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CO Control in Waste Incineration: Polishing Flue Gas After the Furnace

Part of the CO Oxidation: The Complete Guide — this article is one of the detailed pages in the guide.

Direct answer: In waste incineration, CO in the flue gas is both a regulated pollutant and the primary indicator of combustion quality — spikes signal incomplete burnout. A CO oxidation catalyst downstream of the gas-cleaning stages polishes residual CO to the emission limit and helps the plant ride through the combustion upsets that create spikes in the first place.

The regulatory logic

Incineration standards (e.g., EU IED and Chinese GB 18484 for medical waste) regulate CO as a surrogate for combustion completeness, often as daily averages with tight spike limits. A plant that cannot hold CO below the limit during charging transients is non-compliant even if its average looks good.

Where the catalyst sits

The catalyst is always downstream of the dedicated gas-cleaning train:

  • Acid gas removal (scrubber or dry reagent injection) — HCl and SO₂ would poison the catalyst quickly.
  • Particulate removal (bag filter) — fly ash and activated-carbon injection dust would blind the face.
  • Then CO oxidation, before or after SCR depending on temperature.

Design considerations

  • Temperature — flue gas after cleaning is often 150–220°C; light-off margin and possible preheating decide viability.
  • Chloride exposure — residual HCl after scrubbing attacks catalysts; monitor and specify chloride-tolerant materials.
  • Spike handling — batch charging produces CO surges; size for the peak and verify the exotherm stays safe.
  • Moisture — wet scrubbing leaves saturated gas; condensation protection is mandatory.

Reported field experience

Field tests on medical waste incineration report CO reduced from over 11,000 mg/Nm³ to below 20 mg/Nm³ under test conditions — but the test gas composition, temperature and moisture are what determine whether such performance is repeatable in continuous service. Pilot confirmation on the actual gas is the standard practice.

Manufacturer perspective

Incineration duty combines everything that hurts a catalyst — acids, metals, moisture and spikes. We treat each stream as a poison audit first and a CO problem second: the upstream gas cleaning defines the catalyst life, and the catalyst must never be the weakest link in the compliance chain.

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