JP2010054083A - Denitration device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the deterioration of NOx removal efficiency by suppressing the formation of a solid matter in an exhaust gas duct. <P>SOLUTION: In this denitration device having an ammonia injection pipe 3 inserted into the exhaust gas duct 1 extending in the horizontal direction from an upper part of the exhaust gas duct 1, an ammonia water injection nozzle 11 disposed in the ammonia injection pipe 3 and atomizing ammonia water, and a denitration catalyst layer 5 disposed at a wake in the exhaust gas flowing direction of the ammonia injection pipe 3, the dust accumulated on a bottom surface in the exhaust gas duct 1 is scattered by a gas injection nozzle 15 for jetting gas toward the bottom surface of the exhaust gas duct 1 at a lower part of the ammonia injection tube pipe 3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exhaust gas denitration apparatus, and more particularly to an NOx removal apparatus that sprays ammonia water as a reducing agent directly in an exhaust gas duct.

  As this type of denitration apparatus, a plurality of ammonia injection pipes having a plurality of ammonia injection nozzles are arranged in a line in an exhaust gas duct through which exhaust gas discharged from a plant that burns coal, heavy oil, or the like is used as a reducing agent. A denitration apparatus is known that reduces nitrogen oxides in the presence of a denitration catalyst after jetting ammonia over the entire cross section of the exhaust gas duct (for example, Patent Document 1). In particular, according to the denitration apparatus of Patent Document 1, air or steam is blown from the side surface of the ammonia injection nozzle to remove dust adhering to the ammonia injection nozzle and prevent the ammonia injection nozzle from being blocked.

  On the other hand, there is known a denitration apparatus in which a filter carrying a denitration catalyst is provided in a denitration apparatus, and a desulfurization agent and ammonia water are supplied from the upstream of the filter to perform desulfurization, denitration, and dust removal with one apparatus. According to this, it is described that the reaction product and dust accumulated on the filter are wiped off by compressed air supplied from a backwash nozzle provided in the downstream of the filter (for example, Patent Document 2).

Japanese Patent Laid-Open No. 9-313891 JP-A-3-12222

However, when the ammonia water is sprayed directly onto the exhaust gas duct by the denitration apparatus of Patent Documents 1 and 2, unevaporated ammonia water is dropped and solidifies the dust accumulated on the bottom surface of the exhaust gas duct extended in the lateral direction. This issue is not considered. In other words, the method of spraying ammonia water directly into the exhaust gas duct uses the heat of the exhaust gas to evaporate the ammonia water, but the ammonia water sprayed from the ammonia injection nozzle near the bottom of the exhaust gas duct stays. Since time is short, it may not evaporate completely. This non-evaporated portion of the ammonia water falls on the bottom surface of the exhaust gas duct below the ammonia injection pipe, and reacts with the accumulated dust to produce cement-like solid matter. If this solid matter grows in the exhaust gas duct, there is a problem that the flow of the exhaust gas is hindered, the flow of the exhaust gas to the NOx removal catalyst layer becomes uneven, and the NOx removal rate decreases.
The problem to be solved by the present invention is to suppress the generation of solid matter in the exhaust gas duct and reduce the decrease in the denitration rate.

  In order to solve the above problems, a denitration apparatus of the present invention includes an ammonia injection pipe inserted from above an exhaust gas duct into an exhaust gas duct extending in a lateral direction, and ammonia that is provided in the ammonia injection pipe and sprays ammonia water. A denitration apparatus having a water injection nozzle and a denitration catalyst layer provided downstream of the ammonia injection pipe in the exhaust gas flow direction, and gas injection means for injecting gas toward the bottom surface of the exhaust gas duct below the ammonia injection pipe It is characterized by having.

  According to this, since the dust accumulated in the exhaust gas duct below the ammonia injection pipe is scattered by the gas injection means, even if unevaporated ammonia water falls, it is evaporated at the bottom surface of the exhaust gas duct, The generation of solid matter in the duct can be suppressed, and the reduction in the denitration rate can be reduced. In this case, the dynamic pressure of the gas injected from the gas injection means can be adjusted to be 670 Pa (70 mmH 2 O) to 880 Pa (90 mm H 2 O) at the bottom surface of the exhaust gas duct.

