JP4635527B2 - Method for recovering hydrofluoric acid - Google Patents
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Description
本発明は、フッ酸の回収方法に関するものであり、詳しくは、ガラス基板のエッチング工程などから排出されたシリカ成分および金属成分含有のフッ酸廃液から蒸留法によりフッ酸を回収するフッ酸の回収方法に関するものである。 TECHNICAL FIELD The present invention relates to a method for recovering hydrofluoric acid, and more specifically, recovering hydrofluoric acid by recovering hydrofluoric acid from a silica component and metal component-containing hydrofluoric acid waste solution discharged from a glass substrate etching process or the like by a distillation method. It is about the method.
ガラスやガラス基板のエッチングには、例えば濃度１５重量％程度のフッ化水素酸（以下、「フッ酸」と言う。）が使用され、斯かるフッ酸は、通常、約５０重量％の高濃度のフッ酸を純水で希釈することによりオンサイトで調製される。そして、上記のエッチング等のフッ酸利用工程においては、シリカ成分および金属成分を含むフッ酸の廃液が排出されるが、斯かる廃液は、反応に利用されなかったフッ酸を多量に含有しているため、これを回収して再利用するのが望ましい。 For etching glass and glass substrates, for example, hydrofluoric acid having a concentration of about 15% by weight (hereinafter referred to as “hydrofluoric acid”) is used, and such hydrofluoric acid is usually a high concentration of about 50% by weight. It is prepared on-site by diluting the hydrofluoric acid with pure water. In the hydrofluoric acid utilization process such as etching, the waste liquid of hydrofluoric acid containing the silica component and the metal component is discharged, but the waste liquid contains a large amount of hydrofluoric acid that has not been used for the reaction. Therefore, it is desirable to collect and reuse it.
フッ酸利用工程において、フッ酸廃液から簡便にフッ酸を回収する方法としては、拡散透析膜を使用した回収方法が挙げられる。斯かるフッ酸の回収方法では、先ず、フィルター又は遠心分離装置を使用し、フッ酸廃液からスラッジを分離した精製原料としてのフッ酸廃液を回収し、次いで、陰イオン交換膜フィルターを利用した拡散透析法により、溶解成分である金属イオンや珪フッ酸などの不純物をフッ酸廃液から除去して精製フッ酸を得る。上記の拡散透析法による回収方法は、設備を小型化でき、オンサイトでフッ酸を再生し得る点で優れている。
ところで、フッ酸廃液からのフッ酸の回収においては、不純物の一層少ないフッ酸をより高い収率で回収すると言う観点からすると、フッ酸を製造する場合と同様に、蒸留法を利用してフッ酸を回収するのが望ましい。しかしながら、上記の様なフッ酸廃液にはＳｉ，Ｂ，Ａｌ，Ｃａ，Ｚｒ等の金属が溶存しており、蒸留法によって回収しようとすると、濃縮液（分離濃縮されるフッ酸廃液）中に金属成分が析出するため、蒸留塔を含む系内でスケーリングが発生し、設備を稼働できなくなる。また、一般的なフッ酸の製造の様に、蒸留法によって一旦フッ化水素を製造しようとすると、設備が大掛かりとなるため、経済的な観点から、オンサイトで実施するのは困難である。 By the way, in the recovery of hydrofluoric acid from the hydrofluoric acid waste liquid, from the viewpoint of recovering hydrofluoric acid with less impurities in a higher yield, as in the case of producing hydrofluoric acid, the hydrofluoric acid is recovered using a distillation method. It is desirable to recover the acid. However, metals such as Si, B, Al, Ca, and Zr are dissolved in the hydrofluoric acid waste liquid as described above, and if it is attempted to be recovered by distillation, the concentrated liquid (hydrofluoric acid waste liquid to be separated and concentrated) Since the metal component is deposited, scaling occurs in the system including the distillation tower, and the facility cannot be operated. Moreover, once it is going to manufacture hydrogen fluoride by a distillation method like manufacture of a general hydrofluoric acid, since an installation will become large, it is difficult to implement on-site from an economical viewpoint.
本発明は、上記の実情に鑑みなされたものであり、その目的は、ガラス基板のエッチング工程などから排出されたフッ酸廃液から蒸留法によりフッ酸を回収する方法であって、スケーリングの発生がなく、不純物の一層少ない精製フッ酸を高い収率で回収できるフッ酸の回収方法を提供することにある。 The present invention has been made in view of the above circumstances, and its purpose is to recover hydrofluoric acid from a hydrofluoric acid waste solution discharged from a glass substrate etching process or the like by a distillation method. It is another object of the present invention to provide a method for recovering hydrofluoric acid that can recover purified hydrofluoric acid with less impurities in a high yield.
上記の課題を解決するため、本発明に係るフッ酸の回収方法は、シリカを含む金属成分含有のフッ酸廃液から蒸留法によりフッ酸を回収するフッ酸の回収方法であって、蒸発釜にフッ酸廃液を一定流量で供給して加熱し、蒸気として粗フッ酸を回収すると共に濃縮廃液を分離する粗フッ酸蒸発工程と、第１の蒸留塔で粗フッ酸を蒸留し、粗フッ酸よりも高濃度で且つフッ酸の共沸濃度未満の濃度の濃縮フッ酸と回収水とに分離する第１蒸留工程と、第２の蒸留塔で濃縮フッ酸を更に蒸留し、濃縮フッ酸と同様の濃度で且つ濃縮フッ酸に比べて不純物の少ない精製フッ酸と廃液とに分離する第２蒸留工程とを備え、前記粗フッ酸蒸発工程のフッ酸廃液に金属成分の析出を抑制するに足る量の硫酸を添加することを特徴とする。 In order to solve the above problems, a hydrofluoric acid recovery method according to the present invention is a hydrofluoric acid recovery method for recovering hydrofluoric acid from a metal component-containing hydrofluoric acid waste liquid containing silica by a distillation method. The hydrofluoric acid waste liquid is supplied at a constant flow rate and heated to recover the crude hydrofluoric acid as a vapor and separate the concentrated waste liquid, and the crude hydrofluoric acid is distilled in the first distillation column. a first distillation step to and separated into concentrated hydrofluoric acid at a concentration of less than the azeotropic concentration of hydrofluoric acid and the recovered water in a concentration higher than, further distilled concentrated hydrofluoric acid in the second distillation column, and concentrated hydrofluoric acid A second distillation step that separates the purified hydrofluoric acid having a similar concentration and less impurities than the concentrated hydrofluoric acid and the waste liquid, and suppresses the precipitation of metal components in the hydrofluoric acid waste liquid of the crude hydrofluoric acid evaporation step. A sufficient amount of sulfuric acid is added.
すなわち、本発明においては、粗フッ酸蒸発工程において、蒸発釜でフッ酸廃液から粗フッ酸を蒸発させる際、フッ酸廃液に硫酸を添加することにより、蒸発釜で濃縮されるフッ酸廃液（濃縮廃液）中に析出せんとする金属成分を硫酸によって溶解させ、これにより、蒸発釜でのスケーリングを防止し、伝熱効率の低下を防止する。そして、後段の第１及び第２蒸留工程において、不純物の極めて少ない粗フッ酸および濃縮フッ酸を蒸留し、精製された精製フッ酸を得る。 That is, in the present invention, when the crude hydrofluoric acid is evaporated from the hydrofluoric acid waste liquid in the crude hydrofluoric acid evaporation step, sulfuric acid is added to the hydrofluoric acid waste liquid to add sulfuric acid to the hydrofluoric acid waste liquid ( The metal component that precipitates in the concentrated waste liquid) is dissolved with sulfuric acid, thereby preventing scaling in the evaporating pot and lowering the heat transfer efficiency. In the subsequent first and second distillation steps, crude hydrofluoric acid and concentrated hydrofluoric acid with very few impurities are distilled to obtain purified purified hydrofluoric acid.
