A method for dephosphorizing high-phosphorus iron ore

Abstract

The present invention relates to a method for dephosphorizing high-phosphorus iron ore, the method including fully mixing high-phosphorus iron ore powder with sodium hydroxide solid according to a certain ratio, roasting at 200 ℃ 400 ℃, then using waste heat to carry out water leaching and acid adjustment pH to 6.5 7, after filtration and drying, finally obtaining a phosphorus content less than 0.2wt%, an iron recovery rate of more than 90%, and a dephosphorization rate greater than 80% low-phosphorus iron ore powder. The roasting temperature of the present invention is greatly reduced, energy consumption is saved, and the recovery rate of iron is increased; compared with traditional acid leaching process, the water leaching acid adjustment pH process of the present invention can reduce the loss of iron and reduce the consumption of acid. The present invention has simple process, low production cost, good phosphorus reduction effect, is suitable for industrial-scale utilization of high-phosphorus iron ore, and can solve the technical problem that current high-phosphorus iron ore cannot be fully utilized.

Description

Technical Field

[0001] The present invention relates to a dephosphorization method for high-phosphorus iron ore, in particular to a dephosphorization method for high-phosphorus oolitic hematite. Background Art

[0002] Although many researchers have begun to study various dephosphorization methods for high-phosphorus iron ores since 1930, such as physical beneficiation, acid leaching, bioleaching, magnetic roasting, and coal-based direct reduction followed by magnetic separation, and have made some progress, there is currently no commercialized and practical process.

[0003] Physical beneficiation methods mainly include gravity separation, magnetic separation, and flotation. They are simple, reasonable, low-cost, and have little environmental pollution. However, due to the complex structure, fine mineral crystal size, and high content of harmful element phosphorus of high-phosphorus oolitic hematite, a single beneficiation process has problems such as low iron recovery rate and low dephosphorization rate, and it is impossible to obtain iron concentrate with high iron grade and low phosphorus content. Acid leaching dephosphorization usually uses hydrochloric acid, nitric acid, or sulfuric acid to acid-leach the ore for dephosphorization. The advantage is that the phosphate minerals do not need to be completely dissociated into monomers, which has a good dephosphorization effect. The disadvantage is that the dephosphorization consumes a lot of acid and is costly, which can easily lead to the dissolution of iron minerals in soluble ores, resulting in iron loss. Microbial leaching mainly uses microbial metabolism to produce acid to lower the pH value, thereby dissolving phosphate minerals and achieving the purpose of dephosphorization. The advantages are low cost and environmental friendliness, but it is usually time-consuming and inefficient. The magnetization roasting process is to add a reducing agent and a dephosphorization agent at a roasting temperature of 700℃~900℃, roast for a period of time to reduce the hematite iron ore to magnetite, and then obtain magnetite concentrate powder after ball milling and magnetic separation. For example, the patent "A method for iron separation and dephosphorization of high-phosphorus oolitic hematite" (application number: 202010903357.6) proposes adding sodium salt to high-phosphorus oolitic hematite to prepare pellets, reducing and roasting at 750-950℃, and then extracting iron and dephosphorizing through acid leaching and alkaline leaching to prepare low-phosphorus magnetite concentrate with an iron grade of 62%~70%, a total iron recovery rate of 68%~77%, and a dephosphorization rate of more than 90%. However, it faces the problems of complex process, high cost and low iron recovery rate. In addition, the use of coal-based direct reduction followed by magnetic separation to treat high-phosphorus iron ore can significantly improve the iron grade and achieve a high dephosphorization rate. However, since coal powder, coke, carbon powder, etc. are used as reducing agents, and the process reduction temperature must be above 1100°C or even higher, not only is the cost high, but the iron recovery rate is also low, making it difficult to fully utilize the advantages of this process. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the shortcomings of the above-mentioned existing dephosphorization technologies and propose a dephosphorization method for high-phosphorus iron ore. This method uses low-temperature roasting with the addition of sodium hydroxide, and then uses the waste heat to directly leaching the ore and adjusting the pH to 6.5-7 with acid. This promotes the dissolution of phosphorus in the solution with virtually no iron loss. Low-phosphorus iron ore powder is then obtained through solid-liquid separation. This method can effectively reduce the phosphorus content in the iron concentrate, improve the iron recovery rate, and obtain low-phosphorus iron ore powder that meets industrial requirements. The method also significantly reduces production costs, overcoming the bottlenecks of high cost and low efficiency of traditional processes, and enabling large-scale utilization of high-phosphorus iron ore resources that are difficult to process using traditional processes.

