JPH0975664A - Flue gas denitration equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably hold the concn. of nitrogen oxide at the outlet of a nitration apparatus to an objective value or less by the min. injection amt. of ammonia. SOLUTION: Split passages 24 demarcating exhaust gas 7 into a plurality of gas streams to guide the same are formed in the exhaust gas duct 8 guiding the exhaust gas 7 to a denitration device 9 and flow rate adjustable dampers 26 adjustable in opening degree and ammonia injection nozzles 10 are provided in each split passage 24.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a flue gas denitration device.

[0002]

2. Description of the Related Art When treating nitrogen oxides contained in the exhaust gas of a boiler or the like, after injecting ammonia into the exhaust gas before the denitration device, nitrogen oxides are treated in the catalyst layer of the denitration device. ing.

An example of the flue gas denitration apparatus conventionally used for this purpose will be described with reference to FIG. 6, in which a combustion air is pushed into the boiler 1 from the blower 2 to burn the fuel injected from the burner 3 to burn the boiler 1. The steam generated in the control valve 4
Is supplied to the steam turbine 5 through the exhaust gas and is generated by the generator 6. The exhaust gas 7 generated by the combustion of the boiler 1 passes through the exhaust gas duct 8 and passes through the catalyst layer 9a.
Is sent to the denitration apparatus 9 in which the nitrogen oxide has been inserted, nitrogen oxide is treated in the denitration apparatus 9, and then discharged to the atmosphere.

In the exhaust gas duct 8 which guides the exhaust gas 7 to the denitration device 9, a plurality of ammonia injection nozzles 10 for injecting ammonia substantially uniformly over the entire cross section of the exhaust gas duct 8 are provided vertically and horizontally. Ammonia injection nozzle 10
Are each connected to the mixer 12 via an injection balance valve 11.

In the mixer 12, the pressurized air is mixed with the ammonia that has passed through the ammonia flow meter 13 and the ammonia flow rate control valve 14, and the ammonia mixed with the air is passed through the injection balance valves 11 described above. It is introduced to the ammonia injection nozzle 10 and is injected into the exhaust gas duct 8 substantially uniformly over the entire cross section, and the catalyst layer 9a of the denitration device 9 treats the nitrogen oxides contained in the exhaust gas 7.

The amount of ammonia injected by the ammonia flow control valve 14 is controlled by the injection flow control signal 16 from the controller 15.

A boiler outlet NOx detection signal 20 from a boiler outlet NOx detector 19 and a gas flow rate signal from a load command signal 21 are input to the control device 15.

The boiler outlet NOx detector 19 is the boiler 1
In the trial operation stage of 1., the gas flow rate and the nitrogen oxide concentration of the cross section of the exhaust gas duct 8 are detected in advance, and the boiler outlet NOx detector 19 is installed at the representative point position indicating the average value of the detected values. I have to.

Further, at the stage of trial operation of the boiler 1,
The change in the boiler outlet NOx detection signal 20 when the load command signal 21 is changed by the load change of the boiler 1 is detected, and the relationship between the change in the load of the boiler 1 and the change in the boiler outlet NOx detection signal 20 is detected. It is obtained in advance and stored in the control device 15.

On the other hand, at the outlet of the denitration device 9, a plurality of denitration device outlet NOx detection probes 22 are arranged to detect the nitrogen oxide concentration at a plurality of positions in the vertical and horizontal directions along the cross section of the exhaust gas duct 8'on the downstream side. Is provided, and at the stage of test operation of the boiler 1, the denitration device outlet N
Each injection balance valve 11 of the ammonia injection nozzle 10 is manually adjusted so that the concentration of nitrogen oxides in each part of the entire cross section of the Ox detection probe 22 becomes a substantially uniform value.

