JPH09136015A - Device and method for purifying gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device which can remove gas of low concentration of NOx and CO2 and gas containing soot and dust at low cost by a method having high safety by utilizing photosynthesis of algae existing in the natural world. SOLUTION: Soots and dusts are removed from a gas 1 containing NOx, CO2 , soots and dusts discharged from an automobile through an electrostatic precipitator 3 and NO in NOx held in the gas is oxidized to NO2 , and the NO2 and CO2 are dissolved into a culture solution in a dissolution tank 6, whereby light is applied from a light source 10 to the culture solution in which NO2 and CO2 are dissolved to effect photosynthesis by means of algae using NO2 and CO2 as nitrogen source and carbon dioxide source to absorb NO2 and CO2 into the algae.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas purifying apparatus and a method therefor, and particularly in automobile tunnels, intersections, indoor parking lots, highways, etc., where a low concentration of nitrogen oxides (hereinafter NOx
The present invention relates to a gas purification apparatus mainly used for the purpose of removing dust and NOx in the gas in a place where the concentration of gas including carbon dioxide gas (hereinafter abbreviated as CO ₂ ) and soot and dust becomes high. is there.

[0002]

2. Description of the Related Art In recent years, with the increase in traffic volume, in vehicles where the traffic volume is particularly high, such as automobile tunnels, intersections, indoor parking lots, highways, etc. The treatment of soot, NOx, and CO ₂ has become a problem. Regarding the treatment of gas containing high concentration of soot dust, NOx, and CO ₂ emitted from thermal power plants, etc., its removal device has been developed. In comparison, the technology for removing low-concentration soot, NOx, and CO ₂ is still immature. As a countermeasure, in automobile tunnels, etc., the gas inside the tunnel is discharged to the outside of the tunnel by using a blower, or as an ancillary equipment. A dust collector was used to remove soot and dust.

Known examples of low-concentration denitration technology are disclosed in JP-A-5-192535 and JP-A-4-25.
0822 exists. In these known examples, the adsorbent adsorbs NOx, and when the adsorbed amount of NOx increases to a predetermined value, the adsorbed NOx is desorbed to form NOx concentrated to a high concentration, and the high concentration of NOx is formed. Is reduced to nitrogen and water by selective catalytic reduction using a reduction catalyst, and gas purification is completed.

FIG. 2 is a block diagram showing the above-mentioned known low-concentration denitration system. Gas 1 is gas duct 1
9 through the ozone addition means 20
Nitric oxide (hereinafter abbreviated as NO) in Ox is oxidized to nitrogen dioxide (hereinafter abbreviated as NO ₂ ) which is easily adsorbed. This step is omitted if the adsorbent has good performance, NO adsorption is good and no oxidation to NO ₂ is required. NO ₂ and NO in this gas are adsorbed in the adsorption tanks 21a to 21c. If this adsorption process is continued, one of the adsorption tanks reaches a predetermined adsorption amount, so that the air passage of the adsorption tank is switched to the high temperature air circulation system 26 by switching the opening / closing means 25. Air is circulated in the switched adsorption tank by the circulation blower 22. Since the circulation air is heated by the heater 23, NOx adhering to the adsorbent is desorbed, and high concentration NOx is generated. Circulating air containing is formed.
The reducing agent 27 is injected into this circulating air, and NOx is reduced to nitrogen and water in the selective catalytic reduction reactor 24. In FIG.
The adsorption tanks 21a and 21c are performing the adsorption operation, and the adsorption tank 21b is in the state of being reduced. At this time, each of the opening / closing means 25 is open on the solid line and closed on the dotted line. The adsorption tanks 21a and 21c adsorb NOx in the gas 1 to purify the NOx and release it as clean air 15. On the other hand, in the adsorption tank 21b, NOx is desorbed from the adsorbent. When the desorption of NOx in the adsorption tank 21b is completed in this state, the reduced air closes both the opening / closing means 25 on the left side of the adsorption tank 21b and opens both the opening / closing means 25 on the right side. , Is released to the atmosphere as clean air 15. Then, the adsorption tank 21b returns to the adsorption operation by switching the opening / closing means 25.

