CN-121976249-A - Method and system for recycling hydrogen fluoride-containing waste gas at cathode of nitrogen trifluoride electrolytic tank

Abstract

The invention provides a method and a system for recycling hydrogen fluoride-containing waste gas of a cathode of a nitrogen trifluoride electrolytic tank, which belong to the technical field of fluorine chemical industry, wherein the method comprises the following steps of (1) mixing the waste gas of the cathode of the nitrogen trifluoride electrolytic tank with ammonia gas and then entering a reactor; the method comprises the steps of (1) reacting ammonia gas in a reactor with hydrogen fluoride in cathode waste gas, enabling the generated mixture of liquid ammonium bifluoride and hydrogen fluoride to flow into a liquid collecting tank, enabling the residual gas to enter a falling film absorber, (3) absorbing the residual gas by the falling film absorber and then sending the residual gas into a discharge tower through a fan, (4) conveying the mixture of ammonium bifluoride and hydrogen fluoride in the collecting tank in the step (2) back into an electrolytic bath for preparing nitrogen trifluoride, and introducing ammonia gas into the electrolytic bath to adjust the required proportion of the ammonium bifluoride and the hydrogen fluoride. The system comprises a reactor, a liquid collecting tank, a five-stage falling film absorber, a fan and a discharge tower which are sequentially connected through pipelines. The invention is easy to realize the recycling of the hydrogen fluoride in the electrolytic preparation of the nitrogen trifluoride.

Inventors

• JI YANZHI
• LU GUANGHUI
• YUE LIPING
• WANG XIAOLIN
• ZHAO YING
• WANG ZHONGBIAO
• WANG XUESONG
• Ma Shuaikang

Assignees

• 中船(邯郸)派瑞特种气体股份有限公司

Dates

Publication Date

20260505

Application Date

20260116

Claims (10)

1. 1. The method for recycling the hydrogen fluoride-containing waste gas of the cathode of the nitrogen trifluoride electrolytic tank is characterized by comprising the following steps of: (1) Mixing the cathode waste gas of the nitrogen trifluoride electrolytic tank with ammonia gas, and then entering a reactor; (2) The ammonia gas in the reactor reacts with the hydrogen fluoride in the cathode waste gas, the generated mixture of liquid ammonium bifluoride and hydrogen fluoride flows into a liquid collecting tank, and the residual gas enters a falling film absorber; (3) Residual gas is sent into a discharge tower through a fan after being absorbed by a falling film absorber; (4) And (3) conveying the mixture of ammonium bifluoride and hydrogen fluoride in the collecting tank in the step (2) back to an electrolytic tank for preparing nitrogen trifluoride, and introducing ammonia gas into the electrolytic tank to adjust the ammonium bifluoride and hydrogen fluoride to the required proportion.
2. 2. The method for recycling hydrogen fluoride-containing waste gas of a cathode of a nitrogen trifluoride electrolytic tank according to claim 1, wherein the operating pressure of the reactor in the step (1) is-5 to 1kpa, the temperature is 30 to 80 ℃, and the reaction time is not more than 1min.
3. 3. The method for recycling hydrogen fluoride-containing waste gas of a cathode of a nitrogen trifluoride electrolytic tank according to claim 1, wherein the operating pressure of the liquid collection tank in the step (2) is-5 to 1kpa, and the temperature is 15 to 80 ℃.
4. 4. The method for recycling hydrogen fluoride-containing waste gas of a nitrogen trifluoride electrolyzer cathode according to claim 1, wherein the falling film absorber in the step (2) is a 5-stage series falling film absorber, the operation pressure is-5-1 kpa, and the temperature is 10-50 ℃.
5. 5. The method for recycling the hydrogen fluoride-containing waste gas of the cathode of the nitrogen trifluoride electrolytic tank according to claim 1, wherein the inlet pressure of the fan in the step (3) is-10 to 0kpa.
6. 6. The method for recycling the waste gas containing hydrogen fluoride at the cathode of the nitrogen trifluoride electrolytic tank as claimed in claim 1, wherein the mass ratio of the ammonium bifluoride to the hydrogen fluoride in the liquid collection tank in the step (2) is 2-3:1, and the mass ratio of the ammonium bifluoride to the hydrogen fluoride in the step (4) is 3-15:1.
7. 7. The method for recycling hydrogen fluoride-containing waste gas of a nitrogen trifluoride electrolyzer cathode as claimed in claim 1, wherein the concentration of fluorine ions in the discharge column in said step (3) is as low as 2ppm or less.
8. 8. The method for recycling hydrogen fluoride-containing waste gas of a cathode of a nitrogen trifluoride electrolyzer as claimed in claim 1, wherein the reactor in the step (1) is a tank reactor or a tubular reactor.
9. 9. The method for recycling hydrogen fluoride-containing waste gas of nitrogen trifluoride electrolyzer cathode as claimed in claim 1, wherein the operating pressure of the discharge tower in said step (3) is normal pressure.
10. 10. A system for recycling hydrogen fluoride-containing waste gas of a nitrogen trifluoride electrolyzer cathode, as claimed in any one of claims 1-9, comprising an electrolyzer, a reactor and a liquid collection tank connected in a closed loop by a pipeline, the reactor further being connected in series by a pipeline to a 5-stage falling film absorber, a fan and a discharge tower, the 5-stage falling film absorber comprising a first-stage falling film absorber, a second-stage falling film absorber, a third-stage falling film absorber, a fourth-stage falling film absorber and a fifth-stage falling film absorber.

