System and method for reducing filtered moisture of finely ground hematite and limonite

Abstract

The invention provides a system and method for reducing filtered moisture of fine-ground hematite and limonite, and the system sequentially comprises a ball mill used for carrying out wet type fine grinding on raw hematite and limonite; the classification cyclone and the ball mill form a closed-loop ore grinding loop and are used for controlling the overflow granularity; the thickener is used for receiving overflow of the grading cyclone and is used for increasing the ore pulp concentration; the disc vacuum filter is connected with the thickener underflow and is used for carrying out vacuum filtration on the concentrated ore pulp; the water ring type vacuum pump is used for providing a filtering vacuum degree for the disc vacuum filter; wherein a cationic polyacrylamide flocculating agent is added into the thickener. According to the system, on the premise that a filter aid is not used and a filter press is not replaced, through four-parameter coupling of'granularity-concentration-flocculation-vacuum ', the filtering driving force is upgraded from'single vacuum degree' to a new mechanism of'controllable capillary channel structure and accurate vacuum degree matching ', and the water content of a filter cake is smaller than or equal to the pelletizing requirement.

Description

Technical Field

[0001] This invention relates to the field of mineral processing and dewatering technology, and in particular to a system and method for reducing the moisture content of finely ground hematite ore. Background Technology

[0002] With the increasing use of blast furnace pellets, domestic iron concentrate resources are scarce and prices are high, forcing steel companies to import large quantities of iron ore fines, mainly hematite and limonite, as substitutes. These fines require wet grinding to at least 80% of -200 mesh to meet pelletizing requirements. However, fine grinding significantly increases the surface area of ​​the slurry, forming a highly stable colloidal system. This results in a high moisture content of 14-15% in the subsequent vacuum filtration filter cake, making it muddy and causing freezing during transportation and a sharp increase in pelletizing energy consumption. Traditional solutions—adding filter aids, mixing in easily filterable minerals, or using a filter press—incur side effects such as increased reagent costs, process complexity, and significantly higher investment. Therefore, how to reduce filter cake moisture by 3-4 percentage points simply through synergistic optimization of process parameters on the basis of existing vacuum filtration equipment has become a common bottleneck that the industry urgently needs to overcome. Summary of the Invention

[0003] In view of this, embodiments of this application provide a system and method for reducing the moisture content of finely ground hematite filtration to solve the following technical problem: how to reduce the moisture content of vacuum filter cake from finely ground hematite without using filter aids or replacing the filter press, so as to meet the requirements for direct pelletizing.

[0004] In a first aspect, embodiments of this application provide a system for reducing the filtration moisture of finely ground hematite, the system comprising, in sequence along the slurry flow direction: Ball mills are used for wet fine grinding of raw hematite ore; A classifying hydrocyclone forms a closed-loop grinding circuit with the ball mill and is used to control the overflow particle size; A thickener receives the overflow from the classifying hydrocyclone and is used to increase the slurry concentration; A disc vacuum filter is connected to the underflow of the thickener and is used to perform vacuum filtration on the concentrated slurry. A water ring vacuum pump provides the filtration vacuum level for the disc vacuum filter. The thickener contains cationic polyacrylamide flocculant.

[0005] Optionally, the filtration coefficient of the disc vacuum filter is 700-900 kg / (m²·h), and the single-cycle filtration time is 2-3 minutes.

[0006] Optionally, the back of the filter cloth of the disc vacuum filter is provided with a micro-spraying device.

[0007] Secondly, embodiments of this application provide a method for reducing the moisture content of finely ground hematite using the system described in any one of the first aspects, characterized by comprising the following steps: The raw hematite ore is fed into the ball mill, and the ball mill performs wet fine grinding on the raw hematite ore to obtain the first slurry. The first slurry is fed into the classifying hydrocyclone, which classifies the first slurry and controls the overflow particle size of the classifying hydrocyclone to be -200 mesh 70-75 wt%, to obtain the second slurry. The second slurry is fed into the thickener, and 4-6 g / t of cationic polyacrylamide is added to the second slurry in the thickener. The thickener concentrates the second slurry to a bottom flow concentration of 70-75 wt% to obtain the third slurry. The third slurry is fed into the disc vacuum filter, and the 2BEA303 water ring vacuum pump provides a vacuum of 0.075-0.08 MPa to the disc vacuum filter. The third slurry is continuously filtered for 2-3 minutes under the vacuum to obtain a filter cake with a moisture content of ≤11.5 wt%.

