JP4169924B2 - Method and apparatus for concentrating dilute hydrochloric acid aqueous solution - Google Patents

Method and apparatus for concentrating dilute hydrochloric acid aqueous solution Download PDF

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JP4169924B2
JP4169924B2 JP2000317174A JP2000317174A JP4169924B2 JP 4169924 B2 JP4169924 B2 JP 4169924B2 JP 2000317174 A JP2000317174 A JP 2000317174A JP 2000317174 A JP2000317174 A JP 2000317174A JP 4169924 B2 JP4169924 B2 JP 4169924B2
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hydrochloric acid
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忠雄 小野田
典貞 清水
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Tsukishima Kankyo Engineering Ltd
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Description

【０００１】
【発明の属する技術分野】
本発明は、高圧塔と低圧塔の２本の蒸留塔を用いて、共沸組成以下の希塩酸を含めた広範囲の濃度の希塩酸水溶液を原料として、高濃度の塩酸に濃縮する方法および装置に関するものである。
【０００２】
【従来の技術】
塩化水素（ＨＣｌ）や塩化水素を水に溶解した塩酸は、各種産業で基本的な薬剤として利用される一方で、いろいろな工程から副生するが、これらは濃度が希薄なためにそのまま利用されることは少なく、実際に使用するに際しては、希薄な塩酸を濃縮することが必要となることが多い。
しかし、濃度の希薄な塩酸を蒸留により濃縮する場合、塩化水素−水系においては大気圧下で塩酸濃度２０．２ｗｔ％に相当する共沸点が存在するために、単純な蒸留により水分を分離して濃度を高めた濃縮塩酸とすることは困難である。このため、圧力によって塩酸の共沸組成が異なることを利用して、減圧塔と高圧塔とを組み合わせた、いわゆる減圧−加圧蒸留法があり、原料としてガス状の塩化水素を用いて塩酸を濃縮する特公昭３４−６４２４号公報や、塩酸水溶液から塩化水素ガスを放散する特公昭５０−２１３１８号公報が知られている。また、特公昭４６−２０１３２号公報等のように硫酸、塩化カルシウム等の抽出剤を用いることによって、塩酸の共沸点が消滅することを利用した抽出蒸留法がある。
【０００３】
【発明が解決しようとする課題】
上述した従来の方法により塩酸の濃縮は可能であるが、減圧−加圧蒸留法および抽出蒸留法共に、加熱に要する蒸気の消費量が多く、経済的に難点がある。すなわち、塩化水素−水系の気液平衡は、最高共沸点を有するため、塩酸と水を分離しようとすると、原料液の塩酸および水をすべて蒸発させて一旦蒸気としなければならない。このために、従来法ではどのような方法をとっても、用役としての蒸気使用量は、原料液以上が必要で、かなりの熱回収を図っても、一般には原料液の１．２から１．５倍程度の蒸気が必要であった。特に原料として用いる塩酸の濃度が低い場合には、水分量が多いためにエネルギー消費が大きすぎて実用的には問題であった。
本発明は、従来の方法の問題点を解決し、原料とする塩酸水溶液の塩酸濃度の広い範囲にわたって適用可能で、エネルギー消費量を大幅に削減することが可能な希塩酸水溶液の濃縮方法および濃縮装置を提案するものである。
【０００４】
【問題を解決するための手段】
本発明は、大気圧未満の圧力で操作される蒸留塔（低圧塔）と、大気圧超の圧力で操作される蒸留塔（高圧塔）を用い、原料の希塩酸水溶液を前述の蒸留塔に供給し、高圧塔の塔頂から原料の塩酸よりも高濃度の塩酸を回収する方法であって、高圧塔の塔頂蒸気を凝縮する際に得られる熱エネルギーを低圧塔の再沸に利用するとともに、低圧塔の塔頂からの蒸気を凝縮させた後に、加圧された水蒸気を駆動源とするエゼクターよりなる圧縮器で圧縮し、低圧塔の再沸器の熱源として利用することを特徴とする希塩酸水溶液の濃縮方法である。
また、本発明は、大気圧未満の圧力で操作される蒸留塔（低圧塔）と大気圧超の圧力で操作される蒸留塔（高圧塔）を備え、原料の希塩酸水溶液を前記の蒸留塔に供給し、高圧塔の塔頂から原料の希塩酸よりも高濃度の塩酸を回収する装置であって、高圧塔の塔頂蒸気を凝縮する際に得られる熱エネルギーを低圧塔の再沸器において利用するとともに、低圧塔の塔頂からの蒸気を凝縮させた後に、加圧された水蒸気を駆動源とするエゼクターよりなる圧縮器で圧縮し、低圧塔の再沸器の熱源として利用することを特徴とする希塩酸水溶液の濃縮装置である。
上記の希塩酸水溶液の濃縮方法における原料の希塩酸水溶液としては、塩酸濃度が２８ｗｔ％以下であることが望ましい。
【０００５】
本発明は、二つの蒸留塔を用いる塩酸の濃縮に際し必要とされる蒸気消費量を低減するために濃縮系内で発生し、これまであまり有効に利用されていない熱エネルギーを利用することを意図したものである。
