What is the reason for setting a low-pressure interlock at the outlet of the air-cooled tower in an air separation unit?
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In air separation units, a low-pressure interlock is generally installed at the outlet of the air cooling tower; in the industry, this is done to prevent water from reaching downstream systems. I can think of three reasons for this, but none of them are entirely valid: 1. When the pressure in the air cooling tower decreases, the water at its outlet cannot return to the circulation water network. However, the liquid level at the bottom of the air cooling tower will trigger a high-pressure interlock, providing protection through that mechanism. Therefore, I don’t think this is the main reason. 2. The pressure at the outlet of the air-cooled tower decreases, resulting in insufficient capacity of the adsorber; this in turn causes the CO2 level at the adsorber’s outlet to exceed the specified limit. However, if this is the cause, it would be more logical to install a CO2 interlock at the adsorber’s outlet. 3. The pressure at the outlet of the air-cooling tower drops momentarily; excessive airflow at that instant causes water to be carried along, but it is not possible to determine a quantitative value for this effect. Moreover, if this were the cause, a short-term drop in pressure should be sufficient to trigger the interlock mechanism. Also, is it possible that it’s due to the effects of the gas flow rate within the air cooling tower itself? I’m not very familiar with this aspect, so I hope experts can share their insights. Thank you.
For devices with a pressurized return water system, it can be affirmed that this statement is correct. Most water systems for such devices these days are of the closed-loop type, with the circulating water being softened. It is recommended to understand this issue by considering the process parameters of the circulating water system, and to analyze it in comparison with the low-pressure interlock values of the air-cooled tower. Without the air pressure provided by the air cooling tower, return water cannot be achieved. You can imagine what happens when the water level in the air-cooling tower reaches the air inlet. For reference.