A continuous preparation method and device for high-purity phosphorus oxyfluoride

Abstract

The invention discloses a continuous preparation method and device for high-purity phosphorus oxyfluoride, and relates to the technical field of production for preparing phosphorus oxyfluoride. The invention preheats a preheating header tank of polyphosphoric acid so that the polyphosphoric acid is converted from a viscous liquid into a liquid that is easy to transmit after preheating. The polyphosphoric acid is transmitted to a constant temperature kettle through a high-level difference pipeline under the control of an electromagnetic valve. The polyphosphoric acid is further heated and stirred in the constant temperature kettle to maintain a constant temperature. The polyphosphoric acid and anhydrous hydrogen fluoride are reacted and separated in a preparation tower through gas-liquid two-phase exchange contact. The prepared phosphorus oxyfluoride gas is separated from the top of the preparation tower, further dried in a spray drying tower, and then a phosphorus oxyfluoride product with a purity of 99.6-99.8% is prepared using a condenser and a gas-liquid separator. The reaction yield is 95-96%. The phosphorus oxyfluoride has high purity, few side reactions in the production process, and high reaction yield.

Description

Technical Field

[0001] The present invention relates to the technical field of production for preparing phosphorus oxyfluoride, and in particular to a continuous preparation method and device for high-purity phosphorus oxyfluoride. Background Art

[0002] Currently, phosphorus oxyfluoride (POF3) is a colorless gas with a pungent odor under normal conditions, emitting faint smoke in the air. The preparation of phosphorus oxyfluoride (POF3) primarily involves reacting CaF2 with anhydrous sulfurous acid to generate CaF(SO3F), which then reacts with H3PO4 to form the intermediate product POF3. However, since CaF2 is a solid, continuous production is difficult, the process is complex, and the production cost is high. Furthermore, the generated CaSO4 seriously pollutes the surrounding soil, necessitating necessary treatment.

[0003] To this end, the applicant previously proposed a method for preparing high-purity phosphorus oxytrifluoride using continuous reactive distillation (patent application number CN2022114628326). The method discloses using polyphosphoric acid and anhydrous hydrogen fluoride as raw materials, and through continuous reactive distillation, first reacting in a reactive distillation tower and then further distilling through a first distillation tower to obtain a product with a purity of more than 99.99%.

[0004] However, in actual application, the method for preparing high-purity phosphorus oxytrifluoride by continuous reactive distillation has been found to require numerous and complex equipment for preparing phosphorus oxytrifluoride due to the use of a reaction-first-separation method. Furthermore, in the reactive distillation column, since polyphosphoric acid is a liquid and anhydrous hydrogen fluoride is a gas, the polyphosphoric acid and anhydrous hydrogen fluoride have little contact time during their two-phase contact through the trays, resulting in an insufficient reaction between the polyphosphoric acid and anhydrous hydrogen fluoride. A controlled reflux method must be used to achieve a circulating reaction, increasing energy consumption for the production reaction. Furthermore, the concentration of the reaction liquid on the trays is uneven, resulting in excessively high concentrations in some parts of the reaction, causing more side reactions, while the concentration in other parts of the reaction is too low, resulting in incomplete reactions. Consequently, a large amount of waste is discharged from the bottom of the reactive distillation column, which is not conducive to improving the yield of the reaction between polyphosphoric acid and anhydrous hydrogen fluoride.

[0005] Therefore, the applicant previously proposed a method for preparing high-purity phosphorus oxyfluoride by continuous reactive distillation. The applicant needs to improve and study the method and design a continuous preparation method and preparation device for high-purity phosphorus oxyfluoride, with the aim of solving the problem of preparing phosphorus oxyfluoride with high purity, few side reactions and high reaction yield. Summary of the Invention

[0006] In view of the technical problems existing in the above-mentioned prior art, the present invention provides a continuous preparation method of high-purity phosphorus oxyfluoride and an apparatus thereof, so as to effectively solve the technical problems existing in the above-mentioned prior art.

[0007] In order to achieve the above object, the present invention is achieved through the following technical solutions:

[0008] A continuous preparation device for high-purity phosphorus oxyfluoride, comprising a preheating header tank, the bottom pipe of the preheating header tank being connected to the feed port of a thermostatic kettle, the thermostatic kettle comprising a discharge pipe extending therein, the discharge pipe being connected to a preparation tower via a pipe, the preparation tower comprising a tower body, the tower body being provided with a feed zone, one or more reaction zones and a separation zone in sequence from bottom to top, the feed zone and the separation zone in the tower body being both filled with a packing section of a packing, wherein the bottom of the packing section in the feed zone is provided with an anhydrous hydrogen fluoride feed port, each of the reaction zones being provided with a shell and tube heat exchanger, the shell and tube heat exchanger The heater is provided with a threaded tube for controlling the reaction temperature, and fillers are also filled between the threaded tubes. The upper part of the reaction zone located in the top layer is provided with a polyphosphoric acid feed port connected to the pipeline between the discharge pipes of the constant temperature kettle. The tower body is provided with a top product outlet at the top, and the top product outlet pipeline is connected to a spray drying tower, and the top product outlet pipeline is connected to the upper part of the side wall of the spray drying tower. The spray drying tower is provided with a sprayer for drying. The spray drying tower is connected to a condenser at its bottom, and the condenser pipeline is connected to a gas-liquid separator.

[0009] Furthermore, a solenoid valve is provided between the preheating high-level tank and the constant temperature kettle.

