From Ammonia Liquor to Reuse Water: Reworking Coking Acidic Wastewater With CDFU and KHC

Coking plants do not produce one acidic wastewater — they produce several, and most of them end up in the same pipe. The sulfur-bearing wastewater generated by coking units originates from moisture carried in with the coal blend, wastewater from coking reactions, distilled ammonia liquor and gas condensate. Specific streams include excess ammonia liquor, phenol-cyanide wastewater, dust-removal scrubbing water, gas seal liquid and desulfurization waste liquor. Each has its own character; together they make a feed few single processes can handle.

A pollutant profile that resists biology

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 if released under-treated.

The mixture is what makes it stubborn. Coke powder provides surface area that stabilises oil films; phenolics and cyanides poison the microorganisms biological stages depend on; heterocyclic compounds resist the hydrolysis steps that would otherwise open them up. Remove the oil and solids first and the biological train gets a fighting chance — which is precisely the design logic behind the flow that follows.

What the conventional route costs

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 — technologies that neither choke up nor drift out of compliance between maintenance windows.

The SINOKLE flow, stage by stage

Addressing 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 centred on ozone catalytic oxidation, cyclonic dissolved-air flotation and coalescing de-oiling:

• Coarse filtration first removes larger suspended particles.
• 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 — a figure that matters because those two parameters are what clog, foul and destabilise everything downstream.

Note what the sequence is doing. Coarse filtration takes out the particles large enough to blind equipment on contact; the CDFU handles the bulk demulsification load physically, without reagents; the 2 μm polishing filter sets a hard ceiling on particle size entering the final stage; and the KHC coalescing de-oiler catches the fine droplets flotation leaves behind. Each stage hands the next one a narrower job, which is why the system holds its removal efficiency across feed swings instead of collapsing the moment the influent shifts.

Why operations teams like it

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 the emulsified oil that conventional processes cannot treat, while also greatly reducing wastewater treatment costs. 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 labour. 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.

Proof from Luoyang

Actual operation at a petrochemical company in Luoyang shows what the numbers look like in service. After treatment by this process, the effluent oil content and suspended solids concentration run 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 keeps the effluent continuously compliant. For coking operators balancing environmental limits against operating budgets, a physical train that delivers reuse-grade water from the industry's most difficult acidic streams is a persuasive proposition — and one that has been running long enough to be judged on history rather than promises.