JP2004205076A - Air liquefying and separating device and its method - Google Patents

Air liquefying and separating device and its method Download PDF

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Publication number
JP2004205076A
JP2004205076A JP2002372275A JP2002372275A JP2004205076A JP 2004205076 A JP2004205076 A JP 2004205076A JP 2002372275 A JP2002372275 A JP 2002372275A JP 2002372275 A JP2002372275 A JP 2002372275A JP 2004205076 A JP2004205076 A JP 2004205076A
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oxygen
air
low
pressure
liquefied
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JP4230213B2 (en
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Shinichiro Yamamoto
伸一郎 山本
Takashi Tatsumi
高司 辰巳
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Japan Oxygen Co Ltd
Nippon Sanso Corp
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Japan Oxygen Co Ltd
Nippon Sanso Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04151—Purification and (pre-)cooling of the feed air; recuperative heat-exchange with product streams
    • F25J3/04187—Cooling of the purified feed air by recuperative heat-exchange; Heat-exchange with product streams
    • F25J3/04218—Parallel arrangement of the main heat exchange line in cores having different functions, e.g. in low pressure and high pressure cores
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04284—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams
    • F25J3/04309—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams of nitrogen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04406—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a dual pressure main column system
    • F25J3/04418—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a dual pressure main column system with thermally overlapping high and low pressure columns
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04624—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using integrated mass and heat exchange, so-called non-adiabatic rectification, e.g. dephlegmator, reflux exchanger
    • F25J3/0463—Simultaneously between rectifying and stripping sections, i.e. double dephlegmator
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/04—Processes or apparatus using separation by rectification in a dual pressure main column system
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/34—Processes or apparatus using separation by rectification using a side column fed by a stream from the low pressure column
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/50—Processes or apparatus using separation by rectification using multiple (re-)boiler-condensers at different heights of the column
    • F25J2200/54—Processes or apparatus using separation by rectification using multiple (re-)boiler-condensers at different heights of the column in the low pressure column of a double pressure main column system

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air liquefying and separating device and its method, producing a reduction in required power by effectively combining a multiple fractioning column and a dephlegmator. <P>SOLUTION: The air liquefying and separating device comprises the multiple fractioning column 14 consisting of a high pressure fractioning column 11, a low pressure fractioning column 12 and a main condensing evaporator 13, the dephlegmator 15 having an oxygen chamber 17 for introducing low purity liquefied oxygen extracted from the low pressure fractioning column 12 and an air chamber 18 for introducing part of raw material air for fractioning the low purity liquefied oxygen while making heat exchange between the air chamber and the oxygen chamber to create liquefied oxygen at the lower part of the oxygen chamber, a reboiler 16 for gasifying the liquefied oxygen extracted from the lower part of the oxygen chamber using part of the raw material air as a heat source, and a passage from which oxygen gas gasified by the reboiler is sampled as product oxygen gas. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、空気液化分離装置及び方法に関し、詳しくは、圧縮，精製，冷却した原料空気を深冷液化分離することにより、少なくとも低純度酸素ガスを製品として採取するための空気液化分離装置及び方法に関する。
【０００２】
【従来の技術】
高炉吹込み用や酸素富化燃焼用等で使用する低純度酸素を供給するための装置として、複精留塔を用いた空気液化分離装置が広く用いられており、従来から、所要動力を削減して原単位を低減するために種々の工夫がなされてきている。
【０００３】
例えば、主凝縮蒸発器とは別に副凝縮器を設け、この副凝縮器で窒素ガスと熱交換させて液化酸素の略全量を気化させるように形成することにより、低圧精留塔下部の液化酸素濃度を低下させるとともに、高圧精留塔上部の窒素ガス圧力を低下させ、これによって原料空気圧力を低くする方法が知られている（例えば、非特許文献１参照。）。
