Method and apparatus for purifying ultra-high purity hydrogen fluoride

Abstract

Disclosed are a method and apparatus for purifying ultra-high purity hydrogen fluoride by directly feeding crude hydrogen fluoride to a multi-stage distillation column in place of hydrogen fluoride and purifying it through a continuous distillation process, and removing impurities in the hydrogen fluoride by contact with fluorine gas having a concentration automatically controlled in accordance with the content of arsenic fluoride as an impurity.

Description

Technical Field

[0001] This invention discloses a purification method and apparatus for preparing ultra-high purity hydrogen fluoride. Background Technology

[0002] Hydrogen fluoride (HF) is used in a variety of industries. It is the most commonly produced of fluorine compounds, supplied in anhydrous form and hydrofluoric acid in an aqueous solution containing ultrapure water.

[0003] Hydrofluoric acid is produced through various purification processes using hydrogen fluoride raw materials, such as distillation, electrolysis, adsorption, and membrane separation (Patent Documents 1 to 3). Among these, distillation using fractionation is widely used.

[0004] Hydrogen fluoride is prepared by heating fluorite (calcium fluoride (CaF2)) while adding sulfuric acid. The crude hydrogen fluoride produced by this reaction contains, in addition to hydrogen fluoride, silicon dioxide (SO2) and trace amounts of various impurities such as arsenic trifluoride (AsF3), boron trifluoride (BF3), phosphorus pentafluoride (PF5), silicon tetrafluoride (SiF4), iron trifluoride (FeF3), and sulfur hexafluoride (SF6). These impurities are removed through multiple purification processes, including pretreatment, to produce industrial-grade hydrofluoric acid from hydrogen fluoride typically with a purity of 99.9%.

[0005] Low-purity hydrofluoric acid, such as industrial-grade hydrofluoric acid, is used for industrial applications, while ultra-high-purity hydrofluoric acid is required for etching and cleaning applications in semiconductors and displays.

[0006] Ultra-high purity hydrofluoric acid used in etching and cleaning processes is hydrofluoric acid diluted in ultrapure water at a specified ratio with anhydrous hydrofluoric acid. If impurities are present in the hydrofluoric acid used in such semiconductor fabrication processes, they will remain on the wafer during etching and cleaning, causing pattern formation defects and reducing semiconductor production yield. Therefore, to reduce the defect rate, ultra-high purity hydrogen fluoride is used, with the concentration of metal impurities controlled at a few parts per trillion (ppt). However, the higher the purity of hydrogen fluoride, the higher the purification cost, requiring attention to environmental issues in storage and disposal, and also has disadvantages such as low production efficiency and low conversion rate to hydrogen fluoride products.

[0007] Most of the impurities contained in hydrogen fluoride can be removed by distillation purification. However, impurities such as arsenic (As) exist as arsenic trifluoride in anhydrous hydrofluoric acid. The boiling point of such impurities is 57.13℃, which is not much different from the boiling point of hydrofluoric acid (HF) at 19.5℃. Because they form an azeopropic, they are difficult to separate by distillation purification.

[0008] Arsenic fluorides not only have adverse effects on semiconductor components, but also cause problems in equipment corrosion and environmental protection. Therefore, it is preferable that they be removed during the preparation process of ultra-high purity hydrogen fluoride.

[0009] In the past, methods have been proposed to prepare high-purity hydrogen fluoride by mixing aqueous solutions of oxidants such as hydrogen peroxide or potassium permanganate with hydrogen fluoride to remove arsenic fluorides from the hydrogen fluoride. However, such methods result in production losses and generate a large amount of reaction byproducts because some of the hydrogen fluoride dissolves in the water of the oxidant solution. Furthermore, the corrosiveness of the aforementioned water-containing hydrogen fluoride increases dramatically compared to hydrogen fluoride itself. This leads to process problems such as reduced productivity due to shortened preventative maintenance (PM) cycles for production equipment, as well as stability issues caused by hydrogen fluoride.

[0010] Furthermore, a pretreatment process to remove impurities such as arsenic is required before the production of hydrofluoric acid from hydrogen fluoride, resulting in additional equipment and increased process costs. Moreover, even with pretreatment, it is difficult to remove residual impurities from hydrogen fluoride during the purification process, making it challenging to produce high-purity, especially ultra-high-purity, hydrogen fluoride.

[0011] Patent Document 1: Korean Patent Publication No. 10-2006-0014138

[0012] Patent Document 2: Korean Patent Publication No. 10-2013-0141402

[0013] Patent Document 3: Japanese Patent Publication No. 1994-144805 Summary of the Invention

[0014] Technical issues

[0015] In the existing technology, hydrogen fluoride is prepared from fluorite (calcium fluoride, CaF2), but the production cost is greatly increased due to the generation of a large amount of environmental waste. In order to solve the above problems, research on the production of high-purity hydrogen fluoride is ongoing.

[0016] The process for producing ultra-high purity hydrogen fluoride involves a pretreatment step and a purification step for crude hydrogen fluoride. This invention proposes a method to prepare ultra-high purity hydrogen fluoride by eliminating the pretreatment step and using crude hydrogen fluoride as raw material for the purification step. Furthermore, this invention is the result of extensive research conducted to produce ultra-high purity hydrogen fluoride without a pretreatment step.

[0017] As a result, by introducing a gas stream capable of oxidizing and removing impurities from crude hydrogen fluoride into a multi-stage distillation column where gas and liquid phases coexist, an Advanced Process Control (APC) module can be used as the processor for the feeding process. Based on the quality of the crude hydrogen fluoride as raw material, it can be immediately applied to the purification process to continuously produce ultra-high purity hydrogen fluoride with high mass production conversion rate.

