Method for preparing reduced iron powder from hydrometallurgy hematite slag

Abstract

The present invention belongs to the technical field of chemical metallurgy, and relates to a method for preparing a reduced iron powder from hydrometallurgy hematite slag. The present invention comprises: crushing hydrometallurgy hematite slag, then uniformly mixing the crushed hydrometallurgy hematite slag with a carbonaceous reducing agent and an activating agent, and subjecting the mixture to a deoxidation and impurity removal reaction under conditions of 800-1300°C, a mass ratio of carbon / iron being 0.6-1.2 and the reaction time being 1-4 h; and finely grinding the impurity-removed product, then subjecting same to magnetic separation, subjecting the obtained magnetic product to deep impurity removal at 700-1050°C by using hydrogen, and after the reaction is finished, subjecting same to rapid cooling by using nitrogen protection, so as to obtain the reduced iron powder. The present method can effectively remove impurity components in hydrometallurgy hematite slag, and the produced reduced iron powder is high quality, and has a fine granularity, a narrow distribution and a good reaction activity.

Description

A method for preparing reduced iron powder from hematite slag using hydrometallurgical processes Technical Field

[0001] This invention relates to a method for preparing reduced iron powder from hematite slag in hydrometallurgical processes, belonging to the field of materials and chemical engineering technology. Background Technology

[0002] The hematite process for iron removal in hydrometallurgical processes involving zinc and nickel is an advanced technology for iron removal. Its principle involves oxidizing, hydrolyzing, crystallizing, and precipitating ferrous ions in a zinc sulfate and nickel sulfate solution containing ferrous sulfate under high temperature and pressure to obtain Fe₂O₃. The iron removal product from this hematite process is called hematite slag. Due to the influence of various sulfates such as zinc sulfate and nickel sulfate coexisting in the solution during the oxidation, hydrolysis, crystallization, and precipitation of the produced ferrous ions, the hematite slag contains certain impurities in addition to ferric oxide. Typical hematite slag composition includes Fe₂O₃ 70%–90%, ZnSO₄ 1%–6%, NiSO₄ 0.2%–2.5%, CaSO₄ 0.5%–5%, S 3%–8%, Mn 0.2%–1%, P ≤ 0.5%, and the remainder mainly water of crystallization.

[0003] Currently, high-quality hematite slag can be used as a raw material for cement, ceramics, and iron smelting. However, due to the high impurity content and low iron content of industrially produced hematite slag, it is difficult to utilize it for high-value purposes. Therefore, how to efficiently remove impurities from hematite slag, how to improve the iron content of hematite slag, and how to prepare hematite slag into higher-value products to realize the utilization of iron resources are common technical challenges faced by the hydrometallurgical industry. In existing technologies, such as patent application CN109607622A, a method for preparing iron oxide red products using hematite slag removal in hydrometallurgical zinc smelting is described, including the following steps:

[0004] Step 1: Wash the slag from the wet zinc smelting hematite process with deionized water to remove soluble sulfates and other salts from the slag.

[0005] Step 2: The slag from the wet zinc smelting hematite method after washing in Step 1 is placed in a sulfuric acid solution for high-temperature hydrothermal purification in an acidic solution. This process removes impurities such as potassium ferric sulfate, sodium ferric vanadium, and basic sulfates of zinc and iron. At the same time, the iron ions decomposed from the ferric vanadium are converted into ferric oxide under high temperature and high pressure.

[0006] Step 3: The slag from the wet zinc smelting hematite process, after being purified by high-temperature hydrothermal treatment with acidic solution in Step 2, is then subjected to high-temperature hydrothermal treatment with neutral solution to obtain the iron oxide red product. This technology employs high-temperature and high-pressure acidic leaching purification and neutral high-temperature hydrothermal purification to obtain an iron oxide red product with a ferric oxide content of 95.8~96.7wt% and an Fe content of 67.3~68.1wt%. Technical issues

[0007] Currently, the publicly available technologies for removing impurities from hematite generally include flotation (including direct and reverse flotation), magnetic separation, gravity separation, roasting beneficiation, and the technology described in CN109607622A. However, the existing technologies are either extremely costly or have significant room for improvement in impurity removal efficiency. Moreover, there are few existing records of using hydrometallurgical hematite slag as raw material to prepare reduced iron powder with high iron content and narrow particle size distribution.

