A smelting method for preparing iron powder and extracting phosphorus from tailings by low-temperature reduction of high-phosphorus iron ore

Abstract

This invention relates to a smelting method for preparing iron powder from high-phosphorus iron ore through low-temperature reduction and for extracting phosphorus from tailings through acid leaching. This invention requires no additives; the high-phosphorus iron ore and reducing agent are simply crushed in a ball mill. The crushed product is then briquetted and subjected to low-temperature reduction to obtain a metal-rich product. The reduction temperature is controlled at 950℃-1000℃. The metal-rich product is then simply crushed and directly subjected to magnetic separation to obtain reduced iron powder with a total iron content of ≥85% and a phosphorus content of ≤0.1wt%. The phosphorus-rich tailings are acid-leached to neutralize and precipitate phosphates with a purity of ≥85%. This invention addresses the challenges of high-phosphorus iron ore's fine particle size and difficulty in reduction by improving the activity of hematite and reducing agent through grinding, effectively lowering the reduction temperature, and preparing a metal-rich product through low-temperature reduction. Simultaneously, magnetic separation extracts iron from the metal-rich product, and its high reactivity further extracts phosphorus from the tailings, achieving comprehensive utilization of high-phosphorus iron ore.

Description

Technical Field

[0001] This invention relates to a smelting method for high-phosphorus iron ore, and particularly to a combined pyrometallurgical-hydrometallurgical process for preparing low-phosphorus iron powder by low-temperature reduction of high-phosphorus iron ore, while simultaneously extracting the valuable element phosphorus. Background Technology

[0002] In recent years, with the rapid development of my country's steel industry, crude steel production has continued to climb, exceeding 1 billion tons in 2020, accounting for more than half of the world's total crude steel production. Currently, my country's dependence on imported iron ore is too high, and the sharp rise in imported iron ore prices is severely restricting the development of China's steel industry. Therefore, finding ways to source materials locally and developing and exploiting my country's existing low-grade iron ore resources is of decisive strategic significance for domestic steel smelting production. The vast reserves, low prices, and untapped high-phosphorus iron ore resources in China are attracting increasing attention.

[0003] Southern China possesses abundant, yet-to-be-developed high-phosphorus iron ore resources, such as the "Ningxiang-type" high-phosphorus oolitic hematite deposits distributed in Hubei, Hunan, Guizhou, Jiangxi, Yunnan provinces, and the Guangxi Zhuang Autonomous Region. These deposits are shallow and easy to mine, with proven reserves exceeding 3 billion tons. A key characteristic is the high phosphorus content of the raw ore (average phosphorus content 0.8%). These massive reserves can effectively alleviate the ore shortage problem. However, because oolitic hematite is a sedimentary iron ore, its structure is dense and heterogeneous. The hematite phase often coexists with or is intertwined with impurities such as quartz, oolitic chlorite, and apatite, forming a layered oolitic structure.

[0004] Physical methods are often insufficient for effectively separating phosphorus and iron. Common physical methods include grinding and mineral processing; mineral processing methods include gravity separation, magnetic separation, and flotation. Physical methods are simple to operate, low in cost, and low in energy consumption. However, due to the complex structure and extremely fine ore phases of high-phosphorus oolitic hematite, these methods suffer from low iron recovery rates, difficulty in dephosphorization, and unsatisfactory results. While chemical leaching and bioleaching can remove phosphorus to some extent, their low reactivity and leaching efficiency lead to long process flows and high production costs. Currently, the reduction roasting-magnetic separation process is the most effective for iron extraction and phosphorus reduction from high-phosphorus oolitic hematite. However, the characteristics of the ore make reduction difficult, requiring high temperatures to improve the reduction effect, which increases energy consumption and the performance requirements of the equipment.

