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Multiphase Desander – Fluid Flow Patterns (B-FSM084)

Fluid flow – both gas and liquid phases – within a hydrocyclone, liquid desander, and multiphase desander are shown graphically below.


  • Operates as a mineral processing classification device per post B-FSM-045
  • Liquid only flow into hydrocyclone
  • Has center free air-core per post B-FSM-049 (due to open U/F and O/F)
  • Air-core exist along entire center line of hydrocyclone

Liquid Desander

  • Operates as a produced water separation device per post B-FSM-045
  • Liquid only flow into desander
  • Dissolved gas may come out of solution, due to pressure drop, and form thin partial gas-core along upper middle portion of desander
  • Thin gas-core will form and dissolve and re-form during operation

Multiphase Desander

  • Operates as a multiphase flow separation device
  • Both gas and liquid fed into desander
  • Free gas removed immediately to vortex finder, forming annular-type flow in this region – the free-gas annular flow pattern is the most significant flow pattern difference with the multiphase desander and aids in separation efficiency by forcing the solids into the annular liquid flow for easier removal
  • Fine gas bubbles combined with effervescing gas forms thin gas-core along cylinder and upper cone sections

The next article covers particle travel within the multiphase desander.


  1. Rawlins, C.H. 2017. “Separating Solids First – Design and Operation of the Multiphase Desander”, paper 185658-MS presented at the SPE Western Regional Meeting, Bakersfield, CA, 23-27 April.
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