JP3677164B2 - Method and apparatus for regenerating glass cleaning solution, and method and apparatus for cleaning silicate glass - Google Patents

Description

【００４５】
一方、ガラス洗浄液としては、フッ化水素酸を含む水溶液が用いられる。洗浄液中の好ましいフッ化水素酸の濃度は、洗浄方法や洗浄の対象となるガラスに応じて決定すればよいが、例えば３〜２０重量％程度である。
【００４６】
ブラウン管用パネルは、洗浄槽１１において、排気口３１から局所排気を行いながら洗浄される。フッ化水素酸を含むガラス洗浄液は、ノズル２１から上方に吐出され、略水平に保持されたブラウン管用パネル２０の内側表面を洗い流す。洗浄液１は、ブラウン管用パネル２０の表面の付着物を洗い出すとともに、微量のガラス成分を溶解する。フッ化水素酸の濃度等を調整すれば、ガラス成分の溶出をごく微量に抑えることは可能である。しかし、このように調整しても、洗浄液を単に循環させながら繰り返し使用したのでは、洗浄液中のガラス成分の量は増加していく。
【００４７】
ガラス成分は、表１に例示したような含有比率を正確に反映した割合で溶出するのではなく、例えばアルカリ成分は含有率を上回って溶出することが多い。しかし、いずれにしても、ガラス成分中の半分以上を占めるＳｉＯ₂は、主要な溶出成分として洗浄液中に存在することになる。ＳｉＯ₂は、以下の反応式に示すように、フッ化水素と反応し、フルオロ珪酸（ヘキサフルオロ珪酸）として上記洗浄液中に溶出する。
【００４８】
ＳｉＯ₂＋６ＨＦ→Ｈ₂ＳｉＦ₆＋２Ｈ₂Ｏ （１）
【００４９】
フルオロ珪酸等の不純物を含んだガラス洗浄液１は、処理槽１３へと流出し、この処理槽において、処理液２と混合される。処理液２は、フッ化物を含む水溶液あるいはフッ化物を含むフッ化水素酸溶液として供給される。ここで、フッ化物としては、無機フッ化物、特にフッ化水素酸塩が好ましい。
【００５０】
混合される処理液２の量は、Ｓｉモニタリングシステム３６によって制御される。Ｓｉモニタリングシステム３６によって測定されるＳｉの濃度が所定の値に達すると、処理液２が処理槽１３へと供給される。処理液２の供給量は、Ｓｉの濃度に応じて定められ、具体的には、Ｓｉに対して所定の比率となるフッ化物を含む量とされる。
【００５１】
洗浄液にフッ化物が添加されるとフッ化水素脱離反応が生じる。即ち、フッ化物は、シリカから生じた上記フルオロ珪酸と反応して、フルオロ珪酸塩とフッ化水素とを生成させる。例えば、フッ化物としてフッ化カリウムを用いた場合のフッ化水素の脱離は、以下の化学反応式により表すことができる。
【００５２】
Ｈ₂ＳｉＦ₆＋２ＫＦ→Ｋ₂ＳｉＦ₆↓＋２ＨＦ （２）
【００５３】
処理液を添加された洗浄液３は、上記反応式により例示されるようなフルオロ珪酸塩の生成反応を進行させながら、処理槽１３の底部に配置された沈殿槽１４へと排出される。沈殿槽１４内において、溶液から析出したフルオロ珪酸塩を含む沈殿物４は、槽の底部に堆積する。この沈殿物４は、沈殿槽の下端に配置された排出コック３４から排出される。一方、洗浄液は、フィルタ２４によりろ過されながら沈殿槽内の区画を上方へと移送され、沈殿槽の液面近傍から調整槽１５へと流出する。
【００５４】
フッ化水素は、上記反応式（２）に示したように、その一部が再生される。しかし、併せて上記反応式（１）を参照すれば明らかなように、ＳｉＯ₂と反応して消費された全てのフッ化水素が再生されるわけではない。そこで、フルオロ珪酸塩が除去された洗浄液５には、調整槽１５において、フッ化水素酸が補充される。フッ化水素酸の添加は、フッ化水素酸モニタリングシステム３０により洗浄液中の濃度を測定しながら行われる。このようにして調整されるフッ化水素酸の好ましい濃度は、上記に例示したとおりである。
【００５５】
なお、処理液２としてフッ化物を含むフッ化水素酸溶液を用いた場合には、調整槽１５におけるフッ化水素酸の補充を省略することができる場合がある。
【００５６】
モニタリングシステム３０により、残存するフルオロ珪酸の濃度を同時に測定することも好ましい。この場合には、測定されたフルオロ珪酸の濃度に応じて、処理槽１３へ供給するフッ化物の量をさらに微調整してもよい。
【００５７】
このようにして、フルオロ珪酸の濃度を低減させ、かつフッ化水素酸の濃度を調整したガラス洗浄液は、循環ポンプ２７により、再び洗浄槽１１へと供給され、再びブラウン管用パネル２０の洗浄に用いられる。
【００５８】
以下、添加するフッ化物について検討する。フッ化物は、上記反応式（２）に示したように、フルオロ珪酸と反応してフルオロ珪酸塩とフッ化水素を生じさせるものであれば特に限定されないが、具体的には、フッ化リチウム（ＬｉＦ）、フッ化ナトリウム（ＮａＦ）、フッ化カリウム（ＫＦ）、フッ化ルビジウム（ＲｂＦ）、フッ化セシウム（ＣｓＦ）、フッ化マグネシウム（ＭｇＦ₂）、フッ化ストロンチウム（ＳｒＦ₂）、フッ化バリウム（ＢａＦ₂）、フッ化コバルト（ＣｏＦ₂）、フッ化マンガン（ＭｎＦ₂）、フッ化銅（ＣｕＦ₂）およびフッ化アンモニウム（ＮＨ₄Ｆ）から選ばれる少なくとも１つの化合物が好適である。
【００５９】
フッ化物は、生成するフルオロ珪酸塩を効率的に除去するためには、対応するフルオロ珪酸塩の水に対する溶解度が小さいことが好ましい。一方、フッ化物自体は、水に対する溶解度がある程度大きいものが好ましい。洗浄液に混合しやすいからである。このような観点からは、フッ化物としては、ＮａＦ、ＫＦ、ＲｂＦ、ＣｓＦがさらに好ましい。これらアルカリ金属（Ｒ）を含むフッ化物（ＲＦ）の水に対する溶解度、およびこれらフッ化物に対応するフルオロ珪酸塩（Ｒ₂ＳｉＦ₆）の水に対する溶解度を表２に示す。なお、溶解度は、ともに水温を２５℃としたときの値である。
【００６０】

【００６１】
上記反応式（２）に従ってガラス洗浄液中の全てのフルオロ珪酸を析出させるためには、理論上は、当該ガラス洗浄液に存在するフルオロ珪酸と同当量のフッ化物を添加することが必要とされる。そこで、実際に必要とされるフッ化物の量を確認するために、ブラウン管用パネルを洗浄した後の洗浄液に、種々の量のフッ化物（ＫＦ）を添加してガラス洗浄液の洗浄能力を調査した。
【００６２】
まず、図１に示したと同様の洗浄槽に、洗浄するガラスとして表１に示した範囲の組成を有するブラウン管用パネルを配置し、ガラス洗浄液を循環させながら、順次洗浄槽へと搬送されてくるブラウン管用パネルを洗浄した。なお、このとき、循環工程においてＫＦは添加せず、フッ化水素酸濃度をモニタリングしながら同濃度が一定となるように洗浄液にフッ化水素酸を添加した。所定時間経過後、洗浄液の一部を採取し、この洗浄液中のＳｉ濃度をＩＣＰ発光分光分析により定量した。そして、洗浄液に、Ｓｉ濃度に対するモル比が所定比率となるようにＫＦを添加した。その後、上記モル比を調整した各洗浄液３０ｍｌに、上記ブラウン管用パネルと同様の組成を有する、厚さ１ｍｍ、直径１５ｍｍのガラス片を浸漬し、室温下、スターラーで攪拌しながら１０分間放置し、浸漬前後のガラス片の重量を測定した。各ガラス片の重量減少率を図２に示す。
