JP2004033987A - Method for cleaning exhaust gas and operation method of decomposition treatment facility - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently clean exhaust gas containing hardly decomposable halogen compounds and to effectively use an activated carbon without loss. <P>SOLUTION: The activated carbon AC is replaced with new one when the concentration of an alkylbenzene reaches a peak which is extracted from the activated carbon AC extracted from a sampling port 27i on the downstream side, whereby the hardly decomposable halogen compounds are surely prevented from passing through an adsorption column 27 of the breakthrough state. That is to say, the breakthrough of the adsorption column 27 is previously detected by checking the concentration of the alkylbenzene preceding in the column 27. Thereby, while the activated carbon AC is utilized to the upper limit of its adsorption ability, the safety is ensured by not allowing even extremely small quantities of hardly decomposable halogen compounds to pass through the column 27. <P>COPYRIGHT: (C)2004,JPO

Description

【００４３】
ここで、検出量の単位は、使用後の活性炭ＡＣの単位重量（１ｋｇ）あたりで検出される吸着成分の重さ（ｇ）となっている。有機物の分析に際しては、５ｇの活性炭ＡＣと２５ｇのｎ−ヘキサンとを混合し、超音波で２０分間処理して吸着成分を抽出する。その後、有機成分を抽出したｎ−ヘキサンを５０倍の体積に希釈化し、希釈化したｎ−ヘキサン中の吸着成分をＦＩＤ−ＧＣを用いて定量した。
【００４４】
表からも明らかなように、トルエンやエチルベンゼンは、中流のサンプリングポート２７ｈで採取した活性炭で最も高い濃度を示すが、下流のサンプリングポート２７ｉで採取した活性炭でほとんど検出できない程度に低濃度となっている。このことは、当初上流側で吸着されたトルエンやエチルベンゼンが中流まで脱離移動したことを示す。なお、ｏ−キシレンも、明確ではないが同様の傾向を示す。一方、ビフェニル、及び電気絶縁油は、上流のサンプリングポート２７ｇで採取した活性炭で最も高い濃度を示すが、中流のサンプリングポート２７ｈで採取した活性炭では、ほとんど検出されない。さらに、下流のサンプリングポート２７ｉで採取した活性炭からは、ビフェニル、及び電気絶縁油のいずれも全く検出されていない。
【００４５】
以上の分析結果から、トルエンやエチルベンゼンの検出ピークが中、下流のサンプリングポート２７ｈ、２７ｉで検出された段階で、吸着塔２７の下流側まで飽和吸着が進んでいることが分かる。よって、例えば中流側のサンプリングポート２７ｈで検出されるトルエンが１０ｇを超えた段階で、吸着塔２７の破過が近いものとして、かかる吸着塔２７内部の活性炭ＡＣを取り替える。また、中流側のサンプリングポート２７ｈで検出されるトルエンが下流側のサンプリングポート２７ｉで検出されるエチルベンゼンよりも少なくなった時点（すなわち、濃度の逆転時）で、吸着塔２７内部の活性炭ＡＣを取り替える。すなわち、反応溶媒または吸収装置に用いる吸収液等に含まれる揮発性成分であり、特に、分子量１５０以下常圧における沸点が２００℃以下の有機物を検出することで効率的に吸着塔の運転を行うことができる。各サンプリングポート２７ｇ〜２７ｉからの活性炭の採取タイミングは、吸着成分の検出結果に影響が現れる程度の期間間隔（例えば数週間毎）とする。また、実際の活性炭の採取量は、トルエンやエチルベンゼンの増減が分かればよいので、ＦＩＤ−ＧＣを用いた定量の場合、数ｇ程度とすることができる。
〔第２実施形態〕
図３は、第２実施形態に係る排気ガス浄化装置を備える分解処理施設の構成を説明するブロック図である。この分解処理施設は、後処理装置３０と、ガス浄化装置１２０とを備える。
【００４６】
後処理装置３０は、反応装置１０と同様に分解処理設備であるが、反応装置１０において脱ハロゲン化反応を行なうことによって得られる反応生成物中に含まれる、難分解性ハロゲン化合物の分解物、未反応の薬剤、活性化剤、溶剤等を分離し、回収を行なって、最終的に廃棄又は再利用可能な状態にする設備である。
【００４７】
後処理装置としては、具体的には、遠心分離機、ろ過装置、中和洗浄装置、分液装置、蒸留装置等が挙げられる。そして、これらの装置を用いて、反応生成物から固形分の分離及び回収、過剰のアルカリ分の分解、溶媒の回収、生成塩の分離、触媒の分離等の作業が行なわれる。
【００４８】
例えば、高濃度の難分解性ハロゲン化合物含有物をアルカリ金属分散体を用いて脱ハロゲン化反応した反応生成物には、電気絶縁油等の溶媒及び固形物（ポリフェニレン型重合体、電気絶縁油、水酸化ナトリウム、食塩、水分等を含む。）が含まれる。この場合、後処理設備は、固液分離する遠心分離機、洗浄装置、分液装置等からなり、これらの装置を使用して、油分と固形物を分離する作業が行なわれる。
【００４９】
また、低濃度の難分解性ハロゲン化合物の含有物を脱ハロゲン化反応させた場合には、反応生成物に水を加えることにより、ビフェニル類、食塩水及び電気絶縁油の混合物が得られる。次いで、上記混合物を洗浄し静置した後、油分、タール分及び排水に分液装置を用いて分液し、排水を蒸発装置により水分を蒸発させ、得られた固形分を回収し、蒸発した水分を水分回収装置によりプロセス水として回収する作業が行なわれる。
【００５０】
一方、ガス浄化装置１２０は、後処理装置３０から排出される排気ガスから難分解性ハロゲン化合物を除去するための排気ガス浄化装置であり、還流器２１、空槽２２、シールトラップ２３、深冷コンデンサ２５、ミストセパレータ２６、活性炭が充填された吸着塔２７、及び逆火防止器２８からなる。ガス浄化装置１２０を構成する各要素については、第１実施形態の場合と同様のものであるので、説明を省略する。なお、本ガス浄化装置１２０では吸収装置２４を設けていないが、これは後処理装置３０の処理対象に含まれる難分解性ハロゲン化合物の濃度が反応装置１０の場合の処理対象に含まれる難分解性ハロゲン化合物の濃度に比較して極めて低いことを考慮したものである。