[0010] Furthermore, the feed port of the thermostatic kettle is connected to a high-pressure nitrogen pipe, and the high-pressure nitrogen pipe is provided with a solenoid valve.

[0011] Furthermore, a horizontal flow pump is provided between the polyphosphoric acid feed port and the discharge pipe.

[0012] Furthermore, the preparation tower is provided with a swirl distributor between the feed zone and the reaction zone, between the separation zone and the reaction zone, and between the multiple reaction zones. The swirl distributor is provided with a plurality of swirl plates arranged along its central circumference, and the swirl plates are inclined at an acute angle θ of 30° to 60° to the bottom surface of the swirl distributor. The swirl distributor can achieve uniform distribution of the rising channels of the airflow within the feed zone and the multiple reaction zones, allowing the reactant gas to be better dispersed between the packing materials within the tower body, achieving sufficient contact between the reactant gas and the reactant liquid, and making the reaction more sufficient and complete. The rising gas in the reaction system is diverted and diffused by the multiple swirl plates arranged at an angle, achieving an axially upward swirl effect.

[0013] Furthermore, the swirl plate is provided with a plurality of corrugated protrusions on both surfaces thereof, arranged in a wavy curve in the vertical direction, and the cross-section of the corrugated protrusions is semicircular. The wavy curves of the corrugated protrusions allow the rising gas on the two surfaces of the swirl plate to increase the fluctuating diffusion effect of the gas in the radial direction through the undulations on both sides of the corrugated protrusions. At the same time, the downwardly sinking reaction liquid is collided and dispersed during its descent due to the wavy curves, thereby preventing the reaction liquid from wall flow. The cross-section of the corrugated protrusions is semicircular, creating an arc transition between the swirl plate surface and the corrugated protrusions, thus avoiding dead corners.

[0014] Furthermore, the shell-and-tube heat exchanger includes inlet and outlet manifolds disposed at the upper and lower portions, each of which is evenly distributed in the axial direction with multiple vertical branch pipes of varying lengths. Multiple threaded tubes are evenly disposed between the corresponding upper and lower branch pipes, each having a spiral inner diameter of 60 to 150 mm and a spiral pitch of 50 to 100 mm. The shell-and-tube heat exchanger is heated by connecting the threaded tubes, which lengthens the heating path of the threaded tubes, further increasing contact with the packing and increasing the heating area of ​​the shell-and-tube heat exchanger. This allows the shell-and-tube heat exchanger to more accurately control the reaction temperature in the reaction zone, ensuring a stable and sufficient reaction. Furthermore, due to the threaded structure, the downwardly flowing polyphosphoric acid liquid in the reaction zone is less likely to form a wall flow effect on the surface of the threaded tube wall of the shell-and-tube heat exchanger, thereby enhancing the complete reaction of the polyphosphoric acid.

[0015] Furthermore, the filler filled in the reaction zone is a saddle-shaped filler.

[0016] Furthermore, for the plurality of reaction zones, the spiral directions of the threaded tubes of the tube-in-tube heat exchangers between the upper and lower adjacent reaction zones are arranged in opposite directions.

[0017] Furthermore, the tower body is provided with a structural redistributor at the upper part of the separation zone.

[0018] Furthermore, the tower body is provided with a wire mesh demister at the upper portion of the structural redistributor.

[0019] The present invention also provides a continuous preparation method of high-purity phosphorus oxyfluoride, which uses polyphosphoric acid and anhydrous hydrogen fluoride to react in a preparation tower to generate phosphorus oxyfluoride, and specifically includes the following steps:

[0020] S1, polyphosphoric acid preheating treatment: Pour polyphosphoric acid into the preheating high-level tank, control the heating temperature of the preheating high-level tank, and control the preheating temperature of the polyphosphoric acid to be 60~80℃;

[0021] S2, constant temperature heating treatment of polyphosphoric acid: polyphosphoric acid preheated to a temperature of 60-80°C is pumped into a constant temperature kettle with a nitrogen protection device and a stirrer through a pipeline controlled by a solenoid valve. The polyphosphoric acid is further heated to 80-100°C in the constant temperature kettle under stirring;

[0022] S3, reaction and separation treatment: polyphosphoric acid heated to 80-100° C. is evenly pumped into the upper part of the reaction zone of the preparation tower through a horizontal flow pump, and anhydrous hydrogen fluoride is introduced into the bottom of the feed zone of the preparation tower. The feed pressure of anhydrous hydrogen fluoride is 0.1-1 MPa, wherein the liquid polyphosphoric acid and anhydrous hydrogen fluoride are fed at a mass ratio of 80-40:1 and a feed rate. The polyphosphoric acid contacts the anhydrous hydrogen fluoride on the packings between the threaded tubes in the reaction zone to form a step-type reaction with a concentration gradient. The reaction zone adopts a two-stage reaction, wherein the temperature of the lower reaction zone is controlled at 80-100° C., and the temperature of the upper reaction zone is controlled at 100-120° C., so that the phosphorus oxyfluoride gas generated by the reaction is fractionated through the packing section on the separation zone and discharged at the top product outlet at the top of the tower body;

[0023] S4, drying: passing phosphorus oxyfluoride from the top product outlet of the tower body into the upper part of the side wall of the spray drying tower, and spraying 20% ​​to 60% fuming sulfuric acid from the top of the spray drying tower;

[0024] S5, separation: Phosphorus oxyfluoride and fuming sulfuric acid are cooled in a condenser at the bottom of the spray drying tower and then separated into liquid sulfuric acid and gaseous phosphorus oxyfluoride. The gaseous phosphorus oxyfluoride is further separated in a gas-liquid separator to produce a phosphorus oxyfluoride product with a purity of 99.6-99.8%.

