Power Plant Oily Wastewater: Why Conventional Treatment Fails and How KHC Coalescing Technology Delivers
A thermal power station - coal-fired, oil-fired, gas-fired, waste-heat recovery, or even burning waste and industrial byproducts - converts chemical energy into electricity through a familiar chain: fuel combustion heats water into steam, steam pressure spins the turbine, and the turbine drives the generator. What the textbook diagrams rarely show is the water side of that chain. Alongside flue gas, daily operation produces a steady stream of oily wastewater, and its sources are scattered across the whole plant.
Where the Oil in Power Plant Water Actually Comes From
Four sources dominate. Fuel storage tanks need cleaning water on a regular cycle. Oil pumps and pipelines leak, and their flushing water carries free oil into the drains. The coal handling system mixes lubricating grease into water as coal is conveyed and sprayed. And auxiliary areas - pump houses, motor pumps and metering units - discharge their own oily sewage. Each stream looks minor on its own; collected together they form a wastewater that is genuinely awkward to handle.
The awkwardness has four faces. Crude oil arrives as both heavy oil and light oil, so no single separation mechanism catches everything. The treatment volume is small, which rules out regeneration-based processes that only pay off at scale. A certain amount of the oil is emulsified, and settling - the workhorse of primary treatment - barely touches it. Coal-washing wastewater adds its own twist: low oil content, many suspended solids and a large amount of residue.
Oil concentrations of only a few hundred milligrams per liter sound harmless. They are not. Disposed of improperly, this water lands on the downstream wastewater treatment system as a serious shock load, greatly affecting the stability of the treatment process and the final discharge compliance rate.
Three Conventional Routes and Where Each One Stalls
Plant designers currently reach for three options. The first is a composite settling tank plus a high-definition filter. This route relies mainly on chemicals and settling to remove oil and suspended solids, and its weaknesses show quickly: a large footprint with high land and infrastructure costs, poor adaptability to working conditions and especially weak shock resistance, low automation, oil that is difficult to recover, periodic manual tank cleaning, and safety and environmental hazards that come with difficult operation.
The second combines an oil separation tank, a flotation tank and filtration. Conventional flotation tanks used in this process cannot remove emulsified, high-density oil droplets, so treatment performance is poor exactly where the wastewater is hardest. Under conditions with high and highly fluctuating oil content, the effluent carries oil and stays unstable; the insignificant flotation effect then lets solids slip through and easily clogs the filter. The footprint problem repeats here, with the same land and infrastructure costs.
The third is a plain oil-water separator. Because the densities of oil and water are close, gravity separation alone cannot meet effluent requirements. Resistance to fluctuation is poor and effluent is unstable, the residence time is long, the footprint is large, and conventional packing gives poor coalescence performance before clogging.
The SINOKLE Answer: a KHC-Based Train for Light-Oil Tank Areas
To solve oily wastewater treatment in thermal power plants, SINOKLE combined its core patented products such as the KHC coalescing oil remover into a process scheme for light-oil tank areas, tailored to the characteristics of different types of thermal power plant wastewater. The flow is short and mainly physical, with stable performance and little oily sludge - an environmentally friendly technology. It runs fully automatically in an enclosed mode with a small footprint, needs little labor and maintenance, and incorporates multiple domestically leading patented technologies.
The reference case comes from Shaanxi Province. In March 2024, the oily wastewater treatment system custom-built by SINOKLE for a large combined heat and power project there was successfully commissioned. Testing showed that effluent quality steadily met the design standards and achieved the expected treatment results. The project paired SINOKLE custom filters with a high-efficiency coalescing pressure oil remover at a design treatment capacity of 10 cubic meters per hour: the wastewater first passes through the filter to remove suspended solids and waste residue, then enters the high-efficiency oil remover for deep oil-water separation, and the final effluent is clear and transparent, complying with relevant national discharge standards.
Inside the High-Efficiency Coalescing Pressure Oil Remover
The vessel is a patented product of SINOKLE. It applies the coarse-graining principle and the shallow-tank principle, with CFD simulation tools used to optimize the internal space and structure of the vessel and arrange the internal flow field rationally, so that oil droplets or suspended solids quickly gather, coalesce, float or sink, and separate in the water. The interior consists of an inlet pre-separation zone built from specially designed swirl separation devices, followed by initial and main separation zones filled with coalescing packing of different specifications. An oil collecting sump is provided at the top of the vessel, and an efficient sand-flushing and desilting device is installed at the bottom.
Four practical advantages follow from this layout. The structure is compact with a small footprint, and oil removal efficiency is above 90%. The internal packing adopts a patented structural design made of stainless steel or reinforced PP, combining high strength with long service life. The specially designed sand-flushing and desilting device keeps the packing from clogging and the equipment from silting up, allowing long-term stable operation and reducing maintenance work. And because the oil remover runs fully enclosed and pressurized automatically, operation stays stable, safe and reliable, with no safety or environmental risks.
Numerous successful applications at home and abroad back this record: the SINOKLE process for thermal power stations operates stably and reliably, equipment service life is long, oil removal efficiency stays high, and wastewater treatment results remain continuously compliant - which is exactly what power station wastewater management needs.