JP2004170197A

JP2004170197A - Method and instrument for measuring bubble diameter in bubble containing liquid

Info

Publication number: JP2004170197A
Application number: JP2002335355A
Authority: JP
Inventors: Kiwamu Matsubara; 極松原
Original assignee: NGK Insulators Ltd
Current assignee: NGK Insulators Ltd
Priority date: 2002-11-19
Filing date: 2002-11-19
Publication date: 2004-06-17
Anticipated expiration: 2022-11-19
Also published as: JP4059756B2

Abstract

<P>PROBLEM TO BE SOLVED: To accurately measure a bubble diameter even in a turbid bubble containing liquid, and to easily measure also a bubble diameter distribution of the bubble containing liquid. <P>SOLUTION: This method/instrument is provided with a suction pipe 1 having a fixed opening cross-section with a tip connected to the bubble containing liquid of the mixed solution, a mixed solution feed pipe 1a connected to the suction pipe 1 and a next measuring tube selection valve V1, the selection valve V1 for selecting a kind in a bubble diameter measuring tube 2, and the plurality of bubble diameter measuring tubes 2a, 2b, 2c of different tube inside diameters connected to the selection valve V1. A suction pump P is arranged in series to suck the mixed solution in order into an equipment to be feed it, and an image photographing device 4 connected to a data processor 5 having an image processing function is provided in the bubble diameter measuring tube 2. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、活性汚泥処理装置のエアレーションタンク混合液など気泡含有液中の気泡径測定方法に関する。
【０００２】
【従来の技術】
エアレーションタンク混合液など気泡含有液中の気泡径を測定する方法として従来は、その気泡含有液中に寸法を示す目盛り板を配置し、その目盛り板の手前を通過する気泡を直接に撮影し、その画像から直径を計測する写真法（非特許文献１を参照）がある。
