JP4005291B2 - Regeneration method of used denitration catalyst - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は使用済脱硝触媒の再生方法に関し、さらに詳しくは窒素酸化物（ＮＯｘ）を含有する排ガスの浄化に使用された、チタン（Ｔｉ）、モリブデン（Ｍｏ）、タングステン（Ｗ）またはバナジウム（Ｖ）の酸化物の少なくとも一種を活性成分として含む脱硝触媒の使用済触媒を、該触媒に含まれるアルミニウム（Ａｌ）の含有量を低減させつつ再生することができる使用済脱硝触媒の再生方法に関する。
【０００２】
【従来の技術】
発電所、各種工場、自動車などから排出される排煙中の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 ）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。この触媒にはＶ、Ｍｏ、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、現在の脱硝触媒の主流になっている。
これらの触媒は、粒状、板状またはハニカム状に成形され、二〜十数年間、触媒の交換をせずに使用されるのが通例である。現在、接触アンモニア還元脱硝法は、主に発電用ボイラを始めとする、大容量ボイラ、ガスタービン等の排ガス浄化に使用されており、プラント当たり通常、数百〜千ｍ3 という膨大な量の触媒が用いられている。これらの触媒は、使用年数を過ぎて廃触媒となった場合には新たな２次公害物質となるため、廃触媒の再使用は環境保護や資源の有効利用において非常に重要な課題となっている。
【０００３】
これに対し、比較的簡素で低コストの再生方法として、使用済み脱硝触媒を硫酸とともに加熱して加水分解後、アルカリ中和して触媒を再生する方法が提案されている（特公昭５８−２９１４３号公報）。この方法は触媒中の酸化チタンと活性成分を混合物として回収することができるため、廃棄物の量が少なくなるというメリットがある。また、この方法により再生した触媒は、通常使用される触媒と同等またはそれ以上の触媒性能を有するため、触媒原料としてそのまま再使用することができ、資源の有効利用にも役立つ。
また、上記脱硝触媒には、通常、Ｗ、Ｍｏ、Ｖなどの活性成分と酸化チタンの混合物の他に、触媒の強度を向上させるために無機繊維成分が添加されている。この無機繊維成分はシリカ（ＳｉＯ2 ）およびアルミナ（Ａｌ2 Ｏ3 ）を主成分とする。この無機繊維成分を触媒調製時に添加して触媒成分とともに高温で焼成することにより、高強度成形体を得ることができるため、板状、ハニカム状など形状にかかわらず触媒には必ず添加されている。
【０００４】
しかしながら、従来技術による方法で触媒を再生する場合には、この無機繊維成分は再生過程で取り除かれず、再生触媒中に残存してしまう。特にアルミナは酸化チタンやＶなどの活性成分と同じく硫酸に溶解するため、そのままでは活性成分と分離させて取り除くことができない。このようなＡｌが再生触媒中に残存すると、触媒の再生を繰返すごとに触媒中のＡｌの割合が増加し、再生原料として再使用することが困難になる。また触媒の基板として板状のＳＵＳ基板が用いられる場合、該基板にアルミ溶射がされる場合があるが、この溶射されたアルミが再生時に触媒に混入した場合も同様に問題となる。
【０００５】
【発明が解決しようとする課題】
本発明の課題は、上記従来技術の問題点を解決し、使用済脱硝触媒の再生過程でＡｌを効率良く除去し、精製度の高い再生触媒を得ることができる使用済脱硝触媒の再生方法を提供することにある。
【０００６】
【課題を解決するための手段】
本発明者らは、上記問題を解決すべく、触媒の再生過程での各成分の沈澱速度や溶解度、特にＡｌの挙動について詳細に検討した結果、使用済触媒を硫酸とともに加熱して加水分解した溶液をアルカリ中和して触媒成分を析出させる前に、該溶液にアルカリ中和に必要なアルカリの一部にアンモニアを用いて該アンモニアを添加し、該溶液中のＡｌを硫酸アルミニウムアンモニウム（アンモニア明礬）として析出させることにより、上記課題を達成できることを見いだし、本発明に到達したものである。すなわち、本願で特許請求される発明は以下の通りである。
（１）チタン、モリブデン、タングステンまたはバナジウムの酸化物を活性成分として含む脱硝触媒の使用済触媒を、硫酸を用いて溶解した後、加水分解し、次いでアルカリ中和して上記触媒成分を析出させて再使用する使用済脱硝触媒の再生方法において、前記アルカリ中和に必要なアルカリの少なくとも一部にアンモニアを用い、該アンモニアを、前記加水分解した後の溶液に添加して静置し、該溶液に含まれるアルミニウムを硫酸アルミニウムアンモニウムとして析出させて除去した後、残りのアルカリを添加して上記触媒成分を析出させることを特徴とする使用済脱硝触媒の再生方法。
（２）前記アルミニウムを析出させるために添加するアンモニア量が、硫酸に溶解したアルミニウム量と等モル以上の量で、かつ前記触媒成分が析出しない量であることを特徴とする（１）に記載の使用済脱硝触媒の再生方法。
