JPH1028840A - Method for removing nitrogen oxide - Google Patents
Method for removing nitrogen oxideInfo
- Publication number
- JPH1028840A JPH1028840A JP8158986A JP15898696A JPH1028840A JP H1028840 A JPH1028840 A JP H1028840A JP 8158986 A JP8158986 A JP 8158986A JP 15898696 A JP15898696 A JP 15898696A JP H1028840 A JPH1028840 A JP H1028840A
- Authority
- JP
- Japan
- Prior art keywords
- oxide
- nitrogen
- exhaust gas
- silver
- nitrogen oxides
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
Landscapes
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
- Catalysts (AREA)
- Treating Waste Gases (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は窒素酸化物と過剰の
酸素を含む燃焼排ガスから、窒素酸化物を効果的に還元
除去することのできる窒素酸化物除去方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing nitrogen oxides from a flue gas containing nitrogen oxides and excess oxygen, which can be effectively reduced and removed.
【０００２】[0002]
【従来の技術及び発明が解決しようとする課題】自動車
用エンジン等の内燃機関や、工場等に設置された燃焼機
器、家庭用ファンヒーター等から排出される各種の燃焼
排ガス中には、過剰の酸素とともに一酸化窒素、二酸化
窒素等の窒素酸化物が含まれている。ここで、「過剰の
酸素を含む」とは、その排ガス中に含まれる一酸化炭
素、水素、炭化水素等の未燃焼成分を燃焼するのに必要
な理論酸素量より多い酸素を含むことを意味する。ま
た、以下における窒素酸化物とは一酸化窒素及び／又は
二酸化窒素を指す。2. Description of the Related Art Excessive combustion exhaust gas emitted from internal combustion engines such as automobile engines, combustion equipment installed in factories, household fan heaters, and the like is excessive. It contains nitrogen oxides such as nitric oxide and nitrogen dioxide together with oxygen. Here, "containing excess oxygen" means that the exhaust gas contains more oxygen than the theoretical amount of oxygen necessary to burn unburned components such as carbon monoxide, hydrogen, and hydrocarbons. I do. In the following, nitrogen oxide refers to nitric oxide and / or nitrogen dioxide.
【０００３】この窒素酸化物は酸性雨の原因の一つとさ
れ、環境上の大きな問題となっている。そのため、各種
燃焼機器が排出する排ガス中の窒素酸化物を除去するさ
まざまな方法が検討されている。[0003] This nitrogen oxide is one of the causes of acid rain and is a major environmental problem. Therefore, various methods for removing nitrogen oxides in exhaust gas discharged from various combustion equipments are being studied.
【０００４】過剰の酸素を含む燃焼排ガスから窒素酸化
物を除去する方法として、特に大規模な固定燃焼装置
（工場等の大型燃焼機等）に対しては、アンモニアを用
いる選択的接触還元法が実用化されている。[0004] As a method for removing nitrogen oxides from a combustion exhaust gas containing excess oxygen, a selective catalytic reduction method using ammonia is used particularly for a large-scale fixed combustion device (a large-scale combustor in a factory or the like). Has been put to practical use.
【０００５】しかしながら、この方法においては、窒素
酸化物の還元剤として用いるアンモニアが高価であるこ
と、またアンモニアは毒性を有すること、そのために未
反応のアンモニアが排出しないように排ガス中の窒素酸
化物濃度を計測しながらアンモニア注入量を制御しなけ
ればならないこと、一般に装置が大型となること等の問
題点がある。However, in this method, ammonia used as a reducing agent for nitrogen oxides is expensive, and ammonia is toxic. Therefore, the nitrogen oxides in the exhaust gas must be removed so that unreacted ammonia is not discharged. There are problems that the amount of injected ammonia must be controlled while measuring the concentration, and that the apparatus generally becomes large.
【０００６】また、別な方法として、水素、一酸化炭
素、炭化水素等のガスを還元剤として用い、窒素酸化物
を還元する非選択的接触還元法があるが、この方法で
は、効果的な窒素酸化物の低減除去を実行するためには
排ガス中の酸素との理論反応量以上の還元剤を添加しな
ければならず、還元剤を多量に消費する欠点がある。こ
のため非選択的接触還元法は、実際上は、理論空燃比付
近で燃焼した残存酸素濃度の低い排ガスに対してのみ有
効となり、汎用性に乏しく実際的でない。As another method, there is a non-selective catalytic reduction method in which a nitrogen oxide is reduced by using a gas such as hydrogen, carbon monoxide, or a hydrocarbon as a reducing agent. In order to reduce and remove nitrogen oxides, it is necessary to add a reducing agent in an amount equal to or more than a theoretical reaction amount with oxygen in exhaust gas, and there is a disadvantage that a large amount of the reducing agent is consumed. For this reason, the non-selective catalytic reduction method is practically effective only for exhaust gas having a low residual oxygen concentration burned near the stoichiometric air-fuel ratio, and is not practical because of poor versatility.
【０００７】そこで、チタニア、アルミナなどの金属酸
化物と希土類酸化物とＲｕ、Ｒｈ、Ｐｄ、銀、Ｐｔの内
の少なくとも一種とからなる炭化水素による窒素酸化物
接触還元用触媒が提案された（特開平4-27431 号) 。し
かしながら、本発明者等の実験結果によると、この触媒
では高い空間速度における窒素酸化物除去率が低く、特
に排ガス温度の低い領域では窒素酸化物の除去が低い。Therefore, a catalyst for catalytic reduction of nitrogen oxides by a hydrocarbon comprising a metal oxide such as titania or alumina, a rare earth oxide and at least one of Ru, Rh, Pd, silver and Pt has been proposed ( JP-A-4-27431). However, according to the experimental results of the present inventors, this catalyst has a low nitrogen oxide removal rate at a high space velocity, and particularly in a region where the exhaust gas temperature is low, the nitrogen oxide removal is low.
