JP2004121902A - Method and apparatus for removing nitrogen oxide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently remove nitrogen oxide contained in a gas. <P>SOLUTION: This nitrogen oxide removing method comprises a removal step to remove the nitrogen oxide contained in the gas by supplying the gas to a nitrogen oxide adsorbing means containing a solid adsorbent for adsorbing/removing nitrogen oxide and a regeneration step to regenerate the nitrogen oxide removing function of the nitrogen oxide adsorbing means lowered at the removal step by removing the nitrogen oxide adsorbed on the solid adsorbent by using a regenerating agent containing a basic or reducing substance. The nitrogen oxide removing apparatus is provided with the nitrogen oxide adsorbing means and a regenerating agent supplying means for supplying the regenerating agent to the nitrogen oxide adsorbing means. <P>COPYRIGHT: (C)2004,JPO

Description

表１において「湿度」は、相対湿度であり、単位は「％」である。「空間速度」は、ガス体積流量計にて測定したものであり、単位は「ｈ^−１」である。「粒子径」の単位は「ｍｍ」である。また、「時間」とは、再生が終了してから窒素酸化物の除去率が７０％以上であった時間のことをいう。
表１に示すように、再生が終了してから３２ｈ後までの窒素酸化物除去率は、いずれも７０％以上であった。
【００５６】
「実施例２」
再生剤として、５％水酸化ナトリウム水溶液を用いた以外は、実施例１と同様にして、窒素酸化物の除去と活性炭の再生とを繰り返し行った。
その結果、表１に示すように、再生が終了してから２４ｈ後までの窒素酸化物除去率は、いずれも７０％以上であった。
【００５７】
「実施例３」
空気の湿度を４０％とした以外は、実施例１と同様にして、窒素酸化物の除去と活性炭の再生とを繰り返し行った。
その結果、表１に示すように、再生が終了してから４ｈ後までの窒素酸化物除去率は、いずれも７０％以上であった。
【００５８】
「実施例４」
空間速度を９６０００ｈ^−１とした以外は、実施例１と同様にして、窒素酸化物の除去と活性炭の再生とを繰り返し行った。
その結果、表１に示すように、再生が終了してから２２ｈ後までの窒素酸化物除去率は、いずれも７０％以上であった。
【００５９】
「実施例５」
空間速度を４８００ｈ^−１とした以外は、実施例１と同様にして、窒素酸化物の除去と活性炭の再生とを繰り返し行った。
その結果、表１に示すように、再生が終了してから７２ｈ後までの窒素酸化物除去率は、いずれも７０％以上であった。
【００６０】
「実施例６」
空間速度を９６００ｈ^−１とした以外は、実施例１と同様にして、窒素酸化物の除去と活性炭の再生とを繰り返し行った。
その結果、表１に示すように、再生が終了してから３８ｈ後までの窒素酸化物除去率は、いずれも７０％以上であった。
【００６１】
「実施例７」
活性炭の粒子径を２〜６ｍｍにした以外は、実施例１と同様にして、窒素酸化物の除去と活性炭の再生とを繰り返し行った。
その結果、表１に示すように、再生が終了してから１０２ｈ後までの窒素酸化物除去率は、いずれも７０％以上であった。
【００６２】
「実施例８」
空気の湿度を８０％とした以外は、実施例１と同様にして、窒素酸化物の除去と活性炭の再生とを繰り返し行った。
その結果、表１に示すように、再生が終了してから２４ｈ後までの窒素酸化物除去率は、いずれも７０％以上であった。
【００６３】
「比較例１」
再生剤として、１００ｍｌのイオン交換水を用いた以外は、実施例１と同様にして、窒素酸化物の除去と活性炭の再生とを繰り返し行った。
その結果、表１に示すように、再生が終了してから５分後で窒素酸化物除去率が、７０％を下回り、固体吸着剤を再生することはできなかった。
【００６４】
【発明の効果】
上述したように、本発明の窒素酸化物の除去方法および除去装置によれば、固体吸着剤を含む窒素酸化物吸着手段に気体を供給することにより気体中に含まれる窒素酸化物を除去し、固体吸着剤が吸着した窒素酸化物を除去することにより窒素酸化物の除去機能が再生されるので、気体中に含まれる窒素酸化物を効率よく除去することができる。
【図面の簡単な説明】
【図１】本発明の窒素酸化物の除去方法の一例を説明するためのフローチャートである。
【図２】本発明の窒素酸化物の除去方法の一例を説明するためのフローチャートである。
【図３】本発明の窒素酸化物の除去装置の一例を示した写真である。
【図４】本発明の窒素酸化物の除去装置の一例を説明するための概略図である。
【図５】本発明の窒素酸化物の除去装置の他の例を説明するための概略図である。
【図６】実施例および比較例に用いた窒素酸化物の除去装置を示した図である。
【符号の説明】
１　　大気供給ライン
２　　窒素酸化物酸化装置
３　　大気供給ライン
４　　窒素酸化物吸着装置
５　　大気排出ライン
６　　再生剤タンク
７　　再生剤供給ライン
８　　再生剤戻りライン[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for removing nitrogen oxides contained in a gas and a device for removing nitrogen oxides, and in particular, a method for removing nitrogen oxides that can efficiently remove nitrogen oxides contained in air and The present invention relates to an apparatus for removing nitrogen oxide which can be suitably used when the above-described removal method is performed.
