A purification process for phosphorus trifluoride

Abstract

The invention discloses a phosphorus trifluoride purification process, comprising the following steps: S1: heating liquid in a first storage tank and then pumping it into a flash evaporator for flash evaporation; S2: passing the flashed gas into a first distillation tower for rectification, condensing the top products of the distillation, phosphorus trifluoride and hydrogen chloride, and then passing them into an intermediate first product storage tank; S3: pumping the material in the intermediate first product storage tank into a second distillation tower for rectification, condensing the top gas of the distillation in the second distillation tower, and passing it into the first product storage tank for storage; S4: pumping the finished product in the first product storage tank into a vaporizer for vaporization and entering a gas-liquid separation tank for separation, discharging the separated gas from the top and sequentially passing it into three phosphorus trifluoride purification devices for purification; S5: passing the purified gas into a filter for filtration, and then entering a filling system for filling after the filtered gas is pressure-stabilized. The invention can completely remove impurities in phosphorus trifluoride, thereby significantly improving the purity of phosphorus trifluoride.

Description

Technical Field

[0001] The present invention relates to a processing technology of phosphorus trifluoride, in particular to a purification technology of phosphorus trifluoride. Background Art

[0002] Phosphorus trifluoride is an important inorganic compound with unique chemical properties and a wide range of applications, especially in the semiconductor and electronics industries. It is used as a dopant, that is, for phosphorus atom implantation to adjust the electrical properties of silicon-based semiconductors; it is used as an etching gas, that is, to etch silicon or metal films in plasma processes, and is milder than other gases.

[0003] The purity of phosphorus trifluoride directly affects its performance. If unpurified phosphorus trifluoride is used for etching, it may affect the conductive properties of the carrier. In the existing technology, phosphorus trifluoride is simply distilled before use. The distilled product is simply filtered to obtain the finished phosphorus trifluoride. As a result, the purity of the phosphorus trifluoride product is very unstable and its purity is difficult to guarantee.

[0004] Therefore, this case aims to provide a phosphorus trifluoride purification process that can perform multi-stage purification on crude phosphorus trifluoride gas. By means of flash evaporation, distillation, gasification, gas-liquid separation, etc., impurities in phosphorus trifluoride can be completely removed, thereby significantly improving the purity of phosphorus trifluoride. Summary of the Invention

[0005] The present invention provides a phosphorus trifluoride purification process, which can effectively solve the above problems.

[0006] The present invention is achieved in that:

[0007] A phosphorus trifluoride purification process comprises the following steps:

[0008] S1: condensing the crude phosphorus trifluoride gas and passing it into a first storage tank for storage, then heating the liquid in the first storage tank and pumping it into a flash evaporator for flash evaporation;

[0009] S2: passing the flashed gas into a first distillation tower for rectification, returning the bottom product hydrogen fluoride from the first distillation tower to the phosphorus trifluoride synthesis step, and condensing the top products phosphorus trifluoride and hydrogen chloride from the distillation into an intermediate first product storage tank;

[0010] S3: Pumping the material in the intermediate first product storage tank into the second distillation tower for rectification, condensing the top gas of the second distillation tower rectification, and refluxing part of the condensed product to the second distillation tower, and passing part to the first product storage tank for storage;

[0011] S4: The finished product in the first product storage tank is pumped into the vaporizer for vaporization. The vaporized gas enters the gas-liquid separation tank for separation. The separated liquid flows back to the vaporizer. The separated gas is discharged from the top and sequentially passed into three phosphorus trifluoride purification equipment for purification;

[0012] S5: The purified gas is filtered into the filter, and the filtered gas enters the second product storage tank. The gas in the second product storage tank is pressurized by the compressor and then enters the buffer tank for pressure-stabilized storage. After pressure stabilization, it enters the filling system for filling.

