A manufacturing system of ammonium metatungstate

Abstract

The application discloses an ammonium metatungstate manufacturing system and relates to the field of ammonium metatungstate manufacturing. The system comprises an automatic pure water pulping unit, a gradient temperature control buffer catalytic conversion unit, a constant temperature aging and standing unit, a multi-stage precise impurity removal and filtration unit, a negative pressure coupled low-temperature gradient concentration and crystallization unit, a mother liquor closed loop circulation and reuse unit, an ammonia waste gas recovery and purification unit and an intelligent PLC central control and regulation unit. The application adopts the gradient temperature control buffer catalytic conversion system, matches the reaction kinetics requirements of each stage by controlling the temperature in sections, cooperates with a weak acid buffer module to inhibit the side reaction, improves the conversion rate of APT, solves the problem of intermediate impurity phase residue, and improves the product purity and stability from the source.

Description

Technical Field

[0001] This invention relates to the field of ammonium metatungstate manufacturing technology, and more specifically to an ammonium metatungstate manufacturing system. Background Technology

[0002] Ammonium metatungstate is a core precursor for the preparation of high-end tungsten-based materials, widely used in cemented carbide, nano-tungsten oxide, semiconductor coating, and industrial catalysts. Product purity, crystal uniformity, and raw material conversion rate directly determine the performance and quality of downstream high-end products. Currently, traditional ammonium metatungstate manufacturing systems have significant technical deficiencies in actual industrial production, hindering the stable mass production of high-quality ammonium metatungstate.

[0003] First, traditional preparation systems generally adopt a crude reaction mode with a single constant temperature and fixed pH, which cannot match the reaction kinetics of the entire conversion process of ammonium paratungstate. The reaction process has many side reactions and incomplete reactions. The system is very prone to residual ammonium paratungstate intermediates and polytungstate impurities. The overall conversion rate of APT is low, which ultimately leads to insufficient purity of the finished product and poor batch stability, making it difficult to meet the requirements of high-end electronic-grade and catalyst-grade products.

[0004] Secondly, traditional processes generally adopt atmospheric pressure and high temperature evaporation crystallization. Under high temperature conditions, ammonium salts in the system are easily decomposed and volatilized, which not only causes a large amount of ammonia loss and continuous imbalance of material ratio, but also the rapid concentration at high temperature can easily cause local supersaturation of the solution and crystallization, resulting in problems such as crystal agglomeration, impurity encapsulation and embedding. The finished crystals have uneven particle size and poor solubility, and the overall quality defects of the product are prominent.

[0005] Third, traditional production systems have strong process independence and no closed-loop circulation structure. The crystallization mother liquor is directly discarded or simply treated and discharged, resulting in large tungsten resource losses and high production costs. At the same time, there are no effective means to recover the ammonia gas volatilized during the production process, which easily leads to material waste and workshop environmental pollution. The amount of waste gas, wastewater, and solid waste is large, which does not meet the requirements of green chemical continuous production and has a low resource utilization rate.

[0006] In summary, existing ammonium metatungstate manufacturing systems suffer from problems such as incomplete conversion, excessive impurity phase residues, and poor crystal quality. There is an urgent need for a new type of ammonium metatungstate manufacturing system to address these shortcomings.

[0007] To address these issues, we provide a manufacturing system for ammonium metatungstate. Summary of the Invention

[0008] To address one of the problems existing in the prior art, the present invention provides a manufacturing system for ammonium metatungstate, which solves the technical problems of incomplete conversion, excessive impurity phase residues, and poor crystal quality in existing ammonium metatungstate manufacturing systems.

