JP4295548B2 - Nitrogen oxide removing catalyst, denitration method and apparatus using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention uses a nitrogen oxide removal catalyst that efficiently purifies nitrogen oxide contained in an atmosphere gas in an intersection, a tunnel or a closed parking lot, an exhaust gas from an internal combustion engine, and an exhaust gas from an industrial facility. The present invention relates to a denitration method and apparatus.
[0002]
[Prior art]
Ventilation equipment in road tunnels is mainly intended to ensure a clear distance due to dust and to reduce harmful substances such as carbon monoxide (CO) and nitrogen oxides (hereinafter also referred to as “NOx”) to below the allowable level. Is installed. As a current ventilation method, a method is generally used in which fresh outside air is sucked from outside the tunnel, dust is removed as necessary, and forced ventilation is performed outside the tunnel. However, this method only diffuses ventilation gas containing harmful substances to the atmosphere, and does not fundamentally improve the environment. Especially in urban areas where air pollution due to automobile exhaust gas is serious, highly contaminated areas will be expanded, which may hinder tunneling and shelter installation in road planning. Therefore, it is desired to develop a new ventilation system that saves energy and does not affect the surrounding environment.
[0003]
However, tunnel ventilation gas has a peculiarity that the NOx concentration is rare at 10 ppm or less at normal temperature and large capacity, and the NOx concentration fluctuates greatly depending on the traffic volume. _Three It is impossible to apply the NOx purification method using NO as a reducing agent.
[0004]
Therefore, various dry methods and wet methods have been proposed as low-concentration NOx purification methods, but the wet methods are difficult to put into practical use because they require a wastewater treatment apparatus. In addition, as a dry method, (1) an adsorption method in which NOx is adsorbed on an adsorbent such as a metal oxide in contaminated air, and (2) NH in contaminated air _Three Is added to irradiate the electron beam to convert NOx and SOx into nitric acid and sulfuric acid mist. _Three There is an electron beam irradiation method in which fine particles such as ammonium nitrate, ammonium sulfate and double salts of both are collected by an electric dust collector or the like.
However, in the electron beam irradiation method (2), an equivalent amount of NH required for the reaction with NOx contained in a trace amount of 10 ppm or less in a large volume of contaminated air. _Three It is difficult to uniformly mix the unreacted NH _Three There is a risk of secondary pollution such as outflow to the outside (Non-patent Document 1).
[0005]
In general, NOx in tunnel exhaust gas is 80 to 90%, NO ₂ As an adsorbent that efficiently adsorbs NO by the method (1), the present applicant uses an adsorbent carrying a noble metal (Pt, Pd, Ru, Rh, Ir). (Patent Document 1).
[0006]
However, a large amount of NO adsorbent is required to be applied to large-capacity tunnel exhaust gas treatment, and the application of noble metal is considered to be economically unsatisfactory because it causes a rise in the adsorbent and depletion of resources.
[0007]
For this reason, as shown in FIG. 24, the polluted air 1 containing a low concentration of nitrogen oxides is adsorbed and removed by an adsorbent at room temperature, and the clean gas 2 is released into the atmosphere. ₂ NO ₂ Adsorbed by the adsorption tower 3 and adsorbed by the NO adsorption tower 4, then the valves 5, 5 are closed, the valves 6, 6 are opened, and the adsorption towers 3, 4 are heated and desorbed by heating means, It was previously proposed that nitrogen oxides be removed by adding ammonia 8 to the desorption gas 7 containing concentrated nitrogen oxides and decomposing it into nitrogen by a denitration catalyst 9 (Patent Document 2).
[0008]
There is also a proposal for a nitrogen oxide removing agent in which an amine such as morpholine is supported on a porous carrier (Patent Document 3).
[0009]
[Non-Patent Document 1]
Industrial Pollution Prevention Association: "Survey and research on automobile exhaust gas treatment technology" (Commissioned by Japan Highway Public Corporation) March 1984, p. 49
[Patent Document 1]
JP-A-5-31357
[Patent Document 2]
JP-A-8-299756
[Patent Document 3]
JP-A-9-262430
[0010]
[Problems to be solved by the invention]
However, in the proposal as in Patent Document 2, the adsorption towers 4 and 5 which are adsorption means for nitrogen oxides and the heating means for raising the temperature to desorb the nitrogen oxides adsorbed in the adsorption towers 4 and 5 are provided. In addition to the necessity, in the desorption, it is necessary to stop the treatment of contaminated air, and there is a problem that nitrogen oxides cannot be treated continuously.
[0011]
Further, the proposal as in Patent Document 3 has a problem that morpholine is designated as a dangerous substance because it has an explosion limit and is not suitable for denitration treatment equipment at an intersection or the like. In addition, in the proposal of Patent Document 3, the denitration action of the removal agent is an adsorption / absorption action in the presence of moisture, and the denitration effect lasts only for a few hours. There is a problem that it is not suitable for maintaining the denitration effect and treatment of the absorbent is required.
