Phosphorus trifluoride purification process

Abstract

The invention discloses a purification process of phosphorus trifluoride. The purification process comprises the following steps: S1, heating liquid in a first storage tank, and pumping the heated liquid into a flash evaporator for flash evaporation; s2, introducing the flashed gas into a first rectifying tower for rectification, condensing the rectified top products phosphorus trifluoride and hydrogen chloride, and introducing the condensed top products into an intermediate first product storage tank; s3, pumping the material in the middle first product storage tank into a second rectifying tower for rectification, condensing the top gas rectified by the second rectifying tower, and introducing the condensed gas into the first product storage tank for storage; s4, a finished product in the first product storage tank is pumped into a gasifier to be gasified and enters a gas-liquid separation tank to be separated, and separated gas is discharged from the top and sequentially introduced into three phosphorus trifluoride purification devices to be purified; s5, the purified gas is introduced into a filter to be filtered, the filtered gas enters a filling system to be filled after pressure stabilization, impurities in phosphorus trifluoride can be completely removed, and the purity of phosphorus trifluoride is improved in a jumping mode.

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 wide applications. In particular, it is used in the semiconductor and electronics industries as a dopant, that is, for phosphorus atom implantation to adjust the electrical properties of silicon-based semiconductors; and as an etching gas, that is, for etching silicon or metal thin films in plasma processes, which is milder than other gases.

[0003] The purity of phosphorus trifluoride will directly affect its use performance. If unpurified phosphorus trifluoride is directly used for etching, it may affect the conductivity of the carrier. In the prior art, only simple rectification is carried out before using phosphorus trifluoride, and the product after rectification is only simply filtered to obtain the finished product of phosphorus trifluoride, resulting in very unstable product purity of phosphorus trifluoride and difficult to guarantee its purity.

[0004] Therefore, the present case aims to provide a purification technology of phosphorus trifluoride, which can carry out multi-stage purification on the crude phosphorus trifluoride gas. Through methods such as flash evaporation, rectification, gasification, and gas-liquid separation, the impurities in phosphorus trifluoride are removed completely, and the purity of phosphorus trifluoride is improved by leaps and bounds. Summary of the Invention

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

[0006] The present invention is implemented as follows: A purification technology of phosphorus trifluoride comprises the following steps: S1: Condense the crude phosphorus trifluoride gas and store it in the first storage tank, then heat the liquid in the first storage tank and pump it into a flash evaporator for flash evaporation; S2: Feed the gas after flash evaporation into the first rectification column for rectification. Return the bottom product hydrogen fluoride from the rectification of the first rectification column to the phosphorus trifluoride synthesis process, and condense the top products phosphorus trifluoride and hydrogen chloride from the rectification and feed them into the intermediate first product storage tank; S3: Pump the material in the intermediate first product storage tank into the second rectification column for rectification, condense the top gas from the rectification of the second rectification column. Part of the condensed product is refluxed to the second rectification column, and part of it is fed into the first product storage tank for storage; S4: Pump the finished product in the first product storage tank into a vaporizer for gasification. The gas after gasification enters a gas-liquid separation tank for separation. The separated liquid is refluxed to the vaporizer, and the separated gas is discharged from the top and sequentially fed into three phosphorus trifluoride purification devices for purification; S5: The purified gas is passed into a filter for filtration. The filtered gas enters the second product storage tank. The gas in the second product storage tank is pressurized by a compressor and then enters a buffer tank for stable storage, and after stabilization, it enters a filling system for filling.

[0007] 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. A plurality of air inlet ends are connected to the upper cover. The bottom of the adsorption tower body is provided with an air outlet end. It further includes: a two-position sliding molecular sieve structure, which includes a first molecular sieve adsorption cylinder arranged at the inner 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 diameter of the second molecular sieve adsorption cylinder is larger than that of the first molecular sieve adsorption cylinder. 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 arranged between the first molecular sieve adsorption cylinder and the second molecular sieve adsorption cylinder. The pressure variable diameter adjustment structure includes an elastic adjustment component arranged on the inner side wall of the adsorption tower body. 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 of the elastic adjustment component. A plurality of holes for passing chlorine trifluoride are opened on the pressure adjustment disk. An inner barrier structure is arranged in the holes. A top bone component is fixedly arranged at the top of the first molecular sieve adsorption cylinder. When the pressure adjustment disk is pressed and descends, it will squeeze the top bone component, and the top bone component will push out the inner barrier structure in the hole, making the inner diameter of the hole smaller; a pressure detection structure arranged inside the adsorption tower body. The pressure detection structure is used to detect the pressure at the upper and lower ends of the two-position sliding molecular sieve structure. The pressure detection structure includes a first pressure detector arranged at the inner top of the adsorption tower body. A second pressure detector is arranged at the inner bottom of the adsorption tower body.