Description

Method and system for recycling hydrogen fluoride-containing waste gas at cathode of nitrogen trifluoride electrolytic tank Technical Field The invention belongs to the technical field of fluoride engineering, and particularly relates to a method for recycling hydrogen fluoride-containing waste gas at a cathode of a nitrogen trifluoride electrolytic tank. Background During the electrolytic process for producing nitrogen trifluoride (NF 3), both the cathode and the anode produce a tail gas containing Hydrogen Fluoride (HF). The hydrogen fluoride content in the waste gas is high, and if the waste gas is directly discharged, the waste gas not only causes environmental pollution, but also causes the waste of fluorine resources. In the prior art, the treatment of the waste gas containing hydrogen fluoride mainly adopts an alkali liquor neutralization method or a water absorption method, but the following problems exist in the methods: And (3) wasting resources, namely, the fluorine element in the waste gas is not recycled, so that the resource waste is caused. The treatment cost is high, the alkali liquor neutralization method can reduce environmental pollution, but a large amount of alkali liquor is consumed, and the generated calcium fluoride needs to be further treated, so that the operation cost is increased. The recovery value is low, and although the process of using water absorption and alkali liquor neutralization in series can reduce alkali liquor consumption, the recovered hydrofluoric acid has lower value. In the prior art, there are some techniques related to hydrogen fluoride recovery or to the preparation of ammonium bifluoride. For example: 1. Chinese patent CN105000576A discloses a method for preparing ammonium bifluoride by using wastewater of tantalum-niobium smelting fluorine ammonia nitrogen, which comprises the steps of adding hydrofluoric acid into the precipitation wastewater of recovered tantalum oxide/niobium oxide for acid regulation, filtering, heating and evaporating the obtained filtrate, cooling, and centrifugally separating to obtain ammonium bifluoride. But the method aims at tantalum-niobium smelting wastewater, rather than hydrogen fluoride-containing waste gas in the process of producing nitrogen trifluoride by electrolysis. 2. Chinese patent CN114028900A discloses a treatment device for anode tail gas of nitrogen trifluoride electrolytic cell, which comprises a cracking tower, a reduction absorption tower and an alkali liquor absorption tower and is used for treating substances such as nitrogen trifluoride, nitrous oxide and the like in the anode tail gas. However, the technology mainly focuses on the treatment of anode tail gas, but not the recycling of hydrogen fluoride in cathode tail gas. 3. A multi-effect evaporation process and a device for preparing ammonium bifluoride by using waste HF acid in China patent CN120094226A are disclosed, wherein HF-containing gas in cathode tail gas of a nitrogen trifluoride electrolytic tank is subjected to a falling film absorption process to obtain hydrofluoric acid solution, and then liquid ammonia is added into the hydrofluoric acid solution to react to obtain the ammonium bifluoride solution. The technology is closer to the invention, but mainly focuses on the multi-effect evaporation technology, and the integrated optimization and the resource recycling of the whole system are not comprehensively considered. 4. The technology of the tail gas treatment system of the ammonium bifluoride electrolyte batching kettle disclosed in the Chinese patent CN222829339U is characterized in that a condenser is added before a primary water washing tower, so that hydrogen fluoride in the tail gas can be hydrolyzed into a liquid phase, the purpose of completely separating hydrogen fluoride in the tail gas is achieved, the technology is not used for treating hydrogen fluoride in cathode gas of an electrolytic cell, and the technology is used for treating cathode gas of the electrolytic cell and has high energy consumption. In summary, the prior art still has room for improvement in terms of comprehensive utilization of resources, reduction of energy consumption and optimization of system. Therefore, a method capable of efficiently recycling hydrogen fluoride in the electrolysis waste gas is developed, and the method has important practical application value. Disclosure of Invention The invention aims to provide a method for recycling hydrogen fluoride-containing waste gas of a cathode of a nitrogen trifluoride electrolytic tank, which has the advantages of simple process, no resource waste, no secondary pollution, low treatment cost and high recycling efficiency. The invention is realized by adopting the following technical scheme: A method for recycling hydrogen fluoride-containing waste gas of a cathode of a nitrogen trifluoride electrolytic tank comprises the following steps: (1) Mixing the cathode waste gas of the nitrogen trifluoride electrolytic