Device and process for preparing phosphorus oxychloride by chemical absorption method

Abstract

The invention discloses a device and a process for preparing phosphorus oxychloride by a chemical absorption method. The device comprises an absorption tower, an oxygen supply system, an oxygen heating device, a phosphorus trichloride condenser, a phosphorus trichloride circulating tank, a phosphorus oxychloride cooler, a tail gas pipe and the like. The process core is as follows: preheated oxygen is introduced from the lower part of an absorption tower and is subjected to countercurrent reaction with phosphorus trichloride circulating liquid added from the upper part of the tower, and a phosphorus oxychloride product is generated at the bottom of the tower; a phosphorus trichloride gas phase discharged from the tower top is subjected to heat exchange through the oxygen preheater and liquidation through the condenser, then returns to the circulating tank and is mixed with the supplemented raw material phosphorus trichloride to form circulating liquid, and the mass flow ratio of oxygen to the phosphorus trichloride circulating liquid is dynamically controlled through the flow proportion control system. According to the invention, the processes of feeding, reacting, cooling, separating and the like are integrated, the continuous production of phosphorus oxychloride is realized, the production efficiency is improved, the production cost is reduced, and the product purity and the operation safety are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical production, in particular to a device and process for completing the chemical absorption of oxygen (O2) in an absorption tower and synthesizing phosphorus oxychloride (POCl3) by circulating liquid-phase phosphorus trichloride in the production process of phosphorus oxychloride (POCl3). BACKGROUND

[0002] The mainstream existing phosphorus oxychloride production process is to add refined phosphorus trichloride into an oxidation kettle, and oxygen is introduced into the oxidation kettle through a pipeline for reaction. A phosphorus oxychloride circulating pump is arranged in the oxidation kettle to circulate the materials in the kettle into an oxidation cooler, and then into a mixer after being cooled by circulating water, and then into the oxidation kettle after being fully mixed with oxygen in the kettle. The pressure in the oxidation kettle is controlled at 0.09-0.15 MPa, and the temperature is kept at about 76-120℃, and after the temperature drops to 40℃, the oxygen supply is stopped, and then the pressure is released to discharge the materials, and the generated phosphorus oxychloride is sent to a tank area for storage.

[0003] The existing phosphorus oxychloride production process has the following defects: 1. Low production efficiency: The batch production is adopted in the production of phosphorus oxychloride, and the processes of phosphorus trichloride liquid feeding, temperature rising, oxygen feeding, temperature dropping, pressure releasing, and phosphorus oxychloride discharging are time-consuming, low in production efficiency, and high in labor intensity. In actual production, the control of the reaction process and the judgment of the reaction end point are very difficult, and repeated sampling is required, and if the sampling is unqualified, the oxygen feeding continues. When the pressure is released and the sampling is performed each time, the unreacted oxygen will take the phosphorus trichloride vapor into the subsequent tail gas system, and the environmental protection pressure is high; 2. Poor product quality: In the batch reaction, the initial reaction is high in the content of phosphorus trichloride, and the reaction temperature and pressure are high, which is beneficial to improve the reaction rate. When the reaction is close to the end point, the content of phosphorus trichloride is very low, and at this time, the temperature and pressure need to be reduced to obtain a good conversion rate. However, due to the presence of the reaction product phosphorus oxychloride, it is impossible to realize the complete conversion of phosphorus trichloride unless the reaction time is unlimitedly prolonged, and therefore, the pressure is released and the materials are discharged when the content of phosphorus oxychloride is controlled at 99.5%, and the quality is occasionally 99.8%, but it is unstable; 3. High energy and material consumption: The processes of phosphorus oxychloride feeding, sampling, pressure releasing, and discharging are accompanied by the overflow of oxygen and phosphorus trichloride gas, and the tail gas absorption system and the subsequent phosphorus-containing wastewater treatment have high pressure, and the utilization rate of oxygen and phosphorus trichloride is low, and the consumption of materials is increased. In the batch reaction, the steam consumption for temperature rising in the start-up and shutdown processes, the circulating water consumption for temperature dropping, the energy consumption for temperature rising and reaction in the judgment of the reaction end point, and the external high-power circulating pump (100 m 3 / h) for promoting the mixing of oxygen and phosphorus trichloride, and the long-time low-efficiency reaction time all result in huge energy consumption per ton of product.

