JP3862134B2 - Ammonia gas injection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ammonia gas injection device, and more particularly to an ammonia gas injection device for injecting ammonia gas into combustion exhaust gas obtained by burning a sulfur-containing fuel.
[0002]
[Prior art]
Conventionally, in a treatment facility for fuel exhaust gas containing sulfur, a method of removing SO ₂ with a wet desulfurization apparatus is generally used. On the other hand, since SO ₃ is mixed with water vapor to form sulfuric acid mist, it is not only difficult to remove with a desulfurization apparatus, but there is a problem that the electrostatic precipitator is corroded by an acid such as the generated sulfuric acid mist.
[0003]
Therefore, in the fuel exhaust gas treatment apparatus containing sulfur, neutralization is performed by injecting an alkaline gas such as NH ₃ into the exhaust gas before introducing the exhaust gas to the desulfurization apparatus and the electrostatic precipitator. At this time, a solid of ammonium sulfate is produced by the reaction of NH ₃ and SO ₃ . This solid is collected by an electrostatic precipitator, and the exhaust gas after passing through the electrostatic precipitator is released to the atmosphere via a wet desulfurization apparatus or the like.
[0004]
The NH ₃ injection amount is preferably in accordance with the SO ₃ concentration. However, since there is currently no device for continuously monitoring SO ₃ , the leak NH ₃ after the dust collector is measured, and the leak NH ₃ The NH ₃ injection amount is controlled so as to be a constant value.
[0005]
[Problems to be solved by the invention]
However, in the conventional method, it is difficult to control the NH ₃ injection amount corresponding to non-uniform concentration due to fluctuations in boiler load, in particular, changes in SO ₃ concentration when the boiler is started and stopped, and drift in the flue.
[0006]
In the exhaust gas duct, it is known that the level difference of the concentration distribution of SO ₃ concentration is about 30% or more, and the conventional method causes a problem that NH ₃ is locally excessive or insufficient in the exhaust gas duct. . When NH ₃ is insufficient, the reaction does not occur completely and acidic ammonium sulfate, etc. is generated and adheres to the dust collection electrode and discharge electrode of the subsequent dust collector, and the adhering dust solidifies and accumulates due to moisture absorption and temperature level. The dust collection rate decreases. Conversely, if the amount of NH ₃ is excessive, there is a problem that the amount of leaked NH ₃ increases.
[0007]
Therefore, as a method corresponding to the SO ₃ concentration distribution in the exhaust gas duct, there is a method in which a large number of nozzles are arranged on a cross section orthogonal to the axis of the duct and this nozzle is divided into a plurality of groups to control the NH ₃ injection amount. is there. In this method, a plurality of nozzles belonging to the same group are attached to one injection tube, and the NH ₃ injection amount for each group is controlled by adjusting the amount of NH ₃ supplied to each injection tube. Then, the NH ₃ concentration is measured in the downstream region corresponding to each group, and the ammonia gas corresponding to the SO ₃ concentration distribution in the exhaust gas duct is controlled by controlling the NH ₃ injection amount of each group based on this measured value. inject.
[0008]
However, the conventional method has a problem in that the amount of NH ₃ blown from a plurality of nozzles belonging to the same group varies, so that local excess or deficiency of NH ₃ occurs.
[0009]
This invention is made | formed in view of such a situation, and it aims at providing the ammonia gas injection apparatus which can equalize the blowing air volume of the ammonia gas which blows off from the several nozzle which belongs to the same group.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 has a plurality of nozzles attached to the injection pipe at intervals in the axial direction of the injection pipe, and the plurality of nozzles are orthogonal to the axis of the duct through which the exhaust gas flows. In the ammonia gas injection device that is disposed on the cross section and injects ammonia gas into the exhaust gas from the plurality of nozzles via the injection pipe, the flow passage area of the injection pipe is on the downstream side in the ammonia gas flow direction. The plurality of nozzles is formed smaller than the upstream side, and a throttle means for restricting the flow rate of ammonia gas flowing through each nozzle is provided inside the plurality of nozzles, and the amount of air blown out from each nozzle by the throttle means is uniform. In addition, the cross section perpendicular to the duct axis is divided into a plurality of sections, and the nozzles included in the section are grouped. The injection pipe is provided, the supply amount of ammonia gas is controlled for each of the injection pipes, a pipe having a substantially elliptical cross section is arranged in a direction perpendicular to the axis of the duct, and a plurality of pipes are provided inside the pipe. The injection pipe is provided, and nozzles provided in the plurality of injection pipes are arranged along the direction of the pipe.
