JP3754953B2

JP3754953B2 - Salt making method and salt making apparatus

Info

Publication number: JP3754953B2
Application number: JP2002336601A
Authority: JP
Inventors: 武志三好; 洋一重
Original assignee: Kimura Chemical Plants Co Ltd
Current assignee: Kimura Chemical Plants Co Ltd
Priority date: 2002-11-20
Filing date: 2002-11-20
Publication date: 2006-03-15
Anticipated expiration: 2022-11-20
Also published as: JP2004166605A

Description

【０００１】
【発明の属する技術分野】
本願発明は、製塩方法及び製塩装置に関し、詳しくは、石膏の含有量を制御して、所望の石膏を含む塩を効率よく製造することが可能な製塩方法及び製塩装置に関する。
【０００２】
【従来の技術】
海水を濃縮し、塩を得る場合、その製法や用途により塩の組成は大きく異なる。
海水中には、代表成分とされるＮａＣｌ以外にも多くの成分が含まれており、これらの成分（以下、ミネラル分ともいう）は、人の生命維持に有用な成分とされている。従って、海水をそのまま濃縮し全量を乾燥させて得られる自然塩は、海水中の全てのミネラルが含まれているため健康上の見地から望ましいものである。
【０００３】
ところで、海水中に含まれるミネラル分の一つに石膏（ＣａＳＯ₄）があり、製品塩中の石膏の存在はミネラル分としての価値だけでなく、味覚の面からも価値が高いものである。
【０００４】
【発明が解決しようとする課題】
しかしながら、石膏は塩を水に溶かして使用する場合に、濁りの原因となるため、歓迎されない場合がある。
【０００５】
また、石膏の存在は、塩と同時に生産される貴重な副生物である苦汁の濁りの原因ともなる。
【０００６】
本願発明は、上記実情に鑑みてなされたものであり、石膏の含有量を制御して、所望の石膏を含む塩を効率よく製造することが可能で、水に溶かして使用する場合に濁りが生じず、また、副成物として濁りのない苦汁を得ることが可能な製塩方法及び製塩装置を提供することを目的とする。
【０００７】
【課題を解決するための手段】
上記目的を達成するために、本願発明（請求項１）の製塩方法は、
海水を、逆浸透膜法、イオン交換膜法などの相変化を伴わない方法で一次濃縮する一次濃縮工程と、
一次濃縮工程で濃縮された一次濃縮液を蒸発させて二次濃縮することにより、石膏を含む塩を析出させる二次濃縮工程と、
二次濃縮工程からの、石膏を含む塩が析出した二次濃縮液の一部について固液分離を行い、製品となる塩を回収するとともに、塩が分離された後の塩分離液を二次濃縮工程に循環供給する塩回収工程と、
二次濃縮工程からの、石膏を含む塩が析出した二次濃縮液の一部を、前記一次濃縮工程で濃縮された一次濃縮液と混合して二次濃縮液中に析出した石膏の主要部分を溶解させることなく塩を溶解させる塩溶解工程と、
前記塩溶解工程で溶解しなかった石膏を分離するとともに、石膏が分離された石膏分離液を二次濃縮工程に供給する石膏分離工程と
を具備することを特徴としている。
【０００８】