[0008] The target of this invention is hematite slag produced during the iron removal process in hydrometallurgical processes of zinc, nickel, and other non-ferrous metals. This slag contains various impurities, including zinc sulfate, nickel sulfate, calcium sulfate, manganese sulfate, sulfate ions in a state combined with oxygen in ferric oxide, and water of crystallization. These impurities exist in the hematite slag in various forms, such as inclusions, encapsulations, complexations, and adsorptions. Existing flotation, magnetic separation, gravity separation, roasting beneficiation, and the methods disclosed in CN109607622A are all insufficient for low-cost and high-efficiency removal of these impurities and preparation of reduced iron powder with a narrow particle size distribution. This makes it difficult to utilize the hematite slag produced during hydrometallurgical iron removal at high value. Technical solutions

[0009] To address the shortcomings of existing methods in effectively removing impurities from hydrometallurgical hematite slag due to its numerous impurity components, complex impurity morphologies, and limited high-value utilization, this invention, based on existing technology, further researches and overcomes key technical challenges to obtain a method for preparing reduced iron powder that achieves thorough impurity component separation, high iron content, and good product quality. This invention is based on this method. The method for preparing reduced iron powder from hydrometallurgical hematite slag includes: pulverizing the hydrometallurgical hematite slag and mixing it uniformly with a carbonaceous reducing agent and an activator; performing a deoxidation and impurity removal reaction at high temperature to efficiently separate components such as zinc, sulfur, and oxygen from the hematite slag; finely grinding the purified product and then magnetically separating it to remove impurities such as calcium oxide, carbon, manganese, and phosphorus; further removing the obtained magnetic product using hydrogen at high temperature to remove participating impurities such as zinc, sulfur, oxygen, and carbon; and finally, rapidly cooling the product under nitrogen protection to obtain reduced iron powder.

[0010] This invention provides a method for preparing reduced iron powder from hydrometallurgical hematite slag. The specific operation process includes: pulverizing the hydrometallurgical hematite slag and mixing it evenly with a carbonaceous reducing agent and an activator, followed by a deoxidation and impurity removal reaction at high temperature. The purified product is then finely ground and magnetically separated. The resulting magnetic product is then subjected to deep impurity removal using hydrogen at high temperature. After the reaction is complete, the mixture is rapidly cooled under nitrogen protection to obtain reduced iron powder. The specific steps are as follows:

[0011] (1) High-temperature deoxidation and impurity removal: The crushed hematite slag is mixed evenly with carbonaceous reducing agent and activator, and high-temperature deoxidation and impurity removal is carried out under the conditions of 800~1300℃, carbon / iron mass ratio of 0.6~1.2, and reaction time of 30min~210min; the activator is calcium oxide and / or strong calcium oxide, and the amount of activator added is 1~5% of the weight of hematite slag;

[0012] (2) Fine grinding and magnetic separation: The impurity-removed product produced in step (1) is finely ground to a particle size ≤74μm and then magnetically separated to obtain magnetic products.

[0013] (3) Deep purification: The magnetic product from step (2) is subjected to deep purification using hydrogen at 700~1050℃. After the reaction is completed, nitrogen is used for rapid cooling to obtain reduced iron powder. The rapid cooling rate is 5-10℃ / min.

[0014] The optimized hematite slag in the hydrometallurgical process comprises hematite slag produced by removing iron from non-ferrous metal hydrometallurgical solutions such as zinc and nickel using the hematite method. Its main chemical components, by mass percentage, include: Fe₂O₃ 70%~90%, ZnSO₄ 1%~6%, NiSO₄ 0.2%~2.5%, CaSO₄ 0.5%~5%, and S 3%~8%. More preferably, the main chemical components of the hematite slag in the hydrometallurgical process are: Fe₂O₃ 70%~90%, ZnSO₄ 1%~6%, NiSO₄ 0.2%~2.5%, CaSO₄ 0.5%~5%, S 3%~8%, Mn 0.2%~1%, P ≤0.5%, with the remainder being mainly water of crystallization.

[0015] The particle size of hydrometallurgical hematite slag is less than or equal to 74 micrometers.

[0016] In the optimized step (1), the carbonaceous reducing agent used for high-temperature deoxidation and impurity removal is one or more of coke powder, anthracite, and reducing coal, and the activator is quicklime or limestone powder. The amount of activator added is 1-5% of the weight of hematite slag, preferably 2%-3%.