[0012]
Further, in recent years, regulations on environmental exhaust gas have increased, and it is desired to further purify the nitrogen oxide concentration that has been reduced by existing ammonia denitration in exhaust gas from industrial equipment such as boiler flue gas treatment equipment. For this reason, the advent of a simple yet efficient processing apparatus attached to existing facilities is eagerly desired.
[0013]
In view of the above problems, an object of the present invention is to provide a nitrogen oxide removal catalyst capable of maintaining denitration efficiency with a simple configuration, and a denitration method and apparatus using the same.
[0014]
[Means for Solving the Problems]
The first invention for solving the above-described problem is as follows. In an inert gas atmosphere at 600-1300 ° C The heat-treated activated carbon fiber carries 0.5% by weight or more of urea, and its moisture content is less than 10% by weight. NO in the gas is changed to NO by the activated carbon fiber. ₂ NO in the gas by the urea while oxidizing to ₂ N ₂ Reduced to Ru Oxide removal catalyst The nitrogen oxide purifying means having a plurality of stages in series, the urea loading amount of the nitrogen oxide purifying means on the gas introduction side is set to 20% by weight or less, and the urea loading amount in the front stage is the urea loading stage in the subsequent stage Denitration device characterized by being less than quantity It is in.
[0024]
First 2 The invention of the 1 In the present invention, there is provided a denitration apparatus comprising a drying means for drying the processing gas.
[0025]
First 3 The invention of the 1 or 2 According to the present invention, there is provided a denitration apparatus comprising a drying means for drying the nitrogen oxide removing catalyst.
[0026]
First 4 The invention of the 1 Thru 3 In any one of the inventions, there is provided a denitration apparatus comprising urea supporting means for supporting urea on the carbon material by spraying or dipping.
[0030]
First 5 The invention of the 1 Thru 4 In any one of the inventions, the denitration apparatus is characterized in that dust removal means is provided on the upstream side of the nitrogen oxide purification means.
[0031]
First 6 The invention of the 1 Thru 5 In any one of the inventions, the denitration apparatus is characterized in that a desulfurization means is provided on the upstream side or the downstream side of the nitrogen oxide purification means.
[0032]
First 7 The invention of the 1 Thru 6 In any one of the inventions, the gas containing nitrogen oxide is any one of an atmosphere gas in an intersection, a tunnel or a closed parking lot, an exhaust gas from an internal combustion engine, and an exhaust gas from an industrial facility. It is in the denitration equipment.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments according to the present invention will be described below, but the present invention is not limited to these embodiments.
[0034]
[First Embodiment]
FIG. 1 is a schematic diagram of a denitration apparatus according to the present embodiment.
As shown in FIG. 1, a denitration apparatus 10 according to the present embodiment includes a catalyst layer 12 that is built in a processing vessel body 11 and is made of a nitrogen oxide removal catalyst formed by supporting urea on a carbon material. The nitrogen oxide purifying means 13 is provided, a gas 14 containing nitrogen oxide (NOx) is introduced from one end side, and the nitrogen oxide purifying means 13 denitrates and purifies the nitrogen oxide NOx in the gas. The gas 15 is discharged.
[0035]
In the present embodiment, activated carbon fibers are used as the carbon material supporting urea. However, the present invention is not limited to this, and activated carbon may be used in addition to the activated carbon fibers. In the following embodiments, a case where activated carbon fibers are used as the carbon material will be described.
[0036]
Here, as shown in FIG. 23 (a), the active carbon fiber (ACF) 100 generally has fine micropores 101 on its surface, the fiber diameter is 1-20 μm, and the specific surface area is 700-. 2500m ² / G, outer surface area 0.2-2.0m ² / G, a pore having a pore diameter of 2 nm or less.
Further, as shown in FIG. 23B, the activated carbon 102 needs to pass through the macropore 103 and the mesopore 104 in order to reach the micropore 101 from the gas phase in addition to the small number of micropores 101. is there.
[0037]
As shown in FIG. 1 (b), the catalyst layer 12 includes a flat plate-like activated carbon fiber sheet 21 and a corrugated plate-like activated carbon fiber sheet 22, which are alternately laminated. The linear space formed between them becomes a passage 23, and the passage 23 extends in the axial direction of gas passage.
The flat activated carbon fiber sheet 21 and the corrugated activated carbon fiber sheet 22 are plate-like, and the corrugated active carbon fiber sheet 22 is further formed into a corrugated shape using, for example, a corrugator. In addition to the corrugated plate shape, the exhaust gas may be formed into a shape that passes in parallel to the activated carbon fiber sheet, such as a honeycomb shape.
[0038]
The activated carbon fiber constituting the catalyst layer 12 supports urea, and the supporting means supports the activated carbon fiber by immersing the activated carbon fiber in a urea solution, or sprays urea in a solution or powder form. Or carry it.
[0039]
In this way, the catalyst layer 12 formed by supporting urea on activated carbon fibers is composed of NO, NO among nitrogen oxides present in the gas. ₂ Directly or NO to NO ₂ The nitrogen oxide is efficiently reduced while being oxidized, and its denitration action is shown in FIGS. 22 (a) to 22 (c).
