A combined process of hematite hydrogen-based mineral phase transformation-magnetic separation-reverse flotation

Abstract

The present application relates to the technical field of iron ore dressing, in particular to a combined process of hydrogen-based mineral phase conversion-magnetic separation-reverse flotation for hematite. In the prior art, the process for dressing hematite has the problems of low concentrate grade, low iron recovery rate, and incomplete reduction of coarse-grained minerals and over-reduction of fine-grained minerals in the hydrogen-based mineral phase conversion technology. To solve the above problems, the present application fully separates hematite and diaspore after grinding and grading, and then converts the hematite Fe2O3.nH2O into Fe2O3 by hydrolysis and then into magnetite Fe3O4, and converts the diaspore Al2O3.nH2O into corundum Al2O3, and then combines the processes of magnetic separation and flotation to obtain high-purity iron concentrate, which reduces energy consumption and reagent use, improves the grade and recovery rate of iron concentrate, and realizes the double optimization of economy and environmental performance.

Description

Technical Field

[0001] This invention relates to the field of iron ore beneficiation technology, specifically to a combined process of hematite hydrogen-based mineral phase conversion-magnetic separation-reverse flotation. Background Technology

[0002] Traditional iron ore beneficiation processes mainly include crushing, grinding, magnetic separation, and flotation. However, these processes have significant shortcomings when handling complex ores such as hematite. Specifically, they result in low concentrate grades (total iron (TFe) content typically between 45% and 48% and SiO2 content above 12%), low iron recovery rates (only 62% to 78%), complex processes, low production efficiency, and high costs, making it difficult to effectively improve resource utilization. In recent years, hydrogen-based mineral phase conversion technology has become a research hotspot for solving the problem of utilizing complex and difficult-to-process iron ores such as hematite. This technology uses hydrogen as a reducing agent to convert weakly magnetic iron minerals (such as hematite) into strongly magnetic iron minerals (such as magnetite) through low-temperature reduction, thereby significantly improving magnetic separation efficiency. This technology not only reduces energy consumption but also achieves ultra-low emissions of dust, sulfur dioxide, and nitrogen oxides, aligning with the development direction of green mining. Furthermore, hydrogen-based mineral phase conversion technology is closely integrated with the clean energy industry, and its large-scale promotion can also promote the development of regional green hydrogen industries.

[0003] However, hydrogen-based mineral phase conversion technology still faces many challenges in practical applications. For example, the reduction efficiency varies significantly among different particle sizes, easily leading to under-reduction of coarse-grained minerals and over-reduction of fine-grained minerals, affecting the separation effect of subsequent magnetic separation. Furthermore, the complex distribution of silica-alumina gangue minerals means that the efficiency of subsequent flotation for impurity removal still needs improvement. Therefore, further optimizing the hydrogen-based mineral phase conversion process, combined with efficient magnetic levitation joint separation technology, to achieve precise control and efficient development of complex iron ore resources is of great significance for solving current mineral processing bottlenecks. Summary of the Invention

[0004] To address the problems existing in current iron ore beneficiation technologies, this invention provides a combined process for hematite hydrogen-based mineral phase transformation, magnetic separation, and reverse flotation. The invention mainly comprises five stages: grinding and classification, hydrogen-based mineral phase transformation, protective gas cooling, magnetic separation, and reverse flotation, to achieve the removal and separation of iron concentrate and gangue minerals from hematite.

[0005] This invention provides a combined process for hematite hydrogen-based mineral phase transformation, magnetic separation, and reverse flotation, comprising the following steps:

[0006] Step 1: Grinding and Classification: The raw hematite ore enters a conical ball mill and classification equipment, and after grinding and classification, roasting raw material is obtained.

[0007] Step 2 Hydrogen-based mineral phase transformation: The roasted raw material obtained in Step 1 is placed in a suspension roasting furnace for hydrogen-based mineral phase transformation suspension roasting. This process dehydrates the hematite Fe2O3·nH2O in the roasted raw material to Fe2O3, which is then converted to magnetite Fe3O4, and the diaspore Al2O3·nH2O is converted to corundum Al2O3, thus obtaining the mineral phase transformation product.

