NOx and SOx Emissions May 21, 2025 sazenviro Post in Uncategorized NOx and SOx gases—nitrogen oxides and sulfur oxides—are among the most harmful emissions from industrial combustion. These gases contribute to acid rain, smog formation, and respiratory illness. As emission norms become stricter worldwide, industries must adopt advanced NOx control systems and SOx scrubber technologies to stay compliant. From selective catalytic reduction (SCR) to flue gas desulfurization equipment, this article explores the most effective solutions. 2. What Are NOx and SOx?Contents1 2. What Are NOx and SOx?2 3. NOx Control Techniques3 4. SOx Control Techniques4 5. System Components5 6. Design Considerations6 7. Industrial Applications7 8. Advantages8 9. Challenges9 10. Maintenance Essentials10 11. Compliance and Regulatory Standards11 12. Conclusion NOx (Nitrogen Oxides): Formed during high-temperature combustion in boilers, engines, and kilns. SOx (Sulfur Oxides): Released from burning sulfur-containing fuels like coal, diesel, and oil. These gases are highly reactive, forming secondary pollutants like ozone and fine particulate matter (PM2.5), which are regulated under national and international laws. 3. NOx Control Techniques Method Description Low-NOx Burners (LNB) Modify combustion to reduce peak temperatures Flue Gas Recirculation (FGR) Recycle flue gases to reduce combustion temperature Selective Non-Catalytic Reduction (SNCR) Ammonia injection without a catalyst Selective Catalytic Reduction (SCR) Ammonia injection with a catalyst for high efficiency Selective catalytic reduction technology can reduce NOx by up to 95%, making it the most effective method for industrial applications. 4. SOx Control Techniques Method Description Wet Flue Gas Desulfurization (FGD) Uses lime or limestone slurry to absorb SO₂ Dry FGD (Spray Dryer Absorber) Atomized lime slurry reacts with SO₂ and dries Duct Injection Direct lime injection into hot gases Activated Carbon Impregnation Used in low-volume gas flows with acid gases Flue gas desulfurization equipment is essential in power plants, fertilizer units, and oil refineries. 5. System Components NOx Reduction Systems: Ammonia or urea dosing system SCR reactor with catalyst beds Control panel and emission sensors SOx Scrubber Systems: Spray nozzles and scrubber vessel Lime or limestone slurry tank Recirculation pump Mist eliminators 6. Design Considerations Parameter Typical Value NOx Removal Efficiency (SCR) 85–95% SOx Removal Efficiency (Wet FGD) 90–98% Flue Gas Temperature (SCR Inlet) 300–400°C Slurry pH (Wet Scrubber) 5.5–6.5 Reagent Consumption Based on inlet gas load 7. Industrial Applications Thermal Power Plants: Coal-based combustion Steel & Cement Industries: Kilns and furnaces Petrochemical Refineries: SO₂ and NOx control from crackers and reformers Glass Manufacturing: High-temperature furnaces Marine Engines: Ship exhaust NOx control (IMO regulations) 8. Advantages High pollutant removal efficiency Modular and scalable systems Online emission monitoring possible Widely supported by international compliance standards 9. Challenges Catalyst poisoning in SCR due to particulate contamination Gypsum sludge disposal in wet FGD Reagent handling safety (e.g., ammonia) High capital and maintenance cost 10. Maintenance Essentials Regular catalyst replacement (SCR) Slurry pH and conductivity monitoring (FGD) Descaling and anti-fouling in wet scrubbers Emission sensor calibration and maintenance 11. Compliance and Regulatory Standards These systems help industries comply with: EPA Clean Air Act (USA) EU IED and LCP BREF CPCB Emission Standards (India) IMO MARPOL Annex VI (Marine) Saudi Arabia PME & UAE MOCCAE norms Dry Sorbent Injection System for Acid Gas and SOx Control Electrostatic Precipitators for Clean Air Activated Carbon Filters for VOC Odor Removal Multi Stage Scrubbing Systems Cartridge Dust Collectors for Fine Particulate Filtration Venturi Scrubber System for Industrial Emissions Fume Extraction System for Laser Cutting and Plasma Operations Industrial Blower for Fume Extraction Wet Scrubber System for VOC Removal in Paint and Coating Industries Air Handling Unit for Industrial Ventilation Mist Collector System for Coolant Fume Extraction 12. Conclusion For industries emitting combustion gases, the implementation of NOx control systems and SOx scrubber technologies is not optional—it’s a regulatory necessity. With solutions like flue gas desulfurization equipment and selective catalytic reduction technology, companies can meet environmental goals while maintaining operational efficiency.