Name two technologies commonly used to control SO2 and NOx in combustion sources.

Name two technologies commonly used to control SO2 and NOx in combustion sources.

• A. Electrostatic precipitators and baghouse filters.
• B. Water spray scrubbers for NOx and ozone for SO2.
• C. Flue gas desulfurization (scrubbers) for SO2 and Selective Catalytic Reduction (SCR) or Selective Non-Catalytic Reduction (SNCR) for NOx.
• D. Carbon capture and biological filtration.

Answer: (C)

The main concept is selecting pollutant-specific control technologies that target SO2 and NOx emitted by combustion sources. Flue gas desulfurization uses a slurry of lime or limestone to scrub the sulfur dioxide from the flue gas, forming gypsum or other sulfite byproducts. This directly reduces SO2, which is the primary acid rain precursor from sulfur in fuels. For NOx, selective catalytic reduction or selective non-catalytic reduction addresses the nitrogen oxides. SCR uses a catalyst and a reductant such as ammonia or urea to convert NOx into nitrogen and water, typically at high temperatures, with high efficiency. SNCR achieves NOx reduction without a catalyst but at higher temperatures with generally lower efficiency and a greater risk of ammonia slip. These two technologies together—FGD for SO2 and SCR or SNCR for NOx—are the standard, complementary approaches for controlling these pollutants from combustion sources. In contrast, equipment designed to remove particulates (like electrostatic precipitators or baghouse filters) or methods not typically used for these gases (such as ozone treatment or biological filtration) do not address both pollutants effectively.

The main concept is selecting pollutant-specific control technologies that target SO2 and NOx emitted by combustion sources. Flue gas desulfurization uses a slurry of lime or limestone to scrub the sulfur dioxide from the flue gas, forming gypsum or other sulfite byproducts. This directly reduces SO2, which is the primary acid rain precursor from sulfur in fuels. For NOx, selective catalytic reduction or selective non-catalytic reduction addresses the nitrogen oxides. SCR uses a catalyst and a reductant such as ammonia or urea to convert NOx into nitrogen and water, typically at high temperatures, with high efficiency. SNCR achieves NOx reduction without a catalyst but at higher temperatures with generally lower efficiency and a greater risk of ammonia slip. These two technologies together—FGD for SO2 and SCR or SNCR for NOx—are the standard, complementary approaches for controlling these pollutants from combustion sources. In contrast, equipment designed to remove particulates (like electrostatic precipitators or baghouse filters) or methods not typically used for these gases (such as ozone treatment or biological filtration) do not address both pollutants effectively.