A method for producing high-purity red phosphorus

Abstract

This invention relates to a method for producing high-purity red phosphorus, comprising: placing high-purity white phosphorus in an inner high-purity quartz tube; after the high-purity white phosphorus cools and solidifies, inserting the inner high-purity quartz tube into an outer high-purity quartz tube; installing a stainless steel pipe joint at the opening of the outer high-purity quartz tube; inserting the sealed outer high-purity quartz tube into an infrared electric heater; inserting the infrared electric heater into a stainless steel sealed pressure vessel and installing a cap; sealing the stainless steel sealed pressure vessel; preheating and liquefying the high-purity white phosphorus under nitrogen protection and atmospheric pressure until all moisture in the high-purity white phosphorus evaporates; pressurizing the outer high-purity quartz tube and maintaining internal and external pressure balance, raising the temperature to 350℃-380℃; and when the temperature drops below 250℃, forcibly cooling and discharging the material from the stainless steel sealed pressure vessel. This invention employs nested inner and outer high-purity quartz tubes, with the material discharging from the inner high-purity quartz tube for easy removal of the red phosphorus; and filling both the inner and outer sides of the outer high-purity quartz tube with nitrogen to maintain pressure balance and ensure safety.

Description

Technical Field

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

[0002] High-purity red phosphorus can be used to synthesize semiconductor materials such as indium phosphide (InP), gallium phosphide (GaP), aluminum gallium arsenide phosphide (AlGaAsP), indium gallium arsenide phosphide (InGaAsP), and gallium arsenide phosphide (GaAsP). These materials have advantages such as high electron mobility, high frequency response, and low noise, and are key components of high-performance electronic and optoelectronic devices.

[0003] Currently, the methods for producing high-purity red phosphorus are basically the direct conversion of yellow phosphorus (white phosphorus) into red phosphorus. The conversion methods can be roughly divided into two types:

[0004] 1. High-pressure conversion: Patent CN101214935B discloses a "production process for electronic-grade red phosphorus". High-purity yellow phosphorus is transferred into a conversion pot. At 20℃~80℃, 1~2kg of inert gas is added; at 80℃~200℃, 2~4kg of inert gas is added; at 200℃~250℃, no inert gas is added; at 250℃~280℃, 1~2kg of inert gas is added; at 280℃~300℃, 1~2kg of inert gas is added; and the mixture is naturally cooled to room temperature to obtain a 99.9999% high-purity red phosphorus product. However, this method has high requirements for equipment, and the high-pressure conditions also pose safety risks.

[0005] 2. Atmospheric pressure conversion: In the latest atmospheric pressure yellow phosphorus to high-purity red phosphorus technology, patent number CN109081320A discloses "an apparatus and method for converting electronic grade high-purity yellow phosphorus to red phosphorus". The apparatus consists of a converter, a heater, a temperature controller, a condenser, and a tail gas water seal. The method is as follows: (1) Place high-purity yellow phosphorus in the converter, cover it with ultra-high purity water, and heat the converter until the water evaporates completely; (2) Continuously introduce warm water into the condenser to condense the yellow phosphorus vapor, while controlling the heater to slowly heat the converter to 350°C, and then control the temperature within 350°C to 370°C for 24 hours; (3) After the yellow phosphorus is completely converted to red phosphorus, stop heating, let it cool down naturally, and at the same time introduce inert gas into the converter. After cooling to room temperature, place the converter in pure water, break the converter, and obtain red phosphorus. This method involves losses during the reaction process, and the yield of high-purity red phosphorus is not high, around 92%. Under the same conversion efficiency, the reaction time is long or the conversion is incomplete, requiring post-treatment such as alkaline purification and washing to ensure quality. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a method for producing high-purity red phosphorus, which enables the mass production of high-purity red phosphorus of grades 6N (99.9999%) to 9N (99.999999%). This method can effectively stabilize the quality of red phosphorus products, maintain high yield requirements, reduce safety risks, is highly operable, has reliable systems, and relatively low costs.

[0007] The objective of this invention is achieved as follows:

[0008] A method for producing high-purity red phosphorus includes the following steps:

[0009] Step 1: Place the high-purity white phosphorus in the inner high-purity quartz tube and cover it with high-purity water. After the high-purity white phosphorus cools and solidifies, insert the inner high-purity quartz tube into the outer high-purity quartz tube. Install a stainless steel pipe joint at the opening of the outer high-purity quartz tube. Insert the sealed outer high-purity quartz tube into the infrared electric heater. After inserting the infrared electric heater into the stainless steel sealed pressure vessel, install the end cap. Seal the stainless steel sealed pressure vessel.