【０００４】
また、副凝縮器で液化酸素と熱交換させるガスとして窒素よりも沸点の高い原料空気の一部を利用するとともに、高圧精留塔上部の窒素ガスを酸素濃度の低い液化酸素と熱交換させることにより、原料空気圧力を低くする方法も提案されている（例えば、特許文献１参照。）。
【０００５】
さらに、高圧精留塔上部の窒素ガスと低圧精留塔下部の液化酸素とを直接熱交換させず、高圧精留塔上部の窒素ガスは高圧精留塔下部に分離した酸素富化液化空と熱交換させ、低圧精留塔下部の液化酸素は原料空気の一部と熱交換させるようにして所要動力を削減する方法も提案されている（例えば、特許文献２参照。）。
【０００６】
一方、複精留塔に代えて、熱交換を行いながら精留操作を同時に行うデフレグメーターを用いることにより、所要動力を抑えながら低純度酸素を製造する方法も提案されている（例えば、特許文献３参照。）。
【０００７】
【非特許文献１】
倉，他２名、「低純度酸素製造装置」、日本酸素技報、日本酸素株式会社、昭和６１年、Ｎｏ．５、ｐ．１５〜１９
【０００８】
【特許文献１】
米国特許第３３２７４８９号明細書
【０００９】
【特許文献２】
米国特許第４４１０３４３号明細書
【００１０】
【特許文献３】
特開平９−１７０８７５号公報
【００１１】
【発明が解決しようとする課題】
しかしながら、副凝縮器で高圧精留塔上部の窒素ガスと熱交換して得られた製品酸素ガスは、低圧精留塔から得られる通常の製品酸素ガスに比べて圧力が低くなるという欠点があった。また、副凝縮器における液化酸素の加熱源として原料空気の一部を用いた場合は、この原料空気が副凝縮器で液化してしまうため、高圧精留塔における処理量が減少して窒素の生成量が少なくなってしまうという欠点があった。
【００１２】
さらに、窒素ガスと液化酸素とを直接熱交換させないものでも、高圧精留塔における処理量が減少して低圧精留塔上部の精留条件が厳しくなってしまうという欠点があった。また、デフレグメーターを使用した場合は、デフレグメーターの原料空気側から抜き出す窒素ガスの濃度を高くすることができず、高純度の製品窒素ガスを採取することが困難であった。
【００１３】
そこで本発明は、複精留塔とデフレグメーターとを効果的に組み合わせて原料空気圧力を低下させることにより所要動力を削減し、製品低純度酸素ガスの原単位を低減できるとともに、必要に応じて高純度の窒素ガスも製品として採取することができる空気液化分離装置及び方法を提供することを目的としている。
【００１４】
【課題を解決するための手段】
上記目的を達成するため、本発明の空気液化分離装置は、圧縮、精製、冷却した原料空気を深冷液化分離して酸素を分離する空気液化分離装置において、前記原料空気を精留して塔上部の高圧窒素ガスと塔下部の酸素富化液化空気とに分離する高圧精留塔と、該高圧精留塔で分離した酸素富化液化空気を精留して塔上部の低圧窒素ガスと塔下部の酸素濃度６０〜９０％の低純度液化酸素とに分離する低圧精留塔と、該低純度液化酸素と前記高圧窒素ガスとを熱交換させて該高圧窒素ガスを液化するとともに前記低純度液化酸素を気化する主凝縮蒸発器と、前記低圧精留塔から抜き出した低純度液化酸素を導入する酸素室と前記原料空気の一部を導入する空気室とを有し、該空気室と前記酸素室とで熱交換を行いながら前記低純度液化酸素を精留して酸素室の下部に液化酸素を生成するデフレグメーターと、前記酸素室の下部から抜き出した液化酸素を原料空気の一部を熱源として気化させるリボイラーと、該リボイラーで気化した酸素ガスを製品酸素ガスとして採取する経路とを備えていることを特徴としている。
【００１５】
さらに、本発明の空気液化分離装置では、前記リボイラーで気化した酸素ガスの一部を前記酸素室の下部に上昇ガスとして導入するための経路と、前記酸素室の上部から抜き出した低純度酸素ガスを前記低圧精留塔に導入する経路と、前記リボイラーで熱源として使用した後の原料空気を前記高圧精留塔に導入する経路と、前記空気室の下部から抜き出した酸素富化液化空気を前記高圧精留塔の酸素富化液化空気に合流させる経路と、該空気室の上部から不純窒素ガスを抜き出す経路とを備えていることを特徴としており、特に、前記空気室の上部から不純窒素ガスを抜き出す経路は、該不純窒素ガスを断熱膨張させて寒冷を発生させる膨張タービンを備えていること、前記リボイラーに加熱源として導入する前記原料空気の一部を、他の原料空気より高い圧力に昇圧する昇圧機を備えるとともに、該リボイラーで熱源として使用した後の原料空気を前記高圧精留塔に導入する前記経路に減圧弁を備えていることを特徴としている。加えて、前記低圧精留塔の上部から製品窒素ガスを採取する経路を備えていることを特徴としている。
【００１６】
また、本発明の空気液化分離方法は、圧縮、精製、冷却した原料空気を深冷液化分離して酸素を分離する空気液化分離方法において、前記原料空気を高圧窒素ガスと酸素富化液化空気とに分離する高圧精留工程と、該高圧精留工程で分離した酸素富化液化空気を低圧窒素ガスと酸素濃度６０〜９０％の低純度液化酸素とに分離する低圧精留工程と、前記低純度液化酸素と前記高圧窒素ガスとを熱交換させることによって該高圧窒素ガスを液化するとともに前記低純度液化酸素を気化する凝縮蒸発工程と、前記低圧精留工程で生成した前記低純度液化酸素と前記原料空気の一部とを熱交換させながら前記低純度液化酸素を精留して液化酸素を生成する熱交換精留工程と、該熱交換精留工程で生成した液化酸素を気化して採取する製品酸素ガス採取工程とを有することを特徴としている。
【００１７】
【発明の実施の形態】
図１は本発明の一形態例を示す空気液化分離装置の系統図である。この空気液化分離装置は、高圧精留塔１１、低圧精留塔１２及び主凝縮蒸発器１３を備えた複精留塔１４と、低純度液化酸素と原料空気の一部とを熱交換させながら精留操作を行うデフレグメーター１５と、デフレグメーター１５から抜き出した液化酸素を気化させるリボイラー（副凝縮器）１６とによって原料空気を深冷液化分離し、酸素濃度が９０〜９８体積％程度の低純度酸素を製品酸素ガスとして採取するように形成されている。
【００１８】
デフレグメーター１５は、低圧精留塔１２から抜き出した低純度液化酸素が上方から導入される酸素室（低圧側）１７と、原料空気の一部が下方から導入される空気室（高圧側）１８とを有するものであって、該空気室１８内の流体と前記酸素室１７内の流体とで熱交換を行いながら前記原料空気及び前記低純度液化酸素をそれぞれ精留し、酸素室１７の下部に所定濃度の液化酸素を生成するように形成されている。
【００１９】
まず、空気濾過器２１を通って大気から導入された原料空気は、原料空気圧縮機２２で、例えば約３９０ｋＰａまで圧縮されて低圧原料空気となり、アフタークーラー２３で圧縮熱を除去された後、空気精製器２４に導入されて水分や二酸化炭素等の不純物が除去される。精製された低圧原料空気は、経路５１と経路５２とに分岐し、経路５１の低圧原料空気は、そのまま主熱交換器２５に導入され、帰還ガスと熱交換を行い、例えば約９４Ｋまで冷却されて経路５３に流出する。経路５３の低圧原料空気は、さらに経路５４と経路５５とに分岐し、経路５４の低圧原料空気が高圧精留塔１１の下部に上昇ガスとして導入され、経路５５の低圧原料空気は、デフレグメーター１５の前記空気室１８に上昇ガスとして導入される。
【００２０】
一方、前記経路５２に分岐した低圧原料空気は、空気昇圧機２６で、例えば約４５０ｋＰａに昇圧されて中圧原料空気となる。この中圧原料空気は、アフタークーラー２７で圧縮熱を除去された後、主熱交換器２５に導入されて帰還ガスと熱交換を行い、例えば約９６Ｋまで冷却されて経路５６に流出する。経路５６の中圧原料空気は、前記リボイラー１６で液化酸素と熱交換を行って液化した後、経路５７の減圧弁２８で減圧されてから高圧精留塔１１の中下部に下降液として導入される。さらに、デフレグメーター１５の前記空気室１８からは、該空気室１８での精留作用によって酸素分が富化した液化空気が抜き出され、経路５８を通って高圧精留塔１１の下部に導入される。
【００２１】
高圧精留塔１１では、前記各経路５４，５７，５８から導入された原料空気の精留操作が行われ、塔上部に高純度の高圧窒素ガスが分離するとともに、塔下部に酸素が濃縮された酸素富化液化空気が分離する。高圧精留塔下部の酸素富化液化空気は、経路５９に抜き出されて過冷器２９で冷却され、過冷液となって減圧弁３０で減圧された後、経路６０から低圧精留塔１２の中部に下降液として導入される。また、高圧精留塔上部の高圧窒素ガスは、経路６１を通って前記主凝縮蒸発器１３に導入され、低圧精留塔下部の液化酸素と熱交換を行い、液化して液化窒素となる。主凝縮蒸発器１３から経路６２に流出した液化窒素は、経路６３と経路６４とに分岐し、経路６３の液化窒素は、高圧精留塔１１の上部に戻って下降液（還流液）となる。一方、経路６４の液化窒素は、前記過冷器２７で冷却されて過冷液となり、減圧弁３１で減圧された後、経路６５から低圧精留塔１２の上部に下降液（還流液）として導入される。
【００２２】
低圧精留塔１２では、精留操作によって塔上部に高純度の低圧窒素ガスが、塔下部に低純度、例えば酸素濃度が約７７％の低純度液化酸素がそれぞれ分離する。塔上部の低圧窒素ガスは、経路６６に抜き出されて前記過冷器２９で前記酸素富化液化空気及び液化窒素を冷却し、前記主熱交換器２５で原料空気を冷却することによって常温に昇温し、経路６７から製品高純度窒素ガスＰＮＧとして採取される。また、低圧精留塔１２の中上部からは経路６８に低純度窒素ガスが抜き出され、同様に過冷器２９及び主熱交換器２５を経て経路６９から廃ガスＷＧとして排出される。
【００２３】
低圧精留塔下部の低純度液化酸素は、経路７１に抜き出されて前記デフレグメーター１５の酸素室１７に下降液として導入される。このデフレグメーター１５は、精留効果を有する熱交換器であって、精留を行いながら高圧側の空気室１８から低圧側の酸素室１７に熱が移動する。
【００２４】
