JP3582446B2 - Gas purification apparatus and method - Google Patents
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【０００１】
【発明の属する技術分野】
本発明は、自動車や各種製造設備等から排出される排気ガス中に含まれる有害成分の浄化装置及び方法に関し、とりわけ、Ｏ2を比較的多量に含む排気ガスであっても、排気ガス中に含まれるＮＯXを常温常圧下で浄化することができる排気ガス装置及び方法に関する。
【０００２】
【従来の技術】
自動車や各種製造設備等から排出される排気ガス中に含まれる有害成分を浄化する方式としては、様々なものが提案されている。
その１つとして、触媒とプラズマの組み合わせた複合系が提案されており、こうした複合系によれば、触媒の選択的反応促進作用とプラズマによる特定化学種の励起作用との相乗効果により、触媒とプラズマのそれぞれの単独の系では得られないガス浄化性能が期待できる。例えば、従来の触媒単独系では実現されていない、下記のようなＮＯXの直接分解反応によるＮＯX浄化である。
ＮＯ → １／２Ｎ2＋１／２Ｏ2
【０００３】
このような触媒とプラズマの複合系に関する先行技術としては、例えば、特開平６−１０６０２５号公報、特開平７−１０２９５５号公報、特開平１０−１６９４３１号公報、特開平１１−３１９４８６号公報があり、ＮＯX浄化等が開示されている。
【０００４】
しかしながら、これらの先行技術においては、処理可能なガスが極めて限られており、さらに、プラズマ発生に要する電力や設備規模に対してガスの処理能力が低いという設備効率上の欠点がある。この理由は、プラズマを発生させる領域と触媒が存在する領域が離れており、反応領域に触媒とプラズマが共存していないためプラズマが有効利用されていない、あるいは、プラズマによって励起されたラジカルが反応領域を素通りしやすく、ラジカルと触媒との接触確率が低い等が推測される。
【０００５】
一方、本発明者らは、特開平６−２６２０３２号公報において、触媒が存在する領域でプラズマを発生させる、即ち、反応領域に触媒とプラズマを共存させるという技術思想に基づき、ガス処理装置を提案している。
さらに、特開平７−１８５２６６号公報と特開平７−２０４４６９号公報において、ガスと触媒との接触確率を高めるべく、回転ファンと反応器内壁の間にプラズマを形成させ、反応器内壁に触媒層を設けたガス浄化装置を提案し、また、国際特許出願ＷＯ９６／２０７８３公開明細書において、回転プレートと静止プレートの間に触媒とプラズマを共存させるガス反応器を提案している。
【０００６】
これらの触媒とプラズマが共存し、かつ電極等に動的機構を設けた系においては、処理可能なガスの種類が拡大し、とりわけ、常温常圧の条件下でＮＯXが浄化できるといった点で成果が得られている。
【０００７】
【発明の解決しようとする課題】
しかしながら、かかる改良によっても、処理可能なガスとして、ＮＯXの浄化においては、Ｏ2を含まないガスに適用対象が限られ、数体積％のＯ2を含むガスでは、ＮＯX浄化性能が発現されないという問題がある。さらに、ガスの処理能力に対して設備規模が大きいといった設備効率上の欠点がある。
一方、自動車に現在搭載されている触媒単独系の三元触媒等は、数１００℃の高温下で始めてＮＯX浄化性能を発揮するため、温度が低い例えば始動時の排気ガスに対してはＮＯXが殆ど浄化されないという問題がある。
【０００８】
したがって、本発明は、かかる触媒とプラズマの複合系をさらに改良し、処理可能なガスの種類を拡大すること、とりわけ、リーン条件下で運転される自動車の排気ガスのような、Ｏ2を比較的多量に含むＮＯX含有ガスであっても、常温常圧下でＮＯX浄化を可能にすることを目的とする。
【０００９】
【課題を解決するための手段】
本発明のガス浄化装置は、表面に触媒材料層を有する第１円筒形導電体と、表面に誘電体層を有する第２円筒形導電体を備え、前記第１円筒形導電体と前記第２円筒形導電体が同軸であり、前記触媒材料層と前記誘電体層が互いに面し、前記触媒材料層と前記誘電体層の間に円筒形微小間隙を設け、前記第１円筒形導電体と前記第２円筒形導電体の少なくとも一方をその円筒形中心軸の周りに回転させる手段、及び前記円筒形微小間隙にプラズマ発生させる手段、を備えたことを特徴とする。
【００１０】
