JP4305719B2 - Organic solvent processing equipment - Google Patents
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Description
【０００１】
【発明が属する技術分野】
本発明は、大気への有機溶剤の飛散を最小限として、有機溶剤を最大限に回収することを可能とした有機溶剤処理装置に関するものである。
【０００２】
【従来の技術】
近年、有害大気汚染物質に対する排出濃度規制が強化されてきており、有機溶剤処理装置からの排ガス中の有機溶剤濃度を最大限に低減することが望まれている。
【０００３】
従来、上記処理装置には吸着材として活性炭素繊維や粒状活性炭が充填されている吸着槽が２基以上設けられている他に、各吸着槽に対する有機溶剤が含有した被処理ガスを供給する手段と水蒸気を噴出する脱着手段とを設け、前記吸着槽にて被処理ガスを吸着処理する吸着工程と脱着手段にて脱着を行う脱着工程とを交互に切り替える手段が設けて構成してあった。
【０００４】
吸着に関与する細孔が粒状活性炭ではマクロポアであるのに対し活性炭素繊維ではミクロポアであることなどから、有機溶剤の吸着・脱着速度が活性炭素繊維の方が速く、また脱着時間が短時間で終了するため回収溶剤の品質が良いことが挙げられる。また、吸着材を水蒸気にて脱着を行うと、一旦吸着材が湿ることにより、吸着性能を長期間の運転において維持するには吸着材を次の脱着までに乾燥させる必要がある。この乾燥が不十分であると運転が進むに連れ吸着材の湿る部分が広がり、吸着性能を大幅に低下させる。活性炭素繊維は粒状活性炭に比べ乾燥が極めて速く行われることから、吸着工程が乾燥を兼ねるケースが一般的であった。
【０００５】
しかしながら、被処理ガスの有機溶剤濃度が増すに連れ、処理風量当たりの吸着材の多くなることから、乾燥を吸着工程で兼ねることは困難となっていき、下記の様々な対策が取られてきた。
(1)単独にて乾燥工程を設ける：乾燥用の吸着槽をもう１槽追加する 必要があることから、装置が大型化となる上、処理系統が複雑にな る問題がある。
(2)被処理ガスの吸着前温度を上げる（特許文献１参照）：吸着温度 を上げるに従い、吸着効率が低下する問題がある。
(3)被処理ガスの吸着前相対湿度を下げる：水分除去の付属装置が必 要である。
(4)被処理ガスを希釈して風量を増加させる（特許文献１参照4）： 吸着する有機溶剤濃度が下がるため、吸着効率も下がる。
【０００６】
これらの対策を行っても、吸着工程特に吸着初期においては乾燥が十分でなく、吸着材が湿っており高温であることから吸着能力が完全に回復していないため処理済ガス中に有機溶剤が漏れだすことがあった。また、吸着材の取付部の隙間や充填による隙間が極微量ではあるが発生するため、これらの隙間から被処理ガスが漏れ出すなどにより、１段のみの吸着工程での除去性能は９８〜９９％が限界となり、さらに除去性能を高めるには直列接続の多段吸着処理を行う必要があった。
【０００７】
メタノール、エタノール、イソプロピルアルコール等の低級アルコールを吸着処理する場合、分子径が小さく、極性が高いため、吸着材における吸着は物理吸着よりもむしろ吸着材に吸着した水分への吸収による吸着が寄与することから、脱着から吸着に切り替わった直後は吸着性能が高く、その後乾燥が進むにつれ吸着性能が低下するため、吸着時間の経過により吸着材の出口濃度が短時間で急激に上昇する。この対策としては、上記のように吸着材の乾燥を優先に行うのではなく、加湿等にて被処理ガスの相対湿度を上げて、吸着材の湿りを維持させる方策により吸着性能の低下を防いできた。
【０００８】
【特許文献１】
特開昭５８−９２４４４号公報
【０００９】
【発明が解決しようとする課題】
近年の環境認識の向上に伴い、排出ガス中の有機溶剤含有量の規制が強化されたことから、有機溶剤含有量の低減化が活発となって来ている。被処理ガスの有機溶剤濃度が高濃度の場合においては、除去性能が９９％以上を求められるため、直列多段処理を行うケースが増して来ている。直列多段処理の順序としては、被処理ガスを最初に吸着処理する１段目の工程を第１吸着工程とし、その後に処理効率が上がるに従い処理経路に直列に接続された吸着処理工程を２段目（第２吸着工程）、３段目（第３吸着工程）と増していくことになる。尚、脱着効率を落とさないために、脱着は吸着処理の１段目である第１吸着工程が終了した後に行うことが最良であり、直列２段吸着処理の例に取ると、特定の吸着槽での処理サイクルは脱着→第２吸着工程→第１吸着工程→脱着となる。
【００１０】
