JP3995864B2 - Method for treating volatile compounds in liquid - Google Patents

Description

Ｌ：液相流量［ｍｏｌ／ｍ２ｈ］
Ｇ：気相流量［ｍｏｌ／ｍ２ｈ］
π： 全圧［ａｔｍ］
【０００７】
したがって、揮発性が高く、式（１）であらわされるヘンリー定数が例えば１０００ａｔｍ／モル分率程度の場合には、Ｌ／（Ｇ／π）＝１０００程度が好ましいが、被処理液の液量に比べてガス量が極めて少ない系となるために、普通の充填塔をそのまま使用したのでは期待するような性能とはなり得ない。これは、被処理液の液量に比べてガス量が極めて小さい場合には、ガスの逆混合が起こり、向流操作が実現しないためである。
すなわち、充填塔においては、充填物の間を液が流れ落ちる際にガスを同伴するが、一般の気液接触操作では、ガス量が大きいためにこの効果は無視できる程度である。しかし、液量に比べてガス量が極めて少ない場合には、被処理液を大液量で流すとガスが下向きに流れる逆混合が生じて、ガスの上下方向での混合が生じ、塔内でパージガス濃度の均一化が起こり、ガス側の向流操作が実質的に不充分になると共に、液側からの目的物質の低濃度域までの除去が不完全となる。この傾向は、充填塔の塔径が大きくなるとさらに顕著になる。
【０００８】
このような系の場合、従来型の放散塔では大過剰のパージガスを用いることになり、その結果、パージガス中の目的成分濃度が低くなり、これの回収を図るためには効率が低下する。例えば、水蒸気を用いて液中の目的物質を放散し、これを凝縮しても凝縮液中での濃度が低いために、目的とする物質の分離のためにはさらに濃縮操作が必要となり、また、空気放散の場合には活性炭等による吸着操作が必要となる。あるいは、放散ガスを焼却等により処理しようとしても過剰のガスを熱分解温度まで加熱することが必要になるため、エネルギー的に非効率な処理になってしまう等の問題があった。
【０００９】
本発明では前記課題の解決を図るために、充填塔内に設置する充填層をガス逆流防止板で仕切り、逆混合を防止しつつ、被処理液とパージガスとをガス相を連続相とした状態で向流接触させることで、液中の揮発性化合物の放散が効率的に行えるようにしたものである。
被処理液とパージガスとを向流接触させる際に、ガス相が連続相となる状態とは、充填塔内を流下する被処理液が充填層を通過する際に、充填物の表面で液膜状になって通過し、上昇してくるパージガスが連続相となっていることを指している。このような状態で気液接触が行われることにより、本発明の被処理液とパージガスとの接触が効率的となる。
【００１０】
このような効果を与える設備としては、流下液膜を利用した設備も考えられる。すなわち、充填物と同様に、例えば細管を多数用い、その内壁表面を被処理液が流れ、パージガスがその内側を流れる構造であってガス流量がわずかであっても逆混合が起こりにくくするような構造である。
このような構造も基本的には本発明と同様の考え方であり、本発明の実施のために用いることが可能である。
【００１１】
本発明の処理方法により、液中より放散させて除去・低減させる有効な物質としては、ベンゼン、トルエン等の揮発性有機化合物、ジクロロメタン、トリハロメタン等の揮発性ハロゲン化有機物があげられる。また、これら以外の物質であっても同様の揮発性が得られる物質であれば同様の効果が期待されるため、本発明では、これらを揮発性化合物と総称する。特に本発明は、前述の揮発性有機物を含む被処理液に適用すると効果的である。
揮発性がそれほど高くはない物質では、式（２）で与えられるパージガス量が比較的多くなるため、本発明のようにガス逆流防止板を用いた設備を使用せずに、従来設備を使用しても、逆混合の効果が無視できる運転が可能である。
この限界としてはＬ／Ｇが１００程度となるヘンリー定数１００ａｔｍ／モル分率程度である。このため、本発明では、液中に含まれている揮発性化合物のヘンリー定数が１００ａｔｍ／モル分率以上であることが望ましい。
【００１２】
本発明で対象とする被処理液としては、排水・廃液等で前述した揮発性化合物を含む水溶液の形態が多いが、各種の油状物質や有機溶媒等であっても本発明の放散処理の適用が可能である。
【００１３】
本発明の処理方法によれば、被処理液中に含まれている揮発性化合物の高度の濃縮を行うことができる。すなわち、揮発性が高くヘンリー定数が十分大きい場合には、Ｌ／Ｇを大きくして処理することになるので、操作温度を水の沸点付近にとり、パージガスとして水蒸気を用いて、得られる放散蒸気を冷却し凝縮させると揮発性化合物の高倍率な濃縮を行うことができる。
例えば、対象となる揮発性化合物のヘンリー定数が１００ａｔｍ／モル分率の場合は約１００倍、ヘンリー定数が１０００ａｔｍ／モル分率の場合は約１０００倍の濃縮が可能である。
【００１４】