[0040]
In the case shown in FIG. 22A, urea (CO (NH) is added to the activated carbon fiber ACF having micropores directly opened on the surface. ₂ ) ₂ In the presence of oxygen on the surface of the activated carbon fiber, N reacts with urea in the presence of oxygen on the surface of the activated carbon fiber. ₂ Reduced to Or NO is NO ₂ Oxidized to react with urea and react with N ₂ Reduced to On the other hand, NO present in the gas ₂ Reacts directly with urea to react with N ₂ Reduced to
[0041]
In the case shown in FIG. 22B, the activated carbon fiber (ACF) is mixed with urea (CO (NH ₂ ) ₂ ) Is supported and activated, nitrogen oxides NO and NO ₂ Reacts directly with urea and N ₂ Reduced to
[0042]
In the case shown in FIG. 22C, the activated carbon fiber (ACF) is mixed with urea (CO (NH ₂ ) ₂ ) Is supported, nitrogen oxide NO reacts directly with urea, and N ₂ Reduced to
[0043]
When the amount of urea supported on the activated carbon fiber is large, the reaction for directly denitrating NO in the nitrogen oxide is slowed down as shown in a test example described later, and FIG. 22 (a) or FIG. 22 (b) The reaction mechanism of) is a more preferable reaction.
[0044]
Therefore, in order to efficiently denitrate NO in nitrogen oxides, NO is changed to NO. ₂ Oxidized to NO in activated carbon fiber ₂ The reaction should be performed under rich conditions.
[0045]
Here, in the present invention, the amount of urea supported on the carbon material is preferably 0.5% by weight or more. This is because if it is less than 0.5% by weight, the denitration efficiency is lowered and the reduction duration is shortened.
On the other hand, the upper limit of the supported amount of urea is not particularly limited, and the denitration duration increases as the supported amount increases as shown in the test examples described later, but if too much, the surface of the activated carbon fiber is coated, Oxidation reaction (NO → NO ₂ ), Which may be about 70% by weight.
[0046]
Further, the denitration reaction temperature can be carried out at room temperature, and there is no need to decompose into ammonia as in the case of conventional urea denitration, so heating is not necessary. In addition, what is necessary is just to set it as 200 degrees C or less which is the temperature decomposed | disassembled into ammonia, when heating.
[0047]
In denitration, the water content is preferably less than 10% by weight, preferably less than 5% by weight, more preferably less than 1% by weight. This is because the presence of moisture is not preferable because the reduction activity is reduced.
[0048]
Further, as shown in FIG. 2 (a), a drying means 31 is provided on the upstream side of the denitration apparatus 10 having the nitrogen oxide purification means 13 to reduce the relative humidity of the introduced gas 14, and the dry gas 14a and Like to do. Note that the nitrogen oxide purification means 13 itself may be in a dry state by directly blowing hot air or the like to the nitrogen oxide purification means 13.
[0049]
Here, the relative humidity in the denitration reaction is preferably 40% or less, more preferably 20% or less. If this exceeds 40%, the surface of the activated carbon fiber is covered with moisture, and the necessary oxidation reaction (NO → NO ₂ This is because the ability to promote) declines.
[0050]
Moreover, it is preferable to heat-treat the activated carbon fiber at a high temperature in an inert gas atmosphere so as to improve the oxidation activity function as a catalyst of the activated carbon fiber. By this high-temperature heat treatment, some or all of the hydrophilic oxygen functional groups present on the surface of the activated carbon fiber are converted to CO, CO ₂ As a result, the oxidation active site of NO and the active site of urea are increased so that the surface is more hydrophobic than before the heat treatment. As a result, NO easily approaches the oxidation active point, and NO ₂ The rate of oxidation to and the rate of reduction with urea are improved.
[0051]
Here, the high temperature treatment temperature of the activated carbon fiber varies depending on the carbon material, but is preferably about 600 to 1300 ° C., for example. This is because a heat treatment effect does not appear at temperatures below 600 ° C., while no further effect is exhibited even when heat treatment is performed at temperatures above 1300 ° C.
[0052]
Here, an example of the activated carbon fiber used in the catalyst layer of the present invention and an example of its production are shown below.
Examples of the activated carbon fiber used in the present invention include pitch-based activated carbon fiber, polyacrylonitrile-based activated carbon fiber, phenol-based activated carbon fiber, and cellulose-based activated carbon fiber, but the present invention is limited to these. However, the activated carbon fibers exhibiting the above catalytic action are not limited in any way.
[0053]
Specific production examples are shown below.
(Production Example 1)
Pitch-based activated carbon fiber (“OG-20A”, manufactured by Adol Co., Ltd.) is used, and this is fired in a nitrogen atmosphere at a temperature range of 900 to 1200 ° C. for 1 hour.
[0054]
(Production Example 2)
Polyacrylonitrile-based activated carbon fiber (“FE-300”, manufactured by Toho Linux Co., Ltd.) is used, and this is fired in a nitrogen atmosphere at a temperature range of 600 to 900 ° C. for 1 hour.
