a method for simultaneous reduction roasting, selective oxidation, and magnetic separation of refractory iron-manganese ore. The method includes the following steps:

[0006] (1) Feeding and grinding operations:

[0007] The difficult-to-process iron-manganese ore is crushed and ground into powder;

[0008] (2) Drying and breaking up:

[0009] Drying, dispersing, and dehydrating powdered ore under air atmosphere;

[0010] (3) Fluidized simultaneous reduction calcination:

[0011] First, the powdered ore is preheated and roasted in air to dehydrate it. Then, it is suspended and magnetized in a mixed atmosphere of H2 and N2. By controlling the reduction reaction conditions, hematite (α-Fe2O3) and pyrolusite (MnO2) in the powdered ore are simultaneously reduced and precisely converted to obtain magnetite (Fe3O4) and rhodochrosite (MnO) reduction products.

[0012] (4) Cooling selective oxidation:

[0013] The reduction product is first cooled by N2 and then cooled by air. The oxidation time is controlled, magnetite (Fe3O4) is selectively oxidized, and the magnetite (γ-Fe2O3) is precisely converted. After the oxidation is completed, N2 is introduced to cool it to room temperature to obtain the cooled product.

[0014] (5) High-efficiency magnetic separation:

[0015] The cooled product is further ground and then separated by efficient magnetic separation equipment to obtain iron concentrate and manganese concentrate products.

[0016] Furthermore, in step (1), the refractory iron-manganese ore has a TFe grade of 35.36%-45.54% and a TMn grade of 11.20%-19.77%.

[0017] Further, in step (1), the refractory iron-manganese ore is ground to -0.074mm with a particle size of ≥70% using a ball mill.

[0018] Furthermore, the chemical reaction principle of step (3) is as follows:

[0019] 3α-Fe2O3(s)+H2(g)=2Fe3O4(s)+H2O(g)

[0020] 2MnO2(s)+H2(g)=Mn2O3(s)+H2O(g)

[0021] 3Mn2O3(s)+H2(g)=2Mn3O4(s)+H2O(g)

[0022] Mn3O4(s)+H2(g)=3MnO(s)+H2O(g)

[0023] Furthermore, in step (3), the temperature for preheating and roasting the ore powder is 200℃-450℃, and the time is 1min-3min.

[0024] Furthermore, the reduction reaction temperature in step (3) is 500℃-700℃, the volume concentration of H2 in the H2 and N2 mixture is 10%-40%, and the reaction time is 15min-60min.

[0025] Furthermore, the chemical reaction principle of step (4) is as follows:

[0026] 4Fe3O4(s)+O2(g)=6γ-Fe2O3(s)

[0027] Furthermore, in step (4), the reduction product is cooled to 100℃-300℃ in N2 and the air-cooled oxidation time is 5min-10min.

[0028] Furthermore, the cooled product from step (5) is further crushed to complete dissociation using a ball mill.

[0029] Furthermore, in step (5), the high-efficiency magnetic separation equipment is a weak magnetic separator with a magnetic field strength of 1000 Oe-1300 Oe.

[0030] Furthermore, the recovery rates of TFe were 80.81%–98.17%, and those of TMn were 81.47%–91.38%.

[0031] An application of a fluidized bed reduction calcination-selective oxidation-high-efficiency magnetic separation method for refractory iron-manganese ore is disclosed, which is used to separate iron concentrate and manganese concentrate products from refractory iron-manganese ore, wherein the Fe grade of the iron concentrate product is >55% and the Mn grade of the manganese concentrate product is >30%.

[0032] In the cooling stage of this invention, air is used to selectively oxidize the reduction products, wherein a small amount of rhodochrosite (MnO) is oxidized to malachite (Mn3O4) and leucite (Mn2O3). The chemical reaction principle is as follows:

[0033] 6MnO(s) + O2(g) = 2Mn3O4(s)

[0034] 4Mn3O4(s) + O2(g) = 6Mn2O3(s)

[0035] Advantages and effects of the present invention:

[0036] 1. Using H2 as a reducing gas to process refractory iron-manganese ore is a green and low-carbon production method for preparing iron concentrate and manganese concentrate products from refractory iron-manganese ore. Compared with traditional wet reduction and pyrometallurgical processes, the reduction reaction involved in this invention does not produce greenhouse gases, so this technology is effective in reducing carbon emissions.

