JPH0796132A - Method for controlling supply of ammonia in denitration system and its controller - Google Patents

Abstract

PURPOSE:To supply an appropriate amt. of NH3 in the denitration system in an incinerator. CONSTITUTION:A first memory 15 for storing the fuel flow rate versus NOx concn. in a table and a second memory 16 for storing the combustible supply versus NOx concn. in a table are provided to a control part 22. The NOx concn. of a waste gas generated when the combustibles are actually burned in the incinerator is obtained from the tables. Meanwhile, a dry gas amt. is obtained as a basis for calculating the fuel flow rate, supply of the material to be incinerated and combustion air. An appropriate flow rate of gaseous ammonia is obtained from the NOx concn. and dry gas amt. thus obtained, and the gaseous ammonia is supplied to a denitrator based on the obtained values.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling a supply amount of a reducing agent such as NH ₃ (ammonia) gas and ammonia water in a denitration system, and a control device therefor.

[0002]

2. Description of the Related Art Exhaust gas discharged from a combustion device generally contains harmful NOx. Therefore, this NOx
Denitration is carried out to remove NH ₃ is generally used for this denitration. In other words, NOx reacts with NH ₃ to decompose into nitrogen gas and water, and NOx
To make it harmless.

By the way, in the supply of NH ₃ ,
Control of the supply amount is extremely important. That is, NH
Processing of the NOx and the supply amount is small in the ₃ becomes insufficient, whereas when the supply amount of NH ₃ is too large, NH ₃ is discharged to the outside as it is. Of course, NH ₃ itself is also harmful. Further, NH ₃ reacts with SO ₃ to produce ammonium sulfate or acidic ammonium sulfate, and the ammonium sulfate or acidic ammonium sulfate adheres to the catalyst used in the denitration device to block or deteriorate the catalytic function, or equipment installed after the denitration device. There is also the problem of corrosion and blockage.

As a representative example of a control method or a control device of the NH ₃ supply amount in a denitration device, Japanese Patent Laid-Open No. 23425/1987.
Those disclosed in the publication can be mentioned. In the prior art shown here, the fuel flow rate is based on the data of each memory that stores the fuel flow rate vs. NOx concentration and the fuel flow rate vs. O ₂ concentration in a table format and the fuel flow rate actually used. The NOx concentration for the fuel gas is read from the memory and the NOx concentration is calculated by the calculating means, and the O ₂ concentration for the fuel flow rate is read from the memory and the dry gas amount is calculated by the dry gas amount calculating means. NH the NH ₃ supply amount from the amount and the NOx concentration ₃
The supply amount calculation means calculates the value.

This conventional control method calculates the amount of dry gas or exhaust gas based on the O ₂ concentration in the exhaust gas,
It is suitable for a denitrification device of a combustion device such as a boiler or a cogeneration facility in which the type of fuel is generally limited to one and the fuel composition is almost constant, in other words, a combustion device with a stable air-fuel ratio. There is. In the case of this control method, it is easy to obtain the reproducibility of the data that is the basis of table creation,
The table stored once does not need to be changed unless the combustion control amount such as the fuel type and the air ratio is changed.

However, in the case of an incinerator different from a boiler, a cogeneration facility, etc., the combusted materials are so-called incinerators (sludge, wood chips, food waste, waste oil, etc.) in addition to the fuel.
Waste liquid, dust, garbage, etc.), that is, the combustion products are multi-components, so it is impossible to calculate and estimate the dry gas amount simply by the relationship between the fuel flow rate and the O ₂ concentration. is there. Therefore, conventionally, an exhaust gas flow meter was installed at the entrance of the denitration device to obtain the exhaust gas, but the exhaust gas flow meter is generally difficult to obtain the accuracy of the measurement result, and therefore the calculation result of the NH ₃ supply amount is obtained. There was a problem in that there was a large error.

