A method for preparing phosphorus-rich direct reduced iron using high-phosphorus iron ore

Abstract

The present application belongs to the field of comprehensive utilization of resources, and particularly relates to a method for preparing phosphorus-rich direct reduced iron from high-phosphorus iron ore. The present application aims at the problem of serious phosphorus volatilization in the existing reduction roasting process. By adding a proper amount of Al2O3 to the high-phosphorus iron ore, the molar ratio of Al to Si in the system is 0.8-1.2; reduction roasting is carried out at 1200-1400 DEG C, which can promote the aggregation of phosphorus in the liquid phase in the direct reduction roasting process, and then the reduced metallic iron absorbs it, inhibits the gasification loss of phosphorus, and realizes the direct utilization of high-phosphorus iron ore as raw material and the effective enrichment of phosphorus in the direct reduced iron. The present application can finally obtain phosphorus-rich direct reduced iron with iron grade greater than 90.0%, magnetic separation iron recovery rate greater than 80.0%, and phosphorus content of about 1.2%-2.5%, and realize the enrichment of more than 80% of phosphorus in the ore to the direct reduced iron. The process method of the present application is simple, the resources are fully utilized, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive resource utilization and provides a method for preparing phosphorus-rich direct reduced iron from high-phosphorus iron ore, particularly a method for simultaneously enriching phosphorus and iron from high-phosphorus oolitic hematite to prepare phosphorus-rich direct reduced iron. Background Technology

[0002] Traditional processing methods for high-phosphorus iron ore emphasize "iron extraction and phosphorus reduction," which involves increasing iron grade and decreasing phosphorus content during ore beneficiation. The presence of phosphorus degrades the quality of steel products, requiring iron concentrate to contain less than 0.2%–0.3% phosphorus. However, due to its unique oolitic structure, iron and phosphorus separation is particularly difficult, leading to high beneficiation costs. While high-quality iron concentrate can be obtained, the resource value of phosphorus remains unrealized, making it difficult to overcome the processing cost bottleneck. On the other hand, unlike phosphorus in iron ore, which is considered a harmful element, phosphorus is an important nutrient in agriculture and is facing depletion worldwide. To address phosphorus shortages and promote the sustainable use of phosphorus resources, recovering phosphorus from high-phosphorus iron ore is of great significance. Therefore, the key to the application of high-phosphorus iron ore lies in the simultaneous value transformation of phosphorus and iron resources within the ore.

[0003] Direct reduction ironmaking refers to the method of reducing iron ore to metallic iron by adding a reducing agent below the ore softening temperature. This method eliminates the need for sintering and ironmaking processes, directly reducing the iron ore to metallic iron, thus improving energy utilization efficiency and offering significant advantages in low-carbon emission reduction smelting. In reduction processes, the reduction behavior of iron is fundamental to iron and steel metallurgy and has been extensively studied. However, for the utilization of high-phosphorus iron ore, based on the traditional concept of "iron extraction and phosphorus reduction," most research focuses on how to achieve phosphorus gasification and overflow and improve the magnetic separation yield of iron, rather than utilizing the iron-bearing ore phase to absorb the reduced phosphorus. If the phenomenon that phosphorus easily accumulates in metallic iron during the reduction of apatite is utilized, and as much phosphorus as possible is transferred from apatite to metallic iron, followed by grinding and magnetic separation to simultaneously enrich the phosphorus and iron in phosphorus-rich direct reduced iron, then the simultaneous value conversion of phosphorus and iron resources can be achieved. However, the current process of direct reduction of high-phosphorus iron ore suffers from severe phosphorus volatilization, and how to reduce phosphorus loss during gasification is one of the challenges in preparing phosphorus-rich direct reduced iron.