[0008] As a further improvement, a guide rail is arranged on the inner side of the adsorption tower body. The outer wall of the adsorption tower body is recessed inward to form an inner groove. The structures of the first molecular sieve adsorption cylinder and the second molecular sieve adsorption cylinder are the same. The first molecular sieve adsorption cylinder includes a material placement frame for carrying molecular sieves. A plurality of matching rib grooves are arranged on the outer side of the material placement frame. After the material placement frame is placed into the adsorption tower body, the matching rib grooves cooperate with the guide rail. A plurality of limit pieces are arranged on the inner groove. The limit pieces penetrate the guide rail and are connected to the matching rib grooves.

[0009] As a further improvement, a positioning hole is opened on the inner groove. The limit piece includes a sealing pad arranged on the positioning hole. A locking nail is installed on the sealing pad. The locking nail penetrates the sealing pad and is connected to a threaded hole on the matching rib groove.

[0010] As a further improvement, the elastic adjustment component includes at least two elastic adjustment seats. Each elastic adjustment seat includes a first limiting spring arranged at the lower end of the second molecular sieve adsorption cylinder, and a second limiting spring is arranged at the edge of the upper end of the first molecular sieve adsorption cylinder. An installation platform is connected between the first limiting spring and the second limiting spring, and a pressure adjustment disc is accommodated in the installation platform.

[0011] As a further improvement, the installation platform includes a C-shaped sleeve connected to the first limiting spring and the second limiting spring. The opening of the C-shaped sleeve is used to accommodate the pressure adjustment disc. A perforation is opened on the side of the pressure adjustment disc away from the opening, and a positioning pin for locking the pressure adjustment disc is connected to the perforation.

[0012] As a further improvement, the pressure adjustment disc includes a pressure movable disc connected to the C-shaped sleeve. The hole is opened in the axial direction of the pressure movable disc. A plurality of axial flow channels are opened on the inner side of the pressure movable disc. The side of the axial flow channel communicates with a reflux channel, and the inner barrier structure is located in the reflux channel.

[0013] As a further improvement, the inner barrier structure includes a trigger part located inside the reflux channel. The trigger part is connected to a barrier part. After the trigger part is lifted by the skull component, the barrier part is pushed out so that the barrier part extends into the axial flow channel.

[0014] As a further improvement, the barrier part is a folding piece, and a plurality of flow holes are opened on the folding piece.

[0015] As a further improvement, the skull component includes an extension rod seat fixed on the top surface of the first molecular sieve adsorption cylinder. A plurality of separation rods are connected to the top surface of the extension rod seat. The separation rods extend into the reflux channel and are arranged at intervals with the trigger part.

[0016] The beneficial effects of the present invention are as follows: Compared with the simple rectification and filtration in the prior art, in the present invention, the crude phosphorus trifluoride gas is first condensed and then flash-vaporized to rapidly vaporize the phosphorus trifluoride, providing a space for gas-liquid separation. At this time, the phosphorus trifluoride gas after flash vaporization is rectified again, so that the purity of the product obtained after rectification is higher, and the bottom product of rectification can also be recovered. After repeating the rectification twice, the phosphorus trifluoride is vaporized and gas-liquid separated again to further separate the impurity components therein, and then quickly introduced into the phosphorus trifluoride equipment for purification after separation. Through three continuously distributed phosphorus trifluoride purification equipment, the impurities in the phosphorus trifluoride are fully removed, and then simple filtration can be carried out for stable pressure filling. Through continuous phase changes, all the crude phosphorus trifluoride gas is converted into high-purity phosphorus trifluoride gas, and the purity of the purified phosphorus trifluoride is extremely high.