Further, in the conventional control method, a NOx concentration meter is also installed at the inlet and outlet of the denitration device, and in particular, the measured NOx concentration at the inlet side is fed back and used for calculation. In control,
Due to the time delay in the analysis of the NOx concentration meter, the change in the NOx concentration at the inlet of the denitration device could not follow the NH ₃ supply amount, and the outlet N
There is a problem that the variation in Ox concentration is large.

[0008]

Therefore, the technical problem to be solved by the present invention is to accurately determine the generated NO _x concentration and to continuously determine the combustion state such as the incineration amount and the air-fuel ratio like an incinerator. Even if it is difficult to accurately calculate the dry gas amount from the table data of the fuel flow rate vs. O ₂ concentration, it is possible to calculate the dry gas amount relatively accurately, and the generated NO _x concentration obtained above. Another object of the present invention is to provide a method and an apparatus for appropriately controlling the supply amount of NH ₃ based on the dry gas amount data.

[0009]

In order to solve the above technical problems, the present invention provides the following NH ₃ supply amount control method and its control device.

That is, this control method is used in a denitration system for purifying exhaust gas from an incinerator or the like by a denitration device,
Based on the used fuel flow rate data from the fuel flow meter and the table of the fuel flow rate versus the NOx concentration when the fuel is burned, the fuel N
In addition to calculating the Ox concentration, the incineration product NOx concentration is calculated from the incineration product supply amount data from the incinerator supply amount measuring device and the incineration product supply amount vs. NOx concentration table when the incineration product is burned, and the fuel NOx is calculated. Comprehensive NOx concentration calculation step to obtain total NOx concentration from concentration and incinerator NOx concentration, used fuel flow rate data from fuel flow meter, incinerator supply amount data from incinerator supply amount measuring device, and combustion air flow meter a dry gas quantity calculation step for obtaining a dry gas amount based on the air flow rate data, based on the total NOx concentration data and dry gas amount data, NH ₃ supply amount calculation for obtaining the NH ₃ supply amount to be supplied to the denitration unit It is characterized by including steps and.

Further, the control device for carrying out the above method is a denitration system for purifying exhaust gas from an incinerator or the like by a denitration device.
a first memory for storing the x concentration in a table format, a second memory for storing the incineration supply amount when burning the incinerator versus the NOx concentration in a table format, the fuel flow rate data used from the fuel flow meter, Fuel No. from 1 memory table
In addition to calculating the x concentration, the incineration product NOx concentration is calculated from the incineration product supply amount data from the incineration product supply amount measuring device and the table of the second memory, and the combustion NOx concentration and the incineration product NO.
Comprehensive NOx concentration calculation unit for obtaining total NOx concentration from x concentration, used fuel flow rate data from fuel flow meter, incinerator supply amount data from incinerator supply amount measuring device, and air flow rate from combustion air flow meter A dry gas amount calculation unit for obtaining a dry gas amount based on the data, and an NH ₃ flow rate set value calculation unit for obtaining an NH ₃ supply amount to be supplied to the denitration device based on the total NOx concentration data and the dry gas amount data. It is characterized by including.

In the above structure, when a plurality of types of fuel are used, the table for obtaining the fuel NOx concentration is
Made for each fuel. In addition, if there are various types of incinerated matter, in this case, a table for the incinerated matter NOx concentration is also created for each type.

As described above, the combustion in the incinerator becomes a multi-component combustion, and the combustion state, that is, the NOx generation concentration, fluctuates greatly. However, according to the present invention,
Since the total NOx concentration is calculated by separately obtaining the fuel NOx concentration and the incineration product NOx concentration, the NOx concentration when burning the incineration product can be accurately obtained.
Moreover, when calculating the dry gas amount, not only the data of the fuel used and the combustion air but also the data of the incinerator supply amount are taken into consideration, so the calculation of the dry gas amount is accurate. Become.

As described above, according to the control method and the control device of the present invention, the exhaust gas generated from the incinerator can be supplied with an accurate amount of N 2.
It becomes possible to perform denitration treatment with H ₃ without excess or deficiency.