しかし、直列２段以上の処理の場合、第１吸着工程では高濃度有機溶剤の吸着熱により、吸着材に吸着していた水分が蒸発し、この水分が次工程の第２吸着工程に移り、第２吸着工程での乾燥を阻害させてしまう。さらに、この水分が第１吸着工程と第２吸着工程との間で循環し、最終的には吸着材の乾燥不良となり、吸着材が湿りだし最終的には濡れることにより吸着効率が大幅に低下する。
【００１１】
この吸着熱は有機溶剤濃度に比例することから、濃度が高ければ高い程吸着熱の発生量が増し、吸着材の温度上昇、処理済ガスの温度上昇及び水分の蒸発などが発生するため、第１吸着工程の吸着材の吸着効率を低下させるだけでなく、後工程である第２吸着工程へ悪影響を及ぼすことを考慮して細心の注意を払って装置設計に取り組む必要があった。また、被処理ガスが高濃度で低風量の場合に顕著となる。吸着熱の発生を抑制する方法としては、被処理ガスの有機溶剤濃度を希釈などにより下げる方法があるが、吸着濃度を下げすぎると吸着効率も大きく低下することから吸着材量を多くしなければならい。また、外気による希釈では加熱手段も用いることのより、年間を通して、ある程度第１吸着工程への乾燥効果に関してある程度期待出来るが、相対湿度（水分濃度）が安定しないため、メタノール等の低級アルコールの吸着効率が大きく変動し、例えば夏期の処理性能は良くて冬期は悪くなるなどの問題があった。
【００１２】
本発明は高濃度（１万ｐｐｍ以上）のメタノール等の低級アルコールを含んだ有機溶剤処理において、高濃度であることから希釈にて吸着熱の影響を回避する場合、第１吸着工程から吸着熱により蒸発した水分を含んだ出口の処理済ガスの一部を第１吸着工程の入口に戻すことにより、第１吸着工程入口処理前ガスの風量及び相対湿度を上げることが出来ることから、従来よりもコンパクトでありランニングコストも安価となる有機溶剤処理装置を提供するものである。
【００１３】
【課題を解決するための手段】
即ち、本発明は高濃度（１万ｐｐｍ以上）のメタノール等の低級アルコールを含んだ有機溶剤処理において、高濃度であることから希釈にて吸着熱の影響を回避する場合、１段目吸着槽出口から１段目吸着槽入口に戻す経路及び流量調節弁を設けて、第１吸着工程から吸着熱により蒸発した水分を含んだ出口の処理済ガスの一部を第１吸着工程の入口の希釈用として使用することにより、第１吸着工程入口の処理ガスの相対湿度を上げて、吸着材の湿り状態を維持し、吸着（乾燥）の進行によるメタノール等の低級アルコールの吸着性能低下を防ぐことが出来る。
【００１４】
被処理ガスに付加する希釈風量（戻り風量）を増やしていき、吸着する有機溶剤の濃度が下がり吸着熱の発生による吸着処理後のガスの温度上昇幅が１５℃以下に好ましくは１０℃以下となるように調整される。
【００１５】
濃度が非常に高く（数万ｐｐｍ以上）希釈倍率を高くとる場合には第１吸着工程出口の処理済ガスの一部を戻すだけでは不足するため、外気取り入れ手段を設けることにより不足分を補うことも可能である。
【００１６】
上記は吸着材の湿り状態を維持させる方法であるが、乾燥が全く不十分となり吸着材が濡れる場合においては、第２吸着工程入口にて処理ガスを外気にて希釈し第２吸着工程に流れる処理ガスの風量を増す方法及び冷却・加熱手段により第２吸着工程に流れる処理ガスの相対湿度を下げる方法等を取ることにより、第１吸着処理によって低濃度となったメタノール等の低級アルコールの吸着処理を行う第２吸着工程においての乾燥を促進させて吸着材が濡れることを防止することがある。
【００１７】
第１吸着工程出口の処理済ガスの一部を用いて第１吸着工程入口において被処理ガスの希釈を行うと、吸着熱によって蒸発した水分の一部が第１吸着工程入口に戻ることにより、第１吸着工程の入口ガスの相対湿度が上がり吸着材の温度上昇を抑えて乾燥を抑制する効果がある。
【００１８】
この結果、本発明により連続的に高濃度有機溶剤含有ガスを高効率に除去することが可能となり非常に操作性に優れるとともに、長期期間にわたっての高性能を維持することが可能となった。
【００１９】
【発明の実施の形態】
本発明の一実施形態を図１にて説明する。有機溶剤含有ガスＡは第１吸着出口の処理済ガスの一部と混合されて、送風機１にて自動ダンパー１１の開閉により第１吸着工程となっている吸着槽２に送られ、有機溶剤は吸着槽２内の吸着材を通過中に吸着されて被処理ガスとなって排出される。しかしこの被処理ガス中には第１吸着工程で漏れだした有機溶剤が含まれていることから、さらに吸着処理を行うため、第２吸着工程へ送風機５にて送られ、第２吸着工程となっている吸着槽２にて処理後清浄ガスとなって系外へ排出される。第２吸着工程の後、第１吸着工程が終了した吸着槽２は脱着工程に切り替わり自動ダンパー１１で封鎖され、吸着槽２内に水蒸気を噴出して、すでに吸着材に吸着された有機溶剤ガスを脱着する。脱着された有機溶剤ガスはコンデンサー６へ送られる。脱着された有機溶剤ガスと水蒸気はコンデンサー６にて凝縮し、凝縮した有機溶剤は回収溶剤として得られる。
【００２０】