[0004] The patent "Method for Preparing Ferrophosphorus Alloy from High-Phosphorus Iron Ore and Medium-to-Low-Grade Phosphate Ore" (Application No.: 201310123248.2) utilizes high-phosphorus iron ore and medium-to-low-grade phosphate ore for blending, and uses coal as a reducing agent for direct reduction at 1150℃~1200℃. After crushing, grinding, and weak magnetic separation, a crude ferrophosphorus alloy with an iron content of 70%~85% and a phosphorus content of 5%~20% is obtained, thus achieving the goal of enriching ferrophosphorus and phosphorus. This patent is simple and practical, but it does not consider how to simultaneously improve the recovery rate of iron and phosphorus. The patent "A Method for Direct Reduction, Dephosphorization, and Iron Extraction from High-Phosphorus Hematite" (application number: 201010534858.8) proposes to mix high-phosphorus iron ore powder, reducing agent, quicklime, and dephosphorizing agent in a certain proportion, and directly reduce them in a high-temperature furnace. After grinding and magnetic separation, the pig iron particles are separated from the slag, and finally, a low-phosphorus rich iron concentrate with an iron recovery rate of over 80% and a dephosphorization rate of up to 95% is obtained. This patent is based on the traditional "iron extraction and dephosphorization" method for the direct reduction of high-phosphorus iron ore, but it does not consider the development cost of high-phosphorus iron ore resources and cannot realize the utilization of valuable phosphorus in high-phosphorus iron ore.

[0005] This invention aims to promote the comprehensive utilization of high-phosphorus iron ore, suppress phosphorus volatilization loss during direct reduction roasting, achieve simultaneous and efficient enrichment and recovery of phosphorus and iron, and reduce the development cost of high-phosphorus iron ore. Summary of the Invention

[0006] This invention addresses the problem of severe phosphorus volatilization during the direct reduction of high-phosphorus iron ore, which hinders the simultaneous value conversion and efficient recovery of phosphorus and iron resources in the ore, by utilizing the abundant untapped high-phosphorus iron ore resources in China. The invention employs the addition of an appropriate amount of Al2O3 to the high-phosphorus iron ore to promote the accumulation of phosphorus in the liquid phase during the direct reduction roasting process. This phosphorus is then absorbed by the reduced metallic iron, thus suppressing phosphorus volatilization loss while achieving efficient enrichment and recovery. Subsequent magnetic separation further enriches phosphorus and iron in the direct reduced iron.

[0007] The design concept of this invention is as follows: In the direct reduction process of high-phosphorus iron ore under the condition of fixed carbon, iron oxides are gradually reduced to metallic iron at temperatures above 737℃, as shown in equations (1)-(3); while the reduction temperature of apatite is relatively high, and with the participation of quartz in the reduction reaction, it is necessary to reduce phosphorus to temperatures above 1250℃, as shown in equation (4). If the abundant SiO2 in the ore can be utilized, and an appropriate amount of Al2O3 is added to fix the CaSiO3 produced after the reduction of apatite, a stable CaAl2Si2O8 is generated, as shown in equation (5), which promotes the aggregation of phosphorus in the liquid phase during the direct reduction roasting process. This not only inhibits the gasification loss of phosphorus and increases the enrichment rate of phosphorus in metallic iron, but also increases the recovery rate of P. At the same time, the introduction of an appropriate amount of Al2O3 can also promote the efficient and high-quality recovery of iron. Finally, phosphorus-rich direct reduced iron is obtained by grinding and magnetic separation. The remaining gangue and a small amount of CaAl2Si2O8 can be used as additives in other smelting processes or as pollution-free tailings.