When the boiler 1 starts operating and the load command signal 21 changes, the load command signal 21 and the boiler outlet NOx detection signal 20 are stored in the control device 15 in advance, so that the load command signal 21 is stored. The injection flow rate control signal 16 is output to the ammonia flow rate control valve 14 so as to follow the change of the signal 21 without causing a time delay, and the ammonia flow rate control valve 14 is adjusted. At this time, the boiler outlet NOx detector 19 and the boiler outlet NOx detection signal 20 are input to the control device 15, so that the injection flow rate control signal 16 is corrected.

The ammonia whose flow rate is adjusted by the ammonia flow rate control valve 14 is supplied to the mixer 12 and mixed with air, and the concentration of nitrogen oxides at the outlet of the denitration device 9 is made substantially uniform in the cross section of the exhaust gas duct 8 '. The flow rate is adjusted by the injection balance valve 11 that is adjusted in advance to be injected into the exhaust gas duct 8 from each ammonia injection nozzle 10, and the nitrogen oxide concentration of the exhaust gas 7 at the outlet of the denitration device 9 is kept below the target value. It is supposed to do.

[0013]

However, the flow velocity of the exhaust gas 7 flowing in the exhaust gas duct 8 is not uniform in the cross section of the exhaust gas duct 8, and a difference in the flow velocity distribution as shown by A in FIG. 6 occurs. This difference in the flow velocity distribution A is generated under the influence of equipment such as a boiler on the upstream side, and changes with the change in the load command signal 21. Further, when the exhaust gas duct 8 has a vertical bend, a vertical flow velocity distribution A having different flow velocities occurs, and when the exhaust gas duct 8 has a horizontal bend, the horizontal flow velocity differs. A flow velocity distribution A is produced.

Thus, the flow velocity distribution A in the exhaust gas duct 8
If the difference occurs, the concentration of nitrogen oxides at the outlet of the denitration device 9 also changes in the cross section of the exhaust gas duct 8 ', and there is a case where the target concentration of nitrogen oxides cannot be kept.

For this reason, conventionally, the injection balance valve 11 is appropriately adjusted so that the nitrogen oxide concentration at the outlet of the denitration device 9 is adjusted to be substantially uniform. If the difference is large, the range of adjustment by the injection balance valve 11 may be exceeded (a part where the amount of ammonia is insufficient even if the injection balance valve 11 is fully opened) occurs. In order to prevent the problem that the nitrogen oxide concentration at the outlet exceeds the target value or the target value is exceeded, measures such as increasing the injection amount of ammonia are taken, but in this case, If the unreacted ammonia is led to the downstream side of the denitration device 9 to generate an offensive odor, or the exhaust gas 7 contains a sulfur content, the amount of ammonia consumed becomes uneconomical. Ammonium sulfate or acidic ammonium sulfate by the reaction with ammonia of the unreacted sulfur occurs, the ammonium sulfate or acidic ammonium sulfate has occurred problems such as adhere to the downstream side equipment to.

The present invention solves such a conventional problem,
An object of the present invention is to provide a flue gas denitration device that can stably maintain the nitrogen oxide concentration at the denitration device outlet at a target value or less with a minimum amount of ammonia injection.

[0017]

The first means of the present invention is to:
An exhaust gas duct that guides the exhaust gas to the denitration device is formed with divided flow passages that divide the exhaust gas into a plurality of passages, and a flow rate adjustment damper that can adjust the opening degree in each of the divided flow passages and an ammonia injection nozzle. It is characterized by having.

The second means of the present invention is characterized in that the divided flow passage extends to the catalyst layer of the denitration device.

The third means of the present invention is characterized in that each of the flow rate adjusting dampers can independently adjust its opening.

The fourth means of the present invention is characterized in that the opening of each of the upper and lower flow rate adjusting dampers can be adjusted independently.

The fifth means of the present invention is characterized in that the flow rate adjusting dampers on the left and right rows can adjust the opening independently for each row.

