JPH0365212B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to the use of harmful gas components such as SO _x and/or
By adding ammonia (hereinafter simply referred to as "NH ₃ ") to exhaust gas containing NO _x and irradiating it with radiation, these harmful components are fixed and recovered as by-products (ammonium sulfate, ammonium nitrate) with fertilizer value. This invention relates to a control device for adding NH ₃ in an irradiation exhaust gas treatment device.

[Prior art]

After adding NH ₃ in the amount necessary to remove harmful components to exhaust gas containing harmful components such as SO _x and /NO _x , the harmful components are converted into ammonium sulfate and/or ammonium nitrate by irradiation with radiation. Methods of recovery are known in the art. In this way the required amount of
NH ₃ is the NO _x concentration in the reactor inlet gas [NO _x ]
ppm, SO _x concentration [SO _x ] ppm and exhaust gas amount (Q
Nm ³ /h) by the following formula.

NH ₃ supply amount (NH ₃ ) = Q・(17.03/22.41)・10 ^-6 ([NO _x ] η _NOX +2 [SO _x ] η _SOx ) Kg/g…(1) Here, η _NOX is the denitrification rate (−), η _SO2 represents the desulfurization rate (−).

On the other hand, in recent years, in order to reduce the emission of harmful components of exhaust gas, pollution treatment equipment has been equipped with a desulfurization rate of 90% or more and a denitrification rate of over 90%.
Extremely strict values are required, with 80% or more leaked NH ₃ less than 10 ppm, and it is expected that this will become even more stringent in the future.

As an exhaust gas treatment method that supplies NH ₃ , there is a catalytic reduction method (hereinafter referred to as "SCR method") for NO _x treatment that has been put into practical use. In this method, the amount of NH ₃ to be supplied is determined from the amount of exhaust gas and the NO _x concentration.

[Problem that the invention seeks to solve]

However, the conventional radiation irradiation method described above
As shown in equation (1), the amount of NH ₃ supplied is also related to the SO _x concentration, and twice that amount is required. Therefore, the radiation irradiation method is characterized in that it is necessary to supply a considerably larger amount of NH ₃ than the above-mentioned SCR method.

Figure 4 shows a typical chart of SO _x and NO _x concentration fluctuations. The average SO _x concentration is 1500 ppm, and the average NO _x concentration is 300 ppm. Calculate the difference in the average NH ₃ supply concentration between this method and the SCR method in the case of Figure 4 (η _NOX : 80
%, _ηNOX : 90%. ) NH ₃ concentration supplied by the radiation irradiation method = 300 x 0.8 + 2 × 1500 × 0.9 = 2940ppm NH ₃ concentration supplied by the SR method 300 ) will also supply a lot of _NH3 .

Also, when comparing the fluctuation patterns of SO _x and NO _x according to Figure 4, the fluctuation of SO _x concentration (±100 ppm) is
The NH ₃ supply in the radiation irradiation method is completely different from that in the SCR method because it is considerably larger than that of NO _x (±20 ppm ₎ and in the case of the radiation irradiation method, it is necessary to supply twice as much NH ₃ as the SO x. It was found that SO _x concentration was the dominant factor.

The control accuracy of NH ₃ addition in the radiation irradiation method (when η _NOX : 80% and η _SOX : 90%) will be described in the case of Figure 4.

According to Figure 4, the minimum supply concentration of NH ₃ is 280×
0.8+2×1400×0.9=2744ppm, and the maximum supply concentration is 320×0.8+2×1600×0.9=3136ppm
becomes. Allowable leak _NH3 (unreacted ammonia)
If 10ppm, the range is 2744ppm to 316ppm.
It will supply NH ₃ with an accuracy of ±10ppm.
This means an accuracy of approximately 0.3 to 0.4% (10/3136, 10/2744), which is considerably smaller than the accuracy of a normal control system (1 to 2% of full scale), and reduces leakage _NH3 to 10ppm. It was very difficult to control the following.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a control device for NH ₃ addition in a radiation irradiation exhaust gas treatment device that can eliminate the above-mentioned problems and suppress leakage NH ₃ to an extremely low level. do.

