JP2004025036A

JP2004025036A - System and method for controlling concentration of water treating chemicals

Info

Publication number: JP2004025036A
Application number: JP2002185079A
Authority: JP
Inventors: Makoto Ideguchi; 井手口　誠; Akihiro Takekuni; 竹國　彰浩; Kazuo Marukame; 丸亀　和雄
Original assignee: Katayama Chemical Inc
Current assignee: Katayama Chemical Inc
Priority date: 2002-06-25
Filing date: 2002-06-25
Publication date: 2004-01-29
Anticipated expiration: 2022-06-25
Also published as: JP4788988B2

Abstract

<P>PROBLEM TO BE SOLVED: To precisely control concentration of water treating chemicals in cooling water regardless of variation of amount of blown water and of diversion of the cooling water to other facilities, thereby economically and efficiently operating cooling equipment. <P>SOLUTION: While replenishing minimum requirement of the water treating chemicals lost from a cooling water system (primary replenishment), concentration of the chemicals in the cooling water is measured and ullage of the chemicals is replenished based on measurement result (secondary replenishment). <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術の分野】
この発明は、冷却水から失われた水処理薬剤の最低必要量を補給（一次補給）すると共に、冷却水中の薬剤濃度を測定し、測定結果に基づいて不足分の薬剤を補給（二次補給）することからなる、冷却水中の薬剤濃度管理方法およびその方法を実施するための薬剤濃度管理システムに関するものである。
【０００２】
【従来の技術】
製鉄、石油化学などの工場では、プロセス冷却用やユーティリティ保全用に、また学校、病院、ホテルなどのビルでは空調用に大量の冷却水が使用されている。開放循環式冷却水系では、冷却塔を設け、水を循環させて再利用し、さらに節水のため可能な範囲で高濃度運転を行い、水の有効利用を図っている。また、密閉循環式冷却水系では、熱交換により温度が上昇した水は、二次冷却水で再冷却され循環使用されるため、通常、系外に排出される量が少なく、蒸発などによる濃縮も起こらない。
【０００３】
これらの冷却水系では、水に起因する腐食、スケール、スライムおよび藻類等の様々な障害が日常的に発生している。ことに、冷却水中の溶存塩類の濃縮に基づく水質の悪化により、これらの障害の発生頻度は高くなり、機器の耐用年数の短縮、機器・配管の閉塞・破損や熱効率の低下など、資源やエネルギーの損失、メンテナンス費用の増大、工場の生産効率の低下や生産停止などの問題を引き起こすことが知られている。
【０００４】
従来、これらの障害を防止するために、水処理薬剤を冷却水に添加することが行われている。
例えば、腐食を防止するためには、モリブデン酸塩、亜硝酸塩、燐酸塩、重合燐酸塩、アゾール類、各種ホスホン酸類等が使用され、スケールを防止するためには、ポリリン酸塩、アクリル酸系重合体、各種ホスホン酸類が使用され、またスライムや藻類を防止するためには、次亜塩素酸塩、ヒダントイン、ブロモニトロアルコール類等が使用されている。
【０００５】
開放循環式冷却水系では、大幅にブロー水量を低減させて補給水量を減らすと、水の使用量だけでなく、水処理薬剤の使用量も節減でき、経済的に好ましい反面、上記のように冷却水中の溶存塩類の濃度が上昇して循環水の水質悪化を招き、種々の障害を生じやすくなる。
【０００６】
溶存塩類の高濃縮化による補給水量の節減効果は、濃縮倍数５倍程度までであり、それ以上に濃縮倍数を上げてもそれに見合った補給水量の低減効果は得られない。その上、添加した水処理薬剤の効力の持続性にも限度があるため、３〜５倍程度の濃縮となるようにブロー水量を調節しながら運転するのが普通である。
【０００７】
つまり、一定量のブロー水を連続して排出したり、水中の塩類濃度や電気伝導率を測定して溶存塩類の濃縮度合いを計測し、その結果に基づいて間欠的にブロー水を排出したりして、溶存塩類の濃縮倍率がほぼ一定となるように、ブロー水量が調節されている。このように、濃縮倍率を調節するためのブロー水を強制ブロー水という。
【０００８】
なお、冷却水系の運転開始後、一定期間を経過したときの濃縮倍数（Ｎ_ｔ）は、次式により算出できる。
Ｎ_ｔ＝Ｍ／（Ｂ＋Ｗ）−｛Ｍ−（Ｂ＋Ｗ）Ｎ_０｝／（Ｂ＋Ｗ）ｅｘｐ（−ｔ／Ｔ_ｒ）
（式中、Ｍは補給水量、Ｂは強制ブロー水量、Ｗは飛散水量、Ｎ_０は運転開始時の循環水の濃縮倍数（通常は１）、ｔは運転開始後の経過時間（ｈｒ）、Ｔ_ｒは滞留時間、なお、Ｍは蒸発水量、ＢおよびＷの合計量である。）
これらの式で、蒸発量と飛散水量は冷却水系の運転条件が一定ならば系固有の値であるため、強制ブロー水量を調整することによって冷却水系の濃縮管理を行なうことができる。
【０００９】
そして、強制ブロー水と共に排出された水処理薬剤の不足分を補給するため、種々の方法が採用されている。
すなわち、連続ブローの場合には上記式により求められる強制ブロー水量に対応して一定量の薬剤をポンプで連続補給する方法、間欠ブローの場合にはブローポンプに連動して薬剤を補給する方法、連続または間欠ブローを冷却水貯水槽の水位変化により感知する場合には補給水ポンプに連動して薬剤を補給する方法、冷却水中の水処理薬剤の濃度を分析測定し、その結果に基づいて薬剤添加量を調節する方法などが採用されている。
【００１０】
【発明が解決しようとする課題】
上記の方法のうち、薬剤の連続添加やブローポンプに連動して薬剤を補給する方法を採用した場合、水処理薬剤は強制ブロー水や冷却設備からの飛散水のみでなく、冷却水を他の施設へ転用する場合、洗浄水として使用する場合等予期できない冷却水の流失（これらを併せて、転用水という）によっても失われることがあるので、失われた水処理薬剤の量を正確に把握することは困難であった。
【００１１】
