Air Pollution Control for Incinerators: From Combustion to Clean Gas
Air-pollution control (APC) should be designed as part of the incineration process, not added after the furnace has been selected. The appropriate system depends on waste chemistry, combustion conditions, required emission limits, gas flow, temperature and the jurisdiction in which the plant operates.
What the APC System Has to Control
| Pollutant / parameter | Potential source | Possible control approach |
|---|---|---|
| Particulate matter | Ash and incomplete combustion | Filtration, cyclonic or other particulate control |
| Acid gases | Chlorine, sulphur and other compounds in feed | Dry, semi-dry or wet scrubbing |
| CO / organic compounds | Incomplete combustion | Combustion optimisation and secondary treatment |
| Dioxins/furans | Combustion chemistry and unsuitable feed | Good combustion plus appropriate gas cleaning |
| Heavy metals | Metal-containing waste | Feed control and suitable APC technology |
| NOx | High-temperature combustion and nitrogen chemistry | Combustion control and, where required, NOx reduction systems |
Combustion Comes First
No APC system should be viewed as a substitute for good combustion. Stable feed conditions, adequate temperature, sufficient residence time and turbulence all influence the composition of the raw flue gas. Poor combustion can increase the burden on downstream equipment.
Filtration Technologies
Ceramic filtration
Ceramic filter systems can be selected for demanding high-temperature applications and fine particulate control. Their suitability depends on gas temperature, chemistry, dust loading, pressure drop and the specific filter design.
Bag filtration
Fabric filters are widely used for particulate control, but temperature and gas chemistry must be compatible with the selected media. Conditioning or upstream gas cooling may be required depending on the process.
Scrubbing
Dry, semi-dry and wet scrubbers remove acid gases through contact with an alkaline reagent or liquid. The selection depends on the required removal performance, reagent handling, water availability, wastewater strategy and site constraints.
Activated Carbon
Activated carbon or similar sorbents may be used in appropriate systems to assist with the capture of certain organic compounds and metals. Feed composition, dosing, contact conditions and downstream filtration all influence performance.
Monitoring and Compliance
The applicable emission limits must be established from the permit and legislation governing the specific installation. Terms such as 'EU compliant' or 'WHO compliant' should never replace a project-specific compliance assessment. Monitoring requirements can differ substantially by jurisdiction and plant category.
How to Select an APC System
- Characterise the waste stream.
- Determine expected flue-gas flow and temperature.
- Identify the pollutants of regulatory concern.
- Establish applicable emission limits.
- Select the combustion system and APC together.
- Assess reagent, water and waste-residue requirements.
- Plan inspection, maintenance and consumables.
- Specify performance testing and monitoring.
Conclusion
Effective flue-gas cleaning is a complete system-engineering problem. Combustion quality, cooling, filtration, scrubbing, sorbent injection and monitoring must work together. The correct APC train cannot be selected responsibly from incinerator capacity alone; it requires a defined waste stream, gas conditions and regulatory target.