JP5089638B2 - Ammonia injection amount correction control apparatus and ammonia injection amount correction control method - Google Patents

Description

  The present invention relates to a control device and method for correcting the amount of ammonia injected into a flue gas denitration device that reduces the NOx concentration of exhaust gas.

  In the ammonia injection control in the flue gas denitration device, the ammonia molar ratio (ammonia amount / NOx amount) set in advance based on the denitration rate calculated as the target value of the outlet NOx concentration with respect to the inlet NOx concentration of the denitration device, The base ammonia injection amount is obtained from the product of the predicted amount of NOx. Then, feed-forward control is performed to output the base ammonia injection amount as an injection amount set value.

  Further, by adding a feedback control signal for correcting the deviation between the target value of the outlet NOx concentration and the actual measurement value to the output signal of the injection amount setting value, the outlet NOx concentration becomes the target value. Is controlling.

  In Patent Document 1, feedback control of the injection amount of ammonia or the like is performed based on the NOx concentration at the outlet of the denitration catalyst device, and the concentration of thermal NOx is predicted from the measured values of oxygen concentration and temperature in the secondary combustion chamber. Further, a NOx treatment method for a waste treatment facility that further feedforward-controls the injection amount of ammonia based on the predicted value is disclosed.

JP 2006-192406 A

  By the way, in the above control method, in order to keep the official environmental standards, the outlet NOx concentration measurement point is located downstream (for example, near the chimney inlet) away from the denitration device. However, if such downstream outlet NOx concentration is reflected in the feedback control signal, a time delay occurs, and the ammonia injection amount to the denitration device cannot be controlled appropriately.

  In addition, when the inlet NOx concentration changes suddenly due to changes in the combustion state in a combustion apparatus such as boiler equipment, the time delay of the feedback control signal becomes significant, and the imbalance between the required amount of ammonia injection and the actual flow rate And the outlet NOx concentration changes suddenly.

  The present invention has been made in view of the above problems, and its main purpose is to stabilize the NOx concentration at the outlet of the flue gas denitration apparatus.

In order to solve the above problems, the present invention is a control device that corrects the amount of ammonia injected into a flue gas denitration device that reduces the NOx concentration of exhaust gas, and is a target value of the outlet NOx concentration of the flue gas denitration device. And a first subtractor that calculates and outputs a NOx concentration deviation by subtracting the measured value from the target value of the NOx concentration, and measuring the inlet NOx concentration of the flue gas denitration device Obtaining a value, calculating a change amount per unit time of the inlet NOx concentration, obtaining the first differentiator to be output, and obtaining the NOx concentration deviation output from the first subtractor; The change amount per unit time of the inlet NOx concentration output from the differentiator is acquired, and the larger one of the NOx concentration deviation and the change amount per unit time of the inlet NOx concentration is the ammonia flow rate setting value. A feedback controller for and outputs the acquired ammonia flow measurements to be injected into the flue gas denitration apparatus, obtains the ammonia flow rate setting value output from the feedback control unit, said from the ammonia flow setpoint And a second subtracter that calculates an ammonia flow rate correction value by subtracting the ammonia flow rate measurement value and outputs the ammonia flow rate correction value to the ammonia flow rate control valve.

  According to this configuration, the increasing tendency of the NOx concentration at the inlet of the flue gas denitration apparatus can be quickly reflected on the ammonia injection amount. According to this, the NOx concentration at the outlet of the flue gas denitration device can be stabilized.

  Further, the present invention is an ammonia injection amount correction control device, further comprising a second differentiator that obtains the burner combustion number in the combustion device, calculates a change amount per unit time of the burner combustion number, and outputs the change amount. The second adder acquires the ammonia flow rate setting value obtained by adding the amount of change per unit time of the burner combustion number output from the second differentiator.

  According to this configuration, by obtaining the change amount per unit time of the burner combustion number as a preceding signal, it is possible to grasp in advance the change in the NOx amount at the inlet of the flue gas denitration device and reflect it in the ammonia injection amount. .

In addition, the present invention is an ammonia injection amount correction control device that acquires a measured value of the inlet NOx concentration and a target value of the outlet NOx concentration, and is a base ammonia injection amount based on the acquired values. A feed-forward control unit that calculates and outputs an ammonia flow rate value; and the second subtractor obtains the ammonia flow rate setting value obtained by adding the ammonia flow rate value output from the feed-forward control unit. It is characterized by.

