JP4033593B2

JP4033593B2 - SF6 gas recovery device

Info

Publication number: JP4033593B2
Application number: JP33081399A
Authority: JP
Inventors: 和潔高野; 光一大熊
Original assignee: 山陽電子工業株式会社
Priority date: 1999-03-19
Filing date: 1999-11-22
Publication date: 2008-01-16
Anticipated expiration: 2019-11-22
Also published as: JP2000334247A

Description

【０００１】
【発明の属する技術分野】
本発明はＳＦ６ガス（６フッ化硫黄ガス、以下同じ）の回収に関する。
【０００２】
【従来の技術】
ＳＦ６ガスは高電圧電力用トランスや電力回路の遮断器に充填し、その熱的安定性，電気的安定性，高絶縁耐圧性を生かして装置の小型化を可能にし、都市の変電所の小容積化でその貢献は大きい。トランスや遮断器に充填されているＳＦ６ガスはその純度１００％のものや窒素ガスにより適度にうすめて充填されるものがある。それ等が用いられている機器の点検保守，修理のときはこれ等のガスを抜き出さなければならないが、従来はこれ等のガスによる人体等への害は少ないので大気中に放出していた。
しかし、ＳＦ６ガスは高価なガスであるため経費的に容易に回収再利用できる範囲の回収装置は従来よりあり回収して再利用していた。
すなわち、抜取加圧と圧縮冷却によって液化回収する装置はあったが、被回収容器内を高真空域まで吸引して回収したり、他のガスが混合しているガスを分離してＳＦ６ガスのみを回収する装置などはなかった。
【０００３】
すなわち、他のガスが混入し、ＳＦ６ガスの濃度が下がっている場合はその分圧が低くなるため高圧に圧縮し、そして低い温度までの冷却が必要となるため高額の装置価格となり、作られていなかった。
そして従来は、ＳＦ６ガスが使用中に遮断時のアークや熱によりわずかに分解されて生ずるＳＦ４や二酸化硫黄，ＳＯＦ２などの分解ガスは使用機器の特性劣化を生ずるものがあるので、これを防止するために除去する装置はあったが回収時に分離精製する装置はなかった。
【０００４】
近年、地球温暖化防止による炭酸ガス等の放出が規制されるようになってきた。１９９７年世界環境会議が京都で開催され、その結果炭酸ガスの２４０００倍の温暖化係数を持つＳＦ６ガスもその放出を厳しく規制されるようになった。
ＳＦ６ガスを大気に漏出する事が無いようにするためには、
「イ」充填機器のシール部より漏れて漏出するガスを無くする。
「ロ」機器据付時，保守修理時，解体廃棄時等で、ガス充填や抜取に係わるときに廃棄されるガスを無くすることが重要である。
この「イ」については、機器のシール部の改良により現在は大変少なくなっている。
また「ロ」については、電力業界は電気共同研究会により「電力用ＳＦ６ガス取扱い基準」を平成１０年１２月に自主制定し、その排出を規制することとした。
すなわち、点検修理時は０．０１５ＭＰａ・ａｂｓ（回収率９７ｖｏｌ％以上）解体撤去時は０．００５ＭＰａ・ａｂｓ（回収率９９ｖｏｌ％以上）の真空域まで吸引回収する自主基準を作成した。高真空域まで回収すると回収に長時間を要する欠点を生ずる。点検時の回収率が低いのは装置停止による停電の時間を可能な限り短くするための妥協値であり、撤去時は十分に時間をとって真空引きするようになっている。すなわち高真空域まで吸引回収し、大気への漏出量を少なく押さえている。
【０００５】
電力業界としては２００５年までに上記基準に合う回収装置を開発し、実施することとしている。
不活性ガスである窒素ガスを５０ｖｏｌ％混入してもインパルス破壊電圧はＳＦ６ガス単独ガス時の８５％，商用周波数破壊電圧は同９６．６％であり、性能低下が少ないのでＳＦ６ガスをトランスや遮断器に封入する際に窒素ガスによりうすめて使用するメーカーと高純度のＳＦ６ガスを使用するメーカーとがある。従来はこのような窒素ガスが混入したガスは回収しにくいガスであったため、点検や廃棄時にその多くは大気中に放出して廃棄していた。
【０００６】
【発明が解決しようとする課題】
トランスや遮断器である被回収容器よりＳＦ６ガスを大気中にほとんど漏出することなく９９ｖｏｌ％以上を回収することであり、しかも短時間に回収できるようにする。また被回収ガス中に窒素ガスや空気の混入があってもそれを分離し、回収できるようにすること。
【０００７】
【課題を解決するための手段】
本発明の目的は上記課題を解決するため、臨界温度４５．６４℃，臨界圧力３．７５ＭＰａ・Ｇ，融点−５０．８℃，昇華点−６３．８℃のＳＦ６ガスの特徴を考慮し、さらに被回収容器としてのトランス又は電路の遮断器は密閉容器でありその中にＳＦ６ガスが高圧（約０．６ＭＰａ・Ｇ〜０．３ＭＰａ・Ｇ）で充填されている。
そして充填ガスは混合されている窒素ガスや放電により少量だが、ＳＦ６ガスが分解し、ＳＦ４，ＳＯＦ２，二酸化硫黄が存在し、水分も混入することがある。但し、ＳＦ６ガスからの分解ガス，ＳＦ４，ＳＯＦ２，二酸化硫黄の除去については別途除去手段があり、そこで大部分取り除くことができるが、ここでの詳細な記述は省く。
電力の供給という公共のインフラクチャーに係わる装置に使用されている装置の点検，保守あるいは修理時に停電する時間を極力短くする事は、ＳＦ６ガスを回収する主性能に次いで重要な課題である。これ等の諸問題を考慮しながら効率の良い回収装置を発明した。
【０００８】
被回収容器（トランス，遮断器など）には被回収ガス（ＳＦ６ガス）が前述のように高圧で充填してある。そしてＳＦ６ガスは易液化ガスであるため、これを加圧する加圧部と冷却液化する液化部を設け、被回収ガス中のＳＦ６ガスの濃度が高い範囲においては、加圧ガス中のＳＦ６ガス分圧も高くなるので、液化ガスの液化温度と圧力の関係から加圧する圧力が比較的低い圧力範囲または液化温度の比較的高い範囲で容易に液化回収できる。
まずかかる方法により被回収容器内の内圧が加圧ポンプにより液化可能な圧力範囲となるまで回収する。前述のように被回収ガスはＳＦ６ガス１００％のものと窒素ガス等によりうすめられている場合がある。この混入ガスが存在していてもこれをＳＦ６ガスと分離するガス分離部を設ける。ガス分離部は特定ガスを吸着する吸着剤を用いたＰＳＡ法（ｐｒｅｓｓｕｒｅＳｗｉｎｇＡｄｓｏｒｐｔｉｏｎ）により行う。特定ガスを含む混合ガスを、該吸着剤を充填した吸着筒に圧力を加えながら送り込むとこの吸着剤に特定ガスが吸着して除かれ、吸着されないガスが吸着筒の他端から分離されて取り出される。この工程を吸着工程という。そして吸着剤に特定ガスが吸着されていっぱいになる少し前に混合（原料）ガスの送入を止め、その吸着筒の入口より吸着筒の圧力を減じてやると、吸着剤に吸着した特定ガスが吸着剤より離脱して排出され、吸着剤の吸着能力が再生する。これを再生工程という。この吸着工程と再生工程を繰り返しながら、すなわち吸着筒に圧力を加えたり、減じたりしながらガスを分離するのでｐｒｅｓｓｕｒｅＳｗｉｎｇＡｄｓｏｒｐｔｉｏｎ（略してＰＳＡ）（圧力変動吸着）法という。
【０００９】
そして吸着剤には対象ガスであるＳＦ６ガスを吸着して、混合ガスを吸着しない吸着剤と、対象ガスであるＳＦ６ガスを吸着せず混合している他のガスを吸着する吸着剤とがある。その使用する吸着剤により、対象ガスを取り出す方法が少し異なる。
例えばＳＦ６ガスを対象ガスとした場合、前者は活性炭に分子篩機能を持たせた分子篩炭がある。後者にはゼオライトの５Ａタイプ，４Ａタイプ他がある。前者の場合は対象ガスであるＳＦ６ガスが吸着剤に吸着し、分離されているのであるから、減圧再生工程で吸着剤より離脱する工程内で濃縮したＳＦ６ガスを回収する。後者では加圧吸着工程でＳＦ６ガスが吸着筒の他端より分離されて出てくるので吸着工程で得られる。
ゼオライトはＳＦ６ガスはほとんど吸着せず窒素ガスや炭酸ガス，水分を良く吸着除去する、酸素ガスはわずかに吸着するのでＳＦ６ガスとこれ等のガスが混合しているガスからＳＦ６ガスを分離するガス分離部に吸着剤として使用する。
【００１０】
