A process for the production of surface-modified bentonite

Abstract

The application provides a production process of surface modified bentonite and belongs to the technical field of bentonite, and comprises the following steps: crushing bentonite raw ore to meet the particle size requirement of feeding through a jaw crusher; continuously and uniformly conveying the crushed material to the feeding port of a Raymond mill main machine through an electromagnetic vibration feeder, and adding a primary grinding additive composition to the outlet of the feeder, wherein the primary grinding additive composition comprises 0.1-0.5 parts of nano silicon dioxide, 0.05-0.2 parts of carboxymethyl cellulose or polyacrylamide; the material is thrown into the grinding roller and the grinding ring in the Raymond mill grinding cavity by a rotating shovel, is crushed into fine powder through centrifugal rolling, and the addition amount of a phosphate ester compound is 0.03-0.1 parts; through the step-by-step addition of the primary grinding, fine grinding and post-treatment additive compositions, the combination of multi-stage crushing and accurate sorting processes, the efficient dry purification of bentonite is realized, and the synergistic effect of the additives can effectively inhibit the agglomeration of mineral particles and improve the grinding efficiency.

Description

Technical Field

[0001] This invention belongs to the field of bentonite technology, specifically a production process for surface-modified bentonite. Background Technology

[0002] Bentonite, a clay mineral with montmorillonite as its main component, is widely used in drilling mud, paper filling, water treatment, and catalyst carriers due to its excellent adsorption, swelling, and colloidal properties. However, natural bentonite ore often contains impurities such as quartz and feldspar, and has a wide particle size distribution and low specific surface area, requiring purification and ultrafine grinding processes to improve its application performance.

[0003] In the industrial production of bentonite powder, the current mainstream process generally uses Raymond mills as the core grinding equipment. However, in actual production, it has been found that when the raw materials have uneven particle size distribution and fluctuating moisture content, a gas-solid two-phase fluidization separation effect easily occurs during the conveying process of the vibrating feeder. For example, under the mechanical action of a vibration frequency of 20-30Hz, fine particles and materials with low moisture content preferentially enter the fluidized state due to their lower effective density, while coarse particles and materials with high moisture content remain at the bottom of the material layer due to their faster settling velocity. This results in the Raymond mill actually processing materials exhibiting a periodic "fine-dry - coarse-wet" feeding characteristic. This chromatographic phenomenon directly causes intermittent moisture fluctuations and abrupt changes in particle size distribution in the powder product, leading to quality instability problems. Traditional improvement measures, such as optimizing the hopper cone angle and adding anti-stratification grids, can provide temporary improvements but cannot form a continuous and stable feeding compensation mechanism.

[0004] In view of the above problems, this invention proposes a production process for surface-modified bentonite. Nano-silica is premixed and uniformly adsorbed onto the particle surface by a feeding wheel, combined with atomized coating of carboxymethyl cellulose / polyacrylamide aqueous solution, forming a dual stabilization mechanism of steric hindrance and electrostatics. Nano-magnesium aluminum hydrotalcite and lithium salt compounds pretreated by ball milling are precisely injected through a Venturi injector and directionally adsorbed onto the surface of newly formed cracks in the airflow of the analyzer, inhibiting secondary agglomeration of fine particles and reducing the cyclic load of Raymond mill. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems in existing technologies by proposing a production process for surface-modified bentonite.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A production process for surface-modified bentonite includes the following steps:

[0008] S1: The bentonite ore is crushed to the particle size required for feeding by a jaw crusher;

[0009] S2: The crushed material is continuously and evenly fed to the feed inlet of the Raymond mill main unit by an electromagnetic vibrating feeder, while a primary grinding additive composition is added at the feeder outlet.

[0010] The primary grinding additive composition comprises the following raw materials in parts:

[0011] 0.1-0.5 parts of nano-silica, and 0.05-0.2 parts of carboxymethyl cellulose or polyacrylamide;

[0012] S3: The material is thrown into the Raymond mill grinding chamber by a rotating blade between the grinding roller and the grinding ring, and is crushed into fine powder by centrifugal crushing. Phosphate ester compounds are then injected through atomizing nozzles on the side wall of the grinding chamber.

[0013] The amount of phosphate ester compounds added is 0.03-0.1 parts;

[0014] S4: The blower's airflow blows fine powder into the analyzer. A fine grinding additive composition is added through a Venturi injector into the analyzer's inlet duct. The particle size is controlled by adjusting the analyzer's speed. Qualified fine powder enters the collection system with the airflow, while coarse particles fall back into the grinding chamber for further pulverization.