また、補給水ポンプに連動して薬剤を補給する方法を採用した場合には、水位変化を感知するまでにタイムラグがあり、適時に薬剤の補給ができないとともに、補給水は薬剤の損失を伴わない蒸発により失われる多量の水を補給するため、薬剤濃度が必要以上に高い水準に維持されることとなり、経済的な面で不利であるとともに、補給水量を的確に把握し、その量に対応した薬剤量を補給するためには、工事や諸設備の設置が必要となり、経済的に高価な投資となるので好ましくない。
【００１２】
さらに、冷却水中の水処理薬剤の濃度を測定し、その結果に基づいて薬剤添加量を調節する方法の場合には、薬剤濃度の測定に計測機器や器具を必要とするため、試料水を一旦分析室まで持ち帰らなければならず、冷却水中の薬剤濃度を適時に調節することができなかった。そのため、冷却水中の薬剤濃度がばらついて、薬剤の効果が期待するように発揮されなかったり、薬剤濃度が必要以上に高く維持されたりする問題があった。
【００１３】
一方、密閉循環式冷却水系では蒸発などによる濃縮が起こらず、しかも冷却塔を有しないために強制ブロー水や飛散水による薬剤の流出もない。しかし、転用水による薬剤の流出が頻繁に起こる場合がある。この場合、転用水の流出によって失われた薬剤量を、１日あたりの補給水量（＝転用水量）の平均値に対応した薬剤量（１日あたりの補給水量×薬剤維持濃度）に換算して冷却水系に連続して定量添加されている。しかし、突発的な転用水の流出があると一時的に薬剤濃度が低下して、所望の効果が発揮されない場合があった。そこで、定期的（一週間に一度程度）に冷却水中の薬剤濃度を持ち帰り分析を行うが、冷却水中の薬剤濃度を適時に調節することができなかった。例えば、補給水量を的確に把握し、その量に対応した薬剤量を補給することで上記問題は解決するのであるが、工事や諸設備の設置等が必要となり、経済的に高価な投資となるので好ましくない。
【００１４】
そこで、本出願人は、有機燐酸系化合物や無機燐酸系化合物の濃度を連続的かつ自動的に測定できる方法やそのための装置（特許第３１９９４６９号）、長期間安定な定量試薬（特許第２００５０３７号）を提案してきた。
【００１５】
これらの水処理薬剤の連続的測定装置による方法や、安定な定量試薬を用いた簡易測定法を採用すれば、試料水を分析室に持ち帰らなくても、現場で薬剤濃度を簡便に測定することができるため、その測定結果に基づいて薬剤注入量を比較的短時間で制御することができ、したがって有効量の薬剤濃度を維持できるという効果を期待できる。
【００１６】
しかしながら、上記連続的測定装置による方法や、安定な定量試薬を用いた簡易測定方法は、薬剤濃度を吸光度で測定するため、その発色に一定の時間を要するため、本発明の二次補給に相当するこれらの方法だけでは、冷却水中の薬剤濃度を的確に管理することはできなかった。
また、強制ブロー水や転用水の流出が突発的に起こると、短時間に失われる薬剤量が大きく変動するため、必要な薬剤量を適時に補給することは困難であった。
【００１７】
この発明は、このような技術的背景のもとになされたものであり、強制ブロー水量や転用水量の突発的な変動にもかかわらず、短時間のうちに冷却水中の水処理薬剤の濃度を所定の値に的確に調節できる、より経済的な水処理薬剤の濃度管理方法および濃度管理システムを提供することを目的とする。
【００１８】
【課題を解決するための手段】
本発明者は鋭意研究の結果、冷却水系から失われた水処理薬剤の最低必要量を補給（一次補給）する共に、冷却水中の薬剤濃度を測定し、測定結果に基づいて不足分の薬剤を補給（二次補給）することにより、強制ブロー水量や転用水量の突発的な変動にもかかわらず、冷却水中の薬剤濃度をほぼ一定の値に適時に調節できることを見出し、この発明を完成した。
【００１９】
【発明の実施の形態】
図１は、本発明の水処理薬剤の濃度管理システムが適用される工業用冷却装置の一例を示すブロック図であり、この図に基づいて本発明を具体的に説明する。
上記の工業用冷却装置は、開放循環式冷却設備３１、薬剤濃度監視部３２および制御部３３からなっている。
そして、冷却設備３１は、冷却水貯水槽１、冷却水送水ポンプ２、冷却水送水管３、熱交換器４、冷却塔５、薬剤貯留槽６、冷却水排出（ブロー）管７、冷却水補給管８、薬剤補給管９および１０、ブロー水流量調節部１１、補給水量調節部１２、ならびに薬剤注入ポンプ１３および１４からなっている。
この冷却設備３１において、冷却水は冷却水貯水槽１から冷却水送水ポンプ２により冷却水送水管３を通って、熱交換器４、冷却塔５、そして貯水槽１へ循環している。
【００２０】
なお、この例では、冷却水の濃縮倍数は一般的な電気伝導率計（図示略）による公知の水質管理方法が採用されており、強制ブロー水量は管の途中に設けられた流量計（図示略）により把握できるようになされており、飛散水量および蒸発水量は冷却塔の規模や様式に対応して計算により求められる。
そして、上記のブロー水量、飛散水量および蒸発水量に見合った補給水が冷却水補給管８から補給される。なお、この補給水量は、冷却水貯水槽１に設けられた水位計（図示略）により行なってもよい。
また、上記の例では、強制ブロー水および飛散水とともに失われた薬剤の最低必要量に見合った薬剤が薬剤注入ポンプ１３から補給（一次補給）されるようになされている。
【００２１】
上記のように強制ブロー水量が流量計により把握される場合には、このブローにより失われた薬剤量と、冷却塔の規模や様式に対応して計算により求められる飛散水の最低量により失われた薬剤量との合計が、一次補給されるべき最低必要量となる。
なお、強制ブロー水量が流量計により把握されない場合には、計算上把握される強制ブロー水量の最低量により失われた薬剤量と、冷却塔の規模や様式に対応して計算により求められる飛散水の最低量により失われた薬剤量との合計が、一次補給されるべき最低必要量となる。
【００２２】
転用水は、一般に冷却水送水ポンプの枝管や冷却送水管などから排出されるため、その量を把握するのは困難であり、その量を把握するための流量計等の設置は、工事や諸設備の設置等が必要となり、このような経済的に高価な投資を負担することは通常できない。しかし、転用水の一部が強制ブロー配管等から排出されその流量が把握できる場合には、その転用水量に見合った薬剤量を一次補給すべき最低量に加えてもよい。
【００２３】
ここで、飛散水量は冷却塔の設計により異なり、計算により算出されるが、一般的に強制通風型の冷却塔の飛散水量は、循環水量の０．０５％〜０．２％と言われている。したがって、飛散水により失われた薬剤の最低量は［循環水量×０．０００５×冷却水中の薬剤の標準濃度］により求められる。
【００２４】
密閉循環方式において、転用水の流出によって失われた薬剤の最低必要量の補給（一次補給）は、１日あたりの補給水量（＝転用水量）の最小値に対応した薬剤量（１日あたりの補給水量×薬剤維持濃度）を換算して冷却水系に連続して定量添加されるのが経済的な点から好ましい。
【００２５】
薬剤濃度監視部３２は、薬剤濃度測定部２１、演算部２２、記録部２３および指令部２４からなっている。
薬剤濃度を測定すべき冷却水は、送水管３の途中で採取され、薬剤濃度測定部２１へ随時送られ、冷却水中の薬剤濃度が測定される。この測定頻度は、特に限定されないが、例えば発色に要する時間を考慮して、通常１５分〜１２０分ごと、好ましくは３０分〜６０分ごとに測定すれば、本発明の効果を得るのに十分である。
【００２６】
