JPH06319943A - Method for removing nox by adsorption - Google Patents

Abstract

PURPOSE:To reduce an installation space and to cut initial and utility costs by omitting a dehumidifier and a heat pump which have been installed before a rotary NOx adsorber and simplifying the composition of an exhaust gas cleaning system as a whole. CONSTITUTION:An exhaust gas containing NOx, the concentration of which is 5ppm or less, is treated with a rotary NOx adsorber 4 to adsorb NOx, and gas from an outlet of a regeneration zone is treated with an auxiliary denitration apparatus 14 equipped with a NH3 supply device for the catalytic reduction of NOx.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention efficiently reduces low-concentration nitrogen oxides (NOx) contained in ventilation exhaust gas in various tunnels such as various road tunnels, mountain tunnels, undersea tunnels, underground roads, and roads with shelters. The present invention relates to an adsorption removal method for removing well.

[0002]

BACKGROUND OF THE INVENTION In various road tunnels, mountain tunnels, underground roads, sheltered roads, etc. (in this specification, these tunnels are collectively referred to as "road tunnels, etc.") For large quantities, it is necessary to provide adequate ventilation for the purpose of protecting the health of passersby and improving the visual distance. In addition, even in a relatively short-distance tunnel, in an urban area or its suburbs, suction and exhaust (ventilation) of air in the tunnel is a method for preventing air pollution due to carbon monoxide (CO), NOx, etc. concentrated in the entrance and exit. There is a way.

However, if ventilation exhaust gas is diffused to the surroundings as it is, it does not improve the local environment, and particularly, the highly polluted area is expanded in the urban area where the exhaust gas from the vehicle spreads in a flat manner or its suburbs. It could lead to. The above-mentioned situation is exactly the same when a tunnel or a shelter is installed as a measure against pollution of the existing road.

The present invention relates to an adsorption removal method for efficiently removing low-concentration NOx contained in exhaust gas from ventilation such as road tunnels.

[0005]

2. Description of the Related Art Ventilation exhaust gas from various tunnels is characterized in that the concentration of NOx contained therein is as low as about 5 ppm or less, the gas temperature is room temperature, and the gas amount greatly changes according to the traffic volume.

The present inventors have previously found that such a low concentration of N
As a device for purifying ventilation exhaust gas such as a road tunnel intended to efficiently adsorb and remove Ox, as shown in FIG. 5, a rotary type that adsorbs NOx in ventilation exhaust gas with a NOx adsorbent and regenerates the NOx adsorbent. A road tunnel in which a dehumidifier (31) and a heat pump (32) for dehumidifying the exhaust gas are provided in the upstream of the NOx adsorbing device (33) to prevent the NOx adsorbing performance from being deteriorated by moisture. And the like have been proposed (see Japanese Patent Laid-Open No. 3-258324). In FIG. 5, (34) is a heater, (35) is an auxiliary denitration device, and (3)
6) is a cooling tower.

[0007]

However, the process using this device has a drawback that the whole structure of the ventilation exhaust gas purification system is complicated and requires a large installation space, resulting in high initial cost and high utility cost.

In view of the above situation, the present invention has a simple structure of the exhaust gas purification system, does not require a large installation space, and requires only a small initial cost and utility cost. Energy saving and simplified NOx adsorption. It is intended to provide a removal method.

[0009]

The NOx adsorption / removal method according to the present invention has been devised to achieve the above-mentioned object.
The rotary NOx adsorption device is treated with an Ox adsorption device to adsorb NOx in the exhaust gas, and the rotary NOx adsorption device is provided with an adsorbent rotor, and the adsorbent is brought to a predetermined temperature in the NOx adsorption zone and in the rotational direction front side of the adsorption zone. A preheating zone for heating,
It consists of a regeneration zone that further heats the adsorbent to desorb and regenerate the adsorbed NOx in the forward direction of rotation of the preheating zone, and a cooling zone that cools the high-temperature adsorbent to near the adsorption zone temperature between the regeneration zone and the adsorption zone. , The adsorbent rotor is arranged over each of the above zones, partially moves through each zone with rotation, and the regeneration zone outlet gas is treated by an auxiliary denitration unit equipped with an NH ₃ supply device, and NO
The purpose is to catalytically reduce x.