[0005]

However, in this conventional method, since the cost of the adsorbent itself is high, the cost of the entire system becomes very high. Further, in order to desorb NOx adhering to the adsorbent, it is usually necessary to add a condition of not less than the temperature at which the adsorbent is attached or less than the pressure at which the adsorbent is attached. Requires a great deal of energy, and the running cost becomes very large.

[0006] An object of the present invention is to provide a gas purifying apparatus which can be operated safely without deteriorating the performance while reducing the apparatus cost, running cost and initial cost by using naturally occurring algae and energy. It is in.

[0007]

The present invention is a gas purifying apparatus for purifying a gas containing at least nitrogen oxides, wherein at least a part of nitrogen monoxide contained in the gas is oxidized to form nitrogen dioxide. An oxidizing means for effecting, a dissolution tank accommodating algae and a culture solution thereof, a dissolution means for dissolving the gas containing nitrogen dioxide generated by the oxidizing means in the culture solution, and a dioxide in the culture solution And a light source for causing the algae to perform photosynthesis using nitrogen as a nitrogen source.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a flow sheet showing an example of a gas purifying apparatus that best represents the present invention. The gas 1 is air containing NOx, soot and CO ₂ which are the removal components of the present invention, and this is sucked by the blower 4 from the apparatus inlet 2. The soot and dust in the sucked gas 1 is removed by the dust collector 3. Here, as the dust collector 3, a dry type electric dust collector,
Either a wet electrostatic precipitator or a simple filter may be used. Some of the gas from which dust has been removed,
NOx and CO ₂ which are the objects to be removed are included.
NO, which is one of the x components, is at least partially NO due to ozone generated by corona discharge of the electrode plate of the electrostatic precipitator 3.
Oxidized to ₂ . Note that this oxidation method is not limited to the oxidation using corona discharge of an electrostatic precipitator, and ozone addition means is provided to inject ozone into gas and NO is converted to NO _2.
You may use the method of oxidizing.

The gas containing the oxidation products NO ₂ and CO ₂ is injected into the culture solution in which the algae are stored in the dissolution tank 6 and is dissolved in the culture solution. The method of this dissolution may be a bubble column method using bubbling in which the above-mentioned gas is released into the culture solution and dissolved in the form of foam, as described later in detail, or the above-mentioned gas is filled. A spray system may be used in which the above-mentioned gas is absorbed by spraying the culture solution into the container. Alternatively, the dissolution may be carried out using another absorption system such as a packed column system or a plate column system. NO
_The gas containing ₂ and CO ₂ may be dissolved in the culture medium by directly dissolving NO ₂ and CO ₂ in the culture medium as described above.
Further, a gas containing NO ₂ and CO ₂ may be absorbed in a neutral solution or an alkaline solution, and then a solution to which nutrients necessary for algae are added may be injected into the dissolution tank 6 as a culture solution.

The algae cultured in the dissolution tank 6 receive light from the light source 10 and absorb NO ₂ and CO ₂ in the solution to perform photosynthesis. At this time, in order to activate the photosynthesis of algae, stirring is performed so that the algae in the dissolution tank 6 are in a uniform floating state. As the stirring method, the above-mentioned bubbling method may also be used as the stirring, or the stirring may be performed by a separately provided stirrer. Materials such as phosphorus necessary for photosynthesis of algae are replenished as needed by the culture solution replenishing device 11. Algae in the dissolution tank consume NO ₂ and CO ₂ by photosynthesis, and oxygen (hereinafter abbreviated as O ₂ )
And the gas is purified. In addition, algae that have undergone cell division by photosynthesis and have become redundant as a result of proliferation, or aged algae, are collected by the algae collection device 12. The O ₂ released by the algae and the purified air are released as clean air 15 from the device outlet 14 by the blower 13. The above is a series of flow of this gas purification system.