[0037] 2. In the cooling stage, the present invention uses air cooling, which can efficiently recover waste heat, save water resources, and reduce dust generated during cooling compared to water cooling. Compared to nitrogen cooling, air cooling can precisely control phase transformation to further optimize subsequent sorting indicators. Moreover, after air cooling, the mineral structure is more porous, which can further reduce the energy consumption of subsequent grinding.

[0038] 3. This invention innovatively introduces fluidized bed roasting technology into the roasting process of refractory iron-manganese ore, achieving accurate control of roasting atmosphere and roasting temperature. Compared with other processes, fluidized bed roasting process has high thermal efficiency, low energy consumption, significantly reduced natural gas consumption, smaller required air volume and generated flue gas volume, and lower flue gas temperature, which has a significant effect on reducing carbon emissions.

[0039] 4. This invention employs a simultaneous reduction roasting process where air is introduced first and then H2 during the reduction stage, and a selective oxidation process where air is introduced during the cooling stage. This allows for precise phase control during the simultaneous reduction and cooling oxidation processes of refractory iron-manganese ores. The precise conversion of magnetite (Fe3O4) and maghemite (γ-Fe2O3) can further optimize subsequent magnetic separation indicators. The maghemite formed during the cooling stage has strong magnetism and low residual magnetism, which can reduce magnetic agglomeration and gangue mineral inclusions, making magnetic separation more efficient. The precise conversion of rhodochrosite (MnO) can reduce the formation of high-valence manganese oxides and reduce the impact on subsequent manganese mineral leaching. This treatment method is more efficient, cleaner, and environmentally friendly based on further optimization of separation indicators. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the fluidized bed reduction roasting-selective oxidation-high-efficiency magnetic separation method for difficult-to-process iron-manganese ore according to the present invention. Detailed Implementation

[0041] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. It should be noted that the embodiments described in this invention are only for further explanation and illustration, and not for limiting their scope of application. All other embodiments obtained by those skilled in the art based on this invention without inventive effort are within the protection scope of this invention.

[0042] like Figure 1As shown, the present invention discloses a method for simultaneous reduction roasting-selective oxidation-magnetic separation of refractory iron-manganese ore. This method comprises four stages: the first stage is the ore processing stage, in which the refractory iron-manganese ore is ground, dried, and dispersed; the second stage is the fluidized bed simultaneous reduction stage, in which the powdered ore is preheated in air to remove adsorbed water, and then hematite and pyrolusite are simultaneously reduced under a mixture of H2 and N2 gas, so that hematite (α-Fe2O3) is precisely converted into magnetite (Fe3O4) and pyrolusite (MnO2) is precisely converted into rhodochrosite (MnO); the third stage is cooling selective oxidation. The process involves several stages: First, the reduction product is cooled by N2, then cooled by air. The newly formed magnetite (Fe3O4) is re-oxidized to maghemite (γ-Fe2O3). The fourth stage is a high-efficiency magnetic separation stage: grinding and magnetic separation further refines the cooled product until complete dissociation. Magnetic separation yields iron and manganese concentrates. This method achieves precise control of the mineral phases in the dehydration, reduction, and selective oxidation processes of refractory iron-manganese ore through stepwise feeding of the system atmosphere (air, H2, N2, and air). It also features low energy consumption, high resource utilization, waste heat recovery, and water conservation, achieving the goal of efficiently and greenly recovering iron and manganese resources from refractory iron-manganese ore.

