JP4186708B2

JP4186708B2 - Humidifier for fuel cell

Info

Publication number: JP4186708B2
Application number: JP2003148887A
Authority: JP
Inventors: 望谷原; 利宗吉永
Original assignee: Ube Industries Ltd
Current assignee: Ube Corp
Priority date: 2002-05-31
Filing date: 2003-05-27
Publication date: 2008-11-26
Anticipated expiration: 2023-05-27
Also published as: JP2004055534A

Description

【０００１】
【発明の属する技術分野】
本発明は、燃料電池の供給ガスを加湿するために好適な、中空糸膜を用いた加湿装置に関する。本発明の燃料電池用加湿装置は、圧力損失を抑制しながら高効率で加湿することが可能であり、水蒸気以外の他成分は透過が抑制され、経済的である。特に、燃料電池から排出された排ガスから水分を回収して燃料電池へ供給される供給ガスを加湿するのに好適な加湿装置である。
【０００２】
【従来の技術】
近年、電気自動車や静置型小型発電装置としてパーフルオロカーボンスルホン酸膜のような固体高分子膜を電解質膜として用いた燃料電池が注目されている。このような固体高分子は含水状態ではプロトン導電性電解質として機能するが、乾燥状態ではプロトン導電性が低下するとともに固体高分子電解質膜と電極との接触不良がおこって出力が急激に低下する。このため、固体高分子型燃料電池システムでは、固体高分子電解質膜が一定の湿度を保つように、供給ガスを加湿して供給している。このため、供給ガスを加湿するための加湿装置が種々検討されている。
特開平６−１３２０３８号公報には、水蒸気透過膜を用いて、燃料電池から排出される排気ガスを加湿用ガスとして燃料電池へ供給する供給ガスを加湿することが開示されている。
特開平８−２７３６８７号公報には、中空糸膜を用いた加湿装置で、燃料電池の供給ガスを加湿することが開示されている。
【０００３】
燃料電池用加湿装置には、燃料電池の運転温度である８０℃程度の温度や水蒸気、酸素、及び、水素などが存在する雰囲気中に長期間暴露されても安定して加湿することができること、低圧ガスを用いても効率よく加湿できること、ガスの圧力損失が抑制されること、水蒸気以外の他成分の透過が抑制できることなどが要求されている。
しかしながら、例えば、特開２００１−３５１６６０号公報では、中空糸水透過膜型加湿装置に加えて凝縮器と水噴射弁からなる補助加湿手段を備えることが提案されている。この提案は、低圧運転で加湿量を増やすためにスケールアップすると圧力損失が増大するので中空糸水透過膜型加湿装置の採用には限界があるという問題を解決るためであった。
このように、中空糸膜を用いた燃料電池用加湿装置には改良すべき余地があった。
【０００４】
本発明の発明者を含む発明者らは、米国特許第６４６４７５５号公報において、高い水蒸気透過速度と、実用的な機械的強度と、更に優れた耐水性及び耐熱水性を併せ持った非対称中空糸ガス分離膜を開示し、この非対称中空糸膜ガス分離膜が燃料電池の供給ガスを加湿するために用いることができる可能性について言及している。しかし、米国特許第６４６４７５５号公報は、本発明のように、中空糸ガス分離膜を燃料電池用加湿装置に適用する場合に有用なパラメータを具体的に検討して開示するものではない。
また、特開２００２−２１９３３９号公報は中空糸膜を用いた加湿モジュールにおいて、中空糸膜束が充填された領域に最短長さＬと当該領域に結ばれる対角線の長さＡとのとの比Ｌ／Ａ、又は中空糸膜束が充填された領域の中空糸膜束の高さＤと当該領域に結ばれる最短長さＬとの比Ｄ／Ｌが特定範囲内であれば、筒状ハウジング内の各中空糸膜の外面に乾燥ガスを均一に行き渡らせられるので、加湿器の加湿能力が向上することを開示している。しかし、特開２００２−２１９３３９号公報は本発明のように加湿モジュールにおける中空糸膜の圧力損失の問題の解決法を開示するものではない。
【０００５】
【特許文献１】
特開平６−１３２０３８号
【特許文献２】
特開平８−２７３６８７号
【特許文献３】
特開２００１−３５１６６０号
【特許文献４】
米国特許第６４６４７５５号
【特許文献５】
特開２００２−２１９３３９号
【０００６】
【発明が解決しようとする課題】
本発明は、燃料電池の運転温度である８０℃程度の温度や水蒸気、酸素、及び、水素などが存在する雰囲気中に長期間暴露されても安定して加湿することができ、低圧ガスを用いてもガスの圧力損失を抑制しながら加湿効率を高くすることができ、水蒸気以外の他成分の透過が抑制され、しかも、経済的な燃料電池用に好適に用いることができる加湿装置を提供することを目的とする。
【０００７】
【課題を解決するための手段】
本発明は、多数本の中空糸膜からなる中空糸膜束の両端部に中空糸膜を開口状態で固着した管板が形成された中空糸膜エレメントを、少なくとも第１のガス供給口、第１のガス排出口、第２のガス供給口、及び、第２のガス排出口を有する容器内に、中空糸膜の中空側へ通じる空間と中空糸膜の外側へ通じる空間とが隔絶するように装着して構成された燃料電池用加湿装置において、
（ａ）中空糸膜の内径が４００μｍ以上、好適には５００μｍ超〜１５００μｍ未満である
（ｂ）中空糸膜の水蒸気透過速度（Ｐ’_Ｈ２Ｏ）が０．５×１０^-3ｃｍ³（ＳＴＰ）／ｃｍ²・ｓｅｃ・ｃｍＨｇ以上である
（ｃ）中空糸膜の水蒸気と酸素ガスとの透過速度比（Ｐ’_H2O／Ｐ’_O2）が１０以上である
（ｄ）中空糸膜が１００℃の熱水中で５０時間熱水処理した後の引張破断伸度が熱水処理前の８０％以上を保持することを特徴とする燃料電池用加湿装置に関し、特に、中空糸膜エレメントの有効長をＬ、前記中空糸膜エレメントを装着する容器の内径をＤとするとき、Ｌ／Ｄが１．８以上である燃料電池用加湿装置に関する。
更に、中空糸膜エレメントを構成する中空糸膜束の膜充填率が３５〜５５％であること、中空糸膜エレメントを構成する中空糸膜束の外周部の５０％以上がフィルム状物質で被覆されていること、中空糸膜の中空側を流れる第１のガスと、中空糸膜の外側の空間を流れる第２のガスとが、中空糸膜を挟んで向流に流れること、中空糸膜エレメントを構成する中空糸膜束の略中心部に中空糸膜束に沿って配した芯管を設け、前記芯管には芯管内と芯管外とを連通する連通孔を形成しており、第２のガスが第２のガスの供給口から前記芯管内へ導かれ前記連通孔を通じて中空糸膜の外側の空間へ導入されるように構成されたことに関する。
また、燃料電池への供給ガスが加湿されるように構成されたこと、第１のガスが燃料電池のカソードからの排ガスであり、第２のガスが燃料電池のカソードへ供給される空気であるように構成された燃料電池用加湿装置に関する。
【０００８】
【発明の実施の形態】
本発明の燃料電池用加湿装置は、多数本の中空糸膜からなる中空糸膜束の両端部に中空糸膜を開口状態で固着した管板が形成された中空糸膜エレメントを、少なくとも第１のガス供給口、第１のガス排出口、第２のガス供給口、及び、第２のガス排出口を有する容器内に、中空糸膜の中空側へ通じる空間と中空糸膜の外側へ通じる空間とが隔絶するように装着して構成されている。
本発明の加湿装置を構成する中空糸膜エレメントの一例の概略の縦断面図を図１に示す。多数本（通常は数十本から数十万本）の中空糸膜１が略平行に束ねられて中空糸膜束を形成している。その中空糸膜束の両端部は、例えばポリオレフィンなどの熱可塑性樹脂やエポキシ樹脂などの硬化性樹脂からなる管板２、２’によって両端面で中空糸膜が開口状態を保持するように固着されて中空糸膜エレメント３を構成している。尚、中空糸膜は１〜１００本毎に中空糸膜束の軸方向に対して３０°以下の低角度で交互に交叉配列されたいわゆる綾織の状態で、中空糸膜束全体としては略平行に集束されていることが望ましい。
図２は、本発明の燃料電池用加湿装置の一例の概略の縦断面図である。前記中空糸膜エレメント３の少なくとも一つが、少なくとも第１のガス供給口４、第１のガス排出口５、第２のガス供給口６、及び、第２のガス排出口７を備えた容器８内に、中空糸膜の中空側へ通じる空間と中空糸膜の外側へ通じる空間とが隔絶するように装着されている。
すなわち、管板によって容器内の空間が間仕切りされており、容器内の２つの管板２、２’の間の空間は各中空糸膜の中空側の空間と中空糸膜の外側の空間とに分けられている。第１のガスの供給口４から供給された第１のガスは管板２端面の中空糸膜の開口から中空糸膜の中空側に導入され、中空糸膜の中空側を流れ、反対側の管板２’端面の中空糸膜の開口から流れ出し、第１のガスの排出口５から排出される。一方、第２のガスの供給口６から供給された第２のガスは中空糸膜の外側の空間を流れて、第２の排出口７から排出される。この間、それぞれのガスは中空糸膜の内外の表面に接触して流れるので、水蒸気分圧が高いガス側の水蒸気が、水蒸気分圧が低いガス側へ中空糸膜を選択的に透過することによって加湿がおこなわれる。
尚、図２中の矢印は、ガスの流れの方向を示している。
【０００９】
固体高分子型燃料電池に供給するガスや排出されるガスの圧力は、その燃料電池の使用条件によって決まるが、概ね１気圧から３気圧程度（ゲージ圧で０〜２気圧）の低圧である。燃料電池のカソードで発生する水分を多量に含むカソードの排出ガスを加湿ガスとして、カソードへ供給される空気を加湿するような場合を考えれば明らかであるが、燃料電池用加湿装置では、低圧のガスを低圧のガスで加湿することができ且つガスを加圧するための動力を極力低減させるために、圧力損失が極めて低レベルに抑制されねばならない。
加湿装置の圧力損失は、ガスが中空糸膜の中空側を流れるときとガスが中空糸膜の外側の空間を流れるときに主に発生する。
中空糸膜の中空側を通過するガスの圧力損失を抑制するための方法として、中空糸膜を短くする方法が考えられる。しかし、短い中空糸膜を用いると、中空糸膜の両端部の管板に包埋されて加湿に用いることができない膜面積の割合が大きくなって経済的な加湿装置を得るのが難しくなる。しかも、中空糸膜を短くして同等の加湿量を得ようとすると、より多数本の中空糸膜が必要になるので、以下で述べるように、中空糸膜エレメントの有効長をＬ、前記中空糸膜エレメントを装着する容器の内径をＤとするとき、Ｌ／Ｄが小さくなることにより、中空糸膜の外側の空間でガスの流れが偏流を起こして加湿効率が低くなる。
【００１０】
本発明の加湿装置で用いる中空糸分離膜の内径の好ましい下限値は５００μｍ超であり、また内径の好ましい上限値は１５００μｍ未満、特に８００μｍ未満である。中空糸分離膜の内径は典型的には５００μｍ超〜１５００μｍ未満の範囲内が好ましい。
中空糸膜の内径が５００μｍ超であれば、内径の数百倍以上の長さの中空糸膜を用いても圧力損失を極めて低レベルに抑制できる。このため、管板によって加湿に用いることができなくなる膜面積の割合が小さくなって経済的な加湿装置が可能になる。更に、以下で述べるように、中空糸膜エレメントの有効長をＬ、前記中空糸膜エレメントを装着する容器の内径をＤとするとき、Ｌ／Ｄを一定以上の大きさにすることができるので加湿効率を高くすることが可能になる。
一方、中空糸膜の内径が１５００μｍ以上になると、所定の容積内に装着できる中空糸膜の本数が制限されて有効膜面積が少なくなって加湿効率を高めることが難しくなるし、さもなくば、装置を大型にする必要が生じるので好ましくない。しかも、中空糸膜の内径が１５００μｍ以上になると、中空糸膜が変形し易くなり中空糸膜の製造が難しくなる。中空糸膜の強度を高めるために膜厚を大きくすると水蒸気透過速度が小さくなるので加湿効率が高い加湿装置を得るのは難しい。
【００１１】
本発明の加湿装置に用いられる中空糸膜の水蒸気透過速度（Ｐ’_Ｈ２Ｏ）は、８０℃の温度において、０．５×１０^-3ｃｍ³（ＳＴＰ）／ｃｍ²・ｓｅｃ・ｃｍＨｇ以上、好ましくは２．０×１０^-3ｃｍ³（ＳＴＰ）／ｃｍ²・ｓｅｃ・ｃｍＨｇ以上であり、また、水蒸気と酸素ガスとの透過速度比（Ｐ’_H2O／Ｐ’_O2）は、８０℃の温度において、１０以上、好ましくは１００以上である。
