JPH0988558A - Nox removal system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the lowering of an NOx removal effect caused by non- uniform of gas density due to drift and turbulent flow of exhaust gas led to flow into the reactor of an NOx removal system. SOLUTION: A rectifying layer 15 is arranged in a reactor 1 so that gas flow velocity is uniformed as well as to rectify drift and turbulent flow of exhaust gas led to flow into the reactor 1 which is positioned between an exhaust gas introducing part 9 and an NOx removing agent 2, in an NOx removal system in which the NOx removing agent 2 consisting of a catalyst formed in a honeycomb-shape is laminated and arranged inside the reactor 1, and the exhaust gas G is led to flow from the introducing part 9, and at the same time, a reducing agent is sprayed from a nozzle 14 so that nitrogen oxides in the exhaust gas is removed on the basis of a contact reduction process. An upper plate 16 and a lower plate 17 to which many holes are opened are arranged on the rectifying layer 15 at a predetermined interval, and many spherical bodies 18, 18 are arranged to be stratified in parallel within this interval.

Description

Detailed Description of the Invention

[0001]

The present invention relates to relates to a denitration apparatus for removing nitrogen oxides contained in the exhaust gas of an internal combustion engine or the like (NO _X).

[0002]

2. Description of the Related Art Conventionally, NO _X treatment technology has been required in various fields. For example, NO _X present in exhaust gas of a diesel engine or the like is harmful to the human body and causes acid rain. since a technique for processing the NO _X in these exhaust gases efficiently is desired.

Generally, the above-mentioned NO _X treatment method has been put into practical use as a flue gas denitration technique. This flue gas denitration technology is roughly classified into a dry method and a wet method. At present, the selective catalytic reduction method, which is one of the dry methods, has been technically preceded, and is attracting attention as an effective denitration method.

The main reaction of the selective catalytic reduction method is as follows.

4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O (1) In this reaction, ammonia, hydrocarbon, and carbon monoxide are used as a reducing agent. since oxygen is removed selectively NO _X even coexist, it is effectively used to remove of the NO _X contained in the exhaust gas such as a diesel engine.

As an example of the above-mentioned denitrification apparatus, as shown in FIG. 4, a large number of denitrification agents 2 and 2 made of a honeycomb catalyst are arranged and laminated inside a closed reactor 1.
The exhaust gas G is introduced from above the reactor 1, and at the same time, the reducing agent stored in the tank 4 is sprayed from the nozzles 3 and 3 to perform the catalytic reduction based on the above formula (1). There is. As a catalyst constituting the denitration agent 2, a noble metal such as platinum or various metal oxides supported on alumina, titanium oxide (TiO ₂ ) or the like is used.

In the above example, in order to enhance the diffusion effect of the exhaust gas G and to prevent the nozzles 3 and 3 from overheating, a large number of holes called punching metal are opened on the upstream side of the nozzles 3 and 3. There is also known an example in which a plurality of plate bodies are arranged at appropriate intervals and exhaust gas is allowed to pass through the holes in the plate bodies.

[0008]

However, in such an example of the conventional denitration apparatus, the exhaust gas G flowing into the reactor 1 is unevenly distributed due to the uneven flow or turbulent flow of the exhaust gas G, and There is a drawback that the diffusion state tends to be insufficient, and a uniform denitration effect based on the catalyst may not be obtained for the entire exhaust gas.

For example, the pipe for feeding the exhaust gas G into the reactor 1 is rarely formed in a straight pipe shape due to the surrounding space and layout, and normally the middle portion of the pipe is usually bent. In particular, since the exhaust gas G is often bent at a steep angle immediately before flowing into the reactor 1, the exhaust gas G flows into the reactor 1 in a nonuniform flow state or a turbulent flow state. Then, the unbalanced or turbulent state remains up to the outlet of the reactor 1, so that the gas flow in the reactor 1 is not uniform, which causes a decrease in the denitration efficiency.

In order to deal with the above, a means for adjusting the flow of the exhaust gas G by installing a guide plate or the like inside the pipe for feeding the exhaust gas G may be considered, but the bending of the pipe located upstream or the reactor 1 Since the inflow state of the exhaust gas G becomes indefinite due to various factors such as the expansion of the flow path after it has flowed into the interior, a stable denitration action cannot be obtained, and the design may be changed depending on the installation conditions of the device. It will be required, which will cause an increase in cost.

