Flue Gas Cleaning

DeNOx SCR Systems

Selective Catalytic Reduction

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The DeNOx SCR unit is used for the reduction of $\ce{NOx}$ content in the flue gas out of the boiler. The process of DeNOx SCR reduces nitrogen oxides $\ce{NOx}$ of combustion flue gases into molecular nitrogen $\ce{N2}$ and water vapor $\ce{H2O}$.


$\ce{NOx}$ breaks down when it reacts with the reducing agent $\ce{NH3}$, in the presence of the catalyst. The ammonia $\ce{NH3}$ is distributed into the flue gas prior to the catalyst The catalyst, by providing active reaction sites, allows the reaction to occur at lower temperatures than usually used for this kind of reaction. The $\ce{NH3}$ diffuses into the catalyst pore structure and is adsorbed onto an active catalyst site. The $\ce{NOx}$ then reacts with the adsorbed $\ce{NH3}$, completing the reaction. The reaction depends primarily on available active sites (a function of geometric surface area, pore volume, and concentration of active catalyst component), flue gas temperature and reagent concentration. A well-balanced process will maintain appropriate output levels of residual $\ce{NOx}$ and $\ce{NH3}$.
The SCR system consists of the SCR reactor, where the catalyst is installed. For reaction of $\ce{NOx}$ and $\ce{NH3}$ to $\ce{N2}$ and $\ce{H2O}$ over the catalyst, an $\ce{NH3}$/air mixture is injected upstream the reactor by means of the ammonia injection grid (AIG).

For the $\ce{NH3}$ supply, aqueous ammonia $\ce{NH4OH}$ or urea is stored in tanks and evaporated by the vaporizer, mixed with hot dilution air and injected into the flue gas before the catalyst.

DeNOx SNCR Systems

Selective Non-Catalytic Reduction

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We provide the leading technologies regarding SNCR designs with ammonia and urea for optimal performance, reducing nitrogen oxides $\ce{NOx}$ in combustion flue gases into molecular nitrogen $\ce{N2}$ and water vapor $\ce{H2O}$.

The simplified reduction with ammonia ($\ce{NH3}$) of the nitrogen oxide is $\ce{4 NO + 4 NH3 + O2 -> 4 N2 + 6 H2O}$. In case of urea ($\ce{NH2CONH2}$) ammonia is first produced: $\ce{NH2CONH2 + H2O -> 2NH3 + CO2}$

$\ce{NOx}$ breaks down when it reacts with the reducing agent $\ce{NH3}$, without the presence of the catalyst at temperatures of $760^\circ\mathrm{C}$ to $1090^\circ\mathrm{C}$.

SNCR provides

• lessening of nitrogen oxide emissions
• simple and agile establishment
• reduced investment expenses