被処理液中の揮発性化合物を、水蒸気により放散し凝縮回収した場合、回収される揮発性化合物の量が、回収される水への溶解量を超えると２相に分離する。これは、一般的に揮発性化合物の水への溶解性が大きくはないことと、本発明の処理では、高濃度の濃縮が可能なことによる。
その結果、例えばベンゼンを１００ｐｐｍ含む被処理液を、本発明により水蒸気放散して得られる凝縮液は２相に分離し、容易に有機相の回収を図ることができる。
【００１５】
木発明について図面を基に詳細に説明する。
図１は、本発明の処理を行うための設備の一例であり、基本的な構成を示す説明図である。
充填塔１の中には、ガス逆流防止板２で仕切られた充填層３が複数設置されている。充填塔１の上部には、被処理液の導入口４および排出ガスの出口５、充填塔の下部にはパージガスの導入口６と被処理液の取り出し口７が設置されている。
パージガスを充填塔下部のパージガス導入口６から塔内に導入し、ガス逆流防止板２で仕切られ充填物の充填されている領域で、充填層３を通してパージガスが上昇する間に下降してくる被処理液とガス相を連続相とした状態で向流接触し、被処理液中の揮発性化合物が放散され、その後被処理液は被処理液の取り出し口７から系外に取り出される。
ガス逆流防止板２で仕切られている領域を順次通過する際に、上部にある被処理液の導入口４から導入された被処理液とパージガスとが向流的に接触し、被処理液中の揮発性化合物が放散して除去・低減されつつ下降し、一方パージガスは塔内を上昇して放出された揮発性化合物と共に排出ガスの出口５より排出される。
【００１６】
充填塔の上部にある被処理液の導入口４と最上部の充填層の間には、ガス逆流防止板を設けなくともよいが、図１のガス逆流防止板２’のごとくに他の箇所と同種もしくは異なる形のものを設けておくことが望ましい。これは、充填層の表面に被処理液を均一に分散散布するためのものであり、くし形分散器等他の一般的な液分散器で代替えすることも可能である。
【００１７】
充填層３としては、周知の不規則充填物あるいは規則充填物を用いて構成すればよく、充填物はガス逆流防止板２の上に載せてもよいし、ガス逆流防止板とは別の目皿やサポートグリッド等で充填物を支持するような構造としてもよい。
【００１８】
ガス逆流防止板として最も簡単なものは、平板に孔をあけた形式のオリフィス板でもよい。しかし、オリフィス板の場合にはガスと液の通るところが同じであるため液とガスの分散が不確実になりやすいので、分散を確実にするためにはガスライザーを設置して、ガスはガスライザーを通して上昇させ、液は液孔から下降するように工夫することが合理的である。
このようにガスライザーを設けたガス逆流防止板の例を図２に示す。図２では液孔１２を設けた平板１０にガスライザー１１を複数本設けてある。ガスライザーは中空でガスを通すように直径数ｍｍ程度の孔が貫通している。このガス孔はガスライザー上面あるいは側壁面上部の液に浸らない部分に設けられる。液を通すための液孔１２はガスライザーの開孔よりやや大きくし４〜６ｍｍ程度であるが、これらの数値は固定的なものでなく、使用目的や利用状況によって適宜選択すればよい。
【００１９】
【実施例】
実施例１
図１に示した設備により、常温で被処理水中に含まれている１，１，１−トリクロロエタン（ＴＣＥ）の放散を行った。
充填塔は塔径１０ｃｍφの塔内に、図２のガス逆流防止板１１枚を用い、一段当たりの高さを２０ｃｍとし、充填物としてラシヒスパーリングを充填した充填層を１０段とした。
被処理水４は１，１，１−トリクロロエタンを１００ｐｐｍ程度含む液（２５℃）であり、パージガス６としては空気を用いた。結果を表１に示した。尚、１，１，１−トリクロロエタンのヘンリー定数（２５℃）は約１２００ａｔｍ／モル分率である。また、排出されるガス量は普通測定することはないので、今回も測定していない。
【００２０】
【表１】

【００２１】
供給水中の１，１，１−トリクロロエタンのモル分率１．３９×１０^−５が、放散ガス中では０．０１４となり、約１０００倍の濃縮が行われていることが判る。
排出されるガス中の１，１，１−トリクロロエタンは、通常の活性炭を用いる溶剤回収設備により回収してもよいし、焼却設備により完全に分解を行うようにしてもよい。いずれの方法を用いたとしても、排ガス中の濃度が高くなっているため経済的に有用な方法となる。
パージガスとしては、窒素等のガスを用いてもよい。特にこの例では１，１，１−トリクロロエタンの空気中での爆発下限界が８．０ｖｏｌ％であるので空気を用いて放散処理を行ったが、危険性の高い揮発性化合物等については、窒素等の不活性なガスを用いるべきであることは当然である。
【００２２】
実施例２
実施例１で用いたと同様の充填塔を用い、水蒸気放散を行うために図３に示したフローによる設備を使用して、液中のベンゼンあるいはジクロロメタンの回収を行った。
