Method for preparing filter aid by activating lime milk

Abstract

The embodiment of the invention provides a method for preparing a filter aid by activating lime milk, which comprises the following steps: carrying out first mixing on lime milk and Bayer process refined liquid to carry out pre-reaction to generate a primary filter aid; carrying out second mixing on the primary filter aid and crude liquid containing sodium aluminate to carry out deepening reaction, so that tricalcium aluminate crystals in the primary filter aid further grow in the crude liquid; carrying out solid-liquid separation on the liquid subjected to the second mixing to obtain a filter aid product; wherein the pre-reaction comprises the following parameters: the reaction temperature is 75-95 DEG C, the reaction time is 40 minutes to 3 hours, the reaction pressure is normal pressure, and the stirring speed is 50-150 revolutions per minute. Through the two stages of pre-reaction and deepening reaction, the generation and growth conditions of tricalcium aluminate crystals are optimized, and finally the technical problem of improving the filtering performance of the filter aid is effectively solved.

Description

Technical Field

[0001] This application relates to the field of sodium aluminate solution filtration and purification technology, and in particular to a method for preparing a filter aid by activating lime milk. Background Technology

[0002] Aluminum, as an important light metal, has wide applications in many fields, and its main raw material, alumina, is mostly produced using the Bayer process. This process extracts high-purity alumina from bauxite through steps such as leaching, red mud separation, refining, decomposition crystallization, and roasting. Among these steps, the filtration and refining of sodium aluminate solution is a critical step, and its efficiency and quality directly affect the smooth progress of subsequent processes and the quality of the final product. To improve filtration efficiency and filtrate quality, filter aids are usually used.

[0003] However, the preparation of filter aids in existing technologies presents numerous problems. The short reaction time between lime slurry and sodium aluminate solution results in small tricalcium aluminate crystals that fail to grow sufficiently, thus affecting the filtration effect. Simultaneously, the viscous nature of lime slurry makes it prone to stratification and sedimentation, leading to pipe blockage and unstable dosage, which impacts the filter's throughput efficiency. Furthermore, in the crude liquor refining process, lime slurry, as a filter aid, uses its main component, calcium hydroxide, to adjust the solution's pH and react with metal ions, promoting impurity precipitation and thus improving the quality of the refined liquor. However, if the amount of lime slurry is improper or the reaction is incomplete, calcium hydroxide may not be fully converted into precipitate, leading to its entry into the refined liquor, increasing impurity content, and affecting product quality. These problems not only limit the efficiency of the filtration and refining process but also increase production costs, reduce economic benefits, and place a certain burden on the environment. Summary of the Invention

[0004] This application provides a method for preparing a filter aid by activating lime slurry, in order to solve the following technical problem: how to improve the filtration performance of the filter aid.

[0005] This application provides a method for preparing a filter aid by activating lime slurry, including:

[0006] The lime milk is first mixed with Bayer process concentrate to carry out a pre-reaction and generate a primary filter aid;

[0007] The primary filter aid is mixed with the crude liquid containing sodium aluminate for a second time to carry out a deeper reaction, so that the tricalcium aluminate crystals in the primary filter aid can grow further in the crude liquid.

[0008] The second mixed liquid is subjected to solid-liquid separation to obtain the filter aid product;

[0009] The pre-reaction includes the following parameters: reaction temperature of 75°C to 95°C, reaction time of 40 minutes to 3 hours, reaction pressure of atmospheric pressure, and stirring speed of 50 to 150 rpm.

[0010] Optionally, the flow ratio of the lime milk to the Bayer semen is 1:1 to 1:2.

[0011] Optionally, the effective calcium concentration of the lime slurry is 150 g / L to 170 g / L.

[0012] Optionally, the mass of the primary filter aid is 2‰ to 5‰ of the mass of the crude liquid.

[0013] Optionally, the deepening reaction includes the following parameters: reaction temperature of 75°C to 95°C, reaction time of 40 minutes to 1 hour, and reaction pressure of atmospheric pressure.

[0014] Optionally, the solid-liquid separation includes one of the following: filtration, centrifugal separation, or pressure filtration.

[0015] Optionally, the filtration parameters include: a filtration pressure of 0.1 to 0.3 MPa and a filtration temperature of 70°C to 90°C.

[0016] Optionally, the method further includes:

[0017] Before the first mixing, the lime slurry is preheated at a temperature of 50°C to 90°C.

[0018] Optionally, the method further includes:

[0019] After the intensified reaction is carried out, the second mixed liquid is homogenized, which includes mechanical stirring or ultrasonic treatment.

[0020] Optionally, the homogenization process takes 10 to 30 minutes, the mechanical stirring speed is 100 to 200 revolutions per minute, and the ultrasonic treatment power is 500 to 1000W.