[0017] In the prior art, molecular sieves are often used to purify the post-processing of phosphorus trifluoride. The molecular sieves are used to perform the last step of treatment on the impurities of phosphorus trifluoride. When arranging the molecular sieves, a very large accommodating framework is usually adopted, and the molecular sieves are filled into the framework. If the molecular sieves in the upper part are pulverized and blocked, it will directly cause the molecular sieves in the lower part to be unusable and need to be directly replaced. Therefore, in the present invention, a two-position sliding molecular sieve structure is provided. By arranging the two 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 diameter is placed at the upper end of the first molecular sieve adsorption cylinder with a larger volume, so that the second molecular sieve adsorption cylinder bears the first-stage pressure of the gas. Even if the second molecular sieve adsorption cylinder is pulverized, only the upper half needs to be replaced. Since the large-volume first molecular sieve adsorption cylinder is arranged at the lower end, the possibility of being directly impacted by a large amount of high-pressure gas is relatively low, so that its blockage phenomenon can be weakened, the service life is longer, and at the same time, the cost for the enterprise is relatively low and the economic benefit is higher.

[0018] 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, whose replacement frequency is higher than that of the first molecular sieve adsorption cylinder, it is necessary to set them to be in a movable state, but they cannot be in a suspended state. Therefore, in the present invention, guide rails are arranged on the inner side of the adsorption tower body, and matching rib grooves are arranged on the outer sides of the first molecular sieve adsorption cylinder and the second molecular sieve adsorption cylinder. By means of a sliding insertion method, the first molecular sieve adsorption cylinder and the second molecular sieve adsorption cylinder can reach and be fixed at the specified positions, and the sealing performance can be ensured during the fixing process.

[0019] Although the second molecular sieve adsorption cylinder is used to bear the pressure for the first molecular sieve adsorption cylinder, the first molecular sieve adsorption cylinder may still be directly affected by high-pressure gas. In order to protect the first molecular sieve adsorption cylinder without affecting the filtration efficiency, a pressure variable-diameter adjustment structure is provided on the basis of the two-position sliding molecular sieve structure in the present invention. When the gas pressure of the incoming phosphorus trifluoride 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 will push out the inner barrier structure in the hole, so that the inner diameter of the hole becomes smaller, and the available passing area of the gas passing through the hole after passing through the second molecular sieve adsorption cylinder becomes smaller, so that the gas pressure and speed are both weakened, so as to ensure that the gas passes through the first molecular sieve adsorption cylinder at a relatively uniform and stable speed, so that while the gas is stably filtered, the service life of the purification equipment is longer.

[0020] In order to sense the gas flow rate and pressure changes and thus automatically adjust its own state changes, in the present invention, a pressure adjustment disc is arranged between the first limit spring and the second limit spring. The pressure when the gas enters is used to change the expansion and contraction amounts of the first limit spring and the second limit spring, and then it is determined whether to trigger the internal blocking structure in the pressure adjustment disc, so that the state can be automatically changed according to the gas changes without manual monitoring.

[0021] During the fixing process of the pressure adjustment disc, it needs to change dynamically according to the states of the first limit spring and the second limit spring. Therefore, the pressure adjustment disc is slidably fixed to the inner side of the adsorption tower body by a C-shaped bushing and can move synchronously with the first limit spring and the second limit spring, thereby achieving the effect of automatic adjustment.

[0022] When adjusting the gas pressure and gas volume, it mainly adjusts the flow rate through the pressure adjustment disc. Therefore, in the present invention, an axial flow channel is arranged on the pressure adjustment disc, and the gas passes through the axial flow channel. When adjustment is required, the ventilation volume of the axial flow channel is changed. Therefore, a return flow channel is arranged beside each axial flow channel, and the internal blocking structure is arranged in the return flow channel, so that the ventilation volume of the axial flow channel can be changed.

[0023] It is the internal blocking structure that changes the diameter of the axial flow channel. One end of the internal blocking structure is triggered by the top bone assembly. When the entire pressure adjustment disc descends, it will contact the top bone assembly, thereby pushing out the triggering part, and then driving the blocking part to be pushed out, thus realizing the transformation of the diameter channel. After the gas pressure drops, the pressure adjustment disc rises, and the blocking part will also automatically swing downward under the action of gravity without hindering the normal flow of the gas.

