JP4399959B2

JP4399959B2 - Method and apparatus for treating waste water containing volatile organic substances

Info

Publication number: JP4399959B2
Application number: JP2000160718A
Authority: JP
Inventors: 望育野; 聡山田
Original assignee: Kurita Water Industries Ltd
Current assignee: Kurita Water Industries Ltd
Priority date: 2000-05-30
Filing date: 2000-05-30
Publication date: 2010-01-20
Anticipated expiration: 2020-05-30
Also published as: JP2001340845A

Description

【０００１】
【発明の属する技術分野】
本発明は揮発性有機物含有排水の処理方法及び処理装置に係り、特に、半導体製造工場等のプロセス排水の回収再利用に当たり、該排水中のアルコールやケトン類を効率的に除去して水回収する方法及び装置に関する。
【０００２】
【従来の技術】
半導体製造工程では、シリコン基板などの洗浄のために大量の超純水が使用されており、環境への負荷低減、水資源の有効活用の観点から、この洗浄排水（リンス排水）の回収再利用が広く行われている。このリンス排水中には、ＩＰＡ（イソプロピルアルコール）などといった揮発性有機物が含まれている場合が多く、リンス排水を再利用するためにはこれらの有機物を除去する必要がある。
【０００３】
従来、リンス排水中に含まれる有機物を除去する技術として、オゾン／過酸化水素、オゾン／ＵＶ（紫外線）、ＵＶ／過酸化水素、オゾン／アルカリなどを組み合わせることにより非常に強い酸化力を有するＯＨラジカルを生じさせ、この強力な酸化力によって有機物を除去する促進酸化法；過硫酸ナトリウム等の酸化剤を用いて高温で反応させる湿式酸化法；微生物を利用する生物的処理方法などが用いられてきた。
【０００４】
【発明が解決しようとする課題】
しかしながら、促進酸化法、湿式酸化法は共に原水のＴＯＣ濃度の増加に伴い酸化剤添加量を増加させなければならず、高濃度ＴＯＣ成分を含む原水を処理するには不向きであった。また、生物的処理による場合は、原水ＴＯＣの濃度変動に十分に対応しきれず、また、発生する余剰菌体の処理に負担がかかるという問題があった。
【０００５】
本発明は、上記従来の問題点を解決し、排水中のＩＰＡのような揮発性有機物を酸化剤や生物処理によることなく、容易かつ効率的に除去して、超純水製造用原水とすることができる高水質の処理水を回収することが可能な揮発性有機物含有排水の処理方法及び処理装置を提供することを目的とする。
【０００６】
【課題を解決するための手段】
本発明の揮発性有機物含有排水の処理方法は、揮発性有機物含有排水中の揮発性有機物を除去する方法において、該排水を７５〜９５℃に調節する第１工程と、該第１工程で温度調節した水をガスと向流接触させる第２工程とを備え、該第２工程におけるガスとの向流接触前の水に対する向流接触後の水の水温低下が１２℃以下であり、該ガスが空気又は窒素ガスであることを特徴とする。
【０００７】
本発明の揮発性有機物含有排水の処理装置は、揮発性有機物含有排水中の揮発性有機物を除去する装置において、該排水を７５〜９５℃に調節する排水温度調節手段と、該排水温度調節手段の処理水をガスと向流接触させるガス向流接触手段とを備え、該ガス向流接触手段は、該ガス向流接触手段の入口の水温に対する出口の水温低下を１２℃以下に調節するための水温差調節手段を備え、該ガスが空気又は窒素ガスであることを特徴とする。
【０００８】
本発明により、所定温度に加熱した水をストリッピングガスと向流接触させることにより、揮発性有機物を効率的にストリッピングガス側へ移行させて除去することができる。
【０００９】
特に、この向流接触に当たり、向流接触前の水に対する向流接触後の水の水温低下が１２℃以下となるように水温の低下を抑えるため、揮発性有機物を効率的に除去することができる。
【００１０】
【発明の実施の形態】
以下に図面を参照して本発明の実施の形態を詳細に説明する。
【００１１】
図１は本発明の揮発性有機物含有排水の処理方法及び処理装置の実施の形態を示す系統図である。
【００１２】
