Cleaning system and method of chlorination kettle for phosphorus trichloride production

Abstract

The invention discloses a system and a method for cleaning a chlorination kettle for phosphorus trichloride production, the system comprises a chlorination kettle, the chlorination kettle is provided with a chlorine feeding pipeline, a yellow phosphorus feeding pipeline and a discharging pipeline, and the discharging pipeline is connected with a feeding port of a primary filtering device through a first material pump; a liquid phase outlet of the first-stage filtering device is connected with a feeding hole of the second-stage filtering device, and a solid phase outlet of the first-stage filtering device is connected with a feeding hole of the third-stage filtering device; a liquid phase outlet of the second-stage filtering device is connected with an inlet of the first-stage buffer tank, and a solid phase outlet of the second-stage filtering device is connected with a feeding hole of the third-stage filtering device; a liquid phase outlet of the third-stage filtering device is connected with a feeding hole of the first-stage filtering device, and a solid phase outlet of the third-stage filtering device is connected with an inlet of the second-stage buffering tank; an outlet of the primary buffer tank is connected with a feeding hole of the phosphorus washing tower through a second material pump; and the discharge hole of the phosphorus washing tower is connected with the reflux inlet of the chlorination kettle through a reflux pipeline. The method avoids the risks of byproduct acid generation, hydrogen accumulation, yellow phosphorus spontaneous combustion and the like, is high in efficiency and is suitable for industrial continuous production.

Description

Technical Field

[0001] This invention relates to the field of phosphorus trichloride production technology, and in particular to a cleaning system and method for a chlorination reactor used in phosphorus trichloride production. It is especially suitable for removing insoluble substances such as phosphorus slag from the chlorination reactor, ensuring the safety of the phosphorus trichloride production process and the quality of the products. Background Technology

[0002] Phosphorus trichloride is an important chemical raw material widely used in pesticides, pharmaceuticals, dyes, and other industries. In its production process, the chlorination reactor is the core reaction equipment, where yellow phosphorus reacts with chlorine gas to produce phosphorus trichloride. Because the raw material yellow phosphorus contains small amounts of impurities, these impurities gradually accumulate during the reaction, forming insoluble substances such as phosphorus slag, which deposit at the bottom and inner wall of the chlorination reactor. The chlorination reactor typically needs to be thoroughly cleaned every six months; otherwise, reaction efficiency, product quality, and even safety accidents may occur.

[0003] Currently, common methods for cleaning chlorination reactors include steam distillation, water washing, and mechanical scraping. For example, residual phosphorus trichloride is first distilled off using steam distillation, followed by hydrolysis and slag removal. However, these methods have several drawbacks: First, improper control during distillation can easily lead to the decomposition of phosphorus trichloride or its reaction with residual yellow phosphorus to form phosphorus pentachloride, affecting the quality of subsequent products. Second, during hydrolysis, phosphorus trichloride reacts violently with water, releasing large amounts of hydrogen chloride gas, which can easily cause equipment corrosion, material spillage, or even explosions. Furthermore, yellow phosphorus exposed to air during slag removal is highly flammable, producing dense smoke and potentially causing environmental accidents.

[0004] To address some of the aforementioned problems, existing technologies include chemical cleaning solutions. For example, Chinese invention patent CN114031055B discloses a cleaning process for a chlorination reactor used in phosphorus trichloride production. This process involves sealing unnecessary pipe openings with blind flanges, first adding a 10-15% caustic soda solution and then vacuuming for initial chemical cleaning, followed by adding a cleaning agent containing distilled water, stirring, and allowing it to stand for a second chemical cleaning, and finally manually opening the manhole cover to clean the reactor. While this process reduces the generation of byproduct acid and equipment corrosion to some extent, it still has significant shortcomings: firstly, the introduction of distilled water and chemical reagents during the cleaning process cannot completely prevent the hydrolysis of phosphorus trichloride, resulting in the generation of a small amount of byproduct acid; secondly, the final manual opening of the reactor for cleaning does not completely eliminate the risk of yellow phosphorus being exposed to air, and the use of chemical reagents increases the cost of waste liquid treatment.