[Means for solving problems]

In order to solve the above problems, the present invention aims to reduce NH ₃ in response to fluctuations in exhaust gas amount and changes in SO _x and _NO
After calculating the supply amount and supplying NH ₃ to the exhaust gas,
In an ammonia addition control device in a radiation irradiation exhaust gas treatment device that processes exhaust gas by irradiating radiation, at least two or more series of NH ₃ supply devices that supply NH ₃ to the exhaust gas are provided, and one of the plurality of series of NH ₃ supply devices The NH ₃ supply amount from at least one series of NH ₃ supply equipment is
The amount of ammonia supplied from the ammonia supply equipment of other series is controlled to a predetermined amount according to the minimum or maximum generation amount of _{SO x and/or NO x .}
The present invention is characterized in that a control means is provided for controlling according to the fluctuation amount of NO _x .

In addition, the _NH3 concentration in the treated exhaust gas is measured.
An NH ₃ concentration measuring device is provided, and the control means is configured to measure the NH _{3 concentration} .
It is characterized by comprising means for correcting the NH ₃ supply amount based on the output of the concentration measuring device.

The present invention is also characterized in that the by-product recovery means for recovering by-products obtained in the radiation irradiation exhaust gas treatment device is a dust collection device that combines an electrostatic precipitator and a vacuum filter.

[Effect]

By configuring the NH ₃ addition control device in the radiation irradiation exhaust gas treatment equipment as described above, information on the combustion state related to the amount of exhaust gas generation, SO _x and NO _x generation, or the flow rate of these exhaust gases, SO _x concentration and NO _x Multiple series of NH ₃ based on measured concentration information
For example _, some of the NH ₃ supply devices in the supply device are controlled to supply NHH ₃ in accordance with the minimum amount of SO _x and NO _x generated, and other NH ₃ supply devices are controlled to
Since it is possible to control the supply of NH ₃ in response to fluctuations in NO _x , leakage NH ₃ can be kept extremely low as will be detailed later.

In addition, the _NH3 concentration in the treated exhaust gas is measured.
An NH ₃ concentration measuring device is provided, and the control device is configured to measure the NH _{3 concentration} .
By modifying the NH ₃ supply amount according to the output of the concentration meter, further leakage can be prevented as detailed later.
NH ₃ can be kept extremely low.

In addition, by using a dust collection device that combines an electrostatic precipitator and a bag filter as a byproduct recovery device to recover byproducts obtained in the exhaust gas treatment device, the powder captured by the bag filter can be removed.
Since SO _x and ammonia are adsorbed and unreacted SO _x and NH ₃ are used as a medium to generate ammonium sulfate, leakage NH ₃ and unreacted SO _x can be particularly suppressed.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a diagram showing the system configuration of an NH ₃ addition control device in a radiation irradiation exhaust gas treatment device that is an embodiment of the present invention. In the figure, 1 is a boiler, 2 is a fly-ash collection machine, 3 is a chimney, 4 is a by-product dust collector, 5 is a reactor, 6 is a radiation irradiation device, 7 is a cooling tower, 8 is an air heater,
9 and 10 are valves, 11 is an NH ₃ generator, 12 is a blower, 13 is an exhaust fan, 14 is a blower, 15 is a by-product processing equipment, 17 is a control device equipped with a computing unit, and 8 is an exhaust gas flow meter , 19 is an SO _x analyzer, and 20 is an NO _x analyzer.

Exhaust gas from the boiler 1 is sent to the cooling tower 7 by the exhaust fan 13 through the fly ash collection and dust collector 2. The exhaust gas sent to the cooling tower 7 is sent to the reactor 5, which is cooled to the optimum temperature for the reaction. At this time, from the NH ₃ generator 11, the valve 9
An A-series NH ₃ supply device comprising: and valve 1
A predetermined amount of NH ₃ , which will be described in detail later, is supplied into the exhaust gas through a B-series NH ₃ supply device comprising 0 NH 3 . In the reactor 5, the exhaust gas mixed with NH ₃ is irradiated with radiation from the radiation beam generator 6a of the radiation irradiation device 6, and SO _x and NO _x are activated.
Reacts with NH ₃ to form ammonium sulfate particles and ammonium nitrate particles.

In the process of the exhaust gas containing ammonium sulfate particles and ammonium nitrate particles passing through the by-product dust collector 4, the ammonium sulfate particles and ammonium nitrate particles are collected by the by-product dust collector 4, and the ammonium sulfate particles and ammonium nitrate particles are removed. The exhaust gas is sent to the chimney 3 by the blower 14 and released into the atmosphere. A control device 17 equipped with a computing unit receives information on the exhaust gas amount, SO x concentration, and _{NO x} concentration from the exhaust gas flow meter 18 , SO _x analyzer 19 , and NO _x analyzer 20 and controls the valves 9 and 10 . Then, calculate the amount of NH ₃ to be supplied from the A-series and B-series NH ₃ supply devices as shown below and supply it to the exhaust gas.