[0005] The present invention provides a method for dephosphorizing high-phosphorus iron ore, comprising the following steps:

[0006] Step 1

[0007] The high-phosphorus iron ore is crushed and ground to less than 74 μm, accounting for more than 80%. The high-phosphorus iron ore powder is mixed with sodium hydroxide solid in a certain ratio and stirred evenly. The mixture is roasted at a temperature of 200° C. to 400° C. and a roasting time of 0.5 h to 2 h. The high-phosphorus iron ore powder contains Ca and P. The mass ratio of Ca in the high-phosphorus iron ore powder to the added sodium hydroxide is 0.40:1-0.75:1 (after conversion, the molar ratio of Ca to NaOH in the mixture is 0.40:1-0.75:1), preferably 0.50:1-0.65:1 (after conversion, the molar ratio of Ca to NaOH in the mixture is 0.40:1-0.75:1), and preferably 0.50:1-0.65:1 (after conversion, the molar ratio of Ca to NaOH in the mixture is 0.50:1-0.65:1). The molar ratio of Ca to NaOH in the mixture is 0.50:1-0.65:1), more preferably 0.50-0.60:1 (after conversion, the molar ratio of Ca to NaOH in the mixture is 0.50:1-0.60:1), and the mass ratio of P in the high-phosphorus iron ore powder to the added sodium hydroxide is 0.04:1-0.09:1 (after conversion, the molar ratio of P to NaOH in the mixture is 0.05:1-0.12:1, preferably 0.06:1-0.07:1 (after conversion, the molar ratio of P to NaOH in the mixture is 0.08:1-0.09:1);

[0008] Step 2

[0009] The mixture obtained in step 1 is directly immersed in water using the residual heat after calcination according to a solid-liquid ratio of 1:5 to 1:10, acid is added and stirred continuously to adjust the pH of the solution to 6.5 to 7;

[0010] Step 3

[0011] The solution obtained in step 2 is filtered, and the filter residue is dried to obtain low-phosphorus iron ore powder.

[0012] The present invention discloses a method for dephosphorizing high-phosphorus iron ore. The calcium in the high-phosphorus iron ore powder exists in the form of apatite and calcite.

[0013] The present invention provides a method for dephosphorizing high-phosphorus iron ore. In step 1, the ore is calcined at 200°C to 400°C, preferably at 260°C to 340°C, for 0.5h to 2h, preferably 50min to 75min. During the heating and calcining process, the high-phosphorus iron ore powder mainly contains apatite (Ca3(PO4)2) in the phosphate ore phase and calcite (CaCO3) in the gangue phase, which reacts chemically with sodium hydroxide to generate sodium phosphate (Na3PO4) and calcium hydroxide (Ca(OH)2), sodium carbonate (Na2CO3) and calcium hydroxide (Ca(OH)2). The sodium phosphate (Na3PO4) and sodium carbonate (Na2CO3) are easily soluble in water, and the calcium hydroxide (Ca(OH)2) is slightly soluble in water.

[0014] Ca3(PO4)2+6NaOH→2Na3PO4+3Ca(OH)2(1)

[0015] CaCO3+2NaOH→Na2CO3+Ca(OH)2(2).

[0016] The present invention provides a method for dephosphorizing high-phosphorus iron ore. In step 1, if the amount of NaOH added is too low, the reaction of generating Na3PO4 cannot proceed, and dephosphorization cannot be performed. If the amount of NaOH added is too high, a large amount of acid will be consumed for subsequent neutralization, which will increase costs. It will also affect the iron recovery rate. In a more serious case, the iron grade in the product will be reduced.

