What determines the amount of nitrogen to be extracted?
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In air separation, the oxygen-to-nitrogen ratio can be 1:1, 1:1.5, or 1:2. What considerations are taken into account when designing this ratio? Also, what determines the amount of nitrogen extracted from the lower column? Does a larger or smaller amount have any effects on the entire process, and what impact does it have on the design of the column itself? Please give me your advice
As saturated air enters the distillation tower, the rising air exchanges heat with the liquid flowing downward. The larger the reflux ratio, the higher the tower resistance; this leads to reduced air evaporation and consequently lower production. As the tower resistance continues to increase, the liquid level at the bottom of the tower rises, the temperature in the lower part of the distillation tower decreases, and the pressure within the tower drops. Therefore, it is necessary to control both the reflux ratio and the amount of nitrogen extracted in order to maintain material balance and heat balance.
I have also thought about this issue for a long time, but I can only gain a partial understanding of it. In my opinion, what the original poster is asking is how this is achieved during the design process. I believe that the amount of nitrogen removed is closely related to the number of tray levels; if nitrogen is removed from the upper part of the tower, increasing the height of that section is necessary in order to boost production； The same is true for pressure; to meet the demand for a large volume of nitrogen production, it is necessary to increase the number of trays in the lower column. During operation, as suggested by the colleagues upstairs, the reflux ratio can be increased to meet the production levels beyond the design specifications; this will certainly affect the oxygen extraction rate. The above is merely my personal understanding; I hope someone who specializes in design can provide a detailed explanation.