I’m a newcomer to the chemical industry; I have a question regarding reflux

Internal reflux takes place within the tower, without any reflux pipes. The external return flow has a return pipeline that is located outside the tower, entering from the bottom or middle of the tower (vessel). Natural backflow relies on pressure difference. Forced return is achieved by a pump, which requires power.

Internal reflux refers to the reflux that occurs within the tower itself; such equipment usually has its top connected directly to a condenser. External reflux means using pipes for the reflux flow; generally, the condenser and the tower are separate entities. Natural backflow is pressure differential backflow, as opposed to forced backflow, which requires the use of a pump. A total condenser and a partial condenser are both heat exchange devices. To find out what it should look like, search on Baidu – there are various formats available.

Our factory is currently using a methanol distillation unit, and I have some knowledge of this type of single-effect distillation, so I will explain it using this unit as an example. By internal reflux, we mean two things. In terms of design, internal reflux refers to the liquid that condenses in the condenser at the top of the tower, which then flows back down from the top of the tower as part of the reflux ratio. However, during operation, due to problems with insulation – either a lack of insulation or damaged insulation – significant temperature loss occurs within the tower, and at this point, internal reflux also takes place inside the tower. The internal recirculation of the latter is something we must eliminate, otherwise it increases energy consumption. Our external reflux involves passing the liquid from the receiving tank through a reflux tank, and then sending it back down from the top of the tower. In the cases of natural reflux and forced reflux, I think the difference lies in whether a pump is used or not. As for the total condenser and the partial condenser, they are actually the same thing – they are heat exchangers. The type we use is a tubular condenser; the one at the top of the tower is a partial condenser, which can only cool a portion of the gas. There is another condenser before the receiving tank, and that one can condense all of the gas. The sub-cooler and the full-cooler differ mainly in the degree of cooling; there isn’t much difference in terms of the actual equipment. Most parts of the over-condenser use circulating water for cooling; the full condenser sometimes uses chilled brine, or circulating water as the primary cooling medium and chilled brine as the secondary one, like that!