[0004] Another micro-channel reactor produces phosphorus oxychloride, but its parallel mode cannot realize the countercurrent contact of oxygen and phosphorus trichloride, and further involves the separation of phosphorus trichloride and phosphorus oxychloride, and the recovery of unreacted oxygen. SUMMARY

[0005] In view of the problems in the prior art, the present application provides a device and process for preparing phosphorus oxychloride by chemical absorption method in automatic continuous large-scale production.

[0006] The device for preparing phosphorus oxychloride by chemical absorption method provided by the present application comprises: an absorption tower, which is provided with an oxygen inlet at the lower part, a phosphorus trichloride circulating liquid inlet at the upper part, a phosphorus trichloride gas phase outlet at the top, and a phosphorus oxychloride liquid phase outlet at the bottom; an oxygen supply system, which is connected with an oxygen source and communicates with the oxygen inlet at the bottom of the absorption tower through a pipeline, and is provided with an oxygen heating device on the pipeline, the oxygen heating device being used for heating the oxygen transported into the reaction tower; a phosphorus trichloride condenser, the inlet of which is connected with the phosphorus trichloride gas phase outlet at the top of the absorption tower, and the outlet of which is connected with a phosphorus trichloride circulating tank, which is used for condensing the phosphorus trichloride gas from the phosphorus trichloride gas phase outlet into phosphorus trichloride liquid and then sending the phosphorus trichloride liquid into the phosphorus trichloride circulating tank; a phosphorus trichloride circulating tank, the inlet of which is connected with the outlet of the phosphorus trichloride condenser and a phosphorus trichloride feeding pipe respectively, and the outlet of which is connected with the phosphorus trichloride circulating liquid inlet at the upper part of the absorption tower through a phosphorus trichloride liquid phase circulation pipe and a phosphorus trichloride circulating pump; a phosphorus oxychloride cooler, the inlet of which is connected with the phosphorus oxychloride liquid phase outlet at the bottom of the absorption tower, and the outlet of which is connected with a phosphorus oxychloride delivery pump; a tail gas pipe, which is arranged at the top of the phosphorus trichloride circulating tank and is used for discharging non-condensable gas, and is provided with an adjusting valve on the tail gas pipe.

[0007] Further, the number of tower plates of the absorption tower is 58-62.

[0008] Further, the oxygen heating device comprises an oxygen start-up preheater and an oxygen preheater connected in sequence, a bypass pipeline is arranged on the pipeline connecting the gas phase outlet of the absorption tower with the phosphorus trichloride condenser, the bypass pipeline is connected to the phosphorus trichloride condenser again after passing through the oxygen preheater, the oxygen start-up preheater is used for heating the oxygen at the initial start-up, and the oxygen preheater is used for heating the oxygen by using the phosphorus trichloride gas after the reaction is stable.

[0009] Further, a flow adjusting valve is arranged on the main pipeline connecting the phosphorus trichloride condenser with the phosphorus trichloride gas phase outlet and the bypass pipeline, which is used for adjusting the flow of the phosphorus trichloride gas passing through the oxygen preheater and controlling the oxygen temperature.

[0010] Further, flow regulating valves are arranged on the conveying pipeline of the oxygen supply system and the liquid phase circulation pipeline of the phosphorus trichloride, and the mass flow ratio of the oxygen and the phosphorus trichloride conveyed into the absorption tower is dynamically controlled through a flow proportional control system.

[0011] Further, an adjusting valve is arranged at the outlet of the phosphorus oxychloride delivery pump to control the liquid level in the absorption tower.

