Reflux valve for liquid nitrogen returning to the lower column
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In the normal operating process, there is a manual valve to control the return of liquid nitrogen to the lower tower. If this valve is not present, apart from having a significant impact on the accumulation of liquid in the main cooler during startup, what other negative effects might there be? Will it work without this valve?
It’s definitely fine without valves; there are processes that don’t use any valves at all. As long as there are pipes for the return fluid, it’s okay, and proper calculations will ensure no issues arise.
What was said upstairs makes sense; the valve is used for opening and closing, as well as for controlling the flow rate of liquid nitrogen. As long as there are return pipes and the flow rate is properly controlled, it can operate normally.
In foreign air separation units, this valve is often not present
If there is no manual valve, regulation can only be achieved through control valves; sometimes the lag in these control valves leads to unstable flow and pressure levels, with significant fluctuations that make control difficult.
It has a significant impact mainly during liquid accumulation; if such a valve is available, it closes during liquid accumulation, reducing the heat exchange in the main cooler and accelerating the accumulation of liquid. This valve is opened only when the liquid level in the upper column reaches a certain level, in order to establish the distillation conditions in the lower column. Without this valve, when liquid accumulates, there is significant heat exchange between nitrogen and liquid oxygen, making it more difficult for liquid to accumulate. This also reflects the \"on-off-on\" operation of the control valve from liquid nitrogen to the upper tower.
Without this valve, how can the main cooler be heated (dried)? This valve can be fully open during the startup phase of the device, but a liquid seal is required as part of the process setup. (For reference)
This post was last edited by fhwfhwfhwfhw on 2011-9-8 22:24. This valve isn’t needed during the heating stage either, right? For the liquid seal, a elbow or an outlet is sufficient as long as it is submerged to a certain liquid level. The fluid accumulation stage, as Brother Tianxia said, can be skipped if necessary. To be honest, I really can’t figure out why this valve is necessary. . .
Without this valve, how can the main cooler be heated (dried)? When I heat it, this valve is closed. I haven’t considered how the absence of this valve might affect heating. Could you give me some ideas on this?
Since I am mostly working with processes that don’t have valves, during heating, the main cooler and the upper column are heated first; once a certain temperature is reached, then the lower column is heated. I can’t see why it’s necessary to close this valve.
This post was last edited by you*n*nyou on 2011-9-9 13:08. I think with this valve in place, heating can occur more quickly. When heating, close this valve, open the valve for removing liquid nitrogen, and keep the exhaust valve wide open so that the heating gas can flow more easily on the nitrogen side, thereby allowing faster heating. But it’s not necessary, hehe!