Technological method and equipment for preparing nitrogen trifluoride gas

Abstract

The present invention relates to a process for preparing NF3 gas and its equipment. It is characterized by that the anodic electrolytic gas in the electrolytic cell is fed into a pressure balancing tank by means of pipe, then fed into a low pressure tank via regulating valve, and said gas is fed into a low-temp. cooling tower by means of pipe to remove high-boiling point impurities of NH4F and HFfrom said anodic electrolytic gas to obtain NF3 gas, then the NF3 gas is fed into an ultralow temp. cold trap to make liquification and collection, and remove low-boiling point impurities or N2 and O2 from it by adopting the measure of evacuating cold trap, after the NF3 gas is collected and liquified in the ultralow-temp. cold trap, heating the cold trap and distilling said NF3 gas and pressing it into crude NF3 gas storage tank, the material of anode in the electrolytic cell is high-purity nickel.

Description

(1) Technical field [0001] The invention relates to a process and equipment for preparing nitrogen trifluoride gas, which is suitable for 4 F-xHF (or add a small amount of KF) for the electrolysis of the electrolyte system to prepare NF 3 gas, this crude NF 3 The gas can be directly used to prepare high-purity NF 3 gas. (two), background technology [0002] NF 3 Gases are widely used in fields such as high-energy lasers, semiconductor technology, and chemical vapor deposition, and have good application prospects. But as an electron gas, it is NF 3 The purity of the gas has higher requirements, generally its purity should not be lower than 99.99%, and the key impurities such as CF 4 The content should not be higher than 50ppm, which makes the preparation of high-purity NF 3 Gas is more difficult. [0003] Prepare NF 3 The method of gas can basically be divided into chemical synthesis method and electrolysis method, and they all have many ways to realize it. The more ...

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Problems solved by technology

[0004] In general, the chemical synthesis method has the characteristics that the synthesis reaction is relatively safe, and its disadvantage is that the NF in the product after the synthesis reaction 3 The content of gas is lower than that of electrolysis, and its CF 4 The content is generally very high (above 0.3%); while using NH 4 F-xHF (or add a small amount of KF) is NF prepared by electrolysis of electrolyte system 3 The gas has a higher yield and purity, which is more conducive to purification and preparation of high-purity NF 3 Gas, its disadvantage is that it is prone to explosion during the electrolysis process

[0005] Usually, in NH 4 F-xHF (or add a small amount of KF) is the electrolytic preparation of NF in the electrolyte system 3 The gas uses carbon as the anode. The carbon material anode has the advantages of long service life and less electrolytic waste residue, but it also has a serious disadvantage: the NF produced by electrolysis 3 CF in gas 4 High content (generally higher than 500ppm)

[0007] To remove NH in the anode electrolysis gas 4 F and HF and other high-boiling impurities, the traditional method is to absorb with solid alkali or wash with lye, these two methods require frequent replacement of reagents, which affects the continuous operation of production, and the operation is more cumbersome

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