A New Process for Electrostatic Desalting Oily Wastewater: Application of High-Efficiency Cyclonic Flotation Technology
With crude oil sources becoming more diversified and quality becoming heavier and poorer, refineries often blend recovered heavy dirty oil into the mixed feed. Although this raises utilization, it causes severe crude oil emulsification and greatly impacts the electric desalting unit. Equipment aging, overload and improper operation often lead to poor demulsification and unstable interface levels, resulting in excessive oil in the effluent — impacting downstream wastewater treatment and wasting crude oil.
The characteristics of desalting wastewater make it extremely difficult to treat: high heavy oil content with a density close to that of the wastewater makes separation difficult; high oil content (over 20%) with fine, severely emulsified oil droplets; large amounts of fine suspended solids that aggravate emulsification and corrode and clog equipment; high salinity and high mineralization that accelerate corrosion and scaling and produce dangerous gases such as sulfides and volatile phenols, threatening health and the environment.
Traditional gravity settling gives unstable results; cyclonic centrifugal separation has higher efficiency but high energy consumption and requires chemicals. Existing technologies struggle to meet the requirements: the high and volatile oil content demands strong shock resistance; severe emulsification makes physical demulsification the core technical bottleneck (chemical methods are unreliable); the oil and water densities are close, so separation by density difference alone performs poorly; strong corrosion, easy scaling and grit content require strong anti-clogging and desanding capability.
To address these difficulties, we have developed a new high-efficiency process for desalting wastewater treatment:
Desalting wastewater treatment process flow diagram
Preliminary separation:After heat exchange and cooling, the oily wastewater enters the high-efficiency coalescing oil-water separator. Floating oil, dispersed oil and part of the emulsified oil quickly gather and coalesce into large oil masses, which separate into the oil collection pocket.
Coalescing oil-water separator unit on site
Advanced demulsification and oil removal:The wastewater after preliminary separation (containing large amounts of emulsified oil) enters the high-efficiency cyclonic dissolved air flotation unit, the CDFU. The emulsified oil is captured by ultrafine bubbles, and under the cyclonic action it gathers, coalesces, demulsifies and forms oil masses that separate out. The treated wastewater (oil content <100 mg/L) is discharged into the sewage treatment plant pipe network.
Desalting wastewater treatment project example (left: effluent, right: influent)
Core advantages of the new process:
Innovative separation mechanism:Breaking through the limitation of relying solely on the oil-water density difference, it comprehensively utilizes the gas-water and oil-gas-water density differences; the oil removal effect is basically unaffected by the density of the dirty oil, and efficiency is greatly improved.
High efficiency and stability:Using a high-efficiency coalescing/inclined-plate pressure oil remover and a compact dissolved air flotation unit (CDFUCDFU), it offers high separation efficiency, strong shock resistance, clog resistance and low energy consumption (working pressure <0.15 MPa).
Reliable operation:Even with drastic fluctuations in influent oil content, the effluent quality remains consistently stable and compliant (oil <100 mg/L).
Automation and safety:Fully enclosed automatic control operation reduces labor and maintenance costs, prevents the leakage of dangerous gases, and safeguards personnel health and environmental safety.
Economic efficiency:The equipment offers high cost performance, bringing significant economic and social benefits to the enterprise.
