Within the framework of the Oslo Paris Convention (OSPAR) for the protection of the marine environment of the North East Atlantic, the Danish Environmental Protection Agency (DEPA) was canying out a Project Plan Setting performance standards for aromatic hydrocarbons in produced water'. As part of this plan Akzo Nobel MPP Systems was requested by DEPA to test and evaluate the MPPE technology for BTEX and PAH's removal from produced water of an oil production platform.
For gas/condensate platforms MPPE is commercially operational and a proven technology. Since the beginning of 2002, 3 MPPE offshore units are successfully operational on Total F15A, NAM K15Aand NAM K15B. Within a tight time schedule oil companies were approached to provide produced water from oil production and tests were completed in the first quarter of 2003. NAM in consultation with Shell provided onshore produced water from the oil production in Rotterdam, coming from before and after centrifuge treatment. TOTAL provided offshore produced water from the Alwyn-North platform offshore Scotland without hydro cyclone treatment, delivered in Aberdeen. The water was transported by Akzo Nobel from Rotterdam and Aberdeen in road tankers (25 m3).
Field tests were carried out in Arnhem with a mobile MPPE unit. The analyses (GC-mass spectrometer) were carried out by a third party Starlab.
Transportation effects (temperature and wall effects) were high (1 test) for the onshore post centrifuge batch from NAM. Because of precautions taken, these effects were less for the pre centrifuge batch and the offshore batch.
The effect of centrifuges on the composition of the produced water (a one time sample!) shows reduced mineral oil and higher aromatics and polyaromatics.
The onshore post centrifuges MPPE inlet levels of Aromatics, PAH's and aliphatics were relative low compared to the on site analyses. This is probably due to wall/temperature effects. An above 99% removal efficiency was obtained.
The onshore pre centrifuge Aromatics and PAH's were removed at 99% levels. Aliphatics were removed at 99% going down to 85-88% levels (mainly due to the lower removal of the >C2o aliphatics over time). For this 25m3 batch only the aliphatics showed a decrease in concentration due to transportation/wall effects.
The offshore produced water MPPE inlet levels compared to samples taken offshore in 2002 showed equal BTEX, somewhat higher PAH's and lower aliphatics levels. Both BTEX and PAH's were consistently removed at >99% levels. Total aliphatics removal was 95% going to 91%. This reduction is due to the reduced removal of >C20 aliphatics over time. For < C20 removal stays consistently high at 95% levels.
At 54-57° C both BTEX and PAH's removal stayed at >99%, and aliphatics at 94%.
Overall observations and conclusions:
- BTEX and PAH's are consistently removed at 99% levels.
- Aliphatics Total Aliphatics will be removed at > 50 to > 80% levels depending on < C20 fraction. (> C20 removal is reduced as a function of time.)
- Separation performance at 57° C is equal to ambient temperature levels.
- No negative effects on the high removal effectiveness of BTEX/PAH's and aliphatics C20)