[0017] The temperature for controlling step (1) of this invention, high-temperature deoxidation and impurity removal, is 800~1300℃, preferably 900~1150℃, and more preferably 1000~1100℃. This is because under these conditions, the removal efficiency of impurities such as zinc, sulfur, and oxygen is high, energy consumption is low, and operating costs are relatively suitable. Although excessively high temperatures can improve the removal efficiency of impurities, they will lead to increased energy consumption and higher operating costs. Excessively low temperatures will result in poorer removal of impurities, or even failure to remove impurities, leading to a deterioration in the quality of reduced iron powder.

[0018] The optimized magnetic field strength of the magnetic separation process in step (2) is 500~1200 Gs.

[0019] The optimized reaction time for deep impurity removal in step (3) is 1 to 4 hours.

[0020] The temperature for deep impurity removal in step (3) of this invention is 700~1100℃, preferably 850~1000℃, because at this temperature, the removal efficiency of impurities such as zinc, oxygen, and carbon is high, the iron powder does not stick together, has good dispersion, low energy consumption, and suitable operating costs. If the temperature is too high, the iron powder will stick together, the dispersion will be poor, and the energy consumption and operating costs will increase. If the temperature is too low, the removal efficiency of impurities will be poor, and the quality of the reduced iron powder will be poor.

[0021] The relative amount of hydrogen used should be controlled at 50~150 Nm. 3 The recommended dosage of / t-iron powder is high because this dosage results in high impurity removal efficiency and a suitable operating cost. Insufficient hydrogen will lead to low impurity removal efficiency and poor quality reduced iron powder. The hydrogen flow rate is controlled at 0.2-1.0 m / min because this flow rate ensures high impurity removal efficiency and high hydrogen utilization efficiency. Too low a flow rate will result in low impurity removal efficiency, while too high a flow rate will result in low hydrogen utilization. Furthermore, this flow rate, combined with the appropriate temperature for deep purification, allows for a narrower particle size distribution in the product.

[0022] Furthermore, the chemical composition of the reduced iron powder produced by this invention is: MFe≥90%, Zn≤0.3%, Ni≤0.6%, S≤0.5%, CaO≤0.5%, Mn≤0.2%, Cr≤0.1%, P≤0.03%, with the remainder being mainly oxygen and carbon.

[0023] The reduced iron powder obtained by this invention has a narrow particle size distribution range, D 90 It can be controlled to be 58 micrometers or less. Beneficial effects

[0024] (1) This invention can effectively remove various impurity components from hematite slag in hydrometallurgical processes. By using multiple process steps and reaction principles, the impurity components such as zinc sulfate, calcium sulfate, and manganese sulfate in hematite slag are removed step by step to achieve deep removal. The resulting reduced iron powder has high iron content and low impurity content, resulting in high-quality reduced iron powder.

[0025] (2) This invention realizes the high-value utilization of hydrometallurgical hematite slag, and prepares hematite slag with low iron content and high impurity content, which is difficult to utilize as a resource, into high-value reduced iron powder, thereby improving the utilization value of hydrometallurgical hematite slag.

[0026] (3) This invention can be connected with the hematite removal process in hydrometallurgy. The resulting reduced iron powder has fine particle size, narrow distribution, and high reactivity. The quality of the reduced iron powder is good, which can realize the high-value utilization of associated iron in hydrometallurgy. Attached Figure Description

[0027] Figure 1 is a SEM image of the reduced iron powder obtained in Example 3;

[0028] Figure 2 shows the particle size distribution of the reduced iron powder obtained in Example 3.

[0029] As can be seen from Figure 1, the reduced iron obtained by this invention has a large specific surface area and a maximum particle size of less than 75 micrometers.

[0030] As can be seen from Figure 2, the particle size distribution of the product obtained in Example 3 of the present invention is relatively narrow. Embodiments of the present invention

[0031] The present invention will be further described below with reference to specific embodiments.

