| 摘要 |
PROBLEM TO BE SOLVED: To produce ultrahigh-purity nitrogen at a high yield. SOLUTION: Carbon dioxide, water, and catalyst poison of an oxidation catalyst in the air fed as raw material are removed by a decarbonization-desiccation device 4 and the resulting air is led into a low-pressure rectifying column 6 where carbon dioxide, water, and catalyst poison are removed further from the air by crude rectification. Next the crude nitrogen gas obtained at the lowpressure rectifying column 6 is led into an oxidation tower 8 where carbon monoxide in the crude nitrogen gas is turned into carbon dioxide and, after turning hydrogen into water, the crude nitrogen gas is led into an adsorption tower 10 where carbon dioxide and water are removed therefrom by adsorption and a crude nitrogen gas is obtained as raw material. This crude nitrogen gas as raw material is further led into a medium-pressure rectifying column 11 for rectification. Nitrogen gas obtainable from the top part of the medium-pressure rectifying column is condensed by a reboil condenser 6RC into a high-purity liquid nitrogen, then returned to the medium-pressure rectifying column 11, and part of the high-purity liquid nitrogen is made to flow as a refluxed liquid and the rest of it is drawn as an end product which is ultrahigh-purity nitrogen gas or ultrahigh-purity liquid nitrogen from a rectification stage positioned several stages below the top rectification stage of the medium-pressure rectifying column. |
