Technical Advantages of the Hydrocyclone-based Oil Recovery and Discharge Unit (Tank-within-Tank Design) in the Treatment of Oily Wastewater from Refining and Chemical Operations

Abstract

Brator’s Tank-within-Tank system addresses the challenge of efficient oil removal and solid impurity separation (e.g., catalyst fines) within limited tank capacity in petroleum refining and chemical wastewater treatment. Its core is an integrated hydrocyclone-based oil recovery and discharge unit, comprising a three-phase hydrocyclone separator and a free oil collector, housed in a dual inner/outer tank structure.

In the field of treating oily wastewater from petroleum refining and chemical processing, achieving efficient oil removal within limited tank capacity—while simultaneously resolving the challenge of separating solid impurities (such as catalyst fines)—has long been a technical hurdle for the industry. The core innovation of the Tank-within-Tank equipment developed by Brator lies in its integrated hydrocyclone-based oil recovery and discharge unit; comprising a three-phase hydrocyclone separator and a free oil collector, and utilizing a dual-structure design featuring an inner tank and an outer tank, this system establishes a comprehensive solution for the efficient separation of oil, water, and solids.

1. Technical Composition of the Combined Device

2. Analysis of Technical Advantages

Advantage 1: Three-Phase Synchronous Separation for Complete Oil-Sludge Separation

In traditional processes, oil and sludge are often discharged together, resulting in high oil content in the sludge (up to 10–30%) and making subsequent treatment difficult and costly. The "Tank-within-Tank" system utilizes hydrocyclone separators to physically isolate oil, water, and sludge; waste oil and sludge are discharged through independent piping systems, achieving true "segregated collection."

Advantage 2: Adaptability to Complex Water Quality, Including Catalyst Fines

Refinery wastewater often contains solid impurities such as catalyst fines, rust, and sand. The hydrocyclone separator uses centrifugal force to direct these solids into the sludge zone, preventing interference with the oil-water separation process and avoiding pipeline blockages.

Advantage 3: Retrofitting Without Increasing the Footprint

The Tank-within-Tank system involves installing an inner tank and a separation assembly within an existing equalization/sedimentation tank. For existing facilities, this requires only a retrofit rather than new construction, resulting in lower investment costs and shorter project timelines.

Advantage 4: Continuous Operation and Flexible Discharge

Waste oil discharge frequency (continuous or periodic) can be determined based on oil content, while sludge discharge frequency can be flexibly adjusted based on sludge content. This flexible operational mode significantly reduces labor costs associated with operation and maintenance.

3. Technical Achievements

Following implementation at a refinery project, the oil content dropped from 30,000 ppm to below 500 ppm, demonstrating remarkable results. Brator Company’s extensive portfolio of patents and fluid dynamics analysis conducted in collaboration with universities provide a solid foundation for the equipment’s efficient and stable operation.

As a specialized, refined, distinctive, and innovative (SRDI) high-tech enterprise in the oil removal sector, Brator Company offers a hydrocyclone-based oil recovery and discharge assembly that represents the cutting edge of oily wastewater pretreatment technology. The system achieves efficient separation and segregated collection of the oil, water, and sludge phases: waste oil is continuously recovered to maximize its residual value; solid sludge—including catalyst fines—is collected separately, significantly reducing the total volume of oily sludge; and the substantial reduction in effluent oil content effectively alleviates the load and operating costs of downstream water treatment systems. This technology not only enables petrochemical enterprises to meet increasingly stringent national environmental emission standards but also makes outstanding contributions to resource recycling and the reduction of solid waste; it is an indispensable core technology and piece of equipment for the nation’s environmental protection efforts and the development of a green petrochemical industry.