[0021] The technical solutions provided in this application have the following advantages compared with the prior art:

[0022] This application provides a method for preparing a filter aid by activating lime slurry. By optimizing the formation and growth process of tricalcium aluminate crystals, the filtration performance of the filter aid is significantly improved. In the pre-reaction stage, calcium hydroxide in the lime slurry reacts chemically with sodium aluminate in the Bayer process concentrate to generate tricalcium aluminate crystals. By controlling the reaction temperature (75°C to 95°C), time (40 minutes to 3 hours), pressure (atmospheric pressure), and stirring speed (50 to 150 rpm), the crystals are uniformly nucleated and gradually grow, thus forming a primary filter aid with a specific particle size and structure. This primary filter aid can form a stable filter cake during filtration, effectively intercepting impurities while maintaining a certain porosity, thereby improving filtration efficiency and reducing filtration resistance. In the advanced reaction stage, the primary filter aid further reacts with the crude liquid containing sodium aluminate, and the tricalcium aluminate crystals continue to grow in the crude liquid, optimizing their size and structure. After crystal growth, the particle size distribution is more uniform, and the resulting filter cake structure is denser and more stable, enabling more effective interception of impurity particles and significantly improving filtration efficiency. Simultaneously, the optimized porosity and pore size distribution reduce filtration resistance and increase filtration speed. Finally, the filter aid obtained through solid-liquid separation possesses an optimized crystal structure and particle size distribution, enabling direct use in the filtration process to form a high-quality filter cake, significantly improving filtration performance, including filtration speed, filtration efficiency, and filter cake stability. This application optimizes the formation and growth conditions of tricalcium aluminate crystals through two stages: pre-reaction and in-depth reaction, ultimately effectively solving the technical problem of improving the filtration performance of filter aids. Attached Figure Description

[0023] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings required in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other related drawings can be derived from these drawings without creative effort.

[0025] Figure 1 This is a flowchart illustrating a method for preparing a filter aid by activating lime slurry, as provided in an embodiment of this application.

[0026] Figure 2 This is a microstructure diagram of the filter aid product obtained in Example 1 of this application;

[0027] Figure 3 This is a microstructure diagram of the filter aid product provided in Example 2 of this application;

[0028] Figure 4 This is a microstructure diagram of the filter aid product prepared in Comparative Example 1 of this application.

[0029] Figure 5 This is a microstructure diagram of the filter aid product provided in Comparative Example 2 of this application. Detailed Implementation

[0030] To more clearly illustrate the purpose, technical solutions, and advantages of the embodiments of this application, the technical solutions of this embodiment will be described in detail below with reference to the accompanying drawings. Please note that the mentioned embodiments are merely examples and not all possible implementations. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0031] 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 to 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 "comprise" 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.

[0032] Figure 1 This is a flowchart illustrating a method for preparing a filter aid by activating lime slurry, as provided in an embodiment of this application.

[0033] Please see Figure 1 This application provides a method for preparing a filter aid by activating lime slurry, comprising:

[0034] S1. The lime milk and Bayer process concentrate are mixed for the first time to carry out a pre-reaction and generate a primary filter aid;

[0035] S2. The primary filter aid is mixed with the crude liquid containing sodium aluminate for a second time to carry out a deeper reaction, so that the tricalcium aluminate crystals in the primary filter aid can grow further in the crude liquid.

[0036] S3. Perform solid-liquid separation on the second mixed liquid to obtain the filter aid product;

[0037] The pre-reaction includes the following parameters: reaction temperature of 75°C to 95°C, reaction time of 40 minutes to 3 hours, reaction pressure of atmospheric pressure, and stirring speed of 50 to 150 rpm.

[0038] Lime milk: An aqueous suspension of calcium hydroxide (Ca(OH)2), commonly used to provide an alkaline environment in chemical reactions. Bayer process concentrate: A solution containing sodium aluminate (NaAlO2) obtained during the Bayer process for alumina production. Filter aid: A substance used in the filtration process to improve filtration performance by forming a filter cake structure to increase filtration efficiency. Tricalcium aluminate (C3A): A calcium aluminate with the chemical formula 3CaO·Al2O3, possessing excellent filtration properties. Lime milk: Prepared by reacting quicklime (CaO) with water, or purchased from chemical reagent suppliers (such as Sinopharm Chemical Reagent Co., Ltd.). Bayer process concentrate: Derived from the Bayer process in alumina production.

