JP4709716B2 - Denitration catalyst for coal combustion exhaust gas and exhaust gas purification method - Google Patents
Denitration catalyst for coal combustion exhaust gas and exhaust gas purification method Download PDFInfo
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Images
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- 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
Description
本発明は石炭燃焼排ガス浄化用触媒及び排ガス浄化方法に係り、特にリン（P)、砒素（As)、カルシウム(Ca)などの蓄積性触媒毒が高濃度で含まれる排ガス脱硝に用いても、長時間高い活性を維持するに好適な窒素酸化物（NOx）のアンモニア（NH3）還元用脱硝触媒及び該触媒を用いた排ガス浄化方法に関する。 The present invention relates to a catalyst for purifying coal combustion exhaust gas and a method for purifying exhaust gas. In particular, even when used for exhaust gas denitration containing a high concentration of a storage catalyst poison such as phosphorus (P), arsenic (As), calcium (Ca), The present invention relates to a denitration catalyst for reducing nitrogen oxide (NOx) to ammonia (NH 3 ) suitable for maintaining high activity for a long time, and an exhaust gas purification method using the catalyst.
発電所、各種工場、自動車などから排出される排煙中の窒素酸化物（NOx）は、光化学スモッグや酸性雨の原因物質であり、その効果的な除去方法として、アンモニア（NH3）等を還元剤とした選択的接触還元による排煙脱硝法が火力発電所を中心に幅広く用いられている。触媒には、バナジウム（V）、モリブデン（Mo）またはタングステン（W）を活性成分にした酸化チタン（TiO2）系触媒が使用されており、特に活性成分の１つとしてバナジウムを含むものは活性が高いだけでなく、排ガス中に含まれている不純物による劣化が小さいこと、より低温から使用できることなどから、現在の脱硝触媒の主流になっている（特許文献１）。 Nitrogen oxides (NOx) in flue gas emitted from power plants, various factories, automobiles, etc. are causative substances of photochemical smog and acid rain. As an effective removal method, ammonia (NH 3 ), etc. is used. A flue gas denitration method using selective catalytic reduction as a reducing agent is widely used mainly in thermal power plants. As the catalyst, a titanium oxide (TiO 2 ) -based catalyst containing vanadium (V), molybdenum (Mo) or tungsten (W) as an active component is used. Particularly, one containing vanadium as an active component is active. In addition to being high, the deterioration due to impurities contained in the exhaust gas is small, and since it can be used from a lower temperature, it has become the mainstream of current denitration catalysts (Patent Document 1).
これらの触媒を石炭焚きボイラなどの排ガス中に多量のダストを含む排ガスの脱硝装置に用いる場合、摩耗強度が低いとダストによって触媒が摩耗し脱硝装置の運転に重大な支障を生じる。このため、触媒の摩耗強度の向上には細心の注意が払われており、このための方法も各種のものが知られている。その代表的なものとして、触媒体にシリカゾルのような結合材を含浸する方法（特許文献２）、酸化モリブデンを多量に添加した触媒を高温で焼成後、硫酸アルミニウムなどの結合剤とともに混練する方法（特許文献３）などが知られている。
上記公知の石炭焚用脱硝触媒は、初期の性能が高く、石炭燃焼灰によっても摩耗することがなく、優れたものであるが、近年、米国や中国産の石炭を燃焼するボイラが多くなるにつれて、その中に多量に含まれるリン（P)、砒素（As),カルシウム（Ca)、鉄（Fe)などの触媒毒が脱硝表面に析出して性能を急激に低下させることが問題となっている。即ち、外見上は摩耗することなく、極めて健全と思われる脱硝触媒が、上記蓄積性毒物により劣化し、頻繁な触媒交換が余儀なくされている。そればかりでなく、これらの蓄積毒物は、広く用いられている脱硝触媒の主成分である酸化チタンに強固に吸着しているため、再生処理も容易ではなく、再利用の観点からも問題が多いことが分った。 The known denitration catalyst for coal soot is excellent in initial performance and is not worn by coal combustion ash. However, in recent years, as the number of boilers that burn coal from the United States and China increases. It is a problem that catalyst poisons such as phosphorus (P), arsenic (As), calcium (Ca), iron (Fe), etc. contained in large quantities in the precipitates are deposited on the denitration surface and the performance is drastically reduced. Yes. That is, the NOx removal catalyst that appears to be extremely healthy without being worn out is deteriorated by the accumulative poison, and frequent catalyst replacement is unavoidable. In addition, these accumulated poisons are strongly adsorbed on titanium oxide, which is the main component of the widely used denitration catalyst, so that the reprocessing is not easy and there are many problems from the viewpoint of reuse. I found out.