[0005] Another related technology, such as Chinese invention patent application CN105668533A, discloses a method for cleaning a reactor during phosphorus trichloride production. This method involves evaporating phosphorus trichloride from the reactor, cooling it, evacuating it, and then adding a 10-15% caustic soda solution. The overflowing HCl is then absorbed using a vacuum unit. This method also relies on a chemical neutralization reaction. The reaction products between the caustic soda solution and the residue in the reactor may adhere to the reactor wall, affecting the cleaning effect, and it does not solve the problem of wastewater pollution caused by chemical cleaning.

[0006] In addition, existing technologies employ solvent rinsing or chemical neutralization, but these methods are often complex, costly, and may introduce new contaminants. Therefore, developing an efficient, safe, and environmentally friendly chlorination reactor cleaning system and process that fundamentally avoids the introduction of moisture and the use of chemical reagents has become an urgent technical problem to be solved in this field. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a cleaning system and method for a chlorination reactor used in the production of phosphorus trichloride. Through multi-stage filtration and closed-loop circulation cleaning, insoluble substances such as phosphorus slag are effectively removed without introducing water and chemical reagents, thus avoiding contamination of the finished phosphorus trichloride product, reducing side reactions, extending equipment service life, and eliminating safety hazards.

[0008] To achieve the above objectives, the technical solution provided by the present invention is as follows: A chlorination reactor cleaning system for phosphorus trichloride production includes a chlorination reactor equipped with a chlorine gas inlet pipeline, a yellow phosphorus inlet pipeline, and an outlet pipeline. The outlet pipeline is connected to the inlet of a primary filtration unit via a first material pump. The liquid phase outlet of the primary filtration unit is connected to the inlet of a secondary filtration unit, and the solid phase outlet is connected to the inlet of a tertiary filtration unit. The liquid phase outlet of the secondary filtration unit is connected to the inlet of a primary buffer tank, and the solid phase outlet is connected to the inlet of the tertiary filtration unit. The liquid phase outlet of the tertiary filtration unit is connected to the inlet of the primary filtration unit, and the solid phase outlet is connected to the inlet of the secondary buffer tank. The outlet of the primary buffer tank is connected to the inlet of a phosphorus washing tower via a second material pump. The outlet of the phosphorus washing tower is connected to the reflux port of the chlorination reactor via a reflux pipeline.

[0009] The primary, secondary, and tertiary filtration devices are all corrosion-resistant filters, with the mesh size decreasing sequentially among them, used to remove phosphorus slag and other insoluble substances in stages.

[0010] In the preferred embodiment, corrosion-resistant pressure gauges are installed at the inlet and outlet of the primary, secondary, and tertiary filtration devices.

[0011] In a further preferred embodiment, the primary filtration device uses a filter screen with a pore size of 80~120μm, the secondary filtration device uses a filter screen with a pore size of 45~55μm, and the tertiary filtration device uses a filter screen with a pore size of 5~15μm, thereby achieving progressively fine filtration.

[0012] In the preferred embodiment, the primary buffer tank is equipped with a level gauge and an exhaust valve, and the secondary buffer tank is equipped with an exhaust valve and a sight glass. The gas discharge port of the exhaust valve is connected to the exhaust gas treatment system to monitor the liquid level and release accumulated gas, preventing the accumulation of dangerous gases such as hydrogen.

[0013] In the preferred embodiment, the first and second material pumps are corrosion-resistant centrifugal pumps, each equipped with a manual valve at its inlet and outlet, and a flow meter at its outlet, facilitating flow regulation and system isolation.

[0014] In a further preferred embodiment, the first and second material pumps are fluoroplastic centrifugal pumps.

[0015] Preferably, the top of the phosphorus washing tower is provided with a gas exhaust port, which is connected to the tail gas treatment system to ensure that the small amount of gas generated during the washing process is treated in compliance with regulations.

