JPH0616813B2 - Ventilation gas purification method in road tunnel - Google Patents

Description

TECHNICAL FIELD The present invention relates to a mountain tunnel for roads, an underground road, a road with a shelter, etc. (in this specification, these are collectively referred to as “road tunnel”) The present invention relates to a method for purifying ventilation gas, in which contaminated air is ventilated and the ventilation gas is subjected to purification treatment such as nitrogen oxide (NOx) removal.

BACKGROUND OF THE INVENTION In a long-distance road tunnel with a lot of cars and traffic,
It is necessary to ventilate the contaminated air inside in order to protect the health of drivers and pedestrians and improve the permeability of soot in the tunnel. In addition, even in a relatively short distance road tunnel, for the one in the urban area or its suburbs, the contaminated air in the tunnel is ventilated in order to cope with the air pollution due to carbon monoxide gas and NOx concentrated in the entrance and exit. There is a need to.

However, if ventilation gas is diffused around the tunnel as it is, it is not only against the improvement of the local environment, but also the pollution level is high especially in the urban area where the exhaust gas pollution is spreading in the plane or its suburbs. It could lead to further expansion of the contaminated area. The above-mentioned situation is exactly the same even when a road is tunneled or a shelter is installed as a measure against pollution of an existing road.

Therefore, there is a demand for a method capable of efficiently removing NOx from ventilation gas emitted from a road tunnel.

2. Description of the Related Art Conventional methods for removing NOx from fixed sources have been mainly studied for the purpose of purification of various boiler combustion exhaust gases, and roughly classified into (1) catalytic reduction method, (2) dry adsorption method,
(3) There is a wet absorption method. Since the conventional and research target boiler exhaust gas as described above, research is conducted assuming that the temperature of the exhaust gas to be treated is 200 ° C. or higher, or that there is a heat source for gas heating in the vicinity. Further, it is considered that the NOx concentration of the exhaust gas to be removed is 100 ppm or more.

Problems to be Solved by the Invention By the way, assuming the general characteristics of a road tunnel,
The NOx concentration of the gas to be treated is a low concentration of 5 ppm or less, and the temperature is almost room temperature. The gas contains carbon monoxide gas, various hydrocarbon vapors, oil mist, diesel soot and other air pollutants. Further, since the ventilation volume is controlled according to the traffic volume in the tunnel, it is considered that it fluctuates in a large range of about 30 to 100% per day.

Taking the above points into consideration, the following items are required to purify ventilation gas in road tunnels.

(1) It is possible to remove NOx with a low concentration of 5 pp or less in the ventilation gas with high efficiency without raising the temperature of the ventilation gas. (2) Energy consumption during operation of the purification equipment is reduced as much as possible, especially around the equipment. (3) Even if installed in an urban area, the purification equipment must be of a scale and form that is in harmony with the surrounding buildings, and it is desirable that the entire equipment can be stored indoors. (4) Purification operation Do not generate waste liquid or solid waste with

On the other hand, in the conventional technique, as described above, the temperature of the target exhaust gas is a high temperature of 200 ° C. or higher, and the NOx concentration of the exhaust gas is a high concentration of 100 ppm or higher. It cannot be applied to the purification of ventilation gases.

In view of the above situation, an object of the present invention is to provide a practical ventilation gas purification method that can efficiently perform NOx removal processing on ventilation gas emitted from a road tunnel.

Means for Solving the Problems In the method for purifying ventilation gas according to the present invention, a ventilation gas having a NOx concentration of 5 ppm or less discharged from a road tunnel is dry-treated with a zeolite adsorbent containing copper and / or vanadium, and is mainly used. It is characterized in that NOx is adsorbed and removed, and the adsorbent in the NOx adsorbed state is treated with hot air containing NH ₃ to be regenerated.

In a preferred embodiment of the present invention, a zeolitic adsorbent containing a metal oxide such as copper or vanadium is used as the adsorbent.

In the regeneration step, NOx is selectively reduced to nitrogen gas by NH ₃ as a reducing agent and desorbed from the adsorbent. As a result, the adsorbent is regenerated. Regeneration of the adsorbent is carried out at a temperature of 100 ° C or higher, preferably 150 ° C or higher.

Adsorption and regeneration are preferably carried out by a moving bed type adsorption section, preheating / cooling section and regeneration section. However, a method may be used in which the fixed bed is filled with the adsorbent and the ventilation gas to be purified and the NH ₃ -containing high temperature air for regeneration are alternately passed through the fixed bed.

The basic process of the present invention will be described with reference to FIG.