【００５１】
以上のガス浄化装置１２０の運転に際しては、定期的に吸着塔２７に充填された活性炭ＡＣを例えば新たなものに交換する。このため、吸着塔２７の３箇所に設けたサンプリングポート２７ｇ〜２７ｉ（図２参照）を利用して、吸着塔２７の上流、中流、及び下流の各箇所における活性炭ＡＣの吸着成分を定期的に監視する。
【００５２】
以下の表２は、後処理装置３０を例えば６ヶ月稼動させて交換時期が近づいている吸着塔２７中の活性炭ＡＣから抽出される有機物の分析結果を示す。
【００５３】
【表２】

【００５４】
ここで、検出量の単位は、第１実施形態における表１と同様のものとなっている。また、有機物の分析方法も、表１の場合と同様とした。
【００５５】
以上の表２も、表１の場合と同様の傾向を示している。つまり、トルエンやエチルベンゼンは、中流のサンプリングポート２７ｈで採取した活性炭で最も高い濃度を示すが、下流のサンプリングポート２７ｉで採取した活性炭で比較的低濃度となっている。なお、ｏ−キシレンも、明確ではないが同様の傾向を示す。一方、ビフェニル、及び電気絶縁油は、上流のサンプリングポート２７ｇで採取した活性炭で最も高い濃度を示すが、中流のサンプリングポート２７ｈで採取した活性炭で低い濃度を示す。また、下流のサンプリングポート２７ｉで採取した活性炭からは、ビフェニル、及び電気絶縁油のいずれも全く検出されていない。
【００５６】
以上の分析結果から、例えば中流側のサンプリングポート２７ｈで検出されるトルエンが５ｇを超えた段階で、吸着塔２７の破過が近いものとして、かかる吸着塔２７内部の活性炭ＡＣを取り替えればよいことが分かる。また、中流側のサンプリングポート２７ｈで検出されるトルエンが下流側のサンプリングポート２７ｉで検出されるエチルベンゼンよりも少なくなった時点で、吸着塔２７内部の活性炭ＡＣを取り替えることもできる。各サンプリングポート２７ｇ〜２７ｉからの活性炭の採取タイミングは、吸着成分の検出結果に影響が現れる程度の期間毎とする。
【００５７】
以上実施形態に即して本発明を説明したが、本発明は、上記実施形態に限定されるものではない。
【００５８】
例えば、第１実施形態の反応装置１０では、アルカリ金属分散体を用いて難分解性ハロゲン化合物の脱ハロゲン化反応を行っているが、これ以外の方法、具体的には、▲１▼溶剤中、難分解性ハロゲン化合物に水素供与体、添加剤及びアルカリを添加した後、窒素雰囲気下、常圧で加熱するアルカリ触媒分解法（ＢＣＤ法）、▲２▼難分解性ハロゲン化合物を、１，３−ジメチル−２−イミダゾリジノン、スルホラン、ポリエチレングリコールジアルキルエーテル等の非プロトン性極性溶媒中、水酸化ナトリウム、水酸化カリウム等のアルカリと反応させる化学抽出分解法、▲３▼難分解性ハロゲン化合物に、カリウムターシャリーブトキシド等の有機アルカリ金属を添加し、加熱することより、脱ハロゲン化反応を行なう有機アルカリ金属法、▲４▼溶剤中、難分解性ハロゲン化合物をパラジウム／カーボン等の水素化触媒の存在下、水素ガス中、常圧で加熱する触媒水素化脱塩素化法（Ｐｄ／Ｃ法）等の処理を行う各種反応設備にも、上記ガス浄化装置２０と同様のガス浄化装置を設けて同様の排気ガス処理を行うことができる。この場合も、吸着塔の中、下流位置に設けたサンプリングポートを利用して活性炭の交換時期を監視することができる。
【００５９】
また、難分解性ハロゲン化合物の分解処理施設には、通常前処理設備が設けられる。この前処理設備は、難分解性ハロゲン化合物又は難分解性ハロゲン化合物の含有物を受入れて、その種類に応じて分別を行なう設備である。前処理設備に受入れられる難分解性ハロゲン化合物の含有物としては、難分解性ハロゲン化合物を含むケロシン、デカリン、電気絶縁油、重油、潤滑油及びこれらの混合物等が挙げられる。具体的には、難分解性ハロゲン化合物含有のトランス又はコンデンサ等の廃棄物が挙げられる。前処理設備では、受入れた難分解性ハロゲン化合物の含有物の解体、切断、破断、分別等を行ない、これらの解体、切断、破断し、分別した物から難分解性ハロゲン化合物を回収するための洗浄が行なわれる。洗浄方法としては、浸漬法、液循環法、超音波法、バブリング法などが挙げられる。用いられる洗浄剤としては、洗浄力が優れ、火災、爆発の危険性が少なく、毒性が低く、洗浄後の乾燥が容易であること等が必要である。洗浄により回収された難分解性ハロゲン化合物は、洗浄剤とともに保管容器に保管され、必要に応じて洗浄剤との分離を行なって、次の反応装置１０送られて、脱ハロゲン化反応が施される。かかる前処理設備においても、上記ガス浄化装置２０と同様のガス浄化装置を設けて同様の排気ガス処理を行う。この場合も、吸着塔の中、下流位置に設けたサンプリングポートを利用して活性炭の交換時期を監視することができる。
【００６０】
また、以上の実施形態では、トルエンやエチルベンゼンといったアルキルベンゼンで吸着塔２７の破過を検出しているが、他の比較的低分子で低沸点の有機物、具体的には分子量が１５０以下、常圧における沸点が２００℃以下の有機物が、中、下流のサンプリングポート２７ｈ、２７ｉで検出される量に基づいて活性炭の交換時期を判定することができる。
【００６１】
【発明の効果】
以上の説明から明らかなように、本発明に係る排気ガス浄化方法や分解処理施設の運転方法によれば、吸着塔中において、難分解性ハロゲン化合物等よりも比較的低分子で低沸点の有機物の方が飽和しつつ迅速に移動すると考えられるので、先行する上記有機物の濃度を監視することで、吸着塔の破過を未然に検知することができる。よって、吸着剤を無駄なく利用しつつ、吸着剤が十分に機能し難分解性ハロゲン化合物等を通過させない安全な段階で、吸着剤を適切に交換することができる。
【図面の簡単な説明】
【図１】第１実施形態に係る難分解性ハロゲン化合物の分解処理施設の概念図である。
【図２】吸着塔の構造を説明する図である。
【図３】第２実施形態に係る難分解性ハロゲン化合物の分解処理施設の概念図である。
【符号の説明】
１０　　　反応装置
１１　　　反応槽
２０　　　ガス浄化装置
２１　　　還流器
２２　　　空槽
２３　　　シールトラップ
２４　　　吸収装置
２５　　　深冷コンデンサ
２６　　　ミストセパレータ
２７　　　吸着塔
２７ｇ〜２７ｉ　　　サンプリングポート
２８　　　逆火防止器
３０　　　後処理装置
ＡＣ　　　活性炭[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for efficiently purifying an exhaust gas containing a hardly decomposable halide such as polychlorinated biphenyl (PCB), and a method for operating a decomposition treatment facility for a hardly decomposable halogen compound.
