A process for the production of anhydrous barium chloride

Abstract

The application belongs to the technical field of barium compound preparation, and discloses a production method of anhydrous barium chloride, which comprises the following steps: dissolving crude barium chloride dihydrate in a mixed solvent of a lower aliphatic alcohol and water to perform recrystallization, so as to obtain precursor crystals with high porosity and regular morphology; and then performing gradient temperature dehydration through a fluidized bed under vacuum or inert gas protection. The recrystallization, solid-liquid separation, pre-drying and fluidized bed dehydration units can be integrated in a closed pipeline system, so that automatic conveying of materials and online monitoring of process parameters are realized, intermediate products are prevented from being exposed to environmental humidity, and the cleanliness and consistency of the whole process are ensured. The fluidized bed dryer can be designed as a multi-chamber series structure corresponding to different temperature zones for dehydration, so that real continuous feeding and discharging are realized, and the industrial scale demand is met.

Description

Technical Field

[0001] This invention belongs to the field of barium compound preparation technology, and relates to a method for producing anhydrous barium chloride. Background Technology

[0002] Anhydrous barium chloride, as an important inorganic chemical raw material, is widely used in electronic ceramics, optical glass, pigment manufacturing, and metal heat treatment. Its purity, particle morphology, and chemical activity directly determine the performance stability and process adaptability of the end product. In industrial production, anhydrous barium chloride is usually produced by thermal dehydration of barium chloride dihydrate. This route has long been dominant due to the availability of raw materials and mature technology. Traditional dehydration processes often employ rotary kilns, box ovens, or static heating furnaces to perform stepwise heating treatment of barium chloride dihydrate under normal or slightly negative pressure conditions to gradually remove the water of crystallization. This method effectively solved the basic requirement of converting hydrates to anhydrous substances in the early stages of industrialization, and it has shown certain economic efficiency and operability, especially in extensive application scenarios where the requirements for the physical form of the product are not high.

[0003] However, during the heating process, the water of crystallization in barium chloride dihydrate crystals is not released uniformly and synchronously, but rather undergoes violent desorption within a specific temperature range. If the heating rate is not properly controlled or heat transfer is uneven, a significant temperature gradient can easily form inside the material, leading to instantaneous overheating in localized areas. Under these conditions, the crystal surface rapidly loses water to form a dense, anhydrous layer, while moisture remains inside. The resulting vapor pressure difference not only promotes molten sintering between particles but also induces lattice reconstruction, forming hard agglomerates.

[0004] Such sintered products have reduced specific surface area and fewer surface active sites, and their internal microporous structure collapses, making them highly susceptible to irreversible caking due to trace moisture adsorption during subsequent storage or use. This severely affects the product's flowability, dispersibility, and reactivity. Fundamentally, this problem stems from the combined effects of multiple factors, including the single heat conduction path between particles under static heating mode, high gas-phase mass transfer resistance, and the difficulty in maintaining dynamic equilibrium at the solid-gas interface during dehydration. Summary of the Invention

[0005] To achieve the above-mentioned objectives, this invention provides a method for producing anhydrous barium chloride. The method involves pre-treating crude barium chloride dihydrate under a specific solvent system with recrystallization in advance, and combining this with a fluidized bed dehydration process under vacuum or inert gas protection. This allows for the synergistic control of the microstructure, particle morphology, and chemical activity of the final anhydrous barium chloride product, thereby obtaining anhydrous barium chloride powder with high purity, high specific surface area, excellent flowability, and anti-caking properties.

[0006] The method of the present invention includes the following steps: First, industrial-grade crude barium chloride dihydrate is dissolved in a mixed solvent composed of lower fatty alcohol and deionized water in a volume ratio of 3:1 to 7:1 to form a saturated or near-saturated solution; second, the solution is subjected to temperature-controlled cooling crystallization to obtain barium chloride dihydrate crystals with modified crystal form; third, the obtained crystals are subjected to solid-liquid separation, washing, and low-temperature pre-drying, and then sent to a fluidized bed dryer; finally, the crystals are subjected to gradient temperature dehydration treatment in a fluidized state under a vacuum of 5 to 50 kPa or an inert gas atmosphere to obtain anhydrous barium chloride product.