[0015] The fine grinding additive composition comprises the following raw materials in parts:

[0016] 0.2-0.8 parts of nano-magnesium aluminum hydrotalcite, and 0.05-0.15 parts of lithium salt compound;

[0017] S5: The powder-containing airflow passes sequentially through a cyclone collector and a bag filter to achieve gas-solid separation. Post-treatment additives are added in the mixing pipe downstream of the cyclone collector's discharge valve to obtain finished bentonite powder.

[0018] The post-treatment additives include: 0.3-1 parts of hydrophobic modified silica powder and 0.1-0.3 parts of sodium citrate;

[0019] S6: The induced draft fan maintains negative pressure in the system, ensuring that the purified exhaust gas meets emission standards.

[0020] Preferably, the method of adding the initial grinding additive in step S2 is as follows:

[0021] Nano-silica and crushed material are premixed in a feed roller mixer at a mass ratio of 1:(10-15), with the feed roller rotating at 20-30 rpm. Carboxymethyl cellulose is prepared into a 5±0.5 wt% aqueous solution, which is then atomized by a high-pressure nozzle and sprayed into the feeder flow.

[0022] Preferably, the atomizing nozzle in step S3 should adopt a dual-fluid internal mixing structure, with nitrogen as the carrier gas, an atomization pressure of 0.3-0.5 MPa, and a droplet size of 10-20 μm.

[0023] Preferably, the Venturi injector setup in step S4 includes the following steps:

[0024] S41: Set the throat diameter to 25±1 mm, the contraction angle to 18±1°, and the diffusion angle to 8±0.5°;

[0025] S42: Set the injector inlet pressure to 0.8-1.0 MPa and the outlet airflow velocity to 18-22 m / s;

[0026] S43: Set the distance between the added point and the analyzer inlet to 1.5 ± 0.2 m.

[0027] Preferably, the mixing tube setup in step S5 includes the following steps:

[0028] S51: Length ≥ 3 m, with 6 sets of SK-type static mixing units inside;

[0029] S52: Cooling water is circulated through the pipe wall to control the temperature at 40-50℃;

[0030] Mixing time ≥ 90 s, mixing uniformity CV ≤ 5%.

[0031] Preferably, the lithium salt compound is lithium carbonate or lithium hydroxide, and is pre-ball-milled to D90≤5 μm.

[0032] Preferably, the surface area of ​​the nano-silica is 180-220 μm. 2 / g, with a primary particle size of 10-20nm and a surface hydroxyl density ≥3.0 hydroxyl groups / nm. 2 .

[0033] Preferably, the phosphate ester compound is triethylhexyl phosphate, with an acid value of 180-220 mgKOH / g and a flash point ≥110℃.

[0034] Preferably, the Venturi injector is equipped with a safety interlock system and includes the following steps:

[0035] S91: When the inlet pressure is <0.7 MPa, the fine grinding additive feed valve will be automatically closed;

[0036] S92: When the airflow velocity is >25 m / s, activate the pressure reducing valve.

[0037] Preferably, the ball milling pretreatment of lithium salt compounds should be carried out under inert gas conditions and with the addition of grinding aids.

[0038] The grinding aid is 0.1-0.3 parts of calcium stearate, the ball-to-material ratio is 8:1, the rotation speed is 250 rpm, and the time is 45 min.

[0039] Compared with existing technologies, the medium-frequency heat treatment process for this support roller has the following advantages:

[0040] 1. The present invention provides a production process for surface-modified bentonite, which achieves efficient dry purification of bentonite by adding a composition of primary grinding, fine grinding and post-treatment additives in stages, combined with multi-stage crushing and precise sorting processes. The synergistic effect of each additive can effectively inhibit the agglomeration of mineral particles and improve grinding efficiency.

[0041] 2. The present invention provides a production process for surface-modified bentonite, which adopts a primary grinding additive addition method that combines premixing with high-pressure atomization using a feeding wheel. This allows nano-silica and carboxymethyl cellulose / polyacrylamide to form a uniform coating layer on the surface of crushed mineral particles. Premixing can prevent the agglomeration of nanoparticles, and the atomized droplets can be precisely adsorbed onto the cracks in the mineral particles, significantly improving the ore liberation efficiency, reducing the energy consumption of Raymond mill grinding, and reducing over-grinding.

[0042] 3. The production process of surface-modified bentonite provided by the present invention achieves ultra-fine atomization of phosphate ester compounds by using a dual-fluid internal mixing atomizing nozzle in combination with nitrogen carrier gas technology. Nitrogen protection prevents the additives from oxidizing and coking. Uniform coverage of the inner wall of the grinding chamber can regulate the surface energy of the material, reduce the phenomenon of sticking to the wall, extend the stable operation time of Raymond mill, and the lubricating effect of phosphate ester can reduce the wear rate of grinding roller.

[0043] 4. The present invention provides a production process for surface-modified bentonite, in which high-surface-area, high-hydroxyl-density nano-silica is firmly anchored to the mineral surface through chemical bonding. Its original particle size can fill the micro-cracks in the ore, improve the compressive strength in the initial grinding stage, and reduce the introduction of new impurities in the subsequent crushing process.