[0013] As a further improvement, the phosphorus trifluoride purification equipment includes an adsorption tower body for adsorbing phosphorus trifluoride, the top of the adsorption tower body is movably provided with an upper cover, the upper cover is connected to a plurality of air inlet ends, and the bottom of the adsorption tower body is provided with an air outlet end, and also includes: a double-position sliding molecular sieve structure, including a first molecular sieve adsorption cylinder arranged at the bottom of the adsorption tower body, a second molecular sieve adsorption cylinder is arranged above the first molecular sieve adsorption cylinder, the first molecular sieve adsorption cylinder and the second molecular sieve adsorption cylinder are both locked on the inner wall of the adsorption tower body, the effective pore size of the second molecular sieve adsorption cylinder is larger than that of the first molecular sieve adsorption cylinder, and the phosphorus trifluoride enters the first molecular sieve adsorption cylinder after being adsorbed by the second molecular sieve adsorption cylinder; a pressure variable diameter adjustment structure is arranged between the first molecular sieve adsorption cylinder and the second molecular sieve adsorption cylinder, the pressure variable diameter adjustment structure includes a pressure variable diameter adjustment structure arranged on the adsorption tower body, An elastic adjustment component is provided on the inner wall of the tower body, and the upper and lower ends of the elastic adjustment component are respectively connected to the first molecular sieve adsorption cylinder and the second molecular sieve adsorption cylinder; a pressure adjustment disk is connected to the middle part of the elastic adjustment component; a plurality of holes for phosphorus trifluoride to pass through are provided on the pressure adjustment disk; an internal barrier structure is provided in the hole; a top bone component is fixedly provided on the top of the first molecular sieve adsorption cylinder; when the pressure adjustment disk is pressurized and lowered, it will squeeze the top bone component and cause the top bone component to push out the internal barrier structure in the hole, so that the inner diameter of the hole becomes smaller; a pressure detection structure is provided inside the adsorption tower body, and the pressure detection structure is used to detect the pressure at the upper and lower ends of the dual-position sliding molecular sieve structure; the pressure detection structure includes a first pressure detector provided on the top of the adsorption tower body, and a second pressure detector is provided at the bottom of the adsorption tower body.

[0014] As a further improvement, a guide rail is provided on the inside of the adsorption tower body, and the outer wall of the adsorption tower body is recessed inward to form an inner groove. The first molecular sieve adsorption cylinder has the same structure as the second molecular sieve adsorption cylinder. The first molecular sieve adsorption cylinder comprises a loading frame for carrying the molecular sieve, and a plurality of matching rib grooves are provided on the outer side of the loading frame. After the loading frame is placed in the adsorption tower body, the matching rib grooves cooperate with the guide rails, and a plurality of limit members are provided on the inner groove, and the limit members pass through the guide rails and are connected to the matching rib grooves.

[0015] As a further improvement, an alignment hole is provided on the inner groove, and the limiting member includes a sealing gasket arranged on the alignment hole. A locking pin is installed on the sealing gasket, and the locking pin passes through the sealing gasket and is connected to the threaded hole on the matching rib groove.

[0016] As a further improvement, the elastic adjustment assembly includes at least two elastic adjustment seats, the elastic adjustment seat includes a first limit spring arranged at the lower end of the second molecular sieve adsorption cylinder, a second limit spring is arranged at the edge of the upper end of the first molecular sieve adsorption cylinder, and a mounting platform is connected between the first limit spring and the second limit spring, and a pressure adjustment disk is placed in the mounting platform.

[0017] As a further improvement, the mounting platform includes a C-type sleeve connected to a first limit spring and a second limit spring respectively, the opening of the C-type sleeve is used to accommodate a pressure regulating disk, and a through hole is provided on a side of the pressure regulating disk away from the opening, and a positioning pin for locking the pressure regulating disk is connected to the through hole.

[0018] As a further improvement, the pressure regulating disk includes a pressure movable disk connected to a C-type ferrule, the hole is opened in the axial direction of the pressure movable disk, a plurality of axial flow channels are opened on the inner side of the pressure movable disk, the axial flow channels are laterally connected to a return flow channel, and the internal barrier structure is located in the return flow channel.

[0019] As a further improvement, the internal barrier structure includes a touch portion located inside the return flow channel, the touch portion is connected to a barrier portion, and the touch portion is lifted up by the top bone component to push the barrier portion out, so that the barrier portion extends into the axial flow channel.

[0020] As a further improvement, the blocking portion is a folded piece, and the folded piece is provided with a plurality of flow holes.

[0021] As a further improvement, the top bone assembly includes an extension rod seat fixed to the top surface of the first molecular sieve adsorption cylinder, the top surface of the extension rod seat is connected to a plurality of separation rods, the separation rods extend to the return flow channel and are spaced apart from the touch portion.

[0022] The beneficial effects of the present invention are:

[0023] Compared with the simple distillation and filtration in the prior art, the present invention condenses crude phosphorus trifluoride gas and then flashes it, so that the phosphorus trifluoride is quickly vaporized, providing space for gas-liquid separation. At this time, the phosphorus trifluoride gas after flashing is further distilled, so that the product obtained after the rectification has higher purity, and the bottom product of the rectification can also be recovered. After repeating the rectification twice, the phosphorus trifluoride is again vaporized and subjected to gas-liquid separation to further separate impurities therein. After separation, the phosphorus trifluoride is quickly introduced into a phosphorus trifluoride device for purification. Impurities in the phosphorus trifluoride are fully removed by the three continuously distributed phosphorus trifluoride purification devices. After simple filtration, the phosphorus trifluoride gas can be filled at a stable pressure. Through continuous phase changes, the crude phosphorus trifluoride gas is completely converted into high-purity phosphorus trifluoride gas, and the purified phosphorus trifluoride has extremely high purity.