本発明の係るフッ酸の回収方法によれば、最初の粗フッ酸蒸発工程において、蒸発釜のフッ酸廃液に硫酸を添加し、濃縮されるフッ酸廃液（濃縮廃液）中に金属成分を溶解させるため、蒸発釜におけるスケーリングを防止でき且つ伝熱効率の低下を防止でき、その結果、不純物の一層少ない精製フッ酸を高い収率で回収できる。そして、従来のフッ酸の製造の様にフッ化水素を製造することなく、粗フッ酸蒸発工程においてフッ酸廃液から直接フッ酸を回収し、第１及び第２蒸留工程で濃縮、精製するため、設備を簡素化できる。 According to the hydrofluoric acid recovery method of the present invention, in the first crude hydrofluoric acid evaporation step, sulfuric acid is added to the hydrofluoric acid waste liquid of the evaporation kettle, and the metal component is dissolved in the concentrated hydrofluoric acid waste liquid (concentrated waste liquid). Therefore, scaling in the evaporating kettle can be prevented and a decrease in heat transfer efficiency can be prevented. As a result, purified hydrofluoric acid with less impurities can be recovered in a high yield. Then, hydrofluoric acid is recovered directly from the hydrofluoric acid waste solution in the crude hydrofluoric acid evaporation step without producing hydrogen fluoride as in the conventional hydrofluoric acid production, and concentrated and purified in the first and second distillation steps. The equipment can be simplified.
本発明に係るフッ酸の回収方法（以下、「回収方法」と言う。）の実施形態を図面に基づいて説明する。本発明の回収方法は、ガラスやガラス基板のエッチング等に使用された少なくとも金属成分含有のフッ酸廃液から蒸留法によりフッ酸を回収する回収方法であり、図１に示す様なフッ酸回収装置を使用し、主に連続処理方式で実施される。図１は、本発明の回収方法および当該回収方法の実施に好適なフッ酸回収装置の主要部の構成例を示すフロー図である。図２〜図４は、フッ酸回収装置における蒸発釜の加熱手段の例を示す縦断面図である。図中、流体を制御するための切替弁や流量調整弁は省略している。なお、以下の説明においては、フッ酸廃液、粗フッ酸、濃縮フッ酸および精製フッ酸の各フッ化水素濃度を「濃度」と言う。 An embodiment of a hydrofluoric acid recovery method (hereinafter referred to as “recovery method”) according to the present invention will be described with reference to the drawings. The recovery method of the present invention is a recovery method for recovering hydrofluoric acid by distillation from at least a metal component-containing hydrofluoric acid waste solution used for etching glass or glass substrate, and a hydrofluoric acid recovery apparatus as shown in FIG. Is mainly implemented in a continuous processing system. FIG. 1 is a flowchart showing a configuration example of a main part of a hydrofluoric acid recovery apparatus suitable for implementing the recovery method of the present invention and the recovery method. 2 to 4 are longitudinal sectional views showing examples of the heating means of the evaporation pot in the hydrofluoric acid recovery apparatus. In the figure, a switching valve and a flow rate adjusting valve for controlling the fluid are omitted. In the following description, each hydrogen fluoride concentration of hydrofluoric acid waste liquid, crude hydrofluoric acid, concentrated hydrofluoric acid, and purified hydrofluoric acid is referred to as “concentration”.
先ず、本発明の回収方法を実施するためのフッ酸回収装置について説明する。本発明に適用されるフッ酸回収装置は、図１に示す様に、処理すべきフッ酸廃液から粗フッ酸を蒸気として回収し且つ濃縮廃液を分離する蒸発釜（１）と、得られた粗フッ酸を濃縮フッ酸と回収水とに分離する第１の蒸留塔（２１）と、濃縮フッ酸を更に精製して精製フッ酸と廃液（図１中の「塔底液」）とに分離する第２の蒸留塔（２２）とを備えている。なお、上記の蒸発釜（１）、第１の蒸留塔（２１）、第２の蒸留塔（２２）及び後述する容器や各流路（配管）等の機器類には、耐食性を有するもの、通常はフッ素樹脂製のもの、または、フッ素樹脂でコーティング若しくはライニングされたものが使用される。 First, a hydrofluoric acid recovery apparatus for carrying out the recovery method of the present invention will be described. As shown in FIG. 1, an apparatus for recovering hydrofluoric acid applied to the present invention obtained an evaporating pot (1) for recovering crude hydrofluoric acid as steam from the hydrofluoric acid waste liquid to be treated and separating the concentrated waste liquid. A first distillation column (21) for separating crude hydrofluoric acid into concentrated hydrofluoric acid and recovered water, and further purifying the concentrated hydrofluoric acid into purified hydrofluoric acid and waste liquid ("column bottom liquid" in FIG. 1). And a second distillation column (22) for separation. In addition, the above-mentioned evaporation pot (1), the first distillation column (21), the second distillation column (22) and the equipment such as containers and each flow path (pipe) described later have corrosion resistance, Usually, those made of fluororesin or those coated or lined with fluororesin are used.
蒸発釜（１）は、フッ酸廃液を加熱して粗フッ酸を蒸気の状態で回収するための炊き上げ装置である。蒸発釜（１）の上部には、処理すべきフッ酸廃液を導入する原料流路（７１）、蒸発させた粗フッ酸を取り出す粗フッ酸流路（７３）、および、後述する様に硫酸を添加する硫酸供給流路（７２）、ならびに、第２の蒸留塔（２２）で分離された廃液である塔底液を当該蒸発釜に戻す塔底液返流流路（９３）が接続される。また、蒸発釜（１）の底部には、濃縮廃液、すなわち、濃縮されたフッ酸廃液を抜き出す廃液抜出し流路（７４）が設けられる。 The evaporating pot (1) is a cooking device for heating the hydrofluoric acid waste liquid to recover the crude hydrofluoric acid in a vapor state. In the upper part of the evaporation pot (1), there are a raw material flow path (71) for introducing a hydrofluoric acid waste liquid to be treated, a crude hydrofluoric acid flow path (73) for taking out evaporated crude hydrofluoric acid, and sulfuric acid as described later. And a column bottom liquid return channel (93) for returning the column bottom liquid, which is a waste liquid separated in the second distillation column (22), to the evaporation kettle. The Moreover, the bottom part of an evaporating pot (1) is provided with the waste liquid extraction flow path (74) which extracts concentrated waste liquid, ie, the concentrated hydrofluoric acid waste liquid.
蒸発釜（１）は、収容したフッ酸廃液を加熱手段によって加熱可能に構成される。蒸発釜（１）に使用される加熱手段としては、処理すべき量のフッ酸廃液から粗フッ酸を十分に蒸発させ得る限り、各種の加熱手段を使用できるが、例えば、図２〜図４に示す様に、ジャケット（１１）、チューブ式熱交換器（１２）、コイル式熱交換器（１３）等が挙げられる。 The evaporation kettle (1) is configured to be able to heat the contained hydrofluoric acid waste liquid by heating means. As the heating means used in the evaporation pot (1), various heating means can be used as long as the crude hydrofluoric acid can be sufficiently evaporated from the hydrofluoric acid waste liquid to be treated. For example, FIGS. As shown in FIG. 2, a jacket (11), a tube heat exchanger (12), a coil heat exchanger (13), and the like can be given.
すなわち、図２に示す蒸発釜（１）は、水蒸気室を構成するジャケット（１１）が釜本体の外周に設けられたものであり、前記の水蒸気室に水蒸気を供給して釜内部のフッ酸廃液を加熱する様になされている。図３に示す蒸発釜（１）は、多数の伝熱管を束ねて成るチューブ式熱交換器（１２）が釜の内部に挿通されたものであり、前記の各伝熱管に水蒸気を供給することにより、釜内部のフッ酸廃液を加熱する様になされている。また、図４に示す蒸発釜（１）は、伝熱管をコイル状に巻回積層して成るコイル式熱交換器（１３）が釜の内部に配置されたものであり、前記の伝熱管に水蒸気を供給することにより、釜内部のフッ酸廃液を加熱する様になされている。各図中の符号（１４）及び（１５）は、各々、水蒸気供給管および水蒸気排出管を示す。 That is, the evaporation pot (1) shown in FIG. 2 has a jacket (11) that constitutes a water vapor chamber provided on the outer periphery of the main body, and supplies water vapor to the water vapor chamber so The waste liquid is heated. The evaporation kettle (1) shown in FIG. 3 has a tube heat exchanger (12) formed by bundling a large number of heat transfer tubes inserted into the kettle, and supplies steam to each of the heat transfer tubes. Thus, the hydrofluoric acid waste liquid inside the kettle is heated. In addition, the evaporating pot (1) shown in FIG. 4 has a coil-type heat exchanger (13) formed by winding and laminating heat transfer tubes in a coil shape. By supplying water vapor, the hydrofluoric acid waste liquid inside the kettle is heated. Reference numerals (14) and (15) in the drawings indicate a steam supply pipe and a steam discharge pipe, respectively.