この本発明の装置によれば、Ｏ 2 を含むガスであっても、含まれるＮＯ X を浄化、即ち、ＮＯ X をＮ 2 に還元することによりガス中のＮＯ X 濃度を低下させることができる。このＮＯ X 浄化は、常温常圧のガスであっても可能である。またこの本発明の装置は、Ｏ2を含まないガスのＮＯX浄化にも適用できる。またさらにこの本発明の装置によれば、同じ処理ガス量に対してプラズマ発生領域をコンパクトにすることができ、設備効率が顕著に改良される。この理由は、プラズマによって励起されたラジカル相互の接触確率、又はラジカルと触媒との接触確率が著しく高められ、相互のエネルギー交換が起こり易くなるためと考えられる。
【００１１】
本発明のガス浄化方法は、表面に触媒材料層を有する第１円筒形導電体と、表面に誘電体層を有する第２円筒形導電体が、同軸に配置されることによって前記触媒材料層と前記誘電体層の間に形成された円筒形微小間隙に、プラズマ発生させ、前記第１円筒形導電体と前記第２円筒形導電体の少なくとも一方をその円筒形中心軸の周りに回転させ、前記円筒形微小間隙に処理すべきガスを導くことを特徴とする。
この本発明の方法によれば、Ｏ 2 を含むガスであっても、含まれるＮＯ X を浄化、即ち、ＮＯ X をＮ 2 に還元することによりガス中のＮＯ X 濃度を低下させることができる。このＮＯ X 浄化は、常温常圧のガスであっても可能である。またこの本発明の方法は、Ｏ2を含まないガスのＮＯX浄化にも適用でき、触媒とプラズマの複合系で適用可能なガスの種類を顕著に拡大することができる。
【００１２】
【発明の実施の形態】
本発明のガス浄化装置及び方法によれば、ＮＯXとＯ2を含むガス中のＮＯXを、触媒とプラズマの共存下で浄化することができる。
即ち、本発明のガス浄化装置及び方法によれば、触媒とプラズマが「共存」する条件下において、条件を適切に選択すれば、Ｏ2を含むガスであってもＮＯXが浄化可能である。
【００１３】
ここで、本明細書の記載における「共存」とは、プラズマが発生している領域に触媒が存在すること、具体的には、触媒が存在する領域内にプラズマを発生させることをいう。
Ｏ2存在下でＮＯXを浄化するための要件は、限定されるものではないが、プラズマによって励起されたラジカル相互の接触確率、又はラジカルと触媒との接触確率が著しく高められた条件であると考えられる。具体的態様は、一概ではなく、当業者は本発明の開示に基づき、容易に確認し、実現することができるものである。
【００１４】
触媒とプラズマが共存してプラズマによって励起されたラジカル相互の接触確率、又はラジカルと触媒との接触確率が著しく高められた条件下では、従来技術の触媒とプラズマの複合系では単に指向されていたに過ぎなかった下記のようなＮＯXの直接分解反応が、実際に生じることができ、この反応がＮＯX浄化に少なからず寄与することができることから、Ｏ2を含む常温常圧下のガスであってもＮＯXを還元浄化することができるものと考えられる。
ＮＯ → １／２Ｎ2＋１／２Ｏ2
本発明のガス浄化方法及び装置においては、Ｏ2濃度として、３体積％以上、さらには５体積％以上含むガスであってもＮＯXを浄化できることが確認されている。
【００１５】
本発明のガス浄化方法及び装置では、とりわけ、触媒材料層又は誘導体層が互いに面して、その少なくとも一方が回転するため、触媒とプラズマが共存し、かつプラズマによって励起されたラジカル相互の接触確率、又はラジカルと触媒との接触確率が著しく高められた条件を提供することができる。
【００１６】
次に、本発明のガス浄化装置を具体的に説明する。
第１円筒形導電体は、表面に触媒材料層を有する。この第１円筒形導電体の表面は、プラズマ生成の電極としても使用されるため、触媒材料層は導電性のある金属からなることが好ましい。
【００１７】
触媒作用のある金属は、好ましくは、遷移金属として分類されるイリジウム、クロム、コバルト、ジルコニウム、セシウム、タングステン、タンタル、チタン、鉄、テルル、ニオブ、ニッケル、白金、バナジウム、ハフニウム、パラジウム、マンガン、モリブデン、ルテニウム、レニウム、ロジウムから選択される。これらの中でも、白金、パラジウム、ルテニウム、ロジウムの貴金属が最も好適に使用される。
【００１８】
これらの触媒金属層は、電気メッキ又は化学メッキによって形成することができ、厚みは、特に限定されるものではないが、３〜１０μｍ程度に形成することが好ましい。
【００１９】
第２円筒形導電体は、表面に誘電体層を有する。誘電体層を形成することにより、プラズマの局在化が抑制され、第１円筒形導電体と第２円筒形導電体の間の円筒形微小間隙の全体で、均一なプラズマが形成されるためであり、また、無声放電が得られるためである。
