Analysis of High‑Efficiency Oil Removal Technology Using a "Tank‑within‑Tank" Configuration Based on Density‑Difference Centrifugal Force Fields

Abstract

Brator’s Tank-within-Tank system integrates three-phase hydrocyclone separation into a conventional equalization/sedimentation tank to treat complex oily wastewater from petroleum refining and chemical processing. Unlike gravity sedimentation—slow and ineffective for emulsified and fine oil droplets—the hydrocyclone generates centrifugal force hundreds to thousands of times stronger than gravity (1g), enabling rapid separation of micron-sized oil droplets and fine solids. Wastewater is pumped in, accelerated through a variable-diameter section, and separated into oil, water, and solid phases within the cyclone, each discharged through independent piping. The system is particularly effective for wastewater containing catalyst fines (e.g., Al₂O₃-SiO₂, density 1.5–2.0 g/cm³) from FCC units, preventing caking and clogging that impair traditional equipment. In a refining project, influent oil of 30,000 ppm was reduced to below 500 ppm, with effective solids capture and improved effluent clarity. Backed by dozens of patents and CFD validation, the technology recovers waste oil, reduces oily sludge, eases downstream treatment loads, and supports green, compliant petrochemical operations.

Oily wastewater generated during petroleum refining and chemical processing has a complex composition, often containing impurities such as emulsified oil, suspended solids, and even catalyst fines. Traditional gravity sedimentation methods are inefficient and require a large footprint. Brator Company’s Tank-within-Tank system innovatively integrates three-phase hydrocyclone separation technology into a conventional equalization/sedimentation tank. By utilizing the centrifugal force field generated by density differences to achieve highly efficient oil removal, it pioneers a cutting-edge approach to oil separation.

I. A Technological Leap: From Gravity Fields to Centrifugal Force Fields

Traditional sedimentation tanks rely on the density difference between oil and water (typically only 0.1–0.9 g/cm³) for natural stratification in a gravity field; this process is slow and largely ineffective against emulsified oil and fine oil droplets. In contrast, the three-phase hydrocyclone within the Tank-within-Tank system spins the wastewater at high speeds, boosting the separation driving force from 1g to hundreds or even thousands of g-force. This enables the rapid separation of even micron-sized oil droplets and fine solid particles.

Operational Workflow

Oily wastewater is pumped into the Tank-within-Tank inlet → accelerated through a variable-diameter pipe section into the three-phase hydrocyclone → undergoes oil-water-solid three-phase separation within the centrifugal force field → the oil phase flows into the oil storage zone via the oil outlet → the water phase enters the water storage zone via a water collection/distribution manifold → the solid phase settles into the sludge zone → each phase is discharged through independent piping systems.

II. Specialized Advantages in Treating Wastewater Containing Catalyst Fines

In units such as fluid catalytic cracking (FCC) plants, oily wastewater often carries catalyst fines (typically Al₂O₃-SiO₂ based, with a density of approximately 1.5–2.0 g/cm³). In traditional equipment, these fines tend to cake and form deposits on the tank bottom, severely impairing separation efficiency. The Tank-within-Tank system’s three-phase hydrocyclone completely separates the catalyst fines from the oil and water within the centrifugal force field; the fines are directed toward the outer wall and into the sludge zone. This prevents interference with the oil-water separation process and protects downstream piping and equipment from clogging.

III. Verification of Practical Performance

In a specific refining and chemical project, the influent oil content reached as high as 30,000 ppm. Following the application of the "Tank-within-Tank" system, the effluent oil content consistently dropped below 500 ppm; simultaneously, solid phases—such as catalyst fines—were effectively captured, resulting in a significant improvement in effluent clarity.

This achievement is underpinned by Brator Company’s extensive technical expertise, backed by dozens of invention and utility model patents, as well as theoretical validation derived from collaborative fluid dynamics simulation analyses conducted with universities.

As a specialized, high-tech enterprise in the field of oil removal, Brator’s "Tank-within-Tank" equipment utilizes a centrifugal force field to achieve precise three-phase separation of oil, water, and sludge. Waste oil can be continuously collected and recovered, turning waste into a valuable resource; sludge containing solid phases (such as catalyst fines) can be discharged separately for volume-reduction treatment; and the substantial reduction in effluent oil content significantly alleviates the load on downstream water treatment units, such as biochemical treatment systems. While enabling efficient resource utilization, this technology drastically reduces the generation of oily sludge and ensures full compliance with national environmental discharge standards, thereby contributing core technological capabilities to the petrochemical industry’s green, low-carbon transformation and the nation’s environmental protection efforts.