JP2007021499A - Removal method of nitrogen oxide and removal apparatus of nitrogen oxide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a removal method of nitrogen oxide capable of efficiently removing a nitrogen oxide contained in a gas. <P>SOLUTION: The removal apparatus of nitrogen oxide of this invention is a removal apparatus of nitrogen oxide for removing a nitrogen oxide contained in a gas by alternately using several nitrogen oxide adsorbing means 41 and 43, which is provided with a regenerating agent tank 61 for storing a regenerating agent for a solid adsorbent, a regenerating agent supplying means 71 for supplying the regenerating agent from the regenerating agent tank to the nitrogen oxide adsorbing means in a suspension of the supply of the gas when the nitrogen oxide removal function of the nitrogen oxide adsorbing means 41 and 43 falls; and which performs the removal of nitrogen oxide by supplying the gas to the nitrogen oxide adsorbing means 41 other than the nitrogen oxide adsorbing means 43 where lowering of removal function is detected, to remove nitrogen oxide, while switching the supply of the gas, so as to supply the regenerating agent to the nitrogen oxide adsorbing means 43 where the lowering of removal function has been detected, to regenerate it with the regenerating agent at the site. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for removing nitrogen oxides contained in a gas and a nitrogen oxide removing apparatus, and more particularly to a method for removing nitrogen oxides capable of efficiently removing nitrogen oxides contained in the atmosphere and The present invention relates to a nitrogen oxide removing apparatus that can be suitably used when performing the removing method.

  Conventionally, as a method for removing nitrogen oxides in a gas, there are an ammonia denitration method and a urea denitration method for removing nitrogen oxides contained in combustion gas of a power generation facility such as a boiler, a gas turbine, or a gas engine. Further, as a method for removing nitrogen oxides contained in automobile exhaust gas, there is a three-way catalyst system method using a hydrocarbon contained in exhaust gas as a reducing agent and removing a nitrogen oxidation catalyst. In the case of removing nitrogen oxides contained in the exhaust gas by the above method, the nitrogen oxides are reduced to nitrogen gas and removed using the energy of several hundreds of degrees Celsius of the exhaust gas. Further, the concentration of nitrogen oxides contained in combustion gas and exhaust gas is generally several hundred ppm.

  When applying the above method for removing nitrogen oxides used in combustion gases and exhaust gases as a method for removing nitrogen oxides contained in the atmosphere, the concentration of nitrogen oxides contained in the atmosphere is low. There arises a problem that the reaction rate when the product is reduced to nitrogen gas is slow. Moreover, since the air | atmosphere which is low temperature compared with combustion gas and waste gas must be heated to several 100 degreeC, there also exists a problem of consuming huge energy.

  In addition, as a method for removing nitrogen oxides contained in the atmosphere, an alkali absorption method using an alkali absorbing solution (Japanese Patent Laid-Open No. 10-211427), a reduction method using a reducing agent, and an adsorption method using a solid adsorbent (special Kaihei 11-9957).

  However, with the alkali absorption method, it is possible to absorb a low concentration of nitrogen oxides, but carbon dioxide coexisting in the atmosphere is also absorbed at the same time as nitrogen oxides, so nitrogen oxides cannot be absorbed efficiently. There is a problem. In addition, the reduction method has a problem that nitrogen oxides cannot be efficiently reduced because the reducing agent is oxidized by oxygen coexisting in the atmosphere. In addition, in the solid adsorption method, if the concentration of nitrogen oxides contained in the atmosphere is low, even if the amount of nitrogen oxides adsorbed on the solid adsorbent is small, the solid adsorbent will break through immediately. There is a problem that nitrogen oxides contained in the atmosphere cannot be sufficiently adsorbed.

Furthermore, as a method for removing low-concentration nitrogen oxides contained in the atmosphere, there is a method that uses a purification function of soil. However, when the soil purification function is used, there is a problem that a sufficient amount of soil must be secured to meet the required nitrogen oxide removal capability, and a huge amount of land may be required.
Japanese Patent Laid-Open No. 55-162331 JP-A-9-225260 JP-A-4-161221 JP-A-1-296000 JP 51-148675 A

  An object of the present invention is to solve the above-mentioned problems and to provide a method for removing nitrogen oxides that can efficiently remove nitrogen oxides contained in a gas.

