JP3939085B2 - Method for treating exhaust gas containing dioxins - Google Patents
Method for treating exhaust gas containing dioxins Download PDFInfo
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- JP3939085B2 JP3939085B2 JP2000295549A JP2000295549A JP3939085B2 JP 3939085 B2 JP3939085 B2 JP 3939085B2 JP 2000295549 A JP2000295549 A JP 2000295549A JP 2000295549 A JP2000295549 A JP 2000295549A JP 3939085 B2 JP3939085 B2 JP 3939085B2
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- 150000002013 dioxins Chemical class 0.000 title claims description 42
- 238000000034 method Methods 0.000 title claims description 21
- 239000007789 gas Substances 0.000 claims description 84
- 239000003054 catalyst Substances 0.000 claims description 34
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 13
- 238000000354 decomposition reaction Methods 0.000 claims description 11
- 229910052736 halogen Inorganic materials 0.000 claims description 10
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- 238000003786 synthesis reaction Methods 0.000 claims description 7
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- 239000012433 hydrogen halide Substances 0.000 claims description 6
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Landscapes
- Treating Waste Gases (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、ダイオキシン類を含む排ガスの処理方法に関する。
【０００２】
【従来の技術】
産業廃棄物や都市廃棄物を処理する焼却施設から発生する排ガス中には、ダイオキシン類が含まれている。特にダイオキシン類は環境ホルモン物質として挙げられることからも、これらを排ガスから高効率で除去することは重要な課題である。しかも、ダイオキシン類は、ガス中にハロゲンやハロゲン化水素が存在すると新たに合成されうる物質であるため、高効率で分解を行うと同時に、いかにこの合成反応を抑えるかが非常に重要な課題である。
従来から触媒を用いてダイオキシン類を含む排ガスを処理する方法は多く知られており、例えば特開平１０−２３５１９１号公報にはチタン系触媒を用いた処理方法が提案されている。
【０００３】
しかしながら、処理する排ガスの組成は様々であるため、排ガスの組成によっては処理効率が低くなることがあり、安定して高効率でダイオキシン類を分解除去するとともにダイオキシン類の新たな合成反応を抑制する方法は未だ見出されていないのが現状である。
【０００４】
【発明が解決しようとする課題】
したがって、本発明の課題は、安定して高効率でダイオキシン類を分解除去するとともにダイオキシン類の新たな合成反応を抑制する方法を提供することにある。
【０００５】
【課題を解決するための手段】