Further, in this embodiment, the NOx concentration is measured at the device inlet 2 and the device outlet 14, and the concentration of algae in the dissolution layer 6 is controlled so that the concentration at the device outlet 14 becomes a predetermined value. . For this reason, the device inlet 2 and the device outlet 14 are provided with NOx amount measuring means 35 and 36 for measuring the inlet NOx concentration and the outlet NOx concentration.
As the NOx amount measuring means 35, 36, a measuring device such as a NOx meter may be used, and any other device capable of measuring the NOx amount may be used. Measuring means 35
The NOx amount at the inlet measured by the controller 3
The alga concentration required to process NOx is transmitted to the control unit 37, and the alga concentration is controlled according to the amount. As a method for controlling the concentration of the algae, the intensity of the light source 10 is adjusted according to the NOx amount at the device inlet 2,
By controlling the growth of algae, the concentration of algae is controlled. As a result, the amount of nitrogen source consumed by algae changes, so the amount of NOx removed can be controlled. As another method, when the required concentration of algae is calculated, a method of controlling the concentration of algae by directly adding or collecting the required amount of algae to the dissolution tank may be used. The processing gas that has passed through the melting tank 6 is the apparatus outlet 14
The residual NOx amount is measured by the NOx measuring means 36 arranged at. The NOx amount is transmitted to the control device 37, and when the NOx amount is equal to or more than a predetermined amount, the required alga concentration is calculated, and the control device 37 determines the alga concentration according to the required amount in the same manner as described above. By controlling the nitrogen source consumption of algae by controlling the
Control is performed so that the x density becomes a predetermined value. Further, when adjusting the amount of these algae, it is necessary to know the amount of algae present in the dissolution tank 6, for example, if the light transmittance of the culture solution changes depending on the amount of algae. Good.

Further, in this embodiment, the amount of ozone generated in the electrostatic precipitator or the amount of ozone added is controlled. Therefore, the required ozone calculated by the control device 38 is injected into the gas by using the NOx concentration measured by the NOx measuring means 35 and 36 arranged at the device inlet 2 and the device outlet 14 as an input. As described above, the ozone may be injected by a method of generating ozone by corona discharge of the electric dust collector 3, or may be directly injected by ozone adding means. The NOx measurement means 36 installed at the gas device outlet 14 that has passed through the dissolution tank 6 measures the NOx amount, and the degree of oxidation is transmitted to the control device 38. Depending on the degree of the oxidation, the control device 38 calculates the required ozone amount or the excess ozone amount, and the required amount of ozone is added or controlled to control the oxidation. Also, the device outlet 14
In addition to the method of installing the NOx amount measuring means 36 in the control unit 38, an ozone amount measuring means such as an ozone meter is arranged at the device outlet 14 to measure the amount of surplus ozone.
It is also possible to use a means for calculating the required ozone amount or excess ozone amount and adding or controlling the required ozone amount.

FIG. 3 is a view showing a dissolution tank (bubble column) in the case of performing the dissolution by the above-mentioned bubbling method. Algae are cultivated in the dissolution tank 6, and the gas containing NO ₂ and CO ₂ passes through the ventilation duct 5, is discharged into the culture solution from the ventilation nozzle 7, and is dissolved in the culture solution by bubbling. A uniform luminescent carrier 8 is installed in the dissolution tank 6 so that the light is uniformly irradiated therein. For algae, the light irradiated from the uniform luminescent carrier 8 and NO ₂ dissolved in the culture solution CO ₂
Is used as a nitrogen source and a carbon dioxide source for photosynthesis. Light is transmitted from the light source 10 to the uniform light emitting carrier 8 through the optical fiber 9. As the light source 10, sunlight may be used or an artificial light source may be used. Further, the uniform light emitting carrier 8 may be used as an artificial light source. The above-mentioned irradiation of light may be performed from the inside of the dissolution tank 6 or from the outside. Algae was photosynthesis, consume NO ₂ and CO _2, to release O _2. Then, the purified air and O ₂ are discharged to the exhaust duct 16
Is more exhausted.