（３）前記アンモニアを添加した後、該溶液を冷却するかおよび／または該溶液に硫酸アルミニウムアンモニウムの結晶を少量添加して静置することを特徴とする（１）または（２）に記載の使用済脱硝触媒の再生方法。
【０００７】
【作用】
触媒を硫酸とともに加熱すると、該触媒に含まれるＴｉＯ2 やＶなどの活性成分は硫酸に溶解して硫酸チタニル、硫酸バナジル等を生成するが、それと同時に該触媒に含まれる無機繊維中のＡｌ2 Ｏ3 も硫酸アルミニウムを生成する。硫酸溶解後の液に水を添加して加水分解するとこれら硫酸塩は溶液となり、これをアンモニア（ＮＨ3 ）などのアルカリで中和すると沈澱を生じる。この段階で、中和に必要な全アルカリを添加してしまうと、Ｔｉ、Ｖ、Ａｌなどの硫酸塩のすべてが沈澱してしまう。
本発明では、アルカリ中和に必要なアルカリの一部にＮＨ3 を用いて該ＮＨ3 を加水分解液に添加し、この液を静置することにより、触媒成分を沈澱させることなく、硫酸アルミニウムアンモニウム（アンモニウム明礬）のみを析出させることができ、また生成したアンモニウム明礬は簡単に濾別して分離することができるため、その後のアルカリ中和で析出する触媒成分（再生触媒）中に残留するＡｌ量を最小限にとどめることができる。
【０００８】
【発明の実施の形態】
本発明の再生方法に用いられる使用済脱硝触媒は、未使用時の組成がＴｉ、Ｍｏ、ＷまたはＶのような金属酸化物を少なくとも一種を活性成分として含む脱硝触媒であって、石炭焚き、重油焚きまたはガス焚きボイラ、ごみ燃焼炉等から排出される排ガス処理などに使用されたものであればどのような排ガスに何年使用されたものでもよく、また粒状、ハニカム状、板状などに成形された無機繊維成分を含有する触媒であればどのような形態の触媒でもよい。使用済脱硝触媒はそのまま、または粉砕して再生処理に供される。また触媒が基体に塗布されている場合には使用済の触媒を基体から剥離して処理に供される。
【０００９】
本発明における使用済脱硝触媒の再生は、例えば、粉砕された使用済触媒を５０〜９８％の濃硫酸とともに１００〜２４０℃に加熱して溶解させ、次いで該硫酸溶液に水を加えて加水分解した後、下記の方法でアルカリ中和が行われる。加水分解は、公知の加熱加水分解の方法が採用できる。
本発明において、アルカリ中和には、中和に必要なアルカリの一部にＮＨ3 が用いられ、該ＮＨ3 があらかじめ加水分解した溶液に添加される。これにより、溶液に含まれるＡｌがＮＨ3 と反応してアルミニウム明礬を生成して沈殿する。該ＮＨ3 の添加量は、溶液中に含まれるＡｌと等モル以上で、かつ触媒成分を沈澱させない量とするのが好ましい。このＮＨ3 の添加量が少なすぎるとＡｌを充分に取り除くことができず、また多すぎると触媒成分が同時に沈澱してしまうため再生触媒の回収率が低下する。触媒成分を沈澱させないＮＨ3 の添加量は、処理する触媒の種類や成分によって異なるため、溶液中のＡｌ濃度、さらには触媒成分の回収率をも考慮しつつ適宜選定するのが好ましい。
【００１０】
生成したアルミニウム明礬は溶液を静置して沈殿させた後、濾別し、除去される。溶液を静置する際には、分離し易いアンモニア明礬の結晶を効率よくかつ速やかに析出させる点から、該溶液を冷蔵庫などに入れて冷却する、および／または該溶液に少量のアンモニア明礬の種結晶を入れることが好ましい。
アンモニア明礬を除去した後の濾液に残りのアルカリを添加してアルカリ中和することにより、触媒成分を析出させることができる。アルカリ中和に必要な上記ＮＨ3 以外のアルカリの種類には特に限定はなく、苛性ソーダなどのアルカリを使用してもよい。
析出した触媒成分は、常法により濾別され、洗浄、乾燥、粉砕等により、また必要に応じて組成調整等がなされて再生触媒として再使用される。
【００１１】
【実施例】
以下、本発明を実施例により詳細に説明するが、本発明はこれらに限定されるものではない。
実施例１
チタニアを担体とする板状脱硝触媒で、触媒組成がＴｉ／Ｍｏ／Ｖ＝９０．５／５／４．５（原子比）であり、無機繊維（ＳｉＯ2 ／Ａｌ2 Ｏ3 比＝１／１）添加量が２０重量％である触媒を、ボイラ燃焼排ガス脱硝に所定期間使用し、脱硝性能が一定以下に低下した廃触媒を得た。触媒成分を板状基板から剥がし、粉砕して処理用触媒とした。
磁性皿に前記廃触媒２５０ｇと濃硫酸（特級、含量９７重量％）４００ｇとを投入、混合し、２２０〜２４０℃のサンドバス中で２時間加温して触媒を硫酸に溶解させた。これに水１．５kgを添加して７０℃で１時間抽出し、加水分解母液とした。
【００１２】
この加水分解母液にＮＨ3 水（特級、含量２８重量％）２５０mlを添加し、さらにアンモニウム明礬の結晶１ｇを加え、冷蔵庫入れて２４時間静置した。静置後の容器の底に無色透明の結晶が得られた。この結晶を濾過し、濾液側に上記のＮＨ3 水を該液が中和するまでさらに添加した。添加したＮＨ3 水量は７５０mlであった。得られたスラリを水洗し、固層を遠心分離機で分離して１５０℃で２時間乾燥し、再生触媒を得た。
【００１３】
上記で濾別した無色透明の結晶を乾燥し、粉砕して蛍光Ｘ線で分析したところ、組成から硫酸アルミニウムアンモニウム（アンモニウム明礬）であることが判明した。
また得られた再生触媒を、５００℃で２時間焼成した後、プレス成形し、その後破砕して１０〜２０メッシュに篩い分けたものを用い、流通式反応装置を用いて表１の条件で脱硝率を測定した。その結果、脱硝率は９２％であり、触媒原料として用いるに充分な性能を有していることがわかった。
