Feedback control method in V-shaped characteristic system, and NH3 injection rate control method for NOx removal apparatus using the same

摘要

In the NH₃ injection rate control method for an NO_x removal apparatus, operating area of the apparatus is divided into first area in which molar ratio of NH₃ injection rate with respect to NO_x flow rate at an inlet of the apparatus is smaller than molar ratio at minimum point where NO_x concentration assumes minimum value and second area in which the molar ratio is equal to or larger than the minimum point molar ratio, and virtual NO_x concentration with respect to the molar ratio is set according to virtual characteristic line which varies monotonically to stride across desired operating point without rising with increase of the molar ratio from the first area to the second area. Moreover, feedback control is implemented for adjusting the NH₃ injection rate with respect to the NO_x flow rate in direction that the virtual NO_x concentration is brought close to the desired NO_x concentration.