JPH11235516A - Denitrification device for exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep te concentration of nitrogen oxides to not more than an environmental regulation value and also minimize the amount of ammonia used for denitrification and the amount of ammonia leakage discharged to the outside. SOLUTION: This nitrification device is provided with a first ammonia injection control means 31 wherein the concentration of NOx is measured on the upstream side from an ammonia injection position I1 of an outlet flue of a pressurized fluidized bed boiler 1 and based on a control signal c0 by the measured NOx concentration, the injected amount of ammonia to the outlet flue of the pressurized fluidized boiler 1 is controlled and a second ammonia injection means 32 wherein NOx concentration and ammonia concentration are measured on the upstream side from an ammonia injection position I2 of an inlet flue of a catalytic denitrification device 11 and from the measured measurement signals i2 , i3 , the injected amount of ammonia to the inlet flue of the catalytic denitrification device 11 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to nitrogen oxides (hereinafter also referred to as "NOx") by injecting ammonia (hereinafter referred to as "NH ₃ ") into exhaust gas generated by burning fuel.
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas denitration apparatus for removing gas, and more particularly to an exhaust gas denitration apparatus for removing nitrogen oxides of exhaust gas generated from a pressurized fluidized bed boiler (PFBC boiler).

[0002]

2. Description of the Related Art In recent years, emission control of environmental pollutants has become stricter as a global environmental problem. Research and development has been conducted on thermal power generation, which generates electricity by burning fossil fuels, to improve environmental performance and power generation efficiency. Among them, a power generation apparatus using a pressurized fluidized-bed boiler, in which a boiler is placed in a pressure vessel and burns coal by pressurization to generate power, is currently attracting attention.

[0003] A power generating apparatus using a pressurized fluidized bed boiler is
Combined power generation using a gas turbine (hereinafter referred to as “GT”) and a steam turbine improves power generation efficiency, and desulfurization is performed by performing in-furnace desulfurization using limestone that forms a fluidized bed. This has the advantage of reducing the NOx concentration at the outlet of the fluidized bed by a reduction reaction with a reducing substance such as carbon in the fluidized bed.

However, in conventional exhaust gas denitration technology, NOx in gas turbine exhaust gas is reduced by denitration using only a catalyst.
Since the concentration was reduced, there was an upper limit to the denitration efficiency in terms of the performance of the denitration device, and no further improvement in the denitration performance was possible.

FIG. 10 is a system diagram showing an example of a conventional exhaust gas denitration apparatus used in a power generation apparatus utilizing a pressurized fluidized bed boiler. The combustion air 5 introduced into the compressor 6 is introduced into the pressurized fluidized-bed boiler 1 in the pressure vessel 3 through the furnace inlet pipe 4. Fuel (CWP (Coal Water P
Exhaust gas generated by burning fuel supplied to the fluidized medium (BM) 2 forming a fluidized bed via the supply nozzle 23 is introduced into the gas turbine 8 through the furnace outlet pipe 7 to generate power. At the same time, the compressor 6 is driven. Exhaust gas leaving the gas turbine 8 is introduced into the economizer 10 through the gas turbine outlet duct 9, but since the exhaust gas temperature is as high as about 400 ° C., heat is recovered by the economizer 10 and the smoke outlet Chimney 29 passing through duct 12
More released.

[0006] Among the power generators using the pressurized fluidized-bed boiler, the only device for reducing and removing NOx is a catalytic denitration device 11 having a denitration catalyst provided in a economizer 10. NOx with catalyst provided at the inlet of catalytic NOx removal device 11
The amount of ammonia required for a catalyst is calculated by the x-concentration measuring device 22a, and the flow rate of ammonia sent from the ammonia vaporizer 15 is adjusted by a catalyst-equipped ammonia flow control valve 19, and ammonia-diluted air 14 is added to the catalyst-ammonia injection nozzle. 13 is injected. Catalytic denitration equipment 11
When the inlet NOx concentration is higher than the planned value, it is necessary to inject ammonia excessively, the amount of leaked ammonia at the outlet of the catalytic denitration device 11 (hereinafter also referred to as “leakage ammonia”) increases, and the ammonia is discharged from the chimney 29. However, on the other hand, the NOx concentration discharged from the chimney 29 is thereby reduced.

FIG. 11 is a system diagram showing an example of another conventional exhaust gas denitration device used in a boiler combustion device. This boiler combustion device has a non-catalytic denitration means 41 provided on the outlet side of the combustion chamber 40, and a catalytic denitration means 43 provided in a flue 42 downstream of the non-catalyst denitration means 41. The heat is exchanged between the exhaust gas and the air in the exchanger 44 (Japanese Utility Model Application Laid-Open No. 53-163347).

FIG. 12 is a system diagram showing an example of another conventional exhaust gas denitration apparatus used in a power generation apparatus utilizing a pressurized fluidized-bed boiler. This exhaust gas denitration system uses GT
55 Ammonia injection 57 at the inlet of the catalytic denitration device 58 according to the NOx concentration 56 at the inlet of the catalytic denitration device 58 downstream
And ammonia injection 52, 54 for non-catalytic denitration with respect to exhaust gas generated in a furnace 51 in a pressurized container 50. Reference numeral 53 indicates a dust removing device, and reference numeral 5
Reference numeral 9 denotes a low-pressure water heater, reference numeral 60 denotes a high-pressure water heater, and reference numeral 61 denotes a chimney. (Tokuhei Hei 5-504290)

[0009]

The exhaust gas denitration apparatus shown in FIG. 10 uses a catalytic denitration apparatus 11 to remove NO from exhaust gas.
The x concentration is reduced and discharged from the chimney as lower than the environmental regulation value.However, it is not possible to obtain the upper limit value of the denitration efficiency, the leaked ammonia becomes excessive, and further improvement of the denitration efficiency is not possible. It was difficult.