[0002]
[Prior art]
Halogen compounds such as PCBs are generally chemically stable and are not easily decomposed in the natural environment (such halogen compounds are referred to as “hardly decomposable halogen compounds”). In addition, these are taken up in animals and plants, accumulated and concentrated, and exert an adverse effect.
[0003]
Therefore, promotion of the detoxification treatment of these hardly decomposable halogen compounds has become an important issue in recent years, and a decomposition treatment facility equipped with a decomposer that performs a dehalogenation reaction on the hardly decomposable halogen compounds to make them harmless. Is running.
[0004]
Here, from a decomposition reaction facility that performs a dehalogenation reaction of the hardly decomposable halogen compound, an exhaust gas containing an environmental pollutant such as a reaction product gas or a vaporized hardly decomposable halogen compound is secondarily generated. . If the exhaust gas containing such environmental pollutants is discharged to the outside as it is, the natural environment will be re-polluted. Therefore, it is necessary to remove hard-to-decompose halogen compounds and the like from the exhaust gas (hereinafter, this operation will be referred to as an operation). "Purification".) In particular, hardly decomposable halogen compounds are regulated substances, and it is necessary to completely purify exhaust gas so that even small amounts do not leak to the outside.
[0005]
As a method of purifying this exhaust gas, an activated carbon packed tower filled with activated carbon is connected to a decomposition reaction facility and installed, and the exhaust gas is passed through the activated carbon packed tower to adsorb hard-to-decompose halogen compounds and the like. There is a known removal method (“PCB processing technology guidebook”).
[0006]
[Problems to be solved by the invention]
However, it is difficult to efficiently and surely remove the hardly decomposable halogen compounds generated from the decomposition reaction equipment, that is, the reaction tank, by the adsorption and removal method using activated carbon.
[0007]
Further, when the amount of the hardly decomposable halogen compound absorbed by the activated carbon is saturated, it is necessary to replace the activated carbon, but it is difficult to grasp the replacement time. For this reason, while the activated carbon has a sufficient adsorptive power, replacement must be performed with safety, and the activated carbon is wastefully used or disposed.
[0008]
The present invention has been made in view of the above circumstances, and can efficiently purify an exhaust gas containing a hardly decomposable halogen compound, and can efficiently use an exhaust gas without wasting activated carbon. It is an object to provide a method and a method for operating a decomposition treatment facility for a hardly decomposable halogen compound.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, an exhaust gas purification method according to the present invention provides an exhaust gas discharged from a decomposition treatment facility for detoxifying a hardly decomposable halogen compound by passing the exhaust gas through an adsorption tower filled with an adsorbent. An exhaust gas purification method for adsorbing and removing a hardly decomposable halogen compound contained in the exhaust gas, wherein a molecular weight of the exhaust gas together with the hardly decomposable halogen compound is reduced in a portion excluding an upstream portion of the adsorption tower. The adsorbent is replaced with, for example, a new adsorbent when the amount of the organic substance having a boiling point of 200 ° C. or less at normal pressure and not higher than 150 ° C. becomes higher than a predetermined concentration.
[0010]
In the above exhaust gas purification method, the amount of organic matter having a molecular weight of 150 or less and a boiling point at normal pressure of 200 ° C. or less adsorbed on the adsorbent in a portion excluding the upstream portion of the adsorption tower (ie, the middle and downstream portions) is reduced. Since the adsorbent is replaced when the concentration becomes equal to or higher than the predetermined concentration, the adsorbent can be used efficiently. That is, in the adsorption tower, it is considered that the relatively low-molecular-weight and low-boiling-point organic substance as described above moves more quickly while saturating than the hardly decomposable halogen compound or the like. By monitoring, the breakthrough of the adsorption tower can be detected in advance. Therefore, the adsorbent can be appropriately replaced at a safe stage in which the adsorbent functions sufficiently and does not allow the hardly decomposable halogen compound or the reaction product to pass while using the adsorbent without waste.
[0011]
In a specific aspect of the exhaust gas purifying method, the adsorbent is replaced when the amount of adsorption to the adsorbent at a downstream portion of the adsorption tower becomes equal to or higher than a predetermined concentration. In this case, since the absorbent is replaced just before the breakthrough of the adsorption tower and at a stage where the passage of the hardly decomposable halogen compound or the like can be surely prevented, the adsorbent can be used most efficiently.