また、図示しないが、上記の蒸発釜（１）は、熱交換能力を高めるため、図２に示す様なジャケット（１１）が釜本体の外周に設けられ且つ図３に示すチューブ式熱交換器（１２）又は図４に示すコイル式熱交換器（１３）が釜内部に配置され、ジャケット（１１）の水蒸気室に水蒸気を供給すると共に、チューブ式熱交換器（１２）又はコイル式熱交換器（１３）の伝熱管に水蒸気を供給することにより、釜の内外からフッ酸廃液を加熱する様になされていてもよい。なお、図３に示す様なチューブ式熱交換器（１２）としては、例えば淀川ヒューテック社製の「ＰＦＡシェル＆チューブ式熱交換器」（商品名）を利用することが出来、図４に示す様なコイル式熱交換器（１３）としては、例えば同社製の「ＰＦＡコイル式熱交換器」（商品名）を利用することが出来る。 Moreover, although not shown in figure, the said evaporative pot (1) is provided with the jacket (11) as shown in FIG. 2 in the outer periphery of the pot main body, and the tube type heat exchanger shown in FIG. (12) or the coil heat exchanger (13) shown in FIG. 4 is disposed inside the kettle, and supplies water vapor to the water vapor chamber of the jacket (11), and at the same time, the tube heat exchanger (12) or coil heat exchange. The hydrofluoric acid waste liquid may be heated from the inside and outside of the kettle by supplying water vapor to the heat transfer tube of the vessel (13). As the tube heat exchanger (12) as shown in FIG. 3, for example, “PFA shell & tube heat exchanger” (trade name) manufactured by Yodogawa Hutec can be used, which is shown in FIG. As such a coil type heat exchanger (13), for example, “PFA coil type heat exchanger” (trade name) manufactured by the same company can be used.
第１の蒸留塔（２１）及び第２の蒸留塔（２２）は、蒸発釜（１）で回収された粗フッ酸を蒸留精製するための蒸留塔であり、第１の蒸留塔（２１）は、粗フッ酸から水を回収水として分離し且つ濃度の高められた濃縮フッ酸を得るために設けられ、第２の蒸留塔（２２）は、濃縮フッ酸を更に精製して不純物の極めて少ない精製フッ酸を得るために設けられる。第１の蒸留塔（２１）及び第２の蒸留塔（２２）は、従来周知の蒸留塔、すなわち、多孔板トレイ等の気液接触用のトレイ（棚段）が空塔内に多数設置された段塔、不規則または規則充填物が空塔内に装填された充填塔などによって構成される。 The first distillation column (21) and the second distillation column (22) are distillation columns for distilling and purifying the crude hydrofluoric acid recovered in the evaporation kettle (1). The first distillation column (21) Is provided to separate the water from the crude hydrofluoric acid as recovered water and to obtain concentrated hydrofluoric acid having an increased concentration, and the second distillation column (22) further refines the concentrated hydrofluoric acid to reduce impurities. Provided to obtain less purified hydrofluoric acid. The first distillation column (21) and the second distillation column (22) are conventionally known distillation columns, that is, a large number of gas-liquid contact trays (shelf) such as a perforated plate tray are installed in the empty column. It is constituted by a plate tower, a packed tower in which irregular or regular packing is loaded in an empty tower.
第１の蒸留塔（２１）は、処理すべき粗フッ酸が蒸発釜（１）から上記の粗フッ酸流路（７３）を通じて塔底部に供給される様になされている。そして、第１の蒸留塔（２１）の塔底部には、粗フッ酸を加熱蒸発させるため、蒸発缶、場合によっては、図１に示す様なリボイラー（５１）を含む炊上げ機構が付設される。斯かる炊上げ機構は、第１の蒸留塔（２１）の塔底部の粗フッ酸を炊き上げる機構であり、第１の蒸留塔（２１）に供給された粗フッ酸を当該第１の蒸留塔の塔底から抜き出す塔底液抜出し流路（８１）と、抜き出された粗フッ酸を水蒸気などの熱媒体との熱交換により加熱蒸発させるリボイラー（５１）と、蒸気化された粗フッ酸を再び塔底部に戻す循環流路（８２）とを備えている。 The first distillation column (21) is configured such that the crude hydrofluoric acid to be treated is supplied from the evaporation kettle (1) to the bottom of the column through the crude hydrofluoric acid flow path (73). And in order to heat and evaporate crude hydrofluoric acid at the bottom of the first distillation column (21), a cooking mechanism including an evaporator and, in some cases, a reboiler (51) as shown in FIG. The Such a cooking mechanism is a mechanism that cooks crude hydrofluoric acid at the bottom of the first distillation column (21), and the crude hydrofluoric acid supplied to the first distillation column (21) is used for the first distillation. A tower bottom liquid extraction flow path (81) withdrawn from the tower bottom of the tower, a reboiler (51) for heating and evaporating the extracted crude hydrofluoric acid by heat exchange with a heat medium such as steam, and a vaporized crude fluorine. And a circulation channel (82) for returning the acid to the bottom of the column again.
リボイラー（５１）としては、複数の伝熱管によって多数の流路が形成された多管式熱交換器を備えたもの等が使用できる。そして、リボイラー（５１）よりも上流側には、第１の蒸留塔（２１）の塔底部の循環する塔底液の一部、すなわち、第１の蒸留塔（２１）で濃縮された濃縮フッ酸を第２の蒸留塔（２２）へ供給する濃縮フッ酸流路（８３）（缶出液流路）が塔底液抜出し流路（８１）から分岐して設けられる。 As the reboiler (51), a reboiler (51) including a multi-tube heat exchanger in which a large number of flow paths are formed by a plurality of heat transfer tubes can be used. Further, on the upstream side of the reboiler (51), a part of the bottom liquid circulating at the bottom of the first distillation column (21), that is, the concentrated hydrocarbon concentrated in the first distillation column (21). A concentrated hydrofluoric acid flow path (83) (bottom liquid flow path) for supplying acid to the second distillation column (22) is branched from the tower bottom liquid discharge flow path (81).
また、第１の蒸留塔（２１）の塔頂には、蒸留分離された回収水蒸気を抜き出して冷却凝縮器（６１）に供給する蒸気流路（８４）が設けられる。冷却凝縮器（６１）としては、通常、多数の流路を形成する複数の伝熱管の管内に冷媒が流れ且つ管外に凝縮性蒸気（蒸留分離された蒸気）を通すことにより前記の凝縮性蒸気を液化する多管式の凝縮器が使用される。冷却凝縮器（６１）の底部には、凝縮した回収水を回収水容器（４１）に送液する凝縮液流路（８５）が設けられ、冷却凝縮器（６１）の上部には、不凝縮ガスを除害装置へ排気する排気流路（８９）が設けられる。 In addition, a steam channel (84) is provided at the top of the first distillation column (21) to extract the recovered water vapor separated by distillation and supply it to the cooling condenser (61). As the cooling condenser (61), usually, the refrigerant flows through the tubes of a plurality of heat transfer tubes forming a large number of flow paths, and the condensable vapor (distilled and separated) passes outside the tubes. A multi-tube condenser that liquefies the vapor is used. The bottom of the cooling condenser (61) is provided with a condensate flow path (85) for sending the condensed recovered water to the recovered water container (41), and the top of the cooling condenser (61) is non-condensing. An exhaust passage (89) for exhausting gas to the abatement device is provided.