記録部２３には、予め設定された冷却水中の標準的な薬剤維持濃度（Ｃｓ）が入力されている。
上記の薬剤濃度測定部２１で得られた薬剤濃度の測定値（Ｃｍ）は、電気信号として演算部２２へ送られる。
【００２７】
演算部２２では、薬剤濃度の測定値（Ｃｍ）と、予め設定されて記録部２３に入力されている標準的な薬剤維持濃度（Ｃｓ）とが比較され、測定値（Ｃｍ）が標準的な薬剤維持濃度（Ｃｓ）を下回るときは、添加すべき薬剤の量が演算部２２で計算され、指令部２３から制御部３３へ信号が出力され、制御信号が制御部３３から薬剤注入ポンプ１４へ出力されて、指示量の薬剤が薬剤貯留槽５から冷却水貯水槽１へ補給（二次補給）される。なお、上記の例では薬剤の補給用に薬剤注入ポンプを二つ（１３および１４）備えているが、これらの薬剤注入ポンプを一つの注入ポンプで兼用することもできる。
上記の流れを示したのが図２のフローチャートである。
【００２８】
上記、標準的な薬剤維持濃度（Ｃｓ）には幅を持たせてもよく、その上限値と下限値の範囲内で薬剤注入ポンプの注入量を制御してもよい。
そして、例えば、測定値（Ｃｍ）が予め設定した薬剤維持濃度（Ｃｓ）の上限値より高い場合には、次の測定結果が出るまで薬剤注入ポンプを停止させ、測定値（Ｃｍ）が薬剤維持濃度（Ｃｓ）の下限値未満の場合には、次の測定結果が出るまで薬剤注入ポンプを運転させるようにしてもよい。この場合の薬剤注入速度は、薬剤の不足量と薬剤濃度の測定間隔とに基づいて計算により求められるが、便宜的に数段階の薬剤注入速度を設定しておき、薬剤の不足量と薬剤濃度の測定間隔を考慮して、数段階の薬剤注入速度のうちで最適の注入速度を選定するようにしてもよい。
【００２９】
また、測定値（Ｃｍ）が薬剤維持濃度範囲（Ｃｓ）の上限値と下限値の間にある場合には、上限値と下限値の差に対する上限値と測定値の差の割合に測定間隔（時間）を乗じた時間だけ薬剤注入ポンプを運転するようにしてもよい。
【００３０】
次に、本発明における水処理薬剤の一例およびそれらの測定方法について説明する。
水処理薬剤としては、公知の腐食防止剤、スケール防止剤、スライム防止剤などが挙げられ、具体的には、オルソ燐酸塩、ヘキサメタリン酸塩等のポリ燐酸化合物、ニトリロトリメチルホスホン酸、エチレンジアミンテトラメチルホスホン酸、トリメチレンジアミンテトラメチルホスホン酸、１，１−ヒドロキシエタンジホスホン酸、１，１−アミノエタン−ジホスホン酸、アミノメチルホスホン酸、２−ホスホノブタン−１，２，４−トリカルボン酸、ビスポリ−２−カルボキシエチルホスフィン酸またはこれらの塩等の有機燐化合物、ポリ（メタ）アクリル酸、ポリマレイン酸等の不飽和カルボン酸重合体、モリブデン酸またはその塩、亜硝酸塩、亜硫酸塩、銅の腐食防止剤であるアゾール化合物、殺藻・殺菌剤である次亜塩素酸塩、次亜臭素酸塩、トリアジン系化合物、イソシアヌール酸、ヒダントイン系化合物、ブロモニトロ系化合物等が挙げられる。
【００３１】
これらの水処理薬剤の測定は公知の方法に従って行われる。例えば、水処理薬剤が有機燐化合物の場合には、特許第３１９９４６９号に記載に記載の測定方法または測定装置を用いて行うことができる。すなわち、分解試薬としては、過硫酸のアンモニウム塩またはアルカリ金属塩、過酸化水素、過塩素酸等の酸化剤が挙げられる。この分解試薬の量は、通常、有機燐化合物含有工程水に対して５〜３０ｇ／ｌが適当である。この発明においては、分解試薬を添加した水処理薬剤を含有する工程水に該薬剤を分解させるに十分な量の紫外線を紫外線ランプ等を用いて照射する。この場合の紫外線の波長は２４０〜３８０ｎｍが好ましく、その強度は５００μＷ／ｃｍ^２以上が好しい。この紫外線の照射は、上記工程水を石英ガラス、シリコン、テフロン（登録商標）、ポリエチレンまたはポリプロピレン等の紫外線透過性材料よりなる配管に注入して行われ、その強度によって影響されるが、通常、５００〜２０００μＷ／ｃｍ^２の強度で３０〜１２０分の間で行われる。紫外線ランプの形状は、円柱状であっても、前面照射状であってもさしつかえなく必要があれば、２個以上の紫外線ランプを設けてもよい。また、配管の形状もとくに制限はなく、紫外線の照射を充分受けやすくするために、その表面積が大きな方が好ましい。その形状としては、蛇管、出入口を有する円筒状中空配管又は偏平直方体状配管が挙げられ、特に好ましい形状は、円柱状の紫外線ランプを配管が螺旋状に覆っている形状である。
【００３２】
上記操作により、有機燐酸系化合物が無機燐酸イオンに分解される。水処理薬剤がオルソ燐酸またはその塩、ポリ燐酸またはその塩の場合には、紫外線照射は必要ではない。分解された無機燐酸イオンは、モリブデン青法として公知の発色試薬が添加され、その後、発色がピークになるまで、通常２０〜３０分回流し、出入口を有するフローセル付の分光光度計に流入させる。ここで、その吸光度を連続的に測定し、予め作成した検量線から有機燐化合物の濃度を測定する。発色試薬として特許第２００５０３７号で提案されている五価のモリブデンと六価のモリブデンとを前者／後者として０．５〜２．０の比で共存するモリブデン酸塩の酸性水溶液に、この酸性水溶液に対し５重量％から溶解度までの範囲の量のリチウム、マグネシウム及び／又はカルシウムの塩化物が含有されてなるリン類の定量試薬を用いるのが、試薬の安定性と取扱い性、定量精度の点で、また、縮合燐酸塩等の加水分解性燐化合物の加水分解も呈色反応時に同時に行える点で好ましい。薬剤がモリブデン酸塩、亜硝酸塩、亜硫酸塩、アゾール化合物、次亜塩素酸塩、次亜臭素酸塩、トリアジン系化合物、イソシアヌール酸、ヒダントイン系化合物の場合には、ＪＩＳ　Ｋ−０１０１、ＪＩＳ　Ｋ−０１０２または上水試験法等に記載の発色吸光度測定手段を用いて行うことができる。
【００３３】
【実施例】
以下の実施例は本発明をより詳細に説明するものであり、本発明を限定するものではない。なお、以下の実施例および比較例では、薬剤濃度測定装置として特許第３１９９４６９号の実施例に記載の装置を用いた。
【００３４】
比較例１
図１と同様の開放循環式冷却設備３１を有する某工場の開放循環冷却水系（保有水量４００ｍ^３、循環水量２４００ｍ^３／ｈ）では、電気伝導度による濃縮倍率の管理を行っていなく、冷却水の濃縮倍率を５倍に維持するため、連続的に強制ブロー水量を約１３ｍ^３／ｈに設定した。試験期間中に強制ブロー水量は１１ｍ^３／ｈ〜１５ｍ^３／ｈの範囲で変化し、平均値は１３ｍ^３／ｈであった。また強制ブロー水、飛散水および蒸発水により流出した保有水を補給するための補給水量の平均値は７７ｍ^３／ｈであった。
【００３５】
そして、スケール防止剤として、１，１−ヒドロキシエタンジホスホン酸を１０重量％含有する水処理薬剤をその薬剤濃度が保有水量に対して、４０ｍｇ／ｌとなるように維持するため、強制ブロー水の平均値である１３ｍ^３／ｈと計算上求められた平均飛散水量２．４ｍ^３／ｈ（循環水量×０．１％）の流失により失われた水処理薬剤を注入補給するとともに、月に３回定期的に当該冷却水を採取して持ち帰り、ＪＩＳ　Ｋ−０１０１に準じて１，１−ヒドロキシエタンジホスホン酸をオートクレーブで分解し、オルトリン酸の合計濃度をモリブデン酸青法により吸光度測定し、その結果に基づいて薬剤の注入量を調節して、１８０日間運転した。その結果を図３に示す。なお、冷却水採取から測定結果に基づいて薬剤の注入量を調節するまでに１週間を要した。試験結果から明らかなように、水処理薬剤濃度は最高値８５．５ｍｇ／ｌから最低値１７ｍｇ／ｌと大幅に変化し、当該濃度を的確にコントロールすることが困難であった。その理由は、冷却水の一部を他の設備に突発的に転用したり、洗浄水として使用しているためであり、その流出量を的確に把握することが困難であったからであると推測される。