【０００８】また、多孔質担体に貴金属元素及びモリブ
デンを担持し、排ガス中の水素による窒素酸化物除去方
法が提案された（特開平8-10574 号) 。しかしながら、
この方法では排ガス温度の低い領域での窒素酸化物除去
率が高いものの、３００℃以上の温度領域での窒素酸化
物除去率が極めて低く、また一酸化炭素、不飽和炭化水
素等を含む排ガスでは窒素酸化物の除去率が著しく低下
する。Further, a method has been proposed in which a noble metal element and molybdenum are supported on a porous carrier and nitrogen oxides are removed by hydrogen in exhaust gas (Japanese Patent Application Laid-Open No. 8-10574). However,
In this method, although the nitrogen oxide removal rate is high in a region where the exhaust gas temperature is low, the nitrogen oxide removal ratio in a temperature region of 300 ° C. or more is extremely low. In the case of exhaust gas containing carbon monoxide, unsaturated hydrocarbon, etc. The nitrogen oxide removal rate is significantly reduced.
【０００９】したがって、本発明の目的は、固定燃焼装
置及び酸素過剰条件で燃焼するガソリンエンジン、ディ
ーゼルエンジン等からの燃焼排ガスのように、窒素酸化
物や、一酸化炭素、水素、炭化水素等の未燃焼分に対す
る理論反応量以上の酸素を含有する燃焼排ガスから、効
率良く窒素酸化物を還元除去することができる窒素酸化
物除去方法を提供することである。Accordingly, it is an object of the present invention to provide a method for producing nitrogen oxides, carbon monoxide, hydrogen, hydrocarbons, and the like, such as combustion exhaust gas from a fixed combustion device and a gasoline engine, a diesel engine, or the like, which burns under oxygen excess conditions. An object of the present invention is to provide a method for removing nitrogen oxides that can efficiently reduce and remove nitrogen oxides from combustion exhaust gas containing oxygen in an amount equal to or more than a theoretical reaction amount with respect to unburned components.
【００１０】[0010]
【課題を解決するための手段】上記課題に鑑み鋭意研究
の結果、本発明者は、多孔質無機酸化物に銀成分を担持
してなる窒素酸化物除去材を用い、排ガス中に還元剤と
して含酸素有機化合物と水との混合物を添加することに
より、広い温度領域で窒素酸化物を効果的に除去するこ
とができることを発見し、本発明を完成した。Means for Solving the Problems In view of the above problems, as a result of intensive research, the present inventor has used a nitrogen oxide removing material in which a silver component is supported on a porous inorganic oxide, and used as a reducing agent in exhaust gas. By adding a mixture of an oxygen-containing organic compound and water, it has been found that nitrogen oxides can be effectively removed in a wide temperature range, and the present invention has been completed.
【００１１】すなわち、本発明の窒素酸化物除去方法
は、多孔質の無機酸化物に銀及び銀化合物からなる群よ
り選ばれる一種以上の元素及び／又は化合物０．２〜１
５重量％（金属元素換算値）を担持してなる窒素酸化物
除去材を用い、窒素酸化物と、共存する未燃焼成分に対
する理論反応量より多い酸素とを含む燃焼排ガスから窒
素酸化物を還元除去する方法であり、前記窒素酸化物除
去材を排ガス導管の途中に設置し、前記除去材の上流側
で含酸素有機化合物からなる群より選ばれた一種以上と
水とを添加した排ガスを、１５０〜６００℃において前
記除去材に接触させ、前記窒素酸化物を除去することを
特徴とする。That is, in the method for removing nitrogen oxides of the present invention, the porous inorganic oxide contains at least one element and / or compound selected from the group consisting of silver and silver compounds.
Nitrogen oxides are reduced from combustion exhaust gas containing nitrogen oxides and oxygen in excess of the theoretical amount of reaction with unburned components coexisting by using a nitrogen oxide removing material carrying 5% by weight (converted to metal elements). It is a method of removing, the nitrogen oxide removing material is installed in the middle of the exhaust gas conduit, exhaust gas added with water and at least one selected from the group consisting of oxygen-containing organic compounds on the upstream side of the removing material, The method is characterized in that the nitrogen oxide is removed by bringing the material into contact with the removing material at 150 to 600 ° C.
【００１２】[0012]
【発明の実施の態様】以下、本発明を詳細に説明する。 ［１］窒素酸化物除去材 本発明で用いる窒素酸化物除去材は、多孔質無機酸化物
に銀及び銀化合物からなる群より選ばれる一種以上の元
素及び／又は化合物を担持してなり、広い温度領域での
窒素酸化物除去に作用する。BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. [1] Nitrogen oxide removing material The nitrogen oxide removing material used in the present invention comprises a porous inorganic oxide carrying one or more elements and / or compounds selected from the group consisting of silver and silver compounds, and has a wide range. It acts to remove nitrogen oxides in the temperature range.
【００１３】多孔質の無機酸化物としては、アルミナ単
独、又はチタニア、シリカ、ジルコニア、酸化亜鉛、酸
化錫、酸化マグネシウム、ゼオライトのいずれかとアル
ミナとの複合又は混合酸化物を用いることができる。好
ましくはγ−アルミナ単独、又はチタニア、シリカ、ジ
ルコニア、酸化亜鉛、酸化錫、酸化マグネシウム、ゼオ
ライトのいずれかとγ−アルミナとの複合又は混合酸化
物である。アルミナ含有複合又は混合酸化物を用いる場
合、アルミナの含有率を５０重量％以上とするのが好ま
しい。アルミナ又はアルミナの複合又は混合酸化物を用
いることにより、触媒の耐熱性及び耐久性が向上する。As the porous inorganic oxide, alumina alone, or a composite or mixed oxide of alumina with any one of titania, silica, zirconia, zinc oxide, tin oxide, magnesium oxide and zeolite can be used. Preferably, γ-alumina alone or a composite or mixed oxide of γ-alumina and any one of titania, silica, zirconia, zinc oxide, tin oxide, magnesium oxide, and zeolite is used. When an alumina-containing composite or mixed oxide is used, the alumina content is preferably 50% by weight or more. The use of alumina or a composite or mixed oxide of alumina improves the heat resistance and durability of the catalyst.
