Continuous preparation method and device of high-purity phosphorus oxyfluoride

Abstract

The invention discloses a continuous preparation method of high-purity phosphorus oxyfluoride and a device thereof, and relates to the technical field of production for phosphorus oxyfluoride preparation.According to the continuous preparation method of the high-purity phosphorus oxyfluoride, by conducting preheating treatment on a preheating head tank of polyphosphoric acid, the polyphosphoric acid is preheated from liquid in a viscous state to obtain liquid easy to convey, and the liquid is controlled through an electromagnetic valve; polyphosphoric acid is conveyed into a constant-temperature kettle through a high-level-difference pipeline, the polyphosphoric acid is further heated and stirred to keep constant temperature through the constant-temperature kettle, the polyphosphoric acid and anhydrous hydrogen fluoride are subjected to gas-liquid two-phase exchange contact in a preparation tower to realize reaction and separation, and prepared phosphorus oxyfluoride gas is separated from the top of the preparation tower; after further drying is achieved through the spray drying tower, the phosphorus oxyfluoride product with the purity reaching 99.6%-99.8% is prepared through the condenser and the gas-liquid separator, the reaction yield is 95%-96%, the purity of phosphorus oxyfluoride is high, few side reactions exist in the production process, and the reaction yield is high.

Description

Technical Field

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

[0002] At present, phosphorus oxyfluoride (POF 3 ) is a colorless gas with a pungent odor under normal conditions, emitting faint smoke in the air. Phosphorus oxyfluoride (POF 3 ) is mainly prepared by using CaF 2 It reacts with anhydrous sulfurous acid to generate CaF(SO 3 F), and then with H 3 PO 4 The intermediate product POF is generated by the reaction 3 However, due to CaF 2 It is solid, and continuous production is difficult. The process is complicated and the production cost is high. Moreover, the generated CaSO 4 The pollution to the surrounding soil is serious and necessary treatment must be carried out.

[0003] To this end, the applicant previously proposed a method for preparing high-purity phosphorus oxytrifluoride by continuous reactive distillation (patent application number CN2022114628326), which discloses 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 the actual application of the method for preparing high-purity phosphorus oxyfluoride by continuous reactive distillation, it is found that the equipment for preparing phosphorus oxyfluoride is numerous and complicated due to the method of using the reaction first and then separation. Moreover, in the reactive distillation tower, since polyphosphoric acid is a liquid and anhydrous hydrogen fluoride is a gas, the polyphosphoric acid and anhydrous hydrogen fluoride have a short contact time during the process of two-phase contact through the tower plate, so that the reaction between polyphosphoric acid and anhydrous hydrogen fluoride is insufficient, and the cyclic reaction must be achieved by controlling the reflux, which increases the energy consumption of the production reaction. The concentration of the reaction liquid on the tower plate is uneven, so that the concentration of some parts of the reaction is too high, and the side reactions become more, and the concentration of some parts of the reaction is too low, so that the reaction is incomplete. Therefore, a lot of waste is discharged at the bottom of the reactive distillation tower, which is not conducive to improving the reaction yield between polyphosphoric acid and anhydrous hydrogen fluoride.

[0005] Therefore, the applicant has previously proposed a method for preparing high-purity phosphorus oxyfluoride by continuous reaction distillation. The applicant needs to improve and study it and design a continuous preparation method for high-purity phosphorus oxyfluoride and a preparation device thereof, with the aim of solving the problem of preparing a continuous preparation method for phosphorus oxyfluoride with high purity, few side reactions and high reaction yield and a preparation device thereof. 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 implemented by the following technical solutions: A continuous preparation device for high-purity phosphorus oxyfluoride, comprising a preheating high-level tank, the bottom pipeline of the preheating high-level tank is connected to the feed port of a thermostatic kettle, the thermostatic kettle comprises a discharge pipe extending inside the tank, the discharge pipe is connected to a preparation tower through a pipeline, the preparation tower comprises a tower body, the tower body is sequentially provided with a feed zone, at least one reaction zone and a separation zone 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 tube-in-tube heat exchanger, the tube-in-tube heat exchanger The heat exchanger 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 at 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 tower top product outlet at the top, and the tower top product outlet pipeline is connected to a spray drying tower, and the tower 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, and the spray drying tower is connected to a condenser at its bottom, and the condenser pipeline is connected to a gas-liquid separator.

