JPH0150445B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flue gas denitrification device. In particular, the present invention relates to a flue gas denitrification device that denitrates exhaust gas from gas turbines used in thermal power generation and the like.

This type of power generation system is used in plants that generate power using only gas turbines, or in so-called combined power generation systems that utilize energy effectively by recovering heat from gas turbine exhaust gas in a heat recovery boiler to drive a steam turbine. It is used for denitration of flue gas from gas turbine exhaust in plants and other plants.

However, with conventional technology, the problem remains that denitrification is incomplete, or conversely, the denitrification liquid used for denitration is discharged unreacted, making it insufficient in terms of environmental measures. . In addition, in order for the denitrification solution to have a sufficient denitrification effect, sufficient adjustment is required for the injection of the denitrification solution, which currently requires a great deal of labor and time.

Hereinafter, the problems of the conventional technology will be explained in more detail using a conventional device in a combined type power generation plant as an example.

In the conventional example shown in FIG. 1, as shown in the figure, air pressurized by a compressor 1 of a gas turbine is once combusted in a combustor 2 to become a high-pressure and high-temperature gas, and at this time, nitrogen oxides ( (hereinafter referred to as NOx)
enters the gas turbine 3 while containing (In addition, lower the temperature of the flame in combustor 2 by cooling with water etc.)
Although there is a technique to prevent NOx generation, the present invention does not adopt that technique because it reduces turbine efficiency.) The combustion gas performs work in the turbine 3, but enters the boiler 6 via the exhaust gas duct 5, with the gas components remaining unchanged. Heat is recovered from the exhaust gas in the boiler 6, that is, the exhaust heat is used to generate steam, and this steam is used to drive the steam turbine. Furthermore, the exhaust gas is released into the atmosphere from the chimney 7. 4 is a generator.

As shown in FIG. 2, denitrification is normally accomplished by the action of a catalyst 8 installed within the boiler 6 at an appropriate temperature range (temperature range where the activity of the catalyst is at its highest). That is, NOx is reduced in the gas phase by this catalyst 8 and released into the atmosphere as nitrogen gas (N ₂ ). At this time, ammonia gas (or mist ammonia water, hereinafter referred to as NH ₃ ) is usually injected from upstream of the catalyst 8 as a reducing agent. This injection is carried out into the boiler 6 via the NH ₃ injection pipe 9 and the injection nozzle 10 provided in the pipe 9. Usually, a plurality of injection pipes 9 are installed in the boiler 6, and the number is determined by the dimensions of the duct of the boiler 6, the amount of NOx, etc.

Figure 3 shows the NH ₃ installed inside the boiler duct 6'.
The situation of the injection tube 9 is shown. _This figure shows a situation in which the injection pipes 9 are arranged perpendicularly to the boiler duct 6' _.
It is ejected from the injection nozzle 10, mixes with exhaust gas, and reaches the catalyst layer 8. Note that, depending on the relationship between the components of the exhaust gas and the denitrification rate, the injection pipes 9 may be arranged in several rows.

The most important thing in terms of denitrification performance in such a denitrification device is that the concentration of NH ₃ in the boiler duct 6' is uniformly diffused in all parts of the cross section of the duct 6' and flows into the catalyst layer 8 at a uniform concentration. It is important to take this into account.

If this is not met, (1) the denitrification performance of the catalyst is insufficient;
The number of reduced moles of NOx decreases.

...(When NH ₃ is low) (2) Reduction is sufficient, but exhaust gas mixed with HN ₃ is released into the atmosphere at the catalyst outlet.

... (in the case of excess _HN3 ), etc. problems occur, and this is insufficient as an environmental measure.

Moreover, generally speaking, as the size of the duct increases, the velocity distribution and its direction within the duct often lack uniformity, so the above-mentioned problem tends to be exacerbated. Conventionally, as a countermeasure for this, the flow velocity distribution and its direction in the duct are measured, the arrangement of the injection pipes 9 and the settings of the nozzle 10 are made accordingly, and the NH ₃ concentration is measured downstream and fine adjustments are made _. The concentration was made uniform. However, in reality, the duct size is several meters.
Because the duct is large and the temperature is over 300℃, measurement itself is not easy, and adjusting the concentration uniformity based on the measurement requires a great deal of effort and time. .

The present invention eliminates the above-mentioned drawbacks, has a simple structure, can easily achieve a uniform NH ₃ concentration without measuring the flow velocity in the duct, its direction, etc., and performs complete denitrification. The purpose of the present invention is to provide a flue gas denitrification device that does not release NH ₃ as it is.

