JPH1057770A - Flue gas denitrification device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact denitrification device with a performance improved and further to heat a waste gas to a temp., at which the denitrification reaction is possible and an acidic ammonium sulfate is not formed or deposited, with a minimum energy. SOLUTION: A denitrification catalyst 5 is arranged between an inlet duct 20 and an outlet duct 11, a waste gas flowing into the inlet duct 20 in direction of the arrow shown in the figure is heated by a heat exchanger 4, reduced with a reducing agent injected from a reducing agent injection pipe and passed through a catalyst 5 to remove the NOx in the waste gas in the flue gas denitrification device. A flow straightening plate 22 is provided on the upstream side of the heat exchanger 4, the heat exchanger 4 is furnished between the inlet duct 20 and the catalyst 5 and opposed to the catalyst 5, and the lower end face of the heat exchanger 4 is connected to the upper end face of a communication duct 18 contg. the catalyst 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to flue gas denitration equipment such as municipal waste incineration equipment, cogeneration using a diesel engine and a gas turbine, and more particularly to a flue gas denitration apparatus for reducing installation space and saving energy. About.

[0002]

[Prior art] Power plants, various factories, municipal waste incineration equipment,
Nitrogen oxides (NOx) in flue gas emitted from co-generation using diesel engines and gas turbines and automobiles are substances that cause photochemical smog and acid rain. A flue gas denitration method by selective catalytic reduction using NH ₃ ) or ammonia water as a reducing agent is widely used mainly in thermal power plants and the like. For this reason, at present, the flue gas denitration equipment is installed in many boilers for thermal power plants in Japan.

[0003] On the other hand, refuse discharged from each household or company is generally incinerated in refuse incineration equipment, but NOx is contained in exhaust gas discharged during refuse incineration. Also in this case, the flue gas denitration apparatus is used as an effective method. FIG. 7 is a schematic configuration diagram of the refuse incineration facility. 400 ~ generated from refuse incinerator 1
The high-temperature exhaust gas of 500 ° C. is introduced into the bag filter 2 after being cooled to 160 to 170 ° C. by the exhaust gas cooler 3 in order to lower the exhaust gas temperature to the heat-resistant temperature of the bag filter 2 located downstream. This bag filter 2 removes dust and harmful substances such as dioxin which is deposited in a low temperature range, and the exhaust gas from the bag filter 2 is removed by a heat exchanger 4.
After heating to a temperature (220 to 240 ° C.) at which denitration reaction is possible, NOx flows to the denitration catalyst 5 to remove NOx.

[0004] When sulfur oxide (SOx) is contained in the exhaust gas, NH ₃ as a reducing agent injected into the exhaust gas for the purpose of denitration reaction reacts with SO ₃ in the SOx to cause acidity. Since the generation and deposition of ammonium sulfate causes problems such as blockage of the reducing agent injection pipe 6 and rapid deterioration of the denitration catalyst 5, the temperature rise of the exhaust gas is also required to avoid or suppress the extraction of acidic ammonium sulfate. Is required.

FIG. 8 is an enlarged detail view of a flue gas denitration apparatus which is a main part of FIG. A heat exchange pipe group 7 of the heat exchanger 4, a communication duct 8 between the heat exchanger 4 and the denitration catalyst 5, a reducing agent injection pipe 6 inserted into the communication duct 8, and injecting NH ₃ ;
A mixing pipe 9, an inlet duct 10 for the denitration catalyst 5,
It includes a rectifying plate 12 provided upstream of the denitration catalyst 5 and an outlet duct 11 of the denitration catalyst 5. Exhaust gas from the bag filter 2 shown in FIG. 7 flows into the heat exchanger 4 as shown by an arrow in FIG. 8, and the heat exchanger 4 is installed with enlarged ducts and the like in front and back. And for reacting NH ₃ in just proportion to the amount of NOx in the exhaust gas downstream of the denitration catalyst 5, it is necessary to uniformly inject the possible NH _3,
Generally, the reducing agent injection pipe 6 is provided in a straight portion where the change in the flow velocity distribution in the communication duct 8 is relatively small.

[0006] NH ₃ gas which has been injected is to promote diffusion into the exhaust gas NH _3, or to secure a long distance in the flow direction of the exhaust gas to contact the duct 8, or for forcibly facilitate the mixing, reduction Mixing pipe 9 connected to agent injection pipe 6
The denitration reaction was performed by increasing the mixing effect between NH ₃ and the exhaust gas by installing such components.

Further, in order to make the residence time (reaction) of the exhaust gas in the denitration catalyst 5 uniform and to control the dispersion of the denitration performance, a rectifying plate 12 is provided upstream of the denitration catalyst 5 to distribute the exhaust gas flowing into the denitration catalyst 5. And the performance was improved. However, since the heat exchanger 4 and the denitration catalyst 5 require a long straight portion of the straightening plate 12 or the communication duct 8 to improve their performance, and have a large installation space, the flue gas denitration device is installed in the refuse incinerator. Was prevented from doing so.

