Using a wet scrubber typically involves spraying the exhaust gas with the scrubbing liquid as it passes through the scrubber chamber to capture pollutants.
Wet scrubbers are air pollution control devices that use a scrubbing liquid, usually water, to remove particulate matter and gaseous pollutants from industrial exhaust streams. The fundamental principle relies on bringing the polluted gas into contact with the liquid to absorb or capture the contaminants.
The Process Explained
The most common way a wet scrubber operates is by introducing the dirty exhaust gas into a chamber where it meets a finely dispersed scrubbing liquid.
Here's a breakdown of the process:
- Gas Entry: Polluted exhaust gas enters the scrubber chamber.
- Liquid Introduction: The scrubbing liquid is misted and sprinkled down onto the gas from nozzles above. This creates a large surface area for contact between the gas and liquid.
- Contact & Capture: As the gas flows through the liquid spray, particulate matter in the gas stream collides with and is captured by the liquid droplets. Gaseous pollutants can also dissolve into the liquid.
- Liquid Collection: The liquid, now containing the captured pollutants (often called "scrubber blowdown" or "slurry"), is collected at the bottom of the chamber.
- Clean Gas Exit: The cleaned gas, free from a significant portion of the pollutants, exits the scrubber and is typically released into the atmosphere.
The reference explicitly states: "The most common method is to spray the exhaust gas with the scrubbing liquid as it passes through the scrubber chamber. The liquid is misted and sprinkled down onto the gas from nozzles above. The scrubbing liquid is typically water which is effective at removing dust and particulate matter." This highlights the core mechanism of liquid-to-gas contact via spraying.
Components of a Typical Wet Scrubber
A basic wet scrubber system includes several key parts:
- Scrubber Tower/Chamber: The main vessel where gas and liquid interact.
- Nozzle System: Sprays the scrubbing liquid into the gas stream.
- Liquid Recirculation System: Pumps, piping, and potentially a tank to recirculate the scrubbing liquid (though some systems use a single pass).
- Liquid/Slurry Outlet: Collects the spent scrubbing liquid.
- Gas Inlet and Outlet: Ports for the polluted gas to enter and the cleaned gas to exit.
Why Use Water?
As mentioned in the reference, the scrubbing liquid is typically water. Water is a common choice because it is:
- Cost-effective: Readily available and inexpensive.
- Effective: Effective at removing dust and particulate matter through impaction and diffusion.
- Versatile: Can dissolve many soluble gaseous pollutants.
However, for specific gaseous pollutants, chemicals may be added to the water to enhance absorption through chemical reactions.
Types of Wet Scrubbers
While the spraying method is common, there are various designs, each optimizing gas-liquid contact differently:
| Scrubber Type | Description | Primary Use |
|---|---|---|
| Spray Tower | Gas passes through liquid spray from nozzles. | Particulate & soluble gas removal. |
| Packed Bed Scrubber | Gas passes through a bed of packing material wetted by liquid. | Highly effective for gas absorption. |
| Venturi Scrubber | Gas accelerates through a constricted area (venturi) where liquid is injected. | Very effective for fine particulate removal. |
The information from the reference primarily describes the principle behind the spray tower or similar designs that rely on direct liquid spraying.
In summary, using a wet scrubber centers on the principle of bringing polluted gas into close contact with a scrubbing liquid, usually water sprayed from nozzles, to capture pollutants.
