JP2004114029A - Method of separating and recovering water-soluble volatile component in waste water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To recover a small amount of volatile component included in a large volume of waste water by distillation with saved energy. <P>SOLUTION: A first step is provided with a steam ejector 10 consisting of a liquid-liquid heat exchanger 2, a flash evaporator 6, and vapor-liquid equilibrium vessel 12, and a steam ejector (1) consisting of 9, 10 and 11, and they are connected like in the figure. The raw waste water 1 is heated up by heat exchange with high-temperature waste water 38 from a second step to obtain a condensate 14 which is sent to a first distillation column 15 of the second step. The quantity of heat held in distilled vapor 19 from the top of the column 15 is recovered in a condenser 16 and is sent as vapor 24 to a vapor compressor 25 where the vapor is boosted. The boosted vapor is blown to the column bottom of 15, thereby drastically reducing the heating quantity of a reboiler 17 and obtaining a high-temperature bottom liquid not containing the volatile component from the column bottom. The bottom liquid is returned to the first step and is utilized for heating the raw waste water 1 while passing the flash evaporator 6 and the liquid-liquid heat exchanger 2. <P>COPYRIGHT: (C)2004,JPO

Description

と膨大な量となる。
このような巨大な加熱負荷を低減する上で、図の液々熱交換器（２）の設置は必須の手段であり、これによって１００℃の高温廃水（３８）を（２）に導き、廃水（５）の温度を３５℃に至るまで下げて利用すれば、その顕熱分６．５×１０^６ｋｃａｌ／ｈが回収利用できることとなり、（２）の設置による省エネ効果は要加熱量の６．５／７．５＝８７％に及ぶ。併しながらこのような効果を生む液々熱交換器（２）の設備費や運転コストが次の問題である。上記の事例につき、設置すべき熱交換器（２）の寸法は、仮に熱伝達係数Ｕ＝１，０００ｋｃａｌ／ｍ^２，ｈ，℃の高性能型を採用するとし、伝熱面積の平均温度差１０℃まで回収するとした場合においても所要伝熱面積は