[0016] The present invention also provides a cleaning method for a chlorination reactor used in the production of phosphorus trichloride using the above system, comprising the following steps: S1. When the reaction in the chlorination reactor is completed and the conditions for cleaning the reactor are met, stop adding yellow phosphorus and chlorine to the chlorination reactor and close the relevant valves on the chlorine feed line and the yellow phosphorus feed line. S2. Start the first material pump to transport the material containing phosphorus slag in the chlorination reactor to the primary filtration device; S3. The material undergoes coarse filtration in the primary filtration unit, where large particles of phosphorus slag are retained (solid phase) and conveyed to the tertiary filtration unit, while the liquid phase enters the secondary filtration unit. The secondary filtration unit further removes fine particles from the liquid phase, and the filtrate (liquid phase) enters the primary buffer tank. The retained solid phase is conveyed to the tertiary filtration unit. The tertiary filtration unit performs final separation of the solid phases from the primary and secondary filtration units. The separated liquid phase is returned to the primary filtration unit for re-filtration, while the solid phase (insoluble matter such as phosphorus slag) is collected in the secondary buffer tank. The gas in the primary buffer tank, secondary buffer tank, and phosphorus washing tower is discharged to the tail gas treatment system for treatment via exhaust valves. S4. When the liquid level in the primary buffer tank reaches the set value, start the second material pump to transport the liquid in the primary buffer tank to the phosphorus washing tower to flush the impurities accumulated in the phosphorus washing tower. S5. Impurities washed down from the phosphorus washing tower are returned to the chlorination reactor through the reflux pipeline and enter the next round of filtration cycle until the insoluble matter in the chlorination reactor is removed. S6. Stop the circulation, turn off the first material pump and the second material pump, open the drain valve of the first material pump and the drain valve of the first-stage buffer tank to drain the residual material in the system and complete the cleaning.

[0017] In the preferred embodiment, the system operates in a cycle for 10-15 hours.

[0018] In a further optimized scheme, the system runs in a 12-hour cycle.

[0019] In the preferred embodiment, the pressure differential of each filter is checked regularly during cleaning, and backwashing or filter replacement is performed as necessary. This includes the following steps: P1. Record the corrosion-resistant pressure gauges on the inlet and outlet pipelines of the primary, secondary and tertiary filtration devices to obtain the initial inlet and outlet pressure difference ΔP0 of each filtration device as the reference value. P2. During system operation, the pressure difference ΔP of each filter should be checked and recorded every 2 hours. P3. When the real-time differential pressure ΔP of the filter reaches 1.5-2 times the initial differential pressure ΔP0, backwashing or inspection should be prepared. P4. Stop feeding the filter, close its inlet and outlet valves, isolate the filter from the production process, and use a backup filter to maintain continuous system operation; P5. Use the liquid in the primary buffer tank as the backwashing medium. Pump the backwashing medium in reverse from the outlet of the filter device to be backwashed through the third material pump and discharge it from the inlet. Carry the intercepted phosphorus residue and other impurities into the chlorination reactor. P6. The backwashing pressure should be controlled at 0.2~0.3 MPa, and the backwashing time should be controlled at 15~30 min until the discharged liquid is clear and the pressure difference returns to close to the initial value. P7. If the pressure differential cannot be effectively restored after backwashing, the filter must be disassembled, and the filter screen removed for manual inspection or replacement. The replaced filter screen should be disposed of according to hazardous waste management regulations. P8. After backwashing or screen replacement, put it back into operation and record the initial differential pressure after recovery.

[0020] In the preferred embodiment, the phosphorus slag collected in the secondary buffer tank is treated as hazardous waste.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention adopts a fully enclosed closed-loop design, which does not introduce water or chemical reagents into the entire cleaning process. This fundamentally avoids the reaction of phosphorus trichloride hydrolysis to generate hydrogen chloride byproduct acid, which reduces equipment corrosion and eliminates the safety hazards caused by byproduct acid. At the same time, the system completely isolates the air, avoiding the risk of spontaneous combustion of yellow phosphorus upon exposure. Furthermore, the exhaust valve of the buffer tank is connected to the tail gas treatment system, which effectively prevents the accumulation of dangerous gases such as hydrogen. This invention solves the problems of water introduction, chemical reagent reaction risks, and safety hazards of manual operation in existing chemical cleaning processes.