[0007] In the recrystallization step, the lower fatty alcohol is any one of methanol, ethanol, or isopropanol, with a purity of not less than 99.5%. In the mixed solvent, the volume ratio of the lower fatty alcohol to deionized water is preferably 5:1. The dissolution operation is carried out at 40 to 60°C with a stirring rate of 150 to 300 rpm for 30 to 60 minutes to ensure complete dissolution of barium chloride dihydrate and the formation of a homogeneous and transparent solution. Subsequently, the solution is cooled to 5 to 15°C at a rate of 0.5 to 2°C / min and is kept at this temperature for crystal growth for 30 to 90 minutes. Under these conditions, the precipitated barium chloride dihydrate crystals exhibit a loose and porous plate-like or layered morphology with an average particle size of 50 to 150 micrometers. The internal porosity of the crystals is increased by 15% to 30% compared to the untreated crude product, and the lattice integrity is optimized. The arrangement of crystal water molecules in the lattice tends to be homogeneous, providing a structural basis for stress release during the subsequent dehydration process.

[0008] The crystals obtained by recrystallization are subjected to solid-liquid separation by filtration or centrifugation. The separated wet crystals are washed 1 to 2 times with an alcohol-water mixed solvent of the same composition as that used for recrystallization. The amount of washing solution used each time is 0.5 to 1 times the mass of the wet crystals. The washing temperature is maintained at 10 to 20°C to remove impurity ions and residual mother liquor adsorbed on the surface to the maximum extent.

[0009] After washing, the crystals are pre-dried in a vacuum drying oven at 40 to 50°C for 2 to 4 hours to reduce the surface free moisture content to below 1%, while preventing structural collapse or agglomeration of the crystals during the pre-drying stage.

[0010] The pre-dried barium chloride dihydrate crystals are fed into a fluidized bed dryer. The fluidized bed dryer has a cylindrical structure with an inner diameter of 200 to 500 mm and a height of 800 to 1500 mm. It has an air distribution plate at the bottom with an opening ratio of 5% to 10% and an aperture of 1 to 3 mm.

[0011] The fluidizing gas is high-purity nitrogen or argon, which is preheated and introduced from below the air distribution plate. The gas flow rate is controlled within a range that ensures the bed is fully fluidized without particle entrainment, specifically 0.3 to 0.8 m / s. In inert gas protection mode, the system maintains a slight positive pressure of 101.3 to 105 kPa; in vacuum mode, the system maintains an internal pressure of 5 to 50 kPa, preferably 20 kPa, through a vacuum pump.

[0012] The dehydration process employs a three-stage gradient temperature increase program:

[0013] In the first stage, the bed temperature is increased from room temperature to 100°C at a rate of 2 to 5°C / min, and held at this temperature for 30 minutes to remove physically adsorbed water from the crystal surface and macropores.

[0014] In the second stage, the temperature is increased to 180°C at a rate of 1 to 3°C / min and held at this temperature for 60 to 120 minutes. This stage is the main area for removing water of crystallization. The fluidized state ensures that there is no contact sintering between particles, the gas phase mass transfer resistance is reduced, and the water vapor partial pressure is rapidly diluted or removed, thereby suppressing lattice distortion caused by vapor pressure difference.

[0015] In the third stage, the temperature is increased to 220°C at a rate of 1°C / minute and held at that temperature for 30 minutes to completely remove the residual bound water and complete the lattice reconstruction, forming a thermodynamically stable anhydrous barium chloride phase.

[0016] Throughout the dehydration process, the particles in the fluidized bed are in a suspended and tumbling state, with a collision frequency of 5 to 15 times per second. However, the collision kinetic energy is controlled to a level insufficient to cause crystal breakage, thus maintaining particle integrity while ensuring uniform heat transfer. After dehydration, the product is cooled to below 50°C under an inert atmosphere or vacuum before being discharged, preventing the high-temperature product from contacting moisture in the air.

[0017] In a preferred embodiment of the present invention, the recrystallization step uses a mixture of ethanol and deionized water at a volume ratio of 5:1, a dissolution temperature of 50°C, a cooling rate of 1°C / min, a crystal growth temperature of 10°C, and a crystal growth time of 60 minutes. The resulting crystals are then centrifuged, washed once with an ethanol-water mixture of the same composition, and pre-dried at 45°C for 3 hours.

[0018] Dehydration is performed using a vacuum fluidized bed with a vacuum of 20 kPa. The fluidizing gas is dry air that has been deeply dehydrated by molecular sieves (used only for fluidization and not participating in the reaction), but the entire system is under negative pressure and the gas flow rate is 0.5 m / s.