  According to this configuration, the ammonia flow rate value by feedforward control can be reflected in the ammonia flow rate set value based on the measured value of the inlet NOx concentration.

  Further, the present invention is an ammonia injection amount correction control device, wherein the feedforward control unit is based on the target value of the denitration rate calculated from the measured value of the inlet NOx concentration and the target value of the outlet NOx concentration, A predetermined ammonia molar ratio (ammonia amount / NOx amount) is obtained, a predicted value of NOx amount is calculated from the combustion gas amount at the inlet of the flue gas denitrification device, the ammonia molar ratio, a measured value of the inlet NOx concentration, The ammonia flow rate value is calculated by multiplying the predicted value of the inlet NOx amount.

  The present invention includes an ammonia injection amount correction control method. In addition, the problems disclosed by the present application and the solutions thereof will be clarified by the description of the mode for carrying out the invention and the drawings.

  According to the present invention, the NOx concentration at the outlet of the flue gas denitration device can be stabilized.

1 is a diagram illustrating a configuration of a NOx treatment facility 1. FIG. 3 is a block diagram showing a configuration of a control device 8. FIG.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The ammonia injection amount correction control device according to the embodiment of the present invention is configured so that the lower limit set value of the feedback control signal for correcting the deviation between the target value of the outlet NOx concentration of the flue gas denitration device and the measured value is the inlet NOx concentration. The amount of change per unit time is used.

  According to this, by using the change amount per unit time of the inlet NOx concentration as the lower limit value of the feedback control signal, not the outlet NOx concentration having a time delay, the correction of the ammonia injection amount even if the combustion state changes. The amount can be adjusted appropriately. Thereby, the outlet NOx concentration can be stabilized.

≪NOx treatment equipment configuration and overview≫
FIG. 1 is a diagram showing the configuration of the NOx treatment facility 1. The NOx treatment facility 1 injects NOx (nitrogen oxide) contained in exhaust gas by injecting a reducing agent (for example, ammonia) into the exhaust gas generated in the waste treatment facility that treats industrial waste, municipal waste, and the like. A treatment for reductive decomposition (denitration) is performed, and the treated exhaust gas is discharged to the outside.

  As shown in FIG. 1, the NOx treatment facility 1 includes a combustion device 2, a flue gas denitration device 3, a chimney 4, an ammonia injection device 5, an ammonia flow rate control valve 6, a flow rate measuring device 7, a control device 8, and a gas analyzer G <b> 1. And G2, and smoke pipes P1 and P2. The combustion apparatus 2 is an apparatus that burns waste, municipal waste, etc., such as a boiler of a waste treatment facility, generates NOx as exhaust gas, the fuel flow rate as the amount of combustion gas, the number of burners burned as a preceding signal The signal is output to the control device 8. The flue gas denitration device 3 is connected to the combustion device 2 by the smoke pipe P1, and performs NOx removal treatment of NOx in the exhaust gas exhausted through the smoke pipe P1, thereby reducing the NOx concentration. The chimney 4 is connected to the flue gas denitration device 3 by the smoke pipe P2, and discharges the exhaust gas exhausted through the smoke pipe P2 to the outside.

  The ammonia injection device 5 is a device that injects ammonia as a reducing agent into the flue gas denitration device 3, and is connected to the flue gas denitration device 3 via an ammonia flow rate control valve 6 and a flow rate measuring device 7. The ammonia flow rate adjustment valve 6 is a valve that adjusts the flow rate of ammonia injected from the ammonia injection device 5 into the flue gas denitration device 3 according to an instruction from the control device 8. The flow rate measuring device 7 is a device that measures the flow rate of ammonia injected from the ammonia injection device 5 into the flue gas denitration device 3 and outputs it to the control device 8.