  Here, the gas injection means only needs to be able to scatter dust on the bottom surface of the exhaust gas duct in which un-evaporated ammonia water falls. For example, ammonia having an inner pipe including an ammonia water injection nozzle and an outer pipe surrounding the inner pipe A gas injection nozzle is provided at the lower end of the injection pipe, and the gas supplied from the upper end of the outer pipe can be injected to scatter dust. Further, a header pipe having a gas injection nozzle can be inserted below the ammonia injection pipe, and dust can be scattered by injecting gas from the gas injection nozzle.

  In this case, the gas injection nozzle is preferably provided so as to be inclined downward with respect to the flow of exhaust gas in the exhaust gas duct, and the inclination angle is perpendicular to the central axis of the ammonia injection pipe or the center of the cross section of the header pipe. The angle can be 30 to 60 degrees.

  According to the present invention, it is possible to suppress the generation of solid matter in the exhaust gas duct and reduce the reduction in the denitration rate.

Hereinafter, the present invention will be described based on embodiments.
(Embodiment 1)
FIG. 1 is an overall configuration diagram of a denitration apparatus according to Embodiment 1 of the present invention, and FIG. 2 is a cross-sectional view of the main part of Embodiment 1 of the present invention viewed from the side of an exhaust gas duct. As shown in FIGS. 1 and 2, in the denitration apparatus of Embodiment 1, an ammonia injection pipe 3 is inserted from above the exhaust gas duct 1 into an exhaust gas duct 1 extending in the lateral direction through which the exhaust gas flows. A denitration catalyst layer 5 is provided downstream of the exhaust gas in the flow direction.

  The ammonia injection pipe 3 has an inner pipe 7 and an outer pipe 9 that surrounds the inner pipe 7. The inner pipe 7 is closed at the lower end, and an ammonia water supply source (not shown) is connected to the upper end. A plurality of ammonia water injection nozzles 11 are provided on the tube wall on the gas downstream side of the exhaust gas duct 1 of the inner tube 7. The ammonia water injection nozzle 11 is a two-fluid nozzle that sprays ammonia water together with compressed air, for example, and is capable of spraying ammonia water uniformly into the exhaust gas duct 1. The outer tube 9 that surrounds the inner tube 7 has a lower end closed, and a gas (not shown) supply source, for example, air, is connected to the upper end. A gas ejection cylinder 13 that surrounds the ammonia water injection nozzle 11 and that ejects air inside is provided on the tube wall on the gas downstream side of the exhaust gas duct 1 of the outer tube 9. The number of the ammonia injection pipes 3 and the ammonia water injection nozzles 11 can be appropriately set according to the cross-sectional area in the exhaust gas duct 1. For example, a plurality of ammonia injection pipes 3 having a plurality of ammonia water injection nozzles 11 are arranged in a row. Can be set.

  Next, the characteristic configuration of the first embodiment will be described. A gas injection nozzle 15 is provided at the lower end of the outer tube 9. The gas injection nozzle 15 can inject air supplied from the upper end of the outer tube 9 and flowing through the outer tube 9 toward the bottom surface in the exhaust gas duct 1 below the ammonia injection tube 3.

  The operation of the denitration apparatus of Embodiment 1 configured as described above will be described. Exhaust gas, for example, exhaust gas containing a large amount of dust discharged from a thermal power plant using coal or heavy oil as fuel, flows through the exhaust gas duct 1 and is guided to a denitration apparatus. Ammonia water is sprayed from the ammonia water injection nozzle 11 to the exhaust gas guided to the denitration apparatus. The sprayed ammonia water is evaporated and vaporized by the heat of the exhaust gas, and is introduced into the denitration catalyst layer 5 along with the exhaust gas. As a result, nitrogen oxides in the exhaust gas, which is a causative substance of photochemical smog and acid rain, are removed from the exhaust gas by selective catalytic reduction reaction using ammonia as a reducing agent as shown in the following formula 1.