しかしＳＦ６ガスに空気が混入した場合も起こり得る。空気はその主成分が窒素７８％，酸素２１％であるので、まず窒素を多く吸着するゼオライトを吸着筒の上流側に入れ、続いて酸素を強く吸着する分子篩炭を吸着剤としてその下流に置くことによりまず窒素ガスを除き濃度の低い酸素を濃縮し、分子篩炭により分圧の高くなった酸素を効率よく吸着除去できるよう、２種の吸着剤を前記のように上流・下流に組み合わせ配置することにより効率のよい空気の分離除去が出来るガス分離部を構成する。そして、ガス分離部で分離したＳＦ６ガス以外のガスは窒素ガスと酸素ガスであり、大気を構成するガスと同一であるので大気中に放気する。再生工程において、大気中に放気されるこの排気ガスはＳＦ６ガスを含まなくする必要があり、吸着工程の終わった吸着筒内にＳＦ６ガスが残らないよう、吸着工程と再生工程の間に均圧工程を入れる。
【００１１】
すなわちガス分離部に吸着剤を充填した複数の吸着筒を用い、ひとつの加圧工程にある吸着筒に被回収ガスを供給し、ＳＦ６ガス中の混合ガスを吸着剤に吸着させ、吸着剤が吸着ガスで満杯になる前に被回収ガスの供給を止め、他のひとつの再生工程の終了した吸着筒と入口同士，出口同士を結合し、吸着工程の終了した吸着筒内のガスを再生工程の終了した吸着筒に移す均圧工程を行った後、吸着工程の終了した吸着筒は減圧し、再生工程に入り、吸着剤に吸着したガスを脱着して大気に排出する。この時、真空ポンプにより真空域まで減圧して再生することもある。そして再生工程の終了した吸着筒は吸着工程に入り、被回収ガスを供給してＳＦ６ガスを分離する。均圧工程を入れることにより、吸着工程の完了した吸着筒の入口，出口及びそれぞれの導管内に存在するＳＦ６ガスを再生工程の終わった吸着筒に移した後（ＳＦ６ガスを無くした後）、再生工程に入ってＳＦ６ガスを含まない吸着ガスを大気中へ排出するようにしたものである。
【００１２】
被回収容器内に存在する被回収ガス（ＳＦ６ガス）は、この被回収容器内の内圧を大気圧レベルにまで回収してもまだ被回収容器内にあるガス中に残存するため、これを点検時は０．０１５ＭＰａ・ａｂｓ，解体時は０．００５ＭＰａ・ａｂｓの真空域まで減圧して回収し、ＳＦ６ガスが大気中へ散逸することを少なくする自主規制としているが、真空値が高まる程、ガスが膨張し、その回収に長時間を要する。そこで鋭意研究の結果、前記ガス分離部にて分離のできるガスを被回収容器に充填し、被回収容器を陽圧又は陽圧に近い圧力に高めてこの分離部にて分離可能なガスをＳＦ６ガスと混合して導出するようにすることにより、ＳＦ６ガスを短時間で目標回収レベル（残留ガスレベル）まで回収する。そのためガス供給部を設ける。
ガス供給部のガスはガス分離部の能力と相まって窒素ガス又は空気を用いることが出来る。
【００１３】
短時間で効率良く回収するため、被回収容器内のＳＦ６ガスの濃度が高い範囲においては容易に液化回収出来るので被回収容器内の被回収ガスを加圧部で加圧し、続いて液化部で冷却液化して回収する。この方法により被回収容器内の内圧が加圧ポンプにより液化可能な圧力範囲までは回収する。（しかしこの圧力は液化部の冷却能力（温度）に左右されて変わることに注意する必要がある。）被回収容器内圧力が一定値以下に下がるとガス供給部より、ガスを被回収容器に供給し、昇圧して加圧部で加圧できるようにする。このとき液化部より非液化ガスを抜き取るようにする。このガスは加圧部より上流側に戻すようにして、再度加圧冷却液化のサイクルに入れる。
【００１４】
被回収ガス中のＳＦ６ガスの濃度が低くなるに従って、ＳＦ６ガスの分圧が下がるので液化のための圧力は高くなり、液化に必要な温度が低くなり液化できなくなるので、一定濃度以下になると被回収ガスをガス分離部に導き、ＳＦ６ガスを濃縮した後に加圧部に加える。この方法により回収を継続していき、被回収ガス中のＳＦ６ガスの濃度をみて０．０１５ＭＰａ・ａｂｓ相当までの回収ができたか判断し、回収を終える。
かかる方法によれば被回収容器より高真空まで引くことの出来る高価な真空ポンプを使うことなく陽圧にて被回収ガスを導出することができるうえ短時間で目標レベル以下の回収ができる。
【００１５】
すなわち、
「あ」ガス供給部とガス分離部で構成されたＳＦ６ガス回収装置において、被回収容器にガス供給部で調圧した高圧ガスを供給し、ＳＦ６ガスと混合した被回収ガスをガス取出口より取り出し、ガス分離部にてＳＦ６を多く含むガスとＳＦ６をほとんど含まないガスに分離し、ＳＦ６をほとんど含まないガスを大気中に排出し、ＳＦ６を含むガスを回収する。
「い」被回収容器中のＳＦ６ガス又は混合ガス（窒素ガス又は空気や炭酸ガス等）を吸着する吸着剤を充填した吸着筒を有するＰＳＡ方式によるガス分離部とガス供給部とで構成するＳＦ６ガス回収装置において、被回収容器にガス供給部で調圧した高圧ガスを供給し、ＳＦ６ガスと混合した被回収ガスを取り出し、該ガス分離部に送入し、加圧吸着工程にて被回収容器内の易吸着ガスを吸着筒内の吸着剤に吸着させて非吸着ガスと分離し、減圧再生工程にて吸着筒を減圧し、吸着剤に吸着しているガスを脱着し、ＳＦ６ガスと分離した混合ガスを大気中に排出するようにした。
「う」ゼオライトを吸着剤として充填した吸着筒を有するＰＳＡ方式によるガス分離部と窒素ガス供給部で構成するＳＦ６ガス回収装置において、被回収容器に窒素ガス供給部で調圧した窒素ガスを供給して被回収容器に充填されているＳＦ６ガスを主とするガスと混合した被回収ガスを取り出し、該ガス分離部に送入し、加圧吸着工程にて窒素ガス等を吸着筒内の吸着剤に吸着除去してＳＦ６ガスと分離し、減圧工程にて吸着筒を減圧し、吸着剤に吸着している窒素ガス等を脱着し、大気中に放出するようにした。
【００１６】
また、
「え」被回収容器中のＳＦ６ガス以外のガスを吸着する吸着剤を充填した吸着筒を２本有するＰＳＡ方式によるガス分離部とガス供給部で構成するＳＦ６ガス回収装置において、被回収容器にガス供給部で調圧した高圧ガスを供給し、被回収容器に充填されているＳＦ６ガスを主とするガスと混合した被回収ガスを取出口より取り出し、該ガス分離部に送入し、１方の加圧吸着工程にある吸着筒にてＳＦ６ガス以外のガスを吸着筒内の吸着剤に吸着させてＳＦ６ガスと分離し、該吸着筒の吸着剤が吸着ガスで満杯になる前に被回収ガスの供給を止め、他方の減圧再生工程の完了した吸着筒と入口同士と出口同士を結合し、吸着工程の完了した吸着筒のガスを減圧再生工程の完了した吸着筒に移す均圧工程を行った後、吸着工程の完了した吸着筒は減圧再生工程に入り、吸着剤に吸着したガスを大気中に排出し、減圧再生工程の終了した吸着筒は吸着工程に入り、被回収ガスを供給してＳＦ６ガスを分離するようにした。
「お」ゼオライトを上流側に分子篩炭を下流側に充填した吸着筒２本を有するＰＳＡ方式によるガス分離部と高圧空気供給部で構成するＳＦ６ガス回収装置において、被回収容器に高圧空気供給部より一定圧の高圧空気を供給してＳＦ６ガスと混合し、取出口より被回収ガスを取り出し、該ガス分離部に送入し、１方の加圧吸着工程にある吸着筒にて窒素ガス，酸素ガス他を該吸着筒内の吸着剤に吸着させてＳＦ６ガスと分離し、該吸着筒の吸着剤が該吸着ガスで満杯になる前に被回収ガスの供給を止め、他方の減圧再生工程の完了した吸着筒と入口同士，出口同士を結合し、吸着工程の完了した吸着筒のガスを減圧再生工程の完了した吸着筒に移す均圧工程を行った後、吸着工程の完了した吸着筒は減圧再生工程に入り、吸着剤に吸着したガスを大気中に排出し、減圧再生工程の終了した吸着筒に被回収ガスを供給して吸着工程に入り、ＳＦ６ガスを分離するようにした。
【００１７】
さらに、
「か」ガス分離部と加圧部と液化部で構成するＳＦ６ガス回収装置において、被回収容器より取り出したＳＦ６を含む被回収ガスをガス分離部に供給し、ＳＦ６ガスとＳＦ６を含まないガスとに分離し、ＳＦ６を含まないガスを大気中に排出し、ＳＦ６ガスを加圧部にて加圧した後、液化部に送り、該液化部は液体窒素タンクより液体窒素ガスの主に気化潜熱の雰囲気にこの液化部を付設して該液化部を冷却し、ＳＦ６ガスを液化させるようにし、ガス化した液化窒素を加圧して被回収容器に供給するようにした。
「き」ガス分離部と加圧部，液化部，ガス供給部で構成するＳＦ６ガス回収装置において、被回収容器中のＳＦ６ガス濃度が濃いときは被回収ガスを加圧部にて直接加圧した後、液化部にて冷却液化し、冷却部内の非液化ガスを加圧部より上流側に戻すよう構成し、該被回収容器内の内圧が略大気圧（約０ＭＰａ・Ｇ）になるまで行ない、その後、ガス供給部より被回収容器内に一定圧のガスを供給し、ＳＦ６ガスと混合し、圧力を高め前記加圧冷却による液化回収を継続し、被回収ガス中のＳＦ6ガス濃度が一定値以下になると被回収ガスをガス分離部に送入し、ＳＦ６ガスと混合ガスとを分離し、混合ガスを大気中に排出し、ＳＦ６ガスを加圧部にて加圧した後、液化部にて冷却液化するようにしたものである。
