A method for converting high-density red phosphorus

Abstract

The present application relates to high-purity phosphorus material preparation technical field, specifically to a kind of conversion method of high-density red phosphorus, including the following steps: pretreatment, conversion, two-stage heating and cooling process: pretreatment is cooled to 15±3 ℃ for 5h after high-purity yellow phosphorus water seal, after inert gas purging water is loaded furnace;Conversion process control pressure 1.2-2MPa, cooling water flow 2m³ / h, temperature 25 ℃, phosphorus liquid surface is 5-8cm from condenser tube;Heating uses two-stage strategy, first stage 285±5 ℃ constant temperature 60±5h, the pressure linear coupling control in the process of temperature rise, second stage 320±5 ℃ constant temperature 20±2h.The red phosphorus density prepared by the present application reaches 2.30-2.33g / cm³, conversion rate is ≥98.2%, purity is ≥99.9999%, process parameters are accurately controllable, equipment requirement is low, batch stability is good, suitable for industrialization large-scale production, can satisfy the application demand of high-end field such as semiconductor.

Description

Technical Field

[0001] This invention relates to the field of high-purity phosphorus material preparation technology, specifically a method for converting high-density red phosphorus. Background Technology

[0002] Red phosphorus is one of the most stable allotropes of phosphorus, possessing moderate chemical reactivity, a high ignition point, and low toxicity. It is widely used in flame-retardant materials, fireworks manufacturing, metallurgy, chemical engineering, and semiconductor electronics. High-density, high-purity red phosphorus with a purity ≥99.9999% and a density ≥2.30 g / cm³ is a core raw material for preparing III-V compound semiconductors such as indium phosphide, gallium phosphide, and aluminum phosphide, directly determining the crystal quality, carrier mobility, and optoelectronic performance of semiconductor epitaxial wafers. With the rapid development of industries such as 5G communication, optoelectronic devices, and new energy vehicles, the market demand for high-density, high-purity red phosphorus is increasing year by year, while simultaneously imposing more stringent requirements on its purity, density, and batch stability.

[0003] Currently, the mainstream industrial method for preparing red phosphorus is the yellow phosphorus thermal conversion method, which can be divided into two main categories based on reaction pressure: atmospheric pressure conversion and high-pressure conversion. The atmospheric pressure conversion process, under 0.1 MPa pressure, gradually converts yellow phosphorus to red phosphorus by programmed temperature increases to 250-350℃. This process has low equipment requirements and low operational risk, but the conversion cycle is over 100 hours, and yellow phosphorus volatilizes significantly, resulting in a raw material yield of only about 85%. It also easily introduces impurities, making it difficult to produce products with a purity of 7N or higher. The high-pressure conversion process, by applying 1-10 MPa pressure in a closed system to suppress yellow phosphorus volatilization, can shorten the conversion cycle to about 80 hours and improve the raw material yield. However, existing high-pressure processes generally suffer from poor parameter matching and low control precision, and the product density is typically only 2.10-2.20 g / cm³, which cannot meet the application requirements of high-end semiconductor fields.

[0004] The existing red phosphorus conversion process suffers from several technical defects that urgently need to be addressed. Firstly, the precision of process parameter control is insufficient; key parameters such as pressure, temperature, and condensation conditions fluctuate significantly, leading to substantial differences in density and crystallinity between different batches, resulting in poor batch stability. Secondly, the heating strategy is simplistic, generally employing a single-stage isothermal heating method, which fails to address the different temperature requirements for crystal nucleation and growth, easily leading to uneven grain size and loose structure, making it difficult to obtain high-density products. Thirdly, the condensation and reflux system design is crude, lacking precise control over the condensation and reflux rates of phosphorus vapor, resulting not only in raw material waste but also in the disruption of the dense structure of red phosphorus crystals due to the impact of the reflux liquid. Fourthly, the pretreatment process is not standardized; residual moisture, oxygen, and other impurities during the loading process can react with yellow phosphorus at high temperatures, generating impurities such as phosphoric acid and phosphorus oxides, reducing product purity and affecting the stable progress of the conversion reaction.

[0005] In response to the aforementioned technical problems, domestic and foreign research institutions and enterprises have conducted extensive research to improve the quality of red phosphorus products by optimizing heating procedures and improving reaction equipment. However, the core problems of low product density and unstable conversion rate have not yet been fundamentally solved. Summary of the Invention

[0006] The purpose of this invention is to provide a method for converting high-density red phosphorus, in order to solve the problems mentioned in the background art, such as low product density, unstable conversion rate, poor batch consistency, and difficulty in preparing 7N grade high-purity red phosphorus.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for converting high-density red phosphorus includes the following steps:

[0009] (1) Pretreatment process: High-purity yellow phosphorus is loaded into the conversion tube and the surface is sealed with water; the conversion tube after loading is cooled, the temperature is controlled at 15±3℃, and the cooling time is 5 hours; the conversion tube is taken out, the water on the surface is poured out, the surface is blown with high-purity inert gas, and after the water is dried, it is loaded into the conversion furnace.

[0010] (2) Conversion process: In the conversion furnace, the pressure of the conversion process is controlled at 1.2-2MPa; the phosphorus vapor is condensed, the cooling water flow rate is 2 cubic meters / hour, the cooling water temperature is controlled at 25℃, and the height of the phosphorus liquid surface from the condenser tube is 5-8cm.

[0011] (3) Heating control process: The temperature of the phosphorus solution in the charging zone of the converter is controlled in two stages: the temperature in the first stage is controlled at 285±5℃, and the pressure is linearly pressurized following the temperature during the heating process, satisfying the formula:

[0012] in For temperature Unit: °C; corresponding pressure inside the converter, unit: MPa. The first stage of temperature control is 60±5 hours; the second stage of temperature control is 320±5℃, and the constant temperature time is 20±2 hours.

[0013] (4) Cooling process: After the conversion is completed, the conversion tube is cooled to room temperature with the furnace and then taken out to obtain high-density red phosphorus product.

[0014] Preferably, the high-purity inert gas in step (1) is selected from one or more of nitrogen, argon or helium, and the number of purgings is not less than 3, the purging time is not less than 2 minutes each time, and the purging gas flow rate is controlled at 0.5-1.5m / s.

[0015] Preferably, the conversion tube in step (1) is a high-purity quartz tube or a high-temperature resistant glass tube, and the ratio of the inner diameter to the length of the conversion tube satisfies the formula:

[0016] in The inner diameter of the conversion tube is in cm. The effective loading length of the conversion tube is in cm.