上記課題を解決するため、本発明のダイオキシン類を含む排ガスの処理方法は、ダイオキシン類を含む排ガスを触媒に接触させて、前記排ガス中のダイオキシン類の分解除去を行うとともにダイオキシン類の新たな合成反応を抑制する、排ガスの処理方法において、前記排ガスの水分濃度が２容積％未満の場合、排ガス線速が０．１ｍ／ｓ（標準状態）以上の状態で排ガス中の水分濃度が２〜４０容積％となる量の水分を添加した後にチタン系触媒と接触させることを特徴とする。
また、本発明のもう一つの有機ハロゲン化合物を含む排ガスの処理方法は、ダイオキシン類を含む排ガスを触媒に接触させて、前記排ガス中のダイオキシン類の分解除去を行うとともにダイオキシン類の新たな合成反応を抑制する、排ガスの処理方法において、前記排ガスの水分濃度が２容積％未満の場合、排ガス中の水分濃度が２〜４０容積％となる量の水素および／または炭化水素化合物を添加した後にチタン系触媒と接触させることを特徴とする。
【０００６】
【発明の実施の形態】
一般に廃棄物を処理する焼却施設から発生する排ガス中には、焼却により水分が生成したり、もともと排ガス中に水分が含まれていたりするため、比較的高い濃度の水分が含まれているが、排ガスによっては水分濃度が低い場合、例えば、２容積％未満の場合があり、このような水分濃度の低い排ガス中に含まれるダイオキシン類を分解除去しようとした場合に、通常の水分濃度の比較的高い排ガスと比べて処理効率が低くなることを本発明者らは見出した。特に排ガス中にある程度以上のハロゲンガスまたはハロゲン化水素ガスが含まれる場合や触媒による処理ガス温度が比較的高い場合には、ダイオキシン類が新たに合成されやすく、さらにこの傾向が顕著であることを見出した。そして、たとえ水分濃度が低い排ガスを処理する場合でも、該排ガスに、水分を添加するか、または、触媒上で水分を生成しうる化合物である水素および／または炭化水素化合物を添加して、水分を富化させた後に触媒と接触させることにより、高い効率でのダイオキシン類処理が可能であることを見出し、本発明を完成するに至った。
【０００７】
この理由については明らかではないが、排ガス中の水分を富化させることによって、ダイオキシン類の分解によって生成したハロゲンによって新たなダイオキシン類が生成する反応を抑制できるためであると推測される。すなわち、排ガス中の水分を富化させることが、ハロゲンの活性化を抑制する、あるいはハロゲンと有機成分との反応を阻害する効果があると考えられる。
本発明では、排ガスに、水分を添加するか、または、触媒上で水分を生成しうる化合物である水素および／または炭化水素化合物を添加して、水分を富化させた後に触媒と接触させて、ダイオキシン類の分解除去を行う。前記炭化水素化合物としては、特に制限はないが、エチレン、プロピレン等の脂肪族炭化水素類やベンゼン、トルエン等の芳香族炭化水素類等が例示される。
【０００８】
このとき、水分または水素および／または炭化水素化合物を添加する方法については特に制限はなく、例えばスプレーノズルを用いて噴霧するなど、一般的に用いられている方法を適宜用いることができる。また、スプレーノズルを用いて水を噴霧する場合には、排ガス線速が０．１ｍ／ｓ（標準状態）以上であることが、水の分散が良くなり好ましい。
水分または水素および／または炭化水素化合物の添加量は、排ガス中の水分濃度が２〜４０容積％となるような量とすることが好ましく、より好ましくは２〜２０容積％である。排ガス中の水分濃度が２容積％未満では、処理効率が低くなり、４０容積％を超える場合には、触媒表面に吸着した水分子がダイオキシン類の分解反応を阻害するため好ましくない。
【０００９】
したがって、本発明は、処理対象とする排ガス（水分または水素および／または炭化水素化合物の添加前の排ガス）の水分濃度が５容積％未満の場合、さらには２容積％未満の場合に特に有効である。このような排ガスとしては、製鋼用電気炉、焼結炉、亜鉛回収施設、アルミニウム精錬施設、灰溶融炉などの排ガスが挙げられる。
本発明において用いられる触媒は、ダイオキシン類を分解除去するのに適した触媒であればよく、公知のものがいずれも好適に用いられる。例えば、特開平１０−２３５１９１号公報や特願平１１−１８０９３３号に記載のチタン系触媒が好適に用いられる。
【００１０】
本発明において用いられる触媒の形状は、特に限定されるものではなく、ハニカム状、板状、波板状、網状、円柱状、円筒状など所望の形状に成形して使用することができる。また、アルミナ、シリカ、コーディライト、ムライト、ＳｉＣ、チタニア、ステンレス金属などからなるハニカム状、板状、波板状、網状、円柱状、円筒状などの所望の形状の担体に担持して使用してもよいが、触媒層での圧力損失が少なく、処理効率の高いハニカム形状が好適に用いられる。
