JPH09141260A - Method for desalination of seawater - Google Patents

Method for desalination of seawater

Info

Publication number
JPH09141260A
JPH09141260A JP7300986A JP30098695A JPH09141260A JP H09141260 A JPH09141260 A JP H09141260A JP 7300986 A JP7300986 A JP 7300986A JP 30098695 A JP30098695 A JP 30098695A JP H09141260 A JPH09141260 A JP H09141260A
Authority
JP
Japan
Prior art keywords
membrane
seawater
reverse osmosis
desalination
fresh water
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.)
Granted
Application number
JP7300986A
Other languages
Japanese (ja)
Other versions
JP2920200B2 (en
Inventor
Yoshio Taniguchi
良雄 谷口
Keiichi Ota
敬一 太田
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
National Institute of Advanced Industrial Science and Technology AIST
Original Assignee
Agency of Industrial Science and Technology
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Agency of Industrial Science and Technology filed Critical Agency of Industrial Science and Technology
Priority to JP7300986A priority Critical patent/JP2920200B2/en
Publication of JPH09141260A publication Critical patent/JPH09141260A/en
Application granted granted Critical
Publication of JP2920200B2 publication Critical patent/JP2920200B2/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
    • Y02A20/124—Water desalination
    • Y02A20/131—Reverse-osmosis

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  • Separation Using Semi-Permeable Membranes (AREA)

Abstract

PROBLEM TO BE SOLVED: To improve the concentration rate while suppressing precipitation of scales by passing seawater through a nano filter membrane (NF membrane) to remove sulfate ion and then passing the filtered water through a reverse osmosis membrane to remove salts. SOLUTION: Seawater is treated in a desalination device having the following structure to change into fresh water. In the device, three flat membrane cells each equipped with an NF membrane comprising a circular flat membrane of a polyvinyl alcohol/polyamide resin are connected in series to constitute an NF filtering device as a first treating device. Then, a second treating device equipped with a reverse osmosis membrane is connected in series to the first treating device to constitute the desalination device to change seawater to fresh water. By this method, seawater can be desalted into fresh water with a high recovering rate, and the plant can be operated for a long period without producing precipitation of scales.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【発明の属する技術分野】本発明は、逆浸透膜法により
海水を淡水化する際に、スケールの析出を抑制して効率
よく淡水化しうる方法に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently desalinating seawater by reverse osmosis to suppress scale precipitation.

【０００２】[0002]

【従来の技術】海水を淡水化する方法としては、逆浸透
法、多段蒸発法、イオン交換法などが知られているが、
膜を介して水だけを透過させ、相変化を与えることなく
溶質を除去しうるという点で逆浸透法が特に注目されて
いる。2. Description of the Related Art Reverse osmosis, multistage evaporation, ion exchange, etc. are known as methods for desalinating seawater.
Reverse osmosis is of particular interest because it allows the permeation of water only through the membrane and the removal of solutes without phase change.

【０００３】ところで、逆浸透法により淡水化する際に
は、一方において海水の濃縮が行われることになるの
で、濃縮の進行とともに海水中の溶解成分が溶解度の小
さいものから析出し、スケールとなって海水淡水化プラ
ントの運転効率を低下させる。On the other hand, when desalination is carried out by the reverse osmosis method, on the one hand, seawater is concentrated. Therefore, as the concentration proceeds, dissolved components in seawater are precipitated from the one having a smaller solubility to form a scale. Reduce the operating efficiency of the seawater desalination plant.

【０００４】このスケール成分で最も問題になるのは硫
酸カルシウム（ＣａＳＯ4）で、常温下においては海水
を３倍以上に濃縮するとＣａＳＯ4・２Ｈ2Ｏとなって析
出してくるため、一般には回収率４０％すなわち濃縮率
として１．６倍程度に止めているのが実情である。しか
しながら、回収率を向上させれば、供給海水の前処理設
備の規模を縮小することができるため、設備費、運転費
が低減する上に、副生物として高濃度の濃縮海水が得ら
れ、海水中の有効成分の回収が容易になるという利点が
ある。The most problematic component of this scale is calcium sulfate (CaSO 4 ), and at normal temperature, when seawater is concentrated three times or more, CaSO 4 · 2H 2 O will be precipitated, so that it generally precipitates. In reality, the recovery rate is 40%, that is, the concentration rate is 1.6 times. However, if the recovery rate is improved, the scale of the pretreatment facility for the supplied seawater can be reduced, which reduces equipment costs and operating costs, and also provides highly concentrated seawater as a by-product. There is an advantage that the active ingredient therein can be easily recovered.

