Since its presentation in 1987 (Ref 1), the rotating de-oiling cyclone has been proven as a technical competitor to existing de-oiling equipment.

Extensive trials in 1989-1990 by an independent testing laboratory using a size 2 (2500 BWPD) rotating cyclone in parallel with a static cyclone and a flotation unit (Ref 2), and a field test with a size 2 and two static cyclones (Ref 3) have demonstrated the superior separation capability of this equipment.

However, in order to answer to the criticism concerning the mechanical reliability of this equipment due to the fact that it is a rotating machine, a one year extended mechanical test has been carried out with a size 2 unit on a petroleum field near Paris, with good results.

At the same time, the need for a larger capacity cyclone led to the construction of a size 4 (10 000 BWPD) rotating cyclone. This cyclone has been hydraulically tested with satisfactory results. The mechanical design is different from the size 2 and uses hydrostatic bearings in order to improve the reliability. This unit will be installed on a North Sea platform by the end of 1992, for full capacity field testing and performance evaluation.

The rotating cyclone has been mathematically modelled and the results compared with the laboratory and test loop data. The model will be used to explore the behaviour of the cyclone in specific ranges of operation (oil concentration and flowrates) and to optimize the inlet/outlet geometry.

Application of rotating cyclone is not limited to produced water de-oiling; it can be applied also to dehydration of crude oil. The results of laboratory trials carried out on the pilot unit are also presented.

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