JP4341865B2 - Power recovery method and apparatus for reverse osmosis membrane seawater desalination equipment - Google Patents

Power recovery method and apparatus for reverse osmosis membrane seawater desalination equipment Download PDF

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JP4341865B2
JP4341865B2 JP23057399A JP23057399A JP4341865B2 JP 4341865 B2 JP4341865 B2 JP 4341865B2 JP 23057399 A JP23057399 A JP 23057399A JP 23057399 A JP23057399 A JP 23057399A JP 4341865 B2 JP4341865 B2 JP 4341865B2
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pressure
reverse osmosis
osmosis membrane
power recovery
water
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JP2001046842A (en
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省三 梶尾
慎治 田畑
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Organo Corp
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    • 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
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    • Y02A20/124—Water desalination
    • Y02A20/131—Reverse-osmosis

Description

【０００１】
【発明の属する技術分野】
本発明は、逆浸透膜方式海水淡水化装置において濃縮水側に動力回収タービンを設けて濃縮水が有するエネルギーを回収できるようにした動力回収方法および装置に関する。
【０００２】
【従来の技術】
逆浸透膜（以下、ＲＯ膜と言うこともある。）を有するＲＯ膜モジュールユニットを用いて、供給されてくる海水を一定の量割合で淡水化するシステムが知られている。
【０００３】
このシステムにおいては、図２に示すように、通常、ＲＯ膜１０１での淡水化に必要な膜間差圧（供給水側の圧力と透過水側の圧力との差圧）を確保するために、給水ポンプ１０２により比較的高圧でＲＯ膜モジュールユニット１０３の供給水側に海水を供給する。たとえば海水の塩濃度が３．５％の場合、供給水の運転圧力は約５５〜７０ｋｇ／ｃｍ2 で運転されている。また、供給水路１０４には、通常、一定の流量で海水を供給するために、入口調整弁１０５が設けられている。ＲＯ膜１０１の供給水側に供給された海水は、そのうちの所定割合（たとえば、４０％）の量の海水が所定の膜間差圧により透過水側に透過され、透過水路１０６を介して淡水として取り出される。残りの海水（たとえば、供給水に対し６０％の量の海水）は濃縮水となり、濃縮水路１０７を介して排出される。この濃縮水は、ＲＯ膜モジュールユニット１０３で約１〜３ｋｇ／ｃｍ2 圧力が低下するものの、約５２〜６７ｋｇ／ｃｍ2 程度の高圧に維持されている。高圧の濃縮水をそのまま排出するのではエネルギーロスが大きいので、濃縮水路１０７に動力回収タービン１０８が設けられ、濃縮水によって動力回収タービン１０８を駆動してそのエネルギーを回収するようにしている。回収されたエネルギーは、たとえば動力回収タービン１０８を給水ポンプ１０２駆動用のモータ１０９に機械的に連結することにより（たとえば、直結することにより）、給水ポンプ１０２駆動用のエネルギーとして回収され、有効に利用される。
【０００４】
このとき、後述の如く、従来システムでは通常所定の淡水化性能を維持するために、ＲＯ膜モジュールユニット１０３の入口圧力を所定圧力に制御する必要が生じることから、その圧力を検出して、濃縮水路１０７に設けた制御弁１１０（減圧により圧力を制御する弁）で制御するようにしている。
【０００５】
【発明が解決しようとする課題】
ところが、上記のような従来システムにおいては、海水の温度変動に伴う、以下のような問題がある。
【０００６】
すなわち、海水の温度が変化すると、ＲＯ膜の膜間差圧が変動する。海水を淡水化するためには、通常、選定したＲＯ膜に応じて、回収率（供給海水量に対する淡水造水量の割合）を所定の一定の回収率に維持することが求められ、この回収率が全ての運転条件に優先する前提条件となっている。
【０００７】
このような回収率を前提条件とする場合、海水の温度が、たとえば１０℃〜３０℃変動した場合（この範囲は通常考えられる一般的な変動範囲である）、維持されるべき膜間差圧はたとえば次のように試算される。
【０００８】
つまり、海水温度が１０℃の場合、ＲＯ膜の膜間差圧としてはたとえば６８ｋｇ／ｃｍ2 （回収率４０％、塩濃度３．５％）にされなければならず、海水温度が３０℃の場合、ＲＯ膜の膜間差圧としてはたとえば５６ｋｇ／ｃｍ2 （回収率４０％、塩濃度３．５％）にされなければならない。
【０００９】
