Spray drying preparation method of anhydrous calcium hydrogen phosphate

Abstract

The invention relates to the technical field of preparation of anhydrous calcium hydrogen phosphate, and particularly discloses a spray drying preparation method of anhydrous calcium hydrogen phosphate, which comprises the following steps: S1, slurry preparation, S2, spray drying, S3, vacuum drying, S4, screening, and S5, weighing and packaging. By optimizing the raw material ratio and controlling the pH value, the method can effectively remove impurities, reduce the generation of byproducts, improve the purity of the final product, and meet the quality requirements in the fields of food, medicine, chemical industry and the like; the spray drying technology can accurately control the size of liquid drops, so that the final product particles are uniformly distributed, the problems of agglomeration and caking are avoided, the fluidity of the powder is improved, subsequent processing and storage are facilitated, and compared with a traditional drying mode, the method can more effectively reduce residual moisture of the product, reduce the risk of wetting and caking, improve the storage stability and prolong the shelf life of the product; anhydrous calcium hydrogen phosphate with different particle size distributions can be obtained by adjusting spray drying and screening parameters, and the applicability of the product is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of anhydrous calcium hydrogen phosphate preparation, and particularly relates to a spray drying preparation method of anhydrous calcium hydrogen phosphate. Background Art

[0002] In the existing anhydrous calcium hydrogen phosphate preparation technology, conventional heating drying methods such as oven drying or fluidized bed drying are generally used. Although these methods can achieve dehydration of calcium hydrogen phosphate to a certain extent, they have many shortcomings.

[0003] Traditional drying methods often make it difficult to accurately control the temperature and humidity conditions during the drying process, resulting in uneven distribution of product particle size and prone to agglomeration and caking. This not only affects the fluidity of the product, but also brings inconvenience to subsequent processing and storage.

[0004] Traditional drying methods are inefficient in removing moisture and often require a long drying time, which not only increases production costs but can also cause product deterioration during the drying process, affecting the quality and stability of the final product. In addition, excessive residual moisture can increase the risk of product moisture and agglomeration, shortening the shelf life of the product.

[0005] In this regard, the inventors proposed a spray-drying preparation method of anhydrous calcium hydrogen phosphate to solve the above problems. Summary of the invention

[0006] The object of the present invention is to provide a spray-drying preparation method of anhydrous calcium hydrogen phosphate to solve the problems raised in the above background technology.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A spray-drying preparation method of anhydrous calcium hydrogen phosphate comprises:

[0009] S1. Slurry preparation: mixing calcium hydrogen phosphate dihydrate with purified water, adding a pH regulator and citric acid monohydrate, and stirring to form a suspension;

[0010] S2, spray drying: the suspension is sent to a spray dryer, the slurry is atomized into tiny droplets through a high-speed centrifugal disk or a pressure nozzle, the inlet air temperature is controlled at 130-160°C, the outlet air temperature is controlled at 60-90°C, and spray drying is performed to obtain a preliminary dry powder;

[0011] S3, vacuum drying: sending the preliminarily dried powder into a double-cone rotary vacuum dryer to further remove moisture at 60-80° C. to obtain anhydrous calcium hydrogen phosphate with a moisture content of ≤0.5%;

[0012] S4, screening: using an automatic screening system to screen the anhydrous calcium hydrogen phosphate to obtain a product that meets the target particle size distribution;

[0013] S5. Weighing and packaging: Weigh the product that meets the target particle size distribution, and use moisture-proof sealed packaging to obtain the final product.

[0014] Preferably, the purity of the calcium hydrogen phosphate dihydrate is ≥99%, and the particle fineness D50 is ≤10 μm.

[0015] Preferably, the stirring rate in the slurry is controlled at 100-200 rpm, and the pH value is controlled at 6.5-7.5.

[0016] Preferably, the spray drying process adopts a high-speed centrifugal atomization method, the rotation speed of the atomizing disk is controlled at 10,000 to 20,000 rpm, and the atomization pressure is 0.5 to 1.5 MPa.

