JP3408852B2 - Nitrogen oxide concentration control denitration method and apparatus - Google Patents

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, and more particularly to a NOx concentration control denitration system for stabilizing the amount of nitrogen oxides (NOx) at the denitration reactor outlet.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional flue gas denitration control system. N in the instant treated gas measured by the NOx analyzer 2 provided in the treated gas flow path on the outlet side of the denitration reactor 1
The difference between the Ox concentration and the base control NOx concentration, that is, the control value A is calculated, and the injection control of the denitration NH ₃ to be supplied to the treated gas flow path on the inlet side of the denitration reactor 1 is performed. Note that N
The NOx concentration in the gas to be processed measured by the Ox analyzer 2 is N
It is recorded in the Ox concentration recorder 3. Further, when the control value A plus several ppm is used as the alarm setting NOx concentration, that is, the alarm setting value F, the alarm device 7 gives an alarm when the instantaneous NOx concentration measured by the NOx analyzer 2 exceeds the alarm setting value F. The system was adopted.

[0003]

SUMMARY OF THE INVENTION The above-mentioned conventional control system has an inlet N of the denitration reactor 1 due to fluctuations in the plant load or the like.
Even when the Ox concentration changes and the NOx concentration at the outlet of the denitration reactor 1 exceeds the alarm setting NOx concentration F for a moment, an alarm is generated, so the frequency of occurrence is high and unstable operation occurs. An object of the present invention is to provide a denitration control system that prevents these frequent alarms and that suppresses the average NOx concentration per unit time after the denitration reaction of the gas to be treated to a regulated value or less.

[0004]

The above objects of the present invention can be achieved by the following constitutions. That is, the invention according to claim 1 is an ammonia catalytic reduction denitration method for injecting ammonia into a gas to be treated to catalytically reduce NOx in the gas to be treated. For example, the unit time is selected as 60 minutes. The same applies hereinafter) The moving average NOx concentration (B) which is the average value of the NOx concentration in the gas to be treated per unit time (60 minutes) for a predetermined time (x minutes) or less. calculates a single position per time after the denitration reaction in the moving average NOx concentration (B) per unit time based on the (60 minutes) the predetermined time (x minutes) the remaining time obtained by subtracting from the (60-x min) NOx as NOx concentration control setting value (C) becomes a value not over a management value (a) of the NOx concentration in average per unit time (60 minutes) of
The concentration control set value (C) is calculated, and the calculated NOx concentration control set value (C) and NO in the gas to be treated after the denitration reaction.
This is a nitrogen oxide concentration control denitration method in which the ammonia injection amount is set based on the deviation of the x concentration. According to a third aspect of the present invention, in an ammonia catalytic reduction denitration method for injecting ammonia into a gas to be treated to catalytically reduce NOx in the gas to be treated, a predetermined time of not more than a unit time in the gas to be treated after the denitration reaction is performed. NOx in the gas to be treated per unit time of time
The moving average NOx concentration (B), which is the average value of the concentration, is calculated, and the unit time within the remaining time is subtracted from the unit time based on the moving average NOx concentration (B).
Rino calculated NOx concentration control setting value (C) is the NOx concentration control value of the average per unit time (A) NOx concentration control setting value to be over non value of (C), the NOx issued the calculated The ammonia injection amount is set based on the deviation between the concentration control set value (C) and the NOx concentration in the gas to be treated after the denitration reaction, and the moving average NOx concentration (B) for the predetermined time is the NOx concentration control value (A ) Is a nitrogen oxide concentration control denitration method in which an excessive amount of ammonia is temporarily injected.