In order to achieve this objective, the present invention is equipped with an ammonia injection nozzle, and a partition plate is provided in the axial direction of the injection pipe through which the denitrification liquid containing ammonia as an effective main component is injected into the exhaust gas. The injection nozzle is positioned symmetrically with respect to the partition plate, and the injection pipe is rotatably provided so that the emission direction of the injection nozzle can be arbitrarily set.

An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 4, the flue gas denitrification device of this example is provided with an injection pipe 9 for injecting a denitrification liquid (ammonia water, etc.) containing ammonia as the main active ingredient into the exhaust gas G. Ammonia injection nozzle 1
0, and the injection pipe 9 is provided with a partition plate 11 in the axial direction as shown in FIGS. 5 and 6, and the injection nozzle 10 is positioned symmetrically with respect to this partition plate 11. . Furthermore, the injection pipe 9 is made rotatable as shown by arrow A in FIG. 4, so that the direction of ejection of the injection nozzle 10 can be set arbitrarily.

With this configuration, the flow direction of the exhaust gas G and the partition plate 11 can be placed in a parallel positional relationship, and the amount of radiation from each injection nozzle 10 can be made to correspond to the flow amount of the exhaust gas G. Can be done. For example, in the example shown in FIG. 7, the partition plate 11 partitions the injection tube 9 into halves, and a pair of injection nozzles 10 are formed facing each other with respect to the partition plate 11. Pressure P ₁ of each part,
Since P ₂ becomes P ₁ = P ₂ , both nozzles 10
The amount of emitted water is equal and proportional to the flow, making uniform injection possible. Therefore, even if the flow rate is not particularly measured, the liquid is always ejected in accordance with the flow rate, so it is possible to achieve uniformity of the NH ₃ concentration with just this configuration.

That is, this effect will be explained in more detail in accordance with this example as follows.

First, the specific configuration of this embodiment will be explained in detail as follows. That is, as mentioned above, the NH ₃ injection pipe 9 of this example has a partition plate 11 in the axial direction at the center thereof, dividing the cross-sectional area into two. Then, the connecting portion between the partition plate 11 and the injection pipe 9 is processed so that there is no communication between the two divided spaces.
The NH ₃ nozzle 10 is installed at a position close to the diameter perpendicular to the partition plate 11 and symmetrically about the partition plate 11. Naturally, a plurality of nozzles are provided along the axial direction at a certain predetermined pitch.

Such an injection pipe 9 is provided at an appropriate location after the exhaust gas, but in this example, this injection pipe is set in the boiler duct. In this case, the partition plate 11 is set to be substantially parallel to the flow direction. The setting method is 2.
The pressure in each divided chamber is measured using a water column manometer or the like, and after rotating the injection tube so that P ₁ =P ₂ as shown in FIG. 7, it is fixed via a seal 5. Naturally, the direction of this flow is different for each injection tube in the duct, so it is necessary to perform the same operation for each injection tube. However, the process is extremely simple and requires little time and effort.

When configured as described above, NH 3 is ejected from the NH ₃ nozzle 10 provided symmetrically with the partition plate 11.
The amount of NH ₃ is ejected in an amount proportional to the flow velocity in the duct near each nozzle 10 for the following reasons. As a result, the NH ₃ concentration distribution becomes almost uniform in the cross section.

The reason for this is as explained below. That is, as shown in FIG. 8, the flow velocity of the fluid upstream of the cylinder is V.
(When the pressure is P ₀ ), the pressure P on the cylindrical wall surface that corresponds to the central angle θ can generally be expressed by the following equation.

(P-P ₀ )/ρ/2V ² =1-4sin ² θ ∴P=P ₀ +ρ/2V ² (1-4sin ² θ) (Here, ρ is the fluid density.) Now, in the injection tube If the pressure of NH ₃ gas is P , the amount of NH ₃ ejected from the nozzle (Q) is (Here, A is the nozzle cross-sectional area.) Now, if P-P ₀ = ΔP = αρ/2V ² Therefore, the amount of NH ₃ ejected from one nozzle can be made proportional to V, that is, the upstream velocity near each nozzle (α is a constant). At this time, the NH ₃ gas pressure in the injection pipe should be selected as P = P ₀ + αρ/2V ² , where α is determined in relation to the nozzle cross-sectional area A, taking into account the denitrification rate, the limit on the outflow NH ₃ concentration, etc. It is of the nature that it should be done. In addition, as for the value of θ in Fig. 8 that displays the nozzle position, ΔP is largest near 90°, so the fifth
The examples shown in FIG. 6 are optimal. Furthermore, when the injection tube 9 is formed in a cylindrical shape, the maximum flow velocity along the cylinder surface is around θ=90°, so
This configuration promotes diffusion of the injected liquid to the surroundings, leading to the advantage that the distance to the catalyst layer 8 can be shortened.

