Intermediate reboiler
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Under what circumstances is it necessary to add an additional intermediate reboiler to a distillation column when there is already a reboiler at the bottom?
A secondary reboiler? I don’t think I’ve heard of that before... If it’s about using the middle part of the tower as a discharge point, then it might be possible to install a heat exchanger there, but that would likely be for cooling purposes rather than heating. If you have any diagrams or examples, feel free to share them so we can discuss them together
The design load does not meet the operational requirements
If a reboiler at the bottom of the tower is not sufficient to provide enough heat, an intermediate reboiler can be used. In the case of a low-temperature distillation column, an intermediate reboiler can be used to recover the cooling capacity. The position of the intermediate reboiler can be arranged at a temperature at which cooling capacity can be extracted as needed.
Answer from Baidu: The side reboiler is an auxiliary heater located in the stripping section of the distillation column, used in the rectification process. For distillation columns where the top overflow temperature is below the ambient temperature, the bottom temperature is above the ambient temperature, and there is a large temperature difference between the top and bottom, installing an intermediate heater in the stripping section allows the use of a heating medium with a temperature slightly lower than that of the bottom reboiler but at a lower cost, thereby achieving energy savings. Personally, I think a tower section of excessive length is necessary for its use; moreover, when adding a reboiler, it is necessary to determine the temperature, location, and heat exchange area based on the actual separation efficiency.