【００２０】
この誘電体層は、特に限定されるものではないが、ガラス膜、アルミナやシリカ等のセラミック膜等を化学蒸着法、真空蒸着法、溶射等によって導電体上にコーティングすることによって形成されたものでよく、厚さは、特に限定されるものではないが、放電電圧を過度に高くしない点からは、５ｍｍ以下が適切であり、好ましくは１ｍｍ以下、より好ましくは約１００μｍの程度である。
なお、第１円筒形導電体と第２円筒形導電体の材料は、導電性の金属が適切であり、銅、銅合金、ステンレス鋼等の広範囲な材料から選択することができる。
【００２１】
第１円筒形導電体と第２円筒形導電体は、これらを回転させたときに第１円筒形導電体上の触媒材料層と第２円筒形導電体上の誘電体層の微小間隙の距離が実質的に変動しないように、同軸に配置される。
【００２２】
触媒材料層と誘電体層は、これらの層が互いに面するように配置される。ここで、触媒材料層が外側に、したがって第１円筒形導電体が第２円筒形導電体の外側に配置され、あるいは、触媒材料層が内側に、したがって第１円筒形導電体が第２円筒形導電体の内側に配置されてよい。
【００２３】
触媒材料層と誘電体層の間の微小間隙は、０．２〜５ｍｍ、好ましくは０．５〜２ｍｍでよい。この微小間隔が約０．２ｍｍを下回ると、ガスを浄化する空間が狭くなってガス処理量が低下し、約２ｍｍを上回るとプラズマ放電を生じさせるための電圧が過度に高くなるためである。
【００２４】
本発明のガス浄化装置は、第１円筒形導電体と第２円筒形導電体の少なくとも一方をその円筒形中心軸の周りに回転させる手段をさらに備える。ここで、回転させるのは、第１円筒形導電体と第２円筒形導電体のいずれでもよく、また、双方の円筒形導電体を同時に回転させてもよい。
この回転手段は、通常のモーター駆動を利用した手段でよく，ガスの処理量や種類によっても異なるが、１０００〜６０００ｒｐｍ、好ましくは２０００〜５０００ｒｐｍの範囲で回転させることができる手段が適切である。
【００２５】
本発明のガス浄化装置は、触媒材料層と誘電体層の間の微小間隙にプラズマを発生させる手段をさらに備える。このプラズマ発生手段は、触媒材料層と誘電体層の間で放電が生じる電圧を印加することができる任意の手段でよい。必要な放電電圧は、主として微小間隙の距離、触媒材料層と誘電体層の材料によって決まるが、３０ｋＶ以下、より好ましくは２０ｋＶ以下となるように、微小間隙の距離等を調整することが望ましい。
【００２６】
この放電電圧の電源は、交流電源と直流電源のいずれを用いてもよいが、触媒材料層と誘電体層の間の微小間隙中のプラズマ密度を高めるためには交流電源のほうが適切である。交流電源を用いた場合の周波数は、処理すべきガスの種類等によって適切に選択されるが、０．１〜５０ｋＨｚが一応の目安である。
このような電源ラインに、第１円筒形導電体と第２円筒形導電体を接続することにより、触媒材料層と誘電体層の間の微小間隙にプラズマを発生させる手段を形成することができる。また交流電源を用いることで、スパッタリングによる電源表面処理物質の消耗を避けることができる。
【００２７】
次に、本発明の方法のガス浄化方法を具体的に説明する。
この方法においては、上述のような触媒材料層と誘電体層の間に形成された円筒形微小間隙にプラズマ発生させ、第１円筒形導電体と第２円筒形導電体の少なくとも一方をその円筒形中心軸の周りに回転させながら、円筒形微小間隙に処理すべきガスを導く。
【００２８】
円筒形微小間隙にプラズマを発生させるための印加電圧、交流電圧又は直流電圧の選択、交流電圧の場合の周波数は、処理されるガスに応じて適宜選択されることができるが、Ｏ2を比較的多量に含むＮＯX含有ガスを処理する場合、５〜１５ｋＶで１〜１０ｋＨｚの高周波電圧を印加するのが適切である。
【００２９】
回転させる第１円筒形導電体又は第２円筒形導電の回転数は、処理されるガスによって適宜選択されるが、Ｏ2を比較的多量に含むＮＯX含有ガスを処理する場合、５００〜５０００ｒｐｍが適切である。
かかる条件下で、円筒形微小間隙にガスを導き、この円筒形微小間隙を単に通過させることで、ガスを浄化することができ、この方法においては、Ｏ2を比較的多量に含むガスであっても、含まれるＮＯXを常温常圧の条件下で浄化することができる。
【００３０】
【実施例】
実施例１