[0010] Step 2: Use a vacuum system and a nitrogen system to evacuate and inject nitrogen into the outer high-purity quartz tube to completely replace the air inside the outer high-purity quartz tube. Then turn on the infrared electric heater to preheat the high-purity white phosphorus inside the inner high-purity quartz tube to liquefy the high-purity white phosphorus. During this process, nitrogen is added to keep the pressure inside the inner quartz tube at atmospheric pressure.

[0011] Step 3: Continue to slowly raise the temperature to 120℃-150℃, and vacuum process again until the moisture in the high-purity white phosphorus is completely evaporated;

[0012] After slowly increasing the pressure of nitrogen gas in the outer high-purity quartz tube to 0.2MPa-0.5MPa, close the nitrogen valve. While increasing the pressure in the outer high-purity quartz tube, simultaneously introduce nitrogen gas through the nitrogen gas filling and releasing port of the stainless steel sealed pressure vessel to maintain the positive pressure difference between the inside and outside of the outer high-purity quartz tube at 0.05MPa-0.10MPa. Then continue to slowly increase the temperature in stages until it reaches 350℃-380℃.

[0013] Step 4: After the heating is completed, allow it to cool naturally for a period of time. Once the temperature drops below 250℃, begin forced cooling and discharge of the stainless steel sealed pressure vessel.

[0014] Preferably, in step one, some high-purity hot water is first added to the inner high-purity quartz tube through the feeding system to one-third of its volume, and the temperature of the high-purity hot water is controlled at 60℃-80℃. Then, the through hole of the inner high-purity quartz tube is inserted into the feeding tube to the level below the high-purity hot water, and the metered liquid high-purity white phosphorus is injected. Then, the inner high-purity quartz tube with added white phosphorus is placed in water at 20℃ to cool and solidify the white phosphorus.

[0015] Preferably, in step two, after preheating to 80℃-90℃, the heating is stopped, and then the vacuum pump is started to perform a vacuuming operation. The vacuum level can be controlled at 200 mmHg-400 mmHg to gradually evaporate the moisture on the surface of the white phosphorus.

[0016] Preferably, in step three, the temperature continues to rise to the range of 350℃-380℃ after the white phosphorus moisture has completely evaporated, for a period of 40 hours, during which heating is paused twice.

[0017] Preferably, in step four, the circulating water pump is started, and circulating water enters and exits the jacket of the stainless steel sealed pressure vessel for cooling. As the temperature decreases, the pressure difference between the inside and outside of the outer high-purity quartz tube will change. At this time, the nitrogen gas is automatically released or replenished by the coordinated action of two automatic control regulating valves, so that the pressure difference between the inside and outside of the quartz tube can always be controlled within 0.1 MPa.

[0018] Preferably, in step one, the stainless steel pipe joint extends out of the end cap of the stainless steel sealed pressure vessel and is connected to the nitrogen system and the vacuum system respectively. The stainless steel sealed pressure vessel is also provided with a nitrogen charging / discharging port, which is connected to the nitrogen system.

[0019] Preferably, the nitrogen system includes a nitrogen buffer tank and a nitrogen cylinder, the vacuum system includes a vacuum buffer tank and a vacuum pump, the nitrogen cylinder is connected to the nitrogen buffer tank, the nitrogen buffer tank is connected to a nitrogen filling / discharging port and a stainless steel pipe joint via pipelines, the stainless steel pipe joint is also connected in parallel to the vacuum buffer tank, the vacuum buffer tank is connected to an exhaust buffer tank via the vacuum pump, the exhaust buffer tank is provided with an exhaust port and a nitrogen replenishment port, and the nitrogen replenishment port is connected to the nitrogen buffer tank.

[0020] Preferably, the lead wire of the infrared electric heater extends out of the stainless steel sealed pressure vessel and is sealed and insulated by the lead wire sealing and heat insulation assembly.

[0021] The beneficial effects of this invention are:

[0022] 1. It can achieve the conversion of white phosphorus under relatively high pressure. At the same time, by controlling the charging and discharging of nitrogen through the internal and external pressure difference, it can balance and control the heated quartz tube and its connection seal at a high temperature of 350℃, thereby reducing the risk of leakage due to high internal pressure.

[0023] 2. By adding sufficient nitrogen pressure to the outer high-purity quartz tube, the boiling point of white phosphorus can be increased, preventing it from volatilizing and producing white phosphorus vapor at the original boiling point of 280℃. This causes the gaseous white phosphorus to overflow from the inner high-purity quartz tube and enter the outer high-purity quartz tube for conversion, reducing the need to clean the red phosphorus in the outer high-purity quartz tube and increasing the total yield of finished red phosphorus.

[0024] 3. Installing a stainless steel sealed pressure vessel outside the infrared electric heater can prevent the safety risk of white phosphorus liquid or gas leakage caused by the quartz tube aging and cracking due to thermal expansion and contraction.