Further, when a means for arranging a plurality of plate bodies having a large number of holes on the upstream side of the nozzle 3 is adopted,
When the amount of the exhaust gas G to be treated is large, the ventilation resistance increases due to the plate body, which may adversely affect the operation of the NO _x generation source such as the engine. In order to avoid an increase in ventilation resistance, it is necessary to increase the ventilation area by the holes, but this requires the reactor 1 itself to be large in size, which causes a problem that a large installation space is required.

Therefore, the present invention solves the problem of such a conventional denitration device and eliminates the denitration effect due to the non-uniformity of the gas density due to the uneven flow or turbulent flow of the exhaust gas flowing into the reactor. It is an object of the present invention to provide a denitration device capable of preventing a decrease.

[0013]

In order to solve the above-mentioned problems, the present invention has a denitrifying agent composed of a honeycomb-shaped catalyst laminated inside a hermetically sealed reactor, and the inside of the reactor is introduced from an inlet. In a denitration device in which the exhaust gas of an internal combustion engine is introduced into the exhaust gas and at the same time a reducing agent is sprayed into the exhaust gas to remove nitrogen oxides in the exhaust gas based on the catalytic reduction method and to release the nitrogen oxides from the exhaust portion. A rectifying layer for rectifying the uneven flow and the turbulent flow of the inflowing exhaust gas and for uniformizing the flow velocity of the gas is disposed in the reactor located between the introduction portion of the exhaust gas and the denitration agent.

The rectifying layer is a structure in which an upper plate and a lower plate having a large number of holes are arranged with a predetermined gap, and a large number of spherical bodies are arranged in layers in the gap. Yes,
Provided is an example in which a spherical body made of the same material as the catalyst constituting the honeycomb denitration agent is used as the spherical body. Further, by providing a large number of projections on the spherical surface of the spherical body, the projections are in contact with each other to secure a space.

According to such a denitration device, the exhaust gas sent from the internal combustion engine to the denitration device in the state of uneven flow and turbulent flow with a non-uniform gas density flows into the reactor and at the same time as the atomized reducing agent gas. After passing through the spherical body arranged in parallel from the hole of the upper plate formed in the rectifying layer in a layered manner, it passes through the hole of the lower plate and passes through the denitrification agent to achieve the uniformity of the selective catalytic reduction method. The nitrogen oxides (NO _x ) contained in the exhaust gas G are removed based on such a main reaction and then released to the outside.

[0016] During such operation, if there is a drift in the exhaust gas flowing into the reactor, it receives a resistance proportional to the square of the gas flow velocity, and the air resistance of the portion of the rectifying layer where the gas flow velocity is high increases. On the other hand, the air resistance in the area where the gas flow velocity is low becomes small, and the exhaust gas flows from the area where the resistance is high to the area where the resistance is low. It is possible to obtain an operation mode in which the gas density is averaged by obtaining the rectifying effect of the uneven flow and the turbulent flow.

Further, by adopting, as the spherical body, a spherical body made of the same material as the catalyst constituting the denitration agent instead of the steel balls etc., the main reaction of the selective catalytic reduction method efficiently proceeds in addition to the rectifying action. The denitration effect is enhanced. Further, by providing a large number of protrusions on the spherical surface of the spherical body, the surface area of each spherical body itself is increased and the protrusions are in contact with each other in the rectifying layer to secure a space, and the amount of exhaust gas is reduced. Even if the number is large, the effect that the ventilation resistance does not increase can be obtained.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the denitration apparatus according to the present invention will be described in detail below with reference to the drawings, in which the same reference numerals are given to the same components as those of the conventional one. FIG. 1 is a cross-sectional view of an essential part showing a concrete example of a denitration device 10 according to the present invention, in which 5 is an outer shell, 6 is a heat insulating material arranged inside the outer shell 5, and 7 is an inner wall of the heat insulating material 6. It is a stretched muffle,
The outer shell 5, the heat insulating material 6, and the muffle 7 make the reactor 1
Is configured. Reference numeral 9 is an exhaust gas G introduction portion, and 11 is an exhaust portion thereof. In this embodiment, a stainless plate is used as the muffle 7.