したがって、上記運転条件を満たすためには、給水ポンプ１０２の仕様としては、１０℃の海水の場合での必要膜間差圧６８ｋｇ／ｃｍ2 を確保するための揚程を有するものが必要となる。しかしこのような給水ポンプ１０２を用いてそのまま３０℃の海水を淡水化しようとすると、ＲＯ膜１０１の膜間差圧としては５６ｋｇ／ｃｍ2 を確保しなければならないから、その膜間差圧にするために入口調整弁１０５で減圧して運転することになる。
【００１０】
このように海水の温度変化に応じてＲＯ膜の供給水側（入口側）の圧力を調整して運転する場合、たとえば上記の如く膜間差圧が６８〜５６ｋｇ／ｃｍ2 となるように運転する場合、ＲＯ膜モジュールユニット１０３での圧力低下分を考慮すると、たとえば約３ｋｇ／ｃｍ2 の圧力低下分を考慮すると、ＲＯ膜モジュールユニット１０３の出口側における濃縮水路１０７の圧力は６５〜５３ｋｇ／ｃｍ2 の範囲で変動することになる。濃縮水路１０７に設けられた動力回収タービン１０８で濃縮水が有するエネルギーを回収する場合には、通常、動力回収タービン１０８をある一定入口圧力のものに設計する必要があるので、上記のように濃縮水路１０７の圧力（つまり、動力回収タービン１０８の入口へと通じる流路の圧力）が６５〜５３ｋｇ／ｃｍ2 に変動する条件下においては、結局５３ｋｇ／ｃｍ2 の圧力水のエネルギーを回収するための動力回収タービン１０８とする必要がある。すなわち、動力回収タービン１０８の入口圧力としてとり得る範囲（または、濃縮水側の圧力としてとり得る範囲）のうちの実質的に最低圧力に設定される。その結果、給水ポンプ１０２で供給水に大きなエネルギーを付与しておきながら、動力回収タービン１０８では５３ｋｇ／ｃｍ2 の圧力水のエネルギー分しか回収できないことになり、エネルギー回収率が低いという問題を含んでいる。
【００１１】
そこで本発明の課題は、上記のような海水の温度変化に起因する問題点に着目し、供給海水量に対し所定の一定の淡水造水比率を維持しつつ、動力回収タービンによって回収される濃縮水側のエネルギー回収率を大幅に高めることにある。
【００１２】
【課題を解決するための手段】
上記課題を解決するために、本発明に係る逆浸透膜方式における動力回収方法は、逆浸透膜の供給水側に給水ポンプにより海水を供給し、逆浸透膜の透過水側から淡水を取り出すとともに、逆浸透膜の濃縮水側に動力回収タービンを設けて濃縮水が有するエネルギーを回収するに際し、透過水側の流量を制御することにより、濃縮水側の圧力を、海水の温度が変化した場合に供給海水量に対し予め定められた所定の淡水造水量の割合を達成するための逆浸透膜の膜間差圧の変動範囲のうちの実質的に最高の圧力から、供給水側から濃縮水側に至る間の圧力低下分を差し引いた圧力に制御して、該濃縮水側の圧力がとり得る範囲内のうちの一定レベル以上の高圧に維持することを特徴とする方法からなる。
【００１３】
この方法においては、たとえば逆浸透膜の膜間差圧の変動範囲が前述と同じ６８〜５６ｋｇ／ｃｍ２で、圧力低下分が３ｋｇ／ｃｍ２であるとすると、動力回収タービンをその入口側圧力として６５ｋｇ／ｃｍ２のものに設計し、その圧力を維持できるように透過水側の流量を制御するのである。
【００１４】
本発明に係る逆浸透膜方式海水淡水化装置における動力回収装置は、逆浸透膜を有する逆浸透膜モジュールユニットと、逆浸透膜モジュールユニットに給水ポンプからの海水を供給する供給水路と、逆浸透膜モジュールユニットからの透過水を淡水として取り出す透過水路と、逆浸透膜モジュールユニットで濃縮された濃縮水を排出する濃縮水路と、濃縮水路に設けられ、濃縮水が有するエネルギーを回収する動力回収タービンとを備えた装置において、透過水路に、濃縮水路における圧力を、海水の温度が変化した場合に供給海水量に対し予め定められた所定の淡水造水量の割合を達成するための逆浸透膜の膜間差圧の変動範囲のうちの実質的に最高の圧力から、供給水側から濃縮水側に至る間の圧力低下分を差し引いた圧力に制御して、予め定められた目標圧力に維持する流量制御弁を設けたことを特徴とするものからなる。
【００１５】
動力回収タービンによって回収されたエネルギーは、たとえば電気的エネルギーの形態で有効利用をはかることも可能であるが、給水ポンプ駆動用モータに動力回収タービンが機械的に連結されている構造に構成しておけば、動力回収タービンによって回収されたエネルギーをそのまま給水ポンプの駆動に利用することが可能になる。
【００１６】
上記のような本発明に係る動力回収方法および装置においては、供給海水の温度が変化しても、供給海水量に対し所定の一定比率の淡水造水量を確保するように、かつ、動力回収タービンの入口側圧力、つまりＲＯ膜の濃縮水側の圧力が一定レベル以上の所定の高圧（たとえば、上記の如く６５ｋｇ／ｃｍ2 ）を維持できるように、透過水側の流量が制御される。換言すれば、透過水側の流量を制御することによって、その流量制御弁部分での圧力損失分も制御されることになり、この圧力損失分が所望の膜間差圧に上乗せされることになって、目標とする高圧のＲＯ膜濃縮水側の圧力（動力回収タービンの入口側圧力）が達成されるのである。すなわち、供給海水の温度が低い場合には、流量制御弁での絞り量を小さくすることによりこの部分での圧力損失が比較的小さく制御され、所定の淡水造水率の条件下において、目標とする比較的大きな膜間差圧が達成されると同時に、濃縮水側の目標とする高圧が維持される。供給海水の温度が高い場合には、流量制御弁での絞り量を大きくすることによりこの部分での圧力損失が比較的大きく制御され、所定の淡水造水率の条件下において、ＲＯ膜の透過水側出口部分（流量制御弁の上流部分）での圧力が比較的高く保たれ、それによって目標とする比較的小さな膜間差圧に維持されつつ、濃縮水側の圧力としては、海水の温度が低い場合と同じ高圧に維持することが可能となる。
【００１７】
したがって、海水温度の変化にかかわらず、濃縮水側の圧力、つまり動力回収タービンの入口側圧力を、従来装置に比べ大幅に高い圧力に設定でき、その高圧回収用の動力回収タービンを濃縮水路に設置することが可能になる。動力回収タービンで回収対象となる高圧水の圧力が高くなる結果、エネルギー回収率が大幅に高められる。