【０００３】
ところが、この方法は透明度の高い清水中であれば適用可能であるが、活性汚泥など汚物が混入すると測定液が濁るため測定が困難になる欠点があり、また、物差しと比較できる気泡は、物差し近傍の気泡に限定されるためデータ数が不足して、分布を持った気泡径の測定には不適当であった。
【０００４】
【非特許文献１】
書名「環境装置ニュース」、発行：日本碍子株式会社、昭和５６年１２月、第７２頁〜７３頁
【０００５】
【発明が解決しようとする課題】
本発明は、上記の問題点を解決するためになされたものであり、混濁した気泡含有液についても、気泡径を正確に測定でき、含有気泡の気泡径分布も容易に計測できる気泡含有液の気泡径測定方法および装置を提供する。
【０００６】
【課題を解決するための手段】
上記の問題は、気泡含有液を一定開口断面積を有する吸引管を介して、一定速度で吸引して管直径が一定な気泡径測定管に導いた後、該測定管の投影映像を画像処理して該混合液内の気泡の直径を求めることを特徴とする本発明の気泡含有液の気泡径測定方法によって、解決することができる。
【０００７】
また、本発明は、前記吸引管の開口断面積が前記混合液中の最大直径気泡の相当断面積の１５倍以上であり、その混合液の吸引速度が、吸引管開口部分で気泡含有液における液上昇速度とスリップ速度の合計値の２倍以上である形態の前記気泡含有液の気泡径測定方法として具体化できる。
さらに、予め準備した複数個の管内径の異なる気泡径測定管から、前記混合液中の最小気泡の直径に応じて使用する気泡径測定管を選択する形態の前記気泡含有液の気泡径測定方法として、好ましく具体化される。
【０００８】
また、上記の問題は、先端を気泡含有液に混合液に接続した一定開口断面積を有する吸引管と、この吸引管と次の測定管選択弁を接続される混合液送給管、気泡径測定管の種類を選択するための測定管選択弁と、この測定管選択弁に接続された管内径の異なる複数の気泡径測定管とを少なくとも装備し、前記混合液を前記機器内に順次吸引して送給するための吸引ポンプを直列に配置するとともに、前記気泡径測定管には、画像処理機能を有するデータ処理装置に接続された映像撮影装置を装備したことを特徴とする本発明の気泡含有液の気泡径測定装置によって、解決することができる。
【０００９】
【発明の実施の形態】
次に、本発明の気泡含有液の気泡径測定方法およびその装置に係る実施形態について、図１〜５を参照しながら説明する。
先ず、図１のフロー図によって、本発明の気泡含有液の気泡径測定装置について説明すると、先端を気泡含有液である混合液に接続した一定開口断面積を有する吸引管１と、この吸引管１と次の測定管選択弁Ｖ１に接続される混合液送給管１ａと、気泡径測定管２の種類を選択するための測定管選択弁Ｖ１、この測定管選択弁Ｖ１に接続された管内径の異なる複数の気泡径測定管２ａ、２ｂ、２ｃとを装備する。
【００１０】
そしてこれには、前記混合液を前記機器内に順次吸引して送給するための吸引ポンプＰを直列に配置するとともに、前記気泡径測定管２には、画像処理機能を有するデータ処理装置５に接続された映像撮影装置４を装備したことを特徴とする。そして、図１の事例では、前記この単数の複数気泡径測定管２ａ、２ｂ、２ｃの後に気泡径測定管内の圧力を大気圧に開放するための圧力開放弁Ｖ２と、測定終了した混合液から気泡気体を分離するための気液分離装置３とが付設され、その後に吸引ポンプＰを配置している。
【００１１】
次に、この装置の機能を、本発明の気泡含有液の気泡径測定方法とともに、エアレーションタンクの気泡を含む混合液を事例にして説明するが、本発明はこれに限定されないのは言うまでもない。
【００１２】