第１吸着工程から吸着熱により蒸発した水分を含んだ出口の処理済ガスの一部Ｈを流量調節弁14の開閉により、第１吸着工程の入口の希釈用として送風機１の吸い込み側にて有機溶剤含有ガスＡと混合する経路を設けることにより、第１吸着工程入口の処理ガスの相対湿度を上げて、吸着材の湿り状態を維持し、吸着（乾燥）の進行によるメタノールの吸着性能低下を防ぐ。
【００２１】
第１吸着工程出口の処理済ガスの一部を用いて第１吸着工程入口において被処理ガスの希釈を行うと共に、吸着熱によって蒸発した水分の一部が第１吸着工程入口に戻ることにより、第１吸着工程の入口ガスの相対湿度が上がり吸着材の温度上昇を抑えて乾燥が抑制され、長期間の連続運転においても、第１吸着工程出口さらに第２吸着工程出口から排出されるメタノール濃度を低減することが可能となった。
【００２２】
【実施例】
図１に示す有機溶剤処理装置を基本フローとして、以下に活性炭素繊維を吸着材として使用した有機溶剤処理装置での実施例を示す。［実施例１］メタノールを２００００ｐｐｍ含む３０℃の溶剤混合ガス風量５０Ｎｍ3／分と第１吸着工程出口の一部である５０Ｎｍ3／分とを混合し希釈した後、送風機１、吸着槽２、送風機３、吸着槽２の順に流し被処理ガスの吸着処理を行った。吸着時間８分間及び脱着時間６分間にて切替を行い、脱着されたメタノールと水蒸気はコンデンサー６へ送られ、コンデンサー７にて凝縮し、メタノールを回収した。
【００２３】
吸着熱の発生により第１吸着工程出口の処理済ガスは吸着前に比べ、温度が３２．５℃から３５℃に、露点が２２．５℃から２４℃に上昇しており、
第１吸着工程出口の一部を戻した第１吸着工程入口の未処理ガスの温度は３２．５℃、露点は２２．５℃となり、外気で希釈した比較例２及び希釈を行わなかった比較例１に比べ露点が上昇している。第１吸着工程出口中のメタノール濃度は平均１７０ppm（除去率９８．３％）、第２吸着工程出口中のメタノール濃度は平均４ppm（除去率９７．６％）となった。
【００２４】
［比較例１］メタノールを２００００ｐｐｍ含む３０℃の溶剤混合ガス風量５０Ｎｍ3／分と外気５０Ｎｍ3／分とを混合し希釈した後、送風機１、吸着槽２、送風機３、吸着槽２の順に流し被処理ガスの吸着処理を行った。吸着時間８分間及び脱着時間６分間にて切替を行い、脱着されたメタノールと水蒸気はコンデンサー６へ送られ、コンデンサー７にて凝縮し、メタノールを回収した。
【００２５】
外気によって希釈された第１吸着工程入口の未処理ガスの温度は３０℃、露点は１６．５℃となり、被処理ガスに比べ露点が６℃低下している。第１吸着工程出口中のメタノール濃度は平均６５０ppm（除去率９３．５％）、第２吸着工程出口中のメタノール濃度は平均２０ppm（除去率９６．９％）となった。
【００２６】
［比較例２］メタノールを２００００ｐｐｍ含む３０℃の溶剤混合ガスを、風量５０Ｎｍ3／分で送風機１、吸着槽２、送風機３、吸着槽２の順に流し被処理ガスの吸着処理を行った。吸着時間８分間及び脱着時間６分間にて切替を行い、脱着された塩化メチレンと水蒸気はコンデンサー６へ送られ、コンデンサー６にて凝縮し、メタノールを回収した。
【００２７】
吸着熱の発生により第１吸着工程出口の処理済ガスは吸着前に比べ、温度が３０℃から４５℃に、露点が２１℃から２４．５℃に上昇している。第１吸着工程出口中のメタノール濃度は平均１４７０ppm（除去率９２．７％）、第２吸着工程出口中のメタノール濃度は平均６８ppm（除去率９５．４％）となった。
【００２８】
実施例、比較例１、比較例２の処理結果を下記の表１に示す。
【表１】
【発明の効果】
以上の様に本発明の有機溶剤処理装置によれば、高濃度（１万ｐｐｍ以上）のメタノール等の低級アルコールを含んだ有機溶剤処理において、高濃度であることから希釈にて吸着熱の影響を回避する場合、第１吸着工程から吸着熱により蒸発した水分を含んだ出口の処理済ガスの一部を第１吸着工程の入口に戻すことにより、第１吸着工程入口処理前ガスを希釈すると共に乾燥を抑制させることが出来ることから、吸着効率が大幅に向上し、従来よりもコンパクトでありランニングコストも安価となる有機溶剤処理装置を提供するものである。
【図面の簡単な説明】
【図１】有機溶剤処理装置の実施例の基本処理フロー図
【図２】有機溶剤処理装置の比較例の基本処理フロー図
【符号の説明】
１：送風機
２：吸着槽
３：送風機
６：コンデンサー
１１：自動ダンパー
１２：水蒸気弁
１３：脱着ガス弁
Ａ：有機溶剤被処理ガス
Ｂ：第１吸着工程出口ガス
Ｃ：第２吸着工程入口ガス
Ｄ：清浄ガス
Ｅ：外気
Ｈ：戻りガス[0001]
[Technical field to which the invention belongs]