[0005] The patent "Method for Preparing Low-Phosphorus Molten Iron Based on High-Temperature Melting of Metallized Products from High-Phosphorus Iron Ore" (application number: 202310007584.4) proposes a method to prepare metallized products from high-phosphorus iron ore that have undergone porosification treatment, while simultaneously preparing dephosphorizing agents and melting additives. The metallized products from the porosified high-phosphorus iron ore, along with the dephosphorizing agent and melting additives, are added in batches to a submerged arc furnace for high-temperature melting. Slag and iron are then tapped, thereby achieving the goal of iron extraction and dephosphorization to obtain low-phosphorus molten iron. However, this method requires oxidation followed by reduction and subsequent melting, making the process complex. Furthermore, the use of various additives significantly increases production costs. Moreover, it does not consider the development of high-phosphorus iron ore resources and fails to enhance the phosphorus resource value of high-phosphorus iron ore. The patent "A Method for Separating Phosphorus and Iron from High-Phosphorus Iron Ore" (application number: 202110633819.1) describes a method for separating phosphorus and iron from high-phosphorus iron ore by pelletizing it with additives, binders, and reducing agents, followed by roasting at a temperature of 950-1100℃ for 25-200 minutes. After separation, metallic iron powder with a reduction rate >85% and a total iron content >91% can be obtained. However, this method does not specifically address the problem of the dense embedding of phosphorus-containing gangue and iron-rich phases in high-phosphorus iron ore, resulting in poor reduction kinetics. This necessitates the addition of a large amount of dephosphorizing agent and leads to a complex and cumbersome subsequent magnetic separation process, resulting in high production costs.

[0006] In order to break through the "bottleneck" of high beneficiation cost and difficulty in utilization of high-phosphorus iron ore over the years, promote the comprehensive utilization of domestic high-phosphorus iron ore resources, and provide new strategic technical support for the utilization of abundant but difficult-to-process high-phosphorus iron ore resources in my country, this invention is proposed. Summary of the Invention

[0007] This invention aims to develop and utilize domestic high-phosphorus iron ore resources and solve the problem that existing high-phosphorus iron ore cannot be industrially utilized due to high development costs. This invention addresses the problem that the fine particle size of high-phosphorus iron ore leads to high reduction costs and the inability to utilize valuable phosphorus. From the perspective of improving the activity of reactants, it adopts low-temperature rapid reduction to provide a method for separating phosphorus and iron from high-phosphorus iron ore and obtaining reduced iron powder and high-purity phosphate.

[0008] The design concept of this invention is as follows: By using ball milling or similar methods to mix the ore with a reducing agent, and simultaneously subjecting it to mechanical activation and refining, hematite can be reduced to metallic iron at very low temperatures. At the same time, apatite is difficult to reduce at low temperatures, allowing iron to enter the reduced iron powder and phosphorus to enter the tailings. Furthermore, at the lower reduction temperature, since no low-melting-point additives are added, sintering effects do not occur between the components in the slag, ensuring the porosity of the agglomerates and improving the reduction effect. This also significantly reduces the difficulty of crushing the reduced slag and iron, and is superior to not adding any flux. After reduction, the product only needs simple crushing followed by magnetic separation to obtain reduced iron powder, thus realizing the utilization of iron. On the other hand, the phosphorus-containing substances in the finely ground phosphorus-rich tailings undergo mechanical activation and low-temperature roasting, greatly enhancing their reactivity. Phosphorus can be extracted through acid leaching to obtain relatively pure phosphate as a high-value-added by-product. This method, from the perspective of improving reactant activity, employs low-temperature rapid reduction to provide a method for separating phosphorus and iron from high-phosphorus iron ore and obtaining reduced iron powder and phosphate. By fully utilizing the different thermodynamic properties of phosphorus and iron phases in high-phosphorus iron ore, and achieving separate resource utilization under the same pretreatment process, we can break through the cost "bottleneck" of the traditional "iron extraction and phosphorus reduction" treatment method and provide a new approach for the development and utilization of high-phosphorus iron ore.

[0009] This invention is mainly achieved through the following technical solutions:

[0010] Step 1

[0011] With a C / O ratio of 1.1-1.5 based on a molar ratio, high-phosphorus iron ore and a solid reducing agent are prepared. The high-phosphorus iron ore and the solid reducing agent are crushed in a ball mill until the powder with a particle size of less than or equal to 40 μm accounts for more than 50% of the total powder mass. The crushed product is briquetteed and subjected to low-temperature reduction to obtain a metal-rich product. The phosphorus content of the high-phosphorus iron ore is greater than or equal to 0.5 wt%. The proportion of metallic iron in the metal-rich product is greater than or equal to 85 wt%, preferably greater than or equal to 90 wt%. The reduction temperature is controlled at 950℃-1000℃ during reduction.

