DeepSweep^® Compact Flotation Unit

DS CFU 3D

Overview

Produced Water Treatment systems have traditionally consisted of Deoiling Hydrocyclone system followed by a simple downstream degassing vessel equipped with an oil skim facility or an induced gas flotation (IGF) unit. However, operators around the world are now looking to further reduce their oil discharges to sea, driven by environmental pressures, regulation and sometimes simply by a desire to reduce their environmental foot print through compliance with ISO 14000.

Therefore, a new approach was 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 B20 Series De-oiling Hydrocyclone, represents Best Available Technology for a two stage produced water treatment system.

Design Philosophy

The underlying design philosophy behind the Cyclotech DeepSweep^® Compact Flotation Unit is to:

Significantly enhance standard, well established Gas Flotation design principles by integrating them with Confined Swirling Flow theory to produce a compact, high performance Produced Water Polishing system;
Ensure suitability for FPSO applications, where the DeepSweep^® CFU design will suppress the negative effects of motion induced sloshing during bad weather.

Principle of Operation

The treatment of produced water using gas flotation relies on the principle that if a gas bubble attaches itself to an oil droplet, the resulting increase in buoyancy will promote a faster separation to the liquid surface due to its enhanced settling velocity.

The inlet water to the DeepSweep^® CFU is first accelerated and then introduced tangentially into the vessel to induce a high velocity swirl. Gas bubbles and oil droplets are driven towards the centre of the vessel to create a radial oil concentration gradient which complements the axial oil concentration gradient induced by gravity which produces a peak oil concentration in the upper centre region of the vessel.

The gas bubbles are created from two sources – dissolved gas and induced gas. Dissolved gas evolves due to the pressure drop across the upstream deoiling hydrocyclone and production separator water level control valve. Induced gas is sourced from the CFU vessel head space ultilising a recycle pump and a dedicated Cyclotech DeepSweep^® eductor and injected into the water inlet. This system has the advantage that it is not a net positive user of high pressure gas unlike systems employing a single pass methodology where the gas is lost to the flare.

The optimisation of both bubble size and attachment mechanisms between the gas bubble and oil droplet is critical and is carefully controlled in the contacting zone prior to vessel entry. In some cases, the concentration and coalescence processes required to achieve separation are further enhanced through the use of flocculent chemicals.

The separated oil is concentrated and skimmed using a proprietary skimming system which minimises the collection of water in the oil outlet stream.

New-Build Systems

Cyclotech’s DeepSweep^® CFU systems form an integral part of our Produced Water Treatment capability. These new build systems can range from fully automated packaged systems to stand alone vessels. Standard pressure vessel designs are available at most design pressures and temperatures and to most common design codes such as PD5500, ASME VIII, AS 1210 or GOST-R. Materials of construction range from standard and low temperature carbon steels (which can be internally lined or clad) through to most stainless steels such as Duplex, 6Mo, Super Duplex, 625, 825 and other alloy steels.

Benefits

The benefits of the DeepSweep^® CFU technology are as follows:

High efficiency. Typical outlet concentrations from 5 to 25 mg/l
Small footprint
Infinite Turndown;
Scalable design;
Very low maintenance;
Insensitive to solids / scale formation
Insensitive to vessel motion
No requirement for adjustable internals
No moving parts inside the vessel
No fine tolerance internals which provides low sensitivity to solids and scale formation

Field Testing.

Cyclotech has a pilot scale DeepSweep^® CFU test skid that can be used to determine the DeepSweep^® polishing performance on live fluids. This test unit is rated for 7500 bpd and is available for rental over short or long term lease periods. Cyclotech can also perform a full oil drop size characterisation of the existing Produced Water Treatment as part of these performance trials.

Please contact us if :

You wish to decrease the oil content in your Produced Water discharge.
You wish to install a state of the art Produced Water Treatment system for an FPSO.
You wish to test/lease a pilot scale DeepSweep^® CFU system

Available Resources