[0032] Example 1

[0033] A method for preparing reduced iron powder from hematite slag produced by hydrometallurgical iron removal includes the following steps: Hematite slag from zinc hydrometallurgical iron removal is pulverized and mixed evenly with a carbonaceous reducing agent and an activator, followed by a deoxidation and impurity removal reaction at high temperature. The removed product is finely ground and magnetically separated. The resulting magnetic product is then subjected to deep impurity removal using hydrogen at high temperature. After the reaction, the product is rapidly cooled under nitrogen protection to obtain reduced iron powder. The specific steps are as follows: 2.0 kg of hematite slag from zinc hydrometallurgical iron removal is taken. Its chemical composition is: Fe2O3 80%, ZnSO4 2.6%, NiSO4 0.2%, CaSO4 1.8%, S 3.5%, Mn 0.20%, P 0.1%, with the remainder mainly being water of crystallization. The hematite slag was pulverized to a particle size ≤74 micrometers and then thoroughly mixed with 1120g of coke powder (carbon / iron mass ratio 1.0) and 100g of quicklime (activator addition 5%). The mixture was heated to 1000℃ and reacted for 3 hours for high-temperature deoxidation and impurity removal. After cooling to room temperature, the purified product was finely ground to a particle size ≤74 micrometers and then subjected to wet magnetic separation under a magnetic field strength of 800 Gs, yielding 1062g of magnetic product. The magnetic product was then subjected to hydrogen gas at a temperature of 950℃ for 2 hours, a hydrogen flow rate of 0.5 m / min, and a hydrogen consumption of 90 Nm³. 3 The iron powder was reacted with nitrogen gas and rapidly cooled at a rate of 8°C / min to obtain 1035g of reduced iron powder. The chemical composition of the reduced iron powder was: MFe 95.7wt%, Zn 0.21wt%, Ni 0.05wt%, S 0.35wt%, CaO 0.38%, Mn 0.05wt%, Cr 0.03wt%, P 0.001wt%, with the balance being oxygen and carbon.

[0034] The iron recovery rate was 93.8%;

[0035] The D of the obtained reduced iron powder 30 10.5 micrometers, D 50 It is 27.3 micrometers, D 75 43.6 micrometers D 90 It is 52.5 micrometers.

[0036] Example 2

[0037] A method for preparing reduced iron powder from hematite slag produced by hydrometallurgical iron removal includes the following steps: Hematite slag from zinc hydrometallurgical iron removal is pulverized and mixed evenly with a carbonaceous reducing agent and an activator, followed by a deoxidation and impurity removal reaction at high temperature. The removed product is finely ground and magnetically separated. The resulting magnetic product is then subjected to deep impurity removal using hydrogen at high temperature. After the reaction, the product is rapidly cooled under nitrogen protection to obtain reduced iron powder. The specific steps are as follows: 2.0 kg of hematite slag from zinc hydrometallurgical iron removal is taken. Its chemical composition is: Fe₂O₃ 74.2%, ZnSO₄ 3.7%, NiSO₄ 0.3%, CaSO₄ 2.5%, S 4.8%, Mn 0.21%, P 0.10%, with the remainder being mainly water of crystallization. The hematite slag was pulverized to a particle size ≤74 micrometers and then thoroughly mixed with 890.4 g of coke powder (carbon / iron mass ratio of 0.6) and 200 g of quicklime (activator addition of 10%). The mixture was heated to 1100℃ and reacted for 4 hours for high-temperature deoxidation and impurity removal. After cooling to room temperature, the purified product was finely ground to a particle size ≤74 micrometers and then subjected to wet magnetic separation under a magnetic field strength of 600 Gs, yielding 1155 g of magnetic product. The magnetic product was then subjected to hydrogen gas at a temperature of 900℃ for 3 hours, a hydrogen flow rate of 0.8 m / min, and a hydrogen consumption of 150 Nm³. 3 The iron powder was reacted with nitrogen gas and rapidly cooled at a rate of 6°C / min to obtain 1035g of reduced iron powder. The chemical composition of the reduced iron powder was: MFe 96.4wt%, Zn 0.10wt%, Ni 0.04wt%, S 0.31wt%, CaO 0.32%, Mn 0.03wt%, Cr 0.01wt%, P 0.001wt%, with the balance being oxygen and carbon.

[0038] The iron recovery rate was 92.5%;

[0039] The D of the obtained reduced iron powder 30 9.5 micrometers, D 50 25.2 micrometers, D 75 47.3 micrometers D 90 It is 55.7 micrometers.

