Cold reflux instead of circulating reflux

Cold reflux is merely an abnormal operating method, generally used during startup and shutdown periods. If it is used on a regular basis, the yield will decrease. Moreover, since the cold reflux system does not involve heat recovery, the preheating at the top of the tower is wasted.

The first floor is the correct answer; the cold reflux at the top of the tower increases the liquid load there, which in turn reduces the yield of gasoline. In other words, a portion of the gasoline produced remains trapped inside the distillation tower. Cold reflux is only used at startup or in the event of accidents such as tower surges. Therefore, it is not advisable to use it to replace the circulating return flow.

Cold reflux at the top of the tower increases the liquid load there, which reduces the yield of gasoline; in other words, a portion of the gasoline produced remains inside the distillation tower, and it is generally possible to recycle some of it back to the tower. Since the corrosion caused by cold backflow is more severe than that of top circulation, it is better to use it less often

Using cyclic reflux can reduce the heat removal load and pressure drop at the top of the tower, thereby increasing the pressure at the inlet of the compressor； Two can also improve the quality of the top heat source

The main purpose of top circulation reflux is to save energy and recover it; cold reflux can also be used, but the focus should be on energy savings as well as ensuring that the cooling load at the top of the tower is sufficient. Generally, top circulation reflux is employed to adjust the dry point of gasoline. If the adjustment effect is not satisfactory, some cold reflux can be utilized for adjustment.

Thank you all for your advice; I’m a newcomer to catalysis. What I want to say is that our system was taken offline due to a leak in the heat exchanger of the top circulation unit some time ago, and we switched to cold reflux operation instead. But what I saw is that it seems there’s no impact on the entire setup; at any rate, I couldn’t identify where the impact would be My idea is that by switching to cold recirculation, at least one pump and two heat exchangers can be eliminated from operation; meanwhile, the risk of corrosion for these two heat exchangers can also be reduced. Another point is to switch to cold reflux, that is, crude gasoline; since most of the water has already been removed from crude gasoline, I believe this can reduce corrosion to a certain extent. In the top circulation, the fluid is drawn from the tower, cooled, and then returned to the top of the tower; in this process, the water remains in liquid form. Doesn’t this increase the likelihood of corrosion? Furthermore, the gas-liquid phase at the top of the tower may experience intense heat exchange due to the cold reflux; but can we control the amount of cold reflux to avoid increasing the load on the liquid phase? These are just my personal opinions; please forgive any mistakes

The most crucial issue is that you, the original poster, haven’t understood the function of the top circulation; the three types of circulation in a distillation tower serve to remove excess heat from within the tower. If you stop the top circulation, the excess heat at the top of the tower will have to be removed by external crude gasoline; in that case, isn’t the gas-liquid phase balance inside the tower completely disrupted?

Cold reflux is only an auxiliary method; the normal product quality as well as mass and heat transfer within the tower are still controlled by regular cyclic reflux