[0012] Step Two

[0013] After simple crushing of the metal-rich product obtained in step one, it is directly subjected to magnetic separation to obtain reduced iron powder with a total iron content of ≥85% and a phosphorus content of ≤0.1wt% and tailings with a phosphorus content of ≥4.0wt% and an iron content of <2.0wt%.

[0014] Step 3

[0015] The phosphorus-rich tailings obtained in step three are acid-leached, filtered, and the filtrate is neutralized to precipitate phosphates with a purity of over 85%.

[0016] The remaining tailings can be used directly as industrial raw materials such as protective slag.

[0017] As a preferred embodiment, a method for smelting high-phosphorus iron ore; the metal-enriched product in step one is obtained through the following scheme:

[0018] High-phosphorus iron ore is first crushed to a particle size of less than or equal to 2.5 mm, preferably around 2 mm, as a reserve raw ore. Then, the reserve raw ore and reducing agent are mixed at a mass ratio of 10:1 to 5:1, with a C / O molar ratio of 1.1 to 1.5. This mixture is then fed into a ball mill for crushing, mixing, and mechanical activation. After crushing, pellets with a particle size of 2-80 μm, and a 2-40 μm powder content of over 50%, are obtained. These pellets are then pelletized or briquetted to obtain carbon-containing pellets. These pellets are then reduced in a furnace, with the reduction temperature controlled at 950℃-1000℃ (preferably 950-975℃) and the reduction time at 30-120 min, preferably 60-120 min. This invention further crushes and mixes the coarser iron ore powder and reducing agent together, improving the activity and contact area of ​​both. By fully utilizing the different thermodynamic properties of phosphorus and iron phases in high-phosphorus iron ore, iron extraction and phosphorus reduction can be achieved at low temperatures. This also provides the necessary conditions for obtaining high-purity leaching products in the future.

[0019] In this invention, no additional additives such as flux, dephosphorizing agent, binder, or pore-forming agent are introduced in this step. Flux and the like will sinter at low temperatures, which will worsen the reduction kinetics and is not conducive to the crushing of the metal-rich product after reduction, as well as the magnetic separation of iron and the acid leaching extraction of phosphorus.

[0020] In this invention, reduction is performed after mixing. The temperature during reduction affects the subsequent metallization rate and recovery rate of iron. Furthermore, the reduction temperature depends on the grinding effect; the finer the pellet powder, the lower the controlled temperature during reduction. Therefore, the ore and reducing agent should be crushed as much as possible. As a further preferred embodiment, the proportion of pellet powder with a particle size of 2-40 μm after crushing is controlled to be above 70%.

[0021] As a further preferred option, the proportion of pellet powder with a particle size of 2-40μm after crushing is controlled to be above 90%.

[0022] The crushing method can be mechanical crushing or airflow crushing. Mechanical crushing can be ball milling, roller milling or vibratory milling.

[0023] This invention discloses a method for smelting high-phosphorus iron ore, wherein the high-phosphorus iron ore is high-phosphorus oolitic hematite or other types of high-phosphorus iron ore, as well as mixed iron ore containing high-phosphorus iron ore. The mixed iron ore refers to a mixed iron ore obtained by mixing high-phosphorus oolitic hematite with other iron ores in a certain proportion.

[0024] As a preferred option, a smelting method for high-phosphorus iron ore is provided; the reducing agent is selected as fixed carbon, such as carbon powder, graphite, coke, bituminous coal or anthracite, etc., and its particle size is controlled within 2 mm.

[0025] As a preferred option, the amount of reducing agent added is controlled at a C / O ratio of 1.1-1.3. During the research and development process, it was found that when the C / O ratio exceeds 1.5, the phosphorus recovery rate decreases, and the quality of reduced iron also decreases.

[0026] In this invention, after the reduction treatment in step one, the metallization rate of iron reaches more than 85%, while phosphorus is hardly reduced and enters the phosphorus-rich tailings.

[0027] The present invention discloses a smelting method for high-phosphorus iron ore, wherein the pellet powder can be pelletized or directly briquetted according to conventional methods in the art, and then the pellets are sent to a heating furnace for reduction.