【００６３】
図２に示したように、Ｓｉに対するＫＦのモル比が増加するにつれてガラス片の重量減少率は増加した。この結果により、上記反応式（２）に示したように、ＫＦの添加によりＨＦを発生する化学反応が進行したことが確認された。一方、Ｓｉに対するＫＦのモル比が２を超えると（換言すればＫＦの当量が洗浄液中のフルオロ珪酸の当量を超えると）、それ以上ＫＦを添加しても、ガラスの重量減少率は微増するのみであった。この傾向も、上記反応式（２）より予想される結果と一致する。
【００６４】
また、ＫＦ添加によるガラス洗浄液中のＳｉ濃度変化およびＳｉ除去率変化を図３に示す。
【００６５】
図３に示したように、ＫＦのＳｉに対するモル比を２とすると（Ｓｉに対するＫＦの当量点）、ガラス洗浄液中のＳｉのほぼ７０％以上が、上記モル比を３とすると、ガラス洗浄液中のＳｉのほぼ９０％が除去された。図３に示した結果より、ＫＦのＳｉに対するモル比は、２〜４（フッ化物のフルオロ珪酸に対する当量で表示すると１〜２）、さらに２〜３．５、特に２．５〜３．５が好ましいことがわかる。もっとも、余剰のＫＦが存在しても差し支えない場合には、現実の装置における反応率等を考慮して、モル比２〜４．５程度のＫＦを添加してもよい。
【００６６】
図２および図３の結果より、以下、ＫＦの添加量はＳｉに対してモル比３とした。
【００６７】
次に、繰り返しガラス洗浄溶液を再生する場合のＫＦ添加の効果、およびガラスから溶出する各種カチオンの挙動を確認するために、以下の検討を行った。
【００６８】
まず、ガラス片をフッ化水素酸に溶解し、Ｓｉ濃度２５００ｐｐｍ、フッ化水素酸１１重量％となるように洗浄液を調製した。この洗浄液３０ｍｌに、表１と同様の組成を有する、厚さ１ｍｍ、直径１５ｍｍのガラス片を浸漬し、洗浄液の温度を３４℃に保ち、スターラーで攪拌しながら１０分間放置した。このときのガラス片の重量減少量および洗浄液中のカチオン濃度を測定した。カチオン濃度の測定は、ＩＣＰ発光分光分析により行った。
【００６９】
続いて、洗浄液中のＳｉに対してモル比３に相当するＫＦを添加し、フッ化水素酸濃度を１１重量％に調整した。この洗浄液３０ｍｌに、表１と同様の組成を有する、厚さ１ｍｍ、直径１５ｍｍのガラス片を浸漬し、洗浄液の温度を３４℃に保ち、スターラーで攪拌しながら１０分間放置した。このときのガラス片の重量減少および洗浄液中のカチオン濃度を測定した。
【００７０】
以上を１サイクルの試験として、１サイクル終了後の上記洗浄液について、さらに１サイクル目と同量のガラス片を溶解し、上記と同様の試験を計４サイクル繰り返し実施した。図４に洗浄液中の各種カチオンの濃度変化を、図５にガラス片の重量減少率を示す。なお、図４には示していないカチオンについても、同時に濃度変化は測定したが、その他のカチオンについては、濃度はＢａ程度またはそれ以下であった。
【００７１】
図４に示したように、ＫＦを添加することにより、Ｓｉの９０％以上を連続的に除去できることが確認された。しかも、ＳｉおよびＫは連続的に蓄積されることがない。また、図５に示したように、ガラスの重量減少量もほぼ一定であり、洗浄液の洗浄能力も維持されていることが確認された。一方、ＫＦを全く添加しない場合には、図６に示したように、ガラスの洗浄能力は単調に低下していった。
【００７２】
【発明の効果】
以上詳細に説明したように、本発明の再生方法によれば、珪酸塩ガラスの表面を洗浄した後のガラス洗浄用溶液にフッ化物を添加することにより、この洗浄用溶液中に含まれ、ガラスに付着して洗浄不良の原因となるフルオロ珪酸をフッ化物に含まれるカチオンとのフルオロ珪酸塩として析出させて除去し、多量のガラス洗浄用溶液を効率的に再生することができる。また、処理槽内洗浄液中のＳｉ濃度を連続的にモニタリングし、その結果をもとにフッ化物を定量的に添加できることから過不足なく最適量のフッ化物を添加でき、ひいてはフルオロ珪酸を効果的に除去できる。
【００７３】
また、本発明の洗浄方法によれば、上記再生方法を利用してフッ化水素酸を含むガラス洗浄用溶液の交換周期を長期化することにより、産業廃棄物を低減することができる。さらに、本発明は、上記再生方法および上記洗浄方法を実施するための再生装置および洗浄装置を提供するものでもある。
【００７４】
このように、本発明は、従来は困難であったフッ化水素酸を含む産業廃棄物の削減を可能とし、同時にガラスの洗浄不良を低減するものであって、ガラス製品製造の技術分野において、利用価値の極めて大なるものである。
【図面の簡単な説明】
【図１】 本発明の洗浄装置の一形態の概略を示す図である。
【図２】 ガラス洗浄用溶液中のＳｉに対する添加ＫＦのモル比と、当該溶液中に浸漬させたガラス片の重量減少率との関係を示す図である。
【図３】 ガラス洗浄用溶液中のＳｉに対する添加ＫＦのモル比と、当該溶液中のＳｉ濃度およびＳｉ除去率との関係を示す図である。
【図４】 連続試験におけるフッ化水素酸洗浄液中のカチオン濃度の変化を示す図である。
【図５】 連続試験におけるガラス片の重量減少率の変化を示す図である。
【図６】 ＫＦを添加しない場合のガラス片の重量減少率の変化を示す図である。
【符号の説明】
１、３、５ 洗浄液
２ 処理液
６ フッ化水素酸
１０ 再生装置
１１ 洗浄槽
１２ 処理液タンク
１３ 処理槽
１４ 沈殿槽
１５ 調整槽
１６ フッ化水素酸タンク
２０ ブラウン管用パネル
２１ ノズル
２２、２６ ポンプ
２４ フィルタ
２７ 循環ポンプ
３０ モニタリングシステム
３１、３５ 排気口
３４ 排出コック
３６ Ｓｉモニタリングシステム[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for regenerating a glass cleaning solution containing hydrofluoric acid, and a method and apparatus for cleaning silicate glass (silicate glass). In particular, the present invention relates to a method and apparatus for providing glass surfaces that require high cleanliness, such as cathode ray tube panels.
[0002]
[Prior art]
