In a full reflux stabilizer, reducing the temperature at the top of the tower leads to a decrease in the reflux rate – will this be the case?
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In a full reflux stabilizer (used for separating H2, C1, C2, C3, and C4), by lowering the temperature of the overhead condensate while keeping the tower pressure, feed rate, and reboiler settings unchanged, will the reflux rate of the tower decrease? (The tower pressure is controlled by the gas phase output, which contains some C4; the liquid phase is in full reflux – the level in the reflux drum is regulated via a feedback loop with a reflux control valve, and the reflux drum is mostly filled with C4.) Viewpoint 1: As the reflux temperature decreases while the reboiling temperature at the bottom of the tower remains unchanged, from the perspective of energy conservation, the heat load on the tower stays the same. However, the amount of cooling required increases; as a result, some of the material in the tray does not evaporate into the reflux drum, so the reflux volume decreases ； Viewpoint 2: In the overhead reflux drum, part of the C4 in the gas phase is cooled down, so the reflux rate increases ； I seek help from experts to resolve this issue.
The question is phrased incorrectly; what should be asked is whether the liquid level in the return tank will increase or decrease The reflux rate is controlled by the reflux valve; it doesn’t change much with variations in the temperature after cooling. If the temperature drops while the heat source at the bottom of the tower remains unchanged, then if the reflux rate doesn’t decrease, it will certainly lead to a drop in the reflux liquid level.
As the top temperature drops, the amount of condensation decreases, the liquid level in the reflux tank falls, and thus the flow rate controlled by your cascade control system also decreases. But with reduced reflux, should the tower top temperature increase again? It’s not common to use backflow to control the tower top temperature like you do.
You have control over the liquid level and reflux rate in this tank; how is the tower top temperature controlled?
What you’re referring to is probably the reflux from the high-pressure depropanization column. The temperature of the reflux tank is directly related to the condensation process; in other words, it’s related to the amount of reflux. A decrease in temperature indicates that the amount of reflux is too high