本願発明（請求項１）の製塩方法は、上述のように、一次濃縮工程と、一次濃縮工程で濃縮された一次濃縮液を蒸発させて二次濃縮することにより、石膏を含む塩を析出させる二次濃縮工程と、二次濃縮液（塩スラリー液）の一部について固液分離を行い、製品となる塩を回収するとともに、塩が分離された後の塩分離液を二次濃縮工程に循環供給する塩回収工程と、石膏を含む塩が析出した二次濃縮液の一部を一次濃縮液と混合して、二次濃縮液中に析出した石膏の主要部分を溶解させることなく塩を溶解させる塩溶解工程と、塩溶解工程で溶解しなかった石膏を分離するとともに、石膏が分離された石膏分離液を二次濃縮工程に供給する石膏分離工程とを備えているので、石膏分離工程で分離する石膏の量を制御して製品である塩に含まれる石膏の量を調整することが可能になり、水に溶かして使用する場合にも濁りが生じないような、所望の石膏を含む塩を効率よく製造することが可能になるとともに、副成物として濁りのない苦汁を得ることが可能になる。
【０００９】
また、請求項２の製塩方法は、前記一次濃縮液は、海水が１．５〜２．５倍に濃縮されたものであり、前記二次濃縮液は、石膏を含む析出塩の含有率が３〜１０重量％のものであることを特徴としている。
【００１０】
一次濃縮濃縮工程で、海水を１．５〜２．５倍に濃縮するとともに、二次濃縮工程で、石膏を含む析出塩の含有率（スラリー濃度）が３〜１０重量％になるまで濃縮することにより、二次濃縮液の一部を、一次濃縮液と混合して二次濃縮液中に析出した石膏の主要部分を溶解させることなく塩（石膏以外の析出塩）を溶解させて、製品である塩に含まれる石膏の量を効率よく調整することが可能になり、水に溶かして使用する場合に濁りが生じないような、所望の石膏を含む塩を効率よく製造することが可能になるとともに、濁りのない苦汁を副成物として得ることが可能になる。
【００１１】
また、請求項３の製塩方法は、二次濃縮液をスラリータンクに溜め、底部から粒径が大きく食塩リッチの固形分を含むスラリーを抜き出して前記塩回収工程に供するとともに、上部から粒径が小さく石膏リッチの固形分を含むスラリーを抜き出して前記塩溶解工程に供することを特徴としている。
【００１２】
二次濃縮液をスラリータンクに溜め、底部から粒径が大きく食塩リッチの固形分を含むスラリーを抜き出して塩回収工程に供するとともに、上部から粒径が小さく石膏リッチの固形分を含むスラリーを抜き出して塩溶解工程に供することにより、石膏の分離効率を高めて、所望の石膏を含む塩を効率よく製造することが可能になる。
【００１３】
また、請求項４の製塩方法は、前記二次濃縮液の、(ａ)塩回収工程に供される部分Ａと、(ｂ)塩溶解工程に供される部分Ｂの割合（Ａ：Ｂ）が重量比で、１：１〜１：３の範囲にあることを特徴としている。
【００１４】
二次濃縮液（塩スラリー液）の、(ａ)塩回収工程における固液分離に供される部分Ａと、(ｂ)塩溶解工程における一次濃縮液との混合による塩の溶解に供される部分Ｂの割合（Ａ：Ｂ）を重量比で、１：１〜１：３の範囲とすることにより、水に溶かして使用する場合にも石膏による濁りが生じないような、実用に適した塩を効率よく製造することが可能になるとともに、濁りのない苦汁を副成物として得ることが可能になる。
【００１５】
また、請求項５の製塩方法は、前記二次濃縮工程では５５〜６５℃の温度条件で蒸発濃縮・晶析を行い、前記塩溶解工程では４３〜５３℃の温度条件で塩の溶解を行うことを特徴としている。
【００１６】
二次濃縮工程では５５〜６５℃の温度条件で蒸発濃縮・晶析を行い、塩溶解工程では４３〜５３℃の温度条件で塩の溶解を行うことにより、製品である塩に含まれる石膏の量を効率よく調整することが可能になり、水に溶かして使用する場合にも石膏による濁りが生じないような、実用に適した塩を効率よく製造することが可能になるとともに、濁りのない苦汁を副成物として得ることが可能になる。
【００１７】
なお、請求項１〜５の製塩方法を適用することにより、海水中の石膏のうちの任意の割合の石膏を製品である塩に含有させる（言い換えると、海水中の石膏のうちの任意の割合の石膏を除去する）ことが可能になり、所望の石膏を含有する塩を効率よく製造することが可能になる。
【００１８】