[0024] During the cooperation process between the top bone assembly and the return flow channels, it needs to cooperate with several return flow channels to achieve the effect of consistent adjustment. Therefore, in the present invention, the top bone assembly is set as several separation rods, and the several separation rods cooperate with the descending return flow channels, so that the ventilation volumes in all the return flow channels can be adjusted consistently, better stabilizing the gas pressure.

[0025] Since the actions of changing the fluid flow rate are all automatically adjusted inside the device, it is difficult for experimenters to know the situation of the molecular sieve inside and difficult to know the replacement cycle of the molecular sieve. Therefore, in the present invention, a pressure detection structure is arranged inside the adsorption tower body. By detecting the gas pressure at different positions of the adsorption tower body, it can be judged whether the gas is subject to resistance when passing through the molecular sieve, and then it can be judged whether the molecular sieve needs to be replaced, thus achieving the effects of mechanical self-adjustment and intelligent self-checking. Description of the Drawings

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show certain embodiments of the present invention, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0027] Figure 1 is the front view structural schematic diagram of the present invention.

[0028] Figure 2 is the front view structural schematic diagram of the phosphorus trifluoride purification equipment of the present invention.

[0029] Figure 3 is the top view structural schematic diagram of the phosphorus trifluoride purification equipment of the present invention.

[0030] Figure 4 is the internal structural schematic diagram of the phosphorus trifluoride purification equipment of the present invention.

[0031] Figure 5 is the structural schematic diagram of the first molecular sieve adsorption cylinder of the present invention.

[0032] Figure 6 is the structural schematic diagram of the pressure regulating disc of the present invention.

[0033] Figure 7 is the structural schematic diagram of the internal barrier structure of the present invention.

[0034] Figure 8 is the structural schematic diagram of the mounting table of the present invention.

[0035] Figure 9 is the structural schematic diagram of the parietal bone assembly of the present invention.

[0036] In the figure: Adsorption tower body 10, guide rail 11, inner groove 12, bearing socket 13, upper cover 20, air outlet end 30, dual-position sliding molecular sieve structure 40, first molecular sieve adsorption cylinder 41, material placement frame 411, matching rib groove 412, limiting member 413, sealing gasket 4131, locking nail 4132, second molecular sieve adsorption cylinder 42, pressure variable diameter adjustment structure 50, elastic adjustment assembly 51, first limiting spring 511, second limiting spring 512, mounting table 513, C-type clamping sleeve 5131, positioning pin 5132, pressure regulating disc 52, hole 521, pressure movable disc 522, axial flow channel 523, return flow channel 524, internal barrier structure 53, triggering part 531, barrier part 532, parietal bone assembly 54, extension rod seat 541, separation rod 542. Detailed implementation manners

[0037] To make the embodiments of the present invention, all fall within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0038] In the description of the present invention, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more, unless otherwise specifically defined. To make the objectives, technical solutions and advantages of the present invention 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 some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0039] Refer to Figures 1 to 9 As shown, a purification process of phosphorus trifluoride includes the following steps: S1: Condense the crude phosphorus trifluoride gas and store it in the first storage tank, then heat the liquid in the first storage tank and pump it into a flash evaporator for flashing. The flashed residual liquid is returned to the phosphorus trifluoride synthesis process. S2: Pass the flashed gas into the first distillation column for distillation. Return the hydrogen fluoride at the bottom of the first distillation column to the phosphorus trifluoride synthesis process. Condense the top products of phosphorus trifluoride and hydrogen chloride after distillation and pass them into the intermediate first product storage tank. S3: Pump the material in the intermediate first product storage tank into the second distillation column for distillation. Condense the top gas of the second distillation column. Part of the condensed product is refluxed to the second distillation column, and part is passed into the first product storage tank for storage. The bottom product of hydrogen chloride in the second distillation column is passed into the device for removing hydrochloric acid. S4: Pump the finished product in the first product storage tank into a vaporizer for vaporization. The vaporized gas enters a gas-liquid separation tank for separation. The separated liquid is refluxed to the vaporizer, and the separated gas is discharged from the top and sequentially passed through three phosphorus trifluoride purification devices for purification. S5: Pass the purified gas into a filter for filtration. The filtered gas enters the second product storage tank. The gas in the second product storage tank is pressurized to 50 - 60 Bar by a compressor and then enters a buffer tank for pressure stabilization storage, and after pressure stabilization, it enters the filling system for filling.

