| 摘要 |
Process for the selective catalytic reduction of nitrogen oxides from exhaust gases, preferably from exhausts gases of motor vehicle diesel engines, with timed superstoichiometric addition of NH3 or NH3-releasing substances, the timed superstoichiometric NH3 addition being controlled in such a manner that the addition, after its start, is only interrupted when the NH3 quantity stored in the catalyst has reached a defined preset upper threshold value, corresponding to the catalyst properties and the catalyst volume, the stored NH3 quantity being calculated from the difference between the metered NH3 amount and the released NOx amount, determined from the NOx concentration in the exhaust gas and the mean release rate, and the NH3 feed being only restarted when the NH3 amount stored in the catalyst, determined in the same way, has reached a preset lower threshold value, this timed NH3 feed being terminated after a predetermined number of cycles until the NH3 amount stored in the catalyst, determined in the manner described, is completely reacted to exhaustion, with which a complete cycle of the timed NH3 feed is concluded.
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