Patent ID: 7901647

Claim:
A method for continuously controlling NO x removal efficiency in an emissions control system for a boiler in response to changes in the boiler operating parameters while controlling ammonia slip, the method comprising the steps of: providing a flue for conveying flue gases from the boiler to a stack for discharge; positioning a NO x reduction system along the flue between the boiler and the stack, the NO x reduction system being constructed so as the remove at least NO x from the flue gas along the flue, wherein the NO x reduction system relies in whole, or in part, upon ammonia introduced into the NO x reduction system via at least one ammoniacal compound injection point; varying, in response to the changes in boiler operating parameters, a stoichiometric ratio of ammonia to NO x introduced into the NO x reduction system to achieve a desired level of NO x removal regardless of the amount of ammonia slip from the NO x reduction system; and positioning an ammonia reduction system downstream of the NO x reduction system, wherein the ammonia reduction system contains at least one ammonia destruction catalyst and the ammonia destruction catalyst permits the NO x reduction system to be operated to achieve a desired level of NO x removal without a corresponding increase in ammonia slip downstream of the ammonia reduction system.