Nitrogen generating device and nitrogen generating method

A nitrogen generating device comprising:

• a main heat exchanger configured to cool feed air;
• a first nitrogen rectification column fluid communication with the main heat exchanger, such that the first nitrogen rectification column is configured to receive the feed air cooled in the main heat exchanger, wherein the first nitrogen rectification column comprises a gas phase portion of a rectification portion or a bottom portion into which the feed air cooled in the main heat exchanger is introduced;
• a first nitrogen condenser configured to condense a vapour stream fed from an upper gas phase portion of the first nitrogen rectification column and circulate the same to the upper gas phase portion;
• a second nitrogen rectification column including a rectification portion that is in fluid communication with the bottom portion of the first nitrogen rectification column, such that the second nitrogen rectification column is configured to receive oxygen-enriched liquid from the bottom portion of the first nitrogen rectification column;
• a second nitrogen condenser configured to condense a vapour stream fed from an upper gas phase portion of the second nitrogen rectification column and circulate the same to the upper gas phase portion;
• a liquid nitrogen buffer configured to store condensate returning to the upper gas phase portion of the second nitrogen rectification column;
• a liquid nitrogen discharge means configured to discharge the stored liquid nitrogen from the liquid nitrogen buffer;
• and
• a control unit configured to control the liquid nitrogen discharge means to discharge the liquid nitrogen from the liquid nitrogen buffer to the upper gas phase portion of the first nitrogen rectification column or the rectification portion in response to an increase in an amount of product nitrogen or an increase in a flow rate of the feed air.