JP2019072697A - Method of treating wastewater in producing polarized film - Google Patents

Method of treating wastewater in producing polarized film Download PDF

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Publication number
JP2019072697A
JP2019072697A JP2017202346A JP2017202346A JP2019072697A JP 2019072697 A JP2019072697 A JP 2019072697A JP 2017202346 A JP2017202346 A JP 2017202346A JP 2017202346 A JP2017202346 A JP 2017202346A JP 2019072697 A JP2019072697 A JP 2019072697A
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polarizing film
concentration
wastewater
film production
potassium iodide
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恵理 鈴木
Eri Suzuki
恵理 鈴木
靖也 岸
Seiya Kishi
靖也 岸
義浩 藤原
Yoshihiro Fujiwara
義浩 藤原
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Sasakura Engineering Co Ltd
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Sasakura Engineering Co Ltd
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Priority to JP2017202346A priority Critical patent/JP2019072697A/en
Priority to TW107131750A priority patent/TWI757543B/en
Priority to CN201811226465.3A priority patent/CN109678182A/en
Publication of JP2019072697A publication Critical patent/JP2019072697A/en
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D3/00—Halides of sodium, potassium or alkali metals in general
    • C01D3/12—Iodides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D3/00—Halides of sodium, potassium or alkali metals in general
    • C01D3/14—Purification
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/02—Treatment of water, waste water, or sewage by heating
    • C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/02—Treatment of water, waste water, or sewage by heating
    • C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
    • C02F1/06—Flash evaporation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2301/00—General aspects of water treatment
    • C02F2301/08—Multistage treatments, e.g. repetition of the same process step under different conditions
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/10—Process efficiency
    • Y02P20/129—Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines

Abstract

To provide a method of treating wastewater in producing a polarizing film capable of efficiently recovering potassium iodide contained in wastewater in producing a polarizing film inexpensively.SOLUTION: A method for treating wastewater in producing a polarizing film which recovers potassium iodide from wastewater in producing a polarizing film, comprises: a first concentration step of adjusting a pH value wastewater in producing the polarizing film to 8.5 to 11 to carry out evaporation concentration; a cooling crystallization step of forming a slurry containing precipitates by performing cooling crystallization while maintaining the pH value of the concentrated wastewater obtained in the first concentration step to 8.5 to 11;a solid-liquid separation step of separating precipitates from the slurry obtained in the cooling crystallization step to produce a filtrate of potassium iodide solution; and a second concentration step of evaporating and concentrating the filtrate obtained in the solid-liquid separation step.SELECTED DRAWING: Figure 1

Description

本発明は、偏光フィルム製造排水の処理方法に関し、より詳しくは、偏光フィルムの製造工程で生じる排水からヨウ化カリウムを回収する偏光板製造排水の処理方法に関する。   The present invention relates to a method of treating a polarizing film-producing wastewater, and more particularly, to a method of treating a polarizing plate-producing wastewater from which potassium iodide is recovered from the wastewater generated in the process of producing a polarizing film.

液晶ディスプレイ等に使用される偏光フィルムの製造工程で生じる排水には、ヨウ素やホウ素、カリウム等の無機物成分や、ポリビニルアルコール（ＰＶＡ）等の有機物成分が含まれており、このような排水の処理方法が従来から検討されている。   Waste water produced in the process of producing a polarizing film used in liquid crystal displays etc. contains inorganic matter components such as iodine, boron and potassium, and organic matter components such as polyvinyl alcohol (PVA), and such waste water treatment The method has been studied conventionally.

例えば、特許文献１には、ヨウ素およびホウ素を含む排水のｐＨ値を８〜１４に調整した後に蒸発濃縮して冷却し、得られた濃縮排水のｐＨ値を硫酸等のｐＨ調整剤により１〜７に調整した後に晶析を行うことにより、ホウ素分を析出させて除去する排水の処理方法が開示されている。   For example, in Patent Document 1, after adjusting the pH value of waste water containing iodine and boron to 8 to 14, the solution is concentrated by evaporation and cooled, and the pH value of the obtained concentrated waste water is 1 to 1 with a pH adjuster such as sulfuric acid. A method of treating waste water is disclosed in which the boron content is precipitated and removed by performing crystallization after adjustment to 7.

特開２００６−２３１３２５号公報JP, 2006-231325, A

ところが、上記従来の排水の処理方法は、濃縮排水のｐＨを酸性にして晶析を行うため腐食の問題が生じ易いことから、晶析装置に高耐食性の材料を使用する必要があり、処理コストが高くなるという問題があった。   However, since the above-mentioned conventional waste water treatment method causes crystallization problems by acidifying the pH of concentrated waste water, it is necessary to use a highly corrosion-resistant material in the crystallizer, since the problem of corrosion is likely to occur. Was a problem.

