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JP4177507B2 - Method and apparatus for producing low purity oxygen - Google Patents

Method and apparatus for producing low purity oxygen Download PDF

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Publication number
JP4177507B2
JP4177507B2 JP06157499A JP6157499A JP4177507B2 JP 4177507 B2 JP4177507 B2 JP 4177507B2 JP 06157499 A JP06157499 A JP 06157499A JP 6157499 A JP6157499 A JP 6157499A JP 4177507 B2 JP4177507 B2 JP 4177507B2
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oxygen
low
fraction
tower
liquid fraction
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JP2000258054A (en
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康浩 村田
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Nippon Sanso Holdings 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
    • F25J3/0446—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 the heat generated by mixing two different phases
    • 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
    • F25J3/0429—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 feed air, e.g. used as waste or product air or expanded into an auxiliary column
    • F25J3/04303—Lachmann expansion, i.e. expanded into oxygen producing or 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
    • F25J2200/04—Processes or apparatus using separation by rectification in a dual pressure main column system
    • F25J2200/06—Processes or apparatus using separation by rectification in a dual pressure main column system in a classical double column flow-sheet, i.e. with thermal coupling by a main reboiler-condenser in the bottom of low pressure respectively top of high 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
    • F25J2200/90—Details relating to column internals, e.g. structured packing, gas or liquid distribution
    • 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
    • F25J2215/00—Processes characterised by the type or other details of the product stream
    • F25J2215/50—Oxygen or special cases, e.g. isotope-mixtures or low purity O2
    • F25J2215/52—Oxygen production with multiple purity O2
    • 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
    • F25J2235/00—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams
    • F25J2235/50—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams the fluid being oxygen
    • 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
    • F25J2250/00—Details related to the use of reboiler-condensers
    • F25J2250/20—Boiler-condenser with multiple exchanger cores in parallel or with multiple re-boiling or condensing streams
    • 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
    • F25J2250/00—Details related to the use of reboiler-condensers
    • F25J2250/30—External or auxiliary boiler-condenser in general, e.g. without a specified fluid or one fluid is not a primary air component or an intermediate fluid
    • F25J2250/42—One fluid being 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
    • F25J2250/00—Details related to the use of reboiler-condensers
    • F25J2250/30—External or auxiliary boiler-condenser in general, e.g. without a specified fluid or one fluid is not a primary air component or an intermediate fluid
    • F25J2250/52—One fluid being oxygen enriched compared to air, e.g. "crude oxygen"
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E20/00—Combustion technologies with mitigation potential
    • Y02E20/16—Combined cycle power plant [CCPP], or combined cycle gas turbine [CCGT]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E20/00—Combustion technologies with mitigation potential
