An Innovative Solution for Treating Highly Emulsified Sour Water in Refineries

1. Technical Background

Throughout the refining and petrochemical production chain, core units such as coking fractionators, catalytic cracking and hydrocracking generate large volumes of highly emulsified sour water, one of the typical difficult-to-treat industrial wastewaters of the refining industry. Its water quality is extremely complex: it not only contains high concentrations of toxic and harmful pollutants such as H₂S, NH₃-N and volatile phenols, but also forms stable water-in-oil (W/O) or oil-in-water (O/W) emulsion systems due to the intense agitation and high-temperature, high-pressure conditions of production, with oil droplet sizes generally below 10 μm — conditions under which conventional gravity separation fails completely.

For a long time, sour water treatment in refineries has faced three major industry pain points. First, demulsification and separation are difficult: the stable emulsion structure leads to low oil-water separation efficiency and excessive oil in the effluent, directly affecting the operating efficiency of the downstream stripper tower and easily causing scaling and equipment corrosion. Second, environmental compliance pressure is high: with the strict implementation of standards such as the Emission Standard of Pollutants for the Petroleum Refining Industry (GB 31570-2015), requirements on oil content, suspended solids and other indicators in pre-treated sour water continue to rise, and conventional processes struggle to comply consistently. Third, resource utilisation is insufficient: incomplete separation leads to low waste oil recovery, which not only wastes resources but also increases sludge disposal costs. Against this background, Shenzhen SINOKLE Technology Co., Ltd., relying on its self-developed core processes, has developed a complete treatment technology for highly emulsified sour water in refineries, providing key support for refining and petrochemical enterprises to resolve the twin challenges of environmental compliance and production.

2. Technical Comparison

The mainstream processes currently used for sour water pre-treatment in refineries have clear limitations. The core differences from SINOKLE's technology are as follows:

Conventional processes generally suffer from the core problems of "incomplete demulsification, low separation efficiency and high operating costs", whereas SINOKLE's technology fundamentally resolves the bottleneck in treating highly emulsified sour water through process integration and structural innovation.

3. Introduction to SINOKLE's Technology

SINOKLE's complete treatment process for highly emulsified sour water in refineries is centred on "CDFUcyclonic dissolved-air flotation + precision filter + KHC coalescing oil remover", forming a three-stage progressive oil-water separation system. The process flow is as follows:

CDFUCyclonic dissolved-air flotation unit: sour water from the coking fractionator first enters the CDFUunit. Through cyclonic intensified air dissolution it generates ultra-fine bubbles 5–30 μm in diameter under high shear, and together with a dedicated demulsifier it rapidly breaks the stable emulsion structure so that fine oil droplets coalesce and float. This achieves preliminary three-phase separation of oil, water and solids. The separated waste oil is discharged to a receiving tank for recovery, and gases such as nitrogen and VOCs released at the top are sent to a gas recovery system for resource utilisation.

Precision filtration unit: CDFUThe effluent is pumped to precision filters A/B (one duty, one standby), where high-precision filter media intercept residual fine oil droplets and suspended impurities, further reducing effluent oil and suspended solids. A backwash water/gas system is provided to periodically backwash the filters on-line, ensuring continuous stable operation; the backwash gas is also sent to the gas recovery system.

KHC coalescing oil remover unit: the precision-filtered effluent enters the KHC coalescing oil remover, where the oleophilic and hydrophobic properties of the dedicated coalescing packing cause residual oil droplets to coalesce and grow further, achieving deep oil-water separation. The final effluent oil content is consistently compliant and is sent to the stripper tower for subsequent deammoniation and desulphurisation. The separated waste oil is likewise recovered to the receiving tank and finally returned to the coking fractionator for resource utilisation.

The process uses a fully enclosed design throughout, effectively preventing the leakage of toxic gases such as H₂S in sour water and safeguarding production safety. The whole flow can also be automatically controlled, greatly reducing manual operation and maintenance costs.

4. Technical Advantages: Reshaping the Value of Produced Fluid Treatment

1. Industry-leading demulsification and separation efficiency

For the stable system of highly emulsified sour water, CDFUcyclonic dissolved-air flotation, through the synergy of cyclonic intensification and ultra-fine bubbles, achieves demulsification efficiency far beyond conventional flotation. Combined with the deep separation of KHC coalescing oil removal, it delivers an emulsified oil removal rate above 95% and keeps effluent oil content steadily below 10 mg/L, far better than standard industry practice. This completely solves the scaling and corrosion problems downstream in the stripper tower and ensures long-cycle operation of the unit.

2. Greatly reduced operating costs

Compared with conventional processes, SINOKLE's technology optimises the air dissolution system and chemical regime: the system adds no chemical agents at all, energy consumption drops by 30%–50%, and sludge production is greatly reduced, significantly lowering the enterprise's operation and maintenance costs. Waste oil recovery rises above 90% and the oil can be returned directly to production units, creating additional economic benefit.

3. Extremely strong adaptability to operating conditions

The system tolerates large fluctuations in influent oil content, degree of emulsification and temperature, perfectly matching the complex water quality and variable operating conditions of refinery sour water. Even under extreme conditions of high sulphur, high emulsification and high suspended solids, it still keeps the effluent consistently compliant, solving the industry pain point that conventional processes exceed limits whenever water quality fluctuates.

4. Modular skid-mounted design with strong adaptability

The complete unit uses a modular, skid-mounted integrated design occupying only one third of the footprint of conventional processes. Installation and commissioning are quick, and it can be rapidly adapted to new refinery projects and to the upgrading of existing units, with no large-scale civil construction, greatly shortening project construction cycles.

5. Safety, environmental protection and resource recovery combined

The fully enclosed design throughout completely eliminates the risk of H₂S and other toxic gas leaks, meeting refinery safety production requirements. It also achieves full recovery of waste oil and gases, turning waste into value and helping enterprises meet the multiple goals of environmental compliance, energy saving, consumption reduction and resource utilisation — fully in line with the refining industry's green transformation needs under the dual carbon goals.

To date, SINOKLE's technology has been successfully applied at several large domestic refining and petrochemical enterprises, with cumulative sour water treatment capacity exceeding one million tonnes per year and 100% consistently compliant effluent indicators, earning high recognition from owners. In the future, SINOKLE will continue to deepen its work in refractory wastewater treatment for refineries, empowering the green, high-quality development of the refining and petrochemical industry through technological innovation and creating greater value for customers.