JP5302618B2 - Nitrogen oxide treatment equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nitrogen oxide treatment apparatus having a high followability to the variation of the concentration of nitrogen oxides. <P>SOLUTION: The nitrogen oxide treatment apparatus treats nitrogen oxides by supplying ammonia, and includes a first measuring instrument 21 measuring the concentration of nitrogen oxides at an outlet side; a second measuring instrument 22 measuring the concentration of nitrogen oxides at the outlet side having a responsive speed faster than that of the first measuring implement 21; and a control device 9 controlling the amount of ammonia supply by setting a target value for controlling the concentration of nitrogen oxides based on the measurement by the first measuring instrument 21 and to make the measurement by the second measuring instrument 22 to be the target value. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a nitrogen oxide treatment apparatus for treating nitrogen oxide with ammonia.

Nitrogen oxides (NO _x ) in the exhaust gas not only directly affect the human body, but also cause acid rain, photochemical smog, and the like. Therefore concentration of NO _X variety in the exhaust gas is regulated, it is necessary to remove the nitrogen oxides in the exhaust gas in order to comply with this regulation.

  As a method for removing nitrogen oxides in the exhaust gas, for example, there is a method in which ammonia is supplied into the exhaust gas and this is reacted with nitrogen oxides in the exhaust gas on a catalyst to form harmless nitrogen and water. Specifically, exhaust gas is allowed to flow through the catalyst layer filled with the catalyst, and ammonia is sprayed and supplied from a plurality of ammonia supply nozzles installed on the upstream side of the catalyst layer to react ammonia and nitrogen oxides. As a result, nitrogen and water are produced and flow out downstream of the catalyst layer.

In determining the supply amount of ammonia in the above reaction, conventionally, a chemiluminescent NO _x concentration analyzer (hereinafter referred to as a chemiluminescent analyzer) is provided on the inlet side and outlet side of the catalyst layer, and the inlet side analysis is performed. The meter is used for advanced control, and the outlet side analyzer is used for feedback control (see, for example, Patent Document 1).
JP 2003-290630 A

However, when a chemiluminescence analyzer is used, the exhaust gas component is measured by sampling, which requires a long measurement time. Therefore, there is a problem that the followability with respect to the change in the NO _x concentration is poor and an appropriate amount of ammonia cannot be supplied.
In order to alleviate the above problems, various advanced controls are performed using the operating status of a boiler or the like as a nitrogen oxide emission source as a parameter. Therefore, there are many parameters that need to be adjusted, the control circuit of the nitrogen oxide processing apparatus becomes complicated, and there is a problem that it takes time for the adjustment.

On the other hand, zirconia-type NO _x concentration analyzers (hereinafter referred to as zirconia-type analyzers) have faster response speeds than chemiluminescence-type analyzers, and have excellent characteristics as NO _x concentration analyzers. Yes. However, the zirconia analyzer has a problem of detecting not only nitrogen oxides but also ammonia. Furthermore, while the chemiluminescence analyzer indicates the dry gas reference concentration, the zirconia analyzer measures the wet gas reference concentration, and therefore there is a problem that the measured values cannot be simply compared.

The present invention has been made to solve the above-described problem, and an object thereof is to provide a nitrogen oxide treatment apparatus having high followability to changes in the NO _x concentration.

In order to solve the above problems, the present invention employs the following means.
That is, the nitrogen oxide treatment device according to the present invention, by supplying ammonia, a nitrogen oxide processing apparatus for processing nitrogen oxide, to measure the concentration of nitrogen oxides at the outlet side, chemiluminescence A first measuring means that is an analyzer, and a second measuring means that is a zirconia analyzer that has a faster response speed than the first measuring means and measures the concentration of nitrogen oxides on the outlet side. Based on the measured value by the first measuring means, a target value for controlling the concentration of the nitrogen oxide is set, so that the measured value by the second measuring means becomes the target value. And a control means for controlling the supply amount.

  According to such a nitrogen oxide processing apparatus, the ammonia supply amount can be controlled by the response speed of the second measuring means, and the followability of the ammonia supply amount with respect to changes in the nitrogen oxide concentration can be improved. Is possible. Further, in the case of controlling only with the first measuring means, it is necessary to control with various parameters in order to compensate for the delay in response speed, but according to the nitrogen oxide treatment apparatus according to the present invention, these Since no parameter is required, control can be facilitated. Furthermore, since the target value of the second measuring means is set by the first measuring means, it is possible to ensure consistency with the case where control is performed only by the first measuring means.