[0040] The phosphorus trifluoride purification equipment includes an adsorption tower body 10 for adsorbing phosphorus trifluoride. An upper cover 20 is movably arranged at the top of the adsorption tower body 10. A plurality of air inlet ends are connected to the upper cover 20. An air outlet end 30 is arranged at the bottom of the adsorption tower body 10. It further includes: a two-position sliding molecular sieve structure 40, which includes a first molecular sieve adsorption cylinder 41 arranged at the inner bottom of the 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 diameter 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 adjustment structure 50 arranged between the first molecular sieve adsorption cylinder 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 side 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. A pressure adjustment disc 52 is connected to the middle of the elastic adjustment component 51. A plurality of holes 521 through which chlorine trifluoride can pass are arranged on the pressure adjustment disc 52. An inner barrier structure 53 is arranged in the holes 521. A top bone component 54 is fixedly arranged at the top of the first molecular sieve adsorption cylinder 41. When the pressure adjustment disc 52 is pressed and descends, it will squeeze the top bone component 54, and the top bone component 54 will push out the inner barrier structure 53 in the holes 521, making the inner diameter of the holes 521 smaller.

[0041] 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 bearing socket 13 is arranged at the inner bottom of the adsorption tower body 10, and the first molecular sieve adsorption cylinder 41 is installed in the bearing socket 13.

[0042] In the prior art, molecular sieves are often used to purify the post-stage processing of phosphorus trifluoride. The molecular sieves are used to perform the last step of treatment on the impurities of phosphorus trifluoride. When arranging the molecular sieves, a very large accommodating framework is usually adopted, and the molecular sieves are filled into the framework. If the molecular sieves in the upper part are pulverized and blocked, it will directly cause the molecular sieves in the lower part to be unusable and need to be directly replaced. Therefore, through the double-position sliding molecular sieve structure 40 provided in the present invention, with the two ends of the first molecular sieve adsorption cylinder 41 and the second molecular sieve adsorption cylinder 42 arranged, the second molecular sieve adsorption cylinder 42 with a larger effective pore diameter is placed at the upper end of the first molecular sieve adsorption cylinder 41 with a larger volume, so that the second molecular sieve adsorption cylinder 42 bears the first-stage pressure of the gas. Even if the phenomenon of pulverization occurs in the second molecular sieve adsorption cylinder 42, only the upper half part needs to be replaced. And the first molecular sieve adsorption cylinder 41 with a large volume, because it is arranged at the lower end, has a lower possibility of being directly flushed by a large amount of high-pressure gas, so that its blockage phenomenon can be weakened, the service life is longer, and at the same time, it is relatively low in terms of enterprise cost and has higher economic benefits.

[0043] The existing molecular sieves need to be regenerated after being taken out, and the regeneration method often adopts the backwashing 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, whose replacement frequency is higher than that of the first molecular sieve adsorption cylinder 41, it needs to be set to a movable state, but it cannot be in a suspended state. Therefore, a guide rail 11 is provided inside the adsorption tower body 10 in this embodiment, an inner groove 12 is formed by the outer wall of the adsorption tower body 10 being recessed inward, the structures of the first molecular sieve adsorption cylinder 41 and the second molecular sieve adsorption cylinder 42 are the same, the first molecular sieve adsorption cylinder 41 includes a material placing frame 411 for carrying the molecular sieves, several matching rib grooves 412 are arranged on the outer side of the material placing frame 411, after the material placing frame 411 is placed into the adsorption tower body 10, the matching rib grooves 412 cooperate with the guide rail 11, and several limiting members 413 are arranged on the inner groove 12, the limiting members 413 penetrate through the guide rail 11 and are connected with the matching rib grooves 412. By providing a guide rail 11 inside the adsorption tower body 10 and arranging 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 specified at the designated positions in a sliding placement manner, and the sealing performance can be ensured during the fixing process.

