JP3295419B2 - Ammonia supply to denitration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a device for supplying ammonia to a denitration device,
In particular, the present invention relates to an ammonia supply device for a denitration device for removing nitrogen oxides in exhaust gas from a cogeneration device installed in an urban area.

[Conventional technology]

Air pollution due to nitrogen oxides (hereinafter simply referred to as NOx) is becoming more serious year by year, and large-scale exhaust gas sources such as commercial boilers have not only improved the conventional combustion, but also used NH ₃ as a reducing agent to reduce the amount of denitration catalysts. Removes NOx in exhaust gas in the presence of
Plants equipped with a dry contact denitration apparatus that performs a so-called denitration function are increasing.

On the other hand, in small-scale cogeneration systems such as small gas turbines and small diesels (hereinafter simply referred to as cogeneration), installation of denitration equipment is being obliged to prevent air pollution by NOx.

FIG. 7 is a typical flue duct system diagram of a commercial boiler in which a denitration device is installed.

In the figure, the combustion air in the air duct 18 is a forced air fan.
The pressure is increased by 19 and exhaust gas duct 21 by air preheater 20
After being heated by the exhaust gas, the air is supplied from the wind box 22 to the boiler 23. Further, the exhaust gas burned in the boiler 23 flows through the exhaust gas duct 21, is mixed with NH ₃ injected from the NH ₃ injection pipe 24, and is denitrated by the denitration catalyst 26 in the denitration device 25 arranged downstream, and After the NOx is removed, the pressure is increased by the induction ventilator 27 through the air preheater 20 and the exhaust gas duct 21 and released to the atmosphere.

On the other hand, liquid ammonia as a reducing agent
From 28 enters the vaporizer 29, where it is vaporized into NH ₃ gas,
It is mixed with the dilution air from the branch air duct 31 by the dilution mixer 32, diluted below the explosion limit, and injected into the exhaust gas of the exhaust gas duct 21 from the NH ₃ injection pipe 24.

In FIG. 7, 33 is an oil burner, 34 is a pulverized coal burner, 35
Is a coal hopper, 36 is a coal feeder, and 37 is a mill.

By the way, in a large-scale exhaust gas source such as a commercial boiler, it is better to install the storage tank 28, the vaporizer 29, etc. as an accessory because it consumes a large amount of liquid ammonia as a reducing agent. As described above, it is not preferable to use liquid ammonia as a reducing agent in small-scale exhaust gas generation sources such as cogeneration. It is a liquid ammonia storage tank 2
8.If the vaporizer 29 is installed as an auxiliary equipment, the cost of the auxiliary equipment in the cogeneration plant will increase.On the other hand, the storage tank for liquid ammonia will be regulated as a high-pressure vessel, and liquid ammonia will be used for cogeneration from the viewpoint of safety. Are not preferred as reducing agents.

Therefore, there is a tendency to use ammonia water, which is safer than liquid ammonia, as a reducing agent for cogeneration. Ammonia water is a solution in which 25 to 30% by weight of ammonia is dissolved. When used as a reducing agent in a denitration device for cogeneration, ammonia is separated from water and used, or ammonia water is evaporated. And used as a gaseous reducing agent.

However, the former method of separating NH ₃ and water and using NH ₃ as a reducing agent requires a separation means for separating NH ₃ and water, which is not preferable because it requires time and effort for separation. Therefore, for cogeneration, it is common to evaporate and vaporize the latter NH ₃ water and use this as a reducing agent for cogeneration. An example of the latter is shown in FIG.

Exhaust heat recovery boiler 11 duct exhaust gas 1 with fan 13
The NH ₃ water is drawn into the NH ₃ water evaporation chamber 14, and the NH ₃ water 2 from the NH ₃ water supply pipe 38 and the spray air 3 from the spray air supply pipe 39 are supplied and sprayed. The returned NH ₃ gas is returned into the duct from the NH ₃ injection pipe 17 again,
This is a process for decomposing NOx by the denitration catalyst 12. Exhaust gas 1
Is usually selected to be 350 to 400 ° C. in consideration of securing the heat quantity of NH ₃ vaporization and the piping material.

