Method of regulating the amount of reducing agent added during catalytic reduction of NOx contained in flue gases

Claim 2

In a process of regulating the amount of reducing agent added during the catalytic reduction of NO x of flue gases originating from a combustion installation fired with fossil fuels with which an adjustment value to be used for regulation of a quantity of reducing agent to be added is determined selectively, in response to a prescribed reducing agent/NO x stoichiometry factor, from the quantity of combustion air supplied to the combustion installation, as well as from the quantity of exiting flue gas, plus the NO x concentration downstream ahead of the catalyzer; the improvement in combination therewith which includes the steps of: returning to the regulation process, as a primary correction value, the value of the NO x concentration in flue gas downstream after said catalyzer corrected via O 2 -concentration in the flue gas always to influence directly the prescribed reducing agent NH 3 -quantity rather than to influence the reducing agent/NO x -stoichiometry factor; returning to the regulation processs, as a secondary correction magnitude, the flue gas temperature ahead of said catalyzer; and influencing the set stoichiometry factor in such a way that, while maintaining the NO x emission limit value as the desired value of the primary correction value, said stoichiometry factor is regulated specifically via the temperature-dependent activity curve of said catalyzer.

Claim 3

In a process for volume control of reducing agent, especially volume control of ammonia, for the catalytic reduction of NO x of flue gases or fumes, originating from a combustion installation fired with fossil fuels, whereby a regulated quantity for the reducing-agent volume control is ascertained and variable from a prescribed and controllable reducing-agent/NO x -stoichiometric-factor and from a NO x -volume or quantity calculated via the flue-gas volume or quantity and the NO x -concentration in flue gas (fumes), the improvement in combination therewith which includes steps of: utilizing NO x -concentration which itself is corrected as to NH 3 -quantity via the oxygen-concentration in flue gas after the catalyzer as primary correction magnitude and the actual value after comparison with the rated or real-specified limiting or boundary value to be maintained, thus primarily changing the regulated quantity or controller output for the reducing-agent volume control; and as secondary correction magnitude the flue gas temperature before or ahead of the catalyzer and the reducingagent concentration after the catalyzer upon departure from prescribed rated value in a predetermined range of 50 ppm to 3 ppm volume preferably less than 10 ppm volume, secondarily influencing the stoichiometric factor to be set or adjusted via NH 3 -concentration and/or flue gas temperature-dependent activity as to stoichiometry factor respresented by a stoichiometry curve of the catalyzer, from which, subsequently via multiplication with the NO x -volume or quantity, there is calculated from the NO x -concentration in flue gas or fumes and the moisture-corrected flue gas quantity or volume before the catalyzer, thereby ascertaining the rated quantity or controller output for the reducing-agent volume control.

Claim 4

In a process for volume control of reducing agent, especially volume control of ammonia, for the catalytic reduction of NO x of flue gases or fumes, originating from a combustion installation fired with fossil fuels, whereby a regulated quantity for the reducing-agent volume control is ascertained and variable from a prescribed and controllable reducing-agent/NO x -stoichiometric-factor and from a NO x -volume or quantity calculated via the flue-gas volume or quantity and the NO x -concentration in flue gas (fumes), the improvement in combination therewith which includes steps of: utilizing NO x -concentration which itself is corrected as to NH 3 -quantity via the oxygen-concentration in flue gas after the catalyzer as primary correction magnitude and the actual value after comparison with the rated or real-specified limiting or boundary value to be maintained, thus primarily changing the regulated quantity or controller output for the reducing-agent volume control; and as secondary correction magnitude the flue gas temperature before or ahead of the catalyzer and the reducingagent concentration after the catalyzer upon departure from prescribed rated value in a predetermined range of 50 ppm to 3 ppm volume preferably less than 10 ppm volume, secondarily influencing the stoichiometric factor to be set or adjusted via NH 3 -concentration and/or flue gas temperature-dependent activity as to stoichiometry factor respresented by a stoichiometry curve of the catalyzer, from which, subsequently via multiplication with the NO x -volume or quantity, there is calculated from the NO x -concentration in flue gas or fumes and the moisture-corrected flue gas quantity or volume before the catalyzer, thereby ascertaining the rated quantity or controller output for the reducing-agent volume control.