[0002]
[Prior art]
BACKGROUND ART 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 power generation equipment such as a boiler, a gas turbine, and a gas engine. As a method for removing nitrogen oxides contained in automobile exhaust gas, there is a three-way catalyst system method in which hydrocarbons contained in exhaust gas are used as a reducing agent to remove a nitrogen oxidation catalyst. In the case of removing nitrogen oxides contained in exhaust gas by the above method, nitrogen oxides are reduced to nitrogen gas and removed using the energy of several hundred degrees Celsius of the exhaust gas. Further, the concentration of nitrogen oxides contained in the combustion gas and the exhaust gas is generally several hundred ppm.
[0003]
When the above-mentioned method for removing nitrogen oxides used in combustion gas and exhaust gas is applied as a method for removing nitrogen oxides contained in the atmosphere, the nitrogen oxides contained in the atmosphere are low in concentration. There is a problem that the reaction rate when reducing the substance to nitrogen gas is low. In addition, there is also a problem that an enormous amount of energy is consumed because the atmosphere, which is lower in temperature than combustion gas and exhaust gas, must be heated to several hundred degrees Celsius.
[0004]
Further, as a method for removing nitrogen oxides contained in the atmosphere, an alkali absorption method using an alkali absorption liquid (Japanese Patent Laid-Open No. Hei 10-212427), a reduction method using a reducing agent, and an adsorption method using a solid adsorbent (special method). Kaihei 11-9957).
[0005]
However, in the alkali absorption method, although it is possible to absorb a low concentration of nitrogen oxides, it is not possible to efficiently absorb nitrogen oxides because carbon dioxide coexisting in the air is also absorbed at the same time as nitrogen oxides. There is a problem. Further, the reduction method has a problem that nitrogen oxides cannot be reduced efficiently because the reducing agent is oxidized by oxygen coexisting in the atmosphere. In addition, in the solid adsorption method, when the concentration of nitrogen oxides contained in the air is low, even if the amount of nitrogen oxides adsorbed on the solid adsorbent is small, the solid adsorbent immediately passes through the adsorption breakthrough. In addition, there is a problem that nitrogen oxides contained in the atmosphere cannot be sufficiently adsorbed.
[0006]
Furthermore, as a method for removing low-concentration nitrogen oxides contained in the air, there is a method that utilizes a purification function of soil. However, when the soil purification function is used, there is a problem in that it is necessary to secure soil enough to meet the required nitrogen oxide removal capability, and an enormous amount of land may be required.
[0007]
[Problems to be solved by the invention]
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 gas.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the method for removing nitrogen oxides of the present invention is a method for removing nitrogen oxides contained in a gas, and includes a solid adsorbent for adsorbing and removing nitrogen oxides. A removing step of removing the nitrogen oxides contained in the gas by supplying the gas to the nitrogen oxide adsorbing means, and a function of removing the nitrogen oxides of the nitrogen oxide adsorbing means reduced by the removing step Regenerating the solid adsorbent by removing the nitrogen oxides adsorbed by the solid adsorbent with a regenerant containing a basic substance or a reducing substance.
Since the method for removing nitrogen oxides is a method including a regeneration step of regenerating the function of removing nitrogen oxides, it is possible to solve the problems in the conventional method for removing nitrogen oxides as described below, Nitrogen oxides contained in gas can be efficiently removed.
[0009]
That is, according to this method for removing nitrogen oxides, even if the solid adsorbent adsorbs and breaks down with the nitrogen oxides in the removing step and the function of removing the nitrogen oxides is reduced, the nitrogen oxides are removed in the regeneration step. Since the function is restored, there is no problem that the solid adsorbent adsorbs and breaks down with nitrogen oxides.
In addition, since the nitrogen oxides contained in the gas are removed by supplying the gas to the nitrogen oxide adsorption means containing the solid adsorbent, gases such as carbon dioxide and oxygen coexist in the gas containing nitrogen oxides. However, there is no problem caused by the coexisting gas.
Furthermore, in this method for removing nitrogen oxides, there is no need to heat when removing nitrogen oxides from a gas, so that there is no problem of energy consumption associated with heating.
Further, according to the above-described method for removing nitrogen oxides, nitrogen oxides can be efficiently removed regardless of the concentration of nitrogen oxides. Therefore, the above-mentioned method of removing nitrogen oxides is a gas that has been difficult to remove nitrogen oxides efficiently by the conventional method of removing nitrogen oxides, for example, in a road tunnel, in an underground parking lot, in a city trunk. The present invention can also be preferably applied to a case where the air near the road is a sampled gas.