According to a fifth aspect of the present invention, in an ammonia catalytic reduction denitration method in which ammonia is injected into a gas to be treated to catalytically reduce NOx in the gas to be treated, a unit time in the gas to be treated after the denitration reaction is performed. The following first predetermined time (x minutes
Interval) , the moving average NOx concentration (B), which is the average of the NOx concentrations in the gas to be treated per unit time (60 minutes) , is calculated, and the unit time is calculated based on the moving average NOx concentration (B).
Unit time (60 minutes ) within the remaining time (60-x minutes) after subtracting the first predetermined time (x minutes) from (60 minutes)
During) NOx concentration control setting value per (C) the NOx concentration control of the average per unit time (A) NOx concentration control setting value to be over non value to calculate the (C), issued the calculated The ammonia injection amount is set on the basis of the deviation between the NOx concentration control set value (C) and the NOx concentration in the gas to be treated after the denitration reaction, and the ammonia injection amount is set to the second predetermined time (y minutes) or less than the unit time (60 minutes) . Unit time in the gas to be treated (60 minutes
This is a nitrogen oxide concentration control denitration method that issues an alarm when the moving average value NOx concentration (D ) per ( interval) is equal to or greater than the alarm transmission set value (F). According to a seventh aspect of the present invention, in an ammonia catalytic reduction denitration method for injecting ammonia into a gas to be treated to catalytically reduce NOx in the gas to be treated, a unit time (60 minutes) in the gas to be treated after the denitration reaction is performed. ) The unit time (60 minutes) of the following first predetermined time (x minutes)
The moving average NOx concentration (B), which is the average value of the NOx concentration in the per-process gas, is calculated, and based on the moving average NOx concentration (B), from the unit time (60 minutes) to the first predetermined time (x minutes). ) Remaining time (60-x minutes)
Units of the inner time (60 minutes) NOx concentration control setting value per (C) is a unit time (60 minutes) Average NOx per
NOx so that the value does not exceed the concentration control value (A)
The concentration control set value (C) is calculated, and the calculated NOx concentration control set value (C) and NO in the gas to be treated after the denitration reaction.
The ammonia injection amount is set based on the deviation of the x concentration, and when the moving average NOx concentration (B) for the first predetermined time (x minutes) exceeds the NOx concentration control value (A), the excess amount is temporarily exceeded. Inject ammonia for a unit time (60 minutes
During the second predetermined time (y minutes ) below
This is a nitrogen oxide concentration control denitration method that issues an alarm when the moving average value NOx concentration (D ) per unit time (60 minutes) is equal to or higher than the alarm emission set value (F). In the nitrogen oxides concentration control denitration method according to each of the above claims 1, 3, 5, and 7, the calculated NOx concentration control set value (C) is an upper limit value or a lower limit value when the upper limit value or more or the lower limit value or less, respectively. The ammonia injection amount can be set based on

The above object of the present invention can also be achieved by the following configuration. That is, the invention according to claim 9 is an ammonia equipped with a denitration reactor for catalytically reducing NOx in the gas to be treated in the presence of ammonia injected from ammonia injection means provided on the inlet side of the denitration reactor. In the catalytic reduction denitrification device, the average value of the NOx concentration in the gas to be treated per unit time (60 minutes) of the first predetermined time (x minutes) that is less than or equal to the unit time (60 minutes) of the NOx concentration at the denitration reactor. And a calculator for calculating the moving average NOx concentration (B), which is a unit time (60 minutes) to a first predetermined time (x
The remaining time minus the min) (60-x minutes) in single of
A calculator for calculating as much time (60 minutes) denitration reactor outlet NOx concentration control setting value (C) of the unit time (60 minutes) average NOx concentration control value per (A) is not over the value of per the An arithmetic unit for calculating and setting the amount of ammonia injected into the ammonia injecting means based on the deviation between the NOx concentration control set value (C) and the NOx concentration at the outlet of the denitration reactor, and a second predetermined time (unit time (60 minutes) or less) Nitrogen oxide provided with an alarm transmitter that issues an alarm when the moving average value NOx concentration (D ) per unit time (60 minutes) in the gas to be treated ( y minutes) is equal to or greater than the alarm transmission set value (F). It is a concentration control denitration device.