そこで、本発明は、偏光フィルム製造排水に含まれるヨウ化カリウムを安価に効率良く回収することができる偏光フィルム製造排水の処理方法の提供を目的とする。   Then, an object of this invention is to provide the processing method of the polarizing film manufacturing drainage which can collect | recover potassium iodide contained in a polarizing film manufacturing drainage cheaply and efficiently.

本発明の前記目的は、偏光フィルム製造排水からヨウ化カリウムを回収する偏光フィルム製造排水の処理方法であって、偏光フィルム製造排水のｐＨ値を８．５〜１１に調整して蒸発濃縮を行う第１の濃縮工程と、前記第１の濃縮工程で得られた濃縮排水のｐＨ値を８．５〜１１に維持したまま冷却晶析を行い析出物を含むスラリーを生成する冷却晶析工程と、前記冷却晶析工程で得られたスラリーから析出物を分離してヨウ化カリウム溶液の濾液を生成する固液分離工程と、前記固液分離工程で得られた濾液を蒸発濃縮する第２の濃縮工程とを備える偏光フィルム製造排水の処理方法により達成される。   The object of the present invention is a method for treating a polarizing film production wastewater which recovers potassium iodide from a polarizing film production wastewater, wherein the pH value of the polarizing film production wastewater is adjusted to 8.5 to 11 to carry out evaporation and concentration A first concentration step, and a cooling crystallization step of performing cooling crystallization while maintaining the pH value of the concentrated waste water obtained in the first concentration step at 8.5 to 11 to generate a slurry containing precipitates; A solid-liquid separation step of separating a precipitate from the slurry obtained in the cooling crystallization step to form a filtrate of a potassium iodide solution, and secondly evaporating and concentrating the filtrate obtained in the solid-liquid separation step And a concentration step.

この偏光フィルム製造排水の処理方法において、前記第１の濃縮工程は、蒸発缶内に伝熱管を備える前段蒸発装置により偏光フィルム製造排水を蒸発濃縮する前濃縮工程と、前記前濃縮工程で濃縮された偏光フィルム製造排水を、蒸発缶内に伝熱管を備えないフラッシュ型の後段蒸発装置により更に蒸発濃縮する後濃縮工程とを備えることが好ましい。   In this method of treating a polarizing film production wastewater, the first concentration step is a preconcentration step of evaporating and concentrating the polarizing film production wastewater by a front-stage evaporator provided with a heat transfer tube in an evaporator, and being concentrated in the preconcentration step. It is preferable to further include a post-concentration step of further evaporating and concentrating the polarizing film production drainage with a flash type post-evaporator without a heat transfer pipe in the evaporator.

また、前記固液分離工程は、析出物に付着するヨウ化カリウムを水洗により回収する工程を備えることが好ましい。   The solid-liquid separation step preferably includes a step of recovering potassium iodide adhering to the precipitate by washing with water.

本発明によれば、偏光フィルム製造排水に含まれるヨウ化カリウムを安価に効率良く回収することができる偏光フィルム製造排水の処理方法を提供することができる。   ADVANTAGE OF THE INVENTION According to this invention, the processing method of the polarizing film manufacturing drainage which can collect | recover potassium iodide contained in a polarizing film manufacturing drainage cheaply and efficiently can be provided.

本発明の一実施形態に係る偏光フィルム製造排水の処理装置のブロック図である。It is a block diagram of the processing device of the polarizing film production drainage concerning one embodiment of the present invention. 図１に示す偏光フィルム製造排水の処理装置の要部を示す構成図である。It is a block diagram which shows the principal part of the processing apparatus of the polarizing film production drainage shown in FIG. 図１に示す偏光フィルム製造排水の処理装置の他の要部を示す構成図である。It is a block diagram which shows the other principal part of the processing apparatus of the polarizing film production drainage shown in FIG. 図１に示す偏光フィルム製造排水の処理装置の更に他の要部を示す構成図である。It is a block diagram which shows the other principal part of the processing apparatus of the polarizing film production drainage shown in FIG.