The adsorbent rotor of a rotary NOx adsorber is usually cylindrical in shape and moves continuously in each zone, preferably at right angles to the gas flow. Thus, rotary NOx
The adsorption device continuously supplies the regenerated adsorbent to the adsorption zone where the untreated ventilation exhaust gas flows, and at the same time, NOx
The used adsorbent that has adsorbed is discharged from the adsorption zone and supplied to the regeneration zone.

The gas to be passed through the preheating zone is preferably heated atmosphere, the gas flow direction in the preheating zone is opposite to the gas flow in the adsorption zone, and the gas temperature at the preheating zone inlet is 175 ° C. or lower, preferably 120 ° C. ~ 140 ° C
To

The gas to be passed through the regeneration zone is preferably heated atmosphere, the gas flow direction in the regeneration zone is opposite to the gas flow in the adsorption zone, and the gas temperature at the inlet of the regeneration zone is 180 to 300 ° C., preferably 200-25
Bring to 0 ° C.

The regeneration zone outlet gas is preferably from 200 to
The temperature is 300 ° C., and it is processed by an auxiliary denitration device equipped with an NH ₃ supply device.

Typical examples of the adsorption / removal agent used (hereinafter simply referred to as an adsorbent) include a ruthenium halide, potassium, sodium, magnesium, calcium, manganese, and copper on a ceramic paper carrier holding anatase-type titania. Zinc, rubidium, zirconium,
It is co-supported with a halide of at least one metal selected from the group consisting of barium, cerium and molybdenum (hereinafter referred to as metal halide) (Japanese Patent Application No. 4-10312).

In order to produce this adsorption-removing agent, ceramic paper is impregnated with anatase-type titania sol and dried or calcined to obtain a carrier, and then the carrier is impregnated with a ruthenium halide and a metal halide. Dry or bake.

The ceramic paper is manufactured by making ceramic fibers. Commercially available ceramic paper can also be used.

As the anatase-type titania sol, for example, hydrated titania (titanic acid slurry) or titanic acid slurry which is an intermediate product in the production of titania by the sulfuric acid method is peptized.
Stabilized ones are used.

The anatase-type titania tends to have a higher NOx adsorption performance as the retained amount increases. When the amount of anatase-type titania retained is 20 g / m ² or less,
Since the NOx adsorption performance sharply decreases, the same retention amount is preferably 20 g / m ² or more.

Next, a ruthenium halide and a metal halide are co-loaded on the carrier. The amount of ruthenium supported is preferably about 0.01% by weight or more of the final adsorbent as the ruthenium metal, and more preferably about 0.1.
5% by weight is preferred. The amount of the metal halide supported is preferably about 0.1% by weight or more of the final adsorbent as a metal, and more preferably about 1 to 10% by weight. The co-support of ruthenium halide and metal halide is
Generally, it is carried out by immersing the above carrier in a mixture solution in which a halide of ruthenium such as ruthenium chloride (RuCl ₃ ) and a metal halide such as chloride of the above metal are dissolved in a suitable solvent. However, this method is not limited, and the ruthenium halide and the metal halide may be supported separately.

After immersion, the adsorbent is separated from the mixture solution,
Dry in air at about 100-120 ° C. Further, the dried product is fired at about 250 to 500 ° C. if necessary. In the case of treating a large amount of gas such as ventilation exhaust gas from a road tunnel or the like, it is necessary to minimize the pressure loss as the flow resistance is small. Therefore, a ruthenium halide and a metal halide are used as an adsorbent carrier having a flat plate / corrugated plate multilayer structure in which flat plate-shaped anatase-type titania-supporting ceramic paper and corrugated plate-like anatase-type titania-supporting ceramic paper are arranged alternately. A honeycomb-shaped adsorbent in which and are co-loaded is desirable.