[0025] 4. It adopts infrared heating, which provides precise temperature control. It can heat without the conventional conduction method of material contact. The characteristic of infrared heating is that it is mainly radiative heat transfer, accounting for about 90%. By mainly using radiative heat transfer, heat is conducted to the inner high-purity quartz tube, which makes the design of inner and outer high-purity quartz tubes possible. When discharging, only the low-cost inner high-purity quartz tube needs to be crushed, while the high-cost outer high-purity quartz tube can be reused, which greatly reduces the equipment cost.

[0026] 5. The lead wire of the infrared electric heater extends out of the stainless steel sealed pressure vessel and is sealed and insulated by the lead wire sealing and insulation component to ensure the sealing and safety of the vessel. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of a high-purity red phosphorus production device according to the present invention.

[0028] Figure 2 This is a schematic diagram of the assembly structure of the stainless steel sealed pressure vessel of the present invention.

[0029] Figure 3 A schematic diagram of the assembly structure of the wire sealing and heat insulation component.

[0030] Figure 4 This is a flowchart of the production process of the present invention.

[0031] The components include: a stainless steel sealed pressure vessel 1; a nitrogen filling / discharging port 1.1; a head 1.2; an infrared electric heater 2; an outer high-purity quartz tube 3; an inner high-purity quartz tube 4; a through hole 4.1; a stainless steel pipe joint 5; a nitrogen buffer tank 6; a nitrogen cylinder 7; a vacuum buffer tank 8; a vacuum pump 9; an exhaust buffer tank 10; a wire sealing and heat insulation assembly 11; an air-cooled connector 11.1; a stainless steel sheath 11.2; a stainless steel thin tube 11.3; a ceramic tube 11.4; high-temperature resin 11.5; a cable external interface plug 11.6; a cooling water tank 12; a circulating water pump 13; and a fixed base 14. Detailed Implementation

[0032] See Figure 1-4This invention relates to a production apparatus for high-purity red phosphorus, comprising a stainless steel sealed pressure vessel 1, an infrared electric heater 2, an outer high-purity quartz tube 3, an inner high-purity quartz tube 4, a nitrogen system, a vacuum system, and a circulating water system. The stainless steel sealed pressure vessel 1 houses the infrared electric heater 2, which contains the outer high-purity quartz tube 3. The outer high-purity quartz tube 3 contains the inner high-purity quartz tube 4. The infrared electric heater 2, outer high-purity quartz tube 3, and inner high-purity quartz tube 4 are concentrically arranged. The inner high-purity quartz tube 4 is cylindrical, with both ends closed. Two through holes 4.1 are provided on its circumferential surface. These through holes serve two functions: firstly, they allow air to pass through and balance the pressure; secondly, they allow high-purity white phosphorus and high-purity water to enter the inner high-purity quartz tube 4. The inner high-purity quartz tube 4 has a wall thickness of 2-6 mm and is not pressure-bearing.

[0033] The outer high-purity quartz tube 3 is cylindrical, with a wall thickness of 6 mm to 20 mm. It needs to withstand pressure, has high cost, and can be reused multiple times. One end of the outer high-purity quartz tube 3 is closed, and the other end has an opening for the inner high-purity quartz tube 4 to enter. The opening is sealed and connected to a stainless steel pipe joint 5. The stainless steel pipe joint 5 extends out of the end cap 1.2 of the stainless steel sealed pressure vessel 1 and is connected to the nitrogen system and the vacuum system respectively. The gap between the stainless steel pipe joint 5 and the stainless steel sealed pressure vessel 1 is sealed.

[0034] The stainless steel sealed pressure vessel 1 is also provided with a nitrogen filling / discharging port 1.1, which is connected to a nitrogen system.

[0035] The nitrogen system includes a nitrogen buffer tank 6 and a nitrogen cylinder 7. The vacuum system includes a vacuum buffer tank 8, a vacuum pump 9, and an exhaust buffer tank 10. The nitrogen cylinder 7 is connected to the nitrogen buffer tank 6. The nitrogen buffer tank 6 is connected to a nitrogen filling / discharging port 1.1 and a stainless steel pipe connector 5 via pipelines. The stainless steel pipe connector 5 is also connected in parallel to the vacuum buffer tank 8. The vacuum buffer tank 8 is used to collect condensed water vapor. The vacuum buffer tank 8 is connected to the exhaust buffer tank 10 via the vacuum pump 9. The exhaust buffer tank 10 is provided with an exhaust port and a nitrogen replenishment port. The nitrogen replenishment port is connected to the nitrogen buffer tank 6. The nitrogen buffer tank 6 continuously releases nitrogen into the exhaust buffer tank 10 to ensure sufficient nitrogen in the exhaust buffer tank and prevent the danger of air backflow caused by abnormal stoppage or operation of the vacuum pump.