以下、本発明の一実施形態について添付図面を参照して説明する。図１は、本発明の一実施形態に係る偏光フィルム製造排水の処理装置のブロック図である。図１に示すように、偏光フィルム製造排水の処理装置は、第１の蒸発濃縮装置１０、冷却晶析装置２０、固液分離装置３０、および、第２の蒸発濃縮装置４０を備えている。第１の蒸発濃縮装置１０には、ｐＨ調整剤によりｐＨ調整された偏光フィルム製造排水が供給され、冷却晶析装置２０、固液分離装置３０、および、第２の蒸発濃縮装置４０において順次処理が行われることにより、ヨウ化カリウム（ＫＩ）溶液が生成される。   Hereinafter, an embodiment of the present invention will be described with reference to the attached drawings. FIG. 1 is a block diagram of a treatment apparatus for polarizing film production drainage according to an embodiment of the present invention. As shown in FIG. 1, the treatment apparatus for polarizing film production wastewater includes a first evaporation / concentration device 10, a cooling crystallization device 20, a solid-liquid separation device 30, and a second evaporation / concentration device 40. The first evaporative concentration apparatus 10 is supplied with the polarized film production wastewater pH-adjusted by the pH adjuster, and is sequentially treated by the cooling crystallization apparatus 20, the solid-liquid separation apparatus 30, and the second evaporative concentration apparatus 40 To produce a potassium iodide (KI) solution.

図２は、図１に示す偏光フィルム製造排水の処理装置が備える第１の蒸発濃縮装置１０の構成図である。図２に示すように、第１の蒸発濃縮装置１０は、前段蒸発装置１１、後段蒸発装置１２および加熱器１３を備えている。   FIG. 2: is a block diagram of the 1st evaporative concentration apparatus 10 with which the processing apparatus of the polarizing film production drainage shown in FIG. 1 is provided. As shown in FIG. 2, the first evaporative concentration apparatus 10 includes a front stage evaporator 11, a rear stage evaporator 12, and a heater 13.

前段蒸発装置１１は、密閉型の蒸発缶１１ａの内部に複数の伝熱管１１ｂを備えており、供給ライン１１ｃから蒸発缶１１ａに供給された偏光フィルム製造排水を、循環ライン１１ｄにより循環させて、ノズル１１ｅから伝熱管１１ｂに散布する。伝熱管１１ｂは、左右のヘッダ１１ｆ，１１ｇ同士を連結する。伝熱管１１ｂの表面に散布された偏光フィルム製造排水は、伝熱管１１ｂの内部を通過する加熱流体との熱交換により加熱されて、蒸発濃縮される。循環ライン１１ｄには分岐ライン１１ｈが接続されており、前段蒸発装置１１により濃縮された偏光フィルム製造排水が、分岐ライン１１ｈを介して後段蒸発装置１２に供給される。   The pre-stage evaporator 11 includes a plurality of heat transfer tubes 11b inside the closed-type evaporator 11a, and the polarized film production drainage supplied from the supply line 11c to the evaporator 11a is circulated by the circulation line 11d, The heat transfer tubes 11b are dispersed from the nozzles 11e. The heat transfer tube 11b connects the left and right headers 11f and 11g to each other. The polarized film production drainage sprayed on the surface of the heat transfer tube 11b is heated by heat exchange with the heating fluid passing through the inside of the heat transfer tube 11b, and is evaporated and concentrated. A branch line 11h is connected to the circulation line 11d, and the polarizing film production drainage concentrated by the front stage evaporator 11 is supplied to the rear stage evaporator 12 via the branch line 11h.

前段蒸発装置１１は、ターボ圧縮機からなるヒートポンプ１１ｉを更に備えている。蒸発缶１１ａの内部で発生した偏光フィルム製造排水の蒸気は、ヒートポンプ１１ｉにより圧縮されてヘッダ１１ｆに導入され、加熱流体として伝熱管１１ｂの内部を通過することにより凝縮されて、ヘッダ１１ｇに供給される。ヘッダ１１ｇには、真空ポンプ１１ｊが接続されており、真空ポンプ１１ｊの作動により蒸発缶１１ａの内部が真空雰囲気に維持される。   The pre-stage evaporator 11 further includes a heat pump 11i which is a turbo compressor. The vapor of the polarizing film production drainage generated inside the evaporator 11a is compressed by the heat pump 11i and introduced into the header 11f, condensed as it passes through the inside of the heat transfer tube 11b as a heating fluid, and supplied to the header 11g Ru. A vacuum pump 11j is connected to the header 11g, and the inside of the evaporator 11a is maintained in a vacuum atmosphere by the operation of the vacuum pump 11j.

