JPS60255132A - Apparatus for denitrating reaction - Google Patents

Abstract

PURPOSE:To mix uniformly ammonia and to increase the denitration efficiency in an apparatus for denitrating reaction by introducing the gaseous mixture of ammonia into the upstream part of the reactor, making the gas to be received on the inside surface of a bowl-shaped instrument and providing a catalytic layer to the rear flow of the bowl-shaped instrument. CONSTITUTION:Gaseous mixture charged with ammonia is introduced into the upstream of a reactor 1 and introduced into the reactor through a gas introducing pipe 2 and a gas guiding pipe 3 together with the gas to be treated. The gas to be treated is injected from the tip port of the gas guiding pipe and allowed to collide against a bowl-shaped instrument 4 and the gas is reversely flowed upward to be flowed to the upper part of the reactor and advanced to the space part of the reactor while causing turbulent flow. Ammonia is uniformly mixed into the gas and thereafter reached to a catalytic layer 5 and converted into nitrogen and water by means of denitrating reaction and discharged from a gas discharging pipe 6.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The denitrification reaction device of the present invention relates to a denitrification device using an ammonia (NHs) catalytic reduction method for exhaust gas containing nitrogen oxides.
In particular, the present invention relates to a reaction device in which exhaust gas and ammonia are suitably mixed.

[Background of the invention]

In recent years, denitrification methods have been used to reduce and remove nitric oxide (NOx) from gases emitted from boilers and chemical plants.
Selective catalytic reduction using ammonia, which is a dry denitrification method, has been put into practice on a large scale.

The NOx concentration in the gas to be treated is from several 10 to several 100 ppm in the case of combustion gas, but can reach several 11,000 pp to several hundreds of ppm in the case of exhaust gas from a nitric acid-related plant.

Catalytic reduction denitrification between NOx in exhaust gas and ammonia
By uniformly mixing x and ammonia and converting it into nitrogen and water using a catalyst, the reaction molar ratio of NOx and ammonia is reduced to N
For exhaust gas rich in nitrogen monoxide (No) among Ox components, the ratio is approximately l:1, but for exhaust gas rich in nitrogen dioxide (NOl), the ratio is l:1.5 to 2.0. Although the amount of ammonia increased, the concentration of ammonia in the exhaust gas to be treated is less than 1%, which is extremely low. In order for the denitrification reaction to proceed stoichiometrically, it is necessary to uniformly mix NOx and ammonia up to the catalyst layer.

Conventionally, the following methods have been used as mixing methods. In the case of large-scale equipment such as denitrification equipment for large-capacity boiler exhaust gas, pressure loss becomes a big problem because a large amount of process gas passes through it. A widely used method is to simply provide a large number of nozzle ports in a gas pipe and inject ammonia. The ammonia concentration required at this time is several tens to several hundred ppm, and ammonia that has been diluted in advance with air or nitrogen to about 10% is usually used. Furthermore, in the case of small- to medium-sized denitrification equipment, since the amount of gas to be processed is relatively small, a gas transportation method that involves some pressure loss, and a gas mixing method using a packed tower, baffle plate, venturi, etc. are adopted. However, as the equipment becomes larger and more complex, and the pressure loss in the system line increases, power costs and the like increase. In particular, in special denitrification processes, the intensifier for the amount of gas to be treated may be disadvantageous, and it is necessary to use highly concentrated ammonia gas with reduced diluent.

However, the above mixing method has the following disadvantages.

Even if ammonia is introduced into the exhaust gas through multiple nozzle ports, it is difficult to mix it sufficiently and uniformly.

In addition, when the space above the catalyst layer in the reactor is filled with particles made of alumina, silica, etc. or Raschig rings, etc. to mix the residue, ammonia has a large catalytic cracking area and decomposition progresses.
It is lost until it reaches the catalyst layer.

Further, when the flow rate of the processing gas fluctuates, especially when the flow rate decreases, the flow rate of the waste at each site within the reaction apparatus decreases, and the mixing efficiency of ammonia decreases.