    • Y02E20/16—Combined cycle power plant [CCPP], or combined cycle gas turbine [CCGT]
    • Y02E20/18—Integrated gasification combined cycle [IGCC], e.g. combined with carbon capture and storage [CCS]

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Separation By Low-Temperature Treatments (AREA)

Description

【０００１】
【発明の属する技術分野】
本発明は、低純度酸素の製造方法及び装置に関し、詳しくは、低温で空気を蒸留分離して低純度酸素を製品として回収するプロセスであって、圧縮機を使用することなく比較的高圧力の製品低純度酸素を製造するための方法及び装置に関する。
【０００２】
【従来の技術及び発明が解決しようとする課題】
低純度酸素は、ガス化複合発電（ＩＧＣＣ）や、直接・溶融還元製鋼及びガラス溶融等で使用される。これらのアプリケーションでは、大量の酸素を消費することから、特に動力原単位が低いことが要求される。
【０００３】
Ｃａｍｂｅｒｌｅｉｎらによる米国特許第５２９１７３７号明細書、Ｓｔｒａｕｂらによる米国特許第５４５４２２７号明細書には、動力原単位の低減を目的とした低純度酸素製造プロセスが記載されている。
【０００４】
米国特許第５２９１７３７号明細書記載のプロセスでは、製品酸素より酸素純度の高い液化酸素を低圧蒸留塔から抜き出し、ポンプで圧縮した後、ｍｉｘｉｎｇ ｃｏｌｕｍｎ（ミキシング塔）で原料空気の一部と気液接触させることにより、原料空気と同程度の圧力の低純度酸素を製造するようにしている。
【０００５】
しかし、このプロセスでは、全空気量の約３０％の空気をミキシング塔に導入して液化酸素と気液接触させて液化させるため、高圧蒸留塔に供給する原料空気量が減少する。その結果、高圧塔の上昇ガスが少なくなり、主凝縮器で液化する量が減少するため、低圧蒸留塔における還流窒素量が減少してＬ／Ｖが低下し、精留効率が悪化して製品酸素の回収率が低下するとともに、得られる窒素の純度も低下してしまう。
【０００６】
すなわち、このプロセスでは、製品酸素の圧縮動力は低減できるが、原料空気圧縮機の動力が増加する。さらに、このプロセスでは、得られる窒素の純度も低いため、ガス化複合発電（ＩＧＣＣ）のように、一定純度以上の窒素を製品として必要とする設備には不適当である。
【０００７】
また、米国特許第５４５４２２７号明細書記載のプロセスでは、低圧蒸留塔底部から抜き出した液化酸素をポンプで圧縮してミキシング塔に供給し、原料空気の一部と気液接触させるようにしている。この空気には、膨張タービンで膨張させた空気と膨張バルブで減圧させた空気とを使用している。
【０００８】
したがって、このプロセスにおいても、前記同様に、高圧蒸留塔に供給する原料空気が減少するため、低圧蒸留塔に供給する還流窒素が減少し、製品回収率が低下する。また、このプロセスでは、高圧に圧縮した原料空気の一部を膨張バルブで減圧してからミキシング塔に供給するようにしているため、減圧による動力のロスを生じる。
【０００９】
そこで本発明は、比較的高圧力の低純度酸素を製造するプロセスにおいて、酸素回収率の向上や圧縮機に要する動力費の削減により原単位の低減が図れ、さらに、同時に得られる窒素の純度低下も防止することができる低純度酸素の製造方法及び装置を提供することを目的としている。
【００１０】
【課題を解決するための手段】
上記目的を達成するため、本発明の低純度酸素の製造方法は、高圧塔、低圧塔及びミキシング塔を有する三塔式蒸留設備に原料空気を導入して低温蒸留することにより、少なくとも低純度酸素を製品として分離回収する低純度酸素の製造方法において、圧縮，精製，冷却した原料空気を前記高圧塔に導入して第一窒素留分と第一酸素富化液留分とに分離する第一蒸留工程と、該第一蒸留工程で分離した第一窒素留分と第一酸素富化液留分とを前記低圧塔に導入して第二窒素留分と第二酸素富化液留分とに分離する第二蒸留工程と、前記第一酸素富化液留分をドライタイプのリボイラ／コンデンサにて前記第一窒素留分の一部と熱交換して気化させた後に前記ミキシング塔の下部に上昇ガスとして導入するとともに、前記第二酸素富化液留分を昇圧した後に前記ミキシング塔の上部に還流液として導入し、低純度酸素留分と塔底液留分とに分離する第三蒸留工程と、該第三蒸留工程で分離した低純度酸素留分を製品として回収する製品回収工程とを含むことを特徴としている。
【００１１】
さらに、本発明の低純度酸素の製造方法は、気化されてミキシング塔に導入される前記第一酸素富化液留分を高圧塔の塔底から少なくとも１理論段上から抜き出すこと、ミキシング塔に導入する前記第二酸素富化液留分を低圧塔の塔底から少なくとも１理論段上から抜き出すとともに、低圧塔の塔底部から高純度の酸素ガスを抜き出すことを特徴としている。さらに、前記ミキシング塔の塔底から抜き出した塔底液留分を該塔底液留分の酸素濃度に対応する位置で前記低圧塔に導入すること、前記ミキシング塔の中間部から液を抜き出し、該液の酸素濃度に対応する位置で前記低圧塔に導入することを特徴としている。
【００１２】
また、本発明の低純度酸素の製造装置は、圧縮，精製，冷却されて導入される原料空気を蒸留して塔上部の第一窒素留分と塔下部の第一酸素富化液留分とに分離する高圧塔と、該高圧塔で分離した第一窒素留分と第一酸素富化液留分とを導入して蒸留することにより塔上部の第二窒素留分と塔下部の第二酸素富化液留分とに分離する低圧塔と、前記高圧塔から前記第一酸素富化液留分を抜き出す第一酸素富化液留分抜出経路と、該第一酸素富化液留分抜出経路に抜き出した第一酸素富化液留分を前記第一窒素留分の一部と熱交換して気化させるドライタイプのリボイラ／コンデンサと、前記低圧塔から前記第二酸素富化液留分を抜き出す第二酸素富化液留分抜出経路と、該第二酸素富化液留分抜出経路に抜き出した第二酸素富化液留分を昇圧する液ポンプと、前記リボイラ／コンデンサで気化した第一酸素富化留分及び前記液ポンプで昇圧された第二酸素富化液留分とを導入して蒸留することにより塔上部の低純度酸素留分と塔底部の塔底液留分とに分離するミキシング塔と、該ミキシング塔で分離した前記低純度酸素留分を製品として回収する製品回収経路とを備えたことを特徴としている。
【００１３】
さらに、本発明の低純度酸素の製造装置は、前記第一酸素富化液留分抜出経路が高圧塔の塔底から少なくとも１理論段上に設けられていること、前記第二酸素富化液留分抜出経路が低圧塔の塔底から少なくとも１理論段上に設けられるとともに、最下段精留段の下に低圧塔底部に分離した高純度の酸素ガスを抜き出す高純度酸素抜出経路が設けられていることを特徴としている。
【００１４】
また、前記ミキシング塔の塔底部に分離した塔底液留分を抜き出し、前記低圧塔の中部に還流液として導入する第一酸素還流経路を備えていること、前記ミキシング塔の中段から液を抜き出し、前記低圧塔の中部より下方の位置に還流液として導入する第二酸素還流経路を備えていることを特徴としている。
【００１５】
【発明の実施の形態】
図１は本発明の一形態例を示す系統図である。この系統図に示す装置は、高圧塔１、低圧塔２及びミキシング塔３を有するとともに、空気を低温蒸留するための付帯設備である原料空気圧縮機４、前処理設備５、主熱交換器６、主凝縮器７、過冷器８、リボイラ／コンデンサ９等の各種機器、各種弁及び配管を備えた三塔式蒸留設備である。
【００１６】