特に排ガス中にハロゲンガスおよび／またはハロゲン化水素ガスが含まれている場合には、ダイオキシン類が新たに合成されやすく、水分濃度が低い場合の処理効率が低下が著しい。そのため、本発明は、排ガス中に１０ｐｐｍ以上のハロゲンガスおよび／またはハロゲン化水素ガスが含まれている場合に特に効果が認められ、特に排ガス中のハロゲンガスおよび／またはハロゲン化水素ガスの濃度が１００ｐｐｍ以上の場合にその効果が顕著に現れる。ハロゲンガスとしては、Ｃｌ2、Ｂｒ2などが例示され、ハロゲン化水素ガスとしては、ＨＣｌ、ＨＢｒなどが例示される。
【００１１】
本発明の処理方法において、触媒層入口での排ガス温度を２００℃以上とすることにより、水分が存在しても活性への影響がなく、温度が高くなることによって触媒性能が向上するため、高効率でのダイオキシン類の分解除去が達成され、触媒反応装置のコンパクト化および低コスト化を図ることができる。
本発明は、ダイオキシン類を含む排ガスの処理方法に関するものであるが、ダイオキシン類とは、ポリハロゲン化ジベンゾダイオキシン、ポリハロゲン化ジベンゾフランおよびポリハロゲン化ビフェニルのうちの少なくとも１種と定義される。
【００１２】
本発明によってダイオキシン類の分解除去を行う際の条件については、特に制限がなく、この種の反応に一般的に用いられている条件で実施することができる。具体的には、排ガスの種類、性状、要求されるダイオキシン類の分解率などを考慮して適宜決定すればよい。
【００１３】
【実施例】
以下に実施例によりさらに詳細に本発明を説明するが、本発明はこれに限定されるものではない。
（実施例１）
市販の酸化チタン粉体（ＤＴ−５１（商品名）、ミレニアム社製）２０ｋｇにメタバナジン酸アンモニウム１．５ｋｇ、シュウ酸１．８ｋｇおよびモノエタノールアミン０．４ｋｇを水５リットルに溶解させた溶液を加え、さらにフェノール樹脂（ベルパール（商品名）、カネボウ（株）製）１ｋｇと成形助剤としてのデンプン０．５ｋｇとを加えて混合し、ニーダーで混練りした後、押出成形機で外形８０ｍｍ角、目開き４．０ｍｍ、肉厚１．０ｍｍ、長さ５００ｍｍのハニカム状に成形した。次いで、８０℃で乾燥した後、４５０℃で５時間空気雰囲気下で焼成して触媒Ａを得た。
【００１４】
触媒Ａを用い、ダイオキシン類（ポリ塩素化ジベンゾダイオキシンとポリ塩素化ジベンゾフランの合計である。以下、ＤＸＮという）約１０ｎｇ−ＴＥＱ／ｍ3（標準状態）を含む排ガスに接触させ、ＤＸＮの除去性能を測定した。排ガス中の水分濃度は１．６容積％、ＨＣｌ濃度は５００ｐｐｍ、触媒層入口での排ガス温度は３５０℃、排ガス線速は０．５ｍ／ｓ（標準状態）であり、空間速度（ＳＴＰ）は６０００Ｈｒ-1であった。
つぎに、触媒層の前で水を添加し、触媒層でのガス中の水分濃度１５容積％にした条件で反応を行った。
【００１５】
そして、それぞれの条件での反応におけるＤＸＮ分解率を下記式にしたがって求めた。
【００１６】
【表１】
（実施例２）
触媒Ａを用い、ＤＸＮ約１ｎｇ−ＴＥＱ／ｍ3（標準状態）を含む排ガスに接触させ、ＤＸＮの除去性能を測定した。排ガス中の水分濃度は１．２容積％、ＨＣｌ濃度は１００ｐｐｍ、触媒層入口での排ガス温度は３００℃、排ガス線速は０．５ｍ／ｓ（標準状態）であり、空間速度（ＳＴＰ）は８０００Ｈｒ-1であった。
つぎに、触媒層の前でプロピレン５容積％を添加した条件で反応を行った。
そして、それぞれの条件での反応におけるＤＸＮ分解率を求めた。
【００１８】
結果を表２に示した。
【００１９】
【表２】
（比較例１および２）
触媒Ａを用いるとともに、有機ハロゲン化合物としてジクロロベンゼン（ＤＣＢ）を用いて、下記条件下で反応を行った。
試験条件
ＤＣＢ：３００ｐｐｍ、Ｏ2：１０％、ＨＣｌ：５００ｐｐｍ、Ｈ2Ｏ：１．６容積％、Ｎ2：バランス
排ガス温度：３５０℃
排ガス線速：０．５ｍ／ｓ（標準状態）
空間速度（ＳＴＰ）：６０００Ｈｒ-1
次に、反応ガス中の水分量を１５容積％にした条件で反応を行った。
【００２１】
そして、それぞれの条件での反応におけるＤＣＢ分解率を下記式にしたがって求めた。
【００２２】
【表３】
【発明の効果】
本発明によると、排ガス中の水分濃度が低い場合であっても、安定して高効率でダイオキシン類を分解除去するとともにダイオキシン類の新たな合成反応を抑制することができるので、高い効率でのダイオキシン類処理が可能となる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for treating exhaust gas containing dioxins.
