On the calculation of the vapor-liquid two-phase reflux ratio

Calculation of the reflux ratio: Reflux ratio: In the distillation process, it is the ratio of the amount of material returning to the column to the amount taken out from the top of the column. It is usually denoted by R. R=L/D: The reflux ratio has two limits – the upper limit is the reflux ratio at full reflux, and the lower limit is the minimum reflux ratio. The larger the reflux ratio, the fewer theoretical plates are required ； Conversely, the smaller the reflux ratio, the more theoretical plates are required. Full reflux § Full reflux: All of the vapor rising from the top of the tower is condensed and then returned back into the tower. § The characteristics are as follows: § During full reflux operation, there is no product at the top of the tower; therefore, once the process reaches stability, neither feed is added to the tower nor is any product taken out from the bottom of the tower. § There is no distinction between a distillation section and a stripping section; the two operation lines are combined into one, coinciding with the diagonal line. § Full reflux is the upper limit of the reflux ratio. Its operation has no practical meaning for the production process since there are no products. However, it is used during the commissioning phase of the distillation tower, during the tuning process, or in experimental studies, in order to facilitate the stabilization and control of the operation process. Minimum reflux ratio § Minimum reflux ratio: The reflux ratio corresponding to an infinite number of theoretical plates being required for a certain separation task. ④Optimal reflux ratio: In engineering design and operation, the actual reflux ratio should be selected between the minimum reflux ratio and full reflux. § Determine the appropriate reflux ratio through economic analysis: The reflux ratio at which the total cost is lowest is the appropriate one. §The economic calculation is complicated; selection is based on experience: §R=(1.2~1.5)Rmin

It should also be calculated based on the ratio of the returning liquid phase to the extracted gas phase, but I’m not sure if this method is correct; I’m still working on it as well. I hope my colleagues can help solve this issue

Thank you to the person on floor 2; it should be the molar ratio.

Brother on the 2nd floor, is the reflux ratio not supposed to be the ratio of the reflux volume to the amount of product? When the product is in gas phase, the liquid phase is completely recycled – how then is the reflux ratio calculated?

Back upstairs; what was mentioned on the 2nd floor about extracting it from the top of the tower must be the product.

The reflux ratio is definitely a molar ratio. I’m sorry; I didn’t make that clear enough

After being extracted from the top of the tower, it is cooled in a condenser to yield a liquid product; part of this product returns to the tower as reflux (as measurable by a flow meter), while the other portion that can be extracted (also measurable by a flow meter) serves as the product； Since the gas phase obtained after extraction is condensed (using a condenser with a storage tank), vapor-liquid equilibrium is reached above the liquid phase. As the gas phase contains a high proportion of light components, it can be vacuum-condensed and then purified in a distillation column, thereby reducing waste of raw materials. This distillation column has a reflux ratio of 3, resulting in high product purity. Incidentally, for the operation of a distillation tower, stability can be achieved by ensuring three types of equilibrium: mass balance, heat balance, and gas-liquid equilibrium: lol

In my opinion, the molar ratio of the liquid phase reflux volume to the production volume is the reflux ratio

(1) In practical operations, it refers to the ratio of the amount of the reflux liquid phase to the amount of the gas phase exiting, usually expressed in terms of moles. (2) If performing calculations, follow these steps: a. Determine the composition of the component at the top of the tower, which is the composition of the material entering the condenser. b. To obtain the vapor-liquid equilibrium data at the pressure and temperature at the top of the tower. c. Based on the vapor-liquid equilibrium data, a material balance is performed to determine the amounts in the liquid phase and the gas phase. This post was last edited by fj170530 on 2009-2-19 09:08.]