JPS61257221A - Controller for amount of ammonia to be blown in catalytic denitration - Google Patents

Abstract

PURPOSE:To contrive decrease of the amount of NH3 to be consumed by measuring NOX concn. in an inlet and an outlet of a reactor, controlling the amount of NH3 to be blown with these measured value and changing the amount of NH3 to be blown when the average value of NOX concn. in the outlet reaches the preset value. CONSTITUTION:Each measured value obtained from an NOX sensor 3, an NOX meter 4 in an inlet side of a catalytic denitration reactor 2 and an NOX sensor 7, an NOX meter 8 in an outlet side and a temp. sensor 5, a thermometer 6 is sent to a calculation control part 9 for the amount of NH3 to be blown. Herein both the average value of NOX concn. in the outlet and the amount of NH3 to be blown on the basis of the average value are calculated and the control of the amount of NH3 to be blown is performed by repeating the ON- OFF every specified time. When the average value of NOX concn. in the outlet reaches the preset value, the amount of NH3 to be blown is changed and the blowing of NH3 is performed by receiving the output in an NH3 blowing device 10.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides ammonia (hereinafter referred to as
The present invention relates to an ammonia injection amount control device for catalytic denitrification that controls the injection amount (NH).

[Prior art]

In garbage incinerators, NOx is generated during the incineration and is contained in the exhaust gas and released.
xjli is being held down. In recent years, this No.
Although regulations on the amount of work are becoming stricter, a catalytic denitrification system is used as a technology for removing NOxi, which injects NH3'6 into the exhaust gas and reduces NO and i through a ring element action.

By the way, in this conventional orange system, the amount of NH and injection is determined by the following method. In other words, if one denitrification vehicle is used, ? w f (y, θ) ・・・・・・・・・−
・It can be expressed by song (1). In the above formula, h″Cr is NH.

/NOx ratio, θ is the reaction temperature. Here 1 reactor degree θ
Since θ usually does not change significantly and its value is considered to be known, it is generally possible to obtain the catalytic denitrification characteristics shown in FIG. 6 for θ.

The gradient of the characteristics shown in the figure varies depending on the reaction temperature θ.

Therefore, if the inlet NOx contained in the exhaust gas on the inlet side of the catalytic denitrification reactor is yo, m NoX'It y*,
The denitrification rate η is: η=(y, -y*)/yoxlOO(%) -...-
・−・It is determined by the formula (2), but 1. This (2)
r can be determined from the characteristics shown in FIG. 6 based on the denitrification rate η in the equation. Then, of this r, the inlet NOxy
Since o is known, the required amount of NH can be calculated from r. Therefore, the operator operates to constantly blow the amount of NH3 determined by the above means into the exhaust gas on the inlet side of the denitrification reactor.

[Problem that the invention seeks to solve]

There is no problem in itself with the conventional means in the sense that the necessary amount of NH is injected by the means described above to obtain the desired target output NOx'i. The amount of injection is kept constant over time, and the dynamic characteristics of the catalytic reaction process are not utilized at all.

For this reason, there were problems in that the reaction efficiency in the catalytic denitrification reactor was poor, and the amount of nitrogen consumed was large, making it uneconomical.

The present invention was made to solve the above-mentioned problems, and it is possible to improve the reaction efficiency and reduce the consumption of NH3 by controlling the NH injection time without considering the dynamic characteristics of the catalytic denitrification reaction. The object of the present invention is to provide an ammonia injection amount control device for catalytic denitrification.

[Means for solving problems]

In order to achieve the above object, the present invention provides nitrogen on the inlet side and outlet side of a catalytic denitrification reactor in an exhaust gas flue containing Nox.
An OXRLK degree analyzer is installed to measure the No.
! NH3
NH that temporally controls the blowing amount and calculates the average value of the NOxd degree on the exit side.

A blowing amount calculation control section is provided, and when the average value of the outlet side NOx concentration obtained by the calculation of this control section becomes a set value, the NH blowing amount is changed and the blowing is performed.

[Effect]

Therefore, by using one or more of the above methods, it is possible to effectively utilize the dynamic characteristics of the catalytic denitrification reaction, control the NH3 injection time, improve the reaction efficiency, and reduce the amount of NH3 consumed. can.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of the apparatus of the present invention, in which a catalytic denitrification reactor 2 is provided in an exhaust gas flue 1. On the exhaust gas inlet side of the reactor 2, in addition to an inlet-side NOxIIk degree analyzer such as a NOx sensor 3 and a NOx meter 4), reaction exhaust gas temperature measuring devices such as a temperature sensor 5 and a thermometer 6 are installed. On the other hand, a KNOx sensor 1 is also installed on the exhaust gas outlet side of the catalytic denitrification reactor 2.
and an outlet-side NOx concentration analyzer such as a NOx meter 8. Note that the temperature measured by the thermometer 6 does not change appreciably as described above, and can be treated as known, so the following explanation will be omitted.