The exhaust gas denitration apparatus shown in FIG. 11 performs non-catalytic denitration by thermal reduction in a high-temperature thermal reduction atmosphere and performs catalytic denitration in a low temperature range. For this purpose, there is no means for optimally controlling the amount of ammonia injected into each part. When this prior art is applied to a pressurized fluidized bed boiler, the high-temperature thermal reduction atmosphere region corresponds to the upstream side of the gas turbine 8 shown in FIG. Due to the high pressure conditions in addition to the high temperature conditions, the oxygen partial pressure in the exhaust gas is about 10 times that of the boiler combustion device shown in FIG. 11, so that the ammonia injected into this region is decomposed into nitrogen and water vapor by oxygen. The resulting ammonia becomes remarkable, and the injected ammonia is not sufficiently effectively used for the denitration reaction. Further, in the pressurized fluidized-bed boiler, since the exhaust gas pressure decreases from 10 atm to about 5 atm at partial load, the decomposition reaction of the injected ammonia is also greatly affected by the operating pressure.

Further, the exhaust gas denitration apparatus used in the boiler combustion apparatus has an economical effect of minimizing the amount of injected ammonia in a pressurized fluidized-bed boiler in which the effective use efficiency of injected ammonia is greatly affected by the operating load. Control cannot be implemented.

The exhaust gas denitration apparatus shown in FIG. 12 can improve the denitration efficiency up to the chimney inlet by a combination of non-catalytic denitration and catalytic denitration. The NOx concentration 56 at the inlet of the catalyst denitration device 58 is determined to be a set value, and the amount of ammonia injected at the inlet of the catalyst denitration device 58 is determined according to the NOx concentration 56 at the catalyst denitration device. No particular consideration was given to the concentration, i.e., the distribution of ammonia injection that minimizes the leaked ammonia.

An object of the present invention is to solve the above problems, maintain the concentration of nitrogen oxides discharged to the outside below environmental regulation values, and determine the amount of ammonia used for denitration of exhaust gas and leakage to the outside. The goal is to minimize the amount of ammonia.

[0014]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a reduced treatment exhaust gas in which ammonia is injected into combustion exhaust gas generated by burning fuel to reduce nitrogen oxides in the combustion exhaust gas. Further, in an exhaust gas denitration apparatus for injecting ammonia into the reduced treatment exhaust gas and removing nitrogen oxides in the reduced treatment exhaust gas based on the presence of a catalyst, the flue gas exhaust gas is disposed upstream of an injection position for injecting ammonia into the combustion exhaust gas. A first ammonia injection control means for measuring the nitrogen oxide concentration and controlling the amount of ammonia injected into the combustion exhaust gas based on a control signal based on the measured nitrogen oxide concentration.

By providing the first ammonia injection control means, NOx in the combustion exhaust gas generated by the pressurized fluidized bed boiler for burning fuel, for example, CWP, is supplied to the ammonia injected by the first ammonia injection control means. Causes a gas phase reduction reaction to be decomposed into nitrogen and water and reduced. At this time, the nitrogen oxide concentration in the combustion exhaust gas to be reduced is measured, and the amount of ammonia to be injected is determined based on the control signal calculated from the measurement signal. Absent.

Further, in the above-mentioned exhaust gas denitration apparatus, the nitrogen oxide concentration and the ammonia concentration of the reduced treatment exhaust gas are measured at a position upstream of the injection position for injecting the ammonia into the reduced treatment exhaust gas. And a second ammonia injection control means for controlling an ammonia injection amount to be injected into the reduced exhaust gas based on a control signal calculated from a measurement signal of the ammonia concentration.

The exhaust gas denitration apparatus provided with the second ammonia injection control means has the function of the above-mentioned exhaust gas denitration apparatus, and has a reduced N gas concentration by the first ammonia injection control means.
Ox is further removed by the second ammonia injection control means to improve the denitration performance of the fluidized bed boiler as a whole.
Here, the first ammonia injection control means is used in a non-catalytic denitration reaction or a gas phase reduction reaction, and the second ammonia injection control means is used in a catalytic denitration reaction.

Further, in the exhaust gas denitration apparatus provided with the second ammonia injection control means, the second ammonia injection control means measures the nitrogen oxide concentration of the exhaust gas passing through the catalyst and passes through the catalyst. The measured nitrogen oxide concentration measurement signal is used to correct the control signal calculated from the measured nitrogen oxide concentration and ammonia concentration measurement signals of the reduced treatment exhaust gas to control the amount of ammonia injected into the reduced treatment exhaust gas. It is to be.

The exhaust gas denitration apparatus in which the second ammonia injection control means corrects the control signal calculated from the nitrogen oxide concentration and ammonia concentration measurement signals and controls the amount of ammonia injected into the reduced treatment exhaust gas, In addition to the function of the exhaust gas denitration device provided with the second ammonia injection control means, a NOx concentration measuring device is installed at the exhaust gas stack or the chimney inlet of the catalyst denitration device, and the NOx concentration value at the catalyst denitration device outlet is higher than the regulation value. If a difference exceeding a certain deviation occurs
In accordance with the deviation width, by supplementarily controlling the ammonia injection amount at the catalytic denitration device inlet or the fluidized bed boiler outlet,
It is possible to improve responsiveness.