[0017] Preferably, the pressure in step (2) is regulated by introducing high-purity inert gas into the converter, with the pressure fluctuation range controlled within ±0.05 MPa. The pressure regulation adopts a PID algorithm, and its control equation is:

[0018] in For the opening degree of the pressure regulating valve, The deviation between the pressure setpoint and the actual value. , , .

[0019] Preferably, the condenser tube in step (2) is a serpentine condenser tube or a spherical condenser tube. The condenser tube is installed vertically with an installation angle of 5°-10°. The lower end of the condenser tube is sealed to the top of the conversion tube through a frosted interface. The condensation system is pre-cooled before starting, with a pre-cooling time of 15-30 minutes and a cooling water flow rate of 1 cubic meter / hour during pre-cooling. The ratio of the heat exchange area of ​​the condenser tube to the charge of the conversion tube is 0.08-0.12 m² / kg. The cooling water flows from bottom to top. The outlet water temperature of the condenser tube is monitored and controlled in real time at 30°C-35°C. When the outlet water temperature exceeds 35°C, the cooling water flow rate is automatically increased by 0.2 cubic meters / hour.

[0020] Preferably, in step (3), the heating rate between the first and second stages is 0.5-3℃ / minute. During the heating process, the pressure is kept constant, and the pressure value is equal to the pressure value at the end of the first stage of constant temperature. During the heating process, the temperature of the upper, middle and lower points of the charging area is detected every 30 minutes. The temperature difference between the three points is controlled within ±5℃. If the temperature difference exceeds 5℃, the heating rate is reduced by 0.5℃ / minute until the temperature difference returns to the allowable range. At the same time, the furnace pressure data is collected every 15 minutes. When the pressure fluctuation exceeds ±0.03MPa, the pressure is compensated by finely adjusting the opening of the air inlet valve. The compensation amount does not exceed 0.01MPa / time.

[0021] Preferably, the first stage of heating in step (3) adopts a three-stage segmented heating strategy, and the specific sub-steps are as follows:

[0022] S3.1.1: The temperature is increased from room temperature to 100°C at a rate of 5°C / min and kept constant for 2 hours. During this period, a small amount of high-purity inert gas is continuously introduced to remove the trace amount of moisture remaining in the furnace with the gas flow.

[0023] S3.1.2: Increase the temperature from 100℃ to 200℃ at a rate of 2℃ / minute. During the heating process, pressurize synchronously according to the linear pressurization formula. The pressure value is calibrated every 20℃ increase.

[0024] S3.1.3: Increase the temperature from 200℃ to 285±5℃ at a rate of 1℃ / minute. During the heating process, calibrate the temperature sensor in the loading area every 10 minutes to ensure that the temperature measurement deviation does not exceed ±2℃.

[0025] Preferably, the purity of the high-purity yellow phosphorus in step (1) is not less than 99.9999%, and the loading amount is 60%-70% of the effective volume of the conversion tube. Before loading, the conversion tube is pretreated by rinsing it with deionized water 3 times and anhydrous ethanol 2 times in sequence, and then drying it in a vacuum drying oven at 120°C for 2 hours. After cooling to room temperature, it is taken out. When loading, the yellow phosphorus is first placed in a constant temperature water bath at 45°C-50°C and completely melted. The liquid yellow phosphorus is slowly transferred into the conversion tube by the polytetrafluoroethylene siphon method. During the transfer process, the surface of the yellow phosphorus is always covered with 1-2 cm of deionized water. After loading, deionized water is added to the conversion tube until the liquid level is 2-3 cm higher than the yellow phosphorus liquid level to complete the water seal. Then, the sealing performance of the conversion tube opening is checked with a leak detection liquid to ensure that no bubbles are generated.

[0026] Preferably, the pressure during the conversion process in step (2) is controlled at 1.5-2.0 MPa, and the height of the phosphorus liquid surface from the condenser is 6 cm; the conversion process specifically includes the following sub-steps:

[0027] S2.1: Smoothly insert the conversion tube containing pretreated yellow phosphorus into the heating chamber of the conversion furnace, seal the furnace flange and connect the condensation system pipeline and the pressure control system pipeline;

[0028] S2.2: Fill the furnace with high-purity inert gas to a pressure of 0.1 MPa, then evacuate to -0.09 MPa. Repeat this replacement operation 3 times. Finally, use an oxygen content analyzer to detect the oxygen content in the furnace to ensure that the oxygen content is below 10 ppm.

[0029] S2.3: According to the linear charging formula described in claim 1, high-purity inert gas is charged into the furnace to the corresponding initial pressure, the condensation system is turned on and the cooling water parameters are adjusted to the set value;

[0030] S2.4: Adjust the height of the conversion tube by the electric lifting device at the bottom of the conversion furnace, and calibrate the vertical distance between the phosphorus liquid surface and the lower end of the condenser tube to 6cm using a laser rangefinder;

[0031] S2.5: During the conversion process, the reflux rate of phosphorus vapor is monitored in real time through a window. The reflux rate is controlled at 5-10 mL / min. If the reflux rate is lower than 5 mL, the cooling water temperature is reduced by 1℃. If it is higher than 10 mL, the cooling water temperature is increased by 1℃.

[0032] Preferably, in step (3), the first stage temperature is controlled at 285℃ for 60 hours; the second stage temperature is controlled at 320℃ for 20 hours; the heating control process specifically includes the following sub-steps:

[0033] S3.1: Start the heating device of the converter to preheat the entire furnace body at a rate of 3℃ / minute. After preheating to 100℃, switch to the precise heating mode of the charging area.

[0034] S3.2: After entering the first stage of constant temperature, check the temperature of each area of ​​the furnace, the pressure inside the furnace, the flow rate and temperature of the cooling water every 2 hours, record the operating data and check for abnormalities;

[0035] S3.3: 30 minutes before the end of the first stage of constant temperature, confirm that the pressure inside the furnace is stable at the set value and without fluctuation, and then heat up to the second stage temperature at the set heating rate.

[0036] S3.4: After entering the second stage of constant temperature, the intensity of the characteristic absorption peak of red phosphorus in the conversion tube is monitored online every hour by an external infrared spectrometer to calculate the real-time conversion rate;

[0037] S3.5: When the real-time conversion rate reaches 95% or more, continue to maintain the temperature for the set 20 hours. After the second stage of temperature maintenance is completed, immediately cut off the heating power and enter the natural cooling process.