【０００５】[0005]

【発明が解決しようとする課題】本発明は、逆浸透法に
よる海水淡水化に際して、スケールの析出を抑制して濃
縮率すなわち回収率を高め、運転効率を大きくすること
を目的としてなされたものである。DISCLOSURE OF THE INVENTION The present invention has been made for the purpose of suppressing the precipitation of scale and increasing the concentration rate, that is, the recovery rate, and increasing the operation efficiency, during desalination by the reverse osmosis method. is there.

【０００６】[0006]

【課題を解決するための手段】本発明者らは、逆浸透法
におけるスケールの発生を抑制する方法について種々研
究を重ねた結果、海水原液を逆浸透膜で処理するに先立
って、ナノろ過膜（以下ＮＦ膜と略す）を透過させると
硫酸イオン（ＳＯ4 --）の大部分が硫酸マグネシウム
（ＭｇＳＯ4）として除去され、硫酸カルシウムすなわ
ちスケールの析出が抑制されることを見出し、この知見
に基づいて本発明をなすに至った。[Means for Solving the Problems] The inventors of the present invention have conducted various studies on a method for suppressing the generation of scale in the reverse osmosis method, and as a result, prior to treating the undiluted seawater solution with the reverse osmosis membrane, the nanofiltration membrane was used. (hereinafter NF membrane abbreviated) when to transmit sulfate ion (SO 4 -) most of the are removed as magnesium sulfate (MgSO 4), found that the precipitation of calcium sulfate that scale is suppressed, this finding The present invention has been completed based on the above.

【０００７】すなわち、本発明は、海水原液をＮＦ膜に
通して、硫酸イオンを除去したのち、その透過水を逆浸
透膜に通し、塩類を除去することを特徴とする海水の淡
水化方法を提供するものである。That is, the present invention provides a method for desalination of seawater, which comprises passing an undiluted solution of seawater through an NF membrane to remove sulfate ions, and then passing the permeated water through a reverse osmosis membrane to remove salts. It is provided.

【０００８】本発明方法においては、ＮＦ膜の透過によ
り、カルシウムイオンよりも硫酸イオンが優先的に除去
されることが重要であり、もしも、カルシウムイオンと
硫酸イオンとが同じ割合で分離されるとＮＦ膜の分離過
程で溶解度の小さい硫酸カルシウムを析出することにな
るので、ＮＦ膜の回収率を高くすることができない。In the method of the present invention, it is important that sulfate ions are preferentially removed over calcium ions by permeation through the NF membrane. If calcium ions and sulfate ions are separated at the same ratio, it is important. Since calcium sulfate having a low solubility is deposited during the separation process of the NF membrane, the recovery rate of the NF membrane cannot be increased.

【０００９】[0009]

【発明の実施の形態】本発明方法で用いるＮＦ膜として
は、操作圧力１４．８ｋｇｆ／ｃｍ2以下、分画分子量
２００〜１０００、塩化ナトリウム阻止率９０％以下の
もので、特に硫酸イオンを選択的に除去しうるものが好
ましい。BEST MODE FOR CARRYING OUT THE INVENTION The NF membrane used in the method of the present invention has an operating pressure of 14.8 kgf / cm 2 or less, a molecular weight cutoff of 200 to 1000, and a sodium chloride rejection rate of 90% or less. Those that can be removed selectively are preferred.

【００１０】このようなＮＦ膜は市販品として容易に入
手することができる。例えば、日東電工（株）から市販
されているＮＴＲ７２５０、ＮＴＲ７４５０、東レ
（株）から市販されている２００Ｓ、フィルムテック
（Ｆｉｌｍ Ｔｅｃ）社から市販されているＮＦ−７
０、ＮＦ−５０、ＮＦ−４０ＨＦなどを用いることがで
きる。Such an NF film can be easily obtained as a commercial product. For example, NTR7250 and NTR7450 commercially available from Nitto Denko Corporation, 200S commercially available from Toray Industries, Inc. and NF-7 commercially available from Film Tec.
0, NF-50, NF-40HF, etc. can be used.