[0018] Therefore, the object of the present invention is to provide a purification method and apparatus for preparing ultra-high purity hydrogen fluoride from crude hydrogen fluoride as raw material.

[0019] Technical solution

[0020] To achieve the above objectives, the present invention provides a method for purifying ultra-high purity hydrogen fluoride, comprising the following steps: supplying crude hydrogen fluoride from a raw material supply unit; performing a continuous distillation process, supplying the crude hydrogen fluoride to a multi-stage distillation column and fractionating it, then removing impurities from the distillation column and transferring the distilled hydrogen fluoride to the next multi-stage distillation column; and injecting a gas stream containing fluorine (F2) gas for removing arsenic trifluoride from impurities and an inert gas into the multi-stage distillation column containing the crude hydrogen fluoride. The gas stream is adjusted according to the arsenic trifluoride content contained in the hydrogen fluoride gas passing through the multi-stage distillation column.

[0021] Furthermore, the gas stream containing the aforementioned fluorine gas and inactive gases is also injected into other multi-stage distillation columns that do not contain crude hydrogen fluoride.

[0022] Furthermore, the present invention provides an ultra-high purity hydrogen fluoride purification apparatus, comprising: a raw material supply unit for supplying crude hydrogen fluoride raw material; a distillation purification unit having multiple multi-stage distillation columns for performing a continuous distillation process; a gas supply unit for supplying a gas stream containing fluorine gas and inert gases into the multi-stage distillation columns; a recovery unit for recovering ultra-high purity hydrogen fluoride; and an advanced process control unit for controlling the process to enable continuous operation. The advanced process control unit supplies a gas stream, the concentration of which is adjusted according to the arsenic trifluoride content in the hydrogen fluoride gas passing through the multi-stage distillation columns, to the multi-stage distillation column containing the crude hydrogen fluoride.

[0023] The effects of the invention

[0024] The ultra-high purity hydrogen fluoride purification process of the present invention is implemented as a continuous supply. When it is necessary to inspect or perform preventive maintenance on the production equipment, the above process can be repeated continuously until it is necessary to stop the flow of hydrogen fluoride and terminate the process.

[0025] Furthermore, crude hydrogen fluoride is used as a raw material without the need for pretreatment, thus simplifying the process and saving pretreatment costs. In particular, impurities can be minimized by introducing a gas stream into the first multi-stage distillation column where the crude hydrogen fluoride is introduced.

[0026] Furthermore, even if the composition or content of impurities in crude hydrogen fluoride is not constant, it is possible to efficiently prepare ultra-high purity hydrogen fluoride with stable quality.

[0027] This method simplifies the process, thus enabling the economical and efficient production of ultra-high purity hydrogen fluoride. Attached Figure Description

[0028] Figure 1 This is a schematic diagram used for the purification of ultra-high purity hydrogen fluoride according to the present invention.

[0029] Figure 2 This is a schematic diagram illustrating an apparatus for purifying hydrogen fluoride according to an example of the present invention.

[0030] Figure 3 This illustrates the sequence of controlling fluorine concentration via the Advanced Process Control (APC) module.

[0031] Figure 4 This is a schematic diagram illustrating an apparatus for purifying hydrogen fluoride, another embodiment of the present invention.

[0032] Best practice

[0033] This invention relates to a method for purifying ultra-high purity hydrogen fluoride, comprising the following steps: supplying crude hydrogen fluoride from a raw material supply unit;

[0034] A continuous distillation process is performed, in which the crude hydrogen fluoride is fed into a multi-stage distillation column and fractionated. Impurities within the distillation column are then removed, and the distilled hydrogen fluoride is transferred to the next multi-stage distillation column.

[0035] A gas stream containing fluorine gas and inactive gases, used to remove arsenic trifluoride from impurities, is injected into the multi-stage distillation column containing the crude hydrogen fluoride.

[0036] The concentration of the gas stream is adjusted according to the content of arsenic trifluoride in the hydrogen fluoride gas passing through the multi-stage distillation column.

[0037] Furthermore, the present invention relates to an ultra-high purity hydrogen fluoride purification apparatus, comprising: a raw material supply unit for supplying crude hydrogen fluoride raw material;

[0038] The distillation and purification section has multiple multi-stage distillation columns for continuous distillation processes;

[0039] The gas supply unit is used to supply a gas stream containing fluorine and inert gases into the aforementioned multi-stage distillation tower.

[0040] The recovery unit is used to recover ultra-high purity hydrogen fluoride; and

[0041] The advanced process control department is used to control processes to enable continuous operation.

[0042] The advanced process control unit supplies a gas stream, whose concentration is adjusted according to the arsenic trifluoride content in the hydrogen fluoride gas passing through the multi-stage distillation tower, to the multi-stage distillation tower into which crude hydrogen fluoride is introduced. Detailed Implementation

[0043] In this specification, the term "ultra-high purity hydrogen fluoride" refers to a gas with a purity of 99.9999% (6N) or higher, as recognized in the technical field to which this invention pertains. The aforementioned ultra-high purity hydrogen fluoride is expressed in parts per billion (ppb). 9 Below that, preferably, in parts per trillion (ppt, part per trillion, 10 12 ), one part per quadrillion (ppq, 10 15 ) removes specific impurities at a certain level.

[0044] The "impurities in ultra-high purity hydrogen fluoride" mentioned in this invention refer to all components other than hydrogen fluoride. The main impurities include silicon dioxide, arsenic trifluoride, boron trifluoride, silicon tetrafluoride, iron trifluoride, sulfur hexafluoride, and phosphorus pentafluoride.