【００１８】
【実施例】
図１に好ましい１実施例のＳＦ６ガス回収装置のフローシートを示す。
トランスや遮断器である被回収容器１の中に充填されているＳＦ６ガスを回収するものである。回収装置の構成はガス分離部３，ガス供給部７，加圧部２，液化部４及び液化したＳＦ６ガスを貯蔵する貯液器５より成っている。
被回収容器１には通常０．３ＭＰａ・Ｇから０．６ＭＰａ・Ｇの圧力でＳＦ６ガスが封入されている。その濃度は１００ｖｏｌ％から、窒素ガスでうすめられても５０ｖｏｌ％以上の濃度で封入されている。そしてＳＦ６ガスは臨界温度４５．６４℃，臨界圧力３．７５ＭＰａ・Ｇ，臨界モル容積２０１ｍＬ／ｍｏｌ，融点−５０．８℃，昇華点−６３．８℃である。
【００１９】
ＳＦ６ガスの蒸気圧は例えば０℃で１．２２ＭＰａ・Ｇであるので被回収ガスを抜き出して加圧部２で２．４４ＭＰａ・Ｇに加圧し、冷却部４で０℃以下に冷却すれば５０ｖｏｌ％以上のＳＦ６ガスは液化回収することができる。
このため被回収容器１より加圧部２に被回収ガスを導入し、バッファタンク２８と加圧ポンプ３０と定圧弁２９による戻し回路で構成する加圧部２により２．４４ＭＰａ・Ｇに加圧し、これを冷却部３１，液化タンク３２と電磁弁３３，３４で構成する液化部４で２０℃以下に冷却し、ＳＦ６を液化回収する。液化ＳＦ６は貯液器５に貯える。
【００２０】
被回収ガスのＳＦ６濃度が５０ｖｏｌ％以上のときは被回収容器内の内圧が０ＭＰａ・Ｇになると、ガス供給部７よりガスを送入口３６より送入し、ＳＦ６ガスと混合し、取出口３５より取り出し、加圧部２で加圧し、液化部で冷却する方法を継続し、ＳＦ６ガスを液化回収する。液化タンク３２内には非液化ガス（窒素ガス）が残るのでこのガスは加圧部より上流側に戻す（図示は省略している）ようにする。そして被回収ガス中のＳＦ６ガスの濃度が５０ｖｏｌ％以下になると前記圧力と温度では液化回収が出来なくなるので、ガス分離部３に電磁弁１０を閉じ９を開いて被回収ガスを導入し、ＳＦ６ガスを分離する。すなわちＳＦ６ガス以外の窒素ガス他を吸着する吸着剤を充填した吸着筒１９，２０と電磁弁１８，２１〜２７と真空ポンプ１５で構成されるガス分離部３の一方の吸着筒１９に電磁弁２１を開いて導入すると、吸着筒１９内の吸着剤に被回収ガス中のＳＦ６以外のガスが吸着されて除去されるのでＳＦ６ガスが濃縮されて吸着筒の他端出口より電磁弁２５，２７を通って導出する、これを吸着工程という。
【００２１】
この導出したガスは加圧部２のバッファタンク２８に貯留され、次に加圧される。吸着筒１９の吸着剤に窒素ガス等が吸着し、満杯になる少し前に電磁弁９と２７を閉とし、被回収ガスの導入とＳＦ６ガスの導出を中止し、再生工程の終了している吸着筒２０の入口の電磁弁２１と２３，出口の電磁弁２５，２６を開とし、吸着工程の終了した吸着筒１９から再生工程の終了している吸着筒２０に、吸着筒１９内や入口・出口導管内に残留するＳＦ６ガスを吸着筒２０に移動させる均圧工程を行った後、吸着筒１９の電磁弁２１と２５を閉とし、電磁弁２２と１８を開にして大気に開放し吸着筒１９の圧力を大気圧まで減圧すると、吸着剤に吸着している窒素ガス等が離脱して、大気中に排出される。続いて電磁弁１８を閉として、真空ポンプ１５により真空域まで引いて吸着剤の再生を十分に行う。（再生工程）
【００２２】
吸着筒２０は電磁弁９と２７を開にして、被回収ガスを電磁弁９，２３から導入し、濃縮したガスを電磁弁２６，２７よりバッファタンク２８に導入し、加圧ポンプ３０により加圧し、前と同じ方法により液化分離する。ガス供給部７は、窒素ボンベ１３と調圧弁１４で構成し、窒素ガスを被回収容器に導入して混合する場合にはＳＦ６ガスと窒素ガスとを分離するのでガス分離部３で使用する吸着剤はゼオライトで良く、他にも窒素ガスを吸着するものであれば使用可能で、ゼオライトは１３Ｘタイプ，５Ａタイプがあり、５Ａタイプをこの実施例で使用している。
【００２３】
また吸着筒の被回収ガスの入口（上流）側にゼオライトと出口（下流）側に分子篩炭（ＣＭＳ・・Ｃａｒｂｏｎ，Ｍｏｌｅｃｕｌａｒ，Ｓｅａｖｅｓ）を充填し、窒素ガスと酸素ガスを吸着除去できるようにすると窒素ガスを用いるガス供給部７に代えて空気を用いた圧縮空気発生部６を用いることができる。これはコンプレッサー１２と空気乾燥器により構成し、乾燥した空気を調節された圧力で被回収容器１に送入し、ＳＦ６ガスと混合した後、前記窒素ガスを用いた方法と同じ原理でＳＦ６ガスを分離回収できるのでどこにでもある空気を用いて行うことが出来る。
【００２４】
そして混合ガス中のＳＦ６ガスの濃度が大気圧換算で、純ＳＦ６ガスの０．０１５ＭＰａ・ａｂｓ相当の約５％になった時、尚ＰＳＡガス分離部に導入する圧力分だけ高圧であるときは、その圧力相当分の１を乗じた濃度まで下げてやる必要がある。
また被回収容器１とガス分離部への導入口の間にガス分離に必要な圧力に昇圧するコンプレッサーを設置することも出来る。この場合は被回収容器１内の圧力は大気圧とすることが出来るので約５％まで達すると終了することが出来る。
【００２５】
図２に別の好ましい１実施例のＳＦ６ガス回収装置のフローシートを示す。
このＳＦ６ガス回収装置の構成は、ガス分離部３，ガス供給部７，加圧部２，液化部４及び液化したＳＦ６ガスを貯蔵する貯液器５より成り立っており、第１の実施例と同一構成であるが、ガス分離部３がＳＦ６ガスを吸着する分子篩炭を吸着剤として吸着筒１９，２０に充填してある。
ここの動作以外は実施例１と同じであるのでこのガス分離部分を中心に説明する。被回収ガス中のＳＦ６ガスの濃度が下がってくると、ガス分離部の電磁弁１０を閉じ、同９を開いて被回収ガスを導入し、ＳＦ６ガスを分離する。すなわちＳＦ６ガスを吸着する吸着剤を充填した吸着筒１９，２０と電磁弁１２，２１〜２７と真空ポンプ１５で構成されるガス分離部３の一方の吸着筒１９に電磁弁２１を開いて導入すると、吸着筒１９内の吸着剤に被回収ガス中のＳＦ６ガスが吸着されて除去される吸着筒の他端出口より電磁弁２５，２７を通って非吸着ガスである混合ガス（ＳＦ６ガスを含まないガス）が導出される。これを吸着工程という。
【００２６】
吸着筒１９の吸着剤にＳＦ６ガスが吸着し、満杯になる前に電磁弁９，２１と２５，２７を閉とし、再生工程の終了した吸着筒２０の電磁弁２３，２４，２６を閉とし、電磁弁３７を開とし、着筒１９と２０の均圧化を行い、吸着筒１９内の非吸着ガスを中心に吸着筒２０内に移す。
この工程は吸着工程の完了した吸着筒内のＳＦ６ガスの濃度を高める働きをする。
その後、次の工程を入れて更にＳＦ６ガスの濃度を高めることも出来る。
すなわち電磁弁１２，２１を開としてＳＦ６ガスで吸着筒１９内をパージして吸着筒１９内の混合ガスを吸着筒２０の方へ追い出す工程である。かかる均圧工程，パージ工程はＳＦ６ガスが液化可能濃度に達していれば全部又は一部を省くことが出来る。そしてこの後（このとき一部ＳＦ６ガスも移る）、電磁弁２１，１２，３７を閉とし、電磁弁２２，１１を開とし、真空ポンプ１５にて吸着筒内１９のＳＦ６ガスを導出してバッファタンク２８に送り、これを加圧部で昇圧する。吸着筒１９は十分に真空引きし、ＳＦ６ガスを回収するとともに吸着剤の再生を行う。吸着筒２０は電磁弁９，２３，２６，２７を開とし、被回収ガスを導入し、吸着筒１９と同様に吸着工程を行う。
以上、ガス分離部に使用する吸着剤にＳＦ６ガスを吸着する分子篩炭を用いるため、ＳＦ６ガスの回収を再生工程で行う以外は、実施例１と同じ動作である。
【００２７】
また、液化部４の冷却部３１及び液化タンク３２は温度を必要な値まで下げなければならない。通常は電気冷凍機を用いて冷却するが、前述の通り、被回収容器にガスを供給するので液体窒素４０を用いてその蒸発潜熱を蒸発器４１を用いて液化部の冷却熱源として用い、その蒸発した窒素ガスを窒素ガス取出口４３より被回収容器に導入し、前記ガス供給源とすることにより、効率化を図るようにすることが出来る。尚、液化部は気密にし、一定の圧力に耐えなければならない。
【００２８】
【発明の効果】
本発明を実施することにより、従来、回収困難あるいは不完全な回収又は高価な設置と長時間を要していたものが、比較的簡単な回収装置で、しかもほぼ完全に、かつ、比較的短時間にＳＦ６ガスを回収することができるという優れた作用効果を奏する。
【図面の簡単な説明】
【図１】本発明の好適な一実施例のフローシートである。
【図２】別の好ましい実施例のフローシートである。
【符号の説明】
１被回収容器
２加圧部
３ガス分離部
４液化部
５貯液器
６高圧空気供給部
７ガス供給部
８，９，１０電磁弁
１１空気乾燥器