【００１１】海水は、塩分３．３〜３．８重量％を含ん
でいるが、本発明方法においては、これをそのままで、
あるいは懸濁物質をろ過したのち、先ずＮＦ膜に通す処
理が行われる。この際のＮＦ膜モジュールは、平膜型、
内圧管型、外圧管型、中空繊維型、渦巻型など、透過膜
に慣用されている任意の形式にすることができる。ま
た、この際の操作条件としては、運転圧力２〜１０ｋｇ
ｆ／ｃｍ2、処理温度１０〜３０℃、通水流量２〜１０
リットル／分の範囲内で選ばれる。Seawater contains a salt content of 3.3 to 3.8% by weight. In the method of the present invention, this is used as it is.
Alternatively, after the suspended substance is filtered, a process of passing it through an NF membrane is first performed. At this time, the NF membrane module is a flat membrane type,
It may be of any type commonly used for a permeable membrane, such as an internal pressure pipe type, an external pressure pipe type, a hollow fiber type, a spiral type and the like. The operating conditions at this time are as follows: operating pressure 2 to 10 kg
f / cm 2 , treatment temperature 10 to 30 ° C, water flow rate 2 to 10
It is selected within the range of liter / minute.

【００１２】このようにＮＦ膜により処理された透過水
は、次いで逆浸透膜に通されるが、この逆浸透膜として
は、海水の逆浸透法による淡水化において、通常使用さ
れている透過膜の中から任意に選んで使用することがで
きる。このような透過膜としては、例えば東洋紡（株）
から市販されているＨＭ８２５５ＦＩ、東レ（株）から
市販されているＳＵ８２０、日東電工（株）から市販さ
れているＮＴＲ７０ＳＷＣ−Ｓ８、デュポン社から市販
されているＢ−１０／６８８０Ｔ、フィルムテック社か
ら市販されている３０−８０４０、フルイドシステム社
から市販されているＴＦＣＬ２８２２などがある。この
逆浸透膜による処理の際の操作条件としては、運転圧力
５５〜７０ｋｇｆ／ｃｍ2、処理温度２５〜３０℃の範
囲が適当である。通水流量は、その規模に応じ慣用され
ている範囲内で適宜選ぶことができる。The permeated water thus treated with the NF membrane is then passed through a reverse osmosis membrane. As this reverse osmosis membrane, a permeable membrane that is usually used in the desalination of seawater by the reverse osmosis method. It can be used by arbitrarily selecting from the above. Examples of such a permeable membrane include Toyobo Co., Ltd.
Commercially available from HM8255FI, Toray Industries, Inc. SU820, Nitto Denko Corporation commercially available NTR70SWC-S8, DuPont Company commercially available B-10 / 6880T, commercially available from Filmtec. 30-8040, and TFCL2822 marketed by Fluid Systems. As operating conditions during the treatment with this reverse osmosis membrane, an operating pressure of 55 to 70 kgf / cm 2 and a treatment temperature of 25 to 30 ° C. are suitable. The water flow rate can be appropriately selected within the range commonly used depending on the scale.

【００１３】本発明方法によると、先ずＮＦ膜による第
一段階の処理で、塩素が１０〜２０％、カルシウムが３
０〜４０％、マグネシウムが４０〜６０％、硫酸イオン
が９５％以上の除去率で除去される。このように、カル
シウムの除去率に比べ硫酸イオンの除去率が著しく高い
ため、ＮＦ膜が硫酸カルシウムを主体とするスケールの
析出により閉鎖されることがない。このように硫酸イオ
ンが優先的に除かれた透過水に、逆浸透膜による第二段
階の処理が施され、この処理により、９９％以上の除去
率で塩類が除去され、淡水化を行うことができる。この
ようにして、本発明によると、逆浸透法による淡水化プ
ラントを８０％又はそれ以上の高い回収率で数か月にわ
たり、なんの支障もなく、稼動させることができる。According to the method of the present invention, first, in the first stage treatment with an NF film, chlorine is 10 to 20% and calcium is 3%.
The removal rate is 0 to 40%, magnesium is 40 to 60%, and sulfate ions are removed at 95% or more. Thus, the removal rate of sulfate ions is significantly higher than the removal rate of calcium, so that the NF film is not closed due to the deposition of scale mainly composed of calcium sulfate. In this way, the permeated water from which sulfate ions have been preferentially removed is subjected to a second-stage treatment with a reverse osmosis membrane, and by this treatment, salts are removed at a removal rate of 99% or more, and desalination is performed. You can In this way, according to the present invention, a desalination plant by the reverse osmosis method can be operated with high recovery rate of 80% or more for several months without any trouble.