[0025] Furthermore, the polyphosphoric acid has a molecular weight of 2000-5000.

[0026] The present invention provides a continuous preparation device for high-purity phosphorus oxyfluoride. The device preheats a preheating header tank of polyphosphoric acid so that the polyphosphoric acid is converted from a viscous liquid into a liquid that is easy to transmit after preheating. The device is controlled by a solenoid valve and transmitted to a constant temperature kettle through a high-level difference pipeline. The polyphosphoric acid is further heated and stirred to maintain a constant temperature in the constant temperature kettle. High-pressure nitrogen is used in the constant temperature kettle to provide nitrogen protection to prevent the polyphosphoric acid from absorbing water. At the same time, the high-pressure nitrogen can be used to pressurize the polyphosphoric acid in the constant temperature kettle into a preparation tower. The polyphosphoric acid and anhydrous hydrogen fluoride are reacted and separated in the preparation tower through gas-liquid two-phase exchange contact. The prepared phosphorus oxyfluoride gas is separated from the top of the preparation tower and further dried in a spray drying tower. A high-purity phosphorus oxyfluoride product is prepared by using a condenser and a gas-liquid separator.

[0027] The present invention utilizes a preparation tower to achieve full reaction and separation of polyphosphoric acid and anhydrous hydrogen fluoride. The preparation tower is provided with a multi-stage reaction zone. Polyphosphoric acid is diverted from the upper portion of the reaction zone to the surface of the filler in the reaction zone and contacts and reacts with the rising anhydrous hydrogen fluoride gas on the reaction zone. In the upper reaction zone, the concentration of polyphosphoric acid is high and the concentration of anhydrous hydrogen fluoride is low, so that polyphosphoric acid can completely react with the anhydrous hydrogen fluoride gas to form phosphorus oxytrifluoride gas, thereby avoiding excess anhydrous hydrogen fluoride passing through the upper reaction zone and the generation zone. The phosphorus oxyfluoride gas is lifted together with the polyphosphoric acid to the separation zone. Therefore, the above arrangement can greatly improve the purity of the phosphorus oxyfluoride gas. In the lower reaction zone, the concentration of polyphosphoric acid is low, but the concentration of anhydrous hydrogen fluoride is high. The anhydrous hydrogen fluoride in the reaction zone completely reacts with the polyphosphoric acid. Therefore, the multi-stage reaction zone adopts a step-by-step concentration reaction, making the reaction between polyphosphoric acid and anhydrous hydrogen fluoride more gentle, stable, and complete, thereby preventing excess polyphosphoric acid from passing through the reaction zone and the feed zone and remaining at the bottom of the tower.

[0028] The shell and tube heat exchanger provided by the threaded tube in the preparation tower of the present invention can better realize the precise control of the temperature of the reaction system in the reaction zone, ensure the temperature stability of the reaction system, avoid the reaction temperature fluctuation of the reaction zone, reduce the occurrence of side reactions in the reaction zone, and, by utilizing the multi-stage reaction zone and the corresponding shell and tube heat exchanger, realize the step-by-step control of the reaction temperature inside the different reaction zones, ensure the reaction temperature requirements of the reaction system at different concentration stages, improve the reaction efficiency between polyphosphoric acid and anhydrous hydrogen fluoride, the separation zone at the top of the tower body is increased by using the filler The resistance and path of the rising phosphorus gas are such that the mist of polyphosphoric acid entrained in the rising phosphorus oxytrifluoride gas is accumulated and absorbed through contact with the surface of the filler and flows back into the reaction zone after settling. Therefore, the separation zone can well realize the separation of phosphorus oxytrifluoride and the entrained polyphosphoric acid mist, thereby improving the purity of the phosphorus oxytrifluoride product. In addition, a structural redistributor and a wire mesh demister are provided at the upper part of the tower body. The phosphorus oxytrifluoride entrained in the phosphorus oxytrifluoride can be further removed by the wire mesh demister, and the captured mist and generated liquid enter the separation zone through the structural redistributor to realize gas-liquid separation.

[0029] The present invention adopts a continuous preparation method for generating phosphorus oxyfluoride by reacting polyphosphoric acid with anhydrous hydrogen fluoride in a preparation tower. The polyphosphoric acid is preheated to ensure a stable reaction temperature in the preparation tower of the polyphosphoric acid and anhydrous hydrogen fluoride, thereby generating the phosphorus oxyfluoride in the preparation tower. The phosphorus oxyfluoride is further dried in a spray drying tower, and then a phosphorus oxyfluoride product with a purity of 99.6-99.8% is prepared by using a condenser and a gas-liquid separator. The reaction yield is 95-96%. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the process flow for the continuous preparation of phosphorus oxytrifluoride.

[0031] Figure 2 This is a schematic diagram of the structure of the preparation tower of phosphorus oxyfluoride.

[0032] Figure 3 Schematic diagram of the three-dimensional structure of the swirl distributor.

[0033] Figure 4 A top view of the swirl distributor.

[0034] Figure 5 Schematic diagram of the cross section of the swirl distributor.

[0035] Figure 6 Schematic diagram of the three-dimensional structure of the tube heater.

[0036] Figure 7 This is the front view of the tube heater.

[0037] Figure 8 A top view of the tube heater.