上記の回収水容器（４１）は、第１の蒸留塔（２１）で蒸留分離され且つ冷却凝縮器（６１）で冷却して得られた回収水を貯留する容器である。斯かる回収水容器（４１）は、蒸留操作の際に回収水の一部を還流として第１の蒸留塔（２１）に戻すため、還流流路（８６）を介して第１の蒸留塔（２１）の塔頂側に接続される。また、最終的に得られる精製フッ酸の希釈に回収水容器（４１）の回収水を使用したり、フッ酸利用工程などに回収水容器（４１）の回収水を供給するため、上記の還流流路（８６）には、回収水を取り出す回収水取出流路（８７）（留出液流路）が分岐して設けられる。 The recovered water container (41) is a container for storing recovered water obtained by distillation separation in the first distillation column (21) and cooling by the cooling condenser (61). Since such a recovered water container (41) returns a part of the recovered water to the first distillation column (21) as reflux during the distillation operation, the first distillation column (86) is returned via the reflux channel (86). 21) is connected to the top side of the tower. Further, since the recovered water in the recovered water container (41) is used for diluting the purified hydrofluoric acid finally obtained, or the recovered water in the recovered water container (41) is supplied to the hydrofluoric acid utilization process or the like, the above reflux is performed. The flow path (86) is provided with a recovered water extraction flow path (87) (distillate liquid flow path) that branches out the recovered water.
一方、第２の蒸留塔（２２）は、第１の蒸留塔（２１）で濃度の高められた被処理液である濃縮フッ酸が上記の濃縮フッ酸流路（８３）によって塔底部に供給される様になされている。第２の蒸留塔（２２）の塔底部には、濃縮フッ酸を更に加熱蒸発させるため、蒸発缶、場合によっては、図１に示す様なリボイラー（５２）を含む炊上げ機構が付設される。 On the other hand, in the second distillation column (22), the concentrated hydrofluoric acid, which is the liquid to be processed whose concentration has been increased in the first distillation column (21), is supplied to the bottom of the column through the concentrated hydrofluoric acid flow path (83). It is made to be done. In order to further heat and evaporate the concentrated hydrofluoric acid at the bottom of the second distillation column (22), a cooking mechanism including an evaporator and, in some cases, a reboiler (52) as shown in FIG. 1 is attached. .
上記の炊上げ機構は、第１の蒸留塔（１）におけるのと同様に、第２の蒸留塔（２２）の塔底部の濃縮フッ酸を炊き上げる機構であり、第２の蒸留塔（２２））に供給された濃縮フッ酸を当該第２の蒸留塔の塔底から抜き出す塔底液抜出し流路（９１）と、抜き出された濃縮フッ酸を水蒸気などの熱媒体との熱交換により加熱蒸発させるリボイラー（５２）と、蒸気化された濃縮フッ酸を再び塔底部に戻す循環流路（９２）とを備えている。 The above cooking mechanism is a mechanism for cooking concentrated hydrofluoric acid at the bottom of the second distillation column (22) as in the first distillation column (1), and the second distillation column (22 )) And the concentrated hydrofluoric acid supplied to the bottom of the second distillation column is extracted from the bottom bottom liquid extraction flow path (91), and the extracted concentrated hydrofluoric acid is exchanged with a heat medium such as steam. A reboiler (52) for heating and evaporating and a circulation channel (92) for returning the vaporized concentrated hydrofluoric acid to the bottom of the column again are provided.
リボイラー（５２）としては、前述のリボイラー（５１）と同様のものが使用される。そして、リボイラー（５１）よりも上流側には、第２の蒸留塔（２２）の塔底部の循環する濃縮フッ酸の一部、すなわち、第２の蒸留塔（２２）に残留し且つ僅かに不純物を含んだ塔底液を再び蒸発釜（１）に戻す塔底液返流流路（９３）（缶出液流路）が塔底液抜出し流路（９１）から分岐して設けられる。 As the reboiler (52), the same reboiler (51) as described above is used. And on the upstream side of the reboiler (51), a part of the concentrated hydrofluoric acid circulating at the bottom of the second distillation column (22), that is, remaining in the second distillation column (22) and slightly A tower bottom liquid return flow path (93) (a bottom liquid flow path) for returning the tower bottom liquid containing impurities back to the evaporation kettle (1) is branched from the tower bottom liquid discharge flow path (91).
また、第２の蒸留塔（２２）の塔頂には、蒸留分離された精製フッ酸を冷却凝縮器（６２）に供給する蒸気流路（９４）が設けられる。冷却凝縮器（６２）としては、前述の冷却凝縮器（６１）と同様のものが使用される。冷却凝縮器（６２）の底部には、凝縮した精製フッ酸を精製フッ酸容器（４２）に送液する凝縮液流路（９５）が設けられ、冷却凝縮器（６２）の上部には、不凝縮ガスを除害装置へ排気するため、前述の排気流路（８９）へ通じる流路が設けられる。 Moreover, the vapor | steam flow path (94) which supplies the refined hydrofluoric acid separated by distillation to a cooling condenser (62) is provided in the tower top of the 2nd distillation tower (22). As a cooling condenser (62), the thing similar to the above-mentioned cooling condenser (61) is used. At the bottom of the cooling condenser (62) is provided a condensate flow path (95) for sending condensed purified hydrofluoric acid to the purified hydrofluoric acid container (42), and at the top of the cooling condenser (62), In order to exhaust the non-condensable gas to the abatement apparatus, a flow path leading to the above-described exhaust flow path (89) is provided.
上記の精製フッ酸容器（４２）は、第２の蒸留塔（２２）で蒸留分離され且つ冷却凝縮器（６２）で冷却して得られた精製フッ酸を貯留する容器である。斯かる精製フッ酸容器（４２）は、蒸留操作の際に精製フッ酸の一部を還流として第２の蒸留塔（２２）に戻すため、還流流路（９６）を介して第２の蒸留塔（２２）の塔頂側に接続される。また、精製フッ酸容器（４２）の精製フッ酸をフッ酸利用工程などに供給するため、上記の還流流路（９６）には、精製フッ酸を取り出す精製フッ酸取出流路（９７）（留出液流路）が分岐して設けられる。 The purified hydrofluoric acid container (42) is a container for storing purified hydrofluoric acid obtained by distillation separation in the second distillation column (22) and cooling by the cooling condenser (62). In such a purified hydrofluoric acid container (42), a part of the purified hydrofluoric acid is returned to the second distillation column (22) as a reflux during the distillation operation, so that the second distillation is performed via the reflux channel (96). Connected to the tower top side of the tower (22). In addition, in order to supply the purified hydrofluoric acid in the purified hydrofluoric acid container (42) to the hydrofluoric acid utilization process or the like, the above-described reflux flow path (96) has a purified hydrofluoric acid take-out flow path (97) (97) ( A distillate flow path) is provided in a branched manner.
また、図１に示すフッ酸回収装置は、蒸留における缶出液および留出液の流量ならびに還流比を制御するため、図示しないが、例えば、第１の蒸留塔（２１）の塔頂側の冷却凝縮器（６１）の下流側、および、第２の蒸留塔（２２）の塔頂側の冷却凝縮器（６２）の下流側に濃縮フッ酸および精製フッ酸の濃度をそれぞれ測定するフッ化水素濃度計が設置される。そして、蒸留プログラムが搭載された制御装置により、予め入力された処理条件および上記のフッ化水素濃度計の検出データに基づき、炊上げ機構の作動、各流路の開閉、切替、流量調整などを制御する様に構成される。 Further, the hydrofluoric acid recovery apparatus shown in FIG. 1 controls the flow rate and reflux ratio of the bottoms and distillate in distillation, and is not shown, but for example, on the top side of the first distillation column (21). Fluoride for measuring the concentration of concentrated hydrofluoric acid and purified hydrofluoric acid on the downstream side of the cooling condenser (61) and on the downstream side of the cooling condenser (62) on the top side of the second distillation column (22), respectively. A hydrogen concentration meter is installed. Based on the processing conditions input in advance and the detection data of the above hydrogen fluoride concentration meter, the operation of the cooking mechanism, opening and closing of each flow path, switching, flow rate adjustment, etc. are performed by a control device equipped with a distillation program. Configured to control.