[0008] 3Fe₂O₃ + C = 2Fe₃O₄ + CO (1)

[0009] Fe3O4 + C = 3FeO + CO (2)

[0010] FeO + C = Fe + CO (3)

[0011] 2Ca5(PO4)3F+9SiO2+15C=9CaSiO3+CaF2+3P2+15CO (4)

[0012] 2Ca5(PO4)3F+18SiO2+9Al2O3+15C=9CaAl2Si2O8+CaF2+3P2+15CO (5)

[0013] This invention is mainly achieved through the following technical solutions:

[0014] This invention discloses a method for preparing phosphorus-rich direct reduced iron from high-phosphorus iron ore, comprising the following steps:

[0015] Step 1: Pretreatment of high-phosphorus iron ore

[0016] Using high-phosphorus iron ore as raw material, the high-phosphorus iron ore is ground to a mass ratio of -0.074mm, which accounts for more than 80%.

[0017] Step 2: Add Al2O3 and mix with high-phosphorus iron ore for direct reduction roasting.

[0018] A certain amount of Al2O3 is added to the raw material and mixed thoroughly. Then, a reducing agent is added for direct reduction calcination. After adding Al2O3, the molar ratio of Al to Si in the mixture is 0.8-1.2, preferably 0.9-1.1. The reduction calcination temperature is 1200℃~1400℃, and the reduction time is greater than or equal to 25min, preferably 30min~120min.

[0019] After adding Al2O3 in this invention, it is particularly important to control the molar ratio of Al to Si in the system to be 0.8-1.2, preferably 0.9-1.1. If it is too low, the FeO generated by reduction will react with SiO2 to form iron olivine (FeSiO4), as shown in equation (6), which is not conducive to the reduction of FeO. If it is too high, the FeO generated by reduction will react with Al2O3 to form aluminum iron spinel (FeAl2O4), as shown in equation (7), which inhibits the reduction of FeO.

[0020] FeO + SiO2 = FeSiO3 (6)

[0021] FeO + Al₂O₃ = FeAl₂O₄ (7)

[0022] Step 3: Grinding and magnetic separation of the reduction product.

[0023] The reduced product is cooled and then ball-milled until 90% of the ground product has a particle size of less than 0.074 mm. Magnetic separation is used to obtain phosphorus-rich direct reduced iron and tailings. The magnetic field strength during magnetic separation is 0.8 kGs to 2.4 kGs.

[0024] This invention discloses a method for preparing phosphorus-rich direct reduced iron from high-phosphorus iron ore; using high-phosphorus iron ore containing 30wt% to 50wt% TFe, 0.3wt% to 1.5wt% P, 5wt% to 20wt% silica, and 2wt% to 15wt% alumina as raw material.

[0025] This invention discloses a method for preparing phosphorus-rich direct reduced iron from high-phosphorus iron ore. In step two, a certain amount of Al2O3 is added to the raw material and thoroughly mixed. Then, a reducing agent is added for direct reduction roasting. The reduction product is crushed, ground, and then separated using a wet weak magnetic separation method to obtain phosphorus-rich direct reduced iron and tailings. The amount of Al2O3 added requires that the molar ratio of Al to Si in the system is 0.8-1.2, preferably 0.9-1.1, and more preferably 0.95-1.

[0026] This invention discloses a method for preparing phosphorus-rich direct reduced iron from high-phosphorus iron ore. In step two, the reduction roasting temperature is 1200℃~1400℃, preferably 1280℃~1400℃, and the reduction time is greater than 25 min, preferably 30 min~120 min, and more preferably 45~75 min. If the reduction roasting temperature is too low, the apatite cannot be reduced, and phosphorus cannot be enriched in the direct reduced iron; if it is too high, the reduced P2 will volatilize severely, consuming a large amount of energy. Therefore, the temperature of this invention is further preferably 1280℃~1320℃. Within the temperature range selected in this invention, when the temperature is higher, a shorter reduction roasting time is generally used, such as less than or equal to 75 min.

[0027] This invention discloses a method for preparing phosphorus-rich direct reduced iron from high-phosphorus iron ore; in step three, the reduced product is naturally cooled to room temperature and then ball-milled, with a grinding mass concentration of 50% to 75% and a grinding time of 10 min to 30 min.