[0017] The present invention provides a method for dephosphorizing high-phosphorus iron ore. In step 1, if the roasting temperature is too low, the reaction kinetic conditions are poor, resulting in an insignificant dephosphorization effect. If the temperature is too high, on the one hand, it will affect the iron recovery rate, the dephosphorization rate and reduce the iron grade in the product; on the other hand, it will cause a large amount of energy consumption.

[0018] The present invention provides a method for dephosphorizing high-phosphorus iron ore. In step 2, the calcined mixture is first added to water at a solid-to-liquid ratio of 1:5 to 1:10, stirred, and then acid is added to the solution to control the pH of the solution to 6.5-7. The calcined mixture is first added to water to utilize waste heat to dissolve sodium phosphate (Na3PO4), sodium carbonate (Na2CO3), and calcium hydroxide (Ca(OH)2). After stirring, acid is then used to adjust the pH of the solution system, thereby continuously consuming the calcium hydroxide generated by the above reaction and preventing the calcium hydroxide from reprecipitating and adsorbing on the solid surface and simultaneously adsorbing phosphate due to a temperature drop. Furthermore, the acid added at this time is diluted by the water and reacts with the calcium hydroxide, preventing excessive Fe dissolution, thereby preventing iron loss.

[0019] In the present invention, the calcined mixture is first added to water and stirred, and then acid is added to the solution and the pH value of the solution is controlled to be 6.5-7. If the pH is too low, the acid consumption will be greatly increased and a large amount of iron loss will be caused. If the pH is too high, it will be detrimental to the dissolution of the dephosphorization product, resulting in poor dephosphorization effect and difficulty in treating the alkaline filtrate.

[0020] The present invention provides a method for dephosphorizing high-phosphorus iron ore. The acid added to the mixed solution is at least one selected from hydrochloric acid, nitric acid, formic acid, and acetic acid. In industrial applications, low-quality, low-cost waste acid can be used as a substitute.

[0021] The present invention discloses a method for dephosphorizing high-phosphorus iron ore. The high-phosphorus iron ore has an iron grade of 38.5wt% to 51wt%, a P content of 0.55wt% to 1.23wt%, a SiO2 content of 8.5wt% to 11.5wt%, and a CaO content of 8.3wt% to 12.5wt%.

[0022] As a preferred high-phosphorus iron ore, the iron grade is 42.20wt%~49.46wt%, the P content is 0.75wt%~1.23wt%, the SiO2 content is 10.55wt%~10.8wt%, and the CaO content is 8.32wt%~9.72wt%.

[0023] Preferably, the P content in the high-phosphorus iron ore is 0.75 wt% to 1.0 wt%, and the CaO content is 9 wt% to 9.7 wt%.

[0024] The invention discloses a method for dephosphorizing high-phosphorus iron ore; the high-phosphorus iron ore is selected from at least one of high-phosphorus oolitic hematite, high-phosphorus limonite and high-phosphorus magnetite.

[0025] Preferably, the present invention provides a method for dephosphorizing high-phosphorus iron ore; when the P content in the high-phosphorus iron ore is 0.8wt%~0.85wt% and the CaO content is 9.5wt%~9.6wt%; the amount of high-phosphorus iron ore powder and sodium hydroxide added is: in parts by weight, 100g~200g of sodium hydroxide is added to 1kg of high-phosphorus iron ore powder.

[0026] As a further preferred embodiment, the present invention provides a method for dephosphorizing high-phosphorus iron ore; when the P content in the high-phosphorus iron ore is 0.8wt%~0.85wt% and the CaO content is 9.5wt%~9.6wt%; the amount of high-phosphorus iron ore powder and sodium hydroxide added is: in parts by weight, 125g~175g of sodium hydroxide is added to 1kg of high-phosphorus iron ore powder.

