Tackling Desalter Wastewater: High Oil Content and Complex Emulsification

Oily wastewater from the desalting stage is complex in composition and difficult to treat, a common challenge for refinery water treatment. The main difficulties fall into three areas.

Core treatment difficulties

• Extremely high oil content: oil concentration in the wastewater typically ranges from 200 to 10,000 mg/L, can jump above 10% under abnormal operating conditions and may even reach 50% in extreme cases, creating a huge shock load on the treatment system.

• Complex oil sources: crude oil being processed may come from many domestic and overseas oilfields and include light oil, heavy oil, condensate and other types, together with large amounts of non-hydrocarbon compounds, with marked differences in properties.

• Stable emulsion layer: the various chemicals added during production (paraffin and scale inhibitors, demulsifiers and so on) leave the crude oil in an extremely stable emulsified state, so that oil and water cannot be separated by conventional settling.

Innovative technical solutions

For these stubborn difficulties the industry has developed efficient physical solutions.

High-efficiency coalescing pressure oil removal. A distinctive bidirectional flow path design with CFD-optimised flow field markedly improves oil-water separation efficiency. The unit is compact, safe in operation and easy to handle.

Cyclonic dissolved gas flotation. This innovatively combines cyclonic centrifugal separation with dissolved gas flotation, and offers high separation efficiency, a small footprint and strong operating stability. It is particularly suited to emulsified oily wastewater that is difficult to treat.

The coordinated application of these core technologies provides a reliable route to breaking the bottleneck in desalting wastewater treatment.