[0012] The application also provides a process for preparing phosphorus oxychloride by the chemical absorption method using the above device, which comprises the following steps: S1, the oxygen supply system supplies oxygen at a constant pressure through the pressure regulating valve, the oxygen is heated to 60-80℃ by the oxygen heating device, and then is introduced from the oxygen inlet at the lower part of the absorption tower; S2, the phosphorus trichloride liquid is added into the absorption tower from the circulation liquid inlet at the upper part of the absorption tower through the phosphorus trichloride circulation pump, and is contacted with the oxygen in countercurrent to complete the chemical absorption reaction and heat transfer on each tower plate; the mass flow ratio of the oxygen and the phosphorus trichloride liquid entering the absorption tower is 1: (71-72) ; S3, the operation conditions of the absorption tower are maintained as follows: the tower bottom pressure is 0.152-0.154 MPa, the tower bottom temperature is 120±2℃; the tower top pressure is 0.136-0.140 MPa, and the tower top temperature is 86±1℃; S4, the phosphorus oxychloride generated at the tower bottom is cooled to room temperature by the phosphorus oxychloride cooler, and then is pumped out by the delivery pump; S5, the phosphorus trichloride gas phase discharged from the top of the absorption tower is heated by the oxygen preheater, and is condensed by the phosphorus trichloride condenser to enter the phosphorus trichloride circulation tank, and is mixed with the added phosphorus trichloride raw material to form the circulation liquid.

[0013] Further, the number of tower plates of the absorption tower is 60±2, and the 10-12 tower plates at the tower bottom of the absorption tower are the main reaction section, and the reaction of 99.99% of the phosphorus trichloride and the oxygen is completed.

[0014] Further, the mass ratio of the condensed phosphorus trichloride and the added phosphorus trichloride raw material in the phosphorus trichloride circulation tank is (7.3-7.4):1, and the temperature of the phosphorus trichloride circulation liquid entering the absorption tower is 26±1℃.

[0015] Further, at the initial start-up, the oxygen is directly heated to 80℃ by the oxygen start-up preheater, after the reaction heat generated by the continuous reaction evaporates the phosphorus trichloride to form a stable gas phase sufficient to heat the oxygen, the oxygen start-up preheater stops heating, and the device enters a stable running state, the oxygen with a temperature of 60-80℃ is obtained by adjusting the flow of the phosphorus trichloride gas passing through the oxygen preheater, and the tower bottom temperature of the absorption tower is fine-tuned to 120±2℃.

[0016] Further, an adjusting valve is arranged on the tail gas pipe, and the tower top pressure is controlled at 0.136-0.140 MPa through the adjusting valve.

[0017] The present application has the following advantages: (1) Automatic continuous scale production: the present application integrates feeding, reaction, cooling, separation and other processes, and all of them can be continuously carried out at the same time, which is in sharp contrast with the existing intermittent operation of feeding, reaction, cooling and discharging of phosphorus oxychloride reaction; and the tower is a typical continuous production device, and is easy to enlarge, compared with the existing kettle reaction, the yield of one kettle of 10 tons is obtained in 6-8 hours, and there is unqualified return material to prolong the reaction time, while the absorption tower can easily realize a single device of 100,000 tons, which is equivalent to 10 phosphorus oxychloride reaction production lines, and also reduces the land occupation, the investment of mechanical and electrical equipment, and the number of operators; (2) Short reaction residence time: the number of tower plates of the absorption tower is 60±2, and each tower plate is equivalent to a reactor; the 50±2th to 60±2th tower plates are the main reaction section, and 99.99% of the reaction of phosphorus trichloride and oxygen is completed; the pressure of the 50±2th tower plate is 0.149-0.151 MPa, and the temperature is 90±2℃, compared with the pressure of 0.152-0.154 MPa and the temperature of 120±2℃ at the tower bottom, the temperature changes dramatically, and the mass fraction of phosphorus oxychloride rapidly rises from 0.1% to more than 99.9%.