[0028] Due to its low reduction temperature, this method has low requirements for heating equipment and can use conventional rotary kilns, tunnel kilns, vertical shaft furnaces, tube furnaces, or belt furnaces. The heating method can be external heating or utilizing the heat from the chemical reaction, such as the secondary combustion of CO.

[0029] The difficulty of crushing the metal-rich product in step two is greatly reduced, and the degree of slag-iron separation after crushing is low. After magnetic separation, fine iron powder with a particle size of 2-40μm and tailings with a phosphorus content of more than 4% can be obtained.

[0030] As a further optimization, the reduced pellets need to be crushed again to a particle size of 2-80μm, and magnetic separation is used to obtain reduced iron powder and high phosphorus tailings.

[0031] As a further preferred option, in step two, the reduced pellets are crushed to less than 74 μm, with powder of 2-40 μm accounting for more than 50%. Since no sintering occurs during the reduction process (especially since no low-melting-point additives are added), the metal-rich product after reduction can be easily crushed, resulting in extremely low energy consumption. The crushed metal-rich product is then subjected to magnetic separation, which can be either dry or wet magnetic separation. The magnetic separation intensity is 55.0 kA / m-80.0 kA / m, and the separation time is 5 min-10 min, yielding reduced iron powder with a total iron content greater than or equal to 85% and a phosphorus content less than or equal to 0.1 wt%, and tailings with a phosphorus content greater than 4.0 wt% and an iron content less than 2.0 wt%.

[0032] As a further preferred option, to accommodate the acid leaching of phosphorus in step three, wet magnetic separation is preferred for magnetic separation in step two; water magnetic separation can improve the magnetic separation effect and also transform the system into hydrometallurgy.

[0033] The reduced iron powder obtained by this method can be used in powder metallurgy or materials fields, or it can be briquetized and fed into blast furnaces, converters, and electric furnaces to produce various steel products.

[0034] As a further preferred embodiment, in step three, during the acid leaching of the phosphorus-rich tailings, the solid-liquid ratio is controlled at 1:5-1:20, the pH is controlled at 0.5-1.5, and the leaching time is 30-120 minutes with stirring. After acid leaching, the residue is filtered to obtain dephosphorized tailings and phosphorus-rich leachate. Alkali or alkaline oxides are added to the phosphorus-rich leachate, the amount depending on the pH of the solution, slowly with stirring, to precipitate phosphate ions. After filtration, phosphate is obtained with a purity of over 85%. As a further preferred embodiment, during the acid leaching of the phosphorus-rich tailings, the solid-liquid ratio is controlled at 1:5-1:10, and the pH is controlled at 0.5-1.0 with acid.

[0035] The acid leaching in step three can be done with sulfuric acid, hydrochloric acid, nitric acid, citric acid, or industrial waste acid.

[0036] As a further preferred option, considering volatility and the working environment, sulfuric acid or industrial waste acid containing sulfuric acid should be used for acid leaching. Its concentration should be controlled between 0.3-0.6 mol / L. Of course, to ensure purity, sulfuric acid should be used for acid leaching. Alternatively, the acid solution after acid leaching treatment using this process can be used.

[0037] As a further preferred option, during the neutralization and precipitation process of phosphorus-rich leachate, the mass ratio of neutralizing agent to filtrate is controlled at 3-6:100, and the specific amount added depends on the type of neutralizing agent added.

[0038] As a further preferred option, after ball milling the high-phosphorus iron ore and reducing agent together, particles smaller than 40 micrometers account for 92% or more of the total particle mass, and the C / O ratio is 1.3; the reduction temperature is 950 degrees Celsius, the reduction time is controlled at 60-65 minutes, and sulfuric acid with a pH of 0.5 is used for acid leaching, with an acid leaching time of 60-65 minutes.

[0039] The acid leaching process should make full use of the residual heat after reduction roasting. By increasing the temperature of the acid leaching system, the acid leaching efficiency can be improved. Therefore, the second step, magnetic separation, is preferably wet magnetic separation. At the same time, magnetic separation before acid leaching effectively avoids iron and acid loss caused by the reaction between iron and acid, and specifically extracts iron and phosphorus.