[0007]

In the present invention, the NOx concentration signal input to the alarm device is set to a unit time (for example, 60 minutes. The same applies hereinafter).
Since the moving average NOx concentration (D) which is the average value of the NOx concentration in the gas to be treated per unit time (60 minutes) within the second predetermined time (y minutes) within is adopted, The measured instantaneous peak NOx concentration is relaxed, the frequency of alarms is reduced, and the first predetermined time (x
Minute) is a moving average NOx concentration (B) which is the average value of the NOx concentration in the gas to be treated per unit time (60 minutes)
From the unit time (60 minutes) to the predetermined time (x
Minutes) minus the remaining time (eg (60-x)
N ) after denitration reaction per unit time (60 minutes)
To operate Ox density control setting value (C) as a value movement without over NOx concentration in a management value (A) of the average unit time (for 60 minutes), the average unit time (60 minutes) NOx It is possible to operate in strict compliance with the concentration regulation value.
At this time, the calculated NOx concentration control set value (C) is
When the value becomes equal to or higher than the upper limit value or equal to or lower than the lower limit value, the NOx concentration control set value (C) is significantly hunted or runaway by setting the ammonia injection amount based on the upper limit value or the lower limit value, respectively. It can be prevented. In addition, when the moving average NOx concentration (D ) per unit time (60 minutes) exceeds the NOx concentration control value (A), an excessive amount of ammonia is temporarily injected, so that the target gas after the denitration treatment is treated. An abnormally high NOx concentration can be avoided.

[0008]

An embodiment of the present invention will be described with reference to the drawings.
FIG. 4 shows the overall denitration system system configuration of this embodiment. NH ₃ for denitration is injected and mixed into the exhaust gas discharged from the exhaust gas generation facility 8 such as a boiler or a gas turbine, and the denitration reaction is performed in the denitration reactor 1, and the purified gas is discharged from the chimney 6 to the atmosphere. This embodiment relates to the NH ₃ injection amount control system of the NH ₃ injection system of FIG. 4 and will be described in detail below. FIG. 1 shows the NH in the flue gas denitration system of this embodiment.
₃ shows the injection control system diagram. In FIG. 1, the denitration reactor 1
The instantaneous NOx concentration in the processed gas measured by the NOx analyzer 2 provided in the processed gas flow path on the outlet side is the moving average N.
It is input to the Ox concentration calculator 4, and is calculated as a moving average NOx concentration D for y minutes (<60 minutes) by this calculator 4. When the NOx concentration D exceeds the alarm set NOx concentration, which is the control value A plus a few ppm, that is, the alarm set value F, the alarm device 7 outputs an alarm. Also,
The calculator 4 can also calculate the moving average NOx concentration B for x minutes (<60 minutes).
Based on the above, the NOx control set value C in the calculator 5 is (2) below.
Calculated according to the formula.

The following equation (2) is derived from the following equation (1) which is a condition that the NOx concentration control set value C does not exceed the base control NOx concentration, which is the average NOx concentration for 60 minutes, that is, the control value A. A = B × x / 60 + C × (60−x) / 60 (1) C = {60 × A−B × x} / (60−x) (2) Then, according to the deviation between the NOx concentration control set value C and the NOx concentration in the gas to be treated measured by the NOx analyzer 2, the ammonia injection amount calculator 9 supplies it to the to-be-treated gas passage on the inlet side of the denitration reactor 1. The injection of NH ₃ for denitration is controlled. The indication of the outlet NOx concentration in the gas to be treated of the denitration reactor 1 measured by the NOx analyzer 2 and the output signal of the NOx concentration recorder 3 are 60-minute moving average concentrations. Thus
For example, the moving average NOx concentration B is calculated for x = 15 minutes, and then the control set value C for 45 minutes from 15 minutes to 60 minutes is calculated.
Is calculated based on the above equation (2) to operate. During this period, if an abnormality occurs and the NOx concentration value at the outlet of the denitration reactor 1 increases, y = 30 minutes of the moving average NOx concentration D and the alarm setting N.
An alarm is generated by checking the Ox concentration F. This alarm is used to check for any abnormalities and take measures so that the regulation value is not exceeded in the remaining 30 minutes.

