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OVERVIEW
Produced water treatment systems have traditionally consisted of deoiling hydrocyclones followed by a simple downstream degassing vessel (using Induced Gas Flotation to effect some oil separation) or flotation units. However, operators around the world are now looking to further reduce their oil discharges to sea, driven by environmental pressures, regulation (eg OSPAR), implementation and sometimes simply by companies desire to reduce their environmental foot print (eg through compliance with ISO 14000).
Therefore, a new approach has been required to meet these goals, leading to the development of the Cyclotech DeepSweep™ Compact Flotation Unit, which, when combined with Cyclotech's state-of-the-art deoiling hydrocyclone, represents Best Available Technology for produced water treatment.
DESIGN PHILOSOPHY
- Vertical orientation, which reduces footprint and maximises the effectiveness of the low g swirl
- Two stage process, with the first zone of the CFU providing Dissolved Gas Flotation and the second zone providing Induced Gas Flotation
- Tangential inlet generates a tangential flow field, and the resultant low g radial acceleration field enhances separation
- Pumped recirculation system provides high efficiency across a wide operating range, and provides induced gas flotation
DESIGN FEATURES
- Optimised inlet provides homogenous distribution of incoming oily water
- The first zone of the DeepSweep™ CFU provides maximum utilisation of the dissolved gas flotation mechanism
- Induced gas is introduced as micro-bubbles, with optimal oil droplet / gas bubble contacting time. Micro-bubble generation achieved through adjustable mixers, allows optimisation across a wide range of operating conditions
- Recirculated water inlet designed to maximise region of DeepSweep™ unit which is swept by induced micro-bubbles
- Gas mixing done externally to avoid plugging of nozzles in vessels, inhibiting plant availability
- Uniform distribution of flotation gas bubbles
- Length / Diameter ratio is selected to minimise axial velocity whilst also minimising radial distance travelled by oil droplets to outlet
- Inlet nozzle height optimised to match predicted axial oil concentration which avoids short circuiting of oily water to clean water outlet and incoming flow from disturbing the separated oil pad
- Flow short circuiting is avoided by the low g acceleration field in combination with the configuration of the internals which account for both the axial and radial oil concentration gradients to maximise effectiveness of oil skimming and clean water removal
- Optimised skimming design concentrates oil to minimise collection of water in the oil outlet stream
- No fine tolerance internals which provides low sensitivity to solids & scale formation
- Particularly suited for Floating Production applications where the design ensures high performance insensitivity to motion
- For more onerous applications two stage systems can be provided
BENEFITS
- High efficiency. Typical outlet concentrations from 5 to 20 mg/l
- Small footprint
- High turndown
- Scalable design
- Very low maintenance
- Insensitive to solids / scale formation
- Reduces or eliminates requirement for chemicals