【００１４】[0014]

【実施例】次に実施例により本発明をさらに詳細に説明
する。なお、各例においては、表１に示す主成分濃度の
海水を使用した。EXAMPLES The present invention will be described in more detail with reference to examples. In addition, in each example, seawater having the main component concentrations shown in Table 1 was used.

【００１５】[0015]

【表１】 [Table 1]

【００１６】参考例 日東電工（株）より市販されているＮＴＲ７２５０（ポ
リビニルアルコール／ポリアミド系樹脂膜）から成る、
直径７５ｍｍの円形平膜を備えた平膜セル３基を、直列
に連結したＮＦろ過装置を用い、入口圧力５．０ｋｇｆ
／ｃｍ2、出口圧力４．９ｋｇｆ／ｃｍ2、水温２５．３
℃、通水流量５．１リットル／分の運転条件下で、残留
塩素をチオ硫酸ナトリウムで還元した海水を処理した。
このようにして得た結果を表２に示す。Reference Example Consisting of NTR7250 (polyvinyl alcohol / polyamide resin film) commercially available from Nitto Denko Corporation,
Using an NF filtration device in which three flat membrane cells each having a circular flat membrane with a diameter of 75 mm were connected in series, the inlet pressure was 5.0 kgf.
/ Cm 2 , outlet pressure 4.9 kgf / cm 2 , water temperature 25.3
Under the operating conditions of ℃ and water flow rate of 5.1 liter / min, the seawater in which residual chlorine was reduced with sodium thiosulfate was treated.
The results thus obtained are shown in Table 2.

【００１７】[0017]

【表２】 [Table 2]

【００１８】この表から明らかなようにＮＦ膜の処理に
より、ＣａＳＯ4 ４９０ｍｇ／リットル、ＭｇＳＯ4 ２
５６９ｍｇ／リットル、ＭｇＣｌ2 ３８５ｍｇ／リット
ル及びＮａＣｌ ４３０８ｍｇ／リットルが除去された
ことが分る。このようにして硫酸イオンの大部分はＭｇ
ＳＯ4として除去される。As is clear from this table, the treatment of the NF film resulted in CaSO 4 490 mg / liter, MgSO 4 2
It can be seen that 569 mg / l, MgCl 2 385 mg / l and NaCl 4308 mg / l were removed. In this way, most of the sulfate ions are Mg
It is removed as SO 4 .

【００１９】実施例１ 参考例で用いたものと同じＮＦ膜を備えた第一処理器と
逆浸透膜（東レ（株）製ＳＵ８２０）を備えた第二処理
器を直列に連結した海水淡水化装置を用い、ＮＦ膜につ
いて運転圧力５ｋｇｆ／ｃｍ2、水温２５〜２６℃、通
水流量５．０リットル／分、回収率８０％の条件下で海
水を処理した。この際の第１処理後及び第２処理後にお
ける各成分の濃度を海水原液における各成分の濃度とと
もに表３に示す。Example 1 Seawater desalination in which a first processor equipped with the same NF membrane as used in the reference example and a second processor equipped with a reverse osmosis membrane (SU820 manufactured by Toray Industries, Inc.) were connected in series. Using the apparatus, seawater was treated for an NF membrane under the conditions of an operating pressure of 5 kgf / cm 2 , a water temperature of 25 to 26 ° C., a water flow rate of 5.0 liter / min, and a recovery rate of 80%. The concentrations of the respective components after the first treatment and the second treatment at this time are shown in Table 3 together with the concentrations of the respective components in the seawater stock solution.

【００２０】[0020]

【表３】 [Table 3]

【００２１】この表から明らかなように、本発明方法に
よると回収率８０％という高い回収率においても、非常
に高い塩類除去率で淡水化が行われる。As is clear from this table, the method of the present invention enables desalination with a very high salt removal rate even at a high recovery rate of 80%.