A-series NH ₃ supply device, the SO _x concentration and NO _x concentration in the exhaust gas were calculated using the minimum (Min) concentrations of each of SO _x and NO _x determined in the fluctuation pattern shown in Figure 4. of _NH3 . That is, it is determined by the following formula (however, η _NOX : 80%, η _SOX : 90%).

(NH ₃ ) _A Q・(17.03/22.41)×10 ^-6 (0.8 [NO _x ] _Nio + 2×0.9 [SO _x ] _Mio ) Kg/h …(2) [NO _x ] _Mio : Minimum concentration of NO _x (ppm) [SO _x ] _Mio : Minimum concentration of SO _x (ppm) Q: Actual measured amount of exhaust gas (Nm ³ /h) B series NH ₃ supply device, using the actually measured SO _x concentration and NO _x concentration in the exhaust gas NH ₃ supply amount (NH ₃ ) calculated by the above formula (1)
NH ₃ amount (NH ₃ ) _B after subtracting the above (NH ₃ ) _A from
supply. In other words, the amount of NH ₃ supplied into the exhaust gas (NH ₃ ) is (NH ₃ ) = (NH ₃ ) _A + (NH ₃ ) _B Kg/h (3), and the required amount of NH ₃ is supplied. , SO _x , and NO _x concentrations can be controlled by the B series. To explain using the example in Figure 4, (NH ₃ ) _A = Q x (17.03/22.41) x 10 ^-6 x 2744Kg/h (NH ₃ ) _B = Q x (17.03/22.41) x 10 ^-6 x ( 0~392)Kg/
h, and the amount of NH ₃ (NH ₃ ) _B supplied from the B series is:
If the leak NH ₃ is 10 ppm, the minimum is 2.6%.
(10ppm/392ppm) accuracy control, extremely easy, inexpensive, and low leakage
It becomes possible to maintain NH ₃ and high removal rate.

Next, details of selection of the supply capacity of the A series and B series, which are NH ₃ supply devices, will be explained.

Based on boiler operation results, the fluctuation patterns of SO _x concentration and NO _x concentration can be roughly divided into two types.
In other words, there are large fluctuations and small fluctuations in the SO _x concentration and NO _x concentration, and FIG. 5 shows a chart that includes both of these fluctuations (the fluctuations shown in FIG. 4 are small fluctuations).
In FIG. 5, the large fluctuations in SO _x and NO _x concentrations are the fluctuations that occur when the type of fuel and the operational status of combustion conditions are changed, for example, by changing the type of coal.
The fluctuations shown in Figure 5 can be estimated in advance based on the fuel used, the actual fluctuation characteristics of the boiler planned to be used, _the planned operation pattern, etc. The capacity of the series is selected as follows based on this analogous SO _x and NO _x fluctuation pattern. The supply capacity of the A-series NH ₃ supply device is selected so as to satisfy the maximum and minimum quantities determined by the following equations (4), (5), (6), and (7).

Case1 = (17.03/22.44)×10 ^-6 Q _naX (η _NOX・MinNO _x +2η _SOX・MinSO _x ) …(4) Case2 = (17.03/22.41)×10 ^-6 Q _nax {η _NOX (MaxNO _x −ΔNO _x ) +2η _SOX (MaxSO _x −ΔSO _x )} (5) Case3 = (17.03/22.41)×10 ^-6 Q _nio (η _NOX・MinNO _x +2η _SOX・MinSO _x ) …(6) Case4 = (17.03/22.41 )×10 ^-6 Q _nio {η _NOX (MaxNO _x −ΔNO _x )＋2η _SOX (MaxSO _x −ΔSO _x } (7) However, ΔNO _x indicates a small variation in NO _x , and ΔSO _x indicates a small variation in SO _x .

On the other hand, the supply capacity of the B-series NH ₃ supply device is determined by the following formula.

Maximum = (17.03/22.41) × 10 ^-6 Q _nax (η _NOX・ΔNO _x +2η _SOX・ΔSO _x ) …(8) Minimum = (17.03/22.41)×10 ^-6 Q _nio (η _NOX・ΔNO _x +2η _SOX・ΔSO _x (9) It is desirable that the B-series NH ₃ supply device satisfies the above maximum and minimum and also satisfies the following formula.

Allowable leak NH ₃ concentration/ΔNO _x + _2ΔSO Allowable leakage NH ₃ can be controlled using the control device. Here, Qmax and Qmin are the maximum and minimum values of exhaust gas determined by the operating pattern, respectively.

