JPH10334A - Gas purification device and gas purification method - Google Patents

Abstract

(57) [Problem] To realize a low-cost vehicle exhaust gas purification apparatus which has a large degree of freedom in installation space and can save space. A part of NOx in exhaust gas is oxidized to NO ₂ by NOx oxidizing means 3 and then absorbed by an absorbing liquid circulating in an absorption section 4 to remove dust components contained in the exhaust gas. It is. Thereafter, the underwater photosynthetic organism cultured in the culture unit 8 and the absorbing solution are mixed. Underwater photosynthetic organisms fix NO ₂ in the absorbing solution by photosynthetic action, and are collected by the collection means 12 as a fixed substance 13. This completes the exhaust gas purification process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to a gas purifier and a gas purification method for purifying a gas containing NO _X of dust and a low concentration which is discharged from a vehicle such as an automobile.

[0002]

2. Description of the Related Art In recent years, with the increase in traffic volume, in places such as automobile tunnels, intersections, indoor parking lots, and highways where traffic is particularly frequent, that is, locations where the concentration of exhaust gas from automobiles is high, gas emissions are low. The treatment of dust and NOx has become a problem. 2. Description of the Related Art Conventionally, in an automobile tunnel or the like, a dust is removed by exhausting a gas inside the tunnel to the outside of the tunnel using a blower or by attaching an electric dust remover. By the way, regarding the treatment of dust, high-concentration dust and gas containing NOx have been treated in thermal power plants and the like, but the treatment of low-concentration dust and NOx required for exhaust gas of automobiles has not yet been performed. It is insufficient, and the development of a gas purification device for exhaust gas from vehicles such as automobiles is required.

[0003] Therefore, in Japanese Patent Application Laid-Open Nos. 5-192535 and 4-250822, NOx is adsorbed on an adsorbent, the adsorbed NOx is desorbed, and then reduced to nitrogen and water by a reducing agent. It describes purifying gas.

[0004]

In the low-concentration denitration method described in the above publication, a plurality of adsorbents are modularized, and most of the modules adsorb NOx on the adsorbent. When the adsorbed amount of NOx in some modules reaches a predetermined value, the adsorbed NOx is desorbed to form highly concentrated NOx. This high concentration of NOx
Is reduced to nitrogen and water by selective catalytic reduction using a reduction catalyst. When the NOx adsorption amount of the adsorbent reaches a predetermined value, the adsorption module is switched to the reduction module. In addition, the module in which the reducing action has been completed is switched to the adsorption module, and this procedure is continuously repeated, whereby NOx adsorption and regeneration of the adsorbent are continuously performed.

However, in this method, since the cost of the adsorbent itself is high, the cost of the entire system becomes very high. In order to adsorb NOx by a required amount due to insufficient performance of the current adsorbent, or to maintain adsorption for a required time, the amount of the adsorbent becomes enormous. For example, to increase the residence time of the gas in the adsorbent,
It is necessary that the length of the adsorbent in the gas flow direction be long, so that the space required for the adsorbing portion becomes large, and the entire apparatus becomes extremely large. Therefore, there is a problem that a large installation space is required.

Further, desorption of the adsorbent requires a very large amount of energy and increases running costs. Furthermore, since adsorption and reduction are carried out using an adsorbent, equipment for adsorbing and regenerating the adsorbent must be provided in the same space, and the degree of freedom in space utilization is greatly limited.

An object of the present invention is to reduce equipment costs, running costs, and initial costs by utilizing fine underwater photosynthetic organisms and natural energy in water that exist naturally. Another object of the present invention is to reduce the size of the exhaust gas purifying apparatus and to allow the installation space to be effectively used by giving the installation space a degree of freedom. Another object of the present invention is to provide a gas purifying apparatus that can recycle and use necessary water, reduce utilities, and operate safely without lowering gas purifying performance.

[0008]

A first aspect of the present invention to achieve the above object, according to an aspect of, in a gas purifying device for purifying exhaust gas from a vehicle, including NOx and soot, NOx in the exhaust gas to NO ₂ It comprises an oxidizing means for oxidizing and a biological fixing means for biologically fixing NO ₂ . And preferably, an absorbing means for absorbing NO ₂ generated by the oxidizing means into the absorbing solution, a culturing means for the underwater photosynthetic organism in the biological fixing means, and the absorbing means and the culturing means are separated from each other. Has a means for circulating the absorbing liquid, provides a collecting means for collecting NO ₂ immobilized by the biological immobilizing means, provides a separating means for separating dust and dust in the absorbing means, or the separating means sprays the absorbing liquid. It is provided with an injection means for causing the injection.

According to a second aspect of the present invention, there is provided a gas purification method for purifying exhaust gas from a vehicle containing NOx and dust, the method comprising the steps of:
Oxidized to _2, to absorb the oxidized NO ₂ to absorb liquid, the been NO ₂ absorbed in the absorption liquid is absorbed into the microorganisms, is intended to recover the microorganism.