なお、上記のフッ化水素濃度計としては、フッ酸における電気伝導率（導電率）を電磁誘導方式で連続測定し、これをフッ化水素濃度に換算する導電率型濃度計、または、フッ酸における超音波伝播速度を計測し、予め作成された所定温度・濃度における超音波伝播速度の関係に基づき、フッ化水素濃度を検出する超音波型濃度計、もしくは、フッ酸における超音波伝播速度および電磁導電率を計測し、予め作成された所定温度・濃度における超音波伝播速度と電磁導電率との関係（マトリックス）に基づき、フッ化水素濃度およびＨ２ＳｉＦ６等の不純物濃度を検出する超音波型多成分濃度計が使用される。 As the hydrogen fluoride concentration meter, a conductivity type concentration meter that continuously measures the electrical conductivity (conductivity) in hydrofluoric acid by an electromagnetic induction method and converts this to a hydrogen fluoride concentration, or hydrofluoric acid. Measure the ultrasonic wave propagation speed in the ultrasonic concentration meter that detects the hydrogen fluoride concentration based on the ultrasonic wave propagation speed relationship at a predetermined temperature and concentration created in advance, or the ultrasonic wave propagation speed in hydrofluoric acid and Ultrasonic that measures electromagnetic conductivity and detects the concentration of impurities such as hydrogen fluoride concentration and H 2 SiF 6 based on the relationship (matrix) between ultrasonic propagation velocity and electromagnetic conductivity at a predetermined temperature and concentration prepared in advance. A sonic multi-component densitometer is used.
特に、上記の超音波型多成分濃度計は、一定温度の溶液中の超音波伝播速度および電磁導電率を測定することにより、３成分系溶液の２成分の濃度を同時にリアルタイムで測定できる。すなわち、多成分濃度計は、溶液の温度が一定ならば、各成分の濃度に応じて液中の超音波の伝播速度および電磁導電率が一義的に特定されると言う原理に基づくものであり、フッ酸の濃度測定に適用する場合、例えば、フッ化水素およびＨ２ＳｉＦ６の各濃度毎に一定温度条件下で予め計測された超音波伝播速度と電磁導電率の関係をマトリックスとして予め準備することにより、前記のマトリックスに基づき、測定値からフッ化水素濃度およびＨ２ＳｉＦ６濃度を正確に演算できる。 In particular, the ultrasonic multi-component concentration meter described above can simultaneously measure the concentration of two components in a three-component solution in real time by measuring the ultrasonic propagation velocity and electromagnetic conductivity in a solution at a constant temperature. That is, the multi-component concentration meter is based on the principle that if the temperature of the solution is constant, the propagation speed and electromagnetic conductivity of the ultrasonic wave in the liquid are uniquely specified according to the concentration of each component. When applying to the concentration measurement of hydrofluoric acid, for example, a matrix is prepared in advance for the relationship between ultrasonic propagation velocity and electromagnetic conductivity measured in advance at a constant temperature for each concentration of hydrogen fluoride and H 2 SiF 6. Thus, based on the matrix, the hydrogen fluoride concentration and the H 2 SiF 6 concentration can be accurately calculated from the measured values.
例えば、上記の様な導電率型濃度計としては、東亜ディーケーケー社製の「電磁誘導式濃度変換器 ＭＢＭ−１０２Ａ型」（商品名）が使用でき、超音波型濃度計としては、富士工業社製の「超音波液体濃度計 ＦＵＤ−１ Ｍｏｄｅｌ−１２」（商品名）が使用でき、また、超音波型多成分濃度計としては、富士工業社製の商品名「ＦＵＤ−１ Ｍｏｄｅｌ−５２」が使用できる。 For example, “Electromagnetic induction type concentration converter MBM-102A type” (trade name) manufactured by Toa DKK Corporation can be used as the conductivity type densitometer as described above, and Fuji Denshi Co., Ltd. as the ultrasonic type densitometer. “Ultrasonic liquid concentration meter FUD-1 Model-12” (trade name) can be used, and as an ultrasonic type multi-component concentration meter, product name “FUD-1 Model-52” manufactured by Fuji Kogyo Co., Ltd. Can be used.
次に、上記のフッ酸回収装置を使用した本発明の回収方法について説明する。本発明に適用されるフッ酸廃液としては、例えば、ガラスやガラス基板にエッチングや洗浄を施したり或いは鋳物のスチール落としを行うフッ酸利用工程から排出される廃液が挙げられる。斯かるフッ酸廃液は、シリカ成分および金属成分、すなわち、被エッチング材などの被処理物の成分との反応により、各種フッ化物として溶解または結晶化した成分、あるいは、生成した反応生成物を含有している。具体的には、Ｓｉ、Ｂ，Ａｌ，Ｃａ，Ｆｅ，Ｓｒ，Ｚｒ，Ｋ，Ｎａ，Ｍｇ等の成分を含有する。また、通常、例えばエッチング液として使用されたフッ酸廃液の濃度は０．１〜２０重量％程度である。 Next, the recovery method of the present invention using the hydrofluoric acid recovery apparatus will be described. Examples of the hydrofluoric acid waste liquid applied to the present invention include waste liquid discharged from a hydrofluoric acid utilization process in which etching or cleaning is performed on glass or a glass substrate or steel casting is removed. Such a hydrofluoric acid waste liquid contains a silica component and a metal component, that is, a component dissolved or crystallized as various fluorides by reaction with a component of an object to be processed such as an etching material, or a reaction product generated. is doing. Specifically, it contains components such as Si, B, Al, Ca, Fe, Sr, Zr, K, Na, and Mg. Moreover, normally, the density | concentration of the hydrofluoric acid waste liquid used, for example as an etching liquid is about 0.1 to 20 weight%.
本発明の回収方法は、上記の様なフッ酸廃液を一定流量で蒸発釜（１）に供給して加熱し、蒸気として粗フッ酸を回収すると共に濃縮廃液を分離する粗フッ酸蒸発工程と、第１の蒸留塔（２１）で粗フッ酸を蒸留し、粗フッ酸よりも高濃度の濃縮フッ酸と回収水とに分離する第１蒸留工程と、第２の蒸留塔（２２）で濃縮フッ酸を更に蒸留し、精製された精製フッ酸と廃液とに分離する第２蒸留工程とを備えている。 The recovery method of the present invention includes a crude hydrofluoric acid evaporation step in which the hydrofluoric acid waste liquid as described above is supplied to the evaporation kettle (1) at a constant flow rate and heated to recover the crude hydrofluoric acid as a vapor and separate the concentrated waste liquid. In the first distillation column (21), the crude hydrofluoric acid is distilled and separated into concentrated hydrofluoric acid and recovered water having a higher concentration than the crude hydrofluoric acid, and the second distillation column (22). A second distillation step of further distilling the concentrated hydrofluoric acid to separate the purified hydrofluoric acid and the waste liquid.
粗フッ酸蒸発工程では、シリカ成分および金属成分を殆ど含まないフッ酸だけをフッ酸廃液から蒸気の状態で粗フッ酸として分離する。具体的には、処理すべきフッ酸廃液を原料流路（７１）を通じて蒸発釜（１）に一定流量で供給すると共に、図２〜図４に示す様な加熱手段またはそれらの組合わせにより、蒸発釜（１）内のフッ酸廃液を加熱し、粗フッ酸としてフッ酸を蒸発分離させる。その際、本発明においては、蒸発釜（１）内のフッ酸廃液の濃縮に伴う当該フッ酸廃液（濃縮廃液）中の金属成分の析出を防止するため、フッ酸廃液に金属成分の析出を抑制するに足る量の硫酸を添加する。 In the crude hydrofluoric acid evaporation step, only hydrofluoric acid containing almost no silica component and metal component is separated from the hydrofluoric acid waste solution as crude hydrofluoric acid in a vapor state. Specifically, the hydrofluoric acid waste liquid to be treated is supplied to the evaporation kettle (1) through the raw material flow path (71) at a constant flow rate, and the heating means as shown in FIGS. The hydrofluoric acid waste liquid in the evaporation kettle (1) is heated to evaporate and separate hydrofluoric acid as crude hydrofluoric acid. At that time, in the present invention, in order to prevent the precipitation of the metal component in the hydrofluoric acid waste liquid (concentrated waste liquid) accompanying the concentration of the hydrofluoric acid waste liquid in the evaporation pot (1), the metal component is deposited in the hydrofluoric acid waste liquid. Add an amount of sulfuric acid sufficient to inhibit.