[0038] Among them: 1-preheating high-level tank, 2-solenoid valve, 3-constant temperature kettle, 31-motor, 32-stirring paddle, 33-jacket, 34-feeding port, 35-discharge pipe, 4-high-pressure nitrogen pipe, 5-horizontal flow pump, 6-preparation tower, 61-tower body, 611-anhydrous hydrogen fluoride feed port, 612-polyphosphoric acid feed port, 613-mounting hole, 614-tower bottom waste outlet, 615-tower top product outlet, 62-packing section, 63-shell and tube heat exchanger, 631-inlet and outlet main pipe, 632-branch pipe, 633-threaded pipe, 634-flange, 64-swirl distributor, 641-swirl plate, 642-corrugated protrusion, 65-structural redistributor, 66-wire mesh demister, 7-spray drying tower, 71-sprayer, 8-condenser, 9-gas-liquid separator. DETAILED DESCRIPTION

[0039] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0040] Reference Figure 1The continuous preparation device of high-purity phosphorus oxyfluoride of the present invention includes a preheating high-level tank 1, which is equipped with a heating device for preheating polyphosphoric acid so that the polyphosphoric acid can maintain better fluidity. The bottom pipe of the preheating high-level tank 1 is connected to the feeding port 34 of the constant temperature kettle 3. The constant temperature kettle 3 is equipped with a jacket 33 for heating and heat preservation inside the constant temperature kettle 3. In order to achieve uniform heating of the constant temperature kettle 3, the constant temperature kettle 3 is equipped with a motor 31 with a stirring paddle 32. During the heating and heat preservation process of the jacket 33, the polyphosphoric acid is slowly stirred by the stirring paddle 32 to achieve temperature balance. A high-pressure nitrogen pipe 4 is also provided on the feeding port 34 of the constant temperature kettle 3. The high-pressure nitrogen pipe 4 is provided with an electromagnetic valve 2 for In order to control the opening of nitrogen, the high-pressure nitrogen pipe 4 is used to ensure that the thermostatic kettle 3 is in a protective atmosphere of nitrogen to protect the polyphosphoric acid from moisture. A discharge pipe 35 is provided in the thermostatic kettle 3, and the discharge pipe 35 extends inside the thermostatic kettle 3, and the opening of the discharge pipe 35 extends below the stirring paddle 32 and is immersed below the liquid level of the polyphosphoric acid, thereby preventing the nitrogen in the thermostatic kettle 3 from being mixed into the preparation tower 6 through the discharge pipe 35 and mixing with the reaction product trifluoride phosphorus gas in the preparation tower 6. At the same time, the high-pressure nitrogen pipe 4 can also maintain a certain pressure in the thermostatic kettle 3, thereby better realizing the smooth feeding of the polyphosphoric acid in the thermostatic kettle 3 to the polyphosphoric acid feed port 612 of the preparation tower 6 through the horizontal flow pump 5.

[0041] Preparation tower 6 of the present invention, with reference to Figure 2 , including a tower body 61, the tower body 61 is provided with a feed zone, more than one reaction zone and a separation zone in order from bottom to top, the feed zone and the separation zone inside the tower body 61 are filled with a packing section 62 of packing, a cyclone distributor 64 is provided between the feed zone and the reaction zone, between the separation zone and the reaction zone, and between multiple reaction zones, the side wall surface of the tower body 61 is provided with mounting holes 613 for the installation and maintenance of packing at both ends of the feed zone, each reaction zone, and the separation zone, wherein the feed zone is located in the middle of the feed zone. An anhydrous hydrogen fluoride feed port 611 is provided at the bottom of the packing section 62. The anhydrous hydrogen fluoride is dispersed through the packing in the packing section 62 and further dispersed by the swirl distributor 64 and lifted to the reaction zone. Each reaction zone is provided with a shell and tube heat exchanger 63. The shell and tube heat exchanger 63 is provided with a threaded tube 633 for controlling the reaction temperature. The threaded tubes 633 are also filled with fillers. The upper part of the reaction zone located in the top layer is provided with a polyphosphoric acid feed port 612 connected to the pipe between the discharge pipe 35 of the constant temperature reactor 3.

[0042] In the present invention, a tower body 61 is provided with a top product outlet 615 at the top, and a pipeline of the tower top product outlet 615 is connected to a spray drying tower 7. The pipeline of the tower top product outlet 615 is connected to the upper part of the side wall of the spray drying tower 7. A sprayer 71 for drying phosphorus oxytrifluoride gas is provided on the spray drying tower 7. The sprayer 71 dries the phosphorus oxytrifluoride gas by spraying 20% ​​to 60% fuming sulfuric acid, thereby further improving the purity of the dried phosphorus oxytrifluoride gas. A condenser 8 is connected to the bottom of the spray drying tower 7. The pipeline of the condenser 8 is connected to a gas-liquid separator 9. After the phosphorus oxyfluoride gas passes through the condenser 8 and the gas-liquid separator 9, a phosphorus oxyfluoride product with a purity of 99.6% to 99.8% is obtained.