[0024] In the prior art, molecular sieves are often used to purify phosphorus trifluoride in the subsequent processing. The impurities of phosphorus trifluoride are treated in the final step by molecular sieves. When the molecular sieve is laid out, a very large containing skeleton is usually used to fill the molecular sieve into the skeleton. If the molecular sieve in the upper part is powdered and blocked, the molecular sieve in the lower part will directly become unusable and need to be replaced directly. Therefore, the present invention adopts a double-position sliding molecular sieve structure, which is set at both ends of the first molecular sieve adsorption cylinder and the second molecular sieve adsorption cylinder. The second molecular sieve adsorption cylinder with a larger effective pore size is placed on the upper end of the first molecular sieve adsorption cylinder with a larger volume, so that the second molecular sieve adsorption cylinder withstands the first section pressure of the gas. Even if the second molecular sieve adsorption cylinder is powdered, it is the upper half that needs to be replaced. The large-volume first molecular sieve adsorption cylinder is set at the lower end, so it is less likely to be directly hit by a large amount of high-pressure gas, thereby reducing its clogging phenomenon, and having a longer service life. At the same time, it is lower than the enterprise cost and has higher economic benefits.

[0025] Since the first molecular sieve adsorption cylinder and the second molecular sieve adsorption cylinder need to be replaced, especially the second molecular sieve adsorption cylinder, which needs to be replaced more frequently than the first molecular sieve adsorption cylinder, it needs to be set to a movable state, but cannot be in a suspended state. Therefore, the present invention provides a guide rail on the inside of the adsorption tower body, and provides matching rib grooves on the outside of the first molecular sieve adsorption cylinder and the second molecular sieve adsorption cylinder. By sliding them in, the first molecular sieve adsorption cylinder and the second molecular sieve adsorption cylinder can reach and be positioned at designated positions, and the sealing can be ensured during the fixing process.

[0026] Although the second molecular sieve adsorption cylinder bears the pressure for the first molecular sieve adsorption cylinder, the first molecular sieve adsorption cylinder may still be directly affected by the high-pressure gas. In order to protect the first molecular sieve adsorption cylinder without affecting the filtration efficiency, the present invention provides a pressure variable diameter adjustment structure based on the double-position sliding molecular sieve structure. When the pressure of the incoming phosphorus trifluoride gas is too high, the pressure adjustment disk installed on the elastic adjustment component will be directly pressed down, so that the pressure adjustment disk touches the top bone component, and the top bone component pushes out the internal barrier structure in the hole, thereby reducing the inner diameter of the hole, allowing the gas after passing through the second molecular sieve adsorption cylinder to pass through the hole with a smaller pass area, so that the pressure and speed of the gas are reduced, thereby ensuring that the gas passes through the first molecular sieve adsorption cylinder at a relatively uniform and stable speed, so that the gas is stably filtered and the life of the purification equipment is extended.

[0027] In order to sense the flow rate and pressure changes of the gas and automatically adjust its own state changes, in the present invention, the pressure regulating disk is set between the first limit spring and the second limit spring, and the expansion and contraction amount of the first limit spring and the second limit spring is changed by the pressure when the gas enters, and then it is determined whether the internal barrier structure in the pressure regulating disk is triggered, so that the state can be automatically changed according to the changes in the gas without manual monitoring.

[0028] During the fixing process of the pressure regulating disk, it needs to change dynamically according to the status of the first limit spring and the second limit spring. Therefore, the pressure regulating disk is fixed to the inner side of the adsorption tower body by sliding the C-type sleeve, and can move synchronously with the first limit spring and the second limit spring, thereby achieving the effect of automatic adjustment.

[0029] When adjusting the gas pressure and volume, it is mainly done by adjusting the flow rate through the pressure regulating disk. Therefore, the present invention provides an axial flow channel on the pressure regulating disk, through which the gas passes. When adjustment is required, the ventilation volume of the axial flow channel is changed. Therefore, a return flow channel is provided next to each axial flow channel, and the internal barrier structure is provided in the return flow channel, so that the ventilation volume of the axial flow channel can be changed.

[0030] It is the internal barrier structure that changes the diameter of the axial flow channel. One end of the internal barrier structure is triggered by the top bone assembly. When the entire pressure regulating disk descends, it will contact the top bone assembly, thereby pushing out the touch part, and then driving the barrier part out, thereby realizing the change of the path. After the gas pressure drops, the pressure regulating disk rises, and the barrier part will automatically swing down under the action of gravity without hindering the normal flow of gas.

[0031] In the process of the top bone component cooperating with the reflux duct, it needs to cooperate with several reflux ducts in order to achieve the effect of consistent regulation. Therefore, the present invention sets the top bone component as several separation rods, so that the several separation rods cooperate with the descending reflux duct, thereby allowing the ventilation volume in all reflux ducts to be consistently regulated and better stabilize the gas pressure.