[0039] In the pre-reaction stage, the calcium hydroxide (Ca(OH)2) in the lime slurry reacts chemically with the sodium aluminate (NaAlO2) in the Bayer process concentrate to form tricalcium aluminate (C3A) crystals. Tricalcium aluminate is an important calcium aluminate with a specific crystal structure, providing a good foundation for the filtration performance of filter aids. Optimizing the formation conditions of tricalcium aluminate crystals is key to rationally controlling the reaction temperature (75℃ to 95℃), reaction time (40 minutes to 3 hours), maintaining the reaction pressure at atmospheric pressure, and controlling the stirring speed between 50 and 150 rpm. By precisely controlling these parameters, uniform nucleation and orderly growth of crystals can be ensured, thereby preparing a primary filter aid with the required particle size and structure. Temperature has a significant impact on the chemical reaction rate. A temperature range of 75℃ to 95℃ provides sufficient energy to promote the reaction between calcium hydroxide and sodium aluminate, while avoiding side reactions or excessive crystal growth caused by excessively high temperatures. A well-designed reaction time (40 minutes to 3 hours) ensures sufficient growth of tricalcium aluminate crystals while effectively preventing excessive crystal aggregation or incomplete reaction due to prolonged exposure. Atmospheric pressure conditions are suitable for large-scale industrial production, avoiding the complexity and cost of high-pressure equipment. Stirring promotes mixing and mass transfer efficiency of the reactants; a suitable stirring speed (50 to 150 rpm) ensures adequate contact between reactants while preventing crystal breakage due to excessive stirring.

[0040] In the advanced reaction stage, the tricalcium aluminate crystals in the primary filter aid react further with the crude liquid containing sodium aluminate, causing the crystals to grow larger in the crude liquid. The high concentration of sodium aluminate in the crude liquid provides ample raw material for the growth of tricalcium aluminate crystals. Crystal growth enhances its mechanical stability and improves its interception capacity and pore size distribution during filtration. After crystal growth, the particle size distribution becomes more uniform, forming a denser and more stable filter cake structure. This filter cake can more effectively intercept impurity particles during filtration, reducing impurity penetration and significantly improving filtration efficiency. During crystal growth, porosity and pore size distribution are optimized, allowing the filter cake to maintain high interception capacity while reducing filtration resistance and increasing filtration speed. Solid filter aid is then separated from the liquid after the advanced reaction using physical methods (such as filtration, centrifugation, and pressure filtration). This process ensures the purity and quality of the filter aid while removing impurities and excess liquid components generated during the reaction. The solid-liquid separation step effectively removes unreacted raw materials and impurities, further ensuring the purity of the filter aid and thus improving its filtration efficiency. The separated filter aid, with its optimized crystal structure and particle size distribution, can be directly applied to the filtration process to efficiently produce high-quality filter cake. Example:

[0041] The lime milk with a concentration of 160 g / L was mixed with Bayer process concentrate, the reaction temperature was 80℃, and the reaction time was 1 hour.

[0042] The pre-reaction was carried out under normal pressure with a stirring speed of 100 rpm.

[0043] The primary filter aid is mixed with the crude liquid containing sodium aluminate, and the reaction time is 50 minutes.

[0044] The filter aid product was obtained by centrifugation at a speed of 3000 rpm.

[0045] Solid-liquid separation is performed using a filter press at a pressure of 0.2 MPa.

[0046] The mass of the primary filter aid is 3‰ of the mass of the crude liquid.

[0047] After the pre-reaction, the mixture is cooled to room temperature before further reaction.

[0048] The second mixture of liquids was homogenized using ultrasonic treatment.

[0049] Homogenization is achieved through mechanical stirring at a speed of 150 rpm.

[0050] After the reaction is intensified, the mixture is filtered at a temperature of 80°C.

[0051] In some embodiments, the flow ratio of the lime milk to the Bayer semen is 1:1 to 1:2.

[0052] Flow ratio: refers to the ratio of the flow rates of two liquids during the mixing process.

[0053] Maintaining a flow ratio between 1:1 and 1:2 ensures the complete chemical reaction and prevents incomplete reaction or impurity formation caused by excessive lime slurry or Bayer process concentrate. In chemical reactions, the molar ratio of reactants is a key factor affecting reaction completeness and product quality. A flow ratio of 1:1 to 1:2 ensures the reaction between calcium hydroxide and sodium aluminate proceeds within the stoichiometric range, resulting in high-quality tricalcium aluminate crystals. This flow ratio improves reaction efficiency and reduces reaction time. Flow ratios that are too low or too high may lead to incomplete reaction or the formation of byproducts, reducing the performance of the filter aid. This flow ratio reduces the amount of unreacted lime slurry or Bayer process concentrate remaining in the reaction system, thereby reducing the possibility of impurity formation and improving the purity of the filter aid. This flow ratio ensures uniform nucleation and growth of tricalcium aluminate crystals, thus optimizing their particle size distribution. Filter aids with a uniform particle size distribution form a more stable filter cake structure during filtration, effectively improving filtration efficiency and reducing resistance during the filtration process. Example:

[0054] The flow ratio can be 1:1, 1:1.5, 1:2, 1:1.2, 1:1.8, 1:1.3, 1:1.7, 1:1.4, 1:1.6, 1:1.9, etc.

[0055] In some embodiments, the effective calcium mass concentration of the lime slurry is 150 g / L to 170 g / L.

[0056] Effective calcium mass concentration: The percentage concentration of calcium hydroxide by mass in lime milk.