[0028] This invention discloses a method for preparing phosphorus-rich direct reduced iron from high-phosphorus iron ore; magnetic separation yields phosphorus-rich direct reduced iron with an iron grade of over 90% and a phosphorus content of 1.2wt% to 2.5wt%, wherein the iron recovery rate is over 80% and the phosphorus recovery rate is greater than or equal to 80%.

[0029] This invention discloses a method for preparing phosphorus-rich direct reduced iron from high-phosphorus iron ore; wherein the high-phosphorus iron ore is high-phosphorus oolitic hematite or a mixed iron ore containing high-phosphorus oolitic hematite.

[0030] This invention discloses a method for preparing phosphorus-rich direct reduced iron from high-phosphorus iron ore; the reducing agent is one or more of pulverized coal, CO, H2, or hydrocarbon gases.

[0031] This invention discloses a method for preparing phosphorus-rich direct reduced iron from high-phosphorus iron ore; wherein the phosphorus gasification loss rate is less than 20%, and more than 80% of the phosphorus in the ore is enriched into direct reduced iron.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] This invention utilizes the addition of an appropriate amount of Al₂O₃ and controls the molar ratio of Al to Si in the mixture before reduction roasting to 0.8-1.2, preferably 0.9-1.1. This significantly promotes the aggregation of phosphorus in the liquid phase during the direct reduction roasting process, which is then absorbed by the reduced metallic iron. This inhibits phosphorus volatilization loss during reduction, and the reduced phosphorus is absorbed by the directly reduced iron to form iron-phosphorus compounds, achieving efficient enrichment and high recovery rate of iron and phosphorus. This invention not only comprehensively utilizes high-phosphorus iron ore resources but also achieves simultaneous and efficient enrichment of phosphorus and iron based on the direct reduction method. Furthermore, it reduces phosphorus volatilization in high-phosphorus iron ore during the direct reduction process, thus lowering gas emissions.

[0034] (1) This invention uses a large amount of high-phosphorus iron ore resources that are yet to be developed and are inexpensive as raw materials to directly prepare high-value-added phosphorus-rich direct reduced iron, providing a new method for the development and utilization of complex and difficult-to-process ores.

[0035] (2) This invention recovers iron and phosphorus components in high-phosphorus iron ore simultaneously through direct reduction roasting-magnetic separation process, realizing the simultaneous value of phosphorus and iron, and promoting the comprehensive utilization of high-phosphorus iron ore.

[0036] (3) This invention cleverly utilizes the promoting effect of gangue components SiO2 and Al2O3 on the reduction of apatite, and innovatively promotes the aggregation of phosphorus and the purification of iron in the liquid phase by adding an extra certain amount of Al2O3. This not only inhibits the volatilization of phosphorus and reduces as much phosphorus in apatite as possible to transfer it to direct reduced iron, but also improves the iron grade in the product, which provides a strong guarantee for the efficient utilization of ferrophosphorus in the later stage.

[0037] (5) The present invention has good raw material adaptability. Using high phosphorus iron ore with TFe 30wt%~50wt% and P 0.3wt%~1.5wt% as raw material, after direct reduction roasting, phosphorus-rich direct reduced iron with about 0.5%~3.0% phosphorus can be magnetically separated, realizing the enrichment of more than 80% of phosphorus in the ore into direct reduced iron, inhibiting the volatilization of phosphorus in high phosphorus iron ore during the direct reduction process, and reducing gas emissions.

[0038] (4) The process of this invention is flexible and the reducing agent is wide-ranging. It can directly use coal as a reducing agent to carry out coal-based direct reduction under solid conditions, or it can use one or more of CO, H2 or hydrocarbon gases as reducing agents to carry out gas-based direct reduction.

[0039] In summary, this invention is a method for preparing direct reduced iron from high-phosphorus iron ore that is simple in process, low in pollution, low in cost, and high in added value. It has broad application prospects and is easy to implement on a large scale. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of a method for preparing phosphorus-rich direct reduced iron from high-phosphorus iron ore.