[0043] Refer to Figure 6. Figure 7 、 Figure 8 The shell and tube heat exchanger 63 is provided with a threaded tube 633 for controlling the reaction temperature. The shell and tube heat exchanger 63 includes an inlet and outlet main pipe 631 arranged at the upper and lower parts. A plurality of vertical and length-distributed branch pipes 632 are evenly arranged in the axial direction of each inlet and outlet main pipe 631. The plurality of threaded tubes 633 are evenly arranged between the upper and lower corresponding branch pipes 632. The plurality of branch pipes 632 are arranged in a circular shape according to the internal cross-sectional shape of the tower body 61, so that the threaded tubes 633 between the plurality of branch pipes 632 can be well evenly distributed vertically in the reaction zone of the tower body 61. A flange 634 is provided at the end of the inlet and outlet main pipe 631 for connection to an external heating steam pipeline. In the reaction zone, the space between the threaded tubes 633 is also filled with Filler, during the liquid phase flow of polyphosphoric acid from the top of the reaction zone to the bottom, part of the polyphosphoric acid will flow along the outer wall surface of the threaded tube 633, forming a wall flow effect. However, after the reaction zone is filled with filler, the filler and the outer wall of the threaded tube 633 come into contact with the filler, and the polyphosphoric acid on the outer wall surface of the threaded tube 633 will be naturally drained and dispersed on the filler surface under the action of swirl inertia. Therefore, the combination of the threaded tube 633 and the filler can well prevent the wall flow effect of the threaded tube 633. At the same time, due to its spiral setting, the threaded tube 633 increases the heating length and heating area of ​​the threaded tube 633, thereby increasing the internal heating effect of the threaded tube 633 on the reaction zone.

[0044] A second feed port 612 for feeding polyphosphoric acid is provided above the top reaction zone. After being fed through the second feed port 612, the polyphosphoric acid is dispersed within the reaction zone by a cyclone distributor 64. The polyphosphoric acid then disperses and flows from the top reaction zone to the lower reaction zone. There, the polyphosphoric acid contacts anhydrous hydrogen fluoride on the packing between the threaded tubes 633 dispersed within the reaction zone, forming a stepwise reaction with a concentration gradient. The reaction temperatures of the multiple reaction zones are controlled upward from the bottom of the tower body 61 via a shell-and-tube heat exchanger 63 to a stepwise reaction temperature of 80-120°C. The phosphorus oxyfluoride gas generated by the reaction is fractionated through the packing section 62 in the separation zone and enters the next process at the top product outlet 615 at the top of the tower body 61. Excess polyphosphoric acid liquid and a small amount of residual side reaction liquid can be regularly discharged through the bottom waste outlet 614 of the tower body 61 for centralized collection and treatment.

[0045] In the present invention, in order to better achieve the dispersion effect of the filler inside the reaction zone, the filler filled inside the reaction zone is preferably a saddle-shaped filler, and the specifications of the saddle-shaped filler are 38mm×30mm×0.8mm (outer diameter×height×thickness) or 50mm×40mm×1.0mm (outer diameter×height×thickness). Correspondingly, the spiral inner diameter of the threaded tube 633 of the shell and tube heat exchanger 63 is 60~150mm, and the pitch of the spiral is 50~100mm, so that one or more saddle-shaped fillers can be placed inside the spiral of the threaded tube 633 and between the pitches of the upper and lower spirals, ensuring the installation and placement of the saddle-shaped filler. During the process of filling the saddle-shaped filler into the spiral interior of the threaded tube 633 of the shell and tube heat exchanger 63, the saddle shape of the saddle-shaped filler is placed in contact with the spiral direction of the threaded tube 633, so that the outer wall surface of the threaded tube 633 and the saddle shape of the saddle-shaped filler are better fitted, further ensuring that the polyphosphoric acid flowing on the outer wall surface of the threaded tube 633 can be well dispersed in the reaction zone through the saddle-shaped filler.

[0046] In the present invention, the spiral directions of the threaded tubes 633 of the shell-and-tube heat exchangers 63 between the upper and lower adjacent reaction zones of the multiple reaction zones are set in opposite directions. In this way, it can be well ensured that the polyphosphoric acid can achieve staggered dispersed flow in the process of passing through the adjacent reaction zones, thereby achieving a better dispersion effect.

[0047] In the present invention, the reaction liquid and reaction gas in the tower body 61 are uniformly dispersed in the packing in the reaction zone by the swirl distributor 64. In order to further improve the dispersion effect, the swirl distributor 64 can refer to Figure 3 、 Figure 4 and Figure 5The swirl distributor 64 is provided with a plurality of swirl plates 641 arranged along its central circumference. The acute angle θ between the swirl plates 641 and the bottom surface of the swirl distributor 64 is set at an angle of 30° to 60°. Preferably, the acute angle θ is set to 45°. The swirl distributor 64 can achieve uniform distribution of the rising channels of the airflow inside the feed zone and the multiple reaction zones, so that the reaction gas can be better dispersed between the fillers inside the tower body 61, achieving sufficient contact between the reaction gas and the reaction liquid, making the reaction more sufficient and complete. The rising gas in the reaction system is turned and diffused by the inclined multiple swirl plates 641 to achieve an axially upward swirl effect. At the same time, as a further embodiment, it can also A number of corrugated protrusions 642 are provided on the two surfaces of the swirl plate 641 in a wavy curve in the vertical direction, and the cross-section of the corrugated protrusion 642 is in the shape of a semicircle. The wavy curve of the corrugated protrusion 642 is in the shape of a semicircle. The wavy curve of the corrugated protrusion 642 is in the shape of a semicircle. The rising gas attached to the two surfaces of the swirl plate 641 can increase the fluctuation and diffusion effect of the gas in the radial direction through the undulations on both sides of the corrugated protrusion 642, thereby further increasing the dispersion effect of the rising gas. At the same time, the reaction liquid settling downward collides and disperses during the descent due to the wavy curve, thereby avoiding the wall flow of the reaction liquid. The cross-section of the corrugated protrusion 642 is in the shape of a semicircle, so that there is an arc transition between the surface of the swirl plate 641 and the corrugated protrusion 642 to avoid dead corners.