[0055]
(Production Example 3)
Phenol-based activated carbon fiber (“Kractive-20”, manufactured by Kuraray Chemical Co., Ltd.) is used, and this is fired in a nitrogen atmosphere at a temperature range of 900 to 1200 ° C. for 1 hour.
[0056]
Furthermore, in the present embodiment, desulfurization means may be provided on the upstream side or the downstream side of the denitration apparatus so that denitration and desulfurization are performed simultaneously.
FIG. 2B shows a desulfurization device 16 as a desulfurization means provided on the downstream side of the denitration device 11. In this way, the sulfur oxide (SOx) present in the purified gas 15a obtained by removing the nitrogen oxide (NOx) in the gas 14 by the denitration device 11 is desulfurized by the desulfurization device 16 to obtain the desulfurized purified gas 15b. Can do. Thereby, not only nitrogen oxide (NOx) but also sulfur oxide (SOx) in the gas can be efficiently purified.
The desulfurization device 14 may be provided on either the upstream side or the downstream side of the denitration device.
[0057]
[Second Embodiment]
FIG. 3 is a schematic view of a denitration apparatus according to the second embodiment.
Since the denitration capability of the catalyst layer 12 in the first embodiment is lowered due to long-term use, the denitration apparatus 10 is provided in parallel to compensate for this, thereby enabling continuous treatment.
[0058]
As shown in FIG. 3, the denitration apparatuses 10-1 and 10-2 are provided in parallel, and the gas flow paths are switched alternately by switching the flow path switching means 33 and the valve 34 interposed in the pipe 32. .
In order to regenerate the denitration apparatus whose catalytic function has been reduced by use, the catalyst solution 36 is supplied from the catalyst tank 37 by the catalyst spraying means 35 provided in each of the denitration apparatuses 10-1 and 10-2. In addition, the denitration ability is regenerated by setting a predetermined amount of urea.
[0059]
[Third Embodiment]
FIG. 4 is a schematic view of a denitration apparatus according to the third embodiment.
As described in the first embodiment, denitration of nitrogen oxide is NO. ₂ Since the rich condition is preferable, the oxidation means 38 is provided on the upstream side of the denitration apparatus 10.
The oxidizing means 38 is not particularly limited, but NO is NO. ₂ For example, an ozone oxidation means, a hydrogen peroxide hydroxylation means, a potassium permanganate oxidation means and the like which can be oxidized efficiently can be mentioned.
In the oxidizing means 38, NO in the gas 14 containing nitrogen oxide to be introduced is changed to NO. ₂ NO is actively oxidized to NO ₂ In the denitration means 10 that is subsequently provided, ₂ Denitration is efficiently performed under rich conditions.
[0060]
NO ₂ Therefore, the denitration apparatus 1 may carry a large amount of urea (70% by weight or more). This is because NO is oxidized by the oxidation means. ₂ Is in a rich state, the oxidation reaction (NO → NO) in the denitration apparatus 10 ₂ ) Is not necessary to promote.
[0061]
In addition, since NO oxidation in the gas 14 has been completed, the humidity in the reaction in the denitration apparatus 10 is not limited to low humidity, and the relative humidity may be 40% or more.
[0062]
[Fourth Embodiment]
FIG. 5 is a schematic view of a denitration apparatus according to the fourth embodiment.
In the third embodiment, the oxidation means 38 is used to convert NO in the gas 14 to NO. ₂ In this embodiment, a plurality of stages (two stages in this embodiment) of denitration devices are arranged in series, and the first stage denitration device 10-1 uses the denitration device 10-1 in the gas 14. NO to NO ₂ To efficiently oxidize. For this reason, the urea loading amount of the activated carbon fiber of the nitrogen oxide purification means 13 of the first stage denitration device 10-1 is set to 20% by weight or less, preferably 5% by weight or less, and the urea completely covers the surface of the activated carbon fiber. Is not coated, leaving many active sites that contribute to oxidation.
[0063]
In the first stage denitration apparatus 10-1, NO in the gas 14 containing nitrogen oxide to be introduced is changed to NO. ₂ NO is actively oxidized to NO ₂ In the second stage denitration means 10-2 that is subsequently provided, the NO ₂ Denitration is efficiently performed under rich conditions.
[0064]
Also in the present embodiment, as in the third embodiment, in the second-stage denitration apparatus 10-2, since NO oxidation has been completed, there is no limitation on the amount of urea loaded and the relative humidity. Become.
[0065]
[Fifth Embodiment]
6 to 8 are schematic views of a denitration apparatus according to the fifth embodiment. 6 is a front view of the nitrogen oxide purifying means, FIG. 7 is a perspective view of FIG. 6, and FIG. 8 is an exhaust gas treatment facility in the underground of an intersection having a denitration device.
As shown in these drawings, the denitration apparatus according to the present embodiment is equipped with a catalyst layer 12 made of a nitrogen oxide removing catalyst that is mounted in a cylindrical body 41 that is annular and open at both ends and that supports urea on a carbon material. A nitrogen oxide purifying means 13 and a urea carrier means 43 in which a part of the cylindrical body 41 is immersed and a urea solution 36 is filled in the urea bath 42, and the nitrogen oxide is provided. Is introduced from the front side, nitrogen oxide NOx in the gas is denitrated by the nitrogen oxide purification means 13, and exhausted as purified gas 15 from the back side.
