An API oil separator works by using gravity and the density differences between oil, water, and solids to separate these components from wastewater.
Here's a breakdown of the process:
The Principle of Gravity Separation
The API (American Petroleum Institute) oil separator is designed to exploit the natural tendency of different density materials to separate when given enough time and a quiescent environment. The key is to slow the flow of wastewater down sufficiently to allow separation to occur.
Process Steps
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Influent Entry: Oily wastewater enters the separator.
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Quiescent Environment: The separator is designed to provide a relatively calm and undisturbed environment, minimizing turbulence. This allows the separation process to occur efficiently.
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Density Separation:
- Oil rises: Oil, being less dense than water, floats to the surface.
- Water remains in the middle: The treated water remains in the middle layer.
- Solids settle: Suspended solids, being denser than water, sink to the bottom.
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Collection and Removal:
- Oil skimming: The separated oil is skimmed from the surface.
- Water discharge: The clarified water is discharged from the separator.
- Sludge removal: Accumulated solids (sludge) are periodically removed from the bottom of the separator.
Design Considerations
The design of an API separator is crucial for its effectiveness. Key considerations include:
- Flow rate: The separator must be sized appropriately to handle the incoming flow rate of wastewater.
- Retention time: Sufficient retention time is necessary to allow for adequate separation.
- Separator geometry: The shape and dimensions of the separator influence flow patterns and separation efficiency. The rectangular design is common.
- Internal baffles and weirs: These features help to control flow and prevent turbulence.
- Sludge removal system: An efficient system is needed to remove accumulated solids.
Summary
In essence, an API oil separator uses gravity to separate oil, water, and solids by providing a slow-moving and undisturbed environment that allows these materials to stratify based on their densities, followed by their separate removal from the system.
