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Produced Water Treatment with Deoiling Hydrocyclones - Misconceptions & Corrections (B-PWT008)

How Deoiling Hydrocyclones Perform

The first and largest commercial Deoilers in the 1980’s had a nominal diameter of approximately 125 mm and separated 98% of oil droplets larger than ~50 microns. This single liner had a required minimum operating pressure of ~80 psig (5.5 bar) corresponding to a capacity of ~2,200 BWPD.  Today, a Deoiler of this size is only used in easy, high-pressure, high-temperature applications.

The second generation Deoilers of the 1990’s were of smaller diameter; in the 70 to 75 mm range.  These liners separate 98% of all droplets larger than ~30 microns.  The minimum pressure required to operate these Deoiler is ~60 psig (4.1 bar), with corresponding capacities ranging from ~ 900 – 1,300 BWPD.  These liners have moderate efficiencies in most cases.

Current generation Deoilers, developed since 2000, are designed to treat ‘tough’ applications, and return high operating efficiencies.  These liners have ~40mm nominal diameter, and separate 98% of droplets larger than 10 microns.  The minimum operating pressure required for these hydrocyclones is ~40 psig (2.8 bar), with corresponding capacities ranging from 200 to 300 BWPD.

The following graphics illustrate the basic characteristics of a Deoiling hydrocyclone for two different sized liners; the 38mm (1.5inch) inlet sized DO15, and the 64mm (2.5inch) inlet sized DO25.

Flowrate through a Deoiler is directly proportional to pressure drop
Smaller Deoilers are more efficient
All Deoilers need a minimum oil reject rate to operate efficiently

All Deoilers have a minimum pressure drop / flowrate below which the centrifugal force is insufficient to generate an effective separation. This minimum figure depends primarily on the Deoiler diameter, but is also influenced by the process conditions.

For the DO15 Deoiler shown in the graphics above, this minimum pressure drop (from inlet to reject overflow) is 40 psig (2.8 bar), and for the larger DO25 Deoiler it is 80 psig (5.5 bar).

For robust Deoiler performance prediction, all the relevant process conditions should be captured, and used in a credible, proven Deoiler Simulation Model.


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