本発明では、低圧塔および高圧塔の塔頂からの蒸気を有効に活用することで、塩酸の濃縮に要する蒸気量を低減するところに特徴があり、低圧塔の再沸に必要な熱量の全部または一部を、低圧塔および高圧塔の塔頂蒸気の凝縮熱でまかなうことが可能であり、全体として塩酸濃縮の熱源として用いる水蒸気の消費量を大幅に削減できる。
【０００６】
【発明の実施の形態】
本発明では、低圧塔と高圧塔の二つの蒸留塔を組み合わせて、濃度の低い塩酸水溶液の効率的な濃縮を行うものであり、以下に本発明の内容を説明する。
本発明で原料とする希塩酸水溶液としては、合成塩酸であっても、各種産業の製造工程で副生する塩酸や、廃棄物等の焼却によって発生する燃焼ガス中に含まれる塩化水素を、水による吸収処理して得られるもの等であってもよい。また、その塩酸の純度を規定するものではないが、可能な限り不純物の少ないものが好ましい。
原料の希塩酸水溶液の濃度としては、熱エネルギーを有効に利用するために、塩酸濃度２８ｗｔ％以下であることが効果的であり、より好ましくは２３ｗｔ％以下である。しかしながら、原料塩酸の塩酸濃度があまり低くなると、ほとんど水を蒸留する状態になるため、経済的にも意味がなく、塩酸濃度として５ｗｔ％程度が下限である。
【０００７】
塩酸水溶液の蒸留に用いる高圧塔と低圧塔とでは、必要となる熱量は必ずしも同じではない。むしろ、通常は低圧塔に供給される原料の塩酸濃度が低いので、高圧塔で必要とする熱量よりも低圧塔で必要とする熱量の方が多くなることが普通である。
高圧塔と低圧塔を併用する場合には、両方の必要熱量のバランスをとるために、各塔の還流比を調整することにより、操作条件を最適化するように制御することができる。前述の方法によってエネルギー消費量を低減することができるが、本発明により、高圧塔の塔頂蒸気を低圧塔の再沸器の熱源として使用することにより、更に大幅にエネルギー消費量を下げることができる。この方法は、特に原料として用いる塩酸の濃度が低い場合に有効である。
後述する実施例に示すように、製品として濃度を高めた塩酸水溶液を回収する場合は、本発明では従来の方法よりも蒸気消費量、冷却水使用量とも非常に少ないことはもちろんであるが、蒸気の必要量を、原料液の量よりも少なくすることができ、経済的に塩酸を回収することができる。
【０００８】
次に本発明の内容を、図１および図２の図面を用いて詳述する。
図１は、濃縮された高濃度の塩酸を回収するための本発明の基本的な構成を示すフローである。本発明では、圧力によって塩化水素−水系における共沸組成が変わることを利用し、大気圧未満で操作する低圧塔１と、大気圧超で操作する高圧塔２との２本の蒸留塔を使用する。低圧塔１と高圧塔２との圧力の差は、０．１ＭＰａ以上とすることが望ましい。尚、低圧塔１内の圧力は、図示していない減圧装置により制御されている。
原料の希塩酸水溶液（原料塩酸）は、低圧塔１と高圧塔２のいずれかに供給し、高圧塔２の塔頂からは、濃縮された塩化水素の蒸気が発生し、低圧塔１の塔頂からは、若干の塩化水素ガスを含む水蒸気が発生する。原料塩酸をどちらの蒸留塔へ供給するかによって、全体の所要熱量が変わってくる。このため、原料塩酸の濃度が、低圧塔の塔底で得られる塩酸の濃度より低い場合には、低圧塔１に原料塩酸を供給した方が、全体の所要エネルギーを少なくでき、原料塩酸の濃度が、低圧塔の塔底で得られる塩酸の濃度より高い場合には、高圧塔２に原料塩酸を供給した方が、全体の所要エネルギーを少なくできる。
【０００９】
高圧塔２内に導入された塩酸は、高圧塔再沸器３に供給される水蒸気により加熱がなされ塔内で蒸留が行われる。一方の低圧塔１では、導入された塩酸は、高圧塔凝縮器４および低圧塔再沸器５からの熱供給により加熱され蒸留が行われる。
高圧塔２の塔頂蒸気を凝縮させるための高圧塔凝縮器４の冷却に際し、本発明では、低圧塔１の塔底液を使用する。双方の沸点が違うことにより、高圧塔２の塔頂からの蒸気は凝縮して液化され、濃縮された高濃度の塩酸になり、一方の低圧塔１の塔底液は、高圧塔の塔頂蒸気の熱エネルギーを受けて蒸発し蒸気になる。尚、低圧塔１の塔底液は、操作条件によっては必ずしも高圧塔凝縮器４内で蒸発させなくてもよく、ポンプ循環で水溶液のまま低圧塔に戻して、塔底でフラッシュ蒸発させてもよい。
高圧塔２からの塔頂蒸気の凝縮液の一部は還流液として高圧塔２に戻され、残りは濃縮塩酸として回収される。この濃縮塩酸は、原料塩酸と熱交換器６により熱交換し、保有熱を有効に利用された後、一旦濃塩酸槽１１に受け、濃塩酸ポンプ１３により系外へ移送される。
一方、低圧塔１の塔頂蒸気は、低圧塔凝縮器７で凝縮され、低圧塔再沸器５の凝縮液と一緒に希塩酸冷却器８で冷却後、一旦希塩酸槽１２に受けてから希塩酸ポンプ１４により系外へ移送され排水となる。低圧塔凝縮器７を経た蒸気は、加圧された水蒸気を駆動源とするエゼクターよりなる圧縮器９で圧縮されてから、低圧塔再沸器５に送られて低圧塔１への熱供給が行われる。これにより、低圧塔１の塔頂蒸気の保有していた熱エネルギーが、低圧塔１における塩酸の加熱のために有効利用されることになる。
【００１０】
図２は、本発明の別の態様として、高圧塔２の塔頂から高濃度の塩化水素ガスを回収する場合のフローである。低圧塔１および高圧塔２の２本の蒸留塔を使用する本発明の基本的な構成は、図１と同様であり、他の構成要素もほぼ同じなため、共通するものについては同一の符号を付けてある。
