Reboilers

Reboilers are heat exchangers located at the bottom of distillation columns. Their primary function is to heat the liquid drawn from the column bottom to its boiling point, generating vapor that rises through the column and drives the separation. The reboiler duty and the vapor rate influence the column’s temperature profile, stage conditions, and overall separation performance. Reboilers are typically heated by steam, but hot oil or furnace-fired arrangements may be used when steam is unavailable or undesirable.

Two main configurations are commonly employed. The kettle reboiler consists of a vessel that holds the boiling liquid and is heated externally by steam jackets or coils. Vapor formed in the liquid is withdrawn from the top and supplied directly to the bottom of the column. The thermosyphon, or tubular, reboiler uses a tubular heat-transfer package and relies on natural circulation to move liquid and vapor; it often has no circulating pump and can handle higher heat duties with compact hardware.

Design considerations include maintaining adequate liquid level in the reboiler, controlling pressure and temperature to protect equipment and maintain product quality, and providing sufficient heat-transfer area to meet the duty without excessive height of vapor. Materials need to resist corrosion by process fluids, and fouling must be managed to avoid reduced heat transfer. Safety practices address steam leaks, overfill, and potential for dangerous pressure buildup.

Reboilers are integral to many petrochemical, refining, and chemical processes, enabling the energy input required for continuous distillation. Their selection and operation are guided by process requirements, utility availability, and reliable control systems to ensure stable column operation.