Industrial flue gas contains two of the most strictly regulated pollutants: particulate matter (PM) and nitrogen oxides (NOx). Traditional approaches treat each pollutant separately – electrostatic precipitators (ESP) or baghouses for PM, selective catalytic reduction (SCR) for NOx – requiring multiple vessels, extensive ductwork, and large footprints. The DePM & NOx System is an integrated technical solution that removes both contaminants simultaneously or in a highly optimized sequence, reducing capital cost, operating cost, and equipment footprint by 30-50%. This system meets ultra-low emission standards (PM <5-10 mg/m³, NOx <50-100 mg/m³) for coal-fired boilers, cement kilns, waste incinerators, industrial furnaces, and diesel engines.
Configuration | Architecture | PM Efficiency | NOx Efficiency | Best Application |
Catalytic Baghouse | NH₃ injection → Catalytic filter baghouse | >99.9% | 80-90% | Waste incineration, biomass |
High-Dust SCR + ESP | NH₃ injection → High-dust SCR → ESP | >99.5% | 85-90% | Coal power, cement (high dust) |
Low-Dust SCR + Baghouse | Baghouse → Reheat → Low-T SCR | >99.9% | 85-95% | Retrofit, gas turbine, post-FGD |
Wet ESP + Low-T SCR | Wet FGD → Wet ESP → Reheat → Low-T SCR | >95% | 80-90% | Waste incineration (wet flue gas) |
How it works – SCR catalyst is integrated directly into the baghouse filter media. PM is captured on the filter surface while NOx is catalytically reduced as gas passes through the catalyst layer. NH₃ is injected upstream. The system simultaneously removes PM, NOx, and dioxins/furans (PCDD/F) – the catalyst decomposes dioxins at 180-260°C.
Catalytic filter media – Woven fiberglass or PTFE fabric coated with low-temperature SCR catalyst (MnOₓ/TiO₂ or V₂O₅/TiO₂). Operating temperature: 180-260°C. Air-to-cloth ratio: 0.8-1.2 m³/min•m². Dioxin destruction: >99% (if present).
Key advantages – Single vessel replaces ESP/baghouse + SCR reactor (50% smaller footprint). No reheat required (SCR operates at baghouse temperature). Lower capital cost (one housing, one ductwork set). Lower pressure drop (no separate SCR vessel). Simultaneous dioxin destruction.
Typical applications – Municipal waste incinerators, medical and hazardous waste incinerators, biomass and waste-to-energy boilers, small to medium industrial boilers (<100 MW), iron ore sintering plants (dioxin control).
How it works – SCR reactor placed directly after the boiler/economizer (300-400°C) before particulate removal. High-dust flue gas (10-30 g/m³) passes through plate-type SCR catalyst with wide channels to prevent dust bridging. NOx is reduced by 85-90% with NH₃ injection. ESP downstream removes PM (>99.5%). No reheat is required – flue gas is already at optimal SCR temperature.
Plate SCR catalyst – Metal mesh coated with V₂O₅/WO₃/TiO₂. Wide pitch (6-10 mm) prevents dust bridging and erosion. Erosion-resistant edges. Alkali and arsenic-tolerant formulations available for challenging fuels.
ESP design – Dry ESP with rapping system. Collection efficiency >99.5% (PM outlet <10-20 mg/m³). Operating temperature: 300-350°C. Low pressure drop (0.5-1.0 kPa). Continuous operation with minimal maintenance.
Key advantages – Maximizes SCR temperature (optimal vanadia activity window). No reheat energy penalty. Proven in thousands of coal-fired plants worldwide. ESP unaffected by NH₃ slip.
Typical applications – Coal-fired power plants (baseload, high availability), cement kiln preheaters (high dust, high alkali), steel sintering plants, industrial boilers burning solid fuels.
How it works – Baghouse or ESP removes PM first (to <10-20 mg/m³). Clean gas (150-250°C) then passes through low-temperature SCR (honeycomb or plate). NH₃ is injected upstream. NOx is reduced by 85-95%. If flue gas temperature is below 150-175°C, a reheat system (burner or heat exchanger) is required.
Low-temperature catalyst options – MnOₓ/CNT: 99% NOx conversion at 150°C, Cu-zeolite: 90-95% at 175-250°C, V₂O₅/TiO₂ (low-temp formulation): 85-90% at 200-250°C. Honeycomb substrate preferred (clean gas allows high cell density, lower cost).