図１の方法では、原水をまず回収用熱交換器１で後段の放散塔３の処理水と熱交換して予備加熱した後、加熱用熱交換器２で加熱する。この回収用熱交換器１は必ずしも必要とされないが、このように回収用熱交換器１を設けて処理水で原水を予熱すると共に、処理水を冷却することにより、熱回収が図れ、加熱コストの低減の面で有利である。また、加熱用熱交換器２の型式としては特に制限はないが、スチームを用いた熱交換器等を用いることができる。この原水の加熱温度は、低過ぎると揮発性有機物を効率的に除去し得ず、高過ぎると水が揮発性有機物側へ移行してしまい、揮発性有機物のみを選択的に分離することが困難となることから、７５〜９５℃とする。
【００１３】
加熱用熱交換器２で加熱した水は、次いで、放散塔３の塔上部から散水し、塔下部から導入したストリッピングガスと向流接触させる。この散水方式には特に制限はないが、均一分散による気液接触効率を高めるために、スプレー式とするのが好ましい。放散塔３は充填材を充填したものであっても、充填材のない空塔式のものであっても良く、また、整流のための棚を設けた多段式のものであっても良いが、気液接触効率を高めるためには、ラシヒリング、ベルルサドル等の充填材を充填するのが好ましい。ストリッピングガスとしては、空気又は窒素ガスが好適である。このストリッピングガスの流量は、原水流量に対するガス流量の割合（Ｇ／Ｌ比）で２０〜１００、特に５０〜８０程度とするのが好ましい。
【００１４】
図１の装置では、放散塔３にスチームが導入されることにより、放散塔３内での水の温度低下が防止されている。即ち、放散塔３でのストリッピングガスとの向流接触に当たり、Ｇ／Ｌ比は大きい程、揮発性有機物の除去率が高くなるが、このＧ／Ｌ比が過度に大きいと、気化熱による放散塔３内での水の温度低下が著しくなり、放散塔３の入口で加熱した水の温度低下で揮発性有機物が揮発し難くなり、その除去効率が悪くなる。
【００１５】
このため、図１の装置では、この放散塔３内での水温低下による揮発性有機物の除去効率の悪化を防止するために、放散塔３の下部からスチームを導入して塔内を加熱する。
【００１６】
このように、水温の低下を防止することにより、Ｇ／Ｌ比を高くして揮発性有機物を効率的に除去することができる。このような水温の調整は、放散塔３の入口側での加熱温度によっても異なるが、放散塔３の入口の水温に対する放散塔３の出口の水温の温度差（以下「放散塔内水温差」と称す場合がある。）が１２℃以下、好ましくは５℃以下となるように行う。
【００１７】
なお、この放散塔３の水温差調整手段としては、特に制限はなく、スチームを添加する方法の他、電磁誘導加熱により放散塔を外部から加温する方法などを採用することができる。
【００１８】
放散塔３から排出される揮発性有機物を含むストリッピングガスは、冷却して凝縮水を分離し、その後活性炭と接触させるなどして有機物を除去した後大気に放出するのが好ましい。一方、揮発性有機物を含む凝縮水は生物処理するのが好ましい。
【００１９】
また、放散塔３で揮発性有機物を除去した後の処理水は、回収用熱交換器１で冷却後又は冷却前に必要に応じオゾン及び／又は過酸化水素により残留有機物を除去することが好ましい。この水は、この酸化分解による有機物の除去の他、逆浸透（ＲＯ）膜分離処理で残留有機物の除去を行っても良い。
【００２０】
このような本発明の方法は、特に、含有される有機物の殆どがアルコールやアセトン等の揮発性有機物である半導体や液晶製造工場等のプロセス排水の処理に有効であり、揮発性有機物を効率的に除去して、回収再利用が可能な高水質の処理水を得ることができる。
【００２１】
【実施例】
以下に実施例及び比較例を挙げて本発明をより具体的に説明する。
【００２２】
実施例１，２
ＩＰＡをＴＯＣとして１００ｍｇ／Ｌ含む水を原水として、図１に示す装置で処理を行った。
【００２３】
この水を８７℃に加熱した後、放散塔（直径８５ｍｍ、高さ２ｍ、充填材なし）に５０Ｌ／ｈｒで通水し、ストリッピングガス（Ｎ_２ガス）４００〜３０００ＮＬ／ｈｒを表１に示すＧ／Ｌ比となるように向流接触させた。また、この放散塔にはスチームを導入して、放散塔入口及び出口の水温を表１に示す水温となるように調整した。
【００２４】
得られた処理水のＴＯＣ濃度からＧ／Ｌ比に対するＴＯＣ残留率を調べ、結果を図２に示した。
【００２５】
比較例１
原水を６０℃に加熱したこと以外は実施例１と同様にして処理を行い、同様にＧ／Ｌ比に対するＴＯＣ残留率を調べ、結果を図２に示した。
【００２６】
比較例２
放散塔において、スチームの導入を行わなかったこと以外は実施例１と同様にして処理を行い、同様にＧ／Ｌ比に対するＴＯＣ残留率を調べ、結果を図２に示した。
【００２７】
【表１】