以下、低純度酸素を製造する手順に基づいて本形態例を説明する。まず、経路１０から吸入された１０２０００Ｎｍ３／ｈの原料空気は、原料空気圧縮４で６．０ｋｇ／ｃｍ２ abs．に圧縮され、アフタークーラー１１で４０℃に冷却された後、前処理設備５で二酸化炭素や水分等の不純物を除去されて精製される。この原料空気は、経路１２から経路１３と経路１４とに分岐し、一方の経路１３に分岐した原料空気は、空気予冷器１５を通ってからブロワー１６で更に圧縮され、アフタークーラー１７及び空気予冷器１５で冷却される。さらに、この原料空気は、経路１８から主熱交換器６を通って中間温度に冷却された後、経路１９を通って前記ブロワー１６に直結した膨張タービン２０に導入され、膨張してプラントに必要な寒冷を発生する。膨張して低圧状態となったこの原料空気は、経路２１を通って低圧塔２の所定の位置に導入される。他方の経路１４に分岐した原料空気は、主熱交換器６で露点温度付近まで冷却された後、経路２２を通って高圧塔１の下部に導入される。
【００１７】
高圧塔１では、塔内を上昇するガスと、塔頂部の主凝縮器７で凝縮して塔内を下降する液との気液接触によって第一蒸留工程が行われ、塔頂部の第一窒素留分と、塔底部の第一酸素富化液留分とに分離する。高圧塔１の頂部から経路２３に抜き出された第一窒素留分、即ち窒素ガスは、その一部が経路２４を通って主凝縮器７に導入され、後述する低圧塔底部の第二酸素富化液留分と熱交換することにより凝縮して液化窒素となり、経路２５に導出し、その一部が経路２６に分岐して高圧塔１の頂部に還流液として戻される。また、経路２３から経路２７に進んだ窒素ガスは、前記リボイラ／コンデンサ９で高圧塔底部からの第一酸素富化液留分と熱交換することにより凝縮して液化窒素となり、経路２８に導出し、その一部が前記経路２６から高圧塔１の還流液として戻される。
【００１８】
還流液となる以外の液化窒素４７０００Ｎｍ３／hは、前記経路２５，２８から経路２９に合流し、前記過冷器８で冷却された後、経路３０を通り、膨張弁３１で低圧塔２の圧力１．３ｋｇ／ｃｍ２ abs．に減圧された後、経路３２を通って低圧塔２の頂部に還流液として導入される。
【００１９】
一方、前記高圧塔１の底部に分離した酸素分約４０％の第一酸素富化液留分は、経路３３に抜き出されて経路３４と経路３５とに分岐する。経路３４に分岐した２３０００Ｎｍ３／ｈの第一酸素富化液留分は、過冷器８で冷却された後、経路３６を通り、膨張弁３７で低圧塔２の圧力１．３ｋｇ／ｃｍ２ abs．に減圧され、経路３８を通って低圧塔２の中上部に還流液として導入される。また、経路３３から経路３５に続く第一酸素富化液留分抜出経路に分岐した２７４００Ｎｍ３／ｈの第一酸素富化液留分は、膨張弁３９で２．６ｋｇ／ｃｍ２ abs．に減圧された後、経路４０を経て前記リボイラ／コンデンサ９に導入され、高圧塔頂部からの前記窒素ガスと熱交換することによりガス化し、経路４１を通って前記ミキシング塔３の底部に上昇ガスとして導入される。
【００２０】
なお、本形態例では、リボイラ／コンデンサ９として、液浸漬型ではなく、ドライ型のリボイラ／コンデンサを使用している。すなわち、液浸漬型の場合は、気化側の液体が液ヘッドによって過冷却状態となるため、この分、気化圧力を低くしなければならないが、ドライタイプの場合には、このようなことがないので、気化圧力を高めることができる。したがって、ミキシング塔３に導入する第一酸素富化液留分の気化圧力を高くすることができるので、ミキシング塔３の運転圧力を高めることができ、最終的にミキシング塔３から回収する製品低純度酸素ガスの圧力を高くすることができる。しかも、ドライタイプは、液浸漬型に比べて保有液量が少ないので、装置の起動時間を短縮できる効果もある。
【００２１】
前記低圧塔２では、前記経路３２，３８からそれぞれ導入される還流液と、塔底部の主凝縮器７で気化した上昇ガスとの気液接触によって第二蒸留工程が行われ、塔頂部の第二窒素留分と、塔底部の第二酸素富化液留分とに分離する。
【００２２】
塔頂部からは、第二窒素留分である窒素ガス７９６５０Ｎｍ３／ｈが経路４２に抜き出され、過冷器８での熱交換により昇温した後、経路４３を通って主熱交換器６で原料空気と熱交換することにより常温まで昇温し、経路４４から製品窒素として抜き出される。本形態例のプロセスでは、原料空気の全量を高圧塔１に導入していることから、低圧塔２の頂部還流液化窒素量を多くすることができるため、低圧塔頂部の窒素濃度は９９．３％であり、製品窒素ガスとして十分に使用可能である。
【００２３】
低圧塔２の底部の第二酸素富化液留分は、酸素濃度９８％の液化酸素であり、６６０００Ｎｍ３／ｈが第二酸素富化液留分抜出経路である経路４５に抜き出され、液ポンプ４６で２．６ｋｇ／ｃｍ２ abs．に圧縮された後、経路４７を通ってミキシング塔３の頂部に還流液として供給される。
【００２４】
ミキシング塔３では、前記経路４１から導入された上昇ガスと、上記経路４７から導入された還流液とが気液接触することにより第三蒸留工程が行われ、塔頂部の低純度酸素留分と、塔底部の塔底液留分とに分離する。塔頂部の低純度酸素留分は、酸素濃度９５％の低純度酸素であり、製品回収経路となる頂部の経路４８から２２３５０Ｎｍ３／ｈが抜き出され、主熱交換器６で常温まで昇温した後、経路４９を通ってブロワー５０で所定圧力に圧縮されて経路５１から取り出される。
【００２５】
ミキシング塔３の底部から第一酸素還流経路である経路５２に抜き出された塔底液留分は、膨張弁５３で低圧塔２の圧力に減圧された後、経路５４を通り、塔底液留分の酸素濃度に対応した位置の低圧塔中部に導入される。また、ミキシング塔３の中間部からは、塔内を下降する液の一部が第二酸素還流経路である経路５５に抜き出され、膨張弁５６で低圧塔２の圧力に減圧された後、経路５７を通り、該液の酸素濃度に対応した位置の低圧塔中部より下方に導入される。
【００２６】
上述のように、高圧塔１から抜き出した第一酸素富化液留分を気化してミキシング塔３の上昇ガスとして用いることにより、原料空気のほとんどを高圧塔１に供給することができるので、低圧塔２の頂部還流液化窒素量を多くすることができる。これにより、低圧塔２のＬ／Ｖが改善されて精留効率が向上し、製品低純度酸素の回収率が増加するとともに、低圧塔２から抜き出す窒素の純度も向上させることができる。したがって、本形態例プロセスは、大量の低純度酸素と共に、一定純度以上の窒素ガスを大量に必要とするガス化複合発電にも好適に用いることができる。
【００２７】
また、高圧塔１からミキシング塔３に供給する第一酸素富化液留分の気化を、高圧塔１から抜き出した第一窒素留分との熱交換で行うことにより、第一酸素富化液留分の気化を、他の加熱源を用意することなく効率よく行えるとともに、第一窒素留分を液化させて高圧塔１や低圧塔２の還流液として使用することができる。さらに、ミキシング塔３から抜き出した液を、低圧塔２の酸素濃度に対応した位置に供給することにより、低圧塔２の運転を乱すことなく安定した効率のよい蒸留操作を行うことができる。
【００２８】
ここで、本形態例に示すプロセスと、従来例として前記米国特許第５２９１７３７号明細書記載のプロセスとにおいて、同条件の低純度酸素を製造する場合のシミュレーションを行った結果を表１に示す。なお、酸素製造原単位には、従来例と条件を合わせるため、酸素を６８ｋｇ／ｃｍ２ abs．まで昇圧するためのブロワー５０の動力も含めている。
【００２９】
【表１】

Figure 0004177507
【００３０】
上記シミュレーションでは、全ての蒸留塔に棚段を使用した場合で計算を行ったが、高圧塔１，低圧塔２，ミキシング塔３の少なくとも１つに充填物を使用することにより、蒸留塔の圧力損失を少なくすることができるので、さらに酸素製造原単位を低減させることができる。
【００３１】
また、本形態例では、高圧塔１の第一酸素富化液留分の一部をミキシング塔３に供給するようにしているが、リボイラ／コンデンサ９における炭化水素の濃縮を防止するため、図１に破線で示すように、高圧塔１の塔底から少なくとも１理論段上の精留段１ａから経路３５ａを通して液を抜き出すようにしてもよい。
【００３２】
また、図２に示すように、ミキシング塔３に還流液として導入する液も、低圧塔２の塔底から数段上の精留段２ａに設けた経路４５ａで抜き出すとともに、最下段の精留段２ｂより下に設けた経路（高純度酸素抜出経路）５８から主熱交換器６，経路５９を通して、純度の高い酸素ガスを抜き出すこともできる。
【００３３】