[0040] Mechanical activation greatly enhances the reactivity of the calcined phosphorus-rich tailings, effectively shortening the acid leaching time required for apatite while reducing acid consumption.

[0041] In this invention, the iron recovery rate is over 90%, and the phosphorus recovery rate is over 90%.

[0042] After optimization, this invention ensures that the recovery rate of iron is 92% or higher, the recovery rate of phosphorus is 92% or higher, and the purity of the obtained phosphate is greater than or equal to 88%, or even reaches 90%.

[0043] Compared with the prior art, the present invention has the following advantages:

[0044] This invention addresses the challenges of fine particle size and difficult reduction of high-phosphorus iron ore. By co-grinding hematite with a reducing agent, the activity of the ore and the reducing agent is enhanced, effectively lowering the reduction temperature. Metal-rich products are then prepared through low-temperature reduction. Simultaneously, iron is extracted from the metal-rich products, and the high reactivity of the ore is used to extract phosphorus from the tailings, achieving comprehensive utilization of high-phosphorus iron ore.

[0045] 1. This invention fully addresses the characteristics of fine-grained intercalated particles and difficulty in separating phosphorus and iron in high-phosphorus iron ore. By crushing and co-grinding with a reducing agent, combined with an appropriate C / O ratio and control of the particle size of the material after co-grinding, and by making full use of the technical characteristics of the difficulty in reducing phosphorus oxides at low temperatures and the different characteristics of reduced iron and slag, efficient separation is achieved. This results in the preparation of reduced iron powder with greater application value and the realization of efficient phosphorus recovery and high-purity phosphate recovery.

[0046] 2. The process used in this invention requires no addition of flux, dephosphorizing agent, binder, pore-forming agent, etc. The reduced pellets are easy to crush, and the acid leaching process is almost free of iron interference, which reduces the consumption of acid. Overall, it greatly saves production costs. More importantly, it is the first time that the absence of additives is found to improve the purity and / or yield of phosphate products, while ensuring high iron grade and high recovery rate.

[0047] 3. The mechanical activation and refining effect of this invention results in a low process reduction temperature, which greatly reduces energy consumption and heat loss. The overall processing technology is simple, easy to implement in industry, and has obvious cost advantages. The equipment investment cost is low, and the industrial application prospects are broad.

[0048] 4. The process used in this invention extracts phosphorus from the slag, fully realizing the simultaneous utilization of iron and phosphorus resources in high-phosphorus iron ore, which can supplement the increasingly scarce phosphorus resources. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the low-temperature reduction of high-phosphorus iron ore and the acid leaching of tailings for phosphorus extraction process of the present invention.

[0050] Figure 2 The images show the XRD results of the low-temperature reduction products of high-phosphorus iron ore under different temperature and reduction time conditions. Reduced iron was obtained under the conditions protected by this invention, with a high metal reduction rate; reduced iron could not be obtained at temperatures below 900℃. Detailed Implementation

[0051] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0052] See Figure 1 This invention mainly includes a low-temperature reduction process for hematite and an acid leaching process for phosphorus extraction from tailings. High-phosphorus iron ore is crushed, then ground together with a carbonaceous reducing agent. The powder is prepared into pellets, which are then subjected to low-temperature reduction in a heating furnace. After crushing, the reduced iron powder is separated from the phosphorus-rich tailings by magnetic separation. The phosphorus-rich tailings are then subjected to an acid leaching process to extract phosphorus resources. The effects of the examples and comparative examples are shown in Table 1.

[0053] Table 1. Results of Examples and Comparative Examples

[0054]

[0055] Note: *η Fe / % represents the iron content in the reduced iron powder * mass of reduced iron / (mass of high-phosphorus iron ore * iron content in high-phosphorus iron ore).

[0056] η P / % represents the phosphorus content in phosphate * apatite / (mass of high-phosphorus iron ore * phosphorus content in high-phosphorus iron ore).

[0057] To better illustrate the present invention, the following examples are selected for further explanation.