According to the present invention, there is provided a method for removing nitrogen oxides contained in a gas from which air is collected in a road tunnel, in an underground parking lot, or in the vicinity of an urban trunk road,
The nitrogen oxide in the gas is supplied to a nitrogen oxide adsorbing means including a solid adsorbent containing carbon-based material particles, and the nitrogen oxide removal function of the solid adsorbent is reduced. A removal step of removing the nitrogen oxide through the gas to a nitrogen oxide adsorbing means other than the nitrogen oxide adsorbing means;
Stopping the supply of the gas to the nitrogen oxide adsorbing means including the solid adsorbing means reduced by the removing step, and introducing the regenerant from the regenerant tank into the nitrogen oxide removing means. A regeneration step for regenerating inside the nitrogen oxide adsorbing means,
There can be provided a method for removing nitrogen oxides, comprising: an on-site treatment step of simultaneously carrying out the on-site treatment of the regeneration step of the nitrogen oxide adsorbing means and the removal step of the other nitrogen oxide removing means.
In the present invention, the regeneration step may include a step of circulating the regenerant between the nitrogen oxide adsorbing means and the regenerant tank storing the regenerant in an inert atmosphere. In the present invention, before the removing step, a pretreatment step of converting the nitrogen oxide contained in the gas into any of nitrogen dioxide, dinitrogen trioxide, dinitrogen tetroxide, and dinitrogen pentoxide is included. Can do. The present invention may further include a detection step of detecting a decrease in the removal function of the solid adsorbent using a nitrogen oxide sensor, and the gas supplied to the nitrogen oxide adsorption means may include humidity.
According to the present invention, a nitrogen oxide removing device that removes nitrogen oxide contained in a gas by alternately using a plurality of nitrogen oxide adsorbing means,
A plurality of nitrogen oxide adsorbing means comprising a solid adsorbent that adsorbs and removes nitrogen oxides and contains carbon-based material particles;
A regenerant tank for storing the regenerant of the solid adsorbent;
When the nitrogen oxide removing function of the nitrogen oxide adsorbing means is lowered, a regenerant supplying means for supplying the regenerant from the regenerant tank to the nitrogen oxide adsorbing means in a state where the supply of the gas is stopped. When,
The nitrogen oxide is removed by using a nitrogen oxide adsorbing means other than the nitrogen oxide adsorbing means according to the reduction in the removing function, and at the same time, the nitrogen oxide adsorbing means in which the reduction in the removing function is detected. An on-site treatment means for supplying the regenerant inside and performing on-site treatment can be provided.
In the present invention, the nitrogen oxide removing device includes a nitrogen oxide sensor, and the regenerant is stored in an inert atmosphere and can be circulated between the regenerant tank and the nitrogen oxide adsorbing device. be able to. In this invention, the pre-processing means which makes the nitrogen oxide contained in the said gas either nitrogen dioxide, dinitrogen trioxide, dinitrogen tetroxide, or dinitrogen pentoxide can be provided. The on-site treatment means of the present invention may include an exchange means for exchanging the nitrogen oxide adsorption means for supplying the gas.

  That is, according to this method of removing nitrogen oxides, even if the solid adsorbent breaks through adsorption with nitrogen oxides and the nitrogen oxide removal function is reduced by the removal step, the removal of nitrogen oxides in the regeneration step Since the function is regenerated, there is no problem due to adsorption breakthrough of the solid adsorbent with nitrogen oxide.

  In addition, nitrogen gas contained in the gas is removed by supplying gas to the nitrogen oxide adsorbing means containing the solid adsorbent, so that gases such as carbon dioxide and oxygen coexist in the gas containing nitrogen oxide. However, there is no problem caused by the coexisting gas.

  Furthermore, in this method for removing nitrogen oxides, it is not necessary to heat when removing nitrogen oxides from the gas, so that the problem of energy consumption associated with heating does not occur.

  Moreover, according to the nitrogen oxide removal method described above, nitrogen oxides can be efficiently removed regardless of the concentration of nitrogen oxides. Therefore, the nitrogen oxide removal method described above is difficult to remove nitrogen oxide efficiently by the conventional nitrogen oxide removal method, for example, in road tunnels, underground parking lots, urban trunk lines. The present invention can also be preferably applied when the atmosphere such as the vicinity of a road is a collected gas.

  Moreover, it is good also as the removal method which performs the said reproduction | regeneration process, when the fall of a removal function is detected by the nitrogen oxide sensor. By adopting such a method for removing nitrogen oxides, it is possible to ensure a function of removing nitrogen oxides of a predetermined level or higher and improve the quality of the gas obtained after removing the nitrogen oxides. .

  Further, by recirculating the regenerant in the above method for removing nitrogen oxides, the regeneration step can be easily performed, and nitrogen oxides contained in the gas can be more efficiently removed. .

  Further, in the nitrogen oxide removal method described above, before the removing step, the nitrogen oxide contained in the gas is any one of nitrogen dioxide, dinitrogen trioxide, dinitrogen tetroxide, and dinitrogen pentoxide. Even if nitrogen monoxide is included in the nitrogen oxide by including the pretreatment step, the nitrogen oxide is efficiently contained in the gas as in the case where nitrogen monoxide is not included. Can be removed.