１２コンプレッサー
１３窒素ボンベ
１４調圧弁
１５真空ポンプ
１６排気口１
１７排気口２
１８電磁弁
１９．２０吸着筒
２１〜２７電磁弁
２８バッファタンク
２９定圧弁
３０加圧ポンプ
３１冷却部
３２液化タンク
３３，３４電磁弁
３５取出口
３６送入口
４０液体窒素タンク
４１蒸発器
４２液化部内窒素ガス出口
４３液化部より窒素ガス取出口
４４ガス取入口[0001]
BACKGROUND OF THE INVENTION
The present invention relates to the recovery of SF6 gas (sulfur hexafluoride gas, hereinafter the same).
[0002]
[Prior art]
SF6 gas fills high-voltage power transformers and power circuit breakers, making use of its thermal stability, electrical stability, and high withstand voltage to reduce the size of the equipment, and reduce the size of substations in cities. The contribution is large in volume. The SF6 gas filled in the transformer and the circuit breaker includes those with a purity of 100% and those filled with nitrogen gas. These gases must be extracted during inspection, maintenance and repair of the equipment in which they are used. Conventionally, these gases have been released into the atmosphere because there is little harm to human bodies. .
However, since the SF6 gas is an expensive gas, there has conventionally been a collection device that can be easily collected and reused in terms of cost, and has been collected and reused.
In other words, although there was an apparatus for liquefying and collecting by sampling pressure and compression cooling, the inside of the container to be collected was collected by sucking up to a high vacuum range, or the gas mixed with other gas was separated and only the SF6 gas was collected. There was no device to collect the.
[0003]
That is, when other gases are mixed and the concentration of SF6 gas is lowered, the partial pressure is lowered, so it is compressed to a high pressure, and cooling to a low temperature is required. It wasn't.
Conventionally, the SF6 gas, which is generated by being slightly decomposed by the arc or heat at the time of interruption during use, has some degradation gases such as SF4, sulfur dioxide, and SOF2, which cause deterioration of the characteristics of the equipment used. Therefore, there was an apparatus to be removed, but there was no apparatus to separate and purify at the time of recovery.
[0004]
In recent years, the release of carbon dioxide and the like due to the prevention of global warming has been regulated. The 1997 World Environment Conference was held in Kyoto, and as a result, the emission of SF6 gas, which has a warming potential of 24,000 times that of carbon dioxide, has been strictly regulated.
To prevent the SF6 gas from leaking into the atmosphere,
“I” Eliminate gas leaking from the sealing part of filling equipment.
“B” It is important to eliminate the gas that is discarded when gas is charged or removed during equipment installation, maintenance repair, dismantling and disposal.
This “I” is currently very small due to the improvement of the seal part of the equipment.
As for “Ro”, the electric power industry established the “SF6 Gas Handling Standards for Electric Power” voluntarily in December 1998 by the Electric Joint Study Group, and decided to regulate its emission.
In other words, a voluntary standard for suction and recovery to a vacuum range of 0.005 MPa · abs (recovery rate of 99 vol% or higher) at the time of dismantling and removal was prepared at the time of inspection and repair. When recovering up to a high vacuum region, there is a disadvantage that recovery takes a long time. The low recovery rate at the time of inspection is a compromise value for shortening the time of power failure due to equipment shutdown as much as possible, and a sufficient time is taken when removing the vacuum. In other words, it is sucked and collected up to a high vacuum range, and the amount of leakage to the atmosphere is reduced.