[0045] In this case, impurities other than arsenic trifluoride in hydrogen fluoride can be easily removed by multi-stage distillation. Therefore, the impurities that are expected to be reduced by the related invention may actually be only arsenic trifluoride.

[0046] That is, in the process of removing impurities using a gas flow according to the present invention, the substantial impurity can be considered to be arsenic trifluoride. In this case, arsenic trifluoride is a fluoride of trivalent arsenic, and its oxidized form, arsenic pentafluoride (AsF5), is a fluoride of pentavalent arsenic.

[0047] The present invention provides the following purification method and purification apparatus: crude hydrogen fluoride can be used as raw material to continuously carry out the purification process for 24 hours and prepare ultra-high purity hydrogen fluoride with impurities removed at a level of less than one part per trillion (ppt), preferably one part per quadrillion (ppq), through automatic control.

[0048] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the embodiments, the same structures are given the same reference numerals, and the description of the same reference numerals will be omitted as appropriate.

[0049] Figure 1 This is a schematic diagram used for the purification of ultra-high purity hydrogen fluoride according to the present invention.

[0050] Reference Figure 1The ultra-high purity hydrogen fluoride purification process includes: a raw material supply unit 100 for supplying crude hydrogen fluoride raw material; a distillation purification unit 200 having multiple multi-stage distillation columns for continuous distillation processes; a gas supply unit 300 for supplying gas streams to the aforementioned multi-stage distillation columns; a recovery unit 400 for recovering ultra-high purity hydrogen fluoride; and an advanced process control unit 500 for controlling the process to enable continuous operation.

[0051] The raw material supply unit 100 is an apparatus for supplying crude hydrogen fluoride, which is used as a raw material for ultra-high purity hydrogen fluoride, and includes a storage tank containing crude hydrogen fluoride produced by the reaction of fluorite and sulfuric acid.

[0052] Conventionally, hydrogen fluoride used as a raw material for hydrogen fluoride purification employs pretreatment to remove impurities to a level of one part per million (ppm). However, in this invention, crude hydrogen fluoride is used as the raw material fed into the raw material supply unit 100 for hydrogen fluoride purification. This crude hydrogen fluoride comprises crude hydrogen fluoride obtained through the reaction of fluorite and sulfuric acid, and excess impurities (%), and is a raw material that has not undergone additional pretreatment. Compared to conventional hydrogen fluoride, the use of such crude hydrogen fluoride significantly reduces raw material acquisition costs, simplifies the process, and reduces production costs by eliminating the pretreatment step.

[0053] The crude hydrogen fluoride in the raw material supply unit 100 can be supplied directly to the next distillation and purification unit 200 in liquid form, or it can be supplied in gaseous form. In this case, the supply in gaseous form only involves a change in properties and does not include the term "additional pretreatment process".

[0054] The distillation and purification unit 200 is an apparatus for obtaining ultra-high purity hydrogen fluoride by removing impurities from crude hydrogen fluoride through a fractionation process.

[0055] Fractionation processes can be either batch distillation processes or continuous distillation processes, with continuous distillation processes being the most common, especially those using multi-stage distillation columns with two or more distillation stages that can continuously distill.

[0056] The continuous distillation process is equipped with a multi-stage distillation column for concentration and purification by vaporizing crude hydrogen fluoride, and a reboiler for generating hydrogen fluoride vapor by heating crude hydrogen fluoride.

[0057] Multistage distillation columns have 2 to 50 theoretical stages; for example, some have 3 to 40 theoretical stages. When heated by a reboiler, liquid crude hydrogen fluoride coexists with gaseous hydrogen fluoride and impurities within the multistage distillation column. The composition of these gaseous components separates towards the top, middle, and bottom regions of the column. Low-boiling-point impurities move towards the top region for discharge, while high-boiling-point impurities move towards the bottom region for discharge. Hydrogen fluoride, located in the middle region, continuously moves towards the next multistage distillation column.

[0058] The distillation and purification unit 200 is connected to two or more, three to forty, or four to twenty-five multi-stage distillation columns, which can be used to prepare ultra-high purity hydrogen fluoride by continuously passing the material through these multi-stage distillation columns. These multi-stage distillation columns are interconnected by piping and can be arranged in series, parallel, or in a mixed configuration; preferably, they can be connected in series.

[0059] The gas supply unit 300 is a device for supplying a gas stream used to remove impurities from crude hydrogen fluoride, particularly arsenic trifluoride. The gas stream contains fluorine gas and inert gases used for conveying and diluting the fluorine gas.

[0060] Fluorine (fluorinated gas) is an expensive gas produced by the electrolysis of hydrogen fluoride. The cost of ultra-high purity hydrogen fluoride depends on how efficient the method used to produce fluorine.

[0061] The existing JP2005-281048 proposes a method of purifying hydrogen fluoride by mixing it with fluorine gas for more than 5 minutes. However, this method is limited by the configuration method and is not suitable for hydrogen fluoride purification through continuous processes. Even if this method is adopted, there is a risk of overuse of fluorine gas.

[0062] This invention employs the APC module of the advanced process control unit 500, as described below, to apply fluorine gas in a continuous process, and designs the most efficient dosing method. The fluorine gas is used in a mixture with an inert gas, and the amount of fluorine gas added is determined based on the concentration of arsenic trifluoride in the crude hydrogen fluoride to be purified.

[0063] The fluorine gas supplied in the gas supply section 300 reacts with the high-boiling-point arsenic trifluoride in the crude hydrogen fluoride to form low-boiling-point arsenic pentafluoride, which is then removed to the top of the column in gaseous form. In addition to this reaction, it also reacts with the ions of hydrogen fluoride present with arsenic pentafluoride to form high-boiling-point hexafluoroarsonic acid (HAsF6), which can be easily removed to the bottom of the column.