[0044] 5. The present invention provides a production process for surface-modified bentonite, which can selectively adsorb impurity ions in slurry through the moderate acid value of triethylhexyl phosphate, and the high flash point characteristics ensure that there is no risk of combustion during the atomization process. The additive forms a temporary hydrophobic film in the grinding cavity, which promotes particle dissociation and prevents corrosion of iron parts.

[0045] In summary, this invention provides a production process for surface-modified bentonite. Through the synergistic effect of four-stage additives—initial grinding to prevent sedimentation, grinding to eliminate static electricity, sorting to adjust charge, and post-treatment to prevent moisture—the interlayer difference is reduced, systematically solving the problems of sedimentation, static electricity, deliquescence, and stratification in bentonite processing, achieving ultra-uniformity, high flowability, zero agglomeration, and stable storage. Detailed Implementation

[0046] The following are specific embodiments of the present invention, which further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0047] Example

[0048] A production process for surface-modified bentonite includes the following steps:

[0049] S1: The bentonite ore is crushed to the particle size required for feeding by a jaw crusher;

[0050] S2: The crushed material is continuously and evenly fed to the feed inlet of the Raymond mill main unit by an electromagnetic vibrating feeder, while a primary grinding additive composition is added at the feeder outlet.

[0051] The primary grinding additive composition comprises the following raw materials in parts:

[0052] 0.1-0.5 parts of nano-silica, and 0.05-0.2 parts of carboxymethyl cellulose or polyacrylamide;

[0053] Table 1 Test Report on Anti-settling Performance of Primary Grinding Additives

[0054]

[0055] Table 1 shows the test report on the anti-settling performance of the primary grinding additive. The sedimentation stratification index is calculated as (D50 of the bottom 10% of powder - D50 of the top 10% of powder) / average D50 × 100%. The results show that, compared with the control group, the experimental group's D50 (15.2~15.8μm) decreased by 44±1% compared with the control group (28.5~29.1μm), the particle size span decreased from 2.8±0.1 to 1.9±0.04, the particle size concentration increased by 41-44%, the stratification index decreased by 72-74%, and the angle of repose decreased from 48.3±0.8° to 35.0±0.8°. According to Stokes' law, smaller particles usually have a larger specific surface area and a slower settling velocity, which is the basis for improving suspension stability. A narrower particle size distribution means that the particle size is closer, reducing the tendency of stratification caused by the large difference in settling velocity between large and small particles, which is beneficial to overall stability. A lower angle of repose means that the friction between particles is reduced, the cohesion is reduced, and the system is easier to flow. For suspended systems, good flowability is generally associated with better dispersibility and lower sedimentation / caking tendency. The significant reduction in the sedimentation stratification index is the most core and direct result of this experiment. It directly demonstrates that the additive effectively inhibits particle sedimentation, significantly improves the suspension stability and homogeneity of the system, and greatly reduces stratification problems during storage and use. Table 1 shows that the tested primary grinding additive is highly effective in improving particle dispersibility, enhancing system flowability, and, most importantly, significantly enhancing anti-settling performance. All key indicators in the experimental group were superior to those in the control group, and these were statistically significant. This additive successfully solved the sedimentation stratification problem present in the control group, significantly improving the overall stability of the system.

[0056] S3: The material is thrown into the Raymond mill grinding chamber by a rotating blade between the grinding roller and the grinding ring, and is crushed into fine powder by centrifugal crushing. Phosphate ester compounds are then injected through atomizing nozzles on the side wall of the grinding chamber.

[0057] The amount of phosphate ester compounds added is 0.03-0.1 parts;

[0058] Table 2. Antistatic Performance Test Report of Phosphate Ester

[0059]

[0060] Table 2 shows the results of the antistatic properties testing of phosphate esters. The results indicate that compared to the control group, the resistivity of the experimental group decreased by four orders of magnitude, the suspension rate increased by 107-118%, and the resistivity decreased from 10... 12 The order of magnitude decreased to 10 Ω·cm 8 The agglomeration index decreased from 35.8±1.0% to 7.3±0.5% (Ω·cm), while the fine powder suspension rate increased from 41.3±1.0% to 87.2±1.1%. This indicates that the polar groups of phosphate esters are directionally adsorbed onto the hydroxyl sites at the edge of montmorillonite, and the hydrophobic chains are arranged outward to form a molecular barrier, blocking electron migration pathways. Phosphate ester molecules typically have both hydrophilic and hydrophobic portions. They can form a conductive film on the material surface or a conductive water film on the surface through hygroscopic action, providing pathways for the conduction and dissipation of static charge, thereby significantly reducing surface resistivity. The significant reduction in the sedimentation stratification index is the most core and direct result of this experiment. It directly proves that the additive effectively inhibits particle sedimentation, significantly improves the suspension stability and uniformity of the system, and greatly reduces stratification problems during storage and use. Static electricity is one of the important factors leading to the agglomeration of fine particles. Antistatic agents effectively weaken the electrostatic attraction between particles by reducing resistivity and dissipating static charge, thereby greatly reducing agglomeration. The particles are more evenly dispersed, the suspension rate of fine powder is more than doubled, the settling trend of fine powder is effectively controlled, and the uniformity of the system is greatly improved.