[0043] The following embodiments employ a simultaneous reduction roasting-selective oxidation-magnetic separation method for refractory iron-manganese ore, comprising the following steps:

[0044] (1) Feeding and grinding operation: Feed the raw ore into the ball mill and grind it to meet the feed particle size;

[0045] (2) Drying and Dispersing: The iron-manganese ore grinding product is first preliminarily dried in the drying and dispersing machine to remove moisture from the material. Then the dried material is dispersed and discharged by a dispersing device installed at the discharge port;

[0046] (3) Fluidized synchronous reduction roasting: The dispersed material enters the phase conversion roasting furnace of the reduction roasting system; the preheating temperature of the powder is controlled at 200℃-450℃, the atmosphere is air, and the time is 1min-3min; the temperature inside the phase conversion roasting furnace is controlled at 500℃-700℃, and a mixture of H2 and N2 gas is introduced. The iron and manganese mineral material in the furnace cavity is fluidized under the action of the bottom airflow; the volume concentration of reducing gas H2 is controlled at 10%-40%, and the reduction time is 15min-60min. After the powdered ore reacts in this equipment, magnetite and rhodochrosite with stable properties are obtained. After the reaction is completed, the reduction product enters the cooling selective oxidation stage.

[0047] (4) Cooling selective oxidation: After the reduction product enters the cooling control stage, N2 is introduced into the cooling furnace to cool it down. The furnace temperature is controlled at a specified temperature of 100℃-300℃ and then air-cooled. The iron-manganese ore reduction product undergoes selective oxidation, and the oxidation time is (5min-10min). After the oxidation is completed, N2 is introduced to cool it to room temperature to obtain the cooled product.

[0048] (5) High-efficiency magnetic separation: The cooled product is finely ground in a ball mill until the minerals are completely dissociated, and then separated by magnetic separation to obtain iron concentrate and manganese concentrate products.

[0049] Example 1

[0050] This embodiment uses iron-manganese ore from a certain location with a TFe grade of 42.26% and a TMn grade of 17.86% as raw material, and the specific steps are as follows:

[0051] (1) Feeding and grinding operation: The raw ore is fed into the ball mill and ground to -0.074mm with a proportion of ≥70%, and then enters the drying and dispersing operation;

[0052] (2) Drying and dispersing: The iron-manganese ore grinding product is dried in a drying and dispersing machine to remove the moisture from the material;

[0053] (3) Fluidized synchronous reduction roasting: The dispersed material enters the roasting furnace of the fluidized reduction roasting system. The preheating temperature of the powder is controlled at 200℃, the atmosphere is air and the time is 3min. The temperature inside the furnace cavity of the mineral phase transformation roasting furnace is controlled at 500℃. N2 is introduced into the furnace cavity for 5min to exhaust the air inside the furnace. Then, a mixture of H2 and N2 is introduced. The iron and manganese mineral material in the furnace cavity is fluidized under the action of the bottom airflow. The concentration of reducing gas H2 is controlled at 20% and the reduction time is 25min. After the powdered ore is reacted in this equipment, magnetite and rhodochrosite with stable properties are obtained. After the reaction is completed, the reduction product enters the cooling and regulation stage.

[0054] (4) Cooling selective oxidation: After the reduction product enters the cooling control stage, N2 is introduced into the cooling furnace for 5 minutes to control the furnace temperature at the specified temperature of 200℃ and then air cooling is performed. The iron-manganese ore reduction product undergoes selective oxidation for 5 minutes. After oxidation, N2 is introduced to cool to room temperature to obtain the cooled product.

[0055] (5) High-efficiency magnetic separation: After the cooled product is finely ground in a ball mill until the minerals are completely liberated, it is separated by a weak magnetic separator at a magnetic field strength of 1000 Oe to obtain iron concentrate and manganese concentrate products. Finally, an iron concentrate product with Fe grade of 69.66% and TFe recovery rate of 98.17% and a manganese concentrate product with Mn grade of 51.60% and TMn recovery rate of 88.48% are obtained.

