No Chemicals, No Sludge: How CDFU and KHC Strip Emulsified Oil From the Toughest Industrial Wastewater

Emulsified oil is the stubborn end of industrial oily wastewater. Conventional treatment throws large chemical doses at it, which inflates operating cost and manufactures secondary pollution in the form of scum and sludge. The chemical-free emulsified oil removal process developed by SINOKLE takes the opposite position: no dosing at all, and separation that outperforms the dosed processes anyway.

Two patented units, one purely physical chain

The core of the process is CDFU (cyclonic dissolved air flotation), which combines cyclonic separation, dissolved air flotation and catalytic oxidation in a single vessel. Micro and nano bubbles generated on board attach to oil droplets and carry them out under strong centrifugal force, and a single unit handles up to 500 m³/h with oil removal above 90%. Because the whole separation is physical, nothing is added to the water and nothing new is created downstream. The KHC coalescing oil-water separator works the other end of the problem. Super-oleophilic, hydrophobic coalescing fibre materials and internal structures integrate cyclonic centrifugal separation, wetting coalescence, collision coalescence and interception filtration, pulling emulsified oil droplets larger than 0.1 μm out of the stream while shrugging off impurities and stripping suspended solids. Its adaptability is the point: complex water quality does not move its performance envelope much.

Laboratory bottle tests confirm what the field record shows. A representative emulsion held for hours barely separates under gravity, yet the same sample processed through a coalescing element and a flotation stage loses the bulk of its oil in minutes, which is the difference between designing around droplet size and designing around droplet density.

What the numbers say on hard water

Highly emulsified acidic water from refining is the traditional graveyard of settling processes. Conventional gravity settling asks for 50-70 hours of residence; the SINOKLE chain reaches efficient separation after treatment measured in minutes. On one coking acidic wastewater project at a refinery the influent oil content hit 160,000 mg/L, and the effluent fell away sharply after treatment, which is about as direct a demonstration of emulsified-water capability as the industry offers.

Emulsified oil earns its reputation in the way it forms. Refinery and petrochemical processes shear oil into the water phase, surfactants stabilise the droplets, and pH excursions harden the interface further, so the oil arrives not as a separate phase but as a stabilized dispersion measured in microns. Dosing chemicals destabilises that dispersion by brute force, but the dose scales with the emulsion and the byproducts scale with the dose. A physical train sidesteps the chemistry: it grows droplets by coalescence and lifts them by flotation, so the operating cost does not rise every time the crude slate or the corrosion programme changes.

Head to head against conventional technology

Put the two approaches on one page and the gaps are specific. Oil removal: the conventional CFU manages 60%-80%, while CDFU exceeds 90%. Suspended solids: conventional units reach 50%-70%, CDFU better than 80%. Fine particles: conventional equipment stops at particles above 5 μm, CDFU handles those above 3 μm. Add the chemistry difference, conventional dosing that produces large scum volumes and weak removal of emulsified oil and fine solids, versus a purely physical train with little scum and high removal rates across the board, and the comparison stops being close. The environmental ledger matters as much as the efficiency one: chemical-free demulsification recovers high-quality, high-concentration crude oil without generating hazardous oily sludge, converting a disposal liability into saleable product.

Retrofitting considerations favour this architecture too. The skid units occupy a fraction of the plot space a settler needs, they connect into an existing flow without long outages, and because no chemicals are dosed there is no reagent logistics chain to maintain. For plants whose conventional CFU capacity is already committed, adding a CDFU stage in parallel or in series is the cheapest route to tighter effluent oil limits.

Where it has been proven

The process has accumulated results across oilfield produced-fluid treatment, comprehensive oily waste liquid handling in oilfield production, and refinery oily wastewater. Two cases bracket the range. At a back-pressure cogeneration project in Shaanxi Province, a filter plus KHC coalescing oil separator train treated power-plant wastewater carrying oil as high as 500,000 ppm and brought the effluent below 5 ppm, a removal rate over 99%. The heavy-oil power plant in Sierra Leone runs a three-stage CDFU+CDFU+KFM chain: influent oil under 50 mg/L and suspended solids under 80 mg/L emerge as oil below 10 mg/L and suspended solids below 20 mg/L, every indicator on spec. Writing the numbers out, the chain takes <50 mg/L oil and <80 mg/L solids in, and delivers <10 mg/L and <20 mg/L out, which is the kind of margin that lets a plant stop worrying about excursions.

As discharge requirements tighten and industrial wastewater grows more awkward, the direction of travel is clear: purely physical separation, high removal rates, low operating cost and no secondary pollution. For emulsified oil in particular, the chemical-dosing era is ending, and SINOKLE equipment is ending it.