これにより、ミキシング塔３から抜き出す低純度の酸素と、低圧塔２から抜き出す高純度の酸素との純度の異なる２種類の製品酸素を得ることができるので、大量の低純度酸素と少量の高純度酸素とを必要とする設備、例えば、コレックス（ＣＯＲＥＸ）製鋼法を基にした新しいグラスルーツ製鋼所等の用途に好適である。
【００３４】
【発明の効果】
以上説明したように、本発明によれば、比較的圧力が高い低純度酸素を効率よく製造でき、回収率の向上や圧縮機に要する動力費の削減により原単位の低減が図れる。さらに、比較的高純度の窒素も同時に製造することが可能であり、低純度の酸素と高純度の酸素とを同時に製造することも可能である。
【図面の簡単な説明】
【図１】 本発明の一形態例を示す系統図である。
【図２】 変形例を示す要部の系統図である。
【符号の説明】
１…高圧塔、２…低圧塔、３…ミキシング塔、４…原料空気圧縮機、５…前処理設備、６…主熱交換器、７…主凝縮器、８…過冷器、９…リボイラ／コンデンサ、１５…空気予冷器、１６…ブロワー、２０…膨張タービン、３１，３７，３９…膨張弁、５０…ブロワー、５３，５６…膨張弁[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for producing low-purity oxygen, and more particularly, a process for recovering low-purity oxygen as a product by distilling and separating air at a low temperature, and using a relatively high pressure without using a compressor. The invention relates to a method and apparatus for producing low purity oxygen.
[0002]
[Prior art and problems to be solved by the invention]
Low-purity oxygen is used in gasification combined power generation (IGCC), direct / melt reduction steelmaking, glass melting, and the like. In these applications, a large amount of oxygen is consumed, so that the power unit is particularly low.
[0003]
U.S. Pat. No. 5,291,737 by Camberlein et al. And U.S. Pat. No. 5,454,227 by Straub et al. Describe low purity oxygen production processes aimed at reducing power consumption.
[0004]
In the process described in US Pat. No. 5,291,737, liquefied oxygen having an oxygen purity higher than that of product oxygen is extracted from a low-pressure distillation column, compressed by a pump, and then mixed with a part of the raw material air in a gas-liquid contact with a mixing column. By doing so, low-purity oxygen having the same pressure as that of the raw air is produced.
[0005]
However, in this process, since about 30% of the total air amount is introduced into the mixing column and brought into gas-liquid contact with liquefied oxygen to be liquefied, the amount of raw material air supplied to the high-pressure distillation column is reduced. As a result, the rising gas in the high-pressure column is reduced, and the amount of liquefaction in the main condenser is reduced, so the amount of reflux nitrogen in the low-pressure distillation column is reduced, L / V is lowered, and the rectification efficiency is deteriorated. As the oxygen recovery rate decreases, the purity of the resulting nitrogen also decreases.
[0006]
That is, in this process, the compression power of product oxygen can be reduced, but the power of the raw air compressor is increased. Furthermore, since the purity of the obtained nitrogen is low in this process, it is not suitable for facilities that require nitrogen of a certain purity or higher as a product, such as gasification combined power generation (IGCC).
[0007]
Further, in the process described in US Pat. No. 5,454,227, liquefied oxygen extracted from the bottom of the low-pressure distillation column is compressed by a pump and supplied to the mixing column so as to be in gas-liquid contact with part of the raw air. As the air, air expanded by an expansion turbine and air decompressed by an expansion valve are used.
[0008]
Therefore, also in this process, since the raw material air supplied to the high-pressure distillation column is reduced as described above, the reflux nitrogen supplied to the low-pressure distillation column is reduced and the product recovery rate is lowered. Further, in this process, a part of the raw material air compressed to a high pressure is decompressed by an expansion valve and then supplied to the mixing tower. Therefore, power loss due to the decompression occurs.