図１の本発明のフローにおいて、エアレーションタンク（図示せず）の混合液は吸引ポンプＰに吸引されて吸引管１へ吸入される。吸引管１の入口開口部１１は円形をしており、開口断面積は吸引する最大気泡の相当断面積の１５倍以上、また吸引速度は、入口開口部１１において混合液上昇速度とスリップ速度の合計値（理論速度）の２倍以上とする必要である。その理由は、この条件を下回ると、吸引管１内で複数の気泡が合一して個数が減少するとともに求めた気泡の直径が実際より大きくカウントされるためである。
ここで、混合液上昇速度とは、吸引管１の入口開口部１１へ向かう混合液そのものの速度、また、スリップ速度とは、液静止時の気泡上昇速度のことで気泡径によって決まる値を意味し、また理論速度とは、混合液の流れに乗った気泡そのものの速度を意味する用語である。
【００１３】
図２は、吸引速度を理論速度の２倍とし、吸引管の入口開口部１１の断面積（図では最大気泡断面積に対する倍数で表示してある）を変化させたときの吸引管直下に存在した１０個の気泡の挙動を示したものである。開口部断面積が小のときは、１０個の気泡を吸引しきれないばかりか、吸引した気泡も吸引管１内で気泡同士が合併して１個の気泡に変化する（以下、合一という）ことが分る。しかし、開口部断面積が最大気泡断面積の１５倍程度以上からは１０個の気泡は全数吸引でき、気泡の合一現象も見られなくなる。
【００１４】
一方、図３は、入口開口部１１の断面積を気泡断面積の１６倍一定の条件で、図２と同様な要領で入口開口部における吸引速度を変化させたときの気泡の挙動を示したものである。実験した開口部断面積の条件では、吸引速度は理論速度の２倍あれば合一することなく、全量吸引できることがわかった。この吸引管開口部１１の吸引速度と適正開口部断面積は密接な関係があり、吸引速度を大きくとれば開口部断面積も大きくすることができる。
【００１５】
このようにして、吸引管１に吸入された気泡は合一することなく気泡含有混合液とともに、吸引管１と同口径以上の流路１ａを通って測定管選択弁Ｖ１に到達する。ここでは、測定対象気泡の最小値を勘案して使用する気泡径測定管２ａ、２ｂ、２ｃを選定する。この理由は次で述べるように、最小気泡でも気泡径測定管２の内壁に少なくとも接することが必要であるからである。ここで、使用する気泡径測定管２が決まれば、選択弁Ｖ１から当該測定管２に気泡含有混合液は連続的に流入する。
【００１６】
気泡径の測定は、気泡を選択した気泡径測定管２に流入させた時点において内部の流体を停止させ、かつ吸引ポンプＰによる吸引圧力を大気開放してから行う。すなわち、吸引ポンプＰの作動に連動して気泡径測定管〜吸引ポンプの流路を形成していた圧力開放弁Ｖ２によって、吸引ポンプ停止と同時にこの流路を遮断した後、気泡径測定管２を大気圧の流路に解放することで、気泡径測定管内を大気圧下に置く。この場合、圧力開放弁Ｖ２から吸引ポンプＰまでの流路も解放して吸引圧を開放しておくのがよい。
【００１７】
このように気泡径測定管２内が大気圧に開放されたときに、気泡径測定管２の投影画像をデジタルカメラで撮影すると、気泡部分が明るく、液体部分が暗い、図４に示すような画像が得られ、気泡部分が明確に識別できる。この画像は、気泡径ｄＢが気泡径測定管内径φに等しいケース（Ａ）、気泡径ｄＢが気泡径測定管内径φより圧倒的に大きいケース（Ｂ）、その中間のケース（Ｃ）区別される。
【００１８】
このような気泡径測定管２の投影画像の明るい部分である気泡部分の長さ（Ｌａ）を、図５に示す（Ａ）（Ｂ）（この（Ｂ）は、図４の（Ｃ）を含むケースである）について、画像上から計測し、撮影倍率を考慮して実際の気泡長さＬａに補正するという、画像処理を行う。同時に混合液の水温ｔを測定して基礎データとする。
【００１９】
ここで、エアレーションタンク内の気泡の形状を真球と、気泡径測定管内の気泡部分の両端部を半球と仮定すれば、前記で得られた各気泡の気泡長さＬａのデータから次のような計算式（１）（２）（３）によって、単一気泡の体積、単一気泡の直径を求めることができ、さらに、平均気泡直径（式４）、気泡体積基準平均気泡直径（式５）、気泡表面積基準平均気泡直径（式７）などの各基準の平均気泡直径を求めることができる。