[0056] Example 2

[0057] This embodiment uses iron-manganese ore from a certain location with a TFe grade of 35.36% and a TMn grade of 19.77% as raw material, and the specific steps are as follows:

[0058] (1) Feeding and grinding operation: The raw ore is fed into the ball mill and ground to -0.074mm with a proportion of ≥70%, and then enters the drying and dispersing operation;

[0059] (2) Drying and dispersing: The iron-manganese ore grinding product is dried in a drying and dispersing machine to remove the moisture from the material;

[0060] (3) Fluidized synchronous reduction roasting: The dispersed material enters the roasting furnace of the fluidized reduction roasting system. The preheating temperature of the powder is controlled at 300℃, the atmosphere is air and the time is 2min. The temperature inside the furnace cavity of the mineral phase transformation roasting furnace is controlled at 560℃. N2 is introduced into the furnace cavity for 5min to exhaust the air inside the furnace. Then, a mixture of H2 and N2 is introduced. The iron and manganese mineral material in the furnace cavity is fluidized under the action of the bottom airflow. The concentration of reducing gas H2 is controlled at 40% and the reduction time is 30min. After the powdered ore is reacted in this equipment, magnetite and rhodochrosite with stable properties are obtained. After the reaction is completed, the reduction product enters the cooling and regulation stage.

[0061] (4) Cooling selective oxidation: After the reduction product enters the cooling control stage, N2 is introduced into the cooling furnace for 5 minutes to control the furnace temperature at the specified temperature of 200℃ and then air cooling is performed. The iron-manganese ore reduction product undergoes selective oxidation for 5 minutes. After oxidation, N2 is introduced to cool to room temperature to obtain the cooled product.

[0062] (5) High-efficiency magnetic separation: After the cooled product is finely ground in a ball mill until the minerals are completely liberated, it is separated by a weak magnetic separator at a magnetic field strength of 1100 Oe to obtain iron concentrate and manganese concentrate products. Finally, an iron concentrate product with Fe grade of 64.07% and TFe recovery rate of 94.59% and a manganese concentrate product with Mn grade of 51.69% and TMn recovery rate of 87.81% are obtained.

[0063] Example 3

[0064] This embodiment uses a certain iron ore with a TFe grade of 43.72% and a TMn grade of 11.20% as raw material, and is carried out according to the following steps:

[0065] (1) Feeding and grinding operation: The raw ore is fed into the ball mill and ground to -0.074mm with a proportion of ≥70%, and then enters the drying and dispersing operation;

[0066] (2) Drying and dispersing: The iron-manganese ore grinding product is dried in a drying and dispersing machine to remove the moisture from the material;

[0067] (3) Fluidized synchronous reduction roasting: The dispersed material enters the roasting furnace of the fluidized reduction roasting system. The preheating temperature of the powder is controlled at 400℃, the atmosphere is air and the time is 1min. The temperature inside the furnace cavity of the mineral phase transformation roasting furnace is controlled at 520℃. N2 is introduced into the furnace cavity for 5min to exhaust the air inside the furnace. Then, a mixture of H2 and N2 is introduced. The iron and manganese mineral material in the furnace cavity is fluidized under the action of the bottom airflow. The H2 concentration of the reducing gas is controlled at 25% and the reduction time is 20min. After the powdered ore is reacted in this equipment, magnetite and rhodochrosite with stable properties are obtained. After the reaction is completed, the reduction product enters the cooling and control stage.

[0068] (4) Cooling selective oxidation: After the reduction product enters the cooling control stage, N2 is introduced into the cooling furnace for 5 minutes to control the furnace temperature at the specified temperature of 100℃ and then air cooling is performed. The iron-manganese ore reduction product undergoes selective oxidation for 5 minutes. After oxidation, N2 is introduced to cool to room temperature to obtain the cooled product.

[0069] (5) High-efficiency magnetic separation: After the cooled product is finely ground in a ball mill until the minerals are completely liberated, it is separated by a weak magnetic separator at a magnetic field strength of 1150 Oe to obtain iron concentrate and manganese concentrate products. Finally, an iron concentrate product with Fe grade of 67.38% and TFe recovery rate of 87.14% and a manganese concentrate product with Mn grade of 30.51% and TMn recovery rate of 87.02% are obtained.