[0010]
Further, the method for removing nitrogen oxides includes a detection step of detecting the removal function by a nitrogen oxide sensor, and when the decrease in the removal function is detected in the detection step, performing the removal step by performing the regeneration step. It is good also as a method.
With such a method for removing nitrogen oxides, a function of removing nitrogen oxides at a predetermined level or more can be secured, and the quality of gas obtained after removing nitrogen oxides can be improved. .
[0011]
In the method for removing nitrogen oxides, the regenerating agent may be circulated between the nitrogen oxide adsorption device and a regenerating agent tank that stores the regenerating agent.
With such a method for removing nitrogen oxides, the regeneration step can be easily performed simply by circulating the regenerant between the nitrogen oxide adsorption device and the regenerant tank, and the efficiency is further improved. Nitrogen oxides often contained in gas can be removed.
[0012]
Further, in the above-described method for removing nitrogen oxides, before the removing step, the nitrogen oxides contained in the gas are replaced with any one of nitrogen dioxide, nitrous oxide, nitrous oxide, and nitrous oxide. The removal method may include a pretreatment step for curing.
Nitrogen dioxide, dinitrogen trioxide, dinitrogen tetroxide, and dinitrogen pentoxide are all more easily adsorbed by the solid adsorbent than nitrogen monoxide. Therefore, with the method for removing nitrogen oxides including the above pretreatment step, even if nitrogen oxides are contained in the nitrogen oxides contained in the gas, no nitrogen monoxide is contained. As in the case, the nitrogen oxides contained in the gas can be efficiently removed.
[0013]
In the above-described method for removing nitrogen oxides, it is preferable that the gas supplied to the nitrogen oxide adsorbing unit contains humidity.
If 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, and the nitrogen oxides are more easily adsorbed by the solid adsorbent, and the nitrogen oxides contained in the gas can be more efficiently removed.
[0014]
Further, in the above-described method for removing nitrogen oxides, it is preferable 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 the nitrogen oxides are more easily adsorbed by the solid adsorbent, and more efficiently in the gas. The contained nitrogen oxides can be removed.
In particular, activated carbon can be mentioned as an example of a carbon-based material having a large specific surface area which is preferably applied as a solid adsorbent.
[0015]
Further, in the above-described method for removing nitrogen oxides, it is preferable 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. Therefore, by making the basic substance an alkali metal hydroxide or an alkaline earth metal hydroxide, the regeneration step can be performed more efficiently, and the nitrogen oxidation contained in the gas can be more efficiently performed. Things can be removed.
[0016]
In the above method for removing nitrogen oxides, the reducing substance is preferably a sulfite.
Sulfite can efficiently reduce nitrogen oxides to nitrogen gas even at room temperature. Therefore, by using a sulfite as the reducing substance, the regeneration step can be performed more efficiently, and nitrogen oxides contained in the gas can be more efficiently removed.
[0017]
In the above-described method for removing nitrogen oxides, when the regenerating agent contains a reducing substance, it is desirable to regenerate the removing function in a nitrogen atmosphere.
With 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 lengthened.
[0018]
Furthermore, in order to solve the above-mentioned problems, a nitrogen oxide removing device of the present invention is a device for removing nitrogen oxides contained in a gas, and a solid adsorbent for adsorbing and removing nitrogen oxides. A nitrogen oxide adsorbing means comprising: and a regenerator for supplying a regenerant containing a basic substance or a reducing substance to the nitrogen oxide adsorbing means when the nitrogen oxide removing function of the nitrogen oxide adsorbing means is reduced. And an agent supply means, wherein the nitrogen oxides adsorbed on the solid adsorbent are removed by the regenerating agent, whereby the reduced removal function is regenerated.
Such an apparatus for removing nitrogen oxides can be suitably used when performing the above-described method for removing nitrogen oxides, and can efficiently remove nitrogen oxides contained in gas.
[0019]
The nitrogen oxide removing device may further include a nitrogen oxide sensor for detecting the removal function, and the nitrogen oxide sensor may detect the removal function when the nitrogen oxide sensor detects a concentration of nitrogen oxide that is equal to or higher than a predetermined concentration. Can be played.
With such a nitrogen oxide removing device, a function of removing nitrogen oxides at a predetermined level or higher can be secured, and the quality of gas obtained after removing nitrogen oxides can be improved. .
[0020]
Further, in the nitrogen oxide removing device, a regenerating agent tank for storing the regenerating agent is provided, and the regenerating agent can be circulated between the regenerating agent tank and the nitrogen oxide adsorption device. It can be said that.