Relying on uniform mixing in the catalyst layer without achieving complete homogeneous mixing of ammonia in the process gas (3) reduces the effective utilization of ammonia. In other words, the catalyst has an ammonia decomposition activity of about 9 or less, and the excess ammonia generated by heterogeneous mixing is ineffectively decomposed in the catalyst layer and reacts with NOx. Therefore, in order to increase the effectiveness of ammonia, it is necessary to uniformly mix NOx in the exhaust gas and ammonia up to the catalyst layer. In response to these needs, there is a need for an apparatus that does not require a complicated structure, suppresses pressure loss in the apparatus system, and can mix a small amount of ammonia into the processing gas well.

[Purpose of the invention]

The object of the present invention is to eliminate the drawbacks of the prior art described above, and to provide a denitrification system that enables ammonia to be uniformly mixed in advance with a processing gas containing nitrogen oxides in an ammonia catalytic reduction reaction apparatus, thereby allowing the denitrification reaction to be carried out with high overall efficiency. The purpose of the present invention is to provide a reactor.

[Summary of the invention]

In the present invention, a gas introduction pipe for introducing a mixed gas obtained by injecting ammonia into a nitrogen oxide-containing gas is disposed so as to be received by the reactor (g) (4) on the inner surface of the bowl-shaped vessel; This is a denitration reactor with a built-in catalyst layer in the downstream section.

In the reactor, the mixed gas of the nitrogen oxide-containing gas and ammonia is introduced into the reactor having a cross-sectional area υ larger than the cross-sectional area of the gas introduction pipe, and the gas is introduced into the reactor where the gas flow rate is reduced and the pressure loss is reduced. A bowl-shaped vessel is provided, and the gas flow ejected from the gas inlet pipe hits the inside of the bowl-shaped vessel and temporarily flows backward to uniformly mix ammonia into the gas, and then advances to the catalyst layer where it reacts.

Note that if the gas introduction pipe is extended into the reactor to form a gas guide pipe, and a bowl-shaped container is provided to receive the mouth of the gas guide pipe, the ammonia gas can be mixed well.

Further, even if some decomposition of ammonia is allowed, it is preferable for the ammonia gas mixture to be filled with an alumina or silica filler in the upper space of the catalyst layer within the permissible pressure loss range of the mixed gas.

As a catalyst, catalysts such as a refractory carrier carrying a platinum metal, iron, etc. (6), activated carbon carrying vanadium, copper, etc., iron oxide with a special crystal structure, etc. are used.

The reaction is as follows: 6 No + 4 NH3→5 Ng + 6 HgO or 2NO+2NHs+O→2Nm+3HtO゛Nitrogen oxides are catalytically reduced to produce nitrogen and water.

[Embodiments of the invention]

Example 1 An example of the denitrification reaction apparatus of the present invention is shown in FIG.

The reactor 1 has a cylindrical vertical shape with an inner diameter of 100 mm and a length of 300 mm, and a gas introduction pipe 2 with an inner diameter of 2 o 11 ml is installed at the top of the reactor.
A gas introduction pipe 2 is extended into the reactor 1 to form a gas guide pipe 3 having a length of 50 iue. The outer shape is 60i11. so as to receive the gas jet from the gas guide pipe 3.
A crucible-shaped bowl-shaped vessel 4 made of quartz with a depth of 50 mm and a wall thickness of 2 mm is placed with its inner surface facing the gas guide pipe 3 at a distance of 20 mm between the gas guide pipe 30 and the bottom of the bowl-shaped vessel 4. It is set up. A catalyst layer 5 is provided at the downstream part of the bowl-shaped vessel 4, that is, at a position 59 m from the bottom of the reactor 1, and the catalyst layer 5 has a zeolite catalyst of 5 to 1 o mesh on a catalyst support wire mesh 6 of 20 mesh.
Filled to a layer height of 011. A gas discharge pipe 7 is provided at the bottom of the reactor l. In addition, equipment other than bowl-shaped vessels is 5US30
It is made of 4.

A denitrification reaction was carried out using the above reaction apparatus.

Reactor 1 was placed in an electric furnace, and the external temperature of the vessel wall was controlled at 440'C. NOx 2000 ppm, Oa 2
0% H2O, 3% H2O, and the remaining 9N2 synthesis gas was injected with NHs and mixed so that the NH3 concentration was 40oOppm.
This gas to be treated was introduced into the reactor 1 through a gas introduction pipe 2 and a gas guide pipe 3 at a rate of 10 l/min.