[0009]
Accordingly, the present invention can reduce the basic unit in the process of producing low-purity oxygen at a relatively high pressure by improving the oxygen recovery rate and reducing the power cost required for the compressor, and further reducing the purity of the nitrogen obtained at the same time. It is an object of the present invention to provide a method and an apparatus for producing low-purity oxygen that can be prevented.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the method for producing low-purity oxygen according to the present invention includes at least low-purity oxygen by introducing raw air into a three-column distillation facility having a high-pressure column, a low-pressure column, and a mixing column and performing low-temperature distillation. In the method for producing low-purity oxygen in which the product is separated and recovered as a product, the compressed, purified, and cooled raw material air is introduced into the high-pressure column to separate the first nitrogen fraction and the first oxygen-enriched liquid fraction. A first nitrogen fraction and a first oxygen-enriched liquid fraction separated in the distillation step, the first nitrogen-enriched liquid fraction, and the second nitrogen fraction and the second oxygen-enriched liquid fraction, A second distillation step that separates the first oxygen-enriched liquid fraction into a lower part of the mixing tower after the first oxygen-enriched liquid fraction is vaporized by heat exchange with a part of the first nitrogen fraction in a dry-type reboiler / condenser As a rising gas and the second oxygen-enriched liquid fraction And the third distillation step for separating into a low-purity oxygen fraction and a bottom-bottom liquid fraction and the low-purity oxygen fraction separated in the third distillation step. And a product recovery process for recovering the product as a product.
[0011]
Furthermore, the manufacturing method of the low-purity oxygen of the present invention, by extracting the first oxygen-enriched liquid fraction is vaporization is introduced into the mixing column at least 1 theoretical stage above the bottom of the high pressure column, a mixing column The second oxygen-enriched liquid fraction introduced into is extracted from the bottom of the low-pressure column from at least one theoretical plate, and high-purity oxygen gas is extracted from the bottom of the low-pressure column. Furthermore, introducing the bottom liquid fraction extracted from the bottom of the mixing tower into the low pressure column at a position corresponding to the oxygen concentration of the bottom liquid fraction, extracting the liquid from the middle part of the mixing tower, The liquid is introduced into the low-pressure column at a position corresponding to the oxygen concentration of the liquid.
[0012]
Further, the low purity oxygen production apparatus of the present invention comprises a first nitrogen fraction at the top of the tower and a first oxygen-enriched liquid fraction at the bottom of the tower by distilling the raw air introduced after being compressed, purified and cooled. A high-pressure column separated into a high-pressure column, a first nitrogen fraction and a first oxygen-enriched liquid fraction separated in the high-pressure column, and distillation to obtain a second nitrogen fraction at the top of the tower and a second nitrogen fraction at the bottom of the tower. A low-pressure column that separates into an oxygen-enriched liquid fraction, a first oxygen-enriched liquid fraction extraction path for extracting the first oxygen-enriched liquid fraction from the high-pressure column, and the first oxygen-enriched liquid fraction A dry-type reboiler / condenser that heats and vaporizes the first oxygen-enriched liquid fraction extracted into the fraction extraction path with a part of the first nitrogen fraction, and the second oxygen-enriched from the low-pressure column. The second oxygen-enriched liquid fraction extraction path for extracting the liquid fraction, and the pressure of the second oxygen-enriched liquid fraction extracted to the second oxygen-enriched liquid fraction extraction path Low purity oxygen at the top of the column by introducing and distilling a liquid pump, a first oxygen-enriched fraction vaporized by the reboiler / condenser and a second oxygen-enriched liquid fraction pressurized by the liquid pump. A mixing tower that separates into a fraction and a bottom liquid fraction at the bottom of the tower and a product recovery path that recovers the low-purity oxygen fraction separated in the mixing tower as a product are provided.
[0013]
Furthermore, the low-purity oxygen production apparatus of the present invention is characterized in that the first oxygen-enriched liquid fraction extraction path is provided at least one theoretical plate above the bottom of the high-pressure column, A liquid fraction extraction path is provided at least one theoretical stage above the bottom of the low-pressure column, and a high-purity oxygen extraction path for extracting high-purity oxygen gas separated at the bottom of the low-pressure column below the bottom rectification stage It is characterized by being provided.
[0014]
Also, a first oxygen reflux path is provided for extracting the bottom liquid fraction separated at the bottom of the mixing tower and introducing it into the middle of the low-pressure tower as a reflux liquid, and extracting the liquid from the middle stage of the mixing tower. It is characterized in that it comprises a second oxygen reflux path for introducing a reflux liquid to a position below the middle of the lower pressure column.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a system diagram showing an embodiment of the present invention. The apparatus shown in this system diagram includes a high-pressure column 1, a low-pressure column 2, and a mixing column 3, and a raw material air compressor 4, a pretreatment facility 5, and a main heat exchanger 6 which are incidental facilities for low-temperature distillation of air. , A three-column distillation facility equipped with various devices such as a main condenser 7, a supercooler 8, a reboiler / condenser 9, and various valves and piping.
[0016]
Hereinafter, this embodiment will be described based on a procedure for producing low-purity oxygen. First, 102000 Nm 3 / h of raw material air sucked from the passage 10 is 6.0 kg / cm 2 abs. After being cooled to 40 ° C. by the aftercooler 11, impurities such as carbon dioxide and moisture are removed and purified by the pretreatment facility 5. This raw material air branches from the path 12 into a path 13 and a path 14, and the raw material air branched into the one path 13 is further compressed by the blower 16 after passing through the air precooler 15, and the aftercooler 17 and the air precooling. Cooled by the vessel 15. Further, the raw material air is cooled to an intermediate temperature from the path 18 through the main heat exchanger 6, and then introduced into the expansion turbine 20 directly connected to the blower 16 through the path 19, and is expanded and necessary for the plant. Generates cold. The raw material air that has expanded to a low pressure state is introduced into a predetermined position of the low pressure column 2 through the path 21. The raw material air branched into the other path 14 is cooled to near the dew point temperature by the main heat exchanger 6 and then introduced into the lower part of the high-pressure tower 1 through the path 22.
[0017]
In the high-pressure tower 1, the first distillation step is performed by gas-liquid contact between the gas rising in the tower and the liquid condensed in the main condenser 7 at the top of the tower and descending in the tower, and the first nitrogen at the top of the tower. Separated into a fraction and a first oxygen-enriched liquid fraction at the bottom of the column. A part of the first nitrogen fraction extracted from the top of the high-pressure column 1 into the path 23, that is, nitrogen gas, is introduced into the main condenser 7 through the path 24, and the second oxygen at the bottom of the low-pressure column described later. Heat exchange with the enriched liquid fraction condenses into liquefied nitrogen, which is led out to the path 25, a part of which branches into the path 26 and is returned to the top of the high-pressure column 1 as a reflux liquid. In addition, the nitrogen gas that has advanced from the path 23 to the path 27 is condensed and converted into liquefied nitrogen by exchanging heat with the first oxygen-enriched liquid fraction from the bottom of the high-pressure tower in the reboiler / condenser 9 and is led to the path 28. Then, a part thereof is returned from the path 26 as the reflux liquid of the high-pressure column 1.