[0036] The lead wire of the infrared electric heater 2 extends out of the stainless steel sealed pressure vessel 1 and is sealed and insulated by the lead wire sealing and heat insulation assembly 11. The lead wire sealing and heat insulation assembly 11 includes an air-cooled connector 11.1, a stainless steel sheath 11.2, and stainless steel thin tubes 11.3. The stainless steel sealed pressure vessel 1 has a flange corresponding to the lead wire of the infrared electric heater 2. The air-cooled connector 11.1 is sealed to the flange of the stainless steel sealed pressure vessel 1. The air-cooled connector 11.1 is connected to the stainless steel sheath 11.2. The stainless steel sheath 11.2 contains three stainless steel thin tubes 11.3. One end of the stainless steel thin tube 11.3 is welded to the air-cooled connector 11.1, and the other end is fixed by casting with high-temperature resin 11.5. A ceramic tube 11.4 is installed inside the steel tube 11.3, and a wire is installed inside the ceramic tube 11.4. The ceramic tube 11.4, which carries the wire, isolates the wire from contact with the stainless steel sheath and the stainless steel tube, thus preventing the wire from contacting the stainless steel and causing a short circuit that could lead to danger. The wire is connected to the cable external interface plug 11.6 through the ceramic tube 11.4. The three wires in the cable external interface plug 11.6 are combined into one wire and then connected to an external power source. A water-cooled cavity is formed between the high-temperature resin 11.5 inside the stainless steel sheath 11.2 and the air-cooled connector 11.1. The water-cooled cavity is equipped with circulating cooling water. Water cooling prevents the high-temperature gas and heat generated inside the stainless steel sealed pressure vessel from being conducted to one end of the high-temperature resin, effectively preventing thermal damage to the high-temperature resin and sealing failure.

[0037] The stainless steel sealed pressure vessel 1 is equipped with a cooling jacket containing circulating water to facilitate cooling after the high-purity white phosphorus conversion is completed.

[0038] The circulating water system simultaneously cools the wire sealing and insulation assembly 11 and the stainless steel sealing pressure vessel. The circulating water system includes a cooling water tank 12 and a circulating water pump 13. The circulating water in the cooling water tank 12 is pumped by the circulating water pump 13 to the jacket of the stainless steel sealing pressure vessel 1 and the water cooling cavity of the wire sealing and insulation assembly 11, respectively, and then flows back into the cooling water tank 12 after heat exchange.

[0039] The stainless steel sealed pressure vessel 1 is cylindrical and placed horizontally, and a fixed base 14 is provided at the bottom of the stainless steel sealed pressure vessel 1.

[0040] The infrared electric heater 2 mainly utilizes radiation heat transfer to conduct heat to the inner high-purity quartz tube, making the design of inner and outer high-layer quartz tubes possible. The infrared electric heater is equipped with a temperature controller, which can accurately control the temperature rise and precisely control the white phosphorus conversion temperature. The temperature rise range and temperature rise rate or staged temperature rise can be freely adjusted and set.

[0041] A method for producing high-purity red phosphorus includes the following steps:

[0042] Step 1: Place the measured high-purity white phosphorus with a purity of 6N-9N into the inner high-purity quartz tube 4. For safe operation, cover the high-purity white phosphorus with high-purity water. The high-purity water and high-purity white phosphorus enter through the through hole 4.1 with the through hole facing upward.

[0043] The inner high-purity quartz tube is first filled with high-purity hot water to one-third of its volume using a feeding system, with the temperature of the high-purity hot water controlled between 60℃ and 80℃. Then, the through hole of the inner high-purity quartz tube is inserted into the feeding pipe until it is below the surface of the high-purity hot water, and metered liquid high-purity white phosphorus is injected. The inner high-purity quartz tube containing white phosphorus is then placed in water at 20℃ to cool and solidify the white phosphorus. After the liquid white phosphorus has solidified, the inner high-purity quartz tube is inserted into the outer high-purity quartz tube. A stainless steel pipe joint is installed in the outer high-purity quartz tube, and the outer high-purity quartz tube is simultaneously inserted into the infrared electric heater. The infrared electric heater is then inserted into a stainless steel sealed pressure vessel and the end cap is installed.

[0044] Step 2: Using a vacuum system and a nitrogen system, evacuate and inject nitrogen into the outer high-purity quartz tube. Replace the air in the outer high-purity quartz tube with nitrogen in 3-4 stages to reduce the oxygen content in the outer high-purity quartz tube to below 100 ppm. Start the infrared electric heater to preheat the high-purity white phosphorus in the inner high-purity quartz tube, slowly increasing the temperature (20℃ / hour) to 80℃-90℃ and then stopping the heating to liquefy the high-purity white phosphorus. Then start the vacuum pump to perform a vacuuming operation, and the vacuum degree can be controlled at 200 mmHg-400 mmHg. Gradually evaporate all the moisture on the surface of the white phosphorus until the vacuum degree rises to above 730 mmHg. Then replenish nitrogen to bring the pressure inside the inner quartz tube to atmospheric pressure.

