Produced Water Treatment with Deoiling Hydrocyclones - Misconceptions & Corrections (B-PWT013)
Misconception 5 : Deoilers are not flexible in dealing with high turndown requirements
Correction 5 : Deoiler systems can handle any online turndown requirements.
This misconception first came about when large numbers of second generation Deoiler liners were first packaged and bundled into single vessel arrangements to handle large flowrates. The turndown was a function of the pressure drop available, and the lower the pressure drop the lower the turndown.
Now this situation was initially dealt with by the provision of blanks which allowed for the slow build-up to the required maximum flowrate, but this also required the unit to be shut down to install more liners. Alternatively, multiple vessels, with multi Deoiler Liners systems could be deployed for higher online turndown, however this required more space, and was more costly.
Then in the mid 1990’s the advent of Packaged Active Cyclone Systems (PACSTM) was introduced to allow a high turndown capability online within a single vessel. This was achieved by segmenting or isolating banks of Deoilers Liners within the pressure vessel, and turning these banks of liners on or off online, as required, with external vessel piping and valve arrangements.
Packaged Active Cyclone System (PACSTM)
Notwithstanding this capability, it should be noted that most of the time the design turndown requirements of a PWT system requested are not warranted. This is due to the fact that most of the time water production rates do not need to match the requested water treatment rates. Often forgotten when specifying water treatment rates is that between the producing wells, and the PWT system, is a production separator – typically one of substantial size.
When located and installed properly on the water outlet leg of the production separator upstream of the LCV, a Deoiler system treats the volume of water between the low and high levels of a production separator, up to a maximum capacity.
If there’s little or no water production, the Deoiler system happily shuts-in, until the required water volume builds up. There’s no problem with this batch operation, as the Deoiler with a 2-3 sec residence starts to work instantaneously when required, and shuts down just as quick.