[0005]
The electric power industry will develop and implement a collection device that meets the above standards by 2005.
Even when 50 vol% of nitrogen gas, which is an inert gas, is mixed, the impulse breakdown voltage is 85% of the SF6 gas alone gas and the commercial frequency breakdown voltage is 96.6% of the same. There are manufacturers that use nitrogen gas for sealing in a circuit breaker and those that use high-purity SF6 gas. Conventionally, such a gas mixed with nitrogen gas has been difficult to recover, and many of them have been discharged into the atmosphere and discarded during inspection and disposal.
[0006]
[Problems to be solved by the invention]
It is to recover 99 vol% or more from the container to be recovered, which is a transformer or a circuit breaker, with almost no leakage of SF6 gas into the atmosphere, and to enable recovery in a short time. In addition, even if nitrogen gas or air is mixed in the gas to be collected, it should be separated and recovered.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the object of the present invention is to consider the characteristics of SF6 gas having a critical temperature of 45.64 ° C., a critical pressure of 3.75 MPa · G, a melting point of −50.8 ° C., and a sublimation point of −63.8 ° C. Further, the transformer or the circuit breaker as a container to be collected is a hermetically sealed container, which is filled with SF6 gas at a high pressure (about 0.6 MPa · G to 0.3 MPa · G).
The filling gas is small due to the mixed nitrogen gas or discharge, but the SF6 gas is decomposed, SF4, SOF2, and sulfur dioxide are present, and moisture may also be mixed. However, there are separate removing means for removing cracked gas, SF4, SOF2, and sulfur dioxide from SF6 gas, and most of them can be removed there, but a detailed description is omitted here.
Shortening the time of power failure during inspection, maintenance, or repair of equipment used for public infrastructure such as power supply is an important issue after the main performance of recovering SF6 gas. An efficient recovery device was invented in consideration of these problems.
[0008]
A container to be collected (transformer, circuit breaker, etc.) is filled with a gas to be collected (SF6 gas) at a high pressure as described above. Since SF6 gas is an easily liquefied gas, a pressurizing unit for pressurizing the SF6 gas and a liquefying unit for cooling and liquefying are provided. In a range where the concentration of SF6 gas in the gas to be recovered is high, the SF6 gas content in the pressurized gas Since the pressure also increases, liquefaction can be easily recovered in a pressure range where the pressure applied is relatively low or a range where the liquefaction temperature is relatively high because of the relationship between the liquefaction temperature and pressure of the liquefied gas.
First, recovery is performed by such a method until the internal pressure in the container to be recovered falls within a pressure range that can be liquefied by a pressure pump. As described above, the gas to be recovered may be diluted with 100% SF6 gas and nitrogen gas. A gas separation unit is provided for separating the mixed gas from the SF6 gas even if it is present. The gas separation unit is performed by a PSA method (pressure Swing Adsorption) using an adsorbent that adsorbs a specific gas. When a mixed gas containing a specific gas is fed into the adsorption cylinder filled with the adsorbent while applying pressure, the specific gas is adsorbed and removed by this adsorbent, and the non-adsorbed gas is separated from the other end of the adsorption cylinder and taken out. It is. This process is called an adsorption process. Then, when the adsorbent is filled with the specific gas, the mixed (raw material) gas is stopped to be delivered and the pressure of the adsorption cylinder is reduced from the inlet of the adsorption cylinder. Is released from the adsorbent and discharged, and the adsorption capacity of the adsorbent is regenerated. This is called a regeneration process. The gas is separated while repeating the adsorption process and the regeneration process, that is, while applying or reducing pressure to the adsorption cylinder. Therefore, this method is called pressure swing adsorption (abbreviated as PSA) (pressure fluctuation adsorption) method.
[0009]
The adsorbent includes an adsorbent that adsorbs SF6 gas that is the target gas and does not adsorb the mixed gas, and an adsorbent that adsorbs another gas that is not adsorbed and does not adsorb the SF6 gas that is the target gas. . The method of extracting the target gas is slightly different depending on the adsorbent used.
For example, when SF6 gas is the target gas, the former is molecular sieve charcoal in which activated carbon has a molecular sieve function. The latter includes zeolite 5A type, 4A type and others. In the former case, the SF6 gas, which is the target gas, is adsorbed and separated by the adsorbent, and the concentrated SF6 gas is recovered in the process of desorbing from the adsorbent in the decompression regeneration process. In the latter case, SF6 gas is separated from the other end of the adsorption cylinder in the pressure adsorption process, and thus is obtained in the adsorption process.
Zeolite hardly adsorbs SF6 gas, and adsorbs and removes nitrogen gas, carbon dioxide gas, and water well. Oxygen gas adsorbs slightly, so gas that separates SF6 gas from gas mixed with SF6 gas. Used as an adsorbent in the separation part.
[0010]
However, it may also occur when air is mixed into the SF6 gas. The main components of air are 78% nitrogen and 21% oxygen. First, zeolite that adsorbs a lot of nitrogen is placed upstream of the adsorption cylinder, and then molecular sieve charcoal that strongly adsorbs oxygen is placed downstream as an adsorbent. First, nitrogen gas is removed and oxygen with low concentration is concentrated, and the two adsorbents are combined upstream and downstream as described above so that the oxygen with high partial pressure can be efficiently adsorbed and removed by molecular sieve charcoal. This constitutes a gas separation unit that can efficiently separate and remove air. Gases other than the SF6 gas separated by the gas separation unit are nitrogen gas and oxygen gas, and are the same as the gas constituting the atmosphere, and are thus released into the atmosphere. In the regeneration process, this exhaust gas released to the atmosphere must be free of SF6 gas, and so that SF6 gas does not remain in the adsorption cylinder after the adsorption process, it is uniform between the adsorption process and the regeneration process. A pressure step is added.
[0011]
That is, using a plurality of adsorption cylinders filled with an adsorbent in the gas separation unit, the gas to be recovered is supplied to the adsorption cylinder in one pressurizing step, the mixed gas in SF6 gas is adsorbed on the adsorbent, and the adsorbent Stop supplying the gas to be collected before it is full of adsorption gas, and combine the adsorption cylinder, inlets, and outlets after the other regeneration process, and regenerate the gas in the adsorption cylinder after the adsorption process. After the pressure equalizing step for transferring to the adsorbing cylinder that has been completed, the adsorbing cylinder that has completed the adsorbing process is depressurized, enters the regeneration process, and the gas adsorbed on the adsorbent is desorbed and discharged to the atmosphere. At this time, it may be regenerated by reducing the pressure to a vacuum range with a vacuum pump. Then, the adsorption cylinder after the regeneration process enters the adsorption process, supplies the gas to be recovered, and separates the SF6 gas. After the SF6 gas existing in the inlet and outlet of the adsorption cylinder where the adsorption process is completed and the respective conduits is transferred to the adsorption cylinder after the regeneration process (after the SF6 gas is eliminated) by adding a pressure equalization process, In the regeneration process, the adsorbed gas not containing SF6 gas is discharged into the atmosphere.
[0012]
The gas to be collected (SF6 gas) present in the container to be collected remains in the gas in the container to be collected even if the internal pressure in the container to be collected is recovered to the atmospheric pressure level. The pressure is 0.015 MPa · abs at the time of dismantling, and 0.005 MPa · abs at the time of dismantling to recover the vacuum, and SF6 gas is less likely to dissipate into the atmosphere, but as the vacuum value increases, The gas expands and takes a long time to recover. Therefore, as a result of earnest research, the gas that can be separated in the gas separation section is filled in the container to be collected, and the gas to be separated in this separation section is increased to SF6 by raising the container to be collected to a positive pressure or a pressure close to positive pressure. By mixing and deriving with gas, SF6 gas is recovered to the target recovery level (residual gas level) in a short time. Therefore, a gas supply unit is provided.
Nitrogen gas or air can be used as the gas of the gas supply unit in combination with the capability of the gas separation unit.
