| 摘要 |
<p>Liquid oxygen and/or liquid nitrogen are made by removing carbon dioxide and water vapour from air, compressing the purified air in a re-cycle compressor and dividing the purified compressed air into first and second streams. Part of the first stream is expanded in a first expander and the refrigeration produced is used to cool both the first and second streams in a first heat exchanger. On leaving the first heat exchanger, the second stream is expanded in a second expander and the refrigeration produced is used to liquify at least part of the remainder of the first stream. The liquid stream is expanded and introduced into a fractionation column from which liquid nitrogen and/or liquid oxygen can be withdrawn. Expanded air from the first and second expanders is returned to the re-cycle compressor although part of the expanded air from the second expander is preferably introduced into the fractionation column. The invention is particularly suited to installations producing in excess of 100 tons of liquid per day and, at this size, preferred designs offer an estimated 51-9% power savings over the known prior art.</p> |