【００１４】
【表１】
実施例２
実施例１において、加水分解母液にＮＨ3 水を５００ml添加し、静置した後にＮＨ3 水を５００ml添加した以外は実施例１と同様にして再生触媒を得た。
実施例３
実施例１において、加水分解母液にＮＨ3 水を７５０ml添加し、静置した後にＮＨ3 水を２５０ml添加した以外は実施例１と同様にして再生触媒を得た。
実施例４
実施例１において、チタニアを担体とする板状脱硝触媒で、触媒組成がＴｉ／Ｗ／Ｖ＝９０．５／５／４．５（原子比）であり、無機繊維（ＳｉＯ2 ／Ａｌ2 Ｏ3 比＝１／１）添加量が２０重量％である触媒を、ボイラ燃焼排ガス脱硝に所定期間使用し、脱硝性能が一定以下に低下した廃触媒を用いた以外は実施例１と同様にして触媒の再生を行い、再生触媒を得た。
【００１６】
比較例１
実施例１で得られた加水分解母液にＮＨ3 水を１０００ml添加した後、水洗して固層を遠心分離機で分離し、１５０℃で２時間乾燥して再生触媒を得た。
比較例２
実施例１において、加水分解母液にＮＨ3 水を１０ml添加し、静置した後にＮＨ3 水を９９０ml添加した以外は実施例１と同様にして再生触媒を得た。
比較例３
実施例１において、加水分解母液にＮＨ3 を９００ml添加し、静置した後にＮＨ3 水を１００ml添加した以外は実施例１と同様にして再生触媒を得た。
【００１７】
実施例１〜４および比較例１〜３で得られた各再生触媒を蛍光Ｘ線で分析し、該触媒に含有するＡｌ2 Ｏ3 の定量を行い、さらにＢＥＴ比表面積分析装置を用いて比表面積を測定し、その結果を表２に示した。
【００１８】
【表２】
表２から、本発明の方法で得られた再生触媒（実施例１〜４）は、Ａｌ含有量が少なく、再生過程で触媒に含まれるＡｌを効率よく除去することができ、しかも得られた再生触媒の比表面積も大きいことがわかる。また回収された触媒量の減少はほとんど見られなかった。
【００２０】
これに対し、比較例１で得られた再生触媒では、Ａｌ成分の除去が行われていないため、再生触媒中のＡｌの含有量が多く、その比表面積も小さかった。また比較例２で得られた再生触媒では、再生過程でＡｌを析出させるために使用したＮＨ3 量が少なすぎるため、アンモニア明礬を充分に析出させることができず、再生触媒中のＡｌ含有量の減少が極めて少なく、また再生触媒の比表面積も小さかった。
一方、比較例３では、Ａｌを析出させるために使用したＮＨ3 量が多いため、Ａｌの除去が充分に行われ、再生触媒中のＡｌ含有量が極めて少なく、再生触媒の比表面積も大きいものであったが、上記Ａｌを析出させるために使用したＮＨ3 量が多すぎるため、アンモニア明礬の析出時に触媒成分も析出してしまい、回収された触媒量が大幅に減少した。
【００２１】
【発明の効果】
本発明の請求項１に係る発明によれば、使用済触媒を硫酸に溶解して再生する際に混入するＡｌ成分を効率よく取り除くことができるため、再生後の触媒中の不純物を最低限に抑えることができ、再利用を繰返す際に生ずる不純物の累積増加を最小限に抑えることができる。
また請求項２に係る発明によれば、アンモニア明礬の析出時に触媒成分が析出することがないため、上記効果に加え、再生触媒の回収率を向上させることができる。
さらに請求項３に係る発明によれば、アンモニア明礬を効率良くかつ速やかに析出させて分離できるため、上記効果に加え、再生処理時間を短縮することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for regenerating a spent denitration catalyst, and more particularly, titanium (Ti), molybdenum (Mo), tungsten (W) or vanadium (V) used for purification of exhaust gas containing nitrogen oxides (NOx). The present invention relates to a method for regenerating a spent denitration catalyst that can regenerate a spent catalyst of a denitration catalyst containing at least one oxide of (2) as an active component while reducing the content of aluminum (Al) contained in the catalyst.
[0002]
[Prior art]