  In the nitrogen oxide removing method, it is preferable that the gas supplied to the nitrogen oxide adsorbing means includes humidity. When water is contained in the gas, a hydration reaction of nitrogen oxide occurs on the surface of the solid adsorbent, and the nitrogen oxide becomes nitrous acid or nitric acid. For this reason, the amount of nitrogen oxides adsorbed by the solid adsorbent increases, nitrogen oxides are more easily adsorbed by the solid adsorbent, and nitrogen oxides contained in the gas can be more efficiently removed.

  Furthermore, in the above method for removing nitrogen oxides, it is desirable that the solid adsorbent is a carbon-based material. By adopting such a method for removing nitrogen oxides, the solid adsorbent has a large specific surface area, so that nitrogen oxides are more easily adsorbed by the solid adsorbent, and more efficiently into the gas. Nitrogen oxide contained can be removed. In particular, activated carbon can be cited as an example of a carbon-based material having a large specific surface area that is preferably applied as a solid adsorbent.

  Further, in the above method for removing nitrogen oxides, it is desirable that the basic substance is an alkali metal hydroxide or an alkaline earth metal hydroxide. Alkali metal hydroxides or alkaline earth metal hydroxides, which are strongly basic substances, can efficiently remove nitrogen oxides adsorbed by the solid adsorbent. For this reason, the basic substance is an alkali metal hydroxide or an alkaline earth metal hydroxide, so that the regeneration process can be performed more efficiently, and the nitrogen oxidation contained in the gas can be performed more efficiently. Things can be removed.

  In the nitrogen oxide removal method, the reducing substance is preferably a sulfite.

  Sulfite can efficiently reduce nitrogen oxides to nitrogen gas even at room temperature. For this reason, a reductive process can be performed still more efficiently by making a reducing substance into a sulfite, and the nitrogen oxide contained in gas can be removed much more efficiently.

  In the nitrogen oxide removal method described above, when the regenerant contains a reducing substance, it is desirable to regenerate the removal function in a nitrogen atmosphere.

  By adopting such a method for removing nitrogen oxides, the reducing substance can be prevented from being deteriorated by oxygen or the like, and the life of the regenerant can be extended.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  1 and 2 are flowcharts for explaining an example of the method for removing nitrogen oxides of the present invention. FIG. 3 is a photograph showing an example of the nitrogen oxide removing apparatus of the present invention, and FIG. 4 is a schematic diagram for explaining an example of the nitrogen oxide removing apparatus of the present invention.

  First, the nitrogen oxide removing apparatus of the present invention will be described in detail.

  The nitrogen oxide removing apparatus shown in FIG. 4 supplies the air collected for removing nitrogen oxides to a nitrogen oxide oxidizing apparatus (corresponding to “pretreatment means” in claims). The air that has passed through the nitrogen oxide oxidizer 2 is supplied to a supply line 1, a nitrogen oxide oxidizer 2, and a nitrogen oxide adsorber (corresponding to “nitrogen oxide adsorbing means” in the claims) 4. An air supply line 3, a nitrogen oxide adsorbing device 4 that adsorbs nitrogen oxides, and an air exhaust line 5 that discharges the air that has passed through the nitrogen oxide adsorbing device 4 as purified air.

  Further, a nitrogen oxide sensor is installed in the atmospheric discharge line 5 shown in FIG. The nitrogen oxide sensor detects the nitrogen oxide removing function of the nitrogen oxide adsorbing device 4 and manages the concentration of nitrogen oxide in the purified air released from the air discharge line 5. Furthermore, the nitrogen oxide removing apparatus shown in FIG. 4 includes a regenerant tank 6 for storing the regenerant, a regenerant supply line 7 for supplying the regenerant from the regenerant tank 6 to the nitrogen oxide adsorption device 4, A regenerant supply means comprising a regenerant return line 8 for returning the regenerant that has passed through the nitrogen oxide adsorber 4 from the nitrogen oxide adsorber 4 to the regenerant tank 6 is provided. Between the nitrogen oxide adsorbing device 4 and the regenerant supply line 7 and the regenerant return line 8, it can be circulated.

  In the nitrogen oxide removing device shown in FIG. 4, the nitrogen oxide removing function of the nitrogen oxide adsorbing device 4 is regenerated when the nitrogen oxide sensor detects a concentration higher than a predetermined concentration. ing.

  The supply line 1 may have any structure as long as it can supply air to the nitrogen oxide oxidizer 2 and is not particularly limited. In addition, the supply line 1 includes a dust collector that prevents clogging of the nitrogen oxide adsorption device 4 and a device that controls the flow rate and flow rate of the atmosphere supplied to the nitrogen oxide oxidation device 2 as necessary. It is attached.