[0009] To achieve the above objectives, the present invention employs an ammonium metatungstate manufacturing system, comprising: The system includes an automated pure water pulping unit, a gradient temperature control buffer catalytic conversion unit, a constant temperature aging and settling unit, a multi-stage precision impurity removal and filtration unit, a negative pressure coupling low temperature gradient concentration and crystallization unit, a mother liquor closed-loop recycling and reuse unit, an ammonia waste gas recovery and purification unit, and an intelligent PLC central control unit. The automated pure water pulping unit is used to accurately proportion and uniformly disperse high-purity raw material pulp, and output standard APT suspension pulp with stable concentration, no lumps and no impurities. The gradient temperature-controlled buffer catalytic conversion unit adopts a three-stage gradient heating structure, combined with organic acid buffer catalysis and online pH dynamic compensation and control mechanism, to achieve the complete conversion of ammonium paratungstate to ammonium metatungstate and eliminate intermediate impurity phase residues. The constant temperature aging and settling unit is used to stabilize the solution system after conversion, promote the precipitation of trace colloidal impurities, and optimize the overall homogeneity of the solution. The multi-stage precision impurity removal and filtration unit adopts a step-by-step filtration structure to sequentially intercept large particulate impurities, colloidal suspended matter and trace metal impurity ions, thereby achieving deep purification of the solution. The negative pressure coupled low temperature gradient concentration crystallization unit reduces the boiling point of the solution by reducing the negative pressure and, in conjunction with the gradient cooling crystallization process, achieves low-temperature, low-ammonia-loss crystallization, avoiding product agglomeration and impurity encapsulation problems. The mother liquor closed-loop recycling unit is used to return all the crystallization mother liquor to the automated pure water pulping unit, so as to realize the closed-loop recycling of tungsten resources. The ammonia waste gas recovery and purification unit is used to condense and recover the ammonia gas volatilized during the production process and prepare dilute ammonia water for reuse. The intelligent PLC central control unit collects system temperature, pressure, pH value, flow rate, concentration, and vacuum data in real time, and links various units to achieve adaptive closed-loop control.

[0010] As a further optimization of the above solution, the automated pure water pulping unit includes an 18.25 MΩ·cm high-purity water storage tank, a high-precision electronic weighing and feeding machine, a sealed corrosion-resistant pulping reactor, a variable frequency high-speed dispersing agitator, an online WO3 concentration sensor, a variable frequency quantitative delivery pump, and self-controlled valves; the pulping reactor adopts a 316L stainless steel polished structure, the weighing and feeding machine has an accuracy of ±0.1kg, the stirring speed adjustment range is 300r / min~1200r / min, and the online WO3 concentration sensor has a detection accuracy of ±1g / L.

[0011] As a further optimization of the above scheme, the gradient temperature control buffer catalytic conversion unit includes a three-stage gradient heating conversion vessel, a coil-type heat transfer oil heating component, a high-precision online pH sensor, an automatic weak acid buffer dosing device, and an electric stirring mechanism. The pH sensor has a detection accuracy of ±0.02, and the conversion vessel is a sealed and pressure-resistant structure.

[0012] As a further optimization of the above scheme, the process control logic of the three-stage gradient heating converter includes: the first stage is low-temperature dissociation, with a temperature of 55℃ and a constant temperature of 40 min; the second stage is a medium-temperature buffer reaction, with the temperature increased to 75℃ at a rate of 2℃ / min and a constant temperature of 60 min, and the pH of the system is stably controlled at 5.2 to 5.5; the third stage is high-temperature shaping conversion, with the temperature increased to 88℃ and a constant temperature of 90 min, and the stirring speed is 450 r / min throughout the process.

[0013] As a further optimization of the above scheme, the constant temperature aging and settling unit includes an aging kettle with a heat-insulating jacket, a temperature fluctuation error of ≤±0.5℃, a constant aging temperature of 70℃, and a sealed aging time of 120min.

[0014] As a further optimization of the above solution, the multi-stage precision impurity removal filtration unit adopts a three-stage filtration structure, consisting of coarse filtration with a 200-mesh stainless steel filter, precision filtration with a 1μm PP filter element, and ultrafiltration precision filtration, with a constant filtration pressure of 0.25MPa.

[0015] As a further optimization of the above scheme, the negative pressure coupled low temperature gradient concentration crystallization unit includes a negative pressure crystallization kettle, a vacuum negative pressure unit, a condensation heat exchange component and a gradient cooling control module, with the working vacuum degree maintained at -0.07MPa to -0.075MPa and the solution boiling point controlled at 72℃ to 75℃.

[0016] As a further optimization of the above scheme, the crystallization process of the negative pressure coupled low temperature gradient concentration crystallization unit is as follows: concentrate at 75℃ to a WO3 concentration of 480g / L, cool down to 42℃ at a gradient of 1℃ / 5min, and maintain the temperature for crystal growth for 150min.

[0017] As a further optimization of the above scheme, the ammonia waste gas recovery and purification unit adopts a circulating water-cooled condensation structure to prepare volatile ammonia gas into dilute ammonia water with a mass concentration of 5% to 8% and reuse it in the pH fine-tuning process of the system.

[0018] The ammonium metatungstate manufacturing system of the present invention has the following beneficial effects: The present invention discloses an ammonium metatungstate manufacturing system that employs a gradient temperature-controlled buffer catalytic conversion system. By segmenting the temperature to match the kinetic requirements of each stage of the reaction, and using a weak acid buffer module to suppress side reactions, the APT conversion rate is improved, the problem of intermediate impurity phase residue is solved, and the purity and stability of the product are improved from the source.