すなわち、デフレグメーター１５では、前記経路５５から空気室１８に導入された低圧原料空気と、前記経路７１から酸素室１７に導入された低純度液化酸素とが熱交換を行い、低圧原料空気から低純度液化酸素に熱が移動するので、酸素室１７内の低純度液化酸素は、前記熱移動により加温されて一部が蒸発しながら室内を下降し、この下降中の液と、蒸発して室内を上昇するガスとの間で精留作用が発生する。これにより、酸素室１７の下部には製品濃度の液化酸素が生成して経路７２に抜き出されるとともに、酸素室１７の上部には製品よりも酸素濃度が低いガス（酸素富化ガス）が生成して経路７３に抜き出される。この経路７３の酸素富化ガスは、低圧精留塔１２の中下部に導入されて上昇ガスとなる。
【００２５】
デフレグメーター１５から前記経路７２に抜き出された液化酸素は、前記リボイラー１６に導入されて前記中圧原料空気により加温され、気化して製品酸素濃度の低純度酸素ガスが生成する。この低純度酸素ガスは、リボイラー１６から経路７４に抜き出されて経路７５と経路７６とに分岐し、経路７５に分岐した低純度酸素ガスが前記主熱交換器２５で原料空気と熱交換して常温となり、経路７７から製品低純度酸素ＰＯＧとして採取される。経路７６に分岐した少量の低純度酸素ガスは、上昇ガスとして酸素室１７に再び導入される。また、リボイラー１６の下部からは、一部の液化酸素が保安液酸ＳＯＬとして経路７８に抜き出される。
【００２６】
一方、空気室１８の低圧原料空気は、酸素室１７に熱を与えることによって自身は冷却されることになり、一部が液化しながら室内を上昇し、この上昇ガスと液化して室内を下降する液との間で精留作用が発生する。これにより、空気室１８の下部には酸素が富化した液化空気が生成して前記経路５８に抜き出されるとともに、空気室１８の上部には窒素が富化したガス（不純窒素ガス）が生成する。この不純窒素ガスは、経路８１に抜き出されて主熱交換器２５で中間温度まで昇温し、さらに、膨張タービン熱交換器３２で常温付近まで昇温した後、経路８２を通って膨張タービン制動ブロワー３３で昇圧される。昇圧した不純窒素は、アフタークーラー３４及び前記膨張タービン熱交換器３２で中間温度まで冷却され、経路８３を通って膨張タービン３５に導入される。昇圧して冷却された不純窒素は、この膨張タービン３５で断熱膨張することによって寒冷を発生し、経路８４を経て主熱交換器２５に導入され、原料空気を冷却した後、経路８５から排窒素ガスＥＮＧとして排出される。
【００２７】
このように形成した空気液化分離装置において、前記デフレグメーター１５では、空気室１８から酸素室１７への熱移動により、酸素室１７の全域にわたって液化酸素の蒸発が生じるので、酸素室１７からリボイラー１６に流入する液化酸素量を少なくすることができる。これにより、リボイラー１６で液化酸素を気化させるために必要となる中圧原料空気量を、従来の副凝縮器方式に比べて減少させることができるので、中圧原料空気を得るための空気昇圧機２６の動力費を削減することができる。
【００２８】
また、空気室１８の上部から抜き出した不純窒素ガスを利用して膨張タービン３５で寒冷を発生させ、装置の運転に必要な寒冷を得るようにすることにより、高圧精留塔１１の負荷を従来よりも軽減できるとともに、高圧精留塔１１で分離生成した高圧窒素ガスの全量を低圧精留塔１２に導入することが可能となるため、低圧精留塔１２の上部から抜き出す高純度の低圧窒素ガス量を増加させることができる。
【００２９】
【実施例】
図１に示した構成の空気液化分離装置を使用して、酸素濃度９５体積％、圧力１３０ｋＰａの低純度酸素ガスを４９７５０Ｎｍ３／ｈ採取する際の主要経路におけるガス又は液の流量、温度、圧力及び酸素濃度を計算した。その結果を表１に示す。
【００３０】
【表１】

Figure 2004205076
【００３１】
また、比較例として、従来の副凝縮器方式の空気液化分離装置において、前記実施例と同じ酸素濃度９５体積％、圧力１３０ｋＰａの低純度酸素ガスを４９７５０Ｎｍ３／ｈ採取するために、高圧精留塔１１の運転圧力を前記実施例と同一としたときの装置構成例を図２に示す。
【００３２】
なお、図２においては、前記実施例との比較を容易とするため、図１に示した装置と同一乃至類似の機器及び経路には同一符号を付すようにしている。また、運転操作は、基本的に前記形態例での説明と同じであるから、その詳細な説明は省略する。
【００３３】
図２に示す空気液化分離装置では、前記デフレグメーター１５に代えて副凝縮器４１を備えた第２低圧精留塔４２を設置し、副凝縮器４１で気化した低純度酸素ガスを、経路９１に抜き出し、主熱交換器２５を通して経路７７から製品として採取するようにしている。低圧精留塔下部に分離した低純度液化酸素の酸素濃度は、高圧精留塔上部の高圧窒素ガスと熱交換して気化可能な酸素濃度、すなわち、前記実施例と同じ酸素濃度（７７体積％）としておく必要があるから、経路７１に抜き出した低純度液化酸素は、第２低圧精留塔４２で精留して酸素濃度を高め、副凝縮器４１で気化するときに製品酸素濃度（９５体積％）の酸素ガスを発生させるように設定する必要がある。このとき、第２低圧精留塔４２での精留操作に必要な上昇ガスは、前記副凝縮器４１における中圧原料空気との熱交換によってのみ得られることになる。
【００３４】
主熱交換器２５で冷却された経路５３の低圧原料空気は、全量が高圧精留塔１１に導入され、経路５６の中圧原料空気は、副凝縮器４１で液化して経路５７に抜き出され、減圧弁２８で減圧されて高圧精留塔１１に導入される。また、高圧精留塔上部から抜き出された高圧窒素ガスの一部は、膨張タービン３５に向かう経路８１に分岐し、残りの高圧窒素ガスが低圧精留塔下部の低純度液化酸素と熱交換するために主凝縮蒸発器１３に導入される。さらに、第２低圧精留塔４２上部に上昇したガス（酸素富化ガス）は、実施例と同様に、経路７３を通って低圧精留塔４２に戻される。
【００３５】
この比較例装置における主要経路のガス又は液の流量、温度、圧力及び酸素濃度を、前記実施例と同様にして計算した結果を表２に示す。また、実施例と比較例とを比較したものを表３に示す。
【００３６】
【表２】
Figure 2004205076
【００３７】
【表３】
Figure 2004205076
【００３８】
また、前記実施例におけるデフレグメーター１５内の温度分布を図３に、デフレグメーター１５内のガス中の酸素濃度を図４に、さらに、前記比較例における副凝縮器４１の温度分布を図５にそれぞれ示す。
【００３９】
本実施例及び比較例において、低圧精留塔１２の下部に分離した液化酸素を主凝縮蒸発器で気化させるために必要な窒素ガスの圧力は、液化酸素の圧力を同じとすれば酸素濃度によって変化する。例えば、気化した酸素ガスをそのまま製品低純度酸素ガスとして採取する場合、気化した酸素ガスの圧力が１４０ｋＰａで酸素濃度が９５体積％のとき、この酸素ガスと気液平衡となる液化酸素は、酸素濃度が９７．３体積％で沸点が９３Ｋであるから、この液化酸素を蒸発させるためには、窒素ガスの圧力を５００ｋＰａ（このときの窒素の沸点は９４Ｋである。）とする必要がある。一方、窒素より沸点の高い空気で前記液化酸素を気化させるとすると、空気の圧力は４２０ｋＰａでよいことになる。
【００４０】
そして、液化酸素の酸素濃度を７７体積％に低下させて蒸発温度を８９Ｋにすると、窒素ガスの圧力を３４０ｋＰａまで下げることができる。したがって、低圧精留塔下部の液化酸素における酸素濃度を７７体積％に設定することにより、高圧精留塔上部の運転圧力を５００ｋＰａから３４０ｋＰａに下げることが可能となり、原料空気圧力をその分低下させることができる。
【００４１】
しかし、比較例の副凝縮器方式では、副凝縮器４１において、酸素濃度が９５体積％の酸素ガスを蒸発させる必要があるから、低圧精留塔下部から抜き出した液化酸素（７７体積％）を精留して酸素濃度を９５体積％まで高めなければならない。このため、第２低圧精留塔４２で精留操作を行うための上昇ガスを確保する必要があり、副凝縮器４１ではこの上昇ガスとして用いる酸素ガスと、製品として採取する酸素ガスとの合計量を蒸発させなければならないため、熱源として大量の中圧原料空気、すなわち、全空気量に対して約４２％を必要としている。
【００４２】
さらに、熱源として中圧原料空気を使用した場合は、空気の露点と酸素の沸点とに差がある関係上、副凝縮器４１では、図５に示すような温度分布となり、温度レベルを有効に活用できていないことがわかる。また、熱源として使用した中圧原料空気は、液化空気として高圧精留塔１１に導入されるため、高圧精留塔内の上昇ガスが減少し、高圧精留塔１１の精留状態が悪化するという問題も出てくる。
【００４３】
一方、実施例のデフレグメーター方式の場合は、図３及び図４に示すように、熱交換と精留とが同時に行われているため、上部に行くほど低温となり、上部に行くほど酸素分が少なくなる状態で、最下部では９５体積％の液化酸素が得られている状態となっている。このように、デフレグメーターを用いることにより、副凝縮器に用いるような通常の熱交換器よりも温度アプローチを接近させることが可能となるので、各流体の温度レベルを有効に利用できる。そして、酸素室での精留操作に必要な上昇ガスは、そのほとんどをデフレグメーター内での熱交換で得ることができるので、リボイラー１６では、製品として採取する酸素ガスに見合う量の液化酸素を蒸発させればよいから、熱源となる中圧原料空気量が少なくてすむ。
【００４４】
この結果、酸素回収率を比較例の９３．３８％から９６．５２％に向上させることができ、同一製品量の場合は、全原料空気量を２４２７００Ｎｍ３／ｈから２３４８００Ｎｍ３／ｈに削減することができる。また、中圧原料空気量も１０１０００Ｎｍ３／ｈから８００００Ｎｍ３／ｈに削減できるので、原料空気圧縮機及び空気昇圧機の合計所要動力を１３９２４ｋＷから１３３３４ｋＷにまで低減することができる。さらに、高純度窒素の採取量も増加させることができるので、製品酸素及び製品窒素を合わせた原単位を大幅に低減することができる。
【００４５】
【発明の効果】