【００３６】
実施例１
比較例１と同じ開放循環式冷却設備を有する冷却水系で、本発明の水処理薬剤管理システムにより１８０日間運転した。すなわち、当該冷却設備に図１と同様の薬剤濃度監視部３２および制御部３３を取り付け、強制ブロー水量および飛散水量に対応して失われた薬剤の最低必要量（強制ブロー水量の最小値である１１ｍ^３／ｈと計算上求められた飛散水量の最小値である１．２ｍ^３／ｈ（循環水量×０．０５％）との流失により失われた水処理薬剤量）を薬剤注入ポンプ１３から補給（一次補給）した。また、冷却水中の薬剤濃度を特許第３１９９４６９号の実施例に記載の測定装置を用いて薬剤濃度測定部２１で３０分ごとに測定し、その結果に基づいて演算部２２で計算し、指令部２３から制御部３３へ信号が出力され、制御信号が制御部３３から薬剤ポンプ１４へ出力し、指示量の薬剤を薬剤貯留槽５から冷却水貯留槽１へ補給（二次補給）した。なお、予め記録部において冷却水中の薬剤濃度（Ｃｓ）を３８〜４２ｍｇ／ｌと入力した。そして、測定値（Ｃｍ）が予め設定した薬剤維持濃度（Ｃｓ）の上限値より高い場合には、次の測定結果がでるまで、薬剤注入ポンプを停止させ、測定値（Ｃｍ）が薬剤維持濃度（Ｃｓ）の下限値未満の場合には、次の測定結果がでるまで、薬剤注入ポンプを運転させる制御を行った。また、測定値（Ｃｍ）が薬剤維持濃度範囲（Ｃｓ）の上限値と下限値の間にある場合には、上限値と下限値の差に対する上限値と測定値の差の割合に測定間隔（時間）を乗じた時間だけ薬剤注入ポンプを運転させる制御を行った。その結果を図４に示す。
【００３７】
比較例２
水処理薬剤の一次補給をしないで、実施例１と同様の二次補給のみで運転した結果を図５に示す。
【００３８】
比較例３
某工場の冷却水系（保有水量４５００ｍ^３、循環水量３４００ｍ^３／ｈ）は、二次クーラーを用いる密閉循環系であるが、冷却水の一部を他の設備に頻繁に転用しているため、短時間で転用水量の変動が著しく、工業用水が間欠的に補給されている。この冷却水系設備は冷却塔を有していないため、冷却水の蒸発や飛散がなく、濃縮もされていない。１日の補給水量は１５０ｍ^３〜２５０ｍ^３の範囲で変化し、その平均値は、２００ｍ^３であった。
【００３９】
この冷却水系では、スケール防止剤として、１，１−ヒドロキシエタンジホスホン酸を１０重量％含有する水処理薬剤を用いて、冷却水中の薬剤濃度が３０ｍｇ／ｌとなるように、１日あたりの補給水量（＝転用水量）の平均値に対応して薬剤が冷却水系に連続して添加されている。
月に３回定期的に当該冷却水を採取して持ち帰り、ＪＩＳ　Ｋ−０１０１に準じて１，１−ヒドロキシエタンジホスホン酸をオートクレーブで分解し、オルトリン酸の合計濃度をモリブデン酸青法により吸光度測定した。
【００４０】
その結果に基づいて、薬剤添加量を変化させ、ほぼ１０か月間試験した。なお、冷却水を採取してから測定結果に基づいて薬剤注入量を制御するまでに１週間を要した。その結果を図６の左側に示す。試験結果から明らかなように、水処理薬剤濃度は最高値９５ｍｇ／ｌから最低値１１ｍｇ／ｌと大幅に変化し、当該濃度を的確にコントロールすることが困難であった。その理由は、冷却水の一部を他の設備に突発的に転用したり、洗浄水として使用しているためであり、その流出量を的確に把握することができないからである。そこで、転用水量に対応して失われた薬剤を補給水量の平均値に対応して補給し、１週間後の薬剤濃度の測定結果に基づいて、薬剤の添加量を調節していたからである。
【００４１】
実施例２
比較例３と同じ冷却水系に実施例１と同様の薬剤濃度監視部と制御部を取り付けた本発明による薬剤濃度管理システムを導入し、上記の比較例３に引き続いて冷却設備を運転した。転用水量に対応して失われた薬剤の最低必要量（１日あたりの補給水量（＝転用水量）の最小値である１５０ｍ^３により失われた水処理薬剤量）を連続的に定量補給（一次補給）した。なお、冷却水中の薬剤濃度（Ｃｓ）を２８〜３２ｍｇ／ｌと入力した以外は、薬剤濃度の測定およびその測定結果に基づく薬剤の二次補給は、実施例１と同様に行った。その結果を比較例３の結果と併せて図６の右側に示す。
図６から明らかなように、実施例２では、本発明の水処理濃度管理システムにより、冷却水中の薬剤濃度がほぼ一定となるように的確に管理されている。
【００４２】
【発明の効果】
この発明によれば、冷却水系から失われた水処理薬剤の最低必要量を補給（一次補給）するとともに、冷却水中の水処理薬剤の濃度を随時測定し、その結果に基づいて不足分の薬剤が補給（二次補給）される。
したがって、強制ブロー水量、飛散水量、転用水量等が大きく変動しても、冷却水中の薬剤濃度をほぼ一定に維持することができるので、期待した通りの薬剤効果が発揮されるとともに、冷却設備を経済的に運転することができる。
【図面の簡単な説明】
【図１】本発明の薬剤濃度管理システムが適用される工業用冷却装置の一例を示すブロック図である。
【図２】本発明の薬剤濃度管理システムの流れを示すフローチャートである。
【図３】比較例１における薬剤濃度の推移を示すグラフである。
【図４】実施例１における薬剤濃度の推移を示すグラフである。
【図５】比較例２における薬剤濃度の推移を示すグラフである。
【図６】比較例３および実施例２における薬剤濃度の推移を示すグラフである。
【符号の説明】
１　　冷却水貯水槽
２　　冷却水送水ポンプ
３　　冷却水送水管
４　　熱交換器
５　　冷却塔
６　　薬剤貯留槽
７　　冷却水排出（ブロー）管
８　　冷却水補給管
９　　薬剤補給管
１０　薬剤補給管
１１　ブロー水量調節部
１２　補給水量調節部
１３　薬剤注入ポンプ
１４　薬剤注入ポンプ
２１　薬剤濃度測定部
２２　演算部
２３　記録部
２４　指令部
３１　冷却設備
３２　薬剤濃度監視部
３３　制御部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention replenishes the minimum required amount of the water treatment chemical lost from the cooling water (primary replenishment), measures the concentration of the chemical in the cooling water, and replenishes the insufficient chemical based on the measurement result (secondary replenishment). The present invention relates to a method for managing a drug concentration in cooling water and a system for managing a drug concentration for implementing the method.