といった巨大な熱交換器を要し、その設備費は莫大なものになる。
以上図３に示す公知のプロセスを用いて説明したように、第１工程で原排水（１）と第２工程より生ずる釜残液の高温廃水（３８）との間の液々熱交換器（２）を公知の既存の熱交換器を設置する方式から脱却して、高効率の新しい熱交換方式に改変することは省エネ的に必須の条件であり、いかに低コスト化するかが解決すべき第１の課題である。
次に解決を要する第２の課題は、図３において（２）により１００℃付近まで昇温した温排水（３）を蒸留にかけて揮発成分とこれを含まぬ排水に分離する第２工程のうち、第１蒸留塔（１５）の省スチーム化である。（１５）の中段に給液された（３）は塔底部に向かって塔内を降下する間に、リボイラー（１７）により炊き上げられた上昇蒸気と接触し、その揮発成分の全量は蒸気にともなわれて塔頂部へ移動し、留出蒸気（１９）として（１５）を離れるが、同時に塔底部よりは揮発成分が消滅した１００℃付近の大量の釜出液（１８）を排出することが、塔（１５）に課せられた条件である。
このときの従来公知の第１塔のリボイラー（１７）に要する加熱エネルギーは、後記第２表に示すように膨大であり、これを大幅に節減する新しいプロセスを見い出すことが、第２工程に課せられた課題である。
【０００５】
【課題を解決するための手段と発明が解決しようとする課題】
上記目的を達成するために、本発明は、図１に示すように全工程を第１工程と第２工程とに分け、第１工程においては、原排水（１）と第２工程より排出する高温廃水（３８）との間に新しい液々熱交換方式を設けて経済性を解決する。
続く第２工程では、第１工程で予熱，昇温された凝縮液（１４）をまず第１蒸留塔（１５）の中段に導き、塔頂部より揮発成分の全量を含む留出蒸気（１９）をコンデンサー（１６）の高温側に送り、冷却凝縮して留出液（２７）を得ると共に、（１６）の低温側で伝熱により発生する回収蒸気（２４）を、蒸気圧縮機（２５）で昇圧，昇温した上で（１５）の塔底部に加熱源として吹き込み、リボイラー（１７）による加熱の代替を行うことが、課題を解決するための手段である。そのさい得られた留出液（２７）を、必要によりさらに第２蒸留塔（２８）の中段に送り、所定濃度の留出液（３５）として得ることが、発明が解決しようとする課題である。
【０００６】
図１により上記［０００５］を詳しく説明する。
原排水（１）は通常大気圧下で常温で供給され、液量は５ｍ^３／ｈより１００ｍ^３／ｈを適当としているが、それ以外でも差し支えない。液温は０℃以上の液体であればとくに制限はない。含有する揮発成分としては、有機化合物で水（Ｈ_２Ｏ）より低沸点のもの、または水と共沸物を作って水より低温で留出する物性であればよく、また無機化合物であっても同様である。実施例では有機系ではメタノール（ＣＨ_３ＯＨ）等のアルコール類，アセトン（Ｃ_３Ｈ_６Ｏ）等のケトン類，酢酸メチル（Ｃ_３Ｈ_６Ｏ_２）等のエステル類等である。また無機系ではアンモニア（ＮＨ_３）等があるが、これ等に限定して使用されるものではない。
【０００７】
上記の第１工程では、液々熱交換器（２）はいわゆる間接熱伝達方式で、伝熱面を介して高・低温の両液が接触して熱交換を行うものである。構造は市場で汎用されるシエルアンドチューブ型のほか、プレート熱交換器型，スパイラル型等いづれも使用可能である。これ等の性能を示す数値として、上記［０００４］で述べた総括熱伝達係数Ｕの大小が目安となる。
本発明を汚れの少ない原排水に適用するときは、Ｕ≧１，０００ｋｃａｌ／ｍ^２，ｈ，℃程度の性能が得られるように液の流速を選ぶことが望ましい。
（２）と並置されるのはフラッシュ缶（６），気液平衡缶（１２）及び（９），（１０），（１１）より構成されるスチームエジェクター１であり、（６）の下部と（１２）の上部とは（８），（９），（１０）を介して流通している。（６）と（１２）の中央部にはそれぞれ充填物（７）および（１３）が適宜配設されており、（７）の全面には第２工程よりの高温廃水（３８）が分散され、下方に向けて灌液される。一方（１３）の全面には（３）の液流と共に、（１０）よりの放出蒸気が同時に混合して下方に向け供給される。かくて（７）および（１３）の表面を通る各々の流体は所定圧力の下で気液平衡に到達し、（７）よりはフラッシュ蒸気（８）が、（１３）よりは飽和沸点に達した凝縮液（１４）がそれぞれ留出する。一方、（７）で生じ、（６）の缶底部より排出するフラッシュ残液（４）は、液々熱交換器（２）へ高温側入口より流入し、（１）との間で熱交換を行ったのち、廃水（５）として流出する。
【０００８】