[0012]
In another specific embodiment of the above method, the organic substance is an aromatic hydrocarbon such as an alkylbenzene or an aliphatic hydrocarbon, ie, toluene, ethylbenzene, decane, decalin, or the like. In this case, it is possible to detect in advance the breakthrough of the adsorption tower due to a relatively high-molecular-weight organic substance such as electric insulating oil.
[0013]
In another specific aspect of the above method, the adsorbent is activated carbon. In this case, the exhaust gas can be efficiently processed.
[0014]
Further, in another specific embodiment of the above method, the decomposition treatment equipment is configured to decompose a hardly decomposable halogen compound by reacting an alkali metal dispersion containing an electrical insulating oil with a hardly decomposable halogen compound. And supplying exhaust gas discharged from the reaction tank to the adsorption tower. In this case, there is no by-product of harmful substances, and post-processing after decomposition is easy.
[0015]
In another specific embodiment of the above method, the method further comprises a step of contacting the exhaust gas containing the hardly decomposable halogen compound discharged from the reaction tank with the absorbing solution before supplying the exhaust gas to the adsorption tower. . In this case, the hardly decomposable halogen compound reaching the adsorption tower can be reliably reduced by the absorbing liquid.
[0016]
Further, in the operation method of the decomposition treatment facility according to the present invention, the decomposition treatment equipment for detoxifying the hardly decomposable halogen compound and the adsorbent are filled, and the exhaust gas discharged from the decomposition treatment equipment is passed. Thereby, an operation method of a decomposition treatment facility comprising: an exhaust gas purification facility having an adsorption tower that adsorbs and removes a hardly decomposable halogen compound contained in the exhaust gas, wherein a portion excluding an upstream portion of the adsorption tower is provided. When the amount of organic matter having a molecular weight of 150 or less contained in the exhaust gas together with the hardly decomposable halogen compound and having a boiling point of 200 ° C. or less at normal pressure to the adsorbent reaches a predetermined concentration or more, the adsorbent Exchange.
[0017]
In the above operation method, in a portion excluding the upstream portion of the adsorption tower, the molecular weight is 150 or less, at the time when the amount of organic matter having a boiling point at normal pressure of 200 ° C. or less to the adsorbent reaches a predetermined concentration or more, Since the adsorbent is replaced with a new adsorbent, the adsorbent can be used efficiently. That is, in the adsorption tower, it is considered that the relatively low-molecular-weight and low-boiling-point organic substances as described above are more likely to move quickly while saturating than the hardly decomposable halogen compounds and the like. By doing so, breakthrough of the adsorption tower can be detected in advance. Therefore, the adsorbent can be appropriately replaced at a safe stage where the adsorbent functions sufficiently and the hardly decomposable halogen compound or the like does not pass while using the adsorbent without waste.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
[First Embodiment]
FIG. 1 is a block diagram illustrating a configuration of a decomposition treatment facility including an exhaust gas purification device according to the first embodiment. This decomposition treatment facility includes a reaction device 10 and a gas purification device 20.
[0019]
The reaction device 10 is a reaction processing equipment for performing a dehalogenation reaction on a hardly decomposable halogen compound, and includes a reaction tank 11 with a stirring device 12, a reaction temperature control device (not shown), and the like. The stirring device 12 includes at least a stirring blade and a stirring motor, can freely adjust the rotation speed of the stirring blade, can sufficiently stir the hardly decomposable halogen compound and necessary chemicals and solvents, and stably perform a predetermined decomposition reaction. And make it uniform. The temperature control device is a device that adjusts the temperature in the reaction tank (the temperature of the decomposition reaction) to a predetermined temperature. From the end of the reaction to the end of the reaction, control is performed such that an appropriate and safe operation is ensured within a standard range of temperature, pressure, and the like.
[0020]
In the reaction apparatus 10, nitrogen gas is supplied to the reaction tank 11 in order to safely perform a dehalogenation reaction during the reaction of the hardly decomposable halogen compound. The gas supplied to the reaction tank 11 is not limited to nitrogen gas, but may be an inert gas such as argon gas.
[0021]
The hardly decomposable halogen compound dehalogenated in the reactor 10 is generally a halogen compound which is chemically stable and is not easily decomposed in a natural environment. Examples of the hardly decomposable halogen compound include PCB; dioxins; polychlorinated benzofurans; aromatic halogen compounds such as polychlorinated benzene and DDT; and alicyclic halogen compounds such as BHC.
[0022]
The solvent used in the dehalogenation reaction is not particularly limited as long as it is inert during the dehalogenation reaction of the hardly decomposable halogen compound. For example, n-hexane, n-heptane, n-octane, n-decane, kerosene, decalin, liquid paraffin, electric insulating oil (for example, electric insulating oil described in JIS C2320-1993), heavy oil (for example, JIS K2205) Hydrocarbon solvents such as heavy oil described); aromatic hydrocarbon solvents such as toluene and xylene; aprotic polar solvents such as 1,3-dimethylimidazoline, sulfolane, and polyethylene glycol dialkyl ether. Among these, use of non-polar organic solvents such as hydrocarbons and aromatic hydrocarbons is preferable, and use of electric insulating oil is particularly preferable.
[0023]
There are various methods for performing a dehalogenation reaction of a hardly decomposable halogen compound in a solvent, but here, a method of performing a dehalogenation reaction of a hardly decomposable halogen compound using an alkali metal dispersion in a solvent is used. I have. As the alkali metal dispersion, for example, a metal sodium dispersion obtained by dispersing metal sodium in a solvent is preferably used.
[0024]
The gas purifying device 20 is an exhaust gas purifying device for removing a hardly decomposable halogen compound from the exhaust gas discharged from the reaction tank 11, and includes a recirculator 21, an empty tank 22, a seal trap 23, an absorbing device 24, It comprises a cold condenser 25, a mist separator 26, an adsorption tower 27 filled with activated carbon, and a flashback preventer 28. When the content of the hardly decomposable halogen compound contained in the exhaust gas is low, the installation of the absorber 24 can be omitted.
