What is Air cooled Steam Condenser?
An Air Cooled Steam Condenser (ACSC) is a type of steam condenser that uses ambient air as the cooling medium instead of water.
It is a direct, water-free solution for condensing steam, making it crucial for power plants in areas where water is scarce.
Simple Definition
An Air Cooled Steam Condenser (ACSC) is a system where exhaust steam from a turbine is circulated through finned tubes, and ambient air is forced over the outside of these tubes by large fans. The air absorbs the heat from the steam, causing it to condense back into water.
- Steam Inlet: Low-pressure exhaust steam from the steam turbine enters a large overhead main steam duct.
- Distribution: This duct distributes the steam to multiple large, inclined tube bundles. These bundles are typically arranged in an “A-Frame” structure to maximize surface area and structural stability.
- Heat Transfer: The tubes inside these bundles are finned to dramatically increase their external surface area for better heat transfer. As the steam flows through the tubes, large axial fans at the base of the structure force cool ambient air over the finned exterior.
- Condensation: The steam releases its latent heat to the air through the tube walls and condenses into water (condensate) inside the tubes.
- Collection: The condensate and any remaining non-condensable gases (like air) are drawn downward by gravity and vacuum into a condensate collection header.
Return & Extraction: The condensate is pumped back to the boiler feed system. The non-condensable gases are removed by an air extraction unit (vacuum pumps) to maintain the necessary vacuum inside the system
Key Components
- Finned Tube Bundles: The heart of the ACC. Tubes are typically made of carbon steel, with aluminum fins mechanically attached to the outside to increase heat transfer area.
- Axial Fans: Massive, electrically-driven fans (similar to aircraft propellers) that provide the cooling airflow. Fan speed is often variable to control condensation pressure based on load and ambient temperature.
- A-Frame Structure: The supporting structure that holds the tube bundles at an optimal angle for condensate drainage and air exposure.
- Steam Distribution Ducting: The large pipes that carry steam from the turbine to the various tube bundles.
- Vacuum System (Air Extraction Pumps): Crucial for maintaining a vacuum and removing non-condensable gases, just like in a water-cooled condenser.