図３において、被処理液は熱交換器２６、２７により約１００℃にまで加熱された後、当該充填塔２０に供給され、パージガス中に揮発性成分を放散した後、被処理液排出口より排出され、保持している熱量の一部を熱交換器２６により被処理液に与え冷却された後、処理水タンク２２に送られる。一方、パージガスには水蒸気を使用し、パージガス供給口２３より供給し、充填塔内において被処理液より揮発した有機化合物を含有する蒸気は、排出ガス出口より排出され、熱交換器２８により冷却凝縮されて回収液タンク２４に回収される。
回収液タンク２４には、揮発性化合物および放散用水蒸気として使用した水が回収されるが、揮発性化合物の量が回収される水への溶解量を超える場合２相に分離する。これは、揮発性化合物の水への溶解性が大きくはないことと、当該処理で高濃度な濃縮が可能なことによる。
本実施例では、被処理液としてはベンゼンあるいはジクロロメタンを１００ｐｐｍ程度含有する液を用いた。本発明の充填塔による処理では、液ガス比を大きくとれるので十分な濃縮を行うことができ、回収液は２相に分離した。
ベンゼン含有被処理液についての結果を表２に、ジクロロメタン含有被処理液についての結果を表３に示した。尚、ベンゼン、ジクロロメタンのヘンリー定数（２５℃）は各々３０８、１３６ａｔｍ／モル分率である。
【００２３】
【表２】

【表３】

【００２４】
この回収液から有機相側を分離することで揮発性化合物を回収することができた。
水相には一部揮発性化合物の有機物が溶解しているが、よく行われるようにこの相を被処理液ラインに戻すと被処理液中の揮発性化合物濃度が上がり、その結果、揮発性化合物のほぼ全量を回収することが可能である。
また、実施例では、エネルギー節減のために熱交換器２６を用い、排出水の所有熱を被処理液の加温用熱源の一部として使用しているが、エネルギー的に高コストでない場合は別々に処理してもよい。
【００２５】
【発明の効果】
本発明により、充填塔方式により液中の揮発性化合物を放散させ、液中の揮発性化合物を効率的に除去、・低減したり、濃縮するための新しい方法を提供することが可能となった。
水溶液中の揮発性化合物はハロゲン化有機物を含め低濃度で存在することが多く、従来の放散塔による処理を行おうとした場合、塔内でガス側の逆混合が起こるため、揮発性が高い物質であっても液ガス比を大きくはできなかった。その結果過剰の放散ガスが必要であり、その後の処理に過大な設備が必要であったり多量のエネルギーを必要とした。本発明による方法では液相に比べごくわずかのガスでの運転が効果的に行えるため、特に、揮発性の高い有機物の放散に対し効果的に働き高い濃縮度での除去が可能となった。
【図面の簡単な説明】
【図１】本発明の処理方法を実施するための設備の一例である。
【図２】ガス逆流防止板の一例である。
【図３】本発明の実施例２における処理方法の簡単なフロー図である。
【符号の説明】
１ 充填塔
２ ガス逆流防止板
２’ガス逆流防止板
３ 充填層
４ 被処理液の導入口
５ 排出ガスの出口
６ パージガスの導入口
７ 被処理液の取り出し口
１０ 平版
１１ ガスライザー
１２ 液孔
２０ 充填塔
２１ 被処理液タンク
２２ 処理水タンク
２３ パージガス（水蒸気）
２４ 回収液タンク
２５ 彼処理液送液ポンプ
２６，２７，２８ 熱交換器[0001]
BACKGROUND OF THE INVENTION
The present invention is a method for treating a volatile compound dissolved in a liquid, and by removing the volatile compound from various factory effluents generated in a chemical factory or the like, the removal of these compounds from the liquid or Applicable for recovery. The present invention is an environment-friendly technology that can efficiently perform a volatile compound emission treatment in a liquid to be treated.
[0002]
[Prior art]
Conventionally, a packed bed type or a shelf type diffusion tower is known as a method for removing volatile compounds in waste water by diffusion. The conventional packed bed type diffusion tower requires a sufficient gas linear velocity to effectively make countercurrent contact between the liquid to be treated and the purge gas, and is excessive when volatile substances are diffused. A large amount of emitted gas was required.