高圧塔２からの塔頂蒸気は、高圧塔第一分縮器１５および高圧塔第二分縮器１６で分縮され、高濃度の塩化水素ガスが回収される。また、前述の分縮器での凝縮液は、高圧塔２内に戻される。
【００１１】
【実施例】
次に、実施例として．蒸留法により塩酸の濃縮を行う場合の蒸気使用量および冷却水使用量について、本発明の方法と他の方法とを比較して示す。
【００１２】
実施例１
原料の塩酸濃度１４ｗｔ％の希塩酸水溶液４，２００ｋｇ／ｈを低圧塔１へ供給し、低圧塔の塔底からは２２ｗｔ％の塩酸５，７５０ｋｇ／ｈを抜出して、高圧塔２へ供給する。さらに、高圧塔の塔底からは１８ｗｔ％の塩酸３，９００ｋｇ／ｈを抜出し、低圧塔１へ戻すようにした。
低圧塔１内の圧力は、図示していない減圧装置により１５０ｍｍＨｇの減圧に制御され、低圧塔再沸器５および高圧塔凝縮器４からのエネルギーを熱源として蒸留が行われ、低圧塔の塔頂からは少量の塩化水素を含む水蒸気が発生し、低圧塔凝縮器７にて分縮される。この低圧塔凝縮器７を経た蒸気と、圧縮器９の駆動蒸気とは併せて低圧塔再沸器５の熱源に利用する。また、低圧塔凝縮器７における凝縮液は、一部が還流液として低圧塔１へ戻され、残りの凝縮液は駆動蒸気の凝縮液と一緒にされて系外に排出される。本実施例では、系外に排出される排水中の塩酸濃度は０．０８ｗｔ％であった。
高圧塔２では、高圧塔再沸器３からのエネルギーを熱源として、０．２ＭＰａＧの加圧操作とし、高圧塔の塔頂からは高濃度の塩化水素を含む水蒸気が発生する。この蒸気は、高圧塔凝縮器４で凝縮された後、一部は還流液として高圧塔２へ戻され、残りは３０ｗｔ％の塩酸として回収した。
操作条件と、同一条件下における従来の加圧−減圧蒸留法との比較を表１．１に示す。
尚、本発明は図１のフローに基づく方法で、比較例である従来の加圧−減圧蒸留法としては、図１における高圧塔２の塔頂蒸気の凝縮器を低圧塔１の再沸器として使用せず、低圧塔１からの塔頂蒸気を処理するための圧縮器９も使用しない単効用蒸留のケースである。
【００１３】

Figure 0004169924
【００１４】
本発明の場合には、蒸気の消費量が、従来法に比べて半分近くの５４％程度に減少した。また冷却水使用量も半分以下の４８％になった。蒸気消費量が、原料塩酸量よりも少ないことは特筆されるべき結果である。ただし、本発明では、低圧塔１への供給蒸気の一部が、圧縮器として用いたエジェクターの駆動蒸気として使われ、この凝縮水が排水中に含まれてくるため、排水量が約２０％ほど増えている。その結果、排水中の塩酸濃度が若干下がっている。
【００１５】
実施例２
実施例１と同様に、原料の塩酸濃度１８．５ｗｔ％の希塩酸水溶液を低圧塔１に供給して、高圧塔より３５ｗｔ％塩酸を回収した。排水は、他の吸収塔の吸収水として再使用されるため、塩酸濃度を３ｗｔ％とした。このケースの操作条件を、抽出蒸留法と比較し、結果を表１．２に示す。尚、本発明は図１のフローに基づく方法で、抽出剤として塩化カルシウムを使用した抽出蒸留法と比較した。
【００１６】
Figure 0004169924
【００１７】
本発明による蒸気の消費量が、従来法の６０％程度となり、冷却水量も同様に６０％程度に下がった。本発明の場合には、蒸気消費量が、原料塩酸量よりも少ないことが特筆される。しかし、本発明では、蒸気の一部が圧縮器として用いたエジェクターの駆動蒸気として使われ、この凝縮水が排水中に含まれる為、排水量がわずかに増え、排水中の塩酸濃度が若干下がっている。
【００１８】
実施例３
実施例１における低圧塔１の塔頂からの蒸気を圧縮せずに、低圧塔凝縮器７にて全凝縮を行った場合を比較例として、実施例１の本発明方法と比較した結果を表１．３に示す。
本発明の場合には、比較例に比べて蒸気の使用量が約９％減少し、冷却水使用量も約１３％減少したことが判る。
【００１９】
Figure 0004169924
【００２０】
実施例４
原料の塩酸濃度１５ｗｔ％の希塩酸水溶液７，３９０ｋｇ／ｈを低圧塔１へ供給し、低圧塔の塔底からは２２ｗｔ％の塩酸５，７５０ｋｇ／ｈを抜出して、高圧塔２へ供給する。さらに、高圧塔の塔底からは１８ｗｔ％の塩酸３，９００ｋｇ／ｈを抜出し、低圧塔１へ戻すようにした。
低圧塔１内の圧力は、図示していない減圧装置により１００ｍｍＨｇの減圧に制御され、低圧塔再沸器５および高圧塔凝縮器４からのエネルギーを熱源として蒸留が行われ、低圧塔の塔頂からは少量の塩化水素を含む水蒸気が発生し、低圧塔凝縮器７にて分縮される。この低圧塔凝縮器７を経た蒸気と、圧縮器９の駆動蒸気とは併せて低圧塔再沸器５の熱源に利用する。また、低圧塔凝縮器７における凝縮液は、一部が還流液として低圧塔１へ戻され、残りの凝縮液は駆動蒸気の凝縮液と一緒にされて系外に排出される。本実施例では、系外に排出される排水中の塩酸濃度は０．０６ｗｔ％であった。
高圧塔２では、高圧塔再沸器３からのエネルギーを熱源として、０．５ＭＰａＧの加圧操作とし、高圧塔の塔頂からは高濃度の塩化水素を含む水蒸気が発生する。この蒸気は、高圧塔凝縮器４で凝縮された後、一部は還流液として高圧塔２へ戻され、残りは９９ｗｔ％の塩化水素ガスとして回収した。
このケースの操作条件を、従来の加圧・減圧法と比較した結果を表１．４に示す。
本発明は図２のフローに基づく方法で、比較例である従来の加圧−減圧蒸留法としては、図２における高圧塔２の塔頂蒸気の凝縮器を低圧塔１の再沸器として使用せず、低圧塔１からの塔頂蒸気を処理するための圧縮器９も使用しない単効用蒸留のケースである。
【００２１】
Figure 0004169924
【００２２】