[0019] This invention proposes a negative pressure coupled low temperature gradient crystallization system to replace the traditional high temperature and normal pressure evaporation process, reducing the volatilization loss of ammonia components, avoiding material imbalance, crystal agglomeration and impurity encapsulation caused by high temperature, and producing finished products with uniform particles and excellent solubility, thus achieving a qualitative improvement in product quality.

[0020] This invention establishes a fully closed-loop mother liquor circulation and waste gas recovery system, realizing the comprehensive recycling of tungsten, water and ammonia resources. The comprehensive tungsten recovery rate is close to 100%, the material loss is extremely low, the production cost is reduced, and there is no emission of waste gas, wastewater, or solid waste, making it green and environmentally friendly.

[0021] Specific embodiments of the present invention are disclosed in detail with reference to the following description and accompanying drawings, indicating how the principles of the present invention can be adopted. It should be understood that the embodiments of the present invention are not limited in scope as a result, and that the embodiments of the present invention include many changes, modifications and equivalents within the spirit and scope of the appended claims. Attached Figure Description

[0022] Figure 1 This is a block diagram of the ammonium metatungstate manufacturing system of the present invention. Detailed Implementation

[0023] Please refer to the instruction manual appendix. Figure 1 The present invention provides a technical solution: an ammonium metatungstate manufacturing system, which solves the problems of low conversion rate, large amount of impurity phase residue and large ammonia loss in the traditional ammonium metatungstate preparation process by constructing a gradient temperature-controlled buffer catalytic conversion module and a negative pressure coupled low temperature gradient crystallization mother liquor full circulation module.

[0024] The present invention includes an automated pure water pulping unit, a gradient temperature-controlled buffer catalytic conversion unit, a constant temperature aging and settling unit, a multi-stage precision impurity removal and filtration unit, a negative pressure coupling low temperature gradient concentration and crystallization unit, a mother liquor closed-loop recycling and reuse unit, an ammonia waste gas recovery and purification unit, and an intelligent PLC central control and regulation unit.

[0025] Among them, the automated pure water pulping unit is used for the proportioning and uniform dispersion of high-purity raw material pulp, providing a standard pulp module with stable concentration, no lumps and no impurities for subsequent conversion reactions.

[0026] The gradient temperature-controlled buffer catalytic conversion unit replaces the traditional single constant temperature and single pH extensive reaction mode. It adopts a three-stage gradient temperature increase combined with organic acid buffer catalysis and online pH dynamic compensation and control mechanism to achieve complete conversion of ammonium paratungstate (APT) to ammonium metatungstate (AMT) and eliminate intermediate impurity phase residues. The constant temperature aging and settling unit is used to stabilize the solution module after conversion, promote the full precipitation of trace colloidal impurities, and optimize the homogeneity of the solution.

[0027] The multi-stage precision filtration unit adopts a step-by-step filtration structure to intercept large particulate impurities, colloidal suspended matter, and trace metal impurity ions, thereby achieving deep purification of the solution.

[0028] The negative pressure coupled low-temperature gradient concentration and crystallization unit lowers the boiling point of the solution by reducing the pressure under negative pressure. Combined with the gradient cooling crystallization process, it replaces the traditional high-temperature atmospheric pressure evaporation process, achieving low-temperature, low-ammonia loss crystallization and avoiding product agglomeration and impurity encapsulation problems.

[0029] The closed-loop recycling unit of the mother liquor returns all the crystallization mother liquor to the front-end pulping process, realizing the zero-loss recycling of tungsten resources.

[0030] The ammonia waste gas recovery and purification unit condenses and recovers trace amounts of volatile ammonia gas during the production process to produce dilute ammonia water for reuse, achieving green and environmentally friendly production.

[0031] The intelligent PLC central control unit collects real-time data on temperature, pressure, pH value, flow rate, concentration, and vacuum level of the entire system, enabling automatic linkage and control of each unit to ensure long-term stable and continuous operation of the entire system.

[0032] The gradient temperature-controlled buffer catalytic conversion system of this invention uses a three-stage gradient temperature rise coupled with a weak acid buffer module and dynamic pH adaptive compensation to regulate the reaction rate of APT dissociation, deammoniation, rearrangement and the entire conversion process, thus solving the problems of incomplete reaction, many impurity phases and low conversion rate in traditional processes, and stably increasing the conversion rate of tungsten raw materials to over 99.2%.