By adopting such a nitrogen oxide removing device, simply circulating the regenerating agent between the nitrogen oxide adsorbing device and the regenerating agent tank allows the easily reduced removal function to be regenerated, and furthermore Nitrogen oxides contained in the gas can be efficiently removed.
[0021]
Further, in the nitrogen oxide removing device, a pretreatment means for converting nitrogen oxides contained in the gas into any one of nitrogen dioxide, nitrous oxide, nitrous oxide, and nitrous oxide is provided. And the gas that has passed through the pretreatment means may be supplied to the nitrogen oxide adsorption device.
With such a device for removing nitrogen oxides, even when nitrogen oxides are contained in the gas containing nitrogen oxides, the efficiency is as high as when nitrogen monoxide is not contained. It is possible to remove nitrogen oxides often contained in a gas.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
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 according to the present invention. FIG. 3 is a photograph showing an example of the nitrogen oxide removing device of the present invention, and FIG. 4 is a schematic diagram for explaining an example of the nitrogen oxide removing device of the present invention.
[0023]
First, the nitrogen oxide removing device of the present invention will be described in detail.
The nitrogen oxide removing device shown in FIG. 4 supplies the air collected for removing the nitrogen oxides to a nitrogen oxide oxidizing device (corresponding to "pretreatment means" in the claims). The air passing 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 adsorber" in the claims). An atmosphere supply line 3, a nitrogen oxide adsorption device 4 for adsorbing nitrogen oxides, and an air exhaust line 5 for discharging the air passing through the nitrogen oxide adsorption device 4 as purified air are provided.
[0024]
In addition, a nitrogen oxide sensor is installed in the atmospheric release line 5 shown in FIG. The nitrogen oxide sensor detects the function of removing the nitrogen oxides of the nitrogen oxide adsorption device 4 and manages the concentration of the nitrogen oxides in the purified air released from the air release line 5. Further, the nitrogen oxide removing device shown in FIG. 4 includes a regenerating agent tank 6 for storing the regenerating agent, a regenerating agent supply line 7 for supplying the regenerating agent from the regenerating agent tank 6 to the nitrogen oxide adsorption device 4, A regenerant supply means comprising a regenerant return line 8 for returning the regenerant having passed through the nitrogen oxide adsorber 4 from the nitrogen oxide adsorber 4 to the regenerant tank 6 is provided. It can be circulated with the nitrogen oxide adsorption device 4 via a regenerant supply line 7 and a regenerant return line 8.
[0025]
In the nitrogen oxide removing device shown in FIG. 4, when the nitrogen oxide sensor detects a concentration equal to or higher than a predetermined concentration, the nitrogen oxide removing function of the nitrogen oxide adsorbing device 4 is regenerated. ing.
[0026]
The supply line 1 may be of any structure as long as it can supply the atmosphere to the nitrogen oxide oxidizing apparatus 2, and is not particularly limited. In addition, the supply line 1 includes a dust collector for preventing clogging of the nitrogen oxide adsorbing device 4 and a device for controlling the flow rate and flow rate of the atmosphere supplied to the nitrogen oxide oxidizing device 2 as necessary. It is attached.
[0027]
The nitrogen oxide oxidizer 2 oxidizes nitrogen oxides contained in the atmosphere to convert nitrogen oxides contained in the atmosphere into one of nitrogen dioxide, nitrous oxide, nitrous oxide, and nitrous oxide. Is what you 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 low-concentration nitrogen oxides. The temperature control of the nitrogen oxide oxidizing apparatus 2 is not particularly required, and the temperature supplied via the atmospheric supply line 1 may be used.
[0028]
The nitrogen oxide adsorbing device 4 is for adsorbing nitrogen oxides, and uses a packed bed formed by filling a container with a solid adsorbent 4a for adsorbing nitrogen oxides. The packed bed filled with the solid adsorbent 4a is not particularly limited, but preferably has a structure capable of flowing the atmosphere with a small pressure loss.
[0029]
The solid adsorbent 4a is preferably crushed particles or molded particles of several mm to several cm, or particles having a honeycomb structure, from the viewpoint of reducing pressure loss. Further, the solid adsorbent 4a preferably has a large specific surface area from the viewpoint of efficiently adsorbing low-concentration nitrogen oxides. The type of the solid adsorbent 4a used in the nitrogen oxide adsorption device 4 may be one type, or two or more types may be used in combination. Examples of the material constituting the solid adsorbent 4a include a carbon-based material and an inorganic-based material. Examples of the carbon-based material include activated carbon, pitch-based activated carbon, carbon fiber, charcoal, fullerene, and carbon nanotube. Examples of the inorganic material include activated clay, alumina, zeolite, silica, magnesia, and titania. Among them, a particularly preferable solid adsorbent 4a is a carbon-based material having a large specific surface area such as activated carbon.
[0030]
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 washing and regenerating the solid adsorbent 4a. Any structure may be used, and there is no particular limitation. Further, 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.
