Ultra-high purity nitrogen generating method

An ultra-high purity nitrogen generating method, which comprises:

• a first step of removing, from feed air, carbon dioxide, moisture and catalyst poisons for an oxidation catalyst contained therein by means of a carbon dioxide eliminator-drier;
• a second step of cooling down the feed air obtained by the first step and introducing the cooled feed air to a primary rectification column, where it is partly rectified, thereby further removing the carbon dioxide, moisture and catalyst poisons therefrom;
• a third step of condensing raw nitrogen gas that is the nitrogen gas obtained by the second step and containing oxygen so that a part thereof is liquefied and causing the liquefied nitrogen gas to circulate to the primary rectification column as a reflux liquid, and at the same time, warming the remaining raw nitrogen gas, and then compressing the warmed nitrogen gas so that it is increased in pressure and raised in temperature;
• a fourth step of introducing the raw nitrogen gas obtained by the third step to an oxidation column, where carbon monoxide in the raw nitrogen gas is converted to carbon dioxide and hydrogen also contained therein to water, and then cooling down the raw nitrogen gas, and introducing the cooled raw nitrogen gas to an adsorption column, where the carbon dioxide and water in the raw nitrogen gas are removed by adsorption;
• a fifth step of cooling down the feed raw nitrogen gas obtained at the fourth step and introducing the cooled feed raw nitrogen gas to a secondary rectification column, where it is rectified;
• a sixth step of expanding the liquid nitrogen obtained from the bottom portion of the secondary rectification column at the fifth step, and then introducing the expanded liquid nitrogen to the primary rectification column as a feed material and cold source;
• and
• a seventh step of supplying a cold source to said primary rectification column.

An ultra-high purity nitrogen generating method, which comprises:

• a first step of removing, from feed air, carbon dioxide, moisture and catalyst poisons for an oxidation catalyst contained therein by means of a carbon dioxide eliminator-drier;
• a second step of cooling down the feed air obtained by the first step and introducing the cooled feed air to a primary rectification column, where it is partly rectified, thereby further removing the carbon dioxide, moisture and catalyst poisons therefrom;
• a third step of condensing raw nitrogen gas that is the nitrogen gas obtained by the second step and containing oxygen so that a part thereof is liquefied and causing the liquefied nitrogen gas to circulate to the primary rectification column as a reflux liquid, and at the same time, warming the remaining raw nitrogen gas, and then compressing the warmed nitrogen gas so that it is increased in pressure and raised in temperature;
• a fourth step of introducing the raw nitrogen gas obtained by the third step to an oxidation column, where carbon monoxide in the raw nitrogen gas is converted to carbon dioxide and hydrogen also contained therein to water, and then cooling down the raw nitrogen gas and introducing the cooled raw nitrogen gas to an adsorption column, where the carbon dioxide and water in the raw nitrogen gas are removed by adsorption;
• a fifth step of cooling down the feed raw nitrogen gas obtained at the fourth step and introducing the cooled feed raw nitrogen gas to a secondary rectification column, where it is rectified;
• a sixth step of expanding oxygen-rich liquid obtained from the bottom portion of the primary rectification column at the second step, and then evaporating the expanded oxygen-rich liquid through heat exchange so as to provide a waste gas;
• a seventh step of heating the waste gas obtained at the sixth step, and then adiabatically expanding the heated waste gas and using the expanded waste gas as a cold source;
• and
• an eighth step of heating the waste gas obtained at the seventh step, and using the heated waste gas in order to regenerate the carbon dioxide eliminator-drier.

An ultra-high purity nitrogen generating method, which comprises:

• a first step of removing, from feed air, carbon dioxide, moisture and catalyst poisons for an oxidation catalyst contained therein by means of a carbon dioxide eliminator-drier;
• a second step of cooling down the feed air obtained by the first step and introducing the cooled feed air to a primary rectification column, where it is partly rectified, thereby further removing the carbon dioxide, moisture and catalyst poisons therefrom;
• a third step of condensing raw nitrogen gas that is the nitrogen gas obtained by the second step and containing oxygen so that a part thereof is liquefied and causing the liquefied nitrogen gas to circulate to the primary rectification column as a reflux liquid, and at the same time, warming the remaining raw nitrogen gas, and then compressing the warmed nitrogen gas so that it is increased in pressure and raised in temperature;
• a fourth step of introducing the raw nitrogen gas obtained by the third step to an oxidation column, where carbon monoxide in the raw nitrogen gas is converted to carbon dioxide and hydrogen also contained therein to water, and then cooling down the raw nitrogen gas and introducing the cooled raw nitrogen gas to an adsorption column, where the carbon dioxide and water in the raw nitrogen gas are removed by adsorption;
• and
• a fifth step of cooling down the feed raw nitrogen gas obtained at the fourth step and introducing the cooled feed raw nitrogen gas to a secondary rectification column, where it is rectified, and at the same time, taking out at least a part of the feed raw nitrogen gas, while it is being cooled, and adiabatically expanding the take-out nitrogen gas and using the expanded nitrogen gas as a cold source.