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How do scrubbers remove harmful pollutants from coal-burning emissions?
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coal utilization
Cross-regenerative coke oven. (A) Cross section, showing the alternating arrangement of flue walls and ovens; (B) longitudinal section, showing (left) a series of combustion flues in a single flue wall and (right) part of a long, slotlike oven.
Scrubbers remove harmful pollutants from coal-burning emissions primarily through flue gas desulfurization (FGD), a process designed to capture sulfur dioxide before it enters the atmosphere.12
Wet and Dry Scrubbing Methods
- Wet Scrubbing: Flue gases are brought into contact with a liquid or a slurry of alkaline sorbent, such as limestone or slaked lime. The sulfur dioxide reacts with or dissolves into the absorbent, becoming trapped. This process often results in the formation of calcium sulfite or calcium sulfate (gypsum), which can be precipitated out as a sludge.12
- Dry Scrubbing: This method uses dry pulverized lime or limestone. Once the sulfur dioxide is absorbed, the resulting solid particles are captured using baghouse filters.1
While primarily engineered for sulfur dioxide, these systems can also help mitigate other pollutants. For example, wet scrubbers and dry FGD systems combined with baghouses are effective at removing mercury from flue gas. These technologies are essential for reducing acid rain and improving air quality, though they involve significant operational costs and produce waste residues that require careful disposal.21