[0066]
In the denitration apparatus of the present embodiment, the activated carbon fiber carries urea in a part of the nitrogen oxide purification means 13 in which the cylindrical body 41 is rotated at a predetermined cycle by a rotating means (not shown) and immersed in the urea bath 42. I try to let them.
The supported urea is dried in a drying region 44 by supplying a drying gas 45 of a drying means (not shown) to a predetermined dry state, and then cooled in a cooling region 46 by supplying a cooling gas 47 of a cooling means (not shown). I am doing so.
In the denitration region 48, nitrogen oxides in the introduced gas 14 are denitrated.
[0067]
Thereby, before the catalyst function is lowered, the cylindrical body 41 is rotated to regenerate the catalyst, so that continuous denitration can be performed.
[0068]
FIG. 8 shows a state in which the denitration apparatus 10 is provided in the basement of the ground 50. The exhaust gas treatment facility includes, for example, an intake duct 51 for sucking a gas 14 having a high nitrogen oxide concentration near an intersection, and a gas pipe. 52, a dust removing means 53 for removing dust in the gas 14, a denitration chamber 54 installed in the basement of the ground 50 and having the above-described denitration apparatus 10 shown in FIG. 7, and a purified purified gas 15 It is comprised from the discharge duct 56 provided in the one end side of the piping 55 which discharges to the exterior.
[0069]
According to this exhaust gas treatment facility, a large amount of nitrogen oxide contained in the exhaust gas from the vehicle floating near the intersection can be efficiently and continuously denitrated. Further, since denitration can be performed at room temperature, power consumption is extremely small.
[0070]
Note that the denitration apparatus according to the present invention is not limited to the purification of the gas in the vicinity of the above-described intersection, but other than the intersection, for example, the atmosphere gas in the tunnel or the closed parking lot, the exhaust gas from the internal combustion engine, the exhaust from the industrial equipment Nitrogen oxides in the gas can be efficiently denitrated.
[0071]
[Sixth Embodiment]
FIG. 9 is a schematic view of a denitration apparatus according to the sixth embodiment.
As shown in FIG. 9, the denitration apparatus according to the present embodiment includes a catalyst layer 12 made of a nitrogen oxide removing catalyst that is mounted in a circular cylindrical body 41 that is open at both ends and that supports urea on a carbon material. The layered nitrogen oxide purifying means 13, the driving means 61 for rotating the cylindrical body 41, and the dry gas supply means 63 for supplying low humidity or dry air 62 to the ¾ portion of the cylindrical body 41. It comprises. Note that dust is removed by the filter 65 when the suction gas is introduced by the suction fan 64 that sucks the introduction gas 14. In addition, dust is removed by a filter 67 when the dry air 62 is introduced by the pushing fan 66 that supplies the nitrogen oxide removing means 13.
[0072]
When the gas 14 containing nitrogen oxides is introduced from the back side of the nitrogen oxide purifying means 13 to denitrate the nitrogen oxides NOx in the gas and discharged as the purified gas 15, the driving means 61 rotates to rotate the cylinder. By rotating the body, the nitrogen oxide purifying means 13 is always in a dry state to improve the denitration efficiency.
[0073]
Hereinafter, although the suitable test example which shows the effect of this invention is demonstrated, this invention is not limited to this.
[0074]
[Test Example 1]
In this test example, activated carbon fiber carrying a predetermined amount of urea was filled inside the cylindrical tube, and 500 ppm of NO was supplied as a simulated gas.
The NO concentration in the gas discharged from the other end of the cylindrical tube was measured.
The activated carbon fiber used is pitch-based (fiber diameter: 16 to 20 μm) “OG-20A” (product name: manufactured by Adol), and is heat-treated at a high temperature (800 ° C.) during manufacture.
[0075]
Those loaded with 8.6%, 12%, 19.2% and 25.4% of urea on 0.5 g of this activated carbon fiber were subjected to the test.
For the adjustment, an aqueous urea solution was used, and a product supported on activated carbon fibers so as to be a predetermined amount was dried under reduced pressure under a condition of 50 ° C. or lower.
In addition, the 0% thing which does not carry | support urea is used for the comparison.
The gas to be supplied has an NO concentration of 500 ppm and O ₂ Concentration 21%, N ₂ Was used as a balance. The gas flow rate was 100 ml / min. The reaction atmosphere temperature was 30 ° C., and the relative humidity was 0%.
The result is shown in FIG.
[0076]
As shown in FIG. 10, the duration of the denitration rate increased as the amount of urea loaded increased.
In addition, at the start of denitration, NO is NO when the denitration rate temporarily decreases ₂ It is presumed that the denitration rate temporarily decreased because of the small amount of oxidation.
In addition, it is guessed that the denitration rate is improved with the transition of the denitration time because urea supported on the surface of the activated carbon fiber is gradually disappeared and the active points of the activated carbon fiber are increased.