[0017] Preferably, during the vacuum drying process, the parameters of the double-cone rotary vacuum dryer are: the drying vacuum degree is controlled at 0.08 to 0.1 MPa, and the drying time is 2 to 4 hours.

[0018] Preferably, the aperture of the sieve used for screening in the automatic screening system is 100-250 μm.

[0019] Preferably, the final product is subjected to quality control, including:

[0020] Moisture content testing, particle size analysis, purity testing and packaging leak testing.

[0021] Preferably, the moisture content is detected by Karl Fischer method;

[0022] The particle size analysis adopts a laser particle size analyzer;

[0023] The purity detection adopts X-ray fluorescence spectroscopy analysis;

[0024] The packaging sealing test adopts a vacuum test method.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) By optimizing the raw material ratio and pH control, the present invention can effectively remove impurities, reduce the generation of by-products, improve the purity of the final product, and meet the quality requirements of the fields of food, medicine and chemical industry; the spray drying technology can accurately control the droplet size, so that the particles of the final product are evenly distributed, avoid agglomeration and caking problems, improve the fluidity of the powder, and facilitate subsequent processing and storage.

[0027] (2) Compared with the traditional drying method, the present invention can more effectively reduce the residual moisture of the product, reduce the risk of moisture and caking, improve storage stability, and extend the shelf life of the product; by adjusting the spray drying and screening parameters, anhydrous calcium hydrogen phosphate with different particle size distributions can be obtained to meet the requirements of different fields such as tablet fillers, food additives, animal feed, etc., thereby improving the applicability of the product.

[0028] (3) The spray drying combined with the vacuum drying process in the present invention can complete water evaporation and particle solidification in a relatively short time, shorten the production cycle, and improve production efficiency. At the same time, the method reduces energy consumption and waste liquid discharge, helps to save energy and reduce emissions, and conforms to the concept of green production; the method adopts modern automated equipment and cooperates with strict process parameter control to ensure stable product quality and strong batch-to-batch consistency, ensuring reliability and safety in terminal applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a flow chart of a method for preparing anhydrous calcium hydrogen phosphate by spray drying. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Embodiment 1:

[0032] See also Figure 1 As shown, a spray-drying preparation method of anhydrous calcium hydrogen phosphate comprises:

[0033] S1. Slurry preparation: mixing calcium hydrogen phosphate dihydrate with purified water, adding a pH regulator and citric acid monohydrate, and stirring to form a suspension;

[0034] S2, spray drying: the suspension is sent to a spray dryer, the slurry is atomized into tiny droplets through a high-speed centrifugal disk or a pressure nozzle, the inlet air temperature is controlled to be 160°C, the outlet air temperature is controlled to be 90°C, and spray drying is performed to obtain a preliminary dry powder;

[0035] S3, vacuum drying: sending the preliminarily dried powder into a double-cone rotary vacuum dryer to further remove moisture at 80° C. to obtain anhydrous calcium hydrogen phosphate with a moisture content of ≤0.5%;

[0036] S4, screening: using an automatic screening system to screen the anhydrous calcium hydrogen phosphate to obtain a product that meets the target particle size distribution;

[0037] S5. Weighing and packaging: Weigh the product that meets the target particle size distribution, and use moisture-proof sealed packaging to obtain the final product.

[0038] Preferably, the purity of the calcium hydrogen phosphate dihydrate is ≥99%, and the particle fineness D50 is ≤10 μm.

[0039] Preferably, the stirring rate in the slurry is controlled at 200 rpm and the pH value is controlled at 7.

[0040] Preferably, the spray drying process adopts a high-speed centrifugal atomization method, the atomizing disk speed is controlled at 10000 rpm, and the atomization pressure is 1.5 MPa.

[0041] Preferably, during the vacuum drying process, the parameters of the double-cone rotary vacuum dryer are: the drying vacuum degree is controlled at 0.1 MPa, and the drying time is 4 hours.

[0042] Preferably, the aperture of the sieve used for screening in the automatic screening system is 100 μm.

[0043] Preferably, the final product is subjected to quality control, including:

[0044] Moisture content testing, particle size analysis, purity testing and packaging leak testing.