[0041] Figure 2 The image shows the morphology of phosphorus-rich direct reduced iron obtained in Example 2.

[0042] Figure 3 The image shows the SEM-EDS image of phosphorus-rich reduced iron obtained in Example 2.

[0043] Figure 4 The image shows the morphology of the directly reduced iron obtained in Comparative Example 5.

[0044] Figure 5The image shows the SEM-EDS plot of the directly reduced iron obtained in Comparative Example 5.

[0045] Figure 6 The image shows the morphology of the directly reduced iron obtained in Comparative Example 7.

[0046] Figure 7 The image shows the SEM-EDS plot of the directly reduced iron obtained in Comparative Example 7. Detailed Implementation

[0047] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Figure 1 The embodiments are as described in Table 1, but the scope of protection of the present invention is not limited to the following embodiments.

[0048] In the examples and comparative examples, the recovery rate of P was calculated as follows: the total mass of phosphorus in the reduced iron obtained by magnetic separation was obtained by multiplying the phosphorus content in the reduced iron obtained by magnetic separation by the mass of the reduced iron obtained by magnetic separation; the recovery rate of P was obtained by dividing the total mass of phosphorus in the reduced iron obtained by magnetic separation by the total mass of phosphorus in the raw material * 100%.

[0049] Example 1: The high-phosphorus iron ore used in this example is high-phosphorus oolitic hematite from western Hubei Province, with a composition of 40.80 wt% TFe, 1.18 wt% P, 10.48 wt% SiO2, 4.69 wt% Al2O3, and 9.55 wt% CaO. Most of the iron exists as Fe2O3, and the phosphorus mainly exists as apatite. The specific operation is as follows:

[0050] First, 5g of raw material was ground to a particle size of -0.074mm, with 85% of the particles being of this size. Then, Al2O3 was added to the ore and mixed thoroughly, with the mass ratio of high-phosphorus oolitic hematite to the added Al2O3 being 1:0.04 (converted to a molar ratio of Al to Si of 0.98:1). The mixture was then placed in a tube furnace at 1200℃ and subjected to CO reduction roasting for 60 minutes. After cooling, the initial grinding concentration was 50%, and the grinding product particle size of -0.074mm accounted for 92%. Magnetic separation was performed under a magnetic field strength of 1.2kGs to obtain 1.90g of phosphorus-rich direct reduced iron with an iron grade of 90.1% and a phosphorus content of 2.5wt%. The total iron recovery rate was calculated to be 83.9%. The total mass of phosphorus in the phosphorus-rich direct reduced iron is obtained by multiplying the phosphorus content in the phosphorus-rich direct reduced iron by the mass of the resulting phosphorus-rich direct reduced iron. The recovery rate of phosphorus (P) is obtained by dividing the total mass of phosphorus in the phosphorus-rich direct reduced iron by the total mass of phosphorus in the raw material multiplied by 100%. In this embodiment, the recovery rate of P is approximately 80.5%.

[0051] Example 2: The high-phosphorus iron ore powder used in this example is high-phosphorus oolitic hematite from western Hubei Province, containing 48.5 wt% TFe, 0.95 wt% P, 10.35 wt% SiO2, 4.65 wt% Al2O3, and 8.05 wt% CaO. Most of the iron exists as Fe2O3, and the phosphorus mainly exists as apatite. The specific operation is as follows:

