Reflux Ratio and Boil-up Ratio

Reflux Ratio: it is the ratio of liquid (L) refluxed over distillate obtained (D). It is given by equation







It is used in the calculation of operating line of rectifying section. After vapor are condensed, part of it is refluxed into upper plate. Refluxing facilitates better rectification. Reflux ratio can also be expressed as ratio of reflux to vapor.







Boil-up Ratio: It is the ratio of vapor formed (Vm+1) in stripping section to bottom product.






Why partial reboiler is used in continuous distillation?

Partial reboiler is used to recover most volatile component (MVCs) from liquid of stripping section which is rich in less volatile product but also contains few of MVCs.


Variation of reflux ratio on McCabe Thiele method:

As the reflux ratio increases, the rectifying internal reflux ratio increases and numerically approaches unity. In McCabe Thiele plot, the two operating line move away from equilibrium line towards 45° line. The individual equilibrium stage steps becomes larger and consequently fewer equilibrium stages are required for given separation.

If the reflux ratio decreases, two operating line move toward equilibrium line. The individual equilibrium stage steps become smaller and consequently more stages are required for given separation.



About Author

Name : Pratiksha Shrestha

Ms. Shrestha holds masters degree in food engineering and bioprocess technology from Asian Institute of Technology (AIT) Thailand. She is currently working for Government of Nepal at Department of Food Technology and Quality Control (DFTQC), Kathmandu. She is also a teaching faculty in College of Applied food and Dairy Technology (CAFODAT) affiliated to Purbanchal university, Nepal.