[0077]
[Test Example 2]
In this test example, a heat treatment temperature of the activated carbon fiber of Test example 1 was set to 1100 ° C.
Those loaded with 7%, 15%, 20.4% and 36.8% of urea on 0.5 g of this activated carbon fiber were used for the test. In addition, the 0% thing which does not carry | support urea is used for the comparison. Other conditions are the same as in Test Example 1.
The result is shown in FIG.
[0078]
As shown in FIG. 11, the duration of the denitration rate increased as the amount of urea loaded increased. Further, the denitration rate is improved as compared with Test Example 1.
[0079]
[Test Example 3]
In this test example, activated carbon fiber carrying a predetermined amount of urea was filled inside the cylindrical tube, and 500 ppm of NO was supplied as a simulated gas.
The NO concentration in the gas discharged from the other end of the cylindrical tube was measured.
The activated carbon fiber used is PAN-based (fiber diameter: 3 to 5 μm) “FE300” (product name: manufactured by Toho Linux Co., Ltd.) and is not subjected to high-temperature heat treatment.
[0080]
Those loaded with 0.9%, 4.6% and 7.2% urea on 0.5 g of this activated carbon fiber were used for the test. In addition, the 0% thing which does not carry | support urea is used for the comparison. Other conditions are the same as in Test Example 1.
The result is shown in FIG.
[0081]
As shown in FIG. 12, the duration of the denitration rate increased as the amount of urea loaded increased.
[0082]
[Test Example 4]
In this test example, activated carbon carrying a predetermined amount of urea was filled in the cylindrical tube, and 500 ppm of NO was supplied as a simulated gas.
The NO concentration in the gas discharged from the other end of the cylindrical tube was measured.
The activated carbon used was coconut shell activated carbon, which was not subjected to high temperature heat treatment.
[0083]
What loaded 7.6% urea with respect to 0.75g of this activated carbon was used for the test. In addition, the 0% thing which does not carry | support urea is used for the comparison. Other conditions are the same as in Test Example 1.
The result is shown in FIG.
[0084]
As shown in FIG. 13, the denitration time could be increased even when coconut shell activated carbon was used as the carbon material.
[0085]
[Test Example 5]
In this test example, the activated carbon fiber loaded with urea in Test Example 1 was once subjected to denitration, and then 17.4% of urea loaded on 0.5 g of activated carbon fiber was reused.
In addition, the comparison is a new product with a urea loading of 19.2% in (4) of Test Example 1.
Other conditions are the same as in Test Example 1.
The result is shown in FIG.
[0086]
As shown in FIG. 14, the reduction in the initial denitration rate was improved.
[0087]
[Test Example 6]
In this test example, the activated carbon fiber of Test example 2 was used, and the relative humidity was changed to 0, 20, 40, 60, and 80%, respectively.
[0088]
In the test, 15% [1], 11.6% [2], 12.2% [3], 12.2% [4], 14.4% [5] with respect to 0.5 g of activated carbon fiber. Each of these loaded with urea was subjected to the test. In addition, the 0% thing which does not carry | support urea is used for the comparison.
Other conditions are the same as in Test Example 1.
The result is shown in FIG.
[0089]
As shown in FIG. 15, when the relative humidity was 60% or more, the denitration rate was reduced by 50%. In particular, when the relative humidity was 0%, a high denitration rate was exhibited.
[0090]
[Test Example 7]
In this test example, the activated carbon fiber of Test example 2 was used, the amount of activated carbon fiber was tripled to 1.5 g, and the amount of urea supported was 11.8%. The concentration of supplied NO was 100 ppm.
Other conditions are the same as in Test Example 1.
The result is shown in FIG.
[0091]
The left vertical axis in FIG. 16 represents the denitration rate, and the right vertical axis represents the gas concentration.
In FIG. 16, NO and NO ₂ Measure the amount of NOx removal and NO, NO ₂ The relationship of emissions is shown.
As shown in FIG. 16, the denitration rate once decreased at the beginning of the treatment was stabilized as the treatment time passed, and the denitration rate was maintained at 360% for 360 hours.
After 385 hours, NO ₂ This is because urea supported on the activated carbon fiber disappeared and the denitration effect decreased.
[0092]
[Test Example 8]
In this test example, the activated carbon fiber of Test Example 2 was used, the amount of activated carbon fiber was 4 times 2 g, and the amount of urea supported was 9.4%. The gas to be supplied is replaced with NO in Test Example 7 ₂ (Concentration 100 ppm).
Other conditions are the same as in Test Example 1.
The result is shown in FIG.
[0093]
The left vertical axis in FIG. 17 represents the denitration rate, and the right vertical axis represents the gas concentration.
In FIG. 17, NO and NO ₂ Measure the amount of NOx removal and NO, NO ₂ The relationship of emissions is shown.
As shown in FIG. 17, it was confirmed that good denitration was maintained without a decrease in the denitration rate once decreasing at the beginning of the treatment shown in FIG. 16.