The present invention relates to an organic solvent processing apparatus capable of maximally recovering an organic solvent while minimizing the scattering of the organic solvent to the atmosphere.
[0002]
[Prior art]
In recent years, emission concentration regulations for harmful air pollutants have been strengthened, and it is desired to reduce the organic solvent concentration in the exhaust gas from the organic solvent treatment apparatus to the maximum.
[0003]
Conventionally, the treatment apparatus is provided with two or more adsorption tanks filled with activated carbon fibers or granular activated carbon as an adsorbent, and means for supplying a gas to be treated containing an organic solvent for each adsorption tank And a desorption means for ejecting water vapor, and a means for alternately switching between an adsorption process for adsorbing the gas to be treated in the adsorption tank and a desorption process for desorption by the desorption means.
[0004]
The pores involved in adsorption are macropores in granular activated carbon, but micropores in activated carbon fiber. Therefore, the adsorption and desorption rate of organic solvents is faster with activated carbon fiber, and the desorption time is shorter. Since the process is completed, the quality of the recovered solvent is good. Further, when the adsorbent is desorbed with water vapor, the adsorbent is once moistened, so that it is necessary to dry the adsorbent before the next desorption in order to maintain the adsorption performance in a long-term operation. If this drying is insufficient, as the operation proceeds, the portion of the adsorbent that gets wet spreads and the adsorption performance is greatly reduced. Since activated carbon fibers are dried much faster than granular activated carbon, the case where the adsorption process also serves as a drying is common.
[0005]
However, as the concentration of the organic solvent in the gas to be treated increases, the amount of adsorbent per processing air volume increases, so it is difficult to combine drying with the adsorption process, and the following various measures have been taken. .