【００２０】
（単一気泡の体積計算）
Ｖａ＝４π・（φ／２）^３／３＋ π・（φ／２）^２（Ｌａ−φ）（１）
（但し、Ｌａ≧φ）
Ｖｓ＝Ｖａ・（２７３＋２０）／（２７３＋ｔ）（２）
ここにＶａ：気泡の実体積（ｍｍ^３）
Ｖｓ：２０℃，大気圧下の気泡の体積（ｍｍ^３）
φ：気泡径測定管直径（ｍｍ）
Ｌａ：気泡長さ（測定値）（ｍｍ）
ｔ：混合液水温≒気泡温度（℃）
【００２１】
（単一気泡の直径計算）
ｄＢ＝（６Ｖｓ／π）^１／３（３）
ここにｄＢ：２０℃、大気圧下の各気泡の直径（ｍｍ）
【００２２】
（平均気泡直径）
ｄＢ_ｕ＝（ｄＢ１＋ｄＢ２＋ｄＢ３＋・・・＋ｄＢｎ）／ｎ（４）
ここにｄＢ_ｕ：２０℃、大気圧下の平均気泡直径（ｍｍ）
ｄＢ１〜ｄＢｎ：各単一気泡直径（ｍｍ）
【００２３】
（気泡体積基準平均気泡直径）
Ｖｓ＝（Ｖｓ１＋Ｖｓ２＋Ｖｓ３＋・・・＋Ｖｓｎ）／ｎ（５）
ｄＢ_ｖ＝（６Ｖｓ／π）^１／３（６）
ここにＶｓ：２０℃，大気圧下の単一気泡の平均体積（ｍｍ^３）
Ｖｓ１〜Ｖｓｎ：２０℃，大気圧下の単一気泡の体積（ｍｍ^３）
ｄＢ_ｖ：気泡体積基準平均気泡直径（ｍｍ）
【００２４】
（気泡表面積基準平均気泡直径）
Ａｓ＝（３６π・Ｖｓ^２）^１／３（７）
Ａｓ’ ＝（Ａｓ１＋Ａｓ２＋Ａｓ３＋・・・＋Ａｓｎ）／ｎ（８）
ｄＢ_ａ＝（Ａｓ’／π）^１／２（９）
ここにＡｓ：２０℃，大気圧下の単一気泡の表面積（ｍｍ^２）
Ａｓ’：２０℃，大気圧下の単一気泡の平均表面積（ｍｍ^２）
Ａｓ１〜Ａｓｎ：２０℃，大気圧下の単一気泡の表面積（ｍｍ^２）
ｄＢ_ａ：気泡表面積基準平均気泡直径（ｍｍ）
【００２５】
本発明では、このように、画像上で気泡長さを計測するという画像解析によって、各基準平均気泡直径を算出する操作をデータ処理装置５で行うのである。
この場合、気泡径測定管２の管内径は、通常の水処理プラントの散気装置であれば、内径でφ＝０．５ｍｍ、１．０ｍｍ、１．５ｍｍ、２．０ｍｍの４種程度を用意すれば十分であることが経験的に知られている。
【００２６】
また、気泡径測定管２の測定部分の長さは測定すべき気泡の個数，気泡存在密度などにより異なるが、０．５〜１．０ｍ程度で十分である。なお、測定すべき気泡の個数は多いほど測定精度は向上するが、通常、１００個／１試料当たり、程度あればよく、この程度の採取個数であれば、測定部分の長さが前記程度であれば、１試料あたり５回程度の繰り返し測定で済む。さらに、この測定部分の材質は、シリコンチューブ，タイゴンチューブ等の市販のものを用いてもよいが、望ましくは、ガラス管がよい。これは、他の材質に比べて汚れが付着しにくく、また、汚れても洗浄しやすいためである。
【００２７】
以上説明したように、気泡径測定管内の気泡長さを測定しつつ、測定すべき気泡の個数に達するまで混合液採取、画像撮影、気泡長さ測定を繰り返し、設定した気泡個数に達したら、（１）式〜（９）式に従って各基準の平均気泡直径を算出する。
【００２８】
この場合、データ処理装置５に計算ソフトを付加して、平均気泡直径以外にも気泡直径の標準偏差も計算でき、また、気泡径測定管２の測定部分の体積と存在気泡の関係から、エアレーションタンク内の気泡存在密度（ｖ／ｖ％）、気泡表面積密度（ｍ^２／ｍ^３混合液）など、酸素移動効率を理論的にもとめる諸データも得ることができる。
【００２９】
【実施例】
本発明を体積１Ｌのエアレーションタンク実験槽に適用した結果を次の表１に示す。散気装置はウレタン性メンブレンディフューザー、測定時の通気率は１３．９ｓＬ^ａｉｒ／Ｌ．Ｈｒ、水温は２３．２℃である。
【００３０】
【表１】