Inside the reactor 1, denitration agents 2 and 2 composed of a large number of honeycomb-shaped catalysts are laminated and arranged. Spacers 12 and 12 for providing heat insulation and impact resistance are inserted between the respective denitration agents 2 and 2.

In the vicinity of the portion 9 for introducing the exhaust gas G, a reducing agent flow pipe 13 is inserted from the outside through the wall portion, and a nozzle 14 is fixed to the inner tip of the flow pipe 13. In addition, the tank 4 storing the reducing agent is arranged at the other end of the flow pipe 13. In addition to the reducing agent flow pipe 13 connected to the nozzle 14, it is also possible to use a two-fluid type in which a compressed air flow pipe is also connected.

Then, the introduction portion 9 for the exhaust gas G and the denitration agent 2,
A rectifying layer 15, which is a characteristic structure of the present invention, is disposed in the reactor 1 located between the rectifying layer 15 and the reactor 1. This rectifying layer 15
Is a large number of holes 16a, 1 as shown in FIG.
The upper plate 16 having the opening 6a and a large number of holes 17 similarly.
a and 17a are arranged with a lower plate 17 opened to maintain a predetermined gap h, and a large number of spherical bodies 18, 18 are arranged in layers in the predetermined gap h. ing.

Although spherical bodies such as steel balls may be used as the spherical bodies 18, 18, spherical bodies made of the same material as the catalyst forming the denitration agents 2 and 2 are also preferably used.

The operation of this embodiment based on the above configuration will be described below. That is, the exhaust gas G generated from the internal combustion engine
Is sent from the introduction part 9 into the reactor 1 as a nonuniform flow or turbulent flow with a non-uniform gas density. At the same time when the exhaust gas G flows in, the tank 4 passes through the reducing agent flow pipe 13.
The reducing agent stored inside is supplied to the nozzle 14, and the reducing agent is sprayed toward the downstream side of the exhaust gas G.

Then, the exhaust gas G becomes integral with the reducing agent gas, passes through the spherical bodies 18, 18 arranged in parallel in layers from the holes 16a formed in the rectifying layer 15, and then the holes 17a After passing through, it passes through the denitration agents 2 and 2. Then, based on the main reaction of the selective catalytic reduction method (see the above formula 1), the nitrogen oxides (N
O _X) is removed by uniform denitration reaction, it is discharged from the discharging section 11 to the outside.

During such an operation, if there is a drift in the exhaust gas G flowing from one side of the reactor 1, resistance is proportional to the square of the gas flow velocity, so that the gas flow velocity in the rectifying layer 15 is large. While the air resistance of the
Since the air resistance of the portion where the gas flow velocity is low becomes small, the exhaust gas G flows from the portion where the resistance is high to the portion where the resistance is low, and as a result, the rectification layer 1
The flow velocity of the gas that has passed through 5 is almost uniform. Therefore, the rectifying layer 15 can provide a rectifying effect of the turbulent flow and the uneven flow of the exhaust gas G, and an operation mode in which the gas density is averaged is obtained.

Further, as the spherical bodies 18, 18 in the rectifying layer 15, spheres made of the same material as the catalyst constituting the denitration agents 2, 2 are adopted in place of steel balls or the like, so that the rectifying action and the selective contact can be achieved. Since the main reaction of the reduction method proceeds efficiently, the denitration effect can be further enhanced.

FIG. 3 shows that, instead of the spherical body 18 employed in the present invention, a large number of protrusions 18a,
Another embodiment in which 18a is attached is shown. Such a protrusion 1
By attaching 8a, 18a, the protrusions 18a, 1
Since 8a are in contact with each other to secure a space, the surface area of each spherical body 18 itself becomes large and the gap between the spherical bodies 18 is widened as compared with the case where the spherical bodies 18 are simply arranged in parallel. Therefore, even if the amount of the exhaust gas G to be treated is large, the ventilation resistance does not increase and the operation of the NO _x generation source such as the engine is not adversely affected.

