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Denitrification System
DeNOx (SNCR)

Selective Non-Catalytic Reduction (SNCR) is a method used to reduce nitrogen oxide (NOX) emissions from industrial combustion processes, particularly in boilers, furnaces, and power plants. SNCR involves injecting a reagent, typically ammonia (NH3) or urea, into the combustion chamber or flue gas ducts at elevated temperatures to react with nitrogen oxides and reduce them to nitrogen (N2) and water vapor (H2O), which are less harmful to the environment.

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Key Components of SNCR Systems:

Injection System: SNCR systems typically include an injection system consisting of one or more injection lances or nozzles located in the combustion chamber or flue gas ducts. The reagent, such as aqueous ammonia or urea solution, is injected into the combustion zone or flue gas stream at controlled rates.

Reaction Zone: The reagent is injected into the combustion zone or flue gas stream, where it reacts with nitrogen oxides (NOX) at elevated temperatures (typically between 816°C to 1149°C). The reaction forms nitrogen (N2), water vapor (H2O), and small amounts of nitrogen-containing compounds, such as nitrogen dioxide (NO2) or nitrous oxide (N2O).

Temperature Control: SNCR systems require specific temperature ranges for effective NOx reduction. The temperature range varies depending on the type of reagent used and the specific reaction kinetics. Control systems may be employed to monitor and adjust the temperature within the reaction zone to optimize NOx reduction efficiency.

The primary reactions involved in SNCR include:

  • For aqueous ammonia (NH3) injection:

    • 4 NH3 + 4 NO + O2 → 4 N2 + 6 H2O

  • For urea injection:

    • CO(NH2)2 + 2 NO → 2 N2 + CO2 + 2 H2O

 

Advantages of SNCR:

Cost-Effectiveness: SNCR systems are generally less expensive to install and operate compared to Selective Catalytic Reduction (SCR) systems, particularly for applications with lower NOx reduction requirements.

Flexibility: SNCR systems can be retrofitted to existing combustion equipment and can accommodate varying load conditions and fuel compositions.

No Catalyst Required: Unlike SCR systems, SNCR does not require a catalyst, reducing initial capital costs and eliminating the need for catalyst replacement and maintenance.

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