ARRANGEMENT FOR DECOMPOSITION OF NITROGEN OXIDES IN A GAS STREAM AND THE USE THEREOF

摘要

The invention relates to an arrangement for decomposition of nitrogen oxides in a gas stream (1) which comprises a plurality of catalysts (3, 4, 5, 6) through which said gas can flow one after the other. Each catalyst (3, 4, 5, 6) has a honeycomb structure with many parallel cells (7) through which the gas (1) can flow, and a predetermined cell density and a predetermined average level of activity, defined as the proportion of weight of the catalytically active agent. The cell density of a second catalyst (4, 5, 6) through which gas (1) flows after the first catalyst (3, 4, 5) is lower than the cell density of the first catalyst (3, 4, 5). The average level of activity of the second catalyst (4, 5, 6) is also higher than the average level of activity of the first catalyst (3, 4,5). The stream (1) of gas is, in particular, exhaust gas from an internal combustion drive unit (9).