中空糸膜の水蒸気透過速度（Ｐ’_Ｈ２Ｏ）が０．５×１０^-3ｃｍ³（ＳＴＰ）／ｃｍ²・ｓｅｃ・ｃｍＨｇ未満では、十分な加湿量が得られないし、同じ加湿量を得るためには中空糸膜を余計に用いる必要が生じるので好ましくない。また、水蒸気と酸素ガスとの透過速度比（Ｐ’_H2O／Ｐ’_O2）が１０未満では、水蒸気以外のガス成分が中空糸膜を透過し易くなるので好ましくない。例えば、カソードへ供給される空気をカソードからの排出ガスで加湿するとき、排出ガスの酸素ガス分圧が空気の酸素ガス分圧よりも小さくなって酸素ガスが空気から排出ガス側へ透過する可能性がある。その場合に、水蒸気と酸素ガスとの透過速度比（Ｐ’_H2O／Ｐ’_O2）が１０未満では、多量の酸素ガスが透過して供給する空気中の酸素ガス濃度が減少し燃料電池の出力が低下するので好ましくない。
【００１２】
さらに、本発明の加湿装置に用いられる中空糸分離膜は、１００℃の熱水中で５０時間熱処理した後の引張破断伸度が熱水処理前の引張破断伸度の８０％以上、好ましくは９０％以上を保持することができる耐熱水性を有する。固体高分子膜型燃料電池のスタックは約８０℃程度の温度で使用されるため、加湿装置も同程度の温度で運転されることになる。従って、中空糸膜は８０℃程度の温度条件で水蒸気を多量に含んだガスと絶えず接触する。１００℃の熱水中で５０時間熱処理した後でも熱処理前の引張破断伸度の８０％以上の引張破断伸度を保持できる中空糸膜は、１００℃の熱水によっても加水分解しないものであるから、長期間に亘って信頼性よく加湿に用いることができる。
【００１３】
本発明の加湿装置に用いられる中空糸分離膜は、多孔性膜でも非多孔性の膜でも構わないが、多孔性膜では水蒸気以外の成分が供給ガスへ混入し易いなどの問題があるため、非多孔性膜が好ましい。特に、非対称の非多孔性膜が水蒸気透過速度が高くなるので好ましい。膜の材質は、８０℃程度の高温で水蒸気や酸素ガスなどに接触する使用条件から、耐熱性、耐薬品性、耐久性、及び、耐加水分解性の優れた材料が好ましい。
多孔性膜では、例えば、スルホン酸基を有するパーフルオロカーボン樹脂、ポリエチレン樹脂、ポリプロピレン樹脂、ポリフッ化ビニリデン樹脂、ポリ四フッ化エチレン樹脂、ポリスルホン樹脂、ポリエーテルスルホン樹脂、ポリアミド樹脂、ポリアミドイミド樹脂、ポリエーテルイミド樹脂、ポリカーボネート樹脂、セルロース誘導体樹脂などを好適に挙げることができる。
非多孔性膜では、例えば、ポリイミド樹脂、ポリスルホン樹脂、スルホン酸基を有するパーフルオロカーボン樹脂、ポリエーテルスルホン樹脂、ポリアミド樹脂、ポリアミドイミド樹脂、ポリエーテルイミド樹脂、ポリカーボネート樹脂、ポリフェニレンオキサイド樹脂、ポリアセチレン樹脂、セルロース誘導体樹脂などを好適に挙げることができる。
本発明の燃料電池用加湿装置に用いる中空糸膜としては、芳香族ポリイミドからなる非対称中空糸膜が特に好ましい。芳香族ポリイミドからなる非対称中空糸膜は、例えば、本発明の発明者を含む発明者の米国特許第６４６４７５５号公報に詳細に記載されているように、耐熱性や耐久性が優れており、水蒸気透過速度が高く、水蒸気の選択透過性が高く、耐熱水性の優れたものを製造することができるので、極めて高効率で高信頼性の加湿装置を得ることができる。
【００１４】
本発明の加湿装置に用いることができる非対称中空糸分離膜は、前記の樹脂を溶解したポリマー溶液を用いて、Ｌｏｅｂらが（例えば、米国特許第３１３３１３２号で）提案した方法、即ち、ポリマー溶液をノズルから押出して目的形状物とし空気又は窒素雰囲気空間を通過させた後で凝固浴に浸漬する、いわゆる乾湿式法により容易に製造することができる。
【００１５】
また、本発明の加湿装置に用いられる中空糸分離膜は、１つの好ましい態様において、米国特許第６４６４７５５公報に開示されているように、スキン層（分離層）と多孔質層（支持層）とから構成される非対称構造を有し、多孔質層のガス透過速度がヘリウムガスの透過速度（Ｐ’_Ｈｅ）で２．５×１０^−３ｃｍ^３（ＳＴＰ）／ｃｍ^２・ｓｅｃ・ｃｍＨｇ以上、より好ましくは３．０×１０^−３ｃｍ^３（ＳＴＰ）／ｃｍ^２・ｓｅｃ・ｃｍＨｇ以上であり、また中空糸膜での引張強度が２．５ｋｇｆ／ｍｍ^２以上、より好ましくは３．０ｋｇｆ／ｍｍ^２以上、破断伸度は１０％以上、より好ましくは１５％以上であることが好ましい。
中空糸分離膜の多孔質層（支持層）のヘリウム透過速度（Ｐ’_Ｈｅ）は膜の多孔質層（支持層）のガス透過抵抗を示すもの（但し、値が大きい方が抵抗が小さい）であり、次のような測定方法で測定した値である。即ち、非対称中空糸膜を酸素プラズマ処理によって表面のスキン層を削り、ヘリウムガスと窒素ガスとの透過速度比が実質的に均質膜の透過速度比とは認められない領域に到達したときのヘリウムガスの透過速度（Ｐ’_Ｈｅ）である。具体的には、プラズマ処理前のヘリウムと窒素の透過速度比（Ｐ’_Ｈｅ／Ｐ’_Ｎ２）が２０以上の膜をプラズマ処理して、前記透過速度比（Ｐ’_Ｈｅ／Ｐ’_Ｎ２）が１．２以下になったときのヘリウムガスの透過速度である。
【００１６】
また、中空糸分離膜の機械的強度は、中空糸膜の引張試験における引張強度と破断伸度で表している。これらは温度２３℃にて引張試験機を用いて試料（中空糸膜）の有効長２０ｍｍ、引張速度１０ｍｍ／分で測定した値である。引張強度は中空糸膜の引張破断時の応力を中空糸の膜断面積で除した値［単位：ｋｇｆ／ｍｍ^２］であり、破断伸度は中空糸膜の元の長さをＬ_０、引張破断時の長さをＬとしたときの（Ｌ_０−Ｌ））／Ｌ_０×１００［単位：％］である。
中空糸膜の引張強度は好ましくは２．５ｋｇｆ／ｍｍ^２以上、破断伸度は好ましくは１０％以上である。このような機械的強度を持った中空糸膜は、容易に破損や破断することなく取扱うことができ、更に、優れた耐圧性や耐久性を持つので特に有用である。
上記のような多孔質層のヘリウムガスの透過速度（Ｐ’_Ｈｅ）、中空糸膜の引張強度及び破断伸度を満たす非対称中空糸分離膜の製法は米国特許第６４６４７５５公報に開示されている。（その記載は参照して本発明に含める。）
【００１７】
本発明の加湿装置に用いることができる非対称中空糸分離膜の膜厚は、通常、スキン層が１０〜２００ｎｍ好ましくは２０〜１００ｎｍであり、多孔質層が２０〜２００μｍ好ましくは３０〜１００μｍである。
【００１８】
本発明の加湿装置において、中空糸膜エレメントの有効長をＬ、中空糸膜エレメントを装着する容器の内径をＤとするとき、Ｌ／Ｄが２〜６であるように構成することが、加湿効率を高くできるので好適である。
容器内に中空糸膜エレメントを装着した一例の概略の縦断面図である図３中に記載してＬおよびＤを示した。尚、図３中の矢印は、ガスの流れの方向を示している。
中空糸膜エレメントの有効長Ｌとは、中空糸膜束の両端部に形成された管板を除いた実際に水蒸気透過に寄与する部分の長さであり、容器の内径Ｄとは、中空糸膜エレメントが装着された容器の中空糸膜束の長手方向に対し垂直な断面の径である。容器が円筒状の場合は、Ｄは円筒の円断面の直径である。通常、この容器は円筒状である。この容器が直方体状であるような場合は、容器の中空糸膜束の長手方向に対し垂直な断面の面積と同じ面積を有する円の直径とする。容器の内径Ｄは、中空糸膜の外側の空間へ導入された第２のガスが、中空糸膜の外側の空間内を流れるときの広がりの程度を示す。
Ｌ／Ｄが１．８以下になると、中空糸膜エレメントの長さが相対的に短いので中空糸膜の中空側を流れる第１のガスの圧力損失を低く抑制するのは容易である。しかし、一方で、中空糸エレメントの有効長に較べて中空糸膜の外側の空間を流れる第２流のガスの広がりの程度が相対的に大きくなるので、前記第２のガス流が中空糸膜の長手方向に流れないで中空糸膜を横切る方向に流れる程度が大きくなる。すなわち、中空糸膜の加湿能力を最大限に発揮させる中空糸膜に沿ったピストンフローから逸脱し、ショートパス流や偏流つまりガス流速の速いところと遅いところが生じる。ショートパス流や偏流が起ると加湿効率が低下するので好ましくない。
Ｌ／Ｄが６を越えると、中空糸膜エレメントの長さが相対的に長いので中空糸膜の中空側を流れる第１のガスの圧力損失を低く抑制するのが困難になる。
尚、用いられた中空糸膜エレメントが、中空糸膜束の外周部をフィルム状物質で被覆して中空糸膜の外側の空間を流れる第２流のガスの広がりの程度が抑制されたものであるときには、Ｄは容器の内径ではなくフィルム状物質で囲まれた空間の内径を意味する。
【００１９】
本発明の加湿装置において、中空糸膜エレメントを構成する中空糸膜束の膜充填率、即ち、中空糸膜エレメントを構成する中空糸膜束の長手方向に垂直な断面積に対する前記中空糸膜束を構成している各中空糸膜の長手方向に垂直な断面積の総和の割合は、３５〜５５％、特に３５〜４５％が好適である。
前記中空糸膜束の膜充填率は、中空糸膜束の長手方向に垂直な断面積における、中空糸膜が占める面積の割合を示し、１００（％）から膜充填率（％）を引いた値（％）は中空糸膜束における中空糸膜の外側の空間の割合を示している。
膜充填率が３５％未満では、中空糸膜束を構成する中空糸膜が少なすぎて効率的な加湿が難しい。かつ、局所的に膜充填率の大きな部分と小さな部分ができ易くなり、ショートパス流や偏流の原因になる。また、膜充填率が４５％特に５５％を越えると、中空糸膜束の中空糸膜の外側の空間が小さくなり、シートパスや偏流の原因になるし、また中空糸膜の外側の空間を流れる第２のガス流の圧力損失を抑制することが困難になる。
【００２０】
本発明の加湿装置において、中空糸膜エレメントの加湿に有効な部分の中空糸膜束の外周部の５０％以上、特に８０％〜９５％程度が、フィルム状物質で被覆されていることが好ましい。
容器内に中空糸膜エレメントが装着されたとき、中空糸膜束の外周部と容器内壁面との間に空間が生じることがある。この空間には中空糸膜の外側の空間に導入された第２のガスが流れるが、この空間を流れる第２のガスは中空糸膜と触れることががないから、水蒸気透過に関しては全く寄与できない流れになる。本発明の加湿装置における中空糸膜束の外周部を被覆するフィルム状物質は、前述の水蒸気透過に対して全く寄与のないガス流を防ぐために設けられるものである。
このフィルム状物質は、容器に設けられた第１のガスの供給口、第１のガスの排出口、第２のガスの供給口、第２のガスの排出口から出入りするガス流を妨げないように配置される。
このフィルム状物質は、装置内に導入されたガスを実質的に透過しないか、難透過性であり、８０℃程度の温度及び水分や酸素ガスが存在する雰囲気中で耐久性があればいかなる材料で形成されても構わないが、例えば、ポリプロピレン、ポリエステル、ポリイミドなどのプラスチック材料や、アルミニウムやステンレスのフィルムを好適に使用できる。フィルム厚も特に限定されないが、数１０μｍ〜数ｍｍ程度までが好適である。
【００２１】
本発明の加湿装置においては、中空糸膜内を流れる第１のガス流と、中空糸膜の外側の空間を流れる第２のガス流とが向流に流れるように構成されることが好適である。
これらのガス流のうち、一方が水蒸気の含有量が高い状態で供給される加湿用のガスであり、他方が水蒸気の含有量が低い状態で供給される被加湿ガスである。水蒸気が膜を透過するドライビングフォースは通常膜を挟んだ２つのガスの膜表面近傍における水蒸気分圧の差である。従って、加湿用ガスを加圧し被加湿ガスを減圧にすれば、非常に大きな水蒸気の透過量を達成できる。しかしながら、燃料電池に供給するガスや燃料電池から排出されるガスの圧力は、その燃料電池の使用条件によって決まっており、特に１気圧から３気圧程度（ゲージ圧で０〜２気圧）の低圧であるので、加湿用ガスの圧力を高めることによって水蒸気透過の効率を高めることには限界がある。
特にこのような条件下では以下の理由により向流が最適である。
すなわち、水蒸気が膜を透過すると、透過側の膜表面近傍の水蒸気分圧が上昇するので、続いて起るはずの水蒸気の膜透過のドライビングフォースが弱まる。この透過側の膜表面近傍の水蒸気分圧が上昇したガスを水蒸気分圧が低い被加湿ガスで置換すると、水蒸気が膜を透過するドライビングフォースが弱まることはない。
中空糸膜の内側と中空糸膜の外側の空間を流れるガス流が向流になるように構成すると、透過側の膜表面近傍の水蒸気分圧が上昇したガスを水蒸気分圧が低い被加湿ガスで連続的に置換することができ、しかも、水蒸気が透過して水蒸気分圧が低下した加湿用ガスが流れるところの膜の透過側をまだ加湿されていない水蒸気分圧が低い被加湿ガスが流れるようになるので中空糸膜全長にわたって水蒸気を透過させることができるようになり、加湿効率を高めることができる。