[0018]
The liquefied nitrogen 47000 Nm 3 / h other than the reflux liquid merges from the paths 25 and 28 to the path 29, is cooled by the supercooler 8, passes through the path 30, and is expanded by the expansion valve 31. Pressure 1.3 kg / cm 2 abs. After being reduced in pressure, it is introduced as a reflux liquid through the path 32 to the top of the low pressure column 2.
[0019]
On the other hand, the first oxygen-enriched liquid fraction having an oxygen content of about 40% separated at the bottom of the high-pressure column 1 is extracted into the path 33 and branched into the path 34 and the path 35. The first oxygen-enriched liquid fraction of 23000 Nm 3 / h branched into the path 34 is cooled by the supercooler 8, then passes through the path 36, and the pressure of the low pressure column 2 is 1.3 kg / cm 2 through the expansion valve 37. abs. And is introduced into the upper part of the low-pressure column 2 through the path 38 as a reflux liquid. In addition, the 27400 Nm 3 / h first oxygen-enriched liquid fraction branched from the path 33 to the first oxygen-enriched liquid fraction extraction path following the path 35 is 2.6 kg / cm 2 abs. After being reduced in pressure, it is introduced into the reboiler / condenser 9 via a path 40, gasified by heat exchange with the nitrogen gas from the top of the high-pressure tower, and the gas rising to the bottom of the mixing tower 3 via the path 41 As introduced.
[0020]
In this embodiment, the reboiler / condenser 9 is not a liquid immersion type but a dry type reboiler / condenser. That is, in the case of the liquid immersion type, since the liquid on the vaporization side is supercooled by the liquid head, the vaporization pressure must be lowered by this amount, but this is not the case in the case of the dry type. So the vaporization pressure can be increased. Therefore, since the vaporization pressure of the first oxygen-enriched liquid fraction introduced into the mixing tower 3 can be increased, the operating pressure of the mixing tower 3 can be increased, and the product recovered finally from the mixing tower 3 can be reduced. The pressure of pure oxygen gas can be increased. In addition, the dry type has an effect that the start-up time of the apparatus can be shortened because the amount of liquid retained is smaller than that of the liquid immersion type.
[0021]
In the low-pressure column 2, a second distillation step is performed by gas-liquid contact between the reflux liquid introduced from the paths 32 and 38 and the rising gas vaporized in the main condenser 7 at the bottom of the column, and A dinitrogen fraction and a second oxygen-enriched liquid fraction at the bottom of the column are separated.
[0022]
From the top of the column, nitrogen gas 79650 Nm 3 / h, which is the second nitrogen fraction, is extracted into the path 42, heated by heat exchange in the subcooler 8, and then passed through the path 43 to the main heat exchanger 6. Then, the temperature is raised to room temperature by exchanging heat with the raw material air, and is extracted as product nitrogen from the path 44. In the process of this embodiment, since the entire amount of raw material air is introduced into the high pressure column 1, the amount of nitrogen at the top reflux of the low pressure column 2 can be increased, so the nitrogen concentration at the top of the low pressure column is 99.3. % And can be used sufficiently as product nitrogen gas.
[0023]
The second oxygen-enriched liquid fraction at the bottom of the low-pressure column 2 is liquefied oxygen having an oxygen concentration of 98%, and 66000 Nm 3 / h is extracted into the path 45 which is the second oxygen-enriched liquid fraction extracting path. , 2.6 kg / cm 2 abs. , And then supplied through the passage 47 to the top of the mixing tower 3 as a reflux liquid.
[0024]
In the mixing tower 3, the third distillation step is performed by the gas-liquid contact between the rising gas introduced from the path 41 and the reflux liquid introduced from the path 47, and the low-purity oxygen fraction at the top of the tower And the bottom liquid fraction at the bottom of the column. The low-purity oxygen fraction at the top of the column is low-purity oxygen having an oxygen concentration of 95%, and 22350 Nm 3 / h is extracted from the top path 48 serving as a product recovery path, and the temperature is raised to room temperature by the main heat exchanger 6. After that, it is compressed to a predetermined pressure by the blower 50 through the path 49 and taken out from the path 51.
[0025]
The bottom liquid fraction withdrawn from the bottom of the mixing tower 3 to the path 52, which is the first oxygen reflux path, is decompressed to the pressure of the low pressure tower 2 by the expansion valve 53, and then passes through the path 54 to pass through the bottom liquid. It is introduced into the middle of the low pressure column at a position corresponding to the oxygen concentration of the fraction. Further, from the middle part of the mixing tower 3, a part of the liquid descending the inside of the tower is withdrawn to the path 55 which is the second oxygen reflux path, and after being reduced to the pressure of the low pressure tower 2 by the expansion valve 56, It passes through path 57 and is introduced below from the middle of the low-pressure column at a position corresponding to the oxygen concentration of the liquid.
[0026]
As described above, most of the raw air can be supplied to the high pressure column 1 by vaporizing the first oxygen-enriched liquid fraction extracted from the high pressure column 1 and using it as the rising gas of the mixing column 3. The amount of nitrogen at the top reflux of the low pressure column 2 can be increased. Thereby, L / V of the low pressure column 2 is improved, the rectification efficiency is improved, the recovery rate of the product low purity oxygen is increased, and the purity of nitrogen extracted from the low pressure column 2 can be improved. Therefore, this embodiment process can be suitably used for gasification combined power generation that requires a large amount of nitrogen gas having a certain purity or higher together with a large amount of low-purity oxygen.