[0038] Compared with the prior art, the beneficial effects of the present invention are:

[0039] (1) This invention solves the technical contradiction of existing single-stage heating processes that cannot simultaneously achieve crystal nucleation and crystal growth by using a two-stage segmented heating and temperature-pressure linear coupling control strategy. In the first stage, the temperature is kept constant for a long time at a temperature slightly higher than the initial temperature of yellow phosphorus conversion, combined with a pressure environment that increases linearly with temperature. This induces yellow phosphorus to undergo a slow crystal transformation in the liquid or near-liquid phase, forming a sufficient number of red phosphorus crystal nuclei that are uniform in size and densely arranged. In the second stage, the temperature is appropriately increased to promote the complete conversion reaction, while the abnormal growth of crystals and the loosening of the structure are avoided by shortening the isothermal time. Compared with the existing single-stage heating process, the density of the red phosphorus product prepared by this invention is increased from 2.15 g / cm³ to 2.30-2.33 g / cm³, the conversion rate is increased from 94.5% to 98.2%-98.8%, and the crystal quality is significantly improved.

[0040] (2) This invention effectively improves product purity and raw material utilization through the synergistic design of standardized pretreatment processes and a precise condensation reflux system. The low-temperature cooling of 15±3℃ in the pretreatment process creates a stable solid-phase interface on the surface of yellow phosphorus. Combined with directional purging of high-purity inert gas, residual moisture on the inner wall of the conversion tube and the surface of yellow phosphorus is thoroughly removed, preventing side reactions between moisture and yellow phosphorus at high temperatures that could generate impurities such as phosphorus oxides and phosphoric acid. The product purity consistently reaches over 99.9999%. The condensation system achieves a dynamic balance between the phosphorus vapor condensation rate and the reflux rate by precisely controlling the cooling water flow rate, temperature, and the distance between the phosphorus liquid surface and the condenser tube. This effectively recovers unreacted yellow phosphorus vapor and avoids the reflux liquid impact damaging the dense structure of red phosphorus crystals, increasing raw material utilization by more than 3% compared to existing processes.

[0041] (3) This invention adopts a moderate pressure range and a quantitative control system for all process parameters, which has good industrial applicability and batch stability. The pressure of the conversion process is controlled at 1.2-2MPa, which can effectively suppress the volatilization of yellow phosphorus and avoid the stringent requirements on equipment materials and sealing performance of the existing 5-10MPa high-pressure process, significantly reducing equipment investment and operating costs. All key process parameters are quantitatively controlled, including the conversion tube diameter-to-length ratio, PID pressure control parameters, three-stage segmented heating rate, condensation heat exchange area ratio, etc. At the same time, multi-point temperature calibration, online pressure compensation and infrared spectral conversion rate monitoring technology are introduced to ensure that the density, purity and conversion rate of different batches of products are controlled within ±1%, the process has strong repeatability and can be directly applied to industrial continuous production. Attached Figure Description

[0042] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are explained in detail together with the embodiments of the invention, but do not constitute a limitation thereof.

[0043] Figure 1 This is a schematic diagram of the high-density red phosphorus conversion process of the present invention;

[0044] Figure 2 This is a schematic diagram of the high-density red phosphorus conversion process of the present invention;

[0045] Figure 3 This is a flowchart illustrating the pretreatment process of the present invention.

[0046] Figure 4 This is a flowchart illustrating the heating control process of the present invention. Detailed Implementation

[0047] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0048] like Figures 1-4 As shown, the high-density red phosphorus conversion process of this invention achieves efficient preparation of high-density, high-purity red phosphorus through precise pretreatment steps, controllable pressure conversion conditions, a two-stage segmented heating strategy, and an optimized condensation reflux system. The linear pressurization formula used in this invention is:

[0049] in For temperature The corresponding pressure inside the converter furnace, in MPa. The value range is from 40℃ to the first stage constant temperature. This is the pressure coefficient, taken as the target first-stage pressure minus 0.01 MPa. This is the first stage of constant temperature.

[0050] The ratio of the inner diameter of the conversion tube to the effective loading length satisfies:

[0051] in This refers to the inner diameter of the conversion tube, in cm. The effective loading length of the conversion tube is in cm.

[0052] Pressure regulation uses a PID algorithm, and the control equation is:

[0053] in For the opening degree of the pressure regulating valve, The deviation between the pressure setpoint and the actual value. The value is 2.5. The value is 0.1. The value is 0.05.

[0054] Example 1

[0055] The specific steps for preparing high-density red phosphorus in this embodiment are as follows:

[0056] Pretreatment process: High-purity yellow phosphorus with a purity of 99.9999% was selected as the raw material, with a loading amount of 5 kg. The conversion tube was first pretreated by rinsing it three times with deionized water and twice with anhydrous ethanol, then drying it in a vacuum drying oven at 120℃ for 2 hours, and finally removing it after cooling to room temperature. High-purity quartz tubes were selected for the conversion tubes, and the tube dimensions were calculated based on the diameter-to-length ratio formula. Set the inner diameter of the conversion tube If the length is 8cm, then the effective loading length is... cm. The effective volume of the conversion tube is cm³. The loading volume is controlled at 65% of the effective volume, corresponding to a yellow phosphorus volume of... cm³, the density of yellow phosphorus is 1.82 g / cm³, corresponding to a mass of g, which is basically consistent with the set loading amount of 5kg.

[0057] During loading, the yellow phosphorus is completely melted in a constant temperature water bath at 45℃ to 50℃. The liquid yellow phosphorus is then slowly transferred into the conversion tube using a polytetrafluoroethylene (PTFE) siphon method, with a 1cm to 2cm layer of deionized water covering the surface of the phosphorus throughout the transfer process. After loading, deionized water is added to the conversion tube until the liquid level is 2cm to 3cm above the yellow phosphorus level to complete the water seal. Subsequently, a leak detection solution is used to check the sealing performance of the conversion tube opening to ensure no air bubbles are generated.

[0058] After loading, the conversion tube is placed in a cooling device, and the cooling temperature is controlled at 15℃ for 5 hours. The conversion tube is then removed, the surface water is poured off, and the surface is purged with high-purity nitrogen gas three times, each time for 2 minutes, with the gas flow rate controlled at 1 m / s. After drying the water, the tube is loaded into the conversion furnace.