[0008] Furthermore, a solenoid valve is provided between the preheating high-level tank and the constant temperature kettle.

[0009] 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.

[0010] Furthermore, a horizontal flow pump is provided between the polyphosphoric acid feed port and the discharge pipe.

[0011] Further, 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 is provided with multiple swirl plates arrayed along its central circumference, and the acute angle θ between the swirl plate and the bottom surface of the swirl distributor is 30° to 60°. The swirl distributor can achieve uniform distribution of the rising channels of the gas flow inside the feed zone and multiple reaction zones, so that the reaction gas can be better dispersed between the fillers inside the tower body, and sufficient contact between the reaction gas and the reaction liquid is achieved, so that the reaction is more sufficient and complete, and the rising gas in the reaction system is turned and diffused by the inclined arrangement of multiple swirl plates to achieve an axially upward swirl effect.

[0012] Furthermore, the swirl plate has a plurality of corrugated protrusions arranged in a wavy curve in the vertical direction on its two surfaces, and the cross section of the corrugated protrusion is in a semicircular arc shape. The wavy curve of the corrugated protrusion is in a wavy shape so that the rising gas attached to the two surfaces of the swirl plate can increase the fluctuating diffusion effect of the gas in the radial direction through the ups and downs on both sides of the corrugated protrusion. At the same time, the reaction liquid settling downwards 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 is in a semicircular arc shape, so that there is an arc transition between the swirl plate surface and the corrugated protrusion to avoid dead corners.

[0013] Furthermore, the shell-and-tube heat exchanger includes inlet and outlet main pipes arranged at the upper and lower parts, and each of the inlet and outlet main pipes is evenly provided with a plurality of horizontal and vertical branch pipes with a distribution of lengths in the axial direction, and a plurality of the threaded pipes are evenly arranged between the corresponding branch pipes at the upper and lower parts, and the spiral inner diameter of the threaded pipe is 60-150 mm, and the pitch of the spiral is 50-100 mm. The shell-and-tube heat exchanger is heated by connecting the threaded pipes, so that the heating path of the threaded pipes becomes longer, further increasing the contact with the filler, increasing the heating area of ​​the shell-and-tube heat exchanger, and enabling the shell-and-tube heat exchanger to more accurately control the reaction temperature of the reaction zone, ensuring the stability and sufficiency of the reaction. Moreover, due to the use of the threaded structure, it is difficult for the polyphosphoric acid liquid flowing downward in the reaction zone to form a wall flow effect on the threaded pipe wall surface on the shell-and-tube heat exchanger, thereby increasing the sufficiency of the reaction of the polyphosphoric acid.

[0014] Furthermore, the filler filled inside the reaction zone is a saddle-shaped filler.

[0015] 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.

[0016] Furthermore, the tower body is provided with a structural redistributor at an upper portion of the separation zone.

[0017] Furthermore, the tower body is provided with a wire mesh demister at an upper portion of the structural redistributor.

[0018] 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 comprises the following steps: S1, polyphosphoric acid preheating treatment: pour the 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 at 60-80°C; S2, constant temperature heating treatment of polyphosphoric acid: the polyphosphoric acid with a preheating 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, and the polyphosphoric acid is further heated to 80-100°C in the constant temperature kettle under stirring; S3, reaction and separation treatment: the 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, and the feed pressure of the anhydrous hydrogen fluoride is 0.1-1MPa, wherein the liquid of the polyphosphoric acid and the anhydrous hydrogen fluoride are fed at a feed rate of 80-40:1 by mass ratio, and the polyphosphoric acid contacts the anhydrous hydrogen fluoride on the fillers between the threaded pipes dispersed in the reaction zone to form a step-by-step reaction of concentration, and 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 after the reaction is fractionated through the filler section on the separation zone and the product outlet is 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 separated after being cooled in a condenser at the bottom of the spray drying tower to separate liquid sulfuric acid and gaseous phosphorus oxyfluoride. The gaseous phosphorus oxyfluoride is further separated in a gas-liquid separator to obtain a phosphorus oxyfluoride product with a purity of 99.6-99.8%.

