JP3252696B2 - Purification method of exhaust gas containing oxidizable nitrogen compound - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a purification method for oxidizing and decomposing oxidizable nitrogen compounds such as ammonia contained in various kinds of exhaust gas into nitrogen gas and water to make them harmless. Furnace exhaust gas, various chemical factory exhaust gas, ammonia stripping exhaust gas, flue gas denitration exhaust gas by ammonia, urban cleaning facility, urban water purification facility,
It can be effectively used for purification treatment of oxidizable nitrogen-containing exhaust gas such as exhaust gas from a sludge treatment facility.

[0002]

2. Description of the Related Art For example, ammonia stripping is a useful method for reducing the total nitrogen concentration in various kinds of wastewater, and has recently received particular attention as a technique for preventing eutrophication in lakes, marshes and closed sea areas. To put this method into practical use, it is necessary to detoxify ammonia-containing gas emitted from wastewater.

[0003] A flue gas denitration method generally used as a method for removing nitrogen oxides from flue gas discharged from a power plant or the like is a selective catalytic reduction using ammonia as a reducing agent. It has been widely used mainly. recent years,
Installation of gas turbines and the like for power plants is being promoted mainly in urban areas in order to cope with the increase in power demand, and nitrogen oxides emitted from these facilities pose a serious problem from the viewpoint of living environment conservation. In addition, the area where these facilities are provided is often an area subject to the regulation of the total amount of nitrogen oxides, and it is desired to reduce the amount of nitrogen oxides in exhaust gas to an extremely low level. For this reason, methods such as enhancing the high-efficiency operation of the denitration device by setting the ammonia injection amount to be larger than the stoichiometric amount are being studied.However, if such a method is adopted, excessive addition of denitration causes denitration. It is necessary to reduce unreacted ammonia (leak ammonia) not used in the reaction. In order to remove excess ammonia, an oxidative decomposition method of ammonia is often used, but a method that does not generate a large amount of nitrogen oxides at that time,
That is, a processing method that can realize high selectivity decomposition into nitrogen and water is required.

[0004] On the other hand, as a method of purifying ammonia-containing exhaust gas, a method of neutralizing and absorbing ammonium dilute sulfuric acid to form ammonium sulfate has been known for a long time. As another method, a treatment method using a catalyst, for example, A purification method as shown in FIG. 5 is often used. In this method, an exhaust gas to be treated is diluted with air, heated to a predetermined temperature by a heat exchanger (1), a heater (4), or the like, and then passed through a single-stage reactor (3) filled with an oxidation catalyst. This is a method for decomposing ammonia. The purified gas discharged from the reactor (3) is
Since the temperature is raised by the oxidative decomposition reaction, the temperature is returned to the heat exchanger (1) and used for raising the temperature of the exhaust gas to be treated. In the figure, B indicates a blower (blower) and F indicates a flow meter.

[0005]

However, in the above-mentioned method for forming ammonium sulfate using a dilute aqueous solution of sulfuric acid, further treatment in a post-process is required in order to prevent eutrophication of lakes, marshes and closed sea areas. Further, the detoxification method of ammonia using the catalyst impregnator single stage, if you want the ammonia and NO _x concentration of the treated gas discharged from the outlet of the reactor was reduced to about several ppm, the reactor inlet When the ammonia concentration on the inlet side is relatively low, not more than 3,000 ppm in terms of nitrogen, the purpose can be achieved for the time being. However, when the ammonia concentration on the inlet side becomes higher than this, the outlet concentration becomes the target concentration. In many cases, it cannot be reduced.

The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce the content of an oxidizable nitrogen compound such as ammonia contained in an exhaust gas to be treated in terms of nitrogen. An object of the present invention is to provide a purification method capable of efficiently decomposing and detoxifying such nitrogen compounds even when applied to the treatment of exhaust gas having a high concentration exceeding 3,000 ppm.

[0007]

Means for Solving the Problems The purification method according to the present invention which can solve the above-mentioned problems is a method for oxidatively purifying an exhaust gas containing an oxidizable nitrogen compound using a catalyst. The reactor is divided into a pre-reactor and a post-reactor in the flow direction of the exhaust gas, and the temperature of the exhaust gas from the pre-reactor is lowered before being introduced into the post-reactor, or discharged from the pre-reactor. A cooling gas is mixed with the upstream processing gas upstream of the downstream reactor to lower the temperature of the upstream processing gas, or heat is exchanged with cooling air or the like by passing the upstream processing gas through a heat exchanger. Or a reactor filled with a catalyst is divided into a pre-reactor and a post-reactor in the exhaust gas flow direction, and the oxidizable nitrogen compound-containing exhaust gas is branched and partially supplied to the pre-reactor. With The remaining portion is introduced into the subsequent reactor together with the pre-process gas discharged from the pre-reactor to oxidatively purify the remaining gas and reduce nitrogen oxides in the pre-process gas. Have. Previous
The purification method according to the present invention comprises:
From the group consisting of titanium, silica, and zirconium
At least one oxide selected; and as the B component:
Consists of vanadium, tungsten, cesium and iron
At least one oxide selected from the group; C component;
Platinum, palladium, rhodium, ruthenium, iri
Select from the group consisting of jium, manganese, chromium and copper
At least one metal and / or oxide
And the gas supplied to the subsequent reactor.
The ratio of the oxidizable compound / reducible compound is 1.5 or more
It also has that characteristic.

