Q3-1 Evolution of HTRI Kettle Reboiler Design Methods

J. W. Palen

Kettle reboilers may have been the first chemical process vaporizers. One of their earliest uses was in distilling alcohol, for which they were termed stills in the early U.S. The separation of chemical components from petroleum followed shortly. Using a simple concept—a steam coil in a pot of liquid—and simple construction, these units served industry for decades before anyone thought to design them. However, with the dawn of chemical engineering and the competition-driven need to operate as efficiently as possible, kettle reboilers joined other classes of exchangers for which engineers estimated heat transfer coefficients and predicted area requirements.

Although kettle reboilers function well in both vacuum and near the thermodynamic critical condition (where thermosiphon reboilers have circulation problems), they are not recommended for wide boiling range mixtures because of their low mean temperature difference and heavy component accumulation. The following sections discuss the evolution of HTRI’s methods for reboilers, progressing from earliest approximations through the current rigorous methodology of IST.