[0032] Since the action of changing the fluid flow rate is automatically adjusted inside the equipment, it is difficult for experimenters to know the condition of the internal molecular sieve and the replacement cycle of the molecular sieve. Therefore, the present invention sets a pressure detection structure inside the adsorption tower body. By detecting the gas pressure at different positions of the adsorption tower body, it can be determined whether the gas encounters resistance when passing through the molecular sieve, and then determine whether the molecular sieve needs to be replaced, thereby achieving the effect of mechanical self-adjustment and intelligent self-inspection. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 It is a front structural schematic diagram of the present invention.

[0035] Figure 2 It is a front view structural schematic diagram of the phosphorus trifluoride purification equipment of the present invention.

[0036] Figure 3 It is a schematic diagram of the top view of the phosphorus trifluoride purification equipment of the present invention.

[0037] Figure 4 It is a schematic diagram of the internal structure of the phosphorus trifluoride purification equipment of the present invention.

[0038] Figure 5 It is a structural schematic diagram of the first molecular sieve adsorption cartridge of the present invention.

[0039] Figure 6 It is a structural schematic diagram of the pressure regulating disk of the present invention.

[0040] Figure 7 Schematic diagram of the structure of the inner barrier structure of the present invention.

[0041] Figure 8 It is a structural schematic diagram of the mounting platform of the present invention.

[0042] Figure 9 It is a schematic structural diagram of the parietal bone component of the present invention.

[0043] In the picture:

[0044] Adsorption tower body 10, guide rail 11, inner groove 12, bearing pocket seat 13, upper cover 20, air outlet end 30, double-position sliding molecular sieve structure 40, first molecular sieve adsorption cylinder 41, material placement frame 411, matching rib groove 412, limiter 413, sealing gasket 4131, locking pin 4132, second molecular sieve adsorption cylinder 42, pressure variable diameter adjustment structure 50, elastic adjustment component 51, first limit spring 511, second limit spring 512, mounting platform 513, C-type ferrule 5131, positioning pin 5132, pressure adjustment disk 52, hole 521, pressure movable disk 522, axial flow channel 523, return flow channel 524, internal barrier structure 53, touch part 531, barrier part 532, top bone component 54, extension rod seat 541, separation rod 542. DETAILED DESCRIPTION

[0045] All embodiments of the present invention are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0046] In the description of the present invention, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as referring to the purpose, technical solutions and advantages of the methods. To be clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work indicate or imply relative importance or implicitly indicate the number of indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0047] Reference Figures 1 to 9 As shown, a purification process of phosphorus trifluoride comprises the following steps:

[0048] S1: condensing the crude phosphorus trifluoride gas and passing it into a first storage tank for storage, then heating the liquid in the first storage tank and pumping it into a flash evaporator for flash evaporation, and returning the flash evaporation residue to the phosphorus trifluoride synthesis process;

[0049] S2: passing the flashed gas into a first distillation tower for rectification, returning the bottom product hydrogen fluoride from the first distillation tower to the phosphorus trifluoride synthesis step, and condensing the top products phosphorus trifluoride and hydrogen chloride from the distillation into an intermediate first product storage tank;

[0050] S3: The material in the intermediate first product storage tank is pumped into the second distillation tower for distillation, and the top gas of the second distillation tower is condensed. A portion of the condensed product is refluxed to the second distillation tower, and a portion is passed to the first product storage tank for storage. The bottom product, hydrogen chloride, of the second distillation tower is passed into the dehydrochlorination device;

[0051] S4: The finished product in the first product storage tank is pumped into the vaporizer for vaporization. The vaporized gas enters the gas-liquid separation tank for separation. The separated liquid flows back to the vaporizer. The separated gas is discharged from the top and sequentially passed into three phosphorus trifluoride purification equipment for purification;

[0052] S5: The purified gas is filtered into the filter, and the filtered gas enters the second product storage tank. The gas in the second product storage tank is pressurized to 50-60 Bar by the compressor and then enters the buffer tank for pressure-stabilized storage. After pressure stabilization, it enters the filling system for filling.