Further, in any one of the exhaust gas denitration apparatuses provided with the second ammonia injection control means, the second ammonia injection control means measures the ammonia concentration of the catalyst passing exhaust gas passing through the catalyst, The measured ammonia concentration measurement signal is used to correct a control signal calculated from the measured nitrogen oxide concentration and ammonia concentration measurement signal of the reduced treatment exhaust gas to control the amount of ammonia injected into the reduced treatment exhaust gas. That is.

An exhaust gas denitration apparatus in which second ammonia injection control means corrects a control signal calculated from the measurement signals of the nitrogen oxide concentration and the ammonia concentration to control the amount of ammonia injected into the reduced exhaust gas, In addition to the operation of any one of the exhaust gas denitration devices provided with the second ammonia injection control means, an ammonia concentration measurement device is installed at a catalyst denitration device outlet flue or chimney inlet to reduce the residual ammonia concentration at the catalyst denitration device outlet. Auxiliary control of the amount of leaked ammonia by auxiliary control of the amount of ammonia injected at the catalytic denitration device inlet or fluidized bed boiler outlet according to the deviation from the measured value so as to be below a certain value Can be done.

Further, in the exhaust gas denitration apparatus provided with the first ammonia injection control means, the nitrogen oxide concentration of the exhaust gas having passed through the catalyst is measured, and a measurement signal of the measured nitrogen oxide concentration is obtained. Based on the control signal calculated from the injection of ammonia into the reduced treatment exhaust gas,
A third ammonia injection control means for controlling the nitrogen oxide concentration of the exhaust gas passing through the catalyst to fall within a preset concentration range is provided.

The exhaust gas denitration apparatus provided with the third ammonia injection control means has the function of the exhaust gas denitration apparatus provided with the first ammonia injection control means, and the NOx concentration at the outlet of the catalyst denitration apparatus is not more than the regulation value. Indicates that the amount of ammonia is in excess, and indicates that the amount of outflow of ammonia has increased. Conversely, the fact that the NOx concentration at the outlet of the catalytic denitrification device becomes equal to or higher than the regulation value indicates that ammonia is consumed in the denitration reaction and the emission amount is decreasing, while the NOx flowing out of the system is increasing. Therefore, NOx measured at the outlet of the catalytic NOx removal device or at the downstream duct
By controlling the amount of ammonia injected into the catalyst denitration device inlet or the upstream duct so that the concentration can be maintained within the range between the upper limit and the lower limit of the regulation value, the NOx emission amount and the ammonia emission amount at the catalyst denitration device outlet can be reduced.

In the exhaust gas denitration apparatus provided with the first ammonia injection control means, the ammonia concentration of the exhaust gas passing through the catalyst which has passed through the catalyst is measured, and the ammonia concentration is calculated from the measurement signal of the measured ammonia concentration. There is provided a fourth ammonia injection control means for injecting ammonia into the reduced treatment exhaust gas based on the control signal and controlling the ammonia concentration of the exhaust gas passing through the catalyst to fall within a preset concentration range.

The exhaust gas denitration apparatus provided with the fourth ammonia injection control means has the same effect as the exhaust gas denitration apparatus provided with the first ammonia injection control means, and the NOx concentration at the outlet of the catalyst denitration apparatus is equal to or less than a regulation value. Indicates that the amount of ammonia is insufficient, and indicates that the NOx outflow amount has increased. Conversely, N at the outlet of the catalytic NOx removal device
The fact that the H ₃ concentration becomes equal to or higher than the regulated value indicates that the emission of NOx is suppressed but the amount of ammonia flowing out of the system is increasing in a state where ammonia is excessively present. Therefore, by controlling the amount of ammonia injected into the catalyst denitration device inlet or the upstream duct so that the NH ₃ concentration measured at the catalyst denitration device outlet or the downstream duct can be maintained within the upper limit and the lower limit of the regulation value, the catalyst denitration device outlet can be controlled. NOx
Emissions and ammonia emissions can be reduced.

By the way, since ammonia has a property of easily causing thermal decomposition due to its physical properties, there is an upper limit to the ability to reduce NOx before the injected ammonia causes thermal decomposition. That is, even if a certain amount or more of excess ammonia is injected in the first ammonia injection means,
From a certain ratio, the NOx concentration tends to equilibrium. Therefore,
The NOx concentration is measured on the upstream side of the ammonia injection position, and appropriate ammonia (minimum necessary excess ammonia contributing to NOx reduction) corresponding to the required NOx / NH ₃ molar ratio calculated from the measurement signal is injected. Thus, unnecessary excessive injection of ammonia can be avoided.

Ammonia remaining without causing thermal decomposition or gas phase reduction reaction with NOx is reused together with ammonia injected by the second ammonia injection means. From the NOx concentration measurement device installed upstream of the ammonia injection position at the entrance of the catalyst denitration device equipped with a denitration catalyst, the amount of ammonia necessary to maintain the NOx concentration at the exit of the catalyst denitration device at the regulated value can be calculated, and the ammonia concentration measurement Since the amount of ammonia remaining in the reduced exhaust gas can be calculated from the device, if the amount of ammonia obtained by subtracting the amount of residual ammonia from the required amount of ammonia is injected into the inlet of the catalytic denitration device, the amount of excess ammonia is injected over the required minimum amount of excess ammonia. The amount of leaked ammonia can be minimized.