本発明では、蒸気の消費量が、従来法に比べて７２％程度に減少した。また、冷却水も７０％になった。ただし、蒸気の一部が圧縮器として用いたエジェクターの駆動蒸気として使われ、この凝縮水が排水中に含まれる為、排水量が約６０％ほど増えている。
【００２３】
【発明の効果】
本発明の濃縮方法および濃縮装置によれば、塩酸の濃縮系内で発生する熱エネルギーを効率良く利用することにより、エネルギー消費量を大幅に削減することができる。また、前述の経済的な効果だけでなく、これまで再利用が困難視されていた比較的低濃度の塩酸水溶液から、効率的に高濃度の塩酸を回収することができ、裨益するところ大である。
さらには、これまで廃棄処理するために、手間と時間をかけていた低濃度の塩酸が、再利用可能なレベルへ濃縮できることから、廃棄物の低減につながり環境的にも貢献するものである。
【図面の簡単な説明】
【図１】本発明の実施態様の一つで、原料塩酸から高濃度の塩酸を回収するためのフローを示す説明図である。
【図２】本発明の実施態様の一つで、原料塩酸から高濃度の塩化水素ガスを回収する場合のフローを示す説明図である。
【符号の説明】
１ 低圧塔 ９ 圧縮器
２ 高圧塔 １０ 低圧塔底液ポンプ
３ 高圧塔再沸器 １１ 濃塩酸槽
４ 高圧塔凝縮器 １２ 希塩酸槽
５ 低圧塔再沸器 １３ 濃塩酸ポンプ
６ 熱交換器 １４ 希塩酸ポンプ
７ 低圧塔凝縮器 １５ 高圧塔第一分縮器
８ 希塩酸冷却器 １６ 高圧塔第二分縮器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for concentrating to high-concentration hydrochloric acid using a dilute hydrochloric acid aqueous solution having a wide range of concentrations including dilute hydrochloric acid having an azeotropic composition or less using two distillation columns, a high-pressure column and a low-pressure column. It is.
[0002]
[Prior art]
Hydrogen chloride (HCl) or hydrochloric acid in which hydrogen chloride is dissolved in water is used as a basic chemical in various industries, but it is produced as a by-product from various processes, but these are used as they are due to their low concentration. In actual use, it is often necessary to concentrate dilute hydrochloric acid.
However, when diluting hydrochloric acid with a low concentration by distillation, the hydrogen chloride-water system has an azeotropic point corresponding to a hydrochloric acid concentration of 20.2 wt% under atmospheric pressure. It is difficult to obtain concentrated hydrochloric acid with increased concentration. For this reason, there is a so-called vacuum-pressure distillation method that combines a vacuum tower and a high-pressure tower by utilizing the fact that the azeotropic composition of hydrochloric acid differs depending on the pressure. Hydrochloric acid is obtained using gaseous hydrogen chloride as a raw material. Japanese Patent Publication No. 34-6424 which concentrates and Japanese Patent Publication No. 50-21318 which emits hydrogen chloride gas from an aqueous hydrochloric acid solution are known. Further, there is an extractive distillation method that utilizes the disappearance of the azeotropic point of hydrochloric acid by using an extractant such as sulfuric acid and calcium chloride as described in Japanese Patent Publication No. 46-20132.