  The nitrogen oxide oxidizer 2 oxidizes nitrogen oxides contained in the atmosphere to convert the nitrogen oxides contained in the atmosphere into any of nitrogen dioxide, dinitrogen trioxide, dinitrogen tetroxide, and dinitrogen pentoxide. To do. The form of the nitrogen oxide adsorbing device 2 is not particularly limited, but is preferably an oxidizing device using ozone generation that can effectively oxidize a low concentration of nitrogen oxide. The temperature control of the nitrogen oxide oxidizer 2 is not particularly necessary, and the temperature supplied via the air supply line 1 may be maintained.

  The nitrogen oxide adsorbing device 4 is for adsorbing nitrogen oxide, and a packed bed is used in which a solid adsorbent 4a that adsorbs nitrogen oxide is filled in a container. The packed bed filled with the solid adsorbent 4a is not particularly limited, but a structure capable of circulating the atmosphere with a small pressure loss is preferably used.

  The solid adsorbent 4a is preferably crushed particles or molded particles of several mm to several cm, or honeycomb structured particles from the viewpoint of keeping the pressure loss low. Furthermore, the solid adsorbent 4a preferably has a large specific surface area from the viewpoint of efficiently adsorbing low-concentration nitrogen oxides. Further, the solid adsorbent 4a used in the nitrogen oxide adsorbing device 4 may be one type or two or more types. Examples of the material constituting the solid adsorbent 4a include carbon materials and inorganic materials. Examples of the carbon-based material include ashigara activated carbon, pitch-based activated carbon, carbon fiber, charcoal, fullerene, and carbon nanotube. Examples of inorganic materials include activated clay, alumina, zeolite, silica, magnesia, titania and the like. Among these, a particularly preferable solid adsorbent 4a includes a carbon-based material having a large specific surface area such as activated carbon.

  Further, the container filled with the solid adsorbent 4a has no air leakage, and can withstand the body pressure from the solid adsorbent 4a and the liquid pressure of the regenerant used when cleaning and regenerating the solid adsorbent 4a. Any structure can be used without any particular limitation. Furthermore, the material of the container filled with the solid adsorbent 4a is not particularly limited, and examples thereof include mild steel, stainless steel, FRP, and PCV.

  Further, the temperature control of the nitrogen oxide adsorbing device 4 is not particularly required as in the case of the nitrogen oxide oxidizing device 2, and the temperature supplied through the air supply line 3 may be maintained. Further, in the nitrogen oxide removing apparatus shown in FIG. 4, the humidity of the atmosphere supplied through the atmosphere supply line 3 is preferably 40% or more, more preferably, in order to effectively adsorb nitrogen oxides. 60% or more, more preferably 80% or more. The humidity of the atmosphere supplied to the nitrogen oxide adsorbing apparatus 4 may be controlled using any method and apparatus. For example, a method of increasing the humidity by spraying water into the atmosphere is preferably used. it can.

Furthermore, in the nitrogen oxide removing apparatus shown in FIG. 4, the space velocity of the atmosphere supplied to the nitrogen oxide adsorption apparatus 4 is controlled by using the control apparatus 9 in order to efficiently adsorb nitrogen oxides. Is set to 1000 to 200,000 h ⁻¹ , more preferably 3000 to 100,000 h ⁻¹ . The space velocity of the atmosphere supplied to the nitrogen oxide adsorption device 4 is determined according to the concentration of nitrogen oxide in the atmosphere to be removed, the type of the solid adsorbent 4a, the size of the nitrogen oxide adsorption device 4, and the like. The The control device 9 is not particularly limited as long as it can control the space velocity of the atmosphere supplied to the nitrogen oxide adsorption device 4.

  In the nitrogen oxide adsorbing device 4, the nitrogen oxide removing function gradually decreases as the solid adsorbent 4a adsorbs and breaks through the nitrogen oxide. However, in the nitrogen oxide removing apparatus shown in FIG. 4, the nitrogen oxide adsorbing apparatus 4 is regenerated by removing nitrogen oxide from the solid adsorbent 4a that has passed through the adsorption using a regenerant. As the regenerant, an aqueous solution containing a basic substance or a reducing substance is used.

  Examples of basic substances include, but are not limited to, alkali metal hydroxides, alkaline earth hydroxides, alkali metal carbonates, alkaline earth metal carbonates, and the like. From the viewpoint of efficiently removing substances, alkali metal hydroxides and alkaline earth hydroxides which are strongly basic substances are particularly preferably used.

  Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide and the like. Examples of the alkaline earth hydroxide include calcium hydroxide and magnesium hydroxide. Examples of the alkali metal carbonate include lithium carbonate, sodium carbonate, and potassium carbonate. Examples of the alkaline earth metal carbonate include calcium carbonate and magnesium carbonate.

  Further, the reducing substance is not particularly limited, and examples thereof include sulfites, thiosulfates, hydrides, hydrogen sulfide, aldehydes, etc. From the viewpoint of reducing nitrogen oxides to nitrogen gas at room temperature, sulfurous acid. It is preferable to use a salt.

  Examples of the sulfite include lithium sulfite, sodium sulfite, potassium sulfite, calcium sulfite, magnesium sulfite, iron sulfite, and copper sulfite. Examples of the thiosulfate include lithium thiosulfate, sodium thiosulfate, potassium thiosulfate, calcium thiosulfate, and magnesium thiosulfate. Examples of the hydride include sodium borohydride and lithium aluminum hydride. Examples of aldehydes include formaldehyde and acetaldehyde.

  When a reducing substance is used as the regenerant, it is desirable to replace the regenerating agent tank 6 with nitrogen in order to prevent the reducing substance from being deteriorated by oxygen or the like. Further, when the nitrogen oxide adsorbing device 4 is regenerated, it is preferable to replace not only the regenerant tank 6 but also the nitrogen oxide adsorbing device 4 with nitrogen.

  The regenerant can be used once or a plurality of times by preparing in consideration of the type and amount of nitrogen oxide in the atmosphere supplied to the nitrogen oxide adsorbing device 4 and the concentration of the regenerant. It is supposed to be.

  Next, a method for removing nitrogen oxides contained in the atmosphere using such a nitrogen oxide removing apparatus will be described in detail.

  The atmosphere containing nitrogen oxides from which nitrogen oxides are removed by the method described below is not particularly limited, but for example, in road tunnels or underground parking lots where nitrogen oxide concentrations of several ppm or less are a problem. Or air collected from the vicinity of a city main road or the like. The atmosphere containing nitrogen oxides desirably has a humidity of 60% or more, more preferably 80% or more.

  In order to remove nitrogen oxides contained in the atmosphere containing such nitrogen oxides, first, as shown in FIG. 1, the atmosphere containing nitrogen oxides is subjected to nitrogen oxide oxidation via the atmosphere supply line 1. Supplyed to the apparatus 2 (S1), the nitrogen oxide in the atmosphere is any one of nitrogen dioxide, dinitrogen trioxide, dinitrogen tetroxide, and dinitrogen pentoxide (in the “pretreatment step” in the claims) (S2).) Next, the air that has passed through the nitrogen oxide oxidizer 2 is supplied to the nitrogen oxide adsorber 4 via the air supply line 3 (S3), and the nitrogen oxide in the air is adsorbed and removed by the solid adsorbent 4a ( This corresponds to the “removal step” in the claims (S4). Then, the air that has passed through the nitrogen oxide adsorbing device 4 is discharged as purified air through the air exhaust line 5 (S6).

  At this time, when nitrogen oxides of a predetermined concentration or more are detected by the nitrogen oxide sensor installed in the atmospheric discharge line 5 (corresponding to “detection step” in the claims (S5)), the atmosphere The supply of air containing nitrogen oxides from the supply line 1 is shut off (S7), and the nitrogen oxide adsorbing device 4 shown below is regenerated ("regeneration" in the claims) with the air supply kept shut off. (S8)) is performed.

  In order to regenerate the nitrogen oxide adsorbing device 4, first, as shown in FIG. 2, the regenerant is supplied from the regenerant tank 6 to the nitrogen oxide adsorbing device 4 via the regenerant supply line 7 (S81). Nitrogen oxides are removed from the solid adsorbent 4a (S82). The removal of nitrogen oxides by the regenerant is performed by a method of immersing the solid adsorbent 4a in the regenerator in the nitrogen oxide adsorbing device 4 or a method of spraying the regenerant on the solid adsorbent 4a. Subsequently, the used regeneration agent is returned to the regeneration agent tank 6 of the solid adsorbent 4a via the regeneration agent return line 8 (S83), thereby completing the regeneration of the nitrogen oxide adsorption device 4.

  When the regeneration of the nitrogen oxide adsorbing device 4 is thus completed, the supply of air containing nitrogen oxides from the air supply line 1 is resumed as shown in FIG. 1 (S9). Then, the above steps are repeated until all air containing nitrogen oxides is released as purified air, and the removal of nitrogen oxides for all air containing nitrogen oxides is completed.