[0045] The moisture content is detected by Karl Fischer method, and the target moisture content is ≤0.5%;

[0046] The particle size analysis uses a laser particle size analyzer to ensure uniform particle size;

[0047] The purity test adopts X-ray fluorescence spectrometry to detect the content of calcium hydrogen phosphate;

[0048] The packaging sealing test adopts a vacuum test method to ensure the integrity of the packaging.

[0049] From the above, it can be seen that the method adopts a spray drying process combined with a vacuum drying optimization technology to make the preparation process of anhydrous calcium hydrogen phosphate more efficient and stable, and significantly improve the product quality.

[0050] By optimizing the raw material ratio and pH control, this method can effectively remove impurities, reduce the generation of by-products, improve the purity of the final product, and meet the quality requirements of food, medicine, chemical and other fields; spray drying technology can accurately control the droplet size, so that the final product particles are evenly distributed, avoid agglomeration and agglomeration problems, improve the fluidity of the powder, and facilitate subsequent processing and storage.

[0051] Compared with traditional drying methods, this method can more effectively reduce the residual moisture of the product, reduce the risk of moisture and caking, improve storage stability, and extend the shelf life of the product; by adjusting the spray drying and screening parameters, anhydrous calcium hydrogen phosphate with different particle size distributions can be obtained to meet the requirements of different fields such as tablet fillers, food additives, animal feed, etc., thereby improving the applicability of the product.

[0052] Spray drying combined with vacuum drying process can complete water evaporation and particle solidification in a relatively short time, shorten the production cycle and improve production efficiency. At the same time, this method reduces energy consumption and waste liquid discharge, helps save energy and reduce emissions, and conforms to the concept of green production; this method uses modern automated equipment and strict process parameter control to ensure stable product quality and strong batch-to-batch consistency, ensuring reliability and safety in terminal applications.

[0053] Embodiment 2:

[0054] Preparation of food grade anhydrous calcium hydrogen phosphate:

[0055] Preparation of anhydrous calcium hydrogen phosphate that meets food additive standards, suitable for food fortification, baking and dairy processing, requiring the product to have low moisture, uniform particles and good fluidity.

[0056] Process parameters and equipment description:

[0057] Slurry preparation stage:

[0058] Raw material ratio:

[0059] Calcium hydrogen phosphate dihydrate: 98.5%;

[0060] Purified water: 1.0%;

[0061] Citric acid monohydrate: 0.5%;

[0062] Equipment: 500L stainless steel stirring tank (with temperature control and online pH detection system);

[0063] Process parameters:

[0064] Temperature: 40℃;

[0065] Stirring speed: 150 rpm;

[0066] pH adjustment: adjust to 6.8 (using dilute phosphoric acid solution);

[0067] Operation Instructions: Add all raw materials into the mixing tank and stir evenly at the set temperature to ensure that the raw materials are fully dissolved and form a stable suspension.

[0068] Spray drying stage:

[0069] Equipment: High-speed centrifugal spray dryer equipped with HEPA filtered air system;

[0070] Process parameters:

[0071] Inlet air temperature: 140℃

[0072] Air outlet temperature: 75℃

[0073] Atomizer disk speed: 12,000rpm

[0074] Atomization pressure: 1.0MPa

[0075] Operation Instructions: Pump the uniform slurry into the spray dryer, disperse the liquid into fine droplets through the atomization system, and quickly dry it into powder under the action of hot air.

[0076] Vacuum drying and screening stage

[0077] Equipment: Double cone rotary vacuum dryer and automatic screening system

[0078] Process parameters:

[0079] Vacuum drying temperature: 70°C

[0080] Vacuum degree: 0.09MPa

[0081] Screening mesh: 200μm

[0082] Operation Instructions: The primary dried product is vacuum dried to further reduce moisture and then sieved to ensure uniform particle size.

[0083] Weighing and packaging stage:

[0084] Equipment: automatic weighing and packaging machine, sealing packaging equipment;

[0085] Operation instructions: Quantitatively package qualified products and use moisture-proof packaging materials to ensure product storage stability.