In carrying out the above purification method,
In order to suppress the generation of nitrogen oxides (NOx) in the latter reactor, it is desirable to keep the temperature of the latter reactor at 450 ° C. or lower. Also Component A: 70 to 99 wt%, B component: 0.
A catalyst containing 5 to 20 % by weight and C component: 0.001 to 20% by weight is particularly effective. Examples of the oxidizable nitrogen compound contained in the exhaust gas to be treated in the present invention include ammonia, a nitrile compound, an amine compound, and an imine compound.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The present inventors have developed a method for purifying oxidizable nitrogen compounds by oxidatively decomposing an oxidizable nitrogen compound by passing the exhaust gas through a one-stage catalyst-filled reactor. We worked hard to overcome the difficulties we saw. as a result,
As described above, the reactor filled with the catalyst is divided into a pre-reactor and a post-reactor in the exhaust gas flow direction.First, the exhaust gas to be treated is heated to an appropriate temperature by a heater, and then the pre- To perform the oxidative decomposition, and then the temperature of the pre-process gas discharged from the pre-stage reactor rises due to the heat of decomposition, and the temperature of the pre-process gas is lowered by heat exchange with a heat exchanger or a cooling gas. Or an oxidative decomposition reaction in a subsequent reactor, or a pretreatment in which the exhaust gas containing the oxidizable nitrogen compound is branched and partially supplied to the former reactor, and the remainder is discharged from the former reactor. By introducing a gas together with the gas into the subsequent reactor to purify the remaining gas oxidatively and reducing the nitrogen oxides in the pretreatment gas, the oxidizable nitrogen compounds contained in the exhaust gas can be reduced. Extremely efficient Solution can be removed and finally the nitrogen compound concentration in the purified gas discharged was confirmed that it is possible to reduce to a very low level of below several ppm.

In this case, the preferable heating temperature of the exhaust gas to be blown into the first-stage reactor is about 200 to 400 ° C., and the ammonia / NO _x ratio in the first-stage processing gas discharged from the first-stage reactor is 1%. .5 or more,
By blowing in a heat exchanger and cooling air lowers the gas temperature, on the other hand, if the ammonia / NO _x ratio is 1.5 or less, the secondary reaction the portion of the nitrogen-containing gas supplied to the front stage reactor A method is preferably employed in which the gas is mixed with the pre-process gas in the upstream side of the reactor or in the latter-stage reactor and subjected to a purification reaction in the latter-stage reactor.

FIG. 1 is a flowchart showing a basic configuration of an exhaust gas purifying method according to the present invention. In FIG. 1, B is a blower and (1)
Is a heat exchanger, (4) is a heater, (5) is a pre-stage reactor,
(7) the latter stage reactor, F is the flow meter, V ₁ ~V ₅ shows the valve respectively.

In a first mode of performing the exhaust gas purifying process by the method shown in FIG. 1, the valves V ₁ and V ₂ are opened, and the valves V ₃ to V ₃ are opened.
The V ₅ leave closed, the treated flue gas blower (blower)
B is heated to an appropriate temperature by the heat exchanger (1) and the heater (4), and then sent to the preceding reactor (5) to perform oxidative decomposition, and the oxidative decomposition reaction in the reactor (5) after lowering the temperature by heat exchange (heating of the treated flue gas) to pre-process gas is discharged heated through the heat exchanger (1) by, is fed into the valve V ₂ subsequent reactor to (7) Purification is performed by performing oxidative decomposition again.

In a second mode, the valves V ₁ , V ₂ , V
₅ is closed and the valves V ₃ and V ₄ are opened, and the exhaust gas to be treated is passed from the blower B to the heat exchanger (1) and the heater (4).
To a moderate temperature (in this case, heating by the heat exchanger (1) is not performed) and then sent to the reactor (5) in the preceding stage to perform oxidative decomposition, and in the reactor (5) the pre-process gas discharged was raised by oxidative decomposition reaction of the reaction part of the treated flue gas coming sent from the valve V ₄ and / or the cooling air from the cooling by an appropriate amount mixed in the subsequent stage Purification is carried out by feeding into the vessel (7) and performing oxidative decomposition again.