[0040] Example 3

[0041] A method for preparing reduced iron powder from hematite slag produced by hydrometallurgical iron removal includes the following steps: Hematite slag from zinc hydrometallurgical iron removal is pulverized and mixed evenly with a carbonaceous reducing agent and an activator, followed by a deoxidation and impurity removal reaction at high temperature. The removed product is finely ground and magnetically separated. The resulting magnetic product is then subjected to deep impurity removal using hydrogen gas at high temperature. After the reaction, the product is rapidly cooled under nitrogen protection to obtain reduced iron powder. The specific steps are as follows: 2.0 kg of hematite slag from zinc hydrometallurgical iron removal is taken. Its chemical composition is: Fe2O3 85.7%, ZnSO4 2.1%, NiSO4 0.2%, CaSO4 1.2%, S 3.0%, Mn 0.15%, P 0.06%, with the remainder mainly being water of crystallization. The hematite slag was pulverized to a particle size ≤74 micrometers and then thoroughly mixed with 1129g of anthracite (carbon / iron mass ratio 0.8) and 50g of quicklime (activator addition 2.5%). The mixture was heated to 1050℃ and reacted for 3.5h for high-temperature deoxidation and impurity removal. After cooling to room temperature, the purified product was finely ground to a particle size ≤74 micrometers and then subjected to wet magnetic separation under a magnetic field strength of 1100 Gs, yielding 1261g of magnetic product. The magnetic product was then subjected to hydrogen gas at a temperature of 950℃ for 4h, a hydrogen flow rate of 1 m / min, and a hydrogen consumption of 100 Nm³. 3 The iron powder was reacted with nitrogen gas and rapidly cooled at a rate of 4°C / min to obtain 1215g of reduced iron powder. The chemical composition of the reduced iron powder was: MFe 95.5wt%, Zn 0.11wt%, Ni 0.06wt%, S 0.33wt%, CaO 0.33%, Mn 0.02wt%, Cr 0.01wt%, P 0.001wt%, with the balance being oxygen and carbon.

[0042] The iron recovery rate was 96.7%;

[0043] The D of the obtained reduced iron powder 30 It is 15.93 micrometers, D 50 It is 25.47 micrometers, D 75 37.96 micrometers, D 90 It is 49.00 micrometers.

[0044] Example 4

[0045] A method for preparing reduced iron powder from hematite slag produced by hydrometallurgical iron removal includes the following steps: Hematite slag from nickel hydrometallurgical iron removal is pulverized and mixed evenly with a carbonaceous reducing agent and an activator, followed by a deoxidation and impurity removal reaction at high temperature. The removed product is finely ground and magnetically separated. The resulting magnetic product is then subjected to deep impurity removal using hydrogen at high temperature. After the reaction, the product is rapidly cooled under nitrogen protection to obtain reduced iron powder. The specific steps are as follows: 2.0 kg of hematite slag from nickel hydrometallurgical iron removal is taken. Its chemical composition is: Fe2O3 90%, ZnSO4 0.2%, NiSO4 1.8%, CaSO4 1.1%, S 2.6%, Mn 0.12%, P 0.04%, with the remainder mainly being water of crystallization. The hematite slag was pulverized to a particle size ≤74 micrometers and then thoroughly mixed with 1075g of reducing coal (carbon / iron mass ratio 0.7) and 150g of limestone powder (activator addition 10%). The mixture was heated to 800℃ and reacted for 4 hours for high-temperature deoxidation and impurity removal. After cooling to room temperature, the purified product was finely ground to a particle size ≤74 micrometers and then subjected to wet magnetic separation under a magnetic field strength of 500 Gs, yielding 1245g of magnetic product. The magnetic product was then subjected to hydrogen gas at a temperature of 1000℃ for 4 hours, a hydrogen flow rate of 0.2 m / min, and a hydrogen consumption of 50 Nm³. 3 The iron powder was reacted with nitrogen gas and rapidly cooled at a rate of 4°C / min to obtain 1241g of reduced iron powder. The chemical composition of the reduced iron powder was: MFe 94.2wt%, Zn 0.1wt%, Ni 0.6wt%, S 0.35wt%, CaO 0.32%, Mn 0.01wt%, Cr 0.01wt%, P 0.001wt%, with the balance being oxygen and carbon.