[0019] The heating program is as follows: 100℃ / 30 minutes → 180℃ / 90 minutes → 220℃ / 30 minutes, with heating rates of 3℃ / minute, 2℃ / minute and 1℃ / minute, respectively.

[0020] In another preferred embodiment of the present invention, the recrystallization is performed using a mixture of isopropanol and deionized water at a volume ratio of 6:1, with a dissolution temperature of 55°C, a cooling rate of 1.5°C / min, a crystallization temperature of 12°C, and a crystallization time of 75 minutes. Solid-liquid separation is achieved by vacuum filtration, followed by two washings and pre-drying at 50°C for 2.5 hours. Dehydration is carried out under high-purity nitrogen protection at a nitrogen flow rate of 0.6 m / s and a system pressure of 102 kPa. The heating program is as follows: 100°C / 40 min → 180°C / 100 min → 220°C / 30 min, with heating rates of 4°C / min, 2.5°C / min, and 1°C / min, respectively.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. The technical solution of this invention fundamentally solves the problems of sintering, agglomeration, and caking caused by uneven heat transfer, impeded gas-phase mass transfer, and accumulated vapor pressure difference in traditional static dehydration processes through the synergistic effect of recrystallization pretreatment and fluidized bed dehydration. The recrystallization step regulates crystal growth kinetics using an alcohol-water mixed solvent to generate a barium chloride dihydrate precursor with high porosity and optimized lattice structure, providing a structural buffer for the dehydration process. Fluidized bed dehydration achieves uniform temperature across the entire bed through the dynamic suspension of particles and accelerates water vapor removal with the aid of a vacuum or inert atmosphere, maintaining a low water vapor partial pressure at the solid-gas interface, thereby suppressing local overheating and lattice distortion. The combination of these two methods not only improves dehydration efficiency but also enables precise control of the morphology and surface properties of anhydrous barium chloride crystals at the microscopic scale.

[0023] 2. The method described in this invention has the potential for continuous production. The recrystallization, solid-liquid separation, pre-drying, and fluidized bed dehydration units can be integrated into a closed piping system, enabling automatic material transport and online monitoring of process parameters. This avoids exposure of intermediate products to environmental moisture, ensuring cleanliness and consistency throughout the entire process. The fluidized bed dryer can be designed as a multi-chamber series structure, each corresponding to a different temperature zone for dehydration, achieving truly continuous feeding and discharging to meet the needs of industrial-scale production.

[0024] 3. When the anhydrous barium chloride obtained by the method described in this invention is used in the field of electronic ceramics, its high specific surface area and uniform particle size distribution help stabilize the dispersion of high solid content in the slurry, reducing the amount of sintering aids required. In optical glass manufacturing, its low impurity content and high chemical activity can lower the melting temperature, shorten the clarifying time, and reduce bubbles and streak defects. In metal heat treatment salt baths, its excellent fluidity and moisture resistance ensure the long-term stability of the bath composition and extend its service life. Therefore, this invention not only solves the core defects of the prior art but also expands the application boundaries of anhydrous barium chloride in the field of high-end materials. Detailed Implementation

[0025] This invention provides a method for producing anhydrous barium chloride. By performing recrystallization pretreatment on crude barium chloride dihydrate in a specific solvent system before dehydration, and combining this with a fluidized bed dehydration process under vacuum or inert gas protection, the microstructure, particle morphology, and chemical activity of the final anhydrous barium chloride product are synergistically controlled, resulting in anhydrous barium chloride powder with high purity, high specific surface area, excellent flowability, and anti-caking properties. This method is systematically optimized from two dimensions: crystal growth kinetics and dehydration thermodynamics, effectively avoiding sintering, agglomeration, and caking problems caused by local overheating, accumulated vapor pressure difference, and limited mass transfer during traditional static heating dehydration processes.

[0026] The technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples, so as to ensure that those skilled in the art can fully understand and implement the present invention.

[0027] Example 1: Recrystallization: Industrial grade crude barium chloride dihydrate was dissolved in a mixed solvent of ethanol and deionized water in a volume ratio of 5:1 at a dissolution temperature of 50°C and a stirring rate of 200 rpm for 45 minutes to form a saturated solution; the solution was then cooled to 10°C at a rate of 1°C / min and kept at a constant temperature for 60 minutes to grow crystals.

