KR20060055088A - Nox reducing apparatus for exhaust gases from diesel engines - Google Patents

Abstract

The present invention provides a NOx purifying apparatus for reducing treatment of diesel engine exhaust gas NOx, comprising: spraying means for injecting ammonia water or urea water in a flow direction and a forward direction of exhaust gas through a spray nozzle extending from the outside to the inside; And a flow diffusion plate installed to be spaced apart from the spray nozzle and spaced apart from the spray nozzle so that the injected ammonia water is uniformly distributed in the NOx catalytic converter flue. It is a useful invention that can achieve the properties, to minimize the unreacted ammonia, and to make the catalyst-to-cycler flue gas velocity more uniform.

Diffusion plate, diesel engine, nitrogen oxide, exhaust gas

Description

NOx reducing apparatus for exhaust gases from diesel engines}

1 is a schematic diagram of a diesel engine exhaust gas NOx purifying apparatus according to the present invention;

2 is a perspective view of a flow diffusion plate employed in the diesel engine exhaust gas NOx purifying apparatus according to the present invention.

* Description of the drawing symbols *

1: engine, 25: exhaust manifold, 17: NOx catalyst

18: spray nozzle, 27: NOx catalytic converter, 28: exhaust pipe

29: reducing agent supply means, 31 injection pipe, 32 air tank

33: compressed air control valve, 34: ammonia supply pipe, 35: ammonia water tank

37: ammonia water supply, 117: flow diffusion plate

The present invention relates to a diesel engine exhaust gas NOx purifying apparatus including a NOx catalyst for purifying NOx in a diesel engine exhaust gas under an oxygen excess atmosphere.

BACKGROUND ART Exhaust gas NOx purifiers are known in which urea water is added to an exhaust gas flow generated from an internal combustion engine and ammonia generated by hydrolysis or ammonia by direct addition is used as a reducing agent of a selective reduction catalyst. . When the NOx purifier is mounted in a vehicle equipped with an internal combustion engine, a selective reduction catalyst (hereinafter referred to as an 'SCR catalyst') for converting NOx in the exhaust gas generated from the internal combustion engine into nitrogen or water under an oxygen excess atmosphere is disposed. And urea water or ammonia from the upstream side of the catalyst is injected into the exhaust gas as a reducing agent to supply the SCR catalyst.

As described above, the SCR catalyst having ammonia as a reducing agent has a higher NOx purification rate as the amount of ammonia adsorption increases, so it is preferable to control the amount of ammonia adsorption in the low temperature band, but there are problems such as ammonia slip. There is a limit to the amount of ammonia injected that can react with the catalyst.

Various means for solving the problem of adsorption amount in the low temperature band as described above are provided, in particular, according to Japanese Patent Application No. 2002-95987, NOx catalyst for adopting ammonia as a reducing agent and selectively reducing NOx in the exhaust gas Is installed in the exhaust system of the engine, the ammonia is supplied to the NOx catalyst from the reducing agent supply means, the NOx emissions from the engine detected or estimated by the NOx emission detection means, and the actual NOx catalyst detected by the NOx purification rate detection means. Adsorption amount detection means for detecting the ammonia consumption adsorbed on the NOx catalyst as a consumption detection means based on the NOx purification rate, and detecting the actual amount of adsorption adsorbed on the NOx catalyst, and the actual amount derived by the adsorption amount detection means. A system comprising a control means for controlling the reducing agent supply means in accordance with the amount of adsorption, While maintaining a high rate exposes the device to effectively suppress the generation of ammonia slim.

