JPH06287777A - Method for lowering corrosiveness of water - Google Patents
Method for lowering corrosiveness of waterInfo
- Publication number
- JPH06287777A JPH06287777A JP9650993A JP9650993A JPH06287777A JP H06287777 A JPH06287777 A JP H06287777A JP 9650993 A JP9650993 A JP 9650993A JP 9650993 A JP9650993 A JP 9650993A JP H06287777 A JPH06287777 A JP H06287777A
- Authority
- JP
- Japan
- Prior art keywords
- water
- calcium
- corrosiveness
- hydroxide
- sodium
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Landscapes
- Preventing Corrosion Or Incrustation Of Metals (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】この発明は、各種用水または排水
用の管路の腐食防止に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to prevention of corrosion of pipelines for various kinds of water or drainage.
【０００２】[0002]
【従来の技術】水処理工程で凝集剤や塩素剤の使用が多
いと、処理水はpH値が低下し、腐食性を強める。このよ
うな水はコンクリ-ト構造物、モルタルライニング管、
石綿セメント管を劣化させ、亜鉛めつき鋼管、銅管、鉛
管に対しては亜鉛、銅、鉛を溶出させたり、鉄管からは
鉄を溶出し、赤水の原因となる等、水道施設に対して様
々な障害を与える。2. Description of the Related Art If a coagulant or a chlorine agent is used in the water treatment process, the pH value of the treated water is lowered and the corrosiveness is increased. Such water is used for concrete structures, mortar lining pipes,
Deteriorate asbestos cement pipes, elute zinc, copper and lead from zinc plated steel pipes, copper pipes and lead pipes, or elute iron from iron pipes, causing red water. Gives various obstacles.
【０００３】このような障害の発生への対策として、pH
値を7.5〜8.0、ランゲリア指数を-1.0程度以上の腐食性
の少ない水にするため、アルカリ剤を注入してpH値を調
整する。アルカリ剤として水酸化カルシウム(消石灰)の
使用は、水中のカルシウム濃度増加し、注入量を多くす
ると金属表面に炭酸カルシウムが沈着して保護被膜を形
成する。一方、アルカリ剤として水酸化ナトリウムや炭
酸ナトリウムを用いると、pH値の調整は可能であるが、
保護被膜を形成する作用はない。As a countermeasure against the occurrence of such troubles, pH
The pH value is adjusted by injecting an alkaline agent in order to adjust the value to 7.5-8.0 and the Langerian index to -1.0 or more with less corrosive water. The use of calcium hydroxide (slaked lime) as an alkaline agent increases the calcium concentration in water, and when the injection amount is increased, calcium carbonate is deposited on the metal surface to form a protective film. On the other hand, if sodium hydroxide or sodium carbonate is used as the alkaline agent, the pH value can be adjusted,
It does not act to form a protective coating.
【０００４】このため、施設の腐食の防止には水酸化カ
ルシウム注入が最も効果的であるが、水酸化カルシウム
は粉末で溶解性に乏しく、高濃度の溶液とすることは不
可能で、スラリ−注入や低濃度での注入を余儀なくさ
れ、水酸化カルシウムの注入に関しては、装置が複雑に
なることや正確な制御が難しい等の問題点があつた（水
道施設設計指針・解説・厚生省監修、日本水道協会、19
90参考）。For this reason, calcium hydroxide injection is most effective in preventing facility corrosion, but calcium hydroxide is a powder and has poor solubility, and it is impossible to form a high-concentration solution. Injecting and injecting at low concentration caused problems such as complicated equipment and difficult precise control of calcium hydroxide injection (design guideline for water facilities, supervision by the Ministry of Health, Japan. Water Works Association, 19
90 Reference).
【０００５】また水酸化カルシウム注入による場合、保
護被膜の形成を目的として所要のカルシウム量を添加し
ようとするると、処理水のpHが上がりすぎるため（高ア
ルカリ性となるため）、炭酸ガス（CO2)の注入や炭酸(H
2CO3)を添加して処理水の中和を余儀なくされるなどの
不都合がある。In the case of calcium hydroxide injection, if a required amount of calcium is added for the purpose of forming a protective film, the pH of the treated water will rise too high (because of high alkalinity), and therefore carbon dioxide (CO 2 2 ) Infusion or carbonic acid (H