  According to such a method and apparatus for removing nitrogen oxide, the nitrogen oxide contained in the atmosphere is removed by supplying the atmosphere to the nitrogen oxide adsorbing apparatus 4 including the solid adsorbent 4a, and the solid adsorbent Since the removal function of nitrogen oxide is regenerated by removing the nitrogen oxide adsorbed by 4a, the nitrogen oxide contained in the atmosphere can be efficiently removed.

  In the method and apparatus for removing nitrogen oxides of the present invention, as shown in the above-described example, the nitrogen oxide adsorbing device 4 is used when nitrogen oxides of a predetermined concentration or more are detected by the nitrogen oxide sensor. However, it may be performed every predetermined period. For example, when the method and apparatus for removing nitrogen oxides of the present invention are continuously applied over a long period of time, considering the ease of maintenance, etc., the cycle is once a day or once a week. You may make it reproduce by.

  Further, in the method and apparatus for removing nitrogen oxides of the present invention, a plurality of nitrogen oxide adsorption devices may be provided. FIG. 5 is a schematic view showing an example of a nitrogen oxide removing device provided with two nitrogen oxide adsorbing devices. The nitrogen oxide removing apparatus shown in FIG. 5 is different from the nitrogen oxide removing apparatus shown in FIG. 4 only in the nitrogen oxide adsorbing apparatuses 41 and 43 and their peripheral portions. The portions other than the nitrogen oxide adsorbing devices 41 and 43 and their peripheral portions are omitted.

  The nitrogen oxide removing apparatus shown in FIG. 5 includes a region A for removing nitrogen oxides, and regions B and C for regenerating the nitrogen oxide adsorbing device. Air is supplied from the air supply line 31 to the nitrogen oxide adsorbing device 43 disposed in the region A where nitrogen oxide is removed and supported by the support member 45. The air that has passed through the nitrogen oxide adsorbing device 43 is released from the air exhaust line 51. Further, the regenerant supply from the regenerant tank 61 is supplied to the nitrogen oxide adsorber 41 which is arranged in the region B where the nitrogen oxide adsorber is regenerated and is connected and integrated by the nitrogen oxide adsorber 43 and the connecting member 44. The regenerant is supplied via the line 71, and the regenerant that has passed through the nitrogen oxide adsorbing device 41 is returned to the regenerant tank 61 via the regenerant return line 81.

  When the nitrogen oxide adsorbing device 43 is regenerated, the nitrogen oxide adsorbing device 43 moves in the direction of the arrow D and is disposed in the region C where the nitrogen oxide adsorbing device is regenerated. The adsorption device 41 is disposed in the region A where nitrogen oxides are removed. In FIG. 5, the nitrogen oxide adsorption device 43 disposed in the region C is indicated by a dotted line and indicated by reference numeral 42. Further, the regenerant is supplied from the regenerant tank 62 to the nitrogen oxide adsorbing device 42 via the regenerant supply line 72, and the regenerant that has passed through the nitrogen oxide adsorbing device 42 passes through the regenerant return line 82. The regenerant tank 62 is returned.

  When removing nitrogen oxides using the nitrogen oxide removing apparatus shown in FIG. 5, the nitrogen oxide adsorbing apparatus 41 is regenerated while the nitrogen oxide adsorbing apparatus 43 is removing nitrogen oxides. Further, the nitrogen oxide adsorbing device 43 is regenerated while the nitrogen oxide adsorbing device 41 is removing the nitrogen oxide.

  As described above, when a plurality of nitrogen oxide adsorption devices are provided, another nitrogen oxide adsorption device is regenerated while at least one of the plurality of nitrogen oxide adsorption devices removes the nitrogen oxide. Since the removal and regeneration of nitrogen oxides can be performed simultaneously, the nitrogen oxides can be removed continuously and efficiently. The number of regenerant supply means installed when a plurality of nitrogen oxide adsorption devices are provided may be one or one as in the example shown in FIG. In addition, the plurality of nitrogen oxide adsorption devices may be connected as in the example shown in FIG. 5, but may not be connected, the region for removing nitrogen oxides, and the nitrogen oxide adsorption device Each of them may be individually movable between the areas for reproducing the images.

  Furthermore, when the nitrogen oxide adsorbing device 4 is small, by making the solid adsorbent into a cassette that can be removed, by the method of removing the solid adsorbent in the cassette and immersing it in the regenerant, It is good also as what can remove the nitrogen oxide of a solid adsorption agent. Further, by making the solid adsorbent into a cassette and making it removable, the solid adsorbent can be easily replaced when it is necessary to replace the solid adsorbent.