The non-catalytic denitration is is obtained by using vapor-phase direct thermal reduction of NOx by NH _3, at the same time NH ₃
The substance itself is thermally decomposed into N ₂ and H ₂ O.

4NH ₃ + 6NO → 5N ₂ + 6H ₂ O 4NH ₃ + 3O ₂ → 2N ₂ + 6H ₂ O Therefore, part of the injected NH ₃ contributes to the reduction of NOx, and the remaining part is decomposed by oxygen to form N ₂ And H ₂ O, and the remaining part is leak ammonia. According to the test results of the present inventors, the NH ₃ / NO molar ratio is 2 to 3
As described above, even if NH ₃ is excessively supplied, NOx almost reaches an equilibrium value, and the effective utilization rate of the supplied NH ₃ as denitration decreases.

FIG. 8 is a graph showing the relationship between the NH ₃ / NOx molar ratio, NOx concentration, and injected NH ₃ in the non-catalytic denitration of exhaust gas from a pressurized fluidized-bed boiler. As shown in this figure, when injecting NH ₃ according to the outlet NOx concentration, NH ₃ / N
Even if the Ox molar ratio is excessive, the effective utilization rate of NH ₃ is not economical at a certain ratio or more because it is not economical.

[0031] In the present invention, it is intended to reduce the NOx concentration to effectively use can range NH ₃ by injecting NH ₃ fixed molar ratio in accordance with the entrance NOx concentration. In a pressurized fluidized-bed boiler, the optimum molar ratio is about 2 to 3. In this case, there is a possibility that the outlet NOx concentration may not comply with the regulation value if only non-catalytic denitration is used. GT) Since there is a catalytic denitration device at the outlet, reduction to the regulation value is performed by catalytic denitration.

In the catalytic NOx removal, the NO at the inlet of the catalytic NOx removal device is
NH ₃ required to remove the x concentration to the regulation value at the outlet of the catalytic denitration device is predicted by calculation from the measured value of the inlet NOx concentration. However, the amount of NH ₃ injected at the inlet of the catalytic denitration apparatus is a calculated expected value (necessary value) because the reduced treatment exhaust gas at the entrance of the catalytic denitration apparatus contains the residual NH _{3 from the} upstream non-catalytic denitration apparatus.
It is sufficient to inject NH ₃ equivalent to the difference obtained by removing the remaining NH ₃ from the above.

[0033] Figure 9, the operation load and the NOx concentration at the catalyst denitration of pressurized fluid Doso boiler exhaust gas, the residual NH ₃ concentration, a relationship curve diagram of the chromatic catalyst inlet NH ₃ concentration. In a pressurized fluidized-bed boiler, the gas temperature and gas pressure from the boiler outlet to the GT fluctuate depending on the load. If the above relationship is arranged on the horizontal axis, the non-catalytic denitration is performed by the injection of NH ₃ due to the thermal reduction reaction. Even when the molar ratio is constant, the NOx concentration at the inlet of the catalytic denitration device tends to increase at a partial load where the exhaust gas temperature decreases, since the NOx concentration decreases (FIG. 9).

On the other hand, in the thermal decomposition reaction of surplus NH ₃ in non-catalytic denitration, the temperature tends to decrease with a partial load, and the decomposition tends to be suppressed as the O ₂ partial pressure decreases due to the decrease in exhaust gas pressure. The proportion of NH ₃ present increases (FIG. 9). Therefore, at the catalyst entrance, NO
x concentration also increased need NH ₃ ratio with respect to the exhaust gas amount to increase (in FIG. 9), the residual NH ₃ in a non-catalytic denitration
Since the concentration also increases, the amount of NH ₃ injected at the catalyst entrance, which is obtained by subtracting the amount of residual NH ₃ from the required amount, does not increase significantly (FIG. 9).

In the case of injecting NH ₃ at a fixed ratio with respect to the NOx concentration at the catalyst inlet, the amount of residual NH ₃ already present in the exhaust gas is added to NH ₃ , so that an excessive amount of NH ₃ Is discharged to the chimney as leak NH ₃ , which is not economical. In addition, residual NH _{3 in} non-catalytic denitration
Since the amount fluctuates depending on the exhaust gas temperature and exhaust gas pressure peculiar to the pressurized fluidized bed as described above, it is difficult to accurately predict the amount by calculation or the like. It is also effective in terms of aspects. As described above, NOx and leak ammonia in the chimney inlet duct can be suppressed to the minimum level.

Next, ammonia is injected into the flue gas generated by burning the fuel to reduce the nitrogen oxides in the flue gas to obtain a reduced treated exhaust gas. In the exhaust gas denitration apparatus for removing nitrogen oxides of the reduced treatment exhaust gas based on the above, controlling the amount of ammonia injected into the combustion exhaust gas in accordance with a load signal of a load applied to a combustion apparatus for burning the fuel, And the above-mentioned third ammonia injection control means or fourth ammonia injection control means.

The exhaust gas denitration device provided with the fifth ammonia injection control means has, for example, a fluid exhaust gas denitration device provided with the third ammonia injection control means or the fourth ammonia injection control means. In the case where the operation condition of the bed boiler is fixed and operated in a fixed pattern depending on the load, the amount of ammonia to be injected is set in advance as a control function correlated with the load without measuring the NOx concentration. It is also possible to control the amount of ammonia injected into the gas phase denitration unit.