However, even if it is not formed at around 90 degrees, as long as it is symmetrical about the partition plate 11, the outflow from the nozzle 10 will be proportional to the exhaust gas flow velocity, so the basic purpose of making the concentration uniform will not be achieved. However, when forming a larger number of nozzles on one circumference instead of one pair, θ=
It may be better not to angle it at 90°.

Further, in the above configuration, as a result of providing the partition plate 11, the strength of the injection tube 9 is also increased, which is effective from the viewpoint of reinforcing the strength.

In the above example, the injection pipe 9 is installed in the boiler duct 6' to perform denitration there, but the injection pipe 9 may be installed in the exhaust gas duct 5 and denitration can be performed there. In plants that use a single gas turbine rather than a combined plant,
Since the exhaust gas is directly discharged without being led to the boiler 6, in that case, denitrification will be performed in the exhaust gas duct 5 as described above.

Moreover, although the above example was constructed using the catalyst 8, it goes without saying that the present invention can also be used in an embodiment in which the catalyst 8 is not used.

As described above, in the flue gas denitrification device of the present invention, the injection pipe having the ammonia injection nozzle is provided with a partition plate in the axial direction, the injection nozzle is positioned symmetrically with respect to the partition plate, and the injection pipe is The feature is that the injection nozzle is rotatable and the emission direction of the injection nozzle can be arbitrarily set. Since the ammonia concentration within the device can be made uniform, denitrification can be achieved extremely easily and reliably, and as a result, ammonia for denitrification is prevented from being released as is, which is advantageous in terms of strength. It has the following.

It should be noted that, as a matter of course, the present invention is not limited to the illustrated embodiment.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing the configuration of a general combined cycle power generation device. 2 and 3 show the prior art, FIG. 2 is a schematic diagram of the denitrification device, and FIG. 3 is a perspective view of the internal configuration showing the detailed structure of the denitrification device. FIG. 4 is a perspective view of the internal structure of a denitrification device according to an embodiment of the present invention, FIG. 5 is a sectional view of its injection tube, and FIG. 6 is a perspective view of its injection tube. FIG. 7 and FIG. 8 are explanatory diagrams for showing the operation of this embodiment. 3... Gas turbine, 5... Smoke exhaust duct, 6... Boiler, 8... Denitration catalyst, 9... Injection pipe, 10... Injection nozzle, 11... Partition plate.

Claims (1)

[Scope of Claims] 1. In a flue gas denitrification device that denitrates exhaust gas after gas combustion of a gas turbine, an injection pipe is provided for injecting a denitrification liquid containing ammonia as an effective main component into the exhaust gas, and the injection pipe has a plurality of ammonia injection nozzles, and the injection pipe is provided with a partition plate in the axial direction so that the injection nozzle is positioned symmetrically with respect to the partition plate, and the injection pipe is rotatably provided to control the injection. A flue gas denitrification device characterized by having a configuration in which the emission direction of a nozzle can be arbitrarily set. 2. The exhaust gas denitrification device according to claim 1, wherein the exhaust gas is heat-recovered and used to drive a steam turbine. 3. The injection pipe is attached to a smoke exhaust duct, the smoke exhaust duct is equipped with a denitration catalyst, and the injection nozzle injects ammonia into the flue gas from upstream of the denitration catalyst. A flue gas denitrification device according to claim 1 or 2. 4. The injection pipe is attached to a flue gas duct or a boiler subsequent to the flue gas duct, and the flue gas duct or boiler is equipped with a denitrification catalyst, and the injection nozzle injects ammonia into the flue gas from upstream of the denitrification catalyst. 3. The flue gas denitrification device according to claim 2, wherein the exhaust gas denitrification device is an injector. 5. The flue gas denitrification device according to any one of claims 1 to 4, wherein the injection pipe has a cylindrical shape or a shape close to that. 6. The flue gas denitrification device according to any one of claims 1 to 5, wherein the partition plate is installed at a position that equally divides the cross-sectional area of the injection pipe. .