[0008] Optionally, the cationic polyacrylamide has a molecular weight of 8-12 million and an ionic degree of 30-50%.

[0009] Optionally, the feed pressure of the classifying hydrocyclone is 0.12-0.18 MPa, and the ratio of the diameter of the sand discharge nozzle to the diameter of the overflow pipe of the classifying hydrocyclone is 0.6-0.8.

[0010] Optionally, the filter cake can be directly fed to the pelletizing process for pelletizing.

[0011] Optionally, the ultimate vacuum of the vacuum pump is 0.098 MPa, and the vacuum fluctuation is maintained at ≤0.005 MPa during operation of the vacuum pump to maintain the filter cake moisture content at ≤11.5 wt%.

[0012] Optionally, the mineral composition of the hematite comprises, by weight percentage: 60-80% hematite, 15-35% limonite, and ≤2% magnetite.

[0013] Optionally, the thickener maintains the solid particle size of the third slurry at -200 mesh (70-75 wt%) and ensures that the underflow concentration of the thickener fluctuates within the range of ≤±2 wt%, so as to stably supply the third slurry to the disc vacuum filter.

[0014] The technical solution provided in this application has at least the following beneficial effects: This application provides a system for reducing the moisture content of finely ground hematite filtration. Addressing the root causes of "hydrophilic surface, easy mud formation, filter media clogging, and dense filter cake" in fine-grained hematite, this system, without the need for filter aids or filter press replacements, upgrades the filtration driving force from "single vacuum degree" to a new mechanism of "controllable capillary channel structure + precise vacuum degree matching" through the coupling of four parameters: particle size, concentration, flocculation, and vacuum. This achieves filter cake moisture content ≤ pelletizing requirements. Particle size control: The ball mill-classification closed-loop system limits P80 to 30-40 μm, ensuring monomer dissociation while avoiding -10 μm > 35%, reducing the total surface hydration film and lowering the capillary water ratio. Concentration-Flocculation Synergy: The underflow concentration of the thickener is increased from 15% to 55-60%, and the high-concentration slurry itself reduces free water. Simultaneously, cationic PAM (1.5-2 g / t) is added, and the positive and negative charges neutralize, causing the -20 μm hematite micro-flocs to rapidly grow into 50-80 μm "pseudo-coarse particles," forming a "loose-porous-high-strength" skeleton layer on the filter cloth. The capillary pore size increases from 0.8 μm to 3-5 μm, and the capillary pressure (Pc∝1 / r) decreases by more than 60%. A vacuum of only -0.04 MPa is sufficient to overcome residual capillary force, avoiding over-compaction of the filter cake. Dynamic Vacuum Matching: The water ring pump operates at a constant pressure of -0.04 MPa, reducing energy consumption by 20% compared to the conventional -0.06 MPa. The low vacuum maintains sufficient removal of gravitational water while preventing floc collapse; the moisture content can be stabilized at 8.5-9.0% when the filter cake thickness is 15 mm. System feedback: The concentrator torque is linked to the underflow concentration. When the -10 μm content fluctuates, the flocculant dosage is automatically fine-tuned to ensure the stable particle size distribution of "pseudo-particles". This keeps the filter cake moisture standard deviation within ±0.3%, meeting the requirements of subsequent direct pelleting for a narrow moisture window. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0016] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1~6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "including" and "contains" as used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships mentioned herein, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared using existing methods.

[0017] In a first aspect, embodiments of this application provide a system for reducing the filtration moisture of finely ground hematite, the system comprising, in sequence along the slurry flow direction: Ball mills are used for wet fine grinding of raw hematite ore; A classifying hydrocyclone forms a closed-loop grinding circuit with the ball mill and is used to control the overflow particle size; A thickener receives the overflow from the classifying hydrocyclone and is used to increase the slurry concentration; A disc vacuum filter is connected to the underflow of the thickener and is used to perform vacuum filtration on the concentrated slurry. A water ring vacuum pump provides the filtration vacuum level for the disc vacuum filter. The thickener contains cationic polyacrylamide flocculant.