[0048] The reaction zone can be provided with two or more sections, so that the step-by-step contact and reaction of polyphosphoric acid and anhydrous hydrogen fluoride in multiple reaction zones can be achieved, and the reaction can be more gentle, stable, and complete. Polyphosphoric acid flows from the upper portion of the reaction zone to the surface of the filler in the reaction zone, and contacts and reacts with the rising anhydrous hydrogen fluoride gas on the reaction zone. In the upper reaction zone, the concentration of polyphosphoric acid is high and the concentration of anhydrous hydrogen fluoride is low, so that the polyphosphoric acid can completely react with the anhydrous hydrogen fluoride gas to form phosphorus oxytrifluoride gas, avoiding excess The anhydrous hydrogen fluoride is lifted to the separation zone together with the generated phosphorus oxyfluoride gas through the upper reaction zone, thereby improving the purity of the phosphorus oxyfluoride gas. In the lower reaction zone, the concentration of polyphosphoric acid is low, but the concentration of anhydrous hydrogen fluoride is high. The anhydrous hydrogen fluoride in the reaction zone completely reacts with the polyphosphoric acid. Therefore, the multi-stage reaction zone uses a step-by-step concentration reaction to prevent excess polyphosphoric acid from passing through the reaction zone and the feed zone and remaining at the bottom of the tower body 61. Therefore, the reaction yield between polyphosphoric acid and anhydrous hydrogen fluoride is effectively increased, and the occurrence of side reactions is reduced. By providing a multi-stage reaction zone, the reaction temperature of the reaction zones in different stages is controlled by the multi-stage shell-and-tube heat exchanger 63, and the temperature control is more precise. The precise control of the temperature of the reaction system ensures the temperature stability of the reaction system, avoids the reaction temperature fluctuation of the reaction zone, reduces the occurrence of side reactions in the reaction zone, and realizes a stepped reaction temperature in different stages, which can well conform to the staged reaction process of polyphosphoric acid and anhydrous hydrogen fluoride, improves the reaction stability between polyphosphoric acid and anhydrous hydrogen fluoride, and reduces the occurrence of side reactions.

[0049] In particular, the reaction zone is provided with two sections, wherein the temperature of the lower reaction zone is controlled at 80-100° C. by the shell-and-tube heat exchanger 63, so that the lower reaction zone is in a low-temperature reaction stage, and the high-concentration anhydrous hydrogen fluoride and the low-concentration polyphosphoric acid react at a relatively low temperature to avoid a violent reaction. The temperature of the upper reaction zone is controlled at 100-120° C., so that the upper reaction zone is in a high-temperature reaction stage, and the low-concentration anhydrous hydrogen fluoride and the high-concentration polyphosphoric acid react at a relatively high temperature, thereby increasing the reaction kinetics and also increasing the upward kinetics of the reaction product phosphorus oxyfluoride, thereby ensuring that phosphorus oxyfluoride can be better lifted to the separation zone in the high-temperature reaction zone, thereby reducing the entrainment of phosphorus oxyfluoride by the liquid polyphosphoric acid toward the bottom of the tower body 61 during its downward process.

[0050] In the present invention, the resistance and path of the rising phosphorus oxytrifluoride gas are increased by using fillers in the upper separation zone. Therefore, the mist of polyphosphoric acid entrained in the rising phosphorus oxytrifluoride gas is accumulated and absorbed through contact with the surface of the fillers and then refluxes into the reaction zone after sedimentation. Therefore, the separation zone can effectively separate the phosphorus oxytrifluoride and the entrained polyphosphoric acid mist, thereby improving the purity of the phosphorus oxytrifluoride product. In addition, a structural redistributor 65 and a wire mesh demister 66 are provided at the upper part of the tower body 61. The phosphorus oxytrifluoride entrained in the phosphorus oxytrifluoride can be further removed by the wire mesh demister 66, and the captured mist and generated liquid enter the separation zone through the structural redistributor 65 to achieve gas-liquid separation.

[0051] The present invention also provides a continuous preparation method of high-purity phosphorus oxyfluoride, which uses polyphosphoric acid and anhydrous hydrogen fluoride in a preparation tower 6 to react and generate phosphorus oxyfluoride.

[0052] Example 1

[0053] use Figure 1 The continuous preparation process shown is a method for preparing high-purity phosphorus oxyfluoride, using polyphosphoric acid and anhydrous hydrogen fluoride to react in a preparation tower 6 to generate phosphorus oxyfluoride, specifically comprising the following steps:

[0054] S1, polyphosphoric acid preheating treatment: Pour polyphosphoric acid with a molecular weight of 2000-2500 into the preheating high-level tank 1, and control the heating temperature of the preheating high-level tank 1 to control the preheating temperature of the polyphosphoric acid at 60°C;

[0055] S2, constant temperature heating treatment of polyphosphoric acid: polyphosphoric acid preheated to 60°C is pumped into a constant temperature kettle 3 with a nitrogen protection device and a stirrer through a pipeline controlled by a solenoid valve 2. The polyphosphoric acid is further heated to 80°C in the constant temperature kettle 3 under stirring;