[0018] (3) Good product quality: through the countercurrent contact of raw materials in the absorption tower, unique reaction conditions are created, that is, the concentration of phosphorus trichloride gradually decreases, and the concentration of oxygen gradually increases from the 50±2th to 60±2th tower plates of the absorption tower, the degree of excess of oxygen is higher and higher, the driving force of reaction equilibrium is also larger and larger, the mass fraction of phosphorus oxychloride is more than 99.9%, and the mass fraction of phosphorus trichloride in the phosphorus oxychloride product is less than 0.1%; (4) Green and environmentally friendly: the reaction heat of the device is mainly taken out by the circulating phosphorus trichloride, part of the heat is recovered through the oxygen preheater, and then cooled to 26±1℃, the temperature can be reached by the conventional heat exchange mode, and the cost of the cooling agent is saved; according to the comparison calculation of a 100,000-ton device, the circulating phosphorus trichloride flow is about 6.3 m 3 / h, compared with the circulating phosphorus trichloride / phosphorus oxychloride flow of 100 m 3 / h in the kettle reaction, and the equipment is frequently started and stopped during feeding, discharging, heating and cooling, so the power saving of the present application is obvious; the device only discharges non-condensable gas, oxygen is completely absorbed, almost no tail gas is generated, and the consumption of oxygen and phosphorus trichloride is very low, which also reduces the pressure of subsequent environmental protection treatment. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a structural schematic view of the device for preparing phosphorus oxychloride by chemical absorption method.

[0020] In the figure: absorption tower 1, oxygen supply system 2, oxygen start-up preheater 3, oxygen preheater 4, phosphorus trichloride condenser 5, phosphorus trichloride circulating tank 6, phosphorus trichloride circulating pump 7, phosphorus trichloride feeding pipe 8, tail gas pipe 9, phosphorus oxychloride cooler 10, phosphorus oxychloride delivery pump 11. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0022] As Figure 1 described, the device for preparing phosphorus oxychloride by chemical absorption method provided by the present application mainly consists of absorption tower 1, oxygen supply system 2, phosphorus trichloride condenser 5, phosphorus trichloride circulating tank 6, phosphorus oxychloride cooler 10, tail gas pipe 9 and the like.

[0023] The absorption tower 1 is the reaction core of the device, and provides a place for gas-liquid countercurrent contact reaction. In the embodiment, the number of tower plates of the absorption tower 1 is 58-62. The lower part of the absorption tower 1 is provided with an oxygen inlet, and the oxygen enters from the bottom to form an ascending gas phase. The upper part of the tower body is provided with a phosphorus trichloride circulating liquid inlet, and the phosphorus trichloride in liquid form is sprayed from the top of the tower and downwardly, and is countercurrently contacted with the ascending oxygen to generate phosphorus oxychloride by oxidation reaction. The top of the absorption tower 1 is provided with a phosphorus trichloride gas phase outlet, and the phosphorus trichloride which does not participate in the reaction absorbs the reaction heat to form phosphorus trichloride ascending vapor, and flows out from the phosphorus trichloride gas phase outlet at the top of the tower. The bottom of the absorption tower 1 is provided with a phosphorus oxychloride liquid phase outlet, and the generated phosphorus oxychloride (in liquid state) is discharged from the bottom of the tower.

[0024] The oxygen supply system 2 is connected with an oxygen source, and is connected with the oxygen inlet at the bottom of the absorption tower 1 through a pipeline to provide the oxygen required by the absorption tower 1 for reaction, and the oxygen is preheated to the required reaction temperature by a heating device arranged on the pipeline. The heated oxygen enters the absorption tower 1 to provide reactants, and also maintains the reaction temperature in the tower through heat exchange to improve the reaction efficiency.

[0025] The phosphorus trichloride condenser 5 is connected with the phosphorus trichloride gas phase outlet at the top of the absorption tower 1 at the inlet, and is connected with the phosphorus trichloride circulating tank 6 at the outlet, and is used to condense the unreacted phosphorus trichloride gas discharged from the phosphorus trichloride gas phase outlet to obtain phosphorus trichloride liquid, and then send the phosphorus trichloride liquid into the phosphorus trichloride circulating tank 6 to realize the recycling of raw materials.