【００１４】アルミナ等の多孔質の無機酸化物の比表面
積は１０ｍ2 ／ｇ以上であるのが好ましい。比表面積が
１０ｍ2 ／ｇ未満であると、銀成分の分散が低下し、良
好な窒素酸化物の除去が行えない。より好ましい多孔質
無機酸化物の比表面積は３０ｍ2 ／ｇ以上である。The specific surface area of a porous inorganic oxide such as alumina is preferably at least 10 m 2 / g. If the specific surface area is less than 10 m 2 / g, the dispersion of the silver component is reduced, and good removal of nitrogen oxides cannot be performed. More preferred specific surface area of the porous inorganic oxide is 30 m 2 / g or more.
【００１５】銀化合物は銀の酸化物、ハロゲン化銀、硫
酸銀及び燐酸銀等からなる群より選ばれた少なくとも一
種であり、好ましくは銀の酸化物、塩化銀及び硫酸銀の
いずれか一種以上であり、更に好ましくは銀の酸化物及
び／又は塩化銀である。銀成分の担持量は、多孔質無機
酸化物１００重量％に対して０．２〜１５重量％（銀元
素換算値）とする。０．２重量％未満では窒素酸化物の
除去率が低下する。また、１５重量％を超す量の銀成分
を担持すると還元剤自身の酸化が起きやすく、窒素酸化
物の除去率はかえって低下する。好ましい銀成分の担持
量は０．５〜１２重量％である。The silver compound is at least one selected from the group consisting of silver oxide, silver halide, silver sulfate, silver phosphate and the like, and preferably at least one of silver oxide, silver chloride and silver sulfate. And more preferably silver oxide and / or silver chloride. The supported amount of the silver component is 0.2 to 15% by weight (in terms of silver element) based on 100% by weight of the porous inorganic oxide. If the amount is less than 0.2% by weight, the removal rate of nitrogen oxides decreases. If the silver component exceeds 15% by weight, oxidation of the reducing agent itself is likely to occur, and the nitrogen oxide removal rate is rather lowered. The preferred loading of the silver component is 0.5 to 12% by weight.
【００１６】アルミナ等の無機酸化物に銀を担持する方
法としては、公知の含浸法、沈澱法等を用いることがで
きる。含浸法を用いる際、銀の硝酸塩、塩化物、硫酸
塩、炭酸塩等の水溶液又はアンモニア性水溶液に多孔質
無機酸化物を浸漬する。又は硝酸銀水溶液に多孔質無機
酸化物を浸漬し、乾燥後、塩化アンモニウム又は硫酸ア
ンモニウムの水溶液に再び浸漬する。沈澱法でハロゲン
化銀を調製するには硝酸銀とハロゲン化アンモニウムと
を反応させて、ハロゲン化銀として多孔質無機酸化物上
に沈澱させる。これを５０〜１５０℃、特に７０℃程度
で乾燥後、１００〜６００℃で段階的に昇温して焼成す
るのが好ましい。焼成は、空気中、酸素を含む窒素気流
下や水素ガス気流下で行うのが好ましい。水素ガス気流
下で行う場合には、最後に３００〜６５０℃で酸化処理
するのが好ましい。アルミナ、アルミナ系混合又は複合
酸化物への銀の担持では、ベーマイト等のアルミナ水和
物を出発物質として利用すると効果的である。As a method of supporting silver on an inorganic oxide such as alumina, a known impregnation method, precipitation method, or the like can be used. When using the impregnation method, the porous inorganic oxide is immersed in an aqueous solution of silver nitrate, chloride, sulfate, carbonate, or the like, or an aqueous ammonia solution. Alternatively, the porous inorganic oxide is immersed in an aqueous solution of silver nitrate, dried, and then immersed again in an aqueous solution of ammonium chloride or ammonium sulfate. To prepare silver halide by the precipitation method, silver nitrate and ammonium halide are reacted to precipitate silver halide on the porous inorganic oxide. After drying at 50 to 150 ° C., particularly at about 70 ° C., it is preferable to raise the temperature stepwise at 100 to 600 ° C. for firing. The calcination is preferably performed in air, under a stream of nitrogen containing oxygen or under a stream of hydrogen gas. When the treatment is performed under a hydrogen gas stream, it is preferable to perform the oxidation treatment at 300 to 650 ° C. at last. In carrying silver on alumina, an alumina-based mixed or composite oxide, it is effective to use alumina hydrate such as boehmite as a starting material.
【００１７】本発明で用いる除去材の第一の好ましい形
態は、上記銀系触媒を除去材基体にコートしてなる除去
材である。除去材の基体を形成するセラミックス材料と
しては、アルミナ、ジルコニア、チタニア−ジルコニア
等の多孔質で表面積の大きい耐熱性のものが挙げられ
る。高耐熱性が要求される場合、コージェライト、ムラ
イト、アルミナ及びその複合物等を用いるのが好まし
い。また、窒素酸化物除去材の基体に公知の金属材料を
用いることもできる。A first preferred form of the removing material used in the present invention is a removing material obtained by coating the above-mentioned silver-based catalyst on a removing material substrate. Examples of the ceramic material forming the substrate of the removing material include heat-resistant porous materials having a large surface area such as alumina, zirconia, and titania-zirconia. When high heat resistance is required, it is preferable to use cordierite, mullite, alumina and a composite thereof. Further, a known metal material can be used for the substrate of the nitrogen oxide removing material.
【００１８】窒素酸化物除去材の基体の形状及び大きさ
は、目的に応じて種々変更できる。またその構造として
は、ハニカム構造型、フォーム型、繊維状耐火物からな
る三次元網目構造型、あるいは顆粒状、ペレット状等が
挙げられる。ウォッシュコート法、ゾル−ゲル法、粉末
法等を用いて上記基体に銀系触媒をコートした後、焼結
することにより窒素酸化物除去材を製造することができ
る。The shape and size of the substrate of the nitrogen oxide removing material can be variously changed depending on the purpose. Examples of the structure include a honeycomb structure type, a foam type, a three-dimensional network structure type formed of a fibrous refractory, a granular shape, a pellet shape, and the like. A nitrogen oxide-removing material can be manufactured by coating the above-mentioned substrate with a silver-based catalyst using a wash coat method, a sol-gel method, a powder method, or the like, and then sintering.