[0019] Furthermore, the polyphosphoric acid is a medium polyphosphoric acid with a molecular weight of 2000 to 5000.

[0020] The invention discloses a continuous preparation device for high-purity phosphorus oxyfluoride. The device preheats a preheating high-level 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 an electromagnetic 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 through the constant temperature kettle. Nitrogen protection is provided by high-pressure nitrogen in the constant temperature kettle to prevent the polyphosphoric acid from absorbing water. The polyphosphoric acid in the constant temperature kettle can also be pressed into a preparation tower by high-pressure nitrogen. The polyphosphoric acid and anhydrous hydrogen fluoride are reacted and separated in one body through gas-liquid two-phase exchange contact in the preparation tower. The prepared phosphorus oxyfluoride gas is separated from the tower top of the preparation tower, and after further drying through a spray drying tower, a high-purity phosphorus oxyfluoride product is prepared by a condenser and a gas-liquid separator.

[0021] The 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. The polyphosphoric acid flows from the upper part 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, thereby avoiding the excess anhydrous hydrogen fluoride passing through the upper reaction zone and the generation zone. The phosphorus oxyfluoride gas is lifted to the separation zone together. Therefore, the above-mentioned arrangement can greatly improve the purity of the phosphorus oxyfluoride gas. In the reaction zone at the lower part, the concentration of polyphosphoric acid is low, but the concentration of anhydrous hydrogen fluoride is high. The anhydrous hydrogen fluoride in the reaction zone reacts the polyphosphoric acid thoroughly. Therefore, the multi-stage reaction zone makes the reaction between polyphosphoric acid and anhydrous hydrogen fluoride more gentle and stable, and the reaction is more complete through the step-by-step reaction of the concentration, thereby avoiding the excess polyphosphoric acid from passing through the reaction zone and the feed zone and remaining at the bottom of the tower body.

[0022] The shell-and-tube heat exchanger arranged 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 use the multi-stage reaction zone and the corresponding shell-and-tube heat exchanger to 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, and the separation zone at the top of the tower body increases the trifluoroacetic acid by using fillers. The resistance and path of the rising phosphorus gas, so the mist of polyphosphoric acid entrained in the rising gas of phosphorus oxytrifluoride is accumulated and absorbed through the contact on the surface of the filler and refluxes into the reaction zone after settling. Therefore, through the separation zone, the separation of phosphorus oxytrifluoride and the entrained polyphosphoric acid mist can be well achieved, and the purity of the phosphorus oxytrifluoride product is improved. In addition, a structural redistributor and a wire mesh demister are arranged on 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 the generated liquid enter the separation zone through the structural redistributor to achieve gas-liquid separation.

[0023] The invention adopts a method for continuously preparing phosphorus oxyfluoride by using a preparation tower as a reaction between polyphosphoric acid and anhydrous hydrogen fluoride, and preheating the polyphosphoric acid to ensure that the reaction temperature in the preparation tower of the polyphosphoric acid and anhydrous hydrogen fluoride is stable, so that the phosphorus oxyfluoride produced in the preparation tower is further dried by 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, and the reaction yield is 95-96%. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the process flow for the continuous preparation of phosphorus oxyfluoride.

[0025] Figure 2 This is a schematic diagram of the structure of a tower for preparing phosphorus oxyfluoride.

[0026] Figure 3 It is a schematic diagram of the three-dimensional structure of the swirl distributor.

[0027] Figure 4 A top view of the swirl distributor.

[0028] Figure 5 It is a cross-sectional schematic diagram of the swirl distributor.

[0029] Figure 6 It is a schematic diagram of the three-dimensional structure of the tube-in-tube heater.

[0030] Figure 7 This is the front view of the tube heater.

[0031] Figure 8 A top view of a tube heater.

[0032] 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-advection pump, 6-preparation tower, 61-tower body, 611-anhydrous hydrogen fluoride feed port, 612-polyphosphoric acid feed port, 613-installation hole, 614-tower bottom waste outlet, 615-tower top product outlet, 62-packing section, 63-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

[0033] 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 in conjunction with the accompanying drawings and embodiments.