[0003]
[Problems to be solved by the invention]
Although it is possible to concentrate hydrochloric acid by the conventional method described above, both the reduced pressure-pressurized distillation method and the extractive distillation method are economically difficult because of the large amount of steam consumed for heating. In other words, since the gas-liquid equilibrium of the hydrogen chloride-water system has the highest azeotropic point, when the hydrochloric acid and the water are to be separated, all the hydrochloric acid and water in the raw material liquid must be evaporated once to form a vapor. For this reason, in any conventional method, the amount of steam used as a utility requires more than the raw material liquid, and even if considerable heat recovery is achieved, generally 1.2 to 1. About 5 times more steam was required. In particular, when the concentration of hydrochloric acid used as a raw material is low, the energy consumption is too large due to the large amount of water, which is a problem in practical use.
The present invention solves the problems of the conventional method, is applicable to a wide range of hydrochloric acid concentrations of the hydrochloric acid aqueous solution used as a raw material, and can concentrate a dilute hydrochloric acid aqueous solution and a concentration apparatus capable of greatly reducing energy consumption. This is a proposal.
[0004]
[Means for solving problems]
The present invention uses a distillation column (low pressure column) operated at a pressure lower than atmospheric pressure and a distillation column (high pressure column) operated at a pressure higher than atmospheric pressure, and supplies the raw dilute hydrochloric acid aqueous solution to the distillation column. In this method, hydrochloric acid having a higher concentration than the raw material hydrochloric acid is recovered from the top of the high-pressure column, and the thermal energy obtained when condensing the top vapor of the high-pressure column is used for re-boiling of the low-pressure column. After condensing the vapor from the top of the low-pressure column, it is compressed by a compressor consisting of an ejector that uses pressurized steam as a drive source, and used as a heat source for the reboiler of the low-pressure column This is a method for concentrating dilute hydrochloric acid aqueous solution.
The present invention also includes a distillation column (low pressure column) operated at a pressure lower than atmospheric pressure and a distillation column (high pressure column) operated at a pressure higher than atmospheric pressure. Supplying and recovering hydrochloric acid with higher concentration than the raw dilute hydrochloric acid from the top of the high-pressure column, using the thermal energy obtained when condensing the top vapor of the high-pressure column in the reboiler of the low-pressure column In addition, after condensing the vapor from the top of the low-pressure column, it is compressed by a compressor consisting of an ejector that uses pressurized steam as a drive source and used as a heat source for the reboiler of the low-pressure column. An apparatus for concentrating dilute hydrochloric acid aqueous solution.
The dilute hydrochloric acid aqueous solution as a raw material in the method for concentrating dilute hydrochloric acid aqueous solution preferably has a hydrochloric acid concentration of 28 wt% or less.
[0005]
The present invention is intended to utilize the thermal energy generated in the concentrating system to reduce the steam consumption required for the concentration of hydrochloric acid using two distillation towers, which has not been used much effectively so far. It is a thing.
The present invention is characterized in that the amount of steam required for the concentration of hydrochloric acid is reduced by effectively utilizing the steam from the top of the low-pressure column and the high-pressure column. Alternatively, a part can be covered by the heat of condensation of the top vapor of the low-pressure column and the high- pressure column, and the consumption of water vapor used as a heat source for hydrochloric acid concentration as a whole can be greatly reduced.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, two distillation columns, a low-pressure column and a high-pressure column, are combined to efficiently concentrate a hydrochloric acid aqueous solution having a low concentration. The contents of the present invention will be described below.
As the dilute hydrochloric acid aqueous solution used as a raw material in the present invention, even if it is synthetic hydrochloric acid, hydrochloric acid by-produced in various industrial manufacturing processes and hydrogen chloride contained in combustion gas generated by incineration of wastes, What was obtained by the absorption process etc. may be used. Moreover, although the purity of the hydrochloric acid is not specified, one having as few impurities as possible is preferable.
The concentration of the dilute hydrochloric acid aqueous solution as a raw material is effectively 28 wt% or less, more preferably 23 wt% or less, in order to effectively use thermal energy. However, when the hydrochloric acid concentration of the raw material hydrochloric acid is too low, water is almost distilled, which is economically meaningless and the lower limit is about 5 wt% as the hydrochloric acid concentration.
[0007]
The amount of heat required for the high pressure column and the low pressure column used for distillation of the hydrochloric acid aqueous solution is not necessarily the same. Rather, since the hydrochloric acid concentration of the raw material normally supplied to the low pressure column is low, the amount of heat required for the low pressure column is usually higher than the amount of heat required for the high pressure column.
When a high pressure column and a low pressure column are used in combination, it is possible to control the operating conditions to be optimized by adjusting the reflux ratio of each column in order to balance the required heat quantity of both. The energy consumption can be reduced by the above-mentioned method. However, according to the present invention, by using the top vapor of the high pressure column as a heat source for the reboiler of the low pressure column, the energy consumption can be further greatly reduced. it can. This method is particularly effective when the concentration of hydrochloric acid used as a raw material is low.
As shown in the examples described later, when recovering an aqueous hydrochloric acid solution having a high concentration as a product, it is a matter of course that in the present invention, both steam consumption and cooling water usage are much smaller than in the conventional method. The required amount of steam can be made smaller than the amount of raw material liquid, and hydrochloric acid can be recovered economically.
[0008]
Next, the contents of the present invention will be described in detail with reference to the drawings of FIGS.