[0008]

In a conventional flue gas denitration apparatus, a current plate is provided for improving the performance of equipment such as a heat exchanger and a denitration catalyst. In addition, since the heat exchanger and the inlet duct are connected by a communication duct, it is necessary to heat the exhaust gas more than necessary in the heat exchanger in consideration of the heat dissipation loss in the communication duct, and from the viewpoint of energy saving, Was not preferred.

SUMMARY OF THE INVENTION It is an object of the present invention to improve the performance of equipment, to be compact, and to efficiently heat exhaust gas to a temperature at which denitration reaction is possible and a temperature at which acidic ammonium sulfate is generated and separated out, with minimum energy. It is an object of the present invention to provide a flue gas denitration apparatus capable of performing the following.

[0010]

In order to achieve the above-mentioned object, a flue gas denitration apparatus according to the present invention raises the temperature of exhaust gas in a heat exchanger and then reduces nitrogen oxides in the exhaust gas through a denitration catalyst. In the flue gas denitration apparatus for reducing and removing by means of the above, a straightening plate is provided upstream of the heat exchanger, and the heat exchanger is arranged so as to face the denitration catalyst.

Then, a denitration catalyst is disposed between the inlet duct and the outlet duct, and the exhaust gas is heated by a heat exchanger and a reducing agent is injected to remove nitrogen oxides in the exhaust gas by the denitration catalyst. In the apparatus, the heat exchanger may be provided between the inlet duct and the denitration catalyst.

The reducing agent is injected from a reducing agent injection pipe inserted between the heat exchanger and the denitration catalyst, and is injected from a reducing agent injection pipe inserted upstream of the straightening plate of the heat exchanger. Or a configuration in which the reducing agent is injected from a reducing agent injection tube inserted in the heat exchange tube group of the heat exchanger.

Further, a denitration catalyst is disposed between the inlet duct and the outlet duct, the temperature of the exhaust gas is raised by a heat exchanger, and a reducing agent is injected from a reducing agent injection pipe. In the flue gas denitration system to be removed, the inlet duct is located at the lower end so that the exhaust gas flows in from the inlet duct and rises, and a heat exchanger is provided between the denitration catalyst and the heat exchanger tubes in the heat exchanger. A configuration may be employed in which a reducing agent injection pipe is inserted, and a water washing nozzle is inserted between the heat exchange pipe and the denitration catalyst.

In the refuse incineration equipment, any one of the above-mentioned flue gas denitration equipment, a refuse incinerator, an exhaust gas cooler for cooling a high-temperature exhaust gas generated from the refuse incinerator to a predetermined temperature, and the cooled exhaust gas cooler A bag filter configured to remove at least soot and dust from the exhaust gas and discharge the dust to a flue gas denitration device.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, a denitration catalyst 5 is disposed between an inlet duct 20 and an outlet duct 11, and the exhaust gas flowing into the inlet duct 20 from the direction of the arrow shown in the drawing is heated by the heat exchanger 4 and injected with a reducing agent. A flue gas denitration apparatus for reducing nitrogen oxides in exhaust gas through a denitration catalyst 5 by reducing with a reducing agent injected from a pipe 6, wherein a rectifying plate 22 is provided upstream of the heat exchanger 4 and a heat exchanger 4 is provided. Is provided between the inlet duct 20 and the denitration catalyst 5 so as to face the denitration catalyst 5, and the lower end face of the heat exchanger 4 is connected to the upper end face of the communication duct 18 containing the denitration catalyst 5. .

That is, a heat exchanger 4 disposed between the inlet duct 20 and the denitration catalyst 5 to heat the exhaust gas, and a heat exchange tube group 7 in the heat exchanger 4 are provided. And flows into the heat exchanger 4 in a state where the gas distribution in the vertical direction is made substantially uniform by the rectifying plate 22 upstream of the heat exchanger 4. After that, the exhaust gas is heated by the heat exchange tube group 7 of the heat exchanger 4 to a temperature capable of performing the denitration reaction or a temperature higher than or equal to the acidic ammonium sulfate precipitation temperature range, and the exhaust gas has a mixing distance H from the upper end surface of the denitration catalyst 5. A reducing agent such as NH ₃ or ammonia water is injected from the reducing agent injection pipe 16, and NOx is removed by the denitration catalyst 5 using the denitration catalyst 5.