2 CO 3 ) has to be added to neutralize the treated water.
【０００６】[0006]
【発明が解決しようとする課題】この発明は、上述のよ
うな水酸化カルシウムの注入に関する従来技術の限界点
の確認のもとに水中に腐食防止のために十分な量のカル
シウムを溶解すると共に、pH調整を行なう、簡便かつ正
確な技術を提供することを目的とする。DISCLOSURE OF THE INVENTION The present invention is intended to dissolve a sufficient amount of calcium in water to prevent corrosion while confirming the limitations of the prior art regarding the injection of calcium hydroxide as described above. The purpose is to provide a simple and accurate technique for adjusting pH.
【０００７】[0007]
【課題を解決するための手段】施設の腐食防止のために
は、弱アルカリ性下で水中のカルシウムイオンを増加さ
せればよい（具体的にはpH7.5〜8.0でランゲリア指数が
-1.0程度以上）こととなる。そこで発明者らは、この目
的のためにはカルシウム源を水酸化カルシウムに限定す
ることなく、他の溶解度の高いカルシウム塩を用い、pH
調整のためにはpH調整効果の高いアルカリ剤を用いれば
よいと考え、様々な検討を行なつた。[Means for Solving the Problems] In order to prevent corrosion of facilities, it is sufficient to increase calcium ions in water under weak alkaline conditions (specifically, at pH 7.5-8.0, the Langerian index is
-About 1.0 or more). Therefore, the inventors did not limit the calcium source to calcium hydroxide for this purpose, but used other highly soluble calcium salts, and
For the adjustment, we thought that it would suffice to use an alkaline agent with a high pH adjustment effect, and conducted various studies.
【０００８】その結果、カルシウム源として塩化カルシ
ウムを用い、アルカリ剤には水酸化ナトリウム、炭酸ナ
トリウム、炭酸水素ナトリウム、水酸化カルシウム等を
もちいれば、初期の目的を達することを見いだした。As a result, it was found that if calcium chloride was used as the calcium source and sodium hydroxide, sodium carbonate, sodium hydrogen carbonate, calcium hydroxide or the like was used as the alkaline agent, the initial purpose was achieved.
【０００９】[0009]
【作用】すなわち、水酸化カルシウム（Ca(OH)2)は０℃
の水100gに0.18gしか溶解しない(化学辞典普及版、志田
正二、森北出版(株)、1981、以下出典同じ)のに対し、
塩化カルシウム(CaCl2)は０℃の水100gに59.5gと水酸化
カルシウムの約330倍の溶解が可能で、この程度の濃度
になれば、通常の水処理操作における薬液濃度と同程度
となり、従来の薬液注入技術がそのまま適用できる。[Function] That is, calcium hydroxide (Ca (OH) 2 ) is 0 ℃
Whereas only 0.18 g is dissolved in 100 g of water (chemical dictionary popular version, Shoji Shida, Morikita Publishing Co., Ltd., 1981, the same source below),
Calcium chloride (CaCl 2 ) can be dissolved in 100 g of water at 0 ° C, 59.5 g and about 330 times as much as calcium hydroxide. At this level of concentration, it will be about the same as the concentration of chemicals in normal water treatment operations. The conventional chemical injection technology can be applied as it is.
【００１０】同じくアルカリ剤として用いる水酸化ナト
リウム(NaOH)は０℃の水100gに42g、炭酸ナトリウム(Na
2(OH3))は０℃の水100gに7.1g溶解、炭酸水素ナトリウ
ム(NaHCO3)は０℃の水100gに6.9g溶解する。また水酸化
カルシウムの溶解度は、前出の通り極めて小さいが、pH
調整に用いる量は僅かであるため、水酸化カルシウムの
水溶液もアルカリ剤として使用可能である。したがつ
て、塩化カルシウムとアルカリ剤の単独あるいは併用に
より、従前から保有している注入技術を用いて、pH値7.
5〜8.0でランゲリア指数が-1.0程度以上という基準は達
成可能となる。Similarly, sodium hydroxide (NaOH) used as an alkaline agent is 42 g per 100 g of water at 0 ° C. and sodium carbonate (NaOH).