[0011]
According to the first aspect of the present invention, since the throttle means (for example, an orifice plate) is provided in each nozzle, the amount of ammonia gas blown from each nozzle can be made uniform, and the local excess amount of ammonia gas can be obtained. Insufficiency can be prevented.
[0013]
According to the first aspect of the present invention, since the flow passage area of the injection pipe is formed smaller on the downstream side in the flow direction of the ammonia gas than on the upstream side, the supply amount of ammonia gas supplied from the injection pipe to each nozzle is small. It is made uniform. Therefore, the amount of ammonia gas blown out from each nozzle is made uniform, and local excess and deficiency of ammonia gas can be prevented. In addition, according to the present invention, since the amount of air blown from each nozzle can be made uniform without increasing the internal resistance of each nozzle, the power for supplying ammonia gas to the injection pipe can be reduced. Can do.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred embodiment of an ammonia gas injection device according to the present invention will be described in detail with reference to the accompanying drawings.
[0015]
FIG. 1 is a flowchart of a combustion gas processing facility to which the ammonia gas injection device 10 of the present embodiment is applied.
[0016]
As shown in the figure, the combustion gas treatment facility includes a boiler 12, a denitration device 14, an air heater 16, an ammonia gas injection device 10, an NH ₃ detection device 18, an electrostatic precipitator 20, a gas gas heat exchanger 22, and a desulfurization device 24. The wet electrostatic precipitator 26 and the chimney 28 are connected by a duct.
[0017]
The boiler 12 combusts fuel containing sulfur, and discharges combustion exhaust gas at about 400 ° C. containing dust, nitrogen oxide, and sulfur oxide to the subsequent stage. A denitration device 14 and an air heater 16 are disposed downstream of the boiler 12, and the exhaust gas is cooled to 170 ° C. in the air heater 16 while nitrogen oxides are removed by the denitration device 14. The air heater 16 cools the exhaust gas with the combustion air supplied to the boiler 12, whereby the combustion air having a raised temperature is supplied to the boiler 12.
[0018]
The ammonia gas injection device 10 is disposed in a duct 30 that connects the denitration device 14 and the electrostatic precipitator 20, and injects a mixed gas of ammonia gas and air into the exhaust gas that passes through the duct 30. As a result, the SO ₃ contained in the exhaust gas is neutralized to produce an ammonium sulfate solid. This solid is removed together with dust in the exhaust gas by the electrostatic precipitator 20 using static electricity.
[0019]
A desulfurizer 24 and a wet electrostatic precipitator 26 are disposed downstream of the electrostatic precipitator 20 via a gas gas heat exchanger 22. The desulfurizer 24 removes SO ₂ in the exhaust gas from the exhaust gas. At the same time, the sulfuric acid mist in the exhaust gas is removed by the wet electrostatic precipitator 26. A chimney 28 communicates with the wet electric dust collector 26 via the gas gas heat exchanger 22, and the exhaust gas discharged from the wet electric dust collector 26 is heated through the gas gas heat exchanger 22. Then, it is discharged from the chimney 28 to the outside of the facility.
[0020]
Next, the ammonia gas injection device 10 according to the present invention will be described.
[0021]
FIG. 2 is a perspective view showing structures of the ammonia gas injection device 10 and the NH ₃ detection device 18. As shown in the figure, the ammonia gas injection device 10 is arranged on the upstream side of the duct 30 and includes a large number of nozzles (partially shown) 34, 34... On the axial section of the duct 30. The plurality of nozzles 34, 34... Are grouped so that the same number of nozzles 34, 34. The following is an example in which the inside of the duct 30 having a height of 4 m and a width of 7 m is divided into 1 m ² having a height of 1 m and a width of 1 m, and four nozzles 34, 34. explain.
[0022]
As shown in FIG. 2, in the ammonia gas injection device 10, seven mother pipes 32 (only one is shown) are installed on the cross section in the axial direction of the duct 30 at intervals of 1 m in the lateral direction. This mother pipe 32 is arranged in the vertical direction at the center of each section. Further, as shown in FIGS. 3 and 4, 16 nozzles 34, 34... Are arranged in the mother pipe 32 at equal intervals of 0.25 m on the downstream side with respect to the flow of the exhaust gas.
