How is seawater desalinated by distillation?

Distillation is a thermal process used to desalinate seawater by converting it into vapour and subsequently condensing it back into a liquid, leaving dissolved salts behind. Because heating large volumes of water is energy-intensive, modern industrial methods rely on lowering the boiling point of water by reducing atmospheric pressure.123

Common thermal desalination techniques include:

• Multistage Flash Distillation: Seawater is heated and passed through a series of closed vessels (stages) set at progressively lower pressures. As the water enters each stage, it rapidly boils or "flashes" into vapour, which is then condensed into fresh water on heat-exchange tubes.13
• Multiple-Effect Distillation: Similar to multistage processes, this involves a series of low-pressure vessels. Preheated seawater is sprayed onto evaporator tubes to promote rapid evaporation in each vessel.1
• Vapour-Compression Distillation: Heat is generated by rapidly compressing vapour, which raises its temperature. This heated vapour is recycled through tubes to facilitate the evaporation of seawater in a reduced-pressure chamber.1
• Solar Humidification: A simple process where sunlight warms seawater in a basin, causing it to vaporize under a transparent cover. The vapour condenses on the underside of the cover and is collected.132