US 5,756,059 AGranted

Advanced reburning methods for high efficiency NO.sub.x control

AssigneeEnergy and Environmental Research Corporation

InventorsVladimir M. Zamansky, Peter M. Maly, William Randall Seeker

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Abstract

The present invention is related to methods and systems for preventing the release of nitrogen oxides with combustion flue gases emitted to the atmosphere. The invention is specifically directed to the removal of nitric oxide, nitrogen dioxide, and nitrous oxide from flue gas in stationary combustion systems. The methods of the invention improve efficiency of conventional reburning and advanced reburning processes by two key improvements, including the injection of a reducing agent into the reburning zone and the use of promoters, which considerably enhance NO.sub.x control. The promoters are metal-containing compounds that can be added to the reducing agents. These improvements allow either one or two stages of reducing agent injection for greater NO.sub.x control.

Claims43

Dependent claims

A method for reducing nitrogen oxides in combustion flue gas comprising the steps of:

(a) injecting a reburning fuel at a temperature in a range from about 2000.degree. F. to about 3000.degree. F. into combustion flue gas including oxygen and nitrogen oxides thereby forming a fuel rich area in a reburning zone;
(b) passing a resulting mixture of reaction products from the fuel rich area of the reburning zone into an overfire air zone;
(c) introducing a stream of overfire air at a temperature in a range from about 1100.degree. F. to about 2400.degree. F. into the overfire air zone;
(d) injecting a reducing agent into the combustion flue gas along with the overfire air, the reducing agent providing a source of nitrogenous reducing species and being a precursor of nitrogenous radicals, the reducing agent selected from the group consisting of ammonia, urea, cyanuric acid, ammonium sulfate, ammonium bisulfate, ammonium sulfite, ammonium bisulfite, ammonium formate, ammonium carbonate, ammonium bicarbonate, biuret, triuret, ammelide, and mixtures thereof;
(e) injecting a promoter compound along with the reducing agent to enhance the effectiveness of the reducing agent, the promoter compound selected from the group consisting of oxides, hydroxides, carbonates, sesquicarbonates, bicarbonates, phosphates, silicates, nitrates, formates, acetates, benzoates, citrates, gluconates, aluminates, borates, and mixtures thereof, the promoter compound including a metal selected from the group consisting of lithium, sodium, potassium, barium, zinc, aluminum, and combinations thereof, the molar ratio of the promoter compound to the reducing agent being in a range from about 0.01 to about 1;
and
(f) allowing the reducing agent to react within the combustion flue gas for a sufficient time to reduce the nitrogen oxides in the combustion flue gas.

4 more elements

A method for reducing nitrogen oxides in combustion flue gas comprising the steps of:

(a) injecting a reburning fuel at a temperature in a range from about 2000.degree. F. to about 3000.degree. F. into combustion flue gas including oxygen and nitrogen oxides;
(b) allowing the reburning fuel to react within the combustion flue gas for a sufficient time to remove a substantial portion of the oxygen, thereby forming a fuel rich area in a reburning zone;
(c) injecting a reducing agent into the combustion flue gas in the fuel rich area at a temperature in a range from about 1900.degree. F. to about 3000.degree. F., the reducing agent providing a source of nitrogenous reducing species and being a precursor of nitrogenous radicals, the reducing agent injected such that a predetermined time delay between injection of the reburning fuel and the reducing agent is from about 0.01 to about 1 second, the reducing agent selected from the group consisting of ammonia, urea, cyanuric acid, ammonium sulfate, ammonium bisulfate, ammonium sulfite, ammonium bisulfite, ammonium formate, ammonium carbonate, ammonium bicarbonate, biuret, triuret, ammelide, and mixtures thereof:
(d) injecting a promoter compound along with the reducing agent to enhance the effectiveness of the reducing agent, the promoter compound selected from the group consisting of oxides, hydroxides, carbonates, sesquicarbonates, bicarbonates, phosphates, silicates, nitrates, formates, acetates, benzoates, citrates, gluconates, aluminates, borates, and mixtures thereof, the promoter compound including a metal selected from the group consisting of lithium, sodium, potassium, barium, zinc, aluminum, and combinations thereof, the molar ratio of the promoter compound to the reducing agent being in a range from about 0.01 to about 1;
(e) allowing the reducing agent to react within the combustion flue gas for a sufficient time to reduce the nitrogen oxides in the combustion flue gas;
and
(f) introducing a stream of overfire air at a temperature in a range from about 1100.degree. F. to about 2400.degree. F. into the combustion flue gas after injecting the reducing agent and the promoter compound.

4 more elements

A method for reducing nitrogen oxides in combustion flue gas comprising the steps of:

(a) injecting a reburning fuel at a temperature in a range from about 2000.degree. F. to about 3000.degree. F. into combustion flue gas including oxygen and nitrogen oxides;
(b) allowing the reburning fuel to react within the combustion flue gas for a sufficient time to remove a substantial portion of the oxygen, thereby forming a fuel rich area in a reburning zone;
(c) injecting a reducing agent into the combustion flue gas in the fuel rich area at a temperature in a range from about 1900.degree. F. to about 3000.degree. F., the reducing agent providing a source of nitrogenous reducing species and being a precursor of nitrogenous radicals, the reducing agent injected such that a predetermined time delay between injection of the reburning fuel and the reducing agent is from about 0.01 to about 1 second, the reducing agent selected from the group consisting of ammonia, urea, cyanuric acid, ammonium sulfate, ammonium bisulfate, ammonium sulfite, ammonium bisulfite, ammonium formate, ammonium carbonate, ammonium bicarbonate, biuret, triuret, ammelide, and mixtures thereof;
(d) injecting a promoter compound along with the reducing agent to enhance the effectiveness of the reducing agent, the promoter compound selected from the group consisting of oxides, hydroxides, carbonates, sesquicarbonates, bicarbonates, phosphates, silicates, nitrates, formates, acetates, benzoates, citrates, gluconates, aluminates, borates, and mixtures thereof, the promoter compound including a metal selected from the group consisting of lithium, sodium, potassium, barium, zinc, aluminum, and combinations thereof, the molar ratio of the promoter compound to the reducing agent being in a range from about 0.01 to about 1;
(e) allowing the reducing agent to react within the combustion flue gas for a sufficient time to reduce the nitrogen oxides in the combustion flue gas;
(f) introducing a stream of overfire air at a temperature in a range from about 1100.degree. F. to about 2400.degree. F. into the combustion flue gas after injecting the reducing agent and the promoter compound;
(g) injecting an additional reducing agent into the combustion flue gas along with the overfire air, the additional reducing agent providing a source of nitrogenous reducing species and being a precursor of nitrogenous radicals;
and
(h) injecting an additional promoter compound along with the additional reducing agent to enhance the effectiveness of the additional reducing agent, the molar ratio of the additional promoter compound to the additional reducing agent being in a range from about 0.01 to about 1.

6 more elements

Dependencies are inferred from the claim text.