[0018] Cationic polyacrylamide: A water-soluble organic polymer with a positively charged molecular chain, which causes negatively charged fine particles to aggregate into loose flocs through charge neutralization and bridging. Closed-circuit grinding loop: After the ore discharged from the ball mill is classified by the classifier hydrocyclone, the underflow is returned to the ball mill for re-grinding, and the overflow enters the next stage, forming a "grind-classify-return" cycle, which is used to precisely control the product particle size.

[0019] This technical solution includes the following functions: (1) Closed-circuit grinding stabilizes the "first slurry" P80 at 30-35 μm and -200 mesh at 70-75 wt%, which ensures the dissociation of hematite monomers and avoids -10 μm > 35%, reducing the total amount of surface hydration film and lowering the proportion of capillary water in the subsequent process. (2) The thickener increases the overflow of about 15 wt% to 70-75 wt%, and the volume of free water is sharply reduced; at the same time, CPAM makes -20 μm particles into 50-80 μm "pseudo-coarse particles", and the filter cloth surface forms a "loose-high porosity-high strength" skeleton layer. The capillary pore size increases from 0.8 μm to 3-5 μm, and the capillary pressure Pc=2γcosθ / r decreases by more than 60%, so that residual capillary water can be removed under a low vacuum of 0.075-0.08 MPa, avoiding over-compaction of the filter cake. (3) The four-stage sequence of "particle size-concentration-flocculation-vacuum" in ball milling → classification → concentration → filtration is fixed. Any parameter drift in any stage will be amplified in real time by the downstream. Therefore, this sequence itself constitutes a negative feedback precondition.

[0020] In some embodiments, the filtration coefficient of the disc vacuum filter is 700-900 kg / (m²·h), and the single-cycle filtration time is 2-3 minutes.

[0021] Filtration coefficient 700-900 kg / (m²·h): Dry solids processing capacity per unit filtration area per hour, reflecting the balance between filter capacity and filter cake thickness.

[0022] This technical solution includes the following functions: (1) Coefficient ≥700 kg / (m²·h) ensures that the thickness of the filter cake on a single disc is 15-18mm. If it is too thin, the vacuum degree will drop sharply due to the "blowing through" of the filter cloth. If it is too thick, the capillary path will be long and the moisture will rebound. The upper limit of 900 kg / (m²·h) avoids overloading of the filter and maintains the filter cake forming integrity within a 2-3 min cycle. (2) 2-3 min matches 0.075-0.08 MPa, so that the filter cake completes the capillary water removal in the "constant pressure section" and is unloaded before entering the "drying section" to prevent excessive compaction that would cause moisture rebound.

[0023] In some embodiments, a micro-spraying device is provided on the back of the filter cloth of the disc vacuum filter.

[0024] Micro-spray device: Instantly rinses the back of the filter cloth with low-pressure water mist of 0.3-0.5 L / (m²·min) without damaging the vacuum seal.

[0025] This technical solution includes the following functions: (1) Fine-grained hematite is easily embedded in the pores, resulting in a reduction in the effective pore size and an increase in Pc; the back spray every 5 s can immediately wash the embedded particles back, maintain the initial resistance of the pores, and make the standard deviation of filter cake moisture ≤ ±0.3 wt%. (2) The back spray replaces the function of "pre-coated filter aid layer", avoiding the introduction of harmful impurities (SiO2, organic matter) into the pelletizing by the filter aid, and achieving the goal of "zero filter aid".

[0026] Secondly, embodiments of this application provide a method for reducing the moisture content of finely ground hematite using the system described in any one of the first aspects, characterized by comprising the following steps: The raw hematite ore is fed into the ball mill, and the ball mill performs wet fine grinding on the raw hematite ore to obtain the first slurry. The first slurry is fed into the classifying hydrocyclone, which classifies the first slurry and controls the overflow particle size of the classifying hydrocyclone to be -200 mesh 70-75 wt%, to obtain the second slurry. The second slurry is fed into the thickener, and 4-6 g / t of cationic polyacrylamide is added to the second slurry in the thickener. The thickener concentrates the second slurry to a bottom flow concentration of 70-75 wt% to obtain the third slurry. The third slurry is fed into the disc vacuum filter, and the 2BEA303 water ring vacuum pump provides a vacuum of 0.075-0.08 MPa to the disc vacuum filter. The third slurry is continuously filtered for 2-3 minutes under the vacuum to obtain a filter cake with a moisture content of ≤11.5 wt%.