[0027] As a further preferred embodiment, the present invention provides a method for dephosphorizing high-phosphorus iron ore; when the P content in the high-phosphorus iron ore is 0.8wt%~0.85wt% and the CaO content is 9.5wt%~9.6wt%; the amount of high-phosphorus iron ore powder and sodium hydroxide added is: 145g~155g of sodium hydroxide is added to 1kg of high-phosphorus iron ore powder.

[0028] The present invention provides a method for dephosphorizing high-phosphorus iron ore. The resulting low-phosphorus iron ore powder has a small, porous particle size. This porous low-phosphorus iron ore powder can be used for subsequent sintering, pelletizing, and blast furnace smelting, and has the advantages of good air permeability, large specific surface area, and good ball-forming properties. Furthermore, after treatment to improve the iron grade, it can be used in electric furnace smelting to produce high-value-added direct reduced iron.

[0029] The invention discloses a method for dephosphorizing high-phosphorus iron ore; the filtering method includes suction filtration.

[0030] The iron ore powder obtained after dephosphorization according to the present invention has a grade of 43.8wt% to 54.7wt%, a TFe recovery rate of 91wt% to 93.5wt%, and a phosphorus content of 0.11wt% to 0.20wt%.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] 1. The process of the present invention is simple, easy to operate, low in production cost and strong in ore adaptability.

[0033] 2. The invention proposes a leaching process of adding an appropriate amount of sodium hydroxide (especially controlling the ratio of sodium hydroxide to calcium and phosphorus in the raw materials within a certain range), low-temperature roasting, and then water leaching to adjust the pH. The dephosphorization efficiency is high and the iron loss is low. The iron recovery rate in the leaching process can reach more than 90%, and the low-phosphorus iron ore powder with a dephosphorization rate of more than 80% greatly improves the utilization efficiency of high-phosphorus iron ore and simplifies the process flow.

[0034] 3. The roasting temperature of the present invention is 200°C to 400°C, preferably 260°C to 340°C. Compared with the high temperatures required by magnetization roasting and direct reduction roasting processes, low-temperature roasting can save a lot of energy consumption.

[0035] 4. The acid used in the leaching process of the present invention is hydrochloric acid, nitric acid, formic acid or acetic acid, and can also be replaced by low-priced waste acid of poor quality. Compared with the acid leaching process, the amount of acid used is greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of a dephosphorization method for high-phosphorus iron ore according to the present invention;

[0037] Figure 2 The XRD patterns of the samples obtained under different treatment processes in Example 2 are shown;

[0038] Figure 3 These are the morphology photos and SEM photos of the raw materials used in Example 2;

[0039] Figure 4 The morphology photo and SEM photo of the low-phosphorus iron ore powder obtained in Example 2;

[0040] Figure 5 The XRD patterns of the samples obtained in Comparative Example 1 and Comparative Example 4 by adding sodium hydroxide to the roasting process are shown.

[0041] In the XRD pattern, H is hematite, Q is quartz, C is calcite CaCO3, A is apatite, N is sodium phosphate Na3PO4, E is calcium hydroxide Ca(OH)2, and F is sodium carbonate Na2CO3. DETAILED DESCRIPTION

[0042] The present invention will be described in detail below with reference to the accompanying drawings and embodiments. Figure 1 and Table 1, but the protection scope of the present invention is not limited to the following examples.

[0043] Example 1:

[0044] The high-phosphorus iron ore used in this embodiment is a high-phosphorus oolitic hematite ore from western Hubei Province in China. The iron grade of the raw ore is 38.89%, and the phosphorus content is 1.05%. Most of the iron element exists in the form of Fe2O3, and the phosphorus element exists mainly in the form of apatite. The remaining main components are as follows by mass percentage: FeO 2.55%, SiO2 11.40%, Al2O3 5.59%, CaO 11.20%, MgO 1.0%, S 0.040%, Na2O 0.075%, and K2O 0.50%. The specific operation is as follows:

[0045] 1. Grind 1 kg of raw ore to a particle size of -74 μm, accounting for 90% by weight. Add 150 g of sodium hydroxide to the ore and mix. The mass ratio of Ca in the high-phosphorus oolitic hematite to the added sodium hydroxide is 0.61:1, and the mass ratio of P in the high-phosphorus iron ore powder to the added sodium hydroxide is 0.08:1. After mixing evenly, place the mixture in a muffle furnace and heat it to 200 ° C and keep it warm for 1 hour.

