APPARATUS FOR CONTROLLING INJECTION AMOUNT OF AMMONIA INTO DENITRATION REACTOR

摘要

PURPOSE:To prevent NOx values at the outlet of a denitration reactor from increasing abruptly by the failure of control when the injection amount of ammonia is decreasing. CONSTITUTION:An apparatus is equipped with: a proportional-plus-integral controller 17 which compares a detected NOx value 12 by a NOx analyzer 11 installed on the outlet side of a denitration reactor 4 with a set NOx value 13 and outputs a signal to an ammonia flow controller 9 to equalize the detected value to the set one; a rate-of-change restricting device 18 installed downstream from the controller 17; a signal switch 21 which switches the changing speed of a signal by the device 18 either to a high speed side 19 or a low speed side 20; a primary delay circuit 22 which inputs the command signal 16 of the outlet of the controller 17 and shapes the signal 16; a differential analyzer 24 which judges the change of a signal 23 from the delay circuit 22 to be increasing or decreasing; and a switch controller 26 which switches a signal switch 21 to a high speed side 19 when a signal 25 from the differential analyzer 24 changes to increase and switches the signal switch 21 to a low speed side 20 when the signal 25 changes to decrease.