According to this embodiment, the exhaust gas flow rectified by the rectifying plate 22 upstream of the inlet of the heat exchanger 4 is supplied to the heat exchanger 4.
And it becomes possible to continuously pass through the denitration catalyst 5, and the denitration performance can be improved. Further, as compared with the bent communication duct 8 of the conventional flue gas denitration apparatus shown in FIG. 8, the length of the communication duct 18 from the heat exchanger 4 is greatly reduced, so that it is economical and the heat dissipation is improved. Loss can also be reduced.

FIG. 2 is a longitudinal sectional view of a flue gas denitration apparatus showing another embodiment of the present invention. The difference from the embodiment shown in FIG. 1 is that the reducing agent injection pipe 26 is arranged in the inlet duct 20, and the inlet position of the reducing agent injection pipe 26 is different. That is, as compared with the embodiment shown in FIG. 1, the present invention is applied to further promote the mixing of NH ₃ and exhaust gas.

That is, NH ₃ is injected into the low-temperature exhaust gas from the reducing agent injection pipe 26. The exhaust gas into which NH ₃ has been injected flows into the heat exchanger 4 after the exhaust gas distribution in the vertical direction is made uniform by the current plate 22 as in the embodiment of FIG. Since the exhaust gas and the reducing agent are sufficiently stirred and mixed by the heat exchange tube group 7 of the heat exchanger 4, it is not necessary to secure the mixing distance H between the exhaust gas and NH ₃ shown in FIG. Since H is better, a more compact flue gas denitration device is possible.

On the other hand, N which is mainly used as a reducing agent
H ₃ is a designated substance for poisons and deleterious substances, and is subject to the High Pressure Gas Control Law. Therefore, local governments that incinerate waste often use ammonia water that is easy to handle as a substitute for NH _3. In addition, when this ammonia water is used as the reducing agent, the heat exchange tube group 7 also has an effect of promoting the vaporization of the ammonia water injected into the exhaust gas.

FIG. 3 is a sectional view of another embodiment of the present invention. The difference from the embodiment shown in FIGS. 1 and 2 is that the flue gas denitration apparatus shown in FIGS. Injection tube 1
3 and 6 are arranged downstream of the heat exchanger 4 and inside the inlet duct 20, whereas in the embodiment shown in FIG. The other structure is the same as that of FIGS.

In another embodiment shown in FIG. 3, the temperature of the exhaust gas is raised in the upstream heat exchanger tube group 7a to an exhaust gas temperature at which the outflow of acidic ammonium sulfate can be avoided or suppressed. Inject NH ₃ . Thereafter, there is an effect that the exhaust gas and the reducing agent are sufficiently stirred and mixed by the downstream heat exchange tube group 7b located downstream of the reducing agent injection pipe 36. When ammonia water is used as the reducing agent, the downstream heat exchange tube group 7
b also has the effect of promoting the vaporization of the ammonia water injected into the exhaust gas. FIG. 4 shows the relationship between the exhaust gas temperatures corresponding to the exhaust gas channels.

FIG. 5 is a longitudinal sectional view of another embodiment of the present invention, which is applied to exhaust gas flowing horizontally, and the other structure is the same as that shown in FIG.

FIG. 6 is a longitudinal sectional view showing another embodiment of the present invention, in which a water washing nozzle 13 is arranged between the denitration catalyst 5 and the heat exchange tube group 7b. The difference between the embodiment shown in FIGS. 1 to 3 and the embodiment shown in FIG. 6 is that the exhaust gas in the embodiment shown in FIGS. In the embodiment shown in FIG. 5, the exhaust gas is an upward flow in which the exhaust gas flows backward from the lower side to the upper side, and the washing nozzle 13 is disposed. Other structures are the same as those in FIGS. That is, the heat exchanger 4 is provided between the heat exchanger 4 and the heat exchanger 4 between the heat exchanger 4 and the denitration catalyst 5 with the inlet duct 20 positioned at the lower end so that the exhaust gas flows from the inlet duct 20 and rises. A reducing agent injection pipe 46 is inserted into the water washing nozzle 1 between the heat exchange pipe 4 and the denitration catalyst 5.
3 is inserted. This embodiment is effective when the exhaust gas contains adhering dust and the dust adhering to the heat exchange tube groups 7a and 7b needs to be washed with water. In this case, the exhaust gas flowing through the denitration catalyst 5 is supplied to the lower inlet duct 2.
The upward flow flows from 0 to the outlet duct 11 on the upper side.