[0058] Example 1:

[0059] The raw ore is a high-phosphorus oolitic hematite from western Hubei province, with an iron content of 46.20% and a phosphorus content of 1.34%. The phosphorus mainly exists in the form of apatite. The remaining major components, by mass percentage, are: FeO 2.05%, SiO2 11.40%, Al2O3 5.59%, CaO 10.80%, MgO 1.0%, S 0.040%, Na2O 0.075%, K2O 0.50%; The specific operation is as follows: The raw ore is pre-crushed and ground to a particle size of about 2mm, and then mixed with a reducing agent at a C / O ratio of 1.2 (molar ratio) and ball-milled. After grinding, the average particle size of the powder is 40μm, and the percentage of <40μm is 92wt%. The powder is briquetized and then reduced and roasted at a temperature of 950℃ for 60min. After cooling, it is crushed and ground to a mass percentage of less than 0.074mm. It is then magnetically separated for 8min under a magnetic field strength of 65.0kA / m to obtain reduced iron powder with an iron grade of 91% and a phosphorus content of 0.08%. The phosphorus in the ore hardly undergoes a reduction reaction. The phosphorus-rich tailings were leached with 0.4 mol / L dilute sulfuric acid under stirring, with the pH controlled at 1.0 and the time at 60 min. The solid-liquid ratio was controlled at 1:10. The resulting acidic solution was filtered to obtain a phosphate-rich solution. The solution was neutralized by adding 4.5% lime by weight of the filtrate. After the reaction was complete, the solution was precipitated and filtered to obtain calcium phosphate with a purity of 86%. The main impurity was calcium sulfate.

[0060] In this embodiment, the iron recovery rate is 92% and the phosphorus recovery rate is 90%.

[0061] Example 2:

[0062] The raw ore is a high-phosphorus oolitic hematite from western Hubei province, with an iron content of 40.30% and a phosphorus content of 0.98%. The phosphorus mainly exists in the form of apatite. The remaining major components, by mass percentage, are: FeO 3.55%, SiO2 14.40%, Al2O3 6.09%, CaO 12.80%, MgO 1.1%, S 0.050%, Na2O 0.079%, K2O 0.55%; The specific operation is as follows: The raw ore is pre-crushed and ground to a particle size of about 2 mm, and then mixed with a reducing agent at a C / O ratio of 1.2 and ball-milled. After grinding, the average particle size of the powder is 42 μm, and the percentage of <40 μm is 78%. The powder is then briquetted and subjected to reduction roasting at a temperature of 975℃ for 60 min. After cooling, it is crushed and ground to a mass percentage of 80% smaller than 0.074 mm. It is then magnetically separated for 8 min under a magnetic field strength of 65.0 kA / m to obtain reduced iron powder with an iron grade of 90% and a phosphorus content of 0.09%. The phosphorus in the ore hardly undergoes a reduction reaction. The phosphorus-rich tailings were leached with 0.5 mol / L dilute sulfuric acid under stirring, with the pH controlled at 1.0 and the time at 60 min. The solid-liquid ratio was controlled at 1:10. The resulting acidic solution was filtered to obtain a phosphate-rich solution. The solution was neutralized by adding 6.0% quicklime by mass of the filtrate. After the reaction was complete, the solution was precipitated and filtered to obtain calcium phosphate with a purity of 88%. The main impurity was calcium sulfate.

[0063] In this embodiment, the iron recovery rate was 93% and the phosphorus recovery rate was 92%.

[0064] Example 3: The raw ore was a high-phosphorus oolitic hematite from western Hubei province, with an iron content of 43.20% and a phosphorus content of 1.54%. The phosphorus mainly existed in the form of apatite. The remaining major components, by mass percentage, were: FeO 2.25%, SiO2 11.80%, Al2O3 5.69%, CaO 11.60%, MgO 1.0%, S 0.045%, Na2O 0.078%, K2O 0.52%; The specific operation is as follows: The raw ore is pre-crushed and ground to a particle size of about 2 mm, and then mixed with a reducing agent at a C / O ratio of 1.1 and ball-milled. After grinding, the average particle size of the powder is 38 μm, and the percentage of <40 μm is 95%. The powder is briquetteed and then subjected to reduction roasting at a roasting temperature of 960℃ for 120 min. After cooling, it is crushed and ground to a mass percentage of less than 0.074 mm. It is then magnetically separated for 8 min under a magnetic field strength of 65.0 kA / m to obtain reduced iron powder with an iron grade of 92% and a phosphorus content of 0.05%. The phosphorus in the ore hardly undergoes a reduction reaction. The phosphorus-rich tailings were leached with 0.5 mol / L dilute sulfuric acid under stirring, with the pH controlled at 1.0 and the time at 60 min. The solid-liquid ratio was controlled at 1:10. The resulting acidic solution was filtered to obtain a phosphate-rich solution. The solution was neutralized by adding 4.5% lime by weight of the filtrate. After the reaction was complete, the solution was precipitated and filtered to obtain calcium phosphate with a purity of 87%. The main impurity was calcium sulfate.

