Treatment Challenges of Highly Emulsified Sour Water (Coking / Atmospheric and Vacuum Overhead) and a Pure-Physical Demulsification Approach
In the refining and chemical industry, the sour water (generally wastewater containing sulfur, ammonia, and phenol) generated by units such as delayed coking and vacuum distillation is a recognized treatment problem. Especially when it is rich in emulsified oil and coke fines, it not only imposes a heavy burden on the wastewater treatment system but also causes severe scaling and blockage of key downstream equipment such as strippers, threatening the plant's safe, stable, long-term, full-capacity, and optimal operation. This article deeply analyzes this industry pain point and explains howCDFUthe pure-physical synergistic process centered on swirl dissolved-air flotation and the KHC high-precision coalescing separator provides an efficient, economical, and green breakthrough path.
1.In-depth analysis of industry pain points: the 'emulsified oil + coke fines' combination
In traditional thinking, the core of sour water treatment lies in desulfurization and deammoniation. However, a growing number of field cases show that the emulsified oil and suspended solids (especially extremely fine coke fines) in the waterare the 'invisible killers' that cause system paralysis. Together they form a difficult-to-treat stable system:
Highly emulsified and stably present:Under surfactants and process conditions, oil forms in water an extremely small particle-size (usually0.1-10 um) 'oil-in-water' emulsion that is extremely stable. Traditional gravity settling and even ordinary flotation are almost ineffective against it.
Coke-fine doping aggravates the harm:The coke fines from coking units are tiny in size and easily wrap around and adsorb onto emulsified oil droplets, forming a more complex 'oil-solid' composite pollutant.
Fatal consequence: stripper scaling and blockage
Scaling:The emulsified oil and coke fines not effectively removed, in the high-temperature environment of the stripper, easily deposit and carbonize on the surfaces of trays, packing, and reboiler tube bundles, forming hard fouling. This causes a sharp drop in heat-transfer efficiency, increased pressure differential, and soaring energy consumption.
Blockage:Finer coke fines and polymerized oil sludge directly block the sieve holes of trays or the gaps in packing, causing stripper flooding and reduced capacity, and ultimately forcing unplanned shutdowns for maintenance, with huge economic losses.
Operating interference: high-oil, high-suspended-solids influent also seriously affects the stripper's vapor-liquid balance and desulfurization/deammoniation efficiency, leading to unqualified purified water and a vicious cycle.
2.The dilemma of traditional processes: the limitations and side effects of chemical methods
Facing such wastewater, the industry long relied on a pretreatment mode of 'large amounts of chemical demulsifier + flocculant.' Although this method has some effect, it is costly and creates new problems:
High cost:Chemical cost is a continuous operating expense, andthe dosage needs frequent adjustment with water-quality fluctuations.
Hazardous waste generation:The chemical method generates large amounts of oily chemical sludge, which is hazardous waste with expensive disposal costs and prominent environmental risks.
Oil deterioration:The waste oil recovered by chemical demulsification has high water and impurity content, poor quality, is difficult to directly re-refine, and has low resource value.
Fragile system:It has poor adaptability to changes in emulsification degree, unstable effluent quality, and cannot provide stable, high-quality influent assurance for the downstream stripper.
3.The path to a breakthrough:CDFU+ KHC pure-physical synergy logic
The solution proposed by SINOKLE abandons the 'treating pollution with chemicals' approach and instead adoptsCDFUa pure-physical demulsification and separation path in synergy with KHC. Its core logic is 'high-efficiency coarse separation at the front end, deep fine treatment at the back end,' forming a seamlessly connected treatment chain.
1. First line of defense:CDFUSwirl dissolved-air flotation - efficiently removes most oil and suspended solids
CDFUThe unit integrates swirl centrifugal separation and ultra-fine-bubble dissolved-air flotation. Its workflow is as follows:
Swirl pre-concentration:Wastewater enters the unit tangentially, forming a strong swirl field; under centrifugal force, heavy coke fines and large particles are flung to the wall, while oil droplets are enriched at the swirl center.
Ultra-fine bubble capture:The system generates a large number of bubbles with a diameter of5-30 um (D50 about 25 um). These bubbles efficiently collide and adhere with the enriched oil droplets and fine particles in the swirl field.
Rapid separation:After the 'bubble-oil droplet' complex forms, it rapidly floats to the liquid surface under buoyancy and is skimmed off; the hydraulic retention time is as short as 1-5 minutes.
Technical advantages:
High oil-removal rate:Single-stage removal rate for free oil >=99%, for emulsified oil 80-90%, and for suspended solids >85%.
Zero chemical addition:A pure physical process that eliminates chemical sludge generation at the source.
Strong shock resistance:It can adapt to influent quality fluctuations and provide stable pretreated effluent for the back end.
2. Second line of defense: KHC high-precision coalescing separator - deeply resolves residual emulsified oil
AfterCDFUtreatment, a small amount of extremely stubborn fine emulsified oil droplets (<10 um) may still remain in the water. This is exactly where the KHC comes into play. The KHC uses coalescing filter elements made of special fiber material; its core principle is 'coalescence and growth':
When fine oil droplets pass through the filter element, they are captured by its super-oleophilic and hydrophobic fiber material.
Numerous captured oil droplets continuously accumulate and merge on the filter surface, gradually growing into large oil droplets large enough to overcome the water-flow shear force.
The large oil droplets finally detach from the filter surface and rapidly float and separate by their density difference with water, thus achieving deep oil removal.
Technical advantages:
Extremely high precision:Emulsified oil removal precision can reach0.1 um, and effluent oil content can be stably below 10 ppm (and free of dissolved oil).
High flux and long life:Single-element processing capacity reaches10 m3/h, and the filter-element life is 2-5 times that of a traditional coalescing element.
Anti-fouling: excellent chemical compatibility, not failing due to the presence of surfactants, ensuring long-term online operation.
4. Synergistic value:The system benefit of 1+1>2
“CDFU+ KHC' combination is not a simple superposition but a synergy designed based on pollutant characteristics:
Ensuring long-term stripper operation:This process can stably produce low-oil-content (down to10 ppm level), low-suspended-solids high-quality influent, fundamentally cutting off the material source of stripper scaling and blockage and extending its operating cycle.
Recovering high-quality waste oil:The oil recovered by physical separation is of high purity, with low water and impurity content, and can be directly returned to the crude oil tank farm for re-refining, realizing resource value.
Greatly reduced operating costs:Completely eliminating the cost of expensive demulsifiers and flocculants as well as hazardous sludge disposal; the equipment has a high degree of automation and low O&M labor cost.
Safe, environmentally friendly, and free of secondary pollution:The whole process runs enclosed and pressurized with no waste-gas escape; being purely physical, it produces no new chemical pollution.
5.Practice verification and conclusion
This synergistic process has been successfully applied in several petrochemical enterprises.
In summary, the treatment of highly emulsified sour water (coking/ atmospheric and vacuum overhead) in refineries lies in precisely breaking the stable 'emulsified oil + coke fines' system. SINOKLE'sCDFUswirl dissolved-air flotation and KHC high-precision coalescing separator provide a pure-physical synergistic path that is not only technologically advanced and reliably effective, but also, through source reduction and resource recovery, transforms environmental investment into economic benefit, providing solid technical support for the green, low-carbon, and high-quality development of the refining and chemical industry.