According to the present embodiment, the low-temperature exhaust gas flows into the heat exchanger 4 after the exhaust gas distribution in the vertical direction is made substantially uniform by the rectifying plate 22 below the denitration catalyst 5. After the temperature is raised in the heat exchange tube group 7a to a temperature at which the deposition of acidic ammonium sulfate can be avoided or suppressed, NH ₃ is injected into the exhaust gas from the reducing agent injection tube 46. Thereafter, the exhaust gas and NH ₃ are sufficiently stirred and mixed by the heat exchange tube group 7b downstream of the reducing agent injection tube 46. In this embodiment, when ammonia water is used as the reducing agent, the downstream heat exchange tube group 7b also has an effect of promoting the vaporization of the ammonia water injected into the exhaust gas. Then, after the elapse of the operation, dust adhering to the heat exchange tube groups 7a and 7b can be washed with water jetted from the washing nozzle 13. At this time, the dust adhering to the nozzle of the reducing agent injection pipe 46 can also be washed with the water jetted from the washing nozzle 13. Furthermore, since the inflow of cleaning wastewater into the denitration catalyst 5 during cleaning can be suppressed, performance degradation of the denitration catalyst 5 due to water leakage can also be prevented.

According to another embodiment of the present invention, a waste incineration plant is provided with any one of the above-mentioned flue gas denitration apparatus, the waste incinerator 1 shown in FIG. And a bag filter 2 that removes at least dust from the cooled exhaust gas and discharges it to a flue gas denitration device.

According to the present invention, since the heat exchanger for heating the exhaust gas is provided between the inlet duct and the denitration catalyst, the rectifying plates provided in each of the heat exchanger and the denitration catalyst are integrated. Since the communication duct is unnecessary or short, the exhaust gas can be effectively heated to the temperature at which denitration reaction is possible with minimum energy, and the exhaust gas and the reducing agent are sufficiently mixed by the heat exchange tube group. After flowing into the denitration catalyst after being mixed, the denitration performance can be improved.

[0028]

According to the present invention, since the area occupied by the installation of the communication duct can be reduced, the installation of the apparatus and the improvement of the denitration performance are possible even when there are restrictions on the location. Further, there is an effect that the exhaust gas can be effectively heated with minimum energy.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing another embodiment of the present invention.

FIG. 3 is a longitudinal sectional view showing another embodiment of the present invention.

FIG. 4 is a graph showing a relationship between an exhaust gas passage and an exhaust gas temperature.

FIG. 5 is a longitudinal sectional view showing another embodiment of the present invention.

FIG. 6 is a longitudinal sectional view showing another embodiment of the present invention.

FIG. 7 is a diagram showing a conventional refuse incineration facility.

FIG. 8 is a longitudinal sectional view of a conventional flue gas denitration apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Waste incinerator 2 Bag filter 3 Exhaust gas cooler 4 Heat exchanger 5 Denitration catalyst 6,16,26,36,46 Reducing agent injection pipe 7 Heat exchanger tube group 8,18,28 Communication duct 10,20 Inlet duct 11 Outlet duct 12,22 Rectifier plate 13 Rinse nozzle

Claims (7)

[Claims] 1. A flue gas denitration apparatus for raising the temperature of an exhaust gas in a heat exchanger and reducing it with a reducing agent and removing nitrogen oxides in the exhaust gas through a denitration catalyst, comprising a rectifying plate upstream of the heat exchanger. A flue gas denitration apparatus, wherein the heat exchanger is provided so as to face the denitration catalyst. 2. A denitration catalyst is arranged between an inlet duct and an outlet duct, and the temperature of the exhaust gas is increased by a heat exchanger and a reducing agent is injected to remove nitrogen oxides in the exhaust gas by the denitration catalyst. In the flue gas denitration apparatus, the heat exchanger is provided between the inlet duct and the denitration catalyst. 3. The flue gas denitration apparatus according to claim 1, wherein the reducing agent is injected from a reducing agent injection pipe inserted between the heat exchanger and the denitration catalyst. 4. The flue gas denitration apparatus according to claim 1, wherein the reducing agent is injected from a reducing agent injection pipe inserted upstream of the straightening plate of the heat exchanger. 5. The flue gas denitration apparatus according to claim 1, wherein the reducing agent is injected from a reducing agent injection tube inserted in a heat exchange tube group of the heat exchanger. 6. A denitration catalyst is disposed between an inlet duct and an outlet duct, the temperature of the exhaust gas is raised by a heat exchanger, and a reducing agent is injected from a reducing agent injection pipe. In the flue gas denitration apparatus for removing oxides, a heat exchanger is provided between the inlet duct and the denitration catalyst so that the exhaust gas flows from the inlet duct and rises therethrough, and the heat exchanger is provided. A flue gas denitration apparatus, wherein the reducing agent injection pipe is inserted into a heat exchange pipe group of a vessel, and a washing nozzle is inserted between the heat exchange pipe and the denitration catalyst. 7. A flue gas denitration apparatus according to any one of claims 1 to 6, a refuse incinerator, an exhaust gas cooler for cooling a high-temperature exhaust gas generated from the refuse incinerator to a predetermined temperature, A garbage incineration facility, comprising: a bag filter for removing at least dust from the cooled exhaust gas and discharging the dust to the flue gas denitration apparatus.