[0027] 2BEA303 Water Ring Pump: A single-stage water ring vacuum pump with a rated pumping speed of 30 m³ / min and an ultimate vacuum of 0.098 MPa. It achieves isothermal compression through a water ring seal and is suitable for dusty and humid gases.

[0028] This technical solution includes the following functions: (1) 0.075-0.08 MPa is only 0.025 MPa higher than the saturated vapor pressure of water, which just overcomes the residual Pc after drag reduction of "floc-skeleton" and avoids capillary water back-absorption caused by excessive compaction. (2) Under the conditions of filter cake thickness of 15 mm and porosity of 42%, according to the Terzaghi consolidation theory, the degree of consolidation reaches 90% at 2 min. If the time is extended further, the moisture content will not decrease but increase. Therefore, 2-3 min is the optimal economic inflection point. (3) The optimal moisture content for hematite pelletizing is 10.5-11.8 wt%. This upper limit leaves a safety margin of 0.5 wt% for natural evaporation during 3-5 min of belt transport, realizing direct connection between "filtration-pelletizing".

[0029] In some embodiments, the cationic polyacrylamide has a molecular weight of 8-12 million and an ionic degree of 30-50%.

[0030] Ionicity: The molar ratio of cationic monomers in the CPAM molecular chain determines the charge density.

[0031] This technical solution includes the following functions: (1) When the ionization degree is <30%, the charge neutralization is insufficient, the flocs are small and the strength is low; when it is >50%, the charge reversal leads to particle redispersibility. 30-50% raises the Zeta potential from -35 mV to -5 mV, which just reaches the "weak flocculation" state, forming a porous skeleton without causing electrochemical adsorption blockage of the filter cloth due to excessive positive charge. (2) Molecular weight 8 million-12 million: The chain length is sufficient to bridge 50-80 μm flocs, and the viscosity is <800 mPa·s, which can be quickly mixed without tangling. Below 8 million, the bridging is insufficient, and above 12 million, the solution viscosity increases sharply, resulting in stirring energy consumption and uneven dispersion.

[0032] In some embodiments, the feed pressure of the classifying hydrocyclone is 0.12-0.18 MPa, and the ratio of the diameter of the sand discharge nozzle to the diameter of the overflow pipe of the classifying hydrocyclone is 0.6-0.8.

[0033] The ratio of the diameter of the underflow nozzle to the diameter of the overflow pipe, referred to as the "underflow-overflow ratio," determines the flow splitting ratio and cutting particle size of the hydrocyclone.

[0034] This technical solution includes the following functions: (1) Applying pressure of 0.12-0.18 MPa corresponds to a centrifugal force of 8-12 g, and a settling-overflow ratio of 0.6-0.8 to stabilize d50 at 18-22 μm, ensuring that -200 mesh 70-75 wt% is not affected by fluctuations in the hardness of the raw ore; if the settling-overflow ratio is <0.6, the amount of sand underflow will be insufficient, and the return sand ratio of the mill will be unbalanced; if it is >0.8, the overflow will be coarse, the filter skeleton layer will be reduced, and the moisture content will increase. (2) 0.12-0.18 MPa is in the "high efficiency and low wear" range of the hydrocyclone. Below 0.12 MPa, the classification efficiency drops sharply, and above 0.18 MPa, the wear of the sand underflow nozzle increases exponentially, ensuring that the continuous operation rate of the system is ≥95%.

[0035] In some embodiments, the filter cake is directly fed to the pelletizing process for pelletizing.

[0036] This technical solution includes the following functions: (1) Elimination of drying section: Moisture content ≤11.5 wt% directly enters the pelletizing plate, eliminating the need for rotary kiln or hot air drying, saving 18-20 kg of standard coal per ton of ore, and reducing CO2 emissions by 50 kg; at the same time, it avoids the problem of reduced hydroxyl groups on the surface of hematite and decreased pelletizing properties caused by over-drying. (2) Heat chain connection: The filter cake temperature is 45-50 ℃ (waste heat from the vacuum pump water ring), slightly higher than room temperature, which can reduce the amount of water added for pelletizing by 1.0-1.2 wt%, further reducing the moisture fluctuation window.

[0037] In some embodiments, the ultimate vacuum of the vacuum pump is 0.098 MPa, and the vacuum fluctuation is maintained at ≤0.005 MPa during operation of the vacuum pump to maintain the filter cake moisture content at ≤11.5 wt%.

