Discussion on the process for preparing nitrogen trifluoride by electrolysis
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Dear sea friends: While researching the production processes for nitrogen trifluoride recently, I found that the method currently used in China for producing NF3 is mainly electrolysis, whereas abroad, AP Company uses a method that involves reacting F2 with ammonium fluoride. I have a few questions I would like to discuss: 1. Does the domestic production process indicate that electrolysis is superior to the reaction method? 2. Why do almost all NF3 manufacturers produce ammonium fluoride electrolyte by synthesizing it themselves from ammonia and hydrogen fluoride? There is a large market for ammonium hydrogen fluoride – why not purchase it directly? Is it because the quality of industrial-grade ammonium fluoride does not meet the requirements for electrolysis, or is the cost of synthesis itself much lower? 3. Is the electrolyte ammonium hydrogen fluoride, or a mixture of ammonium fluoride, ammonium hydrogen fluoride, hydrogen fluoride/ammonia, etc.? 4. Currently, the production capacity of each individual electrolyzer is relatively low; is it because scaling up is not possible or because of intermittent operation that many electrolyzers are needed to address the issue of continuous production? 5. Process safety issues: Some reports mention explosions of hydrogen, while others refer to explosions in distillation towers during the NF3 purification process. Is there any compilation of such safety accident cases in the industry?
The first question: When it comes to processes that can be scaled up for mass production, several factors need to be considered. These include process safety and controllability, a short production process, simplicity of operation, reliable sources of raw materials, and also cost-effectiveness.
The second issue is that when synthesizing ammonium fluoride on one’s own, the requirements for electron-grade ammonium fluoride are much higher than those for industrial-grade versions. By carrying out the synthesis oneself, the manufacturing process and the resulting quality parameters can be kept stable and under control, which helps to reduce costs. Industrial-grade ammonium hydrogen fluoride is mostly obtained through processes for recovering hydrogen fluoride emissions; therefore, it is difficult to achieve electronic-grade quality. If I’m not mistaken, electronic-grade ammonium hydrogen fluoride is produced by reacting anhydrous hydrogen fluoride with ammonia water. If it’s not for users of electronic-grade ammonium fluoride, there is a high risk involved in doing this.
Thirdly, the paper mentions ammonium hydrogen fluoride; strictly speaking, it is necessary to examine the relevant patents to see how the scope is defined, and it is best to conduct tests one by one.
The fourth issue is that the main approach taken is to reduce the volume of the gas phase space and thus the amount of hydrogen stored; the chlor-alkali ion-exchange membrane electrolysis process can serve as a reference.
The fifth question – this can only be asked to the relevant manufacturing units.
I’m about to proceed to gather information on chlor-alkali electrolysis and water electrolysis. Aside from the hydrogen issue you mentioned, I aim to use knowledge from these two industries to address the engineering challenges related to continuous addition of electrolyte, continuous electrolysis, and continuous gas production.
Just looking back at previous posts, I noticed that engineers from domestic factories aren’t very interested in discussing technology
Regarding the first issue, it is also necessary to take into account that the types of impurities in the products produced by electrolytic and synthetic methods differ. The electrolytic process is relatively short, but it generates carbon tetrafluoride as an impurity; separating this substance from nitrogen trifluoride is extremely difficult. The synthetic method can help avoid this impurity to a certain extent.