[0023]
In the mother pipe 32, four injection pipes 36, 36... Are inserted and arranged at equal intervals along the axial direction of the duct 30 in the vertical direction. The injection pipe 36 is formed with a constant inner diameter, and four nozzles 34, 34. Therefore, by adjusting the flow rate of the ammonia gas supplied to each injection pipe 36, the amount of air blown from the four nozzles 34, 34. Thereby, the blown air volume of the nozzles 34, 34... Is controlled by being divided into groups of four. Here, it is assumed that the four nozzles 34, 34,... Belonging to the same group are 34A, 34B, 34C, 34D in order from the upper side.
[0024]
As shown in FIG. 2, the injection pipe 36 is provided with a flow rate control means 38 such as a flow meter and a flow rate control valve, and an ammonia gas supply pump (not shown) is connected to the flow rate control means 38. . As shown in FIG. 1, each flow control means 38 is connected to the control device 40, and the ammonia gas supply amount is controlled by a command signal from the control device 40. Therefore, the supply amount of ammonia gas is controlled for each injection pipe 36 by the control device 40, and the amount of air blown out from the nozzles 34, 34... Is controlled for each group. Thus, the injection amount of ammonia gas is controlled every 1 m ² in the axial cross section of the duct 30.
[0025]
As shown in FIG. 5A, the inside of the nozzle 34 has a double structure comprising an inner tube 44 and an outer tube 46 having a coaxial axis 43. Ammonia gas flows into the inner tube 44, and the outer tube Air flows into 46 (ie, outside the inner tube 44). Thereby, since air is blown out around the ammonia gas blown out from the inner pipe 44, the ammonia gas immediately after being blown out is prevented from coming into direct contact with the exhaust gas. Thereby, it is possible to prevent ammonium sulfate from being generated in the vicinity of the injection port of the nozzle 34.
[0026]
The inner pipe 44 and the outer pipe 46 are tapered at the end on the injection port side. Thereby, the flow of ammonia gas and air is rectified at the ends of the inner tube 44 and the outer tube 46. That is, as shown in FIG. 5B, ammonia gas and air do not generate a vortex on the downstream side of the end surfaces of the inner tube 44 and the outer tube 46. The inner tube 44 and the outer tube 46 may have any shape with a sharp end on the injection port side, and an inclined surface may be formed on the inner peripheral surface side.
[0027]
Further, as shown in FIG. 6, an orifice plate 48 in which a hole having an orifice diameter d is formed is attached inside the inner tube 44. The relationship between the orifice diameter d and the nozzle diameter D will be described in detail later.
[0028]
FIG. 8 is a plan view of the ammonia gas injection device 10 shown in FIG.
[0029]
As shown in the figure, the mother pipe 32 is formed in an approximately elliptical shape, the downstream end thereof is formed at an acute angle with respect to the flow direction of the exhaust gas, and each nozzle 34 is disposed at the downstream end. Yes. Thereby, the flow of the exhaust gas in the vicinity of the nozzle 34 is rectified, and the generation of vortices in the vicinity of the nozzle 34 is suppressed. Therefore, the ammonia gas blown out from the nozzle 34 is not caught in the vortex of the exhaust gas, and it is possible to prevent dust from adhering to the jet outlet of the nozzle 34 and becoming enlarged.
[0030]
On the other hand, the NH ₃ detector 18 shown in FIG. 2 is provided on the downstream side of the duct 30, that is, at the entrance of the electrostatic precipitator 20 (see FIG. 1), and has a plurality of measurement sensors 42, 42. Yes. The measurement sensor 42 is installed at a distance of one second or more after the dwell time on the downstream side of the nozzle 34, and is arranged at the center of the section obtained by dividing the inside of the duct 30 on the axial cross section at intervals of 1 m ² . . That is, each measurement sensor 42 is installed facing the center of the nozzles 34A to 34D.
[0031]
Further, the measurement sensors 42, 42... Of the NH ₃ detection device 18 are connected to the control device 40 as shown in FIG. The control device 40 computes the measurement values of the respective measurement sensors 42 and sends the results to the flow rate control means 38 as command signals. Thereby, the flow rate of the ammonia gas supplied to each injection pipe 36 is controlled, and an appropriate amount of ammonia gas is blown out from the nozzles 34 </ b> A to 34 </ b> D facing each measurement sensor 42.
