| The most widely
used NOx control technology, selective catalytic
reduction (SCR), involves mixing the exhaust air
with gaseous reagent, typically ammonia or urea,
and passing the homogenous mixture over a bed of
catalyst designed for reaction completion at the
airstream temperature. The catalyst promotes a reaction
between NH3, NOx and the excess oxygen (O2) in the
exhaust stream, forming nitrogen (N2) and water
(H2O).
Historically, the typical operating
temperatures of vanadia/titania catalysts are between
500°F and 800°F, and that has satisfied many
industrial applications. Low temperature gases can be
treated using heat recovery systems, but advances in
catalyst technology have created catalysts that can
directly treat operating temperatures as low as 250°F.
For high temperature applications up to 1100°F,
zeolite catalyst provides for high performance and stability.
In these times of ever increasing utility costs, properly
matching the catalyst to the process temperature will
optimize performance and result in lower costs of operation.
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