[0008] The mineral phase transformation equation is as follows:

[0009] Fe₂O₃·nH₂O→Fe₂O₃+nH₂O

[0010] 3Fe₂O₃ + H₂ → 2Fe₃O₄ + H₂O

[0011] Al₂O₃·nH₂O→Al₂O₃+H₂O

[0012] Step 3: Protective gas cooling: After roasting, a protective gas is introduced to cool the mineral phase transformation products and obtain the cooled products; the protective gas can prevent the reverse oxidation of the mineral phase transformation products.

[0013] Step 4: Weak magnetic separation: The cooled product is subjected to weak magnetic separation to obtain magnetic concentrate and magnetic tailings, thus achieving the initial separation of gangue minerals.

[0014] Step 5: Reverse flotation separation: The magnetic concentrate is subjected to reverse flotation to obtain iron concentrate.

[0015] Furthermore, in step 1, the content of particles with a diameter of 12μm to 74μm in the ore after grinding and classification is 55% to 75%, and the corresponding slurry concentration of the ore is 30% to 40%. The slurry is then dried to become the roasting raw material.

[0016] Furthermore, in step 2, the roasting raw material is first preheated in an air atmosphere at 100℃-200℃ to remove all crystal water and adsorbed water. Then, nitrogen and reducing hydrogen are introduced as roasting gases for suspension roasting. The suspension roasting temperature is 500℃~700℃, the concentration of suspension roasting hydrogen gas is 15%~25%, and the roasting gas flow rate is 1000 m³ / h per ton of roasting raw material at ambient temperature and pressure. 3 / h-1400m 3 / h, the suspension roasting time is 20min-40min.

[0017] Furthermore, in step 3, the cooling environment is nitrogen, the cooling time is 10-30 minutes, and the product temperature is ≤100℃.

[0018] Furthermore, in step 4, the magnetic field strength of the weak magnetic selection is 800 Oe to 3000 Oe.

[0019] Furthermore, in step 5, reverse flotation of the magnetic concentrate refers to preparing a reverse flotation slurry from the magnetic concentrate and then entering the reverse flotation operation. This reverse flotation operation includes a first-stage roughing, a first-stage cleaning, and three or four stages of scavenging. A combination collector, inhibitor, and pH adjuster are added to the reverse flotation slurry and it enters the roughing operation. After the roughing operation, a roughing concentrate slurry and a roughing tailings slurry are obtained. The roughing tailings slurry enters the scavenging operation, and gangue minerals are separated after the scavenging operation. A combination collector and pH adjuster are added to the roughing concentrate slurry and it enters the cleaning operation, so that the silica-alumina gangue minerals can fully adsorb the collector to achieve reverse flotation. After the cleaning operation, iron concentrate is obtained.

[0020] Furthermore, in step 5, the pH adjuster in the reverse flotation operation includes lime and sodium carbonate, the combined collector is a mixture of dodecylamine and hexadecyltrimethylammonium chloride in a mass ratio of 1:1 to 4:1, and the inhibitor includes starch;

[0021] Furthermore, in step 5, when entering the roughing operation, the concentration of the reverse flotation slurry is 35wt% to 70wt%, and the following materials are added per ton of reverse flotation slurry: 100g to 400g of inhibitor, 100g to 400g of combined collector, 200g to 800g of lime, and 100g to 500g of sodium carbonate to make the pH 8.8 to 9.2;

[0022] Furthermore, in step 5, when entering the fine separation operation, lime is added to the roughing concentrate slurry to adjust the pH to 8-10 (without adding sodium carbonate), and 20g-200g of combined collector is added per ton of roughing concentrate slurry.

[0023] Furthermore, in step 5, the obtained iron concentrate has a grade higher than 60% and an iron recovery rate higher than 90%.

[0024] Compared with traditional technologies, the combined process of hematite hydrogen-based mineral phase transformation-magnetic separation-reverse flotation for preparing iron concentrate in this invention has the following advantages:

[0025] 1. This invention achieves narrower particle size separation by precisely controlling the grinding particle size and adopting a combined grinding-classification process, which enables hematite and gibbsite to be fully liberated, avoiding secondary mudding problems caused by over-grinding of ore and improving separation efficiency and mineral output quality.