Since hydrofluoric acid has a property of dissolving silicic acid, it is used for etching processing of the glass surface in the manufacturing process of decorative glass. It is also used in the process of cleaning glass by utilizing the property of eroding the glass surface. For example, when impurities remain on the inner surface of a glass panel for a cathode ray tube, the phosphor layer formed thereon is adversely affected and the performance of the cathode ray tube is deteriorated. Therefore, in a process for producing a glass product that requires a very clean surface, such as a cathode ray tube panel, a cleaning process using hydrofluoric acid is an essential process.
[0003]
In the CRT panel cleaning process, a glass cleaning solution containing hydrofluoric acid is repeatedly used for cleaning the panel while being circulated by a circulation device connected to the panel cleaning tank. However, when the cleaning liquid is repeatedly used in this way, the glass surface deposits and glass components are eluted in the cleaning liquid as the number of cleanings increases, and the cleaning performance of the cleaning liquid decreases. In addition, impurities such as eluted glass components adhere to the cathode ray tube panel, causing a panel failure. Under such circumstances, conventionally, the cleaning liquid is periodically replaced in the cleaning process of the cathode ray tube panel. The cleaning liquid containing impurities after use is treated as industrial waste.
[0004]
If the reduction of the cleaning ability is compensated by supplementing with hydrofluoric acid, it is possible to lengthen the cleaning liquid replacement cycle to some extent. However, just replenishing hydrofluoric acid does not provide a solution to reduce industrial waste. Further, impurities in the cleaning liquid cannot be removed. Among the impurities, a particular problem is fluorosilicic acid (H ₂ SiF ₆ ) produced by the reaction of silicic acid (SiO ₂ ) and hydrogen fluoride (HF) in the glass. The fluorosilicic acid forms a gel-like fluorosilicate with various cations contained in the cleaning liquid. Since this low-fluidity gel-like substance is transparent, when it adheres to the glass surface, it is difficult to see when the glass surface is wet, and it is likely to cause a glass product to be defective.
[0005]
By removing impurities from the cleaning liquid and regenerating hydrofluoric acid, it becomes possible to reduce industrial waste and to reduce defects in glass products due to insufficient cleaning and adhesion of impurities. Conventionally, as a method for regenerating hydrofluoric acid containing impurities, for example, a method using electrolysis is known as described in Japanese Patent Publication No. 46-15768.
[0006]
[Problems to be solved by the invention]
However, electrolysis is not suitable as a method for efficiently removing impurities from a glass cleaning solution discharged in a large amount. Moreover, although it is excellent as a method for removing a small amount of cations from hydrofluoric acid, it is not an effective method for removing fluorosilicic acid.