[0056] S3, reaction and separation treatment: polyphosphoric acid heated to 80° C. is evenly pumped into the upper portion of the reaction zone of preparation tower 6 via horizontal flow pump 5. Anhydrous hydrogen fluoride is introduced into the bottom of the feed zone of preparation tower 6 at a feed pressure of 0.5 MPa. The liquid feed rate of polyphosphoric acid is controlled to 850 kg / h, and the gas feed rate of anhydrous hydrogen fluoride is controlled to 13.83 kg / h. The polyphosphoric acid contacts the anhydrous hydrogen fluoride on the packing dispersed between the threaded tubes 633 in the reaction zone to form a step-wise reaction with a concentration gradient. The reaction zone adopts a two-stage reaction, wherein the temperature of the lower reaction zone is controlled at 90° C., and the temperature of the upper reaction zone is controlled at 110° C. The phosphorus oxyfluoride gas generated after the reaction is fractionated through the packing section 62 in the separation zone and discharged through the top product outlet 615 at the top of the tower body 61. The residual waste liquid is collected at the bottom of the tower body 61 on a shift basis (one shift is 8 hours) to obtain 280 kg;

[0057] S4, drying: phosphorus oxyfluoride from the top product outlet 615 at the top of the tower body 61 is introduced into the upper side wall of the spray drying tower 7, and 20% to 60% fuming sulfuric acid is sprayed from the top of the spray drying tower 7;

[0058] S5, separation: Phosphorus oxyfluoride and fuming sulfuric acid are cooled and separated in a condenser 8 at the bottom of a spray drying tower 7 to separate liquid sulfuric acid and gaseous phosphorus oxyfluoride. The gaseous phosphorus oxyfluoride is further separated in a gas-liquid separator 9 to obtain a phosphorus oxyfluoride product with a purity of 99.83%.

[0059] According to calculation, the residual waste liquid content of preparation tower 6 is 4.05%, that is, the reaction yield is 95.95%.

[0060] Example 2

[0061] The process flow and steps are the same as those in Example 1. The molecular weight of the polyphosphoric acid used is 2000-3000. The difference is that the constant temperature of the polyphosphoric acid is raised to 90°C. In the reaction zone, the temperature of the lower reaction zone is 100°C, and the temperature of the upper reaction zone is 120°C, that is, the constant temperature and the reaction temperature of the polyphosphoric acid are increased. At the bottom of the tower body 61 of the preparation tower 6, 260 kg of residual waste liquid is collected on a shift basis (one shift is 8 hours). After calculation, the residual waste liquid content of the preparation tower 6 is 3.76%, that is, the reaction yield is 96.24%. The gaseous phosphorus oxyfluoride is further separated in the gas-liquid separator 9 to produce a phosphorus oxyfluoride product with a purity of 99.75%.

[0062] Compared with Example 1, Example 2 shows that the reaction effect between polyphosphoric acid and anhydrous hydrofluoric acid is better and the reaction yield is improved when the reaction temperature is increased. However, after the temperature is increased, the purity of the phosphorus oxyfluoride product is reduced due to the generation of a small amount of side reactions.

[0063] Example 3

[0064] The process flow and steps are the same as those in Example 1. The process conditions, the liquid feed rate of the polyphosphoric acid, and the gas feed rate of the anhydrous hydrogen fluoride are all unchanged. The difference is that the molecular weight of the polyphosphoric acid used is 4000-5000. 268 kg of residual waste liquid is collected at the bottom of the tower body 61 of the preparation tower 6 on a shift basis (one shift is 8 hours). The residual waste liquid content of the preparation tower 6 is calculated to be 3.88%, that is, the reaction yield is 96.12%. The gaseous phosphorus oxyfluoride is further separated in the gas-liquid separator 9 to produce a phosphorus oxyfluoride product with a purity of 99.78%.

[0065] Compared with Example 1, Example 3 shows that after the polymerization degree of the polyphosphoric acid is increased, the reaction effect between the polyphosphoric acid and anhydrous hydrofluoric acid is better and the reaction yield is improved. However, after the polymerization degree of the polyphosphoric acid is increased, the generation of side reactions is increased, and therefore the purity of the phosphorus oxytrifluoride product is reduced.

[0066] Example 4

[0067] The process flow and steps were the same as those in Example 1. The molecular weight of the polyphosphoric acid used was 2000-3000. The difference was that the feed ratio of polyphosphoric acid and anhydrous hydrogen fluoride was changed. The liquid feed rate of polyphosphoric acid was controlled to 850 kg / h, and the gas feed rate of anhydrous hydrogen fluoride was controlled to 20.25 kg / h. Residual waste liquid was collected from the bottom of the tower body 61 of the preparation tower 6 on a shift basis (one shift was 8 hours) to obtain 243 kg. The residual waste liquid content of the preparation tower 6 was calculated to be 3.49%, i.e., the reaction yield was 96.51%. The gaseous phosphorus oxyfluoride was further separated in the gas-liquid separator 9 to produce a phosphorus oxyfluoride product with a purity of 99.60%.

[0068] Compared with Example 1, Example 4 shows that changing the feed ratio of polyphosphoric acid and anhydrous hydrogen fluoride, that is, increasing the amount of anhydrous hydrogen fluoride, improves the reaction yield, but reduces the purity of the phosphorus oxytrifluoride product.