[0046] 2. After calcination, take out the sample and add 7L of water. After stirring, add 1mol / L hydrochloric acid to the mixed solution to adjust the pH value to 6.8-7. Continue stirring for 1 hour. During the stirring period, hydrochloric acid is continuously added dropwise to maintain the pH value of the solution at 6.8-7. During stirring, control the speed to 500r / min.

[0047] 3. The solution was then filtered by solid-liquid separation, and the resulting filter residue was dried to obtain 809 g of low-phosphorus iron ore powder with an iron grade of 43.8% and a phosphorus content of 0.20 wt%, of which the iron recovery rate was 91.1% and the dephosphorization rate was 80.95%.

[0048] Example 2:

[0049] The high-phosphorus iron ore powder used in this embodiment is high-phosphorus oolitic hematite from western Hubei Province in China. The iron grade of the raw ore is 45.08%, and the phosphorus content is 0.82%. Most of the iron element exists in the form of Fe2O3, and the phosphorus element exists mainly in the form of apatite. The remaining main components are as follows by mass percentage: FeO 2.00%, SiO2 10.75%, Al2O3 5.65%, CaO 9.55%, MgO 0.74%, S 0.05%, Na2O 0.062%, and K2O 0.49%. The specific operation is as follows:

[0050] 1. Grind 1 kg of raw ore to a particle size of -74 μm, accounting for 90% by weight. Add 150 g of sodium hydroxide to the ore and mix. The mass ratio of Ca in the high-phosphorus oolitic hematite to the added sodium hydroxide is 0.52:1, and the mass ratio of P in the high-phosphorus iron ore powder to the added sodium hydroxide is 0.06:1. After mixing evenly, place the mixture in a muffle furnace and heat it to 300 ° C and keep it warm for 1 hour.

[0051] 2. After calcination, take out the sample and add 7L of water. After stirring, add 1mol / L hydrochloric acid to the mixed solution to adjust the pH value to 6.8-7. Continue stirring for 1 hour. During the stirring period, hydrochloric acid is continuously added dropwise to maintain the pH value of the solution at 6.8-7. During stirring, control the speed to 500r / min.

[0052] 3. The solution was then filtered by solid-liquid separation, and the resulting filter residue was dried to obtain 835 g of low-phosphorus iron ore powder with an iron grade of 50.5% and a phosphorus content of 0.13 wt%. The iron recovery rate was 93.5% and the dephosphorization rate was 84.15%.

[0053] 4. Figure 2The XRD patterns of samples obtained under different treatment processes in Example 2 are shown. XRD analysis reveals that the peak intensities of the calcite and apatite phases decrease in the sample calcined with sodium hydroxide, while peaks of the sodium phosphate, calcium hydroxide, and sodium carbonate phases appear. This indicates that under 300°C calcination conditions, the added sodium hydroxide reacts chemically with the calcite and apatite to produce sodium phosphate, calcium hydroxide, and sodium carbonate. The peaks of the sodium phosphate, calcium hydroxide, and sodium carbonate phases disappear in the sample after washing and pH adjustment. This indicates that after washing and adjusting the pH to 6.8-7, the sodium phosphate and sodium carbonate dissolve in water, while the calcium hydroxide is consumed by hydrochloric acid to produce calcium chloride dissolved in water. Finally, filtration and drying yield low-phosphorus iron ore powder with a phosphorus content of less than 0.2wt%.