[0038] This technical solution includes the following functions: (1) Vacuum fluctuation ≤ 0.005 MPa: This is achieved by combining a 2BEA303 water ring pump, a 0.5 m³ vacuum pressure stabilizing tank, and a PID air supply valve, so that the Pc fluctuation is < 2%, and the standard deviation of filter cake moisture is reduced from ±0.6 wt% to ±0.3 wt%, meeting the process tolerance of ±0.5 wt% for pelletizing moisture. (2) The ultimate vacuum of 0.098 MPa provides a 15% safety margin for the system. When the resistance of the filter cloth increases in the later stage of operation, dehydration can still be completed within 0.080 MPa, extending the filter cloth life by 15-20%.

[0039] In some embodiments, the mineral composition of the hematite comprises, by weight percentage: 60-80% hematite, 15-35% limonite, and ≤2% magnetite.

[0040] This technical solution includes the following functions: (1) 60-80% hematite is plate-shaped and 15-35% limonite is needle-shaped. The natural porosity of both is higher than that of magnetite. Magnetite ≤2% can avoid magnetic flocculation leading to dense filter cake. This composition ensures that the natural porosity of the skeleton layer is ≥40%, providing a physical template for CPAM flocculation. (2) The surface hydroxyl density of hematite and limonite is 4-6 hydroxyl groups / nm², which form hydrogen bonds and electrostatic dual adsorption with CPAM cationic groups, increasing the shear resistance index of flocs by 30%. They do not break under the condition of disk rotation speed of 1.5 r / min, maintaining high permeability.

[0041] In some embodiments, the thickener maintains the solid particle size of the third slurry at -200 mesh (70-75 wt%) and ensures that the underflow concentration of the thickener fluctuates within a range of ≤±2 wt%, so as to stably supply the third slurry to the disc vacuum filter.

[0042] "-200 mesh 70-75wt%" is a common way of writing particle size and content in the mineral processing industry. It means that in all solid particles, the part with a particle size of less than 0.074 mm (200 mesh) accounts for 70%-75% (by mass).

[0043] This technical solution includes the following functions: (1) Underflow concentration fluctuation ≤ ±2 wt%: By using a three-parameter closed loop of thickener torque, flocculant addition amount, and underflow pump speed, the solid content per unit volume entering the filter is kept constant, and the filter cake thickness fluctuation is < ±1 mm, thereby reducing the moisture fluctuation from ±0.8 wt% to ±0.3 wt%. (2) The residence time in the large well area of ​​the thickener is 3-4 hours, which allows for secondary "gravity classification" to stabilize the -200 mesh ratio at 70-75 wt%, avoiding the risk of sudden reduction of the filter skeleton layer and a surge in moisture due to "fine particles floating" during the thickening process.

[0044] In summary, this application achieves direct pelleting by coupling five principles: particle size control, concentration increase, flocculation framework, low vacuum matching, and fluctuation suppression, without adding filter aids or changing the filter press, to stabilize the moisture content of finely ground hematite filter cake at ≤11.5wt%.

[0045] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national / industry standards; if there is no corresponding national / industry standard, they are performed according to general international standards, conventional conditions, or conditions recommended by the manufacturer.

[0046] Example 1 The steps are as follows: The raw hematite ore (73.5 wt% hematite, 25.6 wt% limonite, and 0.9 wt% magnetite) is fed into a ball mill, which forms a closed-circuit grinding system with a classifying hydrocyclone. The overflow particle size of the hydrocyclone is controlled at -200 mesh 75 wt%; The overflow enters the thickener, and 5 g / t of cationic PAM flocculant is added; The concentration of the thickener underflow is controlled at 70 wt%; The underflow is fed to a disc vacuum filter, where the filtration vacuum is 0.08 MPa. The filtration coefficient is 800 kg / (m²·h), and the filtration time is 3 minutes; The resulting filter cake had a moisture content of 11.0 wt%, which met the requirements for subsequent pelletizing.

[0047] Example 2 The steps are as follows: The raw hematite ore (33.8 wt% hematite, 65.5 wt% limonite, and 0.7 wt% magnetite) is fed into a ball mill to form a closed-circuit grinding system; The overflow particle size of the hydrocyclone is controlled at -200 mesh 73 wt%; The overflow enters the thickener, and 5 g / t of cationic PAM flocculant is added; The concentration of the thickener underflow is controlled at 70 wt%; The underflow is fed to a disc vacuum filter, where the filtration vacuum is 0.08 MPa. The filtration coefficient is 700 kg / (m²·h), and the filtration time is 3 minutes; The resulting filter cake has a moisture content of 11.8 wt% and can be used directly for pelleting.

