1. Distillation Modeling CHEN 4470 – Process Design Practice
Dr. Mario Richard Eden Department of Chemical Engineering Auburn University
Lecture No. 13 – Reboiler Selection and Design
February 26, 2013
Material Developed by Dr. Jeffrey R. Seay, University of Kentucky - Paducah

2. Overview Purpose of Reboilers Types of Reboilers
Provide vapor flow up a column and acts as an additional theoretical stage below the trays/packing
Types of Reboilers
Thermosyphon
Forced circulation
Kettle
Internal reboiler (rarely used in continuous columns)
Proper reboiler design is critical to the optimum operation of a column!

3. Thermosyphon Reboiler
Return piping to the column must be sized for two-phase flow.
Thermosyphons operate based on thermodynamic principles, rather than gravity.
Therefore, design detail is important.
Thermosyphon operation is simple, but they are often difficult to design for a wide operating range.
Proper elevation is critical!
2-Phase Flow Region
All-Liquid Flow Region

4. Forced Circulation Reboiler
Forced circulation reboilers are designed to operate liquid full.
Flashing occur as the liquid crosses the control valve.
Valve should be located close to the column shell.
Forced circulation reboilers offer greater operational flexibility than thermosyphons, yet have a smaller footprint than kettle reboilers.
Elevation is less critical due to pump and control valve.

5. Kettle Reboiler
All-Vapor Flow Region
Cross Section of
Kettle
Vapor-Liquid disengagement occurs in the vapor space, therefore return piping is sized for all-vapor flow.
Proper elevation is critical to kettle reboiler operation.
Kettles have a large footprint, but require less elevation than a thermosyphon.
Works by gravity, rather than thermodynamics.
All-Liquid Flow Region

6. Reboiler Design Thermosyphon Kettle Forced Circulation
Reboiler Selection Flowchart
Cost Comparison of Reboiler Types
Thermosyphon
Kettle
Forced Circulation

7. Reboilers in ASPEN Plus