以上説明したように、本発明によれば、高圧精留塔の運転圧力を低く設定して原料空気圧縮機の負荷を軽減できるとともに、製品低純度酸素ガスを蒸発させるための中圧原料空気量も削減でき、全体としての原料空気量も削減できるので、従来に比べて所要動力の低減と酸素回収率の向上とが図れる。
【図面の簡単な説明】
【図１】本発明の一形態例を示す空気液化分離装置の系統図である。
【図２】実施例において比較した空気液化分離装置の系統図である。
【図３】実施例におけるデフレグメーター内の温度分布を示す図である。
【図４】実施例におけるデフレグメーター内のガス中の酸素濃度を示す図である。
【図５】比較例における副凝縮器４１の温度分布を示す図である。
【符号の説明】
１１…高圧精留塔、１２…低圧精留塔、１３…主凝縮蒸発器、１４…複精留塔、１５…デフレグメーター、１６…リボイラー、１７…酸素室、１８…空気室、２１…空気濾過器、２２…原料空気圧縮機、２３…アフタークーラー、２４…空気精製器、２５…主熱交換器、２６…空気昇圧機、２７…アフタークーラー、２８…減圧弁、２９…過冷器、３０…減圧弁、３１…減圧弁、３２…膨張タービン熱交換器、３３…膨張タービン制動ブロワー、３４…アフタークーラー、３５…膨張タービン、４１…副凝縮器、４２…第２低圧精留塔、ＰＮＧ…製品高純度窒素ガス、ＰＯＧ…製品低純度酸素[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an air liquefaction separation apparatus and method, and more particularly, to an air liquefaction separation apparatus and method for collecting at least low-purity oxygen gas as a product by cryogenic liquefaction separation of compressed, purified, and cooled raw material air. About.
[0002]
[Prior art]
Air liquefaction separation equipment using double rectification towers has been widely used as equipment for supplying low-purity oxygen used for blast furnace injection and oxygen-enriched combustion, etc. Various ideas have been made to reduce the basic unit.
[0003]
For example, a sub-condenser is provided separately from the main condensing evaporator, and heat is exchanged with nitrogen gas in this sub-condenser so as to vaporize substantially the entire amount of liquefied oxygen. A method is known in which the concentration is lowered and the nitrogen gas pressure in the upper part of the high-pressure rectification column is lowered, thereby lowering the raw material air pressure (for example, see Non-Patent Document 1).
[0004]
In addition, a part of the raw air having a boiling point higher than that of nitrogen is used as a gas to exchange heat with liquefied oxygen in the sub-condenser, and the nitrogen gas in the upper part of the high-pressure rectification tower is heat-exchanged with liquefied oxygen having a low oxygen concentration. Thus, a method of lowering the raw material air pressure has also been proposed (see, for example, Patent Document 1).
[0005]
Furthermore, the nitrogen gas at the top of the high-pressure rectification column and the liquefied oxygen at the bottom of the low-pressure rectification column are not directly subjected to heat exchange. A method has also been proposed in which the required power is reduced by heat exchange so that the liquefied oxygen in the lower part of the low-pressure rectification column exchanges heat with a part of the raw air (for example, see Patent Document 2).
[0006]
On the other hand, a method for producing low-purity oxygen while suppressing required power by using a defregmeter that simultaneously performs rectification operation while performing heat exchange instead of the double rectification column has been proposed (for example, patents). Reference 3).
[0007]
[Non-Patent Document 1]
Kura, et al., “Low Purity Oxygen Production Equipment”, Nippon Oxygen Technical Bulletin, Nippon Oxygen Co., Ltd., 1986, No. 1 5, p. 15-19
[0008]
[Patent Document 1]
US Pat. No. 3,327,489 specification
[Patent Document 2]
US Pat. No. 4,410,343
[Patent Document 3]
JP-A-9-170875 [0011]
[Problems to be solved by the invention]
However, the product oxygen gas obtained by heat exchange with the nitrogen gas at the top of the high-pressure rectification column in the sub-condenser has the disadvantage that the pressure is lower than the normal product oxygen gas obtained from the low-pressure rectification column. It was. In addition, when a part of the raw air is used as a liquefied oxygen heating source in the sub-condenser, the raw air is liquefied in the sub-condenser, so that the processing amount in the high-pressure rectification column is reduced and the nitrogen There was a drawback that the amount produced was reduced.
[0012]
Furthermore, even if nitrogen gas and liquefied oxygen are not directly heat-exchanged, there is a drawback that the amount of treatment in the high-pressure rectification column is reduced and the rectification conditions at the top of the low-pressure rectification column become severe. Further, when a dephlegmator is used, the concentration of nitrogen gas extracted from the raw air side of the dephlegmator cannot be increased, and it has been difficult to collect high purity product nitrogen gas.