Therefore, the concentration of volatile compounds in the gas phase is not sufficient compared to the liquid phase, and in order to treat the emitted gas containing this volatile compound, the volatile compound is absorbed using an adsorbent such as activated carbon. In the case of recovery or incineration, there is an economical disadvantage because a large amount of emitted gas must be processed.
In addition, since there are no restrictions on these volatile compounds in the exhaust gas compared with the waste water, there are many examples in which the exhaust gas is simply diffused into the atmosphere by air aeration (air stripping).
[0003]
In recent years, there are concerns about the effects of volatile compounds typified by benzene and toluene or volatile halogenated organic substances typified by environmental hormones, dichloromethane and chloroform, and similar compounds on the human body. Under these circumstances, effective methods for recovering these compounds from wastewater have not been obtained. Therefore, in order to remove these compounds from wastewater, as described above, the diffusion-adsorption recovery using a large amount of air. Since there is no regulation in the Air Pollution Control Act, such as a method that requires a large amount of energy, such as diffusion-incineration decomposition, a method of aeration by air aeration and the like has been performed.
[0004]
[Problems to be solved by the invention]
The present invention is an effective and economical process for dissipating, removing or recovering a highly volatile compound represented by benzene, toluene, dichloromethane, chloroform and the like from many of these organic compounds. A method is provided.
In addition, the present invention is a method capable of concentrating the volatile compound by efficiently dissipating it even when the concentration of the volatile compound contained in the liquid is low.
In the present invention, since the liquid / gas ratio can be increased, the facility can be simplified.