FIG. 1 is a flow showing a basic configuration of the present invention for recovering concentrated high concentration hydrochloric acid. In the present invention, two distillation columns of a low-pressure column 1 operated at a pressure lower than atmospheric pressure and a high-pressure column 2 operated at a pressure higher than atmospheric pressure are used by utilizing the change in the azeotropic composition in the hydrogen chloride-water system depending on the pressure. To do. The pressure difference between the low pressure column 1 and the high pressure column 2 is desirably 0.1 MPa or more. Note that the pressure in the low-pressure column 1 is controlled by a decompression device (not shown).
The raw dilute hydrochloric acid aqueous solution (raw hydrochloric acid) is supplied to either the low-pressure column 1 or the high-pressure column 2, and concentrated hydrogen chloride vapor is generated from the top of the high-pressure column 2. , Water vapor containing some hydrogen chloride gas is generated. The total amount of heat required varies depending on which distillation column the raw hydrochloric acid is supplied to. For this reason, when the concentration of the raw material hydrochloric acid is lower than the concentration of hydrochloric acid obtained at the bottom of the low-pressure column, supplying the raw material hydrochloric acid to the low-pressure column 1 can reduce the total required energy, and the concentration of the raw material hydrochloric acid However, when the concentration of hydrochloric acid obtained at the bottom of the low pressure column is higher, the total required energy can be reduced by supplying the raw material hydrochloric acid to the high pressure column 2.
[0009]
The hydrochloric acid introduced into the high-pressure column 2 is heated by steam supplied to the high-pressure column reboiler 3 and distilled in the column. In one low-pressure column 1, the introduced hydrochloric acid is heated and distilled by supplying heat from the high-pressure column condenser 4 and the low-pressure column reboiler 5.
In cooling the high-pressure tower condenser 4 for condensing the top vapor of the high-pressure tower 2, the bottom liquid of the low-pressure tower 1 is used in the present invention. Due to the difference in boiling point, the vapor from the top of the high pressure column 2 is condensed and liquefied to become concentrated high-concentration hydrochloric acid, while the bottom liquid of the low pressure column 1 is the top of the high pressure column. It receives the heat energy of steam and evaporates to become steam. The bottom liquid of the low-pressure column 1 may not necessarily be evaporated in the high-pressure column condenser 4 depending on the operating conditions, but may be returned to the low-pressure column as an aqueous solution by pump circulation and flash evaporated at the bottom. Good.
A part of the condensate of the top vapor from the high pressure column 2 is returned to the high pressure column 2 as a reflux liquid, and the rest is recovered as concentrated hydrochloric acid. The concentrated hydrochloric acid is heat-exchanged with the raw material hydrochloric acid by the heat exchanger 6 and the stored heat is effectively utilized, then once received in the concentrated hydrochloric acid tank 11 and transferred to the outside by the concentrated hydrochloric acid pump 13.
On the other hand, the top vapor of the low pressure column 1 is condensed by the low pressure column condenser 7, cooled together with the condensate of the low pressure column reboiler 5 by the dilute hydrochloric acid cooler 8, and once received in the dilute hydrochloric acid tank 12, then the dilute hydrochloric acid pump. 14 is transferred out of the system to be drained. The steam that has passed through the low-pressure column condenser 7 is compressed by a compressor 9 composed of an ejector that uses pressurized steam as a drive source, and then sent to the low-pressure column reboiler 5 to supply heat to the low-pressure column 1. Done. Thereby, the thermal energy possessed by the top vapor of the low pressure column 1 is effectively used for heating hydrochloric acid in the low pressure column 1.
[0010]
FIG. 2 shows a flow when high concentration hydrogen chloride gas is recovered from the top of the high pressure column 2 as another embodiment of the present invention. The basic configuration of the present invention using the two distillation columns of the low-pressure column 1 and the high-pressure column 2 is the same as that in FIG. 1, and the other components are almost the same. Is attached.
The top vapor from the high-pressure tower 2 is fractionated by the high-pressure tower first partial condenser 15 and the high-pressure tower second partial condenser 16 to recover a high concentration hydrogen chloride gas. Further, the condensate in the above-described partial condenser is returned into the high-pressure column 2.
[0011]
【Example】
Next, as an example. The steam usage amount and cooling water usage amount when hydrochloric acid is concentrated by the distillation method are shown in comparison with the method of the present invention and other methods.
[0012]
Example 1
A dilute hydrochloric acid aqueous solution of 4,200 kg / h having a hydrochloric acid concentration of 14 wt% as a raw material is supplied to the low-pressure column 1, and 22,750 kg / h of 22 wt% hydrochloric acid is extracted from the bottom of the low-pressure column and supplied to the high-pressure column 2. Further, 3,900 kg / h of 18 wt% hydrochloric acid was extracted from the bottom of the high pressure column and returned to the low pressure column 1.
The pressure in the low-pressure column 1 is controlled to a reduced pressure of 150 mmHg by a decompression device (not shown), and distillation is performed using the energy from the low-pressure column reboiler 5 and the high-pressure column condenser 4 as a heat source. From which water vapor containing a small amount of hydrogen chloride is generated and is condensed in the low-pressure column condenser 7. The steam that has passed through the low-pressure column condenser 7 and the driving steam of the compressor 9 are used together as a heat source for the low-pressure column reboiler 5. A part of the condensate in the low-pressure column condenser 7 is returned to the low-pressure column 1 as a reflux liquid, and the remaining condensate is discharged together with the condensate of the drive steam. In this example, the hydrochloric acid concentration in the wastewater discharged out of the system was 0.08 wt%.