本発明の課題は、上記従来技術の問題点に鑑み、蓄積性の触媒毒を高濃度で含む石炭排ガスに用いても、可及的に性能低下の小さい脱硝触媒及び脱硝方法を提供すること、不純物の多い低質石炭を環境への負荷を少なく使用できるようにすること、加えて、上記用途に用いた触媒の再利用法を提供し、循環型社会の建設に貢献することにある。 An object of the present invention is to provide a denitration catalyst and a denitration method that have as little performance degradation as possible even when used in coal exhaust gas containing a high concentration of accumulative catalyst poisons in view of the problems of the prior art. It is intended to contribute to the construction of a recycling society by making it possible to use low quality coal with a lot of impurities and reducing the burden on the environment, as well as providing a method for reusing the catalyst used in the above applications.
上記課題を達成するため、本願で特許請求される発明は、以下のとおりである。
（１）メタルラス基材に酸化チタンを主成分とする触媒成分をラス目を埋めるように添着した板状脱硝触媒であって、該触媒の表裏両面にメタルラスの切り目の凸部が点状に露出されており、かつメタルラスの切り目を埋める触媒成分の細孔容積が0.3ml/g以上であることを特徴とする蓄積性触媒毒を含有する石炭燃焼排ガス用脱硝触媒。
（２）（１）記載の触媒を用いた触媒反応器に、還元剤を注入した窒素酸化物を含む石炭燃焼排ガスを導入して窒素酸化物の還元を行うと共に、排ガスに含まれる石炭燃焼灰で触媒表面を徐々に摩耗させ、新しい触媒面を露出させることを特徴とする、蓄積性触媒毒を含有する石炭燃焼排ガスの浄化方法。
（３）（２）記載の排ガスの浄化方法において、触媒表面が摩滅した触媒を抜出し、該触媒表面に細孔容積が0.3ml/g以上の触媒成分を担持後、該触媒を前記反応器に戻して再使用することを特徴とする排ガスの浄化方法。
To achieve the above object, the invention claimed in the present application is as follows.
(1) A plate-type denitration catalyst in which a catalyst component mainly composed of titanium oxide is attached to a metal lath base material so as to fill the lath, and the convex portions of the metal lath notches are exposed on both sides of the catalyst in the form of dots. A denitration catalyst for coal combustion exhaust gas containing an accumulative catalyst poison, wherein the pore volume of the catalyst component filling the metal lath cut is 0.3 ml / g or more.
(2) The coal combustion ash contained in the exhaust gas is introduced into the catalytic reactor using the catalyst described in (1) by introducing the coal combustion exhaust gas containing nitrogen oxide into which the reducing agent is injected to reduce the nitrogen oxide. A method for purifying coal combustion exhaust gas containing an accumulative catalyst poison, wherein the catalyst surface is gradually worn to expose a new catalyst surface.
(3) In the exhaust gas purification method according to (2), the catalyst with a worn catalyst surface is extracted, and a catalyst component having a pore volume of 0.3 ml / g or more is supported on the catalyst surface, and then the catalyst is placed in the reactor. A method for purifying exhaust gas, wherein the exhaust gas is returned and reused.
本発明によれば、触媒成分の改良では防止することのできないリン、砒素などの蓄積性触媒毒による急激な脱硝性能の低下を防止できる。また触媒成分が摩損した触媒は、簡単な操作で再生することができるため、急激な触媒活性の低下後、新しい触媒に取り替えざるを得ない従来の方法に比べれ、経済的にも優れている。 According to the present invention, it is possible to prevent a rapid decrease in the denitration performance due to a storage catalyst poison such as phosphorus and arsenic that cannot be prevented by improving the catalyst component. In addition, since a catalyst with a worn catalyst component can be regenerated by a simple operation, it is economically superior to a conventional method in which a new catalyst must be replaced after a rapid decrease in catalyst activity.