[0033] The present invention utilizes a negative pressure coupled low-temperature gradient crystallization and mother liquor full circulation system. It employs negative pressure low-temperature boiling concentration combined with segmented gradient cooling crystallization to solve the problems of ammonia decomposition and volatilization caused by high temperature and local supersaturation and impurity encapsulation. At the same time, it is combined with a fully closed-loop mother liquor recycling link to improve product purity and finished product solubility, and reduce production losses and production costs.

[0034] This invention discloses two embodiments, wherein the first embodiment is adapted to a large-scale continuous production system for industrial-grade ammonium metatungstate.

[0035] This embodiment discloses a complete manufacturing system structure and controllable process parameters adapted to the mass production of industrial-grade ammonium metatungstate with high capacity, high stability, and low cost. The system can process slurry volume of 5000L per batch, achieve 24-hour continuous production, and the finished ammonium metatungstate has a purity of ≥99.5%, excellent water solubility, no insoluble impurities, batch deviation of products ≤0.2%, and tungsten comprehensive recovery rate ≥99.2%.

[0036] The automated pure water pulping unit is configured using existing mature technology and includes: an 18.25 MΩ·cm high-purity water storage tank, a high-precision electronic weighing feeder, a 5000L sealed corrosion-resistant pulping reactor, a variable frequency high-speed dispersing agitator, an online WO3 concentration sensor, a variable frequency quantitative delivery pump, and matching automatic control valves.

[0037] The slurry reaction vessel is constructed entirely of 316L stainless steel with a polished and corrosion-resistant inner wall to prevent metal ion leaching and contamination of the material. The electronic weighing feeder has a dynamic weighing accuracy of ±0.1kg, enabling quantitative addition of APT powder raw materials. The high-speed dispersing agitator has a speed adjustment range of 300r / min to 1200r / min, which can be adapted to the dispersion speed according to the slurry concentration. The online concentration sensor monitors the tungsten trioxide concentration of the slurry in real time with a detection accuracy of ±1g / L, and feeds back the data to the central control system in real time.

[0038] The specific controllable process parameters for the pulping process in this embodiment are as follows: Under normal temperature and pressure, high-purity water and industrial-grade ammonium paratungstate powder are precisely proportioned to prepare the pulp, and the WO3 mass concentration in the pulp is kept stable at 250 g / L; the mass ratio of APT powder to high-purity water is 1:4.0; after feeding, a high-speed dispersing agitator is started, with a constant speed of 800 r / min, and continuous dispersion and stirring for 25 min to ensure that the powder is completely wetted, there is no dry material clumping, and the pulp is uniform overall, thus preparing an APT suspension pulp with excellent stability; after pulping, it is uniformly transported to the gradient temperature-controlled buffer catalytic conversion unit by a variable frequency pump, and the conveying flow rate is stably controlled at 800 L / h to ensure continuous and stable feeding of materials.

[0039] The gradient temperature-controlled buffer catalytic conversion unit is specifically configured as follows: a three-stage gradient temperature-increasing conversion vessel, an internal coil heating element, a high-precision online pH sensor, an automatic weak acid buffer dosing device, an electric stirring mechanism, a temperature acquisition module, and a pressure monitoring module. The conversion vessel employs a sealed, pressure-resistant structure to prevent the leakage of trace amounts of ammonia gas during the reaction. The internal coil heating element uses a circulating heat transfer oil heating mode, ensuring uniform heating and eliminating localized overheating defects. The online pH sensor has a detection accuracy of ±0.02, enabling real-time acquisition of solution acid and alkalinity values ​​and dynamic compensation in conjunction with the automatic dosing device.

[0040] The three-stage gradient heating catalytic conversion process parameters in this embodiment are as follows: This invention replaces the traditional single constant temperature 100℃ high-temperature conversion mode and adopts a three-stage gradient heating reaction logic of low-temperature dissociation, medium-temperature buffering and high-temperature rearrangement. It is combined with an acetic acid weak acid buffer module to suppress violent hydrolysis reaction and avoid the generation of impurity phases.