In the embodiment shown in FIG. 2, the moving average NOx for x minutes is used.
If the concentration B exceeds the control value A, a temporary excess N
1 shows a control system for injecting H ₃ to reduce the NOx concentration in a gas to be treated. That is, the moving average N
When the Ox concentration B becomes a value exceeding the control value A, the ammonia preceding excess computing unit 10 operates to allow excessive injection of ammonia into the gas to be treated. FIG. 3 shows a restriction of the system of the embodiment shown in FIG. 1, which further limits the upper limit or the lower limit of the control set value C in order to prevent the control set value C from hunting to a large extent up and down or runaway. 2 shows a restriction system provided with a container 11. Of course, the limiter 11 can be applied to the system shown in FIG. 2, but it is not shown.

[0011]

EFFECTS OF THE INVENTION By adopting the present invention, the frequency of alarm generation is reduced, and optimal denitration NH ₃ is injected to reduce the leak NH ₃ and exceed the regulation value of the average value NOx concentration per unit time. It is possible to operate a stable denitration device that does not allow it.

[Brief description of drawings]

FIG. 1 is a diagram showing a moving average NOx control denitration system according to an embodiment of the present invention.

FIG. 2 is a diagram showing a moving average NOx control denitration system according to an embodiment of the present invention.

FIG. 3 is a diagram showing a moving average NOx control denitration system according to an embodiment of the present invention.

FIG. 4 is a configuration diagram of the entire denitration system of the present invention.

FIG. 5 is a diagram showing a conventional NOx control denitration system.

[Explanation of Codes] 1 ... Denitration reactor, 2 ... NOx analyzer, 3 ... NOx concentration recorder, 4 ... Moving average NOx concentration calculator, 5 ... NOx concentration control set value calculator, 7 ... Alarm device, 8 ... Exhaust gas generation equipment, 9 ... Ammonia injection amount calculator, 10 ... Ammonia preceding excess calculator, 11 ... Limiter, A ... Control value, B ...
x minute moving average NOx concentration, C ... control set value, D ... y minute moving average NOx concentration, E ... 60 minute moving average NOx concentration, F
… Alarm set value

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noriho Korenaga 6-9 Takara-cho, Kure-shi, Hiroshima Babcock Hiritsu Co., Ltd. Kure Factory (58) Fields investigated (Int.Cl. ⁷ , DB name) B01D 53 / 56,53 / 90

Claims (9)