[0061] S4: The blower airflow blows the fine powder into the analyzer. The fine grinding additive composition is added into the air inlet duct of the analyzer through the Venturi injector. The particle size is controlled by adjusting the speed of the analyzer. The qualified fine powder enters the collection system with the airflow, while the coarse particles fall back into the grinding chamber for further crushing. The fine grinding additive composition includes the following raw materials in parts: 0.2-0.8 parts of nano magnesium aluminum hydrotalcite and 0.05-0.15 parts of lithium salt compound.

[0062] Table 3 Test Report on Charge Regulation Performance of Fine Grinding Additives

[0063]

[0064] Table 3 shows the results of measuring the charge regulation performance of the fine grinding additive, including Zeta potential, centrifugal stratification gradient, and tap density difference. The Zeta potential increased from -33.0±0.8 mV to -18.3±0.5 mV, with a charge neutralization rate of 43.2-44.8%. The centrifugal stratification gradient decreased from 23.1±0.9% to 4.3±0.3%, a reduction of 81-83%. The tap density difference decreased from 8.5±0.3% to 1.6±0.1%, improving compaction uniformity by 81%. The absolute value of the Zeta potential approaching zero indicates that the additive may have partially neutralized the original surface charge by adsorbing onto the particle surface, or introduced ions / molecules with opposite charges for shielding. The goal is to achieve a charge state more conducive to overall stability. The significant reduction in the centrifugal stratification gradient indicates a qualitative improvement in the stability of the system under strong external forces, resulting in better mixing uniformity of particles of different densities or sizes under strong separation forces, and significantly enhanced packing uniformity of the powder during storage and transportation. The results showed that the fine grinding additive added to the experimental group effectively regulated the charge state on the particle surface, significantly reduced the tendency of particles to separate under centrifugation and tapping conditions, and significantly improved the uniformity and stability of the system.

[0065] S5: The powder-containing airflow passes through a cyclone collector and a bag filter in sequence to achieve gas-solid separation. Post-treatment additives are added to the mixing pipe downstream of the discharge valve of the cyclone collector to obtain bentonite finished powder. The post-treatment additives include: 0.3-1 parts of hydrophobic modified silica powder and 0.1-0.3 parts of sodium citrate.

[0066] Table 4. Post-treatment additive moisture-proof performance test report

[0067]

[0068] The moisture-proof performance of the post-treatment additives was tested. The results showed that, compared with the control group, the moisture absorption rate of the experimental group decreased from 6.9±0.3% to 2.1±0.1% in 72 hours, and the flowability index increased from 41±2 to 87±2. The results indicate that the post-treatment additives added to the experimental group significantly reduced the hygroscopicity of the material, effectively prevented the particles from agglomerating and hardening due to moisture absorption, and greatly improved the flowability of the powder in a humid environment.

[0069] S6: The induced draft fan maintains negative pressure in the system, ensuring that the purified exhaust gas meets emission standards.

[0070] Table 5 System Overall Anti-Layering Verification Report

[0071]

[0072] Table 5 verifies the overall anti-stratification effect of the system. The results show that the content at the top, middle, and bottom is extremely close with minimal differences. There is no obvious regularity of higher content at the top and lower content at the bottom, indicating that the target component is uniformly distributed within the container. Compared with the traditional process, the new process using additives improves the prevention of material stratification and ensures the uniformity of the system. The additive process not only solves the stratification problem but may also improve the effective content or measurement accuracy of the target component.

[0073] Table 6. Analysis of variance results of the anti-stratification effect of additives in each process.

[0074]

[0075] In summary, the additive system, through the synergistic effect of four mechanisms—particle size control, electrostatic elimination, charge optimization, and moisture protection—fundamentally optimizes the core failure modes of powder sedimentation, agglomeration, stratification, and deliquescence, forming a steady-state suspension system.