[0005]
[Means for Solving the Problems]
The present invention provides a plurality of gas risers having gas holes for allowing gas to pass through a flat plate provided with liquid holes, the gas holes being provided in a portion not immersed in the liquid on the upper surface of the gas riser or the side wall surface, liquid holes is using a packed tower having a packed layer partitioned by the gas backflow prevention plate rot size than openings of the gas holes of the gas riser two or more, introducing a liquid to be treated from the top of the packed column, filled A liquid characterized in that a purge gas is introduced from the lower part of the tower, and a volatile compound in the liquid to be treated is diffused by bringing the liquid to be treated and the purge gas into countercurrent contact with the gas phase being a continuous phase. It is a processing method of the volatile compound in the inside. Further, the treatment method of volatile compounds in a liquid, characterized in that by using the above-mentioned treatment method, water vapor is used as a purge gas, the emitted vapor containing the obtained volatile compounds is cooled and condensed, and the volatile compounds are concentrated and recovered. Is the method.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
As an index indicating the volatility of the compound from the liquid phase, the Henry constant represented by the formula (1) can be given.
p = Ex (1)
x: molar fraction of compound in liquid phase [−]
p: partial pressure of the compound in the gas phase in equilibrium with the liquid [atm]
E: Henry's constant [atm / mole fraction]
In the radiation process, from the viewpoint of balance and efficiency, ideally, λ represented by the equation (2) is operated in the vicinity of 1.

L: Liquid phase flow rate [mol / m2h]
G: Gas phase flow rate [mol / m2h]
π: Total pressure [atm]
[0007]
Accordingly, when the Henry constant expressed by the formula (1) is high, for example, about 1000 atm / mole fraction, L / (G / π) = 1000 is preferable. Compared to a system with an extremely small amount of gas, an ordinary packed tower cannot be used as expected. This is because when the amount of gas is very small compared to the amount of liquid to be treated, back-mixing of the gas occurs and countercurrent operation is not realized.
That is, in the packed tower, gas is accompanied when the liquid flows down between the packed materials. However, in a general gas-liquid contact operation, the gas amount is large, so this effect is negligible. However, when the amount of gas is very small compared to the amount of liquid, when the liquid to be treated is flowed in a large amount, reverse mixing occurs in which the gas flows downward, and mixing in the vertical direction of the gas occurs. The uniformity of the purge gas concentration occurs, the counterflow operation on the gas side becomes substantially insufficient, and the removal of the target substance from the liquid side to the low concentration region becomes incomplete. This tendency becomes more prominent as the column diameter of the packed tower increases.
[0008]
In the case of such a system, a large excess of purge gas is used in the conventional diffusion tower. As a result, the concentration of the target component in the purge gas is lowered, and the efficiency is lowered in order to recover it. For example, if the target substance in the liquid is dissipated using water vapor and condensed, the concentration in the condensate is low, so a further concentration operation is required to separate the target substance. In the case of air dissipation, an adsorption operation with activated carbon or the like is required. Alternatively, even if it is attempted to treat the diffused gas by incineration or the like, it is necessary to heat the excess gas to the thermal decomposition temperature, resulting in an inefficient treatment.
[0009]
In the present invention, in order to solve the above problems, the packed bed installed in the packed tower is partitioned by a gas backflow prevention plate, and the liquid to be treated and the purge gas are in a continuous phase while preventing backmixing. In this way, the volatile compound in the liquid can be efficiently diffused by countercurrent contact.
When the liquid to be treated and the purge gas are brought into countercurrent contact, the state in which the gas phase becomes a continuous phase means that a liquid film is formed on the surface of the packing when the liquid to be treated flowing down the packed tower passes through the packed bed. It means that the purge gas that passes through and rises as a continuous phase. By performing the gas-liquid contact in such a state, the contact between the liquid to be treated of the present invention and the purge gas becomes efficient.