In the above construction, in the case of incineration conditions in which the odor (gas) is also supplied to the incinerator when the incinerator is burned, the odor gas flow rate data from the odor gas flow meter is also included in the dry gas amount calculation step. It is preferable to use it as a basis for calculation in the dry gas amount calculation step. In general, there are many cases where incineration work is carried out in a factory, and in this case, it is preferable to process odors in the factory at the same time. In this case, the odors may be incinerated through an incinerator. In this case, of course, it is necessary to add the amount of the odorous gas as basic data for calculating the dry gas amount.

Further, the above-mentioned configuration further includes a correction calculation step, and in the correction calculation step, the NOx concentration of the exhaust gas at the outlet of the denitration device and the target N
It is preferable to obtain a correction value for correcting the calculation in the NH ₃ supply amount calculation step based on the Ox concentration at regular time intervals. By executing the correction calculation step in this manner, the NOx concentration remaining in the purified gas discharged from the denitration device can be made as close as possible to the target value. Then, in this correction calculation step, the correction value is not fed back to the NH ₃ flow rate setting value calculation unit one after another, but the correction value is calculated by sampling NOx data at the outlet of the denitration device at regular time intervals. Since the moving average value of the average NOx concentration is calculated at regular time intervals and the correction value is sent to the NH ₃ flow rate set value calculation unit, the NH ₃ supply amount depends on the combustion state of the incinerator. It can be controlled precisely.

Further, in the present invention, it is preferable that the temperature data at the outlet of the incinerator is also used as the basis for the calculation of the total NOx concentration calculation step. As described above, in the incinerator, the temperature inside the furnace changes drastically as the combustion state changes, and this temperature change has a great influence on the NOx concentration. Therefore, in the present invention, the NOx concentration can be accurately measured by measuring the outlet exhaust gas temperature of the incinerator and / or the temperature of each zone in the furnace and using the temperature data as the basic data for calculating the NOx concentration, and thus, it is appropriate. It is possible to supply a sufficient amount of NH ₃ to the denitration device.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A NH ₃ supply amount control method and apparatus according to an embodiment of the present invention will be described in detail below with reference to FIGS.

FIG. 1 is a diagram of a denitration system including an NH ₃ supply amount control device. As shown in FIG. 1, the fuel, the incineration product, the combustion air, and the odor are supplied to the incinerator 5 through the flowmeters or measuring devices 1, 2, 3, and 4, respectively. Here, the odor means odor gas generated in a factory or the like in addition to combustion air. In other words, this odorous gas is also incinerator 5 at the same time.
It is sent to and deodorized. The exhaust gas generated in the incinerator 5 is sent to the denitration device 7, where it is purified and then the chimney 9
Emitted from. A thermometer 6 is incorporated on the outlet side of the incinerator 5 to measure the temperature of exhaust gas from the incinerator 5. Further, an NOx analyzer 8 is incorporated at the outlet of the denitration device 7 to measure the NOx concentration in the purified gas.

On the other hand, NH ₃ passes through the flow meter 11 and passes through NH ₃
The flow rate is controlled by the control valve 12, and the denitration device 7 is supplied.

The data measured by the flowmeters or measuring devices 1, 2, 3, 4, 11 and the data measured by the thermometer 6 are input to the control unit 22. Further, the data measured by the thermometer 6 is also input to the control unit 22. On the other hand, the control signal from the controller 22 is sent to the NH ₃ regulating valve 12, the opening degree of NH ₃ control valve 12 is controlled by the signal.

FIG. 2 shows the NH ₃ controller described above.

The control unit 22 has a first memory 15 for storing the fuel flow rate vs. NOx concentration in a table format, and a second memory 16 for storing the incineration supply amount vs. NOx concentration in a table format. ing. The tables of the memories 15 and 16 are created in advance by collecting data during the trial run. The table creation method is as follows.

[0024] First, in the case of the memory 15, the fuel flow rate by changing several points to burn fuel, measuring the NOx concentration in the NOx analyzer 8 inlet NO _X analyzer or outlet to be installed at the time of commissioning of the denitration apparatus 7 By doing so, the characteristic of the fuel flow rate of the incinerator 5 versus the NOx concentration is obtained, and based on the characteristic, the table is input to the first memory 15 from the key input device 13 and created.