[0052] First, 5g of raw material was ground to a particle size of -0.074mm, with 88% of the particles being of this size. Then, Al2O3 was added to the ore and mixed thoroughly, with the mass ratio of high-phosphorus oolitic hematite to Al2O3 being 1:0.04 (equivalent to a molar ratio of Al to Si of 0.98:1 in the mixture). The mixture was then placed in a tube furnace at 1300℃ and subjected to CO reduction roasting for 60 minutes. After cooling, the initial grinding concentration was 60%, and the grinding product particle size of -0.074mm was 90%. Magnetic separation was then performed under a magnetic field strength of 1.2kGs. Finally, 2.27g of phosphorus-rich direct reduced iron with an iron grade of 91.5% and a phosphorus content of 1.82wt% was obtained. The total iron recovery rate was calculated to be 85.7%, and the phosphorus recovery rate was approximately 87.0%. Figure 2 The image shows the morphology of the phosphorus-rich direct reduced iron obtained in Example 2. The phosphorus-rich reduced iron was subjected to SEM-EDS, and the results are shown below. Figure 3 .from Figure 3 It can be seen that phosphorus-rich reduced iron mainly consists of two phases: a blackish-gray phosphorus-rich phase and a gray iron phase. Subsequent EDS analysis of the different phases revealed that point 1 in the phosphorus-rich phase contained a phosphorus content as high as 15.88 wt%, while point 2 in the iron phase contained 1.25 wt%, with a phosphorus content ratio of 12.70. Furthermore, the iron phase grains were coarse and intact, and the phosphorus-rich phase region located at the grain boundaries exhibited a higher phosphorus content.

[0053] Example 3: The high-phosphorus iron ore powder used in this example is high-phosphorus oolitic hematite from western Hubei Province, containing 49.46 wt% TFe, 0.68 wt% P, 10.54 wt% SiO2, 4.82 wt% Al2O3, and 8.36 wt% CaO. Most of the iron exists as Fe2O3, and the phosphorus mainly exists as apatite. The specific operation is as follows:

[0054] First, 5g of raw material was ground to a particle size of -0.074mm, with 90% of the particles being of this size. Then, Al2O3 was added to the ore and mixed thoroughly, with the mass ratio of high-phosphorus oolitic hematite to Al2O3 being 1:0.04 (equivalent to a molar ratio of Al to Si of 0.98:1 in the mixture). The mixture was then placed in a tube furnace at 1400℃ and subjected to CO reduction roasting for 60 minutes. After cooling, the initial grinding concentration was 75%, and the grinding product particle size of -0.074mm accounted for 91%. Magnetic separation was then performed under a magnetic field strength of 1.2kGs. Finally, 2.35g of phosphorus-rich direct reduced iron with an iron grade of 91.6% and a phosphorus content of 1.2wt% was obtained. The total iron recovery rate was calculated to be 85.0%, and the phosphorus recovery rate was approximately 81.7%.

[0055] Example 4: This example is basically the same as Example 2, except that the mass ratio of high-phosphorus oolitic hematite to Al2O3 is 1:0.02 (after conversion, the molar ratio of Al to Si in the mixture is 0.8:1). Finally, 2.25g of phosphorus-rich direct reduced iron with an iron grade of 90.5% and a phosphorus content of 1.7wt% can be obtained. The total iron recovery rate is calculated to be 84.0%, and the P recovery rate is about 80.6%.

[0056] Example 5: This example is basically the same as Example 2, except that the mass ratio of high-phosphorus oolitic hematite to Al2O3 is 1:0.03 (after conversion, the molar ratio of Al to Si in the mixture is 0.9:1). Finally, 2.21g of phosphorus-rich direct reduced iron with an iron grade of 91.0% and a phosphorus content of 1.75wt% can be obtained. The total iron recovery rate is calculated to be 83.0%, and the P recovery rate is about 81.5%.

[0057] Example 6: This example is basically the same as Example 2, except that the mass ratio of high-phosphorus oolitic hematite to Al2O3 is 1:0.05 (after conversion, the molar ratio of Al to Si in the mixture is 1.1:1). Finally, 2.24g of phosphorus-rich direct reduced iron with an iron grade of 90.2% and a phosphorus content of 1.78wt% can be obtained. The total iron recovery rate is calculated to be 83.2%, and the P recovery rate is about 83.8%.