[0041] The first stage of low-temperature dissociation: the initial temperature is controlled at 55℃ and kept constant for 40 minutes to promote the full and slow dissociation of APT powder, release ammonium ions and tungstate ions, and avoid local agglomeration and precipitation caused by rapid high-temperature hydrolysis. The second stage is a medium-temperature buffer reaction: the temperature is raised to 75℃ at a constant rate of 2℃ / min, and the reaction is carried out at a constant temperature for 60min. Acetic acid buffer is added in small amounts through an automatic dosing device to stabilize the pH value in the system within the optimal weak acid range of 5.2 to 5.5, thereby weakening the local hydrolysis reaction of strong acid and ensuring the uniform rearrangement of tungstate ions. The third stage, high-temperature shaping and conversion: The temperature is continuously increased at a constant rate to 88℃ and maintained for 90 minutes to complete all deamination and molecular rearrangement reactions, converting the solution into a homogeneous ammonium metatungstate solution, avoiding the residue of ammonium paratungstate intermediates and polytungstate impurities. The stirring speed is kept constant at 450 r / min throughout the process to ensure uniform reaction in the modules, ultimately achieving complete conversion of APT to AMT with a conversion rate of up to 99.3%.

[0042] Specific configuration and process parameters of the constant-temperature aging and settling unit: The homogeneous ammonium metatungstate solution after conversion is transported to the constant-temperature aging reactor. The reactor adopts an insulated jacket structure, with a temperature fluctuation error ≤ ±0.5℃. The aging temperature is controlled at a constant 70℃, and the reactor is sealed and settling for 120 minutes. Constant-temperature aging allows trace colloidal impurities and incompletely reacted microparticles in the solution to fully precipitate, eliminating localized concentration unevenness and further improving the overall uniformity and stability of the solution. This lays the foundation for subsequent impurity removal, filtration, and crystallization processes, preventing localized impurity enrichment and uneven color in the finished product.

[0043] Specific configuration and process parameters of the multi-stage precision impurity removal filtration unit: The multi-stage precision impurity removal filtration unit adopts a three-stage progressive filtration structure to achieve gradient depth impurity removal. The first stage is a 200-mesh stainless steel filter screen for coarse filtration, intercepting large unreacted powder particles and agglomerated impurities. The second stage is a precision pleated PP filter cartridge with a filtration accuracy of 1μm, intercepting suspended colloidal particles in the solution. The third stage is an ultrafiltration precision filtration component, which retains trace amounts of large molecular organic impurities and fine metal particles. The entire filtration system adopts a closed pressure filtration mode, with the filtration pressure stably controlled at 0.25MPa and the filtration speed uniform and stable. After three stages of progressive impurity removal, the ammonium metatungstate solution is clear and transparent, without any suspended impurities, ensuring the purity and appearance quality of the subsequent crystallized product.

[0044] The specific configuration and process parameters of the negative pressure coupled low temperature gradient concentration crystallization unit: The negative pressure coupled low temperature gradient concentration crystallization unit is the low-loss, high-quality crystallization system of this invention. It includes a closed negative pressure crystallization kettle, a vacuum negative pressure unit, a condensation heat exchange component, a gradient cooling control module, and a crystal collection and discharge mechanism. Compared with the traditional atmospheric pressure 105℃ high temperature evaporation crystallization, this system reduces the boiling point of the solution by reducing the negative pressure, thereby achieving low temperature concentration and crystallization, and reducing the volatilization loss of ammonia components from the source.

[0045] Specific process parameters for this embodiment: Start the vacuum negative pressure unit to stabilize the vacuum inside the crystallization kettle at -0.07MPa to -0.075MPa. At this time, the boiling point of the solution drops to 72℃ to 75℃, and concentration and evaporation are carried out in a low temperature negative pressure environment. The concentration process adopts a gradient cooling crystallization mode. First, the solution is concentrated at a constant temperature of 75℃ until the WO3 concentration reaches 480g / L. Then, the temperature is uniformly reduced at a rate of 1℃ / 5min, and finally cooled to 42℃ for crystal growth for 150min, which promotes the slow and uniform precipitation of ammonium metatungstate crystals.

[0046] Low-temperature gradient crystallization can effectively avoid crystal agglomeration, clumping, and uneven particle size caused by rapid cooling. At the same time, it inhibits the high-temperature decomposition and volatilization of ammonium salts, reducing ammonia loss by more than 85% compared to traditional processes. The finished crystal particles are loose and uniform, with good flowability and excellent water solubility.

[0047] The specific configuration and working logic of the mother liquor closed-loop recycling unit: After crystallization, the high-purity ammonium metatungstate crystals precipitated at the bottom are discharged through the discharge mechanism for centrifugal dehydration and drying. The remaining crystallization mother liquor is collected in a mother liquor buffer storage tank.