  Furthermore, as shown in the above-described example, it is desirable that the atmosphere containing nitrogen oxides is supplied to the nitrogen oxide adsorption device 4 after passing through the nitrogen oxide oxidation device 2, but contains nitrogen oxides. If the nitrogen oxide removal rate in the atmosphere is low, there is no problem, or the nitrogen oxide contained in the gas is from one or more selected from nitrogen dioxide, dinitrogen trioxide, dinitrogen tetroxide, dinitrogen pentoxide In this case, the air supply line 1 is directly connected to the air supply line 3 so that air containing nitrogen oxides is supplied to the nitrogen oxide adsorbing device 4 without going through the nitrogen oxide oxidizing device 2. May be.

  Further, as shown in the above-described example, the present invention can be preferably applied when removing nitrogen oxides contained in the atmosphere. In the present invention, the gas from which nitrogen oxides are removed is the atmosphere. There is no particular limitation.

  EXAMPLES Hereinafter, the Example and comparative example of this invention are shown and this invention is demonstrated in detail.

"Example 1"
Using the nitrogen oxide removing apparatus shown in FIG. 6, the following tests were conducted.

That is, the nitrogen oxide adsorbing device 14 obtained by filling a glass container having an inner diameter of 16 mm with 1 ml (0.43 g) of a solid adsorbent made of activated carbon (manufactured by Nacalai Tesque, particle diameter of 0.5 to 3 mm). In addition, by controlling using the control device 10, air having a temperature of 25 ° C. and 1% humidity containing 1 ppm of nitrogen dioxide is circulated at a space velocity of 48000 h ⁻¹ , and nitrogen oxidation detected by the nitrogen oxide sensor 15 is detected. The removal rate of nitrogen oxides was determined from the concentration of the product.

  Then, 32 hours after the nitrogen oxide removal rate reached 70%, the solid adsorbent in the nitrogen oxide adsorbing device 14 was immersed in 10 ml of a regenerant (an aqueous solution containing 1% sodium sulfite) for 30 minutes. Replayed. Thereafter, the circulation of air was resumed, and the solid adsorbent was regenerated in the same manner as described above four times every 32 h, and the nitrogen oxide removal rate was determined in the same manner as described above.

  The results are shown in Table 1.

In Table 1, “humidity” is relative humidity, and the unit is “%”. “Space velocity” is measured with a gas volume flow meter, and the unit is “h ⁻¹ ”. The unit of “particle diameter” is “mm”. In addition, “time” refers to a time when the removal rate of nitrogen oxides is 70% or more after the regeneration is completed.

  As shown in Table 1, the nitrogen oxide removal rate from the end of regeneration to 32 hours later was 70% or more.

"Example 2"
Nitrogen oxide removal and activated carbon regeneration were repeated in the same manner as in Example 1 except that a 5% aqueous sodium hydroxide solution was used as the regenerant.

  As a result, as shown in Table 1, the nitrogen oxide removal rate from the end of regeneration to 24 hours later was 70% or more.

"Example 3"
Nitrogen oxide removal and activated carbon regeneration were repeated in the same manner as in Example 1 except that the air humidity was 40%.

  As a result, as shown in Table 1, the nitrogen oxide removal rate from 4 hours after the completion of regeneration was 70% or more.

Example 4
The removal of nitrogen oxides and regeneration of activated carbon were repeated in the same manner as in Example 1 except that the space velocity was 96000 h- ¹ .

  As a result, as shown in Table 1, the nitrogen oxide removal rate from the end of regeneration to 22 hours later was 70% or more.

"Example 5"
Nitrogen oxide removal and activated carbon regeneration were repeated in the same manner as in Example 1 except that the space velocity was set to 4800 h- ¹ .

  As a result, as shown in Table 1, the nitrogen oxide removal rate from the end of regeneration to 72 hours later was 70% or more.

"Example 6"
Nitrogen oxide removal and activated carbon regeneration were repeated in the same manner as in Example 1 except that the space velocity was 9600 h- ¹ .

  As a result, as shown in Table 1, the nitrogen oxide removal rate from the end of regeneration to 38 hours later was 70% or more.

"Example 7"
Nitrogen oxide removal and activated carbon regeneration were repeated in the same manner as in Example 1 except that the particle diameter of the activated carbon was changed to 2 to 6 mm.

  As a result, as shown in Table 1, the nitrogen oxide removal rate from the end of regeneration to 102 hours later was 70% or more.

"Example 8"
Nitrogen oxide removal and activated carbon regeneration were repeated in the same manner as in Example 1 except that the air humidity was 80%.

  As a result, as shown in Table 1, the nitrogen oxide removal rate from the end of regeneration to 24 hours later was 70% or more.

“Comparative Example 1”
Nitrogen oxide removal and activated carbon regeneration were repeated in the same manner as in Example 1 except that 100 ml of ion-exchanged water was used as the regenerant.