[0059] Conversion process: The conversion tube containing pretreated yellow phosphorus is smoothly installed into the heating chamber of the conversion furnace. The furnace flange is sealed, and the condensation system pipeline and pressure control system pipeline are connected. High-purity nitrogen is introduced into the furnace to a pressure of 0.1 MPa, and then a vacuum is drawn to -0.09 MPa. This replacement operation is repeated 3 times. Finally, the oxygen content in the furnace is detected using an oxygen content analyzer to ensure that the oxygen content is below 10 ppm.

[0060] In this embodiment, the first stage constant temperature is 285℃, and the target pressure is 1.5MPa. Substituting these values ​​into the linear pressurization formula yields the pressure coefficient. The pressurization formula is: The initial temperature is 40℃. Substituting this into the formula, we get... High-purity nitrogen gas was introduced into the furnace at 0.01 MPa.

[0061] The condenser tubes are serpentine and installed vertically at a 7° angle. The lower end of the condenser tube is sealed to the top of the converter tube via a frosted interface. The ratio of the condenser tube heat exchange area to the charge weight is 0.1 m² / kg, therefore the heat exchange area is... m². Start the condensation system for pre-cooling for 20 minutes at a cooling water flow rate of 1 m³ / h. After pre-cooling, adjust the cooling water flow rate to 2 m³ / h and control the cooling water temperature at 25℃. The cooling water should flow from bottom to top. Adjust the height of the conversion tube using the electric lifting device at the bottom of the converter, and calibrate the vertical distance between the phosphorus liquid surface and the lower end of the condenser tube to 6 cm using a laser rangefinder.

[0062] During the conversion process, the pressure is regulated using a PID algorithm, with pressure fluctuations controlled within ±0.05 MPa. When a pressure deviation is detected... At MPa, substitute the values ​​into the PID control equation to calculate the valve opening adjustment. Assuming the instantaneous integral term is 0.01 and the derivative term is 0, then... This means the pressure regulating valve opening is increased by 5.1% until the pressure returns to the set value. Simultaneously, the reflux rate of phosphorus vapor is monitored in real-time via a viewing window, and the reflux rate is controlled between 5 mL / min and 10 mL / min. In this embodiment, the initial reflux rate is 7 mL / min, and after 30 hours of conversion, the reflux rate drops to 4 mL / min. At this point, the cooling water temperature is lowered by 1°C, and the reflux rate recovers to 6 mL / min, meeting the control requirements. The condenser outlet water temperature is monitored in real-time and controlled between 30°C and 35°C; in this embodiment, the outlet water temperature is stable at 32°C.

[0063] Heating control process: The heating device of the conversion furnace is started to preheat the entire furnace body at a rate of 3℃ / min. After preheating to 100℃, the process switches to the precise heating mode for the charging area. The first stage of the heating process adopts a three-stage segmented heating strategy: First, the temperature is increased from room temperature to 100℃ at a rate of 5℃ / min and held constant for 2 hours. During this period, a small amount of high-purity nitrogen is continuously introduced to expel any residual moisture in the furnace. Second, the temperature is increased from 100℃ to 200℃ at a rate of 2℃ / min. During the heating process, the pressure is synchronously charged according to the linear charging formula, and the pressure value is calibrated every 20℃ increase. When the temperature reaches 200℃, the linear charging formula is substituted to obtain... MPa, calibrate the furnace pressure to 0.98 MPa; the third step is to increase the temperature from 200℃ to 285℃ at a rate of 1℃ / min, calibrating the temperature sensor in the charging area every 10 minutes during the heating process to ensure that the temperature measurement deviation does not exceed ±2℃. When the temperature reaches 285℃, substituting into the linear pressurization formula yields... The pressure inside the furnace was calibrated to 1.5 MPa and kept at a constant temperature for 60 hours.

[0064] Thirty minutes before the end of the first stage of constant temperature control, the furnace pressure was confirmed to be stable at 1.5 MPa without fluctuation. Then, the temperature was uniformly increased to 320°C at a rate of 2°C / min, maintaining a constant pressure of 1.5 MPa throughout the heating process. The temperature at three points (top, middle, and bottom) in the charging area was monitored every 30 minutes during the heating process, with the temperature difference between the three points controlled within ±5°C. In this embodiment, the maximum temperature difference between the three points was 3°C, requiring no adjustment of the heating rate. Simultaneously, furnace pressure data was collected every 15 minutes. When the pressure fluctuation exceeded ±0.03 MPa, pressure compensation was performed by fine-tuning the opening of the air inlet valve, with the compensation amount not exceeding 0.01 MPa per instance.

[0065] After entering the second stage of temperature control, the intensity of the characteristic absorption peak of red phosphorus in the conversion tube is monitored online every hour using an external infrared spectrometer to calculate the real-time conversion rate. When the second stage of temperature control has been in progress for 15 hours, the intensity of the characteristic absorption peak of red phosphorus is detected to be 96% of the initial value, that is, the real-time conversion rate has reached 96%. The temperature control continues for 20 hours. After the second stage of temperature control ends, the heating power is immediately cut off and the tube enters the natural cooling process.

[0066] Cooling process: After conversion, heating is stopped, and the conversion tube is cooled to room temperature with the furnace before being removed, yielding a high-density red phosphorus product. Testing showed that the density of the obtained red phosphorus product was 2.32 g / cm³. 3 The conversion rate reached 98.5%, and the product purity reached over 99.9999%.

[0067] Example 2

[0068] The specific steps for preparing high-density red phosphorus in this embodiment are as follows:

[0069] Pretreatment process: High-purity yellow phosphorus with a purity of 99.9999% was selected as the raw material, with a loading amount of 10 kg. The conversion tube was first pretreated by rinsing it three times with deionized water and twice with anhydrous ethanol, then dried in a vacuum drying oven at 120℃ for 2 hours, and removed after cooling to room temperature. High-purity quartz tubes were selected for the conversion tubes, and the tube dimensions were calculated based on the diameter-to-length ratio formula. Set the inner diameter of the conversion tube If it is 10cm, then the effective loading length is... cm. The effective volume of the conversion tube is cm³. The loading amount is controlled at 60% of the effective volume, corresponding to a yellow phosphorus volume of... cm³, the density of yellow phosphorus is 1.82 g / cm³, corresponding to a mass of g, which is basically consistent with the set loading amount of 10kg.

[0070] During loading, the yellow phosphorus is completely melted in a constant temperature water bath at 45℃ to 50℃. The liquid yellow phosphorus is then slowly transferred into the conversion tube using a polytetrafluoroethylene (PTFE) siphon method, with a 1cm to 2cm layer of deionized water covering the surface of the phosphorus throughout the transfer process. After loading, deionized water is added to the conversion tube until the liquid level is 2cm to 3cm above the yellow phosphorus level to complete the water seal. Subsequently, a leak detection solution is used to check the sealing performance of the conversion tube opening to ensure no air bubbles are generated.