Fig. 5, shows a prior art aqueous NH ₃ evaporation chamber is an enlarged view of the NH ₃ water evaporation chamber 14 of Figure 6. NH ₃ NH ₃ water 2 from the water supply pipe 38, the atomizing air 3 from the atomizing air supply pipe 39 is atomized as a medium, a spray nozzle 4, NH ₃ as ammonia particles 9 through the blowout portion 5 It is sprayed into the water evaporation chamber 14.
Then, the sprayed NH ₃ water 9 is vaporized by the exhaust gas 1.

Here, the following two points can be cited as problems of the related art.

1. The spray nozzle 4, the blowout section 5, the NH ₃ supply pipe 38, and the spray air supply pipe 39 are connected by screwing.
The high temperature gas in the NH ₃ water evaporation chamber 14 repeatedly expands and contracts due to heat, so that a gap is formed in the threaded portion, and NH ₃ water 2 leaks out from this gap to become a drain and becomes a drain.
The water drops or flows down into the inside, and the necessary NH ₃ is not vaporized, which hinders the operation of the denitration apparatus.

2. The above screwed portion where the NH ₃ water 2 comes in contact with the exhaust gas 1 in a liquid state, and the SO ₃ in the exhaust gas at the nozzle blowing portion 5
Is SO ₃ + NH ₃ + H ₂ O → NH ₄ HSO ₄ and becomes acidic ammonium sulphate, and NO ₂ in exhaust gas becomes NH ₃ compound such as 2NO ₂ + 2NH ₃ → NH ₄ NO ₃ + N ₂ + H ₂ O Dust and the like adhere to the nozzles, causing nozzle clogging and pipe corrosion.

[Problems to be solved by the invention]

Although the above prior art has the advantage of evaporating and evaporating NH ₃ water using exhaust heat of exhaust gas, the components in the exhaust gas, especially NO ₂ , SO ₃ , dust, etc., combine with NH ₃ No consideration has been given to the problem of producing NH ₃ compounds and blocking the spray nozzle, and NH ₃
It also remained unresolved in terms of water dripping and drain leakage.

An object of the present invention is to remedy the above-mentioned disadvantages of the prior art,
An object of the present invention is to provide an ammonia supply device for a denitration device for cogeneration having a highly reliable NH ₃ water spray nozzle.

[Means for solving the problem]

An object of the present invention described above is to connect an evaporator for evaporating ammonia water, an apparatus for supplying combustion exhaust gas at a predetermined temperature to the evaporator, and an ammonia water supply pipe and a spray air supply pipe provided in the evaporator. A spray nozzle that sprays ammonia water into the evaporator with air, and a device that supplies the ammonia component vaporized in the evaporator to the denitration apparatus, wherein a device that covers an outer periphery of the spray nozzle with an air curtain by spray air is provided. An ammonia supply device to a denitration device, characterized by being provided, and an evaporator for evaporating ammonia water, a device for supplying combustion exhaust gas into the evaporator, and provided in the evaporator,
And a spray nozzle connected to the ammonia water supply pipe and the air supply pipe for spraying, and spraying ammonia water to the evaporator with air, wherein the ammonia component vaporized in the evaporator is supplied to the denitration apparatus, A guide that covers the connecting portion of the spray nozzle with the ammonia water supply pipe and the spray air supply pipe and that has an opening at the outer periphery of the nozzle outlet is provided, and a device for supplying air for the air curtain is provided in the guide. This is achieved by an apparatus for supplying ammonia to a denitration apparatus characterized by the following.

[Action]

In the present invention, in Eyakaten of pressurized air, by shielding from the exhaust gas nozzle unit, generates an NH ₃ compound compound and the component and NH _3, such as (1) NO _2, SO ₃ in the exhaust gas Can be prevented.

(2) The nozzle portion has two functions of preventing direct exposure to high-temperature exhaust gas. The former function can prevent the spray nozzle blowing portion from being blocked by an NH ₃ compound. In addition, the latter function makes it difficult for the screw portion to have a gap due to thermal expansion and contraction, and makes it difficult for drain NH ₃ to leak from the screw portion. In the unlikely event of leakage, the problem of drain leakage can also be solved by blowing off with pressurized air and vaporizing with exhaust heat of exhaust gas.