図１に、本発明のガス浄化装置のプラズマ生成部を例示しており、このプラズマ生成部は、表面に触媒材料層１を有する第１円筒形導電体２と、表面に誘電体層３を有する第２円筒形導電体４で形成される。第１円筒形導電体は第２円筒形導電体の外側に配置され、第１円筒形導電体の内側面には厚さ５μｍの触媒材料層１が存在し、第２円筒形導電体の外側面には厚さ３ｍｍのガラス誘電体層３が存在する。触媒材料層１と誘電体層３で挟まれた空間が反応部５である。
【００３１】
第１円筒形導電体と第２円筒形導電体は、いずれもステンレス鋼で作製した。第１円筒形導電体として、その内側面に触媒層として白金層を５μｍの厚さで堆積させたものを用いた。
第１円筒形導電体の外径は３００ｍｍで、プラズマ生成部の間隙は１ｍｍ、間隙の長さは２０ｍｍとした。
【００３２】
図２に、図１のプラズマ生成部を備えたガス浄化装置を例示する。この装置は、プラズマ生成部、円筒形導電体の回転制御部、ガス流路を備える。
【００３３】
この装置を用い、第１円筒形導電体と第２円筒形導電体の間に１０ｋＶで５ｋＨｚ高周波電圧を印加して円筒形微小間隙にプラズマを発生させ、第１円筒形導電体を３０００ｒｐｍで回転させ、下記の組成の常温常圧のガスをマスフローコントローラーで制御しながら５００ｃｃ／分の流量で流した。
【００３４】
ガス組成：
５００ｐｐｍＮＯ＋６５０ｐｐｍＣ3Ｈ6＋５〜１０％Ｏ2（残余窒素）
出ガスのＮＯX濃度を測定し、下記の式によってＮＯX浄化率を求めた。
ＮＯX浄化率＝〔（入ガス濃度−出ガス濃度）÷入ガス濃度〕×１００
【００３５】
実施例２
第１円筒形導電体として、その内側面に触媒層として銅層を電気メッキによって５μｍの厚さで堆積させたものを用いた以外は実施例１と同様にして、ＮＯX浄化率を求めた。
【００３６】
比較例１
第１円筒形導電体として、その内側面に触媒層を堆積させていないものを用いた以外は実施例１と同様にして、ＮＯX浄化率を求めた。
【００３７】
比較例２
第１円筒形導電体と第２円筒形導電体の間に高周波電圧を印加せず、筒形微小間隙にプラズマを発生させない以外は実施例１と同様にして、ＮＯX浄化率を求めた。
【００３８】
比較例３
第１円筒形導電体と第２円筒形導電体の間に高周波電圧を印加せず、筒形微小間隙にプラズマを発生させない以外は実施例２と同様にして、ＮＯX浄化率を求めた。
【００３９】
−ＮＯX浄化率の結果−
図３に、上記の実施例と比較例において求めたＮＯX浄化率をまとめて示す。
結果より、実施例においては、Ｏ2を５％以上含むガスでも、常温常圧の条件下でＮＯX浄化ができている。これに対し、プラズマのみ又は触媒のみの系では、ＮＯXが全く浄化されていない。したがって、プラズマとＮＯXを複合することの効果が明らかに分かる。
【００４０】
このように、本発明では、Ｏ2を含むガスであっても、常温常圧の条件下でＮＯX浄化が実現できており、したがって、例えば、三元触媒のような触媒単独系では浄化できなかった温度が低い始動時の自動車の排気ガス等に対しても適用できる可能を見出していると言える。
【００４１】
【発明の効果】
Ｏ2を比較的多量に含むガスであっても、含まれるＮＯXを常温常圧で浄化することができ、また、ガス浄化装置の設備効率を高めることができる。
【図面の簡単な説明】
【図１】本発明のガス浄化装置のプラズマ発生部を示す。
【図２】本発明のガス浄化装置を示す。
【図３】実施例と比較例のＮＯX浄化率を示す図である。
【符号の説明】
１…触媒材料層
２…第１円筒形導電体
３…誘電体層
４…第２誘電体層
５…反応部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus and a method for purifying harmful components contained in exhaust gas discharged from automobiles and various manufacturing facilities, and more particularly, to an exhaust gas containing a relatively large amount of O 2 even in an exhaust gas. The present invention relates to an exhaust gas device and a method capable of purifying contained NO X under normal temperature and normal pressure.