[0048] This invention establishes a complete mother liquor reflux pipeline, returning all the mother liquor to the front-end automated pulping unit. This replaces a portion of the high-purity water in the next round of pulping production, achieving a closed-loop recycling of tungsten resources. Trace amounts of unprecipitated ammonium metatungstate and tungstate ions remaining in the mother liquor can completely participate in the reaction and crystallization again, eliminating tungsten resource waste. The overall tungsten recovery rate of the entire system is consistently maintained above 99.2%, reducing raw material production costs.

[0049] The specific configuration and working logic of the ammonia waste gas recovery and purification unit: The entire system operates in a completely closed system. During the production process, trace amounts of ammonia-containing waste gas are collected through the gas collection pipeline to the condensation and recovery device. The circulating water-cooled condensation mode is adopted to condense and absorb gaseous ammonia gas to prepare dilute ammonia water with a mass concentration of 5% to 8%. The recovered dilute ammonia water can be reused as needed in the pH fine-tuning process of the reaction system, realizing the resource reuse of waste gas. This solves the problems of ammonia volatilization polluting the workshop environment and raw material imbalance in traditional processes, and meets the standards of green chemical production.

[0050] The intelligent PLC central control unit operates as follows: All temperature, pressure, pH, flow, and vacuum measurement points in the entire system are connected to the PLC intelligent central control system, which collects operational data in real time and automatically links each actuator. When module temperature, pH value, or vacuum level fluctuates, the system can automatically adjust heating power, reagent dosage, negative pressure unit frequency, and delivery pump flow rate, achieving adaptive closed-loop control across the entire process. This eliminates the need for frequent manual intervention, ensuring long-term continuous steady-state production and extremely high batch product consistency.

[0051] Example 2: Adapted to a high-purity electronic-grade ammonium metatungstate fine production system; This embodiment is based on the same system architecture as the present invention. It optimizes the equipment precision, filtration level, process parameters and control logic to meet the production needs of ultra-high purity ammonium metatungstate in the fields of high-end electronics, semiconductors and precision catalysts. It achieves the fine preparation of electronic-grade ultra-high purity ammonium metatungstate with a finished product purity ≥99.95%, total metal impurity content ≤5ppm, no agglomeration, no impurity phase, and 100% solubility. It meets the stringent material standards for semiconductor coating, nano-tungsten powder preparation and high-end catalyst carriers. The entire system has a single batch processing volume of 3000L and is suitable for the production of fine, small-batch, high-value-added products.

[0052] The automated pure water pulping unit features a refined configuration: This embodiment employs an ultrapure water preparation system with a constant effluent resistivity of 18.25 MΩ·cm, preventing water contamination by impurities; it is equipped with a high-precision micro-weighing module with a weighing accuracy of ±0.05 kg, enabling precise proportioning of APT ultrapure raw materials; the inner wall of the pulping vessel is mirror-polished with a roughness Ra≤0.8μm, preventing material residue and metal precipitation; the stirring speed is optimized to 900 r / min, and the dispersion time is 30 min, producing an ultra-highly homogeneous slurry with a WO3 concentration of 240 g / L. The slurry is free of trace agglomerates, providing the basic conditions for the ultrapure conversion reaction.

[0053] Refined process parameters for the gradient temperature-controlled buffer catalytic conversion unit: This embodiment optimizes the three-stage gradient heating rate and precise pH control range, using high-purity acetic acid as a buffer regulator to avoid introducing impurities with ordinary regulators. The first stage involves a low-temperature dissociation temperature of 52℃, maintained at a constant temperature for 45 min, with slow dissociation to avoid localized hydrolysis; the second stage involves a buffer reaction temperature of 72℃, with a heating rate of 1.5℃ / min, ensuring precise temperature control, and the pH value in the system is stably locked within a narrow range of 5.3–5.4, suppressing the formation of side reactions; the third stage involves a shaping conversion temperature of 85℃, maintained at a constant temperature for 100 min, with slow and thorough rearrangement to eliminate trace impurities. The stirring speed is 380 r / min throughout the process, with low-speed uniform stirring to avoid impurities entrained by bubbles in the module, improving conversion purity and uniformity.

[0054] Optimized constant temperature aging and ultra-fine impurity removal process: The aging temperature is kept constant at 68℃ with temperature fluctuations ≤ ±0.3℃. The aging process is carried out in a sealed environment for 150 minutes to fully extract trace amounts of nano-sized colloidal impurities. The impurity removal unit is upgraded to a four-stage ultra-fine filtration system, with the addition of a 0.1μm precision ultrafiltration and metal ion adsorption filtration component. This system is specifically designed for deep adsorption and interception of trace metal impurities such as iron, copper, calcium, and magnesium. The total content of metal impurities in the final solution is controlled within 5ppm, meeting the standards for electronic-grade products.