(1) Establishing a drying process independently: Since it is necessary to add another adsorption tank for drying, there is a problem that the apparatus becomes large and the processing system becomes complicated.
(2) Raising the pre-adsorption temperature of the gas to be treated (see Patent Document 1): There is a problem that the adsorption efficiency decreases as the adsorption temperature is raised.
(3) Lowering the relative humidity before adsorption of the gas to be treated: A water removal accessory is required.
(4) Diluting the gas to be treated to increase the air volume (see Patent Document 1 4): Since the concentration of the adsorbed organic solvent is lowered, the adsorption efficiency is also lowered.
[0006]
Even if these measures are taken, drying is not sufficient in the adsorption process, particularly in the early stage of adsorption, and the adsorption capacity is not completely recovered because the adsorbent is moist and high temperature. There was a leak. Further, since the gap between the adsorbent attachment portions and the gap due to filling is generated in a very small amount, the removal performance in only one stage of the adsorption process is 98 to 99 due to leakage of the gas to be treated from these gaps. % Was the limit, and in order to further improve the removal performance, it was necessary to perform a multi-stage adsorption treatment connected in series.
[0007]
When adsorbing lower alcohols such as methanol, ethanol, and isopropyl alcohol, the molecular diameter is small and the polarity is high. Therefore, the adsorption in the adsorbent contributes to the adsorption to the moisture adsorbed to the adsorbent rather than the physical adsorption. Therefore, immediately after switching from desorption to adsorption, the adsorption performance is high, and as the drying proceeds thereafter, the adsorption performance decreases, so that the outlet concentration of the adsorbent rapidly increases in a short time as the adsorption time elapses. As a countermeasure against this, rather than prioritizing drying of the adsorbent as described above, the relative humidity of the gas to be treated is increased by humidification or the like to prevent the adsorption performance from being lowered. did it.
[0008]
[Patent Document 1]
JP-A-58-92444 [0009]
[Problems to be solved by the invention]
With the recent improvement in environmental awareness, regulations on the content of organic solvents in exhaust gas have been strengthened, so that the reduction of organic solvent content has become active. When the concentration of the organic solvent in the gas to be treated is high, the removal performance is required to be 99% or more, and therefore, the number of cases where serial multistage treatment is performed is increasing. As the order of the serial multi-stage process, the first stage process for first subjecting the gas to be treated to adsorption is the first adsorption process, and thereafter, the adsorption process process connected in series to the treatment path as the treatment efficiency is increased to two stages. The number will increase with the second stage (second adsorption process) and the third stage (third adsorption process). In order not to reduce the desorption efficiency, it is best to perform desorption after the completion of the first adsorption process, which is the first stage of the adsorption process. In the example of the series two-stage adsorption process, a specific adsorption tank is used. The treatment cycle is as follows: desorption → second adsorption step → first adsorption step → desorption.
[0010]
However, in the case of the treatment of two or more stages in series, the moisture adsorbed on the adsorbent is evaporated by the adsorption heat of the high concentration organic solvent in the first adsorption step, and this moisture moves to the second adsorption step of the next step, The drying in the second adsorption process is hindered. Furthermore, this moisture circulates between the first adsorption step and the second adsorption step, eventually resulting in poor drying of the adsorbent, and the adsorbent begins to get wet and eventually gets wet, greatly reducing the adsorption efficiency. To do.
[0011]
Since this heat of adsorption is proportional to the concentration of the organic solvent, the higher the concentration, the greater the amount of heat generated, causing the temperature of the adsorbent to rise, the temperature of the treated gas to rise, the evaporation of moisture, etc. In addition to reducing the adsorption efficiency of the adsorbent in the first adsorption process, it was necessary to pay close attention to the device design in consideration of adverse effects on the second adsorption process, which is a subsequent process. Moreover, it becomes remarkable when the gas to be treated has a high concentration and a low air volume. As a method of suppressing the generation of heat of adsorption, there is a method of lowering the organic solvent concentration of the gas to be treated by dilution, etc. However, if the adsorption concentration is lowered too much, the adsorption efficiency will greatly decrease, so the amount of adsorbent must be increased. Goodbye. In addition, the use of heating means for dilution with outside air can be expected to some extent with respect to the drying effect on the first adsorption process throughout the year, but the relative humidity (moisture concentration) is not stable, so adsorption of lower alcohols such as methanol. The efficiency fluctuated greatly, for example, there was a problem that the processing performance in summer was good and bad in winter.