[0031]
In addition, similarly to the nitrogen oxide oxidizing apparatus 2, temperature control of the nitrogen oxide adsorbing apparatus 4 is not particularly necessary, and the temperature supplied via the air supply line 3 may be used. In the nitrogen oxide removing device shown in FIG. 4, the humidity of the air supplied through the air supply line 3 is preferably 40% or more, more preferably, in order to effectively adsorb the nitrogen oxides. It is set to be 60% or more, more preferably 80% or more. The humidity of the atmosphere supplied to the nitrogen oxide adsorption device 4 may be controlled by using any method and any device. For example, a method of increasing the humidity by spraying water on the atmosphere is preferably used. it can.
[0032]
Further, in the nitrogen oxide removing device shown in FIG. 4, in order to adsorb nitrogen oxides efficiently, control is performed using the control device 9 so that the space velocity of the atmosphere supplied to the nitrogen oxide adsorbing device 4 is improved. But, 1000-200000h ^-1 , More preferably 3000 to 100000h ^-1 It is to be. The space velocity of the air supplied to the nitrogen oxide adsorption device 4 is determined according to the concentration of the nitrogen oxide in the air to be removed, the type of the solid adsorbent 4a, the size of the nitrogen oxide adsorption device 4, and the like. You. The control device 9 may be any device as long as it can control the space velocity of the air supplied to the nitrogen oxide adsorption device 4, and is not particularly limited.
[0033]
In the nitrogen oxide adsorbing device 4, the function of removing the nitrogen oxides gradually decreases as the solid adsorbent 4a adsorbs and breaks down with the nitrogen oxides. However, in the nitrogen oxide removing device shown in FIG. 4, the nitrogen oxide is removed from the solid adsorbent 4a that has absorbed and passed through by using a regenerant to regenerate the nitrogen oxide adsorbing device 4. As the regenerating agent, an aqueous solution containing a basic substance or a reducing substance is used.
[0034]
Examples of the basic substance include, but are not particularly 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 strong basic substances, are particularly preferably used.
[0035]
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.
[0036]
Examples of the reducing substance include, but are not particularly limited to, sulfites, thiosulfates, hydrides, hydrogen sulfides, aldehydes, and the like.From the viewpoint of reducing nitrogen oxides to nitrogen gas at ordinary temperature, sulfurous acid is used. Preferably, a salt is used.
[0037]
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 the aldehyde include formaldehyde and acetaldehyde.
[0038]
When a reducing substance is used as the regenerating agent, 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 adsorption device 4 is regenerated, it is preferable that not only the regenerant tank 6 but also the nitrogen oxide adsorption device 4 be purged with nitrogen.
[0039]
The regenerating agent can be used one or more times by preparing in consideration of the type and amount of nitrogen oxide in the atmosphere supplied to the nitrogen oxide adsorption device 4, the concentration of the regenerating agent, and the like. It is assumed.
[0040]
Next, a method for removing nitrogen oxides contained in the air by using such a nitrogen oxide removing device 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. For example, in a road tunnel or an underground parking lot where a nitrogen oxide concentration of several ppm or less is a problem. From the vicinity of the city, or from the vicinity of an urban main road. It is desirable that the atmosphere containing nitrogen oxides has a humidity of 60% or more, more preferably 80% or more.
[0041]
In order to remove the nitrogen oxides contained in the atmosphere containing the nitrogen oxides, first, as shown in FIG. Supplied to the apparatus 2 (S1), the nitrogen oxides in the atmosphere are selected from the group consisting of nitrogen dioxide, nitrous oxide, nitrous oxide, and nitrous oxide (in the “pretreatment step” in the claims). (S2). Next, the air passing through the nitrogen oxide oxidizing device 2 is supplied to the nitrogen oxide adsorbing device 4 via the air supply line 3 (S3), and the nitrogen oxides in the air are adsorbed and removed by the solid adsorbent 4a (S3). This corresponds to the “removing step” in the claims (S4).) Then, the air that has passed through the nitrogen oxide adsorption device 4 is released as purified air via the air exhaust line 5 (S6).
[0042]
At this time, when nitrogen oxide having a predetermined concentration or more is detected by the nitrogen oxide sensor installed in the atmosphere release line 5 (corresponding to the “detection step” in the claims (S5)), the atmosphere is released. The supply of the atmosphere containing nitrogen oxides from the supply line 1 is shut off (S7), and the nitrogen oxide adsorption device 4 described below is regenerated (in the claims, "regeneration") with the air supply being shut off. (Step S8)).
[0043]
In order to regenerate the nitrogen oxide adsorbing device 4, first, as shown in FIG. 2, a regenerating agent is supplied from the regenerating agent tank 6 to the nitrogen oxide adsorbing device 4 via the regenerating agent supply line 7 (S81). The nitrogen oxide is removed from the solid adsorbent 4a (S82). The removal of the nitrogen oxides by the regenerant is performed by a method of immersing the solid adsorbent 4a in the regenerant in the nitrogen oxide adsorption device 4 or the like, or a method of spraying the regenerant on the solid adsorbent 4a. Subsequently, the used regenerant is returned to the regenerant tank 6 of the solid adsorbent 4a via the regenerant return line 8 (S83), whereby the regeneration of the nitrogen oxide adsorption device 4 is completed.