[0055] The parameters for the negative pressure ultra-low temperature gradient crystallization refinement process are as follows: In this embodiment, the system vacuum is increased to -0.08MPa to -0.085MPa, and the solution boiling point is lowered to 68℃ to 70℃, achieving lower temperature concentration, protecting the purity of the material, and avoiding ammonium salt decomposition. The WO3 concentration at the concentration endpoint is controlled at 460g / L, the gradient cooling rate is slowed to 1℃ / 8min, the final crystal growth temperature is 38℃, and the constant temperature crystal growth is 180min. Slow crystallization results in a regular crystal structure, dense arrangement, no agglomeration, and no impurity encapsulation. The particle size uniformity deviation of the finished crystal is ≤0.1%, and the quality far exceeds that of products produced by traditional processes.

[0056] High-precision mother liquor circulation and refined waste gas recovery: In this embodiment, a precision filtration and purification process is added before the mother liquor is refluxed to intercept trace impurities in the mother liquor and avoid accumulation during circulation; the ammonia recovery system adopts multi-stage condensation absorption, with an ammonia recovery rate of ≥99.5%, no waste gas leakage, and higher purity of the recovered ammonia water, which can be used for system fine-tuning to ensure stable high-purity production conditions.

[0057] Intelligent high-precision central control and regulation: This embodiment adopts a high-precision sensor module with temperature detection accuracy of ±0.1℃, pH detection accuracy of ±0.01℃, and vacuum fluctuation error ≤±0.001MPa, realizing precise control of all parameters with micro-errors, avoiding product quality deviations caused by parameter fluctuations, and ensuring a high degree of consistency in the performance of each batch of electronic-grade products.

[0058] In summary, this invention first uses an automated pure water slurry preparation unit to precisely proportion and rapidly disperse high-purity APT powder and ultrapure water, preparing a standard suspension slurry with uniform concentration, free of impurities and lumps. The slurry is then quantitatively transported by a variable frequency pump to a gradient temperature-controlled buffer catalytic conversion unit. Through a three-stage gradient temperature increase coupled with weak acid buffer catalysis and dynamic pH adaptive compensation, the complete conversion of APT to a high-purity ammonium metatungstate solution is achieved, eliminating intermediates and impurity phase residues. The converted solution enters a constant-temperature aging unit for static stabilization, promoting the full aggregation of trace colloidal impurities. Subsequently, it enters a multi-stage precision impurity removal and filtration unit, progressively intercepting large particles, colloidal particles, and trace metal impurities. The process involves purifying the ammonium metatungstate mother liquor to obtain a clear, high-purity solution. The purified solution is then transported to a negative pressure coupled low-temperature gradient crystallization unit, where it is concentrated under a gradient and slowly cooled to grow crystals, resulting in the precipitation of high-purity ammonium metatungstate crystals. After centrifugation, dehydration, and low-temperature drying, the crystals are used to obtain the finished ammonium metatungstate material. All remaining mother liquor from crystallization is recycled back to the upstream pulping process via a closed-loop mother liquor circulation unit, achieving 100% recycling of tungsten resources. Trace amounts of volatile ammonia gas generated during production are condensed and recovered by an ammonia waste gas recovery and purification unit to produce dilute ammonia water for reuse. All process operating parameters are monitored in real time and adaptively controlled by an intelligent PLC central control unit, enabling the entire system to achieve continuous, stable, and intelligent closed-loop production 24 hours a day.