[0012]
In the present invention, in the treatment with an organic solvent containing a lower alcohol such as methanol having a high concentration (10,000 ppm or more), when the influence of the heat of adsorption is avoided by dilution because of the high concentration, the heat of adsorption is changed from the first adsorption step. Since it is possible to increase the air volume and relative humidity of the gas before the first adsorption step inlet treatment by returning a part of the treated gas at the outlet containing the water evaporated by the above to the inlet of the first adsorption step, The present invention provides an organic solvent processing apparatus that is compact and has a low running cost.
[0013]
[Means for Solving the Problems]
That is, in the present invention, in the treatment of an organic solvent containing a lower alcohol such as methanol having a high concentration (10,000 ppm or more), when the influence of heat of adsorption is avoided by dilution because of the high concentration, the first stage adsorption tank A path for returning from the outlet to the first stage adsorption tank inlet and a flow rate adjusting valve are provided, and a part of the treated gas at the outlet containing moisture evaporated by the heat of adsorption from the first adsorption process is diluted at the inlet of the first adsorption process. By increasing the relative humidity of the processing gas at the inlet of the first adsorption process and maintaining the wet state of the adsorbent, the adsorption performance of lower alcohols such as methanol due to the progress of adsorption (drying) is prevented. I can do it.
[0014]
The dilution air volume (return air volume) added to the gas to be treated is increased, the concentration of the adsorbed organic solvent decreases, and the temperature rise of the gas after the adsorption treatment due to the generation of adsorption heat is 15 ° C. or less, preferably 10 ° C. or less. It is adjusted to become.
[0015]
If the concentration is very high (tens of thousands ppm or more) and the dilution ratio is high, it is not sufficient to return only a part of the treated gas at the outlet of the first adsorption process, so the shortage is compensated by providing outside air intake means. It is also possible.
[0016]
The above is a method for maintaining the wet state of the adsorbent. However, when the adsorbent gets wet because the drying is completely insufficient, the process gas is diluted with the outside air at the second adsorption step inlet and flows to the second adsorption step. Adsorption of lower alcohols such as methanol, etc., which have been reduced in concentration by the first adsorption process by increasing the air volume of the process gas and reducing the relative humidity of the process gas flowing into the second adsorption process by means of cooling / heating. The adsorbent may be prevented from getting wet by promoting drying in the second adsorption step in which the treatment is performed.
[0017]
When the gas to be processed is diluted at the first adsorption process inlet using a part of the treated gas at the first adsorption process outlet, a part of the water evaporated by the adsorption heat returns to the first adsorption process inlet, The relative humidity of the inlet gas in the first adsorption step is increased, and the temperature of the adsorbent is suppressed and drying is suppressed.
[0018]
As a result, according to the present invention, it is possible to continuously remove the high-concentration organic solvent-containing gas with high efficiency, and it is possible to maintain excellent performance over a long period of time while being extremely excellent in operability.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIG. The organic solvent-containing gas A is mixed with a part of the treated gas at the first adsorption outlet and sent to the adsorption tank 2 which is the first adsorption process by opening and closing the
[0020]
A part H of the treated gas at the outlet containing moisture evaporated by the heat of adsorption from the first adsorption step is organically formed on the suction side of the blower 1 for dilution of the inlet of the first adsorption step by opening and closing the
[0021]
A portion of the treated gas at the first adsorption process outlet is used to dilute the gas to be treated at the first adsorption process inlet, and a part of the water evaporated by the adsorption heat returns to the first adsorption process inlet. The relative humidity of the inlet gas in the first adsorption process is increased, the temperature rise of the adsorbent is suppressed and drying is suppressed, and the methanol concentration discharged from the first adsorption process outlet and further from the second adsorption process outlet even in continuous operation for a long period of time. Can be reduced.
[0022]
【Example】
The organic solvent processing apparatus shown in FIG. 1 is used as a basic flow, and an example of an organic solvent processing apparatus using activated carbon fibers as an adsorbent will be described below. [Example 1] After mixing and diluting 50Nm 3 / min of 30 ° C solvent mixed gas containing 20000 ppm of methanol and 50Nm 3 / min which is a part of the first adsorption step outlet, the blower 1, the adsorption tank 2, The blower 3 and the adsorption tank 2 were flowed in this order to perform the adsorption treatment of the gas to be treated. Switching was performed with an adsorption time of 8 minutes and a desorption time of 6 minutes, and the desorbed methanol and water vapor were sent to the condenser 6 and condensed in the condenser 7 to recover the methanol.