[0026] The phosphorus trichloride circulating tank 6 is used for storing and adjusting phosphorus trichloride, forming a circulating-supplementing system, the inlet of which is connected with the outlet of the phosphorus trichloride condenser 5 and the phosphorus trichloride feeding pipe 8 respectively, and the outlet is connected with the phosphorus trichloride circulating liquid inlet at the upper part of the absorption tower 1 through the phosphorus trichloride liquid phase circulating pipe and the phosphorus trichloride circulating pump 7, and the opening degree of the valve of the phosphorus trichloride feeding pipe 8 is adjusted by the circulating tank liquid level interlocking control, so as to maintain the stability of the circulating tank liquid level.

[0027] The inlet of the phosphorus oxychloride cooler 10 is connected with the phosphorus oxychloride liquid phase outlet at the bottom of the absorption tower 1, the phosphorus oxychloride discharged from the bottom of the absorption tower 1 is cooled, and the outlet is connected with the output of the phosphorus oxychloride delivery pump 11 to output the finished product. An adjusting valve is arranged at the outlet of the phosphorus oxychloride delivery pump 11 to control the liquid level in the absorption tower 1.

[0028] The tail gas pipe 9 is arranged at the top of the phosphorus trichloride circulating tank 6 and is used for discharging non-condensable gas, and an adjusting valve is arranged on the tail gas pipe 9.

[0029] In the embodiment, the oxygen heating device comprises the oxygen start-up preheater 3 and the oxygen preheater 4 connected in sequence, a bypass pipe is arranged on the pipeline connecting the gas phase outlet of the absorption tower 1 with the phosphorus trichloride condenser 5, the bypass pipe is connected with the phosphorus trichloride condenser 5 again after passing through the oxygen preheater 4, the oxygen start-up preheater 3 is used for heating oxygen during initial start-up, and the oxygen preheater 4 is used for heating oxygen by using phosphorus trichloride gas after the reaction is stable. The design utilizes the reaction heat carried by the phosphorus trichloride gas phase, recovers part of the heat through the oxygen preheater 4, and then cools, so as to realize the cyclic utilization of heat and save the cost of the coolant. Flow adjusting valves are arranged on the main pipeline connecting the phosphorus trichloride condenser 5 with the phosphorus trichloride gas phase outlet and the bypass pipe, which are used for adjusting the amount of the discharged phosphorus trichloride gas, and the flow of the phosphorus trichloride gas passing through the oxygen preheater 4 is adjusted to control the oxygen temperature.

[0030] In order to realize the accurate control of the mass flow of oxygen and the mass flow of phosphorus trichloride delivered into the absorption tower 1, flow adjusting valves are arranged on the delivery pipeline of the oxygen supply system 2 and the phosphorus trichloride liquid phase circulating pipe respectively, and the mass flow ratio of oxygen and phosphorus trichloride delivered into the absorption tower 1 is dynamically controlled through the flow proportional control system linkage.