【００３１】
【発明の効果】
本発明の気泡含有液の気泡径測定方法および装置は、以上説明したように構成されているので、次のような優れた効果が得られる。よって本発明は、従来の問題点を解消したものとして、技術的、実用的価値はきわめて大なるものがある。▲１▼気泡採取個数が任意に設定できるとともに、多数の気泡採取が可能なことから測定精度が従来に比べて格段によい。
▲２▼測定が自動化できるので、測定作業の負荷が軽減できる。
▲３▼データ処理装置への計算ソフトの追加により、エアレーションタンクの酸素移動効率を理論的に求められる諸データを採取できる。
▲４▼従来のエアレーションタンク内の写真法とは異なり、活性汚泥などを含む混濁液の場合でも測定可能である。
【図面の簡単な説明】
【図１】本発明の装置を示す要部フロー図。
【図２】吸引管の開口部大きさを変化させ、吸引管直下から吸引した１０個の気泡の挙動を示したグラフ。
【図３】吸引管の吸引速度を変化させ、吸引管直下から吸引した１０個の気泡の挙動を示したグラフ。
【図４】測定管内の気泡の代表的状態を示すグラフ。
【図５】気泡画像における気泡の長さを示すグラフ。
【符号の説明】
１吸引管、１ａ混合液送給管、２、２ａ、２ｂ、２ｃ気泡径測定管、３気液分離装置、４映像撮影装置、５データ処理装置、Ｖ１測定管選択弁、Ｖ２圧力開放弁、Ｐ吸引ポンプ。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for measuring a bubble diameter in a bubble-containing liquid such as an aeration tank mixed liquid of an activated sludge treatment apparatus.
[0002]
[Prior art]
Conventionally, as a method for measuring the bubble diameter in a bubble-containing liquid such as an aeration tank mixed liquid, a scale plate showing dimensions is arranged in the bubble-containing liquid, and the bubbles passing in front of the scale plate are directly photographed, There is a photographic method for measuring the diameter from the image (see Non-Patent Document 1).
[0003]
However, this method can be applied to fresh water with high transparency. Since the number of data is insufficient because it is limited to nearby bubbles, it is not suitable for measurement of a bubble diameter having a distribution.
[0004]
[Non-Patent Document 1]
Book title "Environmental Equipment News", published by Nippon Isogo Co., Ltd., December 1981, pages 72-73
[Problems to be solved by the invention]
The present invention has been made in order to solve the above-described problems. For a turbid bubble-containing liquid, the bubble diameter can be accurately measured, and the bubble diameter distribution of the included bubbles can be easily measured. A bubble diameter measuring method and apparatus are provided.
[0006]
[Means for Solving the Problems]
The above problem is that the bubble-containing liquid is sucked at a constant speed through a suction tube having a constant opening cross-sectional area and guided to a bubble diameter measurement tube having a constant tube diameter, and then the projection image of the measurement tube is subjected to image processing. This can be solved by the method for measuring the bubble diameter of the bubble-containing liquid of the present invention, wherein the diameter of the bubbles in the mixed solution is obtained.
[0007]
Further, according to the present invention, the opening cross-sectional area of the suction pipe is 15 times or more the equivalent cross-sectional area of the maximum diameter bubble in the liquid mixture, and the suction speed of the liquid mixture is in the bubble-containing liquid at the opening of the suction pipe. It can be embodied as a method for measuring the bubble diameter of the bubble-containing liquid in a form that is twice or more the total value of the liquid rising speed and the slip speed.
Further, the method for measuring the bubble diameter of the bubble-containing liquid in a form of selecting a bubble diameter measurement tube to be used according to the diameter of the smallest bubble in the mixed liquid from a plurality of bubble diameter measurement tubes having different tube inner diameters prepared in advance. It is preferably embodied as
[0008]
In addition, the above problem is that a suction pipe having a constant opening cross-sectional area connected to a liquid mixture containing bubbles at the tip, a liquid feed pipe connecting the suction pipe and the next measurement pipe selection valve, a bubble diameter Equipped with at least a measurement tube selection valve for selecting the type of measurement tube and a plurality of bubble diameter measurement tubes with different tube inner diameters connected to the measurement tube selection valve, and sequentially sucking the mixed solution into the device In addition, the suction pumps for feeding the liquids are arranged in series, and the bubble diameter measuring tube is equipped with a video photographing device connected to a data processing device having an image processing function. This can be solved by a bubble diameter measuring device for the bubble-containing liquid.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment according to a method for measuring a bubble diameter of a bubble-containing liquid and an apparatus therefor according to the present invention will be described with reference to FIGS.
First, the bubble diameter measurement apparatus for a bubble-containing liquid of the present invention will be described with reference to the flow chart of FIG. 1. A suction tube 1 having a constant opening cross-sectional area whose tip is connected to a mixed liquid that is a bubble-containing liquid, and the suction tube 1 and a mixed liquid feed pipe 1a connected to the next measurement pipe selection valve V1, a measurement pipe selection valve V1 for selecting the type of the bubble diameter measurement pipe 2, and a pipe connected to the measurement pipe selection valve V1 A plurality of bubble

