Refinery Wastewater Treatment Process Flow: Pretreatment Plus Advanced Oil Removal
Refinery wastewater, with its high oil content, complex composition and abundance of refractory organics, has long been a focus and a difficulty in industrial wastewater treatment. SINOKLE Technology Co., Ltd. has relied on its independently developed CDFU cyclonic dissolved gas flotation, CDOF ozone catalytic oxidation and other core technologies to build a highly efficient, green and resource-recovering refinery wastewater treatment process system.
1. Core process flow
The SINOKLE refinery wastewater process consists of two stages: pretreatment and advanced oil removal.
Pretreatment uses a coalescing pressure oil separator for coarse-graining separation, quickly removing dispersed oil droplets larger than 30 μm with oil removal efficiency above 90%. The unit integrates cyclonic pre-separation and an automatic sand-washing system, giving strong anti-clogging capability and tolerance of high-oil shock loads.
The core equipment in the advanced oil removal stage is the CDFU cyclonic dissolved gas flotation unit, which generates 5-30 μm micro-bubbles to separate emulsified oil efficiently. Its purely physical demulsification needs no chemicals; effluent oil content is held stably below 10 ppm and suspended solids removal exceeds 85%. The unit operates fully enclosed under pressure, with a single-stage retention time of no more than 5 minutes and a footprint only one third that of conventional flotation.
Figure 1. Process flow diagram for electric desalting effluent treatment
2. Technical highlights
Green and resource-recovering: the whole train uses purely physical separation, the recovered oil is of high quality and can be returned directly to refining, and no oily sludge (hazardous waste) is generated, achieving both pollution control and resource recovery.
Efficient and stable: CDFU the technology removes more than 98% of suspended solids above 2 μm and tolerates flow fluctuations of up to 50%. At PetroChina's Dushanzi Petrochemical project, inlet oil content of ≤2000 ppm was reduced to ≤10 ppm, a marked improvement in oil removal.
Smart and compact: skid-mounted design cuts the footprint by 30%-50% and supports online installation. A fully automatic control system enables unattended operation and reduces O&M costs by more than 50%.
3. Typical applications
At Sinopec Cangzhou Petrochemical's electric desalting wastewater project, SINOKLE applied a "coalescing pressure oil separator + CDFU " combined process at a capacity of 50 m³/h; effluent oil content fell from >20,000 mg/L to 35 mg/L, and the equipment footprint is only 16.5 m × 2.2 m.
Figure 2. Cangzhou Petrochemical electric desalting wastewater project
For oil depot draw-off water, the SINOKLE process reduces inlet oil content of ≤3000 mg/L to ≤5 mg/L and suspended solids from ≤300 mg/L to ≤20 mg/L, fully resolving the discharge problem at oil depots.
Figure 3. Crude oil tank farm draw-off water project at a petrochemical site in Sichuan
4. Outlook
As environmental requirements tighten, SINOKLE's purely physical separation technology offers refineries a practical route to green transformation. Its modular and intelligent features suit both revamps and new builds: it achieves compliant discharge while creating economic value through recovered oil. The technology is expected to be applied more widely across refining and petrochemical enterprises, supporting the industry's sustainable development.
