Coalescence Oil Removal + CDFU Process Package: How Pure Physical Equipment Cuts Desalting Wastewater from 250,000 mg/L Inlet to 150 mg/L Outlet

For the treatment of electric-desalting wastewater,"the ceiling --"how high can it go? The answer from this project in Weifang, Shandong, is: an inlet oil content of250000mg/L, and an outlet oil content of<150mg/L. Note: zero chemical agents throughout. The project was undertaken by Shenzhen SINOKLE Technology, and its core weapons are the"coalescence pressure oil remover+ CDFUand cyclonic dissolved-air flotation unit,"a combined process.

Today we won't discuss industry trends; we'll purely take apart the principles of this process package.

Stage One: Coalescence Pressure Oil Remover——The engineering of physical coalescence

Coalescence oil removal is not a new concept. The principle, in one sentence: let tiny oil droplets collide, adsorb, and coalesce as they flow through a specific medium, forming large oil masses that naturally float up and separate by density difference. It sounds simple, but engineering implementation has three difficulties:

First is the coalescence medium. The efficiency of oil-droplet collision and coalescence depends on the surface energy, porosity, and wettability of the medium. Under an oil content of250,000 mg/Lmg/L, the medium faces a serious risk of oil-fouling clogging, so material selection must balance oleophilic coalescence capability and anti-fouling regeneration performance.

Second is the flow-channel design. If the flow velocity is too high, oil droplets are washed away before they can collide; if it is too low, treatment efficiency cannot be raised. The coalescence pressure oil remover operates inside a closed pressure vessel and, by precisely controlling the flow-channel cross-section and residence time, achieves a stable coalescence effect at30m³/hthe given throughput.

Third is oil-water separation. After large oil masses form, phase separation must be completed inside the equipment:——the oil floats up to the oil-collection zone at the top and is discharged, while the water flows out from the bottom into the next stage. This step is completed inside the pressure vessel, avoiding the volatileVOCsescape caused by open, atmospheric-pressure operation.

The oil content of the Stage-One effluent has already been greatly reduced from the original250,000 mg/Lmg/Llevel, but the residual emulsified oil and suspended solids still need the second stage to deal with them.

Stage Two:CDFUCyclonic Dissolved-Air Flotation——Four technologies in a single unit

CDFUIts full name isCyclonic Dissolved Gas Flotation Unit, a SINOKLE patented product and China's first new-generation, high-efficiency, compact, closed, pressurized flotation technology. This equipment integrates four separation technologies into one skid-mounted tank body:

① Ultra-fine bubble generation technology

The bubble diameter of traditional dissolved-air flotation is in the30-100μmrange,CDFUwhereas this technology produces bubbles at the level of a few microns to a dozen or so microns. The smaller the bubble, the larger the specific surface area:——for the same volume of gas, the adhesion area of micro-bubbles is tens of times that of large bubbles. More importantly, micron-scale bubbles have a stronger ability to capture emulsified oil droplets whose diameters lie in the1-10μmrelevant range, which is the crux of why traditional flotation performs poorly on emulsified oil.

The path of bubble generation: under pressurized conditions, water is made to super-saturate and dissolve gas (usually nitrogen or natural gas); then pressure is instantaneously released through a special releaser, and the dissolved gas is precipitated in large quantities in the form of micro-bubbles.

② Dissolved-air flotation

The micro-bubbles are evenly distributed in the wastewater, colliding with and adhering to residual oil droplets and suspended particles to form a composite far less dense than water,"gas-oil-solid"which quickly floats up to the liquid surface to form a scum layer. The removal of emulsified oil is the core contribution of this step.

③ Cyclonic centrifugal separation

This isCDFUthe key that distinguishes it from traditional rectangular flotation tanks. A cyclonic flow-guiding structure is designed inside the device; after the bubble-laden wastewater enters, it rotates tangentially at high speed, producing centrifugal acceleration dozens of times that of gravity. In the centrifugal force field, the least-dense flotation composite is pushed toward the center and moves upward, while the denser water is thrown toward the outer wall and moves downward,——so the three-phase separation efficiency is an order of magnitude higher than pure gravity settling, and the equipment volume is thus greatly reduced.

④ Coalescence demulsification

CDFUA coalescence module is also integrated inside; for the hardest-to-treat emulsified oil droplets, a round of demulsification and coalescence is performed before flotation. Once the interfacial film of the oil droplets is broken up, they are more easily captured by micro-bubbles.

The logic of process connection

The two stages are not simply connected in series but have a clear division of labor:

Stage One removes"the main oil load"——reducingthe 250,000 mg/Lmg/Lthe bulk of the oil, reducing the load on the second stage; Stage Two handles"water quality"——the fine removal of residual emulsified oil and suspended solids, ensuring the effluent quality.<150mg/L。

Why no chemical agents are needed

The whole process relies on physical forces: surface tension (coalescence), buoyancy (bubble adhesion), and centrifugal force (cyclonic separation). Oil and water undergo no chemical change from start to finish;——they are merely"separated"by physical means. Therefore, no chemical sludge is produced, and the separated oil retains its properties and can be directly recovered.

The engineering significance of skid-mounting

The entire device is made into a skid-mounted module, assembled and commissioned before leaving the factory; on site, it only needs to be connected to the inlet/outlet pipelines and power supply to be put into use.30m³/hAt the given throughput, the entire equipment group occupies only a few dozen square meters. In the land-scarce process areas of petrochemical plants, this is a real, tangible advantage.

The delivery time of this project in Shandong was2025. Going from an inlet ofhundreds of thousands down to an outlet of150mg/L，99.9%, the oil-removal efficiency was achieved not by"piling on chemical dosing,"but by the engineering precision of physical principles.