Flue Gas Desulfurization (FGD): An Overview Flue Gas Desulfurization (FGD) is a critical technology used to remove sulfur dioxide (SO₂) from exhaust flue gases generated by industrial processes, particularly coal-fired power plants, refineries, and other combustion-based facilities. SO₂ is a major air pollutant responsible for acid rain, respiratory issues, and environmental degradation. FGD systems play a vital role in reducing these harmful emissions, ensuring compliance with environmental regulations, and promoting sustainable industrial operations. Types of FGD Systems FGD technologies are broadly categorized into wet and dry systems, each with distinct mechanisms and applications. 1. Wet FGD Systems - The most widely used method, wet scrubbers employ an alkaline slurry (typically limestone or lime) to absorb SO₂ from flue gases. - The chemical reaction produces calcium sulfite (CaSO₃), which is further oxidized to gypsum (CaSO₄·2H₂O), a usable byproduct in construction materials. - Wet systems achieve high removal efficiencies (over 90%) but require significant water usage and wastewater treatment. 2. Dry FGD Systems - Dry scrubbers inject a dry sorbent (e.g., hydrated lime or sodium bicarbonate) into the flue gas stream, where it reacts with SO₂ to form solid particles. - These systems consume less water and are suitable for plants with limited water resources, though their efficiency (70–90%) is generally lower than wet systems. 3. Semi-Dry Systems - A hybrid approach, such as spray dryer absorbers, uses a fine mist of alkaline slurry that evaporates quickly, leaving a dry waste product. - These systems balance efficiency and water consumption, making them adaptable to varying operational needs. Key Components and Process A typical FGD system includes: - Absorber Tower: Where flue gas contacts the sorbent slurry or powder. - Reagent Preparation System: Prepares and feeds the alkaline material. - Waste Treatment Unit: Processes byproducts like gypsum or fly ash. - Pumps, Fans, and Ductwork: Facilitate gas flow and reagent circulation. Environmental and Economic Benefits FGD significantly reduces SO₂ emissions, mitigating acid rain and improving air quality. By converting waste into gypsum, some systems also support circular economy practices. However, challenges include high capital costs, energy consumption, and the need for proper waste disposal. Future Trends Advancements focus on improving efficiency, reducing costs, and integrating FGD with carbon capture technologies. Research into novel sorbents and hybrid systems aims to enhance sustainability while meeting stricter emission standards. In summary, FGD is indispensable for modern industrial emissions control, balancing environmental protection with operational feasibility. Its continued evolution will be crucial in the transition toward cleaner energy and industrial processes.