diameter measuring tubes

2a, 2b and 2c having different inner diameters are provided.
[0010]
For this purpose, a suction pump P for sequentially sucking and feeding the mixed solution into the device is arranged in series, and the bubble diameter measuring tube 2 has a data processing device 5 having an image processing function. It is characterized in that it is equipped with a video photographing device 4 connected to. In the case of FIG. 1, the pressure release valve V2 for releasing the pressure in the bubble diameter measuring tube to the atmospheric pressure after the single plural bubble

diameter measuring tubes

2a, 2b, 2c, and the mixed liquid after the measurement. A gas-liquid separator 3 for separating the bubble gas is attached, and a suction pump P is disposed thereafter.
[0011]
Next, the function of this apparatus will be described using the mixed liquid containing bubbles in the aeration tank as an example together with the method for measuring the bubble diameter of the bubble-containing liquid of the present invention. Needless to say, the present invention is not limited to this.
[0012]
In the flow of the present invention shown in FIG. 1, the liquid mixture in the aeration tank (not shown) is sucked into the suction pump P and sucked into the suction pipe 1. The inlet opening 11 of the suction tube 1 has a circular shape, and the opening cross-sectional area is 15 times or more the equivalent cross-sectional area of the largest bubble to be sucked. The total value (theoretical speed) needs to be twice or more. The reason for this is that, if the condition is below, the plurality of bubbles are united in the suction tube 1 to decrease the number of bubbles and the calculated bubble diameter is counted larger than the actual one.
Here, the liquid mixture rising speed means the speed of the liquid mixture itself toward the inlet opening 11 of the suction tube 1, and the slip speed means the bubble rising speed when the liquid is stationary and means a value determined by the bubble diameter. In addition, the theoretical velocity is a term that means the velocity of the bubble itself that is on the flow of the mixed liquid.
[0013]
FIG. 2 shows the state immediately below the suction pipe when the suction speed is twice the theoretical speed and the cross-sectional area of the inlet opening 11 of the suction pipe (indicated by a multiple of the maximum bubble cross-sectional area in the figure) is changed. This shows the behavior of the 10 bubbles. When the cross-sectional area of the opening is small, not only the 10 bubbles can be sucked, but also the sucked bubbles are merged in the suction tube 1 to be changed into one bubble (hereinafter referred to as unity). ) However, if the opening cross-sectional area is about 15 times or more the maximum bubble cross-sectional area, all 10 bubbles can be sucked, and the bubble coalescence phenomenon cannot be seen.
[0014]
On the other hand, FIG. 3 shows the behavior of bubbles when the suction speed at the inlet opening is changed in the same manner as in FIG. 2 under the condition that the cross-sectional area of the inlet opening 11 is constant 16 times the bubble cross-sectional area. Is. Under the condition of the experimental cross-sectional area of the opening, it was found that if the suction speed is twice the theoretical speed, the whole volume can be sucked without being united. There is a close relationship between the suction speed of the suction tube opening 11 and the appropriate opening cross-sectional area. If the suction speed is increased, the opening cross-sectional area can be increased.
[0015]
In this way, the bubbles sucked into the suction tube 1 do not coalesce with the bubble-containing mixed solution, and reach the measurement tube selection valve V1 through the flow path 1a having the same diameter or more as the suction tube 1. Here, the bubble

