System and method for sequential injection of reagent to reduce NOx from combustion sources
AssigneePeerless Mfg. Co.
InventorsJeffrey Michael Broderick, Scott H. Lindemann, Eric Lindemann, James M. Valentine
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Abstract
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.
Claims24
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 together as a group, 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.
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,
- wherein the plurality of injectors comprises a first injector, a second injector and a third injector, and wherein said controller:
- (a) causes the first injector to inject while the second and third injectors are caused to be not injecting;
- (b) causes the second injector to inject while the first and third injectors are caused to be not injecting;
- and
- (c) causes the third injector to inject while the first and second injectors are caused to be not injecting;
- and wherein steps (a)-(c) are sequentially repeated.
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,
- wherein the plurality of injectors comprises an even number of four or more injectors and the injectors are operated and sequenced in groups.
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,
- wherein the lean burn combustion source comprises two lean burn combustion sources exhausting into a common duct and the common duct further comprises a second plurality of injectors that substantially continuously inject reagent into the exhaust gases of the combustion sources during operation thereof.
A method of reducing pollutant emissions from a lean burn combustion source equipped with a plurality of injectors that inject reagent into exhaust gases of the combustion source, said method comprising the steps of:
- operating the plurality of injectors 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
- allowing the reagent to decompose in the exhaust gases and to react across a downstream catalyst to reduce pollutant emissions,
- wherein the plurality of injectors comprises a first injector, a second injector and a third injector, and wherein said operating step comprises the steps of:
- (a) causing the first injector to inject while the second and third injectors are caused to be not injecting;
- (b) causing the second injector to inject while the first and third injectors are caused to be not injecting;
- and
- (c) causing the third injector to inject while the first and second injectors are caused to be not injecting;
- and wherein steps (a)-(c) are sequentially repeated.
A method of reducing pollutant emissions from a lean burn combustion source equipped with a plurality of injectors that inject reagent into exhaust gases of the combustion source, said method comprising the steps of:
- operating the plurality of injectors 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
- allowing the reagent to decompose in the exhaust gases and to react across a downstream catalyst to reduce pollutant emissions,
- wherein the plurality of injectors comprises an even number of four or more injectors and the injectors are operated and sequenced in groups, and
- wherein the plurality of injectors comprises an even number of four or more injectors and the injectors are operated and sequenced in groups.
A method of reducing pollutant emissions from a lean burn combustion source equipped with a plurality of injectors that inject reagent into exhaust gases of the combustion source, said method comprising the steps of:
- operating the plurality of injectors 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
- allowing the reagent to decompose in the exhaust gases and to react across a downstream catalyst to reduce pollutant emissions,
- wherein the plurality of injectors comprises an even number of four or more injectors and the injectors are operated and sequenced in groups, and
- wherein the lean burn combustion source comprises two lean burn combustion sources exhausting into a common duct and the common duct is further equipped with a second plurality of injectors that substantially continuously inject reagent into the exhaust gases of the combustion sources during operation thereof.
Dependencies are inferred from the claim text.