【００２８】
図２より次のことが明らかである。
【００２９】
即ち、実施例１，２と比較例１とを対比することにより、少ないガス流量でＩＰＡを確実に処理するためには、原水水温は高い方がよいことがわかる。しかしながら、水の沸点が１００℃であるため原水水温は１００℃以下に調整しなければならず、安全性を考慮した場合、７５〜９５℃に調整することが好ましいと言える。
【００３０】
また、実施例１，２と比較例２とを対比することにより、スチームを添加しないと、表１から明らかなようにＧ／Ｌ比が大きくなるにつれて放散塔内水温差が大きくなることがわかる。これは、ガス吹き込みにより原水中の熱量が気化熱として奪われるために起こる。この水温差がＴＯＣ除去率に影響を及ぼし、スチームなしの場合、ＴＯＣ残留率３０％で横ばいとなる（比較例２）。そこで気化熱として奪われる熱量分をスチームで補うことにより、Ｇ／Ｌ比６０でＩＰＡ除去率９５％（ＴＯＣ残留率５％）に達するという結果が得られた（実施例１，２）。
【００３１】
また、実施例１，２より放散塔内水温差を約１２℃にするのも約３℃にするのも除去率に大差がないことから、放散塔内水温差は１２℃以内で適宜調整するのが好ましいと言える。
【００３２】
【発明の効果】
以上詳述した通り、本発明の揮発性有機物含有排水の処理方法及び処理装置によれば、揮発性有機物含有排水中のアルコール、ケトン類等の揮発性有機物を容易かつ効率的に除去することができる。
【００３３】
従って、本発明の方法によれば、半導体製造工程等のプロセス排水の回収再利用に当たり、揮発性有機物を効率的に除去することにより、低コストで効率的な水処理を行える。
【図面の簡単な説明】
【図１】本発明の揮発性有機物含有排水の処理方法及び処理装置の実施の形態を示す系統図である。
【図２】実施例１，２及び比較例１，２におけるＧ／Ｌ比とＴＯＣ残留率との関係を示すグラフである。
【符号の説明】
１回収用熱交換器
２加熱用熱交換器
３放散塔[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a method and apparatus for treating volatile organic matter-containing wastewater, and in particular, in collecting and reusing process wastewater such as semiconductor manufacturing plants, alcohol and ketones in the wastewater are efficiently removed to recover water. The present invention relates to a method and an apparatus.
[0002]
[Prior art]
In the semiconductor manufacturing process, a large amount of ultrapure water is used to clean silicon substrates, etc., and this waste water (rinse waste water) is collected and reused from the viewpoint of reducing environmental impact and effective use of water resources. Is widely practiced. The rinse wastewater often contains volatile organic substances such as IPA (isopropyl alcohol), and it is necessary to remove these organic substances in order to reuse the rinse wastewater.
[0003]
Conventionally, as a technique for removing organic substances contained in rinse wastewater, OH having a very strong oxidizing power by combining ozone / hydrogen peroxide, ozone / UV (ultraviolet light), UV / hydrogen peroxide, ozone / alkali, etc. Accelerated oxidation methods that generate radicals and remove organic substances by this strong oxidizing power; wet oxidation methods that react at high temperatures using oxidizing agents such as sodium persulfate; biological treatment methods that use microorganisms have been used. It was.
[0004]
[Problems to be solved by the invention]
However, both the accelerated oxidation method and the wet oxidation method have to increase the amount of oxidant added with the increase in the TOC concentration of the raw water, and are not suitable for treating raw water containing a high concentration TOC component. In addition, in the case of biological treatment, there is a problem that it cannot sufficiently cope with the concentration fluctuation of the raw water TOC, and a burden is imposed on the treatment of surplus microbial cells that are generated.
[0005]
The present invention solves the above-mentioned conventional problems, and easily and efficiently removes volatile organic substances such as IPA in waste water without using an oxidizing agent or biological treatment, thereby obtaining raw water for producing ultrapure water. It is an object of the present invention to provide a volatile organic matter-containing wastewater treatment method and treatment apparatus capable of recovering high-quality treated water that can be collected.
[0006]
[Means for Solving the Problems]
The method for treating volatile organic matter-containing wastewater according to the present invention includes a first step of adjusting the wastewater to 75 to 95 ° C. in the method for removing volatile organic matter in the volatile organic matter-containing wastewater, and a temperature in the first step. and a second step of the adjusting water contacting gas countercurrent state, and are water temperature decreases 12 ° C. or less of water after countercurrent contact with water prior to countercurrent contact with the gas in the second step, the gas, wherein air or nitrogen gas der Rukoto.
[0007]
The apparatus for treating volatile organic matter-containing wastewater according to the present invention comprises a wastewater temperature adjusting means for adjusting the wastewater to 75 to 95 ° C., and a wastewater temperature adjusting means in the device for removing volatile organic matter in the volatile organic matter-containing wastewater. comprising a the treated water and gas and the gas flow contact means for countercurrent contact, the gas countercurrent contact means adjusts the temperature decrease in the exit for the inlet water temperature of the gas countercurrent contact means 12 ° C. or less comprising a water temperature difference adjusting means for, the gas is characterized by an air or nitrogen gas der Rukoto.
[0008]
According to the present invention, volatile organic substances can be efficiently transferred to the stripping gas side and removed by bringing the water heated to a predetermined temperature into countercurrent contact with the stripping gas.
[0009]
In particular, in this countercurrent contact, in order to suppress a decrease in the water temperature so that the decrease in the water temperature after the countercurrent contact with respect to the water before the countercurrent contact is 12 ° C. or less, volatile organic substances can be efficiently removed. it can.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0011]
FIG. 1 is a system diagram showing an embodiment of a method and apparatus for treating volatile organic substance-containing wastewater of the present invention.
[0012]
