FSM: Liquid Desander – Cyclonic Technology Part 1 (B-FSM043)
The Liquid Desander is a derivative of Hydrocyclone Technology which is a subset of Cyclonic Technology. To fully understand the produced water desander we must first start with fundamentals of Cyclonic Technology.
Definition of Cyclonic Unit Process:
Unit process converting potential energy of a fluid (pressure) at the inlet into rotating kinetic energy using only the shape of the device in order to partition two or more phases in that fluid into the respective number of concentrated outlet streams
What makes cyclonic technology so valuable for the offshore oil & gas industry is that it has the highest throughput-to-size ratio of any partitioning device. For a given flow rate a cyclone will have the smallest size and weight of any separation piece of equipment.
A cyclone however is technically not a separation device – it is a classification piece of equipment. Classification is partitioning based on particle weight, which is combination of size & density, while Separation is partitioning based on size alone. If all the particles in a fluid stream (i.e. sand in water) have the same density then only the particle size matters – hence the cyclone becomes a separator. If the particles have mixed density then each type of particle is treated differently.
The nature of the fluid continuous phase is the first delineation in naming cyclonic unit equipment. If the fluid is a gas then the unit is termed a Pneumatic Cyclone – if the fluid is a liquid then the unit is a Hydrocyclone.
There are pneumatic cyclones for separating gas of different densities (vortex tube), removing liquid droplets from a gas stream (demisting cyclones), or removing solid particles from a gas stream (dust collector).
Correspondingly for hydrocyclones a unit that removes oil droplets from produced water is a deoiler, removing sand from produced water is a desander, and classifying solids of different weights is used in the mineral processing industry for closed-circuit grinding of ore.
The next article will discuss key factors for cyclonic unit processes and where this equipment is used in the oil & gas industry.
- Green, D.W. 2007. Perry’s Chemical Engineers’ Handbook, 8th Edition, McGraw-Hill, New York.