[0086] Test steps and data description:

[0087] Moisture content test:

[0088] Method: Karl Fischer method;

[0089] Steps: Take samples and perform pretreatment before titration, and record the moisture content.

[0090] The test result was 0.3%, which is lower than the food standard limit.

[0091] Particle size analysis:

[0092] Method: Laser particle size analyzer measurement:

[0093] Steps: Take a sample and disperse it in a suitable medium, and measure the particle D50 value.

[0094] The D50 was about 45 μm, indicating that the particles were evenly distributed.

[0095] Purity test:

[0096] Methods: X-ray fluorescence spectrometry;

[0097] Steps: Take samples and grind them for XRF testing to determine the calcium and phosphorus content.

[0098] The test results show that the product meets food grade purity requirements.

[0099] From the above, we can see that the product has low and uniform moisture content and excellent fluidity, which facilitates uniform dispersion in food production.

[0100] The precise process parameter control ensures consistent product quality between batches and meets food safety standards.

[0101] The whole process is energy-saving and environmentally friendly, and is suitable for continuous large-scale production.

[0102] Embodiment three:

[0103] Preparation of pharmaceutical grade anhydrous calcium hydrogen phosphate:

[0104] Preparation of high-purity, low-impurity pharmaceutical-grade anhydrous calcium hydrogen phosphate as a tablet or capsule filler requires uniform particles, good compressibility, and extremely low impurity content.

[0105] Process parameters and equipment description:

[0106] Slurry preparation stage:

[0107] Raw material ratio:

[0108] Calcium hydrogen phosphate dihydrate: 99.0%;

[0109] Purified water: 0.7%;

[0110] Citric acid monohydrate: 0.3%;

[0111] Equipment: 300L high-cleanliness mixing tank (equipped with online pH meter and temperature control device);

[0112] Process parameters:

[0113] Temperature: 45℃;

[0114] Stirring speed: 200 rpm;

[0115] pH adjustment: adjust to 7.2 (using dilute sodium hydroxide solution);

[0116] Operating Instructions: Mix the raw materials in a strictly clean environment to ensure that the slurry is free of microbial and foreign matter contamination.

[0117] Spray drying stage:

[0118] Equipment: pharmaceutical grade spray dryer;

[0119] Process parameters:

[0120] Inlet air temperature: 150℃;

[0121] Air outlet temperature: 70℃;

[0122] Atomizing disc speed: 15000rpm;

[0123] Atomization pressure: 1.2MPa;

[0124] Instructions:

[0125] High-speed centrifugal atomization technology is used to quickly dry the homogenized slurry into powder, ensuring pharmaceutical-grade sterility and particle uniformity.

[0126] Vacuum drying and screening stage

[0127] Equipment: Double cone rotary vacuum dryer and high-precision automatic screening equipment;

[0128] Process parameters:

[0129] Vacuum drying temperature: 65°C;

[0130] Vacuum degree: 0.095MPa;

[0131] Screening mesh: 150μm;

[0132] Operating Instructions: Subsequent drying under vacuum conditions further removes moisture, followed by screening to obtain fine and uniform particles.

[0133] Weighing and packaging stage:

[0134] Equipment: high-precision automatic weighing and packaging machine;

[0135] Operation Instructions: Automatic packaging is carried out in a clean room to ensure that the product has no cross contamination and clearly marked with batch information.

[0136] Test steps and data description:

[0137] Moisture content test:

[0138] Method: Karl Fischer method;

[0139] Steps: After sampling, pre-treat and perform titration determination.

[0140] The detection value is 0.25%, ensuring pharmaceutical grade requirements.

[0141] Particle size and distribution test:

[0142] Method: Laser particle size analyzer detection;

[0143] Procedure: The sample is measured in a dispersion medium and the D50 value is recorded.

[0144] D50 is about 30μm, the particles are uniform and suitable for tableting.

[0145] Heavy metal and microbial testing:

[0146] Methods: Heavy metals were tested by I CP-MS, and the total colony count was detected by standard microbial culture method.

[0147] From the above, it can be seen that all test indicators are below the medical standard limits.

[0148] The product has high purity and extremely low impurities, meeting strict pharmaceutical application standards.