【００１９】本発明で用いる除去材の第二の好ましい形
態は、上記銀系触媒をハニカム構造型、フォーム型、板
状、ペレット状又は顆粒状に成形したものを焼結した
後、所望形状のケーシングに充填してなる除去材であ
る。A second preferred form of the removing material used in the present invention is that the above-mentioned silver catalyst is formed into a honeycomb structure, foam, plate, pellet or granule and then sintered to obtain a desired shape. It is a removal material filled in a casing.
【００２０】なお、除去材の形態を上述した第一の好ま
しい形態とする場合、除去材基体上に設ける銀系触媒の
厚さは、一般に、基体材と、この触媒との熱膨張特性の
違いから制限される場合が多い。除去材基体上に設ける
触媒の厚さを３００μｍ以下とするのがよい。このよう
な厚さとすれば、使用中に熱衝撃等で除去材が破損する
ことを防ぐことができる。除去材基体の表面に銀系触媒
を形成する方法は公知のウォッシュコート法等によって
行われる。In the case where the form of the removing material is the first preferred form described above, the thickness of the silver-based catalyst provided on the removing material base generally depends on the difference in thermal expansion characteristics between the base material and this catalyst. Is often restricted from. It is preferable that the thickness of the catalyst provided on the removing material substrate is 300 μm or less. With such a thickness, it is possible to prevent the removal material from being damaged by a thermal shock or the like during use. The method of forming the silver-based catalyst on the surface of the removing material substrate is performed by a known wash coat method or the like.
【００２１】また、除去材基体の表面上に設ける銀系触
媒の量は、除去材基体の２０〜３００ｇ／リットルとす
るのが好ましい。触媒の量が２０ｇ／リットル未満では
良好なNOx の除去が行えない。一方、触媒の量が３００
ｇ／リットルを超えると除去特性はそれほど上がらず、
圧力損失が大きくなる。より好ましくは、除去材基体の
表面上に設ける銀系触媒を除去材基体の５０〜２００ｇ
／リットルとする。The amount of the silver-based catalyst provided on the surface of the removing material substrate is preferably 20 to 300 g / liter of the removing material substrate. If the amount of the catalyst is less than 20 g / liter, good NOx removal cannot be performed. On the other hand, when the amount of the catalyst is 300
When the amount exceeds g / liter, the removal characteristics do not increase so much.
Pressure loss increases. More preferably, the silver-based catalyst provided on the surface of the removing material substrate is 50 to 200 g of the removing material substrate.
/ Liter.
【００２２】上述した構成の除去材を用い、下記の方法
に従えば、１５０〜６００℃の広い温度領域において、
良好な窒素酸化物の除去を行うことができる。According to the following method using the removing material having the above-described structure, in a wide temperature range of 150 to 600 ° C.,
Good removal of nitrogen oxides can be performed.
【００２３】［２］窒素酸化物除去方法 次に、本発明の方法について説明する。まず、上記窒素
酸化物除去材を排ガス導管の途中に設置する。[2] Method for Removing Nitrogen Oxide Next, the method of the present invention will be described. First, the above-mentioned nitrogen oxide removing material is installed in the middle of the exhaust gas conduit.
【００２４】排ガス中には、残留炭化水素としてエチレ
ン、プロピレン等がある程度は含まれるが、一般に排ガ
ス中のNOx を還元するのに十分な量ではないので、外部
から還元剤として排ガス中に導入する。還元剤の導入位
置は、除去材を設置した位置より上流側である。Although the exhaust gas contains ethylene, propylene and the like to some extent as residual hydrocarbons, it is generally not enough to reduce NOx in the exhaust gas, so it is introduced into the exhaust gas as a reducing agent from outside. . The introduction position of the reducing agent is on the upstream side of the position where the removing material is installed.
【００２５】本発明では、還元剤として含酸素有機化合
物からなる群より選ばれた一種以上と水とを混合して用
いる。含酸素有機化合物として、エタノール、イソプロ
パノール、ｎ−プロパノール等のアルコール、アセトア
ルデヒド、アセトン等のアルデヒド、ケトン等が挙げら
れ、好ましくはエタノール、イソプロピルアルコール等
の炭素数２以上のアルコール類である。In the present invention, water is mixed with one or more selected from the group consisting of oxygen-containing organic compounds as a reducing agent. Examples of the oxygen-containing organic compound include alcohols such as ethanol, isopropanol and n-propanol, aldehydes such as acetaldehyde and acetone, ketones and the like, and preferably alcohols having 2 or more carbon atoms such as ethanol and isopropyl alcohol.
【００２６】外部から導入する還元剤の量は、重量比
（添加する還元剤の重量／排ガス中の窒素酸化物の重
量）が０．１〜５となるようにするのが好ましい。この
重量比が０．１未満であると、窒素酸化物の除去率が大
きくならない。一方、５を超えると、燃費悪化につなが
る。The amount of the reducing agent introduced from the outside is preferably such that the weight ratio (weight of the reducing agent to be added / weight of the nitrogen oxide in the exhaust gas) is 0.1 to 5. If the weight ratio is less than 0.1, the removal rate of nitrogen oxides does not increase. On the other hand, if it exceeds 5, fuel efficiency will be degraded.