In addition, ΔSO _x when the exhaust gas amount changes,
Although it is assumed here that ΔNO _x and ΔSO _x and ΔNO _x before and after the large fluctuation are substantially the same, it is of course necessary to take into account if they are different.

If a single set of both the A-series NH ₃ supply device and the B-series NH ₃ supply device cannot be used satisfactorily, for example, two sets of A-series NH ₃ supply devices (NO.A-1, NO.A- 2) Two sets of B-series NH ₃ supply equipment (NO.B-1, NO.B-2) can also be used. In that case, it is desirable to know from the amount of exhaust gas, for example, Qmax ~ 1/2 (Qmax +
Qmin) is NO.A-1, NO.B-1 NH ₃ supply device, and 1/2 (Qmax + Qmin) ~ Qmin is
It is conceivable to control it with the NH ₃ supply device of NO.A-2 and NO.B-2.

On the other hand, the time interval determination for determining the minimum values of NO _x and SO _x concentrations during operation is as follows.

Basically, within any set time (for example, 5 minutes,
10 minutes, 30 minutes, ₆₀ minutes) _is adopted. If the transition time of the fluctuation is short, the above-mentioned setting time is shortened.

FIG. 2 is a diagram showing a system configuration of an NH ₃ addition control device in a radiation irradiation exhaust gas treatment device according to another embodiment of the present invention. In the same figure, the first
Parts with the same reference numerals as those in the drawings indicate the same or equivalent parts (hereinafter, the same applies to other drawings). In the figure, 21 is fuel component information. In this embodiment, the information necessary for controlling the supply of NH ₃ is the amount of exhaust gas, the amount of NO _x generated, and the amount of SO _x generated as described above. These components are closely related to the amount of combustion air, the temperature inside the combustion furnace, the temperature at the outlet of the combustion furnace, and the component 21 of the fuel used, and if changes in these are known, fluctuations in the above three components can be estimated.

Figure 2 shows the actual measurement of exhaust gas flow rate and the actual flow rate of exhaust gas.
This is a device that predicts fluctuations in the exhaust gas flow rate, SO _x and NO _x concentrations in advance based on the information on the combustion furnace, without relying on measurements of SO _x and NO _x concentrations, and calculates and supplies the amount of NH ₃ in advance. In this case as well, the two series A and B
It has an NH ₃ supply device, and supplies the amount of (NH ₃ ) determined from the lowest values of SO _x and NO _x concentrations into the exhaust gas from the B-series NH ₃ supply device. Further, the A-series NH ₃ supply device supplies an amount (NH 3 ) obtained by subtracting (NH ₃ ) from the (NH ₃ ) amount calculated based on actual information from a combustion furnace or the _like .

FIG. 3 is a diagram showing a system configuration of a control device for adding NH ₃ in a radiation irradiation exhaust gas treatment device according to an embodiment of the present invention. In the figure, 22 is an NH ₃ analyzer 2 that measures the NH ₃ concentration in the treated exhaust gas.
It is 2.

The apparatus shown in Figure 3 is the same as the apparatus shown in Figure 2 with NH ₃ analyzer 2.
This is an example of a radiation irradiation exhaust gas treatment device that can stably maintain even lower leakage NH ₃ by combining feedback control that feeds back the NH ₃ concentration in the treated exhaust gas from 2. That is, the output of the control device 17 of the feedforward device is corrected based on the measured value of NH ₃ concentration in the treated exhaust gas.

It goes without saying that a combination of control based on the measured information shown in FIG. 1 and control based on the boiler information shown in FIG. 2 is also desirable.

As the byproduct dust collector 4 of the radiation irradiation exhaust gas treatment device, an electrostatic precipitator, a combination of mechanical filtration devices such as an electrostatic precipitator and a bag filter, a bag filter, etc. are used. In particular, in the case of a combination of an electrostatic precipitator and a bag filter or a bag filter, the powder captured by the bag filter adsorbs SO _x and ammonia, and these unreacted SO _x and NH ₃ are released into the powder as a medium. By generating _ammonium sulfate _as
It is suitable for cases where NH ₃ emission regulations are strict.

Note that the radiation used in the present invention includes electron beams, β rays, γ rays, α rays, x rays, neutron rays, and the like. In the embodiment, an electron beam from an electron beam generator is preferable.

〔Effect of the invention〕

As explained above, according to the present invention, the following excellent effects can be obtained.

