Glossary
KPIs and measurements
NOx, SOx and CO emissions
Also known as NOx, SOx, SO2, CO emissions, nitrogen oxides, sulphur oxides, carbon monoxide.
NOx (nitrogen oxides — NO and NO₂), SOx (sulphur oxides — primarily SO₂ with smaller SO₃), and CO (carbon monoxide) are the principal regulated gaseous emissions from combustion plants, alongside particulate matter. All three are measured continuously by CEMS and permit-limited under most jurisdictions' emission codes.
Sources and controls
| Pollutant | Formation | Control |
|---|---|---|
| NOx | Thermal NOx (high flame temperature) + fuel NOx | Combustion control + SCR / SNCR |
| SO₂ | Fuel sulphur oxidation | Fuel selection + FGD (wet scrubber, dry sorbent injection) |
| SO₃ | Catalytic oxidation of SO₂ over V₂O₅ in SCR | Catalyst formulation + temperature control |
| CO | Incomplete combustion | Combustion control (excess air, residence time, temperature) |
How cleaning affects gaseous emissions
Sonic horns do not directly capture gaseous pollutants but support gaseous-emission control indirectly:
- NOx — clean SCR catalysts achieve their rated NOx reduction; fouled catalysts under-perform
- SO₃ and downstream ABS — keeping the cold end clean reduces ammonium-bisulphate accumulation
- CO — preserved boiler performance maintains stable combustion
Related terms
Related terms
- Selective Catalytic ReductionSCR is the dominant NOx-control technology on industrial combustion plant. Ammonia is injected upstream of a catalyst that converts NOx to nitrogen and water.
- Continuous Emissions Monitoring SystemCEMS instruments measure stack emissions in real time — opacity, PM, NOx, SOx, CO, O2, moisture — providing the data on which environmental compliance is judged.
- Opacity (stack)Opacity is the percentage of light obscured by particulate in stack flue gas. The headline visual KPI for ESP performance; continuously monitored and permit-limited.
- Industrial Emissions DirectiveThe IED (2010/75/EU) is the umbrella EU directive on industrial pollution control. Sets BAT (Best Available Techniques) as the basis for emission limits across major industrial sectors.