At this time, if only the cooling air is blown in, the temperature of the pre-process gas can be lowered thereby, and if a method of mixing a part of the exhaust gas to be processed is adopted, the mixing of the exhaust gas can be reduced. In addition to the above, the following effects can be obtained in addition to the temperature reduction of the pre-process gas. That is, the reaction in the first-stage reactor (5) is preferably maintained at a temperature of about 500 ° C. or less in order to suppress the generation of NO _x due to an excessive temperature rise, as described in detail later. A quantity of NO _x may be produced. However, if the method of mixing a part of the exhaust gas to be treated into the pre-process gas and subjecting it to the treatment in the latter-stage reactor (7) as described above is adopted, the oxidizable nitrogen compound contained in the exhaust gas to be treated is adopted. As a result, NO _x is reduced and removed, and the amount of NO _x mixed into the purified gas can be effectively suppressed.

In addition, the first stage processing gas is cooled by utilizing heat exchange with cooling air or the like taken in from the outside air, or by combining the first and second embodiments, and raising the temperature in the first stage reactor (5). (1) for cooling the pre-process gas discharged
It is also possible to use a mixing of the treated flue gas (or air) is fed from the heat exchanger and the valve V ₄ at.

FIG. 2 shows another flow chart when the present invention is carried out, and shows two heat exchangers (1) and (3).
This shows an example in which the thermal efficiency is further improved by the method. That is, the basic configuration of this figure is the same as that of FIG. 1, but the pre-process gas discharged from the pre-reactor (5) passes through the heat exchanger (1) to exchange heat, and the post-reactor (7) ) Is also passed through the heat exchanger (3) so that it can be effectively used for raising the temperature of the exhaust gas to be treated, and other configurations are substantially the same as those in FIG. FIG. 3 is a flow chart showing still another embodiment, in which air and / or a part of the exhaust gas to be treated is used to lower the temperature of the pre-process gas discharged from the pre-reactor (5), and the post-reactor (7) is used. ) Is passed through the heat exchanger (3) so that it can be effectively used. That is, the Atsushi Nobori was the pretreatment gas preceding reactor (5), the temperature was lowered by the incorporation of cooling air supplied through a valve V ₆ or V _7, and / or treated exhaust gas supplied through the valve V ₄ The temperature is lowered by mixing a part of the mixture, and then the mixture is supplied to the subsequent reactor (7).

FIG. 4 is a flow chart showing still another embodiment, in which a pre-process gas discharged from a pre-reactor (5) is passed through a heat exchanger (8) to be mixed with cooling air taken in from outside air. The temperature of the pre-process gas is lowered by heat exchange and then sent to the post-reactor (7), and the other configuration is essentially the same as the above-described example.

As described above, in the present invention, instead of performing oxidative decomposition in a single-stage reactor, oxidative decomposition is performed in separate reactors in the first and second stages, and the oxidative decomposition is performed in the first-stage reactor (5). By adopting a method in which the temperature of the heated pre-process gas is lowered before being subjected to the oxidative decomposition reaction in the post-reactor (7), the nitrogen oxides in the exhaust gas to be treated are efficiently decomposed, and in particular, the post-process gas is decomposed. by mixing a portion of the gas to be treated in the pretreatment gas prior to treatment in the reactor (7), it is possible to suppress the generation amount of the NO _x as much as possible.

In carrying out the method of the present invention, the dispensing ratio of the exhaust gas to be treated when using the cooling gas, that is,
The ratio of the amount of exhaust gas for cooling between the upstream and downstream reactors to the amount of exhaust gas supplied to the upstream reactor (the amount of exhaust gas for cooling / the amount of exhaust gas to the upstream reactor) is 1 when the pipette is shared with the heat exchanger. .
0 or less, more preferably 0.7 or less, still more preferably 0.4 or less. If the dispensing ratio exceeds 1.0, the gas temperature becomes too low and ammonia, NO _x tends to remain easily. On the other hand, when performing gas cooling by dispensing alone without using a heat exchanger, a preferable dispensing ratio is 0.01 to 1.0, more preferably 0.1 to 1.0.
02 to 0.7, more preferably in the range of 0.02 to 0.4, easily remain NO _x is less than 0.01, 1.
If it exceeds 0, the gas temperature will drop too much and ammonia, NO _x
Both become easier to remain.

A preferable injection ratio when the exhaust gas to be treated and air are used together for gas cooling, that is, the ratio of the amount of cooling air between the upstream and downstream reactors to the amount of exhaust gas supplied to the upstream reactor (cooling amount) The amount of air / the amount of exhaust gas to the pre-reactor) is preferably 0.4 or less for the same reason as above when the heat exchanger and the cooling air are shared, and 0.02 for the same reason as above when cooling air alone is used. A range of -0.4 is preferred.

Examples of the nitrogen compound contained in the exhaust gas to be treated in the present invention include ammonia, various nitriles, amine compounds and imine compounds as oxidizable compounds. Even when the reducing compounds (NO _x ) are mixed, they are effectively reduced and removed by the oxidizable nitrogen compounds such as ammonia contained in the gas to be treated as described above. Therefore, the oxidizable compound contained in the exhaust gas to be treated provided in the present invention /
The ratio of the reducible compound is 1.1 or more, more preferably 1.5 or more, and still more preferably 2.5 or more.
In less than 1, there is a tendency for NO _x residual amount after treatment is more unfavorable.