[0002]
[Prior art]
Various methods have been proposed for purifying harmful components contained in exhaust gas discharged from automobiles, various types of manufacturing equipment, and the like.
As one of them, a composite system in which a catalyst and a plasma are combined has been proposed. According to such a composite system, a synergistic effect of a selective reaction promoting action of the catalyst and an exciting action of a specific chemical species by the plasma causes the catalyst and the catalyst to be combined. Gas purification performance that cannot be obtained with each single system of plasma can be expected. For example, not been realized in the conventional catalyst alone system, a NO X purifying by direct decomposition reaction of the NO X as follows.
NO → 1 / 2N 2 + 1 / 2O 2
[0003]
As prior art relating to such a composite system of a catalyst and plasma, for example, there are JP-A-6-106025, JP-A-7-109555, JP-A-10-169431 and JP-A-11-319486. , NO x purification and the like are disclosed.
[0004]
However, in these prior arts, the gas that can be processed is extremely limited, and furthermore, there is a defect in equipment efficiency that the gas processing capacity is low with respect to the power required for plasma generation and the equipment scale. The reason for this is that the region where the plasma is generated is far from the region where the catalyst is present, and the catalyst and plasma do not coexist in the reaction region, so the plasma is not effectively used, or radicals excited by the plasma react with each other. It is presumed that the catalyst easily passes through the region and the contact probability between the radical and the catalyst is low.
[0005]
On the other hand, the present inventors have proposed in Japanese Patent Application Laid-Open No. 6-262032 a gas treatment apparatus based on the technical idea of generating plasma in a region where a catalyst is present, that is, coexisting a catalyst and plasma in a reaction region. are doing.
Further, in JP-A-7-185266 and JP-A-7-204469, in order to increase the contact probability between a gas and a catalyst, plasma is formed between a rotating fan and the inner wall of a reactor, and a catalyst layer is formed on the inner wall of the reactor. And a gas reactor in which a catalyst and a plasma coexist between a rotating plate and a stationary plate is proposed in International Patent Application WO 96/20783.
[0006]
These catalysts and plasma coexist, and in a system having a dynamic mechanism to the electrode or the like, the type of processable gas will expand, especially in terms such as NO X under the conditions of normal temperature and pressure can be purified Results have been obtained.
[0007]
[Problems to be solved by the invention]
However, even by such improvement, as can be processed gas, in the purification of NO X, Applies to gas containing no O 2 is limited, the gas containing several% by volume of O 2, NO X purification performance expression There is a problem that is not done. In addition, there is a disadvantage in terms of equipment efficiency that the equipment scale is large with respect to gas processing capacity.
On the other hand, the three-way catalyst or the like of the catalyst alone systems currently mounted on an automobile, in order to exert a NO X purification performance beginning at a high temperature of several 100 ° C., NO for an exhaust gas temperature is low for example at start-up There is a problem that X is hardly purified.
[0008]
Accordingly, the present invention provides such a catalyst and to composite systems further improvement of the plasma, to expand the types of processable gases, among other things, comparing such as automotive exhaust gas which is operated under lean conditions, an O 2 even NO X containing gas comprising the multimer, and an object thereof is to enable NO X purification under normal temperature and pressure.
[0009]
[Means for Solving the Problems]
The gas purifying apparatus of the present invention includes a first cylindrical conductor having a catalyst material layer on a surface thereof, and a second cylindrical conductor having a dielectric layer on a surface thereof. The cylindrical conductor is coaxial, the catalyst material layer and the dielectric layer face each other, a cylindrical minute gap is provided between the catalyst material layer and the dielectric layer, and the first cylindrical conductor and you comprising the means for plasma generation means, and the cylindrical small gap rotates around its cylindrical central axis at least one of said second cylindrical conductor.
