Patent ID: 6638487
Filing Date: 2003-10-28
Classification: B01D

Abstract:
A method for controlling a NOx removal system (7) in which reductant supply is adjusted according to combustion level in a boiler (1) in which the combustion level is controlled in multiple stages, the method comprising for a decrease of the combustion level from a higher level (A) to a lower level (B), the steps of:reducing the reductant supply from a high level (C) to a level (E) which is lower than a level (D) corresponding to a changeover-target combustion level and keeping the reductant supply at said level (E) for a period of a set time (F) from the time at which changeover of the combustion level was effected and, at the end of time period (F) measured from the time at which the reductant supply was reduced from level (C) to level (E), increasing the reductant supply to said level (D).