[0076] Example

[0077] A production process for surface-modified bentonite includes the following steps:

[0078] S1: The bentonite ore is crushed to the particle size required for feeding by a jaw crusher;

[0079] S2: The crushed material is continuously and evenly conveyed to the feed inlet of the Raymond mill via an electromagnetic vibrating feeder. Simultaneously, a primary grinding additive composition is added at the feeder outlet. This composition comprises the following raw materials in parts: 0.1-0.5 parts nano-silica and 0.05-0.2 parts carboxymethyl cellulose or polyacrylamide. Primary grinding additive dosage limits: Lower limit: 0.1 parts nano-SiO2 + 0.05 parts carboxymethyl cellulose; Upper limit: 0.5 parts nano-SiO2 + 0.2 parts carboxymethyl cellulose.

[0080] Table 1 Test Report on Anti-settling Performance of Primary Grinding Additives

[0081]

[0082] Table 1 shows the test report on the anti-settling performance of the primary grinding additive. The sedimentation stratification index is calculated as (D50 of the bottom 10% of powder - D50 of the top 10% of powder) / average D50 × 100%. The results show that, compared with the control group, the experimental group's D50 (15.2~15.8μm) decreased by 44±1% compared with the control group (28.5~29.1μm), the particle size span decreased from 2.8±0.1 to 1.9±0.04, the particle size concentration increased by 41-44%, the stratification index decreased by 72-74%, and the angle of repose decreased from 48.3±0.8° to 35.0±0.8°. According to Stokes' law, smaller particles usually have a larger specific surface area and a slower settling velocity, which is the basis for improving suspension stability. A narrower particle size distribution means that the particle size is closer, reducing the tendency of stratification caused by the large difference in settling velocity between large and small particles, which is beneficial to overall stability. A lower angle of repose means that the friction between particles is reduced, the cohesion is reduced, and the system is easier to flow. For suspended systems, good flowability is generally associated with better dispersibility and lower sedimentation / caking tendency. The significant reduction in the sedimentation stratification index is the most core and direct result of this experiment. It directly proves that the additive effectively inhibits particle sedimentation, significantly improves the suspension stability and uniformity of the system, and greatly reduces stratification problems during storage and use. Table 1 shows that the tested primary grinding additive is highly effective in improving particle dispersibility, enhancing system flowability, and, most importantly, significantly enhancing anti-settling performance. All key indicators in the experimental group were superior to those in the control group, and were statistically significant. This additive successfully solved the sedimentation stratification problem present in the control group, significantly improving the overall stability of the system. S3: The material is thrown into the Raymond mill grinding chamber by a rotating shovel between the grinding roller and the grinding ring, and is crushed into fine powder by centrifugal crushing. Phosphate ester compounds are injected through atomizing nozzles on the side wall of the grinding chamber, wherein the amount of phosphate ester compounds added is 0.03-0.1 parts;

[0083] Table 2. Antistatic Performance Test Report of Phosphate Ester

[0084]

[0085] Table 2 shows the results of the antistatic properties testing of phosphate esters. The results indicate that compared to the control group, the resistivity of the experimental group decreased by four orders of magnitude, the suspension rate increased by 107-118%, and the resistivity decreased from 10... 12 The order of magnitude decreased to 10 Ω·cm 8The agglomeration index decreased from 35.8±1.0% to 7.3±0.5% (Ω·cm), while the fine powder suspension rate increased from 41.3±1.0% to 87.2±1.1%. This indicates that the polar groups of phosphate esters are directionally adsorbed onto the hydroxyl sites at the edge of montmorillonite, and the hydrophobic chains are arranged outward to form a molecular barrier, blocking electron migration pathways. Phosphate ester molecules typically have both hydrophilic and hydrophobic portions. They can form a conductive film on the material surface or a conductive water film on the surface through hygroscopic action, providing pathways for the conduction and dissipation of static charge, thereby significantly reducing surface resistivity. The significant reduction in the sedimentation stratification index is the most core and direct result of this experiment. It directly proves that the additive effectively inhibits particle sedimentation, significantly improves the suspension stability and uniformity of the system, and greatly reduces stratification problems during storage and use. Static electricity is one of the important factors leading to the agglomeration of fine particles. Antistatic agents effectively weaken the electrostatic attraction between particles by reducing resistivity and dissipating static charge, thereby greatly reducing agglomeration. The particles are more evenly dispersed, the suspension rate of fine powder is more than doubled, the settling trend of fine powder is effectively controlled, and the uniformity of the system is greatly improved.

[0086] S4: The blower's airflow blows fine powder into the analyzer. A fine grinding additive composition is added through a Venturi injector into the analyzer's air inlet duct. The particle size is controlled by adjusting the analyzer's speed. Qualified fine powder enters the collection system with the airflow, while coarse particles fall back into the grinding chamber for further crushing. The fine grinding additive composition includes the following raw materials in parts: 0.2-0.8 parts of nano-magnesium aluminum hydrotalcite and 0.05-0.15 parts of lithium salt compound. Fine grinding additive boundaries: Lower limit: 0.2 parts of nano-magnesium aluminum hydrotalcite + 0.05 parts of lithium salt compound; Upper limit: 0.8 parts of nano-magnesium aluminum hydrotalcite + 0.15 parts of lithium salt compound.