[0010]
According to the apparatus of the present invention, be a gas containing O 2, the NO X contained purified, i.e., it is possible to reduce the concentration of NO X in the gas by reducing the NO X to N 2 . This NO X purification is possible even with a gas at normal temperature and normal pressure. The apparatus of the present invention can also be applied to NO x purification of a gas containing no O 2 . Further, according to the apparatus of the present invention, the plasma generation region can be made compact for the same processing gas amount, and the equipment efficiency is remarkably improved. It is considered that the reason for this is that the probability of contact between radicals excited by plasma or the probability of contact between radicals and the catalyst is significantly increased, and mutual energy exchange is likely to occur.
[0011]
The gas purification method of the present invention is characterized in that the first cylindrical conductor having a catalyst material layer on the surface and the second cylindrical conductor having a dielectric layer on the surface are coaxially arranged so that the catalyst material layer Plasma is generated in a cylindrical minute gap formed between the dielectric layers, and at least one of the first cylindrical conductor and the second cylindrical conductor is rotated around the cylindrical central axis, it characterized by directing gas to be treated to the cylindrical small gap.
According to the method of the present invention, be a gas containing O 2, the NO X contained purified, i.e., it is possible to reduce the concentration of NO X in the gas by reducing the NO X to N 2 . This NO X purification is possible even with a gas at normal temperature and normal pressure. The method of the present invention can also be applied to NO x purification of a gas containing no O 2 , and the type of gas applicable in a combined system of catalyst and plasma can be significantly expanded.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
According to gas purification apparatus and method of the present invention, the NO X in the gas containing NO X and O 2, it can be cleaned in the presence of a catalyst and the plasma.
That is, according to the gas purifying apparatus and method of the present invention, under conditions where the catalyst and the plasma is "coexist", by selecting appropriate conditions, be a gas containing O 2 NO X is in purifying available- is there.
[0013]
Here, “coexistence” in the description of this specification means that a catalyst is present in a region where plasma is generated, specifically, that plasma is generated in a region where the catalyst is present.
Requirements for purifying NO X in O 2 presence is not limited, excited radicals mutual contact probability by plasma, or the probability of contact between the radical and the catalyst is significantly elevated condition it is conceivable that. Specific embodiments are not exhaustive, and those skilled in the art can easily confirm and realize them based on the disclosure of the present invention.
[0014]
Under the condition that the contact probability between radicals excited by the plasma in the coexistence of the catalyst and the plasma, or the contact probability between the radical and the catalyst was significantly increased, the conventional catalyst / plasma composite system was simply directed. However, the following direct decomposition reaction of NO X can actually occur, and since this reaction can contribute to NO X purification to a considerable extent, it is a gas containing O 2 at normal temperature and normal pressure. it is believed to be able to reduce and purify the NO X even.
NO → 1 / 2N 2 + 1 / 2O 2
In the gas purification method and apparatus of the present invention, it has been confirmed that NO X can be purified even with a gas containing O 2 concentration of 3% by volume or more, and even 5% by volume or more.
[0015]
In the gas purification method and apparatus according to the present invention, in particular, since the catalyst material layer or the derivative layer faces each other and at least one of them rotates, the catalyst and the plasma coexist, and the contact probability of radicals excited by the plasma with each other. Or a condition in which the probability of contact between the radical and the catalyst is significantly increased.
[0016]
Next, specifically described gas purifying apparatus of the present invention.
The first cylindrical conductor has a catalyst material layer on the surface. Since the surface of the first cylindrical conductor is also used as an electrode for plasma generation, the catalyst material layer is preferably made of a conductive metal.
[0017]
Catalytic metals are preferably iridium, chromium, cobalt, zirconium, cesium, tungsten, tantalum, titanium, iron, tellurium, niobium, nickel, platinum, vanadium, hafnium, palladium, manganese, which are classified as transition metals. It is selected from molybdenum, ruthenium, rhenium and rhodium. Among these, the noble metals of platinum, palladium, ruthenium and rhodium are most preferably used.
[0018]
These catalyst metal layers can be formed by electroplating or chemical plating, and the thickness is not particularly limited, but is preferably formed to about 3 to 10 μm.
[0019]
The second cylindrical conductor has a dielectric layer on the surface. By forming the dielectric layer, localization of plasma is suppressed, and uniform plasma is formed over the entire cylindrical minute gap between the first cylindrical conductor and the second cylindrical conductor. And silent discharge is obtained.