【００２７】本発明では、アルコール等の含酸素有機化
合物とともに水を還元剤として用いる。水を用いること
により、特に低温領域で選択的に一酸化窒素と、エタノ
ール、酸素との反応が起こるために窒素酸化物の除去率
が向上すると思われるが、詳しい反応機構についてはま
だ不明である。排ガス中にはもともとある程度の水分を
含有しているので、本発明では、窒素酸化物除去材の直
前の排ガス中における含酸素有機化合物からなる群より
選ばれた一種以上の有機化合物と水との重量比は１：１
００〜１００：１になるように水を添加する。有機化合
物と水との重量比が１：１００未満で、水過剰な場合で
は、低温側での窒素酸化物除去率の更なる向上が見られ
ず、逆に重量比が１００：１を超えて、有機化合物過剰
な場合では、低温側での窒素酸化物除去率が向上しな
い。好ましい有機化合物と水との重量比は１：５０〜１
０：１である。より好ましい有機化合物と水との重量比
は１：５０〜１０：１である。なお、還元剤添加後（除
去材直前）の排ガス中における水分の含有率は１〜５０
容量％が好ましく、５〜３０容量％がより好ましく、６
〜２５容量％が特に好ましい。In the present invention, water is used as a reducing agent together with an oxygen-containing organic compound such as alcohol. It is thought that the use of water will increase the removal rate of nitrogen oxides due to the selective reaction of nitric oxide with ethanol and oxygen particularly in the low temperature range, but the detailed reaction mechanism is still unknown. . Since the exhaust gas originally contains a certain amount of water, in the present invention, one or more organic compounds selected from the group consisting of oxygen-containing organic compounds in the exhaust gas immediately before the nitrogen oxide removing material and water 1: 1 weight ratio
Water is added so as to be 100 to 100: 1. If the weight ratio of the organic compound to water is less than 1: 100 and the amount of water is excessive, no further improvement in the nitrogen oxide removal rate on the low temperature side is observed, and conversely, the weight ratio exceeds 100: 1. On the other hand, if the organic compound is excessive, the nitrogen oxide removal rate on the low temperature side does not improve. The preferred weight ratio of the organic compound to water is 1:50 to 1
0: 1. A more preferable weight ratio of the organic compound to water is 1:50 to 10: 1. The water content in the exhaust gas after the addition of the reducing agent (immediately before the removal material) is 1 to 50.
% By volume, more preferably 5 to 30% by volume, and 6% by volume.
-25% by volume is particularly preferred.
【００２８】還元剤の添加位置から除去材までの距離が
短いために、含酸素有機化合物と排ガス中にもともと含
有する水分とは十分に混合されない。同様に、水を添加
する場合、含酸素有機化合物と水とを別々の注入口から
添加すると、含酸素有機化合物と水分との混合が十分で
はない。従って、水をあらかじめ含酸素有機化合物と水
とをあらかじめ混合した後添加した方が、水の作用が十
分に発揮できるので好ましい。水を含酸素有機化合物と
混合して添加する場合、含酸素有機化合物からなる群よ
り選ばれた一種以上の有機化合物と水との重量比は１：
１００〜１００：１になるように水を添加する。有機化
合物と水との重量比が１：１００未満で、水過剰な場合
では、低温側での窒素酸化物除去率の更なる向上が見ら
れず、逆に重量比が１００：１を超えて、有機化合物過
剰な場合では、低温側での窒素酸化物除去率が向上しな
い。好ましい有機化合物と水との重量比は１：５０〜１
０：１である。より好ましい有機化合物と水との重量比
は１：５０〜１：１である。Since the distance from the addition position of the reducing agent to the removing material is short, the oxygen-containing organic compound and the water originally contained in the exhaust gas are not sufficiently mixed. Similarly, when adding water, if the oxygen-containing organic compound and water are added from separate injection ports, the mixing of the oxygen-containing organic compound and water is not sufficient. Therefore, it is preferable to add water after mixing the oxygen-containing organic compound and water in advance, since the action of water can be sufficiently exhibited. When water is added as a mixture with an oxygen-containing organic compound, the weight ratio of one or more organic compounds selected from the group consisting of oxygen-containing organic compounds to water is 1:
Add water to make 100-100: 1. When the weight ratio of the organic compound to water is less than 1: 100 and the amount of water is excessive, no further improvement in the nitrogen oxide removal rate on the low temperature side is observed, and conversely, the weight ratio exceeds 100: 1. On the other hand, if the organic compound is excessive, the nitrogen oxide removal rate on the low temperature side does not improve. The preferred weight ratio of the organic compound to water is 1:50 to 1
0: 1. A more preferable weight ratio of the organic compound to water is 1:50 to 1: 1.
【００２９】本発明では、還元剤による窒素酸化物の還
元除去を効率的に進行させるために、除去材の空間速度
は 300,000ｈ-1以下、好ましくは 200,000ｈ-1以下とす
る。[0029] In the present invention, in order to advance the reduction removal of nitrogen oxides with a reducing agent efficiently, the space velocity of the removed material 300,000H -1 or less, preferably 200,000 -1 or less.
【００３０】また、本発明では、還元剤と窒素酸化物と
が反応する部位である除去材設置部位における排ガスの
温度を１５０〜６００℃に保つ。排ガスの温度が１５０
℃未満であると還元剤と窒素酸化物との反応が進行せ
ず、良好な窒素酸化物の除去を行うことができない。一
方、６００℃を超す温度とすると還元剤自身の燃焼が始
まり、窒素酸化物の還元除去が行えない。好ましい排ガ
ス温度は２００〜６００℃である。In the present invention, the temperature of the exhaust gas is maintained at 150 to 600 ° C. at the portion where the reducing agent and the nitrogen oxide react, where the removing material is provided. Exhaust gas temperature is 150
If the temperature is lower than 0 ° C., the reaction between the reducing agent and the nitrogen oxide does not proceed, and good removal of the nitrogen oxide cannot be performed. On the other hand, if the temperature exceeds 600 ° C., combustion of the reducing agent itself starts, and reduction and removal of nitrogen oxides cannot be performed. The preferred exhaust gas temperature is from 200 to 600C.