FIG. 4 is a view showing a dissolution tank in the case of performing the dissolution by the above-mentioned spray method. Algae are cultured in the dissolution tank 6, and the gas containing NO ₂ and CO ₂ passes through the ventilation duct 5 and is filled in the absorption tower 34. The culture solution in the dissolution tank 6 is sent to the spray 31 by the circulation pump 32,
It is jetted into the absorption tower 34. NO ₂ and C in the absorption tower 34
O ₂ is absorbed by the culture solution that is jetted and atomized, and is recovered as condensate in the dissolution tank 6. The algae in the dissolution tank 6 absorb the light emitted by the uniform luminescent carrier 8 and the absorbed NO ₂
And CO ₂ are consumed as a nitrogen source and a carbon dioxide source to perform photosynthesis and release O ₂ . The uniform light emitting carrier 8 is the same as that shown in FIG. 3, and it does not matter whether sunlight is used or an artificial light source is used. The purified air and O ₂ are dehumidified by the demister 33 and discharged from the exhaust duct 16.

[0015]

Industrial Applicability The gas purification apparatus of the present invention uses naturally occurring algae and utilizes its photosynthesis to produce NOx.
Are being removed. Therefore, the apparatus cost can be reduced as compared with the conventional method using an adsorbent used for NOx removal. Further, due to the photosynthesis of algae, NOx and CO ₂ are absorbed by the action and O ₂ is released. Therefore, not only the harmful substances in the gas can be removed, but also effective oxygen can be supplied to the living things. Also, unlike the conventional NOx removal method that uses an adsorbent, there is no need to depressurize the adsorbent to a high temperature or decompress it in order to desorb the NOx adhering to the adsorbent. Can be reduced. Further, usually, the reducing agent used for reducing NOx to nitrogen and water uses ammonia or urea, but in the present invention, since the reducing agent as described above is not used, it is highly safe and reliable. high. Also,
The algae collected as a by-product can be reused as feed for livestock, fertilizer for farm products, and fuel.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing an example of a gas purifying apparatus according to the present invention.

FIG. 2 is a block diagram of a conventional low concentration denitration system.

FIG. 3 is a view showing a bubbling type dissolution tank.

FIG. 4 is a view showing a spray type dissolution tank.

[Explanation of symbols]

 1 Gas 2 Device Inlet 3 Dust Collector 4 Blower 5 Ventilation Duct 6 Dissolution Tank 7 Ventilation Nozzle 8 Uniform Luminescent Carrier 9 Optical Fiber 10 Light Source 11 Culture Solution Replenishing Device 12 Algae Recovery Device 13 Blower 14 Device Outlet 15 Clean Air 16 Exhaust Duct 31 Spray 32 Circulation pump 33 Demister 34 Absorption tower 35, 36 NOx amount measuring means 37, 38 Control device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaru Namba 7-1, 1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Jita Yukitake 7 Omika-cho, Hitachi-shi, Ibaraki 1-1-1, Hitachi, Ltd. Hitachi Research Laboratory

Claims (19)