The gas to be treated is ejected from the tip of the gas guide pipe into a bowl-shaped vessel 4.
At this time, the gas flows backwards upward, flows above the reactor L, and advances into the reactor L space in a turbulent flow, and the ammonia is uniformly mixed into the gas to be treated, and then reaches the catalytic reduction catalyst layer 5. 9 The denitrification reaction results in nitrogen and water, and the gas discharge pipe 6
I threw it all out.

Analysis of NoX and ammonia in the exhaust gas produced by this operation revealed that each was 3 ppm or less, and the NOx removal rate was 99.8% or more.

Comparative Example 1 In the apparatus of Example 1, the gas guide pipe 3 and the bowl-shaped vessel 4 were
The denitrification operation was performed in the same manner as in Example 1 using the equipment in which the denitrification was removed. As a result, NOx in the exhaust gas was 140
ppm, the NOx removal rate was 93%. The test catalyst had high ammonia catalytic cracking activity, and the ammonia content in the exhaust gas was 3 ppm or less.

From the results of Example 1 and this comparative example, it is clear that in the denitration reaction apparatus of the present invention, ammonia is mixed extremely uniformly, and the denitration reaction is performed quickly.

Example 2 A denitrification test was conducted under the same operating conditions as in Example 1, except that the length of the reactor was changed to 20011I and the length of the space above the catalyst layer was shortened from 200u to 100u.

As a result, NoX in the exhaust gas was 23 ppm. Even when the volume of the ammonia mixing section in the reactor was set to 172, the NOx removal rate was 98.9, indicating that a high NOx removal rate was achieved by the apparatus of the present invention.

Example 3 In Example 2, a denitrification test was conducted under the same operating conditions as in Example 1, except that a silica Raschig ring (diameter 5 s+i+) was filled in the space between the bowl-shaped container and the catalyst layer.

As a result, NOx in exhaust gas was less than 5 PPM, and N
The Ox removal rate was 99.7%. By using an auxiliary tool such as a Raschig ring, mixing of cyanmonya was improved, and even in this example, which is a smaller reactor than that of Example 1, the same denitrification efficiency was obtained.

Example 4 In Example 1, in order to examine the length of the gas guide pipe (caliber 20), the lengths were set to 0.10.3o, 70, and l.
It was changed to OOIll, and the length to diameter ratio was set to θ~5. The distance between the tip of the gas guide tube and the bottom of the bowl is 0,
10.30Illll+ is 70.60.4 respectively Q
In the case of a dragon with a length of 70.10 mm, the length was 20 in all cases. When a denitration test was conducted under the same operating conditions as in Example 1, the NOx removal rate was 98% or higher in all of the results.

Example 5 In Example 1, in order to examine the gas guide tube diameter for the reactor inner diameter of 100 mm, the gas guide tube diameter 't-l0
130 and 50, and the ratio of the reactor inner diameter to the gas guide pipe diameter? O, 1 to 0.5. In addition, the diameter of the bowl-shaped vessel is 0.30, and 30.50 and 7Qu+ for 5Qi+i+, respectively, and the depth is 50 for both.
Nm was used. A denitrification test was conducted under the same operating conditions as in Example 1, and the NOx removal rate was 98% or higher in all cases.

Example 6 In Example 1, in order to examine the relationship between the bowl diameter and the gas guide pipe diameter, the bowl shape and diameter 9Q used in Example 5 were used.
A bowl-shaped container with a depth of 50 mm was used, and the ratio of the diameter of the gas guide tube to the diameter of the bowl was set to 1.4 to 4.5.

A denitrification test was conducted under the same operating conditions as in Example 1, and as a result, NO.
The x removal rate was 98% or more in all cases.

Example 7 In Example 1, in order to examine the relationship between the diameter of the bowl-shaped vessel and the depth, the depth was set to 25.70 mm for a bowl-shaped vessel with a diameter of 50 tm.
．． and 10011N were used, and the depth to diameter ratio of the bowl-shaped vessel was set to 0.5 to 2.0.