向流に流さないで、例えば、加湿用ガスと被加湿ガスとを中空糸膜に沿って同一方向に流すと、両ガスが導入されて膜の両側を流れ始めたときには、膜の両側の水蒸気分圧差が最大であって水蒸気が多量に透過するけれども、膜に沿って流れていくと加湿用ガスの水蒸気分圧は低下し且つ被加湿ガスの水蒸気分圧は上昇して膜の両側の水蒸気分圧差は小さくなり水蒸気の透過がおこり難くなる。この結果、中空糸膜全体としては加湿効率を低下させることになる。
【００２２】
本発明の加湿装置において、加湿用ガスと被加湿ガスとを中空糸膜に沿って向流に流すために、第１のガスが中空糸膜エレメントの一方の端部の管板の開口から中空糸膜内に導入されて中空糸内を流れて中空糸膜メレメントの他方の端部の管板の開口から排出され、第２のガスが第１のガスが排出する側の中空糸エレメントの管板の近傍で容器内の中空糸膜外の空間へ導入され、容器内の中空糸膜外の空間を流れて第１のガスが導入される側の中空糸膜エレメントの管板の近傍で容器から排出されるように、第１のガスの供給口、第１のガスの排出口、第２のガスの供給口、及び、第２のガスの排出口を容器に配置されるのが好適である。
【００２３】
第２のガスの供給口は、第２のガスが供給口から直接に容器内の中空糸膜の外側の空間へ導入されるように容器に配置されてもよい。
特に好ましくは、中空糸膜エレメントの中空糸膜束の略中心部に中空糸膜に沿って配した芯管を設け、その芯管は、第１のガスが中空糸膜外へ流れ出る側の管板を貫通しており、且つ、その管板の近傍で中空糸膜の外側の空間に面して芯管内外を連通する連通孔を形成し、第２のガスの供給口から供給された第２のガスが前記芯管に導かれ、前記連通孔から容器内の中空糸膜の外側の空間へ流れ出し、中空糸の外側の空間を中空糸に沿って流れ、第１のガスが中空糸膜内に導入される側の管板の近傍で中空糸膜の外側の空間から容器に備えられた第２のガスの排出口から容器外へ排出されるように構成された加湿装置である。
導入された第２のガスは、中空糸膜束の中心部から中空糸膜に沿って向流に流れながら且つ中空糸膜束の外側方向へ放射状に均一に流れることが可能になり、シートパス流や偏流が発生し難くなって加湿効率をより高めることができる。
【００２４】
本発明の加湿装置において、中空糸膜の内側を流れる第１のガスが加湿用ガスであり、中空糸膜の外側の空間を流れる第２のガスが被加湿ガスであることが好ましい。
【００２５】
本発明の加湿装置において、容器などの材料は８０℃程度の温度及び水分や酸素ガスが存在する雰囲気中で耐久性があればいかなる材料で形成されても構わないが、ステンレスやアルミ合金などの金属でもよいし樹脂や繊維強化樹脂で形成されたものでも構わない。容器は、一体物でなく筒部とキャップ部から組立てられていても構わない。必要に応じてパッキン類、接着剤、ボルトナット類などが用いられる。また、本発明の加湿装置は、ガス中の不純物や膜性能を劣化する可能性がある物質、例えば、オイルミスト、塵埃、ガス中に含まれる微量の化学物質を除去するためにフルター類などの前処理装置を備えても構わない。更に、ガスの温度を調整するための熱交換器やヒーター類、ガスの圧力を調整するためのコンプレッサーなどの圧力調整装置類を、必要に応じて備える。
【００２６】
以下、本発明の加湿装置の別の一例の概略の縦断面図を示した図４によって更に説明する。
図４において、中空糸膜１からなる中空糸膜束の両端部は管板２、２’で中空糸膜の端部が開口状態を保つように固着されている。中空糸膜束の略中心部には中空糸膜に沿って芯管９が備えられている。芯管９は、第１のガスの供給口４側の管板２には包埋されており、第１のガスの排出口５側の管板２’は貫通して第２のガスの供給口６と通じている。また、芯管９には、管板２’の近傍に、芯管内部と中空糸膜の外側の空間とを連通する連通孔１０が芯管の外周に沿って配置されている。中空糸膜束の外周部にはフィルム状物質１１が被覆されている。このフィルム状物質１１は第１のガスの排出口側の管板２’に埋め込まれて固定されており、管板２の近くに設けられた第２のガスの排出口７に面する部分は、中空糸膜束はフルム状物質で被覆されていない。
この装置において、水蒸気を多く含んだ加湿用ガスは第１のガスの供給口４から導入され中空糸膜内を流れて第１のガスの排出口５から排出される。一方、加湿されるべき被加湿ガスは第２のガスの供給口６から導入され、芯管９内を流れ芯管の連通孔１０から中空糸膜の外側の空間へ導入され、中空糸膜に沿って実質的に加湿用ガスの流れと向流に流れて、第２のガスの排出口７から排出される。この間、中空糸膜の内外表面には、加湿用ガスと被加湿ガスがそれぞれ接触するから、水蒸気分圧が高い加湿用カス中の水蒸気が中空糸膜内から中空糸膜外へ中空糸膜を透過する。この結果、中空糸膜の外側の空間を流れる被加湿ガスは加湿されて第２のガスの排出口から排出される。
尚、図４中の矢印は、ガスの流れの方向を示している。
【００２７】
本発明の加湿装置は、中空糸膜を用いているので小型で軽量であり、複雑な駆動や操作を必要としない加湿装置である。その上、燃料電池の運転温度である８０℃程度の温度や水蒸気、酸素、及び、水素などが存在する雰囲気中に長期間暴露されても安定して加湿することができ、低圧ガスを用いてもガスの圧力損失を抑制しながら加湿効率を高くすることができ、水蒸気以外の他成分の透過が抑制され、しかも、経済的であるので、燃料電池用に好適に用いることができる
本発明の加湿装置は、特に、燃料電池のカソードへ供給される空気をカソードからの排出ガスで加湿するような場合に好適に用いることができる。
【００２８】
図５は、本発明の燃料電池用加湿装置の使用形態の一例を示す概略図である。尚、図５中の矢印は、ガスの流れの方向を示している。
図５において、固体高分子型燃料電池１２はアノード１３、固体高分子電解質膜１４、カソード１５から構成されている。カソード１５へは空気が供給される。該空気は、外気から採取されて先ず本発明の加湿装置へ第２のガスの供給口６から供給され、連通孔１０を通って装置内の中空糸膜の外側の空間へ導入されて、第２のガスの排出口７から排出され、燃料電池のカソード１５へ供給される。カソード１５から排出された排出ガスは、本発明の加湿装置の第１のガスの供給口４へ導かれて装置内へ導入される。次いで、前記排出ガスは管板２の中空糸の開口部から中空糸膜の中空側に入り中空内を流れて管板２’の中空糸の開口部から流出し第１のガスの排出口５から装置外へ排出される。
カソード５から排出された排出ガスは約８０℃程度の温度であり又燃料電池１２で生成した水を多量に含んでいる。加湿装置へ導入された前記排出ガスと空気とは、中空糸膜を挟んで膜に接触しながらお互いに向流方向に流れる。その間に前記排出ガス中の水蒸気が膜を透過してから空気を加湿する。更に、この過程で空気は前期排出ガスの熱を受け取って加温される。加湿加温された空気が第２のガスの排出口７から排出されて燃料電池のカソードへ供給される。
【００２９】
【実施例】
以下、実施例によって本発明の加湿装置について更に説明する。尚、本発明は以下の実施例に限定されるものではない。
【００３０】
実施例における測定方法は以下のとおり。
（回転粘度の測定方法）
ポリイミド溶液の回転粘度は、回転粘度計（ローターのずり速度１．７５／ｓｅｃ）を用い温度１００℃で測定した。
【００３１】
（中空糸膜の水蒸気透過性能の測定方法）
約１０本の中空糸膜と、ステンレスパイプと、エポキシ樹脂系接着剤とを使用して有効長が２０ｍｍの透過性能評価用のエレメントを作成し、これをステンレス容器に装着してペンシルモジュールとした。このペンシルモジュールの中空糸膜の外側へ水蒸気濃度約２３体積％の窒素ガスを一定量供給し、透過側へは一定量のキャリアガス（Ａｒガス）を流しながら水蒸気分離をおこない、非透過ガス及び透過ガスの水蒸気量を鏡面式の露点計で検出した。測定した水蒸気量（水蒸気分圧）と供給ガス量及び有効膜面積から膜の水蒸気透過速度を算出した。尚、これらの測定は８０℃でおこなった。
【００３２】
（中空糸膜の酸素ガス透過性能の測定方法）
約１５本の中空糸膜と、ステンレスパイプと、エポキシ樹脂系接着剤とを使用して有効長が１０ｃｍの透過性能評価用のエレメントを作成し、これをステンレス容器に装着してペンシルモジュールとした。それに一定圧力の酸素純ガスを供給して透過流量を測定した。測定した透過酸素ガス量と供給圧力及び有効膜面積から酸素ガスの透過速度を算出した。尚、これらの測定は８０℃でおこなった。
【００３３】
（中空糸膜の引張破断伸度の測定）
引張試験機を用いて有効長２０ｍｍ、引張速度１０ｍｍ／分で測定した。尚、測定は２３℃で行った。
（中空糸膜の耐熱水性の測定）
引張破断伸度が既知の中空糸膜を試料として、ステンレス容器内にイオン交換水と前記中空糸膜を入れて密封し、前記容器を１００℃のオーブン中に入れ５０時間保持して中空糸膜を熱水処理した。熱水処理後の中空糸膜は容器から取り出され１００℃のオーブン中で乾燥した。乾燥後の中空糸膜は前記の引張試験方法に従って引張破断伸度を測定した。引張破断伸度の保持率［％］を耐熱水性の指標として表わした。
【００３４】
（加湿試験）
供給ガスの圧力がほぼ大気圧のときは、加湿装置の第１のガスの供給口と第２のガスの供給口に、所定の圧力、温度、相対湿度を持った空気をそれぞれの供給口の手前のガス流量調節弁で流量を調節しながら供給した。排出口はいずれも大気へ開放とした。また、供給ガスの圧力が０．２ＭＰａＧのときは、加湿装置のそれぞれの供給口に、所定の圧力、温度、相対湿度を持った空気を供給し、排出口から排出される流量を流量調節弁で調節した。
第１のガスと第２のガスの供給口の直前及び排出口の直後には水マノメーターを取付けて圧力を測定した。
また、第１のガス及び第２のガスともに、供給するガスと排出したガスとを鏡面式の露点計で水分含有量を測定した。尚、露点計で測定できない範囲の水分含有量を持った空気は、露点が既知の空気と所定の割合で混合して露点を下げてから露点を測定した。水分含有量は測定した露点から算出した。
【００３５】
（ポリイミド（ａ）溶液の調製）
３，３’，４，４’−ビフェニルテトラカルボン酸二無水物５２．９６０ｇと、２，２’−ビス（３，４−ジカルボキシフェニル）ヘキサフルオロプロパン二無水物５３．３０９ｇと、４，４’−ジアミノジフェニルエーテル６０．７９３ｇとを、溶媒のパラクロロフェノール８２０．３７ｇと共にセパラブルフラスコ中にて重合温度１８０℃で１１時間重合し、回転粘度が１７１６ポイズ、ポリマー濃度が１６重量％のポリイミド（ａ）溶液を得た。
【００３６】
（ポリイミド（ｂ）溶液の調製）
３，３’，４，４’−ビフェニルテトラカルボン酸二無水物８８．２６６ｇと、ジアミノジフェニルエーテル６１．２７３ｇとを、溶媒のパラクロロフェノール７２８．３８ｇと共にセパラブルフラスコ中にて重合温度１８０℃で７時間重合し、回転粘度１８２３ポイズ、ポリマー濃度１６重量％のポリイミド（ｂ）溶液を得た。
【００３７】
（非対称ポリイミド中空糸膜の製造）
前記ポリイミド（ａ）溶液２８０ｇと、前記ポリイミド（ｂ）溶液１２０ｇとを、セパラブルフラスコにて温度１３０℃で３時間攪拌してポリイミド混合物溶液を得た。この混合物溶液のポリマー濃度は１６重量％であり、回転粘度は１８０４ポイズであった。
このポリイミド混合物溶液を、４００メッシュの金網で濾過したあと、円形開口部と芯部開口部を持つ中空糸紡糸ノズルの円形開口部から吐出させ、同時に芯部開口部から窒素ガスを吐出して中空糸状体とし、吐出した中空糸状体を窒素雰囲気中に通した後、温度０℃の所定濃度（７０〜８０重量％）のエタノール水溶液からなる凝固液に浸漬し湿潤糸とした。これを温度５０℃のエタノール中に２時間浸漬し脱溶媒処理を完了し、更に、温度７０℃のイソオクタン中に３時間浸漬洗浄して溶媒を置換後、温度１００℃で絶乾状態まで乾燥し、その後所定温度（２００〜３００℃）で１時間の熱処理をおこなった。
【００３８】
寸法の異なる中空糸紡糸ノズルを用いたり、ポリイミド溶液の吐出量及び芯部開口部から吐出する窒素ガスを調節することによって、６種類の非対称ポリイミド中空糸膜Ａ〜Ｆを製造した。得られた非対称ポリイミド中空糸膜Ａ〜Ｆの寸法や水蒸気透過性能を表１に示した。
【表１】