In the first means of the present invention, the exhaust gas duct for introducing the exhaust gas into the denitration device is divided into a plurality of divided flow passages, and the flow rate adjusting damper and the ammonia injection nozzle are arranged in each divided flow passage. Therefore, even if there is an exhaust gas flow velocity distribution in the exhaust gas duct, the flow velocity of the exhaust gas flowing through each of the divided flow paths can be adjusted so that it is almost uniform. It is possible to stably maintain the concentration of nitrogen oxides at the outlet of the denitration device at a target value or less with a minimum amount of injected ammonia.

In the second means, when the divided flow path extends to the catalyst layer of the denitration device, the exhaust gas is guided in the catalyst layer while maintaining a uniform flow rate, so that more uniform denitration is performed.

According to the third means, if the opening degree of each of the flow rate adjusting dampers can be adjusted independently, it is possible to cope with a case where the flow velocity distribution of the exhaust gas is different in any of up, down, left and right directions.

In the fourth means, if the flow rate adjusting dampers at the upper and lower stages can be independently adjusted for the respective stages, particularly when the difference in the flow velocity distribution of the exhaust gas is generated in the vertical direction, a simple structure can be obtained. Can be dealt with.

In the fifth means, if the flow rate adjusting dampers of the left and right rows can be adjusted in opening degree independently for each row, especially when the difference in the flow velocity distribution of the exhaust gas is generated in the left and right direction, it is simplified. The configuration can accommodate this.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show an embodiment of the present invention. In the drawings, the same parts as those in FIG. 6 are designated by the same reference numerals and detailed description thereof will be omitted.

As shown in FIGS. 1 and 2, in the exhaust gas duct 8 which guides the exhaust gas 7 to the denitration device 9, a divided flow path 24 is formed so as to guide the exhaust gas 7 in a plurality of sections. The divided flow channels 24 are partitioned by partition walls 25 fixed in the exhaust gas duct 8. In the case of FIGS. 2 and 3, the divided flow channels 24 are vertically arranged in four stages and horizontally arranged in four columns, for a total of 16 parts. However, the number of partitions can be changed arbitrarily.

The downstream end of the partition wall 25 preferably extends to the position of the catalyst layer 9a of the denitration device 9, but it may be located near the denitration device 9.

Inside each of the divided flow paths 24, a flow rate adjusting damper 26 whose opening degree can be adjusted is provided, and an ammonia injection nozzle 10 is provided downstream of the flow rate adjusting damper 26. ing.

As shown in FIG. 3, in each of the upper and lower stages of the flow rate adjusting damper 26, the two flow rate adjusting dampers 26 on the left and right sides are driven by the inner shafts 27 on the left and right, and the two flow rate adjusting dampers on the left and right sides are adjusted. The damper 26 is driven by the left and right outer shafts 28, and the inner shaft 27 and the outer shaft 28 can be driven separately.
9 and 30 are connected to each other, so that the openings of all the flow rate adjusting dampers 26 can be independently adjusted. The driving units 29 and 30 may be manually driven, or may be automatically driven by a driving device.

The ammonia injection nozzle 10 is shown in FIG.
As shown in (4), four pieces arranged corresponding to each stage of the divided flow path 24 are grouped together and connected to one injection balance valve 11. Reference numeral 31 in FIG. 1 denotes a flow velocity detector that is inserted into each of the divided flow passages 24 to detect the flow velocity of the exhaust gas 7 in each of the divided flow passages 24.

Next, the operation of the apparatus shown in FIGS. 1 to 4 will be described.

At the stage of test operation of the boiler 1, the flow velocity of the exhaust gas 7 flowing through each divided flow passage 24 is detected by the flow velocity detector 31, and the flow velocity detection value of the flow velocity detector 31 is made substantially uniform as shown in FIG. The opening degree of each flow rate adjustment damper 26 shown in FIG. 3 is adjusted manually or automatically.