[0013]
Therefore, the present invention effectively reduces the required power by reducing the raw air pressure by effectively combining the double rectification column and the dephlegmator, and can reduce the basic unit of the product low-purity oxygen gas. Another object of the present invention is to provide an air liquefaction separation apparatus and method capable of collecting high purity nitrogen gas as a product.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, an air liquefaction separation apparatus according to the present invention is an air liquefaction separation apparatus that separates oxygen by subjecting compressed, refined, and cooled raw material air to cryogenic liquefaction separation. A high-pressure rectification column that separates high-pressure nitrogen gas at the top and oxygen-enriched liquefied air at the bottom of the column; A low-pressure rectification column that separates into low-purity liquefied oxygen having a lower oxygen concentration of 60 to 90%, and heat-exchanges the low-purity liquefied oxygen and the high-pressure nitrogen gas to liquefy the high-pressure nitrogen gas and the low-purity A main condensing evaporator for vaporizing liquefied oxygen, an oxygen chamber for introducing low-purity liquefied oxygen extracted from the low-pressure rectification column, and an air chamber for introducing a part of the raw air, The low-purity liquefied oxygen is purified while exchanging heat with the oxygen chamber. A dephlegmator that generates liquefied oxygen in the lower part of the oxygen chamber, a reboiler that vaporizes liquefied oxygen extracted from the lower part of the oxygen chamber using a part of the raw air as a heat source, and oxygen gas vaporized by the reboiler And a route for collecting oxygen gas.
[0015]
Furthermore, in the air liquefaction separation apparatus of the present invention, a path for introducing a part of the oxygen gas vaporized by the reboiler as a rising gas into the lower part of the oxygen chamber, and a low-purity oxygen gas extracted from the upper part of the oxygen chamber A path for introducing the raw material air after being used as a heat source in the reboiler to the high pressure rectification tower, and an oxygen-enriched liquefied air extracted from the lower part of the air chamber. A path for joining the oxygen-enriched liquefied air of the high-pressure rectification column and a path for extracting impure nitrogen gas from the upper part of the air chamber, and particularly, impure nitrogen gas from the upper part of the air chamber The extraction path is provided with an expansion turbine that adiabatically expands the impure nitrogen gas to generate cold, and a part of the raw air introduced as a heating source to the reboiler is supplied to another source. Provided with a booster that boosts higher than air pressure, is characterized in that said path for introducing the feed air after using as a heat source in the reboiler to the high pressure rectification column and a pressure reducing valve. In addition, it is characterized by having a path for collecting product nitrogen gas from the upper part of the low-pressure rectification column.
[0016]
The air liquefaction separation method of the present invention is an air liquefaction separation method for separating oxygen by subjecting the compressed, purified, and cooled raw material air to a cryogenic liquefaction separation, wherein the raw material air is divided into high-pressure nitrogen gas and oxygen-enriched liquefied air. A high-pressure rectification step for separating the oxygen-enriched liquefied air separated in the high-pressure rectification step into low-pressure nitrogen gas and low-purity liquefied oxygen having an oxygen concentration of 60 to 90%; A condensation evaporation step for liquefying the high-pressure nitrogen gas and vaporizing the low-purity liquefied oxygen by exchanging heat between the pure liquefied oxygen and the high-pressure nitrogen gas; and the low-purity liquefied oxygen produced in the low-pressure rectification step; A heat exchange rectification step for producing liquefied oxygen by rectifying the low-purity liquefied oxygen while exchanging a part of the raw material air, and collecting by vaporizing the liquefied oxygen produced in the heat exchange rectification step Products to collect oxygen gas It is characterized by a step.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a system diagram of an air liquefaction separation apparatus showing an embodiment of the present invention. This air liquefaction separation apparatus heat-exchanges the double rectification column 14 provided with the high pressure rectification column 11, the low pressure rectification column 12, and the main condensation evaporator 13, and low purity liquefied oxygen and a part of raw material air. Raw material air is subjected to cryogenic liquefaction separation by a dephlegmator 15 for performing a rectification operation and a reboiler (sub-condenser) 16 for vaporizing liquefied oxygen extracted from the dephlegmator 15 so that the oxygen concentration is about 90 to 98% by volume. The low-purity oxygen is collected as product oxygen gas.
[0018]
The dephlegmator 15 includes an oxygen chamber (low pressure side) 17 into which low-purity liquefied oxygen extracted from the low pressure rectification column 12 is introduced from above, and an air chamber (high pressure side) into which a part of the raw air is introduced from below. 18 and rectifying the raw material air and the low-purity liquefied oxygen while performing heat exchange between the fluid in the air chamber 18 and the fluid in the oxygen chamber 17, A lower part is formed so as to generate liquefied oxygen having a predetermined concentration.
[0019]
First, the raw material air introduced from the atmosphere through the air filter 21 is compressed to, for example, about 390 kPa by the raw material air compressor 22 to become low-pressure raw material air, and after the compression heat is removed by the aftercooler 23, Introduced into the purifier 24, impurities such as moisture and carbon dioxide are removed. The purified low-pressure raw material air is branched into a path 51 and a path 52, and the low-pressure raw material air in the path 51 is directly introduced into the main heat exchanger 25 to exchange heat with the return gas, and is cooled to, for example, about 94K. Then flows out into the path 53. The low-pressure feed air in the path 53 is further branched into a path 54 and a path 55, and the low-pressure feed air in the path 54 is introduced into the lower portion of the high-pressure rectification column 11 as an ascending gas. It is introduced into the air chamber 18 of the meter 15 as a rising gas.
[0020]
On the other hand, the low-pressure source air branched into the path 52 is boosted to, for example, about 450 kPa by the air booster 26 and becomes medium-pressure source air. After the compression heat is removed by the aftercooler 27, the intermediate-pressure raw material air is introduced into the main heat exchanger 25 to exchange heat with the return gas, and is cooled to, for example, about 96K and flows out to the path 56. The medium pressure raw material air in the path 56 is liquefied by performing heat exchange with the liquefied oxygen in the reboiler 16, then depressurized by the pressure reducing valve 28 in the path 57, and then introduced as a descending liquid into the lower part of the high pressure rectification column 11. The Further, liquefied air enriched in oxygen content is extracted from the air chamber 18 of the dephlegmator 15 by the rectification action in the air chamber 18, and passes through the path 58 to the lower part of the high-pressure rectification column 11. be introduced.
[0021]
In the high-pressure rectification column 11, the rectification operation of the raw air introduced from each of the paths 54, 57, 58 is performed, so that high-purity high-pressure nitrogen gas is separated in the upper part of the tower and oxygen is concentrated in the lower part of the tower. Oxygen-enriched liquefied air separates. The oxygen-enriched liquefied air in the lower part of the high-pressure rectification column is extracted to the path 59 and cooled by the supercooler 29, becomes a supercooled liquid, and is depressurized by the pressure reducing valve 30. 12 is introduced as a descending liquid in the middle. The high-pressure nitrogen gas at the upper part of the high-pressure rectification column is introduced into the main condensing evaporator 13 through the path 61, exchanges heat with liquefied oxygen at the lower part of the low-pressure rectification column, and is liquefied to become liquefied nitrogen. The liquefied nitrogen that has flowed out of the main condenser evaporator 13 into the path 62 is branched into a path 63 and a path 64, and the liquefied nitrogen in the path 63 returns to the upper part of the high-pressure rectification column 11 and becomes a descending liquid (reflux liquid). . On the other hand, the liquefied nitrogen in the path 64 is cooled by the supercooler 27 to become a supercooled liquid, and after being depressurized by the pressure reducing valve 31, descends (refluxed liquid) from the path 65 to the upper portion of the low pressure rectification tower 12. be introduced.
[0022]
In the low-pressure rectification column 12, high-purity low-pressure nitrogen gas is separated at the top of the column and low-purity liquefied oxygen having a low purity, for example, an oxygen concentration of about 77%, is separated at the bottom of the column. The low-pressure nitrogen gas at the top of the tower is withdrawn into a path 66, the oxygen-enriched liquefied air and liquefied nitrogen are cooled by the supercooler 29, and the raw air is cooled by the main heat exchanger 25 to normal temperature. The temperature is raised and the product 67 is collected as product high purity nitrogen gas PNG. Further, low-purity nitrogen gas is extracted from the middle upper portion of the low-pressure rectification column 12 to the path 68, and is similarly discharged as waste gas WG from the path 69 via the supercooler 29 and the main heat exchanger 25.