[0007]
The reduction of industrial waste is no longer a social issue, and it is also an issue in continuing corporate activities with the establishment of the international environmental standard (ISO14001). Even in such a situation, in order to restore the cleaning ability of the glass cleaning solution and prevent the adhesion of impurities to the glass product, there is currently no effective method other than replacing the glass cleaning solution. It has become a big problem in glass product manufacturing.
[0008]
In order to solve the above problems, the present invention provides an efficient regeneration method and regeneration apparatus for a glass cleaning solution containing hydrofluoric acid which is used for cleaning and processing silicate glass and discharged in large quantities. With the goal. Another object of the present invention is to provide a glass cleaning solution regenerating method and a regenerating apparatus that can reduce glass cleaning defects caused by the fluorosilicate contained in the solution. Furthermore, an object of this invention is to provide the washing | cleaning method and washing | cleaning apparatus of silicate glass using the reproduced | regenerated washing | cleaning solution.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the method for regenerating a glass cleaning solution of the present invention measures the concentration of Si in a glass cleaning solution containing hydrofluoric acid after cleaning the surface of the silicate glass,
A defined amount of fluoride based on the Si concentration is added to the glass cleaning solution, which is required to convert all Si in the glass cleaning solution to fluorosilicate. By adding more than the amount of fluoride, the fluorosilicic acid in the glass cleaning solution reacts with the fluoride to precipitate fluorosilicate,
The fluorosilicate is removed from the glass cleaning solution.
[0010]
According to such a regeneration method, a large amount of glass cleaning solution can be efficiently regenerated. In particular, according to the above method, the fluorosilicic acid contained in the glass cleaning solution can be efficiently removed by precipitating as fluorosilicate. Further, according to the above method, hydrogen fluoride is generated in the precipitation reaction of fluorosilicate, and this hydrogen fluoride contributes to the recovery of the cleaning ability of the glass cleaning solution. Thus, according to the said regeneration method, since the glass cleaning solution can be regenerated by a technique that can be applied industrially, the replacement cycle of the glass cleaning solution can be prolonged.
[0011]
In addition, according to the above regeneration method, an amount of fluoride corresponding to the Si concentration is added, so that excess fluoride becomes an impurity in the cleaning solution, causing new problems or removing fluorosilicic acid. Can be prevented from becoming insufficient.
[0012]
The amount of fluoride to be added in the reproducing method, specifically, shall be the amount more than necessary for all the Si in the glass cleaning solution is changed to fluorosilicate.
[0013]
In the above regeneration method, it is preferable to add fluoride together with hydrofluoric acid. The hydrogen fluoride produced by the above regeneration method does not replenish all the hydrogen fluoride consumed for producing fluorosilicic acid. Therefore, according to this preferred example, the cleaning ability of the glass cleaning solution is further recovered, and the replacement cycle of the glass cleaning solution can be further prolonged.
[0014]
In the above regeneration method, the fluoride is lithium fluoride, sodium fluoride, potassium fluoride, rubidium fluoride, cesium fluoride, magnesium fluoride, strontium fluoride, barium fluoride, cobalt fluoride, manganese fluoride, It is preferable to include at least one compound selected from copper fluoride and ammonium fluoride. It is because fluorosilicic acid can be effectively removed by using these fluorides.
[0015]
Moreover, in the said reproduction | regeneration method, it is preferable to replenish hydrofluoric acid to the solution for glass washing after removing fluorosilicate. This is because, similarly to the above, it is effective in restoring the cleaning ability of the glass cleaning solution and prolonging the replacement cycle.
[0016]
In order to achieve the above object, the silicate glass cleaning method of the present invention is characterized in that the surface of the silicate glass is cleaned using the glass cleaning solution regenerated by the regenerating method.
[0017]
Further, another cleaning method of the silicate glass of the present invention includes a regeneration step of regenerating the glass cleaning solution regenerated by the above regenerating method, and a surface of the silicate glass using the glass cleaning solution obtained in the regenerating step. The glass cleaning solution is used while regenerating the glass cleaning solution by regenerating the glass cleaning solution used in the cleaning step in the regeneration step. To do.
[0018]
According to these cleaning methods, it becomes possible to reduce the amount of industrial waste containing hydrofluoric acid than before, and it is also possible to reduce defects in glass products due to adhesion of fluorosilicate. Become.
[0019]
In the cleaning method, the silicate glass is preferably a cathode ray tube panel. Since the cathode ray tube panel requires a particularly clean surface and is cleaned using a glass cleaning solution containing a large amount of hydrofluoric acid, the effect of applying the cleaning method becomes remarkable.
[0020]
In order to achieve the above object, the glass cleaning solution regenerator according to the present invention measures the Si concentration in the glass cleaning solution containing hydrofluoric acid after cleaning the surface of the silicate glass. A measuring device;
A treatment tank comprising means for adding, to the glass cleaning solution, more fluoride than the amount required to convert all Si in the glass cleaning solution into fluorosilicate based on the Si concentration. When,
And fluorosilicate recovery means for removing from the glass cleaning solution the fluorosilicate precipitated by the reaction between the fluorosilicic acid in the glass cleaning solution and the fluoride.
[0021]
According to such a regenerating apparatus, a large amount of glass cleaning solution can be efficiently regenerated. In particular, according to the said apparatus, the fluorosilicate contained in the glass washing | cleaning solution can be efficiently removed by depositing as a fluorosilicate. Furthermore, according to the said apparatus, hydrogen fluoride produces | generates in precipitation reaction of fluorosilicate, This hydrogen fluoride will contribute to recovery | restoration of the washing | cleaning capability of a glass washing | cleaning solution. Thus, according to the said reproducing | regenerating apparatus, since the solution for glass washing | cleaning can be reproduced | regenerated with the technique which can be applied industrially, it becomes possible to lengthen the replacement period of the solution for glass washing | cleaning.
