State-of-the-art control of nitrogen oxides requires both minimizing the formation of nitrogen oxides in the furnace and transforming them into nitrogen and water. Strategies for minimizing formation include using appropriate furnace designs (such as flue gas recirculation and dual-chambered furnaces) and operating practices (such as optimal temperatures and amount of excess air). See Section 5.22. Techniques for destroying nitrogen oxides involve injecting chemicals that neutralize them.
Chemical injection devices use ammonia, urea, or other compounds to react with nitrogen oxides to form nitrogen and water. The technologies for neutralizing and re moving nitrogen oxides from flue gases are called selective noncatalytic reduction (SNCR) and selective catalytic reduction (SCR). (See Section 5.23.) Both technologies have been successfully demonstrated on MSW incinerators. Wet scrubbing and condensation also have the capacity to control nitrogen oxides.
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