In carrying out the present invention, the concentration of the nitrogen compound in the exhaust gas supplied to the pre-stage reactor is 3,000 to 50,000 p.
pm, preferably in the range of 5,000 to 30,000 ppm, and if it is less than 3,000 ppm, it is possible to sufficiently cope with the above-described one-step catalytic oxidative decomposition, and thus it is not necessary to employ the present invention. Also 50,000p
If the concentration is excessively higher than pm, the calorific value in the reactor becomes too large, and the catalyst is exposed to a high temperature and is susceptible to thermal deterioration.

In the ammonia water vapor stripping treatment, sometimes the ammonia gas concentration is 200,000 p.
pm in some cases, but in such a case, it may be diluted and supplied with air or the like.

On the other hand, the ratio of the oxidizable compound / reducible compound of the gas supplied to the subsequent reactor, that is, the pre-process gas discharged from the pre-reactor, or the post-reactor or upstream thereof When the exhaust gas to be treated and / or the cooling air is introduced, the ratio of the oxidizable compound / reducible compound in the mixed gas is 1.5 or more , preferably 2.5 or more. If it is less than 1.5, it is not preferable because it is impossible to perform advanced treatment of NOx.

The nitrogen compound concentration in the gas supplied to the latter reactor, that is, when a part of the cooling gas or the exhaust gas to be treated is mixed in the upstream gas or the upstream reactor of the downstream reactor or the downstream reactor. The preferred concentration of nitrogen compounds in the mixed gas is 2% in terms of nitrogen for oxidizable compounds.
0 to 8,000 ppm, preferably 100 to 5,000 ppm
It is 0 ppm. If it is less than 20 ppm, advanced treatment of NO _x becomes difficult, and if it exceeds 8,000 ppm, the temperature rise due to heat generation during the oxidative decomposition reaction becomes so severe that the advanced treatment of nitrogen compounds tends to be difficult.

In carrying out the purification method of the present invention, the preferred space velocity (S
V) is a catalyst packed bed in the pre-reactor of 500 to 20,000
00Hr ^-1 , more preferably 1,000 to 10
It is 0.001 hr ^-1 . If it is less than 500 Hr ^-1 , the processing apparatus must be excessively large with respect to the processing amount, which is not practical. If it exceeds 200,000 Hr ^-1 , it becomes difficult to obtain a sufficient decomposition efficiency. The preferred space velocity of the catalyst packed bed in the downstream reactor is from 600 to 100,0.
00Hr ^-1 , more preferably 1,000 to 50,000
A ^Hr-1, is less than 600Hr ^-1 would have to excessively increase the processing apparatus, whereas 100000Hr
Beyond ^-1, advanced treatment control of the NO _x becomes difficult.

The preferred inlet temperature of the first stage reactor is 100 to
500 ° C, more preferably in the range of 150 to 450 ° C.
If the temperature is lower than 100 ° C., the processing efficiency is not sufficiently increased.
If the temperature exceeds 500 ° C., the concentration of nitrogen compounds in the non-process gas becomes
As the temperature increases, the temperature of the catalyst packed bed rises remarkably and NO
_x The generation rate increases. The preferred inlet temperature of the downstream reactor is
150-450 ° C, more preferably 200-400 ° C
Below 150 ° C, oxidative decomposition of nitrogen compounds
It does not proceed sufficiently, whereas if it exceeds 450 ° C, NO_xAltitude removal
It becomes difficult to leave. In addition, prior to the treatment in the subsequent reactor,
When adopting the method of mixing part of the processing exhaust gas,
As described above, some NO is contained in the pre-process gas. _x Is mixed
However, these are oxidizable compounds contained in the exhaust gas to be treated.
Temperature, the temperature of the pre-reactor is slightly reduced.
Or you can set it higher.

The catalyst used in the present invention includes at least one oxide selected from aluminum, titanium, silica and zirconium as the component A, and at least one oxide selected from vanadium, tungsten, cesium and iron as the component B. One kind of oxide, C component, platinum, palladium, rhodium, ruthenium, iridium,
At least three components of A, B and C composed of at least one metal and / or oxide selected from manganese, chromium and copper are used, and if these mixed catalysts are used, NO _x is contained in exhaust gas. Even if the nitrogen compound such as ammonia is present several times, the ammonia component and NOx can be simultaneously and efficiently removed without strict flow control unlike a normal denitration catalyst.

The catalyst is obtained by adding at least one of the B component and the C component to a molded body made of the oxide as the A component.
The compounds and / or oxides of the species may be supported simultaneously or separately, or one or more of the above components A, B and C may be mixed and molded.

The catalyst charged in the first-stage reactor is A
The total of at least one oxide constituting the component is 70 to
It is preferable that the catalyst contains 99% by weight. If it is less than 70% by weight, the activity and durability of the catalyst may be insufficient.
If it exceeds 9% by weight, the catalytic activity tends to be insufficient. Further, the catalyst to be charged into the latter-stage reactor contains 8% of the A component in order to enhance the selective reactivity of the nitrogen compound to N ₂ .
Those containing 0 to 95% by weight are preferred. The component A is preferably contained in the catalyst as an oxide and / or a composite oxide, thereby providing a catalyst having excellent activity and durability.