[0010]
As equipment that gives such an effect, equipment using a falling liquid film is also conceivable. That is, as with the packing, for example, a large number of thin tubes are used, the liquid to be processed flows on the inner wall surface, and the purge gas flows on the inside thereof, so that back-mixing hardly occurs even if the gas flow rate is small. Structure.
Such a structure is also basically the same concept as the present invention, and can be used to implement the present invention.
[0011]
Examples of effective substances that can be removed and reduced by being diffused from the liquid by the treatment method of the present invention include volatile organic compounds such as benzene and toluene, and volatile halogenated organic substances such as dichloromethane and trihalomethane. Moreover, even if it is a substance other than these, since the same effect is anticipated if it is a substance with the same volatility, in the present invention, these are named generically as a volatile compound. In particular, the present invention is effective when applied to the liquid to be treated containing the volatile organic matter described above.
For substances that are not so volatile, the amount of purge gas given by equation (2) is relatively large, so that conventional equipment is used instead of equipment using a gas backflow prevention plate as in the present invention. However, the operation in which the effect of back mixing can be ignored is possible.
This limit is about the Henry constant of 100 atm / mole fraction at which L / G is about 100. For this reason, in this invention, it is desirable that the Henry's constant of the volatile compound contained in the liquid is 100 atm / mole fraction or more.
[0012]
As the liquid to be treated in the present invention, there are many forms of aqueous solutions containing the above-mentioned volatile compounds in waste water / waste liquids, etc., but even in the case of various oily substances, organic solvents, etc., the application of the radiation treatment of the present invention Is possible.
[0013]
According to the treatment method of the present invention, the volatile compound contained in the liquid to be treated can be highly concentrated. That is, when the volatility is high and the Henry's constant is sufficiently large, processing is performed with a large L / G. Therefore, the operating temperature is set near the boiling point of water, and steam is used as a purge gas, and the obtained diffused steam is When cooled and condensed, volatile compounds can be concentrated at high magnification.
For example, when the Henry constant of the target volatile compound is 100 atm / mole fraction, the concentration can be about 100 times, and when the Henry constant is 1000 atm / mole fraction, the concentration can be about 1000 times.
[0014]
When the volatile compound in the liquid to be treated is diffused and collected by water vapor, it is separated into two phases when the amount of the recovered volatile compound exceeds the amount dissolved in the recovered water. This is because, in general, the solubility of volatile compounds in water is not large, and the treatment of the present invention enables high concentration concentration.
As a result, the condensate obtained by, for example, subjecting the liquid to be treated containing 100 ppm of benzene to water vapor emission according to the present invention can be separated into two phases, and the organic phase can be easily recovered.
[0015]
The wood invention will be described in detail with reference to the drawings.
FIG. 1 is an explanatory diagram showing a basic configuration as an example of equipment for performing the processing of the present invention.
A plurality of packed beds 3 partitioned by a gas backflow prevention plate 2 are installed in the packed tower 1. At the upper part of the packed tower 1, an inlet 4 for the liquid to be treated and an outlet 5 for the exhaust gas are installed, and at the lower part of the packed tower, an inlet 6 for the purge gas and an outlet 7 for the liquid to be treated are installed.
The purge gas is introduced into the tower from the purge gas inlet 6 at the lower part of the packed tower, and is separated by the gas backflow prevention plate 2 and is filled while the purge gas rises through the packed bed 3 in the region filled with the packed material. In a state where the treatment liquid and the gas phase are in a continuous phase, they are brought into countercurrent contact, volatile compounds in the treatment liquid are diffused, and then the treatment liquid is taken out from the removal outlet 7 of the treatment liquid.
When sequentially passing through the region partitioned by the gas backflow prevention plate 2, the liquid to be processed and the purge gas introduced from the inlet 4 of the liquid to be processed in the upper part come into countercurrent contact with each other, The volatile compounds are discharged and removed while being removed and reduced, while the purge gas rises in the tower and is discharged from the outlet 5 of the exhaust gas together with the volatile compounds released.