[0013]
In order to recover efficiently in a short time, it can be easily liquefied and collected within a high concentration of SF6 gas in the container to be recovered. Therefore, the gas to be recovered in the container to be recovered is pressurized by the pressurization unit, and then in the liquefaction unit. Cool and recover. By this method, the internal pressure in the container to be recovered is recovered up to a pressure range that can be liquefied by the pressure pump. (However, it should be noted that this pressure changes depending on the cooling capacity (temperature) of the liquefaction unit.) When the internal pressure of the recovery container falls below a certain value, the gas is supplied from the gas supply unit to the recovery container. Supply, pressurize, and pressurize in the pressurizing unit. At this time, the non-liquefied gas is extracted from the liquefying portion. This gas is returned to the upstream side of the pressurizing section and is again entered into the cycle of pressurized cooling and liquefaction.
[0014]
As the concentration of SF6 gas in the gas to be recovered decreases, the partial pressure of SF6 gas decreases, so the pressure for liquefaction increases, and the temperature required for liquefaction becomes low and cannot be liquefied. The recovered gas is guided to the gas separation unit, and the SF6 gas is concentrated and then added to the pressurization unit. Recovery is continued by this method, and the concentration of SF6 gas in the gas to be recovered is determined to determine whether the recovery can be performed up to 0.015 MPa · abs, and the recovery ends.
According to this method, the gas to be recovered can be derived at a positive pressure without using an expensive vacuum pump that can draw a high vacuum from the container to be recovered, and recovery below the target level can be performed in a short time.
[0015]
That is,
“Ah” In the SF6 gas recovery device composed of the gas supply unit and the gas separation unit, the high-pressure gas regulated by the gas supply unit is supplied to the recovery container, and the recovery gas mixed with the SF6 gas is supplied from the gas outlet. The gas is separated and separated into a gas containing a large amount of SF6 and a gas containing little SF6 in the gas separation unit, a gas containing little SF6 is discharged into the atmosphere, and the gas containing SF6 is recovered.
“I” SF6 composed of a gas separation unit by a PSA method and a gas supply unit having an adsorption cylinder filled with an adsorbent that adsorbs SF6 gas or mixed gas (nitrogen gas, air, carbon dioxide gas, etc.) in a container to be collected In the gas recovery device, the high-pressure gas regulated by the gas supply unit is supplied to the recovery container, the recovery gas mixed with the SF6 gas is taken out, sent to the gas separation unit, and recovered in the pressurized adsorption process The adsorption gas in the container is adsorbed by the adsorbent in the adsorption cylinder and separated from the non-adsorption gas, the adsorption cylinder is depressurized in the decompression regeneration step, the gas adsorbed on the adsorbent is desorbed, and the SF6 gas The separated mixed gas was discharged into the atmosphere.
"U" In the SF6 gas recovery system, which consists of a PSA system gas separation unit and a nitrogen gas supply unit with an adsorption cylinder filled with zeolite as an adsorbent, supply nitrogen gas regulated by the nitrogen gas supply unit to the container to be recovered Then, the gas to be collected mixed with the gas mainly containing SF6 gas filled in the container to be collected is taken out and sent to the gas separation unit, and nitrogen gas or the like is adsorbed in the adsorption cylinder in the pressure adsorption process. Adsorbed and removed by the adsorbent and separated from SF6 gas, the adsorption cylinder was depressurized in the depressurization step, and the nitrogen gas adsorbed on the adsorbent was desorbed and released into the atmosphere.
[0016]
Also,
“E” In an SF6 gas recovery apparatus comprising a gas separation unit and a gas supply unit by a PSA system having two adsorption cylinders filled with an adsorbent that adsorbs a gas other than the SF6 gas in the recovery container. A high-pressure gas regulated by a gas supply unit is supplied, a recovery gas mixed with a gas mainly containing SF6 gas filled in a recovery container is taken out from an outlet, and sent to the gas separation unit. Gas other than SF6 gas is adsorbed to the adsorbent in the adsorption cylinder by the adsorption cylinder in the pressure adsorption process, and separated from the SF6 gas. Before the adsorbent in the adsorption cylinder is filled with the adsorption gas, A pressure equalization process in which the supply of the recovered gas is stopped, the adsorption cylinder that has completed the other decompression regeneration process is joined to the inlets and the outlets, and the gas in the adsorption cylinder that has completed the adsorption process is transferred to the adsorption cylinder that has completed the decompression regeneration process. After the adsorption process is completed The cylinder enters the decompression regeneration process, and the gas adsorbed by the adsorbent is discharged into the atmosphere. The adsorption cylinder after the decompression regeneration process enters the adsorption process, and the recovered gas is supplied to separate the SF6 gas. .
"O" In the SF6 gas recovery system consisting of a PSA-type gas separation unit and two high-pressure air supply units having two adsorption cylinders filled with zeolite on the upstream side and molecular sieve charcoal on the downstream side, a high-pressure air supply unit is provided in the recovery container. More high-pressure air of a constant pressure is supplied and mixed with SF6 gas, the gas to be recovered is taken out from the take-out port, sent to the gas separation unit, and nitrogen gas is absorbed in the adsorption cylinder in one pressurized adsorption process. Oxygen gas and the like are adsorbed on the adsorbent in the adsorption cylinder and separated from the SF6 gas, the supply of the gas to be recovered is stopped before the adsorbent in the adsorption cylinder is filled with the adsorption gas, and the other decompression regeneration step After completing the pressure equalization process, which joins the adsorption cylinder, inlet and outlet, and transfers the gas in the adsorption cylinder completed in the adsorption process to the adsorption cylinder completed in the decompression regeneration process, the adsorption cylinder completed in the adsorption process Entered the decompression regeneration process and adsorbed on the adsorbent The gas was discharged into the atmosphere, and the gas to be recovered was supplied to the adsorption cylinder after the decompression regeneration process, and the adsorption process was started to separate the SF6 gas.
[0017]
further,
“Ka” In an SF6 gas recovery apparatus composed of a gas separation unit, a pressurization unit, and a liquefaction unit, a gas to be collected including SF6 taken out from a container to be collected is supplied to the gas separation unit, and a gas not containing SF6 gas and SF6 The gas containing no SF6 is discharged into the atmosphere, and the SF6 gas is pressurized by the pressurizing unit and then sent to the liquefying unit. The liquefying unit mainly vaporizes liquid nitrogen gas from the liquid nitrogen tank. The liquefying portion was attached to the latent heat atmosphere to cool the liquefied portion to liquefy SF6 gas, and the gasified liquefied nitrogen was pressurized and supplied to the container to be collected.
"Ki" In the SF6 gas recovery system consisting of a gas separation unit, pressurization unit, liquefaction unit, and gas supply unit, when the SF6 gas concentration in the recovery container is high, the gas to be recovered is directly pressurized by the pressurization unit After that, the liquid is cooled and liquefied in the liquefying unit, and the non-liquefied gas in the cooling unit is returned to the upstream side from the pressurizing unit, and the internal pressure in the container to be collected becomes substantially atmospheric pressure (about 0 MPa · G). After that, a gas of a constant pressure is supplied from the gas supply unit into the recovery container, mixed with SF6 gas, the pressure is increased and liquefaction recovery by the pressurized cooling is continued, and the SF6 gas concentration in the recovery gas is increased. When the gas falls below a certain value, the gas to be recovered is fed into the gas separation unit, the SF6 gas and the mixed gas are separated, the mixed gas is discharged into the atmosphere, and the SF6 gas is pressurized in the pressurizing unit and then liquefied. The liquid is cooled and liquefied at the part.
[0018]
【Example】
FIG. 1 shows a flow sheet of the SF6 gas recovery apparatus of one preferred embodiment.
The SF6 gas filled in the container 1 to be recovered, which is a transformer or a circuit breaker, is recovered. The configuration of the recovery device includes a gas separation unit 3, a gas supply unit 7, a pressurization unit 2, a liquefaction unit 4, and a liquid reservoir 5 for storing liquefied SF6 gas.
The recovery container 1 is normally filled with SF6 gas at a pressure of 0.3 MPa · G to 0.6 MPa · G. The concentration is from 100 vol%, and even when diluted with nitrogen gas, it is sealed at a concentration of 50 vol% or more. SF6 gas has a critical temperature of 45.64 ° C., a critical pressure of 3.75 MPa · G, a critical molar volume of 201 mL / mol, a melting point of −50.8 ° C., and a sublimation point of −63.8 ° C.