[0058] Example 7: This example is basically the same as Example 2, except that the mass ratio of high-phosphorus oolitic hematite to Al2O3 is 1:0.06 (after conversion, the molar ratio of Al to Si in the mixture is 1.2:1). Finally, 2.21g of phosphorus-rich direct reduced iron with an iron grade of 90.0% and a phosphorus content of 1.72wt% can be obtained; the total iron recovery rate is calculated to be 82.1%, and the P recovery rate is approximately 80.1%.

[0059] Comparative Example 1: This comparative example is basically the same as Example 2, except that the calcination temperature is 1000℃, and 1.95g of iron powder with an iron grade of 60.9% and a phosphorus content of 0.8wt% can be obtained. The total iron recovery rate is calculated to be 48.9%, and the phosphorus recovery rate is about 32.8%.

[0060] Comparative Example 2: This comparative example is basically the same as Example 2, except that the calcination temperature is 1100℃. Finally, 2.03g of iron powder with an iron grade of 79.5% and a phosphorus content of 0.9wt% can be obtained. The total iron recovery rate is calculated to be 66.7%, and the phosphorus recovery rate is about 38.5%.

[0061] Comparative Example 3: This comparative example is basically the same as Example 2, except that the calcination temperature is 1500℃. Finally, 2.25g of iron powder with an iron grade of 85.2% and a phosphorus content of 1.1wt% can be obtained. The total iron recovery rate is calculated to be 78.9%, and the phosphorus recovery rate is about 52.0%.

[0062] Comparative Example 4: This comparative example is basically the same as Example 2, except that the calcination temperature is 1550℃ and Al2O3 is not added (after conversion, the molar ratio of Al to Si in the mixture is 0.5:1). Finally, 2.20g of iron powder with an iron grade of 80.2% and a phosphorus content of 1.0wt% can be obtained. The total iron recovery rate is calculated to be 72.6%, and the P recovery rate is about 46.2%.

[0063] Comparative Example 5: This comparative example is basically the same as Example 2, except that Al2O3 was not added (after conversion, the molar ratio of Al to Si in the mixture is 0.5:1). Finally, 2.13 g of iron powder with an iron grade of 90.5% and a phosphorus content of 1.2 wt% was obtained. The total recovery rate of iron was calculated to be 79.0%, and the recovery rate of P was about 53.8%. Figure 4 To obtain the morphological image of the directly reduced iron obtained in Comparative Example 5, the reduced iron was subjected to SEM-EDS, and the results are shown in [Figure 5]. Figure 5 .from Figure 5 It can be seen that there are two main phases in the reduced iron: a blackish-gray phosphorus-rich phase and a gray iron phase. Subsequent EDS analysis of different phases revealed that spot 3 in the phosphorus-rich phase contained 10.64 wt% phosphorus, while spot 4 in the iron phase contained 1.04 wt% phosphorus, with a phosphorus content ratio of 10.23. Furthermore, the iron phase has finer grains and a lower phosphorus content compared to the iron phase in Example 2. The phosphorus-rich phase region at the grain boundaries also exhibits a lower phosphorus content compared to the phosphorus-rich phase in the phosphorus-rich direct reduced iron obtained in Example 2.

[0064] Comparative Example 6: This comparative example is basically the same as Example 2, except that the mass ratio of high-phosphorus oolitic hematite to Al2O3 is 1:0.01 (after conversion, the molar ratio of Al to Si in the mixture is 0.6:1). Finally, 2.19 g of iron powder with an iron grade of 88.5% and a phosphorus content of 1.3 wt% can be obtained. The total iron recovery rate is calculated to be 80.0%, and the P recovery rate is about 60.0%.