In the method of FIG. 1, the raw water is first preliminarily heated by exchanging heat with the treated water in the subsequent diffusion tower 3 in the recovery heat exchanger 1, and then heated in the heat exchanger 2 for heating. Although this recovery heat exchanger 1 is not necessarily required, heat recovery can be achieved by providing the recovery heat exchanger 1 and preheating raw water with treated water and cooling the treated water. It is advantageous in terms of reduction of. Moreover, there is no restriction | limiting in particular as a model of the heat exchanger 2 for a heating, The heat exchanger using a steam etc. can be used. If the heating temperature of the raw water is too low, volatile organic substances cannot be removed efficiently, and if it is too high, water moves to the volatile organic substances side, making it difficult to selectively separate only the volatile organic substances. Therefore, the temperature is set to 75 to 95 ° C.
[0013]
The water heated by the heating heat exchanger 2 is then sprinkled from the upper part of the stripping tower 3 and brought into countercurrent contact with the stripping gas introduced from the lower part of the tower. Although there is no restriction | limiting in particular in this watering system, In order to improve the gas-liquid contact efficiency by uniform dispersion | distribution, it is preferable to use a spray system. The stripping tower 3 may be filled with a filler, may be an empty tower without a filler, or may be a multi-stage with a shelf for rectification. In order to increase the gas-liquid contact efficiency, it is preferable to fill with a filler such as Raschig ring or Berle saddle. The stripping gas, air or nitrogen gas is preferred. The flow rate of the stripping gas is preferably 20 to 100, particularly about 50 to 80 in terms of the ratio of gas flow rate to the raw water flow rate (G / L ratio).
[0014]
In the apparatus of FIG. 1, the introduction of steam into the stripping tower 3 prevents the temperature of the water in the stripping tower 3 from lowering. That is, in countercurrent contact with the stripping gas in the stripping tower 3, the larger the G / L ratio, the higher the removal rate of volatile organic substances. However, if this G / L ratio is excessively large, The temperature drop of the water in the stripping tower 3 becomes remarkable, and the temperature drop of the water heated at the entrance of the stripping tower 3 makes it difficult for the volatile organic substance to volatilize, and the removal efficiency thereof deteriorates.
[0015]
For this reason, in the apparatus of FIG. 1, steam is introduced from the lower part of the stripping tower 3 to heat the inside of the tower in order to prevent deterioration of the removal efficiency of volatile organic substances due to a decrease in water temperature in the stripping tower 3.
[0016]
Thus, by preventing the water temperature from decreasing, the G / L ratio can be increased and volatile organic substances can be efficiently removed. Such adjustment of the water temperature varies depending on the heating temperature on the inlet side of the stripping tower 3, but the temperature difference of the water temperature at the outlet of the stripping tower 3 with respect to the water temperature at the inlet of the stripping tower 3 (hereinafter referred to as "water temperature difference in the stripping tower"). ) Is 12 ° C. or lower, preferably 5 ° C. or lower.
[0017]
In addition, there is no restriction | limiting in particular as a water temperature difference adjustment means of this stripping tower 3, The method of heating a stripping tower from the outside by electromagnetic induction heating other than the method of adding steam, etc. are employable.
[0018]
It is preferable that the stripping gas containing the volatile organic matter discharged from the stripping tower 3 is cooled and separated from the condensed water, and thereafter contacted with activated carbon to remove the organic matter, and then released to the atmosphere. On the other hand, it is preferable to biologically treat condensed water containing volatile organic substances.
[0019]
Moreover, it is preferable that the treated water after removing the volatile organic substances in the diffusion tower 3 is removed by ozone and / or hydrogen peroxide as needed after cooling in the recovery heat exchanger 1 or before cooling. . In addition to the removal of organic substances by this oxidative decomposition, this water may be subjected to removal of residual organic substances by reverse osmosis (RO) membrane separation treatment.
[0020]
Such a method of the present invention is particularly effective for the treatment of process wastewater from semiconductors and liquid crystal manufacturing plants where most of the organic substances contained are volatile organic substances such as alcohol and acetone, and the volatile organic substances are efficiently removed. It is possible to obtain high-quality treated water that can be removed and recovered and reused.
[0021]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.
[0022]
Examples 1 and 2
The treatment was performed with the apparatus shown in FIG. 1 using water containing 100 mg / L of IPA as TOC as raw water.
[0023]
After heating this water to 87 ° C., water was passed through a stripping tower (diameter: 85 mm, height: 2 m, no filler) at 50 L / hr, and stripping gas (N ₂ gas) of 400 to 3000 NL / hr is shown in Table 1. Countercurrent contact was made so that the G / L ratio shown was achieved. Further, steam was introduced into the stripping tower, and the water temperature at the stripping tower inlet and outlet was adjusted to the water temperature shown in Table 1.
[0024]
The TOC residual ratio with respect to the G / L ratio was examined from the TOC concentration of the treated water, and the results are shown in FIG.
[0025]
Comparative Example 1
The treatment was performed in the same manner as in Example 1 except that the raw water was heated to 60 ° C., and the TOC residual ratio with respect to the G / L ratio was similarly examined. The result is shown in FIG.
[0026]
Comparative Example 2
In the stripping tower, the treatment was performed in the same manner as in Example 1 except that the introduction of steam was not performed. Similarly, the TOC residual ratio with respect to the G / L ratio was examined, and the result is shown in FIG.
[0027]
[Table 1]