In the present invention, a fine underwater photosynthetic organism in water which exists in nature is used, and NOx is removed by utilizing the photosynthesis. Therefore, the cost of the apparatus is reduced as compared with the conventional method using an adsorbent used for NOx removal. Further, unlike the conventional method for removing NOx using an adsorbent, there is no need to raise the temperature or reduce the pressure for desorption, which saves energy and reduces running costs. Dust removal and NOx absorption are performed simultaneously to make the equipment compact. Since the absorption unit that absorbs NOx and the culture unit that cultures fine underwater photosynthetic organisms in water are separated and independent, the absorption unit and the culture unit can be installed in different spaces, and the installation space can be used effectively.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a gas purification device according to the present invention. The gas 1 is air containing dust and NOx, and is sucked from the gas inlet 2 by the blower 17. The sucked gas 1 is subjected to NOx
Some or all of x is oxidized to NO ₂ . This is an operation to be performed by a later-described absorbing liquid to absorb NO ₂ better than normal NO, and to improve absorption performance. But,
This operation may be omitted if the absorbing liquid does not oxidize to NO ₂ but shows sufficient absorbing performance. NOx oxidation means 3
May be a method of adding ozone or a method of oxidizing by discharge. The gas and dust containing the oxidized NO ₂ are sent to the absorption section 4.

FIG. 2 shows the details of the structure of the absorbing section 4. The absorption unit 4 includes a spray-type absorption tower that sprays the absorption liquid 26 using the spray 21. When the gas 27 containing dust and NO ₂ is sent to the absorption section 4, the spray 2
From 1 the absorbing liquid 26 is injected. The absorbing liquid 26 may be neutral, such as water, or may be alkaline, such as caustic soda, carbonated water, and sodium sulfite. The absorbing liquid 26 sprayed from the spray 21 comes into gas-liquid contact with dust and NO ₂ in the gas 27 containing NO ₂ , causing a chemical reaction, and absorbs the reaction product into the absorbing liquid 26. Dust in the gas 27 containing dust and NO ₂ is removed from the gas by inertial collision with droplets of the absorbing liquid 26 generated by the spray 21. The absorbing liquid 26 and the dust that have absorbed NO ₂ are stored in the tank 22. Absorbent liquid 2 stored in tank 22
6 is again guided to the spray 21 by the circulation pump 20 and is ejected from the spray 21. This operation is performed with absorbing solution 2
6 is repeated until the absorption performance decreases and reaches a predetermined value.

The gas from which NO ₂ and dust have been removed is released from the gas outlet 5 to the atmosphere as a purified gas 6, and the purification of the gas is completed. After the absorption solution 26 having reduced absorption performance is subjected to removal of impurities such as dust by the filtration means 23, the absorption solution 26 is passed through the communication pipe 25 as the solution 7 containing NO _2, and the culture unit 8 is removed.
Sent to The removed impurities and the like are collected and processed as waste 24. In the absorbing section 4, the absorbing liquid 26 is newly replenished by the absorbent adding means 16, and by these series of operations, NO ₂ is continuously absorbed and dust is removed. In this absorption unit, since absorption of NO ₂ and removal of dust are simultaneously performed, it is not necessary to separately provide equipment for absorption and dust removal, which can reduce equipment cost and installation space. is there.

By the way, the absorbing liquid having absorbed NO ₂ in the absorbing section 4 is guided to the culturing section 8. In the present invention, since the absorbing section 4 and the culturing section 8 are provided separately and independently, the absorbing section 4 is provided. 4 and the culture unit 8 can be arranged in different installation spaces. This makes it possible to effectively use the installation space and realize a gas purification facility as long as the absorption unit 4 or the culture unit 8 can be installed in a separate place even if there is only a narrow space.

The culture section 8 may be of the open-pound type or may be a culture tank. Fine underwater photosynthetic organisms are cultured in the culturing unit 8, and the fine underwater photosynthetic organisms cultured in the culturing unit 8 are irradiated with light received from the light source 14.
Photosynthesis is performed using NO ₂ in the solution as a necessary nitrogen source. Light source 1
As 4, direct sunlight may be used, a light-collecting device may be used, or an artificial light source such as a fluorescent lamp may be used.
As a method of irradiating light, either a method of irradiating from inside the culture unit 8 or a method of irradiating from outside may be used.

Substances such as phosphorus necessary for photosynthesis of fine underwater photosynthetic organisms are supplied from the nutrient source adding means 15 as needed. Fine underwater photosynthetic organisms
Consumes O ₂ releasing O _2, NO ₂ is biologically immobilized. Further, as a result of cell division and proliferation caused by photosynthesis, surplus fine underwater photosynthetic organisms or obsolete fine underwater photosynthetic organisms are separated by the solid-liquid separation means 10 into fine underwater photosynthetic organisms and a solution. The fine underwater photosynthetic organism is collected by the collection means 12 as a collection 13.