[0087] Table 3 Test Report on Charge Regulation Performance of Fine Grinding Additives

[0088]

[0089] Table 3 shows the results of measuring the charge regulation performance of the fine grinding additive, including Zeta potential, centrifugal stratification gradient, and tap density difference. The Zeta potential increased from -33.0±0.8 mV to -18.3±0.5 mV, with a charge neutralization rate of 43.2-44.8%. The centrifugal stratification gradient decreased from 23.1±0.9% to 4.3±0.3%, a reduction of 81-83%. The tap density difference decreased from 8.5±0.3% to 1.6±0.1%, improving compaction uniformity by 81%. The absolute value of the Zeta potential approaching zero indicates that the additive may have partially neutralized the original surface charge by adsorbing onto the particle surface, or introduced ions / molecules with opposite charges for shielding. The goal is to achieve a charge state more conducive to overall stability. The significant reduction in the centrifugal stratification gradient indicates a qualitative improvement in the stability of the system under strong external forces, resulting in better mixing uniformity of particles of different densities or sizes under strong separation forces, and significantly enhanced packing uniformity of the powder during storage and transportation. The results showed that the fine grinding additive added to the experimental group effectively regulated the charge state on the particle surface, significantly reduced the tendency of particles to separate under centrifugation and tapping conditions, and significantly improved the uniformity and stability of the system.

[0090] S5: The powder-containing airflow passes sequentially through a cyclone collector and a bag filter to achieve gas-solid separation. Post-treatment additives are added in the mixing pipe downstream of the cyclone collector's discharge valve to obtain finished bentonite powder.

[0091] The post-treatment additives include: 0.3-1 parts of hydrophobic modified silica powder and 0.1-0.3 parts of sodium citrate;

[0092] Table 4. Post-treatment additive moisture-proof performance test report

[0093]

[0094] The moisture-proof performance of the post-treatment additives was tested. The results showed that, compared with the control group, the moisture absorption rate of the experimental group decreased from 6.9±0.3% to 2.1±0.1% in 72 hours, and the flowability index increased from 41±2 to 87±2. The results indicate that the post-treatment additives added to the experimental group significantly reduced the hygroscopicity of the material, effectively prevented the particles from agglomerating and hardening due to moisture absorption, and greatly improved the flowability of the powder in a humid environment.

[0095] S6: The induced draft fan maintains negative pressure in the system, ensuring that the purified exhaust gas meets emission standards.

[0096] Table 5 System Overall Anti-Layering Verification Report

[0097]

[0098] Table 5 verifies the overall anti-stratification effect of the system. The results show that the content at the top, middle, and bottom is extremely close with minimal differences. There is no obvious regularity of higher content at the top and lower content at the bottom, indicating that the target component is uniformly distributed within the container. Compared with the traditional process, the new process using additives improves the prevention of material stratification and ensures the uniformity of the system. The additive process not only solves the stratification problem but may also improve the effective content or measurement accuracy of the target component.

[0099] Table 6. Analysis of variance results of the anti-stratification effect of additives in each process.

[0100]

[0101] In summary, the additive system, through the synergistic effect of four mechanisms—particle size control, electrostatic elimination, charge optimization, and moisture protection—fundamentally optimizes the core failure modes of powder sedimentation, agglomeration, stratification, and deliquescence, forming a steady-state suspension system.

[0102] The method of adding the primary grinding additive in step S2 is as follows:

[0103] Nano-silica and crushed material are premixed in a feed roller mixer at a mass ratio of 1:(10-15) with a feed roller speed of 20-30 rpm. Carboxymethyl cellulose is prepared into a 5±0.5 wt% aqueous solution, which is injected into the material flow through a high-pressure nozzle. Lithium carbonate + 0.2 parts calcium stearate are ball-milled under argon protection to obtain powder with D90=4.8μm. This method can improve the uniformity of additive dispersion and reduce the angle of repose. The initial grinding additive addition method of feed roller premixing and high-pressure atomization is adopted to form a uniform coating layer of nano-silica and carboxymethyl cellulose / polyacrylamide on the surface of crushed mineral particles. Premixing can prevent nanoparticle agglomeration, and the atomized droplets can be precisely adsorbed at the cracks of mineral particles, significantly improving the ore liberation efficiency, reducing Raymond mill grinding energy consumption by 10-15%, and reducing over-grinding.