[0002]
[Prior art]
Dioxins are contained in exhaust gas generated from incineration facilities that process industrial and municipal waste. In particular, since dioxins are listed as environmental hormone substances, it is an important issue to remove them from exhaust gas with high efficiency. Moreover, since dioxins are substances that can be newly synthesized when halogens or hydrogen halides are present in the gas, how to suppress this synthesis reaction at the same time as performing high-efficiency decomposition is a very important issue. is there.
Conventionally, many methods for treating exhaust gas containing dioxins using a catalyst are known. For example, JP-A-10-235191 proposes a treatment method using a titanium-based catalyst.
[0003]
However, since the composition of the exhaust gas to be treated varies, the treatment efficiency may be lowered depending on the composition of the exhaust gas, and the dioxins can be stably decomposed and removed with high efficiency and the new synthesis reaction of the dioxins is suppressed. At present, no method has yet been found.
[0004]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a method for stably decomposing and removing dioxins with high efficiency and suppressing a new synthesis reaction of dioxins.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the method for treating exhaust gas containing dioxins according to the present invention comprises contacting exhaust gas containing dioxins with a catalyst to decompose and remove dioxins in the exhaust gas, and newly synthesize dioxins. In the exhaust gas treatment method for suppressing reaction, when the moisture concentration of the exhaust gas is less than 2% by volume , the moisture concentration in the exhaust gas is 2 to 40 when the exhaust gas linear velocity is 0.1 m / s (standard state) or more. It is characterized in that it is brought into contact with a titanium-based catalyst after adding water in an amount of volume%.
In addition, another method for treating exhaust gas containing an organic halogen compound according to the present invention is to bring exhaust gas containing dioxins into contact with a catalyst to decompose and remove dioxins in the exhaust gas and to perform a new synthesis reaction of dioxins. In the method of treating exhaust gas, when the moisture concentration of the exhaust gas is less than 2% by volume, titanium is added after adding hydrogen and / or hydrocarbon compound in an amount such that the moisture concentration in the exhaust gas becomes 2 to 40% by volume. It is made to contact with a system catalyst.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
In general, exhaust gas generated from incineration facilities that treat waste contains moisture at a relatively high concentration because moisture is generated by incineration or moisture is originally contained in the exhaust gas. When the moisture concentration is low depending on the exhaust gas, for example, it may be less than 2% by volume. When attempting to decompose and remove dioxins contained in the exhaust gas having such a low moisture concentration, The present inventors have found that the treatment efficiency is low compared to high exhaust gas. In particular, when the exhaust gas contains a certain amount of halogen gas or hydrogen halide gas or when the treatment gas temperature by the catalyst is relatively high, dioxins are easily synthesized, and this tendency is remarkable. I found it. Even when treating an exhaust gas having a low moisture concentration, moisture is added to the exhaust gas, or hydrogen and / or a hydrocarbon compound, which is a compound capable of generating moisture on the catalyst, is added to the moisture. It was found that dioxins can be treated with high efficiency by contacting with a catalyst after enriching the catalyst, and the present invention has been completed.