A denitrification test was conducted under the same operating conditions as in Example 1, and as a result, NO.
The x removal rate was 98% or more in all cases.

Example 8 In Example 2, in order to examine the throttling effect at the tip of the gas guide tube, a gas guide tube with a diameter of 20 fins was narrowed to a diameter of 10 fl toward the tip, and a denitrification test was conducted under the same operating conditions as in Example. As a result, NOx in exhaust gas is 3 ppm or less,
It was found that the NOx removal rate was 99.8%, indicating that ammonia was mixed well. This shows that reducing the diameter of the gas guide pipe within the allowable pressure loss range and increasing the gas ejection speed makes the present invention more effective.

From the above examples, it can be seen that in the denitrification apparatus of the present invention, by receiving the ejected flow of the gas to be treated in a bowl-shaped container, the ammonia is mixed uniformly and the denitrification reaction is carried out quickly.

Regarding the size ratio of the bowl-shaped vessel and the gas guide pipe, the ratio of the diameter of the bowl-shaped vessel to the depth is 0.5 to 2. O, the ratio of the length of the gas guide tube to the diameter θ ~ 5, the ratio of the diameter of the gas guide tube to the inner diameter of the reactor 0.1 to 0.5, the ratio of the diameter of the bowl-shaped vessel to the diameter of the gas guide tube 1.4 ~4.5 is the amount of gas to be treated, N
If it is selected appropriately depending on the Ox concentration, etc., denitrification can be performed efficiently.

In addition, the pressure loss due to the bowl-shaped vessel and the gas introduction pipe, as well as the piping system and the catalyst layer, is extremely small, and the entire apparatus can be downsized by filling it with a Raschig ring or the like to improve ammonia mixing. However, in the case of a large amount of processing gas, the pressure loss of this device cannot be ignored, and although it can be used within the permissible pressure loss range, it is preferable to use the processing gas on a relatively small scale of less than tens of thousands of Nm'/h. suitable for the device.

In addition, the shape of the bowl-shaped container used crucible shop in the example,
In general, it may be a curved surface such as a spherical surface or a paraboloid, a polygonal shape, or a vessel shape with a flat bottom.

Furthermore, it is easily inferred that the shape of the gas guide tube is not limited to a circular tube, but may also be an elongated cylinder, square, polygon, etc. These selections are determined based on the selection factors of the gas guide pipe, including the shape of the reactor, bowl-shaped vessel support fittings, etc. Note that as the process gas flow rate decreases, the use of a deeper bowl will benefit gas mixing.

〔Effect of the invention〕

The present invention is a denitrification reaction apparatus using an ammonia selective reduction method, and is equipped with a bowl-shaped vessel that receives a jet of gas to be treated, so that ammonia is completely and uniformly mixed into the gas to be treated. The contained NOx is quickly reduced to nitrogen scum, and the denitrification reaction can be carried out efficiently.

[Brief explanation of the drawing]

The denitrification reaction apparatus of the present invention is shown in FIG. l... Reactor, 2... Gas introduction pipe, 3... Gas guide pipe, 4... Bowl-shaped vessel, 5... Catalyst layer, 6... Catalyst support wire mesh, 7... Gas exhaust pipe. Agent Tatsuyuki Unuma Figure 1

Claims (1)

[Scope of Claims] (1) A gas introduction pipe for introducing a mixed gas in which ammonia is injected into a nitrogen oxide-containing gas is provided in the upstream part of the reactor, and a bowl-shaped vessel receives the gas ejected from the gas introduction pipe. A denitrification reaction device, characterized in that a catalyst layer is disposed so as to be received on an inner surface thereof and is built in a downstream part of the bowl-shaped vessel. (2. In claim 1, the gas introduction pipe is extended into the reactor to form a gas guide pipe,
A denitrification reaction apparatus, characterized in that the bowl-shaped vessel is disposed at the mouth of the gas guide tube. (3) The denitrification reaction apparatus according to claims 1 and 2, wherein the bowl-shaped vessel has a spherical or parabolic curved surface, or a polyhedral shape. (4) A denitrification reaction apparatus according to any one of claims 1 to 3, characterized in that the upper space of the catalyst layer is filled with a filler made of alumina or silica.