However, the adsorbent used in the method of the present invention is not limited to the above.

The auxiliary denitration device is operated by NH _{3 in} the presence of a denitration catalyst.
Is used as a reducing agent to selectively catalytically reduce NOx to N ₂ and H ₂ O.

[0023]

EXAMPLES Next, examples of the present invention will be described.

NOx adsorption / removal system An example of the NOx adsorption / removal system for exhaust gas from a road tunnel ventilation is shown in the flow chart of FIG.

In the same flow, the ventilation exhaust gas containing NOx is blown by the blower (1) to the rotary NOx adsorption device.
Introduced in (4). The configuration of the rotary NOx adsorbing device (4) will be described below.

As shown in FIGS. 2 to 4, the rotary NOx adsorption device (4) has an upper cover (5) having a sliding flange portion (5a) at the lower end and a sliding flange portion (18a) at the upper end. And a cylindrical NOx adsorbent rotor (6) arranged between the upper and lower covers (5) and (18).
The adsorbent rotor (6) has sliding flanges (19
It comprises a shell (19) having a) and a honeycomb type adsorbent (20) filled in the shell. And adsorbent rotor (6)
Is the upper and lower flanges (19a) of the shell (19) and the upper and lower covers.
(5) By sliding the flanges (5a) and (18a) of (18), the upper and lower covers (5) and (18) are rotatable in the direction of arrow (A).

A plurality of partitions are provided inside each of the opposed upper and lower covers (5) (18). These partitions are
A semi-circular NOx adsorption zone (4a) as viewed in the axial direction inside the rotary NOx adsorption device (4) and a preheating zone for heating the adsorbent up to a predetermined temperature in the rotation direction forward of the adsorption zone.
(4b) and a regeneration zone (4c) for further heating the adsorbent to desorb and regenerate the adsorbed NOx in front of the preheating zone in the rotation direction.
And a cooling zone (4d) for cooling the high-temperature adsorbent to a temperature near the adsorption zone between the regeneration zone and the adsorption zone. The preheating zone (4b), the regeneration zone (4c) and the cooling zone (4d) are respectively three fan-shaped portions of the remaining semicircular portion.

The NOx adsorbent rotor (6) is arranged over each of the above-mentioned zones, and partially moves sequentially in each zone as it rotates.

In FIG. 4, the NOx adsorbent rotor (6)
The NOx adsorbing part of the NOx adsorbing part is a part located in the NOx adsorbing zone (4a) during its operation, and the preheating part ahead of the NOx adsorbing part in the rotation direction is a part located in the preheating zone (4b). The regeneration part in the front of the direction is the part located in the regeneration zone (4c), and the cooling part in the front of the rotation direction is the cooling zone.
This is the part located within (4d).

A ventilation exhaust gas introduction pipe (7) is arranged from the ventilation device to the NOx adsorption zone (4a) of the rotary NOx adsorption device (4), and the treated gas exhaust pipe (8) is discharged from the NOx adsorption zone (4a) to the outside of the system. ) Is arranged.

In the cooling zone (4d), a cooling gas introducing pipe (9) for supplying the outside air for cooling the NOx adsorbent is arranged,
From the cooling zone (4d) to the preheating zone (4b)
0) is arranged, and a preheating gas discharge pipe (11) for discharging the preheated gas from the preheating zone (4b) is arranged. Preheating gas introduction pipe
(10) is located on the side opposite to the ventilation exhaust gas introducing pipe (7) with respect to the rotary NOx adsorbing device (4). Therefore, the gas flow direction in the preheating zone is opposite to the gas flow direction in the adsorption zone.

In addition, in the regeneration cooling zone (4c), N
Regeneration gas introduction pipe (12) for supplying outside air for regeneration of Ox adsorbent
And a regeneration gas discharge pipe (13) for discharging the gas after regeneration from the regeneration zone (4c). Regeneration gas exhaust pipe (1
3) is provided with an auxiliary denitration device (14) equipped with an NH ₃ supply device.