On the other hand, even if the problem of the low temperature band is solved, it is known that SCR catalyst performance can be significantly affected by non-uniform flue gas flow. Accordingly, NOx catalyst manufacturers are studying to have the maximum allowable nonuniformity of flue gas velocity at the SCR catalyst inlet, and the SCR system is currently operated to provide optimum values of flow and chemical uniformity. Therefore, design goals such as regional ammonia injection grids (AIG), static mixing, and flow compensators to provide flow conditions, include uniform flue gas velocity and uniform ammonia to NOx molar ratio at the SCR catalyst inlet. To create an environment. The purpose of the design is to eventually promote the effective use of ammonia and SCR catalysts while minimizing ammonia slip. Ammonia slip can affect the air heater clogging and the like. Korea Patent Publication No. 2001-47050 may be referred to as a technical prior art for improving the uniformity of the ammonia and nitrogen oxides. The patent application relates to an ammonia-water direct injection type nitrogen oxide treatment apparatus employed in the exhaust gas treatment equipment, by atomizing ammonia water in a direction opposite to the flow direction of the exhaust gas through a spray hole extending from the outside to the inside of the exhaust passage. Spraying means for injecting; And a main fixed mixer which is installed to be spaced apart from the spray hole and is distributed uniformly in the exhaust passage while the sprayed ammonia water passes through; It is provided with an ammonia-water direct injection type nitrogen oxide treatment apparatus employed in the exhaust gas treatment equipment that can improve the reaction efficiency and reduce installation manufacturing and operation maintenance costs. However, the apparatus is suitable for the method of treating the hot exhaust gas combusted in the waste incineration plant and the steam generation plant, and is not suitable for the treatment of diesel vehicles and diesel engine exhaust gas NOx.

It is an object of the present invention to provide a new system in which uniform flowability of exhaust gas and ammonia is ensured in diesel engine exhaust gas NOx treatment.

Another object of the present invention is to provide a novel apparatus for minimizing the consumption of reducing agent ammonia in diesel engine exhaust gas NOx treatment.

Accordingly, the NOx treatment apparatus having improved flow characteristics in the diesel engine exhaust gas NOx treatment includes spraying means for atomizing ammonia water in the flow direction and the forward direction of the exhaust gas through a spray nozzle extending from the outside to the inside; And a flow diffusion plate which is installed to be spaced apart from the spray nozzle and spaced apart from the spray nozzle so that the injected ammonia water is distributed evenly in the catalytic converter flue. It is made, including.

According to the invention, it is preferable that the flow diffusion plate is formed with a plurality of perforations of increasing diameter in the radial direction.

Various novelties which characterize the invention appear as a feature of the claims appended to the specification and which form part of the detailed description, in which specific advantages obtained by operating and applying for a better understanding of the invention are directed to embodiments of the invention. Reference is made to the accompanying drawings and the accompanying drawings.

1 illustrates a diesel engine exhaust gas NOx purifying apparatus as an embodiment. In Fig. 1, reference numeral 1 denotes a diesel engine mounted on a vehicle (not shown), and the diesel engine 1 is output controlled by an engine control device (not shown).

The NOx purifier is installed in an exhaust pipe 28 constituting the exhaust system following the exhaust manifold 25 of the engine 1 to selectively reduce and reduce NOx in exhaust gas, and the NOx catalyst 17. Flow diffusion plate 117 spaced apart at predetermined intervals at the inlet, and reducing agent supply means 29 for supplying ammonia to the NOx catalyst.

The NOx catalyst 17 is coated with a catalyst component on a honeycomb structured catalyst carrier and is housed in a casing of the NOx catalytic converter 27 provided in the exhaust pipe 28. As the selective reduction catalyst, the NOx catalyst 17 includes, but is not limited to, vanadium-based, platinum-based, zeolite-based, and the like. Normally NOx catalysts are equipped with a catalyst temperature sensor (not shown) that outputs the catalyst temperature.