[0028]
The following is clear from FIG.
[0029]
That is, by comparing Examples 1 and 2 with Comparative Example 1, it can be seen that a higher raw water temperature is better in order to reliably process IPA with a small gas flow rate. However, since the boiling point of water is 100 ° C., the raw water temperature must be adjusted to 100 ° C. or lower, and it is preferable to adjust to 75 to 95 ° C. in consideration of safety.
[0030]
Further, by comparing Examples 1 and 2 with Comparative Example 2, it can be seen that if steam is not added, the water temperature difference in the diffusion tower increases as the G / L ratio increases, as is apparent from Table 1. . This occurs because the amount of heat in the raw water is taken away as the heat of vaporization by gas blowing. This water temperature difference affects the TOC removal rate, and in the case of no steam, the TOC residual rate remains at 30% (Comparative Example 2). Thus, by supplementing the amount of heat lost as vaporization heat with steam, an IPA removal rate of 95% (TOC residual rate of 5%) was achieved at a G / L ratio of 60 (Examples 1 and 2).
[0031]
Moreover, since the removal rate does not have a big difference in whether the water temperature difference in the diffusion tower is about 12 ° C. or about 3 ° C. from Examples 1 and 2, the water temperature difference in the diffusion tower is appropriately adjusted within 12 ° C. It can be said that it is preferable.
[0032]
【The invention's effect】
As described in detail above, according to the method and apparatus for treating volatile organic substance-containing wastewater of the present invention, it is possible to easily and efficiently remove volatile organic substances such as alcohol and ketones in volatile organic substance-containing wastewater. it can.
[0033]
Therefore, according to the method of the present invention, efficient water treatment can be performed at low cost by efficiently removing volatile organic substances when recovering and reusing process wastewater such as semiconductor manufacturing processes.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of a method and apparatus for treating volatile organic matter-containing wastewater according to the present invention.
FIG. 2 is a graph showing the relationship between the G / L ratio and the TOC residual ratio in Examples 1 and 2 and Comparative Examples 1 and 2.
[Explanation of symbols]
1 Heat exchanger for recovery 2 Heat exchanger for heating 3 Stripping tower