〔Example〕

FIG. 1 is an enlarged view of an NH ₃ water injection nozzle according to one embodiment of the present invention. The overall process flow is as described in FIG.

This embodiment, NH ₃ in the NH ₃ water evaporation chamber 14 of Figure 6
It is related to the water spray nozzle, and differs from the prior art NH ₃ water injection nozzle shown in FIG. 5 in that the air blowing hole 6 is provided in the spray air supply pipe 39. As shown in FIG. 1, the outside of the spray nozzle 4 and the blowing section 5 is covered with an air curtain 8 by the air from the air blowing hole 6. This air curtain 8 cools the screwed parts such as the spray nozzle 4 and the blow-out part 5, the NH ₃ water supply pipe 38, the spray air supply pipe 39, etc., so that the leakage of ammonia water due to the difference in elongation is eliminated. Even if it does, since it does not come into direct contact with the exhaust gas 1 in the vicinity of the screwed portion, no NH ₃ compound is generated.

FIG. 1A is an enlarged view of an NH ₃ water injection nozzle according to another embodiment of the present invention. The difference from the embodiment shown in FIG. 1 is that a guide 7 covering the spray nozzle 4 is provided. One end of the guide 7 is fixed to the spray air supply pipe 39 by welding. This is NH from the threaded part of guide 7
₃ To prevent water leakage. On the other hand, it is desirable that the other end has an opening end substantially at the same position as the blowing section 5 of the nozzle. This is because if the length of the guide 7 is short, the air curtain 8 becomes unstable, and if it is too long, the sprayed NH ₃ water collides with the inner surface of the guide 7 to generate droplets.

The NH ₃ water 2 is sprayed from the spray nozzle 4 by the spray air 3. On the other hand, the air for forming the air curtain 8 is discharged from the air blowing holes 6 and covers the outer surface of the spray nozzle 4. If there is NH ₃ water 2 leaking to the outer surface of the spray nozzle 4, the NH ₃ water 2 is blown off. Is released into the guide 7 while covering the blow-out portion 5. Spray air 3
5 kg of air for chores in a plant of about 5 to 10 kg / cm ² g
The pressure is reduced to not more than / cm ² g, and the pressure of the NH ₃ water 2 is balanced so as to be substantially the same as the spray air pressure.

As described above, since the outer circumferences of the spray nozzle 4 and the blowing section 5 are covered by the air curtain 8 and the guide 7, direct contact with the exhaust gas 1 is eliminated, and generation of an NH ₃ compound can be prevented.

The diameter of the air blowing hole 6 must maintain the required spray air pressure.
Is smaller than the opening of the blowing section 5. In other words, the speed of the blown air is faster in the air blowout hole 6 in the guide 7 than in the blowout portion 5, and this high-speed air collides with the inner wall of the guide 7 or is reflected from the inner wall of the guide 7, Eventually, an air curtain 8 is formed along the inner wall of the guide 7. This air curtain 8 is sprayed NH
From the blowing unit of ₃ 9, the part of the number 10 centimeters can be thermally shielded from the exhaust gas 1.

FIG. 2 shows the precipitation temperature range of a compound of SO ₃ and NO ₂ components and NH ₃ in the exhaust gas. At 350-400 ° C exhaust gas temperature,
It can be explained that NH ₄ NO ₃ and NH ₄ HSO _{4 in the} gaseous state are easily formed by the spray nozzle 4 cooled below the deposition temperature. Therefore, the above-mentioned shielding of the NH ₃ water around the blowing portion in the low temperature region from the exhaust gas by the air curtain 8 has an effect of preventing the generation of the NH ₃ compound in the nozzle portion.

Further, the spray nozzle 4 described in the section of the problem of the prior art is used.
Also, for the NH ₃ water leaking from the threaded portion, by shielding the threaded portion from the high-temperature exhaust gas, a gap is hardly generated, and the leaked NH ₃ can be minimized. In the unlikely event of leakage, it can be dealt with by holding it with the guide 7 and blowing it off with high-speed air from the air blowing hole 6.