[0064] Most impurities in crude hydrogen fluoride have low boiling points and high boiling points compared to hydrogen fluoride itself. Therefore, most impurities are removed during the distillation process in a multi-stage distillation column. However, it is difficult to remove trivalent arsenic fluoride (arsenic trifluoride). That is, although high-purity hydrogen fluoride contains trace amounts of arsenic trifluoride (bp=62.8℃) and other substances with high boiling points, they form chelates with hydrogen fluoride, thus lowering their boiling points and forming boiling points similar to or azeotropic with hydrogen fluoride. Therefore, separation is extremely difficult.

[0065] When fluorine gas is injected to remove trivalent arsenic fluoride, the most problematic impurity contained in hydrogen fluoride, the reaction shown in the following reaction formula occurs.

[0066] Reaction 1

[0067] AsF3+F2→AsF5

[0068] Reaction 2

[0069] AsF5+HF→HAsF6

[0070] Through the above oxidation reaction, arsenic trifluoride, a trivalent arsenic fluoride, reacts with fluorine gas to be converted into arsenic pentafluoride, a pentavalent arsenic fluoride. The boiling point (bp) of this pentavalent arsenic fluoride is -52.8°C, which differs from the boiling point of hydrogen fluoride (19.5°C), thus allowing for separation during the distillation process. Furthermore, the reaction with hydrogen fluoride to generate a high-boiling-point compound further facilitates separation.

[0071] In reality, the crude hydrogen fluoride fed into the first multi-stage distillation column contained arsenic trifluoride at a level of one part per million (ppm). When using pure 100% fluorine gas, the boiling point difference between fluorine and hydrogen fluoride was too great, making it difficult to meet sufficient reaction conditions and thus significantly increasing process costs. Therefore, in order to achieve low cost and high efficiency, this invention uses a mixed gas by diluting the fluorine gas with an inert gas.

[0072] When crude hydrogen fluoride in liquid or gaseous state is introduced into the first multi-stage distillation column, it is converted to a gaseous state via a reboiler. In this case, an oxidation reaction occurs through gas-to-gas contact between the gaseous crude hydrogen fluoride and fluorine gas. Conversely, an oxidation reaction also occurs through liquid contact between the crude hydrogen fluoride and fluorine gas. These two reactions occur simultaneously, thereby maximizing the oxidation reaction in Equation 1 above.

[0073] Fluorine gas can be introduced into the multistage distillation column that introduces crude hydrogen fluoride, or additionally into all remaining multistage distillation columns. The arsenic fluoride content varies in each multistage distillation column; to ensure the best effect with the smallest amount, the fluorine gas is diluted to a specified concentration and introduced into the multistage distillation column in a manner corresponding to the residual arsenic fluoride content.

[0074] The inactive gas in the gas flow of the present invention is one or more gases selected from helium (He), nitrogen (N2) and argon (Ar), preferably nitrogen.

[0075] The concentration of fluorine gas to inactive gas in the gas stream can be varied within a weight percentage range of 10:90 to 90:10. The higher the fluorine content, the greater the likelihood of arsenic trifluoride participating in the oxidation reaction to arsenic pentafluoride; however, the residence time of crude hydrogen fluoride in the multi-stage distillation column limits the contact between arsenic trifluoride and fluorine gas. Therefore, considering cost, it is preferable to adjust the fluorine gas concentration according to the impurity concentration of the crude hydrogen fluoride.

[0076] The fluorine gas and inactive gas in the above gas stream can be simultaneously introduced into a multi-stage distillation column, or introduced in the form of a pre-mixed gas.

[0077] As an example, when the content of arsenic trifluoride in the hydrogen fluoride passing through the first multi-stage distillation column is 100 ppm or more, the concentration of fluorine gas is made to be 0.1% to 0.2%, and when the content of arsenic trifluoride in the hydrogen fluoride is 10 ppb to 100 ppb, the concentration of fluorine gas is made to be 0.005% to 0.01%.

[0078] The recovery unit 400 is a device for recovering ultra-high purity hydrogen fluoride purified by the distillation and purification unit 200. The ultra-high purity hydrogen fluoride is recovered in a gaseous state after passing through the last multi-stage distillation column, or in a liquefied liquid state after passing through a condenser.

[0079] In order to control the continuous process of purifying ultra-high purity hydrogen fluoride from crude hydrogen fluoride through the aforementioned raw material supply unit 100, distillation and purification unit 200, gas supply unit 300 and recovery unit 400, automatic control is performed in the advanced process control unit 500.

[0080] The Advanced Process Control Unit 500 is a device that includes an Advanced Process Control (APC) module.

[0081] An APC module consists of a mathematical module that simultaneously considers the dynamic characteristics of multiple process operating parameters. It refers to a multivariable predictive control technique that maintains stable and economical optimal operating conditions through control. The aforementioned APC module utilizes software to improve the overall efficiency and operational convenience of a factory without requiring additional equipment.

[0082] By using APC modules to control the purification process from crude hydrogen fluoride to ultra-high purity hydrogen fluoride, product yield can be improved and upgraded, thereby reducing operating costs and giveaways. Furthermore, even if the quality of the crude hydrogen fluoride used as raw material varies, the final ultra-high purity hydrogen fluoride can be made of uniform quality, thus improving operational flexibility. Simultaneously, by increasing process efficiency, benefits such as increased production and throughput can be achieved while reducing energy consumption.