[0023]
Due to the generation of adsorption heat, the treated gas at the first adsorption process outlet has a temperature rising from 32.5 ° C. to 35 ° C. and a dew point from 22.5 ° C. to 24 ° C.
The temperature of the untreated gas at the first adsorption process inlet after returning a part of the first adsorption process outlet was 32.5 ° C., the dew point was 22.5 ° C., and Comparative Example 2 diluted with outside air and comparison without dilution Compared to Example 1, the dew point is increased. The methanol concentration at the outlet of the first adsorption step averaged 170 ppm (removal rate 98.3%), and the methanol concentration at the second adsorption step outlet averaged 4 ppm (removal rate 97.6%).
[0024]
[Comparative Example 1] After mixing and diluting 50Nm 3 / min of solvent mixed gas at 30 ° C. containing 20000 ppm of methanol and 50Nm 3 / min of outside air, the blower 1, the adsorption tank 2, the blower 3 and the adsorption tank 2 are flowed in this order. The gas to be treated was adsorbed. Switching was performed with an adsorption time of 8 minutes and a desorption time of 6 minutes, and the desorbed methanol and water vapor were sent to the condenser 6 and condensed in the condenser 7 to recover the methanol.
[0025]
The temperature of the untreated gas at the inlet of the first adsorption step diluted with outside air is 30 ° C., and the dew point is 16.5 ° C. The dew point is 6 ° C. lower than the treated gas. The methanol concentration at the outlet of the first adsorption step averaged 650 ppm (removal rate 93.5%), and the methanol concentration at the outlet of the second adsorption step averaged 20 ppm (removal rate 96.9%).
[0026]
[Comparative Example 2] A solvent mixed gas containing 20000 ppm of methanol was passed through the blower 1, the adsorption tank 2, the blower 3, and the adsorption tank 2 in this order at an air volume of 50 Nm 3 / min to carry out the adsorption treatment of the gas to be treated. Switching was performed at an adsorption time of 8 minutes and a desorption time of 6 minutes, and the desorbed methylene chloride and water vapor were sent to the condenser 6 and condensed in the condenser 6 to recover methanol.
[0027]
Due to the generation of heat of adsorption, the temperature of the treated gas at the outlet of the first adsorption step is raised from 30 ° C. to 45 ° C. and the dew point is raised from 21 ° C. to 24.5 ° C. compared to before the adsorption. The methanol concentration at the outlet of the first adsorption step averaged 1470 ppm (removal rate 92.7%), and the methanol concentration at the outlet of the second adsorption step averaged 68 ppm (removal rate 95.4%).
[0028]
The processing results of Examples, Comparative Examples 1 and 2 are shown in Table 1 below.
[Table 1]
【The invention's effect】
As described above, according to the organic solvent treatment apparatus of the present invention, in the treatment of an organic solvent containing a lower alcohol such as methanol having a high concentration (10,000 ppm or more), the influence of the heat of adsorption due to dilution is high. In order to avoid this, the gas before the first adsorption process inlet treatment is diluted by returning a part of the treated gas at the outlet containing water evaporated by the heat of adsorption from the first adsorption process to the inlet of the first adsorption process. In addition, since the drying can be suppressed, the organic solvent processing apparatus is provided which has a significantly improved adsorption efficiency, is more compact than conventional ones, and has a lower running cost.
[Brief description of the drawings]
FIG. 1 is a basic process flow diagram of an embodiment of an organic solvent treatment apparatus. FIG. 2 is a basic process flow chart of a comparative example of an organic solvent treatment apparatus.
1: Blower 2: Adsorption tank 3: Blower 6: Condenser 11: Automatic damper 12: Water vapor valve 13: Desorption gas valve A: Organic solvent treated gas B: First adsorption process outlet gas C: Second adsorption process inlet gas D : Clean gas E: Outside air H: Return gas
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| JPH0584417A (en) * | 1991-09-26 | 1993-04-06 | Kobe Steel Ltd | Method and equipment for recovering solvent |
| JPH10286426A (en) * | 1997-04-15 | 1998-10-27 | Kuraray Eng Kk | Continuous adsorption device and utilizing method of the same |
| JP2000300943A (en) * | 1999-04-15 | 2000-10-31 | Toho Kako Kensetsu Kk | Method for treatment of solvent-containing gas |
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