[0053] The phosphorus trifluoride purification equipment includes an adsorption tower body 10 for adsorbing phosphorus trifluoride, the top of the adsorption tower body 10 is movably provided with an upper cover 20, the upper cover 20 is connected to a plurality of air inlet ends, and the bottom of the adsorption tower body 10 is provided with an air outlet end 30, and further includes: a double-position sliding molecular sieve structure 40, including a first molecular sieve adsorption cylinder 41 provided at the bottom of the adsorption tower body 10, a second molecular sieve adsorption cylinder 42 is provided above the first molecular sieve adsorption cylinder 41, the first molecular sieve adsorption cylinder 41 and the second molecular sieve adsorption cylinder 42 are both locked on the inner wall of the adsorption tower body 10, the effective pore size of the second molecular sieve adsorption cylinder 42 is larger than that of the first molecular sieve adsorption cylinder 41, the phosphorus trifluoride enters the first molecular sieve adsorption cylinder 41 after being adsorbed by the second molecular sieve adsorption cylinder 42; 41 and the second molecular sieve adsorption cylinder 42, the pressure variable diameter adjustment structure 50 includes an elastic adjustment component 51 arranged on the inner wall of the adsorption tower body 10, the upper and lower ends of the elastic adjustment component 51 are respectively connected to the first molecular sieve adsorption cylinder 41 and the second molecular sieve adsorption cylinder 42, the middle part of the elastic adjustment component 51 is connected to a pressure regulating disk 52, the pressure regulating disk 52 is provided with a plurality of holes 521 for phosphorus trifluoride to pass through, and an internal barrier structure 53 is provided in the hole 521. A top bone component 54 is fixed on the top of the first molecular sieve adsorption cylinder 41. When the pressure regulating disk 52 is pressurized and dropped, it will squeeze the top bone component 54, and cause the top bone component 54 to push out the internal barrier structure 53 in the hole 521, so that the inner diameter of the hole 521 becomes smaller.

[0054] The first molecular sieve adsorption cylinder 41 is located below the second molecular sieve adsorption cylinder 42 . In order to fix the first molecular sieve adsorption cylinder 41 , a supporting pocket 13 is provided at the bottom of the adsorption tower body 10 . The first molecular sieve adsorption cylinder 41 is installed in the supporting pocket 13 .

[0055] In the prior art, molecular sieves are often used to purify phosphorus trifluoride in the subsequent processing. The impurities of phosphorus trifluoride are treated in the final step by molecular sieves. When the molecular sieve is laid out, a very large containing skeleton is usually used to fill the molecular sieve into the skeleton. If the molecular sieve in the upper part is powdered and blocked, the molecular sieve in the lower part will directly become unusable and need to be replaced directly. Therefore, the present invention adopts a double-position sliding molecular sieve structure 40, and adopts a first molecular sieve adsorption cylinder 41 and a second molecular sieve adsorption cylinder 42 at both ends. The second molecular sieve adsorption cylinder 42 with a larger effective pore size is placed on the upper end of the first molecular sieve adsorption cylinder 41 with a larger volume, so that the second molecular sieve adsorption cylinder 42 withstands the first section pressure of the gas. Even if the second molecular sieve adsorption cylinder 42 is powdered, it is the upper half that needs to be replaced. Since the large-volume first molecular sieve adsorption cylinder 41 is set at the lower end, it is less likely to be directly hit by a large amount of high-pressure gas, thereby reducing its clogging phenomenon, and having a longer service life. At the same time, it is lower than the enterprise cost and has higher economic benefits.

[0056] The existing molecular sieve needs to be regenerated after being taken out, and its regeneration method often adopts the backflushing regeneration method. Since the first molecular sieve adsorption cylinder 41 and the second molecular sieve adsorption cylinder 42 need to be replaced, especially the second molecular sieve adsorption cylinder 42, the replacement frequency will be higher than the first molecular sieve adsorption cylinder 41, so it needs to be set to a movable state, but it cannot be in a suspended state. Therefore, the inner side of the adsorption tower body 10 of this embodiment is provided with a guide rail 11, and the outer wall of the adsorption tower body 10 is recessed inward to form an inner groove 12. The first molecular sieve adsorption cylinder 41 and the second molecular sieve adsorption cylinder 42 have the same structure. The first molecular sieve adsorption cylinder 41 includes a loading frame 411 for carrying molecular sieves, and a plurality of matching rib grooves 412 are provided on the outer side of the loading frame 411. After the loading frame 411 is placed in the adsorption tower body 10, the matching rib grooves 412 cooperate with the guide rail 11. A plurality of limiting members 413 are provided on the inner groove 12. The limiting members 413 pass through the guide rail 11 and are connected to the matching rib grooves 412. By providing the guide rail 11 on the inner side of the adsorption tower body 10 and providing the matching rib grooves 412 on the outer sides of the first molecular sieve adsorption cylinder 41 and the second molecular sieve adsorption cylinder 42, the first molecular sieve adsorption cylinder 41 and the second molecular sieve adsorption cylinder 42 can reach and be positioned at the designated positions by sliding them in, and the sealing can be ensured during the fixing process.

[0057] When the first molecular sieve adsorption cylinder 41 and the second molecular sieve adsorption cylinder 42 are replaced, the upper cover 20 needs to be removed. Once the upper cover 20 is removed, the residual gas in the equipment will leak out, which may cause pollution. Therefore, before removing the upper cover 20, the gas in the adsorption tower body 10 needs to be replaced. During the gas replacement, nitrogen is introduced through the nitrogen inlet at the top of the equipment, and the nitrogen is allowed to pass the gas in the adsorption tower body 10 and the molecular sieve through the nitrogen outlet at the bottom of the adsorption tower body 10, thereby ensuring safety after opening the upper cover 20.