【００１８】
【発明の実施の形態】
以下に、本発明の望ましい実施の形態を、図面を参照しながら説明する。
図１は、本発明の一実施態様に係る逆浸透膜方式海水淡水化装置における動力回収装置を示している。図１において、１はＲＯ膜を模式的に示しており、該ＲＯ膜１は、スパイラル状膜や中空糸膜等の形態でモジュールとして形成され、そのモジュールが複数ＲＯ膜モジュールユニット２として組み込まれている。このＲＯ膜モジュールユニット２の供給水室３（供給水側）に、供給水としての海水が、給水ポンプ４により供給水路５を介して供給される。供給水路５には、流量センサ６と入口調整弁７（主として流量を制御する弁）が設けられており、本実施態様ではさらに、ＲＯ膜モジュールユニット２の入口側圧力を検知する圧力センサ８が設けられている。
【００１９】
ＲＯ膜モジュールユニット２では、供給水室３に供給された高圧の海水のうち、予め定められた所定割合（たとえば、４０％）の量の海水が、ＲＯ膜１を透過され、塩濃度が十分に低い淡水として、透過水室９から取り出される。このように造水された淡水は、透過水路１０を介して取り出されるが、この透過水路１０に、流量センサ１１によって検知される透過水量が、供給海水量に対し上記所定割合となるように制御可能な流量制御弁１２が設けられている。この流量制御弁１２は、本発明においては、同時に、ＲＯ膜１の濃縮水側の圧力を、後述の動力回収タービンに応じた所定の高圧に維持するように制御する。
【００２０】
ＲＯ膜モジュールユニット２の供給水室３からは、濃縮水路１３を介して濃縮水が排出される。この濃縮水路１３に、動力回収タービン１４が設けられている。動力回収タービン１４は、本実施態様では、給水ポンプ４駆動用のモータ１５に機械的に直結されており、回収動力がそのまま給水ポンプ４の駆動用エネルギーとして利用できるようになっている。
【００２１】
なお本実施態様では、上記濃縮水路１３に圧力制御弁１６が設けられており、前述の圧力センサ８からの信号に基づいて、ＲＯ膜モジュールユニット２の入口側圧力を所望の圧力にコントロールできるようになっている。ただし、この圧力制御系は、本発明においては、流量制御弁１２による濃縮水側の圧力制御によって結果的にＲＯ膜モジュールユニット２の入口側圧力も制御されることになるから、省略することも可能である。
【００２２】
上記のように構成された装置は、たとえば次のように運転される。
前述したと同様に、海水温度が１０℃の場合、ＲＯ膜１の膜間差圧として６８ｋｇ／ｃｍ2 （回収率４０％、塩濃度３．５％）、海水温度が３０℃の場合、ＲＯ膜１の膜間差圧として５６ｋｇ／ｃｍ2 （回収率４０％、塩濃度３．５％）にすることを運転の絶対前提条件とすると、かつ、そのときのＲＯ膜モジュールユニット２における、供給水側から濃縮水側へと至るときの圧力低下分を３ｋｇ／ｃｍ2 とすると、流量制御弁１２は、実質的に常時、ＲＯ膜モジュールユニット２への入口圧力が６８ｋｇ／ｃｍ2 となるように、および、動力回収タービン１４の入口側圧力が６５ｋｇ／ｃｍ2 となるように制御される。つまり、とくに海水の温度が上昇した場合のＲＯ膜の膜間差圧の過剰分を調節するように、流量制御弁１２が制御され、ＲＯ膜モジュールユニット２への入口圧力（ＲＯ膜１の供給水側圧力）が最高圧を維持できるように制御される。
【００２３】
このように入口圧力を最高圧、たとえば６８ｋｇ／ｃｍ2 に維持できれば、ＲＯ膜モジュールユニット２での圧力低下分（３ｋｇ／ｃｍ2 ）を考慮すると、動力回収タービン１４の入口圧力（つまり、動力回収タービン１４のエネルギー回収対象となる高圧水の圧力）を６５ｋｇ／ｃｍ2 に設定することが可能となり、この条件で運転を続けることが可能となる。
【００２４】
この状態では、動力回収タービン１４の回収対象圧力が、前述した従来の５３ｋｇ／ｃｍ2 から６５ｋｇ／ｃｍ2 に高められ、エネルギー回収率を約１．２３倍（〔６５ｋｇ／ｃｍ2 〕／〔５３ｋｇ／ｃｍ2 〕）に上げることが可能となる。
【００２５】
上記動力回収タービン１４の入口圧力６５ｋｇ／ｃｍ2 は、海水温度の変化にかかわらず常時維持されることにより、海水温度の変化に起因する、制御すべきＲＯ膜膜間差圧の変動は、全て流量制御弁１２部分で調節される圧力損失分によって吸収されることになる。したがって、動力回収タービン１４部分では、常時高エネルギー回収率が達成される。
【００２６】
なお、上記実施態様では、流量制御弁１２による流量制御系およびそれに伴う濃縮水側の圧力制御系と、圧力制御弁１６によるＲＯ膜モジュールユニット２の入口圧力制御系とが併存されているが、各制御系の応答ゲインの調整により、たとえば流量制御弁１２による制御を主制御とし、圧力制御弁１６による制御を従制御とすることにより、各制御系が干渉し合ってハンチング等を起こすことは防止でき、両制御系の併存により、より正確に目標とする圧力制御が可能となる。
【００２７】
また、上記実施態様の説明では、動力回収タービン１４の入口圧力を６５ｋｇ／ｃｍ2 に設定したが、膜間差圧からして濃縮水側のとり得る圧力の範囲のうちの一定レベル以上の高圧に設定することにより、程度の差こそあれ、エネルギー回収率の向上効果は得られる。
【００２８】
【発明の効果】
以上説明したように、本発明の逆浸透膜方式海水淡水化装置における動力回収方法および装置によれば、逆浸透膜の透過水側の流量を制御して濃縮水側の圧力を一定レベル以上の高圧に制御することにより、動力回収タービンによるエネルギー回収率を大幅に高めることができる。
【図面の簡単な説明】
【図１】本発明の一実施態様に係る逆浸透膜方式海水淡水化装置における動力回収装置の機器系統図である。
【図２】従来の逆浸透膜方式海水淡水化装置における動力回収装置の機器系統図である。