[0045] Step 3: Continue to slowly increase the temperature (30℃ / hour) to 120℃-150℃, and then perform vacuum treatment again until the vacuum degree reaches above 730 mmHg. Maintain this for about 15 minutes, then add nitrogen, and vacuum again and replace with nitrogen two to three times. After replacement, slowly pressurize the outer high-purity quartz tube with nitrogen to 0.2MPa-0.5MPa and then close the nitrogen valve. While pressurizing the outer high-purity quartz tube, simultaneously introduce nitrogen through the nitrogen filling and discharging port 1.1 of the stainless steel sealed pressure vessel 1 to maintain the positive pressure difference between the inside and outside of the outer high-purity quartz tube at 0.05MPa-0.10MPa. Then continue to slowly increase the temperature in stages until it reaches 350℃-380℃.

[0046] By regulating the internal and external pressures, an operating pressure of at least 0.2MPa-0.5MPa is maintained in the inner high-purity quartz tube to increase the boiling point of white phosphorus, reduce the amount of white phosphorus volatilized from the inner high-purity quartz tube 4 and deposited on the inner wall of the outer high-purity quartz tube 3, and reduce the need for cleaning the broken red phosphorus formed on the inner wall of the outer high-purity quartz tube later and the reduction in the amount of red phosphorus in the finished product.

[0047] The temperature is initially raised from around 150℃ to the range of 350℃-380℃ over approximately 40 hours, with two pauses during this period. Specifically, the heating rate is controlled at 2℃ to 3℃ per hour. When the temperature reaches 265℃, heating is paused. At this point, the white phosphorus in the inner quartz tube will automatically heat up for a period of time as it converts to red phosphorus. After the automatic temperature rise ends, wait for the temperature to stabilize for 20 minutes before slowly raising the temperature to 285℃. Heating is then paused again and maintained for 20 minutes to observe whether the temperature rise continues. Once the temperature stabilizes, infrared heating is resumed, with the heating rate controlled at 2℃ per hour, until the temperature reaches 330℃ and is maintained for 2 hours. Then, the temperature is raised to 350℃ and maintained for 3 hours.

[0048] Step 4: After the heating is completed, allow it to cool naturally for about 5 hours until the temperature drops below 250℃. Then, begin forced cooling and discharge of the stainless steel sealed pressure vessel.

[0049] The circulating water pump is started, and circulating water enters and exits the jacket of the stainless steel sealed pressure vessel for cooling. As the temperature drops, the pressure difference between the inside and outside of the outer high-purity quartz tube changes. At this time, the two automatic control regulating valves work together to automatically release or replenish nitrogen, so that the pressure difference between the inside and outside of the quartz tube can always be controlled within 0.1 MPa. After the system temperature drops to room temperature, the stainless steel sealed pressure vessel is opened, and the outer and inner high-purity quartz tubes are simultaneously removed and placed underwater in a high-purity water container to isolate them from air. The inner high-purity quartz tube 4 is broken underwater to obtain blocky high-purity red phosphorus. The blocky high-purity red phosphorus is cut into small particles with a special tool, and then placed in a vacuum drying oven with nitrogen protection at a temperature above 80°C for drying. After drying, the high-purity red phosphorus is weighed and packaged in a clean brown glass container or special bottle filled with nitrogen protection for storage. After passing the test, it can be sold. Example 1

[0050] A method for producing high-purity red phosphorus includes the following steps:

[0051] (1) Place 6 kg of high-purity yellow phosphorus with a purity of 6N-9N in the inner high-purity quartz tube, cover it with ultra-high purity water, and install the inner high-purity quartz tube containing solid white phosphorus after cooling and solidification in the outer high-purity quartz tube. Seal all pipelines and after the system pressure test and leak test are normal, turn on the vacuum pump and connect the outer high-purity quartz tube to evacuate the vacuum four times. At the same time, replace it with high-purity nitrogen four times to reduce the air in the outer high-purity quartz tube to less than 100 ppm. Then replenish nitrogen to normal pressure, turn on the infrared heater to heat the temperature in the outer high-purity quartz tube to 85°C and then stop heating. Then turn on the vacuum pump to evacuate the air until the water on the top of the white phosphorus in the outer high-purity quartz tube is completely evaporated and the vacuum degree rises until it no longer rises.

[0052] (2) Add nitrogen to the inside of the quartz tube to maintain normal pressure, continue to turn on the infrared heater to slowly raise the temperature of the white phosphorus in the quartz tube to 130°C, and start the vacuum pump again to completely evaporate any bound water or water vapor that may exist in the system and at the bottom of the white phosphorus.