[0070] Example 4

[0071] This embodiment uses iron-manganese ore from a certain location with a TFe grade of 45.54% and a TMn grade of 16.86% as raw material, and the specific steps are as follows:

[0072] (1) Feeding and grinding operation: The raw ore is fed into the ball mill and ground to -0.074mm with a proportion of ≥70%, and then enters the drying and dispersing operation;

[0073] (2) Drying and dispersing: The iron-manganese ore grinding product is dried in a drying and dispersing machine to remove the moisture from the material;

[0074] (3) Fluidized synchronous reduction roasting: The dispersed material enters the roasting furnace of the fluidized reduction roasting system. The preheating temperature of the powder is controlled at 450℃, the atmosphere is air and the time is 1min. The temperature inside the furnace cavity of the mineral phase transformation roasting furnace is controlled at 570℃. N2 is introduced into the furnace cavity for 5min to exhaust the air inside the furnace. Then, a mixture of H2 and N2 is introduced. The iron and manganese mineral material in the furnace cavity is fluidized under the action of the bottom airflow. The concentration of reducing gas H2 is controlled at 20% and the reduction time is 15min. After the powdered ore is reacted in this equipment, magnetite and rhodochrosite with stable properties are obtained. After the reaction is completed, the reduction product enters the cooling and control stage.

[0075] (4) Cooling selective oxidation: After the reduction product enters the cooling control stage, N2 is introduced into the cooling furnace for 5 minutes to control the furnace temperature at the specified temperature of 200℃ and then air cooling is performed. The iron-manganese ore reduction product undergoes selective oxidation for 8 minutes. After oxidation, N2 is introduced to cool to room temperature to obtain the cooled product.

[0076] (5) High-efficiency magnetic separation: After the cooled product is finely ground in a ball mill until the minerals are completely liberated, it is separated by a weak magnetic separator at a magnetic field strength of 1200 Oe to obtain iron concentrate and manganese concentrate products. Finally, an iron concentrate product with Fe grade of 69.73% and TFe recovery rate of 93.44% and a manganese concentrate product with Mn grade of 48.30% and TMn recovery rate of 91.38% are obtained.

[0077] Example 5

[0078] This embodiment uses a certain iron manganese ore with a TFe grade of 37.82% and a TMn grade of 18.80% as raw material, and is carried out according to the following steps:

[0079] (1) Feeding and grinding operation: The raw ore is fed into the ball mill and ground to -0.074mm with a proportion of ≥70%, and then enters the drying and dispersing operation;

[0080] (2) Drying and dispersing: The iron-manganese ore grinding product is dried in a drying and dispersing machine to remove the moisture from the material;

[0081] (3) Fluidized synchronous reduction roasting: The dispersed material enters the roasting furnace of the fluidized reduction roasting system. The preheating temperature of the powder is controlled at 380℃, the atmosphere is air and the time is 2min. The temperature inside the furnace cavity of the mineral phase transformation roasting furnace is controlled at 700℃. N2 is introduced into the furnace cavity for 5min to exhaust the air inside the furnace. Then, a mixture of H2 and N2 is introduced. The iron and manganese mineral material in the furnace cavity is fluidized under the action of the bottom airflow. The concentration of reducing gas H2 is controlled at 10% and the reduction time is 60min. After the powdered ore is reacted in this equipment, magnetite and rhodochrosite with stable properties are obtained. After the reaction is completed, the reduction product enters the cooling and regulation stage.

[0082] (4) Cooling selective oxidation: After the reduction product enters the cooling control stage, N2 is introduced into the cooling furnace for 5 minutes to control the furnace temperature at the specified temperature of 300℃ and then air cooling is performed. The iron-manganese ore reduction product undergoes selective oxidation for 10 minutes. After oxidation, N2 is introduced to cool to room temperature to obtain the cooled product.

[0083] (5) High-efficiency magnetic separation: After the cooled product is finely ground in a ball mill until the minerals are completely liberated, it is separated by a weak magnetic separator at a magnetic field strength of 1300 Oe to obtain iron concentrate and manganese concentrate products. Finally, an iron concentrate product with Fe grade of 55.50% and TFe recovery rate of 80.81% and a manganese concentrate product with Mn grade of 44.55% and TMn recovery rate of 81.47% are obtained.