【符号の説明】
１ 逆浸透膜
２ 逆浸透膜モジュールユニット
３ 供給水室
４ 給水ポンプ
５ 供給水路
６ 流量センサ
７ 入口調節弁
８ 圧力センサ
９ 透過水室
１０ 透過水路
１１ 流量センサ
１２ 流量制御弁
１３ 濃縮水路
１４ 動力回収タービン
１５ 給水ポンプ駆動用モータ
１６ 圧力制御弁[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power recovery method and apparatus in which a power recovery turbine is provided on the concentrated water side in a reverse osmosis membrane seawater desalination apparatus so that the energy of the concentrated water can be recovered.
[0002]
[Prior art]
There is known a system that desalinates seawater supplied at a constant rate using an RO membrane module unit having a reverse osmosis membrane (hereinafter also referred to as RO membrane).
[0003]
In this system, as shown in FIG. 2, in order to ensure the transmembrane pressure difference (the pressure difference between the supply water side pressure and the permeate side pressure) that is usually required for desalination at the RO membrane 101. The seawater is supplied to the supply water side of the RO membrane module unit 103 at a relatively high pressure by the water supply pump 102. For example, when the salt concentration of seawater is 3.5%, the operation pressure of the supplied water is about 55 to 70 kg / cm 2 . In addition, an inlet regulating valve 105 is usually provided in the supply water channel 104 in order to supply seawater at a constant flow rate. As for the seawater supplied to the supply water side of the RO membrane 101, a predetermined proportion (for example, 40%) of seawater is permeated to the permeate side by a predetermined transmembrane pressure difference, and fresh water is passed through the permeate channel 106. As taken out. The remaining seawater (for example, seawater in an amount of 60% with respect to the supply water) becomes concentrated water and is discharged through the concentrated water channel 107. This concentrated water is maintained at a high pressure of about 52 to 67 kg / cm 2 , although the pressure is reduced by about 1 to 3 kg / cm 2 in the RO membrane module unit 103. If the high-pressure concentrated water is discharged as it is, there is a large energy loss. Therefore, a power recovery turbine 108 is provided in the concentrated water channel 107, and the power recovery turbine 108 is driven by the concentrated water to recover the energy. The recovered energy is recovered as energy for driving the feed water pump 102 by, for example, mechanically connecting the power recovery turbine 108 to the motor 109 for driving the feed water pump 102 (for example, by directly connecting the power recovery turbine 108). Used.