[0028] Solid-liquid separation and pre-drying: Separate wet crystals by centrifugation, wash once with a mixed alcohol-water solvent of the same composition (the washing liquid volume is 0.8 times the mass of the wet crystals, and the temperature is 15℃); pre-dry in a vacuum drying oven at 45℃ for 3 hours until the surface free moisture content is reduced to below 1%.

[0029] Fluidized bed dehydration: A vacuum fluidized bed with a vacuum degree of 20 kPa is used. The fluidizing gas is deep dehydrated and dried air with a flow rate of 0.5 m / s. The gradient temperature program is as follows: 3℃ / min to 100℃ and hold for 30 minutes, 2℃ / min to 180℃ and hold for 90 minutes, and 1℃ / min to 220℃ and hold for 30 minutes.

[0030] Example 2: Recrystallization: Industrial grade crude barium chloride dihydrate was dissolved in a mixed solvent of isopropanol and deionized water in a volume ratio of 6:1 at a dissolution temperature of 55°C and a stirring rate of 250 rpm for 50 minutes to form a saturated solution; the solution was then cooled to 12°C at a rate of 1.5°C / min and kept at a constant temperature for 75 minutes to grow crystals.

[0031] Solid-liquid separation and pre-drying: Wet crystals were separated by vacuum filtration and washed twice with a mixed alcohol-water solvent of the same composition (each washing solution was 0.6 times the mass of the wet crystals, at a temperature of 18°C); pre-drying was carried out in a vacuum drying oven at 50°C for 2.5 hours until the surface free moisture content was reduced to below 1%.

[0032] Fluidized bed dehydration: The fluidized bed is protected by nitrogen, the system pressure is 102 kPa, and the nitrogen flow rate is 0.6 m / s; the gradient temperature program is as follows: 4℃ / min to 100℃ and hold for 40 minutes, 2.5℃ / min to 180℃ and hold for 100 minutes, and 1℃ / min to 220℃ and hold for 30 minutes.

[0033] Example 3: Recrystallization: Industrial grade crude barium chloride dihydrate was dissolved in a mixed solvent of methanol and deionized water in a volume ratio of 4:1 at a dissolution temperature of 45°C and a stirring rate of 180 rpm for 55 minutes to form a saturated solution; the solution was then cooled to 8°C at a rate of 0.8°C / min and kept at a constant temperature for 45 minutes to grow crystals.

[0034] Solid-liquid separation and pre-drying: Wet crystals were separated by vacuum filtration and washed once with a mixed solvent of alcohol and water of the same composition (the washing liquid volume was 0.5 times the mass of the wet crystals, and the temperature was 12℃); pre-drying was carried out in a vacuum drying oven at 42℃ for 3.5 hours until the surface free moisture content was reduced to below 1%.

[0035] Fluidized bed dehydration: Argon gas is used to protect the fluidized bed. The system pressure is 103 kPa and the argon flow rate is 0.4 m / s. The gradient heating program is to raise the temperature to 100℃ at 2℃ / min and hold it for 30 minutes, raise the temperature to 180℃ at 1℃ / min and hold it for 120 minutes, and raise the temperature to 220℃ at 1℃ / min and hold it for 30 minutes.

[0036] Example 4: Recrystallization: Industrial grade crude barium chloride dihydrate was dissolved in a mixed solvent of ethanol and deionized water in a volume ratio of 7:1 at a dissolution temperature of 60°C and a stirring rate of 300 rpm for 30 minutes to form a saturated solution; the solution was then cooled to 15°C at a rate of 2°C / min and kept at a constant temperature for 30 minutes to grow crystals.

[0037] Solid-liquid separation and pre-drying: The wet crystals were separated by centrifugation and washed twice with a mixed alcohol-water solvent of the same composition (each washing solution was 1 times the mass of the wet crystals, at a temperature of 20°C); the crystals were pre-dried in a vacuum drying oven at 48°C for 2 hours until the surface free moisture content was reduced to below 1%.

[0038] Fluidized bed dehydration: A vacuum fluidized bed with a vacuum degree of 50 kPa is used. The fluidizing gas is deep dehydrated and dried air with a flow rate of 0.7 m / s. The gradient temperature program is as follows: 5℃ / min to 100℃ and hold for 30 minutes, 3℃ / min to 180℃ and hold for 60 minutes, and 1℃ / min to 220℃ and hold for 30 minutes.

