JPH03238024A - Exhaust gas denitrification control device - Google Patents

Abstract

PURPOSE:To reduce the amount of nitrogen oxide to a predetermined value or less on the basis of the optimum removing matter blow-in amount by receiving the data of the combustion state related to the generation amount of nitrogen oxide by a blow-in control means and changing a blow-in amount control signal on the basis of this data corresponding to the combustion state. CONSTITUTION:The amount of the nitrogen oxide component contained in combustion waste gas is detected and the blow-in amount control signal of removing matter (e.g. ammonia) for removing nitrogen oxide is formed from the detected component amount and a nitrogen oxide set value to set the amount of nitrogen oxide to a predetermined value. A blow-in amount control means 10 receives respective combustion data such as the combustion air amount due to a combustion air flowmeter 13, the temp. in a combustion furnace due to a furnace thermometer 11, the furnace outlet temp. due to a furnace outlet thermometer 12 and the oxygen concn. of waste gas due to a waste gas oxygen densitometer 14 to calculate the estimated generation amount of nitrogen oxide from a preset nitrogen oxide generating function and adds the control signal based on this estimated generation amount of nitrogen oxide to a blow-in control signal. As a result, the amount of nitrogen oxide can be suppressed to a predetermined value or less.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an exhaust gas denitrification control device that controls the amount of nitrogen oxides contained in exhaust gas from a garbage incinerator or the like.

[Technical background of the invention]

In garbage incinerators, nitrogen oxides (NOx) are produced by incineration.
Since NOx is generated and released as part of the exhaust gas, efforts are being made to suppress the amount of NOx.

The first technology to suppress the amount of NOx is to inject ammonia NH3 etc. into the exhaust gas and reduce NOx through the reduction action.
There is a non-catalytic denitrification method that removes NOx, and this method is effective in keeping the amount of NOx below a specified value. Note that this method cannot control the amount of NOx with high accuracy simply by blowing a certain amount of NH into the exhaust gas because the amount of NOx fluctuates greatly.

Therefore, the amount of NH to be blown is controlled according to the amount of NOx in the exhaust gas.

Further, as a second technique, there is a technique described in Japanese Unexamined Patent Publication No. 153869/1983. This technology uses at least two of a fuel flow rate transmitter, a fuel flow rate transmitter, an exhaust gas oxygen concentration detector, an exhaust smoke film acid gas concentration detector, a combustion air flow rate transmitter, and a combustion gas flow rate transmitter. a computing device that estimates the concentration of nitrogen oxides in flue gas from the output signal of the measuring device; a device that controls the supply amount of the nitrogen oxide removing reducing agent based on the output of the computing device; The apparatus includes a nitrogen oxide concentration detection device that detects the nitrogen oxide concentration in the exhaust gas from the oxide removal device, and a device that corrects the output of the arithmetic device based on the output of the nitrogen oxide concentration detection device.

Furthermore, there is a third technique described in Japanese Unexamined Patent Publication No. 54-99771. This technology is related to the ammonia injection control method in the dry flue gas denitrification method.In high load and high temperature ranges, the NH3/NOx ratio is increased to prevent a decrease in the denitrification rate, and in low load and low temperature ranges, the NH3/NOx ratio is increased. This is a technology to reduce the amount of NH adsorbed onto the catalyst.

[Problems with background technology]

However, the above technology has the following problems. First, in the first technology, ■In a waste incinerator, the furnace outlet (-1'
Since NH is injected into the υ1 gas of f, it is difficult to continuously analyze NOX ffi generated by combustion.

■Also, it takes time to obtain measurements of NOx after the mixing/reaction of NH and NOx and the denitrification reaction, and there is a delay on the order of minutes before the removal results after NH3 injection appear in the NOx measurement values. arise. For this reason, it is very difficult to optimally control the amount of NH, by feeding back so that the NOx measurement value becomes the set value.

(2) The characteristics of the non-catalytic denitrification reaction between NH3 and NOx vary greatly depending on the amount of NoX generated depending on temperature conditions and combustion conditions. FIG. 6 shows the relationship between the temperature of the NH3 blowing section and the denitrification rate, and FIG. 7 is a diagram showing the relationship between the NH3 blowing section, temperature, and process delay.

In addition, in FIG. 6, R1, R2, and R3 are (NH.