[0022]
In addition, according to the above-mentioned regenerating apparatus, since an amount of fluoride corresponding to the Si concentration is added, excess fluoride becomes an impurity in the cleaning solution, causing new problems or removing fluorosilicic acid. Can be prevented from becoming insufficient.
[0023]
In the above regenerating apparatus, the fluorosilicate recovery means may be an apparatus having a solid-liquid separation function capable of separating solid and liquid, and may be a filtration apparatus such as a filter. It is preferable to include a discharge cock provided at the bottom of the settling tank that receives the glass cleaning solution from the bottom of the tank. This is because efficient separation is possible and it is suitable for continuous operation of the regenerator.
[0024]
In the said reproducing | regenerating apparatus, it is preferable to further provide the adjustment tank which replenishes hydrofluoric acid to the glass-cleaning solution from which the fluorosilicate was removed. According to this preferable example, the replacement cycle of the glass cleaning solution can be further prolonged. Moreover, although it does not specifically limit, it is preferable that the said adjustment tank is arrange | positioned so that the solution for glass washing | cleaning may be received from the liquid level vicinity of the said precipitation tank.
[0025]
In order to achieve the above object, the silicate glass cleaning device of the present invention is supplied with a glass cleaning solution from the regenerator and the regenerator, and cleans the surface of the silicate glass with the glass cleaning solution. And a washing tank.
[0026]
Further, another silicate glass cleaning device of the present invention includes the above-described regenerating device and a cleaning tank that is supplied with a glass cleaning solution from the regenerating device and cleans the surface of the silicate glass with the glass cleaning solution. In addition, the glass cleaning solution used in the cleaning tank is further regenerated in the regenerator, so that the glass cleaning solution is used while being regenerated.
[0027]
According to these regenerators, it is possible to reduce the amount of industrial waste containing hydrofluoric acid than before, and it is also possible to reduce defects in glass products due to adhesion of fluorosilicate. Become.
[0028]
Moreover, in the said washing | cleaning apparatus, it is preferable that silicate glass is a panel for cathode-ray tubes.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[0030]
FIG. 1 is a cross-sectional view schematically showing a silicate glass cleaning apparatus of the present invention. In this cleaning apparatus, the glass cleaning solution regenerator 10 and the glass cleaning tank 11 constitute a circulation path for the glass cleaning solution.
[0031]
The regenerator 10 includes a processing tank 13, a sedimentation tank 14, and an adjustment tank 15, and the processing tank 13 and the adjustment tank 15 are respectively provided with a processing liquid tank 12 and a hydrofluoric acid tank 16 with pumps 22 and 26, respectively. Are connected via a pipe.
[0032]
The processing tank 13 receives the glass cleaning liquid 1 discharged from the cleaning tank 11 and the processing liquid 2 injected by the pump 22 from the processing liquid tank 12, and these liquids are mixed. The treatment liquid tank 12 stores a solution containing a fluoride exemplified later. In addition, you may install the stirring apparatus which is equipped in the processing tank 13 with the adjustment tank mentioned later.
[0033]
A Si monitoring system 36 is installed in the processing tank 13. By this system, Si in the glass cleaning liquid 3 is quantitatively analyzed. This system also includes an addition amount control means (controller) for adjusting the amount of the treatment liquid 2 to be added. The controller calculates the amount of processing liquid required according to the amount of Si obtained by measurement, and adjusts the amount of processing liquid 2 to be injected by sending an operation signal to the pump 22 based on this value. As described above, the Si monitoring system 36 monitors the amount of Si in the glass cleaning liquid 3 and feeds back an appropriate amount of the processing liquid 2 while feeding back.
[0034]
Thus, since the processing liquid 2 can be added while confirming the effect, the Si monitoring system 36 is preferably installed in the processing tank 13.
[0035]
A sedimentation tank 14 is disposed below the processing tank 13. The cleaning liquid 3 mixed with the processing liquid is discharged from the bottom of the processing tank 13 to the precipitation tank 14. The precipitate 4 deposited from the cleaning liquid 3 by mixing the treatment liquid settles in the liquid and accumulates at the bottom of the precipitation tank 14. A discharge cock (drain cock) 34 is installed at the bottom of the precipitation tank 14, and the precipitate 14 can be discharged out of the apparatus through the discharge cock 34. On the other hand, the cleaning liquid from which the precipitate 4 has been removed moves upward while passing through the filter 24 through the section partitioned by the inner wall in the precipitation tank, and flows out to the adjustment tank 15. The solid remaining in the solution is filtered by the filter 24.
[0036]
In addition, when the precipitate can be sufficiently deposited in the treatment tank 13, the discharge cock is provided at the bottom of the treatment tank 13 without providing the precipitation tank 14 as described above, and the precipitate is discharged from the discharge cock. May be discharged.
[0037]
The adjustment tank 15 is electrically connected to the precipitation tank at the top so as to have a common liquid level with the precipitation tank 14. As described above, the supernatant of the cleaning liquid from which the precipitate is separated in the precipitation tank 14 flows into the adjustment tank 15. A hydrofluoric acid tank 16 is connected to the adjustment tank 15, and a predetermined amount of hydrofluoric acid 6 is injected from the hydrofluoric acid tank 16 by a pump 26. Further, the adjustment tank 15 is provided with a stirrer 25 for mixing the cleaning liquid 5 to which the hydrofluoric acid 6 has been added and an exhaust port 35 for performing local exhaust.
[0038]
The adjustment tank 15 is provided with a monitoring system 30 near the drainage port arranged at the bottom thereof. The monitoring system 30 is an HF monitor that measures the concentration of hydrofluoric acid in the cleaning liquid, but is also provided with a controller for controlling the amount of hydrofluoric acid. This controller transmits an operation signal to the pump 26 according to the concentration of hydrofluoric acid, the state of the cleaning liquid, etc., and controls the amount of hydrofluoric acid 6 added.
