Reboil

Reboil is the act of boiling something again after it has already boiled. In everyday language, it refers to reheating liquids such as soups or sauces to return them to a full boil, often for safety, texture, or concentration. In scientific and industrial contexts, reboil describes a controlled heat step used to generate vapors from a liquid that resides in a lower part of a system, most notably within distillation equipment.

In a distillation column, the reboil is provided by a reboiler, a heat exchanger that heats the bottom liquid to generate vapors that ascend the column. The vaporization at the bottom creates the driving force for separation based on volatility. Common reboiler designs include kettle (pot) reboilers and thermosiphon reboilers, chosen to match process requirements and energy efficiency. Operating conditions are coordinated with the column's temperature profile and reflux ratio to achieve target product purity.

Safety and maintenance considerations apply to industrial reboilers, including material compatibility, corrosion resistance, and control to prevent overpressure, flooding, or coking. In food preparation, reboiling must be done with care to avoid overcooking and microbial safety concerns, recognizing that repeated boiling can alter flavor and texture.

See also: reboiler, boiling, distillation, reflux.