In order to ensure the distillation process in the distillation column, a certain amount of downstream liquid must flow down to the tray one by one. For sieve tray column, the overflow hopper is installed at the overflow port of the tray. More importantly, the rising gas and the downstream liquid can completely contact the tray, so that the steam can rise through the sieve hole without short circuit from the overflow port, that is, the overflow hopper can act as a liquid seal. The lower part of the overflow bucket is lower than the height of the position increasing plate. When the liquid flows on the tray, the liquid level must be higher than the height of the additional plate, so that the "liquid seal" is located at the outlet of the overflow bucket, so the steam can not be short circuited.
At the same time, because the vapor pressure of the lower part of the tray is higher than that of the upper part, in order to ensure the smooth flow of liquid, the liquid must be accumulated in the overflow bucket. The liquid level is higher than that on the tray and flows downward due to the static pressure of the liquid column. In addition, the overflow bucket can also separate the vapor bubbles, which are entrained in the downstream liquid, and prevent the gas with improved nitrogen purity after distillation from returning to the tray with lower nitrogen concentration.