[0071] After loading, the conversion tube is placed in a cooling device, and the cooling temperature is controlled at 12℃ for 5 hours. The conversion tube is then removed, the water on the surface is poured off, and the surface is purged with high-purity argon gas three times, with each purging lasting 3 minutes and the purging gas flow rate controlled at 1.2 m / s. After drying the water, the tube is loaded into the conversion furnace.

[0072] Conversion process: The conversion tube containing pretreated yellow phosphorus is smoothly installed into the heating chamber of the conversion furnace. The furnace flange is sealed, and the condensation system pipeline and pressure control system pipeline are connected. High-purity argon gas is introduced into the furnace to a pressure of 0.1 MPa, and then a vacuum is drawn to -0.09 MPa. This replacement operation is repeated 3 times. Finally, the oxygen content in the furnace is detected using an oxygen content analyzer to ensure that the oxygen content is below 8 ppm.

[0073] In this embodiment, the first stage constant temperature is 280℃, and the target pressure is 1.7MPa. Substituting these values ​​into the linear pressurization formula yields the pressure coefficient. The pressurization formula is: The initial temperature is 40℃. Substituting this into the formula, we get... High-purity argon gas was introduced into the furnace at a pressure of MPa until it reached 0.01 MPa.

[0074] The condenser tubes are serpentine and installed vertically at an 8° angle. The lower end of the condenser tube is sealed to the top of the converter tube via a frosted interface. The ratio of the condenser tube heat exchange area to the charge weight is 0.09 m² / kg, therefore the heat exchange area is... m². Start the condensation system for pre-cooling for 25 minutes at a cooling water flow rate of 1 m³ / h. After pre-cooling, adjust the cooling water flow rate to 2 m³ / h and control the cooling water temperature at 25℃. The cooling water should flow from bottom to top. Adjust the height of the conversion tube using the electric lifting device at the bottom of the converter, and calibrate the vertical distance between the phosphorus liquid level and the lower end of the condenser tube to 5 cm using a laser rangefinder.

[0075] During the conversion process, the pressure is regulated using a PID algorithm, with pressure fluctuations controlled within ±0.05 MPa. When a pressure deviation is detected... At MPa, substitute the values ​​into the PID control equation to calculate the valve opening adjustment. Assuming the instantaneous integral term is 0.008 and the derivative term is 0, then... This means the pressure regulating valve opening is increased by 3.83% until the pressure returns to the set value. Simultaneously, the reflux rate of phosphorus vapor is monitored in real-time via a viewing window, and the reflux rate is controlled between 6 mL / min and 11 mL / min. In this embodiment, the initial reflux rate is 8 mL / min, and after 40 hours of conversion, the reflux rate rises to 12 mL / min. At this point, the cooling water temperature is increased by 1°C, and after adjustment, the reflux rate drops back to 9 mL / min, meeting the control requirements. The condenser outlet water temperature is monitored in real-time and controlled between 30°C and 35°C; in this embodiment, the outlet water temperature is stable at 33°C.

[0076] Heating control process: The heating device of the conversion furnace is started to preheat the entire furnace body at a rate of 3℃ / min. After preheating to 100℃, the process switches to the precise heating mode for the charging area. The first stage of the heating process adopts a three-stage segmented heating strategy: First, the temperature is increased from room temperature to 100℃ at a rate of 5℃ / min and held constant for 2 hours. During this period, a small amount of high-purity argon gas is continuously introduced to expel any residual moisture in the furnace. Second, the temperature is increased from 100℃ to 200℃ at a rate of 2℃ / min. During the heating process, the pressure is synchronously charged according to the linear charging formula, and the pressure value is calibrated every 20℃ increase. When the temperature reaches 200℃, the linear charging formula is substituted to obtain... MPa, calibrate the furnace pressure to 1.14 MPa; the third step is to increase the temperature from 200℃ to 280℃ at a rate of 1℃ / min, calibrating the temperature sensor in the charging area every 10 minutes during the heating process to ensure that the temperature measurement deviation does not exceed ±2℃. When the temperature reaches 280℃, substituting into the linear pressurization formula yields... The pressure inside the furnace was calibrated to 1.7 MPa and kept at a constant temperature for 65 hours.

[0077] Thirty minutes before the end of the first stage of constant temperature control, the furnace pressure was confirmed to be stable at 1.7 MPa without fluctuation. Then, the temperature was uniformly increased to 315℃ at a rate of 1.5℃ / min, maintaining a constant pressure of 1.7 MPa throughout the heating process. The temperature at three points (top, middle, and bottom) in the charging area was monitored every 30 minutes during the heating process, with the temperature difference between the three points controlled within ±5℃. In this embodiment, the maximum temperature difference between the three points was 4℃, requiring no adjustment of the heating rate. Simultaneously, furnace pressure data was collected every 15 minutes. When the pressure fluctuation exceeded ±0.03 MPa, pressure compensation was performed by fine-tuning the opening of the air inlet valve, with the compensation amount not exceeding 0.01 MPa per instance.

[0078] After entering the second stage of temperature control, the intensity of the characteristic absorption peak of red phosphorus in the conversion tube is monitored online every hour using an external infrared spectrometer to calculate the real-time conversion rate. When the second stage of temperature control has been in progress for 16 hours, the intensity of the characteristic absorption peak of red phosphorus is detected to be 95.5% of the initial value, meaning the real-time conversion rate has reached 95.5%. Temperature control continues for another 22 hours. After the second stage of temperature control ends, the heating power is immediately cut off, and the tube enters the natural cooling process.

[0079] Cooling process: After conversion, heating is stopped, and the conversion tube is cooled to room temperature with the furnace before being removed, yielding a high-density red phosphorus product. Testing showed that the density of the obtained red phosphorus product was 2.30 g / cm³, the conversion rate reached 98.2%, and the product purity exceeded 99.9999%.