[0084] Comparative Example 1

[0085] This comparative example uses iron-manganese ore from a certain location with a TFe grade of 42.26% and a TMn grade of 17.86% as raw material, and the specific steps are as follows:

[0086] (1) Feeding and grinding operation: The raw ore is fed into the ball mill and ground to -0.074mm with a proportion of ≥70%, and then enters the drying and dispersing operation;

[0087] (2) Drying and dispersing: The iron-manganese ore grinding product is dried in a drying and dispersing machine to remove the moisture from the material;

[0088] (3) Fluidized synchronous reduction roasting: The dispersed material enters the roasting furnace of the fluidized reduction roasting system. The temperature inside the furnace is controlled at 500℃. N2 is introduced into the furnace for 5 minutes to purge the air inside the furnace. Then, a mixture of H2 and N2 is introduced. The iron and manganese mineral material in the furnace is fluidized under the action of the bottom airflow. The concentration of reducing gas H2 is controlled at 20% and the reduction time is 25 minutes. After the powdered ore has reacted in the equipment, magnetite and rhodochrosite with stable properties are obtained. After the reaction is completed, the reduction product enters the cooling and control stage.

[0089] (4) Water cooling: The reduction product is cooled to room temperature by water cooling to obtain the cooled product;

[0090] (5) High-efficiency magnetic separation: After the cooled product is finely ground in a ball mill until the minerals are completely liberated, it is separated by a weak magnetic separator at a magnetic field strength of 1000 Oe to obtain iron concentrate and manganese concentrate products. Finally, an iron concentrate product with Fe grade of 65.66% and TFe recovery rate of 94.17% and a manganese concentrate product with Mn grade of 49.60% and TMn recovery rate of 84.31% are obtained.

[0091] Compared to Example 1, the separation indicators decreased. The Fe grade of the iron concentrate decreased by 6.09%, the TFe recovery rate decreased by 4.25%, the Mn grade of the manganese concentrate decreased by 4.03%, and the TMn recovery rate decreased by 4.95%. The possible reasons are that during the magnetic separation process, the strongly magnetic iron minerals exhibit magnetic agglomeration, which leads to the inclusion of certain manganese minerals in the iron ore, thus affecting the separation of iron and manganese. In addition, compared to Example 1, water cooling wastes more water resources and generates a large amount of dust, which is not easy to implement in water-scarce areas.

[0092] Comparative Example 2

[0093] This comparative example uses iron-manganese ore from a certain location with a TFe grade of 42.26% and a TMn grade of 17.86% as raw material, and the specific steps are as follows:

[0094] (1) Feeding and grinding operation: The raw ore is fed into the ball mill and ground to -0.074mm with a proportion of ≥70%, and then enters the drying and dispersing operation;

[0095] (2) Drying and dispersing: The iron-manganese ore grinding product is dried in a drying and dispersing machine to remove the moisture from the material;

[0096] (3) Fluidized synchronous reduction roasting: The dispersed material enters the roasting furnace of the fluidized reduction roasting system. The temperature inside the furnace is controlled at 500℃. N2 is introduced into the furnace for 5 minutes to purge the air inside the furnace. Then, a mixture of H2 and N2 is introduced. The iron and manganese mineral material in the furnace is fluidized under the action of the bottom airflow. The concentration of reducing gas H2 is controlled at 20% and the reduction time is 25 minutes. After the powdered ore has reacted in the equipment, magnetite and rhodochrosite with stable properties are obtained. After the reaction is completed, the reduction product enters the cooling and control stage.

[0097] (4) N2 cooling: The reduction product N2 is cooled to room temperature to obtain the cooled product;

[0098] (5) High-efficiency magnetic separation: After the cooled product is finely ground in a ball mill until the minerals are completely liberated, it is separated by a weak magnetic separator at a magnetic field strength of 1000 Oe to obtain iron concentrate and manganese concentrate products. Finally, an iron concentrate product with Fe grade of 68.14% and TFe recovery rate of 97.35% and a manganese concentrate product with Mn grade of 50.12% and TMn recovery rate of 86.52% are obtained.