硫酸は、硫酸供給流路（７２）を通じて蒸発釜（１）に供給されるが、蒸発釜（１）のフッ酸廃液に対し、含有する金属成分およびその濃度に応じて、少なくとも、フッ酸廃液中の金属成分を溶解するに足る量だけ添加される。硫酸の添加方法としては、一定濃度の硫酸を一定流量で連続して添加してもよいし、高濃度の硫酸を間欠的に添加してもよい。上記の様に、粗フッ酸蒸発工程においては、フッ酸の蒸発によって蒸発釜（１）のフッ酸廃液を濃縮する際、硫酸を添加することにより、フッ酸廃液（濃縮廃液）中で金属成分を溶解状態に維持できるため、蒸発釜（１）におけるスケールの付着や加熱手段の伝熱効率の低下を防止できる。 Sulfuric acid is supplied to the evaporation kettle (1) through the sulfuric acid supply flow path (72). The hydrofluoric acid waste liquid in the evaporation kettle (1) is at least a hydrofluoric acid waste liquid depending on the metal component contained and its concentration. An amount sufficient to dissolve the metal component therein is added. As a method for adding sulfuric acid, a constant concentration of sulfuric acid may be continuously added at a constant flow rate, or a high concentration of sulfuric acid may be intermittently added. As described above, in the crude hydrofluoric acid evaporation step, when the hydrofluoric acid waste liquid in the evaporation pot (1) is concentrated by the evaporation of hydrofluoric acid, by adding sulfuric acid, the metal components are contained in the hydrofluoric acid waste liquid (concentrated waste liquid). Therefore, it is possible to prevent the scale from adhering to the evaporation pot (1) and the heat transfer efficiency of the heating means from being lowered.
蒸気として分離された粗フッ酸は、粗フッ酸流路（７３）を通じて第１の蒸留塔（２１）に供給する。また、分離された濃縮廃液は、廃液抜出し流路（７４）を通じて蒸発釜（１）の底部から抜き出し、最初の原料であるフッ酸廃液の貯槽（図示省略）などに戻すか、あるいは、除外装置に送液して無害化処理する。なお、粗フッ酸蒸発工程において、例えば、濃度５〜１０重量％程度のフッ酸廃液を処理する場合は、フッ酸を蒸発させることにより、蒸発釜（１）内のフッ酸廃液を濃度３０〜３５％程度に濃縮する。 The crude hydrofluoric acid separated as the vapor is supplied to the first distillation column (21) through the crude hydrofluoric acid flow path (73). The separated concentrated waste liquid is extracted from the bottom of the evaporation pot (1) through the waste liquid extraction channel (74) and returned to a storage tank (not shown) of hydrofluoric acid waste liquid as the first raw material, or an exclusion device. The solution is sent to and detoxified. In the crude hydrofluoric acid evaporation step, for example, when treating a hydrofluoric acid waste liquid having a concentration of about 5 to 10% by weight, the hydrofluoric acid waste liquid in the evaporation kettle (1) is concentrated to 30 to 30% by evaporating the hydrofluoric acid. Concentrate to about 35%.
第１蒸留工程では、蒸発釜（１）から供給される粗フッ酸を第１の蒸留塔（２１）で蒸留し、粗フッ酸中の主に水を回収水として回収する。第１の蒸留塔（２１）での蒸留操作は、通常、系内の圧力を大気圧以下の所定圧力に保持して行われる。具体的には、蒸発釜（１）から粗フッ酸流路（７３）を通じて第１の蒸留塔（２１）に粗フッ酸を一定流量で供給する。第１の蒸留塔（２１）においては、塔底液抜出し流路（８１）を通じ、当該第１の蒸留塔の塔底部の粗フッ酸をリボイラー（５１）に供給して加熱蒸発させ、蒸気の状態で循環流路（８２）を通じて塔底部に戻す。すなわち、第１の蒸留塔（２１）においては、炊上げ機構により、塔底側の粗フッ酸を蒸気にして蒸留操作を行い、多量の水分を分離する。 In the first distillation step, the crude hydrofluoric acid supplied from the evaporation kettle (1) is distilled in the first distillation column (21), and mainly water in the crude hydrofluoric acid is recovered as recovered water. The distillation operation in the first distillation column (21) is usually performed while maintaining the pressure in the system at a predetermined pressure equal to or lower than atmospheric pressure. Specifically, crude hydrofluoric acid is supplied at a constant flow rate from the evaporation kettle (1) to the first distillation column (21) through the crude hydrofluoric acid flow path (73). In the first distillation column (21), the crude hydrofluoric acid at the bottom of the first distillation column is supplied to the reboiler (51) through the column bottom liquid extraction channel (81) to be heated and evaporated, The state is returned to the bottom of the column through the circulation channel (82). That is, in the first distillation column (21), the cooking mechanism performs distillation operation using the crude hydrofluoric acid at the bottom of the column as a vapor to separate a large amount of water.
第１の蒸留塔（１）で蒸留分離された水蒸気は、塔頂から一定流量で取り出し、蒸気流路（８４）を通じて冷却凝縮器（６１）に供給し、当該冷却凝縮器で液化した後、凝縮液流路（８５）を通じて回収水容器（４１）に送液し、当該回収水容器に回収水として貯留する。また、上記の蒸留を行う際、回収水容器（４１）に貯留された回収水の一部は、還流流路（８６）を通じて還流として第１の蒸留塔（２１）に一定流量で戻す。 The water vapor distilled and separated in the first distillation column (1) is taken out at a constant flow rate from the top of the column, supplied to the cooling condenser (61) through the vapor channel (84), and liquefied by the cooling condenser. The liquid is sent to the recovered water container (41) through the condensate flow path (85) and stored as recovered water in the recovered water container. When performing the above-mentioned distillation, a part of the recovered water stored in the recovered water container (41) is returned to the first distillation column (21) at a constant flow rate as reflux through the reflux channel (86).
上記の様な第１の蒸留塔（２１）における蒸留操作は、分離される濃縮フッ酸が粗フッ酸よりも高濃度で且つフッ酸の共沸濃度未満の濃度となる様に行う。換言すれば、水だけが蒸留分離される条件下で行う。例えば、斯かる蒸留操作により、当初の濃度が０．５〜２０重量％の粗フッ酸から、回収水と共に、濃度１０〜３０重量％程度の濃縮フッ酸を回収する。そして、第１の蒸留塔（２１）の塔底側に得られる濃縮フッ酸の一部は、塔底液抜出し流路（８１）から一定流量で抜き出し、濃縮フッ酸流路（８３）を通じて第２の蒸留塔（２２）に供給する。なお、回収された回収水容器（４１）の回収水の一部は、回収水取出流路（８７）を通じ、必要に応じてフッ酸利用工程などへ濃度調整水として供給する。 The distillation operation in the first distillation column (21) as described above is performed so that the concentrated hydrofluoric acid to be separated has a higher concentration than the crude hydrofluoric acid and less than the azeotropic concentration of hydrofluoric acid. In other words, it is carried out under conditions where only water is distilled off. For example, by such distillation operation, concentrated hydrofluoric acid having a concentration of about 10 to 30% by weight is recovered together with the recovered water from crude hydrofluoric acid having an initial concentration of 0.5 to 20% by weight. A part of the concentrated hydrofluoric acid obtained on the column bottom side of the first distillation column (21) is withdrawn at a constant flow rate from the column bottom liquid extraction flow path (81), and is passed through the concentrated hydrofluoric acid flow path (83). To the second distillation column (22). A part of the recovered water in the recovered water container (41) that has been recovered is supplied as concentration adjustment water to the hydrofluoric acid utilization step or the like as needed through the recovered water extraction flow path (87).
