Double distillation column, oxygen production

In 1910, Linde found the answer the double distillation column (Figure 5). The double-column system improved the production of high-purity oxygen by dramatically increasing the fraction of oxygen produced from the feed air (22). If one invention can be said to have created an industry, this one created the air separation industry. 

The nitrogen purity from the Linde double column system is limited to about 5 ppm oxygen. In order to produce a higher purity nitrogen product, additional trays in the low pressure distillation column and some additional complexity is required in the process. 

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