Key advantages – Clean gas means no catalyst erosion. Longer catalyst life (5-8 years vs. 3-5 years for high-dust). Smaller catalyst volume (10-30% less than high-dust). Suitable for retrofit projects (SCR added after existing baghouse). Honeycomb catalyst can be used (lower cost than plate).
Typical applications – Waste incinerators (post-FGD, 150-200°C), industrial boilers with heat recovery (exhaust cooled below 250°C), gas turbines (post-HRSG), glass furnaces (post-ESP), retrofit projects where high-dust SCR cannot be accommodated.
How it works – Wet electrostatic precipitator (WESP) removes PM and acid mists from saturated flue gas (50-80°C). Low-temperature SCR downstream requires reheat to 150-250°C. The system provides simultaneous PM, NOx, and acid gas (SO₃, HCl, HF) removal.
Performance – PM outlet: <5 mg/m³ (>95% efficiency). NOx efficiency: 80-90% (with low-T SCR and reheat). Acid gas removal: >90% (with alkaline scrubbing upstream). SO₃ removal: >95% (prevents visible plume and corrosion).
Key advantages – Handles saturated flue gas (after wet FGD) – dry ESP would have dust cake adhesion issues. Removes acid mists (submicron H₂SO₄ aerosol) – prevents blue plume. No dust re-entrainment (unlike dry ESP rapping). Low pressure drop (0.5-1.5 kPa).
Typical applications – Waste incinerators (after wet FGD), biomass boilers (high moisture flue gas), marine exhaust (SO₂ scrubber + WESP + SCR), chemical plants with wet gas streams, power plants burning high-sulfur coal (with wet FGD).
Configuration | PM Outlet | NOx Outlet | Operating Temp | Reheat Required | Relative Cost |
Catalytic Baghouse | <5-10 mg/m³ | <50-100 mg/m³ | 180-260°C | No | Medium |
High-Dust SCR + ESP | <10-20 mg/m³ | <50-100 mg/m³ | 300-400°C | No | Medium-High |
Low-Dust SCR + Baghouse | <5-10 mg/m³ | <30-50 mg/m³ | 150-250°C | Yes (if <175°C) | Medium |
Wet ESP + Low-T SCR | <5 mg/m³ | <50-100 mg/m³ | 50-80°C (WESP) + 150-250°C (SCR) | Yes | High |
Dust loading (low <1 g/m³, medium 1-10 g/m³, high >10 g/m³). Dust composition (abrasive, sticky, hygroscopic). Temperature (measure at potential SCR location). SO₂/SO₃, HCl, HF concentration. Moisture content (dry or saturated). Flow rate (m³/hr).
Required PM outlet (mg/m³). Required NOx outlet (ppm or mg/m³). Regulatory limit (EPA, EU, China GB). Available footprint (new build vs. retrofit). Reheat fuel cost (natural gas, electricity, steam).
High dust (>10 g/m³) + 300-400°C → High-dust SCR + ESP. Moderate dust + 180-260°C + tight footprint → Catalytic Baghouse. Retrofit + existing baghouse + 150-250°C → Low-Dust SCR + Baghouse (add reheat if needed). Wet flue gas (post-FGD) + acid mist control → Wet ESP + Low-T SCR (add reheat).
We engineer complete DePM & NOx systems for any industrial application. Whether you require a catalytic baghouse for a municipal waste incinerator (<5 mg/m³ PM, <50 mg/m³ NOx, dioxin destruction >99%), a high-dust plate SCR + ESP for a coal-fired boiler (PM <10 mg/m³, NOx <50 mg/m³, 300-400°C operation), a low-temperature SCR retrofit after an existing baghouse for a cement kiln (NOx <100 mg/m³, no catalyst erosion), or a wet ESP + low-T SCR for a wet FGD-equipped waste incinerator (PM <5 mg/m³, blue plume eliminated), our team tailors the catalyst formulation (vanadia, Cu-zeolite, Mn-based), filtration media or ESP design, reactor configuration, NH₃ injection grid (CFD optimized), reheat system (if required), and control strategy to your specific flue gas composition, plant layout, and regulatory target.
Partner with us to define your path to compliance – DePM & NOx, integrated efficiency.