Reboilers, or vaporizers, are heat exchangers that provide heat to the bottom of a distillation tower. They boil the bottom liquid to generate vapors which are returned to the tower to drive the distillation separation process. The reboiler may partially or completely vaporize the stream it receives from the bottom of the tower.
Excess reboiler liquids (bottoms or blow-down) overflow a baffle where level is controlled by means of a level controller. If the reboiler level becomes too low, it will affect the maximum flow rate of bottoms product that can be drawn off. Inaccurate reboiler level can also degrade composition control for material balance control configurations.