[0053] (3) Introduce high-purity nitrogen again and pressurize it to 0.3MPa. At the same time, supplement the pressure of the outer layer of the outer quartz tube with nitrogen to offset the internal pressure, so as to balance and control the pressure difference between the inner and outer layers of the outer quartz tube to keep it at a relatively low pressure difference. The pressure difference control method can be switched to automatic control.

[0054] (4) After nitrogen purging is completed, continue to turn on the temperature control system to raise the temperature at a rate of 8°C per hour. When the temperature reaches 265°C, stop raising the temperature. At this time, the white phosphorus in the inner quartz tube will automatically rise for a period of time due to the conversion to red phosphorus. After the automatic temperature rise ends, continue to slowly raise the temperature to 290°C at a rate of 8°C per hour. Stop heating and maintain the temperature for 30 minutes to observe whether the temperature rise continues. After the temperature stabilizes, turn on the infrared heating gas to raise the temperature at a rate of 5°C per hour until the temperature reaches 330°C and is maintained for 2 hours. Then raise the temperature to 350°C and maintain it for 2 hours. Then stop heating and allow the temperature to cool down naturally for about 3 hours before starting to cool down and discharge the material.

[0055] (5) When cooling down, start the water pump when the temperature inside the jacket is below 250°C and control the jacket to slowly fill with water to prevent the jacket from cooling down rapidly and causing uneven stress on the shell. The cooling water tank should be replenished with fresh cooling water as appropriate. After cooling to room temperature, the container can be opened, the quartz tube can be disassembled, the inner high-purity quartz tube containing red phosphorus can be taken out and placed in high-purity water for further cooling. Then, the quartz tube can be broken, the red phosphorus can be taken out, and the red phosphorus can be cut into small particles underwater with a special tool. The particles can be placed in a vacuum drying system to dry, and then weighed and packaged into a brown clean glass container with nitrogen protection for storage, resulting in 5.95 kg of high-purity red phosphorus.

[0056] After the product was sampled and processed, it was tested by a professional testing agency. The results of the impurity content analysis are shown in Table 1.

[0057] Table 1. Detection and analysis results of impurity content in Example 1 (unit: ppb, ND indicates not detected).

[0058]

[0059] It is evident that the product quality obtained by the method of this invention fully meets the quality requirements of red phosphorus needed for compound semiconductors such as indium phosphide (InP) and gallium phosphide (GaP). Example 2

[0060] A method for producing high-purity red phosphorus includes the following steps:

[0061] (1) Place 8 kg of high-purity yellow phosphorus with a purity of 6N-9N in the inner high-purity quartz tube, cover it with ultra-high purity water, and install the inner high-purity quartz tube containing solid white phosphorus after cooling and solidification in the outer high-purity quartz tube. Seal and connect all pipelines. After the system pressure test and leak test are normal, turn on the vacuum pump and connect the outer high-purity quartz tube to evacuate the vacuum four times. At the same time, replace it with high-purity nitrogen four times to reduce the air in the outer high-purity quartz tube to less than 100 ppm. Then replenish nitrogen to normal pressure, turn on the infrared heater to heat the temperature in the outer high-purity quartz tube to 90℃ and then stop heating. Then turn on the vacuum pump to evacuate the air until the water on the top of the white phosphorus in the outer high-purity quartz tube is completely evaporated and the vacuum degree rises until it no longer rises.

[0062] (2) Add nitrogen to the inside of the quartz tube to maintain normal pressure, continue to turn on the infrared heater to slowly raise the temperature of the white phosphorus in the quartz tube to 150°C, and start the vacuum pump again to completely evaporate any bound water or water vapor that may exist in the system and at the bottom of the white phosphorus.

[0063] (3) Introduce high-purity nitrogen again and pressurize it to 0.3MPa. At the same time, supplement the pressure of the outer layer of the outer quartz tube with nitrogen to offset the internal pressure, so as to balance and control the pressure difference between the inner and outer layers of the outer quartz tube to keep it at a relatively low pressure difference. The pressure difference control method can be switched to automatic control.

[0064] (4) After nitrogen purging is completed, continue to turn on the temperature control system to raise the temperature at a rate of 9°C per hour. When the temperature reaches 265°C, stop raising the temperature. At this time, the white phosphorus in the inner quartz tube will automatically rise for a period of time due to the conversion to red phosphorus. After the automatic temperature rise ends, continue to slowly raise the temperature to 290°C at a rate of 9°C per hour. Stop heating and maintain the temperature for 30 minutes to observe whether the temperature rise continues. After the temperature stabilizes, turn on the infrared heating gas to raise the temperature at a rate of 6°C per hour until the temperature reaches 330°C and is maintained for 2 hours. Then raise the temperature to 350°C and maintain it for 1 hour. Then stop heating and allow the temperature to cool naturally for about 3 hours before starting to cool down and discharge the material.