[0054] 5. Figure 3 and Figure 4 The figures are the morphology photos and SEM photos of the raw materials used and the morphology photos and SEM photos of the obtained low-phosphorus iron ore powder respectively. Through comparison, it was found that after the pH leaching process was adjusted by water leaching after adding sodium hydroxide and low-temperature roasting, the sample changed from a structure with larger particles and dense combination to a structure with smaller particles and more loose and porous.

[0055] Example 3:

[0056] The high-phosphorus iron ore powder used in this embodiment is high-phosphorus oolitic hematite from western Hubei Province in China. The iron grade of the raw ore is 50.46%, and the phosphorus content is 0.55%. Most of the iron element exists in the form of Fe2O3, and the phosphorus element exists mainly in the form of apatite. The remaining main components are as follows by mass percentage: FeO 1.02%, SiO2 8.54%, Al2O3 3.80%, CaO 8.7%, MgO 0.70%, S 0.035%, Na2O 0.050%, and K2O 0.40%. The specific operation is as follows:

[0057] 1. Grind 1 kg of raw ore to a particle size of -74 μm, accounting for 90% by weight. Add 150 g of sodium hydroxide to the ore and mix. The mass ratio of Ca in the high-phosphorus oolitic hematite to the added sodium hydroxide is 0.48:1, and the mass ratio of P in the high-phosphorus iron ore powder to the added sodium hydroxide is 0.04:1. After mixing evenly, place the mixture in a muffle furnace and heat it to 400 ° C and keep it warm for 1 hour.

[0058] 2. After calcination, take out the sample and add 7L of water. After stirring, add 1mol / L hydrochloric acid to the mixed solution to adjust the pH value to 6.8-7. Continue stirring for 1 hour. During the stirring period, hydrochloric acid is continuously added dropwise to maintain the pH value of the solution at 6.8-7. During stirring, control the speed to 500r / min.

[0059] 3. The solution was then filtered by solid-liquid separation, and the resulting filter residue was dried to obtain 850 g of low-phosphorus iron ore powder with an iron grade of 54.7% and a phosphorus content of 0.11 wt%, with an iron recovery rate of 92.1% and a dephosphorization rate of 80.00%.

[0060] Example 4:

[0061] This embodiment is basically the same as Example 2, except that 200 g of sodium hydroxide is added, wherein the mass ratio of Ca in the high-phosphorus oolitic hematite to the added sodium hydroxide is 0.41:1, and the mass ratio of P in the high-phosphorus iron ore powder to the added sodium hydroxide is 0.05:1, and the final filter residue is dried to obtain low-phosphorus iron ore powder with an iron grade of 50.0% and a phosphorus content of 0.15wt%, wherein the iron recovery rate is 91.5% and the dephosphorization rate is 81.71%.

[0062] Example 5:

[0063] This embodiment is basically the same as Example 2, except that 100 g of sodium hydroxide is added, wherein the mass ratio of Ca in the high-phosphorus oolitic hematite to the added sodium hydroxide is 0.75:1, and the mass ratio of P in the high-phosphorus iron ore powder to the added sodium hydroxide is 0.09:1. After drying, the final filter residue obtained finally obtains 825 g of low-phosphorus iron ore with an iron grade of 49.7% and a phosphorus content of 0.16 wt%, wherein the iron recovery rate is 91.0% and the dephosphorization rate is 80.49%.

[0064] Example 6:

[0065] This embodiment is basically the same as Example 2, except that 125 g of sodium hydroxide is added, wherein the mass ratio of Ca in the high-phosphorus oolitic hematite to the added sodium hydroxide is 0.61:1, and the mass ratio of P in the high-phosphorus iron ore powder to the added sodium hydroxide is 0.07:1. After drying, the final filter residue obtained finally obtains 817 g of low-phosphorus iron ore powder with an iron grade of 50.3% and a phosphorus content of 0.14%, wherein the iron recovery rate is 91.2% and the dephosphorization rate is 82.93%.