[0023]
The low-purity liquefied oxygen in the lower part of the low-pressure rectification column is extracted into the passage 71 and introduced into the oxygen chamber 17 of the dephlegmator 15 as a descending liquid. The dephlegmator 15 is a heat exchanger having a rectifying effect, and heat is transferred from the high pressure side air chamber 18 to the low pressure side oxygen chamber 17 while performing rectification.
[0024]
That is, in the dephlegmator 15, the low-pressure raw material air introduced into the air chamber 18 from the passage 55 and the low-purity liquefied oxygen introduced into the oxygen chamber 17 from the passage 71 exchange heat, and from the low-pressure raw material air. Since heat moves to the low-purity liquefied oxygen, the low-purity liquefied oxygen in the oxygen chamber 17 is heated by the heat transfer and descends while partially evaporating, and the falling liquid is evaporated. Rectification occurs between the gas rising in the room. As a result, liquefied oxygen having a product concentration is generated in the lower portion of the oxygen chamber 17 and extracted into the path 72, and a gas (oxygen-enriched gas) having a lower oxygen concentration than the product is generated in the upper portion of the oxygen chamber 17. Then, it is extracted to the path 73. The oxygen-enriched gas in this path 73 is introduced into the lower part of the low-pressure rectification column 12 and becomes a rising gas.
[0025]
The liquefied oxygen extracted from the dephlegmator 15 to the path 72 is introduced into the reboiler 16, heated by the medium-pressure raw material air, and vaporized to generate low-purity oxygen gas having a product oxygen concentration. This low-purity oxygen gas is extracted from the reboiler 16 into a path 74 and branched into a path 75 and a path 76, and the low-purity oxygen gas branched into the path 75 exchanges heat with the raw air in the main heat exchanger 25. It becomes normal temperature and is collected as product low purity oxygen POG from the route 77. A small amount of low-purity oxygen gas branched into the path 76 is reintroduced into the oxygen chamber 17 as rising gas. Further, a part of the liquefied oxygen is extracted from the lower part of the reboiler 16 to the path 78 as the protective liquid acid SOL.
[0026]
On the other hand, the low-pressure raw material air in the air chamber 18 is cooled by applying heat to the oxygen chamber 17, and rises in the room while a part is liquefied, and liquefies with this rising gas and descends in the room. A rectifying action occurs with the liquid to be used. As a result, liquefied air enriched with oxygen is generated in the lower part of the air chamber 18 and extracted into the passage 58, and a gas (impure nitrogen gas) enriched in nitrogen is generated in the upper part of the air chamber 18. To do. The impure nitrogen gas is extracted to the path 81, heated to an intermediate temperature by the main heat exchanger 25, further heated to near normal temperature by the expansion turbine heat exchanger 32, and then passed through the path 82 to expand the expansion turbine. The pressure is increased by the brake blower 33. The increased impure nitrogen is cooled to an intermediate temperature by the aftercooler 34 and the expansion turbine heat exchanger 32, and is introduced into the expansion turbine 35 through a path 83. The impure nitrogen that has been pressurized and cooled is adiabatically expanded by the expansion turbine 35 to generate cold, and is introduced into the main heat exchanger 25 through the path 84 to cool the raw air, and then exhaust nitrogen from the path 85. It is discharged as gas ENG.
[0027]
In the air liquefaction separation apparatus formed in this way, in the dephlegmator 15, due to heat transfer from the air chamber 18 to the oxygen chamber 17, liquefied oxygen evaporates throughout the oxygen chamber 17. The amount of liquefied oxygen flowing into 16 can be reduced. As a result, the amount of medium-pressure raw material air necessary for vaporizing liquefied oxygen by the reboiler 16 can be reduced as compared with the conventional sub-condenser system, so an air booster for obtaining medium-pressure raw material air 26 power costs can be reduced.
[0028]
Further, the impure nitrogen gas extracted from the upper part of the air chamber 18 is used to generate cold in the expansion turbine 35 so as to obtain the cold necessary for the operation of the apparatus, so that the load on the high pressure rectification column 11 is conventionally increased. In addition, the entire amount of high-pressure nitrogen gas separated and generated in the high-pressure rectification column 11 can be introduced into the low-pressure rectification column 12, so that high-purity low-pressure nitrogen extracted from the upper portion of the low-pressure rectification column 12 can be obtained. The amount of gas can be increased.
[0029]
【Example】
Using the air liquefaction separation apparatus having the configuration shown in FIG. 1, the flow rate, temperature, and pressure of the gas or liquid in the main path when collecting low-purity oxygen gas having an oxygen concentration of 95 vol% and a pressure of 130 kPa of 49750 Nm 3 / h And the oxygen concentration was calculated. The results are shown in Table 1.
[0030]
[Table 1]
Figure 2004205076
[0031]
Further, as a comparative example, in a conventional sub-condenser type air liquefaction separation apparatus, in order to collect 49750 Nm 3 / h of low-purity oxygen gas having an oxygen concentration of 95% by volume and a pressure of 130 kPa as in the previous example, FIG. 2 shows an apparatus configuration example when the operation pressure of the tower 11 is the same as that in the above embodiment.
[0032]
In FIG. 2, the same reference numerals are assigned to the same or similar devices and routes as those of the apparatus shown in FIG. 1 for easy comparison with the above-described embodiment. Further, since the driving operation is basically the same as the description in the embodiment, the detailed description thereof is omitted.
[0033]
In the air liquefaction separation apparatus shown in FIG. 2, a second low-pressure rectification tower 42 having a sub-condenser 41 is installed in place of the dephlegmator 15, and low-purity oxygen gas vaporized by the sub-condenser 41 is routed. The product is extracted as a product from the passage 77 through the main heat exchanger 25. The oxygen concentration of the low-purity liquefied oxygen separated at the lower part of the low-pressure rectification column is the oxygen concentration that can be vaporized by heat exchange with the high-pressure nitrogen gas at the upper part of the high-pressure rectification column, that is, the same oxygen concentration (77% by volume) as in the previous example. Therefore, the low-purity liquefied oxygen extracted into the path 71 is rectified in the second low-pressure rectification column 42 to increase the oxygen concentration and vaporize in the sub-condenser 41 (95). (Volume%) oxygen gas must be set to be generated. At this time, the rising gas necessary for the rectification operation in the second low-pressure rectification column 42 is obtained only by heat exchange with the medium-pressure raw material air in the sub-condenser 41.
[0034]
The entire amount of the low-pressure feed air in the path 53 cooled by the main heat exchanger 25 is introduced into the high-pressure rectification column 11, and the medium-pressure feed air in the path 56 is liquefied by the sub-condenser 41 and extracted into the path 57. The pressure is reduced by the pressure reducing valve 28 and introduced into the high pressure rectification column 11. Further, a part of the high-pressure nitrogen gas extracted from the upper part of the high-pressure rectification column branches into a path 81 directed to the expansion turbine 35, and the remaining high-pressure nitrogen gas exchanges heat with the low-purity liquefied oxygen at the lower part of the low-pressure rectification column. In order to do so, it is introduced into the main condensing evaporator 13. Furthermore, the gas (oxygen-enriched gas) rising to the upper part of the second low-pressure rectification column 42 is returned to the low-pressure rectification column 42 through the path 73 as in the embodiment.