[0007]
Although the reason for this is not clear, it is presumed that the reaction in which new dioxins are generated by halogen generated by the decomposition of dioxins can be suppressed by enriching the moisture in the exhaust gas. That is, it is considered that enriching the moisture in the exhaust gas has an effect of suppressing the activation of the halogen or inhibiting the reaction between the halogen and the organic component.
In the present invention, moisture is added to the exhaust gas, or hydrogen and / or a hydrocarbon compound that is a compound capable of generating moisture on the catalyst is added to enrich the moisture, and then contacted with the catalyst. Decompose and remove dioxins. The hydrocarbon compound is not particularly limited, and examples thereof include aliphatic hydrocarbons such as ethylene and propylene, and aromatic hydrocarbons such as benzene and toluene.
[0008]
At this time, there is no restriction | limiting in particular about the method of adding a water | moisture content, hydrogen, and / or a hydrocarbon compound, For example, generally used methods, such as spraying using a spray nozzle, can be used suitably. In addition, when water is sprayed using a spray nozzle, it is preferable that the exhaust gas linear velocity is 0.1 m / s (standard state) or more because water dispersion is improved.
The amount of water or hydrogen and / or hydrocarbon compound added is preferably such that the water concentration in the exhaust gas is 2 to 40% by volume, more preferably 2 to 20% by volume. If the moisture concentration in the exhaust gas is less than 2% by volume, the treatment efficiency is low, and if it exceeds 40% by volume, the water molecules adsorbed on the catalyst surface inhibit the decomposition reaction of dioxins, which is not preferable.
[0009]
Therefore, the present invention is particularly effective when the moisture concentration of the exhaust gas to be treated (exhaust gas before addition of moisture or hydrogen and / or hydrocarbon compound) is less than 5% by volume, or even less than 2% by volume. is there. Examples of such exhaust gas include exhaust gas from a steelmaking electric furnace, a sintering furnace, a zinc recovery facility, an aluminum refining facility, an ash melting furnace, and the like.
The catalyst used in the present invention may be any catalyst suitable for decomposing and removing dioxins, and any known catalyst is preferably used. For example, titanium-based catalysts described in JP-A-10-235191 and Japanese Patent Application No. 11-180933 are preferably used.
[0010]
The shape of the catalyst used in the present invention is not particularly limited, and can be used after being formed into a desired shape such as a honeycomb shape, a plate shape, a corrugated plate shape, a net shape, a columnar shape, or a cylindrical shape. It is also used by supporting it on a carrier of desired shape such as honeycomb, plate, corrugated, mesh, columnar, cylindrical, etc. made of alumina, silica, cordierite, mullite, SiC, titania, stainless steel, etc. However, a honeycomb shape having a low processing loss and high processing efficiency is preferably used.
In particular, when halogen gas and / or hydrogen halide gas is contained in the exhaust gas, dioxins are likely to be newly synthesized, and the treatment efficiency is significantly reduced when the water concentration is low. Therefore, the present invention is particularly effective when the exhaust gas contains 10 ppm or more of halogen gas and / or hydrogen halide gas, and the concentration of the halogen gas and / or hydrogen halide gas in the exhaust gas is particularly high. In the case of 100 ppm or more, the effect appears remarkably. Examples of the halogen gas include Cl 2 and Br 2, and examples of the hydrogen halide gas include HCl and HBr.
[0011]
In the treatment method of the present invention, by setting the exhaust gas temperature at the catalyst layer inlet to 200 ° C. or higher, there is no influence on the activity even if moisture is present, and the catalyst performance is improved by increasing the temperature. Efficient decomposition and removal of dioxins can be achieved, and the catalytic reactor can be made compact and low in cost.
The present invention relates to a method for treating exhaust gas containing dioxins, and dioxins are defined as at least one of polyhalogenated dibenzodioxins, polyhalogenated dibenzofurans, and polyhalogenated biphenyls.