In the high-pressure column 2, the pressure from the high-pressure column reboiler 3 is used as a heat source, and the pressure is increased to 0.2 MPaG. Steam containing high-concentration hydrogen chloride is generated from the top of the high-pressure column. This steam was condensed in the high-pressure tower condenser 4, and then a part thereof was returned to the high-pressure tower 2 as a reflux liquid, and the rest was recovered as 30 wt% hydrochloric acid.
A comparison between the operating conditions and the conventional pressure-vacuum distillation method under the same conditions is shown in Table 1.1.
The present invention is a method based on the flow of FIG. 1, and as a conventional pressure-vacuum distillation method as a comparative example, the condenser of the top vapor of the high-pressure column 2 in FIG. This is a single-effect distillation case in which the compressor 9 for treating the top vapor from the low-pressure column 1 is not used.
[0013]
Figure 0004169924
[0014]
In the case of the present invention, the consumption of steam has been reduced to about 54%, which is almost half that of the conventional method. The amount of cooling water used was 48%, less than half. It should be noted that the steam consumption is less than the amount of raw hydrochloric acid. However, in the present invention, a part of the steam supplied to the low pressure column 1 is used as driving steam for the ejector used as the compressor, and this condensed water is contained in the waste water, so the amount of waste water is about 20%. is increasing. As a result, the concentration of hydrochloric acid in the waste water is slightly lowered.
[0015]
Example 2
In the same manner as in Example 1, a dilute hydrochloric acid aqueous solution having a hydrochloric acid concentration of 18.5 wt% as a raw material was supplied to the low pressure column 1, and 35 wt% hydrochloric acid was recovered from the high pressure column. Since the waste water is reused as the absorption water of other absorption towers, the hydrochloric acid concentration is set to 3 wt%. The operating conditions in this case were compared with the extractive distillation method, and the results are shown in Table 1.2. The present invention is a method based on the flow of FIG. 1 and compared with an extractive distillation method using calcium chloride as an extractant.
[0016]
Figure 0004169924
[0017]
The consumption of steam according to the present invention was about 60% of the conventional method, and the amount of cooling water was similarly reduced to about 60%. In the case of the present invention, it is noted that the steam consumption is smaller than the raw hydrochloric acid amount. However, in the present invention, a part of the steam is used as driving steam for the ejector used as a compressor, and this condensed water is contained in the waste water, so the amount of waste water is slightly increased and the concentration of hydrochloric acid in the waste water is slightly reduced. Yes.
[0018]
Example 3
Table 1 shows the result of comparison with the method of the present invention in Example 1, with the case where total condensation was performed in the low pressure column condenser 7 without compressing the vapor from the top of the low pressure column 1 in Example 1 as a comparative example. Shown in 1.3.
In the case of the present invention, it can be seen that the amount of steam used is reduced by about 9% and the amount of cooling water used is also reduced by about 13% compared to the comparative example.
[0019]
Figure 0004169924
[0020]
Example 4
A dilute hydrochloric acid aqueous solution (7,390 kg / h) having a hydrochloric acid concentration of 15 wt% as a raw material is supplied to the low-pressure column 1, 22 wt% hydrochloric acid (5,750 kg / h) is extracted from the bottom of the low-pressure column and supplied to the high-pressure column 2. Further, 3,900 kg / h of 18 wt% hydrochloric acid was extracted from the bottom of the high pressure column and returned to the low pressure column 1.
The pressure in the low-pressure column 1 is controlled to a reduced pressure of 100 mmHg by a decompression device (not shown), and distillation is performed using the energy from the low-pressure column reboiler 5 and the high-pressure column condenser 4 as a heat source. From which water vapor containing a small amount of hydrogen chloride is generated and is condensed in the low-pressure column condenser 7. The steam that has passed through the low-pressure column condenser 7 and the driving steam of the compressor 9 are used together as a heat source for the low-pressure column reboiler 5. A part of the condensate in the low-pressure column condenser 7 is returned to the low-pressure column 1 as a reflux liquid, and the remaining condensate is discharged together with the condensate of the drive steam. In this example, the hydrochloric acid concentration in the waste water discharged out of the system was 0.06 wt%.
In the high-pressure column 2, the energy from the high-pressure column reboiler 3 is used as a heat source, and the pressure is adjusted to 0.5 MPaG. Steam containing high concentration hydrogen chloride is generated from the top of the high-pressure column. This steam was condensed by the high-pressure tower condenser 4, and then a part thereof was returned to the high-pressure tower 2 as a reflux liquid, and the rest was recovered as 99 wt% hydrogen chloride gas.
Table 1.4 shows the results of comparing the operating conditions of this case with the conventional pressurization / depressurization method.
The present invention is a method based on the flow of FIG. 2, and the conventional pressurized-vacuum distillation method as a comparative example uses the condenser of the top vapor of the high pressure column 2 in FIG. 2 as the reboiler of the low pressure column 1. In addition, this is a case of single-effect distillation in which the compressor 9 for treating the top vapor from the low-pressure column 1 is not used.
[0021]
Figure 0004169924
[0022]
In the present invention, the steam consumption is reduced to about 72% compared to the conventional method. The cooling water also became 70%. However, since a part of the steam is used as driving steam for the ejector used as a compressor and this condensed water is contained in the wastewater, the amount of wastewater is increased by about 60%.