[0035]
Table 2 shows the results of calculating the flow rate, temperature, pressure, and oxygen concentration of the gas or liquid in the main path in this comparative example device in the same manner as in the previous example. Table 3 shows a comparison between the examples and the comparative examples.
[0036]
[Table 2]
Figure 2004205076
[0037]
[Table 3]
Figure 2004205076
[0038]
3 shows the temperature distribution in the dephlegmator 15 in the embodiment, FIG. 4 shows the oxygen concentration in the gas in the dephlegmator 15, and further shows the temperature distribution of the sub-condenser 41 in the comparative example. 5 respectively.
[0039]
In this example and the comparative example, the pressure of nitrogen gas required for vaporizing the liquefied oxygen separated in the lower part of the low-pressure rectification column 12 by the main condensing evaporator depends on the oxygen concentration if the pressure of the liquefied oxygen is the same. Change. For example, when the vaporized oxygen gas is collected as a product low-purity oxygen gas as it is, when the pressure of the vaporized oxygen gas is 140 kPa and the oxygen concentration is 95% by volume, the liquefied oxygen in vapor-liquid equilibrium with this oxygen gas is oxygen Since the concentration is 97.3% by volume and the boiling point is 93K, in order to evaporate this liquefied oxygen, the pressure of the nitrogen gas needs to be 500 kPa (the boiling point of nitrogen at this time is 94K). On the other hand, if the liquefied oxygen is vaporized with air having a boiling point higher than that of nitrogen, the pressure of the air may be 420 kPa.
[0040]
When the oxygen concentration of liquefied oxygen is reduced to 77% by volume and the evaporation temperature is 89K, the pressure of nitrogen gas can be reduced to 340 kPa. Therefore, by setting the oxygen concentration in the liquefied oxygen at the lower part of the low-pressure rectification column to 77% by volume, the operating pressure at the upper part of the high-pressure rectification column can be lowered from 500 kPa to 340 kPa, and the raw material air pressure is reduced accordingly. be able to.
[0041]
However, in the sub-condenser system of the comparative example, it is necessary to evaporate oxygen gas having an oxygen concentration of 95% by volume in the sub-condenser 41. Therefore, liquefied oxygen (77% by volume) extracted from the lower portion of the low-pressure rectification column It must be rectified to increase the oxygen concentration to 95% by volume. For this reason, it is necessary to secure the rising gas for performing the rectification operation in the second low-pressure rectification column 42, and the sub-condenser 41 is the sum of the oxygen gas used as the rising gas and the oxygen gas collected as a product. Since the amount must be evaporated, a large amount of medium pressure raw material air, that is, about 42% of the total air amount is required as a heat source.
[0042]
Furthermore, when medium-pressure raw material air is used as a heat source, the sub-condenser 41 has a temperature distribution as shown in FIG. 5 due to the difference between the dew point of air and the boiling point of oxygen, and the temperature level is effectively increased. You can see that it has not been used. Moreover, since the medium pressure raw material air used as a heat source is introduced into the high pressure rectification column 11 as liquefied air, the rising gas in the high pressure rectification column is reduced, and the rectification state of the high pressure rectification column 11 is deteriorated. The problem that comes out.
[0043]
On the other hand, in the case of the dephlegmator method of the embodiment, as shown in FIG. 3 and FIG. 4, since heat exchange and rectification are performed simultaneously, the temperature decreases toward the top and the oxygen content increases toward the top. With 95% by volume of liquefied oxygen being obtained at the lowermost part. Thus, by using a dephlegmator, it becomes possible to bring a temperature approach closer to that of a normal heat exchanger such as that used in a sub-condenser, so that the temperature level of each fluid can be used effectively. Since most of the ascending gas required for the rectification operation in the oxygen chamber can be obtained by heat exchange in the dephlegmator, the reboiler 16 has an amount of liquefied oxygen corresponding to the oxygen gas collected as a product. Therefore, the amount of medium-pressure raw material air used as a heat source can be reduced.
[0044]
As a result, the oxygen recovery rate can be improved from 93.38% of the comparative example to 96.52%, and in the case of the same product amount, the total raw material air amount is reduced from 242700 Nm 3 / h to 234800 Nm 3 / h. be able to. Further, since the medium pressure raw material air amount can be reduced from 101000 Nm 3 / h to 80000 Nm 3 / h, the total required power of the raw material air compressor and the air booster can be reduced from 13924 kW to 13334 kW. Furthermore, since the amount of high purity nitrogen collected can be increased, the basic unit of product oxygen and product nitrogen combined can be greatly reduced.
[0045]
【The invention's effect】
As described above, according to the present invention, the operating pressure of the high-pressure rectification column can be set low to reduce the load of the raw air compressor, and the medium-pressure raw material air amount for evaporating the product low-purity oxygen gas Since the amount of raw material air can be reduced as a whole, the required power can be reduced and the oxygen recovery rate can be improved as compared with the prior art.
[Brief description of the drawings]
FIG. 1 is a system diagram of an air liquefaction separation apparatus showing an embodiment of the present invention.
FIG. 2 is a system diagram of an air liquefaction separation apparatus compared in Examples.
FIG. 3 is a diagram showing a temperature distribution in a dephlegmator according to an embodiment.
FIG. 4 is a diagram showing an oxygen concentration in a gas in a dephlegmator according to an example.
FIG. 5 is a view showing a temperature distribution of a sub-condenser 41 in a comparative example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... High pressure rectification column, 12 ... Low pressure rectification column, 13 ... Main condensation evaporator, 14 ... Double rectification column, 15 ... Dephlegmator, 16 ... Reboiler, 17 ... Oxygen chamber, 18 ... Air chamber, 21 ... Air filter, 22 ... Raw air compressor, 23 ... After cooler, 24 ... Air purifier, 25 ... Main heat exchanger, 26 ... Air booster, 27 ... After cooler, 28 ... Pressure reducing valve, 29 ... Supercooler 30 ... Pressure reducing valve, 31 ... Pressure reducing valve, 32 ... Expansion turbine heat exchanger, 33 ... Expansion turbine braking blower, 34 ... After cooler, 35 ... Expansion turbine, 41 ... Sub-condenser, 42 ... Second low pressure rectification tower , PNG ... Product high purity nitrogen gas, POG ... Product low purity oxygen

Claims (6)

