Core Principles of Sinokle Coalescing Pressure Oil Separator: Coalescence & Shallow Tank Theory
1. Coalescing Pressure Oil Separator
The Coalescing Pressure Oil Separator is a device specially designed to remove suspended oil droplets and solid impurities from liquids. It is widely applied in liquid transmission systems across multiple industries including petroleum, chemical engineering, metallurgy, electric power, textile and food processing. The working principle of this equipment is based on electrochemical technology, which can effectively agglomerate fine suspended oil contaminants and solid particles into large clusters, followed by their separation via gravity sedimentation or filtration methods to achieve liquid purification.
The High-efficiency Coalescing Pressure Oil Separator is a patented technology product of Sinokle. Leveraging the coalescence principle, shallow tank principle and CFD simulation tools, it optimizes the internal space and structure of the tank body, and rationally arranges the internal flow field, enabling the rapid agglomeration, coalescence, floating (or sedimentation) and separation of oil droplets and suspended solids in water.
The interior of the oil separator tank consists of an inlet pre-separation zone, a primary separation zone and a main separation zone. The inlet pre-separation zone is composed of a specially designed cyclonic separation device, while the primary and main separation zones are filled with coalescing packing materials of different specifications respectively. An oil collection chamber is installed at the top of the tank body, and a high-efficiency sand flushing and sludge discharge device is arranged at the bottom.
2. Coalescence Principle
Coalescence refers to the utilization of the significant difference in affinity between oil and water phases for coalescing materials. When oily wastewater passes through the packed bed filled with coalescing materials, oil particles are captured and adhere to the surfaces and pores of the materials. As the number of captured oil particles increases, the oil particles deform and further merge and coalesce into larger oil particles. It can be known from Stokes' Law that the rising velocity of oil particles in water is directly proportional to the square of the oil particle diameter, and the larger coalesced oil particles can be easily separated from water.
Coalescence treatment is mainly targeted at dispersed oil in water, and oil removal by coalescence is a general term for the coalescence process and its corresponding sedimentation process. The floating of oil droplets conforms to Stokes' Law. For specific sewage at a constant temperature, its dynamic viscosity coefficient, sewage density, oil density and gravitational acceleration are all constant values, which can be simplified as follows:
It can be seen from the above formula that the rising velocity of oil droplets is directly proportional to the square of the oil droplet particle size. If the oil droplet particle size is increased before sewage sedimentation, the rising velocity of oil droplets can be greatly improved, thereby increasing the downward flow velocity of sewage in the sedimentation tank and further enhancing the sedimentation efficiency.
3. Shallow Tank Principle
The shallow tank theory proposed by Hazen in the 20th century states that: for an inclined tube sedimentation tank with tank length L, tank depth H, horizontal flow velocity v and particle settling velocity u₀, the relationship L/H=V/u₀holds under ideal conditions. It is evident that with constant L and v, the smaller the tank depth H, the smaller the suspended solid particles that can be removed. If horizontal baffles are used to divide H into 3 layers with each layer depth of H/3, the particles with settling velocity u₀ can be removed with only L/3 of the original tank length under the condition of constant u₀ and v, which means the total volume can be reduced to 1/3 of the original. If the tank length remains unchanged, the horizontal flow velocity can be increased to 3v with the tank depth reduced to H/3, and the particles with settling velocity u₀ can still be removed, i.e., the treatment capacity is tripled. In the same way, dividing the sedimentation tank into n layers can increase the treatment capacity by n times.
The removal efficiency of oil droplets with a certain particle size can be expressed as:
In the formula: ρ = density of water, ρ₀ = density of oil, d₁ = oil droplet diameter, A_T = rising area, μ = viscosity of water, Q = oil-containing sewage treatment capacity.
It can be seen from the above formula that the removal efficiency of oil droplets is only related to the oil droplet particle size, physical properties of oil and water, treatment capacity and rising area, and has no correlation with the rising height — this is the shallow tank principle.
4. Inclined Plate Packing / Corrugated Plate Packing
The Pressure Oil Separator is based on the coalescence principle and shallow tank principle, and adopts multi-layer corrugated plate (inclined plate) assemblies to improve the oil droplet separation efficiency by shortening the rising height of oil droplets. Meanwhile, during the flow of the oil-water mixture in the plate assemblies, the continuous change of the flow cross-section and the corrugated flow channels result in the constant variation of fluid flow velocity and direction, thereby increasing the probability of oil droplet collision and coalescence. Small oil droplets continuously coalesce and grow during movement, form an oil film on the lower surface of the corrugated plates through wetting, adsorption and coalescence effects, then move along the plate surface and detach from it. The aqueous phase settles under the action of gravity, reaches the upper surface of the lower corrugated plates, and ultimately realizes oil-water separation more efficiently.
5. Application Case
The electric desalting and tank farm black water treatment project of a petrochemical enterprise in Xinjiang was put into operation in December 2023. The oil content of the inlet sewage was 5~10%, and the combined process with the high-efficiency coalescing pressure oil separator and two-stage Cyclonic Dissolved Gas Flotation Unit (CDFU) as the core equipment was adopted, with a treatment capacity of 150 m³/h. After treatment, the oil content of the effluent was reduced to below 150 ppm, meeting the requirements of subsequent production process indicators.