The ventilation gas discharged from the road tunnel (1) by the ventilation blower (2) is guided to the adsorption tower (3) and is dry-processed by the adsorbent filled in the adsorption tower (3), and the processed gas is discharged outside the system. Is released. As the adsorbent, a zeolite adsorbent containing a metal oxide such as copper or vanadium is used.

The adsorbent that has adsorbed NOx is continuously or intermittently discharged from the adsorption tower (3) and sent to the regeneration tower (4). Regeneration tower
In (4), the adsorbent is contact-treated with hot air containing NH ₃ . This air is sent to the regeneration tower (4) by the circulation blower (5) and heated to 100 ° C. or higher by the heater (6). N
H ₃ is added to the heated air from the cylinder (7). As a result, NOx is reduced to nitrogen gas by NH ₃ as a reducing agent, desorbed from the adsorbent, and the adsorbent is regenerated.
The regenerated adsorbent is continuously or intermittently discharged from the regeneration tower (4) and supplied to the adsorption tower (3) again.

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

Operation Process The purification method according to the present invention is applied to a road tunnel under the traffic conditions shown in Table 1 below. Calculated from the conditions in Table 1, the ventilation volume is required to be 1.5 million Nm ³ / h per 1 km of the tunnel in order to keep the soot permeability in the tunnel at 40% or more. The characteristics of the ventilation gas in this case are as shown in Table 2. Assuming that one ventilation gas purification facility is installed for every 333 m of tunnel, the treatment capacity of the purification facility is 500,000 Nm ³ / h.
Becomes

Next, a ventilation gas purification facility will be described.

In FIGS. 2 and 3, the ventilation gas discharged from the road tunnel (11) by the ventilation blower (12) is guided to the adsorption section (13) of the purification installation. The purification equipment consists of a NOx adsorber (13) that adsorbs NOx in the ventilation gas with an adsorbent and a NOx adsorbent.
A preheating / cooling unit (18) that preheats the unregenerated adsorbent in an adsorbed state and cools the adsorbent after regeneration, and an adsorbent regeneration unit that NOx desorbs the adsorbent that came from the preheating / cooling unit (18). It is mainly composed of (14). NOx adsorption part (13), preheating
Both the cooling unit (18) and the adsorbent regeneration unit (14) are of a moving bed type, and have a plurality of moving blocks holding NOx adsorbent.
(19) are arranged in a line inside the NOx adsorbent (13) and the preheating / cooling section (18). The moving block (19) is intermittently moved in the NOx adsorbing part (13) in a countercurrent direction to the ventilation gas flow, and the one reaching the end of the NOx adsorbing part (13) passes through the passage (20). It is sent to the preheating / cooling section (18), and the inside of this is also intermittently moved from the start end to the end.
Then, the moving block (19) is withdrawn in the middle of the preheating / cooling section (18), and passes through the passage (21) to regenerate the adsorbent (14).
Sent to the moving block (19) after regeneration of the adsorbent.
It is inserted into the original position of the block row of the preheating / cooling section (18) via (21). The moving block (19) is then connected to the preheating / cooling unit (1
It is returned from the end of 8) to the start of the NOx adsorbing section (13) via the passage (22).

As the adsorbent, a zeolite adsorbent containing a metal oxide such as copper or vanadium is used. The processing gas from which NOx has been removed by the dry processing in the NOx adsorbent (13) is
It is released to the outside of the system through the chimney (26). Further, a part of the processing gas is circulated in the preheating / cooling unit (18) from the terminal end to the starting end by the blower (25), that is, in the counterflow direction with respect to the moving direction of the moving block. As a result, this processing gas is used for preheating the adsorbent to be regenerated on the starting end side of the preheating / cooling section (18) and for cooling the heated regenerated adsorbent on the termination end side.

In the adsorbent regeneration unit (14), the unregenerated adsorbent of the moving block (19) coming from the preheating / cooling unit (18) is contact-treated with high-temperature air containing NH ₃ . This air is sent to the adsorbent regeneration section (14) by the circulation blower (15), and 100% by the heater (16).
It is heated above ℃. NH ₃ is added to the heated air from the cylinder (17). As a result, NOx is NH as a reducing agent.
_It is reduced to asphyxiation gas by ₃ and desorbed from the adsorbent, and the adsorbent is regenerated.

The air that has passed through the adsorbent regeneration unit (14) is further denitrified (2
NOx removal treatment is carried out in 3), and it is circulated and reused in the circulation blower (15). Further, a part of this air is extracted from the circulation line, and after recovering heat to a part of the above-mentioned processing gas by the heat exchanger (24), it is discharged to the chimney (26). On the other hand, heat exchanger
A part of the process gas that has obtained the heat of recovery in (24) is supplemented to the circulating air.

