VOCs, CO, odour or NOx — the right abatement technology depends on the pollutant. A practical selection guide, including cost drivers and a decision checklist.
Industrial plants that exceed their permitted emission limits face a choice between several abatement technologies. The right answer depends first on which pollutant you need to remove: volatile organic compounds (VOCs), carbon monoxide and odour respond to thermal oxidation, while nitrogen oxides (NOx) require selective catalytic reduction. Choose wrong and you invest in equipment that cannot solve your problem. This guide explains how each technology works, the variants within each family, what drives operating cost, and when you need both.
A thermal oxidizer (also called an afterburner) destroys combustible pollutants by raising the process exhaust to 750–1200 °C and holding it there long enough for complete oxidation — the classic “three T’s” of temperature, time and turbulence. VOCs, CO and odour components are converted into CO₂ and water vapour with a destruction efficiency above 99%.
Because the pollutants themselves are fuel, a well-designed oxidizer runs at surprisingly low net gas consumption. Three main variants exist, differing in how they recover heat:
Recovered heat that the oxidizer itself cannot use can often be returned to your process — drying air, boiler feed or thermal oil — further improving the business case.
Selective catalytic reduction (SCR) targets a different problem: NOx formed during combustion itself. Flue gas passes over a catalyst while a precisely dosed ammonia or urea solution is injected; NOx is converted into harmless nitrogen and water. A properly engineered SCR system removes 90% or more of NOx with minimal ammonia consumption.
Two engineering details decide whether an SCR installation performs:
The simpler cousin, SNCR (injection without catalyst at high temperature), costs less but typically reaches only 30–50% reduction — rarely sufficient where permits demand deep NOx cuts.
| Your emission problem | Technology | Typical performance |
|---|---|---|
| VOCs / solvents / odour | Thermal oxidizer | >99% destruction at 750–1200 °C |
| Carbon monoxide (CO) | Thermal oxidizer | >99% conversion |
| NOx from combustion | SCR | Up to 90%+ reduction |
| NOx, moderate targets | SNCR | 30–50% reduction |
| VOCs and NOx | Combined system | Oxidizer first, SCR downstream |
The two technologies are complementary, not competing. A thermal oxidizer actually produces some NOx while destroying VOCs; where permits are strict on both, ICE engineers a combined line: oxidation for VOCs and CO, followed by SCR — with a reheat burner where needed to bring the flue gas into the catalyst’s optimal window.
ICE Industrial Solutions starts every emission project with an exhaust gas audit: on-site measurement of flue gas composition and actual emission levels. From that data we size the right technology, engineer it in-house, commission it under our own supervision and deliver the official emission measurements your permit requires — one contracting party from analysis to compliance, throughout Europe and beyond.
A thermal oxidizer destroys VOCs, CO and odour by high-temperature oxidation (750–1200 °C, >99% destruction). SCR removes NOx from flue gas using a catalyst and controlled ammonia injection (up to 90%+ reduction). They target different pollutants and are often combined.
Not in a single stage. Where permits limit both, a thermal oxidizer is placed first to destroy VOCs and CO, with an SCR system downstream for NOx — if needed with a reheat burner to reach the catalyst's optimal temperature window.
A recuperative oxidizer preheats incoming exhaust with a heat exchanger (typically 50–70% heat recovery). A regenerative oxidizer (RTO) uses ceramic beds that alternately store and release heat, reaching 90–97% thermal efficiency — preferred for large, lean exhaust flows.
SCR uses a catalyst and achieves 90%+ NOx reduction with precise low-temperature dosing. SNCR injects reagent at high temperature without a catalyst and typically reaches only 30–50% reduction — cheaper, but rarely sufficient for strict permits.
Operating cost depends mainly on VOC concentration, flow rate and heat recovery. Rich streams are largely self-sustaining above the autothermal point; with integrated heat recovery the oxidiser's thermal energy is returned to your process, substantially reducing net fuel consumption.
Start with an exhaust gas audit: measuring flue gas composition, flow and actual emission levels against your permit. ICE performs these audits on site and engineers the appropriate solution from measured data.
Facing an emission compliance challenge?
Request an emission control analysis — our engineers measure your actual emissions and recommend the right technology.