[0080] Example 3

[0081] The specific steps for preparing high-density red phosphorus in this embodiment are as follows:

[0082] Pretreatment process: High-purity yellow phosphorus with a purity of 99.999% was selected as the raw material, with a loading amount of 800g. The conversion tube was first pretreated by rinsing it three times with deionized water and twice with anhydrous ethanol, then drying it in a vacuum drying oven at 120℃ for 2 hours, and finally removing it after cooling to room temperature. High-purity quartz tubes were selected for the conversion tubes, and the tube dimensions were calculated based on the diameter-to-length ratio formula. Set the inner diameter of the conversion tube If the length is 4cm, then the effective loading length is... cm. The effective volume of the conversion tube is cm³. The loading amount is controlled at 70% of the effective volume, corresponding to a yellow phosphorus volume of... cm³, the density of yellow phosphorus is 1.82 g / cm³, corresponding to a mass of g is exactly the same as the set loading amount.

[0083] During loading, the yellow phosphorus is completely melted in a constant temperature water bath at 45℃ to 50℃. The liquid yellow phosphorus is then slowly transferred into the conversion tube using a polytetrafluoroethylene (PTFE) siphon method, with a 1cm to 2cm layer of deionized water covering the surface of the phosphorus throughout the transfer process. After loading, deionized water is added to the conversion tube until the liquid level is 2cm to 3cm above the yellow phosphorus level to complete the water seal. Subsequently, a leak detection solution is used to check the sealing performance of the conversion tube opening to ensure no air bubbles are generated.

[0084] After loading, the conversion tube is placed in a cooling device, and the cooling temperature is controlled at 18℃ for 5 hours. The conversion tube is then removed, the surface water is poured off, and the surface is purged with high-purity nitrogen gas three times, each time for 2 minutes, with the purging gas flow rate controlled at 0.8 m / s. After drying the water, it is loaded into the conversion furnace.

[0085] Conversion process: The conversion tube containing pretreated yellow phosphorus is smoothly installed into the heating chamber of the conversion furnace. The furnace flange is sealed, and the condensation system pipeline and pressure control system pipeline are connected. High-purity nitrogen is introduced into the furnace to a pressure of 0.1 MPa, and then a vacuum is drawn to -0.09 MPa. This replacement operation is repeated 3 times. Finally, the oxygen content in the furnace is detected using an oxygen content analyzer to ensure that the oxygen content is below 10 ppm.

[0086] In this embodiment, the first stage constant temperature is 290℃, and the target pressure is 2.0MPa. Substituting these values ​​into the linear pressurization formula yields the pressure coefficient. The pressurization formula is: The initial temperature is 40℃. Substituting this into the formula, we get... High-purity nitrogen gas was introduced into the furnace at 0.01 MPa.

[0087] Spherical condenser tubes are selected and installed vertically at a 10° angle. The lower end of the condenser tube is sealed to the top of the converter tube via a frosted interface. The ratio of the condenser tube heat exchange area to the charge weight is taken as 0.12 m² / kg, therefore the heat exchange area is... m². Start the condensation system for pre-cooling for 15 minutes at a cooling water flow rate of 1 m³ / h. After pre-cooling, adjust the cooling water flow rate to 2 m³ / h and control the cooling water temperature at 25℃. The cooling water should flow from bottom to top. Adjust the height of the conversion tube using the electric lifting device at the bottom of the converter, and calibrate the vertical distance between the phosphorus liquid surface and the lower end of the condenser tube to 8 cm using a laser rangefinder.

[0088] During the conversion process, the pressure is regulated using a PID algorithm, with pressure fluctuations controlled within ±0.05 MPa. When a pressure deviation is detected... At MPa, substitute the values ​​into the PID control equation to calculate the valve opening adjustment. Assuming the instantaneous integral term is 0.005 and the derivative term is 0, then... This means the pressure regulating valve opening is increased by 2.55% until the pressure returns to the set value. Simultaneously, the reflux rate of phosphorus vapor is monitored in real-time via a viewing window, and the reflux rate is controlled between 5 mL / min and 9 mL / min. In this embodiment, the initial reflux rate is 6 mL / min, and the reflux rate remains stable within this range during the conversion process, requiring no adjustment of the cooling water temperature. The condenser outlet water temperature is monitored in real-time and controlled between 30°C and 35°C; in this embodiment, the outlet water temperature is stable at 31°C.

[0089] Heating control process: The heating device of the conversion furnace is started to preheat the entire furnace body at a rate of 3℃ / min. After preheating to 100℃, the process switches to the precise heating mode for the charging area. The first stage of the heating process adopts a three-stage segmented heating strategy: First, the temperature is increased from room temperature to 100℃ at a rate of 5℃ / min and held constant for 2 hours. During this period, a small amount of high-purity nitrogen is continuously introduced to expel any residual moisture in the furnace. Second, the temperature is increased from 100℃ to 200℃ at a rate of 2℃ / min. During the heating process, the pressure is synchronously charged according to the linear charging formula, and the pressure value is calibrated every 20℃ increase. When the temperature reaches 200℃, the linear charging formula is substituted to obtain... MPa, calibrate the furnace pressure to 1.28 MPa; the third step is to increase the temperature from 200℃ to 290℃ at a rate of 1℃ / min, calibrating the temperature sensor in the charging area every 10 minutes during the heating process to ensure that the temperature measurement deviation does not exceed ±2℃. When the temperature reaches 290℃, substituting into the linear pressurization formula yields... The pressure inside the furnace was calibrated to 2.0 MPa and kept at a constant temperature for 55 hours.

[0090] Thirty minutes before the end of the first stage of constant temperature control, the furnace pressure was confirmed to be stable at 2.0 MPa without fluctuation. Then, the temperature was uniformly increased to 325℃ at a rate of 3℃ / min, maintaining a constant pressure of 2.0 MPa throughout the heating process. The temperature at three points (top, middle, and bottom) in the charging area was monitored every 30 minutes during the heating process, with the temperature difference between the three points controlled within ±5℃. In this embodiment, the maximum temperature difference between the three points was 2℃, requiring no adjustment of the heating rate. Simultaneously, furnace pressure data was collected every 15 minutes. When the pressure fluctuation exceeded ±0.03 MPa, pressure compensation was performed by fine-tuning the opening of the air inlet valve, with the compensation amount not exceeding 0.01 MPa per instance.

[0091] After entering the second stage of temperature control, the intensity of the characteristic absorption peak of red phosphorus in the conversion tube is monitored online every hour using an external infrared spectrometer to calculate the real-time conversion rate. When the second stage of temperature control has been in progress for 14 hours, the intensity of the characteristic absorption peak of red phosphorus is detected to be 96.5% of the initial value, meaning the real-time conversion rate has reached 96.5%. Temperature control continues for another 18 hours. After the second stage of temperature control ends, the heating power is immediately cut off, and the tube enters the natural cooling process.