4NO + 4NH3 + O2 → 4N2 + 6H2O (1)
The exhaust gas from which nitrogen oxides have been removed is subjected to a necessary exhaust gas purification treatment and discharged from a chimney or the like.

  Next, the characteristic operation of the present invention will be described. The air flowing through the outer tube 9 is injected toward the bottom surface in the exhaust gas duct 1 through the gas injection nozzle 15. The dust deposited on the bottom surface in the exhaust gas duct 1 below the ammonia injection pipe 3 is scattered by the injected air. Further, since air is continuously supplied into the outer tube 9 during operation of the denitration apparatus, air is constantly injected from the gas injection nozzle 15, so that dust accumulates on the bottom surface in the exhaust gas duct 1. It is prevented. The dynamic pressure of the blast air is adjusted, for example, from 670 Pa (70 mmH 2 O) to 880 Pa (880 Pa) on the bottom surface in the exhaust gas duct 1 by adjusting the opening area of the gas blast nozzle 15 and the pressure of the air supplied to the outer tube 9. 90 mmH2O).

  According to this, since ammonia water is used as the reducing agent, transportation and storage can be performed safely as compared with the case where anhydrous ammonia is used. Furthermore, since the ammonia water is evaporated and vaporized using the heat of the exhaust gas, a fan that supplies a heat source such as a heater for evaporating and vaporizing the ammonia water and air for diluting the vaporized ammonia. Can be eliminated, and the equipment cost and operation cost can be reduced.

  Further, since air is ejected from the gas ejection cylinder 13 surrounding the ammonia water injection nozzle 11, dust can be prevented from adhering, accumulating and blocking the ammonia water injection nozzle 11, and the reduction of the denitration rate can be reduced. it can. Further, since dust accumulated in the exhaust gas duct 1 below the ammonia injection pipe 3 is scattered by the gas injection nozzle 15, even if unevaporated ammonia water falls, it is evaporated at the bottom surface in the exhaust gas duct 1. Further, the contact between ammonia water and dust can be reduced to suppress the formation of solids, and the reduction in the denitration rate can be further reduced. As a result, it is possible to prevent the plant from being stopped due to a decrease in the denitration rate, and the plant can be stably operated.

In addition, the ammonia water used for Embodiment 1 can use a thing with a density | concentration of 19 to 29%.
(Embodiment 2)
FIG. 3 shows a cross-sectional view of the main part of another embodiment of the first embodiment as viewed from the side of the exhaust gas duct. The difference between the second embodiment and the first embodiment is that the gas injection nozzle 15 is inclined downward with respect to the flow of exhaust gas as shown in the figure. Since other configurations are the same as those of the first embodiment, the same reference numerals are given and description thereof is omitted.

According to this, since it is easy to disperse the dust near the position where the non-evaporated ammonia water on the bottom surface of the exhaust gas duct 1 falls, the production of solid matter can be efficiently suppressed. That is, since the non-evaporated ammonia water falls on the bottom surface in the exhaust gas duct 1 downstream of the gas flow in the ammonia injection pipe 3, the ammonia injection pipe 3 is inclined by tilting the gas injection nozzle 15 downward in the flow of the exhaust gas. The air can be jetted downstream in the gas flow direction, and dust can be efficiently scattered. The inclination angle of the gas injection nozzle 15 is preferably set to 30 to 60 degrees with respect to the central axis of the ammonia injection pipe 3.
(Embodiment 3)
4 and 5 show the configuration of the main part of another embodiment of the first and second embodiments. FIG. 4 is a front view of the main part of the third embodiment, and FIG. 5 is a cross-sectional view seen from the side of the exhaust gas duct. The third embodiment differs from the first and second embodiments in that the gas injection nozzle 15 is not provided at the lower end of the ammonia injection pipe 3 as shown in the figure, and the header pipe 18 is provided in the exhaust gas duct 1 below the ammonia injection pipe 3. The gas injection nozzle 15 is provided on the tube wall on the bottom side of the exhaust gas duct of the header pipe 18, and the air supplied to the header pipe 18 is injected from the gas injection nozzle 15. The gas injection nozzle 15 is provided so as to be inclined downward with respect to the exhaust gas flow in the exhaust gas duct 1. Since other configurations are the same as those of the first and second embodiments, the same reference numerals are given and description thereof is omitted.