[0058] In order to ensure the sealing effect, an alignment hole is opened on the inner groove 12, and the limiting member 413 includes a sealing gasket 4131 arranged on the alignment hole. A locking pin 4132 is installed on the sealing gasket 4131. The locking pin 4132 passes through the sealing gasket 4131 and is connected to the threaded hole on the matching rib groove 412. The limiting member 413 can fix the molecular sieve adsorption cylinder while preventing the gas flowing therein from leaking out.

[0059] Although the second molecular sieve adsorption cylinder 42 bears the pressure for the first molecular sieve adsorption cylinder 41, the first molecular sieve adsorption cylinder 41 may still be directly affected by the high-pressure gas. In order to protect the first molecular sieve adsorption cylinder 41 without affecting the filtration efficiency, the present invention provides a pressure variable diameter adjustment structure 50 on the basis of the double-position sliding molecular sieve structure 40. When the pressure of the incoming phosphorus trifluoride gas is too high, the pressure adjustment disk 52 installed on the elastic adjustment component 51 will be directly pressed down, so that the pressure adjustment disk 52 touches the top bone component 54, and the top bone component 54 pushes out the internal barrier structure 53 in the hole 521, thereby reducing the inner diameter of the hole 521, so that the gas after passing through the second molecular sieve adsorption cylinder 42 can pass through the hole 521 with a smaller area, so that the pressure and speed of the gas are reduced, thereby ensuring that the gas passes through the first molecular sieve adsorption cylinder 41 at a relatively uniform and stable speed, so that the gas is stably filtered and the life of the purification equipment is extended.

[0060] In order to sense the flow rate and pressure changes of the gas and automatically adjust its own state changes, in this embodiment, the elastic adjustment component 51 includes at least two elastic adjustment seats, and the elastic adjustment seat includes a first limit spring 511 arranged at the lower end of the second molecular sieve adsorption cylinder 42, and a second limit spring 512 is arranged on the edge of the upper end of the first molecular sieve adsorption cylinder 41. A mounting platform 513 is connected between the first limit spring 511 and the second limit spring 512, and the mounting platform 513 contains a pressure regulating disk 52. The pressure regulating disk 52 is set between the first limit spring 511 and the second limit spring 512, and the expansion and contraction amount of the first limit spring 511 and the second limit spring 512 is changed by the pressure when the gas enters, and then it is determined whether the internal barrier structure 53 in the pressure regulating disk 52 is triggered, so that the state can be automatically changed according to the change of the gas without manual monitoring.

[0061] It should be emphasized that the first limiting spring 511 and the second limiting spring 512 are sleeve-type springs, that is, the springs are limited by the sleeves to prevent them from falling out directly.

[0062] During the fixing process of the pressure regulating disk 52, it needs to dynamically change according to the status of the first limit spring 511 and the second limit spring 512. Therefore, the mounting platform 513 of this embodiment includes a C-type sleeve 5131 connected to the first limit spring 511 and the second limit spring 512 respectively. The opening of the C-type sleeve 5131 is used to accommodate the pressure regulating disk 52. The pressure regulating disk 52 is provided with a through hole on the side away from the opening. A positioning pin 5132 for locking the pressure regulating disk 52 is connected to the through hole. The pressure regulating disk 52 is slidably fixed to the inner side of the adsorption tower body 10 by the C-type sleeve 5131, and can move synchronously with the first limit spring 511 and the second limit spring 512, thereby achieving the effect of automatic adjustment.

[0063] When adjusting the gas pressure and volume, it is mainly done by adjusting the flow through the pressure regulating disk 52. Therefore, the pressure regulating disk 52 of this embodiment includes a pressure movable disk 522 connected to the C-type sleeve 5131, and the hole 521 is opened in the axial direction of the pressure movable disk 522. A plurality of axial flow channels 523 are opened on the inner side of the pressure movable disk 522. The axial flow channels 523 are laterally connected to a return flow channel 524, and the internal barrier structure 53 is located in the return flow channel 524. By providing the axial flow channel 523 on the pressure regulating disk 52, the gas passes through the axial flow channel 523, and when adjustment is required, the ventilation volume of the axial flow channel 523 is changed. Therefore, a return flow channel 524 is provided next to each axial flow channel 523, and the internal barrier structure 53 is provided in the return flow channel 524, so that the ventilation volume of the axial flow channel 523 can be changed.

