JPH0771619B2 - Exhaust gas denitration control device - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to an exhaust gas denitration control device for controlling the amount of nitrogen oxides contained in exhaust gas from a refuse incinerator or the like.

[Technical background of the invention]

In a refuse incinerator or the like, nitrogen oxide NO _X is generated by the incineration and is contained in exhaust gas and released, so that the NO _X amount is suppressed.

Ammonia NH ₃ is the first technology to reduce the amount of NO _x.
There is a non-catalytic denitration method in which NO _x is blown into exhaust gas to remove NO _x by a reducing action, and this method is effective for keeping the amount of NO _x below a specified value. Note that this method cannot be accurately controlled because the amount of NO _X greatly fluctuates simply by blowing a fixed amount of NH ₃ into the exhaust gas. Therefore,
The amount of NH ₃ blown in is controlled according to the amount of NO _X in the exhaust gas.

As a second technique, there is a technique described in JP-A-52-153869. This technology uses a fuel flow rate transmitter,
Alternatively, a measuring device including at least two of a fuel flow rate transmitting device, a flue gas oxygen concentration detecting device, a flue gas carbon dioxide concentration detecting device, a fuel air flow rate transmitting device, and a combustion gas flow rate transmitting device, and a measuring device of the measuring device. An arithmetic device for estimating the nitrogen oxide concentration in the flue gas from the output signal, and a device for controlling the supply amount of the nitrogen oxide removing reducing agent by the output of this arithmetic device,
The device is provided with a nitrogen oxide concentration detecting device for detecting the nitrogen oxide concentration in the exhaust gas of the nitrogen oxide removing device, and a device for correcting the output of the arithmetic unit by the output of the nitrogen oxide concentration detecting device. .

A third technique is disclosed in Japanese Patent Laid-Open No. 54-99771. This technology relates to an ammonia injection control method in the dry flue gas denitration method, high load, prevents reduction denitration rate by raising the NH ₃ / NO _X ratio in a high temperature range, and low load, NH ₃ / NO _X in a low temperature region This is a technique to lower the ratio and reduce the amount of NH ₃ adsorbed on the catalyst.

[Problems of background technology]

However, the above technique has the following problems. First, with the first technique, in a refuse incinerator, NH ₃ is blown into the exhaust gas near the furnace outlet, which is in a high temperature state, so it is difficult to continuously analyze the amount of NO _X generated by combustion.

In addition, it takes time to obtain the measurement of NO _X after mixing / reaction of NH ₃ and NO _X and denitration reaction, and it takes a minute order until the removal result after NH ₃ injection appears in the NO _X measurement value. Will be delayed. For this reason, it is very difficult to feed back the measured NO _X value to the set value and optimally control the blowing amount of NH ₃ .

Characteristics of uncatalyzed denitration reaction between NH ₃ and NO _X varies greatly depending _the amount of NO _X generated by a temperature condition and the combustion condition. Fig. 6 shows the relationship between the temperature of the NH ₃ blowing part and the denitration rate,
FIG. 7 is a diagram showing the relationship between the NH ₃ blowing part, temperature and process delay. In addition, in FIG. 6, R1, R2, and R3 are (NH ₃ / NO
_X ratio) is shown. As can be seen from each figure, even if the temperature is close to the optimum condition and the control is optimized in this state, the denitration rate decreases and the process delay increases as the temperature changes. Furthermore, in the waste incinerator, the temperature conditions and combustion conditions vary greatly due to the non-uniformity of the type of dust, so if a certain amount of NH ₃ is blown in, the amount of NO _X after denitration also varies greatly. I will end up. Therefore, fluctuating NO _X
If a large amount of NH ₃ is blown to keep the amount below the specified value, odor is generated and NH ₃ is wasted.

Next, in the second technique, the control is performed so that the deviation between the reducing agent supply amount and the reducing agent supply target value that is determined based on the estimated nitrogen oxide generation amount is set to zero. Need to increase. Therefore, a device for correcting the estimated value of nitrogen oxide concentration based on the measured value of the concentration of nitrogen oxide in the exhaust gas of the nitrogen oxide removing device is required. Then, as described above, the value is corrected in order to improve the accuracy of the nitrogen oxide concentration estimated value, but the reducing agent supply amount uniquely determined from the value naturally includes an error. Moreover, even when the reducing agent supply amount is calculated from the estimated value, an error occurs from the calculation formula, so there is a limit in improving the accuracy of the control result. The error generated from this arithmetic expression is actually quite large, and varies depending on various conditions.