[0039] Example 5: Recrystallization: Industrial grade crude barium chloride dihydrate was dissolved in a mixed solvent of isopropanol and deionized water in a volume ratio of 3:1 at a dissolution temperature of 40°C and a stirring rate of 150 rpm for 60 minutes to form a saturated solution; the solution was then cooled to 5°C at a rate of 0.5°C / min and kept at a constant temperature for 90 minutes to grow crystals.

[0040] Solid-liquid separation and pre-drying: Wet crystals were separated by vacuum filtration and washed once with a mixed solvent of alcohol and water of the same composition (the washing liquid volume was 0.7 times the mass of the wet crystals, and the temperature was 10℃); they were pre-dried in a vacuum drying oven at 40℃ for 4 hours until the surface free moisture content was reduced to below 1%.

[0041] Fluidized bed dehydration: The fluidized bed is protected by nitrogen, the system pressure is 105 kPa, and the nitrogen flow rate is 0.3 m / s; the gradient temperature program is 3℃ / min to 100℃ and hold for 30 minutes, 2℃ / min to 180℃ and hold for 80 minutes, and 1℃ / min to 220℃ and hold for 30 minutes.

[0042] Example 6: Recrystallization: Industrial grade crude barium chloride dihydrate was dissolved in a mixed solvent of methanol and deionized water in a volume ratio of 5:1 at a dissolution temperature of 52°C and a stirring rate of 220 rpm for 40 minutes to form a saturated solution; the solution was then cooled to 11°C at a rate of 1.2°C / min and kept at this temperature for 50 minutes to grow crystals.

[0043] Solid-liquid separation and pre-drying: The wet crystals were separated by centrifugation and washed twice with a mixed alcohol-water solvent of the same composition (each washing solution was 0.9 times the mass of the wet crystals, at a temperature of 16℃); they were pre-dried in a vacuum drying oven at 46℃ for 2.8 hours until the surface free moisture content was reduced to below 1%.

[0044] Fluidized bed dehydration: A vacuum fluidized bed with a vacuum degree of 10 kPa is used. The fluidizing gas is deep dehydrated and dried air with a flow rate of 0.6 m / s. The gradient temperature program is as follows: 4℃ / min to 100℃ and hold for 30 minutes, 1.5℃ / min to 180℃ and hold for 90 minutes, and 1℃ / min to 220℃ and hold for 30 minutes.

[0045] Example 7: Recrystallization: Industrial grade crude barium chloride dihydrate was dissolved in a mixed solvent of ethanol and deionized water in a volume ratio of 6:1 at a dissolution temperature of 58°C and a stirring rate of 280 rpm for 35 minutes to form a saturated solution; the solution was then cooled to 14°C at a rate of 1.8°C / min and kept at this temperature for 40 minutes to grow crystals.

[0046] Solid-liquid separation and pre-drying: Wet crystals were separated by vacuum filtration and washed once with a mixed solvent of alcohol and water of the same composition (the washing liquid volume was 0.8 times the mass of the wet crystals, and the temperature was 19℃); they were pre-dried in a vacuum drying oven at 47℃ for 3 hours until the surface free moisture content was reduced to below 1%.

[0047] Fluidized bed dehydration: Argon gas is used to protect the fluidized bed. The system pressure is 101.3 kPa and the argon flow rate is 0.8 m / s. The gradient heating program is as follows: 5℃ / min to 100℃ and hold for 30 minutes, 2.5℃ / min to 180℃ and hold for 70 minutes, and 1℃ / min to 220℃ and hold for 30 minutes.

[0048] Comparative Example 1: Industrial-grade crude barium chloride dihydrate was taken directly without recrystallization.

[0049] Placed in a box-type drying oven under normal pressure air atmosphere, without pre-drying step.

[0050] Heating program: Increase to 100℃ at a rate of 2℃ / min and hold for 60 minutes, increase to 180℃ at a rate of 3℃ / min and hold for 120 minutes, increase to 220℃ at a rate of 2℃ / min and hold for 60 minutes, then discharge after natural cooling.

[0051] Comparative Example 2: The recrystallization procedure was exactly the same as that in Example 1 (ethanol to deionized water volume ratio 5:1, dissolution temperature 50°C, cooling rate 1°C / min, crystal growth at 10°C for 60 minutes, centrifugation and washing followed by pre-drying at 45°C for 3 hours).