続く第２工程では第１工程よりの凝縮液（１４）が第１蒸留塔（１５）の適当な中段に供給される。（１５）の内部には圧損失の少ない気液接触手段、たとえば低圧損失形の充填物とこれを支える適当な塔内容物が設置され、塔底部にはリボイラー（１７）のほか、加圧蒸気（２６）を送る蒸気管が配設される。（１５）の塔頂部よりの留出蒸気（１９）はコンデンサー（１６）の高温側に流入し、冷却されて凝縮液（２０）となって還流器（２１）に入り、所定の還流比の下で一部は還流液（２２）として（１５）の頂部に、残りは留出液（２７）として排出する。
一方、（１６）の低温側には減圧下で冷却用の補給水（２３）が供給されるが、内部の伝熱面を介して高温側の（１９）の蒸気により加熱されて蒸発し、回収蒸気（２４）として蒸気圧縮機（２５）に吸引・圧縮され、上記のごとく加圧蒸気（２６）となって（１５）の塔底部に吹き込まれる。通常の蒸留操作では、上記のごとくリボイラー（１７）により（１５）の塔底部で発生した蒸気は上記凝縮液（１４）と塔内で気液接触を重ね、塔頂部より（１９）として留出し（１６）を経て（２０），（２１）より（２７）に至るが、本発明の第２工程で、リボイラー（１７）に要する通常の加熱量と、上記の蒸気圧縮機（２５）で得られ加圧蒸気（２６）として吹き込まれる蒸気流量は熱量換算ではほぼ同一であるため、（１５）が連続定常運転に入ればリボイラー（１７）の存在は不要となる。また（１７）に小量の不足熱量が生じても、それに見合う追加生蒸気を塔底部に吹き込むことで足りる。
このようにして第１蒸留塔（１５）は、その運転に必要な熱量をリボイラー（１７）による加熱に頼らずに、塔頂部の（１６）で回収される（１９）の凝縮熱を補給水（２３）の蒸発熱に変えて回収蒸気（２４）を得た上で、蒸気圧縮機（２５）により加圧して（１５）の塔底へ直接吹き込むという、ヒートポンプの公知原理による蒸留方式（たとえば［特公開昭５７−２０９６０２］）を採用することで、第２工程の第１塔（１５）の大幅な省エネルギー化を達成することが可能である。
【０００９】
上記第２工程の第１蒸留塔（１５）で、得られる釜出液（１８）の揮発成分を指定の低濃度とし、かつ留出液（２７）を指定の高濃度で同時に得ることは、原排水（１）に含まれる揮発成分の初期濃度によっては理論上または実用上限界がある。
したがってそのような際には、第１蒸留塔（１５）の操作条件を緩和し、釜出液（１８）のみを指定濃度に保ちつつ留出液（２７）の揮発成分濃度を低濃度に抑えたのち、それを受けて第２蒸留塔（２８）を設け、留出液（３５），釜出液（３６）をそれぞれ指定された揮発成分の仕様に適合させることが効果的である。
【００１０】
【発明の実施の形態と発明の効果】
本発明を構成する要素は、［請求項１］および［請求項２］で述べたように、第１工程と第２工程からなる。
本発明者は、発明の［実施の形態］と［その効果］は一覧性をもった表として、数字により表示することが好ましいと考え、そのように説明する。
【００１１】
図３の公知のプロセスのフローシートの例として、メタノール（ＣＨ_３ＯＨ）を微量揮発成分含む大量の原排水（１）を蒸留によって分離し、高濃度のメタノールを留出液（３５）と、また殆どこれを含まない廃水（５）を釜出液（３８）として収得するプロセスを選び、これを基準点として、以下本発明の各種の実施形態を述べ、発明の効果を比較する。まず第１表に公知の図３に対する仕様を示す。

【００１２】
第１表の基準となる仕様データを用いて、第２表においては図３の公知標準プロセスとその第１工程のみを［請求項１］，［請求項２］に示すような新しい熱交換方式に変更する新しい図４のプロセスを実施例で示している。
また、これによる［発明の効果］を、数字により、図４を図３の公知標準方式と比較しながら説明している。
第２表で留意すべきは、双方とも全体で（２），（１６），（１７），（２９），（３０）の５基の熱交換器を使用しているが、その使用の効率の相異である。そのうち熱交換量で見れば、第２工程の２塔に属する４基の熱交換器（１６），（１７），（２４），（３０）の合計値は、双方とも約２２．５×１０^６ｋｃａｌ／ｈである。
この数値は、第１工程に属する図３の公知方式の液々熱交換器（２）の熱交換料の６．８６×１０^６ｋｃａｌ／ｈの約３．３倍もあるのに対して、伝熱面積から見れば逆に（２）は１，２７０ｍ^２と、第２工程の（１６），（１７），（２９），（３０）の４基の合計値４５５ｍ^２の２．８倍にも達する巨大な点に注目する。これは伝熱面積１ｍ^２あたりの熱交換量で評価すると、蒸留塔で使われるリボイラー，コンデンサーのそれに較べて、図３の公知標準方式で使われる液々熱交換器（２）では約１／１０といかに低レベルであるかを意味する。