[0092] Cooling process: After conversion, heating is stopped, and the conversion tube is cooled to room temperature with the furnace before being removed, yielding a high-density red phosphorus product. Testing showed that the density of the obtained red phosphorus product was 2.33 g / cm³, the conversion rate reached 98.8%, and the product purity exceeded 99.9999%.

[0093] Comparative Example 1

[0094] This comparative example uses an existing single-stage heating process to prepare red phosphorus. Except for the heating control process, the other pretreatment, conversion and cooling processes are exactly the same as those in Example 1.

[0095] The heating control process is as follows: the heating device of the conversion furnace is started, and the temperature is uniformly increased to 300℃ at a heating rate of 1℃ / min. During the heating process, the pressure is linearly pressurized to 1.5MPa and maintained at a constant temperature for 80 hours. During the constant temperature process, the furnace body temperature, pressure and cooling water parameters are checked every 2 hours, and the temperature difference at three points in the charging area is checked every 4 hours, controlling the temperature difference to be within ±5℃.

[0096] After conversion, the red phosphorus product was cooled to room temperature in the furnace and then removed. Testing showed that the density of the obtained red phosphorus product was 2.15 g / cm³, the conversion rate was 94.5%, and the product purity was 99.999%.

[0097] The results of the above embodiments and comparative examples show that the two-stage segmented heating process adopted in this invention, combined with precise pressure control and a condensation reflux system, can significantly improve the density and conversion rate of red phosphorus products, while ensuring high product purity. The process parameters are stable and controllable, making it suitable for large-scale industrial production.

[0098] This invention solves the technical contradiction of existing single-stage heating processes, which cannot simultaneously achieve crystal nucleation and crystal growth, through a two-stage segmented heating and temperature-pressure linear coupling control strategy. In the first stage, a prolonged isothermal temperature slightly above the yellow phosphorus conversion initiation temperature, combined with a pressure environment that increases linearly with temperature, induces a slow crystal transformation of yellow phosphorus in the liquid or near-liquid phase, forming a sufficient number of uniformly sized and densely packed red phosphorus nuclei. In the second stage, the temperature is moderately increased to promote complete conversion, while shortening the isothermal time prevents abnormal grain growth and structural loosening. Compared to existing single-stage heating processes, the density of the red phosphorus product prepared by this invention increases from 2.15 g / cm³ to 2.30-2.33 g / cm³, the conversion rate increases from 94.5% to 98.2%-98.8%, and the crystal quality is significantly improved.

[0099] This invention effectively improves product purity and raw material utilization through the synergistic design of standardized pretreatment processes and a precise condensation reflux system. The low-temperature cooling of 15±3℃ in the pretreatment process creates a stable solid-phase interface on the surface of yellow phosphorus. Combined with directional purging of high-purity inert gas, residual moisture on the inner wall of the conversion tube and the surface of yellow phosphorus is thoroughly removed, preventing side reactions between moisture and yellow phosphorus at high temperatures that could generate impurities such as phosphorus oxides and phosphoric acid. The product purity consistently reaches over 99.9999%. The condensation system achieves a dynamic balance between the phosphorus vapor condensation rate and the reflux rate by precisely controlling the cooling water flow rate, temperature, and the distance between the phosphorus liquid surface and the condenser tube. This effectively recovers unreacted yellow phosphorus vapor while preventing the reflux liquid from impacting and damaging the dense structure of red phosphorus crystals, increasing raw material utilization by more than 3% compared to existing processes.

[0100] This invention employs a moderate pressure range and a quantitative control system for all process parameters, exhibiting excellent industrial applicability and batch stability. The conversion process pressure is controlled at 1.2-2 MPa, effectively suppressing yellow phosphorus volatilization while avoiding the stringent requirements on equipment materials and sealing performance imposed by existing 5-10 MPa high-pressure processes, significantly reducing equipment investment and operating costs. All key process parameters are quantitatively controlled, including the conversion tube diameter-to-length ratio, PID pressure control parameters, three-stage segmented heating rate, and condensation heat exchange area ratio. Simultaneously, multi-point temperature calibration, online pressure compensation, and infrared spectral conversion rate monitoring technologies are introduced to ensure that the density, purity, and conversion rate fluctuations of different batches of products are controlled within ±1%. The process exhibits strong repeatability and can be directly applied to continuous industrial production.

[0101] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for converting high-density red phosphorus, characterized in that, Includes the following steps: (1) Pretreatment process: High-purity yellow phosphorus is loaded into the conversion tube and the surface is sealed with water; the conversion tube after loading is cooled, the temperature is controlled at 15±3℃, and the cooling time is 5 hours; the conversion tube is taken out, the water on the surface is poured out, the surface is blown with high-purity inert gas, and after the water is dried, it is loaded into the conversion furnace. (2) Conversion process: In the conversion furnace, the pressure of the conversion process is controlled at 1.2-2MPa; the phosphorus vapor is condensed, the cooling water flow rate is 2 cubic meters / hour, the cooling water temperature is controlled at 25℃, and the height of the phosphorus liquid surface from the condenser tube is 5-8cm. (3) Heating control process: The temperature of the phosphorus solution in the charging zone of the converter is controlled in two stages: the temperature in the first stage is controlled at 285±5℃, and the pressure is linearly pressurized following the temperature during the heating process, satisfying the formula: ; in For temperature Unit: °C; corresponding pressure inside the converter, unit: MPa. The first stage of temperature control is 60±5 hours; the second stage of temperature control is 320±5℃, and the constant temperature time is 20±2 hours. (4) Cooling process: After the conversion is completed, the conversion tube is cooled to room temperature with the furnace and then taken out to obtain high-density red phosphorus product.

2. The conversion process for high-density red phosphorus according to claim 1, characterized in that, The high-purity inert gas mentioned in step (1) is selected from one or more of nitrogen, argon or helium. The number of purgings is not less than 3, the purging time is not less than 2 minutes each time, and the purging gas flow rate is controlled at 0.5-1.5m / s.

3. The conversion process for high-density red phosphorus according to claim 1, characterized in that, The conversion tube mentioned in step (1) is a high-purity quartz tube or a high-temperature resistant glass tube, and the ratio of the inner diameter to the length of the conversion tube satisfies the formula: ; in The inner diameter of the conversion tube is in cm. The effective loading length of the conversion tube is in cm.