[0046] The iron recovery rate was 92.8%;

[0047] The D of the obtained reduced iron powder 30 12.2 micrometers, D 50 27.1 micrometers, D 75 43.2 micrometers D 90 It is 56.7 micrometers.

[0048] Example 5

[0049] The other conditions were the same as in Example 1, except that the reaction temperature for high-temperature deoxidation and impurity removal of hematite slag, coke powder, and quicklime was 1300℃. The chemical composition of the reduced iron powder obtained under these conditions was: MFe 97.2wt%, Zn 0.12wt%, Ni 0.03wt%, S 0.32wt%, CaO 0.30%, Mn 0.04wt%, Cr 0.02wt%, P 0.001wt%, with the balance being oxygen and carbon.

[0050] The iron recovery rate was 94.6%;

[0051] The D of the obtained reduced iron powder 30 9.7 micrometers, D 50 24.6 micrometers, D 75 36.1 micrometers D 90 It is 49.5 micrometers.

[0052] Example 6

[0053] The other conditions were the same as in Example 1, except that the reaction temperature for high-temperature deoxidation and impurity removal of hematite slag, coke powder, and quicklime was 800℃. The chemical composition of the reduced iron powder obtained under these conditions was: MFe 90.1wt%, Zn 0.87wt%, Ni 0.03wt%, S 0.95wt%, CaO 0.76%, Mn 0.15wt%, Cr 0.04wt%, P 0.002wt%, with the balance being oxygen and carbon.

[0054] The iron recovery rate was 90.2%; compared with Example 1, the iron recovery rate was significantly lower and the iron content in the product was also significantly lower.

[0055] The D of the obtained reduced iron powder 30 12.1 micrometers, D 50 25.6 micrometers, D 75 39.2 micrometers D 90 It is 51.4 micrometers.

[0056] Comparative Example 1

[0057] Other conditions were the same as in Example 1, except that the reaction temperature for high-temperature deoxidation and impurity removal of hematite slag, coke powder, and quicklime was 700℃. The chemical composition of the reduced iron powder obtained under these conditions was: MFe 76.5wt%, Zn 1.58wt%, Ni 0.03wt%, S 2.13wt%, CaO 1.06%, Mn 0.21wt%, Cr 0.05wt%, P 0.003wt%, with the balance being oxygen and carbon.

[0058] The iron recovery rate was 83.1%;

[0059] The D of the obtained reduced iron powder 30 14.2 micrometers, D 50 28.1 micrometers, D 75 42.4 micrometers D 90 It is 55.3 micrometers.

[0060] Comparative Example 2

[0061] All other conditions are the same as in Example 1, except that:

[0062] After the first magnetic separation, with a carbon / iron mass ratio of 1.0, the coke powder and magnetic products were mixed evenly and reacted at 950℃ for 2 hours. After the reaction, the mixture was cooled to room temperature in the furnace (cooling rate 1℃ / min), and then subjected to magnetic separation again (under the same conditions as the first magnetic separation), yielding 1045g of reduced iron. The chemical composition of the reduced iron was: MFe 92.5wt%, Zn 0.18wt%, Ni 0.03wt%, S 0.35wt%, CaO 0.35%, Mn 0.05wt%, Cr 0.03wt%, P 0.001wt%, with the balance being oxygen and carbon.

[0063] At this point, the reduced iron obtained is mostly in block form, with excess carbon trapped in the middle.

[0064] Comparative Example 3

[0065] All other conditions are the same as in Example 1, except that:

[0066] The magnetic product was heated to 950℃ under the influence of hydrogen gas for 2 hours, with a hydrogen flow rate of 0.1 m / min and a hydrogen consumption of 18 Nm³. 3 The iron powder was reacted with nitrogen gas and rapidly cooled at a rate of 3°C / min to obtain 1041g of reduced iron powder. The chemical composition of the reduced iron was: MFe 93.6wt%, Zn 0.22wt%, Ni 0.03wt%, S 0.35wt%, CaO 0.31%, Mn 0.04wt%, Cr 0.03wt%, P 0.001wt%, with the balance being oxygen and carbon.

[0067] The iron recovery rate was 95.1%;

[0068] The D of the obtained reduced iron powder 30 40.6 micrometers, D 50 75.2 micrometers, D 75 98.5 micrometers D 90 It is 120 micrometers.