[0002]
[Prior art]
Factories such as steel mills and petrochemicals use large amounts of cooling water for process cooling and utility maintenance, and for schools, hospitals, hotels, and other buildings for air conditioning. In the open-circulation cooling water system, a cooling tower is provided, water is circulated and reused, and high-concentration operation is performed as much as possible to save water, thereby effectively using water. In the closed circulation cooling water system, the water whose temperature has risen due to heat exchange is recooled by the secondary cooling water and is circulated for use. Does not happen.
[0003]
In these cooling water systems, various obstacles such as corrosion, scale, slime, and algae caused by water occur on a daily basis. In particular, due to the deterioration of water quality due to the concentration of dissolved salts in cooling water, the frequency of occurrence of these obstacles increases, shortening the service life of equipment, clogging and breakage of equipment and piping, and lowering thermal efficiency, etc. It is known to cause problems such as loss of power, increase of maintenance cost, reduction of factory production efficiency and production stoppage.
[0004]
Conventionally, in order to prevent these obstacles, a water treatment chemical has been added to cooling water.
For example, to prevent corrosion, molybdate, nitrite, phosphate, polymerized phosphate, azoles, various phosphonic acids, etc. are used, and to prevent scale, polyphosphate, acrylic acid-based Polymers and various phosphonic acids are used, and hypochlorite, hydantoin, bromonitro alcohols and the like are used to prevent slime and algae.
[0005]
In the open-circulation type cooling water system, if the amount of blow water is greatly reduced and the amount of makeup water is reduced, not only the amount of water used but also the amount of water treatment chemicals can be reduced, which is economically favorable. The concentration of dissolved salts in the water increases, leading to deterioration of the quality of the circulating water, which tends to cause various obstacles.
[0006]
The effect of reducing the amount of replenishing water due to the high concentration of dissolved salts is up to about 5 times the concentration factor. Even if the concentration factor is increased further, the effect of reducing the amount of replenishing water cannot be obtained. In addition, since the durability of the added water treatment chemical is limited, the operation is usually performed while adjusting the amount of blow water so that the concentration is about 3 to 5 times.
[0007]
In other words, a certain amount of blow water is continuously discharged, or the concentration of dissolved salts is measured by measuring the salt concentration or electric conductivity in the water, and the blow water is discharged intermittently based on the result. Then, the blow water amount is adjusted so that the concentration ratio of the dissolved salts becomes substantially constant. Thus, blow water for adjusting the concentration ratio is called forced blow water.
[0008]
After a certain period of time has elapsed since the start of the operation of the cooling water system, the concentration multiple (N _t ) Can be calculated by the following equation.
N _t = M / (B + W)-｛M- (B + W) N ₀ ｝ / (B + W) exp (−t / T _r )
(Where M is the amount of makeup water, B is the amount of forced blow water, W is the amount of splashed water, N ₀ Is the concentration multiple of circulating water at the start of operation (usually 1), t is the elapsed time (hr) after the start of operation, T _r Is the residence time, and M is the total amount of evaporating water, B and W. )
In these equations, the evaporation amount and the scattered water amount are values peculiar to the system if the operating condition of the cooling water system is constant. Therefore, the concentration management of the cooling water system can be performed by adjusting the forced blow water amount.
[0009]
In order to replenish the shortage of the water treatment chemical discharged together with the forced blow water, various methods are employed.
That is, in the case of continuous blow, a method of continuously replenishing a certain amount of medicine with a pump corresponding to the forced blow water amount obtained by the above equation, in the case of intermittent blow, a method of replenishing medicine in conjunction with the blow pump, When continuous or intermittent blow is detected by a change in the water level of the cooling water storage tank, a method of replenishing the chemical in conjunction with the makeup water pump, analyzing the concentration of the water treatment chemical in the cooling water, and measuring the chemical based on the result A method of adjusting the amount of addition is employed.
[0010]
[Problems to be solved by the invention]
When the method of replenishing the drug in conjunction with the continuous addition of the drug or the blow pump is adopted among the above methods, the water treatment chemical is not only the forced blow water and the water scattered from the cooling equipment, but also the cooling water is used for other purposes. When diverted to a facility, it may be lost due to unexpected spills of cooling water (such as diverted water), such as when used as washing water, so the amount of lost water treatment chemicals can be accurately determined. It was difficult to do.
[0011]
In addition, when a method of replenishing a drug in conjunction with a replenishing water pump is employed, there is a time lag before a change in the water level is sensed, the replenishment of the drug cannot be timely performed, and the replenishing water does not involve loss of the drug. In order to replenish a large amount of water lost due to evaporation, the concentration of the drug was maintained at an unnecessarily high level, which was disadvantageous in terms of economics. In order to replenish the amount of the medicine, construction and installation of various facilities are required, which is an economically expensive investment, which is not preferable.
[0012]
Furthermore, in the case of measuring the concentration of the water treatment chemical in the cooling water and adjusting the amount of the chemical added based on the result, since measuring equipment and instruments are required for measuring the chemical concentration, the sample water is temporarily removed. It had to be brought back to the analysis room and the drug concentration in the cooling water could not be adjusted in a timely manner. For this reason, there has been a problem that the drug concentration in the cooling water varies and the effect of the drug is not exhibited as expected, or the drug concentration is maintained higher than necessary.
[0013]
On the other hand, in the closed circulation type cooling water system, concentration due to evaporation or the like does not occur, and since there is no cooling tower, there is no outflow of chemicals due to forced blow water or flying water. However, the outflow of the drug due to the diverted water may occur frequently. In this case, the amount of medicine lost due to the outflow of diverted water is converted into the amount of medicine (amount of replenished water per day × drug maintenance concentration) corresponding to the average value of the amount of replenished water per day (= amount of diverted water). A fixed amount is continuously added to the cooling water system. However, if there is a sudden outflow of diversion water, the drug concentration temporarily drops, and the desired effect may not be exhibited. Therefore, the drug concentration in the cooling water is regularly taken back (about once a week) and the analysis is performed, but the drug concentration in the cooling water cannot be adjusted in a timely manner. For example, the above problem can be solved by accurately grasping the amount of replenishing water and replenishing the amount of the chemical corresponding to the amount, but requires construction and installation of various facilities, which is an economically expensive investment. It is not preferred.
[0014]
Therefore, the present applicant has proposed a method and an apparatus for continuously and automatically measuring the concentration of an organic phosphate compound or an inorganic phosphate compound (Japanese Patent No. 3199469), and a long-term stable quantitative reagent (Japanese Patent No. 2005037). ) Has been proposed.