The preferred content of the B component in the catalyst charged into the pre-stage reactor is in the range of 0.5 to 20 % by weight. No activity can be expected, and even if it is added in excess of 20 % by weight, no further improvement in catalytic activity can be obtained. Further, the catalyst filled in the latter reactor contains at least one oxide selected from vanadium, tungsten and iron in total of 1 to 20% by weight in order to enhance the selective reactivity of nitrogen compounds to N ₂ . More preferably, those containing 2 to 15% by weight are more desirable.

The catalyst used in the present invention comprises, in addition to the above-mentioned A and B components, a C component, ie, platinum, palladium, rhodium,
Preferably, it contains at least one metal selected from the group consisting of ruthenium, iridium, manganese, chromium and copper and / or an oxide thereof in a total amount of 0.001 to 20% by weight. At least one metal and / or oxide selected from palladium, rhodium, ruthenium and iridium with C
And _one component, manganese, when at least one metal selected from chromium and copper and / or oxide was C ₂ components, 0.001 to 10% by weight of C ₁ component in total and / or C ₂ components It is preferable to contain 1 to 20% by weight in total. When the C ₁ component is contained as the C component, the catalytic activity is particularly high. However, if the content of the C component as a whole is less than 0.001% by weight, the activity tends to be insufficient, and the content of the C ₁ component is low. If it exceeds 10% by weight, no further activity improvement effect can be expected. C
When using only the C ₂ component as the component, it is preferable that the content thereof to obtain a sufficient catalytic activity to 20% by weight. The preferred content of the component C is substantially the same for the catalyst charged in the reactors in both the first and second stages.

The shape of the above-mentioned catalyst used in the present invention is not limited at all, and it may be a plate, corrugated plate, net, sphere, column, cylinder, honeycomb, or honeycomb. It may be supported on a plate-like, corrugated, net-like, spherical, cylindrical, cylindrical, or honeycomb carrier made of silica, silica-alumina, cordierite, titania, stainless steel wire mesh, or the like. Further, the BET specific surface area of the catalyst is 30 m ² / g or more, more preferably 40 m ² , in the case of a molded article, from the viewpoint of exhibiting sufficient catalytic activity effectively.
/ G or more, and in the case of supporting a carrier, it is recommended to be preferably 5 m ² / g or more, more preferably 7 m ² / g or more.

[0034]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples, and the present invention is not limited thereto. Of course, the present invention can be implemented with modifications, and all of them are included in the technical scope of the present invention.

Catalyst Preparation Example 1 A composite oxide composed of titania and silica was prepared by the following method. After adding 35.5 kg of 20 wt% silica sol to 700 liter of 10 wt% ammonia water and stirring and mixing, an aqueous solution of titanyl sulfate in sulfuric acid (125 g · T
iO ₂ / liter, 0.55 g H ₂ SO ₄ / liter)
300 liters were gradually added dropwise with stirring. The resulting gel was aged, washed with filtered water, dried at 150 ° C. for 10 hours, and then calcined at 500 ° C. for 6 hours. The obtained powder composition was TiO ₂ : SiO ₂ = 4: 1 (molar ratio), and the BET specific surface area was 200 m ² / g. 20 kg of this powder is added to 2.00 kg of ammonium metavanadate.
And 12 kg of a 15% aqueous solution of monoethanolamine containing 0.77 kg of ammonium paratungstate. Starch was added as a molding aid and kneaded with a kneader.
m, a wall thickness of 0.5 mm, and a length of 450 mm. This was dried at 80 ° C. and then fired at 450 ° C. for 5 hours in an air atmosphere. The composition of this honeycomb formed body is as follows: Ti—Si composite oxide: V ₂ O ₅ : WO ₃ = 90:
7: 3 (weight ratio). The molded body is impregnated with an aqueous solution of palladium nitrate, dried at 150 ° C. for 3 hours, and then dried at 450 ° C.
Calcination was performed in an air atmosphere at a temperature for 3 hours. The composition of the obtained catalyst was as follows: Ti—Si composite oxide: V ₂ O ₅ : WO ₃ : Pd
= 88.2: 6.9: 2.9: 2 (weight ratio) and B
ET specific surface area is 120 m ² / g, pore volume is 0.45 c
c / g.

Catalyst Preparation Example 2 Ti-Z was prepared in the same manner as in Catalyst Preparation Example 1 except that an aqueous solution of zirconium chloride was used in place of the silica sol.
A honeycomb formed body of r composite oxide: V ₂ O ₅ : WO ₃ = 90: 3: 7 (weight ratio) was obtained. This compact was impregnated with an aqueous solution of copper nitrate and platinum nitrate, and a Ti—Zr composite oxide: V ₂
O ₅ : WO ₃ : Cu: Pt = 84.6: 2.8: 6.
A catalyst having a composition of 6: 5: 1 (weight ratio) was obtained. The BET specific surface area of this catalyst was 90 m ² / g.