[0027]
Further, the first oxygen-enriched liquid fraction supplied from the high-pressure tower 1 to the mixing tower 3 is vaporized by heat exchange with the first nitrogen fraction extracted from the high-pressure tower 1, whereby the first oxygen-enriched liquid is obtained. The vaporization of the fraction can be efficiently performed without preparing another heating source, and the first nitrogen fraction can be liquefied and used as the reflux liquid of the high pressure column 1 and the low pressure column 2. Furthermore, by supplying the liquid extracted from the mixing column 3 to a position corresponding to the oxygen concentration of the low pressure column 2, a stable and efficient distillation operation can be performed without disturbing the operation of the low pressure column 2.
[0028]
Here, Table 1 shows the results of simulations for producing low-purity oxygen under the same conditions in the process shown in this embodiment and the process described in US Pat. No. 5,291,737 as the conventional example. In addition, in order to match the oxygen production basic unit with the conventional example, oxygen was supplied at 68 kg / cm 2 abs. The power of the blower 50 for boosting the pressure is also included.
[0029]
[Table 1]
Figure 0004177507
[0030]
In the above simulation, calculation was performed when plates were used for all distillation columns. However, by using a packing material for at least one of the high pressure column 1, the low pressure column 2, and the mixing column 3, the pressure of the distillation column was calculated. Since the loss can be reduced, the oxygen production unit can be further reduced.
[0031]
In the present embodiment, a part of the first oxygen-enriched liquid fraction of the high-pressure column 1 is supplied to the mixing column 3, but in order to prevent hydrocarbon concentration in the reboiler / condenser 9, As indicated by a broken line in FIG. 1, the liquid may be extracted from the bottom of the high-pressure column 1 from the rectification stage 1a at least one theoretical stage through the path 35a.
[0032]
Further, as shown in FIG. 2, the liquid to be introduced into the mixing tower 3 as a reflux liquid is also extracted from the bottom of the low-pressure tower 2 through a path 45a provided in several stages of rectification stages 2a, and the bottom rectification stage. High purity oxygen gas can be extracted from the path (high purity oxygen extraction path) 58 provided below the stage 2b through the main heat exchanger 6 and the path 59.
[0033]
This makes it possible to obtain two types of product oxygen having different purity, that is, low-purity oxygen extracted from the mixing column 3 and high-purity oxygen extracted from the low-pressure column 2, so that a large amount of low-purity oxygen and a small amount of high-purity oxygen are obtained. It is suitable for use in facilities that require oxygen, for example, a new Grassroots steel mill based on the COREX steelmaking process.
[0034]
【The invention's effect】
As described above, according to the present invention, low-purity oxygen having a relatively high pressure can be efficiently produced, and the basic unit can be reduced by improving the recovery rate and reducing the power cost required for the compressor. Furthermore, relatively high-purity nitrogen can be produced at the same time, and low-purity oxygen and high-purity oxygen can be produced simultaneously.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an example of an embodiment of the present invention.
FIG. 2 is a system diagram of a main part showing a modification.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... High pressure column, 2 ... Low pressure column, 3 ... Mixing column, 4 ... Raw material air compressor, 5 ... Pretreatment equipment, 6 ... Main heat exchanger, 7 ... Main condenser, 8 ... Subcooler, 9 ... Reboiler / Condenser, 15 ... air precooler, 16 ... blower, 20 ... expansion turbine, 31, 37, 39 ... expansion valve, 50 ... blower, 53, 56 ... expansion valve

Claims (10)

高圧塔、低圧塔及びミキシング塔を有する三塔式蒸留設備に原料空気を導入して低温蒸留することにより、少なくとも低純度酸素を製品として分離回収する低純度酸素の製造方法において、圧縮，精製，冷却した原料空気を前記高圧塔に導入して第一窒素留分と第一酸素富化液留分とに分離する第一蒸留工程と、該第一蒸留工程で分離した第一窒素留分と第一酸素富化液留分とを前記低圧塔に導入して第二窒素留分と第二酸素富化液留分とに分離する第二蒸留工程と、前記第一酸素富化液留分をドライタイプのリボイラ／コンデンサにて前記第一窒素留分の一部と熱交換して気化させた後に前記ミキシング塔の下部に上昇ガスとして導入するとともに、前記第二酸素富化液留分を昇圧した後に前記ミキシング塔の上部に還流液として導入し、低純度酸素留分と塔底液留分とに分離する第三蒸留工程と、該第三蒸留工程で分離した低純度酸素留分を製品として回収する製品回収工程とを含むことを特徴とする低純度酸素の製造方法。In a low-purity oxygen production method in which at least low-purity oxygen is separated and recovered as a product by introducing raw air into a three-column distillation facility having a high-pressure tower, a low-pressure tower, and a mixing tower, A first distillation step in which cooled raw air is introduced into the high-pressure column and separated into a first nitrogen fraction and a first oxygen-enriched liquid fraction; and a first nitrogen fraction separated in the first distillation step; A second distillation step in which a first oxygen-enriched liquid fraction is introduced into the low-pressure column and separated into a second nitrogen fraction and a second oxygen-enriched liquid fraction; and the first oxygen-enriched liquid fraction Is exchanged with a part of the first nitrogen fraction by a dry type reboiler / condenser and vaporized, and then introduced into the lower part of the mixing tower as a rising gas, and the second oxygen-enriched liquid fraction is After increasing the pressure, introduced as a reflux liquid at the top of the mixing tower, A third distillation step that separates into a pure oxygen fraction and a bottom liquid fraction, and a product recovery step that collects the low-purity oxygen fraction separated in the third distillation step as a product. A method for producing pure oxygen. 