以下、本発明を詳細に説明する。
石炭排ガスに含まれる蓄積性毒物は、酸化チタンを主成分にする脱硝触媒と極めて親和力が強く、下記のように挙動する。
(1) 触媒の表面に集中的に吸着され、その後徐々に内部に吸着されるようになる。
(2) 触媒層の上流側に選択的に吸着され易く、入り口部の表面が吸着飽和に達すると徐々に出口部分に吸着される。
(3) 触媒活性の劣化は、触媒毒成分による活性点への吸着に因るものと、大量の毒物が触媒表面に吸着・析出して細孔を閉塞し、健全な内部に存在する触媒にガスが接触することができなくなるものとの二つの原因がある。蓄積性の毒物が徐々に増加することに対し急激な活性低下を引き起こすのは、後者によるものが大きい。
Hereinafter, the present invention will be described in detail.
The accumulative poison contained in coal exhaust gas has extremely strong affinity with a denitration catalyst mainly composed of titanium oxide, and behaves as follows.
(1) It is intensively adsorbed on the surface of the catalyst and then gradually adsorbs inside.
(2) It is easily adsorbed selectively on the upstream side of the catalyst layer, and when the surface of the inlet reaches adsorption saturation, it is gradually adsorbed on the outlet.
(3) Deterioration of catalyst activity is due to adsorption to active sites by catalyst poison components, and a large amount of poisons are adsorbed and deposited on the catalyst surface to block pores, resulting in a catalyst present in a healthy interior. There are two causes, the gas being unable to contact. The latter causes a large decrease in activity against the gradual increase in accumulative poisons.
このように、蓄積性触媒毒による劣化は、触媒成分の改良だけで防止することは不可能であり、蓄積性毒物による被毒現象に基づく対策が必要であることは明らかである。他方、若し、触媒表層部に析出した触媒毒を排ガスに含まれる灰粒子などで摩耗・除去し、常に新しい未劣化の触媒面を露出させることができれば、急激な活性低下を防止することが可能である。 As described above, it is impossible to prevent the deterioration due to the accumulative catalyst poison only by improving the catalyst component, and it is clear that a countermeasure based on the poisoning phenomenon due to the accumulative poison is necessary. On the other hand, if the catalyst poison deposited on the catalyst surface layer is worn and removed with ash particles contained in the exhaust gas, and a new undegraded catalyst surface can always be exposed, a rapid decrease in activity can be prevented. Is possible.
本発明の狙いは正にここにあり、そのためには次の事柄が実現される必要がある。
(1)板状触媒の表裏の摩耗が同一速度で進行すること。
(2)ガス流れが層流に近くなる触媒層内部でも摩耗が進行すること。
(3)また、摩耗量が入り口部のみに集中しないこと。
(4)触媒の摩損によりガス流れによる圧損変化が小さいこと。
本発明の触媒がこれらの点を如何に達成しているかを以下に示す。
The aim of the present invention is exactly here, and for that purpose, the following matters need to be realized.
(1) The front and back wear of the plate catalyst proceeds at the same speed.
(2) Wear also proceeds inside the catalyst layer where the gas flow is close to laminar flow.
(3) Also, the amount of wear should not be concentrated only at the entrance.
(4) Change in pressure loss due to gas flow is small due to catalyst wear.
The following shows how the catalyst of the present invention achieves these points.