[0057] Maintaining the effective calcium concentration of lime slurry within the range of 150 g / L to 170 g / L ensures sufficient calcium hydroxide participation in the reaction, resulting in the formation of adequate tricalcium aluminate crystals. This concentration range provides enough calcium hydroxide to ensure complete reaction with sodium aluminate. Calcium within this range effectively increases the reaction rate and shortens the overall reaction time. Too low a concentration slows the reaction rate, while too high a concentration may cause an overly vigorous reaction, leading to the formation of byproducts. Calcium hydroxide at this concentration promotes the uniform nucleation and growth of tricalcium aluminate crystals, forming a primary filter aid with a specific particle size and structure. This calcium concentration optimizes the crystal growth environment and improves crystal quality. This effective calcium concentration optimizes the particle size distribution and porosity of the filter aid, thereby improving its filtration performance. Filter aids with uniform particle size distribution and appropriate porosity form a more stable filter cake structure, improving filtration efficiency and reducing filtration resistance. Example:

[0058] The effective calcium concentration of the lime slurry can be 155 g / L, 160 g / L, 170 g / L, 158 g / L, 165 g / L, 152 g / L, 168 g / L, 156 g / L, 162 g / L, 169 g / L, etc.

[0059] In some embodiments, the mass of the primary filter aid is 2‰ to 5‰ of the mass of the crude liquid.

[0060] Crude solution: A solution containing sodium aluminate, which usually contains impurities.

[0061] Controlling the mass of the primary filter aid to 2‰ to 5‰ of the crude liquid mass ensures sufficient growth space and reaction raw materials for tricalcium aluminate crystals, while preventing excessive filter aid from causing filter cake thickening and increasing filtration resistance. In the advanced reaction, the tricalcium aluminate crystals in the primary filter aid need to further react with the sodium aluminate in the crude liquid. A ratio of 2‰ to 5‰ ensures the stoichiometry between reactants, allowing for sufficient crystal growth. Using an appropriate amount of primary filter aid results in a dense and stable filter cake structure. Too little primary filter aid may lead to a loose filter cake structure, failing to effectively intercept impurities; too much primary filter aid may result in an excessively thick filter cake, increasing filtration resistance. Appropriately adjusting the amount of primary filter aid can optimize the porosity and pore size distribution of the filter cake, thereby improving filtration efficiency. An appropriate amount of filter aid effectively intercepts impurities while maintaining a high filtration rate. Example:

[0062] The quality of the primary filter aid can be 3‰, 4‰, 2‰, 5‰, 3.5‰, 2.5‰, 4.5‰, 3.2‰, 4.2‰, 3.8‰, etc., based on the mass of the crude liquid.

[0063] In some embodiments, the deepening reaction includes the following parameters: reaction temperature of 75°C to 95°C, reaction time of 40 minutes to 1 hour, and reaction pressure of atmospheric pressure.

[0064] The advanced reaction stage further optimizes the growth conditions of tricalcium aluminate crystals by controlling the reaction temperature (75℃ to 95℃), reaction time (40 minutes to 1 hour), and reaction pressure (atmospheric pressure), enabling crystal growth and enhancing their filtration performance. The suitable temperature range of 75℃ to 95℃ provides just the right amount of energy for tricalcium aluminate crystal growth, promoting healthy crystal growth while effectively avoiding excessive crystal growth or adverse side reactions that may be caused by excessive temperature. Temperature has a significant impact on the crystal growth rate and quality. A reaction time of 40 minutes to 1 hour ensures sufficient crystal growth while avoiding excessive crystal aggregation or incomplete reaction due to excessive time. The reaction time determines the crystal growth time and has a significant impact on the crystal particle size and structure. Atmospheric pressure conditions are suitable for large-scale industrial production while avoiding the complexity and cost of high-pressure equipment. Atmospheric pressure conditions ensure the stability and safety of the reaction. In the advanced reaction, tricalcium aluminate crystals grow further, with a more uniform particle size distribution, forming a denser and more stable filter cake structure. This type of filter cake can more effectively intercept impurity particles during filtration, reducing impurity penetration and thus significantly improving filtration efficiency. During crystal growth, porosity and pore size distribution are optimized, allowing the filter cake to maintain high interception capacity while reducing filtration resistance and increasing filtration speed. Example:

[0065] The reaction temperature was 70℃ and the reaction time was 50 minutes.

[0066] The reaction temperature was 60℃ and the reaction time was 40 minutes.

[0067] The reaction temperature was 80℃ and the reaction time was 1 hour.

[0068] The reaction temperature was 65℃ and the reaction time was 45 minutes.

[0069] The reaction temperature was 75℃ and the reaction time was 55 minutes.

[0070] The reaction temperature was 68℃ and the reaction time was 48 minutes.

[0071] The reaction temperature was 72℃ and the reaction time was 52 minutes.

[0072] The reaction temperature was 85℃ and the reaction time was 1 hour.

[0073] The reaction temperature was 78℃ and the reaction time was 58 minutes.

[0074] The reaction temperature was 76℃ and the reaction time was 54 minutes.

[0075] In some embodiments, the solid-liquid separation includes one of the following: filtration, centrifugation, or pressure filtration.