[0025]
Here, the reflux unit 21 partially liquefies and condenses the gas discharged from the reaction tank 11 by cooling. The condensed liquid is returned to the reaction tank 11. The empty tank 22 and the seal trap 23 are provided to prevent the liquid or the exhaust gas from flowing backward. The absorbing device 24 is a gas-liquid countercurrent type filled with an absorbing liquid, and removes a hardly decomposable halogen compound from exhaust gas passing through the empty tank 22 and the seal trap 23. The cryogenic condenser 25 cools the exhaust gas to liquefy and condense gas components in the exhaust gas. The mist separator 26 is a separation device for removing mist (droplets) from gas. The adsorption tower 27 is a device filled with activated carbon, and performs an adsorption treatment of a hardly decomposable halogen compound and various organic substances remaining in the exhaust gas passing through the mist separator 26. The backfire prevention device 28 is installed to prevent the ingress of fire from the outside.
[0026]
Among these, the absorption device 24 draws out and circulates the absorbing liquid that absorbs the hardly decomposable halogen compound from the lower end while sending it from the upper end of the absorption tower. By sending the exhaust gas from the lower part of the absorption tower in this state, the absorbing solution and the exhaust gas can be brought into contact, and the hardly decomposable halogen compound in the exhaust gas can be taken into the absorbing solution.
[0027]
As the absorbing solution used for the contact treatment, those having excellent dissolving power for hardly decomposable halogen compounds and the like are preferable. Specific examples thereof include n-hexane, n-heptane, n-octane, n-decane, kerosene, decalin, liquid paraffin, electric insulating oil (for example, electric insulating oil described in JIS C2320-1993), and heavy oil (for example, And heavy oils described in JIS K2205); aromatic hydrocarbons such as toluene and xylene; aprotic polar solvents such as 1,3-dimethylimidazoline, sulfolane and polyethylene glycol dialkyl ether.
[0028]
Among these, from the viewpoint that the absorbent that has absorbed the hardly decomposable halogen compound can be used as it is as the solvent for the dehalogenation reaction, and the absorbed hardly decomposable halogen compound can be used again for the dehalogenation reaction, It is more preferable to use a solvent used for performing a dehalogenation reaction of a hardly decomposable halogen compound in the tank 11 for the contact treatment.
[0029]
The mist separator 26 provided at the next stage of the absorption device 24 and the cryogenic condenser 25 can be omitted, but is preferably installed from the viewpoint of completely removing the hardly decomposable halogen compound and the like.
[0030]
FIG. 2 is a diagram illustrating the structure of the adsorption tower 27. The adsorption tower 27 is a container including a cylindrical pipe material 27a and flanges 27b and 27c fixed to a pair of ends of the pipe material 27a, and introduces exhaust gas into an inlet tube 27d provided on a lower flange 27c. Then, exhaust gas is drawn out from an outlet tube 27e provided on the upper flange 27b. The inside of the container is filled with activated carbon AC. The type of the activated carbon AC to be filled is not particularly limited, and any of a coconut shell type, a wood type, and a coal type can be used, and granular charcoal or crushed charcoal can be pulverized and used. Sampling ports 27g to 27i for partially sampling the filled activated carbon AC are formed at three places, a lower part, a middle part, and an upper part of the pipe material 27a. Thereby, the operation state of the adsorption tower 27, that is, the degree of breakthrough progress can be sequentially monitored without taking out all the activated carbon AC from the adsorption tower 27.
[0031]
Returning to FIG. 1, the flashback arrestor 28 is installed for safety. Particularly, it is considered that the exhaust gas generated from the reaction tank 11 provided in the reactor 10 for performing the dehalogenation reaction of the hardly decomposable halogen compound also contains a combustible gas such as hydrogen gas.
[0032]
Hereinafter, the operation of the gas purification device 20 shown in FIG. 1 will be described. The exhaust gas generated from the reaction tank 11 is first cooled by the reflux unit 21, and the solvent vapor is liquefied (condensed) and returned to the reaction tank 11. Next, the exhaust gas passes through an empty tank 22 and a seal trap 23 for preventing backflow of the exhaust gas and the liquid, and is sent to an absorber 24.
[0033]
The exhaust gas sent into the absorbing device 24 comes into contact with the absorbing liquid, and almost no hardly decomposable halogen compounds and the like contained in the exhaust gas are absorbed and removed.
[0034]
The exhaust gas that has undergone such an absorption step is sent to a cooling step. In the cooling step, the exhaust gas usually heated to 20 to 30 ° C. is rapidly cooled to 0 ° C. or lower, preferably −10 ° C. or lower by the cryogenic condenser 25 to liquefy (condensate) gas components contained in the exhaust gas. . By cooling the exhaust gas which has been subjected to the contact treatment with the absorbent by the cryogenic condenser 25, a trace amount of the hardly decomposable halogen compound or the like can be condensed. The condensed liquid is collected by a condenser (not shown). The hardly decomposable halogen compound or the like collected in the condenser is returned to, for example, the reaction device again and subjected to a dehalogenation reaction.
[0035]
Next, the exhaust gas that has passed through the cryogenic condenser 25 is sent to the mist separator 26. By passing the exhaust gas cooled by the cryogenic condenser 25 through the mist separator 26, fine mist-like substances (solvents and hardly decomposable halogen compound components) which are not collected in the condenser of the cryogenic condenser 25 are removed. It can be completely separated from gaseous components.
[0036]
Next, the exhaust gas that has passed through the mist separator 26 is passed through an adsorption tower 27 filled with activated carbon to perform an exhaust gas adsorption process using activated carbon AC. The temperature at which the exhaust gas is brought into contact with the activated carbon AC is usually 0 ° C to 30 ° C. Further, the usage amount of the activated carbon AC is not particularly limited, and can be appropriately set according to the flow rate of the exhaust gas.