【００３９】
（実施例１）
ポリイミド中空糸膜Ａ（中空糸膜の内径＝７１０μｍ）を用いて、内径１６５ｍｍの円筒状容器内に、中空糸膜束の有効長（Ｌ）が３６０ｍｍ（管板の長さはそれぞれ５０ｍｍである。以下同じ。）、膜充填率４０％、中空糸膜束の外周に沿って外周面積の約８０％がポリイミドフィルムで被覆され、その被覆された円筒状フィルムの内径が１５０ｍｍ（Ｄ）の中空糸膜エレメントを装着して、図４で示したような加湿装置とした。（Ｌ／Ｄ＝２．４）
第１のガスとしてほぼ大気圧、温度８０℃、相対湿度９５％の空気を流量５００Ｎリットル／分で中空糸膜の中空側へ、第２のガスとしてほぼ大気圧、温度２５℃、相対湿度１０％の空気を流量５００Ｎリットル／分で中空糸膜の外側の空間へ、第１のガスと第２のガスとが向流になるように供給した。
それぞれのガスの圧力と露点を測定した結果、第１のガスが中空糸膜の中空側を流れるときの圧力損失は２．４ｋＰａ、第２のガスが中空糸膜の外側の空間を流れるときの圧力損失は０．１ｋＰａであり、合計の圧力損失は２．５ｋＰａであった。また、第１のガスが含有していた水分量のうち中空糸膜を透過して第２のガスへ移動した水分量の割合は８２％であった。
【００４０】
（比較例１）
ポリイミド中空糸膜Ｂ（中空糸膜の内径＝２８５μｍ）を用いて、実施例１と実質的に同じ有効膜面積を持ち、実施例１と同じ内径１６５ｍｍの円筒状容器からなる加湿装置を作製した。具体的には、中空糸膜束の有効長（Ｌ）が１３５ｍｍ、膜充填率４０％、中空糸膜束の外周に沿って外周面積の約８０％がポリイミドフィルムで被覆され、その被覆された円筒状フィルムの内径が１５０ｍｍ（Ｄ）の中空糸膜エレメントを装着して、図４で示したような加湿装置とした。（Ｌ／Ｄ＝０．９）
この装置に、実施例１と同一ガスを同一条件で流れるように供給した。
それぞれのガスの圧力と露点を測定した結果、第１のガスが中空糸膜の中空側を流れるときの圧力損失は８．０ｋＰａ、第２のガスが中空糸膜の外側の空間を流れるときの圧力損失は０．１ｋＰａであり、合計の圧力損失は８．１ｋＰａであった。また、第１のガスが含有していた水分量のうち中空糸膜を透過して第２のガスへ移動した水分量の割合は３６％であった。
【００４１】
（実施例２）
ポリイミド中空糸膜Ａ（中空糸膜の内径＝７１０μｍ）を用いて、内径２００ｍｍ（Ｄ）の円筒状容器内に、中空糸膜束の有効長（Ｌ）が６００ｍｍ、膜充填率４０％の中空糸膜エレメントを装着して、図２で示したような加湿装置とした。（Ｌ／Ｄ＝３．０）
第１のガスとしてほぼ大気圧、温度８０℃、相対湿度９５％の空気を流量１５００Ｎリットル／分で中空糸膜の中空側へ、第２のガスとしてほぼ大気圧、温度２５℃、相対湿度１０％の空気を流量１５００Ｎリットル／分で中空糸膜の外側の空間へ、第１のガスと第２のガスとが向流になるように供給した。
それぞれのガスの圧力と露点を測定した結果、第１のガスが中空糸膜の中空側を流れるときの圧力損失は３．６ｋＰａ、第２のガスが中空糸膜の外側の空間を流れるときの圧力損失は０．４ｋＰａであり、合計の圧力損失は４．０ｋＰａであった。また、第１のガスが含有していた水分量のうち中空糸膜を透過して第２のガスへ移動した水分量の割合は８７％であった。
【００４２】
（比較例２）
ポリイミド中空糸膜Ｂ（中空糸膜の内径＝２８５μｍ）を用いて、実施例２と実質的に同じ有効膜面積を持ち、実施例２と同じ容器内径２００ｍｍ（Ｄ）の円筒状容器からなる加湿装置を作製した。具体的には、中空糸膜束の有効長（Ｌ）が２４０ｍｍ、膜充填率４０％の中空糸膜エレメントを装着して、図２で示したような加湿装置とした。（Ｌ／Ｄ＝１．２）
この装置に、実施例２と同一ガスを同一条件で流れるように供給した。
それぞれのガスの圧力と露点を測定した結果、第１のガスが中空糸膜の中空側を流れるときの圧力損失は１８．８ｋＰａ、第２のガスが中空糸膜の外側の空間を流れるときの圧力損失は０．６ｋＰａであり、合計の圧力損失は１９．４ｋＰａであった。また、第１のガスが含有していた水分量のうち中空糸膜を透過して第２のガスへ移動した水分量の割合は４３％であった。
【００４３】
（実施例３）
ポリイミド中空糸膜Ｃ（中空糸膜の内径＝５７０μｍ）を用いて、内径１００ｍｍ（Ｄ）の円筒状容器内に、中空糸膜束の有効長（Ｌ）が３２０ｍｍ、膜充填率４０％の中空糸膜エレメントを装着して、図２で示したような加湿装置とした。（Ｌ／Ｄ＝３．２）
第１のガスとして圧力０．２ＭＰａＧ、温度８０℃、相対湿度９５％の空気を流量５００Ｎリットル／分で中空糸膜の中空側へ、第２のガスとして圧力０．２ＭＰａＧ、温度２５℃、相対湿度５％の空気を流量５００Ｎリットル／分で中空糸膜の外側の空間へ、第１のガスと第２のガスとが向流になるように供給した。それぞれのガスの圧力と露点を測定した結果、第１のガスが中空糸膜の中空側を流れるときの圧力損失は２．６ｋＰａ、第２のガスが中空糸膜の外側の空間を流れるときの圧力損失は０．２ｋＰａであり、合計の圧力損失は２．８ｋＰａであった。また、第１のガスが含有していた水分量のうち中空糸膜を透過して第２のガスへ移動した水分量の割合は８５％であった。
【００４４】
（比較例３）
ポリイミド中空糸膜Ｄ（中空糸膜の内径＝１４５μｍ）を用いて、実施例３と実質的に同じ有効膜面積を持ち、実施例３と同じ容器内径１００ｍｍ（Ｄ）の円筒状容器からなる加湿装置を作製した。具体的には、中空糸膜束の有効長（Ｌ）が８０ｍｍ、膜充填率４０％の中空糸膜エレメントを装着して、図２で示したような加湿装置とした。（Ｌ／Ｄ＝０．８）
この装置に、実施例３と同一ガスを同一条件で流れるように供給した。
それぞれのガスの圧力と露点を測定した結果、第１のガスが中空糸膜の中空側を流れるときの圧力損失は１７．５ｋＰａ、第２のガスが中空糸膜の外側の空間を流れるときの圧力損失は０．４ｋＰａであり、合計の圧力損失は１７．９ｋＰａであった。また、第１のガスが含有していた水分量のうち中空糸膜を透過して第２のガスへ移動した水分量の割合は４０％であった。
【００４５】
（実施例４）
ポリイミド中空糸膜Ｃ（中空糸膜の内径＝５７０μｍ）を用いて、内径１３０ｍｍ（Ｄ）の円筒状容器内に、中空糸膜束の有効長（Ｌ）が３８０ｍｍ、膜充填率４０％の中空糸膜エレメントを装着して、図２で示したような加湿装置とした。（Ｌ／Ｄ＝２．９）
第１のガスとして圧力０．２ＭＰａＧ、温度８０℃、相対湿度９５％の空気を流量１５００Ｎリットル／分で中空糸膜の中空側へ、第２のガスとして圧力０．２ＭＰａＧ、温度２５℃、相対湿度５％の空気を流量１５００Ｎリットル／分で中空糸膜の外側の空間へ、第１のガスと第２のガスとが向流になるように供給した。
それぞれのガスの圧力と露点を測定した結果、第１のガスが中空糸膜の中空側を流れるときの圧力損失は５．２ｋＰａ、第２のガスが中空糸膜の外側の空間を流れるときの圧力損失は０．５ｋＰａであり、合計の圧力損失は５．７ｋＰａであった。また、第１のガスが含有していた水分量のうち中空糸膜を透過して第２のガスへ移動した水分量の割合は８０％であった。
【００４６】
（比較例４）
ポリイミド中空糸膜Ｄ（中空糸膜の内径＝１４５μｍ）を用いて、実施例４と実質的に同じ有効膜面積を持ち、実施例４と同じ容器内径１３０ｍｍ（Ｄ）の円筒状容器からなる加湿装置を作製した。具体的には、中空糸膜束の有効長（Ｌ）が９０ｍｍ、膜充填率４０％の中空糸膜エレメントを装着して、図２で示したような加湿装置とした。（Ｌ／Ｄ＝０．７）
この装置に、実施例４と同一ガスを同一条件で流れるように供給した。
それぞれのガスの圧力と露点を測定した結果、第１のガスが中空糸膜の中空側を流れるときの圧力損失は３３．７ｋＰａ、第２のガスが中空糸膜の外側の空間を流れるときの圧力損失は１．１ｋＰａであり、合計の圧力損失は３４．８ｋＰａであった。また、第１のガスが含有していた水分量のうち中空糸膜を透過して第２のガスへ移動した水分量の割合は３２％であった。
【００４７】
（実施例５）
ポリイミド中空糸膜Ｅ（中空糸膜の内径＝５１０μｍ）を用いて、内径１００ｍｍ（Ｄ）の円筒状容器内に、中空糸膜束の有効長（Ｌ）が２８０ｍｍ、膜充填率４０％の中空糸膜エレメントを装着して、図２で示したような加湿装置とした。（Ｌ／Ｄ＝２．８）
第１のガスとして圧力０．２ＭＰａＧ、温度８０℃、相対湿度９５％の空気を流量５００Ｎリットル／分で中空糸膜の中空側へ、第２のガスとして圧力０．２ＭＰａＧ、温度２５℃、相対湿度５％の空気を流量５００Ｎリットル／分で中空糸膜の外側の空間へ、第１のガスと第２のガスとが向流になるように供給した。それぞれのガスの圧力と露点を測定した結果、第１のガスが中空糸膜の中空側を流れるときの圧力損失は２．９ｋＰａ、第２のガスが中空糸膜の外側の空間を流れるときの圧力損失は０．２ｋＰａであり、合計の圧力損失は３．１ｋＰａであった。また、第１のガスが含有していた水分量のうち中空糸膜を透過して第２のガスへ移動した水分量の割合は８０％であった。
【００４８】
（参考例１）
ポリイミド中空糸膜Ｆ（中空糸膜の内径＝４１０μｍ）を用いて、内径１００ｍｍ（Ｄ）の円筒状容器内に、中空糸膜束の有効長（Ｌ）が２３０ｍｍ、膜充填率４０％の中空糸膜エレメントを装着して、図２で示したような加湿装置とした。（Ｌ／Ｄ＝２．３）
第１のガスとして圧力０．２ＭＰａＧ、温度８０℃、相対湿度９５％の空気を流量５００Ｎリットル／分で中空糸膜の中空側へ、第２のガスとして圧力０．２ＭＰａＧ、温度２５℃、相対湿度５％の空気を流量５００Ｎリットル／分で中空糸膜の外側の空間へ、第１のガスと第２のガスとが向流になるように供給した。それぞれのガスの圧力と露点を測定した結果、第１のガスが中空糸膜の中空側を流れるときの圧力損失は３．９ｋＰａ、第２のガスが中空糸膜の外側の空間を流れるときの圧力損失は０．２ｋＰａであり、合計の圧力損失は４．１ｋＰａであった。また、第１のガスが含有していた水分量のうち中空糸膜を透過して第２のガスへ移動した水分量の割合は７１％であった。
【００４９】
（実施例７）
ポリイミド中空糸膜Ｅ（中空糸膜の内径＝５１０μｍ）を用いて、内径１３０ｍｍ（Ｄ）の円筒状容器内に、中空糸膜束の有効長（Ｌ）が３４０ｍｍ、膜充填率４０％の中空糸膜エレメントを装着して、図２で示したような加湿装置とした。（Ｌ／Ｄ＝２．６）
第１のガスとして圧力０．２ＭＰａＧ、温度８０℃、相対湿度９５％の空気を流量１５００Ｎリットル／分で中空糸膜の中空側へ、第２のガスとして圧力０．２ＭＰａＧ、温度２５℃、相対湿度５％の空気を流量１５００Ｎリットル／分で中空糸膜の外側の空間へ、第１のガスと第２のガスとが向流になるように供給した。
それぞれのガスの圧力と露点を測定した結果、第１のガスが中空糸膜の中空側を流れるときの圧力損失は５．９ｋＰａ、第２のガスが中空糸膜の外側の空間を流れるときの圧力損失は０．６ｋＰａであり、合計の圧力損失は６．５ｋＰａであった。また、第１のガスが含有していた水分量のうち中空糸膜を透過して第２のガスへ移動した水分量の割合は７５％であった。
【００５０】
【発明の効果】
本発明は以上説明したようなものであるから、以下のような効果を奏する。
すなわち、本発明は、燃料電池の運転温度である８０℃程度の温度や水蒸気、酸素、及び、水素などが存在する雰囲気中に長期間暴露されても安定して加湿することができ、低圧ガスを用いてもガスの圧力損失を抑制しながら加湿効率を高くすることができ、水蒸気以外の他成分の透過が抑制され、しかも、経済的な燃料電池用に好適に用いることができる加湿装置を提供する。
【図面の簡単な説明】
【図１】本発明の燃料電池用加湿装置を構成する中空糸膜エレメントの一例の概略の縦断面図である。
【図２】本発明の燃料電池用加湿装置の一例の概略の縦断面図である。
【図３】本発明の燃料電池用加湿装置の一例の概略の縦断面図である。Ｌ及びＤを示してある。
【図４】本発明の燃料電池用加湿装置の別の一例の概略の縦断面図である。
【図５】本発明の燃料電池用加湿装置の使用形態の一例を示す概略図である。
【符号の説明】
１：中空糸膜
２、２’：管板
３：中空糸膜エレメント
４：第１のガスの供給口
５：第１のガスの排出口
６：第２のガスの供給口
７：第２のガスの排出口
８：容器
９：芯管
１０：連通孔
１１：フィルム状物質
１２：燃料電池
１３：アノード
１４：固体高分子電解質膜
１５：カソード[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a humidifier using a hollow fiber membrane, which is suitable for humidifying a supply gas of a fuel cell. The humidifier for a fuel cell of the present invention can humidify with high efficiency while suppressing pressure loss, and other components other than water vapor are suppressed in permeation and are economical. In particular, the humidifier is suitable for humidifying the supply gas supplied to the fuel cell by collecting moisture from the exhaust gas discharged from the fuel cell.
[0002]
[Prior art]
In recent years, fuel cells using solid polymer membranes such as perfluorocarbon sulfonic acid membranes as electrolyte membranes have attracted attention as electric vehicles and stationary small power generators. Such a solid polymer functions as a proton conductive electrolyte in a water-containing state. However, in a dry state, proton conductivity is lowered, and contact between the solid polymer electrolyte membrane and the electrode is poor, and output is drastically reduced. For this reason, in the polymer electrolyte fuel cell system, the supply gas is humidified and supplied so that the polymer electrolyte membrane maintains a constant humidity. For this reason, various humidifiers for humidifying the supply gas have been studied.
Japanese Patent Laid-Open No. 6-132038 discloses that a supply gas to be supplied to a fuel cell is humidified by using a water vapor permeable membrane as exhaust gas discharged from the fuel cell.
Japanese Patent Application Laid-Open No. 8-273687 discloses that a fuel cell supply gas is humidified by a humidifier using a hollow fiber membrane.
[0003]
The fuel cell humidifier can be stably humidified even if it is exposed to a temperature of about 80 ° C., which is the operating temperature of the fuel cell, or in an atmosphere where water vapor, oxygen, hydrogen, etc. are present for a long time, There is a demand for efficient humidification using low-pressure gas, suppression of gas pressure loss, and suppression of permeation of components other than water vapor.
However, for example, Japanese Patent Laid-Open No. 2001-351660 proposes to include auxiliary humidifying means including a condenser and a water injection valve in addition to the hollow fiber water permeable membrane type humidifier. This proposal was made to solve the problem that there is a limit to the use of the hollow fiber water permeable membrane humidifier because the pressure loss increases when the scale is increased to increase the amount of humidification in low pressure operation.
As described above, there is room for improvement in the humidifier for a fuel cell using the hollow fiber membrane.
[0004]
Inventors including the inventors of the present invention disclosed in US Pat. No. 6,464,755 an asymmetric hollow fiber gas separation having both high water vapor transmission rate, practical mechanical strength, and excellent water resistance and hot water resistance. A membrane is disclosed and mentions the possibility that this asymmetric hollow fiber membrane gas separation membrane can be used to humidify the fuel cell feed gas. However, US Pat. No. 6,464,755 does not specifically examine and disclose parameters useful when a hollow fiber gas separation membrane is applied to a fuel cell humidifier as in the present invention.
Japanese Patent Application Laid-Open No. 2002-219339 discloses a humidification module using a hollow fiber membrane in which a ratio between a shortest length L and a diagonal length A connected to the region is filled with a hollow fiber membrane bundle. If the ratio D / L between L / A or the height D of the hollow fiber membrane bundle in the region filled with the hollow fiber membrane bundle and the shortest length L connected to the region is within a specific range, the cylindrical housing It is disclosed that the humidifying ability of the humidifier is improved because the drying gas can be uniformly distributed to the outer surface of each hollow fiber membrane. However, JP 2002-219339 A does not disclose a solution to the problem of pressure loss of the hollow fiber membrane in the humidification module as in the present invention.
[0005]
[Patent Document 1]
JP-A-6-132038
[Patent Document 2]
JP-A-8-273687
[Patent Document 3]
JP 2001-351660
[Patent Document 4]
US Pat. No. 6,464,755
[Patent Document 5]
JP 2002-219339
[0006]
[Problems to be solved by the invention]
The present invention can stably humidify the fuel cell even when exposed to a temperature of about 80 ° C., which is the operating temperature of the fuel cell, or in an atmosphere where water vapor, oxygen, hydrogen, and the like are present for a long time. However, it is possible to increase the humidification efficiency while suppressing the pressure loss of gas, to suppress the permeation of other components other than water vapor, and to provide a humidifier that can be suitably used for an economical fuel cell. For the purpose.
[0007]
[Means for Solving the Problems]
The present invention provides a hollow fiber membrane element in which a tube sheet in which a hollow fiber membrane is fixed in an open state is formed at both ends of a hollow fiber membrane bundle comprising a plurality of hollow fiber membranes, at least a first gas supply port, The space that leads to the hollow side of the hollow fiber membrane and the space that leads to the outside of the hollow fiber membrane are isolated from each other in the container having the first gas discharge port, the second gas supply port, and the second gas discharge port. In a humidifying device for a fuel cell configured to be attached to
(A) The inner diameter of the hollow fiber membrane is 400 μm or more, preferably more than 500 μm to less than 1500 μm
(B) Water vapor transmission rate (P ′) of the hollow fiber membrane_H2O) Is 0.5 × 10^-3cm^Three(STP) / cm²・ It is more than sec · cmHg
(C) Permeation rate ratio (P ′) between water vapor and oxygen gas in the hollow fiber membrane_H2O/ P ’_O2) Is 10 or more
(D) A humidifying device for a fuel cell, wherein the hollow fiber membrane retains 80% or more of the tensile breaking elongation after hydrothermal treatment in hot water at 100 ° C. for 50 hours, In particular, the present invention relates to a humidifier for a fuel cell in which L / D is 1.8 or more, where L is the effective length of the hollow fiber membrane element and D is the inner diameter of the container in which the hollow fiber membrane element is mounted.
Further, the membrane filling rate of the hollow fiber membrane bundle constituting the hollow fiber membrane element is 35 to 55%, and 50% or more of the outer peripheral portion of the hollow fiber membrane bundle constituting the hollow fiber membrane element is covered with a film-like substance. The first gas flowing through the hollow side of the hollow fiber membrane and the second gas flowing through the space outside the hollow fiber membrane flow counter-currently across the hollow fiber membrane, the hollow fiber membrane A core tube arranged along the hollow fiber membrane bundle is provided at a substantially central portion of the hollow fiber membrane bundle constituting the element, and a communication hole is formed in the core tube to communicate between the inside of the core tube and the outside of the core tube. The present invention relates to a configuration in which the second gas is introduced into the core tube from the second gas supply port and introduced into the space outside the hollow fiber membrane through the communication hole.
Further, the supply gas to the fuel cell is configured to be humidified, the first gas is exhaust gas from the cathode of the fuel cell, and the second gas is air supplied to the cathode of the fuel cell. It is related with the humidification apparatus for fuel cells comprised in this way.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The humidifying device for a fuel cell according to the present invention includes at least a hollow fiber membrane element in which a tube sheet having a hollow fiber membrane fixed in an open state is formed at both ends of a hollow fiber membrane bundle composed of a plurality of hollow fiber membranes. In the container having the gas supply port, the first gas discharge port, the second gas supply port, and the second gas discharge port, the space leading to the hollow side of the hollow fiber membrane and the outside of the hollow fiber membrane are communicated. It is configured so that it is isolated from the space.
FIG. 1 shows a schematic longitudinal sectional view of an example of a hollow fiber membrane element constituting the humidifying device of the present invention. A large number (usually several tens to several hundreds of thousands) of hollow fiber membranes 1 are bundled approximately in parallel to form a hollow fiber membrane bundle. Both ends of the hollow fiber membrane bundle are fixed so that the hollow fiber membranes are kept open at both end surfaces by tube plates 2 and 2 'made of a thermoplastic resin such as polyolefin or a curable resin such as epoxy resin. Thus, the hollow fiber membrane element 3 is configured. Incidentally, the hollow fiber membranes are in a so-called twilled state in which the hollow fiber membranes are alternately arranged at a low angle of 30 ° or less with respect to the axial direction of the hollow fiber membrane bundles every 1 to 100, and the hollow fiber membrane bundles as a whole are substantially parallel. It is desirable to be focused on.
FIG. 2 is a schematic longitudinal sectional view of an example of a fuel cell humidifier according to the present invention. At least one of the hollow fiber membrane elements 3 includes a container 8 including at least a first gas supply port 4, a first gas discharge port 5, a second gas supply port 6, and a second gas discharge port 7. Inside, the space leading to the hollow side of the hollow fiber membrane and the space leading to the outside of the hollow fiber membrane are mounted so as to be isolated.
That is, the space in the container is partitioned by the tube plate, and the space between the two