With the flow rate of the exhaust gas 7 flowing through each of the divided flow passages 24 adjusted so as to be substantially constant, injection is performed so that the ammonia flow rate supplied to each ammonia injection nozzle 10 shown in FIG. 4 becomes uniform. Adjust the balance valve 11. At this time, the denitration device outlet N provided at the denitration device 9 outlet
The nitrogen oxide concentration in the cross section of the exhaust gas duct 8'is detected by the Ox detection probe 22, and the ammonia injection nozzle 10 is adjusted so that the detected value of the nitrogen oxide concentration becomes a substantially uniform value in the cross section of the exhaust gas duct 8 '. Each injection balance valve 11 of is finely adjusted.

Further, the flow velocity detector 31 detects the flow velocity of the exhaust gas 7 in each of the divided flow passages 24, and the opening degree of the flow control damper 26 is adjusted so that the flow velocity detection value of the flow velocity detector 31 becomes substantially uniform. By the method other than the adjusting method, the divided channel 2
The flow velocity of the exhaust gas 7 of No. 4 can be adjusted uniformly. That is, the injection balance valve 11 is adjusted so that the flow rate of ammonia supplied to each of the ammonia injection nozzles 10 is uniform, and in this state, the exhaust gas duct 8 is discharged by the NOx detection outlet 22 of the NOx removal device provided at the outlet of the NOx removal device 9. '
By detecting the nitrogen oxide concentration in the cross section of, and adjusting the opening degree of the flow rate adjusting damper 26 so that the detected value of the nitrogen oxide concentration becomes a substantially uniform value in the cross section of the exhaust gas duct 8 ′, The flow velocity of the exhaust gas 7 flowing through each of the divided flow paths 24 can be adjusted to be substantially uniform.

In the above-described structure, when the boiler 1 starts to operate and the load command signal 21 changes, the load command signal 21 and the boiler outlet NOx detection signal 2 are preliminarily obtained as in the conventional case.
Since the relationship with 0 is stored in the control device 15, the injection flow rate control signal 16 is output to the ammonia flow rate control valve 14 without causing a time delay by following the change of the load command signal 21, and the ammonia flow rate is controlled. The control valve 14 is adjusted. At this time, the boiler outlet NOx detector 19
Boiler outlet NOx detection signal 20 from the controller 15
Is input to the injection flow control signal 1
6 is corrected.

The ammonia whose flow rate is adjusted by the ammonia flow rate control valve 14 is supplied to the mixer 12 and mixed with air, and the concentration of nitrogen oxides at the outlet of the denitration device 9 is made substantially uniform in the cross section of the exhaust gas duct 8 '. The flow rate is adjusted by the injection balance valve 11 that is adjusted in advance so as to be injected into each divided flow path 24 from each ammonia injection nozzle 10.

At this time, even if the exhaust gas 7 flowing in the exhaust gas duct 8 has a difference in the flow velocity distribution A as shown in FIG. 6, the flow velocity of the exhaust gas 7 flowing in each of the divided flow passages 24 is changed by the flow rate adjusting damper 26. Since it is adjusted in advance so as to be substantially uniform, even if the difference in the flow velocity distribution A varies, the change in the flow velocity of the exhaust gas 7 with respect to each of the divided flow passages 24 is small. Ammonia can be uniformly injected into the exhaust gas 7 only by finely adjusting the injection balance valve 11 based on the detected value of 22.

As described above, the exhaust gas duct 8 for introducing the exhaust gas 7 into the denitration device 9 is divided into a plurality of divided flow passages 24, and the flow rate adjusting damper 26 capable of adjusting the opening degree in each of the divided flow passages 24. Since the ammonia injection nozzle 10 is arranged, even if there is a large difference in the flow velocity distribution of the exhaust gas 7 in the exhaust gas duct 8, the flow velocity of the exhaust gas 7 flowing through each divided flow path 24 is adjusted to be substantially uniform. Therefore, ammonia can be uniformly injected into the exhaust gas 7, so that the nitrogen oxide concentration at the outlet of the denitration device 9 can always be stably maintained below the target value with a minimum amount of ammonia injection.