後段蒸発装置１２は、前段蒸発装置１１により濃縮された偏光フィルム製造排水を貯留可能なフラッシュ缶１２ａを備えるフラッシュ型蒸発器である。後段蒸発装置１２は、蒸発缶であるフラッシュ缶１２ａの内部に伝熱管を備えておらず、ノズル１２ｂからフラッシュ缶１２ａ内に偏光フィルム製造排水を散布して、フラッシュ蒸発させる。フラッシュ缶１２ａから排出される蒸気の一部は、エジェクタからなるヒートポンプ１２ｃの駆動蒸気により吸引されて昇圧され、駆動蒸気と共に加熱器１３で加熱された後、フラッシュ缶１２ａから排出される蒸気の残部と合流して、前段蒸発装置１１のヘッダ１１ｇに導入される。   The post-stage evaporator 12 is a flash type evaporator equipped with a flash can 12 a capable of storing the polarized film production wastewater concentrated by the front-stage evaporator 11. The post-stage evaporation device 12 does not have a heat transfer pipe inside the flash can 12a which is an evaporator, and sprays polarized film production drainage into the flash can 12a from the nozzle 12b to flash evaporate. A part of the steam discharged from the flash can 12a is sucked and boosted by the drive steam of the heat pump 12c consisting of an ejector, and is heated by the heater 13 together with the drive steam, and the remainder of the steam discharged from the flash can 12a And is introduced into the header 11 g of the pre-stage evaporator 11.

後段蒸発装置１２で更に濃縮された偏光フィルム製造排水は、排出ライン１２ｄを介して一部が加熱器１３に導入され、残部が濃縮排水として回収される。   A part of the polarizing film production drainage further concentrated by the post-stage evaporator 12 is introduced into the heater 13 through the discharge line 12d, and the remaining part is recovered as concentrated drainage.

加熱器１３は、後段蒸発装置１２で濃縮された偏光フィルム製造排水が導入される複数の伝熱管１３ａをケーシング１３ｂの内部に備えている。伝熱管１３ａの内部を通過する偏光フィルム製造排水は、後段蒸発装置１２のヒートポンプ１２ｃからケーシング１３ｂ内に供給される蒸気により加熱された後、ノズル１２ｂからフラッシュ缶１２ａの内部に散布される。一方、凝縮された蒸気は凝縮水となってケーシング１４ｂ内に貯留され、前段蒸発装置１１のヘッダ１１ｇに導入される。   The heater 13 is provided with a plurality of heat transfer tubes 13a into which the polarized film production wastewater concentrated by the rear-stage evaporator 12 is introduced, inside the casing 13b. The polarized film production drainage passing through the inside of the heat transfer tube 13a is heated by the steam supplied from the heat pump 12c of the rear-stage evaporator 12 into the casing 13b, and then dispersed from the nozzle 12b into the inside of the flash can 12a. On the other hand, the condensed vapor is condensed in the casing 14 b as condensed water, and is introduced into the header 11 g of the front stage evaporator 11.

図３は、図１に示す偏光フィルム製造排水の処理装置が備える冷却晶析装置２０および固液分離装置３０の構成図である。図３に示すように、冷却晶析装置２０は、周囲がジャケット２１により覆われた容器２２を備えており、容器２２の内部には撹拌装置２３が設けられている。第１の蒸発濃縮装置１０（図２参照）から供給ライン２２ａを介して容器２２に供給された濃縮排水は、ジャケット２１を通過するチラー水との熱交換により冷却され、析出物が生成されてスラリーとなり、排出部２４から排出される。容器２２の冷却方式は特に限定されるものではなく、例えば、ジャケット２１を備える代わりに内部コイル式であってもよく、あるいは外部循環冷却式等であってもよい。   FIG. 3: is a block diagram of the cooling crystallization apparatus 20 and the solid-liquid separation apparatus 30 with which the processing apparatus of the polarizing film production drainage shown in FIG. 1 is provided. As shown in FIG. 3, the cooling crystallization apparatus 20 includes a container 22 whose periphery is covered by a jacket 21, and a stirring device 23 is provided inside the container 22. Concentrated drainage water supplied to the vessel 22 from the first evaporation / concentration device 10 (see FIG. 2) through the supply line 22a is cooled by heat exchange with chiller water passing through the jacket 21 to form precipitates. It becomes a slurry and is discharged from the discharge unit 24. The cooling system of the container 22 is not particularly limited, and may be, for example, an internal coil system instead of the jacket 21 or an external circulation cooling system.

固液分離装置３０は、不図示のモータにより回転駆動される円筒状のバスケット３１がケーシング３２の内部に配置されており、冷却晶析装置２０から供給されたスラリーが分散板３３に衝突してバスケット３１内に飛散する。これにより、スラリーに含まれる析出部が、バスケット３１の内壁面に付着して落下することにより回収され、スラリーの濾液がバスケット３１とケーシング３２との間を通過して濾液タンク３４に貯留される。ケーシング３２の内部には、バスケット３１の内壁面に付着した析出物に向けて噴射孔３５ａから洗浄水を噴射する噴射管３５が配置されている。固液分離装置３０は、本実施形態のように遠心分離方式とする代わりに、例えば、加圧ろ過（フィルタープレス）、真空ろ過、遠心ろ過などの各種ろ過方式であってもよい。   In the solid-liquid separation device 30, a cylindrical basket 31 rotationally driven by a motor (not shown) is disposed inside the casing 32, and the slurry supplied from the cooling crystallization device 20 collides with the dispersion plate 33. Scatter into the basket 31. Thereby, the precipitation part contained in the slurry adheres to the inner wall surface of the basket 31 and is recovered by falling, and the filtrate of the slurry passes between the basket 31 and the casing 32 and is stored in the filtrate tank 34 . In the inside of the casing 32, the injection pipe 35 which injects wash water from the injection hole 35a toward the deposit adhering to the inner wall surface of the basket 31 is arrange | positioned. The solid-liquid separator 30 may be, for example, various filtration methods such as pressure filtration (filter press), vacuum filtration, centrifugal filtration or the like instead of using the centrifugal separation method as in the present embodiment.