[0019]
The vapor pressure of SF6 gas is, for example, 1.22 MPa · G at 0 ° C., so that the gas to be recovered is extracted and pressurized to 2.44 MPa · G by the pressurizing unit 2 and cooled to 0 ° C. or less by the cooling unit 4 to 50 vol. % Or more of SF6 gas can be liquefied and recovered.
For this reason, the gas to be recovered is introduced from the container 1 to be pressurized to the pressurizing unit 2 and pressurized to 2.44 MPa · G by the pressurizing unit 2 constituted by a return circuit including the buffer tank 28, the pressurizing pump 30 and the constant pressure valve 29. Then, this is cooled to 20 ° C. or less by the liquefying unit 4 constituted by the cooling unit 31, the liquefaction tank 32 and the electromagnetic valves 33, 34, and SF6 is liquefied and recovered. The liquefied SF 6 is stored in the liquid reservoir 5.
[0020]
When the SF6 concentration of the gas to be collected is 50 vol% or more, when the internal pressure in the container to be collected becomes 0 MPa · G, the gas is fed from the gas supply unit 7 through the inlet 36, mixed with the SF6 gas, and the outlet 35 Then, the method of continuing the method of taking out pressure, pressurizing with the pressurizing unit 2, and cooling with the liquefying unit is continued to liquefy and recover SF6 gas. Since non-liquefied gas (nitrogen gas) remains in the liquefaction tank 32, this gas is returned to the upstream side of the pressurizing unit (not shown). When the concentration of SF6 gas in the gas to be recovered is 50 vol% or less, liquefaction recovery cannot be performed at the pressure and temperature. Therefore, the gas to be recovered is introduced by closing the electromagnetic valve 10 in the gas separation unit 3 and opening 9. Separate the gas. That is, the adsorption cylinders 19 and 20 filled with an adsorbent that adsorbs nitrogen gas other than the SF6 gas, the electromagnetic valves 18 and 21 to 27, and the one adsorption cylinder 19 of the gas separation unit 3 constituted by the vacuum pump 15 When 21 is opened and introduced, gas other than SF6 in the gas to be collected is adsorbed and removed by the adsorbent in the adsorption cylinder 19, so that the SF6 gas is concentrated and the solenoid valves 25 and 27 are discharged from the other end outlets of the adsorption cylinder. This is referred to as an adsorption process.
[0021]
The derived gas is stored in the buffer tank 28 of the pressurizing unit 2 and then pressurized. Shortly before the adsorbent in the adsorption cylinder 19 adsorbs nitrogen gas and becomes full, the solenoid valves 9 and 27 are closed, the introduction of the gas to be collected and the derivation of the SF6 gas are stopped, and the regeneration process is completed. The electromagnetic valves 21 and 23 at the inlet of the adsorption cylinder 20 and the electromagnetic valves 25 and 26 at the outlet are opened, and the adsorption cylinder 19 from the adsorption cylinder 19 after the adsorption process is completed to the adsorption cylinder 20 after the regeneration process is completed. -After performing the pressure equalization process to move the SF6 gas remaining in the outlet conduit to the adsorption cylinder 20, the electromagnetic valves 21 and 25 of the adsorption cylinder 19 are closed, and the electromagnetic valves 22 and 18 are opened and opened to the atmosphere. When the pressure in the adsorption cylinder 19 is reduced to atmospheric pressure, nitrogen gas adsorbed on the adsorbent is released and discharged into the atmosphere. Subsequently, the electromagnetic valve 18 is closed, and the adsorbent is sufficiently regenerated by pulling the vacuum valve 15 to the vacuum range. (Regeneration process)
[0022]
The adsorption cylinder 20 opens the solenoid valves 9 and 27, introduces the gas to be collected from the solenoid valves 9 and 23, introduces the concentrated gas into the buffer tank 28 through the solenoid valves 26 and 27, and adds the gas by the pressurizing pump 30. And liquefy and separate by the same method as before. The gas supply unit 7 is composed of a nitrogen cylinder 13 and a pressure regulating valve 14. When nitrogen gas is introduced into a container to be collected and mixed, the gas supply unit 7 separates SF6 gas and nitrogen gas. The agent may be zeolite, and any other material that adsorbs nitrogen gas can be used. There are 13X type and 5A type zeolite, and 5A type is used in this embodiment.
[0023]
In addition, zeolite is collected on the inlet (upstream) side of the gas to be collected and the molecular sieve charcoal (CMS · Carbon, Molecular, Seaves) on the outlet (downstream) side so that the nitrogen gas and oxygen gas can be adsorbed and removed. Instead of the gas supply unit 7 using nitrogen gas, a compressed air generation unit 6 using air can be used. This is composed of a compressor 12 and an air dryer, and the dried air is fed into the collection container 1 with a regulated pressure, mixed with SF6 gas, and then SF6 gas on the same principle as the method using nitrogen gas. Can be separated and recovered so that air can be used everywhere.
[0024]
When the concentration of SF6 gas in the mixed gas is about 5% equivalent to 0.015 MPa · abs of pure SF6 gas in terms of atmospheric pressure, when the pressure is higher than the pressure introduced into the PSA gas separation unit Therefore, it is necessary to reduce the concentration to a value obtained by multiplying the pressure equivalent by one.
In addition, a compressor for increasing the pressure necessary for gas separation can be installed between the container 1 to be collected and the inlet to the gas separation section. In this case, the pressure in the container 1 to be collected can be set to atmospheric pressure, and can be terminated when it reaches about 5%.
[0025]
FIG. 2 shows a flow sheet of the SF6 gas recovery apparatus according to another preferred embodiment.
The configuration of this SF6 gas recovery apparatus comprises a gas separation unit 3, a gas supply unit 7, a pressurization unit 2, a liquefaction unit 4, and a liquid storage unit 5 for storing liquefied SF6 gas. Although it is the same structure, the gas separation part 3 has filled the adsorption cylinders 19 and 20 by making into the adsorbent the molecular sieve charcoal which adsorb | sucks SF6 gas.
Since this operation is the same as that of the first embodiment, the gas separation portion will be mainly described. When the concentration of the SF6 gas in the gas to be recovered decreases, the electromagnetic valve 10 of the gas separation unit is closed, and the gas 9 is opened to introduce the gas to be recovered, thereby separating the SF6 gas. That is, the solenoid valve 21 is opened and introduced into one of the adsorption cylinders 19 of the gas separation unit 3 including the adsorption cylinders 19 and 20 filled with the adsorbent for adsorbing SF6 gas, the electromagnetic valves 12 and 21 to 27, and the vacuum pump 15. Then, SF6 gas in the gas to be collected is adsorbed to the adsorbent in the adsorption cylinder 19 and is removed from the other end outlet of the adsorption cylinder through the electromagnetic valves 25 and 27 and mixed gas (SF6 gas). Gas not contained) is derived. This is called an adsorption process.
[0026]
Before the SF6 gas is adsorbed by the adsorbent of the adsorption cylinder 19 and becomes full, the electromagnetic valves 9, 21, 25, and 27 are closed, and the electromagnetic valves 23, 24, and 26 of the adsorption cylinder 20 after the regeneration process are closed. Then, the solenoid valve 37 is opened, pressure equalization of the receiving cylinders 19 and 20 is performed, and the non-adsorbing gas in the adsorption cylinder 19 is moved into the adsorption cylinder 20 as a center.
This step serves to increase the concentration of SF6 gas in the adsorption cylinder after the adsorption step is completed.
Thereafter, the concentration of the SF6 gas can be further increased by adding the next step.