【００１３】
第２表によれば、液々熱交換器（２）について［０００７］で述べた総括熱伝達係数を同一のＵ＝１，０００ｋｃａｌ／ｍ^２，ｈ，℃に保った上で、図３の公知標準方式から実施例の図４の新熱交方式に変更することで、その熱交換量は６５％に下がり、その一方で温度差は２．６倍に増加するため、所要伝熱面積は３４４ｍ^２と公知標準方式の１２８０ｍ^２から一挙に１／４に縮小し、設備費の点では画期的なコストダウンが予想される。一方、省エネルギー効果として、第２工程の両者のスチーム消費量を見ると、第１塔と第２塔に割り当てられる仕様条件には本質的な変化はなく、図３と図４はほぼ同一の２２．１〜２２．９ｔｏｎ／ｈの範囲で収まっており、図４のスチームエジェクター１の消費量の分２．１ｔｏｎ／ｈ，約１０％近くが、それのない公知標準方式の図３より増加する。これら等の数字を基に経済性を判断すると、原排水（１）が多量になるにつれ、図４の新しい熱交換器方式による液々熱交換器（２）の所要伝熱面積を大幅にカットする方式が、スチームエジェエクター１の駆動蒸気（１１）の若干の上乗せを考えても、公知標準の図３方式より経済的には有利となる。
【００１４】
［００１２］においては、本発明を構成する第１工程に関して、公知のプロセス図３にはなかった新熱交換方式を、実施例図４のごとく導入することにより、大規模な熱回収を低廉な設備費の投資で実施できることを示した。これに対して第３表の実施例図１，実施例図２で示すプロセスは、いづれもその第１工程に上記実施例図４の第１工程で述べた新熱交換方式を採用するのに加えて、さらにその第２工程も図４の形式を抜本的に変更する。即ち、実施例図１のプロセスにおいては請求項１，２，３の条件を、実施例図２のプロセスにおいては請求項１，２，３，４の条件を、第１，第２工程全体に適用して、それぞれの工程に大幅な省エネルギー的効果と共に設備費の低下による経済的効果を図るものである。
【００１５】
実施例図１についての説明は、既に上記［０００８］に述べた通りである。
一方、実施例図２のプロセスは、次のように図１とは第２工程の構成において大きく異なる。即ち［請求項４］に示すように、第１蒸留塔（１５）のコンデンサー（１６）の低温側より出た回収蒸気（２４）は、新たに設置するスチームエジェクター２の吸引部（３９）に流入し、駆動蒸気（４１）と共にディフェーザー（４０）を通過し、その先端部より放出蒸気（４２）となって低圧縮比の蒸気圧縮機（２５）で吸引・圧縮され、加圧蒸気（２６）として分配弁（４３）に至る。（２６）は分配弁（４３）で２分割され、一部は吹込蒸気（４４）として第１蒸留塔（１５）の塔底部に送られ、残りは第２蒸留塔（２８）の塔底部への吹込蒸気（４５）として送られる。これによって、蒸留塔（１５），（２８）については、それぞれ付属するリボイラー（１７），（３０）による加熱量が激減または不要となる。即ち、第１蒸留塔（１５）よりの回収蒸気（２４）と、スチームエジェクター２の駆動蒸気（４１）が加算され、［請求項４］のヒートポンプ方式により回収利用されて、第１蒸留塔（１５）のみならず第２蒸留塔（２８）の加熱量までを賄うことが可能となる。

このように図２のプロセスの第２工程は、（１５）に供給される凝縮液（１４）の変動に対応しつつ最終的に得られる留出液（３５）と釜出液（３６）の濃度を予め定められた仕様を満足するようにスチームエジェクター２への駆動蒸気量（４１）の制御と続く蒸気圧縮機（２５）の圧縮比の制御とを同時に行うことにより実施できる。
【００１６】
第３表の［実施の形態］の欄には、図１，図２のプロセスの実施例につき、各主要機器の予想される運転結果を列挙し、上記の第２表に述べた実施例も含めて比較検討している。次の［その効果］の欄には、各々のケースに対応する主要エネルギー消費量である蒸気量，電力量を推算している。
注目すべきは、蒸気圧縮機（２５）の電力消費量が図２では図１の約１／８に激減しているのに対し、スチーム消費はほぼ同一である点である。これはスチームエジェクター２がそれに続く蒸気圧縮機の圧縮比の低下に大きく役立つのに加え、その駆動蒸気（４１）の排蒸気が（４４）及び（４５）として上乗せされて第１塔及び第２塔の加熱に利用されるためである。
【００１７】
第４表では、上記第２表に示す図３，図４に対応し、また第３表に示す図１，図２に対応する合計４プロセスについて、一括して各々の工程のエネルギー消費に関係して予想される数値を列記して、その経済性を比較検討している。

２００２年８月時点の工業用の単価を蒸気３，０００円／トン，電力１７円／ｋＷｈとすれば、第３表における図１および図２の各プロセスの経済性が格段に高いことが分かる。
【００１８】
図５に示すプロセスは、まず水溶性揮発成分を含む空気等の大量の原ガス（４６）を吸収塔（４８）の底部より送風機（５１）によって送り、吸収液（４９）を塔頂部より灌液することで、塔内で気液混合・接触による上記揮発成分の（４９）への吸収が行われて、廃ガス（４７）と回収液（５０）とを得る公知のプロセスに関するものである。［請求項５］は、［請求項１］乃至［請求項４］の方法を活用して、上記図５で得られた回収液（５０）を経済的に処理し、かつ得られた廃水（５）は吸収塔（４８）に吸収液（４９）として戻して再利用することを範囲とするものである。第５表は図５と連結して後段を図２のプロセスに連結して一体として［実施の形態］をまとめたものである。