On the other hand, in the case of the table of the memory 16,
In a state where the fuel flow rate constant, and combustion by changing the supply amount of the particular material to be incinerated, to measure the NOx concentration at the inlet NO _X analyzer or the outlet of the NOx analyzer 8 to be installed at the time of commissioning of the denitration apparatus 7. Then, the characteristic of the NOx concentration obtained by the table of the fuel flow rate versus the NOx concentration is subtracted from the measured NOx concentration to calculate the supply amount of the combustion product itself versus the NOx concentration, and the table is stored in the second memory 16 from the key input device 13. Enter and create.

When the types of fuel used in the incinerator 5 and the incinerated substances to be incinerated are one or more, a table is created for each different fuel or incinerated substance.

The constants necessary for calculating the dry gas amount and the NH ₃ supply amount are calculated from the key input device 13 as initial settings, and the calculation constant unit 20 in the control unit 22 is used.
Enter and remember it.

The control unit 22 further includes the NOx concentration calculation unit 1.
7, NH ₃ flow rate set value calculation unit 18, dry gas amount calculation unit 1
9, a correction calculation unit 21 based on the outlet NOx concentration, a PID controller 23, and an NH ₃ control valve opening calculation unit 10 are provided. These will be described in more detail below.

The fuel flow rate F1 and the incinerated material supply amount F2 measured by the fuel flow meter 1 and the incinerated material supply amount measuring device 2, respectively, are sent to the NOx concentration calculation unit 17 of the control unit 22. Here, the NOx concentration for the fuel flow rate F1 and the NOx concentration for the incineration material supply amount F2 are stored in the memories 15 and 16, respectively.
Then, the NOx concentration calculator 17 appropriately calculates the actual NOx concentration by the interpolation method. And N
The Ox concentration calculator 17 sums the NOx concentration with respect to the actual fuel flow rate and the NOx concentration with respect to the actual incinerated substance supply amount.
(Sometimes the total is multiplied by the correction coefficient), and the total value is sent to the NH ₃ flow rate set value calculation unit 18.

Further, the NOx concentration calculator 17 receives temperature data measured by the thermometer 6 at the outlet of the incinerator 5, and corrects the NOx concentration when calculating the NOx concentration. This is because the NOx concentration exponentially increases as the furnace temperature increases.

The calculation in the dry gas amount calculation unit 19 is performed by the fuel flow meter 1, the incinerator supply amount measuring device 2, and the combustion air flow meter 3.
And calculated based on each data from the odorous gas flow meter 4. The dry gas amount calculation unit 19 has a table (not shown) showing the relationship between the fuel flow rate and the dry gas amount corresponding thereto. Then, regarding the calculation of the dry gas amount corresponding to the incinerated substance supply amount, the incinerated substance supply amount is converted into the fuel flow rate based on the heat generation amount of the fuel from the heat generation amount of the incinerated substance obtained in advance, and The data is input to the dry gas amount calculation unit 19 by the incinerator supply amount measuring device.

In the above method, the incineration supply amount is once converted into the fuel flow rate to obtain the dry gas amount. However, in order to obtain the dry gas amount more accurately, a table is prepared in advance. It is preferable to calculate the dry gas amount according to the table. That is, in this case, the fuel and the incineration product are burned experimentally, and a table of the relationship between the fuel flow rate and the generated steam amount and the relationship between the dry matter of the incineration product and the generated incineration steam amount is created in advance. Of. Then, from this table, the generated steam amount F5 with respect to the fuel flow rate and the generated steam amount F6 with respect to the supply amount of the incineration product are obtained, and the dry gas amount is obtained by the following equation.

