Apparatus for recovering hydrogen fluoride from anode gas in a process for the electrolytic production of nitrogen trifluoride

Abstract

The utility model provides a kind of hydrogen fluoride recovery device in the process of anodic gas of electrolytic preparation nitrogen trifluoride, the recovery device is realized the solidification and pre-removal of ammonium hydrogen fluoride by setting buffer tank on anode pipeline, ammonium hydrogen fluoride particulate is removed in depth again through filter, condensation unit is used to make ammonium hydrogen fluoride liquefaction separation and efficient collection, the efficient recovery of anodic fluorine gas of electrolytic device can be realized by the recovery device, and it is suitable for industrialization to realize cost reduction and efficiency increase.

Description

Technical Field

[0001] This utility model relates to a gas recovery device, and in particular to a device for recovering hydrogen fluoride from the anode gas in the electrolytic preparation of nitrogen trifluoride. Background Technology

[0002] Nitrogen trifluoride is widely used in LCD panel cleaning and etching and cleaning processes in ultra-large-scale integrated circuit manufacturing.

[0003] Nitrogen trifluoride is produced using a mixed electrolytic process involving high-purity ammonia and hydrogen fluoride. The advantages of this process are relatively safe and stable operation, high gas purity (99.996%), and high product purity. The disadvantage is the high cost. During the electrolytic production of nitrogen trifluoride, the anode gas also contains a high amount of hydrogen fluoride in addition to nitrogen trifluoride. If this hydrogen fluoride is recovered and reused, it is expected to reduce costs and increase efficiency.

[0004] Patent document CN1450202A discloses a process and equipment for preparing nitrogen trifluoride (NF3) gas. The anolyte gas from an electrolytic cell enters a pressure balance tank via a pipeline. Gas exiting the pressure balance tank enters a low-pressure tank via a regulating valve. Gas exiting the low-pressure tank then enters a cryogenic cooling tower via a pipeline to remove high-boiling-point impurities such as NH4F and HF from the anolyte gas. After the high-boiling-point impurities are removed in the cryogenic cooling tower, the NF3 gas enters an ultra-low temperature cold trap via a pipeline for liquefaction and collection. Low-boiling-point impurities such as N2 and O2 are removed by evacuating the cold trap. After the NF3 gas is collected and liquefied in the ultra-low temperature cold trap, the cold trap is heated, and the NF3 gas is distilled and pressurized into a crude NF3 gas storage tank. This method only removes high-boiling-point impurities such as NH4F and HF through a cryogenic cooling tower; it does not effectively recover HF. Utility Model Content

[0005] This invention proposes a hydrogen fluoride recovery device for the anode gas in the electrolytic preparation of nitrogen trifluoride, achieving efficient recovery of hydrogen fluoride gas.

[0006] The technical solution of this utility model is implemented as follows: A device for recovering hydrogen fluoride from the anode gas in the electrolytic preparation of nitrogen trifluoride includes a demister, a buffer tank, a filter, a condenser unit, and a hydrogen fluoride storage tank connected in sequence. The feed end of the demister is connected to the anode discharge end of the electrolytic cell via an anode pipe. The buffer tank is used to condense and collect ammonium hydrogen fluoride solid. The condenser unit is used to condense the hydrogen fluoride to below its boiling point and separate nitrogen trifluoride. It has a nitrogen trifluoride output pipe at the top and is connected to the hydrogen fluoride storage tank at the bottom.

[0007] Furthermore, the condensation unit includes multiple condensers arranged in parallel.

[0008] Preferably, the medium input and output pipelines of each condenser are connected in parallel, and the input and output pipelines are respectively connected to the refrigerant tank.

[0009] Furthermore, the upper part of the condensation unit is provided with a nitrogen trifluoride output pipe.

[0010] Furthermore, the hydrogen fluoride storage tank is connected to an electrolyte preparation vessel via a circulation pipe, and the lower part of the electrolyte preparation vessel is connected to an electrolytic cell.

[0011] Preferably, the electrolyte preparation vessel is also connected to a hydrogen fluoride supply tank.

[0012] The beneficial effects of this utility model are as follows: This invention achieves the solidification and pre-removal of ammonium bifluoride by setting a buffer tank on the anode pipeline, and then removes ammonium bifluoride particles through a filter. The condensation unit enables the liquefaction, separation, and efficient collection of hydrogen fluoride. This recovery device can achieve efficient recovery of hydrogen fluoride gas generated at the anode of the electrolysis device, and is suitable for industrialization to reduce costs and increase efficiency. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the overall structure of the hydrogen fluoride recovery device in the anode gas during the electrolytic preparation of nitrogen trifluoride according to this utility model.

[0015] The attached figures are labeled as follows: C1, Buffer tank; C2, Condenser 1; C3, Condenser 2; D1, Demister; F1, Filter; L1, Anode tube; L2, Condensate tube; L3, Nitrogen trifluoride output tube; L4, Circulation tube; S1, Hydrogen fluoride storage tank; S2, Hydrogen fluoride replenishment tank; R1, Electrolyte preparation vessel; RT1, Refrigerant tank. Detailed Implementation

[0016] The technical solution of this utility model will be clearly and completely described below with reference to its embodiments. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0017] It should be understood that the terms "upper", "lower", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0018] It should also be noted that, unless otherwise explicitly specified and limited, terms such as "installation," "connection," "linking," "fixing," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in this utility model can be understood according to the specific circumstances.