図１(A)は本発明の触媒を模式的に示したものである。本発明の触媒は、その表裏面の、添着した触媒成分面にメタルラス基材の切断面が突起状に露出した構造を有する。かかる構造の場合、灰を含むガスが流入すると、ガスが突起部分で乱され、渦流を作り、その下流部で摩耗が進行する。本発明の触媒では、突起部が表裏に存在するため、図１(B)の如く表裏両面から均等に摩耗が進行するため、摩耗が局部的に起こり、例えば触媒成分が大きな塊で脱落することがなくなる。すなわち、図２(A)のように、メタルラス基材の突起部が片面にのみ存在すると、摩耗が図２(B)の如く、突起の存在する面のみ進行し、触媒成分の塊状脱落の原因になる。また、金属基板表面に、触媒成分が大量に存在し、突起部分が無い場合には、図３のように摩耗が触媒層入り口部の乱流域に限られ、析出した触媒毒の除去が内部の方に十分進行しないという問題を生じる。 FIG. 1 (A) schematically shows the catalyst of the present invention. The catalyst of the present invention has a structure in which the cut surface of the metal lath substrate is exposed in a protruding manner on the attached catalyst component surface on the front and back surfaces. In the case of such a structure, when a gas containing ash flows in, the gas is disturbed at the protruding portion, creating a vortex, and wear progresses downstream thereof. In the catalyst of the present invention, since the protrusions are present on the front and back surfaces, wear progresses evenly from both the front and back surfaces as shown in FIG. 1B, so wear occurs locally, for example, catalyst components fall off in large lumps. Disappears. That is, as shown in FIG. 2 (A), if the protrusion of the metal lath substrate exists only on one side, the wear proceeds only on the surface where the protrusion exists as shown in FIG. become. Further, when a large amount of catalyst components are present on the surface of the metal substrate and there are no protrusions, wear is limited to the turbulent flow region at the entrance of the catalyst layer as shown in FIG. Cause the problem of not progressing sufficiently.
さらに、押し出し成形ハニカム触媒体のように金属基材を用いない場合には、図３(A)の如く入り口部から摩耗が進行し、触媒の摩損した流路が発生する。摩損した部分の圧損は他部に比し低下しているため、その部分に灰を含むガスが集中的に流れるようになり、摩損進行速度が更に加速される。その結果、図３(B)の如く流路が侵食的に欠損した部分が発生し、問題を引き起こす。これに対し、本発明では、図１(B)のような均一の摩耗が実現できる上、仮に図４のように摩耗したとしても、金属基板が残るため、圧損のアンバランスを生じない。このように本発明の触媒は、触媒表面に析出した毒物を均一に除去する好適な形を有する。 Further, when a metal substrate is not used as in the case of an extruded honeycomb catalyst body, wear proceeds from the entrance as shown in FIG. 3A, and a flow path in which the catalyst is worn is generated. Since the pressure loss of the worn portion is lower than that of the other portion, the gas containing ash flows intensively in that portion, and the wear progressing speed is further accelerated. As a result, as shown in FIG. 3B, a portion where the flow path is eroded is generated, causing a problem. On the other hand, in the present invention, uniform wear as shown in FIG. 1 (B) can be realized, and even if it is worn as shown in FIG. Thus, the catalyst of the present invention has a suitable form for uniformly removing poisons deposited on the catalyst surface.
一方、触媒に付着した蓄積性毒物を摩耗により除去するためには、通常の脱硝条件で触媒が適度な速度で摩耗することが必要である。このため、本発明者等は、公知の各種触媒成分について、石焚燃焼灰による摩耗速度を調べ、(i)酸化チタン系触媒では図５のように細孔容積と明確な関係が有ること、(ii)通常の条件では、触媒の細孔容積を0.3ml/g以上、好ましくは0.3ml/gを越えた近傍（0.3〜0.4ml/g）に選定すればよいこととを見出した。 On the other hand, in order to remove the accumulative poison attached to the catalyst by abrasion, it is necessary that the catalyst is worn at an appropriate speed under normal denitration conditions. For this reason, the present inventors investigated the wear rate due to stalagmite combustion ash for various known catalyst components, and (i) the titanium oxide-based catalyst has a clear relationship with the pore volume as shown in FIG. (ii) It has been found that under normal conditions, the pore volume of the catalyst may be selected in the vicinity of 0.3 ml / g or more, preferably exceeding 0.3 ml / g (0.3 to 0.4 ml / g).