2 (OH 3 )) is dissolved in 100 g of water at 0 ° C. and 7.1 g is dissolved therein, and sodium hydrogen carbonate (NaHCO 3 ) is dissolved in 100 g of water at 0 ° C. and 6.9 g is dissolved therein. Also, the solubility of calcium hydroxide is extremely small as described above, but
Since the amount used for the adjustment is small, an aqueous solution of calcium hydroxide can be used as the alkaline agent. Therefore, by using calcium chloride and an alkaline agent alone or in combination, the pH value of 7.
It is possible to achieve the standard that the Langerian index is about -1.0 or more at 5 to 8.0.
【００１１】使用する塩化カルシウムは、当初からCaCl
3の形態であるものに限定される必要はなく、貝殻や石
灰石あるいは水酸化カルシウムなどを塩酸で処理して用
いていもよい。また、対象水がもとから高アルカリ性で
ある場合には、アルカリ剤に代えて炭酸ガスや炭酸等の
酸を用いることとなる。The calcium chloride used is CaCl from the beginning.
The form is not limited to that of 3 , and shells, limestone, calcium hydroxide or the like may be treated with hydrochloric acid before use. Further, when the target water is originally highly alkaline, an acid such as carbon dioxide gas or carbonic acid is used instead of the alkaline agent.
【００１２】[0012]
【実施例】アルカリ度や硬度の低い河川水に、無水塩化
カルシウム（CaCl3)の20%溶液を、カルシウム濃度が40m
g/lとなるように添加した。この試水を1リットルづつ分
取し、それぞれを0.1規定の水酸化ナトリウム、0.1規定
の炭酸ナトリウム、0.1規定の炭酸水素ナトリウム及び
0.01規定の水酸化カルシウムを用いて、pHを約7.5に調
整した。河川水、塩化カルシウム添加試水及び塩化カル
シウム添加試水をpH調整した、それぞれの試料のpH、カ
ルシウム濃度、総アルカリ度、溶解性物質およびランゲ
リア指数を表１に示す。[Example] A 20% solution of anhydrous calcium chloride (CaCl 3 ) was added to river water with low alkalinity and hardness, and the calcium concentration was 40 m.
It was added to be g / l. Take 1 liter of this sample water, and add 0.1N sodium hydroxide, 0.1N sodium carbonate, 0.1N sodium bicarbonate and
The pH was adjusted to about 7.5 using 0.01N calcium hydroxide. Table 1 shows the pH, calcium concentration, total alkalinity, soluble substances and Langerian index of each sample obtained by adjusting pH of river water, calcium chloride added sample water and calcium chloride added sample water.
【００１３】[0013]
【表１】 [Table 1]
【００１４】当初、ランゲリア指数が-2.48で腐食性の
高い河川水は、塩化カルシウムを約40mg/l(as Ca)添加
することにより、ランゲリア指数は-1.59にまで上昇し
た。更に、この塩化カルシウム添加試水をpH調整したと
ころ、何れのアルカリ剤を用いても、ランゲリア指数は
-1.0程度となり、腐食性の低い水に変化していることが
分かつた。Initially, river water with a Langeria index of -2.48 and high corrosiveness increased to -1.59 by adding about 40 mg / l (as Ca) of calcium chloride. Furthermore, when the pH of this calcium chloride-added sample water was adjusted, the Langerian index was
It became about -1.0, and it was found that the water had changed to low corrosiveness.
【００１５】ランゲリア指数（飽和指数）とは、水の実
際のpH値と、理論的pH値(pHs、水中の炭酸カルシウムが
溶解も析出もしない平衡状態にあるときのpH値)との差
をいい、炭酸カルシウムの被膜形状の目安としている。
指数が正の値で絶対値の大きいほど、炭酸カルシウムの
析出が起こりやすく、ゼロであれば平衡状態にあり、負
の値では炭酸カルシウム被膜は形成されず、その絶対値
が大きくなるほど、水の腐食傾向は強くなる。炭酸カル
シウム被膜の形成には、-1.0程度以上であればよいとさ
れている。The Langerian index (saturation index) is the difference between the actual pH value of water and the theoretical pH value (pHs, the pH value when calcium carbonate in water is in an equilibrium state in which neither dissolution nor precipitation occurs). Good, it is used as a guide for the coating shape of calcium carbonate.