[0020]
The dielectric layer is not particularly limited, but is formed by coating a glass film, a ceramic film such as alumina or silica on a conductor by a chemical vapor deposition method, a vacuum vapor deposition method, thermal spraying, or the like. The thickness is not particularly limited, but is suitably 5 mm or less, preferably 1 mm or less, more preferably about 100 μm, from the viewpoint of not excessively increasing the discharge voltage.
The material of the first cylindrical conductor and the second cylindrical conductor is suitably a conductive metal, and can be selected from a wide range of materials such as copper, copper alloy, and stainless steel.
[0021]
When the first cylindrical conductor and the second cylindrical conductor are rotated, the distance between the minute gap between the catalyst material layer on the first cylindrical conductor and the dielectric layer on the second cylindrical conductor is changed. Are coaxially arranged so that does not substantially vary.
[0022]
The catalyst material layer and the dielectric layer are arranged such that the layers face each other. Here, the catalyst material layer is disposed outside and therefore the first cylindrical conductor is disposed outside the second cylindrical conductor, or the catalyst material layer is disposed inside and thus the first cylindrical conductor is disposed in the second cylindrical conductor. It may be arranged inside the shaped conductor.
[0023]
The minute gap between the catalyst material layer and the dielectric layer may be 0.2-5 mm, preferably 0.5-2 mm. If the minute interval is less than about 0.2 mm, the space for purifying the gas becomes narrow and the gas throughput decreases, and if it exceeds about 2 mm, the voltage for generating plasma discharge becomes excessively high.
[0024]
The gas purifying apparatus of the present invention further includes means for rotating at least one of the first cylindrical conductor and the second cylindrical conductor around a central axis of the cylinder. Here, either the first cylindrical conductor or the second cylindrical conductor may be rotated, or both cylindrical conductors may be rotated simultaneously.
This rotating means may be a means using a normal motor drive, and although it varies depending on the amount and type of gas treatment, a means capable of rotating in the range of 1000 to 6000 rpm, preferably 2000 to 5000 rpm is appropriate.
[0025]
The gas purification device of the present invention further includes a means for generating plasma in a minute gap between the catalyst material layer and the dielectric layer. The plasma generating means may be any means capable of applying a voltage at which a discharge occurs between the catalyst material layer and the dielectric layer. The required discharge voltage is mainly determined by the distance between the minute gaps and the materials of the catalyst material layer and the dielectric layer. It is desirable to adjust the distance between the minute gaps and the like so as to be 30 kV or less, more preferably 20 kV or less.
[0026]
As the power source for the discharge voltage, either an AC power source or a DC power source may be used, but the AC power source is more suitable for increasing the plasma density in the minute gap between the catalyst material layer and the dielectric layer. The frequency when an AC power supply is used is appropriately selected depending on the type of gas to be processed and the like, but 0.1 to 50 kHz is a rough guide.
By connecting the first cylindrical conductor and the second cylindrical conductor to such a power supply line, a means for generating plasma in a minute gap between the catalyst material layer and the dielectric layer can be formed. . In addition, by using an AC power supply, consumption of a power supply surface treatment substance due to sputtering can be avoided.
[0027]
Next, specifically described gas purification method of the process of the present invention.
In this method, plasma is generated in the cylindrical minute gap formed between the catalyst material layer and the dielectric layer as described above, and at least one of the first cylindrical conductor and the second cylindrical conductor is placed in the cylindrical shape. The gas to be treated is introduced into the cylindrical minute gap while rotating around the central axis of the shape.
[0028]
Applied voltage for generating plasma in cylindrical minute gap, selection of AC voltage or DC voltage, frequency when the AC voltage may be appropriately selected according to the gas to be treated, compared to O 2 when processing NO X containing gas comprising the multimer, it is appropriate to apply a high frequency voltage 1~10kHz in 5～15KV.
[0029]
If the rotational speed of the first cylindrical conductor or second cylindrical conductive rotating is appropriately selected depending on the gas to be treated, for processing the NO X containing gas containing O 2 in a relatively large amount, 500～5000Rpm Is appropriate.
Under such conditions, the gas can be purified by introducing the gas into the cylindrical minute gap and simply passing through the cylindrical minute gap. In this method, the gas containing a relatively large amount of O 2 is used. Even so, the contained NO X can be purified under the condition of normal temperature and normal pressure.
[0030]
【Example】
Example 1
FIG. 1 illustrates a plasma generation unit of the gas purification apparatus of the present invention. The plasma generation unit includes a first
[0031]
The first cylindrical conductor and the second cylindrical conductor were both made of stainless steel. The first cylindrical conductor used was a platinum layer having a thickness of 5 μm deposited on its inner surface as a catalyst layer.