[0022] 2. This invention uses a three-stage corrosion-resistant filter with progressively smaller pore sizes for fine filtration, which can efficiently remove insoluble substances such as phosphorus slag of different particle sizes. Compared with the reaction products that may remain in the existing chemical cleaning process, the physical filtration method of this invention cleans more thoroughly. In addition, the liquid phase circulation washes the phosphorus washing tower and returns it to the chlorination reactor, forming a comprehensive cleaning loop, avoiding product contamination caused by insoluble residues and ensuring the quality of phosphorus trichloride finished product.

[0023] 3. This invention does not use chemical reagents and only generates phosphorus slag, a type of hazardous waste (which can be disposed of in compliance with regulations), thus reducing the generation of waste gas and waste liquid from the source and meeting the requirements of green and environmentally friendly production. At the same time, the cleaning process does not require time-consuming steps such as distillation and settling, and the cycle time is only 10-15 hours. Compared with the long-cycle operation of traditional steaming + water washing process and some chemical cleaning processes, the equipment downtime is shortened and the utilization rate is increased by more than 30%, which is suitable for continuous industrial production and has both good environmental and economic benefits.

[0024] 4. The corrosion-resistant filters, fluoroplastic centrifugal pumps, and other components used in the system of this invention are all adapted to the corrosiveness of phosphorus trichloride media. The level gauge, exhaust valve, and sight glass design of the buffer tank ensure the monitorability and safety of the system operation process. The process steps are simple, and the cleaning time can be flexibly adjusted according to the impurity content of the material to meet the needs of different production conditions. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the chlorination reactor cleaning system for phosphorus trichloride production according to the present invention; in the figure: 1, chlorination reactor; 2, chlorine gas feed line; 3, yellow phosphorus feed line; 4, discharge line; 5, first material pump; 6, primary filtration device; 7, secondary filtration device; 8, tertiary filtration device; 9, primary buffer tank; 10, secondary buffer tank; 11, second material pump; 12, phosphorus washing tower; 13, reflux line; 14, inlet vent valve of the first material pump; 15, vent valve of the primary buffer tank.

[0026] Figure 2 This is a schematic diagram of the filter backwashing system of the present invention; in the figure: 1, chlorination vessel; 9, primary buffer tank; 15, primary buffer tank drain valve; 16, third material pump; 17, filter device to be backwashed. Detailed Implementation

[0027] The technical solution of the present invention will be further described and illustrated below through examples. All raw materials used in the examples are commercially available or prepared using conventional methods.

[0028] Example 1 A cleaning system for chlorination reactors used in phosphorus trichloride production, such as Figure 1 As shown, the system includes a chlorination reactor 1, to which are connected a chlorine inlet pipeline 2, a yellow phosphorus inlet pipeline 3, and an outlet pipeline 4. The outlet pipeline 4 is connected to the inlet of a primary filtration unit 6 via a first material pump 5. The liquid phase outlet of the primary filtration unit 6 is connected to the inlet of a secondary filtration unit 7, and the solid phase outlet is connected to the inlet of a tertiary filtration unit 8. The liquid phase outlet of the secondary filtration unit 7 is connected to the inlet of a primary buffer tank 9, and the solid phase outlet is connected to the inlet of the tertiary filtration unit 8. The liquid phase outlet of the tertiary filtration unit 8 is connected to the inlet of the primary filtration unit 6, and the solid phase outlet is connected to the inlet of a secondary buffer tank 10. The outlet of the primary buffer tank 9 is connected to the inlet of a phosphorus washing tower 12 via a second material pump 11. The outlet of the phosphorus washing tower 12 is connected to the reflux port of the chlorination reactor 1 via a reflux pipeline 13. Among them, the primary filtration device 6 uses a filter screen with a pore size of 100 μm, the secondary filtration device 7 uses a filter screen with a pore size of 50 μm, and the tertiary filtration device 8 uses a filter screen with a pore size of 10 μm to achieve fine filtration step by step; the primary buffer tank 9 is equipped with a level gauge and an exhaust valve, and the secondary buffer tank 10 is equipped with an exhaust valve and a sight glass to ensure safe operation; the first material pump 5 and the second material pump 11 are fluoroplastic centrifugal pumps, which are highly corrosion resistant and suitable for phosphorus trichloride media. The inlet and outlet of the pumps are equipped with manual valves, and the inlet and outlet of the pumps are equipped with control valves and flow meters; the inlet and outlet of the primary filtration device 6, the secondary filtration device 7 and the tertiary filtration device 8 are all equipped with corrosion resistant pressure gauges; the top of the phosphorus washing tower (12) is equipped with a gas discharge port, which is connected to the tail gas treatment system.