[0015]
By adopting a method using a continuous measurement device for these water treatment chemicals or a simple measurement method using stable quantitative reagents, it is possible to easily measure the drug concentration on site without bringing the sample water back to the analysis room. Therefore, it is possible to control the drug injection amount in a relatively short time based on the measurement result, and it can be expected that an effect that an effective amount of the drug concentration can be maintained.
[0016]
However, the method using the continuous measurement device and the simple measurement method using a stable quantitative reagent require a certain time for color development because the drug concentration is measured by absorbance, which is equivalent to the secondary replenishment of the present invention. These methods alone could not accurately control the drug concentration in the cooling water.
In addition, if the forced blow water or the diverted water suddenly occurs, the amount of medicine lost in a short time fluctuates greatly, and it has been difficult to replenish the required amount of medicine in a timely manner.
[0017]
The present invention has been made under such a technical background. In spite of sudden fluctuations in the amount of forced blow water and the amount of diverted water, the concentration of the water treatment chemical in the cooling water is reduced in a short time. It is an object of the present invention to provide a more economical water treatment chemicals concentration management method and concentration management system that can be appropriately adjusted to a predetermined value.
[0018]
[Means for Solving the Problems]
As a result of earnest research, the present inventor has replenished (primary replenishment) the minimum required amount of the water treatment chemical lost from the cooling water system, measured the chemical concentration in the cooling water, and based on the measurement result, determined the insufficient chemical. By replenishing (secondary replenishment), it has been found that the concentration of the drug in the cooling water can be adjusted to a substantially constant value in a timely manner despite spontaneous fluctuations in the amount of forced blow water and the amount of diverted water, thus completing the present invention.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a block diagram showing an example of an industrial cooling apparatus to which a concentration management system for a water treatment chemical of the present invention is applied, and the present invention will be specifically described based on this drawing.
The industrial cooling device includes an open-circulation-type cooling facility 31, a drug concentration monitoring unit 32, and a control unit 33.
The cooling equipment 31 includes a cooling water storage tank 1, a cooling water supply pump 2, a cooling water supply pipe 3, a heat exchanger 4, a cooling tower 5, a medicine storage tank 6, a cooling water discharge (blow) pipe 7, a cooling water It comprises a supply pipe 8, chemical supply pipes 9 and 10, a blow water flow rate control unit 11, a supply water quantity control unit 12, and drug injection pumps 13 and 14.
In the cooling facility 31, the cooling water is circulated from the cooling water storage tank 1 to the heat exchanger 4, the cooling tower 5, and the water storage tank 1 through the cooling water supply pipe 3 by the cooling water supply pump 2.
[0020]
In this example, a known water quality management method using a general electric conductivity meter (not shown) is adopted for the concentration multiple of the cooling water, and the forced blow water amount is measured by a flow meter (shown in the drawing) provided in the middle of the pipe. The amount of scattered water and the amount of evaporated water can be obtained by calculation according to the size and style of the cooling tower.
Then, replenishing water corresponding to the blow water amount, the scattered water amount, and the evaporating water amount is supplied from the cooling water supply pipe 8. In addition, this replenishing water amount may be measured by a water level meter (not shown) provided in the cooling water storage tank 1.
Further, in the above example, a medicine corresponding to the minimum necessary amount of the medicine lost together with the forced blow water and the scattered water is supplied from the medicine injection pump 13 (primary supply).
[0021]
When the amount of forced blow water is determined by the flow meter as described above, the amount of medicine lost due to this blow and the minimum amount of splash water calculated by the scale and style of the cooling tower are lost. The sum of the amount of the medicine and the amount of the medicine that has been supplied is the minimum necessary amount to be refilled.
If the amount of forced blow water is not determined by the flow meter, the amount of chemicals lost due to the minimum amount of forced blow water calculated and the amount of scattered water calculated by the scale and style of the cooling tower are calculated. The sum of the amount of the medicine lost by the minimum amount of the medicine and the minimum amount of the medicine becomes the minimum necessary amount to be primarily refilled.
[0022]
Diverted water is generally discharged from the branch pipe or cooling water pipe of the cooling water feed pump, so it is difficult to determine its amount. Installation of various facilities is required, and it is usually impossible to bear such an economically expensive investment. However, when a part of the diverted water is discharged from the forced blow pipe or the like and its flow rate can be grasped, the amount of the chemical corresponding to the diverted water amount may be added to the minimum amount to be refilled first.
[0023]
Here, the amount of scattered water differs depending on the design of the cooling tower and is calculated by calculation. Generally, the amount of scattered water in the forced-ventilation type cooling tower is said to be 0.05% to 0.2% of the circulating water amount. I have. Therefore, the minimum amount of the medicine lost by the scattered water is obtained by [circulating water amount × 0.0005 × standard concentration of the medicine in the cooling water].
[0024]
In the closed circulation system, the replenishment of the minimum required amount of the medicine lost due to the outflow of the diverted water (primary replenishment) is performed by the amount of the medicine corresponding to the minimum value of the replenished water amount per day (= the amount of diverted water) (per day). It is preferable from an economic point of view that the amount is continuously added to the cooling water system by converting the amount of replenishment water × the concentration of drug maintenance).
[0025]
The drug concentration monitoring unit 32 includes a drug concentration measurement unit 21, a calculation unit 22, a recording unit 23, and a command unit 24.
The cooling water for which the drug concentration is to be measured is collected in the middle of the water pipe 3 and is sent to the drug concentration measuring unit 21 as needed to measure the drug concentration in the cooling water. The frequency of the measurement is not particularly limited. For example, taking into account, for example, the time required for color development, it is usually sufficient to measure every 15 to 120 minutes, preferably every 30 to 60 minutes, to obtain the effect of the present invention. It is.
[0026]
In the recording unit 23, a preset standard drug maintenance concentration (Cs) in the cooling water is input.
The measured value (Cm) of the drug concentration obtained by the drug concentration measuring section 21 is sent to the calculating section 22 as an electric signal.
[0027]
The calculation unit 22 compares the measured value (Cm) of the drug concentration with a standard drug maintenance concentration (Cs) preset and input to the recording unit 23, and determines the measured value (Cm) as a standard value. When the concentration is lower than the drug maintenance concentration (Cs), the amount of the drug to be added is calculated by the calculation unit 22, a signal is output from the command unit 23 to the control unit 33, and the control signal is sent from the control unit 33 to the drug injection pump 14. The output and the indicated amount of medicine are supplied from the medicine storage tank 5 to the cooling water storage tank 1 (secondary supply). In the above example, two drug injection pumps (13 and 14) are provided for replenishing the drug. However, these drug injection pumps can be shared by one injection pump.
The above flow is shown in the flowchart of FIG.
[0028]
The standard drug maintenance concentration (Cs) may have a range, and the injection amount of the drug injection pump may be controlled within the range between the upper limit and the lower limit.
Then, for example, when the measured value (Cm) is higher than the preset upper limit of the drug maintenance concentration (Cs), the drug infusion pump is stopped until the next measurement result is obtained, and the measured value (Cm) is changed to the value of the drug maintenance concentration (Cm). If the concentration (Cs) is less than the lower limit, the drug infusion pump may be operated until the next measurement result is obtained. The drug injection speed in this case can be obtained by calculation based on the amount of the drug deficiency and the measurement interval of the drug concentration. For convenience, several levels of the drug injection speed are set, and the amount of the drug deficiency and the drug concentration are determined. The optimum injection speed may be selected from the several drug injection speeds in consideration of the measurement interval.