diameter measuring tubes

2a, 2b, and 2c to be used are selected in consideration of the minimum value of the bubbles to be measured. The reason for this is that, as will be described below, even the smallest bubbles need to contact at least the inner wall of the bubble diameter measuring tube 2. Here, if the bubble diameter measuring tube 2 to be used is determined, the bubble-containing mixed solution continuously flows into the measuring tube 2 from the selection valve V1.
[0016]
The bubble diameter is measured after the internal fluid is stopped and the suction pressure by the suction pump P is released to the atmosphere when the bubbles flow into the selected bubble diameter measuring tube 2. That is, after the suction pump is shut off at the same time as the suction pump is stopped by the pressure release valve V2 that forms the flow path of the bubble diameter measuring pipe to the suction pump in conjunction with the operation of the suction pump P, the bubble diameter measuring pipe 2 Is released to the atmospheric pressure flow path to place the bubble diameter measuring tube under atmospheric pressure. In this case, it is preferable to release the suction pressure by releasing the flow path from the pressure release valve V2 to the suction pump P.
[0017]
When the bubble diameter measuring tube 2 is opened to the atmospheric pressure in this way and the projection image of the bubble diameter measuring tube 2 is taken with a digital camera, the bubble portion is bright and the liquid portion is dark, as shown in FIG. An image is obtained, and the bubble portion can be clearly identified. This image is distinguished from the case (A) where the bubble diameter dB is equal to the bubble diameter measuring tube inner diameter φ, the case (B) where the bubble diameter dB is overwhelmingly larger than the bubble diameter measuring tube inner diameter φ, and the middle case (C). The
[0018]
The length (La) of the bubble portion which is a bright portion of the projection image of the bubble diameter measuring tube 2 is shown in FIG. 5 (A) and (B) (this (B) is the same as (C) of FIG. In this case, image processing is performed such that measurement is performed from the top of the image and the actual bubble length La is corrected in consideration of the photographing magnification. At the same time, the water temperature t of the mixed solution is measured and used as basic data.
[0019]
Here, assuming that the shape of the bubbles in the aeration tank is a true sphere and the both ends of the bubble portion in the bubble diameter measuring tube are hemispheres, the following is obtained from the data on the bubble length La of each bubble obtained above. From the calculation formulas (1), (2), and (3), the volume of a single bubble and the diameter of a single bubble can be obtained. Furthermore, the average bubble diameter (Formula 4), the bubble volume reference average bubble diameter (Formula 5) ), The average bubble diameter of each reference such as the bubble surface area reference average bubble diameter (formula 7).
[0020]
(Single bubble volume calculation)
^{Va = 4π · (φ / 2} ) 3/3 + π · (φ / 2) 2 (La-φ) (1)
(However, La ≧ φ)
Vs = Va · (273 + 20) / (273 + t) (2)
Here, Va: actual volume of bubbles (mm ³ )
Vs: Volume of bubbles under atmospheric pressure at 20 ° C. (mm ³ )
φ: Bubble diameter measurement tube diameter (mm)
La: Bubble length (measured value) (mm)
t: Water temperature of mixed liquid ≒ bubble temperature (° C)
[0021]
(Single bubble diameter calculation)
dB = (6Vs / π) ^1/3 (3)
Where dB: diameter of each bubble at 20 ° C. and atmospheric pressure (mm)
[0022]
(Average bubble diameter)
dB _u = (dB1 + dB2 + dB3 +... + dBn) / n (4)
Where dB _u : average bubble diameter (mm) at 20 ° C. and atmospheric pressure
dB1 to dBn: Diameter of each single bubble (mm)
[0023]
(Bubble volume standard average bubble diameter)
Vs = (Vs1 + Vs2 + Vs3 +... + Vsn) / n (5)
dB _v = (6Vs / π) ^1/3 (6)
Here, Vs: 20 ° C., average volume of single bubbles under atmospheric pressure (mm ³ )
Vs1 to Vsn: Volume of single bubbles at 20 ° C. and atmospheric pressure (mm ³ )
dB _v : Bubble volume-based average bubble diameter (mm)
[0024]
(Bubble surface area standard mean bubble diameter)
As = (36π · Vs ² ) ^1/3 (7)
As ′ = (As1 + As2 + As3 +... + Asn) / n (8)
dB _a = (As ′ / π) ^1/2 (9)
Where As: 20 ° C., single bubble surface area under atmospheric pressure (mm ² )
As ′: average surface area of single bubbles at 20 ° C. and atmospheric pressure (mm ² )
As1 to Asn: 20 ° C., single bubble surface area under atmospheric pressure (mm ² )
dB _a : Bubble surface area standard average bubble diameter (mm)
[0025]
In the present invention, the operation for calculating each reference average bubble diameter is thus performed by the data processing device 5 by image analysis of measuring the bubble length on the image.
In this case, the inner diameter of the bubble diameter measuring tube 2 is about four types of inner diameters of φ = 0.5 mm, 1.0 mm, 1.5 mm, and 2.0 mm in the case of a diffuser of a normal water treatment plant. It is empirically known that preparation is sufficient.
[0026]
The length of the measurement part of the bubble diameter measuring tube 2 varies depending on the number of bubbles to be measured, the bubble existence density, etc., but about 0.5 to 1.0 m is sufficient. Although the measurement accuracy improves as the number of bubbles to be measured increases, it is generally sufficient that the number per 100 samples / sample. If there is, it is sufficient to repeat measurement about 5 times per sample. Further, as a material of the measurement part, a commercially available material such as a silicon tube or a Tygon tube may be used, but a glass tube is preferable. This is because dirt is less likely to adhere compared to other materials, and it is easy to clean even if it is dirty.
[0027]
As described above, while measuring the bubble length in the bubble diameter measurement tube, repeated sampling of the liquid mixture, imaging, and bubble length measurement until the number of bubbles to be measured is reached. The average bubble diameter of each reference is calculated according to equations (1) to (9).
[0028]
In this case, calculation software can be added to the data processing device 5 to calculate the standard deviation of the bubble diameter in addition to the average bubble diameter, and from the relationship between the volume of the measurement part of the bubble diameter measuring tube 2 and the existing bubbles, aeration Various data that theoretically determine the oxygen transfer efficiency, such as the bubble density in the tank (v / v%) and the bubble surface area density (m ² / m ³ mixture), can also be obtained.
[0029]
【Example】
The results of applying the present invention to a 1 L volume aeration tank test tank are shown in Table 1 below. The diffuser is a urethane membrane diffuser, and the air permeability during measurement is 13.9 sL ^air / L. Hr, water temperature is 23.2 ° C.
[0030]
[Table 1]

