Selective Noncatalytic Reduction – In SNCR a reducing
agent (typically ammonia or urea) is injected into
the furnace above the combustion zone, where it reacts
with NOx to form nitrogen gas and water vapor, thus reducing
NOx emissions. The critical factors in applying
SNCR are sufficient residence time in the appropriate
temperature range and even distribution and mixing of
the reducing agent across the full furnace cross section.