In the exhaust gas denitration apparatus of the present invention, the NOx reduced by the non-catalytic denitration apparatus which is the first ammonia injection control means 31 or the fifth ammonia injection control means 35.
Can be further removed by the ammonia injected by the second to fourth ammonia injection control means 32, 33, 34 in the catalytic denitration device 11 and the denitration efficiency can be improved to the upper limit or more when only the catalytic denitration device 11 is used. Becomes possible,
Comply with strict environmental regulations.

The amount of ammonia used in non-catalytic and decatalyzed denitration is controlled by controlling the amount of ammonia that decomposes and disappears and the amount of ammonia that is unreacted and discharged outside the system while maintaining the NOx concentration at the chimney inlet below a regulated value. Control to minimize.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an exhaust gas denitration apparatus according to the present invention will be described in detail with reference to the drawings.
1 to 7, the same or equivalent parts are denoted by the same reference numerals, and the description of the same reference numerals in FIGS.

FIG. 1 shows a first example of an exhaust gas denitration apparatus according to the present invention used in a power generation apparatus using a pressurized fluidized bed boiler.
It is a system diagram showing an embodiment. The combustion air 5 introduced into the compressor 6 driven by the gas turbine 8 is
It is introduced into the pressurized fluidized bed boiler 1 in the pressure vessel 3 through the furnace inlet pipe 4. Fluid medium (BM) forming fluidized bed
CWP as fuel supplied by 2 to CWP supply nozzle 23, generating combustion gas G ₁ by burning. Combustion exhaust gas G generated in pressurized fluidized bed boiler 1
_{In 1} , non-catalytic denitration by a gas phase reduction reaction is performed in a furnace outlet pipe 7. The reduced treatment exhaust gas G ₂ in which the nitrogen oxides have been reduced is further introduced into the gas turbine 8 through the furnace outlet pipe 7 to generate power and drive the compressor 6 at the same time. The reduced-treatment exhaust gas G _{2 that} has exited the gas turbine 8 is introduced into the economizer 10 upstream of the gas turbine outlet duct 9. However, since the exhaust gas temperature is as high as about 400 ° C., the economizer upstream is reduced. Heat is recovered through the fuel cell 10 and the downstream economizer 10, passes through the chimney inlet duct 12, and is discharged from the chimney 29.

Here, the exhaust gas denitration apparatus of the first embodiment is a pressurized fluidized bed boiler 1 that burns CWP as fuel.
In reduction processing to reduce the nitrogen oxides in the combustion exhaust gas G ₁ by injecting ammonia into generated flue gas G ₁ gas G ₂
And then, to remove additional denitration catalyst device 11 reduction process of nitrogen oxides of the exhaust gas G ₂ in having ammonia injected denitration catalyst (catalyst) in the reducing process gas G _2, the catalyst passes through the exhaust gas G ₃
Is discharged out of the system. The furnace outlet NO for measuring the NOx concentration in the combustion exhaust gas G ₁ from the injection position I ₁ for injecting ammonia into the combustion exhaust gas G ₁ on the upstream side
x NOx concentration measuring device 21
And a first ammonia injection control means 31 for controlling the ammonia injection amount to be injected into the combustion exhaust gas G ₁ based on the control signal c ₀ by a nitrogen oxide concentration measured by 1.

[0043] Further, to measure the chromatic catalyst inlet NOx concentration measuring apparatus 22a and the ammonia concentration to measure the concentration of nitrogen oxides reduction process flue gas G ₂ from the injection position I ₂ for injecting ammonia to the reduction process flue gas G ₂ on the upstream side NH with catalyst
₃ concentration measuring device 22b is installed to inject the reducing process gas G ₂ based on the control signal c ₁ which is calculated from the measurement signal i _2, i ₃ of the nitrogen oxide concentration and the ammonia concentration measured by these measuring devices A second ammonia injection control means 32 for controlling the ammonia injection amount is provided.

In the exhaust gas denitration apparatus of the first embodiment, the first ammonia injection control means 31 measures the NOx concentration at the furnace outlet by the NOx concentration measuring device 21 at the furnace outlet. After the calculation, the control signal c ₀ is sent to the non-catalytic ammonia flow control valve 20 for control. Upon receiving the control signal c ₀ , the non-catalytic ammonia flow control valve 20 increases the required amount of ammonia from the ammonia vaporizer 15, which is also used for catalytic denitration, to a pressure equal to or higher than the pressure in the furnace outlet pipe 7. ) Send to 16. The ammonia sent from the non-catalyst ammonia booster fan 16 is supplied to the mixer 30
The ammonia diluted air 17 is mixed and injected into the furnace outlet pipe 7 from the non-catalytic ammonia nozzle 18.

The injected ammonia is supplied to the furnace outlet pipe 7.
It diffuses into the exhaust gas inside and reduces NOx by a gas phase reduction reaction, and at the same time, reaches the inlet of the catalytic denitration device 11 via the gas turbine 8 while causing thermal decomposition. NO at this time
NOx concentration measuring device 22a for x concentration and ammonia concentration
And NH ₃ concentration measurement device 22b, and the measurement signals i ₂ and i ₃ are taken into the catalyst layer inlet NH ₃ injection amount calculation device 25, and the amount of injected ammonia required for catalyst denitration is calculated and calculated. The control signal c ₁ is sent to and controlled by the catalyzed ammonia flow control valve 19, and the ammonia sent from the catalyzed ammonia flow control valve 19 is diluted with the ammonia dilution air 14 and injected through the catalyzed ammonia injection nozzle 13.