Further, in the third technology, when the ammonia supply amount is uniquely determined by the function of the amount of produced nitrogen oxides (NH ₃ / NO _x ratio), attention is paid to the fact that the denitration performance depends on the combustion exhaust gas temperature. This function is modified by. And, it does not matter what value the nitrogen oxide concentration finally becomes in the exhaust gas. Therefore, it is not possible to keep the stable concentration of generated nitrogen oxides below the specified value.

Therefore, it is an object of the present invention to provide an exhaust gas denitration control device capable of suppressing the amount of nitrogen oxides to a predetermined value or less with an optimum amount of removed substances blown in.

[Outline of Invention]

INDUSTRIAL APPLICABILITY The present invention is to inject a removal product for removing nitrogen oxides so that the amount of nitrogen oxides contained in combustion exhaust gas discharged from a combustion furnace maintains a preset nitrogen oxide set value. In the exhaust gas denitration control device for controlling the amount, the nitrogen oxide component amount detecting means for detecting the amount of nitrogen oxide component contained in the combustion exhaust gas, and the nitrogen oxide component detected by the nitrogen oxide component amount detecting means Amount feedback control means for performing a predetermined control calculation on the deviation amount between the amount and the nitrogen oxide set value to calculate the injection amount, and a furnace opening temperature detecting means for detecting the furnace opening temperature of the combustion furnace. And a parameter adjusting means for adjusting a control parameter for executing a control calculation based on the temperature detected by the furnace opening temperature detecting means.

Example of Invention

 The first embodiment will be described below with reference to the drawings.

FIG. 1 is a configuration diagram of an exhaust gas denitration control device. In the figure, 1 is an incinerator in a refuse incinerator, 2 is the inside of the furnace, 3 is an ammonia blowing part, and 4 is an exhaust gas detecting part. The exhaust gas detection unit 4 is provided with an exhaust gas nitrogen oxide concentration meter (NO _X meter) 5, and the measurement signal output from the exhaust gas nitrogen oxide concentration meter 5 is a subtractor into which the nitrogen oxide set point NS is input. It will be sent to 6. The output signal of the subtractor 6 is sent to the injection amount feedback control unit 7, which calculates the injection amount of NH ₃ so that the NO _X amount contained in the exhaust gas becomes the nitrogen oxide set value NS. It has a function of sending the control signal of the blowing amount to the ammonia blowing device 9 via the adder 8.

Blow-in amount control means 10 receives information on each combustion state of the combustion furnace temperature, the combustion furnace outlet temperature, the amount of combustion air to the combustion furnace, the exhaust gas oxygen concentration from the combustion furnace and the above flow rate, and is preset from these information. The estimated nitrogen oxide generation amount is obtained from the generated nitrogen oxide generation function, and a control signal based on this estimated nitrogen oxide generation amount is added to the blow control signal. Explaining the specific configuration, the combustion furnace 1 is provided with a furnace temperature meter 11, a furnace outlet temperature meter 12, a combustion air flow meter 13, an exhaust gas oxygen concentration meter 14 and a steam flow meter 15, and these output signals are generated. It is designed to be sent to the NO _X amount estimator 16. This generated NO _X amount estimator 16 has a built-in systematic mathematical model (NO regression model, multiple regression model, etc.) of NO _X generation due to combustion as a nitrogen oxide generation function, based on the mathematical model from each combustion information. It has a function to estimate the amount of NO _x generated. The calculation formula is as follows. ₀ = a ₁₀ x ₁ + a ₂₀ x ₂ + a ₃₀ x ₃ + a ₄₀ x ₄ + a ₅₀ x ₅ + a _{01 0} (1) + a ₁₁ x ₁ (1) + a ₂₁ y ₂ (1) + a ₃₁ x ₃ (1) + a ₄₁ y ₄ (1) + a ₅₁ x ₅ (1) + a _{02 0} (2) + a ₂₁ x (2) + ... (1) where ₀ is the estimated NO _x amount generated and x ₁ is the combustion air flow rate. , X ₂ is the furnace temperature, x ₃ is the furnace outlet temperature, x ₄ is the exhaust gas oxygen concentration, x ₅ is the steam flow rate of the boiler, and a _ji (i, j = 1,2,3
() Indicates a coefficient, (m) indicates data m times before, and () does not indicate current data.

