Efficient De-oiling Technology for Coking Sulfur-Bearing Wastewater

The sulfur-bearing wastewater generated by coking units originates from multiple sources, including moisture carried in with the coal blend, wastewater from coking reactions, distilled ammonia liquor and gas condensate. Specific wastewater types include excess ammonia liquor, phenol-cyanide wastewater, dust-removal scrubbing water, gas seal liquid and desulfurization waste liquor. This acidic wastewater features complex and variable composition, large discharge volumes, high oil and salt content, significant emulsification and elevated suspended solids. Its main pollutants include coke powder, phenolic compounds, cyanides and nitrogen-, oxygen- and sulfur-containing heterocyclic compounds; overall biodegradability is poor, treatment is difficult, and the wastewater poses a significant threat to the ecological environment and human health.

In conventional treatment flows, the wastewater is usually first pretreated to improve biodegradability and then combined with biological treatment. Pretreatment options include stripping, adsorption, extraction, filtration, ion exchange and coagulation, yet these methods are relatively costly to operate and prone to system blockage that prevents effluent quality from meeting requirements. There is therefore an urgent need for efficient coking acidic wastewater treatment technologies capable of deep purification and improved effluent standards.

To address the pain points of conventional processes — severe secondary pollution, fluctuating treatment efficiency and difficulty sustaining stable operation — SINOKLE has developed an acidic wastewater treatment process centered on ozone catalytic oxidation, cyclonic dissolved-air flotation and coalescing de-oiling. The flow first removes larger suspended particles through coarse filtration; the wastewater then enters the highly efficient and compact CDFU cyclonic dissolved-air flotation system, achieving stable demulsification in a purely physical manner and separating most of the suspended solids; a polishing filter then removes particulate impurities larger than 2 μm. The wastewater subsequently enters the KHC high-efficiency coalescing de-oiler, which further removes extremely fine residual oil droplets and suspended matter. Field engineering data show that this technology system can effectively remove 99% of the oil and suspended solids in refinery acidic wastewater.

The unit achieves demulsification by purely physical means, with stable and efficient performance and no chemical dosing, reducing sludge generation and the risk of secondary pollution; it is particularly effective at removing emulsified oil that conventional processes cannot treat, while also greatly reducing wastewater treatment costs. At the same time, the oil residue separated by the CDFU has a low water content and can be re-refined, avoiding waste of resources. The unit operates fully enclosed and pressurized with no risk of tail gas leakage, and its high degree of automation saves labor. The skid-mounted design allows rapid, convenient installation and flexible adjustment of the process scheme according to different influent quality and effluent standards, giving it broad application potential. Compact in structure, efficient, safe and environmentally friendly, the unit has been validated by multiple large-scale engineering cases and delivers excellent purification of coking and refinery wastewater.

Field application cases are as follows:

Figure. Coking acidic wastewater treatment site at a petrochemical company in Luoyang

Figure. Comparison of influent and effluent water samples from the coking acidic wastewater treatment project in Luoyang

Actual operation at a petrochemical company in Luoyang shows that after treatment by this process, the effluent oil content and suspended solids concentration are stably below 20 mg/L and the water is clear and transparent, meeting reuse standards. The system runs stably with strong resistance to water quality fluctuations; even under large variations in influent load it can keep the effluent continuously compliant.