  The control device 8 inputs data signals from each instrument and device, performs feedforward control and feedback control processing, and outputs a signal indicating the correction amount of the ammonia flow obtained as a result to the ammonia flow control valve 6. A CPU (Central Processing Unit) that executes a program on a memory. The gas analyzer G1 measures the NOx concentration of the exhaust gas passing through the smoke pipe P1, and outputs it to the control device 8 as the NOx removal NOx concentration. The gas analyzer G2 measures the NOx concentration of the exhaust gas passing through the smoke pipe P2, and outputs it to the control device 8 as the NOx removal NOx concentration. The smoke pipe P <b> 1 is interposed between the combustion device 2 and the flue gas denitration device 3, and conducts exhaust gas from the combustion device 2 to the flue gas denitration device 3. The smoke pipe P <b> 2 is interposed between the flue gas denitration device 3 and the chimney 4, and conducts exhaust gas from the flue gas denitration device 3 to the chimney 4.

≪Control device configuration and processing≫
FIG. 2 is a block diagram showing a configuration of the control device 8. The control device 8 includes a feedforward control program (hereinafter referred to as “feedforward control unit”) 81 of the theoretical ammonia injection amount calculation circuit, and a feedback control program (hereinafter referred to as “feedback control unit”) 82 of the NOx removal NOx concentration control circuit. , A target value setting unit 83, a PID (Proportional Integral Differential) control unit 84, adders A1 and A2, subtracters S1 and S2, and differentiators D1, D2 and D3.

  The feedforward control unit 81 acquires the fuel flow rate as the amount of combustion gas from the combustion device 2, the NOx removal NOx concentration measured value from the gas analyzer G 1, and the NOx removal NOx concentration target value from the target value setting unit 83. Then, the NOx removal target NOx concentration target value is subtracted from the NOx removal NOx concentration measurement value to obtain the NOx removal target value. Based on the NOx removal rate target value obtained by dividing the NOx removal target value by the NOx removal measured NOx concentration value, a preset ammonia molar ratio (ammonia amount / NOx amount) is obtained. The base ammonia injection amount (ammonia flow rate value) is obtained by multiplying three values of the molar ratio, the NOx concentration measurement value at the NOx removal inlet, and the predicted combustion gas amount calculated from the fuel flow rate. Here, the NOx removal NOx concentration predicted value obtained by multiplying the NOx concentration measurement value of the NOx removal inlet and the combustion gas amount calculated from the fuel flow rate can be obtained as a value more approximate to actual operation.

  The feedforward control unit 81 includes a denitration rate / molar ratio calculation program, an ammonia injection amount calculation program, and a predicted NOx amount calculation program.

  The feedback control unit 82 indicates the NOx concentration deviation correction signal at the denitration outlet from the subtractor S1 and the change amount of the NOx concentration NOx concentration measurement value from the differentiator D1 (change rate = change amount per unit time; the same applies hereinafter). The signal is acquired, and the larger one (the smaller one) is output to the adder A1 as the feedback control set value. This means that the amount of change in the inlet NOx concentration is set as the lower limit value, that is, when the amount of change in the inlet NOx concentration is larger than the correction amount of the outlet NOx concentration deviation, feedback control is performed using the amount of change. To do. According to this, even if the NOx removal NOx concentration suddenly changes due to a change in the combustion state in the combustion device 2, feedback control is performed so that it does not become smaller than the change in NOx removal NOx concentration. Control can be realized.

  The feedback control unit 82 includes an outlet NOx concentration deviation correction program and an outlet NOx concentration correction leakage prevention program. Further, since the feedback control set value becomes a disturbance signal when it is increased, for example, the feedback control set value is limited to be a predetermined value or less.

  The target value setting unit 83 is a storage device that sets a target value for the NOx removal NOx concentration based on official standards and the like, and may store an externally input value or may store it in advance. The PID control unit 84 acquires the deviation between the measured value of the ammonia flow rate and the set value from the subtractor S2, creates an opening degree command according to the deviation, and outputs it to the ammonia flow rate control valve 6. The adder A1 acquires a feedforward control set value from the feedforward unit 81, a feedback control set value from the feedback unit 82, and a set value based on a differential value from the adder A2, adds each value, and the added value Is output to the subtracter S2 as the ammonia flow rate set value. The adder A2 includes a change amount of the NOx concentration measured value from the differentiator D1, a change amount of the burner combustion number due to burner ignition / extinguishing from the differentiator D2 (a change amount per unit time, the same applies hereinafter) and a differentiator. The amount of change in the generator output from D3 (the amount of change per unit time; the same applies hereinafter) is acquired, each value is added, and the added value is output to adder A1.

