| abstract |
This apparatus produces ultra-high purity nitrogen gas employed in fields such as the electronics industry when manufacturing a silicon semiconductor, for example. Conventional cryogenic liquefaction and PSA nitrogen gas production apparatuses often break down, and the nitrogen gas obtained by these conventional apparatuses is expensive, but its purity is not particularly high. In the apparatus of the present invention, a liquid nitrogen storage means (23) is connected to heat exchange means (13), (14) by an inlet path (16), and compressed air arriving at the heat exchanger means (13), (14) through an air compression means (9) and an elimination means (12) is cooled to an ultra-low temperature by the heat of evaporation of liquid nitrogen, and is pumped into a fractionating tower (15) from which nitrogen is taken out in a gaseous state leaving oxygen as a liquid, making use of the difference in boiling points therebetween. The obtained nitrogen gas is mixed with vaporized liquid nitrogen from the liquid nitrogen storage means (23) to obtain the final nitrogen gas. This makes it possible to produce inexpensive, high-purity nitrogen gas, with little likelihood of mechanical failure. |