[0065] (5) When cooling down, start the water pump when the temperature inside the jacket is below 250°C and control the jacket to slowly fill with water to prevent the jacket from cooling down rapidly and causing uneven stress on the shell. The cooling water tank should be replenished with fresh cooling water as appropriate. After cooling to room temperature, the container can be opened, the quartz tube can be disassembled, the inner high-purity quartz tube containing red phosphorus can be taken out and placed in high-purity water for further cooling. Then, the quartz tube can be broken, the red phosphorus can be taken out, and the red phosphorus can be cut into small particles underwater with a special tool. The particles can be placed in a vacuum drying system to dry, and then weighed and packaged into a brown clean glass container with nitrogen protection for storage, resulting in 7.9 kg of high-purity red phosphorus.

[0066] After the product was sampled and processed, it was tested by a professional testing agency. The results of the impurity content analysis are shown in Table 2.

[0067] Table 2. Detection and analysis results of impurity content in Example 2 (unit: ppb, ND indicates not detected).

[0068]

[0069] It is evident that the product quality obtained by the method of this invention fully meets the quality requirements of red phosphorus needed for compound semiconductors such as indium phosphide (InP) and gallium phosphide (GaP). Example 3

[0070] A method for producing high-purity red phosphorus includes the following steps:

[0071] (1) Place 10 kg of high-purity yellow phosphorus with a purity of 6N-9N in the inner high-purity quartz tube, cover it with ultra-high purity water, and install the inner high-purity quartz tube containing solid white phosphorus after cooling and solidification in the outer high-purity quartz tube. Seal all pipelines and after the system pressure test and leak test are normal, turn on the vacuum pump and connect the outer high-purity quartz tube to evacuate the vacuum four times. At the same time, replace it with high-purity nitrogen four times to reduce the air in the outer high-purity quartz tube to less than 100 ppm. Then replenish nitrogen to normal pressure, turn on the infrared heater to heat the temperature in the outer high-purity quartz tube to 86℃ and then stop heating. Then turn on the vacuum pump to evacuate the air until the water on the top of the white phosphorus in the outer high-purity quartz tube is completely evaporated and the vacuum degree rises until it no longer rises.

[0072] (2) Add nitrogen to the inside of the quartz tube to maintain normal pressure, continue to turn on the infrared heater to slowly raise the temperature of the white phosphorus in the quartz tube to 145°C, and start the vacuum pump again to completely evaporate any bound water or water vapor that may exist in the system and at the bottom of the white phosphorus.

[0073] (3) Introduce high-purity nitrogen again and pressurize it to 0.3MPa. At the same time, supplement the pressure of the outer layer of the outer quartz tube with nitrogen to offset the internal pressure, so as to balance and control the pressure difference between the inner and outer layers of the outer quartz tube to keep it at a relatively low pressure difference. The pressure difference control method can be switched to automatic control.

[0074] (4) After nitrogen purging is completed, continue to turn on the temperature control system to raise the temperature at a rate of 10°C per hour. When the temperature reaches 270°C, stop raising the temperature. At this time, the white phosphorus in the inner quartz tube will automatically rise for a period of time due to the conversion to red phosphorus. After the automatic temperature rise ends, continue to slowly raise the temperature to 295°C at a rate of 10°C per hour. Stop heating and maintain the temperature for 30 minutes to observe whether the temperature rise continues. After the temperature stabilizes, turn on the infrared heating gas to raise the temperature at a rate of 8°C per hour until the temperature reaches 330°C and is maintained for 3 hours. Then raise the temperature to 350°C and maintain it for 1 hour. Then stop heating and allow the temperature to cool down naturally for about 2.5 hours before starting to cool down and discharge the material.

[0075] (5) When cooling down, start the water pump when the temperature inside the jacket is below 250°C and control the jacket to slowly fill with water to prevent the jacket from cooling down rapidly and causing uneven stress on the shell. The cooling water tank should be replenished with fresh cooling water as appropriate. After cooling to room temperature, the container can be opened, the quartz tube can be disassembled, the inner high-purity quartz tube containing red phosphorus can be taken out and placed in high-purity water for further cooling. Then, the quartz tube can be broken, the red phosphorus can be taken out, and the red phosphorus can be cut into small particles underwater with a special tool. The particles can be placed in a vacuum drying system to dry, and then weighed and packaged into a brown clean glass container with nitrogen protection for storage, resulting in 9.85 kg of high-purity red phosphorus.

[0076] After the product samples were processed, they were tested by a professional testing agency. The results of the impurity content analysis are shown in Table 3.

[0077] Table 3. Detection and analysis results of impurity content in Example 3 (unit: ppb, ND indicates not detected).

[0078]

[0079] It is evident that the product quality obtained by the method of this invention fully meets the quality requirements of red phosphorus needed for compound semiconductors such as indium phosphide (InP) and gallium phosphide (GaP).

[0080] In addition to the above embodiments, the present invention also includes other embodiments. All technical solutions formed by equivalent transformation or equivalent substitution should fall within the protection scope of the claims of the present invention.