Catalyst Preparation Example 3 Ammonium metavanadate was dissolved in an aqueous solution of monoethanolamine, and oxalic acid was added.
² / g of γ-alumina powder was charged to form a slurry. This is made into a honeycomb-shaped cordierite carrier (outside dimensions 80 mm
Square, aperture 2.0mm, wall thickness 0.5mm, length 200m
m), and dried and calcined to prepare a catalyst support. The Al ₂ O ₃ and V ₂ O ₅ contents of the catalyst support were 15% by weight and 1% by weight, respectively. This is impregnated with an aqueous solution of platinum nitrate and dried at 100 ° C.
Calcination was performed at 50 ° C. for 3 hours in an air atmosphere. Pt of the catalyst
The carried amount was 0.2% by weight.

Example 1 The following experiment was conducted using the apparatus schematically shown in FIG. At this time, the operation was performed with the valves V ₃ and V ₄ closed. That is, exhaust gas containing 9,000 ppm of ammonia and 13% of oxygen is supplied from the blower B at 50 Nm ³ / Hr, and the temperature is raised to 350 ° C. in the heat exchangers (3), (1) and the heater (4). 5 liters of the catalyst obtained in Catalyst Preparation Example 1 was introduced into the pre-reactor (5) loaded with the catalyst (SV: 10,000 hours).
^-1 )). The temperature of the gas discharged from the outlet of the catalyst packed bed of the reactor (5) was 440 ° C., the ammonia concentration was 90 ppm, and the NO _x concentration was 25 ppm. After passing this gas through the heat exchanger (1) to lower the temperature to 400 ° C., the latter reactor (7) loaded with 5 liters of the same catalyst
Introduced into (Total SV: 5,000 hr ^-1) to was subjected to a process, ammonia at the outlet portion of the catalyst-packed layer, NO _x
Were not detected.

Comparative Example 1 The following experiment was carried out using the apparatus schematically shown in FIG. That is, an exhaust gas containing 9,000 ppm of ammonia and 13% of oxygen was supplied from a blower B at 50 Nm ³ / Hr, passed through a heat exchanger (1) and a heater (4), and heated to 350 ° C., followed by catalyst preparation. Introduced into reactor (3) loaded with 10 liters of catalyst obtained in Example 1 (total SV: 5,000 Hr
^-1 ) to perform a purification treatment. As a result, the reactor (3)
Ammonia at the outlet portion of the catalyst-packed layer in was detected but, NO _x was 60 ppm.

Example 2 The following experiment was conducted using the apparatus schematically shown in FIG. That is
Exhaust gas containing 3,000 ppm of ammonia and 8% of oxygen
150 Nm from blower B^Three / Hr, heat exchange
42 through exchangers (3), (1) and heater (4)
After heating to 5 ° C., 5 liters of the catalyst obtained in Catalyst Preparation Example 1
(SV: 30, SV)
000Hr^-1)did. Outlet of the catalyst packed bed of the reactor (5)
The temperature of the gas discharged from the section is 450 ° C.
Monia concentration is 230ppm, NO _x The concentration is 150ppm
Met.

This gas is supplied to the heat exchanger (1) and the valves V ₁ ,
Through V _2, and was the feed gas having the same composition of the gas was added at 10 Nm ³ / Hr by adjusting the valve V _4, the gas temperature became 410 ° C.. When this gas was introduced into the subsequent reactor (7) loaded with 5 liters of the same catalyst (total SV: 16,000 Hr ^-1 ), the gas discharged from the outlet of the catalyst packed bed of the reactor (7) was removed. the ammonia 5ppm, NO _x was 4ppm.

Example 3 The following experiment was conducted using the apparatus schematically shown in FIG. At this time, the operation was performed with the valves V ₄ and V ₇ closed. Exhaust gas containing 10,000 ppm of ammonia and 15% of oxygen was supplied from a blower B at 100 Nm ³ / Hr, passed through a heat exchanger (3) and a heater (4) and heated to 360 ° C., and then a catalyst preparation example 5 liters of the catalyst obtained in Step 1 was introduced into the first reactor (5) (SV: 20,000 Hr
^-1 )). The temperature of the gas at the outlet of the catalyst packed bed of the reactor (5) was 440 ° C., and the ammonia concentration was 1,500.
ppm, NO _x concentration was 25 ppm.

To this gas, air at normal temperature was added at 8 Nm ³ / Hr
After the gas temperature was lowered to 405 ° C., this gas was introduced into the latter-stage reactor (7) loaded with 10 liters of the same catalyst (total SV: 7,200 Hr ⁻¹ ) to perform a purification treatment. As a result, the ammonia content in the gas discharged from the outlet of the catalyst packed bed of the reactor (7) was 6 ppm,
NO _x was 2ppm.