[0029] Example 2 A cleaning method for a chlorination reactor used in phosphorus trichloride production using the system described in Example 1 includes the following steps: S1. When the reaction in chlorination reactor 1 is completed and the conditions for cleaning the reactor are met, stop adding yellow phosphorus and chlorine to chlorination reactor 1, close the relevant valves on chlorine feed line 2 and yellow phosphorus feed line 2, and stop feeding. S2. Start the first material pump 5 to transport the material containing phosphorus slag in the chlorination reactor 1 to the primary filtration device 6; S3. The material undergoes coarse filtration in the primary filtration device 6, where large solid particles are retained and transported to the tertiary filtration device 8, and the liquid enters the secondary filtration device 7. The secondary filtration device 7 performs fine filtration on the liquid phase to further remove fine particles, and the filtrate enters the primary buffer tank 9. The retained solids are transported to the tertiary filtration device 8. The tertiary filtration device 8 performs final separation of the solids from the primary filtration device 6 and the secondary filtration device 7. The separated liquid is returned to the primary filtration device 6 for re-filtration, and the solids (insoluble matter such as phosphorus slag) are collected in the secondary buffer tank 10. The phosphorus slag collected in the secondary buffer tank 10 is observed through a sight glass. When the secondary buffer tank 10 is full of phosphorus slag, the phosphorus slag is removed and handed over to a professional unit for disposal as hazardous waste. S4. When the level gauge in the primary buffer tank 9 shows that the liquid level has reached 50% of the buffer tank level, the second material pump 11 is started to transport the liquid in the primary buffer tank 9 to the phosphorus washing tower 12 to flush the impurities accumulated in the phosphorus washing tower 12; the gas in the primary buffer tank 9, the secondary buffer tank 10 and the phosphorus washing tower 12 is discharged to the tail gas treatment system for treatment by the exhaust valve. S5. Impurities washed down from the phosphorus washing tower 12 are returned to the chlorination reactor 1 through the return pipeline 13 and enter the next round of filtration cycle. The system runs in a cycle for 12 hours. During this period, the pressure difference of each filter is checked regularly, and backwashing or filter screen replacement is performed when necessary. S6. Stop the circulation, turn off the first material pump 5 and the second material pump 11, open the drain valve 14 of the first material pump 5 and the drain valve 15 of the first-stage buffer tank 9 to drain the residual material in the system, perform a final inspection of the chlorination reactor 1, and the cleaning work is completed. The method for backwashing or replacing the filter screen includes the following steps: P1. Record the corrosion-resistant pressure gauges on the inlet and outlet pipelines of the primary filter device 6, the secondary filter device 7, and the tertiary filter device 8 to obtain the initial inlet and outlet pressure difference ΔP0 of each filter device as the reference value. P2. During system operation, the pressure difference ΔP of each filter should be checked and recorded every 2 hours. P3. When the real-time differential pressure ΔP of the filter reaches 1.5-2 times the initial differential pressure ΔP0, backwashing or inspection should be prepared. P4. Stop feeding the filter, close its inlet and outlet valves, isolate the filter from the production process, and use a backup filter to maintain continuous system operation; P5. The liquid in the primary buffer tank 9 is used as the backwashing medium. The backwashing medium is pumped in reverse from the outlet end of the filter device 17 to be backwashed through the third material pump 16 and discharged from the inlet end, carrying the intercepted phosphorus residue and other impurities into the chlorination reactor 1. P6. The backwashing pressure should be controlled at 0.2~0.3 MPa, and the backwashing time should be controlled at 15~30 min until the discharged liquid is clear and the pressure difference returns to close to the initial value. P7. If the pressure differential cannot be effectively restored after backwashing, the filter must be disassembled, and the filter screen removed for manual inspection or replacement. The replaced filter screen should be disposed of according to hazardous waste management regulations. P8. After backwashing or screen replacement, put it back into operation and record the initial differential pressure after recovery.