At least two or more series of ammonia supply devices that supply ammonia to the exhaust gas are provided, and the amount of ammonia supplied from at least one series of the ammonia supply devices among the plurality of series of ammonia supply devices is set to the minimum of the SO _x and /NO _x or The amount of ammonia supplied from other systems of ammonia supply equipment is controlled to a predetermined amount according to the maximum generation amount, and the amount of ammonia supplied from the ammonia supply equipment of other series _is
A control means is provided to control according to the fluctuations in NO _x ,
Since the control means receives information on the combustion state related to the amount of exhaust gas generated or actual measurement information on the flow rate of these exhaust gases, SO _x concentration, and NO _x concentration, and controls the ammonia supply amount, leaking ammonia can be suppressed to an extremely low level.

In addition, by adjusting the ammonia supply amount depending on the NH ₃ concentration in the treated exhaust gas, leakage can be further reduced.
NH ₃ can be kept low.

In addition, leakage NH ₃ can be further suppressed by using a dust collection device that combines an electrostatic precipitator and a bag filter, or a bag filter alone as a by-product recovery device for recovering by-products.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the system configuration of an ammonia addition control device in a radiation irradiation exhaust gas treatment device which is an embodiment of the present invention, and FIG. 2 is a diagram showing the system configuration of an ammonia addition control device in a radiation irradiation exhaust gas treatment device which is another embodiment of the present invention. A diagram showing the system configuration of the control device,
Fig. 3 is a diagram showing the system configuration of the ammonia addition control device in the radiation irradiation exhaust gas treatment equipment which is an embodiment of the present invention, Fig. 4 is a fluctuation chart of SO _x and NO _x concentration, and Fig. 5 is an analogous SO This is a chart of fluctuations in _x and NO _x concentrations. In the figure, 1...Boiler, 2...Fly assemblage dust collector, 3...Chimney, 4...Chimney, 5...Reactor, 6...Radiation irradiation device, 7...Cooling tower, 8
... Air heater, 9 ... Valve, 10 ... Valve, 11 ... NH ₃ generator, 12 ... Blower,
13... Exhaust fan, 14... Blower, 15... By-product processing equipment, 17... Control device, 18... Exhaust gas flow meter, 19... SO _x analyzer, 20... NO _x analyzer.

Claims (1)

[Claims] 1. A means for guiding exhaust gas containing sulfur oxides (SO _x ) and/or nitrogen oxides (NO _x ) to a radiation irradiation area, and a means for introducing ammonia into the exhaust gas before or after radiation irradiation. An ammonia addition control device in a radiation irradiation exhaust gas treatment device, comprising a means for supplying NH ₃ and a means for collecting formed by-products (ammonium sulfate and/or ammonium nitrate) with a dust collector and then releasing the exhaust gas into the atmosphere. At least two or more lines of ammonia supply devices for supplying ammonia to the exhaust gas are provided, and the amount of ammonia supplied from at least one line of the ammonia supply devices among the plurality of lines of ammonia supply devices is adjusted to the amount of ammonia supplied from the ammonia supply device to the SO _x and/or NO. The amount of ammonia supplied from the ammonia supply equipment of other series is controlled to the specified amount according to the minimum or maximum generation amount of _x .
An ammonia addition control device in a radiation irradiation exhaust gas treatment device, characterized in that it is provided with a control means for controlling according to fluctuations in SO _x and/or NO _x . 2. The control means includes means for receiving actual measurement information from an exhaust gas flow rate measurement means, an SO _x concentration measurement means, and a NO _x concentration measurement means, and calculating an ammonia supply amount from the measurement information. Ammonia addition control device in the radiation irradiation exhaust gas treatment device according to scope 1. 3 The control means controls the amount of exhaust gas generated, SO _x and NO _x
The radiation irradiation exhaust gas treatment according to claim 1, further comprising means for receiving detection information from the information detection means on the combustion state related to the amount generated and calculating the amount of ammonia supplied from the detected information. Ammonia addition control device in the equipment. 4. An ammonia concentration measuring device for measuring the ammonia concentration in the treated exhaust gas is provided, and the control means includes means for correcting the ammonia supply amount based on the output of the ammonia concentration measuring device. An ammonia addition control device in the radiation irradiation exhaust gas treatment device according to item 1, item 2, or item 3. 5. Claims 1 or 2 or 3, or 5. Ammonia addition control device in the radiation irradiation exhaust gas treatment device according to item 4. 6. In the radiation irradiation exhaust gas treatment apparatus according to claim 1, 2, 3, 4, or 5, wherein the radiation is an electron beam from an electron beam generator. Ammonia addition control device.