【００３１】[0031]
【実施例】本発明を以下の具体的実施例によりさらに詳
細に説明する。実施例１ 市販のγ−アルミナ粉末（比表面積２００ｍ2 ／ｇ）に
硝酸銀水溶液を用いて３重量％（金属元素換算値）の銀
を担持し、乾燥後、空気中で段階的に６００℃まで焼成
して、銀触媒を調製した。銀触媒０．７８ｇをスラリー
化し、コージェライト製ハニカム状成形体（４００セル
／インチ2 、直径２０ｍｍ、長さ１２．６ｍｍ）にコー
トし、乾燥させた後空気中で６００℃まで段階的に焼成
し、窒素酸化物除去材を調製した。The present invention will be described in more detail with reference to the following specific examples. Example 1 Commercially available γ-alumina powder (specific surface area: 200 m 2 / g) was loaded with 3% by weight (in terms of metal element) of silver using an aqueous silver nitrate solution, dried, and gradually heated to 600 ° C. in air. By calcining, a silver catalyst was prepared. A slurry of 0.78 g of a silver catalyst is coated on a cordierite honeycomb-shaped formed body (400 cells / inch 2 , diameter 20 mm, length 12.6 mm), dried, and then fired stepwise to 600 ° C. in air. Then, a nitrogen oxide removing material was prepared.
【００３２】反応管内に上記窒素酸化物除去材をセット
し、表１に示す組成のガス（一酸化窒素、酸素、エタノ
ール、水分及び窒素）を毎分２．６リットル（標準状
態）の流量で流して（除去材の見かけ空間速度は約４
０，０００ｈ-1である。）、反応管内の排ガス温度を１
５０〜６００℃の範囲に保ち、窒素酸化物の還元除去を
行った。ただし、エタノールはあらかじめ表１に示す水
分で希釈してから用いた。The nitrogen oxide removing material was set in a reaction tube, and a gas (nitrogen monoxide, oxygen, ethanol, water and nitrogen) having a composition shown in Table 1 was supplied at a flow rate of 2.6 liters per minute (standard state). Flow (the apparent space velocity of the removed material is about 4
It is 0000h- 1 . ), The temperature of the exhaust gas in the reaction tube
The temperature was kept in the range of 50 to 600 ° C., and nitrogen oxides were reduced and removed. However, ethanol was used after being diluted with the water shown in Table 1 in advance.
【００３３】反応管通過後のガスの窒素酸化物の濃度を
化学発光式窒素酸化物分析計により測定し、窒素酸化物
除去率を求めた。結果を表４に示す。The concentration of nitrogen oxides in the gas after passing through the reaction tube was measured by a chemiluminescent nitrogen oxide analyzer to determine the nitrogen oxide removal rate. Table 4 shows the results.
【００３４】 表１ 成分 濃度 一酸化窒素 800 ppm 酸素 10 容量％ エタノール 1565 ppm （一酸化窒素の質量の３倍） 水分 5 容量％（エタノールの重量の１２．５倍） 窒素 残部 [0034] Table 1 Component Concentration (3 times the weight of nitrogen monoxide) nitric 800 ppm oxygen 10 volume% ethanol 1565 ppm water 5 volume% (12.5 times the weight of ethanol) Nitrogen balance
【００３５】実施例２ 実施例１と同じ窒素酸化物除去材を反応管内にセット
し、表１に示す組成のうち、水分含有量を１０容量％
（エタノールの重量の２５倍）に変更したガスを実施例
１と同じ条件で（流量２．６リットル／分（標準状
態）、除去材の見かけ空間速度は約４０，０００ｈ-1で
ある。）、反応管内の排ガス温度を１５０〜６００℃の
範囲に保ち、窒素酸化物の還元除去を行った。ただし、
エタノールはあらかじめ水分で希釈してから用いた。実
施例１と同じ方法で求めた窒素酸化物除去率を表２に示
す。 Example 2 The same nitrogen oxide removing material as in Example 1 was set in a reaction tube, and the water content of the composition shown in Table 1 was 10% by volume.
The gas changed to (25 times the weight of ethanol) was used under the same conditions as in Example 1 (at a flow rate of 2.6 L / min (standard condition), the apparent space velocity of the removing material was about 40,000 h -1 ). The temperature of the exhaust gas in the reaction tube was kept in the range of 150 to 600 ° C., and nitrogen oxides were reduced and removed. However,
Ethanol was used after being diluted with water in advance. Table 2 shows the nitrogen oxide removal rates determined by the same method as in Example 1.
【００３６】実施例３ 実施例１と同じ方法で、硝酸銀水溶液を用いて粉末状シ
リカ・アルミナ（シリカ含有率３重量％、比表面積３５
０ｍ2 ／ｇ）に３重量％（金属元素換算値）の銀を担持
し、実施例１と同じ方法で焼成して、銀触媒を作製し
た。銀触媒０．７８ｇをスラリー化し、コージェライト
製ハニカム状成形体（４００セル／インチ2 、直径２０
ｍｍ、長さ１２．６ｍｍ）にコートし、乾燥させた後空
気中で６００℃まで段階的に焼成し、窒素酸化物除去材
を調製した。 Example 3 In the same manner as in Example 1, powdery silica-alumina (silica content 3% by weight, specific surface area 35
0 m 2 / g), 3% by weight (in terms of a metal element) of silver was supported and calcined in the same manner as in Example 1 to produce a silver catalyst. A slurry of 0.78 g of a silver catalyst was formed into a cordierite honeycomb formed body (400 cells / inch 2 , diameter 20
mm, 12.6 mm in length), dried, and fired stepwise in air to 600 ° C. to prepare a nitrogen oxide removing material.
【００３７】反応管内に上記窒素酸化物除去材をセット
した。表１に示す組成のうち、水分含有量を２０容量％
（エタノールの重量の５０倍）に変更したガスを実施例
１と同じ条件で（流量２．６リットル／分（標準状
態）、除去材の見かけ空間速度は約４０，０００ｈ-1で
ある。）、反応管内の排ガス温度を１５０〜６００℃の
範囲に保ち、窒素酸化物の還元除去を行った。ただし、
エタノールはあらかじめ水分で希釈してから用いた。実
施例１と同じ方法で求めた窒素酸化物除去率を表２に示
す。The above-mentioned nitrogen oxide removing material was set in a reaction tube. Of the compositions shown in Table 1, the water content was 20% by volume.