本発明の触媒は、酸化チタンを主成分とし、これにタングステン（W)、モリブデン（Mo)またはバナジウム（V)の化合物を添加した公知の触媒成分に、必要に応じて無機繊維、結合剤などを加えて混練したペースト状物を、SUS製メタルラス基材にローラプレス機を用いて圧着することにより得られる。この時、基材とローラとの間に吸水紙、ポリエチレンシートなど、弾性または可塑性のあるシート状物を挿入することにより、図１のように触媒成分層からメタルラス基材の突起部を最上部として突出させることが可能である。また、シート厚さを変えることにより、露出する突起部分の高さをコントロールすることも可能である。このようにして得られた触媒体は、波型成形などでスペーサ部分に相当する形状を付された後、枠に入れてユニット状にされると共に、乾燥、焼成など周知の方法で触媒構造体（ユニット）とされる。 The catalyst of the present invention contains titanium oxide as a main component, and a known catalyst component in which a compound of tungsten (W), molybdenum (Mo) or vanadium (V) is added thereto, and if necessary, inorganic fibers, binders, etc. The paste-like material kneaded with and added to the SUS metal lath substrate is pressure-bonded using a roller press. At this time, by inserting an elastic or plastic sheet material such as water-absorbing paper or polyethylene sheet between the base material and the roller, the protrusion of the metal lath base material from the catalyst component layer as shown in FIG. Can be projected as It is also possible to control the height of the exposed protrusion by changing the sheet thickness. The catalyst body thus obtained is given a shape corresponding to the spacer portion by wave forming or the like, and then put into a frame to form a unit, and the catalyst structure is formed by a known method such as drying and firing. (Unit).
このようにして得られた触媒ユニットは多数段積層して脱硝反応器内に装填され、これに還元剤としてNH3を注入した排ガスを350-400℃で供給して該排ガスの脱硝処理が行なわれる。その場合、全段を本発明の触媒で構成してもよいし、反応器のガス流入方向の一部に本願の触媒を用いてもよい。前述したように蓄積性触媒毒は入り口部分に優先的に析出傾向がある上、本発明方法では入り口部の触媒は摩耗により常に更新されているため、析出物が後流部に至る割合は極めて小さく、通常の触媒を用いても劣化は小さい。 The catalyst units obtained in this way are stacked in multiple stages and loaded into a denitration reactor, and exhaust gas into which NH 3 has been injected as a reducing agent is supplied at 350-400 ° C. to perform denitration treatment of the exhaust gas. It is. In that case, you may comprise all the stages with the catalyst of this invention, and may use the catalyst of this application for a part of gas inflow direction of a reactor. As described above, the accumulation catalyst poison tends to be preferentially deposited at the entrance portion, and in the method of the present invention, the catalyst at the entrance portion is constantly renewed due to wear. Therefore, the ratio of the deposit to the wake portion is extremely high. Even if a normal catalyst is used, the deterioration is small.
また本発明の変形として、反応器の入り口部に充填する触媒に酸化チタンのみを成分とする触媒を選び、その後流部にW、Mo、Vなどの活性成分を含む公知の触媒を用いることもできる。この場合、入り口部は蓄積性毒物を効率良く吸着除去するガード触媒として機能する。 As a modification of the present invention, it is also possible to select a catalyst containing only titanium oxide as a catalyst charged in the inlet of the reactor, and use a known catalyst containing an active component such as W, Mo, V in the downstream part. it can. In this case, the entrance functions as a guard catalyst for efficiently adsorbing and removing the accumulative poison.
かかる脱硝反応器で処理する排ガスの流速は、通常5〜6m/sに選定される。これより低いと灰が流路を閉塞するようになり、これより高いと圧損が高く、構造体の摩耗も進行し易くなるからである。それ故、通常6m/sでの摩耗速度が適切になるように触媒仕様を選定しておけば、大半の蓄積性触媒毒を含有する排ガスに対応することが可能である。 The flow rate of the exhaust gas treated in such a denitration reactor is usually selected to be 5 to 6 m / s. If it is lower than this, the ash will block the flow path, and if it is higher than this, the pressure loss is high, and the wear of the structure is likely to proceed. Therefore, if the catalyst specification is selected so that the wear rate at 6 m / s is appropriate, it is possible to deal with exhaust gas containing most of the accumulative catalyst poison.