[0037]
Finally, the exhaust gas purified as described above is discharged outside through the flashback prevention device 28.
[0038]
In the operation of the gas purification device 20 described above, it is necessary to periodically exchange the activated carbon AC filled in the adsorption tower 27 with a new one. That is, since the adsorption capacity of the activated carbon AC is limited, when a certain amount of exhaust gas is passed through the adsorption tower 27, the adsorption tower 27 breaks through and the hardly decomposable halogen compounds in the exhaust gas are removed. There is a risk of passing through. In order to avoid this, activated carbon AC is adsorbed at each of the upstream, middle, and downstream portions of the adsorption tower 27 by using sampling ports 27g to 27i provided at three locations upstream, middle, and downstream of the adsorption tower 27. Analyze components regularly. For example, the sampled adsorbed component of activated carbon AC is extracted with n-hexane, and quantitative analysis of the adsorbed component of interest is performed using FID-GC (gas chromatography with a flame ionization detector).
[0039]
At this time, it is conceivable to directly detect a hardly decomposable halogen compound such as PCB. However, the hardly decomposable halogen compound reaching the adsorption tower 27 is a trace component, and in this case, toluene and ethylbenzene which are relatively easy to detect are used. And aromatic hydrocarbons such as decane and decalin. These aromatic hydrocarbons or aliphatic hydrocarbons (hereinafter sometimes referred to as “aromatic hydrocarbons”) may be used as a solvent for dissolving a hardly decomposable halogen compound or a solvent used for decomposing a hardly decomposable halogen compound. Since it is contained in the exhaust gas at a relatively high concentration as a volatile component in the absorbing solution used in the absorbing device 24, the detection is relatively easy. In addition, aromatic hydrocarbons and the like are organic substances having a low molecular weight and a low boiling point as compared with the hardly decomposable halogen compounds, and are considered to move quickly downstream while saturating the activated carbon AC in the adsorption tower 27. . Therefore, the activated carbon AC sampled from the downstream sampling port 27i is analyzed for the adsorption component, and when the concentration of the aromatic hydrocarbons or the like reaches a certain level or more, it is determined that the adsorption tower 27 is saturated and the breakthrough is near. can do. That is, when a certain concentration of alkylbenzene reaches the downstream of the adsorption tower 27, the activated carbon AC in the middle stream from the upstream of the adsorption tower 27 does not function due to adsorption of a relatively high polymer, a high boiling point biphenyl, an electric insulating oil and the like. Therefore, it is considered that the breakthrough of the adsorption downstream is also a matter of time.
[0040]
For the above reasons, when the concentration of the alkylbenzene extracted from the activated carbon AC collected at the sampling port 27i on the downstream side reaches the peak, the activated carbon AC in the adsorption tower 27 is replaced with new activated carbon or activated carbon that has been regenerated. I do. Thereby, it is possible to prevent the hardly decomposable halogen compound from passing through the adsorption tower 27 in the breakthrough state. In other words, by monitoring the concentration of the aromatic hydrocarbon or the like that moves ahead in the adsorption tower 27, the breakthrough of the adsorption tower 27 can be detected in advance and prevented. As a result, it is possible to ensure the safety of the environment by utilizing the activated carbon AC close to the limit of its adsorption capacity and preventing the trace amount of the hardly decomposable halogen compound from passing through the adsorption tower 27 even if the amount is very small.
[0041]
Table 1 below shows the results of analysis of the organic matter extracted from the activated carbon AC in the adsorption tower 27 whose replacement time is approaching by operating the reactor 10 for, for example, six months. The molecular weight of toluene to be analyzed is 90 and the boiling point under normal pressure is 110 ° C., the molecular weight of ethylbenzene is 106 and the boiling point under normal pressure is 136 ° C., and the molecular weight of o-xylene is 106 and the boiling point under normal pressure Is 142 ° C., the molecular weight of decane is 141 and the boiling point under normal pressure is 174 ° C., and the molecular weight of biphenyl is 154 and the boiling point under normal pressure is 255 ° C.
[0042]
[Table 1]

[0043]
Here, the unit of the detection amount is the weight (g) of the adsorption component detected per unit weight (1 kg) of the activated carbon AC after use. In the analysis of organic substances, 5 g of activated carbon AC and 25 g of n-hexane are mixed and treated with ultrasonic waves for 20 minutes to extract adsorbed components. Then, the n-hexane from which the organic component was extracted was diluted to 50 times the volume, and the adsorbed component in the diluted n-hexane was quantified using FID-GC.
[0044]
As is clear from the table, toluene and ethylbenzene show the highest concentration in activated carbon collected at the sampling port 27h in the middle stream, but have such low concentrations as to be hardly detectable in the activated carbon collected at the sampling port 27i downstream. I have. This indicates that toluene and ethylbenzene initially adsorbed on the upstream side desorbed to the middle stream. In addition, o-xylene shows the same tendency although it is not clear. On the other hand, biphenyl and electric insulating oil show the highest concentration in the activated carbon collected at the upstream sampling port 27g, but are hardly detected in the activated carbon collected at the midstream sampling port 27h. Furthermore, neither biphenyl nor electrical insulating oil was detected from the activated carbon collected at the downstream sampling port 27i.
[0045]
From the above analysis results, it can be seen that the saturated adsorption has progressed to the downstream side of the adsorption tower 27 when the detection peaks of toluene and ethylbenzene are detected at the middle and downstream sampling ports 27h and 27i. Therefore, for example, when the amount of toluene detected at the sampling port 27h on the middle stream side exceeds 10 g, it is determined that the breakthrough of the adsorption tower 27 is near and the activated carbon AC inside the adsorption tower 27 is replaced. Further, when the amount of toluene detected at the sampling port 27h on the middle stream side becomes smaller than the amount of ethylbenzene detected at the sampling port 27i on the downstream side (that is, when the concentration is reversed), the activated carbon AC inside the adsorption tower 27 is replaced. . That is, a volatile component contained in a reaction solvent or an absorbing solution used in an absorption device and the like, and in particular, an efficient operation of an adsorption tower is achieved by detecting an organic substance having a molecular weight of 150 or less and a boiling point at normal pressure of 200 ° C. or less. be able to. The timing of collecting the activated carbon from each of the sampling ports 27g to 27i is set to a period interval (for example, every several weeks) that affects the detection result of the adsorbed component. Also, the actual amount of activated carbon to be collected can be about several g in the case of quantification using FID-GC, since the amount of toluene or ethylbenzene may be determined.