[0032]
Next, the operation of the ammonia gas injection device 10 configured as described above will be described.
[0033]
Since the four nozzles 34A to 34D belonging to the same group are attached to one injection pipe 36 formed with a constant inner diameter, the ammonia gas supplied to the injection pipe 36 has four nozzles 34A to 34A. 34D is distributed and injected. Therefore, when the orifice plate 48 is not installed in the nozzle 34, the nozzle 34 disposed on the upstream side (that is, the upper side) has a smaller amount of blown air of ammonia gas, and conversely disposed on the downstream side (that is, the lower side). As the nozzle 34 is made, the amount of ammonia gas blown out increases.
[0034]
FIG. 11 is a diagram showing the blowing speed of ammonia gas for each nozzle. As shown by the dotted line in FIG. 11, the conventional ammonia gas injecting apparatus has a large blowing speed of the nozzle 34A and the blowing speed of the nozzle 34D. The wind speed is low. Thus, if there is variation in the speed of the blown air blown from the nozzles 34A to 34D of the same group, the ammonia gas is locally excessive or insufficient.
[0035]
On the other hand, as shown in FIG. 6, the ammonia gas injection device 10 of the present embodiment has an orifice plate 48 attached to the inside of each of the nozzles 34 </ b> A to 34 </ b> D. Accordingly, the blown wind speed from each nozzle 34 </ b> A to 34 </ b> D is made uniform according to the orifice diameter d of the orifice plate 48.
[0036]
FIG. 7 shows the influence of the orifice diameter d on the blown air velocity, and shows Vn / Vave with respect to d / D. Here, Vn is the blowing speed of ammonia gas blown out from each of the nozzles 34A to 34D, and Vave is the average blowing speed of the nozzles 34A to 34D.
[0037]
As shown in the figure, the difference in the blown air speed between the nozzle 34A and the nozzle 34D becomes smaller as the orifice diameter d is made smaller than the nozzle diameter D. The difference between the nozzle 34A and the nozzle 34D is the largest among the nozzles 34A to 34D. Therefore, when the difference between the nozzle 34A and the nozzle 34D becomes small, the blowing air speeds of all the nozzles 34A to 34D are made uniform. That is, the smaller the orifice diameter d, the more uniform the blowing air speed of all the nozzles 34A to 34D. Therefore, in order to make the blown air speeds of the nozzles 34A to 34D uniform, it is preferable to reduce the orifice diameter d. In particular, when d / D is 0.5 or less, variations in the blown air speeds of the nozzles 34A to 34D are reduced. It can be suppressed within ± 0.5%.
[0038]
As described above, according to the ammonia gas injection device 10 of the present embodiment, since the orifice plate 48 is provided in the nozzle 34, the blown air speed from each of the nozzles 34A to 34D can be made uniform. Thereby, since ammonia gas of substantially the same air volume is injected from each nozzle 34A to 34D, local excess and deficiency of ammonia gas can be suppressed, and adverse effects on the downstream processing apparatus due to excess and deficiency of ammonia gas can be suppressed. can do.
[0039]
Further, since the ammonia gas injection device 10 is tapered at the injection port side end portions of the inner tube 44 and the outer tube 46 of the nozzle 34, a vortex may be generated immediately after the ammonia gas and air are blown out. Absent. Further, since the mother pipe 32 is formed in a substantially elliptic shape and the downstream end thereof is formed at an acute angle, the exhaust gas does not generate a vortex in the vicinity of the nozzle 34. Therefore, since ammonia gas, air, and exhaust gas do not generate vortex, it is possible to prevent the ammonium sulfate solid from adhering to the end portion of the nozzle 34 due to the vortex and from being enlarged.
[0040]
The shape of the mother pipe 32 is not limited to the above-described embodiment. For example, as shown in FIG. 9, the blowing direction of the nozzle 34 is directed outward, and the downstream end of the mother pipe 32 is You may form in V shape. In this case, the ammonia gas is easily diffused, and the generation of vortex near the nozzle 34 is prevented.
[0041]
Next, an ammonia gas injection device according to a second embodiment will be described.