[0012]
The conditions for performing decomposition and removal of dioxins according to the present invention are not particularly limited, and can be carried out under conditions generally used for this type of reaction. Specifically, it may be appropriately determined in consideration of the type and properties of exhaust gas, the required decomposition rate of dioxins, and the like.
[0013]
【Example】
The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.
Example 1
A solution prepared by dissolving 1.5 kg of ammonium metavanadate, 1.8 kg of oxalic acid and 0.4 kg of monoethanolamine in 5 liters of water in 20 kg of commercially available titanium oxide powder (DT-51 (trade name), manufactured by Millennium). In addition, 1 kg of phenolic resin (Bellpearl (trade name), Kanebo Co., Ltd.) and 0.5 kg of starch as a molding aid were added and mixed, kneaded with a kneader, and then 80 mm square with an extruder. And formed into a honeycomb shape having a mesh size of 4.0 mm, a wall thickness of 1.0 mm, and a length of 500 mm. Subsequently, after drying at 80 degreeC, it baked in the air atmosphere at 450 degreeC for 5 hours, and the catalyst A was obtained.
[0014]
Using catalyst A, contact with exhaust gas containing about 10 ng-TEQ / m 3 (standard state) of dioxins (the total of polychlorinated dibenzodioxins and polychlorinated dibenzofurans, hereinafter referred to as DXN), and removing DXN Was measured. The moisture concentration in the exhaust gas is 1.6% by volume, the HCl concentration is 500 ppm, the exhaust gas temperature at the catalyst layer inlet is 350 ° C., the exhaust gas linear velocity is 0.5 m / s (standard state), and the space velocity (STP) is 6000 Hr −1 .
Next, water was added in front of the catalyst layer, and the reaction was performed under the condition that the water concentration in the gas in the catalyst layer was 15% by volume.
[0015]
And the DXN decomposition rate in reaction on each condition was calculated | required according to the following formula.
[0016]
[Table 1]
(Example 2)
Using catalyst A, it was brought into contact with exhaust gas containing about 1 ng-TEQ / m 3 (standard state) of DXN, and the removal performance of DXN was measured. The moisture concentration in the exhaust gas is 1.2% by volume, the HCl concentration is 100 ppm, the exhaust gas temperature at the catalyst layer inlet is 300 ° C., the exhaust gas linear velocity is 0.5 m / s (standard state), and the space velocity (STP) is 8000 Hr −1 .
Next, the reaction was performed under the condition that 5% by volume of propylene was added in front of the catalyst layer.
And the DXN decomposition rate in reaction on each condition was calculated | required.
[0018]
The results are shown in Table 2.
[0019]
[Table 2]
(Comparative Examples 1 and 2)
While using Catalyst A, the reaction was carried out under the following conditions using dichlorobenzene (DCB) as the organic halogen compound.
Test conditions DCB: 300 ppm, O 2 : 10%, HCl: 500 ppm, H 2 O: 1.6% by volume, N 2 : balance exhaust gas temperature: 350 ° C.
Exhaust gas linear velocity: 0.5 m / s (standard condition)
Space velocity (STP): 6000 Hr −1
Next, the reaction was performed under the condition that the water content in the reaction gas was 15% by volume.
[0021]
And the DCB decomposition rate in reaction on each condition was calculated | required according to the following formula.
[0022]
[Table 3]
【The invention's effect】
According to the present invention, even when the moisture concentration in the exhaust gas is low, the dioxins can be stably decomposed and removed with high efficiency and the new synthesis reaction of the dioxins can be suppressed. Dioxins can be treated.
Claims (5)
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| JP2000295549A JP3939085B2 (en) | 2000-09-28 | 2000-09-28 | Method for treating exhaust gas containing dioxins |
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| Application Number | Priority Date | Filing Date | Title |
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| JP2000295549A JP3939085B2 (en) | 2000-09-28 | 2000-09-28 | Method for treating exhaust gas containing dioxins |
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| JP3939085B2 true JP3939085B2 (en) | 2007-06-27 |
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