[0094]
[Test Example 9]
In this test example, denitration was performed in two stages using the activated carbon fiber of Test example 2. As the first-stage cylindrical tube, an activated carbon fiber that does not carry urea is used. The activated carbon fiber was 0.5 g.
In the second stage cylindrical tube, 0.5 g of activated carbon fiber supporting 18% urea was used.
Other conditions are the same as in Test Example 1.
The result is shown in FIG.
[0095]
The left vertical axis in FIG. 18 represents the denitration rate, and the right vertical axis represents the gas concentration.
In FIG. 18, NO and NO ₂ Measure the amount of NOx removal and NO, NO ₂ The relationship of emissions is shown.
As shown in FIG. 18, it was confirmed that good denitration was maintained without a decrease in the denitration rate once decreasing at the beginning of the treatment shown in FIG.
[0096]
[Test Example 10]
In this test example, the activated carbon fiber of Test Example 2 was used, the activated carbon fiber was 0.5 g, the urea loading was 21%, and the relationship between the denitration reaction and humidity was tested.
At the initial stage of the reaction, the relative humidity was set to 70%, and switched to 0% after 13.5 hours.
Other conditions are the same as in Test Example 1.
The result is shown in FIG.
[0097]
The left vertical axis in FIG. 19 represents the denitration rate, and the right vertical axis represents the gas concentration.
In FIG. 19, NO and NO ₂ Measure the amount of NOx removal and NO, NO ₂ The relationship of emissions is shown.
As shown in FIG. 19, when the humidity was 70%, the denitration efficiency decreased to 20%. On the other hand, when the humidity was 0%, the denitration rate was improved, and a high denitration rate of 80% could be maintained.
[0098]
[Test Example 11]
In this test example, 1 g of urea powder (60-200 mesh) is mixed with 0.5 g of silica wool (1-6 μm), and the presence or absence of denitration reaction when NO with a gas concentration of 500 ppm is passed is determined. Tested.
Other conditions are the same as in Test Example 1.
The result is shown in FIG.
[0099]
The left vertical axis in FIG. 20 represents the denitration rate, and the right vertical axis represents the gas concentration.
In FIG. 20, NO and NO ₂ Measure the amount of NOx removal and NO, NO ₂ The relationship of emissions is shown.
As shown in FIG. 20, even when urea is mixed, the oxidation reaction by the carbon material (NO → NO ₂ ), NO was discharged almost 100% as it was.
[0100]
[Test Example 12]
In this test example, 1 g of urea powder (60-200 mesh) is mixed with 0.5 g of silica wool (1-6 μm), and NO concentration with a gas concentration of 500 ppm is mixed. ₂ The presence or absence of the denitration reaction when passing through was tested.
Other conditions are the same as in Test Example 1.
The result is shown in FIG.
[0101]
The left vertical axis in FIG. 21 represents the denitration rate, and the right vertical axis represents the gas concentration.
In FIG. 21, NO and NO ₂ Measure the amount of NOx removal and NO, NO ₂ The relationship of emissions is shown.
As shown in FIG. 21, in the presence of urea alone, the removal rate was only about 8%.
[0102]
【The invention's effect】
As described above, according to the present invention, urea is supported and activated on the carbon material, and NO and NO of nitrogen oxides in the gas. ₂ Therefore, the denitration efficiency is improved and the reaction is performed at room temperature, so that the power consumption of the denitration facility can be reduced.
[0103]
Further, urea is supported on a carbon material, and NO in the gas is changed to NO. ₂ Since the nitrogen oxide is reduced while being oxidized, the denitration efficiency is improved and the reaction is performed at room temperature, so that the power consumption of the denitration facility can be reduced.
[0104]
Further, since the amount of urea supported may be 0.5% by weight or more, efficient denitration can be performed using a small amount of urea.
[0105]
Moreover, denitration efficiency will improve by making a moisture content less than 10 weight%.
[0106]
Further, by subjecting the carbon material to high temperature heat treatment under an inert gas atmosphere, the oxidizing power to NO, the activation of the supported urea, the water resistance are improved, and the denitration efficiency is improved.
[0107]
Moreover, NO is made into NO by making the said carbon material into activated carbon or activated carbon fiber. ₂ It is possible to provide a nitrogen oxide removal catalyst having improved oxidizing power.
[0108]
Further, denitration can be performed continuously for a long time by reducing the nitrogen oxide in the gas using the nitrogen oxide removing catalyst.
[0109]
Further, the denitration efficiency is improved by treating the relative humidity in the reaction at 40% or less.
[0110]
In addition, the reduction of the processing cost can be achieved by performing the reduction treatment in a low temperature region of 200 ° C. or lower.
[0111]
Moreover, by using a denitration apparatus equipped with a nitrogen oxide purification means having the nitrogen oxide removal catalyst, it is possible to efficiently denitrate nitrogen oxides in the gas.
[0112]
Further, by providing the denitration apparatus with a drying means for drying the processing gas, the denitration can be performed in a dry atmosphere, and the denitration efficiency is improved.
