JPH0728908Y2 - Exhaust gas reducing agent spraying device - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas reducing agent spraying device used for purification of exhaust gas using a reducing catalyst.

[0002]

2. Description of the Related Art NOx in exhaust gas from diesel engines
Reduction is an urgent and important issue. At present, reduction of NOx generation by improving the engine side has reached a limit, and purification of exhaust gas, that is, denitration (reduction of NOx) using a reduction catalyst is required. As a reducing agent used in such a reduction reaction, ammonia gas,
Ammonia water and urea water are available. However, ammonia gas and ammonia water are dangerous substances and are restricted in handling from the viewpoint of occupational safety and health, so it is difficult to use for denitration in a small-to-medium-sized cogeneration system. Therefore, it was the current situation that the denitration device for diesel exhaust gas was difficult to spread in equipment of this scale.

[0003]

Since urea water is easy to handle without any danger, it is strongly desired to establish a technique for using urea water as a reducing agent for denitration. However, when trying to spray urea water by providing a spray nozzle in the exhaust pipe through which the high-temperature exhaust gas flows and after stopping spraying,
Due to the high temperature of the urea water in the supply pipe and in the spray nozzle, the water evaporates, and urea is precipitated or denatured and the pores of the nozzle are clogged. Especially the exhaust gas temperature is high,
When operating at a low denitration rate, there is a problem that the urea water itself has a small cooling effect because the amount of the urea water is small, and the urea water is clogged even when the urea water is flowing in the supply pipe.

An object of the present invention is to prevent clogging of a spray nozzle in a spray device for injecting urea water inside an exhaust pipe.

[0005]

The spraying device of the present invention is configured so that water can be selectively supplied from the middle of the supply pipe to the urea water spraying nozzle inside the exhaust pipe that guides the exhaust gas to the denitration reactor. There is.

[0006]

[0007]

[0008]

According to the spraying device of the present invention, the urea water can be expelled by spraying water in place of the urea water so that the precipitation or deterioration of the urea, which causes the clogging of the spray nozzle, does not occur. Further, water can be supplied immediately before the start of spraying to cool the supply pipe and the spray nozzle.

[0009]

EXAMPLE As shown in FIG. 1, a denitration reactor 3 having a catalyst is connected to an exhaust pipe 2 of a diesel engine 1. A NOx concentration measuring device 4 is provided at the outlet of the denitration reactor 3.

The exhaust pipe 2 is provided with a spraying device 5 for urea water, which is an exhaust gas reducing agent, for spraying urea water into the exhaust pipe 2.

The spraying device 5 is connected to a urea water supply unit 6. This supply unit 6 has a pure water device 7 for producing pure water from tap water, and a urea water supply tank 10 equipped with a flow rate control valve 8 and a pump 9, and the spray device 5 is supplied with pure water and pure water. Urea water can be supplied.

In the example shown in FIG. 2, the spraying device 5 has two sprayers 11, 11 projecting into the exhaust pipe 2, and a switching unit 12 for supplying urea water or pure water to these sprayers 11. is doing.

As shown in FIG. 2, the sprayer 11 is attached to a mounting port 14 of the exhaust pipe 2 by a mounting flange 13. As shown in FIG. 3, a supply pipe 15 is provided so as to penetrate the mounting flange 13, and the supply pipe 1
The tip side of 5 projects inside the exhaust pipe 2 in a direction orthogonal to the longitudinal direction of the exhaust pipe 2. And this supply pipe 15
A spray nozzle 17 is attached to the tip of the spray nozzle 17 via a holder 16, and the direction of the nozzle hole 18 of the spray nozzle 17 coincides with the longitudinal direction of the exhaust pipe 2.

The supply pipe 15 protruding into the exhaust pipe 2 is provided with the outer cylinder 1.
A heat insulating material 20 as a heat insulating portion is filled between the outer cylinder 19 and the supply pipe 15. The holder 16 and the spray nozzle 17 project outside the outer cylinder 19 through holes provided in the side peripheral wall of the outer cylinder 19.

As shown in FIG. 2, the switching unit 1
2 has two three-way valves 21 and 21. The urea water pipe 22 led from the supply unit 6 is branched into two via a filter and connected to one inlet of each of the three-way valves 21 and 21. The pure water pipe 23 led from the supply unit 6 is branched into two through a filter,
Each of the three-way valves 21 and 21 is connected to the other population. The outlets of the three-way valves 21 and 21 are connected to the supply pipes 15 and 15 of the sprayers 11 and 11, respectively.

With the above construction, when the diesel engine 1 is in operation, as shown in FIG.
Supplies urea water to the spraying device 5. The switching unit 12 of the spraying device 5 switches each of the three-way valves 21, 21 to the urea water supply side, and the spray nozzle 17 of each sprayer 11 sprays urea water into the exhaust pipe 2, whereby the denitration reactor 3 is discharged.
Then, NOx is efficiently reduced.

