Reboiler

In a typical classical distillation column, all the vapor driving the separation comes from the reboiler.

In this reboiler type, steam flows through the tube bundle and exits as condensate.

There is a retaining wall or overflow weir separating the tube bundle from the reboiler section where the residual reboiled liquid (called the bottoms product) is withdrawn, so that the tube bundle is kept covered with liquid and reduce the amount of low-boiling compounds in the bottoms product.

There are many types of thermosyphon reboilers including vertical, horizontal, once-through or recirculating.

A pump is required to circulate the column bottoms through the heat transfer tubes in the furnace's convection and radiant sections.