図４は、図１に示す偏光フィルム製造排水の処理装置が備える第２の蒸発濃縮装置４０の構成図である。図４に示すように、第２の蒸発濃縮装置４０は、蒸発装置４１および凝縮器４２を備えている。   FIG. 4 is a block diagram of a second evaporative concentration apparatus 40 provided in the processing apparatus for treatment of polarizing film production shown in FIG. As shown in FIG. 4, the second evaporation and concentration device 40 includes an evaporation device 41 and a condenser 42.

蒸発装置４１は、密閉型の蒸発缶４１ａの内部に複数の伝熱管４１ｂを備えており、固液分離装置３０（図３参照）から供給ライン４１ｃを介して蒸発缶４１ａに供給された濾液を、循環ライン４１ｄにより循環させて、ノズル４１ｅから伝熱管４１ｂに散布する。伝熱管４１ｂは、左右のヘッダ４１ｆ，４１ｇ同士を連結する。伝熱管４１ｂの表面に散布された濾液は、伝熱管４１ｂの内部を通過する加熱流体との熱交換により加熱されて、蒸発濃縮される。循環ライン４１ｄには回収ライン４１ｈが接続されており、蒸発装置４１により濃縮されたＫＩ溶液の濾液が、回収ライン４１ｈを介して回収される。   The evaporator 41 includes a plurality of heat transfer tubes 41b inside the closed-type evaporator 41a, and the filtrate supplied from the solid-liquid separator 30 (see FIG. 3) to the evaporator 41a through the supply line 41c is The heat is circulated by the circulation line 41d and dispersed from the nozzle 41e to the heat transfer pipe 41b. The heat transfer tube 41b connects the left and right headers 41f and 41g to each other. The filtrate spread on the surface of the heat transfer tube 41b is heated by heat exchange with the heating fluid passing through the inside of the heat transfer tube 41b, and is evaporated and concentrated. A recovery line 41h is connected to the circulation line 41d, and the filtrate of the KI solution concentrated by the evaporator 41 is recovered through the recovery line 41h.

凝縮器４２は、冷却水が導入される複数の伝熱管４２ａをケーシング４２ｂの内部に備えている。蒸発装置４１からケーシング４２ｂ内に供給される蒸気は、伝熱管４２ａの内部を通過する冷却水と熱交換することにより凝縮水となってケーシング４２ｂに貯留され、蒸発装置４１のヘッダ４１ｇに導入される。 凝縮器４２には、ケーシング４２ｂの内部を減圧する真空ポンプ４２ｃが接続されている。   The condenser 42 includes a plurality of heat transfer pipes 42a into which the cooling water is introduced, inside the casing 42b. The steam supplied from the evaporator 41 to the inside of the casing 42 b exchanges heat with the cooling water passing through the inside of the heat transfer pipe 42 a to be condensed water and stored in the casing 42 b and introduced into the header 41 g of the evaporator 41 Ru. Connected to the condenser 42 is a vacuum pump 42c that reduces the pressure inside the casing 42b.

次に、上記の偏光フィルム製造排水の処理装置を用いた偏光フィルム製造排水の処理方法を説明する。   Next, the treatment method of the polarizing film production drainage using the above-mentioned treatment apparatus of the polarizing film production drainage will be described.

