Reboiler recirculation ratio

Calculate the liquid flow rate leaving the reboiler for the vapour rate and recirculation ratio. 

The amount of liquid vaporized in the reboiler should not be more than 80%, otherwise this will tend to lead to excessive fouling of the reboiler. For kettle reboilers, there is no recirculation. But for thermosyphon reboilers, a recirculation ratio can be defined as ... 

This usually lies between 0.25 and 6. The greater the value of recirculation ratio, the less fouling there is in the reboiler. Lower values tend to be used in horizontal thermosyphons and higher values (greater than 4) used in vertical thermosyphons. The recirculation ratio is a degree of freedom at the discretion of the designer. This should be fixed later when the detailed design is carried out. 

Estimate the heat transfer area, using the maximum allowable heat flux. Take as 39,700 W/m for vertical and 47,300 W/m for horizontal reboilers. Choose the tube diameters and length. Calculate the number of tubes required. Estimate the recirculation ratio, not less than 3. 

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