[0052] Dehydration was performed using static vacuum drying: the pre-dried crystals were placed in a vacuum drying oven with a vacuum degree of 20 kPa. The heating program was the same as in Example 1 (heating to 100°C at 3°C / min and holding for 30 minutes, heating to 180°C at 2°C / min and holding for 90 minutes, and heating to 220°C at 1°C / min and holding for 30 minutes). The crystals were kept statically throughout the process without fluidization.

[0053] Comparative Example 3: Industrial grade crude barium chloride dihydrate was directly taken and pre-dried in a vacuum drying oven at 45°C for 3 hours without recrystallization (the surface free moisture content was reduced to below 1%).

[0054] The fluidized bed dehydration procedure was exactly the same as in Example 1 (vacuum degree 20 kPa, fluidizing gas was deep dehydrated and dried air, flow rate 0.5 m / s, gradient temperature program was the same as in Example 1).

[0055] Example and comparative test methods:

[0056] Purity test: The chlorine content is determined by silver nitrate titration and the barium content is determined by EDTA complexometric titration. The difference between the sum of the two contents and the impurity content is the purity.

[0057] Barium content test: Weigh the sample and dissolve it in deionized water, add ammonia buffer solution to adjust the pH to 10, use Chrome Black T as an indicator, titrate with EDTA standard solution to the endpoint, and calculate the barium content.

[0058] Chlorine content test: Weigh the sample and dissolve it in deionized water, add potassium chromate indicator, and titrate with silver nitrate standard solution until a brick-red precipitate is formed. Calculate the chlorine content.

[0059] Moisture content test: A Karl Fischer moisture analyzer was used. The sample was weighed and added to the titration cell. The solution was titrated to the endpoint with Karl Fischer reagent and the moisture content was recorded.

[0060] Sulfate test: After the sample is dissolved, it is acidified with hydrochloric acid, and barium chloride solution is added to generate barium sulfate precipitate. The absorbance is measured by spectrophotometry, and the sulfate content is calculated by comparing with the standard curve.

[0061] Iron content test: The o-phenanthroline spectrophotometric method was used. After the sample was dissolved, hydroxylamine hydrochloride was added to reduce iron ions, o-phenanthroline was added for color development, and the absorbance was measured and compared with the standard curve to calculate the iron content.

[0062] Specific surface area test: The low-temperature nitrogen adsorption BET method was used. After the sample was degassed at 105℃, the nitrogen adsorption isotherm was measured and the specific surface area was calculated.

[0063] Average particle size and particle size distribution span test: The particle size distribution is measured by a laser particle size analyzer, and the average particle size and D10, D50 and D90 are read. The particle size distribution span is calculated by (D90-D10) / D50.

[0064] Flowability index test: Fixed funnel method, the sample falls into a horizontal tray through a funnel of fixed height, and the angle of repose of the stacked cone is measured. The smaller the angle of repose, the better the flowability.

[0065] Anti-caking test: The sample was sealed and stored in a constant temperature and humidity chamber at 25 degrees Celsius and 60% relative humidity for 30 days. After taking it out, the caking condition was observed and the looseness was judged by gently rubbing it with fingers.

[0066] Test data comparison table 1:

[0067]

[0068] Test data comparison table 2:

[0069]

[0070] Comparison of Examples and Comparative Example 1: The traditional static process has obvious defects: Comparative Example 1 uses static heating without recrystallization, resulting in a purity of only 98.5%, far lower than the 99.95% or more of the Examples; the impurities (sulfate 500 ppm, iron 80 ppm) are much higher than those of the Examples; the specific surface area is only 0.8 m² / g, less than 1 / 3 of that of the Examples; the angle of repose is 55 degrees, resulting in poor fluidity and severe caking after storage. This indicates that the traditional process, due to the lack of crystal form modification and dynamic heat transfer, cannot solve the problems of local overheating and impaired mass transfer, leading to the deterioration of product performance.

[0071] Comparison of Example 1 and Comparative Example 2: Fluidized bed dehydration is indispensable. Although Comparative Example 2 underwent recrystallization purification (purity 99.90%), static dehydration reduced the specific surface area to 1.5 m² / g, increased the average particle size to 180 μm due to agglomeration, and resulted in an angle of repose of 45 degrees and slight caking. This indicates that recrystallization alone cannot prevent particle contact sintering during dehydration, while the dynamic suspension state of the fluidized bed can achieve uniform temperature throughout the bed (temperature difference less than ±3℃), reduce particle agglomeration, and ensure high specific surface area and fluidity.