[0030] This system achieves efficient and safe cleaning of chlorination reactors through a combination of physical filtration and circulating rinsing. In practical applications, the cleaning time can be flexibly adjusted according to the impurity content of the material, typically controlled between 10-15 hours. No water is introduced during the entire process, avoiding side reactions and significantly improving cleaning efficiency and safety.

[0031] It should be understood that the above embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A cleaning system for a chlorination reactor used in phosphorus trichloride production, characterized in that, The system includes a chlorination reactor (1), which is equipped with a chlorine inlet pipeline (2), a yellow phosphorus inlet pipeline (3), and an outlet pipeline (4). The outlet pipeline (4) is connected to the inlet of a primary filtration device (6) via a first material pump (5). The liquid phase outlet of the primary filtration device (6) is connected to the inlet of a secondary filtration device (7), and the solid phase outlet is connected to the inlet of a tertiary filtration device (8). The liquid phase outlet of the secondary filtration device (7) is connected to a primary buffer. The inlet of the tank (9) is connected, and the solid phase outlet is connected to the feed inlet of the three-stage filtration device (8); the liquid phase outlet of the three-stage filtration device (8) is connected to the feed inlet of the first-stage filtration device (6), and the solid phase outlet is connected to the inlet of the second-stage buffer tank (10); the outlet of the first-stage buffer tank (9) is connected to the feed inlet of the phosphorus washing tower (12) through the second material pump (11); the outlet of the phosphorus washing tower (12) is connected to the reflux port of the chlorination reactor (1) through the reflux pipeline (13).

2. The chlorination reactor cleaning system for phosphorus trichloride production according to claim 1, characterized in that, The primary filtration device (6), secondary filtration device (7) and tertiary filtration device (8) are all corrosion-resistant filters, and the mesh size of the three decreases sequentially.

3. The chlorination reactor cleaning system for phosphorus trichloride production according to claim 1 or 2, characterized in that, In a further preferred embodiment, the primary filtration device (6) uses a filter screen with a pore size of 80~120μm, the secondary filtration device (7) uses a filter screen with a pore size of 45~55μm, and the tertiary filtration device (8) uses a filter screen with a pore size of 5~15μm.

4. The chlorination reactor cleaning system for phosphorus trichloride production according to claim 1, characterized in that, The primary buffer tank (9) is equipped with a level gauge and an exhaust valve, and the secondary buffer tank (10) is equipped with an exhaust valve and a sight glass. The gas discharge port of the exhaust valve is connected to the exhaust gas treatment system.

5. The chlorination reactor cleaning system for phosphorus trichloride production according to claim 1, characterized in that, The first material pump (5) and the second material pump (11) are corrosion-resistant centrifugal pumps, and both their inlet and outlet are equipped with manual valves, and both their outlets are equipped with flow meters.

6. The chlorination reactor cleaning system for phosphorus trichloride production according to claim 5, characterized in that, The first material pump (5) and the second material pump (11) are fluoroplastic centrifugal pumps.