NOx in flue gas emitted from power plants, various factories, automobiles, etc. is a causative substance of photochemical smog and acid rain, and selective catalytic reduction using ammonia (NH 3 ) as a reducing agent as an effective removal method. Is widely used mainly in thermal power plants. As this catalyst, a titanium oxide (TiO 2 ) -based catalyst containing V, Mo, and W as active components is used, which is the mainstream of current denitration catalysts.
These catalysts are usually formed into a granular shape, a plate shape, or a honeycomb shape, and are usually used without replacement of the catalyst for 2 to 10 or more years. At present, the catalytic ammonia reduction and denitration method is mainly used for purification of exhaust gas from large-capacity boilers, gas turbines, etc., including power generation boilers, and usually a huge amount of several hundred to 1,000 m 3 per plant. A catalyst is used. Since these catalysts become new secondary pollutants when they become waste catalysts after the years of use, the reuse of waste catalysts is a very important issue for environmental protection and effective use of resources. Yes.
[0003]
On the other hand, as a relatively simple and low-cost regeneration method, a method has been proposed in which a used denitration catalyst is heated with sulfuric acid to hydrolyze and then neutralized with alkali to regenerate the catalyst (Japanese Patent Publication No. 58-29143). Issue gazette). This method has an advantage of reducing the amount of waste because the titanium oxide and the active component in the catalyst can be recovered as a mixture. In addition, since the catalyst regenerated by this method has a catalyst performance equal to or higher than that of a normally used catalyst, it can be reused as it is as a catalyst raw material, which is useful for effective utilization of resources.
In addition to the mixture of active components such as W, Mo and V and titanium oxide, an inorganic fiber component is usually added to the denitration catalyst in order to improve the strength of the catalyst. This inorganic fiber component is mainly composed of silica (SiO 2 ) and alumina (Al 2 O 3 ). Since this inorganic fiber component is added at the time of catalyst preparation and fired at a high temperature together with the catalyst component, a high-strength molded body can be obtained. Therefore, it is always added to the catalyst regardless of the shape such as plate shape or honeycomb shape. .