[Second embodiment]
FIG. 3 is a block diagram illustrating a configuration of a decomposition treatment facility including an exhaust gas purification device according to the second embodiment. This decomposition treatment facility includes a post-treatment device 30 and a gas purification device 120.
[0046]
The post-treatment device 30 is a decomposition treatment facility similar to the reaction device 10, but includes a decomposition product of a hardly decomposable halogen compound contained in a reaction product obtained by performing a dehalogenation reaction in the reaction device 10. This is a facility that separates and recovers unreacted drugs, activators, solvents, etc., and finally puts them in a state where they can be discarded or reused.
[0047]
Specific examples of the post-treatment device include a centrifuge, a filtration device, a neutralization washing device, a liquid separation device, a distillation device, and the like. Using these devices, operations such as separation and recovery of solids from reaction products, decomposition of excess alkali, recovery of solvent, separation of generated salts, and separation of catalysts are performed.
[0048]
For example, a reaction product obtained by performing a dehalogenation reaction of a high concentration of a hardly decomposable halogen compound-containing substance using an alkali metal dispersion includes a solvent such as an electric insulating oil and a solid (a polyphenylene polymer, an electric insulating oil, Sodium hydroxide, salt, water, etc.). In this case, the post-processing equipment includes a centrifuge for solid-liquid separation, a washing device, a liquid separation device, and the like, and an operation of separating oil and solids is performed using these devices.
[0049]
When a low-concentration halogen-containing compound containing a low concentration is subjected to a dehalogenation reaction, water is added to the reaction product to obtain a mixture of biphenyls, salt solution, and electric insulating oil. Next, after the above mixture was washed and allowed to stand, the oil, tar, and waste water were separated using a liquid separation device, and the waste water was evaporated with a vaporizer, and the obtained solid was collected and evaporated. An operation of recovering water as process water by a water recovery device is performed.
[0050]
On the other hand, the gas purifying device 120 is an exhaust gas purifying device for removing hard-to-decompose halogen compounds from exhaust gas discharged from the post-processing device 30, and includes a recirculator 21, an empty tank 22, a seal trap 23, It comprises a condenser 25, a mist separator 26, an adsorption tower 27 filled with activated carbon, and a flashback preventer 28. The components of the gas purifying device 120 are the same as those in the first embodiment, and thus the description is omitted. The gas purifying device 120 does not include the absorption device 24. However, this is because the concentration of the hardly decomposable halogen compound included in the target of the post-processing device 30 is low. Considering that the concentration is extremely low as compared with the concentration of the neutral halogen compound.
[0051]
In the operation of the gas purifier 120 described above, the activated carbon AC filled in the adsorption tower 27 is periodically replaced with a new one, for example. Therefore, using the sampling ports 27g to 27i (see FIG. 2) provided at three places of the adsorption tower 27, the adsorption component of the activated carbon AC at each of the upstream, middle and downstream parts of the adsorption tower 27 is periodically checked. Monitor.
[0052]
Table 2 below shows the analysis results of the organic matter extracted from the activated carbon AC in the adsorption tower 27 whose replacement time is approaching by operating the post-treatment device 30 for, for example, six months.
[0053]
[Table 2]

[0054]
Here, the unit of the detection amount is the same as in Table 1 in the first embodiment. The method of analyzing organic substances was the same as in Table 1.
[0055]
Table 2 above also shows the same tendency as in Table 1. In other words, toluene and ethylbenzene show the highest concentration in activated carbon collected at the middle sampling port 27h, but have relatively low concentrations in activated carbon collected at the downstream sampling port 27i. In addition, o-xylene shows the same tendency although it is not clear. On the other hand, biphenyl and electric insulating oil show the highest concentration in the activated carbon collected at the upstream sampling port 27g, but show low concentrations in the activated carbon collected at the midstream sampling port 27h. Neither biphenyl nor electrical insulating oil was detected at all from the activated carbon collected at the downstream sampling port 27i.
[0056]
From the above analysis results, for example, when the amount of toluene detected at the sampling port 27h on the middle stream side exceeds 5 g, it is assumed that the breakthrough of the adsorption tower 27 is close and the activated carbon AC inside the adsorption tower 27 may be replaced. You can see that. Further, when the amount of toluene detected at the sampling port 27h on the middle stream side becomes smaller than the amount of ethylbenzene detected at the sampling port 27i on the downstream side, the activated carbon AC inside the adsorption tower 27 can be replaced. The timing of collecting activated carbon from each of the sampling ports 27g to 27i is set to a period during which the detection result of the adsorbed component is affected.
[0057]
Although the present invention has been described with reference to the embodiment, the present invention is not limited to the above embodiment.
[0058]
For example, in the reaction apparatus 10 of the first embodiment, a dehalogenation reaction of a hardly decomposable halogen compound is performed using an alkali metal dispersion. However, other methods, specifically, (1) An alkali-catalyzed decomposition method (BCD method) in which a hydrogen donor, an additive, and an alkali are added to a hardly decomposable halogen compound and then heated at normal pressure under a nitrogen atmosphere; Chemical extraction decomposition method of reacting with an alkali such as sodium hydroxide or potassium hydroxide in an aprotic polar solvent such as 3-dimethyl-2-imidazolidinone, sulfolane or polyethylene glycol dialkyl ether; An organic alkali metal such as potassium tertiary butoxide is added to the compound and heated to perform an organic alkali metal dehalogenation reaction. (4) Treatment such as catalytic hydrodechlorination (Pd / C method) in which a hardly decomposable halogen compound is heated at normal pressure in hydrogen gas in a solvent in the presence of a hydrogenation catalyst such as palladium / carbon. The same exhaust gas treatment can be performed by providing the same gas purification device as the above-described gas purification device 20 also in various types of reaction equipment that performs the above. Also in this case, the replacement time of the activated carbon can be monitored using a sampling port provided in the adsorption tower at a downstream position.