7. The chlorination reactor cleaning system for phosphorus trichloride production according to claim 1, characterized in that, The phosphorus washing tower (12) is provided with a gas discharge port at the top, which is connected to the tail gas treatment system.

8. A method for cleaning a chlorination reactor used in phosphorus trichloride production using the system according to any one of claims 1-7, characterized in that, Includes the following steps: S1. When the reaction in the chlorination reactor (1) is completed and the conditions for cleaning the reactor are met, stop adding yellow phosphorus and chlorine to the chlorination reactor (1) and close the relevant valves on the chlorine feed line (2) and the yellow phosphorus feed line (3). S2. Start the first material pump (5) to transport the material containing phosphorus slag in the chlorination kettle (1) to the first-stage filtration device (6); S3. The material is coarsely filtered in the primary filter (6), and large particles of phosphorus slag are intercepted and transported to the tertiary filter (8). The liquid phase enters the secondary filter (7). The secondary filter (7) performs fine filtration on the liquid phase to further remove fine particles. The filtrate enters the primary buffer tank (9), and the intercepted solid phase is transported to the tertiary filter (8). The tertiary filter (8) performs final separation on the solid phase from the primary filter (6) and the secondary filter (7). The separated liquid phase is returned to the primary filter (6) for re-filtration, and the solid phase is collected in the secondary buffer tank (10). S4. When the liquid level in the primary buffer tank (9) reaches the set value, the second material pump (11) is started to transport the liquid in the primary buffer tank (9) to the phosphorus washing tower (12) to flush the impurities accumulated in the phosphorus washing tower (12); the gas in the primary buffer tank (9), the secondary buffer tank (10) and the phosphorus washing tower (12) is discharged to the tail gas treatment system for treatment by the exhaust valve. S5. Impurities washed down from the phosphorus washing tower (12) are returned to the chlorination reactor (1) through the return pipeline (13) and enter the next round of filtration cycle until the insoluble matter in the chlorination reactor (1) is removed. S6. Stop the circulation, turn off the first material pump (5) and the second material pump (11), open the drain valve (14) of the first material pump (5) and the drain valve (15) of the first buffer tank (9) to drain the residual material in the system and complete the cleaning.

9. The cleaning method for the chlorination reactor used in phosphorus trichloride production according to claim 8, characterized in that, The system runs in a cycle for 10-15 hours.

10. The cleaning method for the chlorination reactor used in phosphorus trichloride production according to claim 9, characterized in that, During cleaning, regularly check the pressure differential of each filter, and backwash or replace the filter screen if necessary. The specific steps include: P1. At the initial stage of the cleaning system startup, with the filter in a clean state, record the corrosion-resistant pressure gauges on the inlet and outlet pipelines of the primary filter (6), secondary filter (7) and tertiary filter (8) to obtain the initial inlet and outlet pressure difference ΔP0 of each filter as the reference value. P2. During system operation, the inlet and outlet pressure difference ΔP of each filter device should be inspected and recorded every 2 hours. P3. When the real-time inlet and outlet pressure difference ΔP of the filter device reaches 1.5-2 times the initial inlet and outlet pressure difference ΔP0, backwashing or inspection should be prepared. P4. Stop feeding the filter device, close its inlet and outlet valves, isolate the filter device from the production process, and use a standby filter device to maintain continuous system operation. P5. The liquid in the primary buffer tank (9) is used as the backwashing medium. The backwashing medium is pumped in reverse from the outlet end of the filter device (17) to be backwashed through the third material pump (16) and discharged from the inlet end, carrying the intercepted phosphorus residue and other impurities into the chlorination kettle (1). P6. The backwashing pressure is controlled at 0.2~0.3 MPa, and the backwashing time is controlled at 15~30 min until the discharged liquid is clear and the pressure difference returns to close to the initial value. P7. If the pressure differential cannot be effectively restored after backwashing, the filter must be disassembled, and the filter screen removed for manual inspection or replacement. The replaced filter screen should be disposed of according to hazardous waste management regulations. P8. After backwashing or screen replacement, put it back into operation and record the initial differential pressure after recovery.

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