第２蒸留工程では、第１蒸留工程で得られた濃縮フッ酸を第２の蒸留塔（２２）で更に蒸留し、第１蒸留工程よりも更に精製された精製フッ酸を回収する。第２の蒸留塔（２２）での蒸留操作も、通常は系内の圧力を大気圧以下の所定圧力に保持して行われる。具体的には、濃縮フッ酸流路（８３）によって第２の蒸留塔（２２）に供給された濃縮フッ酸を前述の蒸留操作と同様に炊上げ機構により蒸気化する。すなわち、第２の蒸留塔（２２）に供給された濃縮フッ酸を当該第２の蒸留塔の塔底から塔底液抜出し流路（９１）を通じて抜き出し、リボイラー（５２）に供給して加熱蒸発させ、蒸気の状態で循環流路（９２）を通じて塔底部に戻し、第２の蒸留塔（２２）において蒸留する。 In the second distillation step, the concentrated hydrofluoric acid obtained in the first distillation step is further distilled in the second distillation column (22), and purified hydrofluoric acid further purified than in the first distillation step is recovered. The distillation operation in the second distillation column (22) is also usually performed while maintaining the pressure in the system at a predetermined pressure equal to or lower than atmospheric pressure. Specifically, the concentrated hydrofluoric acid supplied to the second distillation column (22) by the concentrated hydrofluoric acid flow path (83) is vaporized by the cooking mechanism in the same manner as the distillation operation described above. That is, the concentrated hydrofluoric acid supplied to the second distillation column (22) is extracted from the bottom of the second distillation column through the column bottom liquid extraction channel (91), and supplied to the reboiler (52) to be heated and evaporated. The vapor is returned to the bottom of the column through the circulation channel (92) and distilled in the second distillation column (22).
上記の様な第２の蒸留塔（２２）における蒸留操作により、一層精製された精製フッ酸を得る。第２の蒸留塔（２２）で蒸留分離された精製フッ酸は、当該第２の蒸留塔の塔頂から蒸気として一定流量で取り出し、蒸気流路（９４）を通じて冷却凝縮器（６２）に供給し、当該冷却凝縮器で液化した後、凝縮液流路（９５）を通じて精製フッ酸容器（４２）に送液して当該精製フッ酸容器に一旦貯留する。また、上記の蒸留を行う際、精製フッ酸容器（４２）に貯留された精製フッ酸の一部は、還流流路（９６）を通じて還流として第２の蒸留塔（２２）に戻す。 By the distillation operation in the second distillation column (22) as described above, further purified hydrofluoric acid is obtained. The purified hydrofluoric acid distilled and separated in the second distillation column (22) is taken out as a vapor from the top of the second distillation column at a constant flow rate and supplied to the cooling condenser (62) through the vapor flow path (94). Then, after being liquefied by the cooling condenser, the liquid is sent to the purified hydrofluoric acid container (42) through the condensate flow path (95) and temporarily stored in the purified hydrofluoric acid container. When performing the above distillation, a part of the purified hydrofluoric acid stored in the purified hydrofluoric acid container (42) is returned to the second distillation column (22) as reflux through the reflux channel (96).
第２蒸留工程では、上記の蒸留操作により、第２の蒸留塔（２２）へ供給される濃縮フッ酸と略同様の濃度であって且つ前記の濃縮フッ酸に比べて不純物の一層少ない精製フッ酸、例えば濃度１５〜３０重量％の精製フッ酸を回収することが出来る。そして、得られた精製フッ酸は、上記の様に精製フッ酸容器（４２）に一旦貯留された後、精製フッ酸取出流路（９７）を通じて例えばフッ酸利用工程などへ供給される。 In the second distillation step, the purified hydrofluoric acid having substantially the same concentration as the concentrated hydrofluoric acid supplied to the second distillation column (22) by the above-described distillation operation and having less impurities compared to the concentrated hydrofluoric acid. Acid, for example purified hydrofluoric acid having a concentration of 15 to 30% by weight, can be recovered. The purified hydrofluoric acid thus obtained is temporarily stored in the purified hydrofluoric acid container (42) as described above, and then supplied to, for example, a hydrofluoric acid utilization step through the purified hydrofluoric acid take-off channel (97).
また、第２蒸留工程で回収された精製フッ酸を利用するにあたり、第１蒸留工程で得られた回収水、すなわち、回収水取出流路（８７）を通じて取り出される回収水によって精製フッ酸を所定濃度に希釈することにより、回収水を有効利用することが出来る。なお、第２の蒸留塔（２２）の塔底部に残留する塔底液の一部、すなわち、濃縮フッ酸の一部は、上記の様な蒸留によって僅かに不純物が蓄積する場合があるため、塔底液抜出し流路（９１）から一定流量で抜き出し、塔底液返流流路（９３）を通じて再び蒸発釜（１）へ戻す。 In addition, when using the purified hydrofluoric acid recovered in the second distillation step, the purified hydrofluoric acid is predetermined by the recovered water obtained in the first distillation step, that is, the recovered water taken out through the recovered water discharge channel (87). By diluting to a concentration, recovered water can be used effectively. In addition, since a part of the bottom liquid remaining in the bottom of the second distillation column (22), that is, a part of the concentrated hydrofluoric acid may accumulate a little by the above distillation, It is withdrawn at a constant flow rate from the column bottom liquid extraction channel (91) and returned to the evaporation kettle (1) again through the column bottom liquid return channel (93).
上記の様に、本発明の回収方法では、粗フッ酸蒸発工程において、蒸発釜（１）でフッ酸廃液から粗フッ酸を蒸発させる際、フッ酸廃液に硫酸を添加することにより、蒸発釜（１）で濃縮されるフッ酸廃液（濃縮廃液）中に析出せんとする金属成分を硫酸によって溶解させ、これにより、蒸発釜（１）のフッ酸廃液における金属成分の析出を防止する。そして、後段の第１蒸留工程および第２蒸留工程において、不純物の極めて少ない粗フッ酸および濃縮フッ酸を蒸留し、より精製された精製フッ酸を得る。 As described above, in the recovery method of the present invention, in the crude hydrofluoric acid evaporation step, when the crude hydrofluoric acid is evaporated from the hydrofluoric acid waste liquid in the evaporation kettle (1), sulfuric acid is added to the hydrofluoric acid waste liquid. The metal component to be precipitated is dissolved with sulfuric acid in the hydrofluoric acid waste liquid (concentrated waste liquid) concentrated in (1), thereby preventing the metal component from being precipitated in the hydrofluoric acid waste liquid in the evaporation pot (1). Then, in the subsequent first distillation step and second distillation step, crude hydrofluoric acid and concentrated hydrofluoric acid with very few impurities are distilled to obtain more purified purified hydrofluoric acid.
従って、本発明の回収方法によれば、粗フッ酸蒸発工程で蒸発釜（１）におけるスケーリングを防止でき、且つ、蒸発釜（１）の加熱手段における伝熱効率の低下を防止でき、その結果、不純物の一層少ないフッ酸を精製フッ酸として高い収率で回収することが出来る。そして、従来のフッ酸の製造の様にフッ化水素を製造することなく、粗フッ酸蒸発工程においてフッ酸廃から直接フッ酸を回収し、第１蒸留工程および第２蒸留工程で濃縮、精製するため、設備を簡素化することが出来る。これにより、ガラス基板のエッチング等のフッ酸利用工程においてオンサイトでフッ酸を回収できる。 Therefore, according to the recovery method of the present invention, scaling in the evaporation pot (1) can be prevented in the crude hydrofluoric acid evaporation step, and reduction in heat transfer efficiency in the heating means of the evaporation pot (1) can be prevented. Hydrofluoric acid with less impurities can be recovered in high yield as purified hydrofluoric acid. Then, hydrofluoric acid is recovered directly from the hydrofluoric acid waste in the crude hydrofluoric acid evaporation process without producing hydrogen fluoride as in the conventional hydrofluoric acid production, and concentrated and purified in the first distillation process and the second distillation process. Therefore, the equipment can be simplified. Thereby, hydrofluoric acid can be recovered on-site in a hydrofluoric acid utilization process such as etching of the glass substrate.