まず、偏光フィルム製造排水が、ｐＨ調整された後、第１の蒸発濃縮装置１０に供給されて蒸発濃縮される（第１の濃縮工程）。偏光フィルム製造排水は、液晶ディスプレイ等に使用される偏光板の製造工程で生じる排水である。偏光板の製造工程においては、一般に、ポリビニルアルコール（ＰＶＡ）からなるフィルムをヨウ化カリウム（ＫＩ）溶液に浸漬させた後、ホウ酸（Ｈ３ＢＯ３）水溶液中で延伸させ、水洗および乾燥を経て偏光板が製造される。このため、偏光フィルム製造排水には、ＰＶＡが含まれており、更に、ＫＩやＨ３ＢＯ３等が主にイオンの状態で含まれている。 First, after the pH adjustment of the polarizing film-producing wastewater, it is supplied to the first evaporative concentration apparatus 10 and is evaporated and concentrated (first concentration step). The polarizing film production drainage is drainage produced in the manufacturing process of the polarizing plate used for a liquid crystal display etc. In the manufacturing process of the polarizing plate, generally, a film made of polyvinyl alcohol (PVA) is immersed in a potassium iodide (KI) solution, then stretched in an aqueous solution of boric acid (H 3 BO 3 ), washed with water and dried. Then, a polarizing plate is manufactured. For this reason, the polarizing film production drainage contains PVA, and further, KI, H 3 BO 3 and the like are mainly contained in the state of ions.

偏光フィルム製造排水のｐＨは、３．５〜８．０の範囲にあり、ホウ酸溶液を含むため通常は酸性であるが、本実施形態においては、水酸化ナトリウムや水酸化カリウム等のｐＨ調整剤を偏光フィルム製造排水に添加することにより、偏光フィルム製造排水のｐＨをアルカリ性に調整した後に、蒸発濃縮を行う。ｐＨ調整後の偏光フィルム製造排水のｐＨ値は、８．５〜１１であることが好ましく、８．５〜９．５であることがより好ましい。   The pH of the polarizing film production wastewater is in the range of 3.5 to 8.0 and is usually acidic because it contains a boric acid solution, but in the present embodiment, the pH adjustment of sodium hydroxide, potassium hydroxide, etc. The agent is added to the polarizing film production wastewater to adjust the pH of the polarizing film production wastewater to alkalinity, and then evaporation concentration is performed. It is preferable that it is 8.5-11, and, as for the pH value of the polarizing film manufacture drainage after pH adjustment, it is more preferable that it is 8.5-9.5.

第１の蒸発濃縮装置１０は、偏光フィルム製造排水を蒸発により濃縮可能であれば特に限定されず、公知の濃縮装置を挙げることができ、これらを一種または二種以上用いて構成することができる。   The first evaporative concentration apparatus 10 is not particularly limited as long as the polarizing film production wastewater can be concentrated by evaporation, and a known concentration apparatus can be mentioned, and one or two or more of these can be used. .

本実施形態の第１の蒸発濃縮装置１０は、図２に示すように、偏光フィルム製造排水が前段蒸発装置１１において蒸発濃縮され（前濃縮工程）、濃縮後の偏光フィルム製造排水が後段蒸発装置１２において更に蒸発濃縮される（後濃縮工程）。前段蒸発装置１１は、蒸発缶１１ａの内部に設けられた伝熱管１１ｂと、伝熱管１１ｂとの熱交換により発生した偏光フィルム製造排水の蒸気を昇圧するヒートポンプ１１ｉとを備える一方、後段蒸発装置１２は、フラッシュ缶１２ａの内部に伝熱管を備えておらず、フラッシュ缶１２ａ内でフラッシュ蒸発により発生した偏光フィルム製造排水の蒸気を昇圧するヒートポンプ１２ｃとを備えている。この構成によれば、濃縮の初期段階において前段蒸発装置１１により偏光フィルム製造排水を高濃縮した後、後段蒸発装置１２でフラッシュ蒸発により更に濃縮することができるので、偏光フィルム製造排水を効率良く濃縮することができる。   In the first evaporation and concentration apparatus 10 of the present embodiment, as shown in FIG. 2, the polarization film production wastewater is evaporated and concentrated in the front stage evaporator 11 (pre-concentration step), and the polarization film production wastewater after concentration is the rear stage evaporation device It is further evaporated at 12 (post-concentration step). The pre-stage evaporator 11 includes a heat transfer pipe 11b provided inside the evaporator 11a and a heat pump 11i for boosting the vapor of the polarizing film production drainage generated by heat exchange with the heat transfer pipe 11b, while the post-stage evaporator 12 The heat pump 12c does not include a heat transfer tube inside the flash can 12a, and includes a heat pump 12c that pressurizes the vapor of the polarizing film production drainage generated by the flash evaporation in the flash can 12a. According to this configuration, after the polarizing film production drainage is highly concentrated by the front-stage evaporator 11 in the initial stage of concentration, it can be further concentrated by flash evaporation by the rear-stage evaporator 12, so the polarizing film production drainage is efficiently concentrated can do.