tube plates

2, 2 ′ in the container is divided into a space on the hollow side of each hollow fiber membrane and a space on the outside of the hollow fiber membrane. It is divided. The first gas supplied from the first gas supply port 4 is introduced into the hollow side of the hollow fiber membrane through the opening of the hollow fiber membrane at the end face of the tube plate 2, flows through the hollow side of the hollow fiber membrane, It flows out from the opening of the hollow fiber membrane at the end face of the tube plate 2 ′ and is discharged from the first gas discharge port 5. On the other hand, the second gas supplied from the second gas supply port 6 flows through the space outside the hollow fiber membrane and is discharged from the second discharge port 7. During this time, since each gas flows in contact with the inner and outer surfaces of the hollow fiber membrane, water vapor on the gas side having a high water vapor partial pressure selectively permeates through the hollow fiber membrane to the gas side having a low water vapor partial pressure. Humidification is performed.
In addition, the arrow in FIG. 2 has shown the direction of the flow of gas.
[0009]
The pressure of the gas supplied to the polymer electrolyte fuel cell and the gas discharged depends on the use conditions of the fuel cell, but is generally a low pressure of about 1 to 3 atmospheres (gauge pressure of 0 to 2 atmospheres). It is obvious when considering the case of humidifying the air supplied to the cathode by using the cathode exhaust gas containing a large amount of water generated at the cathode of the fuel cell as the humidifying gas. In order to be able to humidify the gas with a low-pressure gas and reduce the power to pressurize the gas as much as possible, the pressure loss must be suppressed to a very low level.
The pressure loss of the humidifier occurs mainly when the gas flows through the hollow side of the hollow fiber membrane and when the gas flows through the space outside the hollow fiber membrane.
As a method for suppressing the pressure loss of the gas passing through the hollow side of the hollow fiber membrane, a method of shortening the hollow fiber membrane can be considered. However, if a short hollow fiber membrane is used, the proportion of the membrane area embedded in the tube plates at both ends of the hollow fiber membrane and not usable for humidification increases, making it difficult to obtain an economical humidifier. Moreover, if the hollow fiber membrane is shortened to obtain the same amount of humidification, more hollow fiber membranes are required. Therefore, as described below, the effective length of the hollow fiber membrane element is L, and the hollow When the inner diameter of the container to which the thread membrane element is mounted is D, L / D becomes small, and thus the gas flow drifts in the space outside the hollow fiber membrane and the humidification efficiency is lowered.
[0010]
The preferable lower limit of the inner diameter of the hollow fiber separation membrane used in the humidifier of the present invention is more than 500 μm, and the preferable upper limit of the inner diameter is less than 1500 μm, particularly less than 800 μm. The inner diameter of the hollow fiber separation membrane is typically preferably in the range of more than 500 μm to less than 1500 μm.
If the inner diameter of the hollow fiber membrane exceeds 500 μm, the pressure loss can be suppressed to an extremely low level even if a hollow fiber membrane having a length several hundred times or more the inner diameter is used. For this reason, the ratio of the film | membrane area which cannot be used for humidification with a tube sheet becomes small, and an economical humidification apparatus is attained. Further, as will be described below, when the effective length of the hollow fiber membrane element is L and the inner diameter of the container in which the hollow fiber membrane element is mounted is D, L / D can be made a certain size or larger. It is possible to increase the humidification efficiency.
On the other hand, when the inner diameter of the hollow fiber membrane is 1500 μm or more, the number of hollow fiber membranes that can be mounted within a predetermined volume is limited, and the effective membrane area is reduced, making it difficult to increase the humidification efficiency. This is not preferable because the apparatus needs to be large. Moreover, when the inner diameter of the hollow fiber membrane is 1500 μm or more, the hollow fiber membrane is easily deformed and it is difficult to produce the hollow fiber membrane. When the film thickness is increased in order to increase the strength of the hollow fiber membrane, the water vapor transmission rate is reduced, so that it is difficult to obtain a humidifier with high humidification efficiency.
[0011]
Water vapor transmission rate (P ′) of the hollow fiber membrane used in the humidifier of the present invention_H2O) 0.5 × 10 at a temperature of 80 ° C.^-3cm^Three(STP) / cm²・ Sec · cmHg or more, preferably 2.0 × 10^-3cm^Three(STP) / cm²· Sec · cmHg or more, and the permeation rate ratio of water vapor to oxygen gas (P '_H2O/ P ’_O2) At a temperature of 80 ° C. is 10 or more, preferably 100 or more.
Water vapor transmission rate of hollow fiber membrane (P '_H2O) Is 0.5 × 10^-3cm^Three(STP) / cm²If it is less than sec · cmHg, a sufficient amount of humidification cannot be obtained, and in order to obtain the same amount of humidification, it is necessary to use an additional hollow fiber membrane, which is not preferable. Further, the permeation rate ratio of water vapor and oxygen gas (P ′)_H2O/ P ’_O2) Less than 10 is not preferable because gas components other than water vapor easily pass through the hollow fiber membrane. For example, when the air supplied to the cathode is humidified with the exhaust gas from the cathode, the oxygen gas partial pressure of the exhaust gas becomes smaller than the oxygen gas partial pressure of the air, and the oxygen gas can permeate from the air to the exhaust gas side. There is sex. In that case, the permeation rate ratio of water vapor to oxygen gas (P ′)_H2O/ P ’_O2) Is less than 10, it is not preferable because the oxygen gas concentration in the air supplied through a large amount of oxygen gas decreases and the output of the fuel cell decreases.
[0012]
Furthermore, the hollow fiber separation membrane used in the humidifier of the present invention has a tensile elongation at break after heat treatment in hot water at 100 ° C. for 50 hours of 80% or more of the tensile elongation at break before hot water treatment, preferably It has hot water resistance that can hold 90% or more. Since the stack of the polymer electrolyte fuel cell is used at a temperature of about 80 ° C., the humidifier is also operated at the same temperature. Therefore, the hollow fiber membrane is constantly in contact with a gas containing a large amount of water vapor at a temperature of about 80 ° C. A hollow fiber membrane that can maintain a tensile breaking elongation of 80% or more of the tensile breaking elongation before heat treatment even after heat treatment in hot water at 100 ° C. for 50 hours is not hydrolyzed by hot water at 100 ° C. Therefore, it can be used for humidification with reliability over a long period of time.
[0013]
The hollow fiber separation membrane used in the humidifying device of the present invention may be a porous membrane or a non-porous membrane, but the porous membrane has a problem that components other than water vapor are likely to be mixed into the supply gas. Non-porous membranes are preferred. In particular, an asymmetric non-porous membrane is preferable because the water vapor transmission rate is increased. The material of the membrane is preferably a material excellent in heat resistance, chemical resistance, durability, and hydrolysis resistance from the use conditions in contact with water vapor or oxygen gas at a high temperature of about 80 ° C.
In the porous membrane, for example, perfluorocarbon resin having sulfonic acid group, polyethylene resin, polypropylene resin, polyvinylidene fluoride resin, polytetrafluoroethylene resin, polysulfone resin, polyethersulfone resin, polyamide resin, polyamideimide resin, poly Preferred examples include ether imide resins, polycarbonate resins, and cellulose derivative resins.
In the non-porous membrane, for example, polyimide resin, polysulfone resin, perfluorocarbon resin having a sulfonic acid group, polyethersulfone resin, polyamide resin, polyamideimide resin, polyetherimide resin, polycarbonate resin, polyphenylene oxide resin, polyacetylene resin, Preferred examples include cellulose derivative resins.
As the hollow fiber membrane used in the fuel cell humidifier of the present invention, an asymmetric hollow fiber membrane made of aromatic polyimide is particularly preferable. The asymmetric hollow fiber membrane made of aromatic polyimide has excellent heat resistance and durability, as described in detail in US Pat. No. 6,464,755 of the inventors including the inventor of the present invention. Since a high permeation rate, high water vapor selective permeability, and excellent hot water resistance can be produced, a highly efficient and highly reliable humidifier can be obtained.
[0014]
An asymmetric hollow fiber separation membrane that can be used in the humidifier of the present invention is a method proposed by Loeb et al. (For example, in US Pat. No. 3,133,132) using a polymer solution in which the above resin is dissolved, that is, a polymer solution. Can be easily produced by a so-called dry-wet method in which the product is extruded from a nozzle to obtain a desired shape, and is immersed in a coagulation bath after passing through an air or nitrogen atmosphere space.
[0015]
In one preferred embodiment, the hollow fiber separation membrane used in the humidifying device of the present invention has a skin layer (separation layer), a porous layer (support layer), as disclosed in US Pat. No. 6,464,755. The gas permeation rate of the porous layer is helium gas permeation rate (P ′_He) 2.5 × 10^-3cm³(STP) / cm²・ Sec · cmHg or more, more preferably 3.0 × 10^-3cm³(STP) / cm²・ Sec · cmHg or more, and the tensile strength at the hollow fiber membrane is 2.5 kgf / mm²Or more, more preferably 3.0 kgf / mm²As described above, the elongation at break is preferably 10% or more, more preferably 15% or more.
Helium permeation rate (P ′) of the porous layer (support layer) of the hollow fiber separation membrane_He) Indicates the gas permeation resistance of the porous layer (support layer) of the membrane (however, the larger the value, the smaller the resistance), which is a value measured by the following measuring method. That is, when the skin layer on the surface of the asymmetric hollow fiber membrane is cut by oxygen plasma treatment, the helium gas reaches a region where the transmission rate ratio of helium gas and nitrogen gas is not substantially recognized as the transmission rate ratio of the homogeneous membrane. Gas permeation rate (P '_He). Specifically, the transmission rate ratio (P ′) of helium and nitrogen before plasma treatment._He/ P ’_N2) Is processed by plasma treatment, and the transmission rate ratio (P ′)_He/ P ’_N2) Is the permeation rate of helium gas when it becomes 1.2 or less.
[0016]
The mechanical strength of the hollow fiber separation membrane is expressed by the tensile strength and the breaking elongation in the tensile test of the hollow fiber membrane. These are values measured at a temperature of 23 ° C. using a tensile tester at an effective length of the sample (hollow fiber membrane) of 20 mm and a tensile speed of 10 mm / min. Tensile strength is the value obtained by dividing the stress at the time of tensile breaking of the hollow fiber membrane by the membrane cross-sectional area of the hollow fiber [unit: kgf / mm²The elongation at break is the original length of the hollow fiber membrane L₀, Where L is the length at the time of tensile fracture (L₀-L)) / L₀× 100 [unit:%].
The tensile strength of the hollow fiber membrane is preferably 2.5 kgf / mm²As described above, the breaking elongation is preferably 10% or more. A hollow fiber membrane having such mechanical strength is particularly useful because it can be easily handled without being broken or broken, and has excellent pressure resistance and durability.
Helium gas permeation rate (P ′) of the porous layer as described above_He), A process for producing an asymmetric hollow fiber separation membrane that satisfies the tensile strength and breaking elongation of the hollow fiber membrane is disclosed in US Pat. No. 6,464,755. (The description is included in the present invention by reference.)
[0017]
The film thickness of the asymmetric hollow fiber separation membrane that can be used in the humidifier of the present invention is usually 10 to 200 nm, preferably 20 to 100 nm for the skin layer, and 20 to 200 μm, preferably 30 to 100 μm for the porous layer. .
[0018]
In the humidifying apparatus of the present invention, when the effective length of the hollow fiber membrane element is L, and the inner diameter of the container to which the hollow fiber membrane element is attached is D, the L / D is configured to be 2-6. Since efficiency can be made high, it is suitable.
L and D are shown in FIG. 3 which is a schematic longitudinal sectional view of an example in which a hollow fiber membrane element is mounted in a container. In addition, the arrow in FIG. 3 has shown the direction of the flow of gas.
The effective length L of the hollow fiber membrane element is the length of the portion that actually contributes to water vapor permeation excluding the tube plates formed at both ends of the hollow fiber membrane bundle, and the inner diameter D of the container is the hollow fiber It is the diameter of a cross section perpendicular to the longitudinal direction of the hollow fiber membrane bundle of a container equipped with a membrane element. If the container is cylindrical, D is the diameter of the circular cross section of the cylinder. Usually this container is cylindrical. When this container is a rectangular parallelepiped shape, it is set as the diameter of the circle | round | yen which has the same area as the area of a cross section perpendicular | vertical with respect to the longitudinal direction of the hollow fiber membrane bundle of a container. The inner diameter D of the container indicates the extent of expansion when the second gas introduced into the space outside the hollow fiber membrane flows in the space outside the hollow fiber membrane.
When L / D is 1.8 or less, since the length of the hollow fiber membrane element is relatively short, it is easy to suppress the pressure loss of the first gas flowing through the hollow side of the hollow fiber membrane. However, on the other hand, since the extent of the spread of the second flow gas flowing in the space outside the hollow fiber membrane is relatively larger than the effective length of the hollow fiber element, the second gas flow is The degree of flow in the direction crossing the hollow fiber membrane without flowing in the longitudinal direction is increased. That is, it deviates from the piston flow along the hollow fiber membrane that maximizes the humidifying ability of the hollow fiber membrane, and short path flow or uneven flow, that is, where the gas flow velocity is fast and slow. If a short-pass flow or uneven flow occurs, the humidification efficiency decreases, which is not preferable.
When L / D exceeds 6, the length of the hollow fiber membrane element is relatively long, so that it is difficult to suppress the pressure loss of the first gas flowing through the hollow side of the hollow fiber membrane.
In addition, the used hollow fiber membrane element is the one in which the outer peripheral portion of the hollow fiber membrane bundle is covered with a film-like substance, and the extent of spreading of the second flow gas flowing in the space outside the hollow fiber membrane is suppressed. In some cases, D means not the inner diameter of the container but the inner diameter of the space surrounded by the film-like substance.
[0019]
In the humidifying device of the present invention, the hollow fiber membrane bundle with respect to the cross-sectional area perpendicular to the longitudinal direction of the hollow fiber membrane bundle constituting the hollow fiber membrane element, that is, the membrane filling rate of the hollow fiber membrane bundle constituting the hollow fiber membrane element The ratio of the sum of the cross-sectional areas perpendicular to the longitudinal direction of the hollow fiber membranes constituting each is preferably 35 to 55%, particularly 35 to 45%.
The membrane filling rate of the hollow fiber membrane bundle indicates the ratio of the area occupied by the hollow fiber membrane in the cross-sectional area perpendicular to the longitudinal direction of the hollow fiber membrane bundle, and the membrane filling rate (%) is subtracted from 100 (%). The value (%) indicates the proportion of the space outside the hollow fiber membrane in the hollow fiber membrane bundle.
When the membrane filling rate is less than 35%, there are too few hollow fiber membranes constituting the hollow fiber membrane bundle, and efficient humidification is difficult. In addition, it becomes easy to form a portion having a large film filling rate and a portion having a small film filling rate locally, which causes a short path flow and a drift. Also, if the membrane filling rate exceeds 45%, especially 55%, the space outside the hollow fiber membrane of the hollow fiber membrane bundle becomes small, causing a sheet path and drift, and the space outside the hollow fiber membrane It becomes difficult to suppress the pressure loss of the flowing second gas flow.
[0020]
In the humidifying device of the present invention, it is preferable that 50% or more, particularly about 80% to 95% of the outer peripheral portion of the hollow fiber membrane bundle, which is an effective portion for humidifying the hollow fiber membrane element, is coated with a film-like substance. .
When the hollow fiber membrane element is mounted in the container, a space may be generated between the outer peripheral portion of the hollow fiber membrane bundle and the inner wall surface of the container. The second gas introduced into the space outside the hollow fiber membrane flows through this space, but the second gas flowing through this space does not come into contact with the hollow fiber membrane, and therefore cannot contribute at all to water vapor transmission. Become a flow. The film-like substance that covers the outer peripheral portion of the hollow fiber membrane bundle in the humidifying device of the present invention is provided to prevent a gas flow that has no contribution to the water vapor transmission.
This film-like substance does not hinder the gas flow entering and exiting from the first gas supply port, the first gas discharge port, the second gas supply port, and the second gas discharge port provided in the container. Are arranged as follows.
This film-like substance can be any material as long as it does not substantially permeate or hardly permeate the gas introduced into the apparatus, and has durability in an atmosphere having a temperature of about 80 ° C. and moisture or oxygen gas. For example, a plastic material such as polypropylene, polyester, or polyimide, or an aluminum or stainless steel film can be preferably used. The film thickness is not particularly limited, but is preferably about several tens of μm to several mm.