In the rotary NOx adsorbing device having the above structure, the ventilation exhaust gas containing NOx is introduced into the ventilation exhaust gas introduction pipe.
(7) sends it to the NOx adsorption zone (4a) of the rotary NOx adsorber (4), where NOx in the ventilation exhaust gas is adsorbed and removed by the NOx adsorber of the NOx adsorbent rotor (6). Adsorbent rotor adsorbing NOx (6)
The preheating part of the is the preheating gas introduction pipe (10) in the preheating zone (4b)
Is preheated by the outside air for preheating, and the regeneration section is desorbed and regenerated by the outside air for regeneration coming from the regeneration gas introduction pipe (12) in the regeneration zone (4c). Before regeneration, the adsorbent and the outside air for regeneration may be heated to a suitable temperature (100 to 300 ° C.) by a heater. NOx adsorbent rotor with desorbed NOx
The cooling section (6) is cooled in the cooling zone (4d) by the outside air for cooling coming from the cooling gas introduction pipe (9). Thus, the rotation of the NOx adsorbent rotor (6) continuously adsorbs NOx in the NOx-containing ventilation exhaust gas, preheats the NOx adsorbent, and regenerates and cools it.

The desorption NOx contained in the purge gas exiting the regeneration zone (4c), in the auxiliary denitration unit (14) is denitration with NH ₃ from NH ₃ supply device is reduced harmless.
The regeneration gas after the auxiliary denitration treatment is sent to the regeneration zone (4c) again through the regeneration gas introduction pipe (12), and part of it is discharged as a treated gas to the outside of the system.

Preparation of adsorbent rotor Commercially available ceramic paper (manufactured by Nippon Inorganic Co., Ltd., ingredient;
Silica: alumina = 50: 50, thickness: 0.25 mm, basis weight: 46 g / m ² ) is cut into a predetermined size and immersed in anatase-type titania sol (TiO ₂ content: about 30% by weight) at room temperature. did. Immediately after the immersion, the ceramic paper was taken out on a flat plate, excess titania sol was dropped by a roller or the like to obtain a uniform thickness, and at the same time, dried by hot air. The plate-shaped titania sol-impregnated ceramic paper thus molded was placed in an electric furnace and heated in air at 400 ° C. for 3 hours.
After firing for a period of time, a plate-shaped titania-supporting ceramic paper carrier was obtained.

Further, the ceramic paper after the immersion of the anatase type titania sol was taken out on the corrugated plate, and thereafter the same operation as above was performed to obtain a corrugated plate-shaped titania holding ceramic paper carrier.

The amount of TiO ₂ supported was calculated from the difference between the weight before impregnation of the titania sol and the weight after drying, and the result was 85 g /
m ² of TiO ₂ was retained.

By the above operation, a plurality of flat plate-shaped titania holding ceramic paper carriers having different widths and a plurality of corrugated plate-shaped titania holding ceramic paper carriers having different widths were respectively manufactured. Then, as shown in FIG.
A flat plate (21) having a required width and a corrugated plate (22) are stacked one by one to form a cylindrical stack, and a honeycomb-type adsorbent carrier having a flat plate / corrugated plate multilayer structure (geometric surface area; 0.0385 m ² , TiO
₂ content; 3.3 g) was obtained.

The adsorbent carrier of the flat plate / corrugated plate multilayer structure is used as ruthenium chloride (RuCl ₃ ) and manganese chloride (MnCl 2).
₂ ) and a mixture aqueous solution (Ru concentration: 0.38% by weight, Mn concentration: 2.07% by weight) in 100 ml at room temperature for 30 minutes.
Soaked for a minute. Then, this was washed with water and dried at about 110 ° C. for 2 hours to form a honeycomb-type adsorbent (20) composed of Ru / Mn co-supported titania (Ru content: 0.55 wt%, Mn
The supported amount was 3.00% by weight).