前段蒸発装置１１および後段蒸発装置１２においてそれぞれ使用するヒートポンプ１１ｉ，１２ｃは、生成された蒸気を昇圧可能であれば特に限定されないが、後段蒸発装置１２で処理される偏光フィルム製造排水は、前段蒸発装置１１で処理される偏光フィルム製造排水と比較して濃縮されていることから、本実施形態では前者をターボ圧縮機とし、後者をエジェクタとしている。このような好ましい他の組み合わせとしては、例えば、前者をターボ圧縮機とし、後者をルーツ圧縮機とすることが挙げられる。   The heat pumps 11i and 12c used in the first-stage evaporator 11 and the second-stage evaporator 12 are not particularly limited as long as the generated vapor can be boosted, but the polarized film production wastewater treated by the second-stage evaporator 12 In the present embodiment, the former is used as a turbo compressor and the latter is used as an ejector because it is concentrated in comparison with the polarizing film production drainage processed by the device 11. As such a preferable other combination, for example, the former may be a turbo compressor and the latter may be a roots compressor.

第１の蒸発濃縮装置１０で生成された濃縮排水は、図３に示す冷却晶析装置２０に供給されて、例えば２０℃程度まで冷却され、濃縮排水に含まれる溶質が結晶化して析出する（冷却晶析工程）。この冷却晶析は、従来とは異なりｐＨ調整剤を添加することなく、濃縮排水のｐＨ値を８．５〜１１に維持して（より好ましくはｐＨ値を８．５〜９．５に維持して）行われるため、ホウ酸ソーダやホウ酸カリウムを主体とする結晶が析出され、更に、ＰＶＡが重合してコロイド状になって析出する。   Concentrated wastewater generated by the first evaporation / concentrator 10 is supplied to the cooling crystallizer 20 shown in FIG. 3 and cooled to, for example, about 20 ° C., and the solute contained in the concentrated wastewater crystallizes and precipitates ( Cooling crystallization process). Unlike the prior art, this cooling crystallization maintains the pH value of concentrated drainage at 8.5 to 11 (more preferably, the pH value is maintained at 8.5 to 9.5, without adding a pH adjuster). As a result, crystals consisting mainly of sodium borate and potassium borate are precipitated, and further, PVA is polymerized to form a colloid and precipitate.

こうして、冷却晶析装置２０で生成された析出物を含むスラリーは、固液分離装置３０に供給されて析出物が分離され、濾液が生成される（固液分離工程）。上記のとおり、スラリーはアルカリ性を維持したまま冷却晶析が行われたものであるため、析出物に含まれるホウ酸ソーダやホウ酸カリウムの結晶からはホウ素の回収が困難である一方、純度の高いヨウ化カリウム溶液を濾液として回収することができる。   Thus, the slurry containing the precipitate generated by the cooling crystallizer 20 is supplied to the solid-liquid separator 30, where the precipitate is separated, and a filtrate is produced (solid-liquid separation step). As described above, since the slurry is subjected to cooling crystallization while maintaining the alkalinity, recovery of boron from the crystals of sodium borate and potassium borate contained in the precipitate is difficult, while the purity is low. The high potassium iodide solution can be recovered as a filtrate.

固液分離装置３０において分離された析出物には、ヨウ化カリウムが若干付着しているため、噴射管３５から析出物に向けて洗浄水を噴射することにより、析出物に付着したヨウ化カリウムを水洗により回収することができる。洗浄水の温度は、析出物が溶解し難い低温であることが好ましく、例えば、１５〜２０℃である。析出物を洗浄後の洗浄水は、濾液と共に濾液タンク３４に貯留される。洗浄水は、例えば、第１の蒸発濃縮装置１０の前段蒸発装置１１から排出される凝縮水を使用することができる。   Since some potassium iodide is attached to the precipitate separated in the solid-liquid separator 30, potassium iodide attached to the precipitate by injecting washing water from the injection pipe 35 toward the precipitate Can be recovered by water washing. The temperature of the washing water is preferably a low temperature at which the precipitates do not easily dissolve, and is, for example, 15 to 20 ° C. The washing water after washing the deposit is stored in the filtrate tank 34 together with the filtrate. As the washing water, for example, condensed water discharged from the pre-evaporator 11 of the first evaporative concentrator 10 can be used.

固液分離装置３０で生成された濾液は、第２の蒸発濃縮装置４０に供給されて、再度蒸発濃縮される（第２の濃縮工程）。濾液に含まれる不純物は、冷却晶析装置２０および固液分離装置３０において十分除去可能であることから、濾液に含まれるヨウ化カリウムの飽和濃度近くまで蒸発濃縮することが可能であり、高濃度のヨウ化カリウム溶液を得ることができる。   The filtrate produced by the solid-liquid separator 30 is supplied to the second evaporation / concentrator 40 and is again evaporated / concentrated (second concentration step). Impurities contained in the filtrate can be sufficiently removed by the cooling crystallizer 20 and the solid-liquid separator 30, and therefore, it is possible to evaporate and concentrate to near the saturation concentration of potassium iodide contained in the filtrate. Potassium iodide solution can be obtained.