[0044] When replacing the first molecular sieve adsorption cylinder 41 and the second molecular sieve adsorption cylinder 42, the upper cover 20 needs to be disassembled. Once the upper cover 20 is disassembled, the gas remaining in the equipment will leak out, which may cause pollution. Therefore, before disassembling the upper cover 20, the gas in the adsorption tower body 10 needs to be replaced. During gas replacement, nitrogen is introduced through the nitrogen inlet at the top of the equipment, and the nitrogen makes the gas in the adsorption tower body 10 and the molecular sieve flow out through the nitrogen outlet at the bottom of the adsorption tower body 10, so as to ensure safety after the upper cover 20 is opened.

[0045] In order to ensure the sealing effect, a positioning hole is provided in the inner groove 12. The limiting member 413 includes a sealing gasket 4131 provided on the positioning hole. A locking nail 4132 is installed on the sealing gasket 4131. The locking nail 4132 penetrates through the sealing gasket 4131 and is connected to the threaded hole on the matching rib groove 412. Through the limiting member 413, the molecular sieve adsorption cylinder can be fixed while preventing the gas flowing through it from leaking out.

[0046] Although the second molecular sieve adsorption cylinder 42 is used to bear the pressure for the first molecular sieve adsorption cylinder 41, in fact, the first molecular sieve adsorption cylinder 41 may still be directly affected by 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, it will directly press down the pressure adjustment disc 52 installed on the elastic adjustment component 51, so that the pressure adjustment disc 52 touches the top bone component 54, and the top bone component 54 will push out the inner barrier structure 53 in the hole 521, so that the inner diameter of the hole 521 becomes smaller, and the available passing area of the gas passing through the hole 521 after passing through the second molecular sieve adsorption cylinder 42 becomes smaller, so that the pressure and speed of the gas are both weakened, so as to ensure that the gas passes through the first molecular sieve adsorption cylinder 41 at a relatively uniform and stable speed, so that while the gas is stably filtered, the purification equipment has a longer service life.

[0047] In order to sense the gas flow rate and pressure changes so as to automatically adjust its own state changes, in this embodiment, the elastic adjustment component 51 includes at least two elastic adjustment seats. The elastic adjustment seat includes a first limit spring 511 provided at the lower end of the second molecular sieve adsorption cylinder 42, and a second limit spring 512 is provided at the edge of the upper end of the first molecular sieve adsorption cylinder 41. An installation platform 513 is connected between the first limit spring 511 and the second limit spring 512. A pressure adjustment disc 52 is accommodated in the installation platform 513. The pressure adjustment disc 52 is arranged between the first limit spring 511 and the second limit spring 512. The expansion and contraction amounts of the first limit spring 511 and the second limit spring 512 are changed by the pressure when the gas enters, and then it is judged whether to trigger the internal blocking structure 53 in the pressure adjustment disc 52, so that the state can be automatically changed according to the gas change without manual monitoring.

[0048] It should be emphasized that the first limit spring 511 and the second limit spring 512 are sleeve-type springs, that is, the springs are limited by the sleeves to prevent them from falling out directly.

[0049] During the fixing process of the pressure adjustment disc 52, it needs to change dynamically according to the states of the first limit spring 511 and the second limit spring 512. Therefore, the installation platform 513 in this embodiment includes a C-shaped bushing 5131 connected to the first limit spring 511 and the second limit spring 512. The opening of the C-shaped bushing 5131 is used to accommodate the pressure adjustment disc 52. A perforation is provided on the side of the pressure adjustment disc 52 away from the opening, and a positioning pin 5132 for locking the pressure adjustment disc 52 is connected to the perforation. The pressure adjustment disc 52 is slidably fixed inside the adsorption tower body 10 through the C-shaped bushing 5131 and can move synchronously with the first limit spring 511 and the second limit spring 512, thus achieving the effect of automatic adjustment.