[0004]
However, when the catalyst is regenerated by the method according to the prior art, the inorganic fiber component is not removed in the regeneration process and remains in the regenerated catalyst. In particular, alumina dissolves in sulfuric acid like active components such as titanium oxide and V, and cannot be separated from the active component and removed as it is. When such Al remains in the regenerated catalyst, the proportion of Al in the catalyst increases every time the regeneration of the catalyst is repeated, making it difficult to reuse as a regenerated raw material. When a plate-like SUS substrate is used as the catalyst substrate, the substrate may be sprayed with aluminum. However, when the sprayed aluminum is mixed into the catalyst at the time of regeneration, the same problem occurs.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a regeneration method for a used denitration catalyst that solves the above-mentioned problems of the prior art, efficiently removes Al in the regeneration process of the used denitration catalyst, and can obtain a regenerated catalyst with a high degree of purification. It is to provide.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the present inventors have studied in detail the precipitation rate and solubility of each component during the catalyst regeneration process, particularly the behavior of Al, and as a result, the spent catalyst was hydrolyzed by heating with sulfuric acid. Before the solution is subjected to alkali neutralization to precipitate catalyst components, the ammonia is added to the solution by using ammonia as a part of the alkali necessary for alkali neutralization, and Al in the solution is added to ammonium ammonium sulfate (ammonia). It has been found that the above-mentioned problems can be achieved by precipitation as an alum, and the present invention has been achieved. That is, the invention claimed in the present application is as follows.
(1) A used catalyst of a denitration catalyst containing an oxide of titanium, molybdenum, tungsten or vanadium as an active component is dissolved using sulfuric acid, then hydrolyzed, and then neutralized with alkali to precipitate the catalyst component. In the method for regenerating a used denitration catalyst that is reused, ammonia is used as at least a part of the alkali necessary for the alkali neutralization, and the ammonia is added to the hydrolyzed solution and left to stand. A method for regenerating a spent denitration catalyst, comprising depositing and removing aluminum contained in a solution as ammonium aluminum sulfate, and then adding the remaining alkali to precipitate the catalyst component.
(2) The amount of ammonia added for precipitating the aluminum is equal to or more than the amount of aluminum dissolved in sulfuric acid, and the amount in which the catalyst component does not precipitate is described in (1) To recycle spent denitration catalyst.
(3) The method according to (1) or (2), wherein after adding the ammonia, the solution is cooled and / or a small amount of aluminum ammonium sulfate crystal is added to the solution and left to stand. Regeneration method of used denitration catalyst.
[0007]
[Action]
When the catalyst is heated together with sulfuric acid, active components such as TiO 2 and V contained in the catalyst dissolve in sulfuric acid to produce titanyl sulfate, vanadyl sulfate and the like. At the same time, Al 2 in the inorganic fibers contained in the catalyst. O 3 also produces aluminum sulfate. When water is added to the solution after dissolution in sulfuric acid and hydrolyzed, these sulfates become a solution. When this is neutralized with an alkali such as ammonia (NH 3 ), precipitation occurs. If all alkalis necessary for neutralization are added at this stage, all sulfates such as Ti, V, and Al are precipitated.
In the present invention, NH 3 is added to a hydrolysis solution using NH 3 as a part of alkali required for alkali neutralization, and this solution is allowed to stand, so that aluminum sulfate can be precipitated without precipitation of catalyst components. Since only ammonium (ammonium alum) can be precipitated, and the produced ammonium alum can be easily filtered and separated, the amount of Al remaining in the catalyst component (regenerated catalyst) precipitated by the subsequent alkali neutralization Can be kept to a minimum.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The used denitration catalyst used in the regeneration method of the present invention is a denitration catalyst whose composition when not in use includes at least one metal oxide such as Ti, Mo, W or V as an active component, It may be used for any exhaust gas for years as long as it is used for exhaust gas treatment from heavy oil fired or gas fired boilers, garbage combustion furnaces, etc. Any form of catalyst may be used as long as it contains a shaped inorganic fiber component. The used denitration catalyst is used as it is or after being pulverized. When the catalyst is applied to the substrate, the used catalyst is peeled off from the substrate and used for the treatment.
