SINOKLE's New Electro-Desalter Wastewater Treatment Process Replaces the Traditional Tank-in-Tank Gravity Settling Process
With environmental requirements in the refining industry becoming ever stricter, electro-desalter wastewater treatment technology is undergoing a major transformation. The "coalescer + CDFU" combination process launched by SINOKLE Technology has, with its outstanding treatment performance and environmental advantages, been progressively replacing the traditional tank-in-tank gravity settling process, bringing a completely new technical solution to the industry.
Bottlenecks of the Traditional Process
The traditional tank-in-tank gravity settling process relies mainly on the density difference between oil and water for natural separation. This passive approach has obvious limitations. When treating highly emulsified oily wastewater, separation performance is poor and the effluent compliance rate is low; moreover, most units are semi-enclosed structures, creating a risk of hazardous gases such as hydrogen sulfide and volatile phenols escaping.
A tank-in-tank unit at a petrochemical plant (2,000 t/d capacity)
The process depends on large storage tanks, requiring a large footprint and high capital and heat-tracing energy costs. Automation is limited, periodic manual tank cleaning is needed, labour intensity is high, and plugging occurs easily. More critically, it tolerates fluctuations in water quality and flow poorly, effluent stability is hard to guarantee, and it can no longer meet the strict environmental and operating-efficiency requirements of modern refineries.
Technical Breakthrough of SINOKLE's New Process
SINOKLE's "coalescer + CDFU" process adopts purely physical separation technology and achieves a major technical breakthrough through the triple combination of high-efficiency coalescence, cyclonic centrifugation and dissolved-air flotation.
Schematic flow diagram of the new electro-desalter wastewater treatment process
The coalescer uses proprietary packing to rapidly coalesce and grow oil droplets; its super-hydrophilic modified surface and enormous specific surface area effectively capture fine oil droplets (down to 0.1 µm). Subsequently, CDFU cyclonic dissolved-air flotation uses ultra-fine bubbles (5-30 µm) that adhere efficiently to oil droplets, completing rapid separation in a strong centrifugal field.
The greatest advantage of this process is purely physical demulsification with no chemical dosing, which avoids secondary pollution while recovering high-quality crude oil for direct refining. The fully enclosed, pressurised design completely eliminates the risk of waste-gas leakage, achieving genuinely safe and environmentally friendly production.
Comparison of Core Technical Advantages
| Comparison item | Tank-in-tank technology (conventional gravity settling) | SINOKLE "coalescer + CDFU cyclonic dissolved-air flotation" process |
| Separation principle and efficiency | Relies on the density difference between oil and water for gravity settling; poor separation of emulsified oil and a low effluent compliance rate. | Triple combination of high-efficiency coalescence + cyclonic centrifugation + flotation; effective demulsification, single-stage oil removal efficiency >90%, and effluent oil content can be stably reduced below 150 mg/L, even to 10 ppm. |
| Environmental performance and secondary pollution | Mostly semi-enclosed, with safety and environmental risks from hazardous gases such as hydrogen sulfide and volatile phenols escaping. | Fully enclosed pressurised operation, no waste-gas leakage. Purely physical demulsification, no chemicals, no oily sludge (hazardous waste) generated, and the recovered oil is of high quality and can be refined directly. |
| Footprint and civil works | Depends on large storage tanks; large footprint, high capital cost and high heat-tracing energy consumption. | Compact, skid-mounted equipment; the footprint is only a fraction of the conventional technology and the construction period is short. |
| Operation, maintenance and automation | Low degree of automation; periodic manual tank cleaning; high labour intensity and prone to fouling. | Fully automatic intelligent control enables unattended operation; no internals such as screens, strong anti-clogging capability and simple maintenance. |
| Shock resistance and stability | Poor tolerance to fluctuations in water quality and flow; unstable effluent. | Strong shock resistance, able to handle flow fluctuations of 10%-120%, with stable and reliable operation. |
In terms of oil removal efficiency: the new process achieves a single-stage oil removal efficiency of over 90% and can reduce influent oil content from ≤100,000 mg/L to ≤150 mg/L, far exceeding conventional performance. Its shock resistance is markedly enhanced, accommodating flow fluctuations of 10%-120% and ensuring effluent stability.
In terms of equipment integration: the new process uses a skid-mounted design with a footprint only a fraction of conventional equipment and a greatly shortened construction period. The fully automatic intelligent control system enables unattended operation, simple maintenance, and a service life of more than 15 years.
In terms of economic benefits: taking a refinery with 5 million tonnes per year of capacity as an example, the new process can recover 864 tonnes of crude oil annually, generating economic benefits of more than 10 million yuan while greatly reducing heavy oily-sludge disposal and wastewater treatment costs.
Successful cases demonstrate technical strength
At the Sinopec Cangzhou Branch electro-desalter wastewater treatment project, after adopting SINOKLE's process, with a capacity of 50 m³/h and an inlet oil content of ≤20,000 ppm, the effluent oil content has remained stably below 100 mg/L, with oil removal efficiency above 95%. Since commissioning in 2020, the unit has operated continuously and stably, effectively solving the problem of emulsified oil carry-over in desalter effluent.
The PetroChina Sichuan Petrochemical electro-desalter wastewater treatment project has also achieved remarkable results. With a capacity of 70 m³/h and under harsh conditions where the inlet oil content averages 10% and peaks at 40%, the effluent oil content is ≤150 ppm (averaging around 50 ppm), fully demonstrating the reliability and stability of the new process.
Technology Driving Industry Transformation
With its advanced technology and significant benefits, SINOKLE's new electro-desalter wastewater treatment process is driving technical upgrading across the industry. Compared with the traditional tank-in-tank gravity settling process, it offers clear advantages in treatment efficiency, environmental safety and operating cost, providing reliable technical support for refining enterprises pursuing a green transition.
As environmental requirements continue to tighten and pressure to save energy and reduce emissions grows, SINOKLE's "coalescer + CDFU" process is expected to become the new standard for electro-desalter wastewater treatment, leading the industry towards greater efficiency and environmental sustainability.