[0076] Solid-liquid separation: The process of separating solid particles from liquids using physical methods.

[0077] Solid filter aids are separated from liquids after intensified reactions using methods such as filtration, centrifugation, or pressure filtration to ensure their purity and quality. Filtration separates solid particles from a liquid using porous media (such as filter cloth or filter paper). During filtration, solid particles are trapped on the porous media, forming a filter cake. Centrifugation effectively separates solid particles from a liquid using centrifugal force, while pressure filtration forces the liquid out of the solid particles by applying pressure. During pressure filtration, the liquid passes through the filter cloth or other porous media under pressure, and solid particles are trapped on the filter cloth. Example:

[0078] Solid-liquid separation was performed using filtration at a pressure of 0.2 MPa.

[0079] Centrifugation was used at a speed of 3000 rpm.

[0080] Pressure filtration is used, with a pressure of 0.3 MPa.

[0081] The filtration temperature for the filtration method is 80℃.

[0082] The centrifugation time for centrifugation separation is 20 minutes.

[0083] The filtration time for the pressure filtration method is 30 minutes.

[0084] The filtration time for the filtration method is 40 minutes.

[0085] The centrifugation speed for centrifugation separation is 2500 rpm.

[0086] The pressure for the pressure filtration method is 0.25 MPa.

[0087] The filtration temperature for the filtration method is 75℃.

[0088] In some embodiments, the filtration parameters include: a filtration pressure of 0.1 to 0.3 MPa and a filtration temperature of 70°C to 90°C.

[0089] By precisely controlling the filtration pressure within the range of 0.1 to 0.3 MPa and the filtration temperature between 70°C and 90°C, the filtration process can be optimized, thereby ensuring the purity and quality of the filter aid. The pressure range of 0.1 to 0.3 MPa provides sufficient driving force to allow the liquid to pass through the filter cloth or other porous media, while preventing excessive pressure from causing filter cake rupture or impurity penetration. The temperature range of 70°C to 90°C reduces the viscosity of the liquid, increases the flowability of solid particles, and thus improves filtration efficiency. These filtration parameters effectively remove impurities and excess liquid components generated during the reaction process, improving the purity of the filter aid. These filtration parameters ensure the quality of the filter aid, enabling the formation of a high-quality filter cake during filtration and improving filtration performance. These filtration pressure and temperature settings increase filtration speed, shorten filtration time, and improve production efficiency. Example:

[0090] The filtration pressure is 0.2 MPa and the filtration temperature is 80℃.

[0091] The filtration pressure is 0.1 MPa and the filtration temperature is 70℃.

[0092] The filtration pressure is 0.3 MPa and the filtration temperature is 90℃.

[0093] The filtration pressure is 0.15 MPa and the filtration temperature is 75℃.

[0094] The filtration pressure is 0.25 MPa and the filtration temperature is 85℃.

[0095] The filtration pressure is 0.18 MPa and the filtration temperature is 78℃.

[0096] The filtration pressure is 0.22 MPa and the filtration temperature is 82℃.

[0097] The filtration pressure is 0.28 MPa and the filtration temperature is 88℃.

[0098] The filtration pressure is 0.21 MPa and the filtration temperature is 76℃.

[0099] The filtration pressure is 0.27 MPa and the filtration temperature is 84℃.

[0100] In some embodiments, the method further includes:

[0101] Before the first mixing, the lime slurry is preheated at a temperature of 50°C to 70°C.

[0102] Preheating: The reactants are heated before mixing to improve reaction efficiency.

[0103] Before the first mixing, the lime slurry is preheated to 50°C to 70°C. Preheating increases the temperature of the reactants, thereby accelerating the chemical reaction and improving efficiency. Specifically, it increases the reaction rate between calcium hydroxide and sodium aluminate, shortening the reaction time. Preheating also ensures uniform mixing of the reactants, preventing uneven reaction or abnormal crystal growth caused by localized temperature differences. Example:

[0104] Preheating temperatures can be 60℃, 50℃, 70℃, 55℃, 65℃, 58℃, 62℃, 68℃, 56℃, 64℃, etc.

[0105] In some embodiments, the method further includes:

[0106] After the intensified reaction is carried out, the second mixed liquid is homogenized, which includes mechanical stirring or ultrasonic treatment.

[0107] Homogenization: Mechanical stirring or ultrasonic treatment is used to make the particle distribution in the mixture more uniform.

[0108] Homogenization treatment ensures uniform distribution of tricalcium aluminate crystals in the mixture, optimizing their particle size distribution and structure, and enhancing the filtration performance of the filter aid. Mechanical stirring or ultrasonic treatment can ensure uniform distribution of solid particles in the mixture, preventing crystal aggregation or precipitation. Uniform crystal distribution leads to a more stable filter cake structure, significantly improving filtration efficiency. Homogenization treatment optimizes the particle size distribution of crystals, making it more uniform. Filter aids with uniform particle size distribution can form a more stable filter cake structure during filtration, improving filtration efficiency and reducing filtration resistance. Ultrasonic treatment, utilizing the cavitation effect, can effectively remove impurities from the crystal surface, optimize their structure, and thus improve filtration performance.

