Flash evaporation

Flash evaporation (or partial evaporation) happens when a hot liquid suddenly moves into a place with lower pressure. When this happens, part of the liquid quickly turns into vapour, while the rest stays as liquid. This usually happens when the liquid passes through a throttling valve or a similar device that reduces pressure. The process is one of the simplest processes used in chemical and process engineering.

If the valve is placed at the entrance of a pressure container, the evaporation happens inside the container. This container is called a flash drum.

Flash evaporation can be dangerous if not controlled. In some cases, it can cause a boiling liquid expanding vapour explosion (BLEVE). This happens when a pressurised liquid suddenly turns into a large amount of vapour.

Flash evaporation can also happen naturally. During earthquakes, rocks can move very quickly. This sudden movement can cause pressure changes that lead to flash vapourization. When this happens, minerals dissolved in water can be deposited inside rocks. Sometimes, this process can even form valuable ores.

References

Other websites
Vapor and Flash Steam Animation, photos and technical explanation of the difference between Flash Steam and Vaporized fraction.
Flash Steam Tutorial The benefits of recovering flash steam, how it is done and typical applications
Water Desalination Technologies in the Middle East and Western Asia
Discussion of spray drying
Flash evaporation program online Flash distillation of the hydrocarbon compounds.

Category:Chemistry
Category:Thermodynamics