[0031] The process for preparing phosphorus oxychloride by the chemical absorption method provided by the application comprises the following steps: S1, the oxygen supply system 2 controls the pressure of the oxygen to be constant through the pressure regulating valve, controls the pressure of the oxygen to be 0.155-0.158 MPa, which is slightly higher than the bottom pressure of the absorption tower 1, and heats the oxygen to 60-80 DEG C through the oxygen heating device, the preheated oxygen is adjusted to a given mass flow through the flow adjusting valve arranged on the oxygen feeding pipe of the absorption tower 1, and is delivered into the absorption tower 1 through the oxygen inlet at the lower part of the absorption tower 1. S2, the phosphorus trichloride liquid is added from the upper part of the absorption tower 1 through the phosphorus trichloride circulating pump 7, and the mass flow rate of the phosphorus trichloride is accurately proportionally controlled through the adjusting valve arranged on the phosphorus trichloride liquid circulating pipe, so that the mass flow rate of the phosphorus trichloride circulating liquid to the mass flow rate of oxygen is (71-72):1, and the liquid phosphorus trichloride and oxygen are countercurrently contacted to complete the chemical absorption reaction on each tower plate of the absorption tower 1; in the present application, the number of tower plates of the absorption tower 1 is 60±2, and each tower plate is equivalent to a reactor, the 50±2th tower plate to the 60±2th tower plate is the main reaction section, and the reaction of 99.99% of the phosphorus trichloride and oxygen is completed, the pressure of the 50±2th tower plate is 0.149-0.151 MPa, and the temperature is 90±2℃, compared with the bottom pressure of 0.152-0.154 MPa and the bottom temperature of 120±2℃, the temperature has changed dramatically, and the mass fraction of phosphorus oxychloride rapidly rises from 0.1% to more than 99.9%; S3, the operation conditions of the absorption tower 1 are maintained: the bottom pressure is controlled to be 0.152-0.154 MPa, the bottom temperature is 120±2℃, the top pressure is 0.136-0.140 MPa, and the top temperature is 86±1℃; the bottom temperature and pressure are increased, which is beneficial to improve the solubility of oxygen and the reaction rate, shorten the reaction residence time, and ensure that the mass fraction of phosphorus trichloride in the phosphorus oxychloride product at the bottom is less than 0.08%; and under the conditions of lower temperature and pressure at the top, it is beneficial to improve the equilibrium conversion rate of the reaction, and the excessive high-purity phosphorus trichloride in the upper part of the tower is beneficial to the absorption of oxygen, so as to ensure that the oxygen content in the phosphorus trichloride gas phase at the top is 0, and reduce the material loss and environmental protection treatment cost caused by the emission of uncondensed oxygen; S4, the generated phosphorus oxychloride at the bottom is cooled to room temperature through the phosphorus oxychloride cooler 10 and then output through the phosphorus oxychloride delivery pump 11; an adjusting valve is arranged at the outlet of the phosphorus oxychloride delivery pump 11 to control the liquid level of the absorption tower 1, so as to prevent the oxygen from breaking through the liquid seal and overflowing from the tower kettle under high pressure to cause a safety accident; S5, the phosphorus trichloride gas phase discharged from the top of the absorption tower 1 is heat-exchanged through the oxygen preheater 4, condensed through the phosphorus trichloride condenser 5, and then enters the phosphorus trichloride circulating tank 6 to mix with the added phosphorus trichloride raw material to form a circulating liquid. In the circulating liquid, the mass ratio of the condensed phosphorus trichloride to the added phosphorus trichloride raw material is (7.3-7.4):1, and the mixed temperature of the phosphorus trichloride circulating liquid is 26±1℃. The raw material phosphorus trichloride does not need to be metered, and is automatically added by controlling the liquid level of the phosphorus trichloride circulating tank 6. The liquid level of the circulating tank is interlocked to control the opening degree of the adjusting valve of the phosphorus trichloride feeding pipe 8, so as to maintain the stability of the liquid level of the circulating tank. The phosphorus trichloride circulating tank 6 plays the roles of supplement, mixing, buffering and redistribution, and provides conditions for accurately proportionally interlocking control of the mass flow rate of the phosphorus trichloride circulating liquid.

[0032] The small amount of non-condensed gas in the device is discharged through the tail gas pipe 9 at the top of the phosphorus trichloride circulating tank 6, and an adjusting valve is arranged on the tail gas pipe 9 to control the pressure at the top of the absorption tower 1 to be 0.136-0.140 MPa by adjusting the gas discharge.

[0033] During initial start-up, the oxygen is directly heated to 80°C by the oxygen start-up preheater 3, and after the reaction heat generated by the continuous reaction evaporates the phosphorus trichloride to form a stable gas phase, the oxygen start-up preheater 3 stops heating, and the device enters a stable operation state. By adjusting the flow of phosphorus trichloride gas passing through the oxygen preheater 4, oxygen with a temperature of 60-80°C is obtained, the oxygen addition temperature is controlled, and the bottom temperature of the absorption tower 1 is fine-tuned to 120±2°C. Example 1