[0065] In this embodiment, the iron recovery rate is 94% and the phosphorus recovery rate is 90%.

[0066] Example 4: This example is basically the same as Example 1, except that the C / O ratio of the reduction roasting is 1.3, and 0.6 mol / L dilute sulfuric acid is used during acid leaching to control the pH at 0.5, resulting in reduced iron powder with an iron content of 92% and a phosphorus content of 0.08%, and calcium phosphate with a purity of 90% is prepared.

[0067] In this embodiment, the iron recovery rate is 93% and the phosphorus recovery rate is 95%.

[0068] Comparative Example 1: The particle size of the material in this comparative example is not within the scope of protection of this invention.

[0069] This comparative example is basically the same as Example 1, except that the material is less crushed. The average particle size of the powder after grinding is 80 μm, and the percentage of <40 μm is 10%. The reduction temperature is 950℃. After magnetic separation, reduced iron powder with an iron grade of 82% and a phosphorus content of 0.12% is obtained, and the purity of calcium phosphate is 80%.

[0070] In this comparative example, the recovery rate of iron was 85% and the recovery rate of phosphorus was 78%.

[0071] Comparative Example 2: The grinding method in this comparative example is not within the scope of protection of this invention.

[0072] This comparative example is basically the same as Example 2, except that the reducing agent and ore were not ground together during grinding. After magnetic separation, reduced iron powder with an iron grade of 84% and a phosphorus content of 0.10% was obtained, and the calcium phosphate purity was 79%.

[0073] In this comparative example, the recovery rate of iron was 86% and the recovery rate of phosphorus was 85%.

[0074] Comparative Example 3: The reduction time in this comparative example is outside the scope protected by this invention.

[0075] This comparative example is basically the same as Example 3, except that the reduction time is 20 min. After magnetic separation, reduced iron powder with an iron content of 80% and a phosphorus content of 0.20% is obtained, and the calcium phosphate purity is 82%.

[0076] In this comparative example, the recovery rate of iron was 83% and the recovery rate of phosphorus was 86%.

[0077] Comparative Example 4: In this comparative example, the carbon ratio and acid leaching pH during reduction are not within the scope of protection of this invention.

[0078] This comparative example is basically the same as Example 1, except that the reduction roasting C / O ratio is 0.8, the acid leaching pH is 2.0, and the reduced iron powder after magnetic separation has an iron grade of 72% and a phosphorus content of 0.15%, and the calcium phosphate purity is 60%.

[0079] In this comparative example, the recovery rate of iron was 78% and the recovery rate of phosphorus was 68%.

[0080] Comparative Example 5

[0081] This comparative example is basically the same as Example 1, except that a low-melting-point additive is added during the grinding process. Fluorite powder and potassium carbonate are used in a 1:1 mass ratio. Water glass and sodium carboxymethyl cellulose (sodium carboxymethyl cellulose) are used as binders, each accounting for 50% by mass. High-phosphorus iron ore powder, coal powder, additives, and binders are mixed in a 100:16.5:5:4 mass ratio. The uniformly mixed powder is briquetteed and then reduced and roasted at 950°C for 60 minutes. After cooling, it is crushed and ground until 80% of the particles are smaller than 0.074 mm by mass. Magnetic separation is then performed for 8 minutes to obtain reduced iron powder with an iron content of only 70% and a phosphorus content of 0.15%. After acid leaching, calcium phosphate with a purity of 78% is obtained, with calcium sulfate being the main impurity.

[0082] In this comparative example, the recovery rate of iron was 80% and the recovery rate of phosphorus was 75%.