[0029]
When the measured value (Cm) is between the upper limit and the lower limit of the drug maintenance concentration range (Cs), the ratio of the difference between the upper limit and the measured value to the difference between the upper limit and the lower limit is determined by the measurement interval ( ) May be operated for the time multiplied by (time).
[0030]
Next, an example of the water treatment chemicals in the present invention and a method for measuring them will be described.
Examples of the water treatment agent include known corrosion inhibitors, scale inhibitors, slime inhibitors, and the like. , Trimethylenediaminetetramethylphosphonic acid, 1,1-hydroxyethanediphosphonic acid, 1,1-aminoethane-diphosphonic acid, aminomethylphosphonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, bispoly-2-carboxyethyl Organic phosphorus compounds such as phosphinic acid or salts thereof, unsaturated carboxylic acid polymers such as poly (meth) acrylic acid and polymaleic acid, molybdic acid or salts thereof, nitrites, sulfites, and azoles as copper corrosion inhibitors Compounds, hypochlorites, which are algicides and fungicides, Bromates, triazine compounds, isocyanuric acid, hydantoin-based compound, Buromonitoro based compounds.
[0031]
The measurement of these water treatment chemicals is performed according to a known method. For example, when the water treatment chemical is an organic phosphorus compound, the measurement can be performed using the measuring method or measuring device described in Japanese Patent No. 3199469. That is, examples of the decomposition reagent include an oxidizing agent such as an ammonium salt or an alkali metal salt of persulfate, hydrogen peroxide, and perchloric acid. Usually, the amount of the decomposition reagent is suitably from 5 to 30 g / l based on the process water containing the organic phosphorus compound. In the present invention, a process water containing a water treatment chemical to which a decomposition reagent has been added is irradiated with ultraviolet rays sufficient to decompose the chemical using an ultraviolet lamp or the like. In this case, the wavelength of the ultraviolet light is preferably 240 to 380 nm, and the intensity thereof is 500 μW / cm. ² I like more. This ultraviolet irradiation is performed by injecting the above process water into a pipe made of an ultraviolet transmitting material such as quartz glass, silicon, Teflon (registered trademark), polyethylene or polypropylene, and is affected by its intensity. 500-2000 μW / cm ² At an intensity of 30 to 120 minutes. The shape of the ultraviolet lamp may be cylindrical or front-illuminated, and if necessary, two or more ultraviolet lamps may be provided. There is no particular limitation on the shape of the pipe, and it is preferable that the pipe has a large surface area in order to sufficiently receive the irradiation of ultraviolet rays. Examples of the shape thereof include a serpentine tube, a cylindrical hollow pipe having an entrance and an entrance, and a flat rectangular parallelepiped pipe. A particularly preferable shape is a pipe in which a cylindrical ultraviolet lamp is spirally covered.
[0032]
By the above operation, the organic phosphate compound is decomposed into inorganic phosphate ions. When the water treatment agent is orthophosphoric acid or a salt thereof, polyphosphoric acid or a salt thereof, ultraviolet irradiation is not required. The decomposed inorganic phosphate ion is added with a coloring reagent known as the molybdenum blue method, and thereafter, is circulated usually for 20 to 30 minutes until the coloring reaches a peak, and then flows into a spectrophotometer equipped with a flow cell having an entrance and exit. Here, the absorbance is continuously measured, and the concentration of the organic phosphorus compound is measured from a calibration curve prepared in advance. An acidic aqueous solution of molybdate in which pentavalent molybdenum and hexavalent molybdenum proposed as a color-forming reagent coexist in a ratio of 0.5 to 2.0 with pentavalent molybdenum and hexavalent molybdenum as the former / the latter is added to the acidic aqueous solution. The use of a reagent for the determination of phosphorus containing lithium, magnesium and / or calcium chlorides in an amount ranging from 5% by weight to the solubility of the reagent is advantageous in terms of the stability, handleability and quantitative accuracy of the reagent. In addition, hydrolysis of a hydrolyzable phosphorus compound such as a condensed phosphate is preferred because it can be performed simultaneously with the color reaction. When the drug is molybdate, nitrite, sulfite, azole compound, hypochlorite, hypobromite, triazine compound, isocyanuric acid, hydantoin compound, JIS K-0101, JIS K It can be carried out by using a colorimetric absorbance measuring means described in -0102 or tap water test method.
[0033]
【Example】
The following examples illustrate the invention in more detail, but do not limit the invention. In the following examples and comparative examples, the device described in the example of Japanese Patent No. 3199469 was used as a drug concentration measuring device.
[0034]
Comparative Example 1
An open-circulation cooling water system of a certain factory having the same open-circulation cooling system 31 as in FIG. ³ , Circulating water volume 2400m ³ / H), the concentration ratio is controlled by the electric conductivity, and the forced blow water amount is continuously reduced to about 13 m in order to maintain the concentration ratio of the cooling water at 5 times. ³ / H. The amount of forced blow water during the test period is 11m ³ / H ~ 15m ³ / H range, average value is 13m ³ / H. The average value of the replenishment water for replenishing the water retained by the forced blow water, splash water and evaporating water is 77 m. ³ / H.
[0035]
In order to maintain the concentration of the water treatment agent containing 10% by weight of 1,1-hydroxyethanediphosphonic acid as a scale inhibitor so that the concentration of the agent becomes 40 mg / l with respect to the retained water amount, forced blow water is used. 13m which is the average value of ³ / H and the calculated average splashing water amount of 2.4 m ³ / H (circulating water volume x 0.1%), the water treatment chemicals lost and replenished are injected, and the cooling water is periodically collected three times a month and brought back home. , 1-Hydroxyethanediphosphonic acid was decomposed in an autoclave, and the total concentration of orthophosphoric acid was measured for absorbance by the molybdate blue method. Based on the results, the injection amount of the drug was adjusted, and the system was operated for 180 days. The result is shown in FIG. In addition, it took one week from the collection of cooling water to the adjustment of the injection amount of the drug based on the measurement result. As is clear from the test results, the concentration of the water treatment chemical changed drastically from the highest value of 85.5 mg / l to the lowest value of 17 mg / l, and it was difficult to control the concentration accurately. The reason is presumed that some of the cooling water was suddenly diverted to other equipment or used as washing water, and it was difficult to accurately grasp the amount of the outflow. Is done.