[0065] Comparative Example 7: This example is basically the same as Example 2, except that the mass ratio of high-phosphorus oolitic hematite to Al2O3 is 1:0.08 (after conversion, the molar ratio of Al to Si in the mixture is 1.4:1). Finally, 2.24 g of iron powder with an iron grade of 81.2% and a phosphorus content of 1.1 wt% can be obtained; the total iron recovery rate is calculated to be 75.0%, and the P recovery rate is about 51.8%. Figure 6 To obtain the morphological image of the directly reduced iron obtained in Comparative Example 7, the reduced iron was subjected to SEM-EDS, and the results are shown in [Figure 7]. Figure 7 .from Figure 7 It can be seen that there are two main phases in the reduced iron: a blackish-gray phosphorus-rich phase and a gray iron phase. Subsequent EDS analysis of different phases revealed that spot 5 in the phosphorus-rich phase contained 8.57 wt% phosphorus, while spot 6 in the iron phase contained 0.84 wt% phosphorus, with a phosphorus content ratio of 10.20. Furthermore, the iron phase had fine grains and contained a small amount of slag. The phosphorus content in the iron phase was also lower than that in the iron phase of Example 2. The phosphorus-rich phase region located at the grain boundaries also had a lower phosphorus content compared to the phosphorus-rich phase in the phosphorus-rich direct reduced iron obtained in Example 2.

[0066] Comparative Example 8: This example is basically the same as Example 2, except that the mass ratio of high-phosphorus oolitic hematite to Al2O3 is 1:0.10 (after conversion, the molar ratio of Al to Si in the mixture is 1.7:1). Finally, 2.32 g of iron powder with an iron grade of 75.2% and a phosphorus content of 0.8 wt% can be obtained; the total iron recovery rate is calculated to be 72.0%, and the P recovery rate is about 39.1%.

[0067] Table 1 Results of Examples and Comparative Examples

[0068]

[0069]

Claims

1. A method for preparing phosphorus-rich direct reduced iron from high-phosphorus iron ore; characterized in that... ； Includes the following steps: Step 1: Pretreatment of high-phosphorus iron ore Using high-phosphorus iron ore with TFe 30wt%~50wt%, P 0.3wt%~1.5wt%, silica content 5wt%-20wt%, and alumina content 2wt%-15wt% as raw material, the high-phosphorus iron ore is ground to -0.074mm and the mass ratio is more than 80%. Step 2: Add Al2O3 and mix with high-phosphorus iron ore for direct reduction roasting. A certain amount of Al2O3 is added to the raw material and mixed thoroughly. Then, a reducing agent is added and the mixture is directly reduced and roasted to obtain the reduced product. After adding Al2O3, the molar ratio of Al to Si in the mixture is 0.95-1.0; the reduction calcination temperature is 1280℃~1320℃, and the reduction time is 45~75min; Step 3: Grinding and magnetic separation of the reduction product. The reduced product is cooled and then ball-milled until 90% of the ground product has a particle size of less than 0.074 mm. Magnetic separation is used to obtain phosphorus-rich direct reduced iron and tailings. The magnetic field strength during magnetic separation is 0.8 kGs to 2.4 kGs. Magnetic separation yields phosphorus-rich direct reduced iron with an iron grade of over 90% and a phosphorus content of 1.2 wt% to 2.5 wt%, with an iron recovery rate of over 80% and a phosphorus recovery rate of greater than or equal to 80%.

2. The method for preparing phosphorus-rich direct reduced iron from high-phosphorus iron ore according to claim 1, characterized in that: In step three, the reduced product is naturally cooled to room temperature and then ball-milled, with a grinding mass concentration of 50% to 75% and a grinding time of 10 to 30 minutes.

3. The method for preparing phosphorus-rich direct reduced iron from high-phosphorus iron ore according to claim 1, characterized in that: The high-phosphorus iron ore is high-phosphorus oolitic hematite or a mixed iron ore containing high-phosphorus oolitic hematite.

4. The method for preparing phosphorus-rich direct reduced iron from high-phosphorus iron ore according to claim 1, characterized in that: The reducing agent is one or more of pulverized coal, CO, H2, or hydrocarbon gases.

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