[0048] Comparative Example 1 (Conventional Filtration Process) The steps are as follows: The raw hematite ore (73.5 wt% hematite, 25.6 wt% limonite, and 0.9 wt% magnetite) is fed into a ball mill to form a closed-circuit grinding system; The overflow particle size of the hydrocyclone is controlled at -200 mesh 80 wt%; Overflow flows into the thickener without adding flocculant; The concentration of the thickener underflow is controlled at 60 wt%; The underflow is fed to a disc vacuum filter, where the filtration vacuum is 0.06 MPa. The filtration coefficient is 800 kg / (m²·h), and the filtration time is 3 minutes; The resulting filter cake had a moisture content of 14.4 wt% and was muddy in nature, which was not conducive to transportation and pelletizing.

[0049] Comparative Example 2 (fineer particle size) The steps are as follows: The raw hematite ore (73.5 wt% hematite, 25.6 wt% limonite, and 0.9 wt% magnetite) is fed into a ball mill to form a closed-circuit grinding system; The overflow particle size of the hydrocyclone is controlled at -200 mesh 85 wt%; The remaining steps are the same as in Example 1 (PAM 5 g / t, underflow 70 wt%, vacuum 0.08 MPa, filtration coefficient 800 kg / (m²·h), 3 minutes); The resulting filter cake had a moisture content of 12.4 wt%, which was higher than that in Example 1, indicating that excessively fine particle size is not conducive to moisture control.

[0050] Comparative Example 3 (without flocculant) The steps are as follows: The raw hematite ore (73.5 wt% hematite, 25.6 wt% limonite, and 0.9 wt% magnetite) is fed into a ball mill to form a closed-circuit grinding system; The overflow particle size of the hydrocyclone is controlled at -200 mesh 75 wt%; Overflow flows into the concentrator without adding cationic PAM; The concentration of the thickener underflow is controlled at 70 wt%; The underflow is fed to a disc vacuum filter, where the filtration vacuum is 0.08 MPa. The filtration coefficient is 800 kg / (m²·h), and the filtration time is 3 minutes; The resulting filter cake had a moisture content of 11.8 wt%, which was higher than that in Example 1, indicating that the flocculant had a significant effect on reducing moisture content.

[0051] Comparative Example 4 (low pulp concentration) The steps are as follows: The raw hematite ore (73.5 wt% hematite, 25.6 wt% limonite, and 0.9 wt% magnetite) is fed into a ball mill to form a closed-circuit grinding system; The overflow particle size of the hydrocyclone is controlled at -200 mesh 75 wt%; Overflow into the concentrator, add 5 g / t of cationic PAM; The concentration of the thickener underflow is controlled at 60 wt%; The underflow is fed to a disc vacuum filter, where the filtration vacuum is 0.08 MPa. The filtration coefficient is 800 kg / (m²·h), and the filtration time is 3 minutes; The resulting filter cake had a moisture content of 13.0 wt%, which was higher than that in Example 1, indicating that a low pulp concentration is not conducive to moisture control.

[0052] Comparative Example 5 (low vacuum level) The steps are as follows: The raw hematite ore (73.5 wt% hematite, 25.6 wt% limonite, and 0.9 wt% magnetite) is fed into a ball mill to form a closed-circuit grinding system; The overflow particle size of the hydrocyclone is controlled at -200 mesh 75 wt%; Overflow into the concentrator, add 5 g / t of cationic PAM; The concentration of the thickener underflow is controlled at 70 wt%; The underflow is fed to a disc vacuum filter, where the filtration vacuum is 0.06 MPa. The filtration coefficient is 800 kg / (m²·h), and the filtration time is 3 minutes; The moisture content of the resulting filter cake was 13.1 wt%, which was higher than that in Example 1, indicating that the low vacuum level significantly affected the dehydration effect.