[0042]
As shown in FIG. 10, in the ammonia gas injection device of the second embodiment, the injection tube 52 is a stepped contraction tube having a small diameter from the top to the bottom. That is, if the diameter of the injection tube 52 at the position of the nozzle 34A is a, the diameter at the position of the nozzle 34B is 0.87a, the diameter at the position of the nozzle 34C is 0.61a, and the diameter at the position of the nozzle 34D is 0.53a. It has become. The nozzles 34A to 34D are formed with a constant diameter of 0.53a, and a control resistor such as an orifice plate is not provided therein. Note that the description of the same or similar members as those in the first embodiment described above is omitted.
[0043]
In the ammonia gas injection device configured as described above, the injection pipe 52 is formed of a stepped contraction pipe, and the flow area of the ammonia gas is gradually reduced. Therefore, the ammonia gas easily flows to all the nozzles 34A to 34D. . For example, since the diameter of the injection pipe 52 which is a at the position of the nozzle 34A is as small as 0.78a at the position of the nozzle 34B, the ammonia gas flowing from the position of the nozzle 34A to the position of the nozzle 34B is reduced. Becomes a resistance and flows sufficiently to the nozzle 34A. Similarly, the ammonia gas sufficiently flows through the nozzles 34B and 34C, and the ammonia gas does not flow only in the nozzle 34D. That is, the blown air speed of each nozzle 34A-34D can be made uniform, and the ammonia concentration can be prevented from becoming locally non-uniform.
[0044]
FIG. 11 shows the distribution of the blown wind speed at each of the nozzles 34A to 34D. The solid line shown in the figure indicates Vn / Vave for each of the nozzles 34A to 34D when the flow rate supplied to the injection pipe 52 is 100, 200, and 300 m ³ / h. Moreover, the dotted line shown in the figure shows Vn / Vave when the injection tube is formed with a constant inner diameter (that is, the conventional apparatus).
[0045]
As shown in the figure, when a stepped contraction tube is used as the injection tube 52, it can be seen that the blown air speeds from the nozzles 34A to 34D are substantially uniform for any flow rate. In particular, as compared with the case where the injection pipe is formed with a constant inner diameter, the blowing air speeds of the nozzles 34A and 34D are greatly improved, and the blowing air speeds of all the nozzles 34A to 34D are within a range of ± 5%.
[0046]
As described above, according to the ammonia gas injection device of the second embodiment, since the stage contraction tube is used as the injection tube 52, it is possible to equalize the blowing speed of the gas blown from the nozzles 34A to 34D. Thereby, it is possible to prevent the ammonia gas from being locally excessive or insufficient in each section.
[0047]
Moreover, since the ammonia gas injection device of the second embodiment does not increase the internal resistance of the nozzles 34A to 34D, the pressure loss in the nozzles 34A to 34D is small.
[0048]
FIG. 12 is a diagram comparing the pressure difference between the case where the injection tube 52 is a stepped contraction tube and the case where the orifice plate 48 is provided inside the nozzles 34A to 34D. Here, the differential pressure is the differential pressure in the injection pipe 36 immediately before the nozzle 34D, and the orifice plate 48 having d / D = 0.5 was used. Moreover, the blowing flow rate of ammonia gas at the time of measurement is 80 to 300 m ³ / h.
[0049]
As shown in the figure, when the injection tube 52 is a stepped contraction tube, the differential pressure is significantly smaller than when the orifice plate 48 is used inside the nozzles 34A to 34D. At s, the differential pressure is 1/10. Therefore, when the injection tube 52 is a stepped contraction tube, the burden on the ammonia gas supply device supplied to the injection tube 52 can be reduced.
[0050]
As described above, the ammonia injection device according to the second embodiment can equalize the blown air speed of each of the nozzles 34A to 34D without installing a control resistor inside the nozzles 34A to 34D. The load of a supply device (not shown) such as a pump for supplying ammonia gas to 52 can be reduced.
[0051]
The injection pipe 52 may be a stepped contraction pipe, and an orifice plate 48 having a relatively large orifice diameter d may be provided inside the nozzles 34A to 34D. Thereby, the blowing air volume of the nozzles 34A to 34D can be made more uniform without greatly increasing the load on the supply device.
[0052]
In the above embodiment, the NH ₃ detection device 18 is provided, and the ammonia gas discharge amount by each injection pipe 36 of the ammonia gas injection device 10 is controlled in accordance with the NH ₃ concentration detected by the detection device 18. However, the NH ₃ detector 18 is not required if an appropriate amount of ammonia gas injected in each section of the duct is obtained in advance by experiments and the amount of ammonia gas injected into each injection pipe 36 is set accordingly. .