Claims

In a method for removing volatile organic matter in wastewater containing volatile organic matter,
A first step of adjusting the drainage to 75 to 95 ° C., and a second step of bringing the water whose temperature has been adjusted in the first step into countercurrent contact with the gas,
Temperature reduction in the water after countercurrent contact with water prior to countercurrent contact with the gas in the second step is Ri der 12 ° C. or less, volatile organics said gas, wherein air or nitrogen gas der Rukoto Treatment method of contained wastewater.

In Claim 1, the ratio (G / L ratio) of the gas flow rate with respect to the flow rate of the water used for the countercurrent contact in this 2nd process is 50-80, The processing method of the volatile organic substance containing waste water characterized by the above-mentioned. .

In a device that removes volatile organic matter from wastewater containing volatile organic matter,
A waste water temperature adjusting means for adjusting the waste water to 75 to 95 ° C., and a gas counter current contact means for making the treated water of the waste water temperature adjusting means counter-contact with the gas,
The gas countercurrent contact means comprises a water temperature difference adjusting means for adjusting the water temperature drop in exit for inlet water temperature of the gas countercurrent contact means 12 ° C. or less, Ru the gas air or nitrogen gas der An apparatus for treating wastewater containing volatile organic substances.

The volatile organic substance-containing wastewater according to claim 3, wherein a ratio (G / L ratio) of a gas flow rate to a flow rate of water provided for countercurrent contact in the gas countercurrent contact means is 50 to 80. Processing equipment.