If the index is a positive value and the absolute value is large, precipitation of calcium carbonate is likely to occur, and if it is zero, there is an equilibrium state, and if the index is a negative value, the calcium carbonate film is not formed. Corrosion tendency becomes stronger. It is said that the formation of the calcium carbonate film should be about -1.0 or more.
【００１６】ランゲリア指数は、水のpH値、カルシウム
イオン量、総アルカリ度及び溶解性物質量から、次式に
よつて求められる。The Langerian index is calculated from the pH value of water, the amount of calcium ions, the total alkalinity and the amount of soluble substances according to the following equation.
【００１７】[0017]
【数１】 [Equation 1]
【００１８】ここに、 8.313：定数 ［Ca2+]：me/lで示されたカルシウムイオン量であつ
て、Ca2+mg/l÷(40.1÷2)で求められる。 ［A]：me/lで示された総アルカリ度であつて、総アルカ
リ度mg/l÷(100÷2)で求められる。 Ｓ：補正値であつて、数式２によつて求められる。Here, 8.313 is a constant [Ca 2+ ]: the amount of calcium ions represented by me / l, which is calculated by Ca 2+ mg / l ÷ (40.1 ÷ 2). [A]: Total alkalinity expressed in me / l, which is calculated by total alkalinity mg / l ÷ (100 ÷ 2). S: A correction value, which is obtained by the mathematical formula 2.
【００１９】[0019]
【数２】 [Equation 2]
【００２０】ここにSdは溶解性物質(mg/l)である。な
お、ランゲリア指数は温度によつても異なり、上記は25
℃における場合で、温度１℃の上昇に対して約1.5×10
-2増加する。Here, Sd is a soluble substance (mg / l). Note that the Langerian index differs depending on the temperature, and the above is 25
Approximately 1.5 × 10 for a temperature increase of 1 ℃ at ℃
-2 increase.
【００２１】[0021]
【発明の効果】この発明により、特別な注入設備を設け
る必要もなく、水中のカルシウム濃度の向上とpH調整が
正確に制御できるようになり、容易に対象水の腐食性を
低減することが可能となる。EFFECTS OF THE INVENTION According to the present invention, it is possible to accurately control the calcium concentration in water and adjust the pH without the need to install special injection equipment, and easily reduce the corrosiveness of the target water. Becomes
【手続補正書】[Procedure amendment]
【提出日】平成５年４月１２日[Submission date] April 12, 1993
【手続補正１】[Procedure Amendment 1]
【補正対象書類名】明細書[Document name to be amended] Statement
【補正対象項目名】００１５[Name of item to be corrected] 0015
【補正方法】変更[Correction method] Change
【補正内容】[Correction content]
【００１５】ランゲリア指数（飽和指数）とは、水の実
際のｐＨ値と、理論的ｐＨ値（ｐＨｓ、水中の炭酸カル
シウムが溶解も析出もしない平衡状態にあるときのｐＨ
値）との差をいい、炭酸カルシウムの被膜形状の目安と
している。指数が正の値で絶対値の大きいほど、炭酸カ
ルシウムの析出が起こりやすく、ゼロであれば平衡状態
にあり、負の値ではその絶対値が大きくなるほど、水の
腐食傾向は強くなる。炭酸カルシウム被膜の形成には、
−１．０程度以上であればよいとされている。The Langería index (saturation index) is the actual pH value of water and the theoretical pH value (pHs, pH when calcium carbonate in water is in an equilibrium state in which neither dissolution nor precipitation occurs).
Value) and is used as a guide for the coating shape of calcium carbonate. If the index is positive and the absolute value is large, precipitation of calcium carbonate is likely to occur, and if the index is zero, the state of equilibrium is reached. If the index is negative, the absolute value is large, and the corrosion tendency of water becomes stronger. To form a calcium carbonate coating,
It is said that it may be about −1.0 or more.