Claims

1. A system for manufacturing ammonium metatungstate, characterized in that, include: The system includes an automated pure water pulping unit, a gradient temperature control buffer catalytic conversion unit, a constant temperature aging and settling unit, a multi-stage precision impurity removal and filtration unit, a negative pressure coupling low temperature gradient concentration and crystallization unit, a mother liquor closed-loop recycling and reuse unit, an ammonia waste gas recovery and purification unit, and an intelligent PLC central control unit. The automated pure water pulping unit is used to accurately proportion and uniformly disperse high-purity raw material pulp, and output standard APT suspension pulp with stable concentration, no lumps and no impurities. The gradient temperature-controlled buffer catalytic conversion unit adopts a three-stage gradient heating structure, combined with organic acid buffer catalysis and online pH dynamic compensation and control mechanism, to achieve the complete conversion of ammonium paratungstate to ammonium metatungstate and eliminate intermediate impurity phase residues. The constant temperature aging and settling unit is used to stabilize the solution system after conversion, promote the precipitation of trace colloidal impurities, and optimize the overall homogeneity of the solution. The multi-stage precision impurity removal and filtration unit adopts a step-by-step filtration structure to sequentially intercept large particulate impurities, colloidal suspended matter and trace metal impurity ions, thereby achieving deep purification of the solution. The negative pressure coupled low temperature gradient concentration crystallization unit reduces the boiling point of the solution by reducing the negative pressure and, in conjunction with the gradient cooling crystallization process, achieves low-temperature, low-ammonia-loss crystallization, avoiding product agglomeration and impurity encapsulation problems. The mother liquor closed-loop recycling unit is used to return all the crystallization mother liquor to the automated pure water pulping unit, so as to realize the closed-loop recycling of tungsten resources. The ammonia waste gas recovery and purification unit is used to condense and recover the ammonia gas volatilized during the production process and prepare dilute ammonia water for reuse. The intelligent PLC central control unit collects system temperature, pressure, pH value, flow rate, concentration, and vacuum data in real time, and links various units to achieve adaptive closed-loop control.

2. The ammonium metatungstate manufacturing system according to claim 1, characterized in that: The automated pure water pulping unit includes an 18.25 MΩ·cm high-purity water storage tank, a high-precision electronic weighing and feeding machine, a sealed corrosion-resistant pulping reactor, a variable frequency high-speed dispersing agitator, an online WO3 concentration sensor, a variable frequency quantitative delivery pump, and automatic control valves. The pulping reactor is made of polished 316L stainless steel. The weighing and feeding machine has an accuracy of ±0.1 kg, the stirring speed can be adjusted from 300 r / min to 1200 r / min, and the online WO3 concentration sensor has a detection accuracy of ±1 g / L.

3. The ammonium metatungstate manufacturing system according to claim 1, characterized in that: The gradient temperature control buffer catalytic conversion unit includes a three-stage gradient heating conversion vessel, a coil-type heat transfer oil heating component, a high-precision online pH sensor, an automatic weak acid buffer dosing device, and an electric stirring mechanism. The pH sensor has a detection accuracy of ±0.02, and the conversion vessel is a sealed and pressure-resistant structure.

4. The ammonium metatungstate manufacturing system according to claim 3, characterized in that: The process control logic of the three-stage gradient heating converter includes: the first stage is low-temperature dissociation, with a temperature of 55℃ and a constant temperature of 40 min; the second stage is a medium-temperature buffer reaction, with the temperature increased to 75℃ at a rate of 2℃ / min and a constant temperature of 60 min, and the pH of the system is stably controlled at 5.2 to 5.5; the third stage is high-temperature shaping conversion, with the temperature increased to 88℃ and a constant temperature of 90 min, and the stirring speed is 450 r / min throughout the process.

5. The ammonium metatungstate manufacturing system according to claim 1, characterized in that: The constant temperature aging and settling unit includes an aging kettle with a heat-insulating jacket, a temperature fluctuation error of ≤±0.5℃, a constant aging temperature of 70℃, and a sealed aging time of 120min.

6. The ammonium metatungstate manufacturing system according to claim 1, characterized in that: The multi-stage precision impurity removal filtration unit adopts a three-stage filtration structure, consisting of a 200-mesh stainless steel filter screen for coarse filtration, a 1μm PP filter element for precision filtration, and ultrafiltration for precision filtration, with a constant filtration pressure of 0.25MPa.

7. The ammonium metatungstate manufacturing system according to claim 1, characterized in that: The negative pressure coupled low temperature gradient concentration crystallization unit includes a negative pressure crystallization kettle, a vacuum negative pressure unit, a condensation heat exchange component and a gradient cooling control module. The working vacuum degree is maintained at -0.07MPa to -0.075MPa, and the solution boiling point is controlled at 72℃ to 75℃.

8. The ammonium metatungstate manufacturing system according to claim 7, characterized in that: The crystallization process of the negative pressure coupled low temperature gradient concentration crystallization unit is as follows: concentrate at 75℃ to a WO3 concentration of 480g / L, then cool down to 42℃ at a gradient of 1℃ / 5min, and maintain the temperature for crystal growth for 150min.

9. The ammonium metatungstate manufacturing system according to claim 1, characterized in that: The ammonia waste gas recovery and purification unit adopts a circulating water-cooled condensation structure to prepare volatile ammonia gas into dilute ammonia water with a mass concentration of 5% to 8% and reuse it in the pH fine-tuning process of the system.

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