[0064] It is the internal barrier structure 53 that changes the diameter of the axial flow channel 523. The internal barrier structure 53 includes a touch portion 531 located inside the return flow channel 524. The touch portion 531 is connected to a barrier portion 532. After the touch portion 531 is lifted up by the top bone component 54, the barrier portion 532 is pushed out, so that the barrier portion 532 extends into the axial flow channel 523. One end of the internal barrier structure 53 is triggered by the top bone component 54. When the entire pressure regulating disk 52 descends, it will contact the top bone component 54, thereby pushing out the touch portion 531, and then driving the barrier portion 532 to be pushed out, thereby realizing the change of the path. After the gas pressure drops, the pressure regulating disk 52 rises, and the barrier portion 532 will automatically swing down under the action of gravity without hindering the normal circulation of gas.

[0065] The blocking portion 532 is a folded piece having a plurality of flow holes. Even if some gas passes through the undeployed blocking portion 532 and enters the reflux channel 524 , it will be blocked by the top bone component 54 .

[0066] In the process of the top bone component 54 cooperating with the return flow channel 524, it needs to cooperate with several return flow channels 524 so as to achieve the effect of consistent regulation. Therefore, the top bone component 54 of this embodiment includes an extension rod seat 541 fixed on the top surface of the first molecular sieve adsorption cylinder 41, and the top surface of the extension rod seat 541 is connected to several separation rods 542. The separation rods 542 extend to the return flow channel 524 and are spaced apart from the touch portion 531. By setting the top bone component 54 to several separation rods 542, several separation rods 542 are coordinated with the descending return flow channel 524, so that the ventilation volume in all the return flow channels 524 can be consistently regulated, and the gas pressure can be better stabilized.

[0067] Since the action of changing the fluid flow rate is automatically adjusted inside the equipment, it is difficult for experimenters to know the condition of the internal molecular sieve and the replacement cycle of the molecular sieve. Therefore, the present invention sets a pressure detection structure inside the adsorption tower body 10. By detecting the gas pressure at different positions of the adsorption tower body 10, it can be determined whether the gas encounters resistance when passing through the molecular sieve, and then determine whether the molecular sieve needs to be replaced, thereby achieving the effect of mechanical self-adjustment and intelligent self-inspection.

[0068] Since the action of changing the fluid flow rate is automatically adjusted inside the equipment, it is difficult for experimenters to know the condition of the internal molecular sieve and the replacement cycle of the molecular sieve. Therefore, the pressure detection structure of this embodiment includes a first pressure detector 141 arranged at the top of the adsorption tower body 10, and a second pressure detector 142 is arranged at the bottom of the adsorption tower body 10. By arranging the pressure detection structure inside the adsorption tower body and detecting the gas pressure at different positions of the adsorption tower body, it is possible to determine whether the gas encounters resistance when passing through the molecular sieve, and then determine whether the molecular sieve needs to be replaced, thereby achieving the effect of mechanical self-adjustment and intelligent self-detection.

[0069] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A purification process for phosphorus trifluoride, characterized in that: The following steps are included: S1: condensing the crude phosphorus trifluoride gas and passing it into a first storage tank for storage, then heating the liquid in the first storage tank and pumping it into a flash evaporator for flash evaporation; S2: passing the flashed gas into a first distillation tower for rectification, returning the bottom product hydrogen fluoride from the first distillation tower to the phosphorus trifluoride synthesis step, and condensing the top products phosphorus trifluoride and hydrogen chloride from the distillation into an intermediate first product storage tank; S3: Pumping the material in the intermediate first product storage tank into the second distillation tower for rectification, condensing the top gas of the second distillation tower rectification, and refluxing part of the condensed product to the second distillation tower, and passing part to the first product storage tank for storage; S4: The finished product in the first product storage tank is pumped into the vaporizer for vaporization. The vaporized gas enters the gas-liquid separation tank for separation. The separated liquid flows back to the vaporizer. The separated gas is discharged from the top and sequentially passed into three phosphorus trifluoride purification equipment for purification; The phosphorus trifluoride purification equipment comprises an adsorption tower body (10) for adsorbing phosphorus trifluoride, wherein an upper cover (20) is movably provided on the top of the adsorption tower body (10), a plurality of air inlet ends are connected to the upper cover (20), and an air outlet end (30) is provided at the bottom of the adsorption tower body (10), and further comprises: A double-position sliding molecular sieve structure (40) comprises a first molecular sieve adsorption cylinder (41) arranged at the bottom of an adsorption tower body (10); a second molecular sieve adsorption cylinder (42) is arranged above the first molecular sieve adsorption cylinder (41); the first molecular sieve adsorption cylinder (41) and the second molecular sieve adsorption cylinder (42) are both locked to the inner wall of the adsorption tower body (10); the effective pore size of the second molecular sieve adsorption cylinder (42) is larger than that of the first molecular sieve adsorption cylinder (41); the phosphorus trifluoride enters the first molecular sieve adsorption cylinder (41) after being adsorbed by the second molecular sieve adsorption cylinder (42); A pressure variable diameter regulating structure (50) is provided between the first molecular sieve adsorption cylinder (41) and the second molecular sieve adsorption cylinder (42), wherein the pressure variable diameter regulating structure (50) comprises an elastic regulating component (51) provided on the inner side wall of the adsorption tower body (10), wherein the upper and lower ends of the elastic regulating component (51) are respectively connected to the first molecular sieve adsorption cylinder (41) and the second molecular sieve adsorption cylinder (42), and the middle part of the elastic regulating component (51) is connected to a pressure regulating disk (52). The pressure regulating disk (52) is provided with a plurality of holes (521) for phosphorus trifluoride to pass through, and an internal barrier structure (53) is provided in the hole (521). A top bone component (54) is fixedly provided on the top of the first molecular sieve adsorption cylinder (41). When the pressure regulating disk (52) is pressed down, the top bone component (54) is squeezed and the top bone component (54) pushes out the internal barrier structure (53) in the hole (521), thereby reducing the inner diameter of the hole (521); The pressure regulating disk (52) includes a pressure movable disk (522) connected to a C-type ferrule (5131), the hole (521) is opened in the axial direction of the pressure movable disk (522), a plurality of axial flow channels (523) are opened on the inner side of the pressure movable disk (522), the axial flow channels (523) are laterally connected to a return flow channel (524), and the internal barrier structure (53) is located in the return flow channel (524); The inner barrier structure (53) includes a touch portion (531) located inside the return flow channel (524), the touch portion (531) is connected to a barrier portion (532), and the touch portion (531) is lifted by the top bone component (54) to push out the barrier portion (532), so that the barrier portion (532) extends into the axial flow channel (523), and the barrier portion (532) is a folding piece, and the folding piece is provided with a plurality of flow holes; S5: The purified gas is filtered into the filter, and the filtered gas enters the second product storage tank. The gas in the second product storage tank is pressurized by the compressor and then enters the buffer tank for pressure-stabilized storage. After pressure stabilization, it enters the filling system for filling.