The gas changed to (50 times the weight of ethanol) was used under the same conditions as in Example 1 (at a flow rate of 2.6 L / min (standard state), the apparent space velocity of the removing material was about 40,000 h -1 ). The temperature of the exhaust gas in the reaction tube was kept in the range of 150 to 600 ° C., and nitrogen oxides were reduced and removed. However,
Ethanol was used after being diluted with water in advance. Table 2 shows the nitrogen oxide removal rates determined by the same method as in Example 1.
【００３８】実施例４ 反応管内に実施例３の窒素酸化物除去材をセットした。
実施例３と同じように表１に示す組成のうち、水分含有
量を２０容量％（エタノールの重量の５０倍）に変更し
たガスを実施例１と同じ条件で（流量２．６リットル／
分（標準状態）、除去材の見かけ空間速度は約４０，０
００ｈ-1である。）、反応管内の排ガス温度を１５０〜
６００℃の範囲に保ち、窒素酸化物の還元除去を行っ
た。ただし、エタノールと水とは混合せずに別々に添加
した。実施例１と同じ方法で求めた窒素酸化物除去率を
表２に示す。 Example 4 The nitrogen oxide removing material of Example 3 was set in a reaction tube.
In the same manner as in Example 3, a gas in which the water content was changed to 20% by volume (50 times the weight of ethanol) in the composition shown in Table 1 under the same conditions as in Example 1 (flow rate 2.6 liters /
Minute (standard condition), apparent space velocity of the removed material is about 40,0
00h -1 . ), The exhaust gas temperature in the reaction tube is 150 ~
The temperature was kept at 600 ° C., and nitrogen oxides were reduced and removed. However, ethanol and water were added separately without mixing. Table 2 shows the nitrogen oxide removal rates determined by the same method as in Example 1.
【００３９】比較例１ 実施例１の窒素酸化物除去材を反応管にセットし、実施
例１と同様の反応条件（見かけ空間速度は約４０，００
０ｈ-1である）で、表１に示す組成のうち水分を除いた
組成のガスを用いて評価を行った。結果を表４に示す。 Comparative Example 1 The nitrogen oxide removing material of Example 1 was set in a reaction tube, and the same reaction conditions as in Example 1 (apparent space velocity was about 40,00
0 h -1 ), and evaluation was performed using a gas having a composition shown in Table 1 from which water was removed. Table 4 shows the results.
【００４０】比較例２ 実施例３の窒素酸化物除去材を反応管にセットし、実施
例１と同様の反応条件（見かけ空間速度は約４０，００
０ｈ-1である）で、表１に示す組成のうち水分を除いた
組成のガスを用いて評価を行った。結果を表４に示す。 Comparative Example 2 The nitrogen oxide removing material of Example 3 was set in a reaction tube, and the same reaction conditions as in Example 1 (apparent space velocity was about 40,00
0 h -1 ), and evaluation was performed using a gas having a composition shown in Table 1 from which water was removed. Table 4 shows the results.
【００４１】 表２ 窒素酸化物の除去率（％）排ガス温度 実施例１ 実施例２ 実施例３ 実施例４ 比較例１ 比較例２ １５０ ８ １０ ２０ １５ ４ ４ ２００ １０ １５ ２５ ２２ ７ ７ ２５０ １５ ２６ ２８ ２７ ９ １０ ３００ ４４ ４５ ４９ ４２ １８ １８ ３５０ ８９ ８９ ９０ ８５ ３２ ３４ ４００ ９８ ９８ ９７ ９６ ９４ ９５ ４５０ ９８ ９８ ９８ ９８ ９８ ９７ ５００ ９０ ９２ ９３ ９４ ９０ ９０ ５５０ ７４ ７９ ８０ ８２ ７０ ６９ ６００ ４０ ４５ ５０ ５０ ３０ ３１ Table 2 Removal rate of nitrogen oxides (%) Exhaust gas temperature Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 150 8 10 20 15 4 4 200 10 15 25 22 7 7 250 15 26 28 27 9 10 300 44 44 45 49 42 18 18 18 350 89 89 90 85 32 34 400 400 98 98 97 96 94 95 95 450 98 98 98 98 98 98 97 500 500 90 92 93 94 90 90 550 74 79 45 80 70 69 69 600 50 50 30 31
【００４２】表２からわかるように、水を添加しなかっ
た比較例１及び２に比べて、エタノールと水とを同時に
用いた実施例１〜４では広い排ガス温度領域で、特に低
い温度領域で窒素酸化物の良好な除去がみられた。ま
た、水分含有量の増加にしたがって除去率の増加が見ら
れ、水分による窒素酸化物除去の促進効果が明らかであ
る。なお、水をエタノールと混合して添加した実施例３
と水とエタノールとを別々に添加した実施例４とを比較
すると、実施例３のほうが除去率が高く、水とエタノー
ルとを混合した方が好ましいことを示した。As can be seen from Table 2, as compared with Comparative Examples 1 and 2 in which water was not added, Examples 1 to 4 in which ethanol and water were used at the same time had a wider exhaust gas temperature range, particularly in a lower temperature range. Good removal of nitrogen oxides was observed. In addition, the removal rate increases as the water content increases, and the effect of promoting the removal of nitrogen oxides by water is apparent. Example 3 wherein water was mixed with ethanol and added
Comparing Example 4 to which water and ethanol were separately added, Example 3 had a higher removal rate, indicating that mixing water and ethanol was preferred.
