TROUBLESHOOTING THERMOSIPHON REBOILERS

Thermosiphon reboilers supply the required heat to distillation columns in the process industry. While operating personnel expect reboilers to reliably supply this heat under a range of operating conditions, operators may have a limited understanding of their performance limits. When columns perform poorly, reboilers are often considered the culprit. Pinpointing the problem not only requires knowledge of column design and operation but also expertise in thermosiphon operation.

Adequate operation of thermosiphons requires a balance of heat flux and circulation. If heat flux is too low, circulation stops; if heat flux is too high, film boiling or mist flow can occur. If circulation is too high due to high liquid levels, long unproductive subcooled lengths can result in vertical units. If circulation is impeded by high friction in the outlet piping, instability can occur. Operators do not have a dashboard to show them the balance between heat flux and circulation.

Members expect thermal predictions with increasing accuracy over a wide range of heat fluxes, column liquid levels, and column pressures. HTRI has developed design guidelines for thermosiphons; however, like most heat exchangers, thermosiphons rarely operate at their design point. Recent research has targeted off-design operations such as turndown. Operating personnel need to know how to diagnose performance problems such as fouling, film boiling, instability, buildup of heavies, and inadequate circulation.

Join us at this year’s Global Conference to participate in a panel session on thermosiphon troubleshooting. We will discuss industry problems, diagnostic methods, corrective measures, and the need for new software features and additional research. Learn some new tricks-of-the-trade, current trade-offs in choosing vertical tubeside vs. horizontal shellside reboilers, and contribute to improvements in HTRI technology.