また、本願発明（請求項６）の製塩装置は、
海水を相変化を伴うことなく一次濃縮する一次濃縮手段と、
一次濃縮手段により濃縮された一次濃縮液を連続的に蒸発して濃縮・晶析を行う蒸発晶析缶と、
前記蒸発晶析缶において石膏を含む塩を析出させた二次濃縮液を溜めるスラリータンクと、
前記スラリータンク内の二次濃縮液の一部について固液分離を行い、製品となる塩を回収するとともに、塩が分離された後の塩分離液を蒸発晶析缶に循環供給する固液分離手段と、
前記スラリータンク内の石膏を含む塩が析出した二次濃縮液の一部を前記一次濃縮手段により濃縮された一次濃縮液と混合して、二次濃縮液中に析出した石膏の主要部分を溶解させることなく塩を溶解させる塩溶解タンクと、
前記塩溶解タンク内の石膏を含む塩溶解液から石膏を分離するとともに、石膏が分離された石膏分離液を蒸発晶析缶に供給する石膏分離手段と
を具備することを特徴としている。
【００１９】
また、本願発明（請求項６）の製塩装置は、上述のように、一次濃縮手段と、蒸発晶析缶（二次濃縮手段）と、スラリータンクと、二次濃縮液の一部について固液分離を行い、製品となる塩を回収するとともに、塩が分離された後の塩分離液を蒸発晶析缶（二次濃縮手段）に循環供給する固液分離手段と、二次濃縮液（塩スラリー液）の一部を一次濃縮液と混合して、二次濃縮液中に析出した石膏の主要部分を溶解させることなく塩を溶解させる塩溶解タンクと、塩溶解タンク内の石膏を含む塩溶解液から石膏を分離するとともに、石膏が分離された石膏分離液を蒸発晶析缶（二次濃縮手段）に供給する石膏分離手段とを具備しているので、本願発明の製塩方法を効率よく実施して、水に溶かして使用する場合にも石膏による濁りが生じないような、実用に適した塩を効率よく製造することが可能になるとともに、濁りのない苦汁を副成物として得ることが可能になる。
【００２０】
【発明の実施の形態】
以下、本願発明の実施の形態を示してその特徴とするところをさらに詳しく説明する。
【００２１】
図１は、本願発明の一実施形態にかかる製塩方法を実施するために用いられる製塩装置を示す図である。
【００２２】
この製塩装置は、
(ａ)海水を相変化を伴うことなく一次濃縮する一次濃縮手段（この実施形態では逆浸透膜法による濃縮装置）１と、
(ｂ)一次濃縮液タンク１４から供給される一次濃縮液を連続的に蒸発して濃縮・晶析を行う蒸発晶析缶（二次濃縮手段）２と、
(ｃ)蒸発晶析缶（二次濃縮手段）２において石膏（ＣａＳＯ₄）を含む塩を析出させた二次濃縮液（塩スラリー液）を溜めるスラリータンク３と、
(ｄ)スラリータンク３内の二次濃縮液の一部について固液分離を行い、製品となる塩を回収するとともに、塩が分離された後の塩分離液を母液タンク１３を経て蒸発晶析缶（二次濃縮手段）２に循環供給する固液分離手段（この実施形態では遠心分離器）４と、
(ｅ)スラリータンク３内の石膏を含む塩が析出した二次濃縮液（塩スラリー液）の一部を一次濃縮手段１により濃縮された一次濃縮液と混合して、二次濃縮液中に析出した石膏の主要部分を溶解させることなく塩を溶解させる塩溶解タンク５と、
(ｆ)塩溶解タンク５内の石膏を含む塩溶解液から石膏を分離するとともに、石膏が分離された石膏分離液を濾液タンク１０を経て蒸発晶析缶（二次濃縮手段）２に供給する石膏分離手段（脱水濾過器）６と
を備えている。
【００２３】
なお、濃縮晶析缶２はヒータ１１を通過しながら液が循環することにより連続的な蒸発と晶析が行われ、蒸発蒸気はコンデンサ１２で冷却され、排水として系外に排出されるように構成されている。
【００２４】
次に、上記のように構成された製塩装置を用いて製塩を行う方法について説明する。
(１)表１に示すような組成の海水を逆浸透膜法による濃縮装置（一次濃縮手段）１により２．０倍に濃縮して、表２に示すような組成の一次濃縮液を得る。
【００２５】
【表１】

