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How do scrubbers remove sulfur dioxide from flue gases?

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Scrubbers remove sulfur dioxide from flue gases through a process known as flue gas desulfurization (FGD), which can be categorized into wet or dry systems.1

Wet Scrubbing

In wet FGD systems, flue gases are brought into contact with a liquid or a slurry of solid material. The sulfur dioxide dissolves in or reacts with the absorbent, becoming trapped within it. Common methods include:1
* Limestone scrubbing: Sulfur dioxide reacts with limestone (calcium carbonate) particles to form calcium sulfite and carbon dioxide.1
* Lime scrubbing: Sulfur dioxide reacts with slaked lime to form calcium sulfite and water.1

Depending on conditions, these products may further react to form calcium sulfate (gypsum), which is then precipitated out as a slurry.1

Dry Scrubbing

In dry FGD systems, the absorbent consists of dry pulverized lime or limestone. Once the sulfur dioxide is absorbed, the resulting solid particles are removed using baghouse filters. While more cost-effective and easier to operate than wet systems, dry scrubbing is generally limited to flue gases produced by burning low-sulfur coal.1