  The subtractor S1 obtains the NOx removal NOx concentration measurement value (oxygen concentration 4% converted value) from the gas analyzer G2 and the NOx removal NOx concentration target value from the target value setting unit 83, and obtains the difference between the values. The difference value is output to the feedback control unit 82 as a NOx concentration deviation correction signal. The subtractor S2 acquires the ammonia flow rate measurement value from the flow rate measuring device 7 and the ammonia flow rate setting value from the adder A1, obtains a difference (ammonia flow rate correction value) between the values, and calculates the difference value as a PID control unit 84. Output to.

  The differentiator D1 acquires a NOx removal NOx concentration measurement value from the gas analyzer G1, obtains a change amount of the NOx removal NOx concentration, and outputs it to the feedback controller 82 and the adder A2. The differentiator D2 acquires the burner combustion number from the combustion device 2, obtains the change in the NOx removal NOx amount predicted by the change amount of the burner combustion number, and outputs the change to the adder A2. As a result, a preceding signal for determining the change in the NOx removal NOx amount predicted by the change in the burner combustion number is added to the feedback control signal, and the change in the measured NOx removal NOx concentration value can be further reduced. It becomes possible. The differentiator D3 acquires the generator output from the power generation facility 9, obtains a preceding signal calculated from the amount of change in the generator output, and outputs it to the adder A2.

  Although the embodiment of the present invention has been described above, in order to cause the control device 8 shown in FIG. 2 to function, a program executed by the CPU is recorded on a computer-readable recording medium, and the recorded program is stored in the computer. It is assumed that the control device 8 according to the embodiment of the present invention is realized by reading and executing. Note that the program may be provided to the computer via a network such as the Internet, or a semiconductor chip or the like in which the program is written may be incorporated in the computer.

  According to the embodiment of the present invention described above, the increasing tendency of the NOx concentration at the inlet of the flue gas denitration apparatus 3 can be quickly reflected on the ammonia injection amount. Further, the feedforward control set value obtained based on the measured value of the inlet NOx concentration can be reflected in the ammonia flow rate set value. Furthermore, by acquiring the change amount of the fuel flow rate and the burner combustion number as a preceding signal, the NOx amount and the change at the inlet of the flue gas denitration device 3 can be grasped in advance and reflected in the ammonia injection amount.

  According to the above, the NOx concentration at the outlet of the flue gas denitration apparatus 3 can be stabilized. According to this, it is possible to observe the environmental regulation value, reduce the environmental load by preventing the NOx concentration from rising, and reduce the amount of ammonia used by increasing the target value of the outlet NOx concentration.

  As mentioned above, although the form for implementing this invention was demonstrated, the said embodiment is for making an understanding of this invention easy, and is not for limiting and interpreting this invention. The present invention can be changed and improved without departing from the gist thereof, and equivalents thereof are also included in the present invention.

DESCRIPTION OF SYMBOLS 1 NOx processing equipment 2 Combustion device 3 Flue gas denitration device 4 Chimney 5 Ammonia injection device 6 Ammonia flow control valve 7 Flow rate measuring device G1, G2 Gas analyzer P1, P2 Smoke tube 8 Control device 81 Feed forward control unit 82 Feedback control unit 83 Target value setting unit 84 PID control unit A1, A2 Adder S1, S2 Subtractor D1, D2, D3 Differentiator

Claims (8)