摩耗が進行した本発明の触媒は、抜出した後、酸化チタンを含む触媒成分のスラリに浸漬後乾燥することにより容易に再生することが可能である。通常このようなスラリコーティング方法は密度が低く、摩耗強度の高いものが得がたい傾向があるが、本発明では適度な摩耗を必要とすることから、このような方法が好適である。従って本発明では、触媒製造、摩耗させながらの使用、触媒成分の再担持というサイクルを繰り返し、触媒基材を再利用することが可能である。 The catalyst of the present invention that has been worn out can be easily regenerated by being extracted and then immersed in a slurry of a catalyst component containing titanium oxide and then dried. Usually, such a slurry coating method tends to be difficult to obtain a low density and high wear strength. However, in the present invention, such a method is suitable because appropriate wear is required. Therefore, in the present invention, the catalyst base can be reused by repeating the cycle of catalyst production, use while being worn, and re-loading of the catalyst component.
以下、本発明を実施例により詳細に説明する。
［実施例１］
酸化チタン（石原産業社製、比表面積250m2/g）12kg、メタタングステン酸アンモニウム4.25kg（粉末状，WO3として93%）、シリカゾル（日産化学社製，商品名OXSゾル）4kgと水をニーダに入れて20分混練後、メタバナジン酸アンモニウム399gを添加して20分混練，シリカアルミナ系セラミック繊維（東芝ファインフレックス社製）を3.2kgを徐々に添加しながら30分間混練して、水分34％の触媒ペーストを得た。得られたペーストを厚さ0.2mmのSUS430製鋼板をメタルラス加工して厚さ0.8mmの基材の上に置き、これを二枚のポリエチレンシートに挟んで一対の加圧ローラを通して、メタルラス基材の網目間及び表面に塗布した。これを風乾後、500℃で2時間焼成して板状触媒を得た。得られた触媒の表裏面にはメタルラス基材の凸部が点状に顔を出しており、細孔容積は0.39ml/gであった。
Hereinafter, the present invention will be described in detail with reference to examples.
[Example 1]
Titanium oxide (Ishihara Sangyo Co., Ltd., specific surface area 250m 2 / g) 12kg, ammonium metatungstate 4.25kg (powder, 93% as WO 3 ), silica sol (Nissan Chemical Co., Ltd., trade name OXS sol) 4kg and water After kneading for 20 minutes in a kneader, add 399 g of ammonium metavanadate and knead for 20 minutes, kneading for 30 minutes while gradually adding 3.2 kg of silica-alumina ceramic fiber (manufactured by Toshiba Fineflex Co., Ltd.) % Catalyst paste was obtained. The obtained paste is made from a SUS430 steel plate with a thickness of 0.2 mm and placed on a 0.8 mm-thick substrate, sandwiched between two polyethylene sheets and passed through a pair of pressure rollers. It was applied between the mesh and the surface. This was air-dried and then calcined at 500 ° C. for 2 hours to obtain a plate catalyst. On the front and back surfaces of the obtained catalyst, the convex portions of the metal lath base material appeared as dots, and the pore volume was 0.39 ml / g.
［実施例２］
酸化チタン粉末（石原産業社製、表面積90m2/g）20kgにモリブデン酸アンモニウム（(NH4)6Mo7O24・4H2O）を2.44kg，メタバナジン酸アンモニウム0.5kg，蓚酸1.9kg，無機繊維（東芝ファインフレックス社製）4.63kgとに水を加えてニーダで混練，水分３３％の基材用ペーストを調製した。他は実施例1と同様にして板状触媒を得た。得られた触媒の細孔容積は0.36ml/gであった。
［実施例３］
実施例２のモリブデン酸アンモニウムを三酸化モリブデン（MoO3）に変更すると共に、シュウ酸をシリカゾル（日産化学社製，商品名OXSゾル）5kgに変更して、水分29%のペーストを作成し、他は同様にして触媒を得た。本触媒の細孔容積は0.30ml/gであった。
[Example 2]
Titanium oxide powder (Ishihara Sangyo Co., Ltd., surface area 90m 2 / g) 20kg, ammonium molybdate ((NH 4 ) 6 Mo 7 O 24 · 4H 2 O) 2.44kg, ammonium metavanadate 0.5kg, oxalic acid 1.9kg, inorganic Water was added to 4.63 kg of fibers (manufactured by Toshiba Fineflex) and kneaded with a kneader to prepare a base material paste with a moisture content of 33%. Otherwise, a plate catalyst was obtained in the same manner as in Example 1. The pore volume of the obtained catalyst was 0.36 ml / g.