[0050] When adjusting the gas pressure and gas volume, it mainly adjusts the flow rate through the pressure adjustment disc 52. Therefore, the pressure adjustment disc 52 in this embodiment includes a pressure movable disc 522 connected to the C-shaped bushing 5131. The hole 521 is opened in the axial direction of the pressure movable disc 522. A plurality of axial flow channels 523 are provided inside the pressure movable disc 522. The side of the axial flow channel 523 communicates with a return flow channel 524. The internal blocking structure 53 is located in the return flow channel 524. By providing the axial flow channels 523 on the pressure adjustment disc 52 and passing the gas through the axial flow channels 523, and when adjustment is required, the ventilation volume of the axial flow channels 523 is changed. Therefore, a return flow channel 524 is provided beside each axial flow channel 523, and the internal blocking structure 53 is exactly arranged in the return flow channel 524, so that the ventilation volume of the axial flow channels 523 can be changed.

[0051] It is the internal barrier structure 53 that changes the diameter of the axial flow channel 523. The internal barrier structure 53 includes a trigger part 531 located inside the return flow channel 524. The trigger part 531 is connected to a barrier part 532. After the trigger part 531 is lifted by the skull assembly 54, the barrier part 532 is pushed out, so that the barrier part 532 extends into the axial flow channel 523. One end of the internal barrier structure 53 is triggered by the skull assembly 54. When the entire pressure regulating disc 52 descends, it will contact the skull assembly 54, thereby pushing out the trigger part 531, and then driving the barrier part 532 to be pushed out, so as to realize the transformation of the diameter. After the gas pressure drops, the pressure regulating disc 52 rises, and the barrier part 532 will also automatically swing downward under the action of gravity, without hindering the normal flow of gas.

[0052] Among them, the barrier part 532 is a folding piece, and several flow holes are opened in the folding piece. Even if part of the gas enters the return flow channel 524 through the unexpanded barrier part 532, it will be blocked by the skull assembly 54.

[0053] During the cooperation process of the skull assembly 54 and the return flow channel 524, it needs to cooperate with several return flow channels 524 to achieve the effect of consistent adjustment. Therefore, the skull assembly 54 in this embodiment includes an extension rod seat 541 fixed on the top surface of the first molecular sieve adsorption cylinder 41. Several separation rods 542 are connected to the top surface of the extension rod seat 541. The separation rods 542 extend to the return flow channel 524 and are arranged at intervals with the trigger part 531. By setting the skull assembly 54 as several separation rods 542, several separation rods 542 cooperate with the descending return flow channel 524, so that the ventilation volume in all the return flow channels 524 can be adjusted consistently, and the gas pressure can be better stabilized.

[0054] Since the actions of changing the fluid flow rate are all automatically adjusted inside the device, it is difficult for the experimenters to know the situation 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 judged whether there is resistance when the gas passes through the molecular sieve, and then it can be judged whether the molecular sieve needs to be replaced, so as to achieve the effects of mechanical self-adjustment and intelligent self-inspection.

[0055] Since the actions of changing the fluid flow rate are automatically adjusted inside the device, it is difficult for the experimenters to know the situation of the molecular sieve inside 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 inside the adsorption tower body 10, and a second pressure detector 142 is arranged at the bottom inside the adsorption tower body 10. By arranging a pressure detection structure inside the adsorption tower body and detecting the gas pressures at different positions of the adsorption tower body, it is possible to determine whether the gas is subject to resistance when passing through the molecular sieve, and further determine whether the molecular sieve needs to be replaced, so as to achieve the effects of mechanical self-adjustment and intelligent self-checking.