[0044]
When the regeneration of the nitrogen oxide adsorption device 4 is completed in this way, as shown in FIG. 1, the supply of the atmosphere containing nitrogen oxides from the atmosphere supply line 1 is restarted (S9). Then, the above steps are repeated until all the air containing nitrogen oxides is released as purified air, and the removal of nitrogen oxides from all the air containing nitrogen oxides is completed.
[0045]
According to such a method and apparatus for removing nitrogen oxides, the nitrogen oxides contained in the atmosphere are removed by supplying the atmosphere to the nitrogen oxides adsorption apparatus 4 including the solid adsorbent 4a, and the solid adsorbent is removed. Since the nitrogen oxide removing function is regenerated by removing the nitrogen oxides adsorbed by 4a, the nitrogen oxides contained in the air can be efficiently removed.
[0046]
In the method and apparatus for removing nitrogen oxides according to the present invention, as shown in the above-described example, when the nitrogen oxide sensor detects nitrogen oxides of a predetermined concentration or more, the nitrogen oxide adsorbing device 4 May be performed, or may be performed at predetermined intervals. For example, when the method and apparatus for removing nitrogen oxides of the present invention are continuously applied over a long period of time, in consideration of ease of maintenance and the like, the cycle is performed once a day or once a week. May be reproduced.
[0047]
Moreover, in the nitrogen oxide removing method and the removing device of the present invention, a plurality of nitrogen oxide adsorbing 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 device shown in FIG. 5 is different from the nitrogen oxide removing device shown in FIG. 4 only in the nitrogen oxide adsorbing devices 41 and 43 and their peripheral portions. Portions other than the nitrogen oxide adsorption devices 41 and 43 and their peripheral portions are omitted.
[0048]
The nitrogen oxide removing device shown in FIG. 5 includes a region A for removing the nitrogen oxide, and regions B and C for regenerating the nitrogen oxide adsorbing device. Atmosphere is supplied from the atmosphere supply line 31 to the nitrogen oxide adsorption device 43 which is arranged in the region A for removing nitrogen oxides and supported by the support member 45. Then, the atmosphere that has passed through the nitrogen oxide adsorption device 43 is released from the atmosphere exhaust line 51. The regenerating agent is supplied from the regenerating agent tank 61 to the nitrogen oxide adsorbing device 41 which is disposed in the region B for regenerating the nitrogen oxide adsorbing device and is connected to the nitrogen oxide adsorbing device 43 by the connecting member 44 and integrated. The regenerating agent is supplied via a line 71, and the regenerating agent that has passed through the nitrogen oxide adsorption device 41 is returned to the regenerating agent tank 61 via a regenerating agent return line 81.
In the case of regenerating the nitrogen oxide adsorption device 43, the nitrogen oxide adsorption device 43 is moved in the direction of arrow D to be disposed in the region C for regenerating the nitrogen oxide adsorption device, and at the same time, the nitrogen oxide adsorption device 43 is regenerated. The adsorption device 41 is disposed in the area A for removing nitrogen oxides. In FIG. 5, the nitrogen oxide adsorption device 43 arranged in the region C is indicated by a dotted line and is indicated by a reference numeral 42. The regenerating agent is supplied from the regenerating agent tank 62 to the nitrogen oxide adsorbing device 42 via the regenerating agent supply line 72, and the regenerating agent passing through the nitrogen oxide adsorbing device 42 is supplied via the regenerating agent return line 82. It is designed to be returned to the regenerating agent tank 62.
[0049]
When removing nitrogen oxides using the nitrogen oxide removing device shown in FIG. 5, the nitrogen oxide absorbing device 41 is regenerated while the nitrogen oxide absorbing device 43 is removing nitrogen oxides. Further, while the nitrogen oxide adsorption device 41 is removing nitrogen oxides, the nitrogen oxide adsorption device 43 is regenerated.
As described above, when a plurality of nitrogen oxide adsorbing devices are provided, while at least one of the plurality of nitrogen oxide adsorbing devices is removing nitrogen oxide, another nitrogen oxide adsorbing device is regenerated. Since the removal and the regeneration of the nitrogen oxide can be performed simultaneously, the removal of the nitrogen oxide can be continuously and efficiently performed. When a plurality of nitrogen oxide adsorbing devices are provided, the number of regenerating agent supply means may be plural or one as in the example shown in FIG. Further, the plurality of nitrogen oxide adsorbing devices may be connected as in the example shown in FIG. 5, but may not be connected. May be individually movable between the area for reproducing.