[0023]
【The invention's effect】
According to the concentration method and concentration apparatus of the present invention, the energy consumption can be greatly reduced by efficiently using the thermal energy generated in the hydrochloric acid concentration system. In addition to the economic effects described above, high-concentration hydrochloric acid can be efficiently recovered from a relatively low-concentration aqueous hydrochloric acid solution that has been considered difficult to reuse. is there.
Furthermore, since the low-concentration hydrochloric acid, which has been time-consuming and time-consuming for disposal, can be concentrated to a reusable level, it leads to a reduction in waste and contributes to the environment.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a flow for recovering high-concentration hydrochloric acid from raw hydrochloric acid in one embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a flow in the case of recovering high-concentration hydrogen chloride gas from raw hydrochloric acid in one embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Low pressure tower 9 Compressor 2 High pressure tower 10 Low pressure tower bottom liquid pump 3 High pressure tower reboiler 11 Concentrated hydrochloric acid tank 4 High pressure tower condenser 12 Dilute hydrochloric acid tank 5 Low pressure tower reboiler 13 Concentrated hydrochloric acid pump 6 Heat exchanger 14 Dilute hydrochloric acid pump 7 Low-pressure tower condenser 15 High-pressure tower first partial condenser 8 Dilute hydrochloric acid cooler 16 High-pressure tower second partial condenser

Claims (3)

大気圧未満の圧力で操作される蒸留塔（低圧塔）と大気圧超の圧力で操作される蒸留塔（高圧塔）を用い、原料の希塩酸水溶液を前記の蒸留塔に供給し、高圧塔の塔頂から原料の希塩酸よりも高濃度の塩酸を回収する方法であって、高圧塔の塔頂蒸気を凝縮する際に得られる熱エネルギーを低圧塔の再沸に利用するとともに、低圧塔の塔頂からの蒸気を凝縮させた後に、加圧された水蒸気を駆動源とするエゼクターよりなる圧縮器で圧縮し、低圧塔の再沸器の熱源として利用することを特徴とする希塩酸水溶液の濃縮方法。Using a distillation column (low pressure column) operated at a pressure lower than atmospheric pressure and a distillation column (high pressure column) operated at a pressure higher than atmospheric pressure, the raw dilute hydrochloric acid aqueous solution was supplied to the distillation column, and A method for recovering hydrochloric acid having a concentration higher than that of dilute hydrochloric acid as a raw material from the top of the column, and using the thermal energy obtained when condensing the top vapor of the high-pressure column for re-boiling of the low-pressure column, A method for concentrating a dilute hydrochloric acid aqueous solution characterized in that after condensing the vapor from the top, it is compressed by a compressor comprising an ejector using pressurized steam as a drive source and used as a heat source for a reboiler of a low pressure column . 原料の希塩酸水溶液の塩酸濃度が２８wt％以下である請求項１記載の希塩酸水溶液の濃縮方法。  2. The method for concentrating a dilute hydrochloric acid aqueous solution according to claim 1, wherein the concentration of the hydrochloric acid in the dilute hydrochloric acid aqueous solution is 28 wt% or less. 大気圧未満の圧力で操作される蒸留塔（低圧塔）と大気圧超の圧力で操作される蒸留塔（高圧塔）を備え、原料の希塩酸水溶液を前記の蒸留塔に供給し、高圧塔の塔頂から原料の希塩酸よりも高濃度の塩酸を回収する装置であって、高圧塔の塔頂蒸気を凝縮する際に得られる熱エネルギーを低圧塔の再沸器において利用するとともに、低圧塔の塔頂からの蒸気を凝縮させた後に、加圧された水蒸気を駆動源とするエゼクターよりなる圧縮器で圧縮し、低圧塔の再沸器の熱源として利用することを特徴とする希塩酸水溶液の濃縮装置。A distillation column (low pressure column) operated at a pressure lower than atmospheric pressure and a distillation column (high pressure column) operated at a pressure higher than atmospheric pressure are provided, and the raw dilute hydrochloric acid solution is supplied to the distillation column. An apparatus for recovering hydrochloric acid having a concentration higher than that of dilute hydrochloric acid as a raw material from the top of the column. The thermal energy obtained when condensing the vapor at the top of the high-pressure column is used in the reboiler of the low-pressure column. Condensation of dilute hydrochloric acid aqueous solution, characterized by condensing the vapor from the top of the column and then compressing it with a compressor consisting of an ejector that uses pressurized water vapor as a driving source and using it as a heat source for the reboiler of the low-pressure column apparatus.
JP2000317174A 2000-09-12 2000-09-12 Method and apparatus for concentrating dilute hydrochloric acid aqueous solution Expired - Lifetime JP4169924B2 (en)

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EP2809644B1 (en) * 2012-01-31 2016-09-28 Covestro Deutschland AG Method and device for manufacturing nitrobenzol
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CN108525337B (en) * 2018-05-29 2023-07-18 杭州东日节能技术有限公司 Dilute hydrochloric acid vacuum concentration tower and its use method
CN210683206U (en) * 2019-07-04 2020-06-05 南通星球石墨设备有限公司 Waste acid treatment system
CN114452668B (en) * 2022-02-28 2023-07-14 中船(邯郸)派瑞特种气体股份有限公司 Method for preparing hydrogen chloride by using device for preparing hydrogen chloride through hydrochloric acid analysis
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