[0104] In step S3, the atomizing nozzle must be a dual-fluid internal mixing nozzle with a nitrogen pressure of 0.35 MPa and a droplet size of 18 μm. The dual-fluid internal mixing nozzle, combined with nitrogen carrier gas technology, achieves ultra-fine atomization of phosphate ester compounds. Nitrogen protection prevents additive oxidation and coking, and uniform coverage of the grinding chamber wall regulates material surface energy, reduces wall adhesion, extends the stable operating time of the Raymond mill by 30%, and the lubricating effect of phosphate esters reduces the wear rate of the grinding rollers by 20%.

[0105] The Venturi injector setup in step S4 includes the following steps:

[0106] S41: Set the throat diameter to 25±1 mm, the contraction angle to 18±1°, and the diffusion angle to 8±0.5°;

[0107] S42: Set the injector inlet pressure to 0.8-1.0 MPa and the outlet airflow velocity to 18-22 m / s;

[0108] S43: Set the distance between the added point and the analyzer inlet to 1.5 ± 0.2 m.

[0109] The Venturi injector structure, combined with optimized airflow parameters, enables the fine grinding additive to be instantly atomized and uniformly dispersed in a high-speed airflow. Precise injection positioning ensures full contact between the additive and the fine powder, improving particle size classification accuracy, reducing the rate of coarse particle re-grinding by 25%, and lowering the system's cyclic load.

[0110] The mixing tube setup in step S5 includes the following steps:

[0111] S51: Length ≥ 3 m, with 6 sets of SK-type static mixing units inside;

[0112] S52: Cooling water is circulated through the pipe wall to control the temperature at 40-50℃;

[0113] A mixing tube with an aspect ratio ≥3m, combined with an SK static mixing unit and temperature control design, ensures that post-treatment additives achieve surface coating with a uniformity of CV ≤5%. Cooling water temperature control prevents sodium citrate from deliquescing and clumping, and the hydrophobic treatment of modified silica powder imparts a contact angle >120° to the finished bentonite, significantly improving its moisture resistance and suspension stability.

[0114] Mixing time ≥ 90 s, mixing uniformity CV ≤ 5%.

[0115] Mixing time ≥ 90 s, mixing uniformity CV ≤ 5%, lithium salt compound is lithium carbonate or lithium hydroxide, pre-ball milled to D90 ≤ 5 μm.

[0116] Extending the mixing time to over 90 seconds and strictly controlling uniformity ensures that a dense passivation layer is formed on the particle surface by the nano-magnesium aluminum hydrotalcite and lithium salt compound. After ball milling pretreatment, the lithium salt has an increased specific surface area, enabling efficient adsorption of impurity ions, thus improving the exchange capacity and expansion ratio of the finished product.

[0117] The surface area of ​​nano-silica is 180-220 μm. 2 / g, with a primary particle size of 10-20nm and a surface hydroxyl density ≥3.0 hydroxyl groups / nm. 2 .

[0118] The phosphate compound is triethylhexyl phosphate, with an acid value of 180-220 mgKOH / g and a flash point ≥110℃. The high surface area and high hydroxyl density of the nano-silica are firmly anchored to the mineral surface through chemical bonding. Its 10-20 nm native particle size can fill micro-cracks in the ore, increasing compressive strength by 20% in the initial grinding stage and reducing the introduction of new impurities during subsequent crushing. Triethylhexyl phosphate, with its moderate acid value, can selectively adsorb Fe in the slurry. 3+ / Al 3+ The presence of impurity ions and a high flash point ensures no risk of combustion during the atomization process. This additive forms a temporary hydrophobic film within the grinding chamber, promoting particle dissociation while preventing corrosion of ferrous components, thus improving the whiteness of the finished product.

[0119] The steps for configuring a safety interlock system for a Venturi injector are as follows:

[0120] S91: When the inlet pressure is <0.7 MPa, the fine grinding additive feed valve will be automatically closed;

[0121] S92: When the airflow velocity is >25 m / s, activate the pressure reducing valve;

[0122] The injector throat is made of YG8 cemented carbide.

[0123] The YG8 carbide throat, combined with a safety interlock system, automatically cuts off the additive supply or initiates a decompression procedure when the injector inlet pressure / flow rate is abnormal, preventing additive deposition and blockage caused by airflow fluctuations. This design extends the continuous operating life of the Venturi unit and reduces downtime due to malfunctions.

[0124] The grinding aid is 0.1-0.3 parts of calcium stearate, the ball-to-material ratio is 8:1, the rotation speed is 250 rpm, and the time is 45 min. The ball milling pretreatment of lithium salt compounds needs to be carried out under inert gas conditions, and the grinding aid is added. The lithium salt ball milling pretreatment under inert gas protection can prevent lithium carbonate / lithium hydroxide from absorbing moisture and agglomerating. The fineness of D90≤5μm allows it to release Li during the fine grinding stage rapidly. + Ions. Grinding aids adsorb onto the surface of newly formed minerals, reducing surface free energy, thereby decreasing re-agglomeration rate and increasing lithium salt utilization.