[0066] Comparative Example 1:

[0067] This comparative example is basically the same as Example 2, except that the roasting temperature is 100°C, the mass ratio of Ca in the high-phosphorus oolitic hematite to the added sodium hydroxide is 0.52:1, and the mass ratio of P in the high-phosphorus iron ore powder to the added sodium hydroxide is 0.06:1. After drying, the final filter residue obtained finally obtained 850g of iron ore powder with an iron grade of 48.9% and a phosphorus content of 0.53wt%, wherein the iron recovery rate is 92.2% and the dephosphorization rate is 35.37%.

[0068] Figure 5This is the XRD pattern of the sample obtained under the calcination process with the addition of sodium hydroxide in Comparative Example 1. Through XRD analysis, it was found that under the calcination condition of 100°C, the peak intensity of the calcite phase and the apatite phase in the sample after calcination with the addition of sodium hydroxide decreased, but compared with Example 2, the peak intensity decrease after calcination at 300°C with the addition of sodium hydroxide was weaker. In addition, no peaks of the sodium phosphate phase, calcium hydroxide phase and sodium carbonate phase appeared, indicating that under the calcination condition of 100°C, the added sodium hydroxide basically did not react with the calcite and apatite, and effective dephosphorization could not be achieved.

[0069] Comparative Example 2:

[0070] This comparative example is basically the same as Example 2, except that the roasting temperature is 500°C, the mass ratio of Ca in the high-phosphorus oolitic hematite to the added sodium hydroxide is 0.52:1, and the mass ratio of P in the high-phosphorus iron ore powder to the added sodium hydroxide is 0.06:1. After drying, the final filter residue obtained finally obtained 798 g of iron ore powder with an iron grade of 49.5% and a phosphorus content of 0.43%, wherein the iron recovery rate is 87.6% and the dephosphorization rate is 47.56%.

[0071] Comparative Example 3:

[0072] This comparative example is basically the same as Example 2, except that the roasting temperature is 700°C, the mass ratio of Ca in the high-phosphorus oolitic hematite to the added sodium hydroxide is 0.52:1, and the mass ratio of P in the high-phosphorus iron ore powder to the added sodium hydroxide is 0.06:1. After drying, the final filter residue obtained finally obtained 790g of iron ore powder with an iron grade of 49.0% and a phosphorus content of 0.48wt%, wherein the iron recovery rate is 85.9% and the dephosphorization rate is 41.46%.

[0073] Comparative Example 4:

[0074] This comparative example is basically the same as Example 2, except that 25 g of sodium hydroxide is added, wherein the mass ratio of Ca in the high-phosphorus oolitic hematite to the added sodium hydroxide is 2.80:1, and the mass ratio of P in the high-phosphorus iron ore powder to the added sodium hydroxide is 0.34:1. After drying, the final filter residue obtained finally obtained 819 g of iron ore powder with an iron grade of 48.8% and a phosphorus content of 0.38 wt%, wherein the iron recovery rate was 88.7% and the dephosphorization rate was 53.66%.

[0075] Figure 5This is the XRD pattern of the sample obtained under the sodium hydroxide addition calcination process in Comparative Example 4. Through XRD analysis, it was found that when only 25 g of sodium hydroxide was added, the peak intensity of the calcite phase and the apatite phase in the sample after sodium hydroxide addition and calcination was reduced, but compared with Example 2, the peak intensity reduction after sodium hydroxide addition and calcination at 300°C was weaker, and peaks of sodium phosphate phase, calcium hydroxide phase and sodium carbonate phase appeared, but compared with Example 2, the above three peak intensities after calcination with 150 g of sodium hydroxide added were weaker, indicating that the addition of 25 g of sodium hydroxide was insufficient in the amount of reactants and could not effectively dephosphorize.