(57) [Claims] 1. An ammonia catalytic reduction denitration method for injecting ammonia into a gas to be treated to catalytically reduce NOx in the gas to be treated, wherein a predetermined time of not more than a unit time in the gas to be treated after denitration reaction The moving average NOx concentration (B), which is the average value of the NOx concentration in the gas to be treated per unit time, is calculated, and within the remaining time after subtracting the predetermined time from the unit time based on the moving average NOx concentration (B). Hit the unit time after denitration reaction
Wherein the Rino NOx concentration control setting value (C) calculates the control value of the NOx concentration in average per unit time (A) NOx concentration control setting value to be over non value of (C), issued the calculated A nitrogen oxide concentration control denitration method, wherein an ammonia injection amount is set based on a deviation between the NOx concentration control set value (C) and the NOx concentration in the gas to be treated after the denitration reaction. 2. The calculated NOx concentration control set value (C)
The method for denitrifying nitrogen oxides according to claim 1, wherein the ammonia injection amount is set based on the upper limit value or the lower limit value above the upper limit value or below the lower limit value, respectively. 3. An ammonia catalytic reduction denitration method for injecting ammonia into a gas to be treated to catalytically reduce NOx in the gas to be treated, wherein a predetermined time of not more than a unit time in the gas to be treated after the denitration reaction. The moving average NOx concentration (B), which is the average value of the NOx concentration in the gas to be treated per unit time, is calculated, and within the remaining time after subtracting the predetermined time from the unit time based on the moving average NOx concentration (B). NOx concentration control set value per unit time (C) is concentrated NOx to be a value that does not over-NOx concentration control value (a) of the average per unit time
Calculated degree control setting value (C), the NOx issued the calculated
Concentration control set value (C) and N in the gas to be treated after denitration reaction
The ammonia injection amount is set based on the deviation of the Ox concentration, and the moving average NOx concentration (B) for the predetermined time is NO.
A nitrogen oxide concentration-controlled denitration method characterized by temporarily injecting an excessive amount of ammonia when the x concentration control value (A) is exceeded. 4. The calculated NOx concentration control set value (C)
The method for denitrifying nitrogen oxides according to claim 3, wherein the ammonia injection amount is set based on the upper limit value or the lower limit value above the upper limit value or below the lower limit value, respectively. 5. An ammonia catalytic reduction denitration method for injecting ammonia into a gas to be treated to catalytically reduce NOx in the gas to be treated, wherein a first predetermined time of unit time or less in the gas to be treated after denitration reaction is satisfied. The moving average NOx concentration (B), which is the average of the NOx concentration in the gas to be treated per unit time, was calculated, and the first predetermined time was subtracted from the unit time based on the moving average NOx concentration (B). N per unit time within the remaining time
Ox concentration control set value (C) is the average N per unit time
Ox concentration control value (A) so that the value does not exceed N
Calculated Ox density control setting value (C), set the ammonia injection amount based on the deviation of the NOx concentration in the processed gas after the calculated issued said NOx concentration control setting value (C) denitration reaction unit time the following second single of the treated gas in a predetermined time
A nitrogen oxide concentration-controlled denitration method which issues an alarm when the moving average value NOx concentration (D) per unit time is equal to or greater than the alarm transmission set value (F). 6. The calculated NOx concentration control set value (C)
The method for denitrifying nitrogen oxides according to claim 5, wherein the ammonia injection amount is set based on the upper limit value or the lower limit value above the upper limit value or below the lower limit value, respectively. 7. A method of ammonia catalytic reduction denitration for injecting ammonia into a gas to be treated to catalytically reduce NOx in the gas to be treated, wherein a first predetermined time of not more than a unit time in the gas to be treated after denitration reaction. The moving average NOx concentration (B), which is the average value of the NOx concentration in the gas to be treated per unit time, is calculated, and the first predetermined time is subtracted from the unit time based on the moving average NOx concentration (B). Further, the NOx concentration control set value (C) per unit time within the remaining time is set to a value that does not exceed the average NOx concentration control value (A) per unit time.
Before calculating the NOx concentration control set value (C),
The ammonia injection amount is set based on the deviation between the NOx concentration control set value (C) and the NOx concentration in the gas to be treated after the denitration reaction, and the moving average NOx concentration (B) for the first predetermined time is the NOx concentration. When the control value (A) is exceeded, an excessive amount of ammonia is temporarily injected, and a moving average value NOx concentration (D) per unit time in the gas to be treated for a second predetermined time that is equal to or shorter than the unit time is alarmed. A nitrogen oxide concentration-controlled denitration method, wherein an alarm is emitted when the transmission set value (F) or more. 8. The calculated NOx concentration control set value (C)
The method for denitrifying nitrogen oxides according to claim 7, wherein the ammonia injection amount is set based on the upper limit value or the lower limit value above the upper limit value or below the lower limit value, respectively. 9. An ammonia catalytic reduction denitration apparatus equipped with a denitration reactor for catalytically reducing NOx in a gas to be treated in the presence of ammonia injected from ammonia injection means provided on the inlet side of the denitration reactor. A unit for calculating a moving average NOx concentration (B) which is an average value of the NOx concentration in the gas to be treated per unit time for a first predetermined time equal to or less than the unit time of the NOx concentration at the outlet of the denitration reactor, and a unit The denitration reactor outlet NOx concentration control set value (C) per unit time within the remaining time obtained by subtracting the first predetermined time from the time is set as a value that does not exceed the average NOx concentration control value (A) per unit time. An arithmetic unit for calculating, and an arithmetic unit for calculating and setting the ammonia injection amount to the ammonia injecting means based on the deviation between the NOx concentration control set value (C) and the NOx concentration at the outlet of the denitration reactor. , The moving average value NOx concentration per unit time to be treated gas of the second predetermined time follows h (D) is provided with alarm transmitter which transmits an alarm is Alarm output setting value (F) or higher A nitrogen oxide concentration control denitration device characterized by the above.