[0149] Uniform particles improve fluidity and compressibility during tableting, ensuring tablet stability.

[0150] Strict quality control procedures ensure that each batch of products meets GMP requirements and provides reliable filling materials for pharmaceutical preparations.

[0151] Embodiment 4:

[0152] Preparation of industrial grade high fluidity anhydrous calcium hydrogen phosphate:

[0153] Preparation of industrial-grade anhydrous calcium hydrogen phosphate for animal feed and chemical raw materials, focusing on improving powder fluidity and anti-caking properties to facilitate large-scale mixing and transportation.

[0154] Process parameters and equipment description:

[0155] Slurry preparation stage:

[0156] Raw material ratio:

[0157] Calcium hydrogen phosphate dihydrate: 98.0%;

[0158] Purified water: 1.5%;

[0159] Anti-caking agent (trace silicon dioxide): 0.5%;

[0160] Equipment: 400L industrial-grade mixing tank (equipped with temperature control and pH monitoring system);

[0161] Process parameters:

[0162] Temperature: 50℃;

[0163] Stirring speed: 180 rpm;

[0164] pH adjustment: adjust to 7.0 (use purified water to mix directly when no additional pH adjuster is needed);

[0165] Instructions:

[0166] The raw materials are mixed at a higher temperature and anti-caking agents are added to ensure that the slurry is evenly dispersed, providing good conditions for subsequent drying.

[0167] Spray drying stage:

[0168] Equipment: Industrial-grade spray dryer;

[0169] Process parameters:

[0170] Inlet air temperature: 160℃;

[0171] Air outlet temperature: 65℃;

[0172] Atomizing disc speed: 10000rpm;

[0173] Atomization pressure: 1.3MPa;

[0174] Operation Instructions: Use high temperature to evaporate water quickly, and adjust atomization parameters to ensure larger product particle size and better fluidity.

[0175] Vacuum drying and screening stage:

[0176] Equipment: Double cone rotary vacuum dryer and efficient automatic screening system:

[0177] Process parameters:

[0178] Vacuum drying temperature: 75°C;

[0179] Vacuum degree: 0.085MPa;

[0180] Screening mesh: 100μm;

[0181] Instructions:

[0182] The product moisture is further reduced under vacuum conditions, and a fine mesh screen is used to ensure that the particle size and shape meet high flow requirements.

[0183] Weighing and packaging stage:

[0184] Equipment: Automatic weighing packaging machine and moisture-proof packaging system:

[0185] Instructions:

[0186] Automatic packaging ensures that each package of product meets industrial standards and is convenient for long-term storage and transportation.

[0187] Test steps and data description:

[0188] Moisture content test:

[0189] Method: Karl Fischer method

[0190] Steps: Take samples for pre-treatment and then titrate to ensure that the water content of the product is below the specified limit.

[0191] The test result was 0.4%, indicating sufficient drying.

[0192] Particle size and fluidity test:

[0193] Method: Laser particle size analyzer was used to measure particle D50, and the angle of repose method was used to measure powder fluidity.

[0194] step:

[0195] Particle size: The median diameter of the particles is measured after dispersing the sample.

[0196] Flowability: The angle of repose was determined using the tilted plate method.

[0197] D50 is about 55μm and the angle of repose is about 27°, both indicating that the product has good fluidity.

[0198] Anti-caking performance test:

[0199] Method: Caking test under simulated long-term storage conditions

[0200] Steps: Place the product in a constant temperature and humidity chamber for a certain period of time and then check its agglomeration condition.

[0201] The product has no obvious agglomeration and meets the requirements of industrial-grade applications.

[0202] Effect: High flowability and anti-caking properties make the product perform well in large-scale conveying, mixing and downstream processing.

[0203] The particles are uniform and stable, making them easy to mix with other raw materials and improving the overall process efficiency.

[0204] This process can achieve high yield, low energy consumption and stable quality in industrial-scale continuous production, and is suitable for the production of animal feed additives and powdered chemical products.