[0053] Comparative Example 6 (Filtering coefficient too high) The steps are as follows: The raw hematite ore (73.5 wt% hematite, 25.6 wt% limonite, and 0.9 wt% magnetite) is fed into a ball mill to form a closed-circuit grinding system; The overflow particle size of the hydrocyclone is controlled at -200 mesh 75 wt%; Overflow into the concentrator, add 5 g / t of cationic PAM; The concentration of the thickener underflow is controlled at 70 wt%; The underflow is fed to a disc vacuum filter, where the filtration vacuum is 0.08 MPa. The filtration coefficient is 1000 kg / (m²·h), and the filtration time is 3 minutes; The resulting filter cake had a moisture content of 12.1 wt%, which was higher than that in Example 1, indicating that the excessively high filtration coefficient led to insufficient compaction of the filter cake and an increase in moisture content.

[0054] The above performance data allows for a direct comparison of the differences between different embodiments and comparative examples. The following conclusions can be drawn: 1. This application enables the filter cake moisture content to be stably controlled at ≤11.5 wt%, which is about 3% lower than that of conventional processes, thus meeting the requirements for direct pelletizing.

[0055] 2. This application requires no filter aid or equipment replacement. It achieves efficient dewatering through system parameter optimization. The process is simple, low-cost, and highly adaptable.

[0056] In summary, this invention effectively solves the problem of high moisture content in finely ground hematite ore filtration by synergistic control of multiple parameters, including particle size, flocculation, concentration, vacuum, and filtration intensity.

[0057] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A system for reducing the moisture content of finely ground hematite ore, characterized in that, The system, along the slurry flow direction, comprises, in sequence: Ball mills are used for wet fine grinding of raw hematite ore; A classifying hydrocyclone forms a closed-loop grinding circuit with the ball mill and is used to control the overflow particle size; A thickener receives the overflow from the classifying hydrocyclone and is used to increase the slurry concentration; A disc vacuum filter is connected to the underflow of the thickener and is used to perform vacuum filtration on the concentrated slurry. A water ring vacuum pump provides the filtration vacuum level for the disc vacuum filter. The thickener contains cationic polyacrylamide flocculant.

2. The system according to claim 1, characterized in that, The filtration coefficient of the disc vacuum filter is 700-900 kg / (m²·h), and the single-cycle filtration time is 2-3 minutes.

3. The system according to claim 1, characterized in that, The disc vacuum filter is equipped with a micro-spraying device on the back of the filter cloth.

4. A method for reducing the moisture content of finely ground hematite using the system described in any one of claims 1 to 3, characterized in that, Includes the following steps: The raw hematite ore is fed into the ball mill, and the ball mill performs wet fine grinding on the raw hematite ore to obtain the first slurry. The first slurry is fed into the classifying hydrocyclone, which classifies the first slurry and controls the overflow particle size of the classifying hydrocyclone to be -200 mesh 70-75 wt%, to obtain the second slurry. The second slurry is fed into the thickener, and 4-6 g / t of cationic polyacrylamide is added to the second slurry in the thickener. The thickener concentrates the second slurry to a bottom flow concentration of 70-75 wt% to obtain the third slurry. The third slurry is fed into the disc vacuum filter, and the 2BEA303 water ring vacuum pump provides a vacuum of 0.075-0.08 MPa to the disc vacuum filter. The third slurry is continuously filtered for 2-3 minutes under the vacuum to obtain a filter cake with a moisture content of ≤11.5 wt%.

5. The method according to claim 4, characterized in that, The cationic polyacrylamide has a molecular weight of 8-12 million and an ionic degree of 30-50%.

6. The method according to claim 4, characterized in that, The feed pressure of the classifying hydrocyclone is 0.12-0.18 MPa, and the ratio of the diameter of the sand discharge nozzle to the diameter of the overflow pipe of the classifying hydrocyclone is 0.6-0.

8.

7. The method according to claim 4, characterized in that, The filter cake is directly fed to the pelletizing process for pelletizing.

8. The method according to claim 4, characterized in that, The ultimate vacuum of the vacuum pump is 0.098 MPa, and the vacuum fluctuation is maintained at ≤0.005 MPa during operation to keep the filter cake moisture content stable at ≤11.5 wt%.

9. The method according to claim 4, characterized in that, The mineral composition of the hematite, by weight percentage, includes: hematite 60-80%, limonite 15-35%, and magnetite ≤2%.

10. The method according to claim 4, characterized in that, The thickener maintains the solid particle size of the third slurry at -200 mesh (70-75 wt%) and ensures that the underflow concentration of the thickener fluctuates within the range of ≤±2 wt%, thereby stably supplying the third slurry to the disc vacuum filter.