Ammonia injection amount control device and ammonia injection amount control method

摘要

PROBLEM TO BE SOLVED: To provide an ammonia injection quantity control device and an ammonia injection quantity control method for a denitrification plant, capable of detecting an abnormality that an ammonia flow transmitter malfunctions, and preventing continuation of operation in an excessive ammonia injection state.SOLUTION: An ammonia injection quantity control device for injecting ammonia into a denitrification plant includes circuits that calculate a denitrification ratio from a deviation between a value obtained by converting a NOx concentration at an inlet of the denitrification plant to a NOx concentration at a predetermined oxygen concentration and a set value of a NOx concentration at an outlet of the nitrification plant to convert the denitrification ratio to a molar ratio, that correct the molar ratio in view of the NOx concentration at the outlet, that determine an ammonia required quantity from the corrected molar ratio and a total NOx quantity, control an ammonia injection quantity based on the ammonia required quantity and an ammonia flow indication value, and detect an abnormality if a deviation between an ammonia required quantity determined from the total NOx quantity and the uncorrected molar ratio and the ammonia flow indication value is not smaller than a predetermined value. By providing the circuits, it is possible to notify surroundings of the abnormality. Therefore, it is possible to prevent continuation of operation in an abnormal state such as an excessive ammonia injection state.