[0076] Comparative Example 5:

[0077] This comparative example is substantially the same as Example 2, except that 300g of sodium hydroxide is added, wherein the mass ratio of Ca to the addition of sodium hydroxide in the high-phosphorus oolitic hematite is 0.30: 1, and the mass ratio of P to the addition of sodium hydroxide in the high-phosphorus iron ore powder is 0.04: 1, and the filter residue finally obtained after drying ultimately obtains an iron grade of 50.1%, 811g of low-phosphorus iron ore powder with a phosphorus content of 0.14%, wherein the iron recovery rate is 90.1%, and the dephosphorization rate is 82.93%, but the addition of excessive NaOH causes a substantial increase in the amount of acid added. Simultaneously, the iron recovery rate also begins to show a downward trend, and even begins to decline compared to the grade of its product in Example 2.

[0078]

Claims

1. A method for dephosphorizing high-phosphorus iron ore; characterized in that ； The steps include: Step 1 The high-phosphorus iron ore is crushed and ground to a size of less than 74 μm, accounting for more than 80%. The high-phosphorus iron ore powder is mixed with sodium hydroxide solid in a certain proportion and stirred evenly. The mixture is roasted at a temperature of 200° C. to 400° C. and a roasting time of 0.5 h to 2 h. The high-phosphorus iron ore powder contains calcium and phosphorus. The mass ratio of calcium in the high-phosphorus iron ore powder to the added sodium hydroxide is 0.40:1-0.75:1, and the mass ratio of phosphorus in the high-phosphorus iron ore powder to the added sodium hydroxide is 0.04:1-0.09:

1. Step 2 The mixture obtained in step 1 is directly immersed in water using the residual heat after calcination according to a solid-liquid ratio of 1:5 to 1:10, acid is added and stirred continuously to adjust the pH of the solution to 6.5 to 7; Step 3 The solution obtained in step 2 is filtered, and the filter residue is dried to obtain low-phosphorus iron ore powder.

2. A high-phosphorus iron ore dephosphorization method according to claim 1, characterized in that: The occurrence forms of calcium in high-phosphorus iron ore powder include apatite and calcite.

3. A high-phosphorus iron ore dephosphorization method according to claim 1, characterized in that: In step 1, calcination is performed at 260°C to 340°C for 50 to 75 minutes.

4. A high-phosphorus iron ore dephosphorization method according to claim 1, characterized in that: In step 2, the calcined mixture is first added into water according to a solid-liquid ratio of 1:5 to 1:10, stirred, and then acid is added into the solution to control the pH value of the solution to 6.5-7.

5. A high-phosphorus iron ore dephosphorization method according to claim 1, characterized in that: The acid added to the mixed solution is at least one selected from hydrochloric acid, nitric acid, formic acid and acetic acid.

6. A high-phosphorus iron ore dephosphorization method according to claim 1, characterized in that: In high-phosphorus iron ore, the iron grade is 38.5wt%~51wt%, the P content is 0.55wt%~1.23wt%, the SiO2 content is 8.5wt%~11.5wt%, and the CaO content is 8.3wt%~12.5wt%.

7. The method for dephosphorizing a high-phosphorus iron ore according to claim 1, wherein: The high-phosphorus iron ore is selected from at least one of high-phosphorus oolitic hematite, high-phosphorus limonite and high-phosphorus magnetite.

8. The method for dephosphorizing a high-phosphorus iron ore according to claim 6, wherein: When the P content in the high-phosphorus iron ore is 0.8wt%~0.85wt% and the CaO content is 9.5wt%~9.6wt%, the amount of high-phosphorus iron ore powder and sodium hydroxide added is: in parts by weight, 100g~200g of sodium hydroxide is added to 1kg of high-phosphorus iron ore powder.

9. A high-phosphorus iron ore dephosphorization method according to claim 8, characterized in that: The addition amounts of high-phosphorus iron ore powder and sodium hydroxide used are as follows: in parts by weight, 125g~175g of sodium hydroxide is added to 1kg of high-phosphorus iron ore powder.

10. The method for dephosphorizing high-phosphorus iron ore according to claim 9, characterized in that: The addition amounts of high-phosphorus iron ore powder and sodium hydroxide used are as follows: in parts by weight, 145g~155g of sodium hydroxide is added to 1kg of high-phosphorus iron ore powder.

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