[0056] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A purification process for phosphorus trifluoride, characterized in that, It includes the following steps: S1: Condense the crude phosphorus trifluoride gas and store it in the first storage tank. Then heat the liquid in the first storage tank and pump it into a flash evaporator for flashing. S2: Feed the flashed gas into the first distillation column for distillation. Return the hydrogen fluoride, which is the bottom product of the distillation in the first distillation column, to the phosphorus trifluoride synthesis process. Condense the top products of the distillation, i.e., phosphorus trifluoride and hydrogen chloride, and feed them into the intermediate first product storage tank. S3: Pump the material in the intermediate first product storage tank into the second distillation column for distillation. Condense the top gas of the distillation in the second distillation column. Part of the condensed product is refluxed to the second distillation column, and part is fed into the first product storage tank for storage. S4: Pump the finished product in the first product storage tank into a vaporizer for vaporization. The vaporized gas enters a gas-liquid separation tank for separation. The separated liquid is refluxed to the vaporizer, and the separated gas is discharged from the top and sequentially fed into three phosphorus trifluoride purification devices for purification. The phosphorus trifluoride purification device includes an adsorption tower body (10) for adsorbing phosphorus trifluoride. An upper cover (20) is movably arranged at the top of the adsorption tower body (10). A plurality of air inlet ends are connected to the upper cover (20). An air outlet end (30) is arranged at the bottom of the adsorption tower body (10). It further includes: A two-position sliding molecular sieve structure (40), which includes a first molecular sieve adsorption cylinder (41) arranged at the inner bottom of the 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 diameter of the second molecular sieve adsorption cylinder (42) is larger than that of the first molecular sieve adsorption cylinder (41). The phosphorus trifluoride is adsorbed by the second molecular sieve adsorption cylinder (42) and then enters the first molecular sieve adsorption cylinder (41). A pressure variable diameter adjustment structure (50) arranged between the first molecular sieve adsorption cylinder (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 side 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). A pressure adjustment disk (52) is connected to the middle of the elastic adjustment component (51). A plurality of holes (521) for passing chlorine trifluoride are arranged on the pressure adjustment disk (52). An inner barrier structure (53) is arranged in the holes (521). A top bone component (54) is fixedly arranged at the top of the first molecular sieve adsorption cylinder (41). When the pressure adjustment disk (52) is pressed and descends, it will squeeze the top bone component (54), and the top bone component (54) will push out the inner barrier structure (53) in the holes (521), making the inner diameter of the holes (521) smaller. S5: Feed the purified gas into a filter for filtration. The filtered gas enters the second product storage tank. The gas in the second product storage tank is pressurized by a compressor and enters a buffer tank for pressure stabilization storage, and then enters a filling system for filling after pressure stabilization.

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

3. The purification process of phosphorus trifluoride according to claim 1, characterized in that, A guide rail (11) is disposed inside the adsorption tower body (10). An inner groove (12) is formed by the inward depression of the outer wall of the adsorption tower body (10). 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 material placement frame (411) for carrying molecular sieves. A plurality of matching rib grooves (412) are disposed on the outside of the material placement frame (411). After the material placement frame (411) is placed into the adsorption tower body (10), the matching rib grooves (412) cooperate with the guide rail (11). A plurality of limiting members (413) are disposed on the inner groove (12). The limiting members (413) penetrate through the guide rail (11) and are connected to the matching rib grooves (412).

4. The purification process of phosphorus trifluoride according to claim 3, characterized in that, Alignment holes are formed on the inner groove (12). The limiting member (413) includes a sealing gasket (4131) disposed on the alignment hole. A locking nail (4132) is installed on the sealing gasket (4131). The locking nail (4132) penetrates through the sealing gasket (4131) and is connected to the threaded hole on the matching rib groove (412).

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

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

7. A purification process for phosphorus trifluoride according to claim 1, characterized in that, The pressure adjustment disk (52) includes a pressure movable disk (522) connected to the C-shaped clamping sleeve (5131). The hole (521) is formed in the axial direction of the pressure movable disk (522). A plurality of axial flow channels (523) are formed inside the pressure movable disk (522). The axial flow channels (523) communicate with a reverse flow channel (524) laterally. The inner blocking structure (53) is located in the reverse flow channel (524).

8. A purification process for phosphorus trifluoride according to claim 1, characterized in that, The internal barrier structure (53) includes a trigger portion (531) located inside the reflux channel (524). The trigger portion (531) is connected to a barrier portion (532). After the trigger portion (531) is lifted by the parietal bone assembly (54), the barrier portion (532) is pushed out, so that the barrier portion (532) extends into the axial flow channel (523).

9. The purification process of phosphorus trifluoride according to claim 8, characterized in that, The barrier portion (532) is a folding piece, and a plurality of flow holes are provided in the folding piece.

10. The purification process of phosphorus trifluoride according to claim 8, characterized in that, The parietal bone assembly (54) includes an extension rod seat (541) fixed on the top surface of the first molecular sieve adsorption cylinder (41). A plurality of separation rods (542) are connected to the top surface of the extension rod seat (541). The separation rods (542) extend to the reflux channel (524) and are arranged at intervals with the trigger portion (531).

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