That is, the solenoid valves 12 and 21 are opened, the inside of the adsorption cylinder 19 is purged with SF6 gas, and the mixed gas in the adsorption cylinder 19 is driven out toward the adsorption cylinder 20. The pressure equalization process and the purge process can be omitted entirely or partially if the SF6 gas reaches a liquefiable concentration. After this (some SF6 gas also moves at this time), the solenoid valves 21, 12, 37 are closed, the solenoid valves 22, 11 are opened, and the SF6 gas in the adsorption cylinder 19 is led out by the vacuum pump 15. This is sent to the buffer tank 28 and the pressure is increased by the pressurizing unit. The adsorption cylinder 19 is sufficiently evacuated to collect SF6 gas and regenerate the adsorbent. The adsorption cylinder 20 opens the electromagnetic valves 9, 23, 26, and 27, introduces a gas to be collected, and performs an adsorption process in the same manner as the adsorption cylinder 19.
As described above, since molecular sieve charcoal that adsorbs SF6 gas is used as the adsorbent used in the gas separation unit, the operation is the same as that of Example 1 except that the recovery of SF6 gas is performed in the regeneration step.
[0027]
Moreover, the temperature of the cooling unit 31 and the liquefaction tank 32 of the liquefaction unit 4 must be lowered to a necessary value. Normally, cooling is performed using an electric refrigerator, but as described above, since gas is supplied to the container to be collected, the latent heat of evaporation is used as a cooling heat source of the liquefaction unit using the evaporator 41 using liquid nitrogen 40, Efficiency can be improved by introducing the evaporated nitrogen gas into the collection container through the nitrogen gas outlet 43 and using the gas supply source. The liquefaction part must be airtight and withstand a certain pressure.
[0028]
【The invention's effect】
By practicing the present invention, it has heretofore been difficult to recover or incomplete recovery or expensive installation and a long time, but it is a relatively simple recovery device, and is almost completely and relatively short. There is an excellent effect that the SF6 gas can be recovered in time.
[Brief description of the drawings]
FIG. 1 is a flow sheet according to a preferred embodiment of the present invention.
FIG. 2 is a flow sheet of another preferred embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Recovery container 2 Pressurization part 3 Gas separation part 4 Liquefaction part 5 Reservoir 6 High pressure air supply part 7 Gas supply part 8, 9, 10 Electromagnetic valve 11 Air dryer 12 Compressor 13 Nitrogen cylinder 14 Pressure regulation valve 15 Vacuum pump 16 Exhaust port 1
17 Exhaust port 2
18 Solenoid valve 19.20 Adsorption cylinder 21-27 Solenoid valve 28 Buffer tank 29 Constant pressure valve 30 Pressurizing pump 31 Cooling part 32 Liquefaction tank 33, 34 Solenoid valve 35 Outlet 36 Inlet 40 Liquid nitrogen tank 41 Evaporator 42 In liquefaction part Nitrogen gas outlet 43 Nitrogen gas outlet 44 from the liquefaction section Gas inlet

Claims

In an SF6 gas recovery apparatus comprising a gas separation unit and a gas supply unit by a PSA system having two adsorption cylinders filled with an adsorbent that adsorbs a gas other than SF6 gas in the recovery container, the gas supply unit is connected to the recovery container. The high-pressure gas regulated in step 1 is supplied, the recovery gas mixed with the gas mainly containing SF6 gas filled in the recovery container is taken out from the outlet, and sent to one adsorption cylinder of the gas separation unit. In the pressure adsorption process, a gas other than SF6 gas is adsorbed on the adsorbent in the adsorption cylinder and separated from the SF6 gas, and the adsorbent in the adsorption cylinder cannot be further adsorbed. The supply of the gas to be recovered is stopped before becoming the other, and the adsorption cylinder that has completed the decompression regeneration process is joined to the inlets and the outlets. Perform pressure equalization process After the adsorption process is completed, the adsorption cylinder enters the decompression regeneration process, and the gas adsorbed by the adsorbent is discharged into the atmosphere. After the decompression regeneration process is completed, the adsorption cylinder enters the adsorption process and supplies the gas to be recovered. SF6 gas recovery device that separates SF6 gas.

In the SF6 gas recovery system consisting of a PSA system gas separation unit and a high pressure air supply unit having two adsorption cylinders filled with zeolite on the upstream side and molecular sieve charcoal on the downstream side, a constant pressure is applied to the recovery container from the high pressure air supply unit. The high pressure air is supplied and mixed with SF6 gas, the gas to be recovered is taken out from the take-out port, sent to the gas separation section, and the nitrogen gas , oxygen gas , etc. in the adsorption cylinder in one pressurized adsorption process Is adsorbed on the adsorbent in the adsorption cylinder and separated from the SF6 gas, the supply of the gas to be recovered is stopped before the adsorbent in the adsorption cylinder reaches a saturation state where no further adsorption is possible , and the other decompression regeneration After the adsorption cylinder that has completed the process is joined, the inlet and outlet are coupled, and the gas in the adsorption cylinder that has completed the adsorption process is transferred to the adsorption cylinder that has completed the decompression regeneration process. The tube enters the decompression regeneration process, Adsorbed gas discharged into the atmosphere Chakuzai, vacuum regeneration finished adsorption column process by supplying the stripping gas enters the adsorption step, SF6 gas recovery device so as to separate the SF6 gas.

Gas separation by a PSA system having two gas supply units that supply high-pressure gas to a container to be collected and two adsorption cylinders filled with an adsorbent that adsorbs a gas other than SF6 gas and into which the gas to be collected is fed. In the SF6 gas recovery apparatus, the SF6 gas recovery device is configured to include the SF6 taken out from the recovery target container, the pressurization unit that pressurizes the SF6 gas separated by the gas separation unit, and the liquefaction unit that liquefies the pressurized SF6 gas The recovered gas is supplied to the gas separation unit, separated into SF6 gas and gas not containing SF6, the gas not containing SF6 is discharged into the atmosphere, and the SF6 gas is pressurized in the pressurization unit, and then the liquefaction unit The SF6 gas recovery device which sends the liquefaction part from the liquid nitrogen tank and attaches this liquefaction part to the atmosphere of latent heat of vaporization of liquid nitrogen gas to cool the liquefaction part and liquefy the SF6 gas.

Gas separation by a PSA system having two gas supply units that supply high-pressure gas to a container to be collected and two adsorption cylinders filled with an adsorbent that adsorbs a gas other than SF6 gas and into which the gas to be collected is fed. In the SF6 gas recovery apparatus, the SF6 gas recovery device is configured to include the SF6 taken out from the recovery target container, the pressurization unit that pressurizes the SF6 gas separated by the gas separation unit, and the liquefaction unit that liquefies the pressurized SF6 gas The recovered gas is supplied to the gas separation unit, separated into SF6 gas and gas not containing SF6, the gas not containing SF6 is discharged into the atmosphere, and the SF6 gas is pressurized in the pressurization unit, and then the liquefaction unit The liquefying portion is attached to the atmosphere of latent heat of vaporization of the liquefied nitrogen gas from the liquid nitrogen tank to cool the liquefied portion to liquefy the SF6 gas. Pressurized SF6 gas recovery device so as to supply to the vessel.

Gas separation by a PSA system having two gas supply units that supply high-pressure gas to a container to be collected and two adsorption cylinders filled with an adsorbent that adsorbs a gas other than SF6 gas and into which the gas to be collected is fed. parts and, a pressing for pressurizing the SF6 gas separated by the gas separation unit, in SF6 gas recovery device constituted by liquefaction unit for liquefying pressurized SF6 gas,
When the SF6 gas concentration in the container to be collected is 50 vol% or more, and the internal pressure in the container to be collected is higher than approximately atmospheric pressure (about 0 MPa · G ) , the gas to be collected is not passed through the gas separation unit. after pressurization by pressing, it cooled liquefied by the liquefaction unit, after the internal pressure of該被collection container becomes substantially lower than atmospheric pressure (about 0 MPa · G) is the collection container from the gas supply unit A constant pressure gas is supplied to the gas, mixed with SF6 gas to increase the pressure, and the gas to be recovered is pressurized in the pressurizing unit without passing through the gas separation unit, and then cooled and liquefied in the liquefaction unit for recovery. Continue,
When SF6 gas concentration of the recovered gas is not more than 50 vol% is to be collected gas was fed to the gas separation unit, a SF6 gas and non SF6 gas were separated, the gas other than SF6 to the atmosphere An SF6 gas recovery device that discharges and pressurizes SF6 gas in a pressurizing unit and then liquefies it in a liquefying unit.