[Example 3]
While changing the ammonium molybdate of Example 2 to molybdenum trioxide (MoO 3 ), oxalic acid was changed to 5 kg of silica sol (trade name OXS sol, manufactured by Nissan Chemical Co., Ltd.), and a paste with a moisture content of 29% was created. The catalyst was obtained in the same manner as others. The pore volume of this catalyst was 0.30 ml / g.
［比較例１］
実施例１の酸化チタンを表面積90m2/gの物に変更すると共に、シリカゾル添加量を8.1kgに変更して水分26%のペーストを得た。他は同様にして触媒化し、細孔容積0.28ml/gの触媒を得た。
［比較例２］
実施例３の三酸化モリブデンの添加量及びシリカゾル添加量を2倍に増加し水分25%のペーストを調製し、他は同様にして触媒を得た。本触媒の細孔容積は0.25ml/gであった。
［比較例３］
実施例１の塗布工程でローラ間に厚さ1.1mmのスペーサを入れ、触媒の裏面にはメタルラス板の凸部が露出しているが、表面は厚さ0.2mmの触媒層で覆われた触媒を得た。
[Comparative Example 1]
The titanium oxide of Example 1 was changed to one having a surface area of 90 m 2 / g, and the amount of silica sol added was changed to 8.1 kg to obtain a paste with a moisture content of 26%. Others were catalyzed in the same manner to obtain a catalyst having a pore volume of 0.28 ml / g.
[Comparative Example 2]
The amount of molybdenum trioxide added in Example 3 and the amount of silica sol added were doubled to prepare a paste with a water content of 25%, and a catalyst was obtained in the same manner as the others. The pore volume of this catalyst was 0.25 ml / g.
[Comparative Example 3]
In the coating process of Example 1, a spacer having a thickness of 1.1 mm is inserted between the rollers, and the convex portion of the metal lath plate is exposed on the back surface of the catalyst, but the surface is covered with a catalyst layer having a thickness of 0.2 mm. Got.
［試験例１］
実施例１〜３、比較例１及び２の触媒の摩耗速度を把握するため、石炭燃焼灰を含む空気を表１の条件でノズルを用いて触媒に吹き付ける摩耗試験を行った。得られた結果を表２に纏めて示した。細孔容積が0.3ml/gを境に摩耗の進行の有無が明確に分かれ、蓄積性毒物を使用環境下で灰粒子で摩耗除去させるためには細孔容積を0.3ml/g以上に選定することが必要であることが分かった。
［試験例２］
実施例２と比較例３の触媒について、表面と裏面とで表１の条件の摩耗試験を実施した。得られた結果を表３に纏めて示す。メタルラス板の凸部が両面に露出している実施例２では表裏の摩耗量は同等であるが、比較例３の凸部が露出していない表面の摩耗量が小さかった。このように表裏から均等に摩耗させるためには、表裏にメタルラス板の凸部を露出させることが必要である。
［試験例３］
蓄積性触媒毒の除去効果を確認するため、実施例１及び比較例１の触媒を亜砒酸(As2O3)を5ppm含む模擬排ガス中に350℃で100ｈ晒した。触媒の表層部に蓄積した亜砒酸の表面濃度は約2.5wt%であった。本触媒の脱硝率及び試験例１の条件で表裏を摩耗させたときの脱硝性能を表４の条件で測定し、表５に纏めて示した。表５から明らかなように実施例の触媒は、摩耗操作により活性が大きく回復したのに対し、比較例の触媒は活性が殆ど回復しなかった。
［実施例４］
触媒成分が摩損後の触媒の再利用を模擬するため、100mm角に裁断した実施例１の触媒に鋼鉄球の破砕品を吹き付け触媒成分を除去したメタルラス基板を作成した。他方、メタバナジン酸アンモン306.5g，および三酸化モリブデン275.9gを2759gの水に混ぜ、約20時間攪拌した後、シリカゾル2800gを混ぜた溶液に、長さ100μmの無機繊維製ミルドファイバー2250g，および酸化チタン3300gを加えて粘度1800cPの触媒成分スラリを得た。
[Test Example 1]
In order to grasp the wear rate of the catalysts of Examples 1 to 3 and Comparative Examples 1 and 2, a wear test was performed in which air containing coal combustion ash was blown onto the catalyst using a nozzle under the conditions shown in Table 1. The obtained results are summarized in Table 2. When the pore volume is 0.3 ml / g, the presence or absence of progress of wear is clearly separated, and the pore volume is selected to be 0.3 ml / g or more in order to remove accumulative poisons with ash particles in the use environment. I found that it was necessary.