[0021]
In the humidifying device of the present invention, it is preferable that the first gas flow flowing in the hollow fiber membrane and the second gas flow flowing in the space outside the hollow fiber membrane flow counter-currently. is there.
Among these gas streams, one is a humidifying gas supplied with a high water vapor content, and the other is a humidified gas supplied with a low water vapor content. The driving force through which water vapor permeates the membrane is usually the difference in water vapor partial pressure in the vicinity of the membrane surface of the two gases sandwiching the membrane. Therefore, if the humidifying gas is pressurized and the humidified gas is decompressed, a very large amount of water vapor can be transmitted. However, the pressure of the gas supplied to the fuel cell and the gas discharged from the fuel cell is determined by the use conditions of the fuel cell, and particularly at a low pressure of about 1 to 3 atm (gauge pressure of 0 to 2 atm). Therefore, there is a limit to increasing the efficiency of water vapor transmission by increasing the pressure of the humidifying gas.
In particular, countercurrent is optimal under these conditions for the following reasons.
That is, when water vapor passes through the membrane, the water vapor partial pressure in the vicinity of the membrane surface on the permeate side increases, so that the driving force of water vapor permeation through the membrane is weakened. If the gas having an increased water vapor partial pressure in the vicinity of the membrane surface on the permeate side is replaced with a humidified gas having a low water vapor partial pressure, the driving force through which the water vapor passes through the membrane is not weakened.
When the gas flow that flows through the space inside the hollow fiber membrane and the space outside the hollow fiber membrane is configured to be countercurrent, a gas with an increased water vapor partial pressure in the vicinity of the membrane surface on the permeate side is converted to a humidified gas with a low water vapor partial pressure. In addition, a humidified gas having a low partial pressure of water vapor that has not yet been humidified flows on the permeation side of the membrane where the humidifying gas in which water vapor has permeated and the partial pressure of water vapor has decreased flows. As a result, water vapor can be permeated over the entire length of the hollow fiber membrane, and the humidification efficiency can be improved.
For example, if the gas for humidification and the gas to be humidified flow in the same direction along the hollow fiber membrane without flowing countercurrent, when both gases are introduced and flow on both sides of the membrane, water vapor on both sides of the membrane Although the partial pressure difference is the largest and a large amount of water vapor permeates, as it flows along the membrane, the water vapor partial pressure of the humidifying gas decreases and the water vapor partial pressure of the humidified gas increases and the water vapor on both sides of the membrane increases. The partial pressure difference becomes small and the permeation of water vapor hardly occurs. As a result, the humidification efficiency of the entire hollow fiber membrane is reduced.
[0022]
In the humidifying device of the present invention, the first gas is hollowed from the opening of the tube plate at one end of the hollow fiber membrane element in order to cause the humidifying gas and the humidified gas to flow countercurrently along the hollow fiber membrane. The hollow fiber element tube on the side from which the first gas is discharged, with the second gas being discharged from the opening of the tube plate at the other end of the hollow fiber membrane mem- brane, introduced into the yarn membrane and flowing through the hollow fiber The container is introduced into the space outside the hollow fiber membrane in the container in the vicinity of the plate, and in the vicinity of the tube sheet of the hollow fiber membrane element on the side where the first gas is introduced through the space outside the hollow fiber membrane in the container The first gas supply port, the first gas discharge port, the second gas supply port, and the second gas discharge port are preferably arranged in the container so as to be discharged from the container. is there.
[0023]
The supply port of the second gas may be arranged in the container so that the second gas is directly introduced into the space outside the hollow fiber membrane in the container from the supply port.
Particularly preferably, a core tube arranged along the hollow fiber membrane is provided at substantially the center of the hollow fiber membrane bundle of the hollow fiber membrane element, and the core tube is a tube on the side from which the first gas flows out of the hollow fiber membrane. A communication hole that penetrates the plate and faces the space outside the hollow fiber membrane in the vicinity of the tube plate and communicates with the inside and outside of the core tube is formed, and the first gas supplied from the second gas supply port 2 gas is guided to the core tube, flows out from the communication hole to the space outside the hollow fiber membrane in the container, flows along the hollow fiber outside the hollow fiber, and the first gas flows through the hollow fiber membrane. It is a humidifier configured to be discharged out of the container from a second gas discharge port provided in the container from a space outside the hollow fiber membrane in the vicinity of the tube plate on the side introduced into the container.
The introduced second gas can flow uniformly in a radial direction from the center of the hollow fiber membrane bundle along the hollow fiber membrane and radially outward from the hollow fiber membrane bundle. As a result, it becomes difficult to generate a flow or a drift, and the humidification efficiency can be further increased.
[0024]
In the humidifying device of the present invention, it is preferable that the first gas flowing inside the hollow fiber membrane is a humidifying gas, and the second gas flowing in the space outside the hollow fiber membrane is a humidified gas.
[0025]
In the humidifying device of the present invention, the material such as the container may be formed of any material as long as it is durable in an atmosphere where there is a temperature of about 80 ° C. and moisture or oxygen gas, such as stainless steel or aluminum alloy. It may be made of metal or resin or fiber reinforced resin. The container may be assembled from a cylindrical portion and a cap portion instead of a single unit. Packings, adhesives, bolts and nuts are used as necessary. In addition, the humidifier of the present invention can be used to remove impurities in the gas and substances that may deteriorate the film performance, such as oil mist, dust, and trace chemical substances contained in the gas. A pre-processing device may be provided. Furthermore, a heat exchanger and heaters for adjusting the temperature of the gas, and pressure adjusting devices such as a compressor for adjusting the pressure of the gas are provided as necessary.
[0026]
Hereinafter, it demonstrates further with FIG. 4 which showed the schematic longitudinal cross-sectional view of another example of the humidification apparatus of this invention.
In FIG. 4, both ends of the hollow fiber membrane bundle made of the hollow fiber membrane 1 are fixed by tube plates 2 and 2 'so that the ends of the hollow fiber membrane are kept open. A core tube 9 is provided along the hollow fiber membrane at a substantially central portion of the hollow fiber membrane bundle. The core tube 9 is embedded in the tube plate 2 on the first gas supply port 4 side, and the tube plate 2 ′ on the first gas discharge port 5 side penetrates to supply the second gas. It communicates with mouth 6. Further, in the core tube 9, a communication hole 10 that communicates the inside of the core tube and the space outside the hollow fiber membrane is disposed in the vicinity of the tube plate 2 ′ along the outer periphery of the core tube. A film-like substance 11 is coated on the outer peripheral portion of the hollow fiber membrane bundle. The film-like substance 11 is embedded and fixed in the tube plate 2 ′ on the first gas discharge port side, and the portion facing the second gas discharge port 7 provided near the tube plate 2 is The hollow fiber membrane bundle is not coated with a flume-like substance.
In this apparatus, the humidifying gas containing a large amount of water vapor is introduced from the first gas supply port 4, flows through the hollow fiber membrane, and is discharged from the first gas discharge port 5. On the other hand, the humidified gas to be humidified is introduced from the second gas supply port 6, flows in the core tube 9, is introduced from the communication hole 10 of the core tube to the space outside the hollow fiber membrane, and enters the hollow fiber membrane. Along with this, the flow of the humidifying gas and the countercurrent flow substantially, and are discharged from the discharge port 7 of the second gas. During this time, since the humidifying gas and the humidified gas are in contact with the inner and outer surfaces of the hollow fiber membrane, the water vapor in the humidifying residue having a high water vapor partial pressure passes through the hollow fiber membrane from the hollow fiber membrane to the outside of the hollow fiber membrane. To Penetrate. As a result, the humidified gas flowing in the space outside the hollow fiber membrane is humidified and discharged from the second gas outlet.
In addition, the arrow in FIG. 4 has shown the direction of the flow of gas.
[0027]
The humidifier of the present invention is a humidifier that uses a hollow fiber membrane and is small and lightweight, and does not require complicated driving and operation. In addition, the fuel cell can be stably humidified even when exposed to a temperature of about 80 ° C., which is the operating temperature of the fuel cell, or in an atmosphere where water vapor, oxygen, hydrogen, etc. are present for a long time. However, it is possible to increase the humidification efficiency while suppressing the pressure loss of gas, and the permeation of other components other than water vapor is suppressed, and it is economical, so it can be suitably used for fuel cells.
The humidifier of the present invention can be suitably used particularly when the air supplied to the cathode of the fuel cell is humidified with the exhaust gas from the cathode.
[0028]
FIG. 5 is a schematic view showing an example of a usage pattern of the fuel cell humidifier of the present invention. In addition, the arrow in FIG. 5 has shown the direction of the flow of gas.
In FIG. 5, the polymer electrolyte fuel cell 12 includes an anode 13, a polymer electrolyte membrane 14, and a cathode 15. Air is supplied to the cathode 15. The air is collected from the outside air, and is first supplied from the second gas supply port 6 to the humidifying device of the present invention, and is introduced into the space outside the hollow fiber membrane in the device through the communication hole 10. 2 is discharged from the gas discharge port 7 and supplied to the cathode 15 of the fuel cell. The exhaust gas discharged from the cathode 15 is led to the first gas supply port 4 of the humidifying device of the present invention and introduced into the device. Next, the exhaust gas enters the hollow side of the hollow fiber membrane from the hollow fiber opening of the tube plate 2 and flows through the hollow, flows out of the hollow fiber opening of the tube plate 2 ′, and flows out from the hollow fiber opening of the tube plate 2 ′. Is discharged out of the device.
The exhaust gas discharged from the cathode 5 has a temperature of about 80 ° C. and contains a large amount of water produced by the fuel cell 12. The exhaust gas and air introduced into the humidifier flow in the counter-current direction while contacting the membrane across the hollow fiber membrane. In the meantime, the water vapor in the exhaust gas permeates the membrane and humidifies the air. Further, in this process, the air is heated by receiving the heat of the exhaust gas in the previous period. The humidified and heated air is discharged from the second gas discharge port 7 and supplied to the cathode of the fuel cell.
[0029]
【Example】
Hereinafter, the humidifying device of the present invention will be further described by way of examples. In addition, this invention is not limited to a following example.
[0030]
The measurement methods in the examples are as follows.
(Method for measuring rotational viscosity)
The rotational viscosity of the polyimide solution was measured at a temperature of 100 ° C. using a rotational viscometer (rotor shear rate of 1.75 / sec).
[0031]
(Measurement method of water vapor permeability of hollow fiber membrane)
Using about 10 hollow fiber membranes, a stainless steel pipe, and an epoxy resin adhesive, an element for evaluating permeation performance having an effective length of 20 mm was prepared, and this was attached to a stainless steel container to form a pencil module. . A fixed amount of nitrogen gas having a water vapor concentration of about 23% by volume is supplied to the outside of the hollow fiber membrane of the pencil module, and water vapor separation is performed while flowing a constant amount of carrier gas (Ar gas) to the permeate side. The amount of water vapor in the permeated gas was detected with a specular dew point meter. The water vapor transmission rate of the membrane was calculated from the measured amount of water vapor (water vapor partial pressure), the amount of supplied gas, and the effective membrane area. These measurements were made at 80 ° C.
[0032]
(Measurement method of oxygen gas permeation performance of hollow fiber membrane)
Using about 15 hollow fiber membranes, a stainless steel pipe, and an epoxy resin adhesive, an element for evaluating permeation performance having an effective length of 10 cm was prepared, and this was attached to a stainless steel container to form a pencil module. . A permeate flow rate was measured by supplying oxygen pure gas at a constant pressure thereto. The permeation rate of oxygen gas was calculated from the measured amount of permeated oxygen gas, supply pressure, and effective membrane area. These measurements were made at 80 ° C.
[0033]
(Measurement of tensile elongation at break of hollow fiber membrane)
Using a tensile tester, measurement was performed at an effective length of 20 mm and a tensile speed of 10 mm / min. The measurement was performed at 23 ° C.
(Measurement of hot water resistance of hollow fiber membranes)
Using a hollow fiber membrane having a known tensile break elongation as a sample, ion-exchanged water and the hollow fiber membrane are placed in a stainless steel container and sealed, and the container is placed in an oven at 100 ° C. and held for 50 hours to hold the hollow fiber membrane. Was treated with hot water. The hollow fiber membrane after the hot water treatment was taken out of the container and dried in an oven at 100 ° C. The hollow fiber membrane after drying was measured for tensile elongation at break according to the tensile test method described above. Retention rate [%] of tensile elongation at break was expressed as an index of hot water resistance.
[0034]
(Humidification test)
When the pressure of the supply gas is approximately atmospheric pressure, air having a predetermined pressure, temperature, and relative humidity is supplied to the first gas supply port and the second gas supply port of the humidifier. The gas was supplied while adjusting the flow rate with the gas flow control valve in front. All outlets were open to the atmosphere. In addition, when the pressure of the supply gas is 0.2 MPaG, air having a predetermined pressure, temperature, and relative humidity is supplied to each supply port of the humidifier, and the flow rate discharged from the discharge port is controlled by a flow control valve. Adjusted.
A water manometer was attached immediately before the supply port of the first gas and the second gas and immediately after the discharge port, and the pressure was measured.
In addition, the moisture content of both the first gas and the second gas was measured with a specular dew point meter for the supplied gas and the exhausted gas. In addition, the air having a moisture content in a range that cannot be measured with a dew point meter was mixed with air having a known dew point at a predetermined ratio, and the dew point was measured after the dew point was lowered. The water content was calculated from the measured dew point.
[0035]
(Preparation of polyimide (a) solution)
3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride 52.960 g, 2,2′-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride 53.309 g, Polyimide having 60.793 g of 4′-diaminodiphenyl ether and 830.37 g of parachlorophenol as a solvent in a separable flask at a polymerization temperature of 180 ° C. for 11 hours, having a rotational viscosity of 1716 poise and a polymer concentration of 16% by weight. (A) A solution was obtained.
[0036]
(Preparation of polyimide (b) solution)
88.266 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 61.273 g of diaminodiphenyl ether were added at a polymerization temperature of 180 ° C. in a separable flask together with 728.38 g of parachlorophenol as a solvent. Polymerization was performed for 7 hours to obtain a polyimide (b) solution having a rotational viscosity of 1823 poise and a polymer concentration of 16% by weight.
[0037]
(Manufacture of asymmetric polyimide hollow fiber membrane)
280 g of the polyimide (a) solution and 120 g of the polyimide (b) solution were stirred in a separable flask at a temperature of 130 ° C. for 3 hours to obtain a polyimide mixture solution. The polymer concentration of this mixture solution was 16% by weight, and the rotational viscosity was 1804 poise.
This polyimide mixture solution is filtered through a 400 mesh wire mesh and then discharged from a circular opening of a hollow fiber spinning nozzle having a circular opening and a core opening, and at the same time, nitrogen gas is discharged from the core opening to create a hollow After forming the filamentous body and passing the discharged hollow filamentous body through a nitrogen atmosphere, it was immersed in a coagulation liquid composed of an aqueous ethanol solution having a predetermined concentration (70 to 80% by weight) at a temperature of 0 ° C. to obtain a wet thread. This was immersed in ethanol at a temperature of 50 ° C. for 2 hours to complete the solvent removal treatment, and further washed by immersion in isooctane at a temperature of 70 ° C. for 3 hours to replace the solvent, and then dried to a completely dry state at a temperature of 100 ° C. Thereafter, heat treatment was performed at a predetermined temperature (200 to 300 ° C.) for 1 hour.
[0038]
Six types of asymmetric polyimide hollow fiber membranes A to F were produced by using hollow fiber spinning nozzles with different dimensions, or adjusting the discharge amount of the polyimide solution and the nitrogen gas discharged from the core opening. The dimensions and water vapor permeation performance of the obtained asymmetric polyimide hollow fiber membranes A to F are shown in Table 1.
[Table 1]

