| 摘要 |
PURPOSE:To get nitrogen gas of high purity by a method wherein raw air is fed from a lower dropping part into a fractionating stage of several higher stages, a heating source is arranged at a lower part or gas containing less amount of component of low boiling point is blown into the lower part as to perform an auxiliary fractionating operation. CONSTITUTION:Raw air GA to be fed into a complex fractionating tower 1 is fed into a fractionating stage 3 higher by several stages than a lower part 2c of a lower tower 2, a re-boiler 4 is arranged at a lower dropping part 2c, liquified air to be separated at a lower part 2c is gasified to generate an ascend ing gas and at the same time the liquified air at the lower part 2c is fed out and at least a part of the air is introduced into an intermediate part of an upper tower 9. Liquified nitrogen at the upper part 2a and/or intermediate part 2b of the lower tower 2 is fed out, its gas and liquid are separated with a gas-liquid separator 12, thereafter or an auxiliary refractionating is carried out with the auxiliary refractionating tower 19, it is fed into an upper tower 9 and it gets nitrogen gas of high purity and then the gas is fed out. In this way, it is possible to reduce an amount of component of low boiling point in the nitrogen gas of high purity fed out as a product. |