NOx at the inlet of the catalytic denitration device 11 is further removed by the catalyst, and the limit value of the denitration efficiency performed only with the denitration catalyst is further improved by combining with the first ammonia injection means 31 for non-catalytic denitration. Will be. Further, since the leak ammonia in the non-catalytic denitration is effectively used in the catalytic denitration, the concentration of the ammonia discharged from the chimney can be minimized. Since the amount of ammonia to be consumed can always be the minimum amount necessary for the NOx concentration upstream of the injection position, the amount of ammonia consumed can be minimized.

FIG. 2 is a system diagram showing the second embodiment. Denitration apparatus of exhaust gas of the second embodiment, the first two of the ammonia injection control means 32, perforated catalyst outlet NOx concentration measuring device 24a that measures the NOx concentration of the catalyst passing the exhaust gas G ₃ having passed through the catalytic denitration device 11 the a, the nitrogen oxide concentration measurement signal i ₄ measured by the chromatic catalyst outlet NOx concentration measuring device 24a, the measurement signal of the nitrogen oxides reduction process flue gas G ₂ measured above concentration and ammonia concentration i _2, i ₃
The control signal c ₁ calculated from the above is corrected by the catalyst layer inlet NH ₃ injection amount correction calculating device 26 and the control signal c ₂ is sent to the catalyzed ammonia flow control valve 19 for control. injected into reducing process gas G _2, and controls. Outlet NOx concentration is set or regulated NOx
Correct so as to be smaller than the density value.

FIG. 3 is a system diagram showing the third embodiment. Denitration apparatus of exhaust gas of the third embodiment, in the second ammonia injection control means 32, a chromatic catalyst outlet NH ₃ concentration measuring device 24b for measuring the ammonia concentration of the catalyst passing through the exhaust gas G ₃ having passed through the catalytic denitration device 11 has, in the measurement signal i ₅ of the NH ₃ concentration measured by the chromatic catalyst outlet NOx concentration measuring device 24b, the measurement of the concentration of nitrogen oxides reduction process flue gas G ₂ measured previously and ammonia concentration signal i _2, i ₃ The control signal c ₁ calculated from the above is corrected by the catalyst layer inlet NH ₃ injection amount correction calculating device 26 to become the control signal c ₃ , and the control signal c ₃ is sent to the catalyzed ammonia flow rate adjusting valve 19 for control to reduce controlling the ammonia injection amount to be injected into the exhaust gas G _2. A correction is made so that the outlet NH ₃ concentration becomes smaller than the set concentration value, the catalytic ammonia flow control valve 19 is controlled, and ammonia is injected from the catalytic ammonia injection nozzle 13.

FIG. 4 is a system diagram showing a fourth embodiment. Denitration apparatus of the exhaust gas of the fourth embodiment, the third ammonia injection control means 33 for controlling to fit in the range of concentrations of nitrogen oxides concentration of the catalyst passing through the exhaust gas G ₃ is set in advance
It has. The third ammonia injection control means 33 includes:
NOx concentration measurement device 2 with a catalyst outlet for measuring the concentration of nitrogen oxides in the exhaust gas G ₃ passing through the catalyst that has passed through the catalyst denitration device 11
NOx concentration measuring device 24a
The measurement signal i ₄ of the nitrogen oxide concentration measured in the above is input to the catalyst layer inlet NH ₃ injection arithmetic unit 27, and the catalyst layer inlet NH ₃
Based on the control signal c ₄ calculated from the injection calculating device 27, the control unit controls the catalyzed ammonia flow control valve 19 to inject ammonia into the reduced exhaust gas G ₂ .

Further, in the exhaust gas denitration apparatus of the fourth embodiment, the ammonia injected into the gas phase reduction denitration section of the furnace outlet pipe 7 is injected by the first ammonia injection means 31. On the other hand, the ammonia to be injected into the inlet of the catalyst denitration device 11 is measured by measuring the NOx concentration at the outlet of the catalyst denitration device 11 and injected by the third ammonia injection control means 33 so that the value falls within the set concentration range. The fact that the NOx concentration at the outlet of the catalytic denitration device 11 becomes equal to or less than the set value indicates that the ammonia is in an excessive state, and indicates that the ammonia may be flowing out. Conversely, the fact that the NOx concentration at the outlet of the catalytic denitration device 11 becomes equal to or higher than the set value means that
Ammonia is used for the reaction and there is no fear of spillage,
NOx will flow out of the system. Accordingly, by controlling the amount of ammonia injected from the catalyzed ammonia injection nozzle 13 so that the NOx concentration measured by the catalyzed outlet NOx concentration measuring device 24a falls within the range of the set upper and lower limits, NOx and NH ₃ emissions can be reduced. In this case, the above effect can be exerted only by the catalyst-exited NOx concentration measuring device 24a.
It does not require many Ox measuring devices and NH ₃ measuring devices.

