What Does a Refinery's Toughest Wastewater Look Like? Inside a 15 m³/h Coking Sour Water Treatment Site
Anyone who has worked on refinery wastewater knows that coking sour water is not to be trifled with.
As a refinery's coking unit produces petroleum coke, it generates a stream of highly concentrated oily wastewater ———coking sour water. This water has three properties that give engineers headaches. First, the oil content is extremely high, routinely well over a hundred thousand milligrams per litre; the inlet oil specification at Sinopec Luoyang Petrochemical is≤150000mg/L. What does that mean in practice? Close to half of a bottle of that water would be oil. Second, emulsification is severe — the oil and water are churned together as stubbornly as sesame paste. Third, water quality swings widely: adjust the unit's operating conditions and the incoming water changes character.
How do conventional processes handle it? Essentially gravity settling tanks plus dissolved-air flotation, then filtration. That works well enough on wastewater carrying 30,000–50,000 mg/L of oil, but faced with coking sour water in the hundred-thousand class, nothing settles, nothing floats, and cartridges blind at speed. Many plants can only fall back on large basins and long quiescent periods — a big footprint, low efficiency, and outright failure under shock loads. Worse still, effluent oil content often sits at several hundred or even over a thousandmg/L, leaving the downstream biological system smothered in oil and barely functioning.
Environmental professionals in the petrochemical sector privately agree: coking sour water is the hardest category to handle in the whole spectrum of refinery wastewater.
SINOKLE's New Process: Multi-Stage Combination, Step-by-Step Oil Reduction
Rather than taking the"single-unit breakthrough"route, SINOKLE designed amulti-stage combination processtailored to the characteristics of coking sour water. The core logic is simple: let each step do what it does best and strip the oil out stage by stage.
The process chain runs like this:coarse filter → CDFUhigh-efficiency compact cyclonic flotation→ fine filter→ KHChigh-efficiency coalescing oil-water separator. Four gates, each taking its cut, bringing final effluent oil content down below 100mg/L .
Let us walk through these core units one by one.
The coarse filter——leads the charge. Large-particle impurities, lumps of oily sludge and silt in the incoming water are stopped here first. This step looks unremarkable, but it is essentially"taking the bullet"for the precision equipment downstream. Without this barrier, the cyclonic flotation unit and fine filter behind it simply could not cope.
CDFUThe high-efficiency compact cyclonic flotation unit——is the"workhorse"of the whole line. Conventional dissolved-air flotation basins routinely take up tens of square metres, whereas theCDFUfuses cyclonic separation with dissolved-air flotation for a small footprint and high treatment efficiency. Water arriving with more than a hundred thousand mg/L of oil enters theCDFU, where the cyclonic force field first throws out most of the free oil and microbubbles then lift the remaining dispersed and emulsified oil to the surface. One unit does the work of two, pulling oil content straight from six figures down to four or even three.
The fine filter——handles the"gap-filling".CDFUWater leaving the previous stage is already far lower in oil, but small amounts of suspended solids and very fine droplets remain. The fine filter intercepts them with high-precision cartridges. The key here is getting cartridge rating and material right: too fine and it blinds easily, too coarse and it does not catch enough. SINOKLE's selection criteria and operating parameters in this area distil years of project experience.
KHCThe high-efficiency coalescing oil-water separator——closes the sequence. Coalescing separation works by merging micron-scale droplets in the water into large droplets and then separating them on the density difference.KHCThe coalescing packing is SINOKLE's own development, an order of magnitude more efficient at separation than conventional corrugated plates.CDFUThe"stubborn holdouts"left in the water after flotation and fine filtration are essentially cleaned up by the time they reach theKHC, and effluent oil content settles firmly below100mg/L .
Stringing four units together is not simply a matter of"1+1+1+1"; the selection and parameters of every step are matched specifically to the oil characteristics, degree of emulsification and flow variability of coking sour water. This is exactly what pure equipment vendors cannot do ———you have to have spent real time on petrochemical sites and made the mistakes yourself to know how to break that"cream-like"emulsion layer in sour water.
Real-World Results at Luoyang Petrochemical
The client is Sinopec Luoyang Petrochemical Company, with a treatment capacity of 15m³/h,the plant was delivered and entered operation.
Inlet oil content ≤150000mg/L, outlet oil content<100mg/L, oil removal efficiency above99.9%.
These are figures you can state with confidence in the field of coking sour water treatment.15 0,000 mg/L down to below, an absolute drop of three orders of magnitude. And these are not pretty numbers from a laboratory bench test; they are the real performance of more than three years of continuous industrial operation.
Luoyang Petrochemical is a major refining base in central China and has always held a tight line on environmental indicators. That this unit passed the client's acceptance and has run steadily ever since is more persuasive than any parameter in a brochure.
What This Project Means
For Luoyang Petrochemical, coking sour water is no longer a bottleneck"dragging environmental compliance down". Treated water meets standards consistently, the biological system runs more reliably, and the operations crew has one less nerve-wracking monitoring point on the night shift.
For SINOKLE, the project carries even greater weight.
First, it concretely validated the technical feasibility of SINOKLE's combined process on coking sour water,——the ceiling of difficulty among petrochemical wastewaters——. From equipment design to process parameters to on-site commissioning, the full loop has been closed.
Second, the benchmark effect within the Sinopec system speaks for itself. The results at Luoyang Petrochemical are a solid calling card in the central China petrochemical market and across the national petrochemical system. In later conversations with sister plants such as Jiujiang Petrochemical, Anqing Petrochemical and Wuhan Petrochemical, there is no need to labour the question of"whether your technology is up to it"; you simply say"the Luoyang project was ours"and that is enough.
Third,15m³/h is neither large nor small — it is exactly the size for a replicable modular solution. Scale up by running multiple modules in parallel to reach30m³/h,45m³/h, or scale down to5-10m³/h to meet the needs of smaller refineries. That flexible granularity is a genuine plus for market expansion going forward.