[0019] Reference Figure 1 This embodiment provides a hydrogen fluoride recovery device in the anode gas during the electrolytic preparation of nitrogen trifluoride, comprising a demister D1, a buffer tank C1, a filter F1, a condenser unit, and a hydrogen fluoride storage tank S1 connected in sequence; the feed end of the demister D1 is provided with an anode tube L1 connected to the anode discharge end of the electrolytic cell EC1; the buffer tank C1 is used to condense and collect ammonium hydrogen fluoride solid; the condenser unit is used to condense to below the boiling point of hydrogen fluoride and separate nitrogen trifluoride, and is connected to a nitrogen trifluoride output pipe L2 at the top and a condensate pipe L3 at the bottom connected to the hydrogen fluoride storage tank S1.

[0020] In the above embodiments, the foam carried by the anode of the electrolysis device is eliminated in advance by the demister D1. Since ammonium bifluoride has a high melting point, the solid ammonium bifluoride can be precipitated by air cooling or water cooling by setting a buffer tank C1. The ammonium bifluoride particles are further removed by the filter, and then the hydrogen fluoride (boiling point 19.5°C) is liquefied by cooling or deep cooling to a suitable temperature using a condenser unit, thereby achieving the separation of nitrogen trifluoride (boiling point -129°C) and the efficient collection of hydrogen fluoride.

[0021] It is understandable that the selected cooling or cryogenic temperatures mentioned above are only for gas-liquid separation purposes. For example, it is preferable to use a temperature control of -20 to -80°C for cryogenic cooling of hydrogen fluoride to improve the purity of the recovered hydrogen fluoride.

[0022] In a preferred embodiment, the condensation unit includes multiple condensers connected in parallel, such as condenser C2 and condenser C3 connected in parallel. The medium pipelines of the two condensers are connected in parallel and connected to the refrigerant tank RT1. The upper parts of the two condensers are respectively connected to the nitrogen trifluoride output pipe L2. The refrigerant tank RT1 can be selected from commonly used refrigerants that can meet the requirements of liquefied hydrogen fluoride, preferably liquid nitrogen.

[0023] It is understood that, in the above embodiments, the hydrogen fluoride recovered from the hydrogen fluoride storage tank S1 can be used in other processes, or reused and configured as an electrolyte for the electrolytic preparation of nitrogen trifluoride.

[0024] In a preferred embodiment, the hydrogen fluoride recovered from the hydrogen fluoride storage tank S1 is used for recycling in electrolyte preparation. The recovered hydrogen fluoride has high purity after multiple separation steps and can be used for precise electrolyte preparation. Specifically, the hydrogen fluoride storage tank S1 is connected to the electrolyte preparation vessel R1 via a circulation pipe L4, and the lower part of the electrolyte preparation vessel R1 is connected to the electrolytic cell EC1.

[0025] It is understandable that the electrolyte preparation required for nitrogen trifluoride electrolysis can be prepared according to common electrolyte composition or actual needs. Specifically, the electrolyte solution can be prepared by adding molten ammonium hydrogen fluoride, hydrogen fluoride and ammonia gas to the electrolyte preparation vessel R1 in proportion, such as the electrolyte chemical formula NH4F·(HF)x (x=2.2~2.7).

[0026] In a preferred embodiment, in order to meet the dosage requirements for preparing the electrolyte, the electrolyte preparation vessel R1 is also connected to a hydrogen fluoride supply tank S2, and the circulation pipe L4 is connected to the upper part of the electrolyte preparation vessel R1 via the hydrogen fluoride supply tank S2.

[0027] It is understandable that the materials of the components used in the above hydrogen fluoride recovery device can be selected according to the requirements of low temperature corrosion resistance, and commonly used instruments, meters or valves can also be selected or added according to the operational requirements. All of the above are within the design scope of this solution and will not be elaborated here.

[0028] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A device for recovering hydrogen fluoride from the anode gas in the electrolytic preparation of nitrogen trifluoride, characterized in that, The system includes a demister (D1), a buffer tank (C1), a filter (F1), a condenser unit, and a hydrogen fluoride storage tank (S1) connected in sequence. The feed end of the demister (D1) is connected to the anode discharge end of the electrolytic cell (EC1) via an anode tube (L1). The buffer tank (C1) is used to condense and collect solid ammonium hydrogen fluoride. The condenser unit is used to condense the hydrogen fluoride to below its boiling point and separate nitrogen trifluoride. Its lower part is connected to the hydrogen fluoride storage tank (S1).

2. The hydrogen fluoride recovery device according to claim 1, characterized in that, The condensation unit includes multiple condensers connected in parallel.

3. The hydrogen fluoride recovery device according to claim 2, characterized in that, The medium input and output pipelines of each condenser are connected in parallel, and the input and output pipelines are respectively connected to the refrigerant tank (RT1).

4. The hydrogen fluoride recovery device according to claim 1, characterized in that, The upper part of the condensation unit is equipped with a nitrogen trifluoride output pipe (L2).

5. The hydrogen fluoride recovery device according to claim 1, characterized in that, The hydrogen fluoride storage tank (S1) is connected to the electrolyte preparation vessel (R1) via a circulation pipe (L4), and the lower part of the electrolyte preparation vessel (R1) is connected to the electrolytic cell (EC1).

6. The hydrogen fluoride recovery device according to claim 5, characterized in that, The electrolyte preparation vessel (R1) is also connected to a hydrogen fluoride supply tank (S2).

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