[0083] The inherent characteristics of chemical processes lie in the fact that when moving an adjustment parameter, not only a target parameter but also multiple conditions must be considered simultaneously. Therefore, the correlation between the required adjustment parameter and the target parameter must be understood. The dynamic characteristic model expressing this correlation, included within the APC module, is a computer-based multivariable predictive control (MRC) technique used to maintain the process more stably and economically. This MRC technique simultaneously controls the adjustment parameters by considering the influence of multiple adjustment parameters on other control parameters, thereby satisfying the target values ​​of each of these control parameters. A dynamic model expressing the relationship between the process's operating parameters (input parameters, adjustment parameters, disturbance parameters) and control parameters (output parameters) is constructed using actual operating data. This dynamic model can be used to predict the future dynamics of the operating and control parameters for control purposes.

[0084] In the structure of the purification method and apparatus of the present invention, the maximum parameter controlled by the APC module can be the concentration of impurities.

[0085] The raw material supply unit 100 can receive an on / off signal through the advanced process control unit 500 and supply crude hydrogen fluoride to the multi-stage distillation column while the distillation purification unit 200 is open. The hydrogen fluoride purified by the multi-stage distillation column is continuously transferred to the next multi-stage distillation column via a transfer line. A gas stream is supplied to the multi-stage distillation column from the gas supply unit 300 to remove impurities.

[0086] In this process, the concentration of the gas stream and the injection rate of the gas stream vary depending on the content of crude hydrogen fluoride and impurities present in the multi-stage distillation column. The content of these impurities can be obtained by measuring the concentration of impurities present in the multi-stage distillation column.

[0087] For concentration analysis, sensors for measuring each concentration are installed, which are displayed on a monitor connected to the advanced process control unit 500 via the analysis device.

[0088] Concentration analysis methods are differentiated based on the type of impurities and measured using more than one analytical instrument, which is not particularly limited in this invention.

[0089] Taking into account the potential damage to inductively coupled plasma mass spectrometry (ICP-MS), we analyze metallic impurities using specialized equipment that pre-processes the material to a uniform concentration and free from contamination. Moisture and ionic impurities are precisely analyzed using Fourier transform infrared spectroscopy (FT-IR), while gaseous impurities are precisely analyzed using gas chromatography (GC).

[0090] Based on the impurity concentration and the appropriate gas flow, the measured impurity concentration is transmitted to the APC module. The gas flow is adjusted during the primary, secondary, and nth gas flow injections, and the injection volume during processing is modified according to the impurity concentration setpoint. Through this modification method, even if the quality of the crude hydrogen fluoride used as raw material varies, the final obtained hydrogen fluoride can be a uniformly high-purity substance.

[0091] In particular, the purification method and purification apparatus of the present invention can be carried out in a continuous process. With the use of APC module to control the process, it can be operated automatically for 24 hours, which has the advantage of being able to increase the production and processing capacity of ultra-high purity hydrogen fluoride at low cost.

[0092] Using the aforementioned structure, the production process of ultra-high purity hydrogen fluoride according to the present invention will be described in detail with reference to the accompanying drawings.

[0093] Although not illustrated, the above-mentioned devices may also include flow regulators, pressure controllers, compressors, coolers, condensers, storage tanks, supply regulating valves, gas-liquid separators, flow meters, analytical devices, analytical sample collection devices, leak detectors, liquid or gas transfer pumps, exhaust devices, overpressure protection devices, automation devices, various sensors, thermometers, mass gauges, pressure gauges, volume measuring instruments, etc.

[0094] Figure 2 This is a schematic diagram illustrating an apparatus for producing ultra-high purity hydrogen fluoride according to an example of the present invention. In this case, three multi-stage distillation columns are shown, but this is only an example for illustration, and the number and arrangement of multi-stage distillation columns used in actual processes can be varied.

[0095] The following describes the process.

[0096] Crude hydrogen fluoride, as a raw material, is transferred from crude hydrogen fluoride storage tank 110 to the bottom of the first distillation column 210 via transfer pump (not shown) or pressurized inactive gas through transfer line 122.

[0097] The crude hydrogen fluoride in the crude hydrogen fluoride storage tank 110 can be added to the first distillation column 210 in liquid form, or added to the first distillation column 210 in gaseous form via an evaporator. The introduction of the crude hydrogen fluoride in gaseous form into the evaporator, along with the high concentration of residual impurities in the lower part of the evaporator, achieves an impurity removal effect.

[0098] The crude hydrogen fluoride fed into the first distillation column 210 is fractionated to remove low-splitting and high-boiling-point impurities via discharge lines 218 and 219 at the top and bottom of the column, respectively. The gas discharged from the first distillation column 210 passes through cooler C1 and recovery section R1, and the hydrogen fluoride, having undergone initial impurity removal, is transferred to the second distillation column 220 via conveyor line 212. In this case, impurities supplied from the first distillation column 210 can be discharged via discharge line 218 at the top of the column after passing through cooler C1 and recovery section R1.

[0099] In the first distillation column 210, most of the impurities in the crude hydrogen fluoride, including silicon dioxide, such as arsenic trifluoride, boron trifluoride, phosphorus pentafluoride, silicon tetrafluoride, iron trifluoride, and sulfur hexafluoride, are removed by fractional distillation.

[0100] In order to remove the difficult-to-separate arsenic trifluoride, a mixture of fluorine gas and inactive gas is injected into the first gas flow mixing device 310, that is, the injected gas flow is used for oxidation reaction.

[0101] The gas stream can be injected using either a downward injection method (spraying from top to bottom) or an upward injection method (spraying from bottom to top). This method can vary depending on the equipment process and can be implemented in a way that increases the contact opportunity between the crude hydrogen fluoride and the fluorine gas. Figure 2 The downward spray pattern is shown for ease of explanation.