When the spraying of the urea water is started, the sprayer 11 in the exhaust pipe 2 is exposed to the hot exhaust gas and the supply pipe 15 and the spray nozzle 17 are at a high temperature. Since the pure water temporarily flows for a short time in advance and the supply pipe 15 and the spray nozzle 17 are cooled, even if urea water flows thereafter, urea is precipitated or denatured from the urea water and the spray nozzle 17 The nozzle hole 18 is not blocked. Therefore, the spray of urea water is stable, and thus the denitration performance of the denitration reactor 3 is also stable.

When the urea water remains in the sprayer 11 when the spraying is stopped, the urea water is dried by the ambient heat, and urea is deposited and deteriorated to close the nozzle hole 18. Therefore, in this embodiment, the three-way valves 21 and 21 of the switching unit 12 are switched to the pure water side before the start of spraying and after the spraying is finished, and the residual urea water in the sprayer 11 is expelled and replaced by pure water. As a result, it is possible to reliably avoid the inconvenience that the spray nozzle 17 is already closed at the start of denitration and spraying cannot be performed.

In this embodiment, two sprayers 11 are provided. Rather than providing one atomizer with a large cross-sectional area of the nozzle hole, providing two atomizers with the same total amount of spray produces finer spray particles and improves denitration performance. There is an advantage that it can be done. Further, when the load of the diesel engine 1 is small and the supply amount of urea water may be small, the one-way valve 21 of the switching unit 12 may be closed and only the one atomizer 11 may be used.

FIG. 4 shows another structural example of the atomizer in the above-mentioned embodiment. In this sprayer 30, a supply pipe 31 to which urea water or water is supplied is provided at the center of the inside of a cylindrical outer cylinder 32. The base end 31a of the supply pipe 31
Is attached to the outer cylinder in a state of protruding from one end surface of the outer cylinder 32, and can be connected to the switching unit 12 side. A spray nozzle 34 is attached to the tip of the supply pipe 31 via a holder 33. The holder 33 and the spray nozzle 34 project from the side peripheral wall of the tip of the outer cylinder 32 to the outside of the outer cylinder 32. It is attached to 32. Further, a pair of partition plates 36 is provided between the inner peripheral surface of the outer cylinder 32 and the outer peripheral surface of the supply pipe 31.
The partition plate 36 extends along the longitudinal direction of the supply pipe 31 from the inner surface of one end surface of the outer cylinder 32 to the vicinity of the holder 33. As a result, the outer cylinder 32 and the supply pipe 3
The space between 1 is divided into two cooling chambers that communicate with each other, and is a forced cooling unit 40 to which a cooling fluid is circulated and supplied. The outer cylinder 32 is provided with a mounting flange 35 that is fixed to the mounting port 14 of the exhaust pipe 2. Further, at the time of mounting, the base end of the outer cylinder 32, which is outside the exhaust pipe 2, is attached to the outer cylinder 32. An inlet 37 and an outlet 38 for the cooling fluid that communicate with the inside are provided.

When the atomizer 30 is attached to the exhaust pipe 2 and is used for urea supply during denitration, the cooling fluid is supplied from the inlet 37 of the outer cylinder 32 and the cooling fluid is discharged from the outlet 38 to supply the pipe 31. The urea water supplied inside is forcibly cooled.

[0022]

[0023]

EFFECTS OF THE INVENTION According to the exhaust gas reducing agent spraying device of the present invention, since the supply pipe through which the urea water is passed is cooled by pure water immediately before the start of spraying, urea is precipitated by the heat of the exhaust gas.
No alteration is observed and the spray nozzle is not blocked. Further, since the residual urea water in the sprayer can be replaced by supplying water even after the spraying of the urea water is stopped, it is possible to prevent the nozzle from clogging due to the precipitation and deterioration of urea.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of a spraying device in the embodiment.

FIG. 3 is a cross-sectional view of a sprayer according to the same embodiment.

4A is a cross-sectional view showing another configuration example of the sprayer according to the embodiment, and FIG. 4B is a cross-sectional view taken along the line bb of FIG. 4A.

[Explanation of symbols]

 2 Exhaust pipe 3 DeNOx reactor 15,31 Supply pipe 17,34 Spray nozzle 20 Adiabatic part as adiabatic part 40 Forced cooling part

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location F01N 3/08 B B01D 53/34 ZAB (72) Inventor Hisao Tanabe 125-Nishishinmachi, Ota-shi Gunma 1 Niigata Iron Works Co., Ltd., Experimental Research Department, Motor Business Division (56) References JP-A-64-47427 (JP, A) JP-A-53-26761 (JP, A) Special Table 1-502495 (JP, A) )

Claims (1)

[Scope of utility model registration request] 1. An exhaust gas reducing agent spraying device configured to selectively supply water to a urea water spraying nozzle provided inside an exhaust pipe for guiding exhaust gas to a denitration reactor.