[0004]
At this time, as will be described later, in the conventional system, in order to maintain the predetermined desalination performance, it is necessary to control the inlet pressure of the RO membrane module unit 103 to a predetermined pressure. Control is performed by a control valve 110 (a valve that controls pressure by reducing pressure) provided in the water channel 107.
[0005]
[Problems to be solved by the invention]
However, the conventional system as described above has the following problems associated with seawater temperature fluctuations.
[0006]
That is, when the seawater temperature changes, the transmembrane pressure difference of the RO membrane fluctuates. In order to desalinate seawater, it is usually required to maintain the recovery rate (the ratio of freshwater freshwater production to the amount of supplied seawater) at a predetermined and constant recovery rate according to the selected RO membrane. Is a precondition that prevails over all operating conditions.
[0007]
When such a recovery rate is assumed as a precondition, when the temperature of seawater fluctuates, for example, by 10 ° C. to 30 ° C. (this range is a generally considered fluctuating range), the transmembrane pressure difference to be maintained Is estimated as follows, for example.
[0008]
That is, when the seawater temperature is 10 ° C., the transmembrane pressure difference of the RO membrane must be, for example, 68 kg / cm 2 (recovery rate 40%, salt concentration 3.5%), and the seawater temperature is 30 ° C. In this case, the transmembrane pressure difference of the RO membrane must be 56 kg / cm 2 (recovery rate 40%, salt concentration 3.5%), for example.
[0009]
Therefore, in order to satisfy the above operating conditions, the specification of the feed water pump 102 needs to have a head for ensuring the necessary transmembrane pressure difference of 68 kg / cm 2 in the case of 10 ° C. seawater. However, if the seawater at 30 ° C. is desalted as it is using such a feed pump 102, the transmembrane differential pressure of the RO membrane 101 must be 56 kg / cm 2. Therefore, the operation is performed by reducing the pressure by the inlet regulating valve 105.
[0010]
In this way, when operating by adjusting the pressure on the supply water side (inlet side) of the RO membrane according to the temperature change of seawater, for example, the operation is performed so that the transmembrane pressure difference is 68 to 56 kg / cm 2 as described above. When considering the pressure drop in the RO membrane module unit 103, for example, considering the pressure drop of about 3 kg / cm 2 , the pressure of the concentrated water channel 107 on the outlet side of the RO membrane module unit 103 is 65 to 53 kg / It will fluctuate in the cm 2 range. When energy stored in the concentrated water is recovered by the power recovery turbine 108 provided in the concentrated water channel 107, it is usually necessary to design the power recovery turbine 108 to have a constant inlet pressure. the pressure of the water channel 107 (i.e., the pressure in the channel leading to the inlet of the power recovery turbine 108) because there is under the condition that varies 65~53kg / cm 2, eventually to recover energy of the pressurized water of 53kg / cm 2 The power recovery turbine 108 is required. That is, it is set to a substantially minimum pressure within a range that can be taken as the inlet pressure of the power recovery turbine 108 (or a range that can be taken as the pressure on the concentrated water side). As a result, the power recovery turbine 108 can recover only the energy of the pressure water of 53 kg / cm 2 while giving a large amount of energy to the supply water by the feed water pump 102, which has a problem that the energy recovery rate is low. It is out.
[0011]
Therefore, the object of the present invention is to focus on the problems caused by the temperature change of the seawater as described above, and to concentrate the water recovered by the power recovery turbine while maintaining a predetermined constant freshwater freshwater ratio with respect to the amount of seawater supplied. It is to greatly increase the energy recovery rate on the water side.
[0012]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the power recovery method in the reverse osmosis membrane method according to the present invention supplies seawater to the supply water side of the reverse osmosis membrane by a feed water pump and takes out fresh water from the permeate side of the reverse osmosis membrane. When the power recovery turbine is installed on the concentrated water side of the reverse osmosis membrane to recover the energy of the concentrated water, the flow on the permeate side is controlled to change the pressure on the concentrated water side and the temperature of the seawater From the supply water side to the concentrated water from the substantially highest pressure within the fluctuation range of the transmembrane differential pressure of the reverse osmosis membrane to achieve a predetermined ratio of the freshwater freshwater production amount to the supply seawater amount. It is controlled to a pressure obtained by subtracting the pressure drop during the period of reaching the side, and is maintained at a high pressure above a certain level within the range that the pressure on the concentrated water side can take.