[0102] The introduction of fluorine / inactive gases into the gas stream can be achieved by removing the concentration of arsenic trifluoride contained in the crude hydrogen fluoride, as determined by the APC module in the first distillation column.

[0103] That is, the concentration of fluorine gas introduced into the first distillation column is controlled in a direction that minimizes the concentration of arsenic trifluoride contained in the hydrogen fluoride passing through the first distillation column 210.

[0104] Figure 3 This illustrates the sequence of controlling fluorine concentration via the APC module.

[0105] observe Figure 3 Crude hydrogen fluoride and fluorine gas are introduced into the first distillation column 210.

[0106] In the APC module settings of this process, the operating parameter is set as the concentration of fluorine gas introduced into the first distillation column 210, and the control parameter is set as the content of arsenic trifluoride passing through the first distillation column 210. The set of optimal normal values ​​(steady state values) for both is calculated through simulation and other methods.

[0107] Next, the content of arsenic trifluoride in the hydrogen fluoride passing through the first distillation column 210 is determined. This arsenic trifluoride content can be measured at the outlet located at the connection point between the first distillation column 210 and the transfer line 212, or at any point on the transfer line 212. In this case, the determination can be performed using an inductively coupled plasma mass spectrometer or similar instrument with pretreatment for analysis.

[0108] The measured arsenic trifluoride content is fed back to the APC module. If it is below the set value (YES), the process continues.

[0109] If the measured value is higher than the set value (NO), the concentration of fluorine gas introduced into the first distillation column 210 is adjusted via the APC module. Using the signal from the APC module, a flow controller (not shown) adjusts the flow rates of the fluorine gas storage tank 301 and the inactive gas storage tank 302, which are connected to the gas flow mixing device 310, to introduce the fluorine gas into the gas flow mixing device 310. In this case, the APC module can pre-store data tables obtained through experiments or simulations, algorithms for calculating flow control values, etc., until a concentration value is received to input the flow control value.

[0110] As described above, the APC module optimizes the operating parameters in the first distillation column by taking into account parameters including setpoints, upper / lower limits, and system disturbances, in a manner that allows for interchangeability with the aforementioned normal values.

[0111] As a result, the APC module can respond quickly and proactively to the continuous changes in the concentration of arsenic trifluoride in hydrogen fluoride during the process, in a manner that is related to the concentration of fluorine gas introduced.

[0112] The first distillation column 210 is operated at a pressure of 0.1 bar to 3 bar and a temperature of 10°C to 60°C, with a residence time of 1 minute to 30 minutes. In this invention, untreated crude hydrogen fluoride is directly introduced into the distillation column, therefore the process conditions in the first distillation column 210 differ from those in other distillation columns.

[0113] By introducing fluorine gas into the first distillation column 210, an oxidation reaction occurs through both gas-to-gas and liquid-to-gas contact between crude hydrogen fluoride and fluorine gas, thereby maximizing the effect of introducing the fluorine gas. This technique differs from the method of introducing fluorine gas to remove arsenic trifluoride from gaseous hydrogen fluoride, where the oxidation reaction only occurs through gas-to-gas contact. This method allows for simultaneous liquid-to-gas contact, thus maximizing the oxidation reaction.

[0114] On the other hand, although not in Figure 3 As shown, when using an upward injection method, the nozzle (not shown) is configured to inject a gas stream from the bottom to the top. The gas stream injected from the nozzle (not shown) has the advantage of increasing injection pressure as it travels from bottom to top. The fluorine gas in the gas stream injected from the nozzle (not shown) has an upward trajectory and, under the influence of gravity, falls from the top to the bottom, increasing the chance of contact with the liquid crude hydrogen fluoride, thereby further improving the purification effect based on the injection of the fluorine gas.

[0115] Then, the hydrogen fluoride that has completed the primary distillation oxidation process is added to the second distillation column 220 for secondary distillation.

[0116] Hydrogen fluoride fed into the second distillation column 220 undergoes fractionation, causing high-boiling-point impurities to be discharged along the bottom discharge line 229. Furthermore, after passing through cooler C2 and recovery section R2, the purified hydrogen fluoride is fed back into the second distillation column 220, while low-boiling-point impurities are discharged through the top discharge line 228. In this case, a portion of the hydrogen fluoride is recycled back into the second distillation column 220.

[0117] Then, the hydrogen fluoride remaining after the second distillation is introduced into the central area of ​​the third distillation column 230 for tertiary distillation.

[0118] Hydrogen fluoride fed into the third distillation column 230 undergoes fractionation, causing high-boiling-point impurities to be discharged via discharge line 239 at the bottom of the column. Furthermore, after passing through cooler C3 and recovery section R3, the hydrogen fluoride is ultimately transferred to the ultra-high purity hydrogen fluoride storage tank 410 via storage line 422, while the low-boiling-point impurities are discharged via discharge line 238 at the top of the column. In this case, a portion of the hydrogen fluoride is recycled back to the third distillation column 230.

[0119] The hydrogen fluoride in the ultra-high purity state after removing impurities from the third distillation column 230 is transferred to the ultra-high purity hydrogen fluoride storage tank 410 by gravity along the storage line 422 via the drop.

[0120] The ultra-high purity hydrogen fluoride storage tank 410 contains ultra-high purity hydrogen fluoride with impurities at a level of one part per quadrillion. Under these circumstances, the storage temperature is lowered below the boiling point to store the ultra-high purity hydrogen fluoride in a liquid state.

[0121] As mentioned above, in addition to the multi-stage distillation column for introducing crude hydrogen fluoride, fluorine gas can also be introduced into other multi-stage distillation columns to further improve the purification effect of hydrogen fluoride.

[0122] The following describes another example of the purification method and apparatus for ultra-high purity hydrogen fluoride.