[0050]
Further, when the nitrogen oxide adsorbing device 4 is small, the solid adsorbent is made into a cassette so that it can be removed, and the solid adsorbent that has been made into a cassette is removed and immersed in a regenerant. It is good also as what can remove nitrogen oxide of a solid adsorbent. Further, by making the solid adsorbent into a cassette and making it removable, when it becomes necessary to replace the solid adsorbent, the solid adsorbent can be easily replaced.
[0051]
Further, as shown in the above-described example, it is desirable that the air containing nitrogen oxides be supplied to the nitrogen oxide adsorbing device 4 after passing through the nitrogen oxide oxidizing device 2. If there is no problem even if the removal rate of nitrogen oxides in the atmosphere is low, or the nitrogen oxides contained in the gas are from one or more selected from nitrogen dioxide, nitrous oxide, nitrous oxide, and nitrous oxide In such a case, the air supply line 1 is directly connected to the air supply line 3, and the air containing nitrogen oxides is supplied to the nitrogen oxide adsorption device 4 without passing through the nitrogen oxide oxidation device 2. You may.
[0052]
Further, as shown in the above-described example, the present invention can be preferably applied to the removal of nitrogen oxides contained in the atmosphere. It does not need to be particularly limited.
[0053]
【Example】
Hereinafter, the present invention will be described in more detail by showing Examples and Comparative Examples of the present invention.
"Example 1"
The following tests were performed using the nitrogen oxide removing apparatus shown in FIG.
That is, a 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 coconut activated carbon (manufactured by Nacalai Tesque, particle size: 0.5 to 3 mm). In addition, by controlling using the controller 10, air having a temperature of 25 ° C. and a humidity of 100% containing 1 ppm of nitrogen dioxide is supplied at a space velocity of 48000 h. ^-1 And the removal rate of nitrogen oxides was determined from the concentration of nitrogen oxides detected by the nitrogen oxide sensor 15.
[0054]
Then, 32 hours after the nitrogen oxide removal rate became 70%, the solid adsorbent in the nitrogen oxide adsorber 14 was immersed in 10 ml of a regenerant (aqueous solution containing 1% sodium sulfite) for 30 minutes to remove the solid adsorbent. Replayed. Thereafter, the circulation of air was restarted, and the solid adsorbent was regenerated in the same manner as above four times every 32 hours, and the removal rate of nitrogen oxides was determined in the same manner as above.
Table 1 shows the results.
[0055]
[Table 1]

In Table 1, “humidity” is a relative humidity, and the unit is “%”. "Space velocity" is measured by a gas volume flow meter, and the unit is "h". ^-1 ". The unit of “particle diameter” is “mm”. Further, “time” refers to the time during which the removal rate of nitrogen oxides was 70% or more after the end of the regeneration.
As shown in Table 1, the nitrogen oxide removal rates from the end of regeneration to 32 hours later were all 70% or more.
[0056]
"Example 2"
Removal of nitrogen oxides and regeneration of activated carbon were repeated in the same manner as in Example 1 except that a 5% aqueous sodium hydroxide solution was used as a regenerant.
As a result, as shown in Table 1, the nitrogen oxide removal rate after 24 hours from the end of the regeneration was 70% or more in each case.
[0057]
"Example 3"
Removal of nitrogen oxides and regeneration of activated carbon were repeated in the same manner as in Example 1 except that the humidity of the air was changed to 40%.
As a result, as shown in Table 1, the nitrogen oxide removal rate after 4 hours from the end of the regeneration was 70% or more.
[0058]
"Example 4"
Space velocity 96,000h ^-1 The removal of nitrogen oxides and the regeneration of activated carbon were repeated in the same manner as in Example 1 except that the above conditions were satisfied.
As a result, as shown in Table 1, the nitrogen oxide removal rate after 22 hours from the end of the regeneration was 70% or more.
[0059]
"Example 5"
Space velocity 4800h ^-1 The removal of nitrogen oxides and the regeneration of activated carbon were repeated in the same manner as in Example 1 except that the above conditions were satisfied.
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 in each case.
[0060]
"Example 6"
Space velocity 9600h ^-1 The removal of nitrogen oxides and the regeneration of activated carbon were repeated in the same manner as in Example 1 except that the above conditions were satisfied.
As a result, as shown in Table 1, the nitrogen oxide removal rate after 38 hours from the end of the regeneration was 70% or more.
[0061]
"Example 7"
Removal of nitrogen oxides and regeneration of activated carbon were repeated in the same manner as in Example 1 except that the particle size 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 in each case.
[0062]
"Example 8"
Removal of nitrogen oxides and regeneration of activated carbon were repeated in the same manner as in Example 1 except that the humidity of the air was 80%.
As a result, as shown in Table 1, the nitrogen oxide removal rate after 24 hours from the end of the regeneration was 70% or more in each case.