[Claims] 1. A gas purifying apparatus for purifying a gas containing at least nitrogen oxides, which comprises oxidizing means for oxidizing at least a part of nitric oxide contained in the gas to nitrogen dioxide, and algae. And a dissolution tank accommodating the culture solution, a dissolution means for dissolving a gas containing nitrogen dioxide generated by the oxidation means in the culture solution, and nitrogen dioxide in the culture solution as a nitrogen source to the algae A gas purification apparatus comprising: a light source for performing photosynthesis; 2. The gas purifying apparatus according to claim 1, further comprising dust collecting means for removing soot and dust contained in the gas before the oxidation treatment of nitric oxide in the gas. Gas purifier to be. 3. The gas purifying apparatus according to claim 1, wherein the oxidizing means comprises ozone adding means. 4. The gas purifying apparatus according to claim 2, wherein the dust collecting means is an electrostatic precipitator, and ozone generated by corona discharge of the electrostatic precipitator is used as the oxidizing means. Purification device. 5. The gas purifying apparatus according to claim 1, wherein the dissolving means is gas injecting means for injecting the gas into the melting tank so as to form bubbles. 6. The gas purifying apparatus according to claim 1, wherein the dissolving means is an absorption tower for filling a gas therein, and a spraying means for spraying the culture solution into the absorption tower. A gas purification device comprising: 7. The gas purifying apparatus according to claim 1, wherein the dissolving means is an absorbing means for absorbing nitrogen dioxide into a neutral liquid or an alkali-containing liquid, and an alkaline solution absorbing nitrogen dioxide by the means. And a liquid injecting means for injecting a nutrient solution into the dissolution tank as a culture solution. 8. The gas purifying apparatus according to claim 1, wherein the light source is configured to irradiate the algae directly with sunlight. 9. The gas purifying apparatus according to claim 1, wherein the light source collects sunlight or light from an artificial light source and guides the light with an optical fiber to a luminescent carrier installed in the melting tank. A gas purifier characterized by irradiating the algae with light from a luminescent carrier. 10. The gas purifying apparatus according to claim 1, wherein the light source is an artificial light source installed in the melting tank. 11. The gas purification apparatus according to claim 1, further comprising stirring means for the algae. 12. The gas purifying apparatus according to claim 5, wherein the gas injecting means is configured to inject gas so as to stir the algae. 13. The gas purification apparatus according to claim 1, wherein nitrogen oxide concentration detecting means at a gas inlet / outlet, algae amount adjusting means for increasing / decreasing the amount of algae in the dissolution tank, and the detecting means. Calculate the required amount of algae from the concentration of nitrogen oxides at the inlet detected by the, the amount of algae so that the detected outlet concentration is within the allowable concentration of nitrogen oxides contained in the output gas A gas purification apparatus comprising: a control unit for controlling the adjusting unit. 14. The gas purifying apparatus according to claim 13, wherein the algae amount adjusting means adjusts the amount of algae in the dissolution tank by changing the light amount from the light source. Purification device. 15. The gas purification apparatus according to claim 13, wherein the algae amount adjusting means detects the amount of algae in the dissolution tank by measuring a light transmittance of a culture solution containing algae. Characteristic gas purification device. 16. The gas purifying apparatus according to claim 3, wherein the nitrogen oxide concentration detecting means at the gas inlet / outlet is supplied from the ozone adding means in accordance with the nitrogen oxide concentration at the inlet / outlet detected by the means. A gas purifier characterized by comprising ozone amount control means for controlling the amount of ozone to be discharged. 17. The gas purifying apparatus according to claim 4, wherein the nitrogen oxide concentration detecting means at the gas inlet and outlet, and the electrostatic precipitating means depending on the nitrogen oxide concentration at the inlet and outlet detected by the means. A gas purifying apparatus comprising an ozone amount control means for controlling the amount of ozone generated. 18. At least a part of nitric oxide contained in the gas is oxidized to nitrogen dioxide, and the gas containing nitrogen dioxide is introduced into a dissolution tank containing algae and a culture solution thereof to be dissolved in the culture solution. Then, the dissolved nitrogen dioxide component is used as a nitrogen source to perform photosynthesis by the algae to remove nitrogen oxides. 19. The gas purification method according to claim 17, wherein soot dust contained in the gas is removed by a dust collector before the oxidation of the nitric oxide.