The outer diameter of the first cylindrical conductor was 300 mm, the gap between the plasma generating sections was 1 mm, and the length of the gap was 20 mm.
[0032]
FIG. 2 illustrates a gas purification apparatus including the plasma generation unit of FIG. This device includes a plasma generation unit, a rotation control unit for a cylindrical conductor, and a gas flow path.
[0033]
Using this device, a high-frequency voltage of 10 kHz is applied between the first cylindrical conductor and the second cylindrical conductor to generate plasma in a small cylindrical gap, and the first cylindrical conductor is rotated at 3000 rpm. Then, a gas having the following composition at normal temperature and normal pressure was flowed at a flow rate of 500 cc / min while controlling with a mass flow controller.
[0034]
Gas composition:
500ppmNO + 650ppmC 3 H 6 + 5~10 % O 2 ( remainder nitrogen)
Out to measure the concentration of NO X gas was determined NO X purification rate by the following equation.
NO X purification rate = [(inlet gas concentration - outlet gas concentration) ÷ inflow gas concentration] × 100
[0035]
Example 2
The NO x purification rate was determined in the same manner as in Example 1 except that the first cylindrical conductor used was a copper layer deposited on the inner surface thereof as a catalyst layer to a thickness of 5 μm by electroplating. .
[0036]
Comparative Example 1
The NO x purification rate was determined in the same manner as in Example 1 except that the first cylindrical conductor having no catalyst layer deposited on its inner surface was used.
[0037]
Comparative Example 2
The NO X purification rate was determined in the same manner as in Example 1 except that no high-frequency voltage was applied between the first cylindrical conductor and the second cylindrical conductor, and no plasma was generated in the minute cylindrical gap.
[0038]
Comparative Example 3
The NO X purification rate was determined in the same manner as in Example 2 except that no high-frequency voltage was applied between the first cylindrical conductor and the second cylindrical conductor, and no plasma was generated in the minute cylindrical gap.
[0039]
-NO X purification rate of the results -
FIG. 3 collectively shows the NO X purification rates obtained in the above example and comparative example.
From the results, in the example, even with a gas containing 5% or more of O 2 , NO X purification was performed under the condition of normal temperature and normal pressure. In contrast, in a system of plasma alone or catalyst alone, NO X is not at all clean. Therefore, it is clearly seen effect of combined plasma and NO X.
[0040]
As described above, in the present invention, even if the gas contains O 2 , NO X purification can be realized under the condition of normal temperature and normal pressure. It can be said that the present invention has been found to be applicable to the exhaust gas of the automobile at the time of starting where the temperature is low.
[0041]
【The invention's effect】
Even if the gas contains a relatively large amount of O 2 , the contained NO X can be purified at normal temperature and pressure, and the equipment efficiency of the gas purification device can be improved.
[Brief description of the drawings]
1 shows a plasma generating portion of the gas purification system of the present invention.
2 shows a gas purification apparatus of the present invention.
FIG. 3 is a diagram showing NO X purification rates of an example and a comparative example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ...
Claims (2)
前記第１円筒形導電体と前記第２円筒形導電体の少なくとも一方をその円筒形中心軸の周りに回転させる手段、及び
前記円筒形微小間隙にプラズマ発生させる手段、
を備えたことを特徴とする、ガス浄化装置。A first cylindrical conductor having a catalyst material layer on the surface and a second cylindrical conductor having a dielectric layer on the surface, wherein the first cylindrical conductor and the second cylindrical conductor are coaxial; The catalyst material layer and the dielectric layer face each other, providing a cylindrical minute gap between the catalyst material layer and the dielectric layer,
Means for rotating at least one of the first cylindrical conductor and the second cylindrical conductor about a central axis thereof, and means for generating plasma in the cylindrical minute gap;
Characterized by comprising a gas purifier.
前記第１円筒形導電体と前記第２円筒形導電体の少なくとも一方をその円筒形中心軸の周りに回転させ、
前記円筒形微小間隙に処理すべきガスを導く、
ことを特徴とする、ガス浄化方法。A first cylindrical conductor having a catalyst material layer on its surface and a second cylindrical conductor having a dielectric layer on its surface are formed coaxially between the catalyst material layer and the dielectric layer. Plasma is generated in the small cylindrical gap,
Rotating at least one of the first cylindrical conductor and the second cylindrical conductor about a central axis thereof;
Guiding the gas to be processed to the cylindrical minute gap,
A gas purification method , characterized in that:
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