[0026] 2. This invention achieves a stable reduction reaction of hematite through suspension roasting technology involving hydrogen-based mineral phase transformation. The fluidized bed roasting process possesses excellent mass and heat transfer properties, significantly improving reaction efficiency while also achieving green and environmentally friendly goals, reducing pollution emissions from traditional roasting processes.

[0027] 3. In this invention, nitrogen gas is introduced for cooling after roasting, which effectively prevents the magnetite in the roasted product from being reverse-oxidized due to the oxidizing atmosphere, thereby improving the magnetic separation quality of the reduction product and ensuring the stability and efficiency of the process.

[0028] 4. This invention employs a multi-step separation process of "hydrogen-based mineral phase transformation - magnetic separation - reverse flotation." First, hematite is converted into strongly magnetic magnetite, and most gangue minerals are removed through weak magnetic separation. Then, reverse flotation is used to further remove silica and aluminum impurities, yielding high-purity iron concentrate. This method not only reduces reagent and energy consumption but also improves separation accuracy, achieving a dual optimization of economic and environmental performance. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a combined process flow of hematite hydrogen-based mineral phase transformation-magnetic separation-reverse flotation according to the present invention. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. It should be noted that the embodiments described in this invention are only for further explanation and illustration, and not for limiting their scope of application. All other embodiments obtained by those skilled in the art based on this invention without inventive effort are within the protection scope of this invention.

[0031] The process flow of this invention is as follows: Figure 1 As shown.

[0032] Example 1

[0033] This example uses hematite from a certain region as raw material, with the main chemical composition being TFe 26.20%, SiO2 4.15%, and Al2O3 5.65%. The specific steps are as follows:

[0034] Step 1: Grinding and Classification: The raw hematite ore is fed into a conical ball mill and classification equipment for ball milling. After ball milling, a ore material with a particle size of 12μm to 74μm and a content of 75% is obtained. The ball mill slurry concentration corresponding to this ore material is 35%. After drying, the roasted raw material is obtained.

[0035] Step 2: Hydrogen-based mineral phase conversion: The roasting feedstock obtained in Step 1 is fed into a hydrogen-based mineral phase conversion suspension roasting furnace. It is first preheated in air at 120°C, then nitrogen and reducing hydrogen are introduced. The suspension roasting process is controlled at 600°C, with a roasting gas flow rate of 1200 m³ / ton of roasting feedstock. 3 The process involves heating a hydrogen gas at a concentration of 20% for 25 minutes per hour to obtain the mineral phase transformation product.

[0036] Step 3: Protective gas cooling: After roasting, the mineral phase transformation product is cooled under a nitrogen atmosphere for 15 minutes, and then cooled to 80°C to obtain the cooled product.

[0037] Step 4: Weak magnetic separation: The cooled product is subjected to magnetic separation with a magnetic field strength of 2000 Oe to obtain magnetic concentrate and magnetic tailings.

[0038] Step 5: Reverse Flotation Separation: The magnetic concentrate is converted into a reverse flotation slurry, which enters the reverse flotation process. This process includes a roughing stage, a cleaning stage, and a scavenging stage. The reverse flotation slurry concentration is 45 wt%. 500 g / t of lime, 300 g / t of sodium carbonate are added to the slurry to adjust the pH to 8.5, along with a combined collector (400 g / t, with dodecylamine and hexadecyltrimethylammonium chloride in a 3:1 mass ratio) and a depressant (300 g / t of starch). This slurry then enters the roughing stage. After this roughing stage, roughing concentrate and roughing tailings slurry are obtained. The roughing tailings slurry is then scavenged without the addition of a collector, separating gangue minerals. Lime is added to the roughing concentrate slurry to adjust the pH to 9, and then 150 g / t of collector is added. This scavenging stage allows the silica-alumina gangue minerals to fully adsorb the collector, achieving reverse flotation. After the cleaning stage, iron concentrate is obtained. The iron concentrate grade is 60.52%, and the iron recovery rate is 91.80%.

[0039] Example 2

[0040] This example uses hematite from a certain region as raw material, with the main chemical composition being TFe 41.58%, SiO2 8.25%, and Al2O3 5.50%. The specific steps are as follows:

[0041] Step 1: Grinding and Classification: The raw hematite ore is fed into a conical ball mill and classification equipment for ball milling. After ball milling, a ore material with a particle size of 12μm to 74μm and a content of 68% is obtained. The ball mill slurry concentration corresponding to this ore material is 32%. After drying, the roasting raw material is obtained.