Reducing agent supply means 29 is provided in the exhaust pipe 28, the spray nozzle 18 for spraying ammonia water toward the upstream opening side of the NOx catalytic converter 27, the injection pipe 31 connected to the spray nozzle 18 ), An air tank 32 connected to an upstream end of the injection pipe 31, a compressed air control valve 33 for controlling the supply of compressed air to the injection pipe 31, and a compressed air control valve 33. The ammonia water supply pipe 34 connected to the injection pipe at the downstream position, the ammonia water tank 35 containing the injection ammonia water, the ammonia water in the ammonia water tank 35 is adjusted from the ammonia water supply pipe 34 to the injection pipe 31 and The ammonia water supply part 37 to supply is provided. These compressed air control valves 33 and ammonia water supply unit 37 are connected to signal control means (not shown). Of course, the alternative configuration of the ammonia water may be urea water.

At the opening side of the NOx catalytic converter 27, a disk-shaped flow diffusion plate 117 having a plurality of perforations is mounted vertically. The plurality of perforations formed in the flow diffusion plate is different in diameter in the radial direction from the central portion, and preferably has a diameter in the radial direction from the center of the diffusion plate. The horizontal speed of the ammonia water injected from the spray nozzle 18 represents the maximum speed at the center of the flow diffusion plate 117, and the horizontal speed of the ammonia water injected radially from the center is reduced. Therefore, by forming a plurality of perforations of increasing diameter in the radial direction of the diffuser plate, a relatively large amount of ammonia water can pass through the flow diffusion plate 117 at a horizontal speed relatively reduced from the center portion, and the ammonia water Diffusion is promoted by a constant velocity of exhaust gas from the diesel engine. The flow diffusion plate 117 may be mounted perpendicular to the flow path direction of the exhaust gas and the ammonia water to generate a uniform flue gas velocity profile. Therefore, it acts to adjust the flue gas flow pattern in the NOx catalytic converter 27, so that the uniformity index of the exhaust gas and ammonia is greatly improved to 0.98 compared to 0.68 without the flow diffusion plate.

The flow diffusion plate 117 may have a structure in which a plurality of perforations having different diameters are formed in the flat plate as shown, but is not limited thereto. For example, the flow diffusion plate 117 may be configured as a network shape instead of a plate shape. The flow diffusion plate 117 according to the present invention may be mounted in a manner known to those skilled in the art, for example, may be installed in the same manner as the NOx catalyst 17 is mounted using an insulating material. .

Hereinafter, the operation of the NOx treatment apparatus according to the present invention will be described in detail.

Exhaust gas containing NOx from the diesel engine 1 flows through the exhaust manifold 25 in the direction indicated by the arrow in the figure.

At this time, the ammonia water is rapidly increased by the pressure of the ammonia water itself through the spray nozzle 18 along the supply path, and is injected into the exhaust pipe 28 in the same direction as the flow of the exhaust gas. The injected ammonia water is mixed with the exhaust gas and diffused to the front of the flow diffusion plate 117, while the central portion having the largest horizontal speed passes through the small diameter diffusion hole 200, while the horizontal speed is gradually decreased. The radial mixture passes through the diffusion perforation 300 having a larger diameter, and flows at a uniform distribution density in the front region of the NOx catalyst 17. In the NOx catalyst, ammonia and nitrogen oxides are converted into harmless nitrogen and water through denitrification and released to the outside.

According to the features of the present invention configured as described above, by installing a flow diffusion plate having a different diameter distribution in front of the NOx catalytic converter, it is possible to achieve the uniformity of the ammonia and the exhaust gas mixture, to minimize the unreacted ammonia In addition, the flue gas velocity of the catalytic rice exchanger can be made more uniform.

Claims (2)

CLAIMS 1. A NOx purifying apparatus for purifying diesel engine exhaust gas NOx by reduction reaction, comprising: spraying means for injecting ammonia water or urea water in a flow direction and a forward direction of exhaust gas through a spray nozzle extending from the outside to the inside; And a flow diffusion plate installed to be spaced apart from the spray nozzle so as to be uniformly distributed in the NOx catalytic converter flue while the injected ammonia water passes through the diesel engine exhaust gas. According to claim 1, The flow diffusion plate is a diesel engine exhaust gas NOx treatment apparatus, characterized in that a plurality of perforations are formed to increase the diameter in the radial direction.

Images