  According to this, since the air injected from the gas injection nozzle 15 can be adjusted independently from the air supply system to the outer tube 9, the pressure of the air to be injected can be adjusted according to the amount of dust in the exhaust gas, etc. Dust can be scattered efficiently. In this case, air may be intermittently injected from the gas injection nozzle 15.

  In addition, the inclination angle of the gas injection nozzle 15 is preferably set to 30 to 60 degrees with respect to the vertical direction of the cross-sectional center of the header pipe 18.

  The insertion position of the header pipe 18 is not limited to the third embodiment, and the header pipe 18 may be moved upstream or downstream of the ammonia injection pipe 3 in the exhaust gas flow direction.

  Further, a necessary number of nozzles may be inserted from the bottom surface of the exhaust gas duct 1 to blow away accumulated dust.

It is a whole block diagram of the denitration apparatus of Embodiment 1 of this invention. It is sectional drawing which looked at the principal part of the denitration apparatus of Embodiment 1 of this invention from the side surface of the exhaust gas duct. It is sectional drawing which looked at the principal part of the denitration apparatus of Embodiment 2 of this invention from the side surface of the exhaust gas duct. It is a front view of the principal part of the denitration apparatus of Embodiment 3 of this invention. It is sectional drawing which looked at the principal part of the denitration apparatus of Embodiment 3 of this invention from the exhaust gas duct side surface.

Explanation of symbols

1 Exhaust Duct 3 Ammonia Injection Pipe 7 Inner Pipe 9 Outer Pipe 11 Ammonia Water Injection Nozzle 15 Gas Injection Nozzle 18 Header Pipe

Claims (6)

In an exhaust gas duct extending in the lateral direction, an ammonia injection pipe inserted from above the exhaust gas duct, an ammonia water injection nozzle provided in the ammonia injection pipe for spraying ammonia water, and the exhaust gas in the ammonia injection pipe A denitration apparatus having a denitration catalyst layer provided downstream in the flow direction,
A denitration apparatus comprising gas injection means for injecting gas toward the bottom surface of the exhaust gas duct below the ammonia injection pipe. The denitration apparatus according to claim 1,
The ammonia injection pipe has an inner pipe and an outer pipe provided surrounding the inner pipe,
The inner pipe has an upper end connected to a supply source of ammonia water, a lower end is closed, and an ammonia water injection nozzle is provided on a pipe wall on the gas downstream side of the exhaust gas duct,
The outer pipe has an upper end connected to a gas supply source, and is provided with a gas ejection cylinder that surrounds the ammonia water injection nozzle on the gas downstream pipe wall of the exhaust gas duct and ejects the gas.
The denitration apparatus, wherein the gas injection means is a gas injection nozzle provided at a lower end of the ammonia injection pipe. The denitration apparatus according to claim 1,
The gas injection means includes a header pipe connected to the gas supply source and inserted below the ammonia injection pipe of the exhaust gas duct, and the header pipe toward the bottom surface of the exhaust gas duct below the ammonia injection pipe A denitration apparatus comprising: a gas injection nozzle provided in the apparatus. In the denitration apparatus of Claim 2 or 3,
The denitration apparatus, wherein the gas injection nozzle is provided to be inclined downward with respect to a flow of exhaust gas in the exhaust gas duct. The denitration apparatus according to claim 4,
The denitration apparatus, wherein an inclination angle of the gas injection nozzle is 30 to 60 degrees with respect to a central axis of an ammonia injection pipe or a vertical direction of a cross-sectional center of the header pipe. The denitration apparatus according to claim 1,
A denitration apparatus, wherein a dynamic pressure of gas injected from the gas injection means is 670 Pa to 880 Pa on the bottom surface of the exhaust gas duct.

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