/NOX ratio). As can be seen from each figure, even if the temperature is close to the optimal condition and the control is optimal in this state, if the temperature fluctuates, the denitrification rate will decrease and the process delay will increase. Furthermore, in a garbage incinerator, temperature conditions, combustion conditions, etc. vary greatly due to non-uniformity in the type of garbage, and therefore, if a constant amount of NH3 is injected, the amount of NOx after denitrification also varies greatly. Therefore,
If a large amount of NH is blown in to suppress the fluctuating amount of NOx below a specified value, an odor will be generated and NH will be wasted.

Next, in the second technique, since the control is such that the deviation between the reducing agent supply amount and the reducing agent supply target value determined based on the estimated amount of nitrogen oxides generated is zero, the accuracy of the estimated nitrogen oxide concentration value is controlled. It is necessary to increase

Therefore, there is a need for a device for correcting the estimated value of the nitrogen oxide concentration based on the actual value of the nitrogen oxide concentration in the exhaust gas from the nitrogen oxide removal device. As described above, the estimated value of nitrogen oxide concentration is corrected in order to improve its accuracy, but the amount of reducing agent supplied that is uniquely determined from the estimated value naturally includes an error. Moreover, even when calculating the reducing agent supply amount from the estimated value, an error occurs from the calculation formula, so there is a limit even if attempts are made to improve the accuracy of the control results. The error resulting from this arithmetic expression is actually quite large and varies depending on various conditions.

Furthermore, in the third technology, when the ammonia supply amount is uniquely determined by a function of the amount of nitrogen oxides produced (NH3/NOx ratio), we focus on the fact that the denitrification performance depends on the flue gas temperature, This is a configuration that modifies this function. The final value of the nitrogen oxide concentration in the exhaust gas does not matter. Therefore, it is not possible to always maintain a stable concentration of produced nitrogen oxides below a specified value.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an exhaust gas denitrification control device that can suppress the amount of nitrogen oxides to a predetermined value or less with an optimum amount of removed material blown into the exhaust gas.

[Summary of the invention]

The present invention detects the amount of nitrogen oxide components contained in combustion exhaust gas, and creates a control signal for the amount of removal material to be blown to remove nitrogen oxides from this amount of components and the nitrogen oxide set value. In an exhaust gas denitrification control device that controls the amount of nitrogen oxides to a predetermined value, the blowing control means receives information on the amount of nitrogen oxides generated and related combustion conditions, and this information changes the blowing amount control signal according to the combustion conditions. This is an exhaust gas denitrification control device that attempts to achieve the above objectives.

[Embodiments of the invention]

A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram of an exhaust gas denitrification control device.

In the figure, 1 is an incinerator in a garbage incinerator,
2 is the inside of the furnace, 3 is an ammonia injection section, and 4 is an exhaust gas detection section. The exhaust gas detection unit 4 is provided with an exhaust gas nitrogen oxide concentration meter (NOX meter) 5, and the measurement signal output from the exhaust gas nitrogen oxide concentration meter 5 is the nitrogen oxide set value N.
The signal is sent to a subtracter 6 to which S is input.

The output signal of this subtractor 6 is sent to the injection amount feedback control section 7, and this control section 7 calculates and calculates the injection amount of NH3 such that the amount of NOx contained in the exhaust gas becomes the nitrogen oxide set value NS. , has a function of sending a control signal for this injection amount to the ammonia blowing device 9 via the adder 8.

The injection amount control means 10 receives information on each combustion state of the combustion furnace internal temperature, combustion furnace outlet temperature, amount of combustion air to the combustion furnace, exhaust gas oxygen concentration from the combustion furnace, and the above flow rate, and presets from this information. It has a function of determining an estimated amount of nitrogen oxide generation using the determined nitrogen oxide generation function, and adding a control signal based on this estimated amount of nitrogen oxide generation to the blowing control signal.

To explain the specific configuration, the combustion furnace 1 includes an in-furnace thermometer 1.
1, a furnace outlet thermometer 12, a combustion air flow meter 13, an exhaust gas oxygen concentration meter 14, and a steam flow meter 15 are provided, and their output signals are sent to a generated NOx amount estimator 16. The generated NOx amount estimator 16 has a built-in systematic mathematical model (autoregressive model, multiple regression model, etc.) of NOx generation due to combustion as a nitrogen oxide generation function, and calculates generated NOx based on the mathematical model from each combustion information. It has the function of estimating the amount. Note that this arithmetic expression is as follows.