【００４３】[0043]
【発明の効果】以上詳述したように、本発明の窒素酸化
物除去方法を用いれば、広い温度領域において過剰の酸
素を含む排ガス中の窒素酸化物を効率良く除去すること
ができる。本発明の窒素酸化物除去方法は、各種燃焼
機、自動車等の排ガス中の窒素酸化物除去に広く利用す
ることができる。As described in detail above, the nitrogen oxide removing method of the present invention can efficiently remove nitrogen oxides in exhaust gas containing excess oxygen in a wide temperature range. INDUSTRIAL APPLICABILITY The method for removing nitrogen oxides of the present invention can be widely used for removing nitrogen oxides from exhaust gas from various combustors, automobiles and the like.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 吉田 清英 埼玉県熊谷市末広四丁目14番１号 株式会 社リケン熊谷事業所内 ──────────────────────────────────────────────────続 き Continued from the front page (72) Inventor Kiyohide Yoshida 4-1-1, Suehiro, Kumagaya-shi, Saitama, Japan
Claims (8)
らなる群より選ばれる一種以上の元素及び／又は化合物
０．２〜１５重量％（金属元素換算値）を担持してなる
窒素酸化物除去材を用い、窒素酸化物と、共存する未燃
焼成分に対する理論反応量より多い酸素とを含む燃焼排
ガスから窒素酸化物を還元除去する窒素酸化物除去方法
において、前記窒素酸化物除去材を排ガス導管の途中に
設置し、前記除去材の上流側で含酸素有機化合物からな
る群より選ばれた一種以上と水とを添加した排ガスを、
１５０〜６００℃において前記除去材に接触させ、前記
窒素酸化物を除去することを特徴とする窒素酸化物除去
方法。1. Nitrogen oxidation comprising a porous inorganic oxide carrying 0.2 to 15% by weight (in terms of metal element) of one or more elements and / or compounds selected from the group consisting of silver and silver compounds. A nitrogen oxide removing method for reducing and removing nitrogen oxides from a combustion exhaust gas containing nitrogen oxides and oxygen that is larger than the theoretical reaction amount for coexisting unburned components using a material removing material. Installed in the middle of an exhaust gas conduit, the exhaust gas added with water and at least one selected from the group consisting of oxygen-containing organic compounds on the upstream side of the removing material,
A method for removing nitrogen oxides, comprising contacting the removal material at 150 to 600 ° C. to remove the nitrogen oxides.
おいて、前記銀化合物は銀の酸化物、ハロゲン化銀、硫
酸銀及び燐酸銀からなる群より選ばれた少なくとも一種
であることを特徴とする窒素酸化物除去方法。2. The method for removing nitrogen oxides according to claim 1, wherein said silver compound is at least one selected from the group consisting of silver oxide, silver halide, silver sulfate and silver phosphate. Nitrogen oxide removal method.
方法において、前記多孔質無機酸化物は、アルミナ単
独、又はチタニア、シリカ、ジルコニア、酸化亜鉛、酸
化錫、酸化マグネシウム、ゼオライトのいずれかとアル
ミナとの複合又は混合酸化物であることを特徴とする窒
素酸化物除去方法。3. The method for removing nitrogen oxides according to claim 1, wherein the porous inorganic oxide is alumina alone or any one of titania, silica, zirconia, zinc oxide, tin oxide, magnesium oxide, and zeolite. A method for removing nitrogen oxides, which is a composite or mixed oxide of silica and alumina.
化物除去方法において、前記窒素酸化物除去材がセラミ
ックス製又は金属製の基体の表面にコートされているこ
とを特徴とする窒素酸化物除去方法。4. The nitrogen oxide removing method according to claim 1, wherein said nitrogen oxide removing material is coated on a surface of a ceramic or metal substrate. Oxide removal method.
化物除去方法において、前記窒素酸化物除去材がハニカ
ム型、フォーム型、板状、ペレット状、顆粒状のいずれ
かに成形されていることを特徴とする窒素酸化物除去方
法。5. The nitrogen oxide removing method according to claim 1, wherein the nitrogen oxide removing material is formed into any one of a honeycomb type, a foam type, a plate shape, a pellet shape, and a granular shape. A method for removing nitrogen oxides.
化物除去方法において、前記窒素酸化物除去材の直前の
排ガス中における前記含酸素有機化合物からなる群より
選ばれた一種以上の含有量と水の含有量の重量比を１：
１００〜１００：１にすることを特徴とする窒素酸化物
除去方法。6. The nitrogen oxide removing method according to claim 1, wherein at least one selected from the group consisting of the oxygen-containing organic compounds in the exhaust gas immediately before the nitrogen oxide removing material. The weight ratio of the content to the water content is 1:
A method for removing nitrogen oxides, wherein the ratio is 100 to 100: 1.
化物除去方法において、前記窒素酸化物除去材の直前の
排ガス中における水の含有量を１〜５０容量％にするこ
とを特徴とする窒素酸化物除去方法。7. The nitrogen oxide removing method according to claim 1, wherein the content of water in the exhaust gas immediately before the nitrogen oxide removing material is 1 to 50% by volume. Nitrogen oxide removal method.
化物除去方法において、前記含酸素有機化合物からなる
群より選ばれた一種以上と水とを混合して還元剤として
排ガス中に添加することを特徴とする窒素酸化物除去方
法。8. The method for removing nitrogen oxides according to claim 1, wherein at least one selected from the group consisting of the oxygen-containing organic compounds and water are mixed to form a reducing agent in the exhaust gas. A method for removing nitrogen oxides, which comprises adding.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8158986A JPH1028840A (en) | 1996-05-15 | 1996-05-30 | Method for removing nitrogen oxide |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8-145005 | 1996-05-15 | ||
| JP14500596 | 1996-05-15 | ||
| JP8158986A JPH1028840A (en) | 1996-05-15 | 1996-05-30 | Method for removing nitrogen oxide |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH1028840A true JPH1028840A (en) | 1998-02-03 |
Family
ID=26476272
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP8158986A Pending JPH1028840A (en) | 1996-05-15 | 1996-05-30 | Method for removing nitrogen oxide |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH1028840A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2015012202A1 (en) * | 2013-07-25 | 2015-01-29 | 日立造船株式会社 | Method for purifying exhaust gas |
-
1996
- 1996-05-30 JP JP8158986A patent/JPH1028840A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2015012202A1 (en) * | 2013-07-25 | 2015-01-29 | 日立造船株式会社 | Method for purifying exhaust gas |
| JP2015024362A (en) * | 2013-07-25 | 2015-02-05 | 日立造船株式会社 | Exhaust gas purification method |
| CN105451863A (en) * | 2013-07-25 | 2016-03-30 | 日立造船株式会社 | Method for purifying exhaust gas |
| US9802155B2 (en) | 2013-07-25 | 2017-10-31 | Hitachi Zosen Corporation | Method for purifying exhaust gas |
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