Example 4 The following experiment was conducted using the apparatus schematically shown in FIG. This time was carried out in state valve V ₆ is a closed. 7 ammonia
5,000 ppm, gas 10 Nm ³ with the balance being water vapor
/ Hr through the heat exchanger (3) to raise the temperature.
₇ was adjusted and air was mixed at 50 Nm ³ / Hr. After 55 Nm ³ / Hr of this gas was heated to 300 ° C. by the heater (4), it was introduced into the first (previous stage) reactor (5) loaded with 5 liters of the catalyst obtained in Catalyst Preparation Example 2 (SV). : 1
1,000 Hr ^-1 ). The temperature is 420 ° C. of the gas discharged from the catalyst-packed layer outlet of the reactor (5), the ammonia concentration is 250 ppm, NO _x concentration 400pp
m.

When the same mixed gas as described above was added at 5 Nm ³ / Hr by adjusting the valve V ₄ , the gas temperature became 390 ° C. This gas was introduced into the latter-stage reactor (7) loaded with 5 liters of the catalyst obtained in Catalyst Preparation Example 1 (total SV: 6,000 Hr ⁻¹ ), and a purification treatment was performed. ammonia concentration of the gas discharged from the catalyst-packed layer outlet is 1 ppm, NO _x was 4 ppm.

Example 5 The following experiment was performed using the apparatus schematically shown in FIG. Ammonia 16,000ppm, acrylonitrile 500p
pm, ethanolamine 100 ppm, hydrogen cyanide 1
A gas to be treated containing 00 ppm and 13% oxygen was supplied from a blower B at 45 Nm ³ / Hr, and heated to 280 ° C. in a heat exchanger (3) and a heater (4). The catalyst was introduced (SV: 9,000 Hr ^-1 ) into the pre-reactor (5) loaded with 5 liters of the catalyst, and purified. The temperature of the gas discharged from the outlet of the catalyst packed bed of the reactor (5) was 440 ° C., and the ammonia concentration was 150 ° C.
ppm, NO _x concentration was 850 ppm.

After passing this gas through the heat exchanger (8), the valve V ₄ was adjusted to supply a gas having the same composition as
After adding at Nm ³ / Hr to bring the gas temperature to 350 ° C.,
When 5 liters of the catalyst obtained in Catalyst Preparation Example 1 were loaded and introduced into the subsequent reactor (7) (total SV: 5,000 Hr ^-1 ) to perform a purification treatment, the catalyst in the reactor (7) was charged. acrylonitrile in a gas discharged from the layer outlet, ethanolamine, hydrogen cyanide is not detected, the ammonia concentration is 1 ppm, NO _x was 7 ppm.

Comparative Example 2 The following experiment was performed using the apparatus schematically shown in FIG. That is, a gas to be treated containing 13,000 ppm of ammonia, 500 ppm of acrylonitrile, 100 ppm of ethanolamine, 100 ppm of hydrogen cyanide and 13% of oxygen is supplied from the blower B at 50 Nm ³ / Hr, and the heat exchanger (1) and the heater (4) After the temperature was raised to 280 ° C. in the reactor, 10 liters of the catalyst obtained in Catalyst Preparation Example 3 was introduced (SV: 5,000 Hr ^-1 ) into the reactor (3) loaded with the catalyst, and a purification treatment was performed. ammonia was detected in the gas discharged from the catalyst-packed layer outlet (3) but, NO _x was 950 ppm.

[0049]

The present invention is constituted as described above, and is used for treating high-concentration exhaust gas in which the content of nitrogen compounds such as ammonia contained in the exhaust gas to be treated exceeds 3,000 ppm in terms of nitrogen. even when applied to, has become the generation of the NO _x with their nitrogen compound efficiently decomposed can be suppressed as much as possible, can effectively detoxify nitrogen compound-containing gas.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an embodiment of the present invention.

FIG. 2 is a flowchart showing another embodiment of the present invention.

FIG. 3 is a flowchart showing yet another embodiment of the present invention.

FIG. 4 is a flowchart showing still another embodiment of the present invention.

FIG. 5 is a flowchart showing a conventional purification treatment method.

[Explanation of symbols]

1 the first heat exchanger 3 and the second heat exchanger 4 Heater 5 first (front) reactor 7 a second (subsequent) reactor V ₁ ~V ₇ valve F flowmeter B blower (blower)

Continuation of front page (56) References JP-A-51-117168 (JP, A) JP-A-7-214044 (JP, A) JP-A-52-68858 (JP, A) JP-A-7-289897 (JP) , A) JP-A-57-119819 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01D 53/86 B01J 21/00-38/74

Claims (10)