[0069] Comparative Example 4

[0070] All other conditions are the same as in Example 1, except that:

[0071] The magnetic product was heated to 1150℃ under the influence of hydrogen gas for 2 hours, with a hydrogen flow rate of 0.2 m / min and a hydrogen consumption of 36 Nm³. 3The iron powder was reacted with nitrogen gas and rapidly cooled at a rate of 2°C / min to obtain 1032g of reduced iron powder. The chemical composition of the reduced iron was: MFe 97.3wt%, Zn 0.12wt%, Ni 0.03wt%, S 0.30wt%, CaO 0.25%, Mn 0.05wt%, Cr 0.02wt%, P 0.001wt%, with the balance being oxygen and carbon.

[0072] The iron recovery rate was 96.2%;

[0073] The D of the obtained reduced iron powder 30 62 micrometers, D 50 135 micrometers, D 75 180 micrometers D 90 It is 220 micrometers.

[0074] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for producing reduced iron powder from hydrometallurgical hematite slag, characterized in that Includes the following steps: (1) High-temperature deoxidation and impurity removal: The crushed hematite slag is mixed evenly with carbonaceous reducing agent and activator, and high-temperature deoxidation and impurity removal is carried out at 800~1300℃, carbon / iron mass ratio of 0.6~1.2, and reaction time of 1~4h; the activator is calcium oxide and / or strong calcium oxide, and the amount of activator added is 1~12% of the weight of hematite slag; (2) Fine grinding and magnetic separation: The impurity-removed product produced in step (1) is finely ground to a particle size ≤74μm, and then magnetically separated to obtain magnetic products; (3) Deep purification: The magnetic product from step (2) is subjected to deep purification at 700~1050℃ using hydrogen gas. After the reaction is completed, nitrogen gas is used for rapid cooling to obtain reduced iron powder. The rapid cooling rate is 5-10℃ / min.

2. A process for the preparation of reduced iron powder from hydrometallurgical hematite slag according to claim 1, characterized in that: The hydrometallurgical hematite slag comprises, by mass percentage: Fe2O3 70%~90%, ZnSO4 1%~6%, NiSO4 0.2%~2.5%, CaSO4 0.5%~5%, and S 3%~8%.

3. A process for the preparation of reduced iron powder from hydrometallurgical hematite slag according to claim 1, characterized in that: The particle size of hematite slag is less than or equal to 74 micrometers.

4. A process for the preparation of reduced iron powder from hydrometallurgical hematite slag according to claim 1, characterized in that: The carbonaceous reducing agent used in step (1) high-temperature deoxidation and impurity removal is one or more of coke powder, anthracite, and reducing coal, and the activator is quicklime or limestone powder. The amount of activator added is 1 to 10% of the weight of hematite slag, preferably 2% to 10%.

5. A process for the preparation of reduced iron powder from hydrometallurgical hematite slag according to claim 1, characterized in that: The temperature for controlling step (1) high-temperature deoxidation and impurity removal is 800~1300℃, preferably 900~1150℃, and even more preferably 1000~1100℃.

6. The method for preparing reduced iron powder from hydrometallurgical hematite slag according to claim 1, characterized in that: The magnetic field strength in the magnetic separation process of step (2) is 500~1200 Gs.

7. The method for preparing reduced iron powder from hydrometallurgical hematite slag according to claim 1, characterized in that: The reaction time for deep impurity removal in step (3) is 1 to 4 hours.

8. The method for preparing reduced iron powder from hydrometallurgical hematite slag according to claim 1, characterized in that: The temperature for deep impurity removal in step (3) is 700~1100℃, preferably 850~1000℃.

9. The method for preparing reduced iron powder from hydrometallurgical hematite slag according to claim 1, characterized in that: In step (3), the relative amount of hydrogen gas is controlled to be 50-150 Nm 3 t-iron powder, the flow rate of hydrogen gas is controlled to be 0.2-1.0 m / min.

10. The method for preparing reduced iron powder from hydrometallurgical hematite slag according to claim 1, characterized in that: The chemical composition of the reduced iron powder produced by this invention, by mass percentage, includes: MFe ≥ 90%, Zn ≤ 0.3%, Ni ≤ 0.6%, S ≤ 0.5%, CaO ≤ 0.5%, Mn ≤ 0.2%, Cr ≤ 0.1%, P ≤ 0.03%; D50 of the resulting reduced iron powder 90 At 58 microns and below.

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