[0042] Step 2: Hydrogen-based mineral phase conversion: The roasting feedstock obtained in Step 1 is fed into a hydrogen-based mineral phase conversion suspension roasting furnace. It is first preheated in air at 100°C, then nitrogen and reducing hydrogen are introduced. The suspension roasting process is controlled at 650°C, with a roasting gas flow rate of 1120 m³ / ton of roasting feedstock. 3 The hydrogen gas concentration was 15% at 1h, and the roasting time was 35 min to obtain the mineral phase transformation product.

[0043] Step 3: Protective gas cooling: After roasting, the mineral phase transformation product is cooled under a nitrogen atmosphere for 25 minutes, and then cooled to 50°C to obtain the cooled product.

[0044] Step 4: Weak magnetic separation: The cooled product is subjected to magnetic separation with a magnetic field strength of 1500 Oe to obtain magnetic concentrate and magnetic tailings.

[0045] Step 5: Reverse Flotation Separation: The magnetic concentrate is converted into a reverse flotation slurry, which enters the reverse flotation process. This process includes a roughing stage, a cleaning stage, and four scavenging stages. The reverse flotation slurry concentration is 62 wt%. 600 g / t of lime, 350 g / t of sodium carbonate are added to the slurry to adjust the pH to 8.1, along with a combined collector (380 g / t, with dodecylamine and hexadecyltrimethylammonium chloride in a 2:1 mass ratio) and a depressant (300 g / t of starch). This slurry then enters the roughing stage. After this roughing stage, roughing concentrate and roughing tailings slurry are obtained. The roughing tailings slurry is then scavenged without the addition of a collector, separating gangue minerals. Lime is added to the roughing concentrate slurry to adjust the pH to 9, and then 180 g / t of collector is added. This scavenging stage allows the silica-alumina gangue minerals to fully adsorb the collector, achieving reverse flotation. After the cleaning stage, iron concentrate is obtained. The iron concentrate grade is 62.73%, and the iron recovery rate is 92.34%.

[0046] Example 3

[0047] This example uses hematite from a certain region as raw material, with the main chemical composition being TFe 32.80%, SiO2 9.70%, and Al2O3 3.20%. The specific steps are as follows:

[0048] Step 1: Grinding and Classification: The raw hematite ore is fed into a conical ball mill and classification equipment for ball milling. After ball milling, a ore material with a particle size of 12μm to 74μm and a content of 61% is obtained. The ball mill slurry concentration corresponding to this ore material is 38%. After drying, the roasting raw material is obtained.

[0049] Step 2: Hydrogen-based mineral phase conversion: The roasted feedstock obtained in Step 1 is fed into a hydrogen-based mineral phase conversion suspension roaster. It is first preheated in an air atmosphere at 150°C, then nitrogen and reducing hydrogen are introduced. The suspension roasting process is controlled at 550°C, with a roasting gas flow rate of 1400 m³ / ton of roasted feedstock. 3 The process involved a hydrogen gas concentration of 17% for 33 minutes per hour to obtain the mineral phase transformation product.

[0050] Step 3: Protective gas cooling: After roasting, the mineral phase transformation product is cooled under a nitrogen atmosphere for 20 minutes, and cooled to 65°C to obtain the cooled product.

[0051] Step 4: Weak magnetic separation: The cooled product is subjected to magnetic separation with a magnetic field strength of 2500 Oe to obtain magnetic concentrate and magnetic tailings.

[0052] Step 5: Reverse Flotation Separation: The magnetic concentrate is converted into a reverse flotation slurry, which enters the reverse flotation process. This process includes a roughing stage, a cleaning stage, and a scavenging stage. The reverse flotation slurry concentration is 54 wt%. 520 g / t of lime, 340 g / t of sodium carbonate are added to the slurry to adjust the pH to 8.7, along with a combined collector (400 g / t, dodecylamine and hexadecyltrimethylammonium chloride in a 4:1 mass ratio) and a depressant (280 g / t of starch). This slurry then enters the roughing stage. After this roughing stage, roughing concentrate and roughing tailings slurry are obtained. The roughing tailings slurry is then scavenged without the addition of a collector, separating gangue minerals. Lime is added to the roughing concentrate slurry to adjust the pH to 9, and then 150 g / t of collector is added. This scavenging stage allows the silica-alumina gangue minerals to fully adsorb the collector, achieving reverse flotation. After the cleaning stage, iron concentrate is obtained. The iron concentrate grade is 64.89%, and the iron recovery rate is 93.12%.