[0072] Comparison of Example 1 and Comparative Example 3: Recrystallization pretreatment is the basis for purity and crystal form. Although Comparative Example 3 used fluidized bed dehydration, the lack of recrystallization resulted in a purity of only 99.0%, with significantly higher levels of impurities (sulfate 300 ppm, iron 50 ppm) compared to Example 2. Furthermore, direct dehydration of the crude product easily led to agglomeration due to irregular crystal form (particle size distribution span 2.0). This indicates that recrystallization, using an alcohol-water mixed solvent to regulate the crystal form and generate a high-porosity precursor, can both purify and remove impurities, and provide a structural buffer for subsequent dehydration, avoiding lattice distortion.

[0073] Consistency among embodiments: The process has good stability. Although the types of alcohols, alcohol-to-water ratios, and dehydration atmospheres were adjusted in the seven embodiments, they all met the requirements of purity ≥99.95%, specific surface area 2.5-4.0 m² / g, angle of repose <35 degrees, and no caking. This shows that the process of the present invention has strong adaptability to parameter fluctuations and can stably produce products that meet the needs of high-end fields.

[0074] In conclusion, this invention solves the core problems of sintering, agglomeration, and caking in traditional processes through a synergistic process of recrystallization pretreatment and fluidized bed gradient dehydration, addressing both crystal form modification (recrystallization) and heat and mass transfer optimization (fluidized bed). The resulting anhydrous barium chloride exhibits high purity, low impurities, large specific surface area, and excellent flowability and anti-caking properties, making it suitable for stable application in demanding fields such as electronic ceramics and optical glass.

[0075] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing anhydrous barium chloride, characterized in that, Includes the following steps: S1. Dissolve industrial-grade crude barium chloride dihydrate in a mixed solvent composed of lower fatty alcohol and deionized water in a volume ratio of 3:1 to 7:1 to form a saturated or near-saturated solution; wherein the lower fatty alcohol is any one of methanol, ethanol or isopropanol. S2. Cool the solution to 5 to 15°C at a rate of 0.5 to 2°C / min, and maintain the temperature at this temperature for 30 to 90 minutes to crystallize and obtain barium chloride dihydrate crystals with modified crystal form. S3. After solid-liquid separation, washing and low-temperature pre-drying, the obtained crystals are sent to a fluidized bed dryer. S4. Under a vacuum of 5 to 50 kPa or an inert gas atmosphere, the crystals are subjected to gradient heating dehydration in a fluidized state. The dehydration process adopts a three-stage gradient heating program: the first stage is heated to 100℃ and held for 30 minutes; the second stage is heated to 180℃ and held for 60 to 120 minutes; and the third stage is heated to 220℃ and held for 30 minutes to obtain anhydrous barium chloride product. During the dehydration process, the bed temperature is monitored in real time by multiple thermocouples, the temperature difference between each measuring point is less than ±3℃, the collision frequency between particles is 5 to 15 times per second, and the average collision kinetic energy is 0.8 to 1.5 millijoules.

2. The method for producing anhydrous barium chloride according to claim 1, characterized in that, The fluidized bed dryer is equipped with an air distribution plate with an opening rate of 5% to 10% and an opening diameter of 1 to 3 mm.

3. The method for producing anhydrous barium chloride according to claim 1, characterized in that, The volume ratio of lower fatty alcohols to deionized water in the mixed solvent is 5:

1.

4. The method for producing anhydrous barium chloride according to claim 1, characterized in that, The solid-liquid separation is performed by centrifugation or filtration. The separated wet crystals are washed 1 to 2 times with an alcohol-water mixed solvent of the same composition as that used for recrystallization. The amount of washing solution used each time is 0.5 to 1 times the mass of the wet crystals, and the washing temperature is 10 to 20°C.

5. The method for producing anhydrous barium chloride according to claim 1, characterized in that, In vacuum dehydration mode, the system vacuum is 20 kPa; in inert gas protection mode, the system maintains a slight positive pressure of 101.3 to 105 kPa.

6. The method for producing anhydrous barium chloride according to claim 1, characterized in that, In the gradient heating program, the heating rate is 2 to 5 °C / min in the first stage, 1 to 3 °C / min in the second stage, and 1 °C / min in the third stage.

7. The method for producing anhydrous barium chloride according to claim 1, characterized in that, After dehydration, the product is cooled to below 50°C at a rate of 1 to 3°C / minute under inert atmosphere or vacuum conditions before being discharged. The discharge port is equipped with a dual-valve isolation system.

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