[0034] Reference Figure 1 The continuous preparation device of high-purity phosphorus oxyfluoride of the present invention comprises a preheating high-level tank 1, which is provided with a heating device for preheating polyphosphoric acid so that the polyphosphoric acid can maintain better fluidity. The bottom pipeline of the preheating high-level tank 1 is connected to the feeding port 34 of the thermostatic kettle 3. The thermostatic kettle 3 is provided with a jacket 33 for heating and heat preservation inside the thermostatic kettle 3. In order to achieve uniform heating of the thermostatic kettle 3, the thermostatic 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 thermostatic kettle 3. The high-pressure nitrogen pipe 4 is provided with an electromagnetic valve 2 for The high-pressure nitrogen pipe 4 is used to control the opening of nitrogen. It 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. 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 stable 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.

[0035] The preparation tower 6 of the present invention, referring to Figure 2The tower body 61 includes a tower body 61, which is provided with a feed zone, at least one reaction zone and a separation zone from bottom to top. The feed zone and the separation zone inside the tower body 61 are filled with a packing section 62 of a 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 installation holes 613 for the installation and maintenance of packing at both ends of the feed zone, each reaction zone, and the separation zone. An anhydrous hydrogen fluoride feed port 611 is provided at the bottom of the packing section 62 in the zone. The anhydrous hydrogen fluoride is dispersed by the packing of the packing section 62, and is further dispersed and lifted to the reaction zone by the cyclone distributor 64. A shell-and-tube heat exchanger 63 is provided in each reaction zone. A threaded tube 633 for controlling the reaction temperature is provided on the shell-and-tube heat exchanger 63. The threaded tubes 633 are also filled with fillers. The upper part of the reaction zone located at the top layer is provided with a polyphosphoric acid feed port 612 connected to the pipeline between the discharge pipe 35 of the constant temperature kettle 3.

[0036] In the present invention, a tower top product outlet 615 is provided at the top of the tower body 61, and the tower top product outlet 615 pipeline is connected to the spray drying tower 7, and the tower top product outlet 615 pipeline is connected to the upper part of the side wall of the spray drying tower 7, and a sprayer 71 for drying phosphorus oxyfluoride gas is provided on the spray drying tower 7, and the sprayer 71 realizes the drying of phosphorus oxyfluoride gas by spraying 20% ​​to 60% oleum, thereby further improving the purity of the dried phosphorus oxyfluoride gas, and a condenser 8 is connected to the bottom of the spray drying tower 7, and the condenser 8 pipeline is connected to the gas-liquid separator 9, and the phosphorus oxyfluoride gas passes through the condenser 8 and the gas-liquid separator 9 for gas-liquid separation to obtain a phosphorus oxyfluoride product with a purity of 99.6% to 99.8%.

[0037] Refer to Figure 6. Figure 7 , Figure 8The 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 horizontal and vertical branch pipes 632 with length distribution 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 with an external heating steam pipeline. In the reaction zone, the threaded tubes 633 are also filled with With fillers, during the liquid phase flow of polyphosphoric acid from the top to the bottom of the reaction zone, 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 fillers, the fillers and the outer wall of the threaded tube 633 come into contact with the fillers, and the polyphosphoric acid on the outer wall surface of the threaded tube 633 by the wall flow will be dispersed on the filler surface by natural drainage under the action of swirl inertia. Therefore, the cooperation between the threaded tube 633 and the fillers can well prevent the wall flow effect of the threaded tube 633. At the same time, due to its spiral setting, the heating length and heating area of ​​the threaded tube 633 are increased, thereby increasing the internal heating effect of the threaded tube 633 on the reaction zone.

[0038] A second feed port 612 for feeding polyphosphoric acid is provided at the upper part of the reaction zone located at the top layer. After the polyphosphoric acid is fed through the second feed port 612, it is dispersed in the reaction zone by the cyclone distributor 64. The polyphosphoric acid flows from the top reaction zone to the lower bottom reaction zone through dispersion. The polyphosphoric acid contacts the anhydrous hydrogen fluoride on the filler between the threaded tubes 633 dispersed in the reaction zone to form a step-by-step reaction of concentration. The reaction temperature of the multiple reaction zones is controlled from the bottom of the tower body 61 to the top through the shell-and-tube heat exchanger 63 to be a step-by-step reaction temperature of 80-120° C., so that the phosphorus oxyfluoride gas generated after the reaction is fractionated through the filler section 62 on the separation zone and enters the next process at the top product outlet 615 at the top of the tower body 61. The excess polyphosphoric acid liquid and a small amount of side reaction liquid residue can be regularly discharged through the bottom waste outlet 614 of the tower body 61 for centralized collection and treatment.