Claims

1. A method for producing high-purity red phosphorus, characterized in that: Includes the following steps: Step 1: Place the high-purity white phosphorus in the inner high-purity quartz tube and cover it with high-purity water. After the high-purity white phosphorus cools and solidifies, insert the inner high-purity quartz tube into the outer high-purity quartz tube. Install a stainless steel pipe joint at the opening of the outer high-purity quartz tube. Insert the sealed outer high-purity quartz tube into the infrared electric heater. After inserting the infrared electric heater into the stainless steel sealed pressure vessel, install the end cap. Seal the stainless steel sealed pressure vessel. Step 2: Use a vacuum system and a nitrogen system to evacuate and inject nitrogen into the outer high-purity quartz tube to completely replace the air inside the outer high-purity quartz tube. Then turn on the infrared electric heater to preheat the high-purity white phosphorus inside the inner high-purity quartz tube to liquefy the high-purity white phosphorus. During this process, nitrogen is added to keep the pressure inside the inner quartz tube at atmospheric pressure. Step 3: Continue to slowly raise the temperature to 120℃-150℃, and vacuum process again until the moisture in the high-purity white phosphorus is completely evaporated; After slowly increasing the pressure of nitrogen gas in the outer high-purity quartz tube to 0.2MPa-0.5MPa, close the nitrogen valve. While increasing the pressure in the outer high-purity quartz tube, simultaneously introduce nitrogen gas through the nitrogen gas filling and releasing port of the stainless steel sealed pressure vessel to maintain the positive pressure difference between the inside and outside of the outer high-purity quartz tube at 0.05MPa-0.10MPa. Then continue to slowly increase the temperature in stages until it reaches 350℃-380℃. Step 4: After the heating is completed, allow it to cool naturally for a period of time. Once the temperature drops below 250℃, begin forced cooling and discharge of the stainless steel sealed pressure vessel.

2. The method for producing high-purity red phosphorus according to claim 1, characterized in that: In step one, some high-purity hot water is first added to the inner high-purity quartz tube through the feeding system to one-third of its volume, and the temperature of the high-purity hot water is controlled at 60℃-80℃. Then, the through hole of the inner high-purity quartz tube is inserted into the feeding tube to the level of the high-purity hot water, and the metered liquid high-purity white phosphorus is injected. Then, the inner high-purity quartz tube with added white phosphorus is placed in water at 20℃ to cool and solidify the white phosphorus.

3. The method for producing high-purity red phosphorus according to claim 1, characterized in that: In step two, after preheating to 80℃-90℃, the heating is stopped, and then the vacuum pump is started to perform a vacuuming operation. The vacuum level is controlled at 200 mmHg-400 mmHg to gradually evaporate all the moisture on the surface of the white phosphorus.

4. The method for producing high-purity red phosphorus according to claim 1, characterized in that: In step three, the temperature continues to rise to 350℃-380℃ after the white phosphorus moisture has completely evaporated, and this process lasts for 40 hours, during which heating is paused twice.

5. The method for producing high-purity red phosphorus according to claim 1, characterized in that: In step four, the circulating water pump is started, and circulating water enters and exits the jacket of the stainless steel sealed pressure vessel for cooling. As the temperature drops, the pressure difference between the inside and outside of the outer high-purity quartz tube will change. At this time, the nitrogen gas is automatically released or replenished through the coordinated operation of two automatic control regulating valves, so that the pressure difference between the inside and outside of the quartz tube can always be controlled within 0.1 MPa.

6. The method for producing high-purity red phosphorus according to claim 1, characterized in that: In step one, the stainless steel pipe joint extends out of the end cap of the stainless steel sealed pressure vessel and is connected to the nitrogen system and the vacuum system respectively. The stainless steel sealed pressure vessel is also provided with a nitrogen charging / discharging port, which is connected to the nitrogen system.

7. The method for producing high-purity red phosphorus according to claim 6, characterized in that: The nitrogen system includes a nitrogen buffer tank and a nitrogen cylinder. The vacuum system includes a vacuum buffer tank and a vacuum pump. The nitrogen cylinder is connected to the nitrogen buffer tank. The nitrogen buffer tank is connected to a nitrogen filling / discharging port and a stainless steel pipe joint via pipelines. The stainless steel pipe joint is also connected in parallel to the vacuum buffer tank. The vacuum buffer tank is connected to an exhaust buffer tank via the vacuum pump. The exhaust buffer tank has an exhaust port and a nitrogen replenishment port, and the nitrogen replenishment port is connected to the nitrogen buffer tank.

8. The method for producing high-purity red phosphorus according to claim 1, characterized in that: The infrared electric heater's wires extend out of the stainless steel sealed pressure vessel and are sealed and insulated by the wire sealing and insulation assembly.

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