[Test Example 2]
About the catalyst of Example 2 and Comparative Example 3, the abrasion test of the conditions of Table 1 was implemented by the surface and the back surface. The obtained results are summarized in Table 3. In Example 2 where the convex portions of the metal lath plate were exposed on both sides, the amount of wear on the front and back surfaces was the same, but the amount of wear on the surface where the convex portions of Comparative Example 3 were not exposed was small. In order to evenly wear from the front and back as described above, it is necessary to expose the convex portions of the metal lath plate on the front and back.
[Test Example 3]
In order to confirm the removal effect of the accumulative catalyst poison, the catalysts of Example 1 and Comparative Example 1 were exposed to simulated exhaust gas containing 5 ppm of arsenous acid (As 2 O 3 ) at 350 ° C. for 100 hours. The surface concentration of arsenous acid accumulated in the surface layer of the catalyst was about 2.5 wt%. The denitration rate of this catalyst and the denitration performance when the front and back surfaces were worn under the conditions of Test Example 1 were measured under the conditions of Table 4, and are summarized in Table 5. As is apparent from Table 5, the activity of the catalyst of the example was greatly recovered by the wear operation, whereas the activity of the catalyst of the comparative example was hardly recovered.
[Example 4]
In order to simulate the reuse of the catalyst after the catalyst component was worn out, a metal lath substrate in which the catalyst component was removed by spraying a crushed steel ball onto the catalyst of Example 1 cut to 100 mm square was prepared. On the other hand, 306.5 g of ammonium metavanadate and 275.9 g of molybdenum trioxide were mixed with 2759 g of water, stirred for about 20 hours, and then mixed with 2800 g of silica sol, 2250 g of milled fiber made of inorganic fibers with a length of 100 μm, and titanium oxide. 3300 g was added to obtain a catalyst component slurry having a viscosity of 1800 cP.
上記で調製したスラリ中に触媒成分を除去したメタルラス基板を浸漬後、垂直に引き上げて触媒スラリでメタルラス板の網目が埋まった状態にし、その後乾燥及び500℃で焼成を行い触媒を得た。本触媒の細孔容積は0.31ml/gであり、蓄積性毒物の除去触媒として使用可能であった。メタルラス基材を基材に用いた触媒の場合、このようにスラリコーティング方法により簡単に触媒成分層を形成できるため、繰り返し基材を利用することが可能である。 After immersing the metal lath substrate from which the catalyst component had been removed in the slurry prepared above, the metal lath plate was pulled up vertically to fill the mesh of the metal lath plate with the catalyst slurry, and then dried and calcined at 500 ° C. to obtain a catalyst. The pore volume of this catalyst was 0.31 ml / g, and it could be used as a catalyst for removing accumulative poisons. In the case of a catalyst using a metal lath base material as the base material, the catalyst component layer can be easily formed by the slurry coating method as described above, so that the base material can be repeatedly used.
１ 脱硝触媒成分、２ メタルラス、３ 摩損部分。 1 DeNOx catalyst component, 2 metal lath, 3 worn parts.
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| JP2638067B2 (en) * | 1988-05-16 | 1997-08-06 | バブコツク日立株式会社 | Catalyst for catalytic reduction of nitrogen oxides |
| JP3496964B2 (en) * | 1993-12-13 | 2004-02-16 | バブコック日立株式会社 | Catalyst for ammonia reduction of nitrogen oxides in exhaust gas and method for producing the same |
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