[0109] In some embodiments, the homogenization process takes 10 to 30 minutes, the mechanical stirring speed is 100 to 200 rpm, and the ultrasonic treatment power is 500 to 1000 W.

[0110] The homogenization time (10 to 30 minutes), mechanical stirring speed (100 to 200 rpm), and ultrasonic power (500 to 1000 W) significantly impact the performance of the filter aid. A homogenization time range of 10 to 30 minutes ensures sufficient and uniform crystal distribution while avoiding crystal breakage or structural damage caused by excessive time. A speed range of 100 to 200 rpm ensures uniform crystal distribution while avoiding crystal breakage caused by excessively rapid stirring. A power range of 500 to 1000 W provides sufficient energy to optimize crystal structure while avoiding crystal breakage or structural damage caused by excessively high power. Example:

[0111] The mechanical stirring speed is 120 rpm, and the homogenization time is 20 minutes.

[0112] The ultrasonic processing power is 700W, and the homogenization processing time is 15 minutes.

[0113] The mechanical stirring speed is 180 rpm, and the homogenization time is 25 minutes.

[0114] The ultrasonic processing power is 900W, and the homogenization processing time is 22 minutes.

[0115] The mechanical stirring speed is 140 rpm, and the homogenization time is 18 minutes.

[0116] The ultrasonic processing power is 650W, and the homogenization processing time is 16 minutes.

[0117] The mechanical stirring speed is 160 rpm, and the homogenization time is 24 minutes.

[0118] The ultrasonic processing power is 750W, and the homogenization processing time is 19 minutes.

[0119] The mechanical stirring speed was 130 rpm, and the homogenization time was 21 minutes.

[0120] The ultrasonic processing power is 850W, and the homogenization processing time is 23 minutes.

[0121] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards. If there is no corresponding industry standard, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0122] Example 1

[0123] Raw material ratio: Lime milk with an effective calcium content of 165g / L is mixed with Bayer process concentrate at a volume ratio of 1:1.

[0124] Pre-reaction conditions: The reaction temperature was controlled at 95℃ and the reaction time was 2 hours, with a stirring speed of 100 rpm.

[0125] Further refine the reaction conditions: Mix the primary filter aid with the crude liquid containing sodium aluminate at a ratio of 3‰ of the mass of the primary filter aid to the mass of the crude liquid, at a reaction temperature of 95℃, and for a reaction time of 1 hour.

[0126] Solid-liquid separation: Filtration is carried out by a leaf filter at a pressure of 0.2 MPa and a temperature of 80℃.

[0127] Figure 2The microstructure diagram of the filter aid product prepared in Example 1 of this application is shown below. Figure 2 As shown.

[0128] Example 2

[0129] Raw material ratio: Lime milk with an effective calcium content of 165g / L is mixed with Bayer process concentrate at a volume ratio of 1:2.

[0130] Pre-reaction conditions: The reaction temperature was controlled at 85℃ and the reaction time was 3 hours, with a stirring speed of 120 rpm.

[0131] Further refine the reaction conditions: Mix the primary filter aid with the crude liquid containing sodium aluminate at a ratio of 4‰ of the mass of the primary filter aid to the mass of the crude liquid, at a reaction temperature of 85℃, and for a reaction time of 1 hour.

[0132] Solid-liquid separation: Filtration is carried out by a leaf filter at a pressure of 0.25 MPa and a temperature of 85°C.

[0133] Figure 3 The microstructure diagram of the filter aid product provided in Example 2 of this application is shown below. Figure 3 As shown.

[0134] Example 3

[0135] Raw material ratio: Lime milk with an effective calcium content of 165g / L is mixed with Bayer process concentrate at a volume ratio of 1:1.5.

[0136] Pre-reaction conditions: The reaction temperature was controlled at 75℃ and the reaction time was 1.5 hours, with a stirring speed of 110 rpm.

[0137] Further refine the reaction conditions: Mix the primary filter aid with the crude liquid containing sodium aluminate at a ratio of 3.5‰ of the mass of the primary filter aid to the mass of the crude liquid, at a reaction temperature of 75℃, and at a reaction time of 40 minutes.

[0138] Solid-liquid separation: Filtration is carried out by a leaf filter at a pressure of 0.18 MPa and a temperature of 75°C.

[0139] Example 4

[0140] Raw material ratio: Lime milk with an effective calcium content of 165g / L is mixed with Bayer process concentrate at a volume ratio of 1:1.

[0141] Pre-reaction conditions: The reaction temperature was controlled at 85℃ and the reaction time was 2 hours, with a stirring speed of 130 rpm.

[0142] Further refine the reaction conditions: Mix the primary filter aid with the crude liquid containing sodium aluminate at a ratio of 2‰ of the mass of the primary filter aid to the mass of the crude liquid, at a reaction temperature of 85℃, and at a reaction time of 50 minutes.