[0039]
Example 1
Using a polyimide hollow fiber membrane A (inner diameter of hollow fiber membrane = 710 μm), the effective length (L) of the hollow fiber membrane bundle is 360 mm (the length of each tube sheet is 50 mm) in a cylindrical container having an inner diameter of 165 mm. The same applies hereinafter.), With a membrane filling rate of 40%, approximately 80% of the outer peripheral area is covered with a polyimide film along the outer periphery of the hollow fiber membrane bundle, and the coated cylindrical film is hollow with an inner diameter of 150 mm (D) A humidifying device as shown in FIG. 4 was obtained by attaching a thread membrane element. (L / D = 2.4)
As the first gas, air of approximately atmospheric pressure, temperature of 80 ° C., and relative humidity of 95% is flowed to the hollow side of the hollow fiber membrane at a flow rate of 500 Nl / min. As the second gas, approximately atmospheric pressure, temperature of 25 ° C., relative humidity of 10 % Air was supplied to the space outside the hollow fiber membrane at a flow rate of 500 Nl / min so that the first gas and the second gas would be countercurrent.
As a result of measuring the pressure and dew point of each gas, the pressure loss when the first gas flows through the hollow side of the hollow fiber membrane is 2.4 kPa, and the pressure loss when the second gas flows through the space outside the hollow fiber membrane. The pressure loss was 0.1 kPa, and the total pressure loss was 2.5 kPa. Moreover, the ratio of the moisture content which permeate | transmitted the hollow fiber membrane and moved to 2nd gas among the moisture content which the 1st gas contained was 82%.
[0040]
(Comparative Example 1)
Using a polyimide hollow fiber membrane B (hollow fiber membrane inner diameter = 285 μm), a humidifying device having a substantially the same effective membrane area as in Example 1 and a cylindrical container having the same inner diameter of 165 mm as in Example 1 was produced. . Specifically, the effective length (L) of the hollow fiber membrane bundle is 135 mm, the membrane filling rate is 40%, and about 80% of the outer peripheral area is covered with the polyimide film along the outer periphery of the hollow fiber membrane bundle. A hollow fiber membrane element having an inner diameter of a cylindrical film of 150 mm (D) was attached to obtain a humidifier as shown in FIG. (L / D = 0.9)
The same gas as in Example 1 was supplied to this apparatus so as to flow under the same conditions.
As a result of measuring the pressure and dew point of each gas, the pressure loss when the first gas flows through the hollow side of the hollow fiber membrane is 8.0 kPa, and when the second gas flows through the space outside the hollow fiber membrane. The pressure loss was 0.1 kPa, and the total pressure loss was 8.1 kPa. Moreover, the ratio of the moisture content which permeate | transmitted the hollow fiber membrane and moved to 2nd gas among the moisture content which the 1st gas contained was 36%.
[0041]
(Example 2)
Using polyimide hollow fiber membrane A (inner diameter of hollow fiber membrane = 710 μm), hollow hollow fiber membrane bundle having an effective length (L) of 600 mm and membrane filling rate of 40% in a cylindrical container having an inner diameter of 200 mm (D) A humidifying device as shown in FIG. 2 was obtained by attaching a thread membrane element. (L / D = 3.0)
As the first gas, air at approximately atmospheric pressure, temperature of 80 ° C., and relative humidity of 95% is flowed to the hollow side of the hollow fiber membrane at a flow rate of 1500 Nl / min, and as the second gas, approximately atmospheric pressure, temperature of 25 ° C., relative humidity of 10 % Air was supplied to the space outside the hollow fiber membrane at a flow rate of 1500 Nl / min so that the first gas and the second gas were counterflowed.
As a result of measuring the pressure and dew point of each gas, the pressure loss when the first gas flows through the hollow side of the hollow fiber membrane is 3.6 kPa, and when the second gas flows through the space outside the hollow fiber membrane The pressure loss was 0.4 kPa, and the total pressure loss was 4.0 kPa. Moreover, the ratio of the moisture content which permeate | transmitted the hollow fiber membrane and moved to the 2nd gas among the moisture content which the 1st gas contained was 87%.
[0042]
(Comparative Example 2)
Using polyimide hollow fiber membrane B (inner diameter of hollow fiber membrane = 285 μm), humidification comprising a cylindrical container having the same effective membrane area as in Example 2 and the same container inner diameter of 200 mm (D) as in Example 2. A device was made. Specifically, a hollow fiber membrane element having an effective length (L) of the hollow fiber membrane bundle of 240 mm and a membrane filling rate of 40% was mounted to obtain a humidifier as shown in FIG. (L / D = 1.2)
The same gas as in Example 2 was supplied to this apparatus so as to flow under the same conditions.
As a result of measuring the pressure and dew point of each gas, the pressure loss when the first gas flows through the hollow side of the hollow fiber membrane is 18.8 kPa, and when the second gas flows through the space outside the hollow fiber membrane The pressure loss was 0.6 kPa, and the total pressure loss was 19.4 kPa. Moreover, the ratio of the moisture content which permeate | transmitted the hollow fiber membrane and moved to 2nd gas among the moisture content which the 1st gas contained was 43%.
[0043]
(Example 3)
Using a polyimide hollow fiber membrane C (inner diameter of hollow fiber membrane = 570 μm), a hollow hollow fiber membrane bundle having an effective length (L) of 320 mm and a membrane filling rate of 40% in a cylindrical container having an inner diameter of 100 mm (D) A humidifying device as shown in FIG. 2 was obtained by attaching a thread membrane element. (L / D = 3.2)
The first gas has a pressure of 0.2 MPaG, a temperature of 80 ° C. and a relative humidity of 95% at a flow rate of 500 Nl / min to the hollow side of the hollow fiber membrane, and the second gas has a pressure of 0.2 MPaG, a temperature of 25 ° C., relative Air having a humidity of 5% was supplied to the space outside the hollow fiber membrane at a flow rate of 500 Nl / min so that the first gas and the second gas were counterflowed. As a result of measuring the pressure and dew point of each gas, the pressure loss when the first gas flows through the hollow side of the hollow fiber membrane is 2.6 kPa, and when the second gas flows through the space outside the hollow fiber membrane. The pressure loss was 0.2 kPa, and the total pressure loss was 2.8 kPa. Moreover, the ratio of the moisture content which permeate | transmitted the hollow fiber membrane and moved to 2nd gas among the moisture content which the 1st gas contained was 85%.
[0044]
(Comparative Example 3)
Using polyimide hollow fiber membrane D (inner diameter of hollow fiber membrane = 145 μm), humidification comprising a cylindrical container having the same effective membrane area as in Example 3 and the same container inner diameter of 100 mm (D) as in Example 3. A device was made. Specifically, a hollow fiber membrane element having an effective length (L) of the hollow fiber membrane bundle of 80 mm and a membrane filling rate of 40% was mounted to obtain a humidifier as shown in FIG. (L / D = 0.8)
The same gas as in Example 3 was supplied to this apparatus so as to flow under the same conditions.
As a result of measuring the pressure and dew point of each gas, the pressure loss when the first gas flows through the hollow side of the hollow fiber membrane is 17.5 kPa, and the second gas flows through the space outside the hollow fiber membrane. The pressure loss was 0.4 kPa, and the total pressure loss was 17.9 kPa. Moreover, the ratio of the moisture content which permeate | transmitted the hollow fiber membrane and moved to 2nd gas among the moisture content which the 1st gas contained was 40%.
[0045]
Example 4
Using a polyimide hollow fiber membrane C (inner diameter of hollow fiber membrane = 570 μm), a hollow hollow fiber membrane bundle having an effective length (L) of 380 mm and a membrane filling rate of 40% in a cylindrical container having an inner diameter of 130 mm (D) A humidifying device as shown in FIG. 2 was obtained by attaching a thread membrane element. (L / D = 2.9)
The first gas is air with a pressure of 0.2 MPaG, a temperature of 80 ° C., and a relative humidity of 95% at a flow rate of 1500 N liters / minute to the hollow side of the hollow fiber membrane, and the second gas has a pressure of 0.2 MPaG, a temperature of 25 ° C., relative Air having a humidity of 5% was supplied to the space outside the hollow fiber membrane at a flow rate of 1500 Nl / min so that the first gas and the second gas were counterflowed.
As a result of measuring the pressure and dew point of each gas, the pressure loss when the first gas flows through the hollow side of the hollow fiber membrane is 5.2 kPa, and when the second gas flows through the space outside the hollow fiber membrane The pressure loss was 0.5 kPa, and the total pressure loss was 5.7 kPa. Moreover, the ratio of the moisture content which permeate | transmitted the hollow fiber membrane and moved to 2nd gas among the moisture content which the 1st gas contained was 80%.
[0046]
(Comparative Example 4)
Using polyimide hollow fiber membrane D (hollow fiber membrane inner diameter = 145 μm), humidification comprising a cylindrical container having the same effective membrane area as in Example 4 and the same container inner diameter of 130 mm (D) as in Example 4. A device was made. Specifically, a hollow fiber membrane element having an effective length (L) of the hollow fiber membrane bundle of 90 mm and a membrane filling rate of 40% was mounted to obtain a humidifier as shown in FIG. (L / D = 0.7)
The same gas as in Example 4 was supplied to this apparatus so as to flow under the same conditions.
As a result of measuring the pressure and dew point of each gas, the pressure loss when the first gas flows through the hollow side of the hollow fiber membrane is 33.7 kPa, and when the second gas flows through the space outside the hollow fiber membrane The pressure loss was 1.1 kPa, and the total pressure loss was 34.8 kPa. Moreover, the ratio of the moisture content which permeate | transmitted the hollow fiber membrane and moved to 2nd gas among the moisture content which the 1st gas contained was 32%.
[0047]
(Example 5)
Using a polyimide hollow fiber membrane E (hollow fiber membrane inner diameter = 510 μm), a hollow hollow fiber membrane bundle having an effective length (L) of 280 mm and a membrane filling rate of 40% in a cylindrical container having an inner diameter of 100 mm (D) A humidifying device as shown in FIG. 2 was obtained by attaching a thread membrane element. (L / D = 2.8)
The first gas has a pressure of 0.2 MPaG, a temperature of 80 ° C. and a relative humidity of 95% at a flow rate of 500 Nl / min to the hollow side of the hollow fiber membrane, and the second gas has a pressure of 0.2 MPaG, a temperature of 25 ° C., relative Air having a humidity of 5% was supplied to the space outside the hollow fiber membrane at a flow rate of 500 Nl / min so that the first gas and the second gas were counterflowed. As a result of measuring the pressure and dew point of each gas, the pressure loss when the first gas flows through the hollow side of the hollow fiber membrane is 2.9 kPa, and when the second gas flows through the space outside the hollow fiber membrane The pressure loss was 0.2 kPa, and the total pressure loss was 3.1 kPa. Moreover, the ratio of the moisture content which permeate | transmitted the hollow fiber membrane and moved to 2nd gas among the moisture content which the 1st gas contained was 80%.
[0048]
(Reference Example 1)
Using a polyimide hollow fiber membrane F (inner diameter of hollow fiber membrane = 410 μm), a hollow hollow fiber membrane bundle having an effective length (L) of 230 mm and a membrane filling rate of 40% in a cylindrical container having an inner diameter of 100 mm (D) A humidifying device as shown in FIG. 2 was obtained by attaching a thread membrane element. (L / D = 2.3)
The first gas has a pressure of 0.2 MPaG, a temperature of 80 ° C., and a relative humidity of 95% to the hollow side of the hollow fiber membrane at a flow rate of 500 Nl / min. The second gas has a pressure of 0.2 MPaG, a temperature of 25 ° C., relative Air having a humidity of 5% was supplied to the space outside the hollow fiber membrane at a flow rate of 500 Nl / min so that the first gas and the second gas were counterflowed. As a result of measuring the pressure and dew point of each gas, the pressure loss when the first gas flows through the hollow side of the hollow fiber membrane is 3.9 kPa, and when the second gas flows through the space outside the hollow fiber membrane The pressure loss was 0.2 kPa, and the total pressure loss was 4.1 kPa. Moreover, the ratio of the moisture content which permeate | transmitted the hollow fiber membrane and moved to 2nd gas among the moisture content which the 1st gas contained was 71%.
[0049]
(Example 7)
Using a polyimide hollow fiber membrane E (hollow fiber membrane inner diameter = 510 μm), a hollow hollow fiber membrane bundle having an effective length (L) of 340 mm and a membrane filling rate of 40% in a cylindrical container having an inner diameter of 130 mm (D) A humidifying device as shown in FIG. 2 was obtained by attaching a thread membrane element. (L / D = 2.6)
The first gas is air with a pressure of 0.2 MPaG, a temperature of 80 ° C., and a relative humidity of 95% at a flow rate of 1500 Nl / min, and the second gas has a pressure of 0.2 MPaG, a temperature of 25 ° C., relative Air having a humidity of 5% was supplied to the space outside the hollow fiber membrane at a flow rate of 1500 Nl / min so that the first gas and the second gas were counterflowed.
As a result of measuring the pressure and dew point of each gas, the pressure loss when the first gas flows through the hollow side of the hollow fiber membrane is 5.9 kPa, and when the second gas flows through the space outside the hollow fiber membrane The pressure loss was 0.6 kPa, and the total pressure loss was 6.5 kPa. Moreover, the ratio of the moisture content which permeate | transmitted the hollow fiber membrane and moved to 2nd gas among the moisture content which the 1st gas contained was 75%.
[0050]
【The invention's effect】
Since the present invention is as described above, the following effects can be obtained.
That is, the present invention can stably humidify even if it is exposed for a long time in an atmosphere in which steam, oxygen, hydrogen, etc., which is the operating temperature of the fuel cell, is about 80 ° C. A humidifier that can increase the humidification efficiency while suppressing gas pressure loss, suppresses the permeation of other components other than water vapor, and can be suitably used for an economical fuel cell. provide.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view of an example of a hollow fiber membrane element constituting a humidifying device for a fuel cell of the present invention.
FIG. 2 is a schematic longitudinal sectional view of an example of a fuel cell humidifier according to the present invention.
FIG. 3 is a schematic longitudinal sectional view of an example of a fuel cell humidifier according to the present invention. L and D are shown.
FIG. 4 is a schematic longitudinal sectional view of another example of a fuel cell humidifier according to the present invention.
FIG. 5 is a schematic view showing an example of a usage pattern of the fuel cell humidifier of the present invention.
[Explanation of symbols]
1: Hollow fiber membrane
2, 2 ': Tube sheet
3: Hollow fiber membrane element
4: First gas supply port
5: First gas outlet
6: Second gas supply port
7: Second gas outlet
8: Container
9: Core tube
10: Communication hole
11: Film-like substance
12: Fuel cell
13: Anode
14: Solid polymer electrolyte membrane
15: Cathode