[0039]
As described above, the regeneration apparatus 10 includes an adjustment mechanism that can control the concentration of hydrofluoric acid in the cleaning liquid within a predetermined range. The drain of the adjustment tank of hydrofluoric acid is connected to the cleaning tank 11 via a pipe having a circulation pump 27, and the regenerated glass cleaning liquid is sent back from the adjustment tank 15 to the cleaning tank 11. .
[0040]
The cleaning liquid regenerated by such a regenerating apparatus 10 is supplied to the cleaning tank 11. The cleaning tank 11 shown in FIG. 1 is a CRT panel cleaning tank. In this cleaning tank, the regenerated cleaning liquid is discharged to the inner surface of the cathode ray tube panel 20 by the nozzle 21 and again enters the processing tank 13 in a state containing impurities present on the surface and a glass component eluted together with the impurities. Supplied with. The CRT panel is continuously carried into the washing tank by a conveying device (not shown), and can be carried out of the washing tank after washing. In the cleaning tank 11, an exhaust port 31 is arranged similarly to the adjustment tank 15.
[0041]
As described above, in the cleaning device, the cleaning liquid continuously cleans the CRT panel while circulating between the cleaning tank and the regenerator.
[0042]
Hereinafter, an embodiment of a glass cleaning method and a glass cleaning liquid regeneration method using this apparatus will be described.
[0043]
The glass to be cleaned is silicate glass (silicate glass) containing silica (SiO ₂ ) as a glass skeleton component. The composition of the silicate glass is not particularly limited, and various compositions such as a general-purpose plate glass composition that can be produced by a float process and a glass composition of a cathode ray tube panel can be used. Table 1 shows examples of CRT glass compositions. One feature of this glass composition is that it contains 5% by weight or more of K ₂ O and 10% by weight or more of BaO.
[0044]

[0045]
On the other hand, an aqueous solution containing hydrofluoric acid is used as the glass cleaning liquid. The preferable concentration of hydrofluoric acid in the cleaning liquid may be determined according to the cleaning method and the glass to be cleaned, and is, for example, about 3 to 20% by weight.
[0046]
The CRT panel is cleaned in the cleaning tank 11 while performing local exhaust from the exhaust port 31. A glass cleaning liquid containing hydrofluoric acid is discharged upward from the nozzle 21 to wash away the inner surface of the CRT panel 20 held substantially horizontal. The cleaning liquid 1 cleans the deposits on the surface of the CRT panel 20 and dissolves a trace amount of glass components. By adjusting the concentration of hydrofluoric acid and the like, it is possible to suppress the elution of the glass component to a very small amount. However, even if it adjusts in this way, the amount of the glass component in the cleaning liquid will increase if the cleaning liquid is repeatedly used while being circulated.
[0047]
The glass component does not elute at a rate that accurately reflects the content ratio as exemplified in Table 1. For example, the alkali component often elutes above the content rate. However, in any case, SiO ₂ occupying more than half of the glass component is present in the cleaning liquid as a major elution component. As shown in the following reaction formula, SiO ₂ reacts with hydrogen fluoride and elutes into the cleaning liquid as fluorosilicic acid (hexafluorosilicic acid).
[0048]
SiO ₂ + 6HF → H ₂ SiF ₆ + 2H ₂ O (1)
[0049]
The glass cleaning liquid 1 containing impurities such as fluorosilicic acid flows out into the processing tank 13 and is mixed with the processing liquid 2 in this processing tank. The treatment liquid 2 is supplied as an aqueous solution containing fluoride or a hydrofluoric acid solution containing fluoride. Here, the fluoride is preferably an inorganic fluoride, particularly a hydrofluoric acid salt.
[0050]
The amount of the processing liquid 2 to be mixed is controlled by the Si monitoring system 36. When the Si concentration measured by the Si monitoring system 36 reaches a predetermined value, the processing liquid 2 is supplied to the processing tank 13. The supply amount of the treatment liquid 2 is determined according to the concentration of Si, and specifically, is an amount containing fluoride having a predetermined ratio with respect to Si.
[0051]
When fluoride is added to the cleaning liquid, a hydrogen fluoride elimination reaction occurs. That is, the fluoride reacts with the fluorosilicic acid generated from silica to produce fluorosilicate and hydrogen fluoride. For example, the elimination of hydrogen fluoride when potassium fluoride is used as the fluoride can be expressed by the following chemical reaction formula.
[0052]
H ₂ SiF ₆ + 2KF → K ₂ SiF ₆ ↓ + 2HF (2)
[0053]
The cleaning liquid 3 to which the treatment liquid has been added is discharged to a precipitation tank 14 disposed at the bottom of the treatment tank 13 while a fluorosilicate formation reaction as exemplified by the above reaction formula proceeds. In the precipitation tank 14, the precipitate 4 containing the fluorosilicate precipitated from the solution is deposited at the bottom of the tank. This deposit 4 is discharged from a discharge cock 34 disposed at the lower end of the settling tank. On the other hand, the cleaning liquid is transferred upward through the section in the precipitation tank while being filtered by the filter 24, and flows out from the vicinity of the liquid level of the precipitation tank to the adjustment tank 15.
[0054]
A part of the hydrogen fluoride is regenerated as shown in the reaction formula (2). However, as is clear from the above reaction formula (1), not all hydrogen fluoride consumed by reacting with SiO ₂ is regenerated. Accordingly, the cleaning liquid 5 from which the fluorosilicate has been removed is supplemented with hydrofluoric acid in the adjustment tank 15. The addition of hydrofluoric acid is performed while measuring the concentration in the cleaning liquid by the hydrofluoric acid monitoring system 30. The preferable concentration of hydrofluoric acid thus adjusted is as exemplified above.