[0143] Solid-liquid separation: Filtration is carried out by a leaf filter at a pressure of 0.22 MPa and a temperature of 88°C.

[0144] Example 5

[0145] Raw material ratio: Lime milk with an effective calcium content of 165g / L is mixed with Bayer process concentrate at a volume ratio of 1:2.

[0146] Pre-reaction conditions: The reaction temperature was controlled at 90℃ and the reaction time was 1.5 hours, with a stirring speed of 140 rpm.

[0147] Further refine the reaction conditions: Mix the primary filter aid with the crude liquid containing sodium aluminate at a ratio of 5‰ of the mass of the primary filter aid to the mass of the crude liquid, at a reaction temperature of 90℃, and for a reaction time of 1 hour.

[0148] Solid-liquid separation: Filtration is carried out by a leaf filter at a pressure of 0.28 MPa and a temperature of 90°C.

[0149] Example 6

[0150] Raw material ratio: Lime milk with an effective calcium content of 165g / L is mixed with Bayer process concentrate at a volume ratio of 1:1.8.

[0151] Pre-reaction conditions: The reaction temperature was controlled at 60℃ and the reaction time was 2.5 hours, with a stirring speed of 150 rpm.

[0152] Further refine the reaction conditions: Mix the primary filter aid with the crude liquid containing sodium aluminate at a ratio of 4.5‰ of the mass of the primary filter aid to the mass of the crude liquid, at a reaction temperature of 60℃, and at a reaction time of 30 minutes.

[0153] Solid-liquid separation: Filtration is carried out by a leaf filter at a pressure of 0.15 MPa and a temperature of 70°C.

[0154] Comparative Example 1

[0155] Raw material ratio: Lime milk with an effective calcium content of 165g / L is mixed with Bayer process concentrate at a volume ratio of 1:1.

[0156] Pre-reaction conditions: The reaction temperature was controlled at 50℃ and the reaction time was 30 minutes, with a stirring speed of 50 rpm.

[0157] Further refine the reaction conditions: Mix the primary filter aid with the crude liquid containing sodium aluminate at a ratio of 2‰ of the mass of the primary filter aid to the mass of the crude liquid, at a reaction temperature of 50℃, and at a reaction time of 20 minutes.

[0158] Solid-liquid separation: Filtration is carried out by a leaf filter at a pressure of 0.1 MPa and a temperature of 60℃.

[0159] Figure 4 The microstructure diagram of the filter aid product prepared in Comparative Example 1 of this application is shown below. Figure 4 As shown.

[0160] Comparative Example 2

[0161] Raw material ratio: Lime milk with an effective calcium content of 165g / L is mixed with Bayer process concentrate at a volume ratio of 1:3.

[0162] Pre-reaction conditions: The reaction temperature was controlled at 70℃ with a stirring speed of 200 rpm and the reaction time was 3 hours.

[0163] Further refine the reaction conditions: Mix the primary filter aid with the crude liquid containing sodium aluminate at a ratio of 6‰ of the mass of the primary filter aid to the mass of the crude liquid, at a reaction temperature of 70℃, and at a reaction time of 1.5 hours.

[0164] Solid-liquid separation: Filtration is carried out by a leaf filter at a pressure of 0.35 MPa and a temperature of 95°C.

[0165] Figure 5 The microstructure diagram of the filter aid product provided in Comparative Example 2 of this application is shown below. Figure 5 As shown.

[0166] Comparative Example 3

[0167] Raw material ratio: Lime milk with an effective calcium content of 165g / L is mixed with Bayer process concentrate at a volume ratio of 1:1.

[0168] Pre-reaction conditions: The reaction temperature was controlled at 40℃ and the reaction time was 1 hour, with a stirring speed of 80 rpm.

[0169] Further refine the reaction conditions: Mix the primary filter aid with the crude liquid containing sodium aluminate at a ratio of 1‰ of the mass of the primary filter aid to the mass of the crude liquid, at a reaction temperature of 40℃, and at a reaction time of 30 minutes.

[0170] Solid-liquid separation: Filtration is carried out by a leaf filter at a pressure of 0.05 MPa and a temperature of 65°C.

[0171] Effect data: The effect data of Examples 1 to 6 and Comparative Examples 1 to 4 are shown in Table 1.

[0172] Experimental methods for obtaining effect data:

[0173] 1. Determination of the average particle size of tricalcium aluminate crystals

[0174] Samples were taken from the filtered sodium aluminate solution and then dried and fixed.

[0175] Use SEM or TEM to observe the sample and take multiple high-resolution images.

[0176] The particle size of tricalcium aluminate crystals was measured using image analysis software, and particle size data of at least 100 crystals were collected.

[0177] Calculate the average particle size.

[0178] 2. Measurement of material flow rate in leaf filter

[0179] Record the flow data before and after filtration while the leaf filter is running normally.

[0180] Calculate the average flow rate during the filtration process.

