Text №17 Thermosyphon reboilers

Thermosyphon reboilers (Image 2) do not require pumping of the column bottoms liquid into the reboiler. Natural circulation is obtained by using the density¹ difference between the reboiler inlet column bottoms liquid and the reboiler outlet liquid-vapor mixture to provide sufficient liquid head² to deliver the tower bottoms into the reboiler. Thermosyphon reboilers (also known as calandrias³) are more complex than kettle reboilers and require more attention from the plant operators. There are many types of thermosyphon reboilers including vertical, horizontal, once-through⁴ or recirculating.

Some fluids are temperature sensitive such as those subject to polymerization by contact with high temperature heat transfer tube walls. High liquid recirculation rates are used to reduce tube wall temperatures, thereby reducing polymerization on the tube and associated foulng⁵.

Fired reboiler

Fired heaters⁶ (Image 3) also known as furnaces⁷ may be used as a distillation column reboiler. A pump is required to circulate the column bottoms through the heat transfer tubes in the furnace's convection and radiant sections. The heat source for the fired heater reboiler may be either fuel gas or fuel oil.

Forced circulation reboilers

A forced circulation⁸ reboiler (Image 4) uses a pump to circulate the column bottoms liquid through the reboilers.

1. Density - плотность

2. Liquid head – напор жидкости

3. Calandria – нагревательный элемент

4. Once-through - однопроходной

5. Fouling – загрязнение, засорение, образование накипи

6. Fired heater – огневой нагреватель

7. Furnace - печь

8. Forced circulation – принудительная циркуляция