[0039] 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, thereby ensuring the installation and placement of the saddle-shaped filler. During the process of filling the saddle-shaped filler inside the spiral of the threaded tube 633 of the shell-and-tube heat exchanger 63, the saddle shape of the saddle-shaped filler and the spiral direction of the threaded tube 633 are placed in contact with each other, 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.

[0040] 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 in 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.

[0041] 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 cyclone distributor 64. To further improve the dispersion effect, the cyclone 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, and the acute angle θ between the swirl plates 641 and the bottom surface of the swirl distributor 64 is inclined at 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 gas flow inside the feed zone and the plurality of reaction zones, so that the reaction gas can be better dispersed between the fillers inside the tower body 61, achieving full 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 plurality of swirl plates 641, achieving an axially upward swirl effect. At the same time, as a further embodiment, it can also A plurality of corrugated protrusions 642 are arranged 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 a semicircular arc shape. The wavy curve of the corrugated protrusion 642 is in a winding shape, so that 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 undulation 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 winding corrugated curve, thereby avoiding the wall flow of the reaction liquid. The cross-section of the corrugated protrusion 642 is in a semicircular arc shape, so that there is an arc transition between the surface of the swirl plate 641 and the corrugated protrusion 642 to avoid dead corners.

[0042] The reaction zone can be provided with two or more sections, so that the multi-stage reaction zone of polyphosphoric acid and anhydrous hydrogen fluoride can be contacted and reacted step by step, and the reaction can be more gentle, stable, and complete. The polyphosphoric acid flows from the upper part 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, and the anhydrous hydrogen fluoride in the reaction zone reacts the polyphosphoric acid thoroughly. Therefore, the multi-stage reaction zone uses a step-by-step concentration step-by-step reaction to avoid excess polyphosphoric acid from passing through the reaction zone and the feed zone and remaining at the bottom of the tower body 61, thereby effectively improving the reaction yield between polyphosphoric acid and anhydrous hydrogen fluoride and reducing the occurrence of side reactions. By setting 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 accurate. The temperature of the reaction system is accurately controlled to ensure the temperature stability of the reaction system, avoid fluctuations in the reaction temperature of the reaction zone, reduce the occurrence of side reactions in the reaction zone, and achieve step-by-step reaction temperatures in different stages, which can well meet the staged reaction process of polyphosphoric acid and anhydrous hydrogen fluoride, improve the stability of the reaction between polyphosphoric acid and anhydrous hydrogen fluoride, and reduce the occurrence of side reactions.

[0043] 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, wherein 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 to improve the reaction power, and at the same time, the rising power of the reaction product phosphorus oxyfluoride can be improved, ensuring that the phosphorus oxyfluoride can be better lifted in the separation zone in the high-temperature reaction zone, reducing the entrainment of phosphorus oxyfluoride by the liquid descending process of polyphosphoric acid toward the bottom of the tower body 61.

[0044] The present invention increases the resistance and path of the rising gas of phosphorus oxyfluoride by using fillers through the upper separation zone, so that the mist of polyphosphoric acid entrained in the rising gas of phosphorus oxyfluoride is accumulated and absorbed through contact with the surface of the fillers and flows back into the reaction zone after sedimentation. Therefore, through the separation zone, the separation of phosphorus oxyfluoride and the entrained polyphosphoric acid mist can be well achieved, thereby improving the purity of the phosphorus oxyfluoride product. In addition, a structural redistributor 65 and a wire mesh demister 66 are arranged on the upper part of the tower body 61, and the phosphorus oxyfluoride entrained in the phosphorus oxyfluoride can be further removed by the wire mesh demister 66, and the captured mist and the generated liquid enter the separation zone through the structural redistributor 65 to achieve gas-liquid separation.

[0045] 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 6 to generate phosphorus oxyfluoride.