[0063]
"Comparative Example 1"
Removal of nitrogen oxides and regeneration of activated carbon were repeated in the same manner as in Example 1 except that 100 ml of ion-exchanged water was used as a regenerant.
As a result, as shown in Table 1, the nitrogen oxide removal rate fell below 70% 5 minutes after the regeneration was completed, and the solid adsorbent could not be regenerated.
[0064]
【The invention's effect】
As described above, according to the nitrogen oxide removing method and the removing device of the present invention, the nitrogen oxide contained in the gas is removed by supplying the gas to the nitrogen oxide adsorbing means including 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.
[Brief description of the drawings]
FIG. 1 is a flowchart illustrating an example of a method for removing nitrogen oxides according to the present invention.
FIG. 2 is a flowchart illustrating an example of a method for removing nitrogen oxides according to the present invention.
FIG. 3 is a photograph showing an example of the nitrogen oxide removing device of the present invention.
FIG. 4 is a schematic diagram for explaining an example of the nitrogen oxide removing device of the present invention.
FIG. 5 is a schematic diagram for explaining another example of the nitrogen oxide removing device of the present invention.
FIG. 6 is a view showing a nitrogen oxide removing apparatus used in Examples and Comparative Examples.
[Explanation of symbols]
1 Atmospheric supply line
2 Nitrogen oxide oxidizer
3 Atmospheric supply line
4 Nitrogen oxide adsorption equipment
5 Atmospheric discharge line
6 Regenerant tank
7 Regeneration agent supply line
8 Regeneration agent return line

Claims (14)

A method for removing nitrogen oxides contained in a gas,
A nitrogen oxide adsorbing means including a solid adsorbent for adsorbing and removing nitrogen oxides, a removing step of removing nitrogen oxides contained in the gas by supplying the gas,
The nitrogen oxide removing function of the nitrogen oxide adsorbing means reduced by the removing step is regenerated by removing the nitrogen oxides adsorbed by the solid adsorbent with a regenerant containing a basic substance or a reducing substance. A method for removing nitrogen oxides. The nitrogen oxide according to claim 1, further comprising a detection step of detecting the removal function by a nitrogen oxide sensor, wherein the regeneration step is performed when a decrease in the removal function is detected in the detection step. Removal method. The method for removing nitrogen oxides according to claim 1, wherein the regenerating agent is circulated between the nitrogen oxide adsorption device and a regenerating agent tank that stores the regenerating agent. Before the removing step, a nitrogen oxide contained in the gas, a nitrogen oxide, nitrous oxide, dinitrogen tetroxide, a pre-treatment step to make any one of dinitrogen pentoxide is characterized by including The method for removing nitrogen oxides according to claim 1. The nitrogen oxide according to any one of claims 1 to 4, wherein the gas is obtained from any one of an atmosphere in a road tunnel, an underground parking lot, and a vicinity of a main road in a city. Removal method. The method for removing nitrogen oxides according to claim 1, wherein the gas supplied to the nitrogen oxide adsorbing means contains humidity. 7. The method for removing nitrogen oxides according to claim 1, wherein the solid adsorbent is a carbon-based material. The method for removing nitrogen oxides according to any one of claims 1 to 7, wherein the basic substance is a hydroxide of an alkali metal or a hydroxide of an alkaline earth metal. The method for removing nitrogen oxides according to any one of claims 1 to 7, wherein the reducing substance is a sulfite. When the regenerating agent contains a reducing substance,
The method for removing nitrogen oxides according to claim 1, wherein the removing function is performed in a nitrogen atmosphere. An apparatus for removing nitrogen oxides contained in a gas,
Nitrogen oxide adsorption means comprising a solid adsorbent for adsorbing and removing nitrogen oxides,
When the nitrogen oxide removing function of the nitrogen oxide adsorbing means is reduced, a regenerant supplying means for supplying a regenerant containing a basic substance or a reducing substance to the nitrogen oxide adsorbing means,
An apparatus for removing nitrogen oxides, wherein the reduced removal function is regenerated by removing nitrogen oxides adsorbed by the solid adsorbent with the regenerating agent. The method according to claim 11, further comprising a nitrogen oxide sensor for detecting the removal function, wherein the removal function is regenerated when the nitrogen oxide sensor detects a concentration of nitrogen oxide that is equal to or higher than a predetermined concentration. An apparatus for removing nitrogen oxides according to the above. A regenerating agent tank for storing the regenerating agent is provided,
13. The nitrogen oxide removing device according to claim 11, wherein the regenerating agent can be circulated between the regenerating agent tank and the nitrogen oxide adsorption device. Nitrogen oxide contained in the gas, nitrogen dioxide, dinitrogen trioxide, dinitrogen tetroxide, comprising a pretreatment means to any of dinitrogen pentoxide,
14. The nitrogen oxide removing device according to claim 11, wherein the gas that has passed through the pretreatment means is supplied to the nitrogen oxide adsorption device.

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