【手続補正２】[Procedure Amendment 2]
【補正対象書類名】明細書[Document name to be amended] Statement
【補正対象項目名】００１８[Correction target item name] 0018
【補正方法】変更[Correction method] Change
【補正内容】[Correction content]
【００１８】ここに、 ８．３１３：定数 ［Ｃａ２＋］：ｍｅ／ｌで示されたカルシウムイオン量
であつて、Ｃａ２＋ｍｇ／ｌ÷（４０．１÷２）で求め
られる。 ［Ａ］：ｍｅ／ｌで示された総アルカリ度であつて、総
アルカリ度ｍｇ／ｌ÷（１００÷２）で求められる。 Ｓ：補正値であつて、数式２によつて求められる。Here, the amount of calcium ions represented by 8.313: constant [Ca 2+ ]: me / l is calculated by Ca 2+ mg / l ÷ (40.1 ÷ 2). [A]: The total alkalinity represented by me / l, which is calculated by total alkalinity mg / l ÷ (100 ÷ 2). S: A correction value, which is obtained by the mathematical formula 2.
Claims (3)
に溶解度の高いカルシウム塩及びアルカリ剤の両者、或
いは一方を注入して腐食性を低下させる方法。1. A method of injecting both or one of a highly soluble calcium salt and / or an alkaline agent into water having a small Langerian index and high corrosiveness to reduce corrosiveness.
ウムである請求項１記載の水の腐食性を低下させる方
法。2. The method for reducing the corrosiveness of water according to claim 1, wherein the highly soluble calcium salt is calcium chloride.
トリウム、炭酸水素ナトリウム、水酸化カルシウム等で
あることを特徴とする請求項１記載の水の腐食性を低下
させる方法。3. The method for reducing the corrosiveness of water according to claim 1, wherein the alkaline agent is sodium hydroxide, sodium carbonate, sodium hydrogen carbonate, calcium hydroxide or the like.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9650993A JPH06287777A (en) | 1993-04-01 | 1993-04-01 | Method for lowering corrosiveness of water |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9650993A JPH06287777A (en) | 1993-04-01 | 1993-04-01 | Method for lowering corrosiveness of water |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH06287777A true JPH06287777A (en) | 1994-10-11 |
Family
ID=14167099
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP9650993A Pending JPH06287777A (en) | 1993-04-01 | 1993-04-01 | Method for lowering corrosiveness of water |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH06287777A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2005116296A1 (en) * | 2004-05-25 | 2005-12-08 | Kurita Water Industries Ltd. | Method of cooling water treatment and treatment chemical |
| JP2010137224A (en) * | 2010-02-12 | 2010-06-24 | Kureha Engineering Co Ltd | Method for cleaning water |
| JP2013188729A (en) * | 2012-03-15 | 2013-09-26 | Kurita Water Ind Ltd | Iron scale inhibitor and iron scale preventing method for steam generator |
| JP2015183285A (en) * | 2014-03-26 | 2015-10-22 | 栗田工業株式会社 | Method of suppressing metal corrosion |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61220793A (en) * | 1985-03-25 | 1986-10-01 | Sasakura Eng Co Ltd | Method for monitoring and controlling water quality |
-
1993
- 1993-04-01 JP JP9650993A patent/JPH06287777A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61220793A (en) * | 1985-03-25 | 1986-10-01 | Sasakura Eng Co Ltd | Method for monitoring and controlling water quality |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2005116296A1 (en) * | 2004-05-25 | 2005-12-08 | Kurita Water Industries Ltd. | Method of cooling water treatment and treatment chemical |
| JPWO2005116296A1 (en) * | 2004-05-25 | 2008-04-03 | 栗田工業株式会社 | Cooling water treatment method |
| JP4725513B2 (en) * | 2004-05-25 | 2011-07-13 | 栗田工業株式会社 | Cooling water treatment method |
| JP2010137224A (en) * | 2010-02-12 | 2010-06-24 | Kureha Engineering Co Ltd | Method for cleaning water |
| JP2013188729A (en) * | 2012-03-15 | 2013-09-26 | Kurita Water Ind Ltd | Iron scale inhibitor and iron scale preventing method for steam generator |
| JP2015183285A (en) * | 2014-03-26 | 2015-10-22 | 栗田工業株式会社 | Method of suppressing metal corrosion |
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