(57) [Claims] 1. A method for oxidatively purifying an oxidizable nitrogen compound-containing exhaust gas using a catalyst, wherein the A component includes aluminum, titanium, silica and diene.
At least one member selected from the group consisting of ruconium
Oxides; vanadium, tungsten,
At least selected from the group consisting of cesium and iron
One oxide; platinum, palladium, platinum
Indium, ruthenium, iridium, manganese, chromium
At least one metal selected from the group consisting of copper and copper
And / or using a catalyst composed of an oxide, the reactor filled with the catalyst is arranged in the exhaust gas flow direction into a first-stage reactor and a second-stage reactor, and the temperature of the exhaust gas from the first-stage reactor is reduced. Of the gas introduced into the latter stage reactor and supplied to the latter stage reactor
A method for purifying exhaust gas containing an oxidizable nitrogen compound, wherein the ratio of the oxidizable compound / reducible compound is 1.5 or more . 2. A method for oxidatively purifying an oxidizable nitrogen compound-containing exhaust gas using a catalyst, wherein the A component includes aluminum, titanium, silica and diene.
At least one member selected from the group consisting of ruconium
Oxides; vanadium, tungsten,
At least selected from the group consisting of cesium and iron
One oxide; platinum, palladium, platinum
Indium, ruthenium, iridium, manganese, chromium
At least one metal selected from the group consisting of copper and copper
And / or an oxide catalyst, the catalyst-filled reactor is divided into a first-stage reactor and a second-stage reactor in the exhaust gas flow direction, and the temperature of the exhaust gas from the first-stage reactor is changed by heat exchange. Characterized in that it is reduced by heat exchange in the reactor and then introduced into the subsequent reactor , and the oxidizable compound of the gas supplied to the latter reactor is
Characterized in that the ratio of product / reducible compound is 1.5 or more
A method for purifying exhaust gas containing an oxidizable nitrogen compound. 3. A method for oxidatively purifying an oxidizable nitrogen compound-containing exhaust gas using a catalyst, wherein the A component includes aluminum, titanium, silica,
At least one member selected from the group consisting of ruconium
Oxides; vanadium, tungsten,
At least selected from the group consisting of cesium and iron
One oxide; platinum, palladium, platinum
Indium, ruthenium, iridium, manganese, chromium
At least one metal selected from the group consisting of copper and copper
And / or a catalyst comprising an oxide, the catalyst-filled reactor is arranged in the exhaust gas flow direction into a pre-reactor and a post-reactor, and the pre-process gas discharged from the pre-reactor is It is characterized in that a cooling gas is mixed on the upstream side of the latter-stage reactor to lower the temperature of the first-stage processing gas and then introduced into the latter-stage reactor.
And and oxidizable compound in the gas supplied to the subsequent stage reactor
The method for purifying exhaust gas containing an oxidizable nitrogen compound, wherein the ratio of / reducible compound is 1.5 or more . 4. A method for oxidatively purifying an oxidizable nitrogen compound-containing exhaust gas using a catalyst, wherein the A component includes aluminum, titanium, silica, and silica.
At least one member selected from the group consisting of ruconium
Oxides; vanadium, tungsten,
At least selected from the group consisting of cesium and iron
One oxide; platinum, palladium, platinum
Indium, ruthenium, iridium, manganese, chromium
At least one metal selected from the group consisting of copper and copper
And / or oxides, and the catalyst-filled reactor is divided into a first-stage reactor and a second-stage reactor in the exhaust gas flow direction, and the oxidizable nitrogen compound-containing exhaust gas is branched and partially separated Is supplied to the first-stage reactor, and the remainder is mixed with the first- stage processing gas discharged from the first-stage reactor, and the oxidizable compound /
After reducing the ratio of the reducing compound to 1.5 or more, the mixture is introduced into the subsequent reactor, the remaining gas is oxidatively purified, and the nitrogen oxides in the pretreatment gas are reduced. A method for purifying exhaust gas containing an oxidizing nitrogen compound. 5. The purification method according to claim 1, wherein the temperature of the latter reactor is suppressed to 450 ° C. or less to suppress the production of nitrogen oxides. 6. The catalyst comprises: A component: 70 to 99% by weight;
Ingredients: 0.5 to 20 wt%, C component: 0.001 to 20
The purification method according to any one of claims 1 to 5, wherein the purification method contains the amount by weight. 7. The oxidizable nitrogen compounds contained in the exhaust gas, ammonia, nitrile compound, according to any one of claims 1 to 6 at least one selected from the group consisting of amine compounds and imine compounds Purification method. 8. An exhaust gas containing an oxidizable nitrogen compound (nitrogenation).
The concentration of the compound is 10,000 ppm or less in terms of nitrogen.
Gas (excluding gas) is supplied to the pre-stage reactor.
Purification method according to any of the above. 9. Nitrogen in exhaust gas supplied to a pre-stage reactor
The concentration of the compound is 3,000 to 50,000 in terms of nitrogen.
0 ppm, The concentration of nitrogen compounds in the gas supplied to the latter
An elementary conversion of 20 to 8,000 ppm.
The purification method according to any one of the above. 10. The reaction in the first-stage reactor is performed in a temperature rising range.
The method according to any one of claims 1 to 9, which is performed at 80 to 160 ° C.
Purification method.