[0205] As can be seen from the above, this method can prepare anhydrous calcium hydrogen phosphate products with different application requirements by adjusting the process parameters of spray drying and vacuum drying, meeting the needs of food, medicine and industry. The key process parameters and quality tests of different embodiments all show that this method can effectively control the moisture content, purity, particle size and fluidity of the product, ensuring that the performance of the final product meets the requirements of specific industries.

[0206] Embodiment five:

[0207] Preparation of anhydrous calcium hydrogen phosphate for agricultural fertilizer:

[0208] Anhydrous calcium hydrogen phosphate suitable for use in agricultural fertilizers is prepared and used as a slow-release phosphorus source to improve soil nutrition and promote crop growth.

[0209] Process parameters and equipment description:

[0210] Slurry preparation stage:

[0211] Raw material ratio:

[0212] Calcium hydrogen phosphate dihydrate: 97.0%;

[0213] Purified water: 2.0%;

[0214] Citric acid monohydrate: 1.0% (as a crystallization inducer);

[0215] Equipment: 600L stainless steel mixing tank, equipped with temperature control and online pH detection system;

[0216] parameter:

[0217] Temperature: 45℃;

[0218] Stirring speed: 160 rpm;

[0219] Adjust pH to 6.5 (using dilute phosphoric acid);

[0220] Spray drying stage:

[0221] Equipment: Industrial-grade spray dryer (with HEPA filtration system);

[0222] parameter:

[0223] Inlet air temperature: 135℃;

[0224] Air outlet temperature: 70℃;

[0225] Atomizer disk speed: 11,000rpm;

[0226] Atomization pressure: 0.9MPa;

[0227] Vacuum drying and screening stage:

[0228] Equipment: double cone rotary vacuum dryer, automatic screening system;

[0229] parameter:

[0230] Vacuum drying temperature: 68°C;

[0231] Vacuum degree: 0.09MPa;

[0232] Drying time: about 3 hours;

[0233] Screening mesh: 250 μm (to produce coarser particles, which is convenient for field application); the test steps are as follows:

[0234] Moisture content test:

[0235] Methods: Karl Fischer method was used;

[0236] Steps: Sampling and pretreatment are performed and titrated to ensure that the moisture content is lower than the specified value. The measured moisture content is about 0.35%, which meets the requirements for fertilizer products.

[0237] Particle size distribution test:

[0238] Method: Laser particle size analyzer;

[0239] Steps: Measure the sample after dispersion and record D50 and D90 data.

[0240] D50 is about 80μm and D90 is about 200μm, which is conducive to sustained release.

[0241] Nutrient release test:

[0242] Method: Soak the sample in water and regularly detect the dissolved phosphorus content;

[0243] Procedure: Samples were taken within 24 hours and the phosphorus release rate was determined by colorimetry.

[0244] About 40% of the total phosphorus was released within 24 hours, showing a slow release curve.

[0245] Bulk density determination:

[0246] Methods: The bulk density of particles was determined according to standard methods;

[0247] The measured volume density is about 0.85g / cm 3 , suitable for mechanical fertilization.

[0248] The effect:

[0249] The resulting fertilizer-grade product has coarse particles, making it easier to apply mechanically in the field;

[0250] The slow-release phosphorus source can continuously provide the nutrients needed by crops;

[0251] The product has low moisture content and is stable in storage and transportation, meeting the needs of large-scale agricultural applications.

[0252] Embodiment six:

[0253] Preparation of anhydrous calcium hydrogen phosphate for environmental engineering:

[0254] Anhydrous calcium hydrogen phosphate is prepared for wastewater treatment, and its excellent pH buffering and adsorption properties can be used to regulate and remove heavy metals or phosphates in wastewater.