Further, nitrogen oxide processing apparatus according to the present invention, the inlet mouth side, provided with a third measuring means for measuring a concentration of nitrogen oxides, the control means, the measured value by the third measuring means An upper limit setting unit for setting an upper limit value, and a comparison unit that compares the upper limit value with a measurement value obtained by the second measurement unit and outputs a smaller value as a comparison value; The ammonia supply amount is controlled so that the comparison value becomes the target value.

  According to such a nitrogen oxide processing apparatus, the ammonia supply amount can be controlled so as not to exceed the upper limit value determined based on the measurement value of the third measuring means. Thereby, even when the zirconia analyzer which is the second measuring means recognizes ammonia as nitrogen oxide, ammonia can be supplied based on the above-described upper limit value. Therefore, it is possible to prevent ammonia from being supplied more than necessary.

Further, nitrogen oxide processing apparatus according to the present invention, prior Symbol control means, the measurement value measured by one of the measuring means, characterized by comprising a correction unit for correcting the value of the other measurement methods.

  According to such a nitrogen oxide treatment apparatus, the first measuring means and the second measuring means are a combination of the first measuring means and the second measuring means in any of the dry measurement method and the wet measurement method. Can be controlled.

  Further, in the nitrogen oxide treatment apparatus according to the present invention, the control unit has a preceding control value setting unit that sets a preceding control value based on a measurement value by the third measuring unit, and the preceding control value The ammonia supply amount is controlled so that an added value obtained by adding the measured value by the second measuring means or the upper limit value becomes the target value.

  According to such a nitrogen oxide treatment apparatus, it is possible to compensate for the delay in control by the first measuring means by performing the preceding control using the third measuring means provided at the inlet, An appropriate amount of ammonia can be supplied.

According to the nitrogen oxide processing apparatus of the present invention, the ammonia supply amount can be controlled by the response speed of the second measuring means while ensuring the reliability of the control by the first measuring means and the third measuring means. It is possible to improve the followability to the change in the NO _x concentration.

Hereinafter, an embodiment of a nitrogen oxide treatment apparatus according to the present invention will be described with reference to the drawings. The nitrogen oxide treatment apparatus according to the present embodiment is an apparatus that supplies ammonia into exhaust gas and reacts with nitrogen oxide in the exhaust gas using a catalyst to form harmless nitrogen and water, upstream of the catalyst and the concentration of NO _X downstream measures and adjusts the ammonia supply amount based on these measurements.
FIG. 1 shows a schematic configuration diagram of a nitrogen oxide treatment system to which the nitrogen oxide treatment according to the present embodiment is applied.
As shown in FIG. 1, the nitrogen oxide treatment system 8 is installed, for example, on the downstream side of the boiler 2 that is a nitrogen oxide generation source. A flue 3 through which exhaust gas flows is connected to the boiler 2. On the downstream side of the boiler 2, the nitrogen oxide treatment device 1, the air preheater 10 for exchanging the heat of the exhaust gas, the dust collector 11 for removing the dust in the exhaust gas, and the exhaust gas in the order in which the exhaust gas flows. And a chimney 12 that emits.

The nitrogen oxide treatment apparatus 1 includes a catalyst layer 4 filled with a catalyst that promotes a reaction between ammonia and nitrogen oxide, a first measuring instrument 21 (first measuring means), and a second measuring instrument 22 ( A second measuring means), a third measuring instrument 23 (third measuring means), an ammonia supply device 6 for supplying ammonia (ammonia supply amount adjusting means), an ammonia supply nozzle 5 for spraying ammonia, A control unit 9 (control means) for controlling the ammonia supply device 6 by determining the ammonia supply amount based on the indicated values of the first measurement device 21, the second measurement device 22 and the third measurement device 23; ing.
A plurality of ammonia supply nozzles 5 connected to the ammonia supply device 6 and a third measuring instrument 23 arranged on the upstream side of the ammonia supply nozzle 5 are arranged on the upstream side of the catalyst layer 4.
Further, on the downstream side of the catalyst layer 4, a first measuring instrument 21 and a second measuring instrument 22 having a response speed faster than that of the first measuring instrument 21 are arranged. In the present embodiment, for example, a chemiluminescence analyzer is used as the first measuring instrument 21, and a zirconia analyzer is used as the second measuring instrument 22 and the third measuring instrument 23.

FIG. 2 shows a functional block diagram of the control unit 9 of the nitrogen oxide treatment apparatus 1. Hereinafter, the control unit 9 will be described with reference to FIG.
The control unit 9 includes a preceding control value setting unit 35 that sets a preceding control value based on the NO _X concentration D3 measured by the third measuring instrument 23, and the NO _X concentration D3 measured by the third measuring instrument 23. Is input, and the upper limit setting unit 34 for setting the upper limit based on the NOx concentration D3, the aforementioned upper limit and the NO _X concentration D2 measured by the second measuring instrument 22, are input, and these are compared. Then, the comparison unit 33 that outputs the smaller value, the NO _x concentration D1 measured by the first measuring instrument 21, and the target value setting unit 31 that sets the target value based on the NOx concentration D1; The preceding control value is input from the preceding control value setting unit 35, the comparison value is input from the comparison unit 33, and the target value is input from the target value setting unit 31, so that the sum of the preceding control value and the comparison value becomes the target value. Set the ammonia supply amount command value to It has and a decree value setting unit 32.