[0069] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A continuous preparation device for high-purity phosphorus oxyfluoride, characterized in that: The invention comprises a preheating high-level tank, the bottom pipeline of the preheating high-level tank is connected to a thermostatic kettle, the thermostatic kettle comprises a discharge pipe extending inside the same, the discharge pipe is connected to a preparation tower through a pipe, the preparation tower comprises a tower body, a feed zone, more than one reaction zone and a separation zone are sequentially arranged on the tower body from bottom to top, the feed zone and the separation zone inside the tower body are both filled with a packing section of a packing, wherein the bottom of the packing section in the feed zone is provided with an anhydrous hydrogen fluoride feed port, each of the reaction zones is provided with a shell and tube heat exchanger, and the shell and tube heat exchanger is provided with a device for controlling the reaction. The spiral tubes are connected to the temperature, and the space between the spiral tubes is also filled with fillers. The upper part of the reaction zone located at the top layer is provided with a polyphosphoric acid feed port connected to the pipe between the discharge pipes of the constant temperature kettle. The tower body is provided with a top product outlet at the top, and the top product outlet pipe is connected to a spray drying tower, and the top product outlet pipe is connected to the upper part of the side wall of the spray drying tower. The spray drying tower is provided with a sprayer for drying. The spray drying tower is connected to a condenser at its bottom, and the condenser pipe is connected to a gas-liquid separator. The preparation tower, wherein a swirl distributor is provided between the feed zone and the reaction zone, between the separation zone and the reaction zone, and between the multiple reaction zones, the swirl distributor being provided with a plurality of swirl plates arrayed along its central circumference, and the acute angle θ between the swirl plates and the bottom surface of the swirl distributor being inclined at 30° to 60°; The swirl plate has a plurality of corrugated protrusions on both surfaces thereof, which are arranged in a wavy curve in the vertical direction, and the cross section of the corrugated protrusions is in the shape of a semicircular arc; The reaction zone is filled with saddle-shaped fillers.

2. The continuous preparation device of high-purity phosphorus oxyfluoride according to claim 1, characterized in that: A solenoid valve is provided between the preheating high-level tank and the constant temperature kettle.

3. The continuous preparation device of high-purity phosphorus oxyfluoride according to claim 1, characterized in that: A horizontal flow pump is further provided between the polyphosphoric acid feed port and the discharge pipe.

4. The continuous preparation device of high-purity phosphorus oxyfluoride according to claim 1, characterized in that: The shell and tube heat exchanger includes inlet and outlet main pipes arranged at the upper and lower parts, and each inlet and outlet main pipe is evenly provided with multiple vertical branch pipes with different lengths in the axial direction. Multiple threaded pipes are evenly arranged between the corresponding branch pipes at the upper and lower parts, and the inner diameter of the spiral of the threaded pipe is 60~150mm, and the pitch of the spiral is 50~100mm.

5. The continuous preparation device of high-purity phosphorus oxyfluoride according to claim 1, characterized in that: For the plurality of reaction zones, the spiral directions of the threaded tubes of the tube-in-tube heat exchangers between the upper and lower adjacent reaction zones are arranged in opposite directions.

6. A continuous preparation method of high-purity phosphorus oxyfluoride, characterized in that: A continuous preparation device for high-purity phosphorus oxyfluoride according to any one of claims 1 to 5 is used, wherein polyphosphoric acid and anhydrous hydrogen fluoride are reacted in a preparation tower to generate phosphorus oxyfluoride, specifically comprising the following steps: S1, polyphosphoric acid preheating treatment: Pour polyphosphoric acid into the preheating high-level tank, control the heating temperature of the preheating high-level tank, and control the preheating temperature of the polyphosphoric acid to be 60~80℃; S2, constant temperature heating treatment of polyphosphoric acid: polyphosphoric acid preheated to a temperature of 60-80°C is pumped into a constant temperature kettle with a nitrogen protection device and a stirrer through a pipeline controlled by a solenoid valve. The polyphosphoric acid is further heated to 80-100°C in the constant temperature kettle under stirring; S3, reaction and separation treatment: polyphosphoric acid heated to 80-100° C. is evenly pumped into the upper part of the reaction zone of the preparation tower through a horizontal flow pump, and anhydrous hydrogen fluoride is introduced into the bottom of the feed zone of the preparation tower. The feed pressure of anhydrous hydrogen fluoride is 0.1-1 MPa, wherein the liquid polyphosphoric acid and anhydrous hydrogen fluoride are fed at a mass ratio of 80-40:1 and a feed rate. The polyphosphoric acid contacts the anhydrous hydrogen fluoride on the packings between the threaded tubes in the reaction zone to form a step-type reaction with a concentration gradient. The reaction zone adopts a two-stage reaction, wherein the temperature of the lower reaction zone is controlled at 80-100° C., and the temperature of the upper reaction zone is controlled at 100-120° C., so that the phosphorus oxyfluoride gas generated by the reaction is fractionated through the packing section on the separation zone and discharged at the top product outlet at the top of the tower body; S4, drying: passing phosphorus oxyfluoride from the top product outlet of the tower body into the upper part of the side wall of the spray drying tower, and spraying 20% ​​to 60% fuming sulfuric acid from the top of the spray drying tower; S5, separation: Phosphorus oxyfluoride and fuming sulfuric acid are cooled in a condenser at the bottom of the spray drying tower and then separated into liquid sulfuric acid and gaseous phosphorus oxyfluoride. The gaseous phosphorus oxyfluoride is further separated in a gas-liquid separator to produce a phosphorus oxyfluoride product with a purity of 99.6-99.8%.

7. The method for continuously preparing high-purity phosphorus oxyfluoride according to claim 6, characterized in that: The polyphosphoric acid has a molecular weight of 2000-5000.

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