【００２２】[0022]

【発明の効果】本発明によると、高い回収率で海水の淡
水化を行うことができ、しかも長期間にわたって、スケ
ールの析出を伴わずにプラントを稼動しうるという利点
がある。EFFECTS OF THE INVENTION According to the present invention, there is an advantage that seawater can be desalinated at a high recovery rate and that the plant can be operated for a long period of time without deposition of scale.

Claims (1)

【特許請求の範囲】[Claims] 【請求項１】 海水原液をナノろ過膜に通して硫酸イオ
ン濃度を低下させたのち、その透過水を逆浸透膜に通し
て塩類を除去することを特徴とする海水の淡水化方法。1. A method of desalination of seawater, which comprises passing a stock solution of seawater through a nanofiltration membrane to reduce the concentration of sulfate ions, and then passing the permeated water through a reverse osmosis membrane to remove salts.
JP7300986A 1995-11-20 1995-11-20 Seawater desalination method Expired - Lifetime JP2920200B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP7300986A JP2920200B2 (en) 1995-11-20 1995-11-20 Seawater desalination method

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP7300986A JP2920200B2 (en) 1995-11-20 1995-11-20 Seawater desalination method

Publications (2)

Publication Number Publication Date
JPH09141260A true JPH09141260A (en) 1997-06-03
JP2920200B2 JP2920200B2 (en) 1999-07-19

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999016714A1 (en) * 1997-10-01 1999-04-08 Saline Water Conversion Corporation Process for desalination of saline water, especially sea water, having increased product yield and quality
JPH11169850A (en) * 1997-12-11 1999-06-29 Hyuunetto Kk Treatment of sea water
WO2001014256A1 (en) * 1999-08-20 2001-03-01 L.E.T. Leading Edge Technologies Limited A salt water desalination process using ion selective membranes
EP1329425A1 (en) * 2002-01-18 2003-07-23 Toray Industries, Inc. Desalination method and desalination apparatus
US6783682B1 (en) * 1999-08-20 2004-08-31 L.E.T., Leading Edge Technologies Limited Salt water desalination process using ion selective membranes
EP1354855A3 (en) * 1999-08-20 2005-01-19 L.E.T. Leading Edge Technologies Limited A salt water desalination process using ion selective membranes
US7144511B2 (en) * 2002-05-02 2006-12-05 City Of Long Beach Two stage nanofiltration seawater desalination system
CN1319878C (en) * 2004-06-12 2007-06-06 杭州水处理技术研究开发中心 Method and equipment for desalting seawater
JP2010137192A (en) * 2008-12-15 2010-06-24 Toray Ind Inc Composite nano-filter membrane
KR100982052B1 (en) * 2003-07-11 2010-09-13 두산중공업 주식회사 The Multi Stage Flashing Distillate Plant with Nano-Filter

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999016714A1 (en) * 1997-10-01 1999-04-08 Saline Water Conversion Corporation Process for desalination of saline water, especially sea water, having increased product yield and quality
US6508936B1 (en) 1997-10-01 2003-01-21 Saline Water Conversion Corporation Process for desalination of saline water, especially water, having increased product yield and quality
JPH11169850A (en) * 1997-12-11 1999-06-29 Hyuunetto Kk Treatment of sea water
WO2001014256A1 (en) * 1999-08-20 2001-03-01 L.E.T. Leading Edge Technologies Limited A salt water desalination process using ion selective membranes
US6783682B1 (en) * 1999-08-20 2004-08-31 L.E.T., Leading Edge Technologies Limited Salt water desalination process using ion selective membranes
EP1354855A3 (en) * 1999-08-20 2005-01-19 L.E.T. Leading Edge Technologies Limited A salt water desalination process using ion selective membranes
US6998053B2 (en) 1999-08-20 2006-02-14 L.E.T., Leading Edge Technologies Limited Water desalination process using ion selective membranes
EP1329425A1 (en) * 2002-01-18 2003-07-23 Toray Industries, Inc. Desalination method and desalination apparatus
US7144511B2 (en) * 2002-05-02 2006-12-05 City Of Long Beach Two stage nanofiltration seawater desalination system
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