| 摘要 |
A method for controlling a combustion process in a combustion plant comprises sensing the content of NOx in the flue gases and affecting, on the basis thereof, the combustion by controlling a parameter to obtain the desired NOx content, wherein interference is caused in said at least one combustion process parameter, preferably the excess of O2 in the flue gases and/or the flow rate of a chemical supplied, e.g. urea, and generating a signal which gives successive values of the parameter and which is low-pass-filtered; measuring the NOx content and the O2 content of the flue gases by means of transducers so as to generate an NOx content signal and an O2 content signal; performing the NOx and O2 content measurements such that the signals obtained are referable to flue-gas measuring points located at any rate in the immediate vicinity of one another; low-pass-filtering the NOx and O2 content signals obtained and sampling these low-pass-filtered signals to obtain NOx and O2 content values successive in time; calculating zero-%-O2-compensated NOx comp content values by using the O2 content values obtained and then utilising O2 content values which are related in time to the corresponding NOx content values; high-pass-filtering the NOx comp content values and the successive parameter values; calculating, on the basis of the high-pass-filtered values, the relationship between NOx comp and the parameter; and controlling the parameter on the basis thereof.
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