2. A phosphorus trifluoride purification process according to claim 1, characterized in that: The adsorption tower body (10) further includes a pressure detection structure arranged inside the adsorption tower body (10), wherein the pressure detection structure is used to detect the pressure at the upper end and the lower end of the dual-position sliding molecular sieve structure (40), and the pressure detection structure includes a first pressure detector (141) arranged at the top of the adsorption tower body (10), and a second pressure detector (142) is arranged at the bottom of the adsorption tower body (10).

3. A phosphorus trifluoride purification process according to claim 1, characterized in that: A guide rail (11) is provided on the inner side of the adsorption tower body (10), and the outer wall of the adsorption tower body (10) is recessed inward to form an inner groove (12). The first molecular sieve adsorption cylinder (41) and the second molecular sieve adsorption cylinder (42) have the same structure. The first molecular sieve adsorption cylinder (41) includes a loading frame (411) for carrying the molecular sieve. The outer side of the loading frame (411) is provided with a plurality of matching rib grooves (412). After the loading frame (411) is placed in the adsorption tower body (10), the matching rib grooves (412) are matched with the guide rail (11). The inner groove (12) is provided with a plurality of limiting members (413), and the limiting members (413) pass through the guide rail (11) and are connected to the matching rib grooves (412).

4. A phosphorus trifluoride purification process according to claim 3, characterized in that: An alignment hole is provided on the inner groove (12), and the limiting member (413) includes a sealing gasket (4131) arranged on the alignment hole. A locking pin (4132) is installed on the sealing gasket (4131), and the locking pin (4132) passes through the sealing gasket (4131) and is connected to a threaded hole on the matching rib groove (412).

5. A phosphorus trifluoride purification process according to claim 1, characterized in that: The elastic adjustment component (51) includes at least two elastic adjustment seats, the elastic adjustment seat includes a first limit spring (511) arranged at the lower end of the second molecular sieve adsorption cylinder (42), a second limit spring (512) is arranged at the edge of the upper end of the first molecular sieve adsorption cylinder (41), and a mounting platform (513) is connected between the first limit spring (511) and the second limit spring (512), and the mounting platform (513) contains a pressure adjustment disk (52).

6. A phosphorus trifluoride purification process according to claim 5, characterized in that: The mounting platform (513) includes a C-type clamping sleeve (5131) connected to the first limit spring (511) and the second limit spring (512), respectively. The opening of the C-type clamping sleeve (5131) is used to accommodate the pressure regulating disk (52). The pressure regulating disk (52) has a through hole on the side away from the opening. A positioning pin (5132) for locking the pressure regulating disk (52) is connected to the through hole.

7. A phosphorus trifluoride purification process according to claim 1, characterized in that: The top bone assembly (54) includes an extension rod seat (541) fixed to the top surface of the first molecular sieve adsorption cylinder (41), and the top surface of the extension rod seat (541) is connected to a plurality of separation rods (542). The separation rods (542) extend to the return flow channel (524) and are spaced apart from the touch portion (531).

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