[0055]
When a hydrofluoric acid solution containing fluoride is used as the treatment liquid 2, replenishment of hydrofluoric acid in the adjustment tank 15 may be omitted.
[0056]
It is also preferable to simultaneously measure the concentration of the remaining fluorosilicic acid by the monitoring system 30. In this case, the amount of fluoride supplied to the treatment tank 13 may be further finely adjusted according to the measured concentration of fluorosilicic acid.
[0057]
In this way, the glass cleaning liquid in which the concentration of fluorosilicic acid is reduced and the concentration of hydrofluoric acid is adjusted is supplied again to the cleaning tank 11 by the circulation pump 27 and is again used for cleaning the CRT panel 20. It is done.
[0058]
Hereinafter, the fluoride to be added will be examined. As shown in the above reaction formula (2), the fluoride is not particularly limited as long as it reacts with fluorosilicic acid to produce fluorosilicate and hydrogen fluoride. Specifically, lithium fluoride ( LiF), sodium fluoride (NaF), potassium fluoride (KF), rubidium fluoride (RbF), cesium fluoride (CsF), magnesium fluoride (MgF ₂ ), strontium fluoride (SrF ₂ ), barium fluoride At least one compound selected from (BaF ₂ ), cobalt fluoride (CoF ₂ ), manganese fluoride (MnF ₂ ), copper fluoride (CuF ₂ ), and ammonium fluoride (NH ₄ F) is preferred.
[0059]
In order to efficiently remove the generated fluorosilicate, the fluoride preferably has a low solubility of the corresponding fluorosilicate in water. On the other hand, it is preferable that the fluoride itself has a certain degree of solubility in water. This is because it is easy to mix with the cleaning liquid. From such a viewpoint, NaF, KF, RbF, and CsF are more preferable as the fluoride. Table 2 shows the solubility of fluoride (RF) containing these alkali metals (R) in water, and the solubility of fluorosilicate (R ₂ SiF ₆ ) corresponding to these fluorides in water. The solubility is a value when the water temperature is 25 ° C.
[0060]

[0061]
In order to precipitate all the fluorosilicic acid in the glass cleaning liquid according to the above reaction formula (2), it is theoretically necessary to add a fluoride equivalent to the fluorosilicic acid present in the glass cleaning liquid. Therefore, in order to confirm the amount of fluoride actually required, various amounts of fluoride (KF) were added to the cleaning solution after cleaning the CRT panel, and the cleaning ability of the glass cleaning solution was investigated. .
[0062]
First, a CRT panel having a composition in the range shown in Table 1 is disposed as a glass to be cleaned in the same cleaning tank as shown in FIG. 1, and the glass cleaning liquid is circulated and sequentially conveyed to the cleaning tank. The CRT panel was washed. At this time, KF was not added in the circulation step, and hydrofluoric acid was added to the cleaning liquid so that the same concentration was maintained while monitoring the concentration of hydrofluoric acid. After a predetermined time, a part of the cleaning solution was collected, and the Si concentration in the cleaning solution was quantified by ICP emission spectroscopic analysis. Then, KF was added to the cleaning liquid so that the molar ratio with respect to the Si concentration was a predetermined ratio. Thereafter, a glass piece having a thickness of 1 mm and a diameter of 15 mm having the same composition as that of the CRT panel is immersed in 30 ml of each cleaning liquid with the above molar ratio adjusted, and left for 10 minutes while stirring with a stirrer at room temperature. The weight of the glass piece before and after immersion was measured. The weight reduction rate of each glass piece is shown in FIG.
[0063]
As shown in FIG. 2, the weight reduction rate of the glass piece increased as the molar ratio of KF to Si increased. From this result, as shown in the above reaction formula (2), it was confirmed that the chemical reaction for generating HF progressed by the addition of KF. On the other hand, when the molar ratio of KF to Si exceeds 2 (in other words, when the equivalent of KF exceeds the equivalent of fluorosilicic acid in the cleaning liquid), the weight reduction rate of the glass slightly increases even if KF is further added. It was only. This tendency is also consistent with the result expected from the above reaction formula (2).
[0064]
FIG. 3 shows changes in Si concentration and Si removal rate in the glass cleaning solution due to the addition of KF.
[0065]
As shown in FIG. 3, when the molar ratio of KF to Si is 2 (equivalent point of KF to Si), about 70% or more of Si in the glass cleaning liquid is 3 in the glass cleaning liquid. Almost 90% of the Si was removed. From the results shown in FIG. 3, the molar ratio of KF to Si is 2 to 4 (1-2 when expressed in terms of the equivalent of fluoride to fluorosilicic acid), 2 to 3.5, especially 2.5 to 3.5. Is preferable. However, if there is no problem even if excess KF is present, KF having a molar ratio of about 2 to 4.5 may be added in consideration of the reaction rate in an actual apparatus.
[0066]
From the results shown in FIGS. 2 and 3, hereinafter, the amount of KF added was set to a molar ratio of 3 with respect to Si.
[0067]
Next, in order to confirm the effect of KF addition when regenerating the glass cleaning solution repeatedly and the behavior of various cations eluted from the glass, the following examination was performed.
[0068]
First, the glass piece was dissolved in hydrofluoric acid to prepare a cleaning solution so that the Si concentration was 2500 ppm and the hydrofluoric acid was 11% by weight. A glass piece having a composition similar to that in Table 1 and having a thickness of 1 mm and a diameter of 15 mm was immersed in 30 ml of this cleaning liquid, and the temperature of the cleaning liquid was maintained at 34 ° C. and left for 10 minutes while stirring with a stirrer. The weight reduction amount of the glass piece at this time and the cation concentration in the cleaning solution were measured. The cation concentration was measured by ICP emission spectroscopic analysis.
