Reflux - Kanryu

In distillation, this refers to the process in which the vapor that leaves the top of the rectification tower is cooled and condensed in a partial or total condenser, and the liquid is returned to the top of the rectification tower. When all of the vapor generated is condensed and returned, it is called total reflux, but since no distillate is obtained in this case, it is not used in actual operation. However, total reflux operation is often used at the start of operation to quickly reach a steady state. Part of the condensed liquid is refluxed, and the remainder is taken out of the system as a distillate and used as the product. This is called partial reflux. The ratio of the reflux amount to the distillate amount is called the reflux ratio, and this value can be changed from 0 to infinity. Also, if the reflux ratio is gradually reduced, an infinite number of stages (theoretical number of stages) is required to obtain the desired distillate concentration. The reflux ratio at this time is called the minimum reflux ratio, and is considered an important value in the design of a rectification tower.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

蒸留において，一度精留塔の塔頂より出た蒸気が，分縮器あるいは全縮器によって冷却凝縮され，液となってふたたび精留塔の塔頂に戻されることをいう．発生した蒸気の全部を凝縮させて戻すとき全還流というが，このときは留出液を得ることができないので，実際の操業では行われない．しかし，運転開始のとき，早く定常状態にするため，しばしば全還流運転が利用されている．凝縮した液の一部を還流し，残りを留出液として系の外に取り出して製品とする．これを部分還流という．還流量の留出量に対する比を還流比といい，この値は0から∞まで変化させることができる．また，還流比をしだいに小さくすると，望む留出濃度を得るためには，無限の段数(理論段数)が必要になる．このときの還流比を最小還流比といい，精留塔の設計上，一つの重要な値とされている．

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