前記気化されてミキシング塔に導入される第一酸素富化液留分が、前記高圧塔の塔底から少なくとも１理論段上から抜き出されることを特徴とする請求項１記載の低純度酸素の製造方法。  2. The low-purity oxygen gas according to claim 1, wherein the first oxygen-enriched liquid fraction that is vaporized and introduced into the mixing column is withdrawn from at least one theoretical plate from the bottom of the high-pressure column. Production method. 前記ミキシング塔に導入する第二酸素富化液留分を、前記低圧塔の塔底から少なくとも１理論段上から抜き出すとともに、前記低圧塔の塔底部から高純度の酸素ガスを抜き出すことを特徴とする請求項１記載の低純度酸素の製造方法。  The second oxygen-enriched liquid fraction to be introduced into the mixing column is extracted from at least one theoretical plate from the bottom of the low-pressure column, and high-purity oxygen gas is extracted from the bottom of the low-pressure column. The method for producing low-purity oxygen according to claim 1. 前記ミキシング塔の塔底から抜き出した塔底液留分を、該塔底液留分の酸素濃度に対応する位置で前記低圧塔に導入することを特徴とする請求項１記載の低純度酸素の製造方法。  2. The low-purity oxygen gas according to claim 1, wherein the bottom liquid fraction extracted from the bottom of the mixing tower is introduced into the low-pressure tower at a position corresponding to the oxygen concentration of the bottom liquid fraction. Production method. 前記ミキシング塔の中間部から液を抜き出し、該液の酸素濃度に対応する位置で前記低圧塔に導入することを特徴とする請求項１記載の低純度酸素の製造方法。  The method for producing low-purity oxygen according to claim 1, wherein a liquid is extracted from an intermediate portion of the mixing tower and introduced into the low-pressure tower at a position corresponding to the oxygen concentration of the liquid. 圧縮，精製，冷却されて導入される原料空気を蒸留して塔上部の第一窒素留分と塔下部の第一酸素富化液留分とに分離する高圧塔と、該高圧塔で分離した第一窒素留分と第一酸素富化液留分とを導入して蒸留することにより塔上部の第二窒素留分と塔下部の第二酸素富化液留分とに分離する低圧塔と、前記高圧塔から前記第一酸素富化液留分を抜き出す第一酸素富化液留分抜出経路と、該第一酸素富化液留分抜出経路に抜き出した第一酸素富化液留分を前記第一窒素留分の一部と熱交換して気化させるドライタイプのリボイラ／コンデンサと、前記低圧塔から前記第二酸素富化液留分を抜き出す第二酸素富化液留分抜出経路と、該第二酸素富化液留分抜出経路に抜き出した第二酸素富化液留分を昇圧する液ポンプと、前記リボイラ／コンデンサで気化した第一酸素富化留分及び前記液ポンプで昇圧された第二酸素富化液留分とを導入して蒸留することにより塔上部の低純度酸素留分と塔底部の塔底液留分とに分離するミキシング塔と、該ミキシング塔で分離した前記低純度酸素留分を製品として回収する製品回収経路とを備えたことを特徴とする低純度酸素の製造装置。A high-pressure column that separates the raw air introduced after being compressed, refined, and cooled into a first nitrogen fraction at the top of the column and a first oxygen-enriched liquid fraction at the bottom of the column, and the high-pressure column A low-pressure column that separates a first nitrogen fraction and a first oxygen-enriched liquid fraction into a second nitrogen fraction at the top of the tower and a second oxygen-enriched liquid fraction at the bottom of the tower by distillation. , A first oxygen-enriched liquid fraction extraction path for extracting the first oxygen-enriched liquid fraction from the high-pressure column, and a first oxygen-enriched liquid extracted into the first oxygen-enriched liquid fraction extraction path A dry-type reboiler / condenser that heats and distills a fraction with a part of the first nitrogen fraction, and a second oxygen-enriched liquid fraction that extracts the second oxygen-enriched liquid fraction from the low-pressure column. An extraction path, a liquid pump for boosting the second oxygen-enriched liquid fraction extracted to the second oxygen-enriched liquid fraction extraction path, and the reboiler / condenser The low-purity oxygen fraction at the top of the tower and the bottom liquid at the bottom of the tower are distilled by introducing and distilling the first oxygen-enriched fraction vaporized in step 2 and the second oxygen-enriched liquid fraction pressurized by the liquid pump. An apparatus for producing low-purity oxygen, comprising: a mixing tower that separates into fractions; and a product recovery path that recovers the low-purity oxygen fraction separated by the mixing tower as a product. 前記第一酸素富化液留分抜出経路が、前記高圧塔の塔底から少なくとも１理論段上に設けられていることを特徴とする請求項６記載の低純度酸素の製造装置。  The apparatus for producing low-purity oxygen according to claim 6, wherein the first oxygen-enriched liquid fraction extraction path is provided at least one theoretical stage from the bottom of the high-pressure column. 前記第二酸素富化液留分抜出経路が、前記低圧塔の塔底から少なくとも１理論段上に設けられているとともに、最下段精留段の下に低圧塔底部に分離した高純度の酸素ガスを抜き出す高純度酸素抜出経路が設けられていることを特徴とする請求項６記載の低純度酸素の製造装置。  The second oxygen-enriched liquid fraction extraction path is provided at least one theoretical stage above the bottom of the low-pressure column, and has a high purity separated to the bottom of the low-pressure tower below the bottom rectification stage. The apparatus for producing low-purity oxygen according to claim 6, wherein a high-purity oxygen extraction path for extracting oxygen gas is provided. 前記ミキシング塔の塔底部に分離した塔底液留分を抜き出し、前記低圧塔の中部に還流液として導入する第一酸素還流経路を備えたことを特徴とする請求項６記載の低純度酸素の製造装置。  7. The low-purity oxygen gas according to claim 6, further comprising a first oxygen reflux path for extracting a bottom liquid fraction separated at the bottom of the mixing tower and introducing it into the middle of the low-pressure tower as a reflux liquid. Manufacturing equipment. 前記ミキシング塔の中段から液を抜き出し、前記低圧塔の中部より下方の位置に還流液として導入する第二酸素還流経路を備えたことを特徴とする請求項６記載の低純度酸素の製造装置。  The apparatus for producing low-purity oxygen according to claim 6, further comprising a second oxygen reflux path for extracting a liquid from a middle stage of the mixing tower and introducing it as a reflux liquid at a position below the middle of the low-pressure tower.
JP06157499A 1999-03-09 1999-03-09 Method and apparatus for producing low purity oxygen Expired - Lifetime JP4177507B2 (en)

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