[0036]
Example 1
In the cooling water system having the same open-circulation type cooling equipment as Comparative Example 1, it was operated for 180 days by the water treatment chemical management system of the present invention. That is, the same chemical concentration monitoring unit 32 and control unit 33 as those in FIG. 1 are attached to the cooling equipment, and the minimum required amount of the medicine lost corresponding to the forced blow water amount and the scattered water amount (the minimum value of the forced blow water amount is the minimum value). 11m ³ / H and 1.2 m which is the minimum value of the calculated amount of splashed water ³ / H (amount of water treatment chemical lost due to the loss with the amount of circulating water × 0.05%) was replenished from the chemical infusion pump 13 (primary replenishment). Also, the drug concentration in the cooling water is measured every 30 minutes by the drug concentration measuring unit 21 using the measuring device described in the example of Japanese Patent No. 3199469, and the calculation unit 22 calculates based on the result, and the command unit A signal was output from 23 to the control unit 33, a control signal was output from the control unit 33 to the drug pump 14, and the indicated amount of drug was replenished from the drug storage tank 5 to the cooling water storage tank 1 (secondary replenishment). In the recording section, the drug concentration (Cs) in the cooling water was previously input as 38 to 42 mg / l. If the measured value (Cm) is higher than the preset upper limit value of the drug maintenance concentration (Cs), the drug infusion pump is stopped until the next measurement result is obtained, and the measured value (Cm) becomes the drug maintenance concentration. When it was less than the lower limit of (Cs), control to operate the drug infusion pump was performed until the next measurement result was obtained. When the measured value (Cm) is between the upper limit and the lower limit of the drug maintenance concentration range (Cs), the ratio of the difference between the upper limit and the measured value with respect to the difference between the upper limit and the lower limit is the measurement interval ( ) Was controlled to operate the drug infusion pump for the time multiplied by (time). The result is shown in FIG.
[0037]
Comparative Example 2
FIG. 5 shows the result of operating with only secondary replenishment similar to that of Example 1 without primary replenishment of the water treatment chemical.
[0038]
Comparative Example 3
Cooling water system of a certain factory (water volume 4500m) ³ , Circulating water volume 3400m ³ / H) is a closed circulation system using a secondary cooler, but since part of the cooling water is frequently diverted to other equipment, the amount of diverted water fluctuates significantly in a short time, and industrial water is intermittent. Has been replenished. Since this cooling water system equipment does not have a cooling tower, there is no evaporation or scattering of cooling water and no concentration. 150m daily replenishing water ³ ~ 250m ³ The average value is 200m ³ Met.
[0039]
In this cooling water system, a water treatment chemical containing 10% by weight of 1,1-hydroxyethanediphosphonic acid is used as a scale inhibitor so that the concentration of the chemical in the cooling water becomes 30 mg / l per day. Chemicals are continuously added to the cooling water system corresponding to the average value of the replenishment water amount (= diverted water amount).
The cooling water is collected and taken back three times a month, and 1,1-hydroxyethanediphosphonic acid is decomposed in an autoclave according to JIS K-0101, and the total concentration of orthophosphoric acid is measured by the molybdate blue method. It was measured.
[0040]
Based on the results, the amount of drug added was changed, and the test was performed for approximately 10 months. In addition, it took one week from collecting the cooling water to controlling the medicine injection amount based on the measurement result. The result is shown on the left side of FIG. As is evident from the test results, the concentration of the water treatment chemical changed drastically from the highest value of 95 mg / l to the lowest value of 11 mg / l, and it was difficult to accurately control the concentration. The reason is that a part of the cooling water is suddenly diverted to other equipment or used as cleaning water, and the amount of the outflow cannot be accurately grasped. Therefore, the medicine lost in accordance with the diverted water amount is replenished in accordance with the average value of the replenishment water amount, and the addition amount of the medicine is adjusted based on the measurement result of the drug concentration one week later.
[0041]
Example 2
A drug concentration management system according to the present invention, in which the same drug concentration monitoring unit and control unit as in Example 1 were attached to the same cooling water system as in Comparative Example 3, was introduced, and cooling equipment was operated following Comparative Example 3 above. The minimum required amount of the medicine lost in accordance with the amount of diversion water (150 m which is the minimum value of the amount of replenishment water per day (= diversion water amount) ³ (The amount of the water treatment chemical lost by the above) was continuously replenished (primary replenishment). The measurement of the drug concentration and the secondary replenishment of the drug based on the measurement result were performed in the same manner as in Example 1, except that the drug concentration (Cs) in the cooling water was input as 28 to 32 mg / l. The result is shown on the right side of FIG. 6 together with the result of Comparative Example 3.
As is clear from FIG. 6, in the second embodiment, the water treatment concentration management system of the present invention accurately manages the chemical concentration in the cooling water to be substantially constant.
[0042]
【The invention's effect】
According to the present invention, the minimum required amount of the water treatment chemical lost from the cooling water system is replenished (primary replenishment), the concentration of the water treatment chemical in the cooling water is measured at any time, and based on the result, the shortage of the water treatment chemical is determined. Is supplied (secondary supply).
Therefore, even if the forced blow water amount, the scattered water amount, the diverted water amount, etc. fluctuate greatly, the drug concentration in the cooling water can be kept almost constant, so that the expected drug effect is exhibited and the cooling equipment is improved. It can be operated economically.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an example of an industrial cooling device to which a drug concentration management system of the present invention is applied.
FIG. 2 is a flowchart showing the flow of the drug concentration management system of the present invention.
FIG. 3 is a graph showing changes in drug concentration in Comparative Example 1.
FIG. 4 is a graph showing a change in drug concentration in Example 1.
FIG. 5 is a graph showing changes in drug concentration in Comparative Example 2.
FIG. 6 is a graph showing changes in drug concentration in Comparative Example 3 and Example 2.
[Explanation of symbols]
1 Cooling water storage tank
2 Cooling water feed pump
3 Cooling water pipe
4 heat exchanger
5 Cooling tower
6 drug storage tank
7 Cooling water discharge (blow) pipe
8 Cooling water supply pipe
9 Drug supply tube
10 Drug supply tube
11 Blow water control unit
12 Replenishment water volume control
13 Drug injection pump
14 Drug injection pump
21 Drug concentration measuring section
22 Operation part
23 Recorder
24 Command part
31 Cooling equipment
32 Drug concentration monitoring unit
33 control unit

Claims

In a cooling water system, a medicine replenishing means for replenishing (primary replenishment) a minimum required amount of a water treatment chemical lost with water discharged from the water system, a medicine concentration monitoring means for monitoring a medicine concentration in the cooling water, Water treatment of a cooling water system, comprising: control means for controlling a medicine replenishing amount based on the monitoring result; and medicine replenishing means for replenishing a shortage of medicine (secondary replenishment) based on the control instruction. Drug concentration management system.

2. The drug concentration management system according to claim 1, wherein the drug concentration monitoring means comprises a drug concentration measurement unit, a calculation unit, and a command unit.

The cooling water system is an open circulation system, and the water discharged from the cooling water system is forced blow water, splash water and diverted water, and the minimum necessary amount of the medicine lost corresponding to these water amounts is primarily replenished. The drug concentration management system according to claim 1 or 2.

The cooling water system is of a closed circulation type, the water discharged from the cooling water system is diverted water, and the minimum required amount of the lost chemical corresponding to the amount of water is primarily replenished. The drug concentration management system as described.

In the cooling water system, the minimum required amount of the water treatment chemical lost with the water discharged from the water system is replenished (primary replenishment), and the concentration of the chemical in the cooling water is measured. A method for controlling the concentration of a water treatment chemical, comprising replenishing (secondarily replenishing) the chemical.

6. The chemical concentration control method according to claim 5, wherein the cooling water system is of an open circulation type, and the minimum required amount of the chemical lost in correspondence with the forced blow water amount and the scattered water amount is primarily replenished.

The drug concentration management method according to claim 5, wherein the cooling water system is of a closed circulation type, and the minimum necessary amount of the drug lost corresponding to the amount of diverted water is primarily replenished.