[0009]
The regeneration of the used denitration catalyst in the present invention is performed, for example, by dissolving the pulverized used catalyst together with 50 to 98% concentrated sulfuric acid by heating to 100 to 240 ° C., and then adding water to the sulfuric acid solution for hydrolysis. Then, alkali neutralization is performed by the following method. For the hydrolysis, a known heat hydrolysis method can be employed.
In the present invention, for the neutralization of alkali, NH 3 is used as a part of the alkali necessary for neutralization, and the NH 3 is added to a previously hydrolyzed solution. As a result, Al contained in the solution reacts with NH 3 to produce aluminum alum and precipitate. The amount of NH 3 added is preferably equimolar or more to Al contained in the solution and does not precipitate the catalyst component. If the amount of NH 3 added is too small, Al cannot be removed sufficiently, and if it is too large, the catalyst components will precipitate at the same time, and the recovery rate of the regenerated catalyst will decrease. Since the amount of NH 3 added that does not precipitate the catalyst component varies depending on the type and component of the catalyst to be treated, it is preferable to select it appropriately in consideration of the Al concentration in the solution and also the recovery rate of the catalyst component.
[0010]
The produced aluminum alum is allowed to settle by allowing the solution to stand, then filtered off and removed. When the solution is allowed to stand, the ammonia alum crystals that are easy to separate are precipitated efficiently and quickly, so that the solution is cooled in a refrigerator and / or a small amount of ammonia alum seeds are added to the solution. It is preferable to put crystals.
The catalyst component can be deposited by adding the remaining alkali to the filtrate after removing ammonia alum and neutralizing with alkali. There are no particular limitations on the type of alkali other than NH 3 required for alkali neutralization, and alkali such as caustic soda may be used.
The precipitated catalyst component is filtered off by a conventional method, and is reused as a regenerated catalyst after washing, drying, pulverization, etc., and if necessary, adjusting the composition.
[0011]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.
Example 1
A plate-shaped denitration catalyst using titania as a carrier, the catalyst composition is Ti / Mo / V = 90.5 / 5 / 4.5 (atomic ratio), and inorganic fibers (SiO 2 / Al 2 O 3 ratio = 1 / 1) A catalyst having an addition amount of 20% by weight was used for boiler combustion exhaust gas denitration for a predetermined period of time to obtain a waste catalyst having a denitration performance lowered below a certain level. The catalyst component was peeled off from the plate-like substrate and pulverized to obtain a treatment catalyst.
In a magnetic dish, 250 g of the waste catalyst and 400 g of concentrated sulfuric acid (special grade, content 97 wt%) were added and mixed, and heated in a sand bath at 220 to 240 ° C. for 2 hours to dissolve the catalyst in sulfuric acid. 1.5 kg of water was added thereto, and the mixture was extracted at 70 ° C. for 1 hour to obtain a hydrolysis mother liquor.
[0012]
To this hydrolyzed mother liquor, 250 ml of NH 3 water (special grade, content 28% by weight) was added, and 1 g of ammonium alum crystals were further added, and placed in the refrigerator for 24 hours. Colorless and transparent crystals were obtained at the bottom of the container after standing. The crystals were filtered, and the above NH 3 water was further added to the filtrate side until the solution was neutralized. The amount of NH 3 water added was 750 ml. The obtained slurry was washed with water, and the solid layer was separated with a centrifuge and dried at 150 ° C. for 2 hours to obtain a regenerated catalyst.
[0013]
The colorless and transparent crystals separated by filtration were dried, pulverized and analyzed by fluorescent X-ray. As a result, the composition was found to be aluminum ammonium sulfate (ammonium alum).
The regenerated catalyst obtained was calcined at 500 ° C. for 2 hours, press-molded, then crushed and sieved to 10 to 20 mesh, and denitrated under the conditions shown in Table 1 using a flow reactor. The rate was measured. As a result, it was found that the denitration rate was 92%, and it had sufficient performance for use as a catalyst raw material.
[0014]
[Table 1]
Example 2
In Example 1, and 500ml added aqueous NH 3 in the hydrolysis mother liquor, is the NH 3 water except for adding 500ml After standing to give the regenerated catalyst in the same manner as in Example 1.
Example 3
In Example 1, a regenerated catalyst was obtained in the same manner as in Example 1 except that 750 ml of NH 3 water was added to the hydrolysis mother liquor, and after standing, 250 ml of NH 3 water was added.
