Although there are many types of reboilers, the shell and tube thermosyphon reboiler is used most frequently. Boiling within the vertical tubes of the exchanger produces liquid circulation and eliminates the need for a pump. A typical arrangement is shown in Figure 9.
For certain duties, particularly when the bottoms liquid has a tendency to foul heat transfer surfaces, it is desirable to pump the liquid through a forced circulation reboiler. Since boiling can be suppressed by use of an orifice plate at the outlet of the unit, fouling is reduced. The liquid being pumped is heated under pressure and then is flashed into the base of the column where vapor is generated.
An alternate approach is the use of a plate heat exchanger as a forced circulation reboiler.
With this technique, the very high liquid turbulent flow which is induced within the heat exchanger through the use of multiple corrugated plates holds fouling to a minimum. Meanwhile, the superior rates of heat transfer that are achieved reduces the surface area required for the reboiler.
Figure 9. Typical shell and tube thermosyphon reboiler arrangement
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