[0013]
In this method, the same 68~56kg / cm 2 for example, the variation range of the transmembrane pressure of the reverse osmosis membrane with the aforementioned, the pressure drop amount is assumed to be 3 kg / cm 2, the inlet pressure of the power recovery turbine as designed ones 65 kg / cm 2, it is to control the flow rate of the permeate side so as to maintain the pressure.
[0014]
The power recovery device in the reverse osmosis membrane type seawater desalination apparatus according to the present invention includes a reverse osmosis membrane module unit having a reverse osmosis membrane, a supply channel for supplying seawater from a water supply pump to the reverse osmosis membrane module unit, and reverse osmosis A permeated water channel that extracts permeated water from the membrane module unit as fresh water, a concentrated water channel that discharges the concentrated water concentrated by the reverse osmosis membrane module unit, and a power recovery turbine that is provided in the concentrated water channel and collects the energy of the concentrated water A reverse osmosis membrane for achieving a predetermined ratio of freshwater freshwater production to a supply seawater amount when the temperature of the seawater changes, the pressure in the concentrated waterway to the permeate waterway from a substantially maximum pressure of the variation range of the transmembrane pressure and controls the pressure obtained by subtracting a decrement pressure between leading from the feed water side to the concentrated water side, Consisting of those characterized by providing a flow control valve to maintain the target pressure defined order.
[0015]
The energy recovered by the power recovery turbine can be effectively used, for example, in the form of electrical energy. However, the energy recovery turbine is mechanically connected to the feedwater pump drive motor. In this case, the energy recovered by the power recovery turbine can be directly used for driving the feed pump.
[0016]
In the power recovery method and apparatus according to the present invention as described above, even if the temperature of the supplied seawater changes, a power recovery turbine is provided so as to ensure a fresh water production amount of a predetermined constant ratio with respect to the supplied seawater amount. The flow rate on the permeate side is controlled so that the pressure on the inlet side, that is, the pressure on the concentrated water side of the RO membrane, can be maintained at a predetermined high pressure (for example, 65 kg / cm 2 as described above). In other words, by controlling the flow rate on the permeate side, the pressure loss at the flow rate control valve is also controlled, and this pressure loss is added to the desired transmembrane pressure difference. Thus, the target pressure on the high-pressure RO membrane concentrated water side (pressure on the inlet side of the power recovery turbine) is achieved. That is, when the temperature of the supplied seawater is low, the pressure loss in this portion is controlled to be relatively small by reducing the throttle amount at the flow rate control valve, and the target is set under the condition of a predetermined freshwater freshwater production rate. A relatively high transmembrane pressure difference is achieved, and at the same time, the target high pressure on the concentrated water side is maintained. When the temperature of the supplied seawater is high, the pressure loss in this portion is controlled to be relatively large by increasing the throttle amount at the flow control valve, and the permeation of the RO membrane is performed under the condition of a predetermined freshwater freshwater production rate. The pressure at the outlet side of the water (upstream part of the flow control valve) is kept relatively high, thereby maintaining the target relatively small transmembrane pressure difference, while the pressure on the concentrated water side is the seawater temperature. It is possible to maintain the same high pressure as when low.
[0017]
Therefore, the pressure on the concentrated water side, that is, the pressure on the inlet side of the power recovery turbine, can be set to a significantly higher pressure than the conventional system regardless of changes in seawater temperature, and the power recovery turbine for high pressure recovery can be used as a concentrated water channel. It becomes possible to install. As a result of the increased pressure of the high-pressure water to be recovered by the power recovery turbine, the energy recovery rate is greatly increased.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a power recovery apparatus in a reverse osmosis membrane seawater desalination apparatus according to an embodiment of the present invention. In FIG. 1, 1 schematically shows an RO membrane. The RO membrane 1 is formed as a module in the form of a spiral membrane or a hollow fiber membrane, and the module is assembled as a plurality of RO membrane module units 2. ing. Seawater as supply water is supplied to the supply water chamber 3 (supply water side) of the RO membrane module unit 2 through the supply water channel 5 by the water supply pump 4. The supply channel 5 is provided with a flow rate sensor 6 and an inlet adjustment valve 7 (mainly a valve for controlling the flow rate). In this embodiment, a pressure sensor 8 for detecting the pressure on the inlet side of the RO membrane module unit 2 is further provided. Is provided.
[0019]
In the RO membrane module unit 2, a predetermined amount (for example, 40%) of seawater in the high-pressure seawater supplied to the supply water chamber 3 is permeated through the RO membrane 1 and the salt concentration is sufficient. The fresh water is taken out from the permeate water chamber 9. The fresh water produced in this way is taken out through the permeate water channel 10, and the permeate water amount detected by the flow sensor 11 is controlled in the permeate water channel 10 so as to be the above-mentioned predetermined ratio with respect to the supplied seawater amount. A possible flow control valve 12 is provided. In the present invention, the flow rate control valve 12 simultaneously controls the pressure on the concentrated water side of the RO membrane 1 to maintain a predetermined high pressure corresponding to a power recovery turbine described later.