3/ o -a +oX l+ a 20X 2 +a
30X 30a4oX4+a5oX5 + a olyo (1) + a ++X + (1
) + 82□Y 2 (1) + 831X 3 (1
)+a4+y4(1) +a5. x5 (1) 10a. 2
”10 (2) +a2□x(2) 10 (1)
) Here, 'IO is the estimated value of the generated NOx amount, Xl is the combustion air flow rate, x2 is the furnace temperature, x3 is the furnace outlet temperature, x4 is the exhaust gas oxygen concentration, X is the steam flow rate of the boiler, and ajl
(l, j-1, 2, 3...) are coefficients, (m) is data from m times ago, and the absence of 0 indicates current data.

The blow feed forward control unit 17 receives the estimated NOx amount from the generated NOx amount estimator 16, calculates the necessary amount of NH3, and sends the control signal to the adder 8. Therefore, this calculation formula is as follows.

η−f(γ,T)...(2
) η-(yo y)/yo represents the denitrification rate, and γ-
NH,/y.

Here, T is the temperature of the blowing section of NH (furnace outlet temperature), y
o is the amount of generated NoX, and y is the amount of NOx after the denitrification reaction.

Next, the operation of the apparatus configured as described above will be explained. When various types of waste are put into a combustion furnace and combusted with combustion air, exhaust gas containing NOx is released to the furnace outlet.

Here, the exhaust gas nitrogen oxide concentration meter 5 measures NO in the exhaust gas.
x member is detected and its measurement signal is sent to the subtracter 6.

Since the nitrogen oxide set value NS is input to this subtracter 6, a deviation of 0 from this set value NS is sent to the blowing feedback control section 7.

The blowing feedback control section 7 sends to the adder 8 a blowing control signal that makes the input deviation signal zero, that is, makes the amount of NOx in the exhaust gas the nitrogen oxide set value NS.

On the other hand, the temperature detection signal from the furnace thermometer 11, the temperature detection signal from the furnace outlet thermometer 12, the flow rate detection signal from the combustion air flow meter 13, the concentration detection signal from the exhaust gas oxygen concentration meter 14, and the steam flow meter 15 The flow rate detection signal from the NOx
is sent to the quantity estimator 16. The generated NOx amount estimator 16 receives the combustion information, calculates the above equation (1) to obtain an estimated value of the generated NOx amount, and sends this to the injection feedforward control section 17. And this control section 17
receives the estimated value of the generated NOx amount, calculates the above equation (2) to determine the necessary amount of NH3 to be blown, and sends the control signal to the adder 8. Thus, the adder 8 sends to the ammonia blowing device 9 an NH blowing control signal corresponding to the currently required amount of NOx to be removed. As a result of the above operations,
A control result as shown in FIG. 2 is obtained. In Figure 2, QN
indicates the estimated value of the amount of NOx generated, and PH indicates the amount of NH3f injected.
f1, and ZN indicates NOxm in the exhaust gas.

In this way, the amount of NOx in the exhaust gas is approximately the nitrogen oxide set value N
It is controlled by S. Note that Tg indicates a time of 5 minutes.

In this way, in the first embodiment, the estimated value of the generated NOx amount is obtained from the nitrogen oxide generation function upon receiving information on each combustion state, and the control signal based on this estimated value is added to the injection amount control signal. Since the configuration is such that a control signal for the amount of NH3 blown is sent out, the amount of NOx can be brought to the nitrogen oxide set value NS, that is, below the specified value, without causing a process delay.

Since the amount of NH3 to be blown is added to the estimated value of the amount of NOx generated, there is no waste in removing NOX, and even more
Since the configuration calculates the estimated value of the amount of Can be controlled below the specified value.

2 Next, a second embodiment of the present invention will be described with reference to the constituent countries shown in FIG. Note that the same parts as in FIG. 1 are given the same reference numerals.

The blowing amount control means 20 has a function of receiving temperature information (furnace outlet temperature) at the blowing section of the NH, and changing settings of control parameters of the blowing amount feedback control section 21 according to this temperature information. be. Specifically, a parameter adjustment unit 22 receives a temperature detection signal output from the furnace outlet thermometer 12, determines a control parameter corresponding to the furnace outlet temperature, and sets this control parameter in the injection amount feedback control unit 21; Injection amount feedback control section 21
and a subtracter 6. Here, the calculation formula for determining the control parameters is as follows.

The number of transmission intervals G (S) in PID control when applied to feedback control is G (S) Kp fl + (1/T + S) + To
S)...(3>) Here, K, T, and TD are each determined as a function of temperature 3 degrees.

Kp=Kp(θ) T+-T+(θ) To=To(θ) Note that θ is NH and the temperature of the blowing section.