圧縮、精製、冷却した原料空気を深冷液化分離して酸素を分離する空気液化分離装置において、前記原料空気を精留して塔上部の高圧窒素ガスと塔下部の酸素富化液化空気とに分離する高圧精留塔と、該高圧精留塔で分離した酸素富化液化空気を精留して塔上部の低圧窒素ガスと塔下部の酸素濃度６０〜９０％の低純度液化酸素とに分離する低圧精留塔と、該低純度液化酸素と前記高圧窒素ガスとを熱交換させて該高圧窒素ガスを液化するとともに前記低純度液化酸素を気化する主凝縮蒸発器と、前記低圧精留塔から抜き出した低純度液化酸素を導入する酸素室と前記原料空気の一部を導入する空気室とを有し、該空気室と前記酸素室とで熱交換を行いながら前記低純度液化酸素を精留して酸素室の下部に液化酸素を生成するデフレグメーターと、前記酸素室の下部から抜き出した液化酸素を原料空気の一部を熱源として気化させるリボイラーと、該リボイラーで気化した酸素ガスを製品酸素ガスとして採取する経路とを備えていることを特徴とする空気液化分離装置。In an air liquefaction separation apparatus that separates oxygen by subjecting the compressed, purified, and cooled raw material air to a cryogenic liquefaction separation, the raw material air is rectified into high-pressure nitrogen gas at the top of the tower and oxygen-enriched liquefied air at the bottom of the tower. A high-pressure rectification column to be separated, and an oxygen-enriched liquefied air separated in the high-pressure rectification column are rectified to be separated into low-pressure nitrogen gas at the top of the column and low-purity liquefied oxygen having an oxygen concentration of 60 to 90% at the bottom A low-pressure rectification column, a main condensing evaporator that liquefyes the high-pressure nitrogen gas by heat-exchanging the low-purity liquefied oxygen and the high-pressure nitrogen gas, and the low-pressure rectification column An oxygen chamber for introducing low-purity liquefied oxygen extracted from the air chamber and an air chamber for introducing a part of the raw material air. Dephlegmator that produces liquefied oxygen at the bottom of the oxygen chamber And a reboiler that vaporizes liquefied oxygen extracted from the lower part of the oxygen chamber using a part of the raw air as a heat source, and a path for collecting oxygen gas vaporized by the reboiler as product oxygen gas. Air liquefaction separation device. 前記リボイラーで気化した酸素ガスの一部を前記酸素室の下部に上昇ガスとして導入するための経路と、前記酸素室の上部から抜き出した低純度酸素ガスを前記低圧精留塔に導入する経路と、前記リボイラーで熱源として使用した後の原料空気を前記高圧精留塔に導入する経路と、前記空気室の下部から抜き出した酸素富化液化空気を前記高圧精留塔の酸素富化液化空気に合流させる経路と、該空気室の上部から不純窒素ガスを抜き出す経路とを備えていることを特徴とする請求項１記載の空気液化分離装置。A path for introducing part of the oxygen gas vaporized by the reboiler as a rising gas into the lower part of the oxygen chamber, and a path for introducing low-purity oxygen gas extracted from the upper part of the oxygen chamber into the low-pressure rectification column; A path for introducing the raw air after being used as a heat source in the reboiler into the high-pressure rectification column, and oxygen-enriched liquefied air extracted from the lower part of the air chamber into the oxygen-enriched liquefied air of the high-pressure rectification column 2. The air liquefaction separation apparatus according to claim 1, further comprising a path for joining and a path for extracting impure nitrogen gas from an upper portion of the air chamber. 前記空気室の上部から不純窒素ガスを抜き出す経路は、該不純窒素ガスを断熱膨張させて寒冷を発生させる膨張タービンを備えていることを特徴とする請求項２記載の空気液化分離装置。The air liquefaction separation apparatus according to claim 2, wherein the path for extracting the impure nitrogen gas from the upper portion of the air chamber includes an expansion turbine that adiabatically expands the impure nitrogen gas to generate cold. 前記リボイラーに加熱源として導入する前記原料空気の一部を、他の原料空気より高い圧力に昇圧する昇圧機を備えるとともに、該リボイラーで熱源として使用した後の原料空気を前記高圧精留塔に導入する前記経路に減圧弁を備えていることを特徴とする請求項２記載の空気液化分離装置。A booster that boosts a part of the raw air introduced into the reboiler as a heating source to a pressure higher than that of the other raw air, and the raw air used as a heat source in the reboiler to the high-pressure rectification column The air liquefaction separation apparatus according to claim 2, further comprising a pressure reducing valve in the introduction path. 前記低圧精留塔の上部から製品窒素ガスを採取する経路を備えていることを特徴とする請求項１記載の空気液化分離装置。The air liquefaction separation apparatus according to claim 1, further comprising a path for collecting product nitrogen gas from an upper portion of the low-pressure rectification column. 圧縮、精製、冷却した原料空気を深冷液化分離して酸素を分離する空気液化分離方法において、前記原料空気を高圧窒素ガスと酸素富化液化空気とに分離する高圧精留工程と、該高圧精留工程で分離した酸素富化液化空気を低圧窒素ガスと酸素濃度６０〜９０％の低純度液化酸素とに分離する低圧精留工程と、前記低純度液化酸素と前記高圧窒素ガスとを熱交換させることによって該高圧窒素ガスを液化するとともに前記低純度液化酸素を気化する凝縮蒸発工程と、前記低圧精留工程で生成した前記低純度液化酸素と前記原料空気の一部とを熱交換させながら前記低純度液化酸素を精留して液化酸素を生成する熱交換精留工程と、該熱交換精留工程で生成した液化酸素を気化して採取する製品酸素ガス採取工程とを有することを特徴とする空気液化分離方法。In an air liquefaction separation method for separating oxygen by separating a compressed, purified, and cooled raw material air into a cryogenic liquid, a high pressure rectification step for separating the raw material air into high pressure nitrogen gas and oxygen enriched liquefied air, and the high pressure The low-pressure rectification step for separating the oxygen-enriched liquefied air separated in the rectification step into low-pressure nitrogen gas and low-purity liquefied oxygen having an oxygen concentration of 60 to 90%; and the low-purity liquefied oxygen and the high-pressure nitrogen gas are heated. By exchanging, the high-pressure nitrogen gas is liquefied and the low-purity liquefied oxygen is vaporized, and the low-purity liquefied oxygen produced in the low-pressure rectification step and a part of the raw air are heat-exchanged. The heat exchange rectification step for rectifying the low-purity liquefied oxygen to produce liquefied oxygen, and the product oxygen gas collection step for vaporizing and collecting the liquefied oxygen produced in the heat exchange rectification step. Characteristic sky Liquefaction separation method.
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Cited By (7)

* Cited by examiner, † Cited by third party
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KR100609169B1 (en) 2004-11-02 2006-08-02 엘지전자 주식회사 Cascade refrigerating cycle
KR100609168B1 (en) 2004-11-02 2006-08-02 엘지전자 주식회사 Cascade refrigerating cycle
JP2009520176A (en) * 2005-12-20 2009-05-21 レール・リキード−ソシエテ・アノニム・プール・レテュード・エ・レクスプロワタシオン・デ・プロセデ・ジョルジュ・クロード Air separation device by cryogenic distillation
JP2010025513A (en) * 2008-07-24 2010-02-04 Taiyo Nippon Sanso Corp Method and device for manufacturing nitrogen
JP2010036056A (en) * 2008-07-31 2010-02-18 Chiyoda Kako Kensetsu Kk Heating module and cooling module
JP2013513775A (en) * 2009-12-11 2013-04-22 レール・リキード−ソシエテ・アノニム・プール・レテュード・エ・レクスプロワタシオン・デ・プロセデ・ジョルジュ・クロード Method and unit for separation of air by cryogenic distillation
JP2013198900A (en) * 2013-05-01 2013-10-03 Chiyoda Kako Kensetsu Kk Cooling module

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100609169B1 (en) 2004-11-02 2006-08-02 엘지전자 주식회사 Cascade refrigerating cycle
KR100609168B1 (en) 2004-11-02 2006-08-02 엘지전자 주식회사 Cascade refrigerating cycle
JP2009520176A (en) * 2005-12-20 2009-05-21 レール・リキード−ソシエテ・アノニム・プール・レテュード・エ・レクスプロワタシオン・デ・プロセデ・ジョルジュ・クロード Air separation device by cryogenic distillation
JP2010025513A (en) * 2008-07-24 2010-02-04 Taiyo Nippon Sanso Corp Method and device for manufacturing nitrogen
JP2010036056A (en) * 2008-07-31 2010-02-18 Chiyoda Kako Kensetsu Kk Heating module and cooling module
JP2013513775A (en) * 2009-12-11 2013-04-22 レール・リキード−ソシエテ・アノニム・プール・レテュード・エ・レクスプロワタシオン・デ・プロセデ・ジョルジュ・クロード Method and unit for separation of air by cryogenic distillation
JP2013198900A (en) * 2013-05-01 2013-10-03 Chiyoda Kako Kensetsu Kk Cooling module

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