4. The conversion process for high-density red phosphorus according to claim 1, characterized in that, The pressure during the conversion process in step (2) is regulated by introducing high-purity inert gas into the converter. The pressure fluctuation range is controlled within ±0.05 MPa. The pressure regulation adopts a PID algorithm, and its control equation is: ; in For the opening degree of the pressure regulating valve, The deviation between the pressure setpoint and the actual value. , , .

5. The conversion process for high-density red phosphorus according to claim 1, characterized in that, The condenser tube mentioned in step (2) is a serpentine condenser tube or a spherical condenser tube. The condenser tube is installed vertically with an installation angle of 5°-10°. The lower end of the condenser tube is sealed to the top of the conversion tube through a frosted interface. The condensation system is pre-cooled before starting, and the pre-cooling time is 15-30 minutes. The cooling water flow rate during pre-cooling is 1 cubic meter / hour. The ratio of the heat exchange area of ​​the condenser tube to the charge of the conversion tube is 0.08-0.12 m² / kg. The cooling water flows from bottom to top. The outlet water temperature of the condenser tube is monitored and controlled in real time at 30°C-35°C. When the outlet water temperature exceeds 35°C, the cooling water flow rate is automatically increased by 0.2 cubic meters / hour.

6. The conversion process for high-density red phosphorus according to claim 1, characterized in that, In step (3), the heating rate between the first and second stages is 0.5-3℃ / minute. During the heating process, the pressure is kept constant and the pressure value is equal to the pressure value at the end of the first stage of constant temperature. During the heating process, the temperature of the upper, middle and lower points of the charging area is detected every 30 minutes. The temperature difference between the three points is controlled within ±5℃. If the temperature difference exceeds 5℃, the heating rate is reduced by 0.5℃ / minute until the temperature difference returns to the allowable range. At the same time, the furnace pressure data is collected every 15 minutes. When the pressure fluctuation exceeds ±0.03MPa, the pressure is compensated by finely adjusting the opening of the air inlet valve. The compensation amount does not exceed 0.01MPa / time.

7. The conversion process for high-density red phosphorus according to claim 1, characterized in that, In step (3), the first stage of the heating process adopts a three-stage segmented heating strategy, and the specific sub-steps are as follows: S3.1.1: The temperature is increased from room temperature to 100°C at a rate of 5°C / min and kept constant for 2 hours. During this period, a small amount of high-purity inert gas is continuously introduced to remove the trace amount of moisture remaining in the furnace with the gas flow. S3.1.2: Increase the temperature from 100℃ to 200℃ at a rate of 2℃ / minute. During the heating process, pressurize synchronously according to the linear pressurization formula. The pressure value is calibrated every 20℃ increase. S3.1.3: Increase the temperature from 200℃ to 285±5℃ at a rate of 1℃ / minute. During the heating process, calibrate the temperature sensor in the loading area every 10 minutes to ensure that the temperature measurement deviation does not exceed ±2℃.

8. The conversion process for high-density red phosphorus according to claim 1, characterized in that, The purity of the high-purity yellow phosphorus mentioned in step (1) is not less than 99.9999%, and the loading amount is 60%-70% of the effective volume of the conversion tube. Before loading, the conversion tube is pretreated by rinsing it with deionized water 3 times and anhydrous ethanol 2 times in sequence, and then drying it in a vacuum drying oven at 120℃ for 2 hours. After cooling to room temperature, it is taken out. When loading, the yellow phosphorus is first placed in a constant temperature water bath at 45℃-50℃ to completely melt it. The liquid yellow phosphorus is slowly transferred into the conversion tube by the polytetrafluoroethylene siphon method. During the transfer process, the surface of the yellow phosphorus is always covered with 1-2cm of deionized water. After loading, deionized water is added to the conversion tube until the liquid level is 2-3cm higher than the yellow phosphorus liquid level to complete the water seal. Then, the sealing performance of the conversion tube opening is checked with leak detection liquid to ensure that no bubbles are generated.

9. The conversion process for high-density red phosphorus according to claim 1, characterized in that, The pressure control during the conversion process in step (2) is 1.5-2.0 MPa, and the height of the phosphorus liquid surface from the condenser is 6 cm; the conversion process specifically includes the following sub-steps: S2.1: Smoothly insert the conversion tube containing pretreated yellow phosphorus into the heating chamber of the conversion furnace, seal the furnace flange and connect the condensation system pipeline and the pressure control system pipeline; S2.2: Fill the furnace with high-purity inert gas to a pressure of 0.1 MPa, then evacuate to -0.09 MPa. Repeat this replacement operation 3 times. Finally, use an oxygen content analyzer to detect the oxygen content in the furnace to ensure that the oxygen content is below 10 ppm. S2.3: According to the linear charging formula described in claim 1, high-purity inert gas is charged into the furnace to the corresponding initial pressure, the condensation system is turned on and the cooling water parameters are adjusted to the set value; S2.4: Adjust the height of the conversion tube by the electric lifting device at the bottom of the conversion furnace, and calibrate the vertical distance between the phosphorus liquid surface and the lower end of the condenser tube to 6cm using a laser rangefinder; S2.5: During the conversion process, the reflux rate of phosphorus vapor is monitored in real time through a window. The reflux rate is controlled at 5-10 mL / min. If the reflux rate is lower than 5 mL, the cooling water temperature is reduced by 1℃. If it is higher than 10 mL, the cooling water temperature is increased by 1℃.

10. The conversion process of high-density red phosphorus according to claim 1, characterized in that, In step (3), the first stage temperature is controlled at 285℃ for 60 hours; the second stage temperature is controlled at 320℃ for 20 hours; the heating control process specifically includes the following sub-steps: S3.1: Start the heating device of the converter to preheat the entire furnace body at a rate of 3℃ / minute. After preheating to 100℃, switch to the precise heating mode of the charging area. S3.2: After entering the first stage of constant temperature, check the temperature of each area of ​​the furnace, the pressure inside the furnace, the flow rate and temperature of the cooling water every 2 hours, record the operating data and check for abnormalities; S3.3: 30 minutes before the end of the first stage of constant temperature, confirm that the pressure inside the furnace is stable at the set value and without fluctuation, and then heat up to the second stage temperature at the set heating rate. S3.4: After entering the second stage of constant temperature, the intensity of the characteristic absorption peak of red phosphorus in the conversion tube is monitored online every hour by an external infrared spectrometer to calculate the real-time conversion rate; S3.5: When the real-time conversion rate reaches 95% or more, continue to maintain the temperature for the set 20 hours. After the second stage of temperature maintenance is completed, immediately cut off the heating power and enter the natural cooling process.

Images