  As a result, as shown in Table 1, 5 minutes after the completion of regeneration, the nitrogen oxide removal rate fell below 70%, and the solid adsorbent could not be regenerated.

  As described above, according to the method and apparatus for removing nitrogen oxides of the present invention, the nitrogen oxides contained in the gas are removed by supplying the gas to the nitrogen oxide adsorbing means containing the solid adsorbent, Since the nitrogen oxide removal function is regenerated by removing the nitrogen oxides adsorbed by the solid adsorbent, the nitrogen oxides contained in the gas can be efficiently removed.

It is a flowchart for demonstrating an example of the removal method of the nitrogen oxide of this invention. It is a flowchart for demonstrating an example of the removal method of the nitrogen oxide of this invention. It is the photograph which showed an example of the removal apparatus of the nitrogen oxide of this invention. It is the schematic for demonstrating an example of the removal apparatus of the nitrogen oxide of this invention. It is the schematic for demonstrating the other example of the removal apparatus of the nitrogen oxide of this invention. It is the figure which showed the removal apparatus of the nitrogen oxide used for the Example and the comparative example.

Explanation of symbols

1 Atmospheric supply line 2 Nitrogen oxide oxidizer 3 Atmospheric supply line 4 Nitrogen oxide adsorber 5 Atmospheric discharge line 6 Regenerant tank 7 Regenerant supply line 8 Regenerant return line

Claims (8)

A method for removing nitrogen oxides contained in a gas obtained by collecting air in a road tunnel, underground parking lot, or near an urban trunk road,
The nitrogen oxide in the gas is supplied to a nitrogen oxide adsorbing means including a solid adsorbent containing carbon-based material particles, and the nitrogen oxide removal function of the solid adsorbent is reduced. A removal step of removing the nitrogen oxide through the gas to a nitrogen oxide adsorbing means other than the nitrogen oxide adsorbing means;
Stopping the supply of the gas to the nitrogen oxide adsorbing means including the solid adsorbing means reduced by the removing step, and introducing the regenerant from the regenerant tank into the nitrogen oxide removing means. A regeneration step for regenerating inside the nitrogen oxide adsorbing means,
A method for removing nitrogen oxide, comprising: an on-site treatment step for simultaneously performing on-site treatment of the regeneration step of the nitrogen oxide adsorbing means and the removal step by the other nitrogen oxide removing means.   2. The nitrogen oxidation according to claim 1, wherein the regeneration step includes a step of circulating the regenerant between the nitrogen oxide adsorbing means and the regenerant tank storing the regenerant in an inert atmosphere. How to remove things.   Or a pretreatment step of converting the nitrogen oxide contained in the gas into any of nitrogen dioxide, dinitrogen trioxide, dinitrogen tetroxide, and dinitrogen pentoxide before the removing step. The method for removing nitrogen oxides according to any one of 2 above.   Furthermore, the detection process which detects the fall of the removal function of the said solid adsorbent using a nitrogen oxide sensor, The said gas supplied to the said nitrogen oxide adsorption | suction means contains humidity. The removal method of the nitrogen oxide in any one. A nitrogen oxide removing device that removes nitrogen oxide contained in a gas by alternately using a plurality of nitrogen oxide adsorption means,
A plurality of nitrogen oxide adsorbing means comprising a solid adsorbent that adsorbs and removes nitrogen oxides and contains carbon-based material particles;
A regenerant tank for storing the regenerant of the solid adsorbent;
When the nitrogen oxide removing function of the nitrogen oxide adsorbing means is lowered, a regenerant supplying means for supplying the regenerant from the regenerant tank to the nitrogen oxide adsorbing means in a state where the supply of the gas is stopped. When,
The nitrogen oxide is removed by using a nitrogen oxide adsorbing means other than the nitrogen oxide adsorbing means according to the reduction in the removing function, and at the same time, the nitrogen oxide adsorbing means in which the reduction in the removing function is detected. A nitrogen oxide removing device comprising: an on-site processing means for supplying the regenerant inside and performing on-site processing.   6. The nitrogen oxide removal apparatus includes a nitrogen oxide sensor, and the regenerant is stored in an inert atmosphere and can be circulated between the regenerant tank and the nitrogen oxide adsorber. The nitrogen oxide removing apparatus described in 1.   The nitrogen oxide according to claim 5 or 6, further comprising pretreatment means for converting the nitrogen oxide contained in the gas into any of nitrogen dioxide, dinitrogen trioxide, dinitrogen tetroxide, and dinitrogen pentoxide. Removal device.   The nitrogen oxide removing apparatus according to any one of claims 5 to 7, wherein the on-site treatment means includes an exchange means for exchanging the nitrogen oxide adsorption means for supplying the gas.