この吸収液は、そのまま図２に示すプロセスに従って処理するものとする。
但し、図２においては第２工程で補給水（２３）と駆動蒸気（４１）および（４１）が系内に水分として供給されるので、その分だけ廃水（５）より廃棄水（５２）として除いた後に、上記の如く吸収液（４９）を５０．９ｔ／ｈ，３５℃と調整して使用する。
【図面の簡単な説明】
【図１】［請求項１］に記載するように、第１工程と第２工程より成り、第１工程には新熱交換方式を、第２工程には蒸気圧縮機を用いるヒートポンプ方式を適用するプロセスのフローシート。
【図２】［請求項４］に記載されるように、図１のプロセスの第２工程の蒸気圧縮機にスチームエジェクター２を直列に接続するプロセスのフローシート。
【図３】多量の排水に含まれる少量の水溶性揮発成分を、加熱，蒸留して、分離・回収する公知のプロセスのフローシート。
【図４】［請求項２］に示すように、図３の公知プロセスに液々熱交換方式を適用して、経済性を高めるプロセスのフローシート。
【図５】［請求項５］に示すように、原ガス中に含まれる水溶性揮発成分を水に吸収した回収液を原排水として図１または図２の第１工程へ供給するプロセスのフローシート。
【符号の説明】
１　原排水　　　　　　　　　　２７　同　留出液
２　液々熱交換器　　　　　　　２８　第２蒸留塔
３　温排水　　　　　　　　　　２９　同　コンデンサー
４　フラッシュ残液　　　　　　３０　同　リボイラー
５　廃水　　　　　　　　　　　３１　同　留出蒸気
６　フラッシュ缶　　　　　　　３２　同　凝縮液
７　充填物　　　　　　　　　　３３　同　還流器
８　フラッシュ蒸気　　　　　　３４　同　還流液
９　吸引部　　　　　　　　　　３５　同　留出液
１０　ディフューザー　　　　　　３６　同　釜出液
１１　駆動蒸気　　　　　　　　　３７　釜残液受器
１２　気液平衡缶　　　　　　　　３８　高温廃水
１３　充填物　　　　　　　　　　３９　吸引部
１４　凝縮液　　　　　　　　　　４０　ディフューザー
１５　第１蒸留塔　　　　　　　　４１　駆動蒸気
１６　同　コンデンサー　　　　　４２　放出蒸気
１７　同　リボイラー　　　　　　４３　分配弁
１８　同　釜出液　　　　　　　　４４　第１塔蒸気管
１９　同　留出蒸気　　　　　　　４５　第２塔蒸気管
２０　同　凝縮液　　　　　　　　４６　原ガス
２１　同　還流器　　　　　　　　４７　廃ガス
２２　同　還流液　　　　　　　　４８　吸収塔
２３　補給水　　　　　　　　　　４９　吸収液
２４　回収蒸気　　　　　　　　　５０　回収液
２５　蒸気圧縮機　　　　　　　　５１　送風機
２６　加圧蒸気　　　　　　　　　５２　廃棄水
Ｐ１，Ｐ２，Ｐ３，Ｐ４　送液ポンプ
９，１０，１１　は　スチームエジェクター１　を構成
３９，４０，４１　は　スチームエジェクター２　を構成[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for separating and recovering a small amount of water-soluble volatile components contained in a large amount of wastewater by heating and raising the temperature of the wastewater itself and performing distillation.
[0002]
[Prior art]
One example of a known technique that is generally performed is a process as shown in the flowchart of FIG. 3, in which the main components are a liquid-liquid heat exchanger (2), a first distillation column (15), and a second distillation column (15). 28).
Each of the distillation columns (15) and (28) has reboilers (17) and (30) at the bottom of each column, condensers (16) and (29) at the top of each column, and a reflux condenser (21) and (33), and between them (19), (20), (22), (27), (18) and (31), (32), (34), (35), ( 36). In the first step of this process, a large amount of raw wastewater (1) containing a small amount of water-soluble volatile components is passed through the low-temperature side of the liquid-liquid heat exchanger (2), while the remaining liquid in the second step is supplied to the high-temperature side. The indirect heat exchange is performed by flowing the high-temperature wastewater (38) collected from the vessel (37) to obtain a heated wastewater (3) and a low-temperature wastewater (5).
The first distillation column (15) and the second distillation column (28) constituting the second step are both known continuous distillation columns. First, (3) is supplied to the middle stage of (15), and the inside of the column is supplied. While flowing down, it comes into countercurrent contact with the steam heated by the boiler (17) from the bottom of the tower, flows toward the top of the tower containing volatile components, and is distilled as distillate vapor (19) from the pipe and condensed by the condenser (16). Then, a distillate (27) is obtained via a reflux condenser (21). At this time, a kettle effluent (18) containing no volatile components is discharged from the bottom of the tower, becomes high-temperature wastewater (38) via a bottom residue receiver (37), passes through the high-temperature side of (2), and is discharged to wastewater (5). ).
At that time, when the data obtained on the amount of the raw wastewater (1) and the volatile components contained therein are not satisfactory, that is, when the residual concentration of the volatile components in the recovered liquid (27) and the wastewater (5) is not satisfactory, The second column (28) further provided with (27) is supplied to the middle stage to concentrate volatile components, and to obtain a result satisfying specifications.
[0003]
[Problems to be solved by the invention]
In the field where the above-mentioned [0002] is carried out, a large amount of raw wastewater is treated and the concentration of volatile components contained therein is often low, and the allowable volatile component concentration in the residual liquid obtained by separating it is as follows. A level of 100 ppm wt or less, sometimes 1 ppm wt or less, may be required. The most important issue in such a large amount of wastewater treatment is the economics of the process, in other words, how low-cost and energy-saving equipment can be realized.
[0004]
For example, suppose that the example of the known process according to FIG. 3 described in [0002] is applied when the raw wastewater (1) is 100 m ³ / h and the water temperature is 25 ° C. In that case, it is necessary to first heat the hot wastewater (3) to the distillation column to 100 ° C, and the required heating amount during that time is