Next, the effect | action of the nitrogen oxide processing apparatus which concerns on this embodiment is demonstrated using FIG. 1 and FIG.
In FIG. 1, the NOx concentration of the exhaust gas output from the boiler 2 is measured by a third measuring instrument 23 and given to the control unit 9. Further, the exhaust gas after the NOx concentration is adjusted by being mixed with ammonia in the catalyst layer 4 is measured by the first measuring instrument 21 and the second measuring instrument 22, respectively, and is supplied to the controller 9. .
In the control unit 9, the NO _X concentration D <b> 3 measured by the third measuring instrument 23 is output to the preceding control value setting unit 35 and the upper limit value setting unit 34, respectively. In the preceding control value setting unit 35, the preceding control value is set based on the NO _x concentration D3 and is output to the command value setting unit 32. In the upper limit setting unit 34, an upper limit is set based on the NO _x concentration D3 and is output to the comparison unit 33. The comparison unit 33 compares the upper limit value from the upper limit value setting unit 34 with the NO _x concentration D2 measured by the second measuring device 22, and the smaller value is compared to the command value setting unit 32 as a comparison value. Is output. On the other hand, in the target value setting unit 31, a target value is set based on the NO _x concentration D < _b > 1 measured by the first measuring instrument 21, and this target value is output to the command value setting unit 32.
In the command value setting unit 32, the sum of the preceding control value output from the preceding control value setting unit 35 and the comparison value output from the comparison unit 33 becomes the target value output from the target value setting unit 31. A command value for the ammonia supply amount is set, and this command value is output to the ammonia supply device 6. In the ammonia supply device 6, the ammonia supply amount is adjusted based on the command value, and an amount of ammonia corresponding to the command value is sprayed from the ammonia supply nozzle 5 (see FIG. 1).

Next, specific control blocks for realizing the various functions of the control unit 9 will be described with reference to FIG. FIG. 3 shows an example of a block diagram of the control unit shown in FIG.
In FIG. 3, the preceding control value preceding unit 35 multiplies the NO _x concentration D3 by the exhaust gas flow rate measured by the exhaust gas flow meter, thereby calculating the NOx flow rate, and the NOx flow rate from the multiplication unit 41. And a multiplying unit 43 that calculates a preceding control value by multiplying by a preset denitration rate. The preceding control value calculated by the multiplication unit 43 is output to the addition unit 57 of the command value setting unit 32 described later.
The upper limit setting unit 34 divides the NO _x flow rate obtained by the multiplication unit 41 and the ammonia flow rate to divide the expected denitration rate, and the expected denitration rate obtained by the division unit 42. a subtracting unit 44 for subtracting from 1, by multiplying the values and NO _X concentrations D3 determined from the subtraction unit 44 and the multiplication unit 45 for calculating the concentration of NO _X surplus, the third to the value determined from the multiplication section 45 And an adding unit 46 for adding the upper limit value of the error of the measuring instrument 23. In the upper limit setting unit 34 configured as described above, the upper limit value of the NO _X concentration to be denitrated is set by adding the upper limit value of the error in the adding unit 46 to the value determined in the multiplying unit 45, and a comparison described later. Is output to the unit 33.
The comparator 33 compares the magnitude of the upper limit value and the NO _X concentration D2 outputted from the addition unit 46, and outputs to subtraction unit 55 of the command value setting unit 32 to be described later smaller value as the comparison value.
The target value setting unit 31 subtracts a predetermined outlet NO _X set value from the NO _X concentration D1, a PI control unit 52, and a measured value obtained by the first measuring instrument 21 as a second measuring instrument. And a correction unit 53 that corrects the value to 22 measurement methods. In the correction unit 53, for example, the correction value is determined by the sum of the generator output, the fuel flow rate, and the constant. In the target value setting unit 31 having the above-described configuration, the value determined by the subtraction unit 51 is processed by the PI control unit 52 and the correction unit 53, thereby being consistent with the measurement value of the second measuring instrument 22, and , it is set a target value of the NO _X concentration to denitration, and output to subtraction unit 55 of the command value setting unit 32 that the target value will be described later.
The command value setting unit 32 sets the command value of the ammonia supply amount so that the sum of the preceding control value and the comparison value becomes the target value, and the command value is output to the ammonia flow control valve 61. The The command value setting unit 32 includes a subtraction unit 55 that subtracts the comparison value output from the comparison unit 33 from the target value output from the correction unit 53, a PI control unit 56, and a preceding control value output from the multiplication unit 43. And a value output from the PI control unit 56, a subtraction unit 58 that subtracts the value output from the addition unit 57 and the ammonia flow rate value, and a PI control unit 59. . In the command value setting unit 32 having the above configuration, the opening command value of the ammonia flow control valve 61 is set and output to the ammonia flow control valve 61.

