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Produced Water Treatment with Deoiling Hydrocyclones - Misconceptions & Corrections (B-PWT006)

Early Challenges, Progress & Development : Part 2

The early challenge in applying Deoiler hydrocyclone technology was – What is the problem we are trying to solve? Yes it was obvious we wanted to treat produced water on offshore facilities with space constraints, but it also became apparent early on that produced water isn’t simply oil in water. We saw earlier in this series the complex, diverse and potentially changing nature of produced water.

Furthermore, the requirements and basic operational criteria of a Deoiler hydrocyclone are completely different to that of its predecessor technologies. The optimal operation of a Deoiler requires an installed location;

  • At the highest available pressure and temperature
  • As far upstream as possible with minimal prior turbulence
  • Treating separate individual produced water streams, not a combination of many

This meant that there is one optimal location for effective and efficient produced water treatment by a Deoiler hydrocyclone – the water outlet leg of the Production separator, upstream of the level control valve.

Now this hasn’t prevented many operators and engineering firms from trying to apply Deoiler technology elsewhere, and in particular, where the previously larger, heavier, older technology was located – with disparaging results.

Deoiling hydrocyclones were originally ‘packaged’ as single liner arrangements. (Note: The use of the terms Deoiler, hydrocyclone, and liner, are used interchangeably with the technology). If you required a capacity higher than that provided by a single liner, you simply installed multiple liners in parallel.

Single Deoiler Liners in parallel

The original Deoilers were larger than the current design, typically with a 120 mm nominal diameter. Today a typical Deoiler is 40 -50 mm nominal diameter. This meant that although early Deoilers could treat large capacities, their performance was similar to primary separators.

Subsequent developments led to smaller Deoiler liners to handle more difficult secondary separation applications, and the liners were bundled together into single vessels to provide high capacities and ever smaller foot-print. 

When higher turndown was required, Packaged Active Cyclone Systems (PACS) were developed. In this configuration ‘banks’ of Deoiler liners are installed and operated – many as one – to provide high turndown flexibility. More discussion of this design will be given later in this series.

To this day ‘experts’ still present and define the characteristic of a Deoiler hydrocyclone as it was in the 1980’s – as a single (larger) liner.  This is an incorrect approach, and is as relevant as defining the performance of an 8 or 12 cylinder engine, with what a single cylinder can do. It’s not applicable or useful in describing the real capabilities of a Deoiler technology ‘package’.

Bibliography:

  1. Ditria, J.C., et al., APS, “The Separation of Solids and Liquids with Hydrocyclone Based Technology for Water Treatment and Crude Processing’, SPE 28815, APOGC Melbourne Australia, November 7-10, 1994.
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