And a huge amount.
In order to reduce such a huge heating load, the installation of the liquid-to-liquid heat exchanger (2) shown in the figure is an indispensable means. If the temperature of (5) is reduced to 35 ° C. and used, the sensible heat component of 6.5 × 10 ⁶ kcal / h can be recovered and used. .5 / 7.5 = 87%. However, the equipment cost and operating cost of the liquid-liquid heat exchanger (2) that produces such effects are the next problems. In the above case, the dimension of the heat exchanger (2) to be installed is assumed to be a high-performance type having a heat transfer coefficient U = 1,000 kcal / m ² , h, ° C., and the average temperature difference of the heat transfer area. Even if the temperature is to be recovered to 10 ° C, the required heat transfer area is

Such a huge heat exchanger is required, and the equipment cost is enormous.
As described above using the known process shown in FIG. 3, the liquid-liquid heat exchanger (1) between the raw wastewater (1) in the first step and the high-temperature wastewater (38) of the bottom liquid generated in the second step is used. It is indispensable for energy saving to deviate from 2) the existing method of installing a heat exchanger and change it to a new heat exchange method with high efficiency, and it is necessary to solve how to reduce the cost. This is the first problem.
The second problem that needs to be solved next is that, in FIG. 3, the second step of subjecting hot wastewater (3) heated to around 100 ° C. to (2) in FIG. Steam saving of the first distillation column (15). (3) fed into the middle stage of (15) comes into contact with the rising steam cooked by the reboiler (17) while descending in the tower toward the bottom of the tower, and the total amount of volatile components is converted to steam. Moved to the top of the column, leaving (15) as distillate vapor (19), but at the same time, discharging a large amount of bottom liquid (18) at around 100 ° C where the volatile components disappeared from the bottom of the column Are the conditions imposed on the tower (15).
At this time, the heating energy required for the reboiler (17) of the first column, which is conventionally known, is enormous as shown in Table 2 below, and it is imperative to find a new process for greatly reducing this in the second step. It is a challenge that was given.
[0005]
Means for Solving the Problems and Problems to be Solved by the Invention
In order to achieve the above object, the present invention divides the entire process into a first process and a second process as shown in FIG. 1, and in the first process, the raw wastewater (1) is discharged from the second process. A new liquid-to-liquid heat exchange system is provided between the high-temperature wastewater (38) and economy is solved.
In the subsequent second step, the condensate (14), which has been preheated and heated in the first step, is first introduced into the middle stage of the first distillation column (15), and the distillate vapor (19) containing the total amount of volatile components is fed from the top of the column. Is sent to the high temperature side of the condenser (16) and cooled and condensed to obtain a distillate (27), and the recovered steam (24) generated by heat transfer on the low temperature side of (16) is sent to the steam compressor (25) The means for solving the problem is to pressurize and raise the temperature and blow into the bottom of the column (15) as a heating source to replace the heating by the reboiler (17). The problem to be solved by the invention is that the distillate (27) obtained at that time is further sent to the middle stage of the second distillation column (28) if necessary to obtain a distillate (35) having a predetermined concentration. is there.
[0006]
The above [0005] will be described in detail with reference to FIG.
Hara drainage (1) is usually supplied at ambient temperature under atmospheric pressure, the liquid volume has been appropriate to 100 m 3 / ^h than 5 m 3 ^{/ h,} no problem other than it. The liquid temperature is not particularly limited as long as it is a liquid of 0 ° C. or higher. The volatile component to be contained may be an organic compound having a boiling point lower than that of water (H ₂ O), or a substance which forms an azeotrope with water and is distilled at a lower temperature than water. The same is true for In the embodiment, in the organic system, alcohols such as methanol (CH ₃ OH), ketones such as acetone (C ₃ H ₆ O), and esters such as methyl acetate (C ₃ H ₆ O ₂ ) are used. In addition, there are ammonia (NH ₃ ) and the like in the inorganic system, but it is not limited to these.
[0007]
In the above-mentioned first step, the liquid-liquid heat exchanger (2) is a so-called indirect heat transfer system in which both high and low temperature liquids come into contact via a heat transfer surface to perform heat exchange. The structure can be any of a shell and tube type commonly used in the market, a plate heat exchanger type and a spiral type. As numerical values indicating these performances, the magnitude of the overall heat transfer coefficient U described in [0004] above is a guide.
When the present invention is applied to raw waste water with less contamination, it is desirable to select the flow rate of the liquid so as to obtain a performance of about U ≧ 1,000 kcal / m ² , h, ° C.
The steam ejector 1 composed of a flash can (6), a gas-liquid equilibrium can (12) and (9), (10) and (11) is juxtaposed with (2). The upper part of (12) is circulated through (8), (9) and (10). Fillers (7) and (13) are appropriately disposed at the center of (6) and (12), respectively, and the high-temperature wastewater (38) from the second step is dispersed over the entire surface of (7). Is irrigated downward. On the other hand, the vapor discharged from (10) is simultaneously mixed with the liquid flow of (3) and supplied downward to the entire surface of (13). Thus, each fluid passing through the surfaces of (7) and (13) reaches a vapor-liquid equilibrium under a predetermined pressure, and the flash vapor (8) reaches the saturation boiling point from (7) and the saturated boiling point from (13). The condensate (14) thus distilled out. On the other hand, the flash residual liquid (4) generated in (7) and discharged from the bottom of the can of (6) flows into the liquid-liquid heat exchanger (2) from the inlet on the high-temperature side, and exchanges heat with (1). After that, it flows out as wastewater (5).
[0008]
In the subsequent second step, the condensate (14) from the first step is supplied to a suitable middle stage of the first distillation column (15). Inside of (15), gas-liquid contact means with low pressure loss, for example, a low pressure loss type packing and appropriate column contents supporting the packing are installed. At the bottom of the column, in addition to the reboiler (17), pressurized steam A steam pipe for sending (26) is provided. The distillate vapor (19) from the top of the column (15) flows into the high temperature side of the condenser (16), is cooled to form a condensate (20), enters the reflux condenser (21), and has a predetermined reflux ratio. A portion is discharged below as a reflux liquid (22) at the top of (15) and the remainder as a distillate (27).
On the other hand, the makeup water (23) for cooling is supplied to the low-temperature side of (16) under reduced pressure, but is heated by the steam of (19) on the high-temperature side via the internal heat transfer surface and evaporates. The collected steam (24) is sucked and compressed by the steam compressor (25), becomes the pressurized steam (26) as described above, and is blown into the bottom of the column (15). In the ordinary distillation operation, as described above, the vapor generated at the bottom of the column (15) by the reboiler (17) comes into gas-liquid contact with the condensate (14) in the column, and is distilled as (19) from the top of the column. From (20) and (21) to (27) through (16), the second step of the present invention is to obtain the normal heating amount required for the reboiler (17) and the amount obtained by the above-mentioned steam compressor (25). Since the flow rate of the steam injected as the pressurized steam (26) is substantially the same in terms of calorific value, the presence of the reboiler (17) becomes unnecessary if (15) enters continuous steady operation. Further, even if a small amount of insufficient heat is generated in (17), it is sufficient to blow additional live steam corresponding to the small amount of heat into the bottom of the tower.
In this way, the first distillation column (15) recycles the heat of condensation (19) recovered at (16) at the top of the column without using the heat required for its operation by heating by the reboiler (17). A distillation method based on a known principle of a heat pump (for example, in which a recovered steam (24) is obtained in place of the heat of evaporation of (23), and then pressurized by a steam compressor (25) and directly blown into the bottom of (15)) By adopting [Japanese Patent Publication No. 57-209602], it is possible to achieve significant energy saving of the first tower (15) in the second step.
[0009]
In the first distillation column (15) in the second step, the volatile components of the obtained bottoms liquid (18) are reduced to a specified low concentration and the distillate (27) is simultaneously obtained at a specified high concentration, There is a theoretical or practical limit depending on the initial concentration of the volatile components contained in the raw wastewater (1).
Therefore, in such a case, the operating conditions of the first distillation column (15) are relaxed, and the concentration of volatile components in the distillate (27) is suppressed to a low level while keeping only the bottoms (18) at the specified concentration. After that, it is effective to provide a second distillation column (28) in response thereto and to adapt the distillate (35) and the bottoms (36) to the specifications of the specified volatile components, respectively.
[0010]
Embodiments of the Invention and Effects of the Invention
As described in [Claim 1] and [Claim 2], an element constituting the present invention includes a first step and a second step.
The present inventor considers that it is preferable that the [embodiment] and the [effect] of the invention be displayed as numbers in a table having a list, and the explanation will be given as such.
[0011]
As an example of the flow sheet of the known process of FIG. 3, a large amount of raw wastewater (1) containing a trace amount of methanol (CH ₃ OH) is separated by distillation, and high-concentration methanol is distilled off (35). In addition, a process for obtaining wastewater (5) containing almost no wastewater as the bottom liquid (38) is selected, and various embodiments of the present invention will be described below with reference to this as a reference point to compare the effects of the present invention. First, Table 1 shows known specifications for FIG.