This honeycomb-type adsorbent (20) is applied to the shell (1
After the outer layer was formed in 9), it was treated for 1 hour in dry air (moisture concentration; about 50 ppm) flowing at about 300 ° C. (2.5 NL / min), and allowed to cool to room temperature. Thus, the adsorbent rotor (6) was prepared.

[0041]

According to the NOx adsorption removal method of the present invention, 5
Exhaust gas containing NOx having a low concentration of ppm or less is treated by a rotary NOx adsorber to adsorb NOx in the exhaust gas, and the regeneration zone outlet gas of the rotary NOx adsorber is treated by an auxiliary denitration device equipped with an NH ₃ supply device. Since the treatment is performed and NOx is catalytically reduced, the dehumidifier and heat pump provided in the upstream of the rotary NOx adsorption device in the conventional NOx adsorption / removal method can be omitted, and the entire exhaust gas purification system can be configured. It can be simplified, the installation space can be reduced, and the initial cost and utility cost can be saved.

[Brief description of drawings]

FIG. 1 is a flow sheet showing the NOx adsorption removal method of the present invention.

FIG. 2 is a schematic view showing a rotary NOx adsorption device.

FIG. 3 is a schematic view showing a NOx adsorbent rotor.

FIG. 4 is a flow sheet showing the NOx adsorption removal method of the present invention.

FIG. 5 is a flow sheet showing a conventional NOx adsorption removal method.

[Explanation of symbols]

 (4)… Rotary NOx adsorption device (4a)… Adsorption zone (4b)… Preheating zone (4c)… Regeneration zone (4d)… Cooling zone (5)… Top cover (5a)… Sliding flange (6) … NOx adsorbent rotor (7)… Ventilation exhaust gas introduction pipe (8)… Treatment gas discharge pipe (9)… Cooling gas introduction pipe (10)… Preheating gas introduction pipe (11)… Preheating gas discharge pipe (12)… Regeneration gas introduction pipe (13)… Regeneration gas discharge pipe (14)… Auxiliary denitration device (18)… Lower cover (18a)… Sliding flange (19)… Shell (19a)… Sliding flange (20)… Honeycomb type adsorbent (21) ... Flat plate (22) ... Corrugated plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiro Usutani 5-328 Nishi Kujo, Konohana-ku, Osaka City Hitachi Shipbuilding Co., Ltd. (72) Inoue Iwamoto 5-3-28 Nishikujo, Konohana-ku, Osaka Hitachi Shipbuilding Co., Ltd. (72) Inventor Shigenori Onizuka 5-3 28 Nishikujo, Konohana-ku, Osaka City Hitachi Shipbuilding Co., Ltd. (72) Masayoshi Ichiki 5-3 28 Nishijojo, Konohana-ku, Osaka Hitachi Shipbuilding Co., Ltd. (72) Inventor Takanobu Watanabe 5-3 28 Nishi-Kujo, Konohana-ku, Osaka City Hitachi Shipbuilding Co., Ltd. (72) Atsushi Fukuju 5-3 28 Nishi-Kujo, Konohana-ku, Osaka Hitachi Shipbuilding Co., Ltd.

Claims (1)

[Claims] 1. A low-concentration NOx-containing exhaust gas of 5 ppm or less is treated by a rotary NOx adsorber to adsorb NOx in the exhaust gas, the rotary NOx adsorbent having an adsorbent rotor and NOx adsorbent. A zone and a preheating zone for heating the adsorbent to a predetermined temperature in the front of the adsorption zone in the rotation direction,
It consists of a regeneration zone that further heats the adsorbent to desorb and regenerate the adsorbed NOx in the forward direction of rotation of the preheating zone, and a cooling zone that cools the high-temperature adsorbent to near the adsorption zone temperature between the regeneration zone and the adsorption zone. The adsorbent rotor is arranged over each of the above zones, and partially moves through each zone with rotation, the regeneration zone outlet gas is processed by an auxiliary denitration device equipped with an NH ₃ supply device, and NOx is contacted. NOx adsorption removal method to reduce.