JPH0716431A - Flue gas denitrification apparatus - Google Patents

Abstract

PURPOSE:To provide a flue gas denitrification apparatus capable of efficiently making nitrogen oxides harmless without causing the corrosion of an apparatus due to ammonia. CONSTITUTION:Some of the waste gas in a flue 4 is extracted from the upstream side of an ammonia injection nozzle 18 with an extracting pipe 16 and introduced to a vaporizer 17. The spraying pipe 19 which introduces an aqueous ammonia or its precursor 8 and the atomizing pipe 20 which introduces air or steam 9 is installed in the vaporizer 17, and the aqueous ammonia is sprayed into a mist. The temp. of the gaseous mixture 12 of the ammonia at the outlet of the vaporizer 17 is detected by a thermometer, and the temp. is controlled so as to keep >=200 deg.C to form an aqueous ammonia vapor. The gaseous mixture 12 of the ammonia from the vaporizer 17 is introduced into the upstream of the catalyst layer of the denitrification apparatus in the flue 4 and sprayed from a spraying nozzle 18. The steam of the aqueous ammonia is injected from the spraying nozzle 18 corresponding to the NOx amount in the flue gas and the NOx in the flue gas is reduced efficiently into a harmless nitrogen and water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flue gas denitration device for removing nitrogen oxides (NO _x ) contained in flue gas.

[0002]

2. Description of the Related Art An example of a conventional flue gas denitration device is a denitration device for combustion flue gas discharged from a gas turbine of a gas turbine power generator, which will be described with reference to FIG. In FIG. 3, the fuel 2 and the air 3 are injected into the gas turbine 1, and the flue gas generated by burning here is sent to the flue 4 to recover the heat contained in the flue gas and generate steam. After passing through a heat exchanger 5 and a denitration device 6 equipped with an ammonia injector, the smoke is emitted from the chimney 7 to the atmosphere. The denitration device 6 provided in the flue 4 is a device that reduces NO _X in the flue gas through a catalyst to harmless nitrogen and water by the injected ammonia.

FIG. 3 shows an example of a device for spraying ammonia water 8 on the denitration device 6 after evaporating the ammonia water 8 by the exhaust gas after denitration extracted from the flue. The flue gas denitrated in FIG. 3 is extracted by the flue gas recirculation fan 10 and guided to the ammonia vaporizer 11. The vaporizer 11 is configured to inject the ammonia water 8 atomized by the atomized air or steam 9 and mixed with the flue gas into a vaporized state into the flue 4 on the upstream side of the denitration device 6 catalyst layer.

An example of a device for directly spraying ammonia water onto the denitration device 6 is shown in FIG. Inside the flue 4 in Figure 4
The spray nozzle 10 is provided on the upstream side of the catalyst layer of the denitration device 6 installed in the above, and is configured so that the ammonia water stored in the ammonia water tank 13 is pumped to the spray nozzle 10 by the pump 14 and injected. In addition, 15 is a mixer.

As shown in FIG. 3, ammonia water (or,
When the precursor water (urea water) is vaporized by denitration flue gas extracted from the outlet side flue of the denitration device 6 and injected again into the flue, sulfur oxides or traces of nitrogen oxides and ammonia in the flue gas When combined, acidic ammonium sulfate or ammonium nitrate is produced as a solid and adheres to the flow rate measuring orifice or damper or the like in the ammonia vapor pipe, which adversely affects the operation of the device. Therefore, the temperature at the outlet of the vaporizer 11, that is, the vapor temperature of the ammonia water is 200 ° C. in the temperature range in which the compound is not produced.
It was necessary to raise it more than that. As a result, a large amount of extracted smoke is required.

Further, the denitration flue gas extracted from the outlet side of the denitration device contains a small amount of leaked ammonia, which causes corrosion of the recirculation fan 10. On the other hand, as shown in FIG. 4, when spraying ammonia water directly into the smoke exhaust,
Since the reaction that vaporizes the liquid is rate-determining and takes 0.5 to 1.0 seconds, it takes a long time from the spray nozzle to the denitration catalyst, and it is necessary to spray finely. It was necessary to install a mixer for premixing.