[0181] The percentage increase in material throughput was calculated by comparing the control group that did not use the method of the present invention.

[0182] 3. Determination of the service life of filter cloth

[0183] Record the time from when the filter cloth is installed until it needs to be replaced.

[0184] The percentage increase in the service life of the filter cloth was calculated by comparing it with a control group that did not use the method of the present invention.

[0185] Table 1

[0186] Experiment number Average particle size (μm) of tricalcium aluminate crystals Leaf filter material throughput increased (%) Filter cloth service life extended (%) Example 1 2.5 30 40 Example 2 2.8 35 45 Example 3 2.3 32 42 Example 4 2.6 33 43 Example 5 2.9 36 46 Example 6 2.4 31 41 Comparative Example 1 1.2 10 10 Comparative Example 2 1.5 15 15 Comparative Example 3 1.0 5 5

[0187] The above effect data table provides a clear comparison of the differences between various embodiments and comparative examples. The following conclusions can be drawn:

[0188] Average particle size of tricalcium aluminate crystals:

[0189] In Examples 1 to 6, the average particle size of tricalcium aluminate crystals ranged from 2.3 to 2.9 micrometers, significantly exceeding the 1.0 to 1.5 micrometer particle size level in the comparative examples. This indicates that the method of the present invention, by optimizing the pre-reaction and intensification reaction conditions, can effectively promote the growth of tricalcium aluminate crystals and generate larger crystals. In Comparative Examples 1 to 3, the average particle size of tricalcium aluminate crystals was smaller, at 1.0, 1.2, and 1.5 micrometers, respectively. This reveals that under unoptimized conditions, the growth of tricalcium aluminate crystals is limited, thereby affecting its filtration performance.

[0190] Increased material throughput in leaf filters:

[0191] In the tests of Examples 1 to 6, the material throughput of the leaf filter increased by 30% to 36%. This indicates that the method of the present invention significantly improves filtration efficiency, reduces resistance during the filtration process, and allows more liquid to pass through the filter cloth. In Comparative Examples 1 to 3, the increase in material throughput of the leaf filter ranged only from 5% to 15%. This shows that under unoptimized conditions, the improvement in filtration efficiency is limited, the filtration process is subject to greater resistance, and production efficiency is affected.

[0192] Extended service life of filter cloth:

[0193] In Examples 1 to 6, the extension of the filter cloth's service life ranged from 40% to 46%. This indicates that the method of the present invention reduces filter cloth clogging, extends filter cloth lifespan, and lowers production costs by generating larger-sized tricalcium aluminate crystals. In Comparative Examples 1 to 3, the extension of the filter cloth's service life ranged only from 5% to 15%. This shows that under unoptimized conditions, the improvement in filter cloth lifespan is limited, and frequent filter cloth replacements increase production costs.

[0194] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. 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 this application. Therefore, this application 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 method for preparing a filter aid by activating lime slurry, comprising: The lime milk is first mixed with Bayer process concentrate to carry out a pre-reaction and generate a primary filter aid; The primary filter aid is mixed with the crude liquid containing sodium aluminate for a second time to carry out a deeper reaction, so that the tricalcium aluminate crystals in the primary filter aid can grow further in the crude liquid. The second mixed liquid is subjected to solid-liquid separation to obtain the filter aid product; The pre-reaction includes the following parameters: reaction temperature of 75°C to 95°C, reaction time of 40 minutes to 3 hours, reaction pressure of atmospheric pressure, and stirring speed of 50 to 150 rpm.

2. The method according to claim 1, characterized in that, The flow ratio of the lime milk to the Bayer process semen is 1:1 to 1:

2.

3. The method according to claim 1 or 2, characterized in that, The effective calcium concentration of the lime slurry is 150 g / L to 170 g / L.

4. The method according to claim 1, characterized in that, The mass of the primary filter aid is 2‰ to 5‰ of the mass of the crude liquid.

5. The method according to claim 1, characterized in that, The in-depth reaction includes the following parameters: reaction temperature of 75°C to 95°C, reaction time of 40 minutes to 1 hour, and reaction pressure of atmospheric pressure.

6. The method according to claim 1, characterized in that, The solid-liquid separation includes the following: filtration, centrifugal separation, and pressure filtration.

7. The method according to claim 6, characterized in that, The filtration parameters include: filtration pressure of 0.1 to 0.3 MPa and filtration temperature of 70°C to 90°C.

8. The method according to claims 1 to 7, characterized in that, The method further includes: Before the first mixing, the lime slurry is preheated at a temperature of 50°C to 70°C.

9. The method according to any one of claims 1 to 7, characterized in that, The method further includes: After the intensified reaction is carried out, the second mixed liquid is homogenized, which includes mechanical stirring or ultrasonic treatment.

10. The method according to claim 9, characterized in that, The homogenization process takes 10 to 30 minutes, the mechanical stirring speed is 100 to 200 revolutions per minute, and the ultrasonic treatment power is 500 to 1000 W.

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