[0053] Example 4

[0054] This example uses hematite from a certain region as raw material, with the main chemical composition being TFe 35.95%, SiO2 9.02%, and Al2O3 3.79%. The specific steps are as follows:

[0055] Step 1: Grinding and Classification: The raw hematite ore is fed into a conical ball mill and classification equipment for ball milling. After ball milling, a ore material with a particle size of 12μm to 74μm and a content of 65% is obtained. The ball mill slurry concentration corresponding to this ore material is 40%. After drying, the roasted raw material is obtained.

[0056] Step 2: Hydrogen-based mineral phase conversion: The roasting feedstock obtained in Step 1 is fed into a hydrogen-based mineral phase conversion suspension roasting furnace. It is first preheated in air at 140°C, then nitrogen and reducing hydrogen are introduced. The suspension roasting process is controlled at 700°C, with a roasting gas flow rate of 1300 m³ / ton of roasting feedstock. 3 The hydrogen gas concentration in the roasting atmosphere was 22% at 2h, and the roasting time was 25 min, to obtain the mineral phase transformation product.

[0057] Step 3: Protective gas cooling: After roasting, the mineral phase transformation product is cooled under a nitrogen atmosphere for 22 minutes, and cooled to 60°C to obtain the cooled product.

[0058] Step 4: Weak magnetic separation: The cooled product is subjected to magnetic separation with a magnetic field strength of 1800 Oe to obtain magnetic concentrate and magnetic tailings.

[0059] Step 5: Reverse Flotation Separation: The magnetic concentrate is converted into a reverse flotation slurry, which enters the reverse flotation process. This process includes a roughing stage, a cleaning stage, and a four-stage scavenging stage. The reverse flotation slurry concentration is 66 wt%. 550 g / t of lime, 330 g / t of sodium carbonate are added to the slurry to adjust the pH to 9.1, along with a combined collector (400 g / t, dodecylamine and hexadecyltrimethylammonium chloride in a 1:1 mass ratio) and a depressant (250 g / t of starch). This slurry then enters the roughing stage. After this roughing stage, roughing concentrate and roughing tailings slurry are obtained. The roughing tailings slurry is then scavenged without the addition of a collector, separating gangue minerals. Lime is added to the roughing concentrate slurry to adjust the pH to 9, and then 190 g / t of collector is added. This scavenging stage allows the silica-alumina gangue minerals to fully adsorb the collector, achieving reverse flotation. After the cleaning stage, iron concentrate is obtained. The iron concentrate grade is 67.41%, and the iron recovery rate is 94.87%.

[0060] Comparative Example 1

[0061] Compared to Example 1, the difference is that step 3 does not use protective gas cooling, but only air cooling; the remaining steps are the same as in Example 1. In step 5, the iron concentrate grade and recovery rate were only 47.65% and 71.28%, respectively. A possible reason is that magnetite was deoxidized to hematite during the cooling process, thus affecting its magnetic separation effect and causing some iron minerals to enter the magnetic separation tailings.

[0062] Comparative Example 2

[0063] Compared to Example 2, the difference lies in that step 2 does not use hydrogen reduction, but instead uses CO instead of hydrogen. The remaining implementation steps are the same as in Example 2. In step 5, the iron concentrate grade is only 55.68%, and the recovery rate is 62.64%. The possible reason is that CO has a weaker reducing power than hydrogen, so it cannot achieve the ideal target, and the reduction process will produce a large amount of greenhouse gases, which is detrimental to environmental protection.