[0007]

In view of the above-mentioned state of the art, the present invention is capable of efficiently detoxifying NO _x in flue gas and preventing the device corrosion due to injected ammonia. It is intended to provide a denitration device equipped with an ammonia (or a precursor thereof) injection device.

[0008]

In order to solve the above-mentioned problems in an apparatus for denitrifying nitrogen oxides contained in flue gas by contacting a denitration catalyst with ammonia or a precursor thereof as a reducing agent, the present invention provides: A bleeder tube that partially removes the exhaust gas in the flue from the upstream region of the ammonia or its precursor injection device, and a vaporizer that sprays and evaporates ammonia or its precursor in the exhaust gas taken out by the bleeder tube,
A configuration including a nozzle for injecting the ammonia or its precursor vaporized in the vaporizer to the upstream flue of the denitration catalyst is adopted.

In addition to the above-mentioned structure, the flue gas denitration apparatus according to the present invention is provided with a thermometer for detecting the temperature of ammonia or its precursor vaporized in the vaporizer, and the temperature in the vaporizer is adjusted to ammonia or its precursor. It is desirable to maintain the temperature at which the vaporization of the substance is sufficiently performed.

[0010]

Since the flue gas denitration apparatus according to the present invention has the above-mentioned structure, a part of the high temperature flue gas upstream of the ammonia injection position in the flue is extracted by the bleed pipe and guided to the carburetor. As a result, the atomized fine particles of the ammonia (or the precursor thereof) water sprayed in the vaporizer are vaporized using the flue gas as a medium to obtain an ammonia mixed gas. Since the flue gas extracted from the flue upstream of the ammonia injection position has a high temperature, ammonia is injected from the ejection nozzle upstream of the denitration catalyst without producing acidic ammonium sulfate and ammonium nitrate.

Further, in the apparatus according to the present invention, since the exhaust gas is extracted from the upstream of the ammonia injection position, the corrosion of the recirculation fan can be prevented. Further, in the flue, ammonia (or a precursor such as urea) water is evaporated, the exhaust gas and ammonia are mixed, and the denitration catalyst upstream (ammonia injection nozzle) is also efficiently mixed in a short time to remove the denitration catalyst. After passing through, denitration is performed efficiently. The denitration device according to the present invention can be widely applied to denitration of flue gas from a gas turbine, a diesel engine, a gas engine, a boiler, a heating furnace, a refuse incinerator, a chemical reaction process, and the like.

[0012]

EXAMPLE A denitration apparatus according to the present invention will be specifically described below with reference to the examples shown in FIGS. In FIGS. 1 and 2, the same components as those of the conventional device shown in FIGS. First, the embodiment shown in FIG. 1 will be described. The flue 4 has a gas turbine (not shown),
Exhaust smoke from diesel engines, gas engines, etc. is being introduced. The ammonia injecting device includes a portion of the extraction pipe 16 that guides the high-temperature exhaust gas from the flue 4 to the vaporizer 17, a vaporizer 17 that mixes and vaporizes the ammonia water and the exhaust gas, and vaporized vapor of ammonia water. It is composed of an ammonia injection nozzle portion 18 for injecting into

More specifically, a portion of high-temperature flue gas is extracted by the recirculation fan 10 from the position of the flue upstream of the ammonia injection nozzle 18, and introduced into the vaporizer 17 via the extraction pipe 16. Ammonia water spray pipe 1 is provided inside the vaporizer 17.
9 and an air or steam atomizing pipe 20 are attached, and ammonia water is sprayed in the form of fine particles. The temperature of the ammonia mixed gas 12 at the outlet of the vaporizer 17 is detected by the thermometer 21, and the temperature is controlled to be maintained at 200 ° C. or higher. In this way, the vapor of ammonia water using the flue gas as a medium is reliably formed.

From the vaporizer 17, the ammonia mixed gas 12 is guided to the upstream side of the catalyst layer of the denitration device 6 in the flue 4 and injected from one or a plurality of injection nozzles 18. From this jet nozzle 18, vapor and gas of ammonia water are injected in an amount corresponding to the NO _X flow rate in the flue gas, and the ammonia mixed gas is efficiently and uniformly mixed with the flue gas in the flue 4 in a short time. After that, it passes through the catalyst layer of the denitration device 6. This time,
NO _x in the flue gas is efficiently reduced to harmless nitrogen and water by the catalytic action of ammonia.