[0020]
Concentrated water is discharged from the supply water chamber 3 of the RO membrane module unit 2 through the concentrated water channel 13. A power recovery turbine 14 is provided in the concentrated water channel 13. In this embodiment, the power recovery turbine 14 is mechanically directly connected to the motor 15 for driving the feed water pump 4, and the recovered power can be used as it is as driving energy for the feed water pump 4.
[0021]
In this embodiment, a pressure control valve 16 is provided in the concentrated water channel 13 so that the inlet side pressure of the RO membrane module unit 2 can be controlled to a desired pressure based on the signal from the pressure sensor 8 described above. It has become. However, in the present invention, this pressure control system may be omitted because the pressure on the concentrated water side by the flow rate control valve 12 will eventually control the inlet side pressure of the RO membrane module unit 2. Is possible.
[0022]
The apparatus configured as described above is operated as follows, for example.
As described above, when the seawater temperature is 10 ° C., the transmembrane pressure difference of the RO membrane 1 is 68 kg / cm 2 (recovery rate 40%, salt concentration 3.5%), and the seawater temperature is 30 ° C. Assuming that the transmembrane differential pressure of the membrane 1 is 56 kg / cm 2 (recovery rate 40%, salt concentration 3.5%) is an absolute prerequisite for operation, and supply in the RO membrane module unit 2 at that time Assuming that the pressure drop when going from the water side to the concentrated water side is 3 kg / cm 2 , the flow rate control valve 12 substantially always has the inlet pressure to the RO membrane module unit 2 of 68 kg / cm 2. In addition, the pressure on the inlet side of the power recovery turbine 14 is controlled to be 65 kg / cm 2 . That is, the flow rate control valve 12 is controlled so as to adjust the excess of the transmembrane pressure difference of the RO membrane particularly when the seawater temperature rises, and the inlet pressure to the RO membrane module unit 2 (supply of the RO membrane 1) The water pressure is controlled so that the maximum pressure can be maintained.
[0023]
If the inlet pressure can be maintained at the maximum pressure, for example, 68 kg / cm 2 , the inlet pressure (that is, power recovery) of the power recovery turbine 14 is taken into consideration when the pressure drop (3 kg / cm 2 ) in the RO membrane module unit 2 is taken into consideration. It is possible to set the pressure of the high-pressure water that is the energy recovery target of the turbine 14) to 65 kg / cm 2 , and it is possible to continue operation under this condition.
[0024]
In this state, the recovery target pressure of the power recovery turbine 14, is increased from conventional 53kg / cm 2 mentioned above to 65 kg / cm 2, about 1.23 times the energy recovery rate ([65 kg / cm 2] / [53kg / Cm 2 ]).
[0025]
Since the inlet pressure 65 kg / cm 2 of the power recovery turbine 14 is constantly maintained regardless of the change in the seawater temperature, all fluctuations in the RO transmembrane differential pressure to be controlled due to the change in the seawater temperature are all It is absorbed by the pressure loss adjusted by the flow control valve 12 portion. Therefore, a high energy recovery rate is always achieved in the power recovery turbine 14 portion.
[0026]
In the above embodiment, the flow rate control system by the flow rate control valve 12 and the accompanying pressure control system on the concentrated water side and the inlet pressure control system of the RO membrane module unit 2 by the pressure control valve 16 coexist, By adjusting the response gain of each control system, for example, the control by the flow control valve 12 is set as the main control, and the control by the pressure control valve 16 is set as the sub control, so that the control systems interfere with each other to cause hunting or the like. It can be prevented, and the coexistence of both control systems enables more accurate target pressure control.
[0027]
In the description of the above embodiment, the inlet pressure of the power recovery turbine 14 is set to 65 kg / cm 2 , but the high pressure is higher than a certain level in the range of pressure that can be taken on the concentrated water side from the transmembrane pressure difference. By setting to, the effect of improving the energy recovery rate can be obtained to some extent.
[0028]
【The invention's effect】
As described above, according to the power recovery method and apparatus in the reverse osmosis membrane seawater desalination apparatus of the present invention, the flow rate on the permeate side of the reverse osmosis membrane is controlled so that the pressure on the concentrated water side exceeds a certain level. By controlling to a high pressure, the energy recovery rate by the power recovery turbine can be significantly increased.
[Brief description of the drawings]
FIG. 1 is an equipment system diagram of a power recovery device in a reverse osmosis membrane seawater desalination apparatus according to an embodiment of the present invention.