[0012]
Using the standard specification data shown in Table 1, in Table 2, only the known standard process shown in FIG. 3 and its first process are described in a new heat exchange system as shown in [Claim 1] and [Claim 2]. 4 shows the new process of FIG.
In addition, the effect of the present invention will be described with reference to figures by comparing FIG. 4 with the known standard system of FIG.
It should be noted in Table 2 that both use a total of five heat exchangers (2), (16), (17), (29) and (30), but the efficiency of their use Is different. In terms of the heat exchange amount, the total value of the four heat exchangers (16), (17), (24) and (30) belonging to the two towers in the second step is about 22.5 × 10 ⁶ kcal / h.
This value is about 3.3 times the 6.86 × 10 ⁶ kcal / h of the heat exchange charge of the known liquid-liquid heat exchanger (2) in FIG. 3 belonging to the first step. Conversely when viewed from the heat transfer area (2) and 1,270M ^2, the second step (16), (17), (29), 2.8 times of four of the total value 455m ² (30) Pay attention to the huge point that reaches even. When this is evaluated in terms of the amount of heat exchange per 1 m ² of the heat transfer area, the liquid-liquid heat exchanger (2) used in the known standard method of FIG. 10 means how low it is.

[0013]
According to Table 2, the overall heat transfer coefficient described in [0007] for the liquid-liquid heat exchanger (2) is kept at the same U = 1,000 kcal / m ² , h, and C, and By changing from the known standard method to the new heat exchange method shown in FIG. 4 of the embodiment, the heat exchange amount is reduced to 65%, while the temperature difference is increased by 2.6 times. 344m ² and reduced to once to 1/4 from 1280M ² known standard method, in terms of equipment cost is expected breakthrough cost. On the other hand, when looking at the steam consumption of both of the second steps as an energy saving effect, there is no substantial change in the specification conditions assigned to the first tower and the second tower, and FIG. 3 and FIG. 0.1 to 22.9 ton / h, and the consumption of the steam ejector 1 in FIG. 4 is 2.1 ton / h, which is about 10%, which is larger than that in the known standard method without it. . When judging the economic efficiency based on these figures, as the amount of raw wastewater (1) becomes large, the required heat transfer area of the liquid-liquid heat exchanger (2) using the new heat exchanger system in FIG. This method is more economically advantageous than the known standard method shown in FIG. 3 even if the drive steam (11) of the steam ejector 1 is slightly added.
[0014]
[0012] In the first step constituting the present invention, a large-scale heat recovery can be performed at a low cost by introducing a new heat exchange method not shown in the known process FIG. 3 as shown in FIG. It was shown that it can be implemented by investing in equipment costs. On the other hand, the processes shown in FIG. 1 and FIG. 2 in Table 3 use the new heat exchange method described in the first step of FIG. In addition, the second step also drastically changes the format of FIG. That is, the conditions of claims 1, 2 and 3 are applied to the entire process of the first and second steps in the process of FIG. 1 and the conditions of claims 1, 2, 3 and 4 are applied to the process of FIG. By applying this method, it is possible to achieve a significant energy saving effect in each process and an economic effect due to a reduction in equipment costs.
[0015]
Embodiment Description of FIG. 1 is as already described in [0008] above.
On the other hand, the process of the embodiment shown in FIG. 2 is greatly different from that of FIG. 1 in the configuration of the second step as follows. That is, as shown in [Claim 4], the recovered steam (24) discharged from the low temperature side of the condenser (16) of the first distillation column (15) is sent to the suction section (39) of the newly installed steam ejector 2. The steam flows in along with the drive steam (41), passes through the dephasor (40), and becomes a discharge steam (42) from its tip, and is sucked and compressed by the low-compression-ratio steam compressor (25). 26) to the distribution valve (43). (26) is divided into two parts by a distribution valve (43), a part of which is sent as blown steam (44) to the bottom of the first distillation column (15), and the remainder to the bottom of the second distillation column (28) As steam (45). Thereby, as for the distillation columns (15) and (28), the amount of heating by the attached reboilers (17) and (30) is drastically reduced or unnecessary. That is, the recovered steam (24) from the first distillation column (15) and the driving steam (41) for the steam ejector 2 are added, and recovered and used by the heat pump method of claim 4, thereby obtaining the first distillation column ( It is possible to cover not only 15) but also the heating amount of the second distillation column (28).

As described above, the second step of the process of FIG. 2 is a step of converting the finally obtained distillate (35) and the bottom discharge (36) while responding to the fluctuation of the condensate (14) supplied to (15). The control can be performed by simultaneously controlling the amount of steam (41) for driving the steam ejector 2 and then controlling the compression ratio of the steam compressor (25) so that the concentration satisfies the predetermined specification.
[0016]
In the column of [Embodiment] of Table 3, the expected operation results of each main device are listed for the example of the process of FIGS. 1 and 2, and the examples described in Table 2 above are also listed. It is comparatively examined including it. In the following [Effect] column, the steam amount and the electric energy, which are the main energy consumptions corresponding to each case, are estimated.
It should be noted that the power consumption of the steam compressor (25) has been drastically reduced to about 1/8 of that of FIG. 1 in FIG. 2, while the steam consumption is almost the same. This, in addition to the steam ejector 2 greatly assisting in lowering the compression ratio of the subsequent steam compressor, the exhaust steam of the driving steam (41) is added as (44) and (45), so that the first tower and the second tower are discharged. This is because it is used for heating the tower.
[0017]
In Table 4, the total of four processes corresponding to FIGS. 3 and 4 shown in Table 2 and corresponding to FIGS. 1 and 2 shown in Table 3 are collectively related to the energy consumption of each step. We have listed the expected numbers and compared their economics.

Assuming that the unit price for industrial use as of August 2002 is 3,000 yen / ton for steam and 17 yen / kWh for electric power, the economics of the processes in FIGS. 1 and 2 in Table 3 are significantly higher. .
[0018]
In the process shown in FIG. 5, first, a large amount of raw gas (46) such as air containing a water-soluble volatile component is sent from the bottom of the absorption tower (48) by a blower (51), and the absorption liquid (49) is irrigated from the top of the tower. The present invention relates to a known process for obtaining a waste gas (47) and a recovered liquid (50) by performing absorption of the above-mentioned volatile components into (49) by gas-liquid mixing and contact in a column by liquefaction. . [Claim 5] utilizes the method of [Claim 1] to [Claim 4] to economically treat the recovered liquid (50) obtained in FIG. 5 and to obtain the obtained wastewater ( 5) The scope of the present invention is to return to the absorption tower (48) as the absorbing liquid (49) and reuse it. Table 5 summarizes [Embodiments] by connecting to FIG. 5 and connecting the subsequent stage to the process of FIG.

This absorbing liquid is to be processed as it is according to the process shown in FIG.
However, in FIG. 2, since the makeup water (23) and the driving steam (41) and (41) are supplied as water in the system in the second step, the wastewater (5) is replaced by the corresponding amount as the wastewater (52). After the removal, the absorbing solution (49) is adjusted to 50.9 t / h at 35 ° C. and used as described above.
[Brief description of the drawings]
FIG. 1 shows a first step and a second step as described in [Claim 1]. The first step uses a new heat exchange method, and the second step uses a heat pump method using a vapor compressor. Flow sheet for the process you want to do.
FIG. 2 is a flow sheet of a process for connecting a steam ejector 2 in series to the vapor compressor in the second step of the process of FIG. 1 as described in [Claim 4].
FIG. 3 is a flow sheet of a known process in which a small amount of a water-soluble volatile component contained in a large amount of wastewater is heated and distilled to separate and recover.
FIG. 4 is a flow sheet of a process for improving economic efficiency by applying a liquid-liquid heat exchange method to the known process of FIG. 3 as shown in [Claim 2].
FIG. 5 is a flowchart showing a process of supplying a recovered liquid, in which water-soluble volatile components contained in a raw gas are absorbed into water, as raw waste water to the first step in FIG. 1 or FIG. Sheet.
[Explanation of symbols]
Reference Signs List 1 raw wastewater 27 distillate 2 liquid heat exchanger 28 second distillation column 3 hot drainage 29 condenser 4 flash residue 30 reboiler 5 wastewater 31 distillate vapor 6 flash can 32 condensate 7 filling 33 Refluxer 8 Flash vapor 34 Reflux 9 Suction unit 35 Distillate 10 Diffuser 36 Bottom discharge 11 Driving steam 37 Bottom residue receiver 12 Gas-liquid equilibrium can 38 High temperature wastewater 13 Filling 39 Suction unit 14 Condensation Liquid 40 Diffuser 15 First distillation column 41 Driving steam 16 Condenser 42 Discharged steam 17 Reboiler 43 Distributing valve 18 Discharge in kettle 44 First column steam pipe 19 Same distillate 45 Second column steam pipe 20 Condensate 46 Raw gas 21 return Refrigerator 47 Waste gas 22 Reflux liquid 48 Absorption tower 23 Makeup water 49 Absorbent liquid 24 Recovered steam 50 Recovered liquid 25 Steam compressor 51 Blower 26 Pressurized steam 52 Wastewater P1, P2, P3, P4 Liquid pumps 9, 10, 11 configures the steam ejector 1 39, 40, 41 configures the steam ejector 2

