Flash evaporation

A regular vapour-liquid separator

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

  1. ↑ Stanley M. Walas (1988). Chemical Process Equipment:Selection and Design. Butterworth-Heinemann. ISBN 0-409-90131-8.
  2. ↑ Gas Processing Suppliers Association (GPSA) (1987). Engineering Data Book (10th Edition, Vol. 1 ed.). Gas Processing Suppliers Association, Tulsa, Oklahoma.
  3. ↑ Mansour, Ahmad; Müller, Norbert (2019-10-01). "A review of flash evaporation phenomena and resulting shock waves". Experimental Thermal and Fluid Science. 107: 146–168. doi:10.1016/j.expthermflusci.2019.05.021. ISSN 0894-1777.
  4. ↑ "Flash Evaporator & Flash Evaporation". EBNER. Retrieved 2025-12-26.
  5. ↑ Hu, Y (2020). "Influence of flash evaporation on safety characteristics of liquid hydrogen leakage and diffusion". IOP Conference Series: Earth and Environmental Science.
  6. ↑ Richard A. Lovett; Nature magazine (March 18, 2013). "Earthquakes Make Gold Veins in an Instant: Pressure changes cause the precious metal to deposit each time the crust moves, a new study finds. The insight suggests that remote sensing could be used to find new deposits in rocks where fault jogs are common". Scientific American. Retrieved March 18, 2013.

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