What describes Thermosyphon reboiler operation?

• A. Natural circulation
• B. Forced circulation
• C. Direct electric heating
• D. No circulation required

Answer: (A)

Natural circulation drives a thermosyphon reboiler. When the reboiler is heated, the liquid boils and becomes less dense, creating a self-sustained loop: the hot liquid/vapor tends to move into the column while the cooler liquid from the bottom returns to the reboiler by gravity. This pump-less circulation transfers heat into the process liquid through boiling, which is the defining feature of a thermosyphon. It isn’t forced circulation, which uses a pump, and it isn’t direct electric heating, where an electric element provides heat rather than relying on boiling and density-driven flow.