Claims

1. A smelting method for preparing iron powder by low-temperature reduction of high-phosphorus iron ore and extracting phosphorus from tailings by acid leaching; characterized in that: Includes the following steps: Step 1 High-phosphorus iron ore is first crushed to a particle size of less than or equal to 2.5 mm as reserve raw ore. Then, the reserve raw ore and solid reducing agent are mixed at a mass ratio of 10:1 to 5:1, with a C / O molar ratio of 1.1 to 1.

5. This mixture is then fed into a ball mill for crushing, mixing, and mechanical activation. After crushing, pellets with a particle size of 2-80 μm and a 2-40 μm powder content of over 50% are obtained. These pellets are then pelletized or briquetted to obtain carbon-containing pellets. These carbon-containing pellets are then reduced in a heating furnace to obtain a metal-enriched product. The reduction temperature is controlled at 950℃-1000℃, and the reduction time is 30-120 minutes. The phosphorus content of the high-phosphorus iron ore is greater than or equal to 0.5 wt%, and the proportion of metallic iron in the total iron content of the metal-enriched product is greater than or equal to 85 wt%. Step Two After crushing the metal-rich product obtained in step one, it is directly subjected to magnetic separation. Reduced iron powder with a total iron content of ≥85% and a phosphorus content of ≤0.1wt% and tailings with a phosphorus content of ≥4.0wt% and an iron content of <2.0wt% were obtained. Step 3 The phosphorus-rich tailings obtained in step two are acid-leached to neutralize and precipitate calcium phosphate with a purity of over 85%. In step three, during the acid leaching process of the phosphorus-rich tailings, the solid-liquid ratio is controlled at 1:5-1:20, acid is added to control the pH at 0.5-1.5, and the acid leaching time is 30-120 minutes.

2. The smelting method for preparing iron powder by low-temperature reduction of high-phosphorus iron ore and extracting phosphorus from tailings by acid leaching, as described in claim 1, is characterized in that: The reduced pellets need to be crushed again to a particle size of 2-80μm, and then magnetically separated to obtain reduced iron powder and high-phosphorus tailings.

3. The smelting method for preparing iron powder by low-temperature reduction of high-phosphorus iron ore and extracting phosphorus from tailings by acid leaching, as described in claim 1, is characterized in that: The reducing agent is selected from at least one of carbon powder, graphite, coke, activated carbon, lignite, bituminous coal, anthracite, and charcoal. The amount of reducing agent added is based on the molar ratio of fixed carbon in the reducing agent to oxygen combined with iron in the ore, i.e., the C / O ratio, which is controlled between 1.1 and 1.

5.

4. The smelting method for preparing iron powder by low-temperature reduction of high-phosphorus iron ore and extracting phosphorus from tailings by acid leaching, as described in claim 1, is characterized in that: The metal-rich product in step two is crushed and then magnetically separated to obtain fine iron powder with a particle size of 2-40μm and tailings containing more than 4% phosphorus.

5. The smelting method for preparing iron powder by low-temperature reduction of high-phosphorus iron ore and extracting phosphorus from tailings by acid leaching, as described in claim 1, is characterized in that: The acid used in step three is at least one of sulfuric acid, hydrochloric acid, nitric acid, citric acid, or industrial waste acid, and the neutralizing agent is an alkali or an alkaline oxide.

6. The smelting method for preparing iron powder by low-temperature reduction of high-phosphorus iron ore and extracting phosphorus from tailings by acid leaching, as described in claim 5, is characterized in that: Sulfuric acid or industrial waste acid containing sulfuric acid is used for acid leaching; its concentration is controlled at 0.3-0.6 mol / L; during the neutralization and precipitation process of phosphorus-rich leachate, the mass ratio of neutralizing agent to filtrate is controlled at 3-6:100, and the specific amount added depends on the type of neutralizing agent added.

7. The smelting method for preparing iron powder by low-temperature reduction of high-phosphorus iron ore and extracting phosphorus from tailings by acid leaching, as described in claim 1, is characterized in that: After ball milling high-phosphorus iron ore and reducing agent together, particles smaller than 40 micrometers account for 92% or more of the total particle mass, and the C / O ratio is 1.

3. The reduction temperature is 950 degrees Celsius, the reduction time is controlled at 60-65 minutes, and sulfuric acid with pH 0.5 is used for acid leaching, with an acid leaching time of 60-65 minutes.

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