[0046] Example 1 use Figure 1 The continuous preparation process shown in the figure 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, and specifically includes the following steps: S1, polyphosphoric acid preheating treatment: pour polyphosphoric acid with a molecular weight of 2000-2500 into the preheating high-level tank 1, control the heating temperature of the preheating high-level tank 1, and control the preheating temperature of the polyphosphoric acid at 60°C; S2, constant temperature heating treatment of polyphosphoric acid: the polyphosphoric acid with a preheating temperature of 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, and the polyphosphoric acid is further heated to 80° C. in a stirring state through the constant temperature kettle 3; S3, reaction and separation treatment: the polyphosphoric acid heated to 80°C is evenly pumped into the upper part of the reaction zone of the preparation tower 6 through the horizontal flow pump 5, and anhydrous hydrogen fluoride is introduced into the bottom of the feed zone of the preparation tower 6, and the feed pressure of anhydrous hydrogen fluoride is 0.5MPa, wherein the liquid feed rate of polyphosphoric acid is controlled to be 850kg / h, and the gas feed rate of anhydrous hydrogen fluoride is controlled to be 13.83 kg / h, and the polyphosphoric acid contacts the anhydrous hydrogen fluoride on the packings between the threaded pipes 633 dispersed in the reaction zone to form a step-by-step reaction of concentration, and 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, and the phosphorus oxyfluoride gas generated after the reaction is fractionated through the packing section 62 on the separation zone and at the top product outlet 615 at the top of the tower body 61, and the residual waste liquid is collected at the bottom of the tower body 61 in shifts (one shift for 8 hours) to obtain 280kg; S4, drying: phosphorus oxyfluoride from the top product outlet 615 at the top of the tower body 61 is introduced into the upper part of the side wall of the spray drying tower 7, and 20% to 60% oleum is sprayed from the top of the spray drying tower 7; 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%.

[0047] According to calculation, the residual waste liquid content of preparation tower 6 is 4.05%, that is, the reaction yield is 95.95%.

[0048] Example 2 The process and steps are the same as those in Example 1. The molecular weight of the polyphosphoric acid used is 2000-3000, and the difference is that the temperature of the polyphosphoric acid thermostat is raised to 90°C, and in the reaction zone, the temperature of the lower reaction zone is 100°C, and the temperature of the upper reaction zone of the reaction zone is 120°C, that is, the temperature of the thermostat and the reaction temperature of the polyphosphoric acid are raised, and the residual waste liquid is collected at the bottom of the tower body 61 of the preparation tower 6 in shifts (one shift for 8 hours) to obtain 260 kg. After calculation, the residual waste liquid content of the preparation tower 6 is 3.76%, that is, the reaction yield is 96.24%, and the gaseous phosphorus oxyfluoride is further separated in the gas-liquid separator 9 to obtain a phosphorus oxyfluoride product with a purity of 99.75%.

[0049] Compared with Example 1, Example 2 shows that when the reaction temperature is increased, the reaction effect between polyphosphoric acid and anhydrous hydrofluoric acid is better and the reaction yield is improved. 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.

[0050] Example 3 The process and steps are the same as those in Example 1. The process conditions and the liquid feed rate of polyphosphoric acid and the gas feed rate of anhydrous hydrogen fluoride are all unchanged, except that the molecular weight of the polyphosphoric acid used is 4000-5000, and 268 kg of residual waste liquid is collected at the bottom of the tower body 61 of the preparation tower 6 in shifts (one shift for 8 hours). After calculation, the residual waste liquid content of the preparation tower 6 is 3.88%, that is, the reaction yield is 96.12%, and the gaseous phosphorus oxyfluoride is further separated in the gas-liquid separator 9 to obtain a phosphorus oxyfluoride product with a purity of 99.78%.

[0051] Compared with Example 1, Example 3 shows that after the polymerization degree of the polyphosphoric acid used 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 oxyfluoride product is reduced.