Example 4
In Example 1, a plate-shaped denitration catalyst using titania as a carrier, the catalyst composition is Ti / W / V = 90.5 / 5 / 4.5 (atomic ratio), and inorganic fibers (SiO 2 / Al 2 O 3 ratio = 1/1) A catalyst with an addition amount of 20% by weight was used for boiler combustion exhaust gas denitration for a predetermined period, and a waste catalyst whose denitration performance was lowered below a certain level was used in the same manner as in Example 1. The catalyst was regenerated to obtain a regenerated catalyst.
[0016]
Comparative Example 1
After adding 1000 ml of NH 3 water to the hydrolysis mother liquor obtained in Example 1, it was washed with water, the solid layer was separated with a centrifuge, and dried at 150 ° C. for 2 hours to obtain a regenerated catalyst.
Comparative Example 2
In Example 1, a regenerated catalyst was obtained in the same manner as in Example 1 except that 10 ml of NH 3 water was added to the hydrolysis mother liquor, and after standing, 990 ml of NH 3 water was added.
Comparative Example 3
In Example 1, a regenerated catalyst was obtained in the same manner as in Example 1 except that 900 ml of NH 3 was added to the hydrolysis mother liquor, and after standing, 100 ml of NH 3 water was added.
[0017]
Each of the regenerated catalysts obtained in Examples 1 to 4 and Comparative Examples 1 to 3 was analyzed by fluorescent X-ray, the Al 2 O 3 contained in the catalyst was quantified, and the ratio was measured using a BET specific surface area analyzer. The surface area was measured and the results are shown in Table 2.
[0018]
[Table 2]
From Table 2, the regenerated catalyst (Examples 1 to 4) obtained by the method of the present invention had a low Al content, and was able to efficiently remove Al contained in the catalyst during the regeneration process. It can be seen that the specific surface area of the regenerated catalyst is also large. Moreover, there was almost no decrease in the amount of recovered catalyst.
[0020]
On the other hand, in the regenerated catalyst obtained in Comparative Example 1, since the Al component was not removed, the Al content in the regenerated catalyst was large and the specific surface area was small. In addition, in the regenerated catalyst obtained in Comparative Example 2, the amount of NH 3 used for precipitating Al during the regeneration process is too small, so that ammonia alum cannot be sufficiently precipitated, and the Al content in the regenerated catalyst The reduction of the catalyst was extremely small, and the specific surface area of the regenerated catalyst was also small.
On the other hand, in Comparative Example 3, since the amount of NH 3 used for precipitating Al was large, Al was sufficiently removed, the Al content in the regenerated catalyst was extremely small, and the specific surface area of the regenerated catalyst was large. However, since the amount of NH 3 used for precipitating the Al was too large, the catalyst component was also precipitated during the precipitation of ammonia alum, and the amount of recovered catalyst was greatly reduced.
[0021]
【The invention's effect】
According to the first aspect of the present invention, since the Al component mixed when regenerating by dissolving the spent catalyst in sulfuric acid can be efficiently removed, the impurities in the regenerated catalyst can be minimized. Therefore, it is possible to suppress the cumulative increase of impurities that occurs when the reuse is repeated.
Further, according to the invention of claim 2, since the catalyst component does not precipitate when ammonia alum is precipitated, the recovery rate of the regenerated catalyst can be improved in addition to the above effects.
Furthermore, according to the invention of claim 3, since ammonia alum can be precipitated efficiently and quickly, the regeneration processing time can be shortened in addition to the above effects.
Claims (3)
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| CN106521165A (en) * | 2016-11-25 | 2017-03-22 | 东莞市联洲知识产权运营管理有限公司 | Method for extracting valuable metal from waste SCR catalyst to prepare alloy |
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| CN103526031B (en) * | 2013-10-09 | 2014-12-24 | 北京科技大学 | Recovery method for SCR waste flue gas denitration catalyst |
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| CN105152205B (en) * | 2015-09-22 | 2017-03-22 | 中国华电科工集团有限公司 | Method and device for recycling Ti and V from waste flue gas denitrification catalyst |
| CN105200236B (en) * | 2015-09-22 | 2017-10-03 | 中国华电科工集团有限公司 | A kind of method and device that W and V is reclaimed from waste flue gas denitration catalyst |
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| CN106521165A (en) * | 2016-11-25 | 2017-03-22 | 东莞市联洲知识产权运营管理有限公司 | Method for extracting valuable metal from waste SCR catalyst to prepare alloy |
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