DENITRIFICATION CASCADE CONTROL METHOD USING NITROGEN OXIDE ANALYZER AT REAR STAGE OF INDUCED DRAFT FAN OF POWER PLANT

摘要

The present invention provides a denitrification cascade control method using a nitrogen oxide (NOx) analyzer at a rear stage of an induced draft fan (IDF) of a power plant to discharge a combustion gas discharged from a combustor, through a selective catalytic reduction (CSR), an electric precipitator (EP), the IDF, and a chimney, comprising the steps of: calculating an amount of NOx to be processed in the CSR of the plant according to an equation (amount of NOx to be processed = concentration of NOx on an entrance side of the SCR measured by the NOx analyzer installed on the entrance side of the SCR-Set value of concentration of chimney NOx)*flow rate, and calculating a supply amount of ammonia supplied to the SCR according to the calculated amount of NOx; calculating a set value of a concentration of NOx at a rear stage of the IDF through proportional integral derivative (PID) controlling using the set value of the concentration of the chimney NOx and an actual concentration of the chimney NOx obtained by the NOx analyzer; calculating an ammonia supply amount correction value through PID controlling using the calculated set value of the concentration of the NOx at the rear stage of the IDF and the actual concentration of the NOx at the rear stage of the IDF measured by the NOx analyzer installed at the rear stage of the IDF; and calculating a final ammonia supply amount by a feedforward value as the calculated ammonia supply amount and a feedback value as the ammonia supply amount correction value. When a NOx generated after combustion of fossil fuel is discharged through a chimney in a thermoelectric power plant or any other plant, a discharge concentration target value is rapidly and accurately reached and maintained.;COPYRIGHT KIPO 2016