The blow feed-forward control unit 17 uses the generated NO _X amount estimator 1
By receiving the estimated NOX amount from 6 and calculating the required NH ₃ amount, the control signal is sent to the adder 8. Therefore, this arithmetic expression is as follows.

η = f (γ, T) (2) η = (y ₀ −y) / y ₀ indicates the denitration rate, and γ = NH ₃ / y.

Here, T is the temperature of the blowing portion of NH ₃ (furnace outlet temperature), y ₀ is the generated NO _X amount, and y is the NO _X amount after the denitration reaction.

Next, the operation of the apparatus configured as described above will be described. When various kinds of dust are thrown into the combustion furnace and combustion air is sent into the combustion furnace for combustion, exhaust gas containing NO _X is released to the furnace outlet by this combustion. Here, the exhaust gas nitrogen oxide concentration meter 5 detects the amount of NO _X in the exhaust gas and sends the measurement signal to the subtractor 6. This subtracter 6 has nitrogen oxide set value NS
Is input, the deviation from the set value NS is sent to the blow-in feedback control unit 7. The blow-in feedback control unit 7 sends a blow-in control signal to the adder 8 so as to make the input deviation signal zero, that is, to set the NOX amount in the exhaust gas to the nitrogen oxide set value NS.

On the other hand, the temperature detection signal from the furnace thermometer 11 and the furnace outlet thermometer
The temperature detection signal from 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 flow rate detection signal from the steam flow meter 15 are sent to the NO _X amount estimator 16. There is. The generated NO _X amount estimator 16 receives the combustion information, calculates the equation (1) to obtain an estimated value of the generated NO _X amount, and sends it to the blow feed-forward control unit 17. Then, the control unit 17 receives the estimated value of the generated NO _X amount, calculates the above equation (2) to obtain the required blowing amount of NH ₃ , and sends the control signal to the adder 8. Thus,
From the adder 8, a blowing control signal of the amount of NH ₃ according to the currently required NO _x removal amount is sent to the ammonia blowing device 9. As a result of the above operation, the control result as shown in FIG. 2 is obtained. In Fig. 2, QN is the estimated amount of NO _X generated, and PH
Indicates the amount of NH ₃ blown in, and ZN indicates the amount of NO _X in the exhaust gas. Thus, the amount of NO _X in the exhaust gas is approximately the nitrogen oxide set value N
It is controlled by S. In addition, Tg has shown the time for 5 minutes.

As described above, in the first embodiment, the estimated value of the generated NO _X amount is obtained from the nitrogen oxide generation function by receiving the information of each combustion state, and the control signal based on this estimated value is added to the injection amount control signal. Since the control signal of the blowing amount of NH ₃ is sent out, the NO _X amount can be set to the nitrogen oxide set value NS, that is, the specified value or less without causing a process delay.
Then, without waste to remove NO _X because spray writes NH ₃ amount to adding the estimated value of the generation amount of NO _X, the arrangement further determining an estimate of the generating amount of NO _X, the reaction of the NO _X and NH ₃ that can be controlled below a specified value _the amount of nO _X to estimate the nO _X generation amount in the case where the detector of the combustion furnace 1 nO _X can not detect of the nO _X without being provided.

Next, a second embodiment will be described with reference to the configuration diagram shown in FIG. The same parts as those in FIG. 1 are designated by the same reference numerals.

The blowing amount control means 20 has a function of receiving temperature information (furnace outlet temperature) at the NH ₃ blowing part and changing the setting of the control parameter of the blowing amount feedback control part 21 according to this temperature information. is there. Specifically, the furnace outlet thermometer 12
A parameter adjustment unit 22 that receives a temperature detection signal output from the control unit, obtains a control parameter according to the furnace outlet temperature, and sets the control parameter in the injection amount feedback control unit 21.
And a blowing amount feedback control unit 21 and a subtractor 6. Here, the arithmetic expression for obtaining the control parameter is as follows.

The transfer function G (S) in the PID control when applied to the feedback control is G (S) = K _P {1+ (1 / T _I S) + T _D S} (3). Here, K _P , T _I , and T _D are defined as functions of temperature.

