Relationship between argon fraction and the night air volume in the upper column
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When the v1 valve fluctuates, the argon retention level also fluctuates. When v1 is opened wider, the retention level decreases; when v1 is closed tighter, the retention level increases. What causes this? What is the principle behind the fluctuations in the argon fraction?
The key issue is that you haven’t yet found a reference point for control. Within the scope of the process requirements, identify the reference points where problems may occur. This reference point is the control accuracy of the oxygen purity in the product, and it must be in accordance with the process specifications. Getting stuck at some stage of the process only leads to blind adjustments. For reference.
Liquefied air is the main reflux stream for the upper column; any changes in it (which also lead to changes in the cooling and heating loads) will naturally cause fluctuations in the argon fraction. Your top priority now is to resolve the issue causing fluctuations in V1~
I’m not entirely sure what fluid flows through your V1 valve. From what I remember, in Hangyang’s systems, V1 is connected to the oxygen-enriched liquid air at the bottom of the lower column. If you increase the flow rate at V1, it means that the total amount of liquid air in the lower column increases. Firstly, changes in the reflux flow in the lower column can result in an excess of liquid air there; and as the reflux increases, the oxygen content in the oxygen-enriched liquid air also decreases. This decrease in oxygen content affects the oxygen-to-nitrogen ratio in the material above the outlet for the argon fraction. In other words, both the oxygen content of the oxygen-enriched liquid air and the amount of this liquid air that flows back to the upper column influence the purity of the argon fraction.