Appeal No. 96-0153
Application No. 08/014,407
This is a decision on an appeal from the final rejection
of claims 1 through 6 which are all of the claims remaining in
the application.
The subject matter on appeal relates to a process for
selective catalytic reduction of nitrogen oxides from exhaust
gases using pulsed superstoichiometric addition of NH or NH -3 3
releasing substances. Claims 1 and 5 are representative of
this appealed subject matter and read as follows:
1. A process for selective catalytic reduction of
nitrogen oxides from exhaust gases, using pulsed
superstoichiometric addition of NH or NH -releasing3 3
substances, which comprises controlling the pulsed
superstoichiometric addition of NH in such a way that, after
3
it has started, the addition is interrupted again only when
the amount of NH stored in the catalyst has reached a
3
specific upper threshold value which is predetermined in
accordance with the catalyst properties and the catalyst
volume, the amount of NH stored being calculated from the
3
difference between the metered amount of NH and the amount of
3
NO separated off, which is determined from the NOx x
concentration in the exhaust gas and the average degree of
separation, and the addition of NH is resumed only when the
3
amount of NH stored in the catalyst, which is determined in
3
the same way, has reached a predetermined lower threshold
value, this pulsed addition of NH being interrupted after a
3
predetermined number of cycles until the amount of NH stored
3
in the catalyst, which is determined in the manner described,
has completely reacted, this completing one entire cycle of
the pulsed addition of NH .
3
5. The process of claim 1, wherein the NO concentration
x
downstream of the catalyst is measured and the interruption in
NH metering after the predetermined number of cycles does not
3
2
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