第２の蒸発濃縮装置４０で蒸発濃縮される濾液は、第１の蒸発濃縮装置１０、冷却晶析装置２０および固液分離装置３０によって大きく濃縮されていることから、蒸発装置４１は、ヒートポンプを使用せずに、ボイラの生蒸気等を熱源として利用してもよい。   Since the filtrate evaporated and concentrated by the second evaporation and concentration device 40 is largely concentrated by the first evaporation and concentration device 10, the cooling and crystallization device 20, and the solid-liquid separation device 30, the evaporation device 41 has a heat pump. Instead of using it, raw steam or the like of the boiler may be used as a heat source.

上記のように、本実施形態の偏光フィルム製造排水の処理方法は、偏光フィルム製造排水のｐＨをアルカリ性に調整した後、アルカリ性を維持したまま蒸発濃縮および冷却晶析が行われるので、偏光フィルム製造排水の処理装置に高価な耐食性の材料を使用する必要がなく、更に、フィルタ等の消耗品の発生がなく、薬剤も不要であることから、偏光フィルム製造排水に含まれるヨウ化カリウムを安価に効率良く回収することができる。   As described above, in the method of treating wastewater for producing a polarizing film according to this embodiment, after the pH of the wastewater for producing a polarizing film is adjusted to be alkaline, evaporation concentration and cooling crystallization are performed while maintaining the alkalinity. There is no need to use expensive corrosion-resistant materials in waste water treatment equipment, and no consumables such as filters are generated, and no chemicals are needed. It can be recovered efficiently.

１０ 第１の蒸発濃縮装置
１１ 前段蒸発装置
１２ 後段蒸発装置
２０ 冷却晶析装置
３０ 固液分離装置
４０ 第２の蒸発濃縮装置 DESCRIPTION OF SYMBOLS 10 1st evaporative concentration apparatus 11 prestage evaporation apparatus 12 2nd stage evaporation apparatus 20 cooling crystallization apparatus 30 solid-liquid separation apparatus 40 2nd evaporative concentration apparatus

Claims (3)

偏光フィルム製造排水からヨウ化カリウムを回収する偏光フィルム製造排水の処理方法であって、
偏光フィルム製造排水のｐＨ値を８．５〜１１に調整して蒸発濃縮を行う第１の濃縮工程と、
前記第１の濃縮工程で得られた濃縮排水のｐＨ値を８．５〜１１に維持したまま冷却晶析を行い析出物を含むスラリーを生成する冷却晶析工程と、
前記冷却晶析工程で得られたスラリーから析出物を分離してヨウ化カリウム溶液の濾液を生成する固液分離工程と、
前記固液分離工程で得られた濾液を蒸発濃縮する第２の濃縮工程とを備える偏光フィルム製造排水の処理方法。 It is a processing method of a polarizing film manufacturing drainage which recovers potassium iodide from a polarizing film manufacturing drainage,
A first concentration step of performing evaporation and concentration by adjusting the pH value of the polarizing film production wastewater to 8.5-11;
A cooling crystallization step of performing cooling crystallization while maintaining the pH value of the concentrated drainage obtained in the first concentration step at 8.5 to 11 to generate a slurry containing precipitates;
A solid-liquid separation step of separating a precipitate from the slurry obtained in the cooling crystallization step to form a filtrate of a potassium iodide solution;
And a second concentration step of evaporating and concentrating the filtrate obtained in the solid-liquid separation step. 前記第１の濃縮工程は、蒸発缶内に伝熱管を備える前段蒸発装置により偏光フィルム製造排水を蒸発濃縮する前濃縮工程と、前記前濃縮工程で濃縮された偏光フィルム製造排水を、蒸発缶内に伝熱管を備えないフラッシュ型の後段蒸発装置により更に蒸発濃縮する後濃縮工程とを備える請求項１に記載の偏光フィルム製造排水の処理方法。   In the first concentration step, a pre-concentration step of evaporating and concentrating polarized film production wastewater with a front-stage evaporator including a heat transfer tube in an evaporator, and a polarizing film production wastewater concentrated in the pre-concentration step The method according to claim 1, further comprising: a post-concentration step of evaporative concentration by means of a flash type post-evaporator having no heat transfer tube. 前記固液分離工程は、析出物に付着するヨウ化カリウムを水洗により回収する工程を備える請求項１または２に記載の偏光フィルム製造排水の処理方法。   3. The method according to claim 1, wherein the solid-liquid separation step comprises a step of recovering potassium iodide adhering to the precipitate by washing with water.
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