K _P = K _P (θ) T _I = T _I (θ) T _D = T _D (θ) where θ is the NH ₃ blowing part temperature.

Next, the operation of the apparatus configured as described above will be described. When the combustion furnace 1 is in a combustion state and exhaust gas is released, the NO _X amount 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 subtractor 6. To be done. From the subtracter 6, a deviation signal from the nitrogen oxide set value NS is sent to the injection amount feedback control unit 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 adjusting unit 22. Now, the parameter adjusting unit 22 calculates the above-mentioned equation (3) from the temperature detection signal taken in and obtains the control parameter according to the blowing amount of NH ₃ . As a result, the setting of the control parameter of the blowing amount feedback control unit 21 is changed. Thus,
The injection amount feedback control unit 21 changes the NO _X amount in the exhaust gas to the nitrogen oxide set value NS according to the changed control parameter.
A blowing control signal for controlling the above is sent to the ammonia blowing device 9. FIG. 4 shows the result of the above operation, and the amount of NO _X in the exhaust gas is controlled to the nitrogen oxide set value NS.

As described above, in the second embodiment, since the parameter adjusting unit 22 for setting and changing the control parameter according to the furnace outlet temperature is provided, the control parameter of the injection amount feedback control unit 21 is set to the furnace outlet related to the generation of NO _X. The temperature can be changed and set according to the temperature, so that the amount of NO _X in the exhaust gas can be kept below the specified value without causing a process delay and blowing a wasteful amount of NH ₃ . This difference is clear when compared with the case where the control parameters are not adjusted as shown in FIG. Further, the amount of NO _X can be controlled to the nitrogen oxide set value NS even when the furnace outlet temperature TD fluctuates.

〔The invention's effect〕

As described above in detail, according to the present invention, it is possible to provide an exhaust gas denitration control device capable of suppressing the amount of nitrogen oxides to a predetermined value or less with an optimum amount of removed substances blown in.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of an exhaust gas denitration control device, FIG. 2 is a diagram showing control results of the device shown in FIG. 1, and FIG. 3 is a second embodiment of an exhaust gas denitration control device. Diagram,
FIG. 4 is a diagram showing a control result of the device shown in FIG. 3, FIG. 5 is a diagram showing a control result of the conventional device, FIG. 6 is a diagram showing a denitration rate with respect to a temperature of a blowing portion, and FIG. It is a figure which shows the process delay with respect to the temperature of a blowing part. 1 ... Incinerator, 2 ... Inside furnace, 3 ... Ammonia blowing part, 4 ... Exhaust gas detecting part, 5 ... Exhaust gas nitrogen oxide concentration meter, 6 ... Subtractor, 7 ... Blowing amount feedback control Part, 8 ... Adder, 9 ... Ammonia blowing device,
10 …… Blowing amount control means 10, 11 …… In-furnace thermometer, 12 ……
Furnace outlet thermometer, 13 ...... Combustion air flow meter, 14 ...... Exhaust gas oxygen concentration meter, 15 ...... Steam flow meter, 16 ...... Estimated NO _X amount, 17 ...... Blow-in amount feed forward controller, 20 ......
Blow-in amount control means, 21 ... Blow-in amount feedback control unit, 22 ... Parameter adjusting unit.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location F23G 5/00 B 5/50 N L F23J 15/00 6908-3K F23J 15/00 A

Claims (1)

[Claims] 1. A removal product for removing nitrogen oxides so that the amount of nitrogen oxides contained in combustion exhaust gas discharged from a combustion furnace maintains a preset nitrogen oxides set value. In an exhaust gas denitration control device for controlling the injection amount, a nitrogen oxide component amount detecting means for detecting the amount of nitrogen oxide component contained in the combustion exhaust gas, and nitrogen detected by the nitrogen oxide component amount detecting means. Injection amount feedback control means for calculating the injection amount by performing a predetermined control calculation on the deviation amount between the oxide component amount and the nitrogen oxide set value, and detecting the furnace opening temperature of the combustion furnace An exhaust gas denitration control device comprising: a furnace opening temperature detecting means, and a parameter adjusting means for adjusting a control parameter for performing the control calculation based on the temperature detected by the furnace opening temperature detecting means.