Claims

1. A combined process of hematite hydrogen-based mineral phase transformation-magnetic separation-reverse flotation, characterized in that, Includes the following: Step 1: Grinding and Classification: The raw hematite ore enters the ball mill and classification equipment. After grinding and classification, the content of particles with a diameter of 12μm~74μm is 55%~75%, and the corresponding slurry concentration is 30%~40%. The slurry is dried to obtain the roasting raw material. Step 2 Hydrogen-based mineral phase transformation: The roasted raw material obtained in Step 1 is placed in a suspension roasting furnace for hydrogen-based mineral phase transformation suspension roasting. This process dehydrates the hematite Fe2O3 •nH2O in the roasted raw material to Fe2O3, and then transforms it into magnetite Fe3O4. The diaspore Al2O3 •nH2O is transformed into corundum Al2O3, thus obtaining the mineral phase transformation product. Step 3: Protective gas cooling: After roasting, a protective gas is introduced to cool the mineral phase transformation product and obtain the cooled product. Step 4: Weak magnetic separation: The cooled product is subjected to weak magnetic separation to obtain magnetic concentrate and magnetic tailings, thus achieving the initial separation of gangue minerals. Step 5: Reverse flotation separation: The magnetic concentrate is subjected to reverse flotation to obtain iron concentrate; In step 2, the raw material is first preheated in air at 100℃~200℃ to remove all crystal water and adsorbed water. Then, nitrogen and reducing hydrogen are introduced as roasting gases for suspension roasting. The suspension roasting temperature is 500℃~700℃, the concentration of hydrogen gas is 15%~25%, and the flow rate of roasting gas per ton of raw material at ambient temperature and pressure is 1000 m³ / h. 3 / h~1400m 3 / h, the suspension roasting time is 20min~40min.

2. The combined process of hematite hydrogen-based mineral phase transformation-magnetic separation-reverse flotation according to claim 1, characterized in that, In step 3, the cooling environment is nitrogen, the cooling time is 10 min to 30 min, and the product temperature is ≤100℃.

3. The combined process of hematite hydrogen-based mineral phase transformation-magnetic separation-reverse flotation according to claim 1, characterized in that, In step 4, the magnetic field strength of the weak magnetic selection is 800 Oe to 3000 Oe.

4. The combined process of hematite hydrogen-based mineral phase transformation-magnetic separation-reverse flotation according to claim 1, characterized in that, In step 5, reverse flotation of magnetic concentrate refers to preparing reverse flotation slurry from magnetic concentrate and feeding it into reverse flotation operation. This reverse flotation operation includes one stage of roughing, one stage of cleaning, and three or four stages of scavenging. A combination of collectors, inhibitors, and pH adjusters are added to the reverse flotation slurry, which is then fed into the roughing operation. After the roughing operation, roughing concentrate and roughing tailings slurry are obtained. The roughing tailings slurry is then fed into the scavenging operation, where gangue minerals are separated. Collectors and pH adjusters are added to the roughing concentrate slurry, which is then fed into the cleaning operation, where the silica-alumina gangue minerals are fully adsorbed by the collectors to achieve reverse flotation. After the cleaning operation, iron concentrate is obtained.

5. The combined process of hematite hydrogen-based mineral phase transformation-magnetic separation-reverse flotation according to claim 4, characterized in that, In step 5, the pH adjuster in the reverse flotation operation includes lime and sodium carbonate, the combined collector is a mixture of dodecylamine and hexadecyltrimethylammonium chloride in a mass ratio of 1:1 to 4:1, and the inhibitor includes starch.

6. The combined process of hematite hydrogen-based mineral phase transformation-magnetic separation-reverse flotation according to claim 4, characterized in that, In step 5, when entering the roughing operation, the concentration of the reverse flotation pulp is 35wt%~70wt%. The materials added per ton of reverse flotation pulp are as follows: 100g~400g of inhibitor, 100g~400g of combined collector, 200g~800g of lime, and 100g~500g of sodium carbonate to make the pH=8.8~9.

2.

7. The combined process of hematite hydrogen-based mineral phase transformation-magnetic separation-reverse flotation according to claim 4, characterized in that, In step 5, when entering the fine separation operation, lime is added to the roughing concentrate slurry to adjust the pH to 8-10, and 20g-200g of combined collector is added per ton of roughing concentrate slurry.

8. The combined process of hematite hydrogen-based mineral phase transformation-magnetic separation-reverse flotation according to claim 4, characterized in that, In step 5, the obtained iron concentrate has a grade higher than 60% and an iron recovery rate higher than 90%.

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