Next, the operation of the apparatus configured as described above will be explained. When the combustion furnace 1 is in a combustion state and exhaust gas is being released, the amount of NOx contained in the exhaust gas is detected by the exhaust gas nitrogen oxide concentration meter 5, and the concentration detection signal is sent to the subtracter 6. Ru.

From this subtractor 6, a deviation signal from the nitrogen oxide set value NS is sent to the injection amount feedback control section 21.

On the other hand, the furnace outlet thermometer 12 detects the temperature at the furnace outlet and sends the temperature detection signal to the parameter adjustment section 22. Now, this parameter adjustment section 22 calculates the above-mentioned equation (3) from the captured temperature detection signal to obtain a control parameter corresponding to the amount of NH blown. As a result, the settings of the control parameters of the blowing amount feedback control section 21 are changed.

Thus, the blowing amount feedback control section 21 sends a blowing control signal to the ammonia blowing device 9 for controlling the NoX amount in the exhaust gas to the nitrogen oxide set value NS based on the changed control parameters.

FIG. 4 shows the result of the above operation, in which the amount of NOx in the exhaust gas is controlled to the nitrogen oxide set value NS.

In this way, in the second embodiment, since the parameter adjustment unit 22 is provided to change the setting of the control parameters according to the furnace outlet temperature, the control parameters of the injection amount feedback control unit 21 are adjusted to the furnace outlet temperature related to the generation of NOx. This allows the amount of NoX in the exhaust gas to be lower than the specified value without causing a process delay or injecting a wasteful amount of NH3. Note that this difference is clear when compared with the case where there is no adjustment of the control parameters shown in FIG. Also, N
The amount of Ox can be controlled to the nitrogen oxide set value NS.

5 [Effects of the Invention] As detailed above, according to the present invention, it is possible to provide an exhaust gas denitrification control device that can suppress the amount of nitrogen oxides to a predetermined value or less with an optimal amount of removed material blown.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the exhaust gas denitrification control device according to the present invention, FIG. 2 is a diagram showing the control results of the device shown in FIG. 1, and FIG. 3 is a diagram showing the exhaust gas denitrification control device according to the present invention. A configuration diagram showing the second embodiment of the device, FIG. 4 is a diagram showing the control results of the device shown in FIG. 3, FIG. 5 is a diagram showing the control results of the conventional device, and FIG. 6 is a diagram showing the temperature of the blowing section. FIG. 7 is a diagram showing the process delay with respect to the temperature of the blowing section. DESCRIPTION OF SYMBOLS 1... Incinerator, 2... Furnace interior, 3... Ammonia blowing section, 4... Exhaust gas detection section, 5... Exhaust gas nitrogen oxide concentration meter, 6... Subtractor, 7 ...Blowing amount feedback control unit, 8...Adder, 9...Ammonia blowing device, 10...Blowing amount control means 10.
11...6 Furnace thermometer, 12...Furnace outlet thermometer, 13...Combustion air flow meter, 14...Exhaust gas oxygen concentration meter, 15...
Steam flow meter, 16... Generated NOX amount estimator determiner 7...
- Injection amount feed forward control section, 20... Injection amount control means, 21... Injection amount feedback control section, 22... Parameter adjustment section.

Claims (4)

[Claims] (1) Detect the component amount of nitrogen oxides contained in the combustion exhaust gas, and create a control signal for the amount of removal material to be blown to remove the nitrogen oxides from this component amount and the nitrogen oxide set value. The exhaust gas denitrification control device that controls the amount of nitrogen oxides to a predetermined value receives information on a combustion state related to the amount of nitrogen oxides generated, and changes the injection amount control signal according to the combustion state based on this information. An exhaust gas denitrification control device characterized by comprising a blowing control means. (2) The removed substance is ammonia (
1) The exhaust gas denitrification control device described in item 1). (3) The injection amount control means estimates the amount of nitrogen oxide generated from a nitrogen oxide generation function set in advance upon receiving combustion information such as combustion air amount, combustion furnace internal temperature, furnace outlet temperature, exhaust gas oxygen concentration, etc. The control signal based on this estimated nitrogen oxide generation amount is added to the blowing control signal.
) Exhaust gas denitrification control device described in section 2. (4) The blowing control means receives information on the temperature inside the combustion furnace,
The exhaust gas denitrification control device according to claim 1, wherein parameters of a control unit that generates an injection amount control signal are changed and set in accordance with this information.