The dry gas amount = (F3 + F4-F5- F6) Nm3 / H where, F3 combustion air flow, F4 odor flow then, NH ₃ flow rate set value the amount of NH ₃ necessary for the purification of combustion exhaust gas The calculation unit 18 calculates the value. This calculation is the above NO
The NOx concentration ([NOx] obtained by the x concentration calculation unit 17, the dry gas amount [Gd] obtained by the dry gas amount calculation unit 19, and the NH ₃ supply molar ratio K and constant stored in the calculation constant unit 20. α,
Based on β. The calculation formula in the NH ₃ flow rate set value calculation unit 18 is as follows.

NH ₃ = K × [NOx] × [Gd] × [α] + β However, normally, the value of K is around 1.0 and the value of β is 0. However, these constants can be appropriately changed and used depending on the types of the incinerator, the denitration device, the combustion product, and the like. The constants K and β used for each calculation are the key input device 13
Is input to the arithmetic constant unit 20 as an initial set value, and is read from the arithmetic constant unit 20 into the NH ₃ flow rate set value arithmetic unit 18.

NH ₃ calculated as described above
The supply amount is supplied to the PID controller 23. Actual flow rate data from the NH ₃ flow meter 11 is input to the PID controller 23. PID controller 2
A PID constant is input to and stored in the key 3 from the key input device 13. Therefore, in the PID controller 23, the PID control amount is calculated from the calculated value from the NH ₃ flow rate setting value calculation unit 18 and the PID constant. Then, according to the PID control amount calculated by the PID controller 23, the NH ₃ control valve opening calculation unit 10 calculates the opening of the NH ₃ control valve 13, and the opening of the control valve 12 is calculated based on the calculation result. Will be controlled.
In this way, the amount of NH ₃ calculated by the NH ₃ flow rate set value calculation unit 18 is supplied to the denitration device 7 to purify the exhaust gas.

The control method, the supply amount control method, and the basics of the apparatus have been described above. The apparatus is equipped with the above-described correction calculation unit 21, and is measured by the NOx analyzer 8 provided at the outlet of the denitration apparatus 7. NOx concentration is the target NOx
If it is different from the concentration, a correction value is calculated, and the correction value is sent to the NH ₃ flow rate set value calculation unit 18. Therefore, the NH ₃ flow rate set value calculation unit 18 performs the calculation in consideration of the correction data from the correction calculation unit 21. More specifically, the supply amount of NH ₃ is calculated by the NOx concentration calculation unit 17 when the kind of combustion product or the combustion state thereof changes.
The Ox concentration and the dry gas amount obtained by the dry gas amount calculation unit 19 are not necessarily theoretical values. Therefore, depending on the type of combusted material or the change in its combustion state, NO
The NH ₃ supply amount is corrected based on the analysis result of the x analyzer 8. The correction calculation unit 21 is NO
It is configured by an x-density average value calculation unit 21A and a table memory 21B. Based on the data from the NOx analyzer 8, the NOx concentration average value calculation unit 21A calculates N at a relatively long time interval of 5 seconds to 30 minutes, preferably about 10 to 20 minutes.
A moving average value of Ox concentration is obtained. On the other hand, the table memory 21B is obtained in advance and stores a table of the difference between the moving average value of NOx concentration and the target NOx concentration versus the corrected NH ₃ supply amount.

The NOx concentration contained in the exhaust gas discharged from the denitration device 7 is successively analyzed and calculated by the NOx analyzer 8, and the value is calculated by the NOx concentration average value calculation unit 21A of the correction calculation unit 21.
Sent to and stored in. Then, the arithmetic unit 2 calculates the moving average value of the NOx concentration at the sampling cycle of about 10 to 20 minutes.
It is calculated by 1. Then, the moving average value of the NOx concentration obtained above is compared with the target NOx concentration given as an initial setting value by the key input device 13. If there is a difference between them, the table memory 2
The corrected NH ₃ supply amount, that is, the correction value is read from 1B, and the corrected value is sent to the NH ₃ supply amount set value calculation unit 18. The calculation unit 18 performs calculation in consideration of the correction value.

[Brief description of drawings]

FIG. 1 is a diagram of a denitration system including an NH ₃ supply amount control device according to an embodiment of the present invention.