[0123] Figure 4 A schematic diagram of an apparatus for producing ultra-high purity hydrogen fluoride, illustrating another example of the present invention.

[0124] Reference Figure 4 The additional gas mixing devices 310, 320, and 330 are connected to the first distillation column 210, the second distillation column 220, and the third distillation column 230, respectively. For example... Figure 2 As shown, these are respectively connected to a fluorine gas storage tank (not shown) and a non-reactive gas storage tank (not shown). Each of these fluorine / non-reactive gas storage tanks, along with the respective flow valves and flow controllers used to control the flow rate, are connected to the APC module. Although not shown separately, the supply of fluorine and non-reactive gases can be individual or connected to a single storage tank. Non-reactive gases can be supplied through supply lines L1, L2, and L3, while fluorine can be supplied through supply lines M1, M2, and M3.

[0125] exist Figure 4 In this process, hydrogen fluoride passing through the first distillation column 210 is distilled through the second distillation column 220 via the transfer line 212, and then transferred to the third distillation column 230 via the transfer line 222 for continuous distillation.

[0126] In this case, the first distillation column 210 measures the arsenic trifluoride content in the crude hydrogen fluoride supplied from the transfer line 212 and sends a signal to the APC module. If the arsenic trifluoride content exceeds a set value, the fluorine concentration in the first gas mixing device 310 is adjusted by regulating the flow valves of the fluorine supply line M1 and the inactive gas supply line L1. The gas stream with this adjusted concentration is then introduced into the first distillation column 210 to carry out the reaction process.

[0127] The same process is carried out in the second distillation column 220 and the third distillation column 230.

[0128] In the first distillation column 210, the second distillation column 220, and the third distillation column 230, the introduced fluorine gas undergoes an oxidation reaction with gaseous hydrogen fluoride gas through gas-to-gas contact. In this case, to enhance the oxidation reaction, vortex generators (not shown) capable of forming vortices can be installed inside the first distillation column 210, the second distillation column 220, and the third distillation column 230, or the oxidation reaction can be maximized by varying the gas flow injection methods.

[0129] The ultra-high purity hydrogen fluoride purification process of the present invention is achieved by continuously supplying raw materials and gas flow. In the event of inspection or preventive maintenance of production equipment, the above process can be repeated continuously until the flow of hydrogen fluoride needs to be stopped.

[0130] Furthermore, crude hydrogen fluoride can be used as a raw material without the need for pretreatment, thus simplifying the process and saving pretreatment costs.

[0131] Furthermore, even if the composition or content of impurities in crude hydrogen fluoride is not constant, it is possible to efficiently prepare ultra-high purity hydrogen fluoride with stable quality. The moisture concentration of the ultra-high purity hydrogen fluoride prepared in this way is also minimized, thus exhibiting excellent stability.

[0132] The hydrogen fluoride recovered according to the present invention is ultra-high purity hydrogen fluoride with an impurity (especially arsenic fluoride) content of one part per quadrillion, which can be preferentially used in fields that require high purity hydrogen fluoride and hydrofluoric acid, such as etching and cleaning of semiconductors and displays.

[0133] Example

[0134] The embodiments of the present invention will be described in detail below, but the present invention is not limited to these embodiments.

[0135] Example 1

[0136] like Figure 1 As shown, a device using three multi-stage distillation columns connected in series is used as a continuous multi-stage distillation column.

[0137] The raw material is crude hydrogen fluoride purchased from Company A in China, which is continuously supplied to the first distillation tower at a rate of 2.19 tons / hour for fractionation.

[0138] The design specifies a bottom temperature of 32°C and a top temperature of 30°C, with continuous distillation under a top pressure of 0.5 bar and a reflux ratio of 1:3. Under these conditions, a mixture of fluorine and nitrogen in a 90:10 ratio is continuously supplied from the bottom of the first distillation column at a flow rate of 1 kg / h to carry out the oxidation reaction, while low-boiling and high-boiling impurities are continuously extracted at a rate of 0.066 tons / h.

[0139] Hydrogen fluoride, after being oxidized and purified at the top of the column and then cooled, is transferred to the second distillation column via a transfer line at a rate of 2.124 tons per hour.

[0140] Under these conditions, the second distillation column operates under the same conditions as the first distillation column, continuously extracting low-boiling and high-boiling impurities at a rate of 0.044 tons / hour.

[0141] Hydrogen fluoride from the second distillation column is supplied to the third distillation column at a rate of 2.08 tons per hour for fractionation. Under these conditions, the operating conditions of the distillation column are the same as those of the first distillation column, continuously removing low-boiling and high-boiling impurities at a rate of 0.043 tons per hour.

[0142] Hydrogen fluoride from the third distillation column is continuously transferred to storage tanks via a transfer line at a rate of 2.037 tons per hour.

[0143] Under the above conditions, after long-term continuous operation, the hourly production of ultra-high purity hydrogen fluoride was 2.037 tons after 500 hours, 2000 hours, 4000 hours, 5000 hours, and 6000 hours, respectively, which was very stable.

[0144] Example 2

[0145] The same procedure as in Example 1 above is followed, but before adding it to the first distillation column, crude hydrogen fluoride is added to the first distillation column in a gaseous state through an evaporator.

[0146] Example 3

[0147] The process is carried out in the same manner as in Example 1 above, with a mixture of fluorine and nitrogen gas in a ratio of 4:6% and 2:8% supplied to the second and third distillation columns respectively at a rate of 1 kg / hour.

[0148] Comparative Example 1

[0149] Hydrogen fluoride was purified using the same method as in Example 1 without injecting a fluorine / nitrogen mixture.

