Innovation and Practice in Coking Sour Wastewater Treatment

Coking sour wastewater is a difficult effluent generated when refineries process sour crude; it contains complex pollutants such as sulfides, ammonia nitrogen, phenols, cyanides and high concentrations of oil. Highly toxic and complex in composition, it causes high energy consumption, low efficiency and secondary pollution in conventional processes, so innovative solutions are urgently needed.

Technical difficulties and challenges

Coking sour wastewater treatment faces multiple challenges: highly concentrated emulsified oil is very stable and the fine coke particles are hard to separate; sulfides and ammonia nitrogen volatilise readily, producing toxic gases; and large pollutant fluctuations demand high shock resistance from the system. Conventional gravity settling needs 50–70 hours of residence time and carries a risk of gas leakage; cyclonic processes are of limited effectiveness on emulsified oil; and membrane technology, though precise, plugs easily and is costly.

Innovative breakthrough

SINOKLE’s CDFU (cyclonic dissolved-air flotation) technology breaks through conventional limits by integrating cyclonic centrifugal separation, ultra-fine bubble generation and dissolved-air flotation in a sealed pressure vessel. By generating 5–30 μm ultra-fine bubbles it achieves efficient oil-water separation within a residence time of less than 5 minutes, with oil removal above 90% and suspended solids removal above 80%. The matching KHC coalescing oil separator uses super-oleophilic hydrophobic fibre media and combines cyclonic centrifugation with coalescence to remove emulsified oil thoroughly.

Process advantages

The technology system has clear advantages: purely physical separation needs no chemicals and the recovered light oily waste can be reused directly; sealed pressurised operation prevents leakage of hydrogen sulfide and other gases; the skid-mounted design needs only 1/3 of the conventional footprint; and fully automatic control enables unattended operation. Compared with conventional processes, energy consumption is more than 30% lower and hazardous waste generation is cut by 2/3, truly delivering both environmental and economic benefits.

SINOKLE emulsified sour water treatment process

Application case

In a project for a Sinopec petrochemical company in Henan, coking sour wastewater with an inlet oil content as high as 150,000 ppm was treated by a combined process of “CDFU + KHC high-efficiency coalescing oil separator”, keeping effluent oil content stably below 100 ppm at a throughput of 15 m³/h. The unit has strong shock resistance, successfully coped with water quality fluctuations, and delivers effluent better than industry standards.

Coking sour wastewater treatment case at a petrochemical enterprise in Henan

Future prospects

The technology offers a reliable path for the green transition of the refining and chemical industry: its modular design makes upgrading existing units easy, and the intelligent control system enables precise operation and maintenance. As environmental requirements tighten, this efficient, energy-saving and safe technology will play a growing role in more difficult wastewater treatment scenarios.