FIG. 2 is a block diagram of the NH ₃ supply amount control device.

[Explanation of symbols]

1 Fuel flow meter 2 Incinerator supply amount measuring device 3 Combustion air flow meter 4 Odor gas flow meter 5 Incinerator 6 Thermometer 7 Denitration device 8 NOx analyzer 9 Chimney 10 NH ₃
Control valve opening calculator 11 Flow meter 12 NH ₃
Control valve 13 Key input device 15,16
Table 17 NOx concentration calculator 18 NH ₃
Flow rate setting value calculation unit 19 Dry gas amount calculation unit 20 Calculation constant unit 21 Correction calculation unit 22 Control unit 23 PID controller

Claims (5)

[Claims] 1. A denitration device (7) for exhaust gas from an incinerator (5)
In the denitration system purifying by NOx, the fuel NOx concentration is calculated from the used fuel flow rate data from the fuel flow meter (1) and the fuel flow rate vs. NOx concentration table (15) when the fuel is burned, and the incineration material is supplied. The incineration product NOx concentration is calculated from the incineration product supply amount data from the amount measuring device (2) and the incineration product supply amount vs. NOx concentration table (16) when the incineration product is burned, and the fuel NOx concentration and the incineration product are calculated. Comprehensive NOx concentration calculation step for obtaining total NOx concentration from NOx concentration, used fuel flow rate data from fuel flow meter (1), incinerator supply amount data from incinerator supply amount measuring device (2), and combustion air flow rate Based on the dry gas amount calculation step for obtaining the dry gas amount based on the air flow rate data from the meter (3) and the total NOx concentration data and the dry gas amount data,
NH ₃ supply amount control method characterized by comprising the NH ₃ supply amount calculation step of determining a NH ₃ supply amount to be supplied to the denitration unit (7). 2. Under the incineration condition in which odorous gas is also supplied to the incinerator (7) at the time of burning the incinerator, the odorous gas flow meter is further added in the dry gas amount calculation step.
2. The NH ₃ supply control method according to claim 1, wherein the odorous gas flow rate data from (4) is also used as a basis for the calculation in the dry gas amount calculation step. 3. Further comprising a correction calculation step, wherein in the correction calculation step, based on the NOx concentration of the exhaust gas at the outlet of the denitration device (7) and the target NOx concentration,
NH ₃ supply amount control method according to claim 1, wherein the determining for each predetermined time interval correction value for correcting the calculation of the NH ₃ supply amount calculating step. 4. The NH ₃ supply according to claim 1, wherein the temperature of the exhaust gas at the outlet of the incinerator (5) and / or the temperature data of each zone in the furnace are also used as the basis for the calculation of the total NOx concentration calculation step. Quantity control method. 5. A denitration device (7) for exhaust gas from the incinerator (5)
In a denitrification system that purifies by NOx, first, the fuel flow rate vs. NOx concentration when fuel is burned is stored in a table format.
A memory (15); a second memory (16) for storing the incinerated substance supply amount vs. NOx concentration when burning the incinerated substance in a table format; and a used fuel flow rate data from the fuel flow meter (1); The fuel NOx concentration is calculated from the table of the memory (15), and the incinerated substance N is calculated from the incinerated substance supply amount data from the incinerator supply amount measuring device (2) and the table of the second memory (16).
Comprehensive NOx concentration calculation unit (17) that calculates the Ox concentration and obtains the total NOx concentration from the combustion NOx concentration and the incinerator NOx concentration
Based on the fuel flow rate data from the fuel flow meter (1), the incinerator supply rate data from the incinerator supply rate measuring device (2), and the air flow rate data from the combustion air flow rate meter (3). Based on the dry gas amount calculation unit (19) for obtaining the gas amount and the total NOx concentration data and the dry gas amount data,
NH _3, characterized in that it comprises NH ₃ flow rate set value calculator for obtaining the NH ₃ supply amount to be supplied to the denitration unit (7) and (18)
Supply control device.