FIG. 5 is a system diagram showing a fifth embodiment. Fifth embodiment of an exhaust gas denitration apparatus, the fourth ammonia injection control means 34 for controlling so that the ammonia concentration of the catalyst passing through the exhaust gas G ₃ falls to a preset concentration range
It has. The fourth ammonia injection control means 34
NH ₃ concentration measuring device 2 with a catalyst outlet for measuring the ammonia concentration of the exhaust gas G ₃ passing through the catalyst that has passed through the catalytic denitration device 11
4b, and this catalyst outlet NH ₃ concentration measuring device 24b
The measurement signal i ₅ of the ammonia concentration measured in step ₃ is input to the catalyst layer inlet NH ₃ injection arithmetic unit 27, and the catalyst layer inlet NH ₃
Based on the control signal c ₅ which is calculated from the injection operation unit 27, for injecting ammonia into reducing process gas G ₂ by controlling the chromatic catalytic ammonia flow control valve 19.

Further, in the exhaust gas denitration apparatus of the fifth embodiment, the ammonia injected into the gas phase reduction denitration section of the furnace outlet pipe 7 is injected by the first ammonia injection means 31. On the other hand, the ammonia to be injected into the inlet of the catalyst denitration device 11 is measured by measuring the NH ₃ concentration at the outlet of the catalyst denitration device 11 and injected by the fourth ammonia injection control means 34 so that the value falls within the set concentration range. . The fact that the NH ₃ concentration at the outlet of the catalytic denitration device 11 becomes equal to or lower than the set value means that NOx
Indicates an excessive state, and indicates that NOx may be flowing out. Conversely, the fact that the concentration of NH _{3 at the} outlet of the catalytic denitration device 11 exceeds the set value means that NOx is used in the reaction and there is no fear of outflow, but NH ₃ flows out of the system. Therefore, NOx is controlled by controlling the amount of ammonia injected from the catalyzed ammonia injection nozzle 13 so that the NH ₃ concentration measured by the catalyzed outlet NH ₃ concentration measuring device 24b falls within the range of the set upper limit and lower limit. And NH ₃ outflow can be reduced. In this case, the above effect can be exerted only by the catalyst-exited NH ₃ concentration measuring device 24b, so that the number of NOx measuring devices and NH ₃ measuring devices is not required.

FIG. 6 is a system diagram showing a sixth embodiment. Denitration apparatus of exhaust gas according to the sixth embodiment, the fifth ammonia to control the ammonia injection amount to be injected into the combustion exhaust gas G ₁ according to the load signal f of the load applied to the pressurized fluid Doso boiler 1 for burning fuel in the CWP An injection control means 35 is provided. Further, the NOx concentration at the outlet of the catalytic denitration apparatus 11 is measured, and a third ammonia injection control means 33 for controlling the ammonia injection amount of ammonia injection position I ₂ of the inlet of the catalytic denitration device 11.

The exhaust gas denitration devices of the first to fifth embodiments are as follows:
The amount of ammonia to be injected into the furnace outlet is pressurized according to the measurement signal c ₀ of the NOx measuring device by installing a furnace outlet NOx concentration measuring device upstream of the ammonia injection position of the pressurized fluidized bed boiler furnace outlet pipe 7. Although the amount of ammonia injected into the fluidized bed boiler outlet flue is controlled, the exhaust gas denitration apparatus according to the sixth embodiment operates when the operating condition of the pressurized fluidized bed boiler is fixed in a fixed pattern depending on the load. NOx
Even if the concentration is not measured, the amount of ammonia to be injected is preset as a control function correlated with the load, and the amount of ammonia to be injected into the gas phase reduction denitration unit is controlled by the load signal f.

FIG. 7 is a system diagram showing a seventh embodiment. The exhaust gas denitration apparatus according to the seventh embodiment generates the combustion exhaust gas G ₁ according to the load signal f of the load applied to the pressurized fluidized bed boiler 1 that burns the CWP fuel, similarly to the exhaust gas denitration apparatus according to the sixth embodiment. The fifth embodiment is provided with fifth ammonia injection control means 35 for controlling the amount of injected ammonia, but the catalyst denitration device 1 in the exhaust gas denitration device of the sixth embodiment.
Yes catalyst outlet NH ₃ measurement device 24b instead of the chromatic catalyst outlet NOx measuring device 24a that measures the NOx concentration in the first outlet
And a fourth ammonia injection control means 34 having the following.

Similar to the exhaust gas denitration apparatus of the sixth embodiment, the exhaust gas denitration apparatus of the seventh embodiment is operated when the operating conditions of the pressurized fluidized bed boiler are operated in a fixed pattern depending on the load. Even if the NOx concentration is not measured, the amount of ammonia to be injected is preset as a control function correlated with the load, and the amount of ammonia to be injected into the gas phase reduction denitration unit is controlled by the load signal f.

[0057]

According to the exhaust gas denitration apparatus of the present invention, the concentration of nitrogen oxides discharged to the outside is kept below the environmental regulation value, the amount of ammonia used for denitration of exhaust gases and the amount of leakage discharged to the outside are reduced. Minimize the amount of ammonia.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a first embodiment of an exhaust gas denitration apparatus according to the present invention used in a power generation apparatus using a pressurized fluidized bed boiler.

FIG. 2 is a system diagram showing a second embodiment.

FIG. 3 is a system diagram showing a third embodiment.

FIG. 4 is a system diagram showing a fourth embodiment.

FIG. 5 is a system diagram showing a fifth embodiment.

FIG. 6 is a system diagram showing a sixth embodiment.

FIG. 7 is a system diagram showing a seventh embodiment.