A control device that corrects the amount of ammonia injected into a flue gas denitration device that reduces the NOx concentration of exhaust gas,
A first subtractor that obtains a target value and a measured value of the outlet NOx concentration of the flue gas denitrification device and calculates and outputs a NOx concentration deviation by subtracting the measured value from the target value of the NOx concentration; ,
A first differentiator that obtains a measured value of the inlet NOx concentration of the flue gas denitrification device, calculates a change amount of the inlet NOx concentration per unit time, and outputs the change;
The NOx concentration deviation output from the first subtractor is acquired, the change amount per unit time of the inlet NOx concentration output from the first differentiator is acquired, and the NOx concentration deviation and the inlet are acquired. A feedback control unit that outputs the larger one of the amount of change in NOx concentration per unit time as an ammonia flow rate set value;
By acquiring the ammonia flow rate measurement value injected into the flue gas denitration device, acquiring the ammonia flow rate setting value output from the feedback control unit, and subtracting the ammonia flow rate measurement value from the ammonia flow rate setting value A second subtractor that calculates an ammonia flow rate correction value and outputs the ammonia flow rate correction value to the ammonia flow rate control valve;
An ammonia injection amount correction control device comprising: The ammonia injection amount correction control device according to claim 1,
A second differentiator that obtains the burner combustion number in the combustion device, calculates a change amount per unit time of the burner combustion number, and outputs the change amount;
The second subtracter obtains the ammonia flow rate setting value obtained by adding the amount of change per unit time of the burner combustion number output from the second differentiator. apparatus. The ammonia injection amount correction control device according to claim 1 or 2,
A feedforward control unit that obtains a measured value of the inlet NOx concentration and a target value of the outlet NOx concentration, calculates an ammonia flow rate value that is a base ammonia injection amount based on the obtained values, and outputs the calculated value; ,
The second subtracter acquires the ammonia flow rate setting value obtained by adding the ammonia flow rate values output from the feedforward control unit. The ammonia injection amount correction control device according to claim 3,
The feedforward control unit obtains an ammonia molar ratio obtained by dividing a preset ammonia amount by the NOx amount based on a denitration rate target value obtained from the measured value of the inlet NOx concentration and the target value of the outlet NOx concentration. The predicted value of the inlet combustion gas amount of the flue gas denitrification device is calculated, and the ammonia flow rate value is calculated by multiplying the ammonia molar ratio, the measured value of the inlet NOx concentration, and the predicted value of the inlet combustion gas amount. An ammonia injection amount correction control device characterized by: A control method for correcting the amount of ammonia injected into a flue gas denitration device that reduces the NOx concentration of exhaust gas by a control device,
The controller is
Obtaining a target value and a measured value of the outlet NOx concentration of the flue gas denitration device, subtracting the measured value from the target value of the NOx concentration, and calculating and outputting a NOx concentration deviation;
Obtaining a measured value of the inlet NOx concentration of the flue gas denitrification device, calculating an amount of change per unit time of the inlet NOx concentration, and outputting;
The change amount per unit time of the output NOx concentration deviation and the inlet NOx concentration is acquired, and the larger one of the NOx concentration deviation and the change amount per unit time of the inlet NOx concentration is the ammonia flow rate setting value. Step to output as
Ammonia flow rate correction value is obtained by obtaining the ammonia flow rate measurement value injected into the flue gas denitration device, obtaining the output ammonia flow rate setting value, and subtracting the ammonia flow rate measurement value from the ammonia flow rate setting value. And a correction value calculating step for outputting to the ammonia flow control valve,
The ammonia injection amount correction control method is characterized in that: The ammonia injection amount correction control method according to claim 5,
The controller is
Obtaining the number of burner burns in the combustion device, calculating the amount of change per unit time of the burner burn number, and further executing the step of outputting,
In the correction value calculating step, the ammonia flow rate setting value obtained by adding the amount of change per unit time of the output burner combustion number is acquired. The ammonia injection amount correction control method according to claim 5 or 6,
The controller is
A measured value of the inlet NOx concentration and a target value of the outlet NOx concentration are acquired, and based on each acquired value , an ammonia flow rate value that is a base ammonia injection amount is calculated, and a feed forward control step for outputting is further executed. And
In the correction value calculating step, the ammonia flow rate setting value obtained by adding the output ammonia flow value is acquired. The ammonia injection amount correction control method according to claim 7,
In the feedforward control step, an ammonia molar ratio obtained by dividing a predetermined ammonia amount by the NOx amount is obtained based on a denitration rate target value obtained from the measured value of the inlet NOx concentration and the target value of the outlet NOx concentration. The predicted value of the inlet fuel gas amount of the flue gas denitrification device is calculated, and the ammonia flow rate value is calculated by multiplying the ammonia molar ratio, the measured value of the inlet NOx concentration, and the predicted value of the inlet fuel gas amount. An ammonia injection amount correction control method characterized by:

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