[0034] Based on the device and process provided by the present application for preparing phosphorus oxychloride by chemical absorption method, the specific process control conditions and data are as follows: oxygen addition amount 126 kg, oxygen inlet temperature 80°C, oxygen inlet pressure 0.156 MPa; phosphorus trichloride circulation amount 9100 kg, phosphorus trichloride circulating liquid temperature 27°C, feed pressure 0.143 MPa; tower bottom temperature 121°C, tower bottom pressure 0.153 MPa, generated phosphorus oxychloride yield 1221 kg. The gas phase composition at the top of the tower is: phosphorus trichloride 100%, oxygen 0%, phosphorus oxychloride 0%; the liquid phase composition at the bottom of the tower is: phosphorus trichloride 0.9%, oxygen 0%, phosphorus oxychloride 99.07%. The ratio of phosphorus oxychloride circulation amount to oxygen is 72.2:1, and the mass fraction of phosphorus oxychloride in the product is 98.5%, which still has a large gap from the target value. Example 2

[0035] Based on the device and process provided by the present application for preparing phosphorus oxychloride by chemical absorption method, the specific process control conditions and data are as follows: oxygen addition amount 126 kg, oxygen inlet temperature 60°C, oxygen inlet pressure 0.156 MPa; phosphorus trichloride circulation amount 9050 kg, phosphorus trichloride circulating liquid temperature 26°C, feed pressure 0.143 MPa; tower bottom temperature 121°C, tower bottom pressure 0.153 MPa, generated phosphorus oxychloride yield 1210 kg. The gas phase composition at the top of the tower is: phosphorus trichloride 100%, oxygen 0%, phosphorus oxychloride 0%; the liquid phase composition at the bottom of the tower is: phosphorus trichloride 0.08%, oxygen 0%, phosphorus oxychloride 99.917%.

[0036] By adjusting the phosphorus trichloride circulation amount to a ratio of 71.8:1 to oxygen, the circulating liquid temperature is reduced to 26°C, and the oxygen feed temperature is reduced to 60°C, the mass fraction of phosphorus oxychloride is rapidly increased to more than 99.9%, which proves that under the same feeding conditions, reducing the material temperature helps to reduce the circulation amount to the index, and can optimize the operation of the absorption tower 1.

[0037] The above is only an example and description of the structure of the present application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace, as long as the modifications or supplements do not deviate from the structure of the present application or exceed the scope defined by the present claims, and should belong to the protection scope of the present application.

Claims

1. An apparatus for the production of phosphorus oxychloride by chemical absorption, characterized in that, include: The absorption tower (1) has an oxygen inlet at the bottom, a phosphorus trichloride circulating liquid inlet at the top, a phosphorus trichloride gas phase outlet at the top, and a phosphorus oxychloride liquid phase outlet at the bottom. The oxygen supply system (2) is connected to the oxygen source and is connected to the oxygen inlet at the bottom of the absorption tower (1) through a pipeline. An oxygen heating device is installed on the pipeline. The oxygen heating device is used to heat the oxygen delivered to the reaction tower. The phosphorus trichloride condenser (5) has its inlet connected to the phosphorus trichloride gas phase outlet at the top of the absorption tower (1) and its outlet connected to the phosphorus trichloride circulation tank (6), which is used to condense the phosphorus trichloride gas from the phosphorus trichloride gas phase outlet to obtain phosphorus trichloride liquid and send it into the phosphorus trichloride circulation tank (6). The phosphorus trichloride circulating tank (6) has its inlet connected to the outlet of the phosphorus trichloride condenser (5) and the phosphorus trichloride feeding pipe (8), respectively. The outlet is connected to the phosphorus trichloride circulating liquid inlet at the top of the absorption tower (1) via the phosphorus trichloride liquid phase circulating pipe and the phosphorus trichloride circulating pump (7). The phosphorus oxychloride cooler (10) has its inlet connected to the phosphorus oxychloride liquid phase outlet at the bottom of the absorption tower (1), and its outlet connected to the phosphorus oxychloride delivery pump (11). The exhaust pipe (9) is located at the top of the phosphorus trichloride circulation tank (6) and is used to discharge non-condensable gases. A regulating valve is installed on the exhaust pipe (9).

2. A device for the production of phosphorus oxychloride by chemical absorption according to claim 1, characterized in that The number of trays in the absorption tower (1) is 58 to 62.