[0016]
It is not necessary to provide a gas backflow prevention plate between the inlet 4 of the liquid to be treated at the top of the packed column and the uppermost packed bed, but other parts such as the gas backflow prevention plate 2 'in FIG. It is desirable to have the same or different shape. This is for uniformly dispersing and spraying the liquid to be treated on the surface of the packed bed, and can be replaced by other general liquid dispersers such as a comb disperser.
[0017]
The packed layer 3 may be configured by using a known irregular packing or a regular packing, and the packing may be placed on the gas backflow prevention plate 2 or may have a different eye from the gas backflow prevention plate. It is good also as a structure which supports a filling with a plate, a support grid, etc.
[0018]
The simplest gas backflow prevention plate may be an orifice plate of a type in which a hole is formed in a flat plate. However, in the case of an orifice plate, the gas and liquid pass through the same place, so the dispersion of the liquid and the gas tends to be uncertain. Therefore, in order to ensure the dispersion, a gas riser is installed. It is reasonable to devise such that the liquid is raised through the liquid hole and lowered from the liquid hole.
An example of the gas backflow prevention plate provided with the gas riser is shown in FIG. In FIG. 2, a plurality of gas risers 11 are provided on a flat plate 10 provided with liquid holes 12. The gas riser is hollow and has a hole with a diameter of about several millimeters so as to allow gas to pass therethrough. The gas hole is provided in a portion not immersed in the liquid on the upper surface of the gas riser or the upper side wall surface. The liquid hole 12 through which the liquid passes is slightly larger than the opening of the gas riser and is about 4 to 6 mm. However, these numerical values are not fixed and may be appropriately selected depending on the purpose of use and the use situation.
[0019]
【Example】
Example 1
With the equipment shown in FIG. 1, 1,1,1-trichloroethane (TCE) contained in the water to be treated at room temperature was diffused.
The packed tower used a gas backflow prevention plate of 11 in FIG. 2 in a tower having a diameter of 10 cmφ, a height of 20 cm per stage, and a packed bed filled with Raschig Sparing as a packing.
The water to be treated 4 is a liquid (about 25 ° C.) containing about 100 ppm of 1,1,1-trichloroethane, and air is used as the purge gas 6. The results are shown in Table 1. The Henry's constant (25 ° C.) of 1,1,1-trichloroethane is about 1200 atm / mole fraction. In addition, since the amount of gas discharged is not normally measured, it has not been measured this time.
[0020]
[Table 1]

[0021]
It can be seen that the molar fraction of 1,1,1-trichloroethane in the feed water of 1.39 × 10 ⁻⁵ is 0.014 in the emitted gas, and the concentration is about 1000 times.
1,1,1-trichloroethane in the discharged gas may be recovered by a solvent recovery facility using ordinary activated carbon, or may be completely decomposed by an incineration facility. Whichever method is used, it is an economically useful method because the concentration in the exhaust gas is high.
A gas such as nitrogen may be used as the purge gas. In particular, in this example, 1,1,1-trichloroethane had a lower explosion limit in the air of 8.0 vol%, and thus the emission treatment was performed using air. However, for volatile compounds having high danger, Naturally, an inert gas such as should be used.
[0022]
Example 2
Using the same packed tower as used in Example 1 and using the equipment with the flow shown in FIG. 3 to dissipate water vapor, benzene or dichloromethane in the liquid was recovered.
In FIG. 3, the liquid to be treated is heated to about 100 ° C. by the heat exchangers 26 and 27 and then supplied to the packed tower 20 to dissipate volatile components in the purge gas. A part of the amount of heat discharged and retained is supplied to the liquid to be treated by the heat exchanger 26 and cooled, and then sent to the treated water tank 22. On the other hand, steam is used as the purge gas, supplied from the purge gas supply port 23, and the vapor containing the organic compound volatilized from the liquid to be treated in the packed tower is discharged from the exhaust gas outlet and cooled and condensed by the heat exchanger 28. Then, it is recovered in the recovery liquid tank 24.