[0150] Comparative Example 2

[0151] The process was carried out in the same manner as in Example 3, by injecting a fluorine / nitrogen mixture into the second and third distillation columns (excluding the first distillation column) to purify hydrogen fluoride.

[0152] Experimental Example 1

[0153] The impurity content in the purified hydrogen fluoride from the examples and comparative examples was determined, and the results are shown in Table 1. In this case, after pretreatment, the impurities were determined by ion chromatography-mass spectrometry and inductively coupled plasma mass spectrometry in ultrapure water at 49% hydrofluoric acid concentration.

[0154] Table 1

[0155]

[0156] Referring to the table above, when the gas stream of fluorine / inactive gas is injected into the multi-stage distillation tower for feeding crude hydrogen fluoride according to the present invention, it can be seen that the final hydrogen fluoride contains impurities at a level of less than one part per trillion, that is, it contains impurities at a level of one part per quadrillion.

[0157] Furthermore, observing the results of purification in the third distillation column of Comparative Example 1 and Comparative Example 2, it can be seen that although the contents of boron, titanium, calcium and iron can be reduced to some extent, the contents of arsenic are very high. Therefore, in order to remove arsenic, it is preferable to carry out the process of Examples 1 to 3.

[0158] In particular, in Examples 1 to 3, the arsenic content was reduced to a significantly lower level than in Comparative Examples 1 and 2 by injecting fluorine / inactive gas into the first multi-stage distillation column. Meanwhile, as shown in Example 3, the best experimental results were observed when gas streams were injected into the second and third distillation columns.

[0159] Explanation of reference numerals in the attached figures

[0160] 100: Raw Material Supply Department

[0161] 200: Distillation and Purification Section

[0162] 300: Gas Supply Department

[0163] 400: Recycling Department

[0164] 500: Advanced Process Control Department

[0165] 110: Crude hydrogen fluoride storage tank

[0166] 122: Raw material transfer line

[0167] 210: First distillation column

[0168] 220: Second distillation column

[0169] 230: Third distillation column

[0170] 218, 219, 228, 229, 238, 239: Exit lines

[0171] 301: Fluorine gas storage tank

[0172] 302: Inactive gas storage tank

[0173] 310: First gas flow mixing device

[0174] 320: Second gas flow mixing device

[0175] 330: Third gas flow mixing device

[0176] 410: Ultra-high purity hydrogen fluoride storage tank

[0177] 422: Storage Line

[0178] C1, C2, C3: Coolers

[0179] R1, R2, R2: Recycler

[0180] L1, L2, L3: Inactive gas supply lines

[0181] M1, M2, M3: Fluorine supply lines

[0182] Industrial availability

[0183] The hydrogen fluoride recovered according to the present invention is ultra-high purity hydrogen fluoride with an impurity content (especially arsenic fluoride) of one part per quadrillion in hydrofluoric acid, which can be preferentially used in fields requiring high purity hydrogen fluoride and hydrofluoric acid, such as etching and cleaning of semiconductors and displays.

Claims

1. A method for purifying ultra-high purity hydrogen fluoride, characterized in that, Includes the following steps: Crude hydrogen fluoride is supplied from the raw material supply department. The crude hydrogen fluoride is generated by the reaction of fluorite and sulfuric acid without any pretreatment process. The crude hydrogen fluoride is fed into a multi-stage distillation column, vaporized in a reboiler, and fractionated in the column. Impurities are removed from the column, and the distilled hydrogen fluoride is transferred to the next multi-stage distillation column for continuous distillation. A mixed gas stream of F2 gas and inert gas is injected into a multi-stage distillation column supplied with crude hydrogen fluoride. The concentration of the mixed gas stream is adjusted according to the AsF3 content in the impurities to remove AsF3; and The aforementioned mixed gas stream of F2 gas and inactive gas was also injected into other multi-stage distillation columns that did not contain crude hydrogen fluoride.

2. The purification method for ultra-high purity hydrogen fluoride according to claim 1, characterized in that, The crude hydrogen fluoride is added in either liquid or gaseous form.

3. The purification method for ultra-high purity hydrogen fluoride according to claim 1, characterized in that, In the above gas stream, the ratio of fluorine gas to inactive gas is 10:90 to 90:10 by weight percentage.

4. The purification method for ultra-high purity hydrogen fluoride according to claim 1, characterized in that, The aforementioned inactive gas is selected from one or more of the group consisting of helium, nitrogen, and argon.

5. The purification method for ultra-high purity hydrogen fluoride according to claim 1, characterized in that, The aforementioned ultra-high purity hydrogen fluoride contains arsenic trifluoride at a concentration below 1 ppt.

6. The purification method for ultra-high purity hydrogen fluoride according to claim 1, characterized in that, The aforementioned gas stream is also fed into the remaining multi-stage distillation column.

7. A device for purifying ultra-high purity hydrogen fluoride, characterized in that, include: The raw material supply department supplies crude hydrogen fluoride, which is generated by the reaction of fluorite and sulfuric acid without any pretreatment process. The distillation and purification section has multiple multi-stage distillation columns for continuous distillation processes; The gas supply section is used to supply a mixed gas stream of F2 gas and inactive gas into the multi-stage distillation tower. The recovery unit is used to recover ultra-high purity hydrogen fluoride; and The advanced process control unit is configured to control the concentration of F2 gas in the mixed gas flow under advanced process control. The mixed gas stream, with its concentration adjusted according to the concentration of AsF3, is fed into a multi-stage distillation column containing crude hydrogen fluoride; and The aforementioned mixed gas stream of F2 gas and inactive gas was also injected into other multi-stage distillation columns that did not contain crude hydrogen fluoride.

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