Claims (5)

In the flowchart shown in FIG. 1, the first step is a liquid-liquid heat exchanger (2), a flash can (6), a filling (7) and a suction unit (9), a diffuser (10), and a driving steam (11). A steam group consisting of a steam ejector 1, a gas-liquid equilibrium can (12), a packing (13), and liquid feed pumps (P1, P2, P3) and a pipe group connecting them and the like or a substance flowing therethrough (1), (3), (4), (5), (8), (14), and (38). The raw wastewater (1) to be introduced and the high-temperature wastewater discharged from the second step described below ( 38) to perform a complex heat exchange to obtain a condensate (14) having a high temperature close to the boiling point. The second step following this is a first distillation column (15) and a condenser (16). , The recirculator (21), the reboiler (17), the vapor compressor (25), the second The components of the distillation tower (28), the condenser (29), the recirculator (33), the reboiler (30), and the bottom liquid receiver (37), and the piping group or the interior connecting them (14), (18), (19), (20), (22), (23), (24), (26), (27), (31), (32), (34) ), (35), (36), and (38). The raw wastewater (1) is received as a condensate (14), and the volatile components therein are concentrated and recovered in each of the distillation columns (15) and (28). To obtain a distillate (35), and circulate the high-temperature bottom liquids (18) and (36) generated from each column as high-temperature wastewater (38) via a bottom residual liquid receiver (37) to the first step. And heat exchange with the raw wastewater (1) by the heat exchange method described above, wherein water-soluble volatile components in the wastewater are separated and recovered. How to. In the first step of claim 1, the low temperature raw wastewater (1) sent by P1 exits the flash can (6) while passing through the liquid-liquid heat exchanger (2) and is fed by P2. The temperature is raised by performing indirect heat exchange with the flash residual liquid (4), and is supplied to the upper part of the gas-liquid equilibrium can (12) as hot waste water (3). ) Is sent to the upper part of the flash can (6) through P3, and is irrigated on the surface of the filling (7) and, while descending, of the steam ejector 1 constituted by (9), (10), and (11) Under the reduced pressure generated in the flash can (6) by the action, a part of the flash can (6) undergoes adiabatic evaporation and is recovered as flash residual liquid (4) from the bottom of (6) and sent to (2) as described above. Flash steam generated in (7), used as a heating source in (1) 8) is sucked from the suction part (9), and the mixed steam which is combined with the driving steam (11) and diffused from the tip of the diffuser (10) is sent to the vapor-liquid equilibrium can (12) together with the hot waste water (3). In the middle stage of the first distillation column (15) in the second step, the condensate (14), which has been brought into contact with each other on its surface and mixed to reach the boiling point of gas-liquid equilibrium when passing through the packing (13), is mixed. The method for separating and recovering water-soluble volatile components in wastewater according to claim 1, which is sent. In the second step of the first aspect, the distillate vapor (19) generated by the ascending vapor from the bottom of the first distillation column (15) is led to the high-temperature side passage of the condenser (16) and is subjected to indirect heat exchange. After cooling to obtain the condensate (20), the low-temperature side of the condenser (16) is appropriately removed when the condensate (20) is subsequently separated into the reflux liquid (22) and the distillate (27) by the reflux condenser (21). Under the regulated reduced pressure, a supply water (23) for cooling is supplied, and (23) is heated through a heat transfer surface to boil and evaporate to recover steam (24), and then to a steam compressor (24). If the pressure is increased by 25) and the steam is directly blown into the bottom of (15) as pressurized steam (26) and used as a heating source for the first column, the required amount of heat of the reboiler (17) can be reduced or completely eliminated. 3. The method according to claim 1, further comprising: Method for separating and recovering water-soluble volatile components in the waste water. In the flowchart shown in FIG. 2, the recovered steam (24) generated under reduced pressure from the condenser (16) attached to the first distillation column (15) is sent to the suction unit (39) constituting the steam ejector 2 to be newly added. Then, after the discharge steam (42) passing through the diffuser (40) is obtained by being combined with the driving steam (41), the discharge steam (42) is further increased to a predetermined pressure by a low-compression steam compressor (25). After obtaining the pressurized steam (26), it is divided by the distribution valve (43), one of which is blown into the bottom of each column from the first column steam pipe (44) and the other from the second column steam pipe (45). 3. The method according to claim 1, wherein the required amount of heat of the reboilers (17) and (30) of each tower is greatly reduced or completely eliminated. Method. In the flowcharts shown in FIGS. 1 and 2, the wastewater (5) generated in the first step is partly discarded out of the system as shown in the flowchart of FIG. Is irrigated as an absorbing solution (49) at the top of the column, and the raw gas (46) containing a water-soluble volatile component supplied from the bottom of the column by a blower (51) is brought into countercurrent gas-liquid contact in the column. A recovery liquid (50) containing a volatile component is obtained from the bottom of the tower, and supplied to the first step as raw wastewater (1) by P1 to contain the volatile component contained therein. The method according to claim 4, wherein the wastewater (5) generated in the first step is partly supplied to the absorption tower (48) as an absorption liquid (49) by P4 as described above. Water-soluble volatile components contained in the raw gas The method for separating and recovering the volatile components in the waste water.

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