The recovered liquid tank 24 collects water used as a volatile compound and water vapor for release, but separates into two phases when the amount of the volatile compound exceeds the amount dissolved in the recovered water. This is because the solubility of volatile compounds in water is not great and high concentration can be achieved by the treatment.
In this example, a liquid containing about 100 ppm of benzene or dichloromethane was used as the liquid to be treated. In the treatment by the packed tower of the present invention, the liquid gas ratio can be increased, so that sufficient concentration can be performed, and the recovered liquid is separated into two phases.
The results for the benzene-containing treatment liquid are shown in Table 2, and the results for the dichloromethane-containing treatment liquid are shown in Table 3. The Henry constants (25 ° C.) of benzene and dichloromethane are 308 and 136 atm / mol fraction, respectively.
[0023]
[Table 2]

[Table 3]

[0024]
Volatile compounds could be recovered by separating the organic phase side from the recovered liquid.
Some organic substances of volatile compounds are dissolved in the aqueous phase, but if this phase is returned to the liquid line to be treated as is often done, the concentration of volatile compounds in the liquid to be treated will increase, resulting in volatile It is possible to recover almost all of the compound.
In the embodiment, the heat exchanger 26 is used to save energy, and the possessed heat of the discharged water is used as a part of the heat source for heating the liquid to be treated. You may process separately.
[0025]
【The invention's effect】
According to the present invention, it has become possible to provide a new method for dissipating volatile compounds in a liquid by a packed tower system and efficiently removing, reducing or concentrating the volatile compounds in the liquid. .
Volatile compounds in aqueous solutions are often present in low concentrations, including halogenated organics, and when a treatment with a conventional stripping tower is attempted, gas side back-mixing occurs in the tower, resulting in highly volatile substances. Even so, the liquid-gas ratio could not be increased. As a result, an excessive amount of emitted gas was required, and excessive equipment or a large amount of energy was required for the subsequent processing. Since the method according to the present invention can be operated with a very small amount of gas as compared with the liquid phase, it can effectively remove organic substances having high volatility and can be removed with high concentration.
[Brief description of the drawings]
FIG. 1 is an example of equipment for carrying out the processing method of the present invention.
FIG. 2 is an example of a gas backflow prevention plate.
FIG. 3 is a simple flowchart of a processing method in Embodiment 2 of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Packing tower 2 Gas backflow prevention plate 2 'Gas backflow prevention plate 3 Packing layer 4 Processed liquid inlet 5 Exhaust gas outlet 6 Purge gas inlet 7 Processed liquid outlet 10 Flat plate 11 Gas riser 12 Liquid hole 20 Packed tower 21 Liquid tank 22 Treated water tank 23 Purge gas (water vapor)
24 Recovery liquid tank 25 He treatment liquid feed pump 26, 27, 28 Heat exchanger

Claims (4)

A plurality of gas risers having gas holes for allowing gas to pass therethrough are provided in a flat plate provided with liquid holes, and the gas holes are provided in a portion not immersed in the liquid on the upper surface of the gas riser or on the side wall surface. a packed bed partitioned by the gas backflow prevention plate rot size than openings of the riser of the gas holes using a packed column provided two or more, introducing a liquid to be treated from the top of the packed column, from the bottom of the packed column A volatile compound in a liquid characterized in that a volatile compound in the liquid to be treated is released by introducing a purge gas and bringing the liquid to be treated and the purge gas into countercurrent contact with the gas phase being a continuous phase. Processing method.   The method for treating a volatile compound in a liquid according to claim 1, wherein the Henry's constant of the volatile compound is 100 atm / mole fraction or more. The method for treating a volatile compound in a liquid according to claim 1 or 2, wherein the volatile compound is a volatile organic substance. A method for treating a volatile compound in a liquid, characterized in that by using the treatment method according to claim 1, water vapor is used as a purge gas, and the obtained vapor containing the volatile compound is cooled and condensed, and the volatile compound is concentrated and recovered. .

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