[0099] Compared to Example 1, the separation indicators decreased slightly. The Fe grade of the iron concentrate decreased by 2.23%, the TFe recovery rate decreased by 0.84%, the Mn grade of the manganese concentrate decreased by 2.95%, and the TMn recovery rate decreased by 2.27%. The possible reason is that during the magnetic separation process, the strong magnetic iron minerals exhibit magnetic agglomeration, which leads to the inclusion of certain manganese minerals in the iron ore, thus affecting the separation of iron and manganese. After air cooling, some magnetite will be precisely converted into maghemite, which reduces the magnetic hysteresis phenomenon to a certain extent, thereby reducing the magnetic agglomeration phenomenon and further improving the separation indicators.

Claims

1. A method for simultaneous reduction roasting-selective oxidation-magnetic separation of refractory iron-manganese ore, characterized in that, Includes the following steps: (1) Ore feeding and grinding operations: The difficult-to-process iron-manganese ore is crushed and ground into powder; (2) Drying and breaking up: Drying, dispersing, and dehydrating powdered ore under air atmosphere; (3) Fluidized bed simultaneous reduction roasting: First, the powdered ore is preheated and roasted in air to dehydrate it. The preheating and roasting temperature is 200℃-450℃ and the time is 1min-3min. Then, it is suspended and magnetized roasted in a mixed atmosphere of H2 and N2. The volume concentration of H2 in the H2 and N2 mixture is 10%-40%. By controlling the reduction reaction conditions, the hematite α-Fe2O3 and pyrolusite MnO2 in the powdered ore are simultaneously reduced and precisely converted to obtain magnetite Fe3O4 and rhodochrosite MnO reduction products. (4) Cooling selective oxidation: The reduction product is first cooled to 100℃-300℃ in N2, and then cooled in air. The oxidation time is controlled to be 5min-10min. Magnetite Fe3O4 is selectively oxidized and precisely converted to obtain magnetite γ-Fe2O3. After the oxidation is completed, N2 is introduced to cool to room temperature to obtain the cooled product. (5) High-efficiency magnetic separation: The cooled product is further ground and then separated by efficient magnetic separation equipment to obtain iron concentrate and manganese concentrate products.

2. The method for simultaneous reduction roasting-selective oxidation-magnetic separation of refractory iron-manganese ore as described in claim 1, characterized in that, Step (1) The TFe grade in the refractory iron-manganese ore is 35.36%-45.54%, and the TMn grade is 11.20%-19.77%.

3. The method for simultaneous reduction roasting-selective oxidation-magnetic separation of refractory iron-manganese ore as described in claim 1, characterized in that, Step (1) Grind the refractory iron-manganese ore to -0.074mm with a particle size of ≥70% using a ball mill.

4. The method for simultaneous reduction roasting-selective oxidation-magnetic separation of refractory iron-manganese ore as described in claim 1, characterized in that, Step (3) The reduction reaction temperature is 500℃-700℃ and the reaction time is 15min-60min.

5. The method for simultaneous reduction roasting-selective oxidation-magnetic separation of refractory iron-manganese ore as described in claim 1, characterized in that, The cooled product from step (5) was further crushed to complete dissociation using a ball mill.

6. The method for simultaneous reduction roasting-selective oxidation-magnetic separation of refractory iron-manganese ore as described in claim 1, characterized in that, Step (5) The high-efficiency magnetic separation equipment is a weak magnetic separator with a magnetic field strength of 10000Oe-13000Oe.

7. The method for simultaneous reduction roasting-selective oxidation-magnetic separation of refractory iron-manganese ore as described in claim 2, characterized in that, The Fe grade of the iron concentrate is 55.50%-69.73%, and the TFe recovery rate is 80.81%-98.17%. The Mn grade of the manganese concentrate is 30.51%-51.69%, and the TMn recovery rate is 81.47%-91.38%.

8. An application of the simultaneous reduction roasting-selective oxidation-magnetic separation method for refractory iron-manganese ore as described in claim 1, characterized in that, Used for separating iron and manganese concentrates from refractory iron-manganese ores, wherein the Fe grade of the iron concentrate is >55% and the Mn grade of the manganese concentrate is >30%.

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