Part or all of the solution separated by the solid-liquid separation means 10 is circulated to the absorption section 4 as a recirculating solution 9. Thereby, the required utility of the water required in the absorption section is reduced, and the running cost is reduced. The recirculating solution 9 contains substances such as absorbents and nutrients, and when the circulation is repeated, these substances accumulate. Therefore, when a substance such as an absorbent reaches a predetermined concentration, the waste liquid 11 is subjected to a waste liquid treatment and then discharged.

By repeating this series of operations, low-concentration exhaust gas discharged from a vehicle such as an automobile can be efficiently and simply removed. That is, according to the present embodiment, NOx can be removed because the photosynthetic action of fine underwater photosynthetic organisms in water that exists naturally is utilized. Therefore, the apparatus cost can be reduced as compared with the method using the adsorbent used in the conventional NOx removal method. Also, as in the conventional NOx removal method using an adsorbent,
There is no need to depressurize the adsorbent at a high temperature or reduce the pressure in order to desorb NOx adhering to the adsorbent, so that the running cost can be reduced.

Further, since dust removal and NOx absorption can be performed simultaneously, the equipment can be made compact, and the installation space can be saved. Since the absorption section for absorbing NOx and the culture section for culturing fine underwater photosynthetic organisms in water are separated and independent, the absorption section and the culture section can be installed in separate spaces, and the installation space can be effectively utilized. Furthermore, the solution used in the culture unit is recirculated to the absorption unit, which reduces the required utilities and eliminates the need for ammonia and urea, which are used as NOx reducing agents for nitrogen and water, thus ensuring safety and reliability. Is also enhanced.

[0020]

According to the present invention, the gas purification apparatus utilizes the photosynthesis of fine underwater photosynthetic organisms in water which exist naturally, so that NOx can be efficiently removed. Therefore, the apparatus cost can be reduced as compared with the conventional method using an adsorbent. Also, unlike the conventional method using an adsorbent, it is not necessary to depressurize the adsorbent to a high temperature or reduce the pressure in order to desorb NOx adhering to the adsorbent, so that the running cost can be reduced.

Further, according to the present invention, there are the following effects. ◆ Since dust removal and NOx absorption can be performed at the same time, the equipment is compact and the installation space can be saved. ◆ Since the absorption part that absorbs NOx and the culture part that cultures fine underwater photosynthetic organisms in water can be separated and independent, the absorption part and the culture part can be installed in separate spaces, and the installation space can be used effectively. ◆ Recycling the solution used in the culture unit to the absorption unit can reduce the required utilities. ◆ High safety and high reliability because no reducing agent is used.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of a gas purification device according to the present invention.

FIG. 2 is a diagram illustrating details of an absorption unit illustrated in FIG. 1;

[Explanation of symbols]

1 ... processing gas, 2 ... gas inlet, 3 ... NOx oxidizing means, 4 ... absorber, 5 ... gas outlet, 6 ... purification gas,
7: NO ₂ -containing solution, 8: Culture section, 9: Recirculating solution, 10: Solid-liquid separation means, 11: Waste liquid, 12: Recovery means, 13: Recovered product, 14: Light source Numeral source adding means, 16 Absorbent adding means, 17 Blower, 20 Circulating pump, 21 spray, 22 Tank, 23 Filtration means, 24 Waste, 25 communication pipe 26 ...... absorption liquid, gas containing 27 ...... dust or NO _2.

Continued on the front page (72) Inventor Jyuta Yukitake 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Masaru Namba 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture No. 1 Inside Hitachi Research Laboratory, Hitachi, Ltd.

Claims (7)

[Claims] 1. A gas purifying apparatus for purifying exhaust gas containing NOx and dust from a vehicle, comprising: oxidizing means for oxidizing NOx in the exhaust gas to NO ₂ ;
A gas purifying apparatus comprising: a biological fixing means for biologically fixing the NO ₂ . _2. An absorbing means for absorbing NO ₂ generated by said oxidizing means in an absorbing solution, a culturing means for aquatic photosynthetic organisms in said biological fixing means, and said absorbing means and said culturing means are provided separately. The gas purifying apparatus according to claim 1, wherein 3. The gas purifying apparatus according to claim 2, wherein said absorbing means has a circulating means for absorbing liquid. 4. The N immobilized by the biological immobilization means.
Claims 1, characterized in that a collecting means for collecting the O ₂ gas purifying apparatus according to any one of 3. 5. A gas purifying apparatus according to claim 2, wherein said absorbing means is provided with a separating means for separating dust. 6. The gas purifying apparatus according to claim 2, wherein said separating means includes an injection means for spraying the absorbing liquid. 7. A gas purification method for purifying exhaust gas from a vehicle containing NOx and dust, wherein NOx in the exhaust gas is oxidized to NO _2, and the oxidized NO ₂
It was absorbed into the absorbent liquid, the NO ₂ which is absorbed in the absorbing liquid is absorbed into the microorganism, a gas purification method, characterized in that the recovery of this microorganism.