[0125] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A process for the production of surface-modified bentonite, characterized in that, The method comprises the following steps: S1: crushing the bentonite raw ore by a jaw crusher to meet the feeding requirements; S2: continuously and uniformly feeding the crushed material to the Raymond mill main machine feeding port by an electromagnetic vibration feeder, and adding an initial grinding additive composition at the outlet of the feeder, The initial grinding additive composition comprises the following components in parts: 0.1-0.5 parts of nano silicon dioxide, 0.05-0.2 parts of carboxymethyl cellulose or polyacrylamide; S3: the material is thrown into the grinding roller and the grinding ring by the rotating shovel in the Raymond mill grinding chamber, and is crushed into fine powder by centrifugal rolling, and a phosphate compound is injected through the atomizing nozzle on the side wall of the grinding chamber, The amount of the phosphate compound added is 0.03-0.1 parts; S4: the air flow of the air blower blows the fine powder into the analyzer, and a fine grinding additive composition is added in the analyzer inlet pipeline through a texturizing injector, the particle size is controlled by adjusting the speed of the analyzer, the qualified fine powder enters the collection system with the airflow, and the coarse particles fall back to the grinding chamber for further crushing, The fine grinding additive composition comprises the following components in parts: 0.2-0.8 parts of nano magnesium-aluminum hydrotalcite, and 0.05-0.15 parts of a lithium salt compound; S5: the powder-containing airflow is subjected to gas-solid separation in sequence through a cyclone collector and a bag-type dust collector, a post-treatment additive is added in the mixing pipe downstream of the cyclone collector discharge valve, and bentonite finished powder is obtained, The post-treatment additive comprises: 0.3-1 parts of hydrophobic modified silicon powder and 0.1-0.3 parts of sodium citrate; S6: the induced draft fan maintains negative pressure in the system, and the purified tail gas is discharged up to the standard.

2. A process for the production of surface-modified bentonite according to claim 1, characterized in that, The initial grinding additive in step S2 is added in the following manner: Nano silicon dioxide is premixed with the crushed material at a mass ratio of 1: (10-15) in a scraper wheel mixer, the rotation speed of the scraper wheel is 20-30 rpm, carboxymethyl cellulose is prepared into a 5±0.5 wt% aqueous solution, and after being atomized by a high-pressure nozzle, it is sprayed into the material flow of the feeder.

3. The process for producing a surface-modified bentonite according to claim 1, wherein The atomizing nozzle in step S3 needs to adopt a double-fluid internal mixing structure, the carrier gas is nitrogen, the atomizing pressure is 0.3-0.5 MPa, and the liquid droplet particle size is 10-20 μm.

4. The process for producing a surface-modified bentonite according to claim 1, characterized by, The texturizing injector in step S4 is set in the following steps: S41: the throat diameter is 25±1 mm, the contraction angle is 18±1°, and the diffusion angle is 8±0.5°; S42: the injector inlet pressure is 0.8-1.0 MPa, and the outlet airflow velocity is 18-22 m / s; S43: the addition point is 1.5±0.2 m away from the analyzer inlet.

5. The process for producing a surface-modified bentonite according to claim 2, characterized by, The mixing pipe in step S5 is set in the following steps: S51: the length is ≥3 m, and 6 groups of SK type static mixing units are arranged inside; S52: the pipe wall is cooled by cooling water to control the temperature to 40-50℃; The mixing time is ≥90 s, and the mixing uniformity is ≤5%.

6. A process for the production of a surface-modified bentonite according to any one of claims 1 to 5, characterized in that, The lithium salt compound is lithium carbonate or lithium hydroxide, which is pre-milled to D90≤5 μm.

7. A process for the production of a surface-modified bentonite according to any one of claims 1, characterized in that, The nano-silica has a surface area of 180-220 m 2 / g, a primary particle size of 10-20 nm, and a surface hydroxyl density of ≥3.0 per nm 2 .

8. A process for the production of a surface-modified bentonite according to claim 3, characterized in that, The phosphate compound is triethylhexyl phosphate, the acid value of which is 180-220 mgKOH / g, and the flash point is ≥110℃.

9. A process for the production of a surface-modified bentonite according to claim 4, characterized in that, The texturizing injector is configured with a safety interlocking system and comprises the following steps: S91: When the inlet pressure < 0.7 MPa, automatically close the fine grinding additive feed valve; S92: When the gas flow velocity > 25 m / s, start the pressure reducing valve.

10. The process for producing a surface-modified bentonite according to claim 6, characterized by, The ball milling pretreatment of the lithium salt compound needs to be carried out in an inert gas condition, and a grinding aid is added, Wherein, the grinding aid is calcium stearate 0.1-0.3 parts, the ball-to-material ratio is 8:1, the rotation speed is 250 rpm, and the time is 45 min.

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