FIG. 8 is a graph showing the relationship between NH ₃ / NOx molar ratio, NOx concentration, and injected NH ₃ in decatalyzed denitration of exhaust gas from a pressurized fluidized-bed boiler.

FIG. 9 shows the operation load, NOx concentration, residual NH ₃ concentration, and NH ₃ inlet with catalyst in catalytic denitration of exhaust gas from a pressurized fluidized-bed boiler.
FIG. 4 is a graph showing a relation curve of density.

FIG. 10 is a system diagram showing an example of a conventional exhaust gas denitration apparatus used for a power generation apparatus using a pressurized fluidized bed boiler.

FIG. 11 is a system diagram showing an example of another conventional exhaust gas denitration device used in a boiler combustion device.

FIG. 12 is a system diagram showing an example of another conventional exhaust gas denitration apparatus used in a power generation apparatus using a pressurized fluidized-bed boiler.

[Explanation of symbols]

31 first ammonia injecting means 32 second ammonia injecting means 33 third ammonia injecting means 34 fourth ammonia injecting means 35 fifth ammonia injecting means I ₁ , I ₂ injecting position i _{2 to} i ₅ measurement signal c _{0 to} c ₅ Control signal f Load signal G ₁ Combustion exhaust gas G ₂ Reduction treated exhaust gas G ₃ Exhaust gas passing through the catalyst

Continued on the front page (72) Inventor Tetsuya Iwase 6-9 Takaracho, Kure-shi, Hiroshima Prefecture Inside the Babcock Hitachi Kure Factory (72) Inventor Naoyuki Kondo 6-9 Takaracho, Kure-shi Hiroshima Prefecture Inside the Babcock Hitachi Kure Factory (72) Inventor Yoshimichi Mori 6-9 Takaracho, Kure-shi, Hiroshima Babcock Hitachi Kure Factory

Claims (7)

[Claims] 1. A reduced exhaust gas, wherein nitrogen oxides in the exhaust gas are reduced by injecting ammonia into a flue gas generated by burning fuel, and the ammonia is injected into the reduced exhaust gas to determine whether a catalyst exists. In the exhaust gas denitration apparatus for removing nitrogen oxides of the reduced exhaust gas based on the measurement, the nitrogen oxide concentration of the combustion exhaust gas is measured at an upstream side from an injection position where ammonia is injected into the combustion exhaust gas, and the measured nitrogen oxide concentration is measured. An exhaust gas denitration apparatus comprising: first ammonia injection control means for controlling an amount of ammonia injected into the combustion exhaust gas based on a control signal based on a substance concentration. 2. The nitrogen oxide concentration and the ammonia concentration of the reduced treatment exhaust gas according to claim 1, wherein the nitrogen oxide concentration and the ammonia concentration of the reduced treatment exhaust gas are measured upstream of an injection position for injecting ammonia into the reduced treatment exhaust gas. An exhaust gas denitration apparatus comprising: a second ammonia injection control means for controlling an ammonia injection amount to be injected into the reduced treatment exhaust gas based on a control signal calculated from a concentration measurement signal. 3. The method according to claim 2, wherein the second ammonia injection control means measures a nitrogen oxide concentration of a catalyst passing exhaust gas passing through the catalyst, and uses the measured nitrogen oxide concentration measurement signal as a signal. An exhaust gas denitration apparatus characterized in that a control signal calculated from a measurement signal of a nitrogen oxide concentration and an ammonia concentration of a measured reduced treatment exhaust gas is corrected to control an amount of ammonia injected into the reduced treatment exhaust gas. 4. The ammonia injection control means according to claim 2, wherein the second ammonia injection control means measures the ammonia concentration of the exhaust gas passing through the catalyst through the catalyst, and performs the measurement using the measurement signal of the measured ammonia concentration. An exhaust gas denitration apparatus, wherein a control signal calculated from a measurement signal of a nitrogen oxide concentration and an ammonia concentration of a reduced treatment exhaust gas is corrected to control an amount of ammonia injected into the reduced treatment exhaust gas. 5. The reduction process according to claim 1, wherein a nitrogen oxide concentration of the exhaust gas passing through the catalyst that has passed through the catalyst is measured, and a control signal calculated from a measurement signal of the measured nitrogen oxide concentration is used. An exhaust gas denitration apparatus comprising: third ammonia injection control means for injecting ammonia into exhaust gas and controlling the concentration of nitrogen oxides in the exhaust gas passing through the catalyst to fall within a preset concentration range. 6. The method according to claim 1, wherein an ammonia concentration of the exhaust gas having passed through the catalyst is measured, and ammonia is added to the reduced exhaust gas based on a control signal calculated from a measurement signal of the measured ammonia concentration. An exhaust gas denitration apparatus comprising: a fourth ammonia injection control means for injecting and controlling the ammonia concentration of the exhaust gas passing through the catalyst to fall within a preset concentration range. 7. A reduced exhaust gas in which nitrogen oxides in the exhaust gas are reduced by injecting ammonia into a flue gas generated by burning fuel, and ammonia is injected into the reduced exhaust gas to determine the presence of a catalyst. In the exhaust gas denitration apparatus for removing nitrogen oxides from the reduced treatment exhaust gas based on a fifth control method, the amount of ammonia injected into the combustion exhaust gas is controlled according to a load signal of a load applied to a combustion device that burns the fuel. The exhaust gas denitration apparatus according to claim 5 or 6, further comprising an ammonia injection control means.