Desalter Draw-Off Water: A CDFU-Based Physical Train That Holds Effluent Oil Below 100 mg/L

Atmospheric-vacuum desalting units produce a draw-off stream that refining engineers know well and rarely enjoy. The oil content is high and it swings, resins and asphaltenes are present in quantity, the emulsion runs deep, and the density difference between oil and water is small enough that gravity alone barely gets the job done. Conventional treatment tends to be costly without being reliable, and the symptoms show up downstream: oil exceedances in the feed to the wastewater plant, unstable compliance, and a long train that eats floor space.

What the SINOKLE Route Does

The answer SINOKLE put forward pairs a high-efficiency coalescing oil remover with CDFU cyclonic dissolved-air flotation. It is a purely physical separation route requiring no chemicals, and its performance sits at an internationally advanced level. The operating promises are modest in number but useful: stable operation with consistently compliant effluent; a compact, skid-mounted footprint; closed and pressurized, fully automatic operation that is safe and environmentally sound; and - often the deciding factor - the ability to be tied in online, without halting desalter production.

Treatment Effect

• Influent oil content in the 0.5~5% range.
• Effluent oil content of <50mg/L after the train.
• Water content of recovered oil of <1%.
• Stably meets downstream influent requirements, with an oil-removal rate of 90%+.

The economic benefit is not an afterthought. The process recovers substantial quantities of high-quality crude oil, avoids generating oily hazardous waste, and cuts solid hazardous-waste treatment costs, so the environmental gain and the commercial gain arrive together.

Process Flow

Draw-off water passes first through a high-efficiency coalescing oil remover, which takes out most of the dispersed oil. It then enters CDFU, where emulsified oil and fine oil droplets are removed. The final effluent oil content stays stably below 100 mg/L, meeting the influent requirements of the downstream wastewater treatment plant. In short: coalescence separation, then cyclonic dissolved-air flotation, then compliant discharge at <100mg/L.

Six Technical Advantages

• An innovative separation principle. The route relies on gas-water and oil-gas-water density differences, so oil removal is unaffected by the density of the contaminated oil. That widens the operating envelope considerably.
• High-efficiency coalescing oil remover. High separation efficiency, strong shock resistance, low fouling tendency and low energy consumption.
• High-efficiency dissolved-air flotation. Compact structure; it removes emulsified oil without any dosing, and performance stays stable.
• High shock resistance. Even under severe swings in oil content, the unit keeps meeting standard.
• Fully automatic control. Automated, intelligent control keeps the labour cost low.
• Safe and environmentally friendly. Fully enclosed operation means no dangerous gas leakage.

Against Traditional Technology

• Separation principle: traditional physical settling or liquid-liquid centrifugation against high-efficiency coalescence plus centrifugation plus three-phase separation here.
• Emulsified oil removal: traditional technology cannot remove it; this route removes most of it.
• Oil removal effect: a low compliance rate traditionally, versus a stable compliant effluent.
• Chemical reagents: traditional treatment needs dosing and carries a high secondary-treatment cost; this is pure physical separation with no secondary cost.
• Shock resistance: poor, with unstable effluent, against good adaptability here.
• Degree of automation: low, with high operating intensity, versus intelligent advanced control.
• Anti-fouling: prone to clogging and periodic cleaning traditionally; not prone to clogging and largely maintenance-free here.
• Safety and environment: semi-enclosed with a gas-leak risk against enclosed, pressurized and safe operation.

Reference Projects

The technology has been applied across a wide range of desalting and tank-farm duties:

• CNPC Yunnan Petrochemical atmospheric-vacuum desalter oil-removal skid project - 105 m3/h - Kunming, Yunnan - 2025.
• A petrochemical enterprise in Shandong, desalter wastewater treatment project - 30 m3/h - Weifang, Shandong - 2025.
• CNPC Urumqi Petrochemical desalter and tank-farm black-water treatment - 150 m3/h - Urumqi, Xinjiang - 2023.
• China's first high-gravity extra-heavy-oil desalter wastewater treatment project - 38 m3/h - Ningbo, Zhejiang - 2022.
• CNPC Jinxi Petrochemical desalter wastewater treatment project - 50 m3/h - Jinxi, Liaoning - 2022.
• CNPC Sichuan Petrochemical desalter wastewater treatment project - 70 m3/h - Chengdu, Sichuan - 2020.
• CNPC Dushanzi Petrochemical desalter wastewater treatment project - 100 m3/h - Dushanzi, Xinjiang - 2019.
• Sinopec Cangzhou Petrochemical desalter wastewater treatment project - 50 m3/h - Cangzhou, Hebei - 2019.

Where the Value Actually Sits

Two of the advantages do the heavy lifting on cost. Removing emulsified oil without reagents eliminates a reagent store, a dosing skid and the secondary treatment that chemical breaking would demand. And because the recovered oil is saleable rather than waste, the operating cost is offset instead of simply reduced. The compliance benefit follows from the same place: when the train tolerates oil-content swings and still discharges below its limit, the plant stops treating every fluctuation as a potential event.

Reading the List

What the project list shows is a spread of capacities, refineries and water qualities rather than a single flagship site. That matters when a plant is weighing adoption, because it suggests the route is not tuned to one narrow feed. For a refinery that wants its desalter draw-off to stop being a compliance worry without shutting the unit down, a purely physical train that recovers saleable oil and needs no reagent store is a fairly attractive shape of solution.