[0255] Process parameters and equipment description:

[0256] Slurry preparation stage:

[0257] Raw material ratio:

[0258] Calcium hydrogen phosphate dihydrate: 98.0%;

[0259] Purified water: 1.5%;

[0260] Citric acid monohydrate: 0.5%;

[0261] Equipment: 400L high-clean mixing tank with temperature control and pH monitoring;

[0262] parameter:

[0263] Temperature: 40℃;

[0264] Stirring speed: 140 rpm;

[0265] Adjust pH to 7.0 (no additional pH adjuster is needed, and can be fine-tuned naturally in purified water);

[0266] Spray drying stage:

[0267] Equipment: Spray dryer for environmental engineering;

[0268] parameter:

[0269] Inlet air temperature: 145℃;

[0270] Air outlet temperature: 72℃;

[0271] Atomizer disk speed: 13000rpm;

[0272] Atomization pressure: 1.1MPa;

[0273] Vacuum drying and screening stage:

[0274] Equipment: double cone rotary vacuum dryer, precision screening device;

[0275] parameter:

[0276] Vacuum drying temperature: 72°C;

[0277] Vacuum degree: 0.08MPa;

[0278] Drying time: about 2.5 hours;

[0279] Screening mesh: 150μm (to obtain fine powder and increase specific surface area);

[0280] Test steps:

[0281] Moisture content test:

[0282] Method: Karl Fischer method;

[0283] The measured moisture is about 0.3%, ensuring good reactivity of the material.

[0284] Particle size distribution test:

[0285] Method: Laser particle size analyzer;

[0286] D50 is about 40μm, ensuring a high specific surface area of the product, which is beneficial to adsorption and reaction.

[0287] pH buffer performance test:

[0288] Method: After preparing the standard suspension, add acidic solution drop by drop to measure the buffer range; the pH changes slowly between 6.8 and 7.2, indicating good buffer performance. Adsorption / removal efficiency test:

[0289] Method: Add the product to the simulated wastewater and detect the change in the concentration of the target ions in the wastewater; the concentration of the target ions in the treated wastewater is reduced by 80%, showing excellent removal effect.

[0290] Effects brought:

[0291] The fine powder form provides a higher surface area and reactivity, enhancing the adsorption or regulation function in wastewater treatment;

[0292] Excellent pH buffering ability helps to stabilize the treatment process;

[0293] The material is stable and low in moisture, suitable for long-term operation and regeneration use, meeting the requirements of the environmental engineering field.

[0294] Example VII:

[0295] Preparation of anhydrous calcium hydrogen phosphate for high-temperature ceramic additives:

[0296] Prepare anhydrous calcium hydrogen phosphate additives for high-temperature ceramics and refractories, and improve the ceramic sintering behavior and mechanical properties by optimizing the microstructure and particle distribution.

[0297] Process parameters and equipment description:

[0298] Slurry preparation stage:

[0299] Raw material ratio:

[0300] Calcium hydrogen phosphate dihydrate: 99.0%;

[0301] Purified water: 0.8%;

[0302] Citric acid monohydrate: 0.2% (helps control crystal growth);

[0303] Equipment: 250L precision mixer, equipped with temperature control and pH monitoring system;

[0304] parameter:

[0305] Temperature: 50℃;

[0306] Stirring speed: 180 rpm;

[0307] Adjust pH to 7.5;

[0308] Spray drying stage:

[0309] Equipment: Spray dryer for high temperature ceramics;

[0310] parameter:

[0311] Inlet air temperature: 155℃;

[0312] Air outlet temperature: 80℃;

[0313] Atomizer disk speed: 14,000rpm;

[0314] Atomization pressure: 1.3MPa;

[0315] Vacuum drying and screening stage;

[0316] Equipment: double cone rotary vacuum dryer, ultrafine screening system;

[0317] parameter:

[0318] Vacuum drying temperature: 75°C;

[0319] Vacuum degree: 0.10MPa;

[0320] Drying time: about 3.5 hours;

[0321] Screening mesh: 100 μm (to obtain fine and uniform powder);

[0322] Test steps and data description:

[0323] Moisture content test:

[0324] Method: Karl Fischer method:

[0325] The moisture content was measured to be about 0.2%, ensuring no interference in the subsequent ceramic sintering process.

[0326] Particle size distribution test:

[0327] Method: Laser particle size analyzer;

[0328] D50 is about 35μm, with narrow distribution, ensuring the uniformity of additives.

