Selective Chemically Induced Denitrification (SCID)

SCID is an innovative gas-phase denitrification technique for reducing nitrogen oxides (NOₓ) and/or ammonia (NH₃) emissions in industrial combustion processes. It enables effective NOₓ removal at mid-range temperatures without the use of solid catalysts and can be integrated directly into existing flue-gas systems of installations such as cement kilns, waste-to-energy plants, and biomass combustion units.

SCID is based on a gas-phase chemical denitrification mechanism that combines key elements of selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR) through the chemical activation of ammonia. The process operates typically within 600–780 °C and relies on the in-situ formation of a gas-phase catalyst (GPC) by co-injecting ammonia with a plant-specific eqinox additive. The additive used is an application-specific mixture of organic nitrogen and oxygen compounds. No aromatic compounds are used. The additive is ash-free and decomposes into nitrogen, carbon dioxide, and water when used.
Under the site-specific thermal and flow conditions, the additive decomposes to form reactive radicals that activate ammonia via hydrogen abstraction, producing NH₂ radicals. These selectively react with NOₓ to form N₂ and H₂O. Unlike conventional SNCR, which depends on thermal activation at 800–1100 °C, SCID achieves activation chemically, enabling effective NOₓ reduction outside a strict reaction window and allowing more flexible integration.

The GPC is self-sustaining and decomposes into environmentally benign species, leaving no catalyst residues. SCID also utilizes residual ammonia already present in the flue gas, thereby reducing ammonia slip and improving overall depollution performance. The technology operates entirely within the existing flue-gas path and does not require structural modification of the primary process or the use of solid catalysts.

DEMONSTRATION
A full-scale demonstration with a mobile SCID installation on a cement kiln confirmed significantly improved performance compared to the existing SNCR system:

- NOₓ-reduction performance doubled relative to the baseline SNCR configuration.

- 25 % higher NOₓ-reduction performance combined with 37.6 % lower ammonia consumption than SNCR configuration.

CONCLUSIONS
A key conclusion from the full-scale mobile testing on the cement installation is that SCID delivers a substantially higher denitrification performance at a significantly lower reaction temperature, confirming the superior effectiveness of chemically induced activation relative to the thermally driven SNCR mechanism. In addition, SCID demonstrated a markedly improved reagent efficiency.

These results demonstrate the potential for major improvements in depollution performance and reagent efficiency. SCID is expected to show similar benefits in other combustion-based sectors, with further validation planned through upcoming pilot installations.

OUTLOOK
An important aspect for upcoming pilot installations is SCID’s ability to manage process-generated ammonia, aside of NOₓ-reduction agents present in the flue gas. Many industrial combustion systems produce ammonia as a by-product. SCID can either:

(i) degrade this ammonia without affecting NOₓ abatement, preventing ammonia slip and maintaining performance of other systems; or
(ii) use it as a reactant to support NOₓ reduction, optimizing the use of internal resources.

The dominant mode will depend on flue-gas composition and plant configuration, and pilot tests will assess both scenarios.

Basic information about the technique

Production data

The SCID evaluation was conducted using a mobile unit connected to a full-scale operational cement kiln. Future pilot installations will generate permanent long-term production-coupled environmental datasets. The flue gas flow at the application zone at the time of testing was approx. 125,000 Nm³/h (dry).

Associated main production process(es) and product(s): Combustion Processes e.g. biomass to energy production, cement production, waste to energy production etc.

Cross media effects

Use of hazardous substances

Participant Companies