In this embodiment, the rectifying layer 15 is set to the exhaust gas G.
Although it has been described as an example in which the rectification layer 15 is arranged in the pipe before the pipe expansion, the grid is separately provided for the pipe expansion. Shaped rectifier is required. Further, by disposing the rectifying layer 15 on the downstream side of the nozzle 14, the reducing agent is mixed more efficiently when the gas flow is disturbed, and the sprayed reducing agent is vaporized. In consideration of the time required for the above, it is preferable to install the nozzle 14 at a considerably upstream side, and since the mixed gas is rectified, the rectification layer 15 and the rectification layer 15 are also promoted because mixing with the reducing agent is promoted. Nozzle 1
Inevitably, 4 is preferably arranged in the position shown in FIG.

[0029]

As described in detail above, according to the denitration apparatus of the present invention, even if the exhaust gas flowing into the reactor has a drift or a turbulent flow, the flow velocity of the gas passing through the rectifying layer is It is possible to obtain a uniform denitration effect based on the catalyst for the entire exhaust gas, because the gas density is averaged by obtaining the rectification effect of the uneven flow and the turbulent flow of the exhaust gas. Therefore, due to the surrounding space or layout, the piping for sending the exhaust gas into the reactor may be bent, or the exhaust gas may have a lopsided or turbulent flow condition when it is bent at a steep angle immediately before it enters the reactor. The exhaust gas is mixed with the reducing agent sprayed from the nozzle and passes through the denitration agent without any unbalanced or turbulent flow remaining at the outlet of the reactor. The concentration becomes uniform and the denitration efficiency can be improved.

By adopting, as the spherical body, a spherical body made of the same material as the catalyst constituting the denitration agent instead of the steel balls,
In addition to the rectifying action, the main reaction of the selective catalytic reduction method efficiently proceeds to enhance the denitration effect. Further, by providing a large number of projections on the spherical surface of the spherical body, the surface area of each spherical body itself is increased and the projections are in contact with each other in the rectifying layer to secure a space, so that exhaust gas Even if the amount is large, the effect that the ventilation resistance does not increase can be obtained. Further, the device itself does not require any special design change according to the installation conditions, and a large installation space is not required, so that the cost required for installation is not likely to increase.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts showing the configuration of an embodiment of a denitration device to which the present invention has been applied.

FIG. 2 is a perspective view showing an enlarged main part of FIG.

FIG. 3 is a front view showing a modified example of the spherical body used in FIG.

FIG. 4 is a schematic diagram showing the configuration of a conventional denitration device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Reactor 2 ... Denitration agent 4 ... (reducing agent) tank 5 ... Outer shell 6 ... Thermal insulation material 7 ... Muffle 9 ... Introducing part 10 ... Denitration device 11 ... Discharging part 12 ... Spacer 13 ... (reducing agent) distribution pipe 14 ... Nozzle 15 ... Straightening layer 16 ... Upper plate 17 ... Lower plate 16a, 17a ... Hole part 18 ... Spherical body 18a ... Protrusion

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location F01N 3/24 B01D 53/34 129E ZAB 53/36 101A 3/28 301

Claims (4)

[Claims] 1. A denitrifying agent comprising a honeycomb-shaped catalyst is laminated in a closed reactor, and exhaust gas of an internal combustion engine is introduced into the reactor from an introduction portion and is simultaneously introduced into the exhaust gas. In a denitration device in which a reducing agent is sprayed to remove nitrogen oxides in exhaust gas based on the catalytic reduction method and is discharged from an exhaust portion, a denitration device is placed between the introduction portion of the exhaust gas and the denitration agent. A denitration device having a rectifying layer for rectifying the uneven flow and the turbulent flow of the inflowing exhaust gas and for uniformizing the gas flow velocity in the reactor. 2. The rectifying layer has a structure in which an upper plate and a lower plate having a large number of holes are arranged with a predetermined gap, and a large number of spherical bodies are arranged in layers in the gap. The denitration apparatus according to claim 1, which is a body. 3. The denitration device according to claim 1, wherein the spherical body is a spherical body made of the same material as the catalyst constituting the honeycomb denitration agent. 4. The denitration device according to claim 1, wherein a plurality of protrusions are provided on the spherical surface of the spherical body so that the protrusions come into contact with each other to secure a space.