[0053]
【The invention's effect】
As described above, according to the ammonia gas injection device according to the present invention, since the throttle means is provided in each nozzle, it is possible to equalize the amount of ammonia gas blown from the same group of nozzles, Local excess and deficiency can be prevented.
[0054]
Further, according to the present invention, the flow passage area of the injection pipe is formed smaller on the downstream side in the flow direction of the ammonia gas than on the upstream side, so that the flow rate of the ammonia gas supplied from the injection pipe to each nozzle can be made uniform. It is possible to prevent local excess or deficiency of ammonia gas.
[Brief description of the drawings]
FIG. 1 is a flow diagram of a combustion gas processing facility to which an ammonia gas injection device according to the present invention is applied. FIG. 2 is a perspective view showing the structure of an ammonia gas injection device according to the present invention. Fig. 4 is a longitudinal sectional view of the ammonia gas injection device. Fig. 4 is a side view of the ammonia gas injection device shown in Fig. 2. Fig. 5 is a half sectional view showing the internal structure of the nozzle. Fig. 6 is an internal structure of the inner tube of the nozzle. FIG. 7 is a diagram showing the effect of the orifice diameter on the wind speed. FIG. 8 is a plan view of the ammonia gas injection device shown in FIG. 2. FIG. 9 is an ammonia gas injection device showing a mother pipe having a different shape from FIG. FIG. 10 is a side view showing an injection pipe which is a characteristic part of the second embodiment of the ammonia gas injection device according to the present invention. FIG. 11 is a diagram showing a wind speed distribution in each nozzle. Action of 10 ammonia gas injection devices Explanatory view showing DESCRIPTION OF SYMBOLS
10 ... ammonia gas injection device, 12 ... boiler, 14 ... denitration apparatus, 16 ... air heater, 18 ... NH ₃ detection device, 20 ... electrostatic precipitator, 22 ... gas-gas heat exchanger, 24 ... desulfurizer, 26 ... wet electrostatic Dust collector, 28 ... Chimney, 30 ... Duct, 32 ... Mother pipe, 34 ... Nozzle, 36 ... Injection pipe, 38 ... Flow control means, 40 ... Control device, 42 ... Measuring sensor, 44 ... Inner pipe, 46 ... Outside Pipe, 48 ... Orifice plate

Claims (4)

A plurality of nozzles are attached to the injection pipe at intervals in the axial direction of the injection pipe, the plurality of nozzles are arranged on a cross section perpendicular to the axis of the duct through which the exhaust gas flows, and the plurality of nozzles are arranged via the injection pipe. In the ammonia gas injection device for injecting ammonia gas into the exhaust gas from the nozzle of
The flow passage area of the injection pipe is formed such that the downstream side in the flow direction of ammonia gas is smaller than the upstream side ,
Inside the plurality of nozzles, a throttle means for reducing the flow rate of the ammonia gas flowing inside each nozzle is provided, and the amount of air blown out from each nozzle by the throttle means is made uniform,
The cross section perpendicular to the axis of the duct is divided into a plurality of sections, the nozzles included in the section are grouped, the injection pipe is provided for each nozzle of each group, and the supply amount of ammonia gas is controlled for each injection pipe. ,
A tube having a substantially elliptical cross section is arranged in a direction perpendicular to the axis of the duct, and a plurality of the injection tubes are provided inside the tube, and nozzles provided in the plurality of injection tubes are provided in the tube. An ammonia gas injection device, which is arranged side by side along a direction. The said injection | pouring pipe | tube is a stage contraction pipe | tube whose diameter in the position of the downstream nozzle of the flow direction of the said ammonia gas is smaller than the diameter in the position of the upstream nozzle. Ammonia gas injection device. The nozzle is composed of a double structure having an inner tube through which the ammonia gas flows and an outer tube through which air flows.
3. The ammonia gas injection device according to claim 1, wherein the inner tube and the outer tube have a sharp end on the injection side. 4. An ammonia detection sensor disposed at a distance of 1 second or more after the residence time downstream of the nozzle with respect to the flow direction of the exhaust gas flowing through the duct, and disposed corresponding to each group;
The ammonia gas injection device according to claim 1, further comprising: a control device that controls a flow rate of the ammonia gas flowing through the injection pipe based on a measurement value of the sensor.

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