| 摘要 |
<p>A method of controlling the concentration of nitrogen oxides (NOx), hydrocarbons (HC) and carbon monoxide (CO) in waste gases, such as burner fumes and the exhaust gases of internal combustion engines, wherein the method comprises passing the waste gases through a catalyst for the catalytic cleansing of said gases, wherein a first lambda value (μ1) of the supplied fuel mixture is caused to be less than a value = 1, and wherein the waste gas is passed through a first catalyst (8) and then through a second catalyst (9), wherein the CO-concentration of the gas in the first catalyst (8) is caused to be sufficiently high to reduce NOx to N2 to an extent such that the NOx concentration is brought down to a predetermined value, and wherein oxygen (O2) is caused to be delivered between the first catalyst (8) and the second catalyst (9) in a quantity sufficient to oxidise both CO and HC to CO2 and H2O to an extent such as to bring the CO-concentration down to a predetermined value.The invention is characterised by measuring a second lambda value (μ2) in the waste gas downstream of said second catalyst with the aid of a measuring device (29) that is adapted to send a signal to a microprocessor (30) or some corresponding device that has an associated memory; and in that a valve (31; 32) for regulating the oxygen supply in relation to the fuel supply is caused to be controlled by said microprocessor such as to cause said second lambda value (μ2) to lie within a predetermined range whose lower limit is higher than a value = 1.</p> |