[0052] Example 4 The process and steps are the same as those in Example 1. The molecular weight of the polyphosphoric acid used is 2000-3000, and the difference is that the feed ratio of polyphosphoric acid and anhydrous hydrogen fluoride is changed, the liquid feed rate of polyphosphoric acid is controlled to 850 kg / h, and the gas of anhydrous hydrogen fluoride is controlled to be 20.25 kg / h. The residual waste liquid is collected at the bottom of the tower body 61 of the preparation tower 6 in shifts (one shift for 8 hours) to obtain 243 kg. After calculation, the residual waste liquid content of the preparation tower 6 is 3.49%, that is, the reaction yield is 96.51%, and the gaseous phosphorus oxyfluoride is further separated in the gas-liquid separator 9 to obtain a phosphorus oxyfluoride product with a purity of 99.60%.

[0053] Example 4 shows, relative to Example 1, that by changing the feed ratio of polyphosphoric acid and anhydrous hydrogen fluoride, that is, increasing the dosage ratio of anhydrous hydrogen fluoride, the reaction yield is improved, but the purity of the phosphorus oxytrifluoride product is reduced.

[0054] Although 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 the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present 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 thermostatic kettle, the discharge pipe is connected to a preparation tower through a pipeline, the preparation tower comprises a tower body, a feeding zone, at least one reaction zone and a separation zone are sequentially arranged in the tower body from bottom to top, the feeding zone and the separation zone in the tower body are both filled with a packing section of a packing, wherein an anhydrous hydrogen fluoride feed port is arranged at the bottom of the packing section in the feeding zone, each of the reaction zones is provided with a tube-in-tube heat exchanger, and the tube-in-tube heat exchanger is provided with a controllable reaction pressure. The threaded tubes are connected to the temperature, and the threaded tubes 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 connected to the pipeline between the discharge pipes of the constant temperature kettle. The tower body is provided with a tower top product outlet at the top, and the tower top product outlet pipeline is connected to a spray drying tower, and the tower 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.

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

4. A continuous preparation device for high-purity phosphorus oxyfluoride according to claim 1, characterized in that: The preparation tower, wherein a cyclone distributor is provided between the feed zone and the reaction zone, between the separation zone and the reaction zone, and between multiple reaction zones, and the cyclone distributor is provided with multiple cyclone plates arrayed along its central circumference, and the acute angle θ between the cyclone plate and the bottom surface of the cyclone distributor is inclined at 30°~60°.

5. A continuous preparation device for high-purity phosphorus oxyfluoride according to claim 4, characterized in that: The swirl plate has a plurality of corrugated protrusions on its two surfaces which are arranged in a corrugated curve in the vertical direction, and the cross section of the corrugated protrusion is in a semicircular arc shape.

6. The continuous preparation device of high-purity phosphorus oxyfluoride according to claim 1, characterized in that: The reaction zone is filled with saddle-shaped fillers.

7. 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 of the inlet and outlet main pipes is evenly provided with a plurality of horizontal and vertical branch pipes distributed in length in the axial direction. The plurality of 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.

8. 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.

9. A continuous preparation method of high-purity phosphorus oxyfluoride, characterized in that: Polyphosphoric acid and anhydrous hydrogen fluoride are used to react in a preparation tower to generate phosphorus oxyfluoride, which specifically includes the following steps: S1, polyphosphoric acid preheating treatment: pour the 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 at 60-80°C; S2, constant temperature heating treatment of polyphosphoric acid: the polyphosphoric acid with a preheating 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, and the polyphosphoric acid is further heated to 80-100°C in the constant temperature kettle under stirring; S3, reaction and separation treatment: the 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, and the feed pressure of the anhydrous hydrogen fluoride is 0.1-1MPa, wherein the liquid of the polyphosphoric acid and the anhydrous hydrogen fluoride are fed at a feed rate of 80-40:1 by mass ratio, and the polyphosphoric acid contacts the anhydrous hydrogen fluoride on the fillers between the threaded pipes dispersed in the reaction zone to form a step-by-step reaction of concentration, and 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 after the reaction is fractionated through the filler section on the separation zone and the product outlet is 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 separated after being cooled in a condenser at the bottom of the spray drying tower to separate liquid sulfuric acid and gaseous phosphorus oxyfluoride. The gaseous phosphorus oxyfluoride is further separated in a gas-liquid separator to obtain a phosphorus oxyfluoride product with a purity of 99.6-99.8%.

10. A continuous preparation method of high-purity phosphorus oxyfluoride according to claim 7, characterized in that: The polyphosphoric acid is a medium polyphosphoric acid with a molecular weight of 2000-5000.

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