[0329] Thermal behavior analysis:

[0330] Methods: Thermal events were detected using differential scanning calorimetry (DSC);

[0331] Steps: thermally scan the sample and record the crystal phase transition temperature;

[0332] Shows specific end heat / exothermic peaks, meeting the sintering requirements of ceramic additives.

[0333] Ceramic composite material performance test:

[0334] Method: Add the additives into the ceramic matrix in a certain proportion, prepare the specimens and then conduct mechanical property tests (such as bending strength and hardness);

[0335] The specimens showed significantly improved mechanical properties compared to the control group, proving that the additives improved the density and strength of the ceramic matrix.

[0336] The effect:

[0337] The additive particles are uniform and low in moisture, which helps the uniformity of the ceramic sintering process;

[0338] Microstructure and thermal behavior control improves the mechanical properties of ceramic composites;

[0339] The product is stable and easy to mix with ceramic raw materials, providing a reliable additive modifier for high-temperature refractory materials.

[0340] From the above, we can see that for the fields of agriculture, environmental engineering and ceramic additives, by adjusting the raw material ratio, process parameters and drying and screening conditions, we have obtained anhydrous calcium hydrogen phosphate products with their own characteristics. The performance of the products has been verified through moisture, particle size, functional tests, etc., and the application effects in their respective fields have been demonstrated.

[0341] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A spray-drying method for preparing anhydrous calcium hydrogen phosphate, characterized in that: The following steps are involved: S1. Slurry preparation: mixing calcium hydrogen phosphate dihydrate with purified water, adding a pH regulator and citric acid monohydrate, and stirring to form a suspension; S2, spray drying: the suspension is sent to a spray dryer, the slurry is atomized into tiny droplets through a high-speed centrifugal disk or a pressure nozzle, the inlet air temperature is controlled at 130-160°C, the outlet air temperature is controlled at 60-90°C, and spray drying is performed to obtain a preliminary dry powder; S3, vacuum drying: sending the preliminarily dried powder into a double-cone rotary vacuum dryer to further remove moisture at 60-80° C. to obtain anhydrous calcium hydrogen phosphate with a moisture content of ≤0.5%; S4, screening: using an automatic screening system to screen the anhydrous calcium hydrogen phosphate to obtain a product that meets the target particle size distribution; S5. Weighing and packaging: Weigh the product that meets the target particle size distribution, and use moisture-proof sealed packaging to obtain the final product.

2. The spray-drying method for preparing anhydrous calcium hydrogen phosphate according to claim 1, characterized in that: The purity of the calcium hydrogen phosphate dihydrate is ≥99%, and the particle fineness D50 is ≤10 μm.

3. The spray-drying method for preparing anhydrous calcium hydrogen phosphate according to claim 1, characterized in that: The stirring rate in the slurry preparation is controlled at 100-200 rpm, and the pH value is controlled at 6.5-7.

5.

4. The spray-drying method for preparing anhydrous calcium hydrogen phosphate according to claim 1, characterized in that: The spray drying process adopts a high-speed centrifugal atomization method, the rotation speed of the atomizing disk is controlled at 10000-20000 rpm, and the atomization pressure is 0.5-1.5 MPa.

5. The spray-drying method for preparing anhydrous calcium hydrogen phosphate according to claim 1, characterized in that: During the vacuum drying process, the parameters of the double-cone rotary vacuum dryer are: the drying vacuum degree is controlled at 0.08-0.1 MPa, and the drying time is 2-4 hours.

6. The spray-drying preparation method of anhydrous calcium hydrogen phosphate according to claim 1, characterized in that: The aperture of the screen used for screening in the automatic screening system is 100-250 μm.

7. The spray-drying method for preparing anhydrous calcium hydrogen phosphate according to claim 1, characterized in that: Perform quality control on the final product, including: Moisture content testing, particle size analysis, purity testing and packaging leak testing.

8. The spray-drying method for preparing anhydrous calcium hydrogen phosphate according to claim 7, characterized in that: The moisture content is detected by Karl Fischer method; The particle size analysis adopts a laser particle size analyzer; The purity detection adopts X-ray fluorescence spectroscopy analysis; The packaging sealing test adopts a vacuum test method.

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