System and Method for Sequential Injection of Reagent to Reduce NOx from Combustion Sources

摘要

In a large exhaust duct from a lean burn combustion source, such as a boiler, diesel engine or gas turbine, multiple injectors can be used to inject a reagent, such as an aqueous solution of urea or ammonia, into the exhaust for use in the catalytic reduction of NOx in a process known in the art as selective catalytic reduction (SCR). When operating at low injection rates, such as during low combustor loads, the injectors are operated individually for short periods of time in a sequential manner.

主权项

1. A lean burn combustion source having reduced pollutant emissions, said lean burn combustion source comprising:
an exhaust duct having exhaust gases passing therethrough; a plurality of injectors positioned so as to inject reagent into the exhaust gases passing through the exhaust duct; a controller in communication with said plurality of injectors, said controller causing said plurality of injectors to operate in an alternating sequence wherein at least one of the plurality of injectors is caused to inject for a period of time while the remaining ones of the plurality of injectors are caused to be not injecting, and a catalyst located downstream of said plurality of injectors and spaced apart from said plurality of injectors such that the reagent is allowed to decompose in the exhaust gases and to react across the catalyst to reduce pollutant emissions.