As another embodiment of the flue gas denitration apparatus of the present invention, an example applied to a gas turbine power generator is shown in FIG. 2, which will be described below. The fuel 2 and the air 3 are fed into the gas turbine 1, and the flue gas generated by burning here is sent to the flue 4 and the heat exchanger 5 that recovers the heat of the flue gas to generate steam and After passing through the denitration device 6 equipped with the ammonia injection nozzle 18, it is emitted to the atmosphere from the chimney 7. The denitration device 6 provided in the flue 4 is a device that reduces NO _x in the flue gas into harmless nitrogen and water through the catalyst 22 by injecting ammonia.

High-temperature exhaust gas is extracted from the upstream side of the heat exchanger 5 and the like in the flue 4 through the extraction pipe 16 and introduced into the vaporizer 17 through the recirculation fan 10. An ammonia water spray pipe 19 is connected to the inside of the vaporizer 17, and an ammonia water pipe 23 in which an air or steam atomizing pipe 20 is joined to the ammonia water spray pipe 19 is connected to the vaporizer 17.
Is sprayed in.

The temperature of the ammonia mixed gas 12 gasified in the vaporizer 17 is detected by a thermometer 21,
By controlling so as to maintain the temperature of 200 ° C. or higher, the vapor of ammonia water using the high-temperature flue gas as a medium is sufficiently formed. Ammonia is vaporized in the vaporizer 17 thus its flue gas is sprayed into flue gas containing NO _X from the ammonia injection nozzle 18 at the upstream side of the denitration catalyst 22 between the heat exchanger 5 in the flue 4 When uniformly mixed and passed through the denitration catalyst 22, NO _X contained in the flue gas is reduced to harmless nitrogen and water.

[0018]

As described above in detail, in the denitrification apparatus according to the present invention, since the flue gas extracted from the upstream side of the ammonia injection position is used for vaporizing the ammonia water, an extremely high temperature is ensured. Therefore, there is no need to worry about precipitation of acidic ammonium sulfate and ammonium sulfate, and there is no need to take measures against corrosion of fans and the like by ammonia. Further, in the flue gas denitration device according to the present invention, since the ammonia water is vaporized by the vaporizer outside the flue, the vaporization time in the flue is not necessary, and the reducing agent can be jetted from a short distance of the catalyst, so that even in a narrow space. It is possible to install denitration equipment and denitration reaction.

[Brief description of drawings]

FIG. 1 is a system diagram of a flue gas denitration device according to an embodiment of the present invention.

FIG. 2 is a system diagram of a power generator including a flue gas denitration device according to another embodiment of the present invention.

FIG. 3 is a system diagram of a power generation device including a conventional flue gas denitration device.

FIG. 4 is a system diagram of a power generator including another conventional flue gas denitration device.

[Explanation of symbols]

 4 Flue 6 Denitration device 8 Ammonia water (or its precursor) 10 Recirculation fan 12 Ammonia mixed gas 16 Extraction pipe 17 Vaporizer 18 Ammonia injection nozzle 19 Ammonia water spray pipe 20 Air or steam atomizing pipe 21 Thermometer 22 Denitration Catalyst 23 Ammonia water pipe

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location B01D 53/86 ZAB F23J 15/00 ZAB B01D 53/34 ZAB 129 B 7704-3K F23J 15/00 ZAB A

Claims (1)

[Claims] 1. A device for denitrifying nitrogen oxides contained in flue gas by contacting a denitration catalyst with ammonia or a precursor thereof as a reducing agent, wherein exhaust gas in a flue gas is discharged onto the ammonia or its precursor injection device. An extraction pipe that partially removes from the basin, a vaporizer that sprays and evaporates ammonia or its precursor into the exhaust gas extracted by the extraction pipe, and the above-mentioned ammonia or its precursor vaporized in the vaporizer is denitrified. A flue gas denitration device comprising a nozzle for injecting into the upstream flue of a catalyst.