本発明の回収方法により、ガラス基板のエッチング工程から排出されたフッ酸廃液からフッ酸を回収した。処理するフッ酸廃液として、濃度が１０重量％、Ｓｉ，Ｂ，Ａｌ，Ｃａ，Ｚｔ等の金属成分濃度が１重量％の廃液を準備した。粗フッ酸蒸発工程においては、蒸発釜（１）にフッ酸廃液を３００ｃｃ／時の流量で供給し、フッ酸廃液を１００Ｔｏｒｒの圧力条件下で７４℃に加熱して粗フッ酸を蒸気として回収し、第１の蒸留塔（２１）に供給した。その際、蒸発釜（１）に９８％硫酸を３ｃｃ／時の流量で添加した。なお、粗フッ酸の製造により、蒸発釜（１）においてフッ酸廃液を濃度３０重量％に濃縮した。 By the recovery method of the present invention, hydrofluoric acid was recovered from the hydrofluoric acid waste liquid discharged from the glass substrate etching step. As the hydrofluoric acid waste liquid to be treated, a waste liquid having a concentration of 10% by weight and a metal component concentration of Si, B, Al, Ca, Zt, etc. of 1% by weight was prepared. In the crude hydrofluoric acid evaporation step, hydrofluoric acid waste liquid is supplied to the evaporation kettle (1) at a flow rate of 300 cc / hour, and the hydrofluoric acid waste liquid is heated to 74 ° C. under a pressure condition of 100 Torr to recover the crude hydrofluoric acid as vapor. And supplied to the first distillation column (21). At that time, 98% sulfuric acid was added to the evaporation kettle (1) at a flow rate of 3 cc / hour. Note that the hydrofluoric acid waste liquid was concentrated to a concentration of 30% by weight in the evaporation kettle (1) by producing crude hydrofluoric acid.
第１蒸留工程においては、第１の蒸留塔（２１）による蒸留により、回収水容器（４１）に２８０ｃｃ／時の流量で回収水を回収し、また、濃縮フッ酸流路（８３）を通じて濃度２５重量％の濃縮フッ酸を１２０ｃｃ／時の流量で回収し、そして、斯かる濃縮フッ酸を第２の蒸留塔（２２）に供給した。第２蒸留工程においては、濃縮フッ酸を第２の蒸留塔（２２）で更に蒸留し、精製フッ酸容器（４２）に１００ｃｃ／時の流量で精製フッ酸を回収した。精製フッ酸容器（４２）に回収された精製フッ酸の濃度は２０重量％であり、塔底液返流流路（９３）から排出された塔底液の濃度は３５重量％であった。 In the first distillation step, the recovered water is recovered at a flow rate of 280 cc / hour in the recovered water container (41) by distillation by the first distillation column (21), and the concentration is passed through the concentrated hydrofluoric acid flow path (83). 25% by weight of concentrated hydrofluoric acid was recovered at a flow rate of 120 cc / hour, and such concentrated hydrofluoric acid was fed to the second distillation column (22). In the second distillation step, the concentrated hydrofluoric acid was further distilled in the second distillation column (22), and the purified hydrofluoric acid was recovered in the purified hydrofluoric acid container (42) at a flow rate of 100 cc / hour. The concentration of the purified hydrofluoric acid recovered in the purified hydrofluoric acid container (42) was 20% by weight, and the concentration of the column bottom liquid discharged from the column bottom liquid return flow path (93) was 35% by weight.
そして、上記の一連の操作を１週間続けた後、蒸発釜（１）、第１の蒸留塔（２１）、第２の蒸留塔（２２）及び配管類を検査したところ、スケーリングの発生は確認されなかった。また、精製フッ酸容器（４２）に回収された精製フッ酸の不純物濃度を測定したところ、金属成分濃度が０．１ｐｐｍ以下であった。 Then, after continuing the above series of operations for one week, when the evaporating pot (1), the first distillation column (21), the second distillation column (22) and the piping were inspected, the occurrence of scaling was confirmed. Was not. Further, when the impurity concentration of the purified hydrofluoric acid collected in the purified hydrofluoric acid container (42) was measured, the metal component concentration was 0.1 ppm or less.
１ ：蒸発釜
１１：ジャケット
１２：チューブ式熱交換器
１３：コイル式熱交換器
１４：水蒸気供給管
１５：水蒸気排出管
２１：第１の蒸留塔
２２：第２の蒸留塔
４１：回収水容器
４２：精製フッ酸容器
５１：リボイラー
５２：リボイラー
６１：冷却凝縮器
６２：冷却凝縮器
７１：原料流路
７２：硫酸供給流路
７３：粗フッ酸流路
７４：廃液抜出し流路
８１：塔底液抜出し流路
８２：循環流路
８３：濃縮フッ酸流路
８４：蒸気流路
８５：凝縮液流路
８６：還流流路
８７：回収水取出流路
８９：排気流路
９１：塔底液抜出し流路
９２：循環流路
９３：塔底液返流流路
９４：蒸気流路
９５：凝縮液流路
９６：還流流路
９７：精製フッ酸取出流路
DESCRIPTION OF SYMBOLS 1: Evaporation pot 11: Jacket 12: Tube type heat exchanger 13: Coil type heat exchanger 14: Steam supply pipe 15: Steam discharge pipe 21: First distillation tower 22: Second distillation tower 41: Recovery water container 42: Purified hydrofluoric acid container 51: Reboiler 52: Reboiler 61: Cooling condenser 62: Cooling condenser 71: Raw material flow path 72: Sulfuric acid supply flow path 73: Crude hydrofluoric acid flow path 74: Waste liquid extraction flow path 81: Tower bottom Liquid extraction flow path 82: Circulation flow path 83: Concentrated hydrofluoric acid flow path 84: Steam flow path 85: Condensate flow path 86: Reflux flow path 87: Recovery water discharge flow path 89: Exhaust flow path 91: Tower bottom liquid extraction Flow path 92: Circulation flow path 93: Tower bottom liquid return flow path 94: Steam flow path 95: Condensate flow path 96: Reflux flow path 97: Purified hydrofluoric acid extraction flow path
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| JP2004260516A JP4635527B2 (en) | 2004-09-08 | 2004-09-08 | Method for recovering hydrofluoric acid |
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| JP2004260516A JP4635527B2 (en) | 2004-09-08 | 2004-09-08 | Method for recovering hydrofluoric acid |
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|---|---|
| JP2006076811A JP2006076811A (en) | 2006-03-23 |
| JP4635527B2 true JP4635527B2 (en) | 2011-02-23 |
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Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5143440B2 (en) * | 2007-02-01 | 2013-02-13 | 森田化学工業株式会社 | Method and apparatus for separating and recovering acid components from waste liquid containing hydrofluoric acid, hydrochloric acid and silicohydrofluoric acid |
| JP5101121B2 (en) * | 2007-02-01 | 2012-12-19 | 森田化学工業株式会社 | Method and apparatus for separating and recovering acid components from waste liquid containing hydrofluoric acid and silicohydrofluoric acid |
| JPWO2009110548A1 (en) * | 2008-03-07 | 2011-07-14 | 三井・デュポンフロロケミカル株式会社 | Electronic component cleaning method and cleaning system |
| WO2009110549A1 (en) * | 2008-03-07 | 2009-09-11 | 三井・デュポンフロロケミカル株式会社 | Method and system for washing electronic component |
| JP2012201554A (en) * | 2011-03-25 | 2012-10-22 | Seiko Epson Corp | Method and apparatus for separation |
| JP2013226480A (en) * | 2012-04-24 | 2013-11-07 | Kimura Chem Plants Co Ltd | Apparatus and method for evaporative concentration of aqueous solution containing acid |
| CN102847480B (en) * | 2012-09-19 | 2014-07-30 | 北京七星华创电子股份有限公司 | Chemical liquid mixing device and method |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS634637B2 (en) * | 1983-01-25 | 1988-01-29 | Outokumpu Oy | |
| JPH03323B2 (en) * | 1984-10-06 | 1991-01-07 | Tokuyama Soda Kk | |
| JP2003146619A (en) * | 2001-11-12 | 2003-05-21 | Air Liquide Japan Ltd | Method for recovering hydrogen fluoride |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS634637B2 (en) * | 1983-01-25 | 1988-01-29 | Outokumpu Oy | |
| JPH03323B2 (en) * | 1984-10-06 | 1991-01-07 | Tokuyama Soda Kk | |
| JP2003146619A (en) * | 2001-11-12 | 2003-05-21 | Air Liquide Japan Ltd | Method for recovering hydrogen fluoride |
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| JP2006076811A (en) | 2006-03-23 |
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