3. A device for the production of phosphorus oxychloride by chemical absorption according to claim 1, characterized in that, The oxygen heating device includes an oxygen start-up preheater (3) and an oxygen preheater (4) connected in sequence. A bypass pipeline is provided on the pipeline connecting the gas phase outlet of the absorption tower (1) to the phosphorus trichloride condenser (5). The bypass pipeline passes through the oxygen preheater (4) and then connects to the phosphorus trichloride condenser (5). The oxygen start-up preheater (3) is used to heat oxygen during initial start-up. The oxygen preheater (4) is used to heat oxygen with phosphorus trichloride gas after the reaction has stabilized.

4. A plant for the production of phosphorus oxychloride by chemical absorption according to claim 3, characterized in that A flow regulating valve is installed on the main pipeline connecting the phosphorus trichloride condenser (5) and the phosphorus trichloride gas outlet, as well as on the bypass pipeline, to regulate the flow rate of phosphorus trichloride gas passing through the oxygen preheater (4) and control the oxygen temperature.

5. A plant for the production of phosphorus oxychloride by chemical absorption according to claim 1, characterized in that, Flow regulating valves are installed on the oxygen supply system (2) delivery pipeline and the phosphorus trichloride liquid phase circulation pipe, respectively, and the mass flow ratio of oxygen and phosphorus trichloride delivered to the absorption tower (1) is dynamically controlled by the flow ratio control system.

6. A plant for the production of phosphorus oxychloride by chemical absorption according to claim 1, characterized in that, A regulating valve is installed at the outlet of the phosphorus oxychloride pump (11) to control the liquid level in the absorption tower (1).

7. A process for the production of phosphorus oxychloride by chemical absorption based on the apparatus according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1, Oxygen supply system (2) pressurizes oxygen through a pressure regulating valve, heats it to 60-80°C through an oxygen heating device, and then introduces it from the oxygen inlet at the bottom of the absorption tower (1); S2. Phosphorus trichloride liquid is added from the upper circulating liquid inlet of the absorption tower (1) through the phosphorus trichloride circulating pump (7), and it comes into countercurrent contact with oxygen to complete the chemical absorption reaction and heat transfer on each tower plate; the mass flow ratio of oxygen to phosphorus trichloride liquid entering the absorption tower (1) is controlled to be 1: (71~72). S3, maintain the absorption tower (1) operating conditions: the bottom pressure is 0.152-0.154 MPa, the bottom temperature is 120±2℃; the top pressure is 0.136-0.140 MPa, the top temperature is 86±1℃; S4, the generated phosphorus oxychloride at the bottom is cooled to normal temperature by phosphorus oxychloride cooler (10) and then pumped out by a delivery pump; S5, the phosphorus trichloride gas phase discharged from the top of the absorption tower (1) is heat exchanged by oxygen preheater (4) and condensed by phosphorus trichloride condenser (5) and then enters phosphorus trichloride circulating tank (6) to mix with the added phosphorus trichloride raw material to form a circulating liquid.

8. The process for the production of phosphorus oxychloride by chemical absorption according to claim 7, characterized in that, The number of plates of the absorption tower (1) is 60±2, and the 10-12 plates at the bottom of the absorption tower (1) are the main reaction section, which completes the reaction of 99.99% of phosphorus trichloride and oxygen.

9. The process for the production of phosphorus oxychloride by chemical absorption according to claim 7, characterized in that, The mass ratio of the condensed phosphorus trichloride to the added phosphorus trichloride raw material in the phosphorus trichloride circulating tank (6) is (7.3-7.4):1, and the temperature of the phosphorus trichloride circulating liquid entering the absorption tower (1) is 26±1℃.

10. The process for the production of phosphorus oxychloride by chemical absorption according to claim 7, characterized in that, When starting, the oxygen is directly heated to 80℃ by oxygen start-up preheater (3), and after the reaction heat generated by the continuous reaction evaporates the phosphorus trichloride to form a stable gas phase, the oxygen start-up preheater (3) stops heating, and the device enters a stable running state. By adjusting the flow of phosphorus trichloride gas through the oxygen preheater (4), oxygen with a temperature of 60-80℃ is obtained, and the bottom temperature of the absorption tower (1) is fine-tuned to 120±2℃.

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