[0113]
Further, by providing a drying means for drying the nitrogen oxide removing catalyst, it is possible to perform denitration in a dry atmosphere, and the denitration efficiency is improved.
[0114]
In addition, the denitration apparatus includes urea support means for supporting urea on the carbon material by spraying or dipping, whereby urea can be supported and continuous denitration can be performed.
[0115]
Further, the denitration efficiency can be improved by providing a plurality of the nitrogen oxide purification means.
[0116]
Further, in the denitration apparatus, by providing an oxidation means on the upstream side of the nitrogen oxide purification means, NO in the gas is changed to NO. ₂ It can be oxidized to improve the denitration efficiency.
[0117]
Further, in the denitration apparatus, the nitrogen oxide purification means is arranged in series, and the amount of urea supported by the nitrogen oxide purification means on the gas introduction side is set to 20% by weight or less, so that NO in the gas can be reduced. NO ₂ It can be oxidized to improve the denitration efficiency.
[0118]
Moreover, in the denitration apparatus, the dust in the gas can be efficiently removed by providing the dust removal means on the upstream side of the nitrogen oxide purification means.
[0119]
Further, in the denitration apparatus, by providing a desulfurization means on the upstream side or the downstream side of the nitrogen oxide purification means, not only nitrogen oxides in the gas but also sulfur oxides can be efficiently removed. .
[0120]
In addition, as a gas applied to the denitration apparatus, nitrogen oxides in the gas can be efficiently used even in any of atmosphere gas at intersections, tunnels or closed parking lots, exhaust gas from internal combustion engines, and exhaust gas from industrial facilities. It can be denitrated.
[Brief description of the drawings]
FIG. 1 is a schematic view of a denitration apparatus according to a first embodiment.
FIG. 2 is a schematic view of another denitration apparatus according to the first embodiment.
FIG. 3 is a schematic view of a denitration apparatus according to a second embodiment.
FIG. 4 is a schematic view of a denitration apparatus according to a third embodiment.
FIG. 5 is a schematic view of a denitration apparatus according to a fourth embodiment.
FIG. 6 is a schematic view of a denitration apparatus according to a fifth embodiment.
FIG. 7 is a perspective view of a denitration apparatus according to a fifth embodiment.
FIG. 8 is a schematic view of an exhaust gas treatment facility provided with a denitration apparatus according to a fifth embodiment.
FIG. 9 is a schematic view of a denitration apparatus according to a sixth embodiment.
10 is a graph showing the results of Test Example 1. FIG.
11 is a graph showing the results of Test Example 2. FIG.
12 is a graph showing the results of Test Example 3. FIG.
13 is a graph showing the results of Test Example 4. FIG.
14 is a graph showing the results of Test Example 5. FIG.
15 is a graph showing the results of Test Example 6. FIG.
16 is a graph showing the results of Test Example 7. FIG.
17 is a graph showing the results of Test Example 8. FIG.
18 is a graph showing the results of Test Example 9. FIG.
19 is a graph showing the results of Test Example 10. FIG.
20 is a graph showing the results of Test Example 11. FIG.
21 is a graph showing the results of Test Example 12. FIG.
FIG. 22 is a schematic view of a denitration reaction mechanism.
FIG. 23 is a schematic view of activated carbon fibers and activated carbon.
FIG. 24 is a schematic view of a conventional denitration apparatus.
[Explanation of symbols]
10 Denitration equipment
11 Processing container body
12 Catalyst layer
13 Nitrogen oxide purification means
14 Nitrogen oxide (NOx)
15 Purified gas
16 Desulfurization equipment

Claims (7)

The activated carbon fiber heat-treated at 600-1300 ° C. in an inert gas atmosphere carries urea at 0.5% by weight or more,
As a moisture content of less than 10 wt%, by the activated carbon fiber while oxidize NO in the gas to NO _2, a reduction to that nitrogen oxide-removing catalyst of the NO ₂ to N ₂ in the gas by the urea Comprising a plurality of stages of nitrogen oxide purification means in series,
The urea loading of the nitrogen oxide purification means on the gas introduction side is 20% by weight or less,
A denitration apparatus characterized in that the amount of urea loaded on the front stage is smaller than the amount of urea loaded on the rear stage. In claim 1 ,
A denitration apparatus comprising a drying means for drying a processing gas. In claim 1 or 2 ,
A denitration apparatus comprising a drying means for drying a nitrogen oxide removing catalyst. In any one of Claims 1 thru | or 3 ,
A denitration apparatus comprising urea supporting means for supporting urea on the carbon material by spraying or dipping. In any one of claims 1 to 4 ,
A denitration apparatus comprising dust removal means provided on the upstream side of the nitrogen oxide purification means. In any one of claims 1 to 5 ,
A denitration apparatus, wherein a desulfurization means is provided on the upstream or downstream side of the nitrogen oxide purification means. In any one of claims 1 to 6 ,
The denitration apparatus, wherein the gas containing nitrogen oxide is any one of an atmosphere gas in an intersection, a tunnel or a closed parking lot, an exhaust gas from an internal combustion engine, and an exhaust gas from an industrial facility.

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