9 is an NH3 injection amount calculation control unit, which controls the NO concentration 7 on the inlet and outlet sides from the NOx meter 4.8 and thermometer 6.
In addition to 1-72 and the reaction temperature, 1 not shown is the output Nox @ degree setting value y*T! - I10 port to import and other data input means, and turn on/off at pre-specified times.
Repeated off and NH.

A timer control means for controlling the blowing amount, and a NOx @ degree average value calculation means for calculating the average value rt of the outlet Nox degree using the inlet/outlet side NOx concentration etc. taken in through the data input means. and a control output means for outputting a control command for the amount of NH5 blown based on the average value obtained by the calculation means. Reference numeral 10 denotes an NH blowing device which blows NH3'i into the exhaust gas inlet side of the reactor 2 in response to the output of the NH3 blowing amount calculation control section 9.

Next, the operation of the device having one or more such configurations will be explained. Now, when the timer control means of the NHs injection amount calculation control unit 9 repeats the injection of air from on to o to on and off, the NOx on the exhaust gas outlet side exhibits a response characteristic as shown in Fig. 2. In this case, As the first-order lag when turning on and turning off such a response characteristic.

However, there is a T2 (time constant when off) between the two.
It was experimentally confirmed that the following relationship exists: = a x T1 (time constant when turned on).

Therefore, in the NH and blowing amount calculation control section 9.

■ First, N as NH5-NH3rn□ for 3T1 hour.
Execute the injection command of H31-. Here, NH3m0 is the maximum NH,fi that establishes a linear relationship with the characteristics shown in Figure 6.
It is t. After this 3T time has elapsed, the amount is set to 0.

(2) Constantly calculate the average value y of the exit NOxfi degree from the start time as NH4-NH3rn. This calculation will be described later.

■Next, when the average value wa of the outlet NOx concentration reaches the set value y* of the outlet NOx concentration, NH5gg.

The process is terminated and the process returns to step (2) above to control the amount of NH3 blown into the process.

Therefore, by controlling the amount of NH and injection as described above,
The response of NOx on the outlet side is similar to that shown in FIG. 2, but the amount of NH and blown can be significantly reduced. Regarding this, calculations will be made especially for τ±3T2 using the symbols shown in FIG.

First, let y1# be the NOx concentration on the inlet side.

3T Average value of NOx on the outlet side for 1 hour On the other hand, τ”xa'r Average value of NOx on the outlet side for 2 hours ζ2
Therefore, it becomes y1+y2.

3T, +372 (y1+2y2)TI+(2y1+y2)T2+
,,+0.1. ．． 1. :(4)3(T,+T2). On the other hand, on-off 1? The average value of the amount of NHs blown between cycles can be expressed by the following equation.

Now, since T #3'r, equation (4) and (5
) can be further expressed as follows.

What is the denitrification rate η at this time?

In order to do this, the required denitrification rate is 7 in equation (6), so it is shown in Figure 4. Therefore, from equations (8) and (9), the present invention apparatus has a higher performance than the conventional means. Calculate how much water and volume can be reduced.

Compared to the conventional method, ■3 the amount of blowing can be significantly reduced.

Incidentally, FIG. 5 is a diagram showing the actual measured value of NOx contained in the exhaust gas on the outlet side when the above-mentioned blowing amount control of (3) is used.

〔Effect of the invention〕

As described in detail above, according to the present invention, the amount of NH and S blown is controlled all the time, the average value of NOx on the outlet side is calculated, and when this becomes the set value, the NH and S blown amount is changed. Therefore, it is possible to provide an ammonia injection amount control device for catalytic denitrification that can improve reaction efficiency and significantly reduce consumption of ammonia.

[Brief explanation of drawings]

1 to 5 are for explaining an embodiment of the ammonia injection amount control device for catalytic denitrification according to the present invention, FIG. 1 is a schematic configuration diagram of the device, and FIG.
3. A diagram showing the relationship between ON/OFF of blowing and the NOx concentration on the exhaust gas outlet side. FIGS. The figure shows the actual measurements of Kibadai using the device of the present invention to control the amount of CNH blowing, and Figure 6 shows the characteristics of catalyst denitrification for determining the required amount using conventional means.2 ...Catalytic denitrification reactor, 3.7・-No Senna, 4
．． 8...NOx meter, 9-NH, injection amount calculation control section, 1
0...NH, blowing device.

Claims (1)

[Claims] A NO_x concentration analyzer that measures the NO_x concentration on the inlet and outlet sides of the catalytic denitrification reactor in the exhaust gas flue containing NO_x (nitrogen oxides), and an injection amount control command to temporally control the ammonia injection amount. At the same time, an average value of the NO_x concentration on the outlet side is determined based on the NO_x concentration from the NO_x concentration analyzer, and when this average value reaches a predetermined NO_x concentration setting value, a change command for the ammonia injection amount is issued. An ammonia injection amount control device for catalytic denitrification, comprising: an ammonia injection amount calculation control unit that outputs an ammonia injection amount calculation control unit; and an ammonia injection device that blows ammonia into an inlet side exhaust gas flue of the catalytic denitrification reactor based on the output of the calculation control unit.