The gas composition and temperature at each location of the ventilation gas purification device are as shown in Tables 3 and 4.

Adsorbent and regeneration test A columnar Y-type zeolite adsorbent having a diameter of 1.5 mm and a length of 3 mm was treated with 0.1 mol / mol of copper amminate to adsorb and support copper ions. 75 g of the adsorbent thus obtained was filled in a quartz adsorption tube having an inner diameter of 18 mm, and NOx was about 200 ppm.
Gas containing about 3% moisture and 4% / min was continuously passed through the adsorption tube at room temperature. The NOx concentration at the outlet of the adsorption tube was measured, and the result of the initial adsorption capacity is shown in FIG. Subsequently, the flow of the NOx-containing gas was stopped, and the adsorbent was heated to 200 ° C.
Pass the air at 00 ° C through the adsorption tube for 2 hours, and
When the x concentration was measured, almost no NOx was observed. This indicates that the adsorbed NOx does not desorb under this condition. After cooling the adsorbent to room temperature, a gas containing about 200 ppm of NOx and about 3% of moisture was passed through the adsorption tube at a rate of 4 / min. As a result, as shown in FIG. 5, almost no NOx adsorption capacity was exhibited. . This indicates that the adsorbent was not regenerated with only air at 200 ° C.

This adsorbent is then heated to 200 ° C. and 200 ppm N
200 ° C. air containing H ₃ was passed through the adsorption tube at 1 / min for 3 hours. Also in this case, almost no NOx at the adsorption tube outlet was observed. Next, after cooling this adsorbent to room temperature,
A gas containing about 200 ppm NOx and about 3% moisture was passed through the adsorption tube at 4 / min. FIG. 6 shows the NOx concentration at the adsorption pipe outlet. The result of FIG. 6 was almost the same as the result of FIG. Therefore, it can be seen that the adsorbent was completely regenerated by the 200 ° C. air containing NH ₃ .

EFFECT OF THE INVENTION According to the ventilation gas purification method of the present invention, the ventilation gas emitted from the road tunnel is dry-processed with a zeolite-based adsorbent,
Since NOx is mainly adsorbed and removed, and the adsorbent in the NOx adsorbed state is treated with NH ₃ -containing high-temperature air to be regenerated, NOx having a low concentration of 5 ppm or less in the ventilation gas is heated without raising the temperature of the ventilation gas. It can be removed with high efficiency and
It is possible to reduce the energy consumption during the purification equipment and operation as much as possible.

In addition, there is no risk of causing heat pollution to the surroundings of the facility, and no waste liquid or solid waste is generated with purification. Further, the purification facility can be of a scale and form that is in harmony with the surrounding buildings, and the entire facility can be housed in the building if necessary.

Further, since a zeolite-based adsorbent is used as the adsorbent, not only NOx in the ventilation gas but also various hydrocarbon vapors, oil mist and the like can be adsorbed and removed at the same time.

[Brief description of drawings]

FIG. 1 is a flow sheet showing the basic concept of the present invention, second.
FIG. 3 is a flow sheet showing an embodiment of the present invention, FIG. 3 is a perspective view showing a ventilation gas purification facility used in the embodiment of the present invention, and FIGS. 4, 5, and 6 are gas passage times and outlets. N
It is a graph which shows the relationship of Ox density. (1) (11) …… Tunnel, (2) (12) …… Ventilation blower,
(3) …… Adsorption tower, (13) …… NOx adsorption section, (4) …… Regeneration tower, (14) …… Adsorbent regeneration section, (5) …… Circulation blower,
(6) (16) …… Heater, (7) (17) …… NH ₃ cylinder, (1
8) …… Preheating / cooling section.

Front Page Continuation (72) Inventor Shigenori Onizuka 1-6-14 Edobori, Nishi-ku, Osaka City, Osaka Prefecture Hitachi Shipbuilding Co., Ltd. (56) Reference JP-A-49-44969 (JP, A) JP-A-50-10282 (JP, A) JP-A-53-28944 (JP, A)

Claims (3)

[Claims] 1. The concentration of NOx emitted from a road tunnel is 5 ppm.
The following ventilation gases are dry-treated with a zeolitic adsorbent containing copper and / or vanadium to adsorb and remove mainly NOx, and the adsorbent having adsorbed NOx is treated with high-temperature air containing NH ₃ to be regenerated. A method for purifying ventilation gas in a road tunnel, which is characterized in that 2. The method according to claim 1, wherein the adsorbent is regenerated at a temperature of 100 ° C. or higher, preferably 150 ° C. or higher. 3. A method according to claim 1 or 2, wherein a moving bed type adsorption unit is used.