[0069]
Subsequently, KF corresponding to a molar ratio of 3 with respect to Si in the cleaning solution was added to adjust the hydrofluoric acid concentration to 11% by weight. A glass piece having a composition similar to that in Table 1 and having a thickness of 1 mm and a diameter of 15 mm was immersed in 30 ml of this cleaning liquid, and the temperature of the cleaning liquid was maintained at 34 ° C. and left for 10 minutes while stirring with a stirrer. At this time, the weight loss of the glass piece and the cation concentration in the cleaning solution were measured.
[0070]
With the above as a one-cycle test, the same amount of glass pieces as in the first cycle were further dissolved in the cleaning solution after the end of one cycle, and the same test was repeated four times in total. FIG. 4 shows changes in the concentration of various cations in the cleaning solution, and FIG. 5 shows the weight reduction rate of the glass pieces. In addition, although the concentration change was measured simultaneously also about the cation which is not shown in FIG. 4, the density | concentration was about Ba or less about the other cation.
[0071]
As shown in FIG. 4, it was confirmed that 90% or more of Si can be continuously removed by adding KF. Moreover, Si and K are not continuously accumulated. Further, as shown in FIG. 5, it was confirmed that the amount of weight reduction of the glass was almost constant and the cleaning ability of the cleaning liquid was maintained. On the other hand, when KF was not added at all, as shown in FIG. 6, the glass cleaning ability decreased monotonously.
[0072]
【The invention's effect】
As described above in detail, according to the regeneration method of the present invention, by adding fluoride to the glass cleaning solution after cleaning the surface of the silicate glass, it is contained in the cleaning solution, and the glass A large amount of glass cleaning solution can be efficiently regenerated by precipitating and removing fluorosilicic acid that adheres to the glass and causes cleaning failure as a fluorosilicate with a cation contained in the fluoride. In addition, the concentration of fluoride can be added quantitatively based on the results of continuous monitoring of the Si concentration in the cleaning liquid in the treatment tank, and the optimum amount of fluoride can be added without excess or deficiency. Can be removed.
[0073]
Moreover, according to the cleaning method of the present invention, industrial waste can be reduced by prolonging the replacement cycle of the glass cleaning solution containing hydrofluoric acid using the above-described regeneration method. Furthermore, the present invention also provides a regeneration apparatus and a cleaning apparatus for performing the regeneration method and the cleaning method.
[0074]
Thus, the present invention enables the reduction of industrial waste containing hydrofluoric acid, which has been difficult in the past, and at the same time reduces poor glass cleaning. In the technical field of glass product production, The utility value is extremely large.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of an embodiment of a cleaning apparatus of the present invention.
FIG. 2 is a graph showing a relationship between a molar ratio of added KF to Si in a glass cleaning solution and a weight reduction rate of a glass piece immersed in the solution.
FIG. 3 is a graph showing the relationship between the molar ratio of added KF to Si in a glass cleaning solution, and the Si concentration and Si removal rate in the solution.
FIG. 4 is a diagram showing changes in cation concentration in a hydrofluoric acid cleaning solution in a continuous test.
FIG. 5 is a diagram showing a change in a weight reduction rate of a glass piece in a continuous test.
FIG. 6 is a diagram showing a change in a weight reduction rate of a glass piece when KF is not added.
[Explanation of symbols]
1, 3, 5 Cleaning liquid 2 Processing liquid 6 Hydrofluoric acid 10 Regeneration device 11 Cleaning tank 12 Processing liquid tank 13 Processing tank 14 Precipitation tank 15 Adjustment tank 16 Hydrofluoric acid tank 20 CRT panel 21 Nozzles 22, 26 Pump 24 Filter 27 Circulating pump 30 Monitoring system 31, 35 Exhaust port 34 Discharge cock 36 Si monitoring system

Claims (7)

Measure the concentration of Si in the glass cleaning solution containing hydrofluoric acid after cleaning the surface of the silicate glass,
A defined amount of fluoride based on the Si concentration is added to the glass cleaning solution, which is required to convert all Si in the glass cleaning solution to fluorosilicate. By adding more than the amount of fluoride, the fluorosilicic acid in the glass cleaning solution reacts with the fluoride to precipitate fluorosilicate,
A method for regenerating a glass cleaning solution, comprising removing the fluorosilicate from the glass cleaning solution. A Si concentration measuring device for measuring the concentration of Si in the glass cleaning solution containing hydrofluoric acid after cleaning the surface of the silicate glass;
A treatment tank comprising means for adding, to the glass cleaning solution, more fluoride than the amount required to convert all Si in the glass cleaning solution into fluorosilicate based on the Si concentration. When,
A fluorosilicate recovery means for removing from the glass cleaning solution fluorosilicate precipitated by the reaction between the fluorosilicic acid in the glass cleaning solution and the fluoride. Playback device. The apparatus for regenerating a glass cleaning solution according to claim 2 , wherein the fluorosilicate recovery means includes a discharge cock provided at the bottom of the processing tank or the precipitation tank that receives the glass cleaning solution from the bottom of the processing tank. The apparatus for regenerating a glass cleaning solution according to claim 2 or 3 , further comprising an adjusting tank for replenishing hydrofluoric acid to the glass cleaning solution after removing the fluorosilicate. 5. A regenerator according to claim 2 , and a cleaning tank that is supplied with a glass cleaning solution from the regenerator and cleans the surface of the silicate glass with the glass cleaning solution. Silicate glass cleaning equipment. A cleaning apparatus comprising: the regenerator according to any one of claims 2 to 4 ; and a cleaning tank that is supplied with a glass cleaning solution from the regenerator and that cleans the surface of the silicate glass with the glass cleaning solution. The glass cleaning solution used in the above is further regenerated in the regenerator so that the glass cleaning solution is regenerated and used. The apparatus for cleaning silicate glass according to claim 5 or 6 , wherein the silicate glass is a panel for a cathode ray tube.

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