Claims

At least a first gas supply port, a first gas exhaust, and a hollow fiber membrane element having a tube sheet in which hollow fiber membranes are fixed in an open state at both ends of a bundle of hollow fiber membranes comprising a plurality of hollow fiber membranes. A container having an outlet, a second gas supply port, and a second gas discharge port is mounted so that the space leading to the hollow side of the hollow fiber membrane is separated from the space leading to the outside of the hollow fiber membrane. In the fuel cell humidifier configured,
(A) The inner diameter of the hollow fiber membrane is in the range of more than 500 μm to less than 1500 μm. (B) The water vapor transmission rate (P ′ _H2O ) of the hollow fiber membrane is 0.5 × 10 ⁻³ cm ³ (STP) / cm ^2. (C) The hollow fiber membrane has a tensile elongation at break of 80% or more after hot water treatment in hot water at 100 ° C. for 50 hours. (D) Hollow fiber When the effective length of the membrane element is L and the inner diameter of the container in which the hollow fiber membrane element is mounted is D, L / D is 2 to 6 (e) The membrane of the hollow fiber membrane bundle constituting the hollow fiber membrane element The filling rate (the ratio of the sum of the cross-sectional areas perpendicular to the longitudinal direction of each hollow fiber membrane constituting the hollow fiber bundle to the cross-sectional area perpendicular to the longitudinal direction of the hollow fiber membrane bundle constituting the hollow fiber membrane element) (F) 1 to 3 atm low pressure first gas or second being 35 to 55% Fuel cell humidifier, characterized in that moving from the gas more than 75% of the water content to the second gas or a first gas of the low pressure of 1-3 atm.

The humidifying device for a fuel cell according to claim 1, wherein 50% or more of the outer peripheral portion of the hollow fiber membrane bundle constituting the hollow fiber membrane element is coated with a film-like substance.

The said 1st gas which flows through the hollow side of a hollow fiber membrane, and the 2nd gas which flows through the space outside a hollow fiber membrane are comprised so that it may flow counterflow across a hollow fiber membrane. The fuel cell humidifier according to any one of -2.

A core tube arranged along the hollow fiber membrane bundle is provided at substantially the center of the hollow fiber membrane bundle constituting the hollow fiber membrane element, and a communication hole for communicating the inside of the core tube with the outside of the core tube is formed in the core tube. The second gas is configured so that the second gas is led into the core tube from the second gas supply port and introduced into the space outside the hollow fiber membrane through the communication hole. A humidifier for a fuel cell according to claim 1.

The humidifier for a fuel cell according to any one of claims 1 to 4, wherein the gas supplied to the fuel cell is humidified.

6. The fuel cell according to claim 1, wherein the first gas is exhaust gas from the cathode of the fuel cell, and the second gas is air supplied to the cathode of the fuel cell. Humidifying device.

At least a first gas supply port, a first gas exhaust, and a hollow fiber membrane element having a tube sheet in which hollow fiber membranes are fixed in an open state at both ends of a bundle of hollow fiber membranes comprising a plurality of hollow fiber membranes. A container having an outlet, a second gas supply port, and a second gas discharge port is mounted so that the space leading to the hollow side of the hollow fiber membrane is separated from the space leading to the outside of the hollow fiber membrane. Configure
(A) The inner diameter of the hollow fiber membrane is in the range of more than 500 μm to less than 1500 μm. (B) The water vapor transmission rate (P ′ _H2O ) of the hollow fiber membrane is 0.5 × 10 ⁻³ cm ³ (STP) / cm ^2. (C) The hollow fiber membrane has a tensile elongation at break of 80% or more after hot water treatment in hot water at 100 ° C. for 50 hours. (D) Hollow fiber When the effective length of the membrane element is L and the inner diameter of the container in which the hollow fiber membrane element is mounted is D, L / D is 2 to 6 (e) The membrane of the hollow fiber membrane bundle constituting the hollow fiber membrane element The filling rate (the ratio of the sum of the cross-sectional areas perpendicular to the longitudinal direction of each hollow fiber membrane constituting the hollow fiber bundle to the cross-sectional area perpendicular to the longitudinal direction of the hollow fiber membrane bundle constituting the hollow fiber membrane element) Using a humidifier that is 35-55%, the first gas with a low pressure of 1-3 atm. Or wherein the moving the more than 75% of the water content of the low pressure of 1-3 atm to a second gas or the first gas from the second gas, a method of humidifying a supply gas of the fuel cell.