# US 2013/0156671 A1 · Method and apparatus to inject reagent in sncr/scr emission system for boiler

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- Number: US 2013/0156671 A1
- Document ID: US20130156671A1
- Status: Published application
- Kind: A1
- Application number: 13/327,121
- Filed: 2011-12-15
- Published: 2013-06-20
- Earliest claimed: 2011-12-15
- Assignees: General Electric Company
- Inventors: David Kelly Moyeda; Wei Zhou; Antonio Marquez; Xu Guang; Santosh Nareddy
- Web page: https://patentgrep.com/patent/US20130156671A1

## CPC

- B01D 53/56: Nitrogen oxides (B01D53/60 takes precedence)
- B01D 53/8631: {Processes characterised by a specific device}
- F23J 15/003: {for supplying chemicals to fumes, e.g. using injection devices}
- B01D 2257/404: Nitrogen oxides other than dinitrogen oxide
- B01D 2258/0283: Flue gases
- F23J 2215/10: Nitrogen; Compounds thereof
- F23J 2219/10: Catalytic reduction devices
- F23J 2219/20: Non-catalytic reduction devices
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- F23J: REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES (combustion apparatus for consuming smoke or fumes, e.g. exhaust gases, F23G7/06)

## Abstract

An apparatus to introduce a reagent to reduce nitrogen oxides in flue gas including: nozzles mounted to a passage for the flue gas, wherein the nozzles are mounted downstream of a SNCR system and upstream of a SCR system, wherein the nozzles are mounted on one or more walls of the passage and are configured to inject a pressurized fluid into the flue gas; a source of the pressurized fluid which is in fluid communication with the nozzles such that the pressurized fluid flows to the nozzles; a source of a NOx reducing reagent and a mixing device which mixes the reagent with the pressurized fluid such that the pressurized fluid flowing to the nozzles includes the reagent.

## Claims

### Claim 1

An apparatus to introduce a reagent to reduce nitrogen oxides in flue gas, the apparatus comprising:
nozzles mounted to a passage for the flue gas, wherein the nozzles are mounted downstream of a SNCR system and upstream of a SCR system, wherein the nozzles are mounted on at least one wall of the passage and are configured to inject a pressurized fluid into the flue gas;
a source of the pressurized fluid which is in fluid communication with the nozzles such that the pressurized fluid flows to the nozzles;
a source of a NOx reducing reagent, and
a mixing device which mixes the reagent with the pressurized fluid such that the pressurized fluid flowing to the nozzles includes the reagent.

### Claim 2 (depends on 1)

The apparatus of claim 1 wherein the source of NOx reducing reagent is a source of at least one of urea and ammonia.

### Claim 3 (depends on 1)

The apparatus of claim 1 wherein the nozzles are mounted on opposite sidewalls of the passage.

### Claim 4 (depends on 3)

The apparatus of claim 3 wherein the nozzles on each sidewall are vertically aligned.

### Claim 5 (depends on 3)

The apparatus of claim 3 wherein the nozzles are arranged in a staggered pattern.

### Claim 6 (depends on 3)

The apparatus of claim 3 wherein the nozzles on each sidewall are not in horizontal alignment with the nozzles on the opposite sidewall.

### Claim 7 (depends on 1)

The apparatus of claim 1 wherein the source of the pressurized fluid is a source of steam.

### Claim 8

A boiler having a system to reduce nitrogen oxides in flue gas, the boiler comprising:
a combustion chamber;
a passage for flue gas generated in the combustion chamber;
a SNCR system including at least one injector injecting a nitrogen oxides reducing reagent into the flue gas, wherein the nozzles are mounted to the passage;
nozzles mounted to the passage downstream of the SNCR system and upstream of a SCR system, wherein the nozzles are mounted on at least one wall of the passage and are configured to inject a pressurized fluid into the flue gas;
a source of the pressurized gas which is in fluid communication with the nozzles such that the pressurized fluid flows to the nozzles;
a source of a NOx reducing reagent;
a mixing device which mixes the reagent with the pressurized gas such that the pressurized fluid ti flowing to the nozzles includes the reagent, and
the SCR system includes a support structure for a catalyst, wherein the support structure is in the passage and exposes to the flue gas.

### Claim 9 (depends on 8)

The apparatus of claim 8 wherein the source of NOx reducing reagent is a source of at least one of urea and ammonia.

### Claim 10 (depends on 8)

The apparatus of claim 8 wherein the nozzles are mounted on opposite sidewalls of the passage.

### Claim 11 (depends on 10)

The apparatus of claim 10 wherein the nozzles on each sidewall are vertically aligned.

### Claim 12 (depends on 10)

The apparatus of claim 10 wherein the nozzles on each sidewall are not in horizontal alignment with the nozzles on the opposite sidewall.

### Claim 13

A method to reduce airborne nitrogen oxides (NOx) in combustion gas comprising:
generating combustion gas and directing the flow of combustion gas through a passage;
reducing the airborne NOx by injecting via a SNCR system a NOx reducing reagent in the combustion gas flowing through the passage, wherein heat energy in the combustion gas promotes a chemical reaction between the reducing reagent and the NOx;
injecting into the passage, downstream of the injection of the NOx reducing reagent, a mixture of steam and the NOx reducing reagent through an array of nozzles arranged on at least one side of the passage, wherein the mixture is formed upsteam of the array of nozzles and distributed to the array of nozzles, and
further reducing the airborne NOx in the combustion gas by using a catalyst to promoting a reaction between combustion gas and the NOx reducing reagent injected with the steam.

### Claim 14 (depends on 13)

The method of claim 13 wherein the first reducing step injects the NOx reducing reagent into the combustion gas, while the gas is at a temperature of at least 1500 degrees Fahrenheit (815 degrees Celsius).

### Claim 15 (depends on 13)

The method of claim 13 wherein the further reducing step is performed while the combustion gas is at a temperature below 1200 degrees Fahrenheit (650 degrees Celsius) as the gas flows over the catalyst.

### Claim 16 (depends on 13)

The method of claim 13 wherein the combustion gas is flue gas flowing through a flue gas duct in a boiler, and the method further comprises transferring heat energy from the combustion gas by passing the combustion gas through a conductive pass pendants in the flue gas duct downstream of the injection of the NOx reducing reagent.

### Claim 17 (depends on 13)

The method of claim 13 wherein the injection of the mixture of steam and the NOx reducing reagent is through nozzles that are mounted on opposite sidewalls of the passage.

### Claim 18 (depends on 13)

The method of claim 13 wherein in the reducing step the introduced NOx reducing reagent is substantially completely reacted by the heat energy and NOx.

### Claim 19 (depends on 13)

The method of claim 13 wherein in the first reducing step a portion of the introduced NOx reducing reagent remains unreacted by the heat energy and flows to be used in the further reducing step.

### Claim 20 (depends on 13)

The method of claim 13 wherein the NOx reducing reagent used in the further reducing step is substantially completely the reagent included with the injected steam.

### Claim 21 (depends on 13)

The method of claim 13 wherein the mixture of steam and the NOx reducing reagent is injected at a velocity of at least Mach 0.5

### Claim 22 (depends on 13)

The method of claim 13 wherein a total flow rate of the mixture of steam and the NOx reducing reagent is no greater than one percent of the total flow rate of the combustion gas.