FIG. 3 is an explanatory view of another effect of the present embodiment, that is, improvement of the NH ₃ water spraying ability. In the present embodiment and the prior art, the point of the opening width 1 of the spray NH ₃ is set at a distance from the nozzle. This is a comparison. The air curtain 8 formed by the guide 7 hits the spray NH ₃ 9 at high speed, and the hit disturbs the shape of the spray NH ₃ 9. The disorder of the shape is
This has the effect of shortening the mixing distance between the spray NH ₃ 9 and the exhaust gas 1,
(L ₁ <L _{2 in the} figure) The performance of the NH ₃ water evaporation chamber 14 can be improved or downsized.

FIG. 4 shows another embodiment of the present invention. In place of the air blowing hole 6 shown in FIG.
This is an example in which is provided. This is effective when the atomizing air supply pipe 39 is small and it is difficult to open a plurality of air blowing holes 6 as shown in FIGS. 1 and 1A.

In the embodiment shown in FIG. 4, the same effects as those of the embodiment described with reference to FIGS. 1 and 1A can be obtained.

〔The invention's effect〕

According to the present invention, NH ₃ in the ammonia water evaporator
It is possible to provide a highly reliable NH ₃ water spray nozzle without blocking the hole of the water spray nozzle and preventing the leaked NH ₃ water drain from the nozzle screw portion from accumulating at the bottom of the chamber. In addition, the regular maintenance work of the nozzle which has been conventionally performed becomes unnecessary, and the plant can be operated continuously for a long period of time.

[Brief description of the drawings]

1 and 1A are side views of an ammonia water spray nozzle according to an embodiment of the present invention. FIG. 2 is a view showing a deposition temperature of a compound in which exhaust gas components SO ₃ and NO ₂ are formed with ammonia.
Fig. 5 is a comparison diagram of the sprayed ammonia water mixing distance between the device of the present invention and the conventional device, Fig. 4 is a diagram of another embodiment of the present invention, Fig. 5 is a side view of a conventional ammonia water spray nozzle, and Fig. 5A is FIG. 5 is a partially enlarged view, FIG. 6 is a system diagram of a denitration process using an ammonia water spray nozzle, and FIG. 7 is a system diagram of a business boiler provided with a denitration device. 1 ... exhaust gas, 2 ... ammonia water, 3 ... spray air, 4 ... spray nozzle, 5 ... blowout section, 6 ... air blowout hole, 7 ... guide, 8 ... air curtain (air zone) ), 9 ... spray ammonia water, 10 ... deposits,
11: Waste heat recovery boiler, 12: Catalyst, 13: Fan, 14
… Ammonia water evaporation chamber, 15… Ammonia water tank, 16… Vaporized ammonia, 17… Ammonia injection pipe, 38… Ammonia water supply pipe, 39… Spray air supply pipe.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoshinori Nagai 6-9 Takara-cho, Kure-shi, Hiroshima Pref. Inside the Kure Plant of Babcock Hitachi Ltd. (56) References JP-A-52-16472 (JP, A)

Claims (2)

(57) [Claims] 1. An evaporator for evaporating ammonia water, a device for supplying combustion exhaust gas at a predetermined temperature to the evaporator, and an ammonia water supply pipe and a spray air supply pipe provided in the evaporator and connected to the ammonia water supply pipe. A spray nozzle for spraying the air into the evaporator with air, and a device for supplying the ammonia component vaporized in the evaporator to the denitration device, wherein a device for covering the outer periphery of the spray nozzle with an air curtain by spray air is provided. An ammonia supply device for a denitration device. 2. An evaporator for evaporating ammonia water, a device for supplying combustion exhaust gas into the evaporator, and an ammonia water supply pipe provided in the evaporator and connected to an ammonia water supply pipe and a spray air supply pipe. A spray nozzle for spraying water to the evaporator with air, for supplying the ammonia component vaporized in the evaporator to the denitration apparatus, wherein a connection portion of the spray nozzle with the ammonia water supply pipe and the spray air supply pipe is provided. An ammonia supply device for supplying air to the denitration apparatus, wherein a guide that covers the outer periphery of the nozzle and that opens at the outer periphery of the nozzle outlet is provided.