In the above construction, each flow rate adjusting damper 26 is used.
Although the case where the opening degree of the exhaust gas can be independently adjusted has been described, it is known in advance that the difference in the flow velocity distribution of the exhaust gas 7 occurs in the vertical direction because the exhaust gas duct 8 is bent in the vertical direction, for example. If there is, the flow rate adjustment damper 26 is used as shown in FIG.
2 and a drive unit 33 that drives the shaft 32 may be used for adjustment.

If it is known in advance that a difference in the flow velocity distribution of the exhaust gas 7 will occur in the horizontal direction due to the exhaust gas duct 8 bending in the horizontal direction, for example, the configuration shown in FIG. Alternatively, the flow rate adjusting damper 26 may be adjusted by the shaft 32 that is common to each of the left and right columns and the drive unit 33 that drives the shaft 32.

[0044]

According to the present invention, an exhaust gas duct for introducing exhaust gas into a denitration device is divided into a plurality of divided flow passages, and a flow rate adjusting damper and an ammonia injection nozzle are arranged in each divided flow passage. Therefore, even if there is a flow velocity distribution of the exhaust gas in the exhaust gas duct, it is possible to adjust the flow velocity of the exhaust gas flowing through each of the divided flow paths to be substantially uniform. It is possible to stably maintain the nitrogen oxide concentration at the outlet of the denitration device at a target value or less with a minimum amount of injected ammonia.

When the divided flow path extends to the catalyst layer of the denitration device, the exhaust gas is guided to the catalyst layer while maintaining a uniform flow rate, so that more uniform denitration is performed.

If the opening of each of the flow rate adjusting dampers can be adjusted independently, it is possible to cope with a case where the flow velocity distribution of the exhaust gas is different in any of the up, down, left and right directions.

If the opening of each of the upper and lower flow rate adjusting dampers can be adjusted independently, it is possible to cope with the difference in the flow velocity distribution of the exhaust gas with a simple configuration. .

If the flow rate adjusting dampers of the left and right rows can be independently adjusted for each row, it is possible to cope with the difference in the flow velocity distribution of the exhaust gas in the left and right directions with a simple structure. it can.

[Brief description of drawings]

FIG. 1 is an overall system diagram showing an embodiment of the present invention.

FIG. 2 is a perspective view showing a part of the flue gas denitration device of FIG. 1 as seen through.

FIG. 3 is a view taken along the line III-III in FIG.

4 is a view taken in the direction of arrows IV-IV in FIG. 2;

FIG. 5 is a view showing another example of the driving method of the adjustment damper as shown in FIG.
It is an arrow equivalent view seen from the II-III direction.

FIG. 6 is an overall system diagram of a conventional device.

[Explanation of symbols]

 7 Exhaust Gas 8 Exhaust Gas Duct 9 Denitration Device 9a Catalyst Layer 10 Ammonia Injection Nozzle 24 Divided Flow Path 26 Flow Control Damper

Claims (5)

[Claims] 1. A flow rate control damper having an adjustable opening in each of the divided flow passages, wherein divided flow passages are formed in the exhaust gas duct for introducing the exhaust gas to the denitration device so as to divide the exhaust gas into a plurality of passages. , A flue gas denitration device comprising an ammonia injection nozzle. 2. The flue gas denitration device according to claim 1, wherein the divided flow path extends to the catalyst layer of the denitration device. 3. The flue gas denitration device according to claim 1 or 2, wherein each of the flow rate control dampers can independently adjust the opening degree. 4. The flue gas denitration device according to claim 1, wherein the upper and lower flow rate adjusting dampers are capable of independently adjusting the opening degree for each stage. 5. The flue gas denitration device according to claim 1 or 2, wherein the flow rate adjustment dampers of the left and right rows are independently adjustable in opening degree for each row.