[0031]
【The invention's effect】
Since the method and apparatus for measuring the bubble diameter of the bubble-containing liquid of the present invention are configured as described above, the following excellent effects can be obtained. Therefore, the present invention has an extremely great technical and practical value as a solution to the conventional problems. (1) The number of bubbles to be collected can be set arbitrarily, and a large number of bubbles can be collected, so the measurement accuracy is much better than before.
(2) Since measurement can be automated, the load of measurement work can be reduced.
(3) By adding calculation software to the data processing device, it is possible to collect various data that can theoretically determine the oxygen transfer efficiency of the aeration tank.
(4) Unlike the conventional photographic method in an aeration tank, it can be measured even in the case of a turbid liquid containing activated sludge.
[Brief description of the drawings]
FIG. 1 is a main part flow diagram showing an apparatus of the present invention.
FIG. 2 is a graph showing the behavior of ten bubbles sucked from directly under the suction pipe while changing the opening size of the suction pipe.
FIG. 3 is a graph showing the behavior of ten bubbles sucked from directly under the suction pipe while changing the suction speed of the suction pipe.
FIG. 4 is a graph showing a typical state of bubbles in a measurement tube.
FIG. 5 is a graph showing the length of bubbles in a bubble image.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Suction pipe, 1a Mixed liquid supply pipe, 2, 2a, 2b, 2c Bubble diameter measuring pipe, 3 Gas-liquid separation apparatus, 4 Video imaging apparatus, 5 Data processing apparatus, V1 Measuring pipe selection valve, V2 Pressure release valve, P Suction pump.

Claims

The bubble-containing liquid is sucked at a constant speed through a suction tube having a constant opening cross-sectional area and led to a bubble diameter measurement tube having a constant tube diameter, and then the projection image of the measurement tube is subjected to image processing and the mixed solution A method for measuring a bubble diameter of a bubble-containing liquid, characterized in that a diameter of a bubble in the inside is obtained.

The opening cross-sectional area of the suction tube is 15 times or more the equivalent cross-sectional area of the maximum diameter bubble in the mixed liquid, and the suction speed of the mixed liquid is the liquid rising speed and slip speed in the bubble-containing liquid at the suction pipe opening portion. The method for measuring a bubble diameter of a bubble-containing liquid according to claim 1, wherein the bubble diameter is 2 times or more of the total value.

The bubble of the bubble-containing liquid according to claim 1 or 2, wherein a bubble diameter measuring tube to be used is selected according to the diameter of the smallest bubble in the mixed liquid from a plurality of bubble diameter measuring tubes having different tube diameters prepared in advance. Diameter measurement method.

Select the type of the suction tube having a constant opening cross-sectional area with the tip connected to the liquid mixture containing air bubbles, the liquid feed pipe connected to this suction tube and the next measurement tube selection valve, and the bubble diameter measurement tube And a plurality of bubble diameter measuring pipes having different pipe inner diameters connected to the measuring pipe selecting valve, and for sequentially sucking and feeding the mixed liquid into the device. A bubble diameter measuring device for a bubble-containing liquid, wherein a suction pump is arranged in series, and the bubble diameter measuring tube is equipped with a video photographing device connected to a data processing device having an image processing function.