| 摘要 |
<p>PURPOSE:To manufacture an ultrahigh purity nitrogen by a method wherein a raw material gas is heat exchanged with a return gas, fed into a rectifying column, nitrogen is taken out in its liquid form, its part is changed into heated gas and heat exchanged with the raw material gas. CONSTITUTION:Raw material air is divided to flow into an air heat exchanger 4 and a nitrogen heat exchanger 5. The air is heat exchanged with waste gas and nitrogen gas and enters a rectifying column 6. High purity nitrogen gas rectified and ascended in a lower column is taken out of a tube 25 under a liquid nitrogen form which is located at a position decreased down to a rectifying stage required for rectifying hydrogen from a top part of the rectifying column 6. Carbon monoxide which cannot be rectified and separated due to its boiling point approximating to that of nitrogen is adsorbed and removed up to its some ppb order. A part of the outputted liquid nitrogen is taken out as a product ultrahigh purity liquid nitrogen, remaining part is guided to a sub-condenser 10 through a pipe 26, a total amount of liquid nitrogen is gasified, heat exchanged with the raw material air at the nitrogen heat exchanger 5, its temperature is recovered to its normal temperature and then the gas is taken out as the product ultrahigh purity nitrogen gas.</p> |