According to the nitrogen oxide treatment apparatus 1 according to the present embodiment, the ammonia supply amount can be controlled by the response speed of the second measuring instrument 22, and the followability of the ammonia supply amount with respect to changes in the NO _x concentration is improved. It is possible to make it. Moreover, when controlling only with the 1st measuring device 21, although it is necessary to control by various parameters in order to compensate for the delay of a response speed, according to the nitrogen oxide processing apparatus 1 which concerns on this embodiment. Since these parameters are unnecessary, control can be facilitated. Furthermore, since the target value of the second measuring instrument 22 is set by the first measuring instrument 21, it is possible to ensure consistency with the case where the control is performed only by the first measuring instrument 21.
Further, the ammonia supply amount can be controlled so as not to exceed the upper limit value determined based on the measurement value of the third measuring instrument 23. Thereby, even when the 2nd measuring instrument 22 which is a zirconia type analyzer recognizes ammonia as nitrogen oxide, it can supply ammonia based on the above-mentioned upper limit. Therefore, it is possible to prevent ammonia from being supplied more than necessary.
Further, by performing the preceding control using the third measuring instrument 23 provided at the inlet of the catalyst layer 4, the control delay by the first measuring instrument 21 can be compensated, and a more appropriate amount can be compensated. Ammonia can be supplied.
Furthermore, the control unit 9 includes a correction unit 53 that corrects the measurement value obtained by the first measurement device 21 to the value of the measurement method of the second measurement device 22, whereby the first measurement device 21 and the second measurement device 21. The measuring instrument 22 can be controlled by combining the first measuring instrument 21 and the second measuring instrument 22 in any of the dry measurement method and the wet measurement method. The same operation and effect can be obtained even when the correction unit 53 corrects the measurement value obtained by the second measuring instrument 22 to the value of the measurement method of the first measuring instrument 21.

By performing the control as described above, the ammonia supply amount can be controlled based on the measured values of the first measuring instrument 21, the second measuring instrument 22, and the third measuring instrument 23, and the reliability is improved. It is possible to improve the followability to the change in the NO _x concentration while ensuring.

1 is a schematic configuration diagram of a nitrogen oxide processing apparatus shown as an embodiment of the present invention. It is a functional block diagram of the nitrogen oxide processing apparatus shown in FIG. It is a block diagram of the control part shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nitrogen oxide processing apparatus 6 Ammonia supply apparatus 9 Control part 21 1st measuring instrument 22 2nd measuring instrument 23 3rd measuring instrument 31 Target value setting part 32 Command value setting part 33 Comparison part 34 Upper limit setting part 35 Prior control value setting unit 53 Correction unit

Claims (4)

A nitrogen oxide treatment apparatus for treating nitrogen oxides by supplying ammonia,
A first measuring means that is a chemiluminescent analyzer for measuring the concentration of nitrogen oxides on the outlet side;
A second measuring means which is a zirconia type analyzer which has a faster response speed than the first measuring means and measures the concentration of nitrogen oxide on the outlet side;
Based on the measured value by the first measuring means, a target value for controlling the concentration of the nitrogen oxide is set, and the ammonia supply is performed so that the measured value by the second measuring means becomes the target value. And a nitrogen oxide treatment apparatus comprising a control means for controlling the amount. The inlet port side, comprises a third measuring means for measuring a concentration of nitrogen oxides,
The control means is
An upper limit setting unit for setting an upper limit based on a measurement value obtained by the third measurement unit;
A comparison unit that compares the upper limit value with the measurement value obtained by the second measurement means and outputs the smaller value as a comparison value;
The nitrogen oxide treatment apparatus according to claim 1, wherein an ammonia supply amount is controlled so that the comparison value becomes the target value. Before SL control means, one of the measurement value measured by the measuring means, nitrogen oxide treatment apparatus according to claim 1 or 2 comprising a correcting unit for correcting the value of the other measurement methods. The control means has a preceding control value setting unit for setting a preceding control value based on a measured value by the third measuring means,
4. The ammonia supply amount is controlled such that an added value obtained by adding the preceding control value and the measured value by the second measuring means or the upper limit value becomes the target value. 5. Nitrogen oxide treatment equipment.

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