[0059]
In addition, a pretreatment facility is usually provided in a decomposition treatment facility for a hardly decomposable halogen compound. This pretreatment facility is a facility that accepts a hardly decomposable halogen compound or a substance containing a hardly decomposable halogen compound and separates it according to its type. Examples of the content of the hardly decomposable halogen compound that can be accepted in the pretreatment equipment include kerosene, decalin, electric insulating oil, heavy oil, lubricating oil, and mixtures thereof containing the hardly decomposable halogen compound. Specifically, waste such as a transformer or a capacitor containing a hardly decomposable halogen compound may be mentioned. The pre-treatment facility performs disassembly, cutting, breaking, sorting, etc. of the content of the received hard-to-decompose halogen compound, and for disassembling, cutting, breaking, and recovering the hard-to-decompose halogen compound from the separated product. Washing is performed. Examples of the washing method include an immersion method, a liquid circulation method, an ultrasonic method, and a bubbling method. The cleaning agent used must have good detergency, low risk of fire and explosion, low toxicity, and easy drying after cleaning. The hard-to-decompose halogen compound recovered by washing is stored in a storage container together with the detergent, separated from the detergent as necessary, sent to the next reaction device 10, and subjected to a dehalogenation reaction. You. In such a pretreatment facility, a gas purifying device similar to the gas purifying device 20 is provided to perform the same exhaust gas treatment. Also in this case, the replacement time of the activated carbon can be monitored using a sampling port provided at a downstream position in the adsorption tower.
[0060]
In the above embodiment, the breakthrough of the adsorption tower 27 is detected with alkylbenzene such as toluene or ethylbenzene. The replacement time of the activated carbon can be determined based on the amount of the organic substance having a boiling point of 200 ° C. or less at the sampling ports 27h and 27i located at the middle and downstream sides.
[0061]
【The invention's effect】
As is apparent from the above description, according to the exhaust gas purifying method and the operation method of the decomposition treatment facility according to the present invention, in the adsorption tower, organic substances having a relatively low molecular weight and a low boiling point compared with the hardly decomposable halogen compound or the like are used. Is considered to move quickly while being saturated. Therefore, by monitoring the preceding concentration of the organic substance, breakthrough of the adsorption tower can be detected in advance. Therefore, the adsorbent can be appropriately replaced at a safe stage where the adsorbent functions sufficiently and the hardly decomposable halogen compound or the like does not pass while using the adsorbent without waste.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a facility for decomposing a hardly decomposable halogen compound according to a first embodiment.
FIG. 2 is a diagram illustrating the structure of an adsorption tower.
FIG. 3 is a conceptual diagram of a facility for decomposing a hardly decomposable halogen compound according to a second embodiment.
[Explanation of symbols]
10 reactor
11 Reaction tank
20 Gas purification device
21 reflux unit
22 empty tank
23 Seal trap
24 Absorber
25 Chilled condenser
26 Mist separator
27 Adsorption tower
27g-27i Sampling port
28 Backfire arrestor
30 Post-processing equipment
AC activated carbon

Claims (7)

By passing the exhaust gas discharged from the decomposition treatment equipment for detoxifying the hardly decomposable halogen compound using an organic solvent through an adsorption tower filled with an adsorbent, the hardly decomposable halogen compound contained in the exhaust gas Exhaust gas purification method for adsorbing and removing
Except for the upstream portion of the adsorption tower, the amount of organic matter having a molecular weight of 150 or less contained in the exhaust gas together with the hardly decomposable halogen compound and a boiling point of 200 ° C. or less at normal pressure to the adsorbent is predetermined. The exhaust gas purifying method, wherein the adsorbent is replaced when the concentration becomes equal to or higher than the concentration. 2. The exhaust gas purifying method according to claim 1, wherein the adsorbent is replaced when the amount of adsorption to the adsorbent in the downstream portion of the adsorption tower becomes equal to or higher than a predetermined concentration. 3. The exhaust gas purification method according to claim 1, wherein the organic substance is an aromatic hydrocarbon or a saturated aliphatic hydrocarbon. The exhaust gas purifying method according to claim 1, wherein the adsorbent is activated carbon. The decomposition treatment equipment has a reaction tank for decomposing a hardly decomposable halogen compound by reacting an alkali metal dispersion containing an electrical insulating oil with a hardly decomposable halogen compound, and exhaust gas discharged from the reaction tank. The exhaust gas purification method according to any one of claims 1 to 4, wherein the exhaust gas is supplied to the adsorption tower. The exhaust gas purification method according to claim 5, further comprising a step of subjecting the exhaust gas containing the hardly decomposable halogen compound discharged from the reaction tank to a contact treatment with an absorbing solution before supplying the exhaust gas to the adsorption tower. A decomposition treatment facility for detoxifying the hard-to-decompose halogen compound, and an adsorbent is filled, and the exhaust gas discharged from the decomposition treatment facility is passed through, so that the hard-to-decompose halogen compound contained in the exhaust gas An exhaust gas purification apparatus having an adsorption tower that adsorbs and removes the gas, and a method for operating a decomposition treatment facility,
When the molecular weight contained in the exhaust gas together with the hardly decomposable halogen compound is 150 or less, an organic substance having a boiling point of 200 ° C. or less at normal pressure, when the amount of adsorption to the adsorbent becomes a predetermined concentration or more, the adsorbent is removed. A method for operating a decomposition treatment facility, wherein the method is replaced.

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