FIG. 2 is a system diagram of a power recovery device in a conventional reverse osmosis membrane seawater desalination apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Reverse osmosis membrane 2 Reverse osmosis membrane module unit 3 Feed water chamber 4 Feed water pump 5 Feed water channel 6 Flow sensor 7 Inlet control valve 8 Pressure sensor 9 Permeate water chamber 10 Permeate water channel 11 Flow sensor 12 Flow control valve 13 Concentrated water channel 14 Power recovery Turbine 15 Water supply pump drive motor 16 Pressure control valve

Claims (4)

逆浸透膜の供給水側に給水ポンプにより海水を供給し、逆浸透膜の透過水側から淡水を取り出すとともに、逆浸透膜の濃縮水側に動力回収タービンを設けて濃縮水が有するエネルギーを回収するに際し、透過水側の流量を制御することにより、濃縮水側の圧力を、海水の温度が変化した場合に供給海水量に対し予め定められた所定の淡水造水量の割合を達成するための逆浸透膜の膜間差圧の変動範囲のうちの実質的に最高の圧力から、供給水側から濃縮水側に至る間の圧力低下分を差し引いた圧力に制御して、該濃縮水側の圧力がとり得る範囲内のうちの一定レベル以上の高圧に維持することを特徴とする、逆浸透膜方式海水淡水化装置における動力回収方法。Seawater is supplied to the supply water side of the reverse osmosis membrane by a feed pump, fresh water is taken out from the permeate side of the reverse osmosis membrane, and a power recovery turbine is provided on the concentrated water side of the reverse osmosis membrane to recover the energy of the concentrated water In this case, by controlling the flow rate on the permeated water side, the pressure on the concentrated water side is set to achieve a predetermined ratio of freshwater freshwater production to a predetermined amount of supplied seawater when the temperature of the seawater changes. By controlling to a pressure obtained by subtracting the pressure drop from the supply water side to the concentrated water side from the substantially highest pressure in the fluctuation range of the transmembrane differential pressure of the reverse osmosis membrane , A power recovery method in a reverse osmosis membrane type seawater desalination apparatus, characterized in that the pressure is maintained at a high pressure above a certain level within a possible range of pressure. 逆浸透膜の供給水側の圧力を、濃縮水の動力回収タービン前での減圧制御によって制御する、請求項１の逆浸透膜方式海水淡水化装置における動力回収方法。The pressure of the feed water side of the reverse osmosis membrane, is controlled by vacuum control before power recovery turbine concentrated water, power recovery method in the reverse osmosis membrane method desalination apparatus according to claim 1. 逆浸透膜を有する逆浸透膜モジュールユニットと、逆浸透膜モジュールユニットに給水ポンプからの海水を供給する供給水路と、逆浸透膜モジュールユニットからの透過水を淡水として取り出す透過水路と、逆浸透膜モジュールユニットで濃縮された濃縮水を排出する濃縮水路と、濃縮水路に設けられ、濃縮水が有するエネルギーを回収する動力回収タービンとを備えた装置において、透過水路に、濃縮水路における圧力を、海水の温度が変化した場合に供給海水量に対し予め定められた所定の淡水造水量の割合を達成するための逆浸透膜の膜間差圧の変動範囲のうちの実質的に最高の圧力から、供給水側から濃縮水側に至る間の圧力低下分を差し引いた圧力に制御して、予め定められた目標圧力に維持する流量制御弁を設けたことを特徴とする、逆浸透膜方式海水淡水化装置における動力回収装置。A reverse osmosis membrane module unit having a reverse osmosis membrane, a supply water channel for supplying seawater from a water supply pump to the reverse osmosis membrane module unit, a permeate water channel for taking out permeate from the reverse osmosis membrane module unit as fresh water, and a reverse osmosis membrane and concentrated water path for discharging the concentrated water which has been concentrated in the module unit, provided to the concentrated water path, the device including a power recovery turbine to recover energy concentrated water has, the transmission waterways, the pressure in the concentration waterways, sea water From the substantially highest pressure in the fluctuation range of the transmembrane differential pressure of the reverse osmosis membrane to achieve a predetermined ratio of the freshwater freshwater production amount to the supply seawater amount when the temperature of by controlling the pressure obtained by subtracting a decrement pressure during the supply water side leads to the concentrated water side, and characterized in that a flow control valve to maintain the target pressure predetermined That, power recovery device in the reverse osmosis membrane method desalination equipment. 給水ポンプ駆動用モータに動力回収タービンが機械的に連結されている、請求項３の逆浸透膜方式海水淡水化装置における動力回収装置。The power recovery apparatus in the reverse osmosis membrane type seawater desalination apparatus according to claim 3 , wherein a power recovery turbine is mechanically connected to a water pump driving motor.
JP23057399A 1999-08-17 1999-08-17 Power recovery method and apparatus for reverse osmosis membrane seawater desalination equipment Expired - Fee Related JP4341865B2 (en)

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