【００２６】
【表２】

【００２７】
(２)それから、一次濃縮手段１により濃縮された海水は蒸発晶析缶（二次濃縮手段）２において、真空度８３．７Torr（１１．２ｋＰａ）、温度６０℃の条件下で連続的に蒸発され、スラリーを３〜１０ｗｔ％含んだ高濃縮海水（二次濃縮液）にまで濃縮される。
析出塩類を除いた二次濃縮液の組成の一例を表３に示す。
【００２８】
【表３】

【００２９】
この高濃縮海水（二次濃縮液）から析出塩類を除いたものがいわゆる苦汁であり、このように高濃度に濃縮された苦汁は石膏に対してほとんど溶解度を持たない。
【００３０】
(３)そして、析出塩類（スラリー）を含んだ二次濃縮液（苦汁）は、蒸発晶析缶２からポンプで抜き出され、スラリータンク３に供給される。ここでは、粒径の大きい結晶は沈降し、微細な結晶は沈降しにくいため、結晶が分級されることになる。
【００３１】
(４)スラリータンクの底部から抜き出された粒径の大きい食塩リッチの結晶は、遠心分離器（固液分離手段）４で脱水分離されて製品の塩となる。一方、分離された濾液は、母液タンク１３を経由して、蒸発晶析缶２に戻される。なお、遠心分離器（固液分離手段）４で食塩リッチの結晶が分離された後の濾液は、濁りのない苦汁として回収することが可能である。
【００３２】
(５)スラリータンク３の上部から抜き出された結晶は塩溶解タンク５に送られ、一次濃縮手段１からの一次濃縮液（２倍濃縮の濃縮海水）と混合される。
なお、抜き出し量は、スラリータンク３の底部からの抜き出し量の約２．３倍に設定する。２倍濃縮の濃縮海水は溶解塩温度が低いため、塩溶解タンク５では塩の結晶は溶解する。石膏も一部溶解するが、主要部分は溶け残り、石膏を含むスラリー液となる。塩溶解タンク５では、液温４８℃、平均滞留時間２０minの条件で塩溶解操作を行う。
このスラリー液の組成の一例を表４に示す。表４に示すように、このスラリー液は、０．１２１重量％の石膏（ＣａＳＯ₄）を含有している。
【００３３】
【表４】

【００３４】
(６)石膏を含むスラリー液は、脱水濾過器（石膏分離手段）６に送られ、石膏の結晶と濾液とに分離される。濾液は蒸発結晶缶（二次濃縮手段）２に送られ、再び濃縮される。
【００３５】
上述のように、二次濃縮液の一部を遠心分離器４に供給して固液分離し、製品となる塩を回収するとともに、石膏を含む塩が析出した二次濃縮液の一部を、一次濃縮液と混合して二次濃縮液中に析出した石膏の主要部分を溶解させることなく塩を溶解させた後、溶解しなかった石膏を脱水濾過器（石膏分離手段）６で分離するようにしているので、石膏分離工程で分離する石膏の量を制御することにより、製品である塩に含まれる石膏の量を調整することが可能になり、水に溶かして使用する場合に濁りが生じないような、所望の石膏を含む塩を効率よく製造することができるようになるとともに、副成物として濁りのない苦汁を得ることができるようになる。
【００３６】
なお、上記実施形態では一次濃縮手段１として逆浸透膜法による濃縮装置を用いているが、他の方法を用いることも可能である。
また、上記実施形態では、一次濃縮手段１により海水を２．０倍に濃縮するようにしているが、本願発明の範囲内において濃縮倍率を調整することが可能である。
また、上記実施形態では、蒸発晶析缶（二次濃縮手段）２で、８３．７Torr、６０℃の条件で蒸発晶析操作を行っているが、本願発明の範囲内で条件を変化させることが可能である。
また、上記実施形態では、塩溶解タンク５において、液温４８℃、平均滞留時間２０minの条件で塩溶解操作を行っているが、本願発明の範囲内で条件を調整することが可能である。
【００３７】
なお、本願発明はさらにその他の点においても上記実施形態に限定されるものではなく、製品となる塩を回収するための固液分離手段や石膏分離手段の構成や型式、製塩装置の具体的な運転条件などに関し、発明の範囲内において種々の応用、変形を加えることが可能である。
【００３８】
【発明の効果】
上述のように、本願発明（請求項１）の製塩方法は、一次濃縮工程と、一次濃縮工程で濃縮された一次濃縮液を蒸発させて二次濃縮することにより、石膏を含む塩を析出させる二次濃縮工程と、二次濃縮液（塩スラリー液）の一部について固液分離を行い、製品となる塩を回収するとともに、塩が分離された後の塩分離液を二次濃縮工程に循環供給する塩回収工程と、石膏を含む塩が析出した二次濃縮液の一部を一次濃縮液と混合して、二次濃縮液中に析出した石膏の主要部分を溶解させることなく塩を溶解させる塩溶解工程と、塩溶解工程で溶解しなかった石膏を分離するとともに、石膏が分離された石膏分離液を二次濃縮工程に供給する石膏分離工程とを備えているので、石膏分離工程で分離する石膏の量を制御して製品である塩に含まれる石膏の量を調整することが可能になり、水に溶かして使用する場合にも濁りが生じないような、所望の石膏を含む塩を効率よく製造することが可能になるとともに、副成物として濁りのない苦汁を得ることが可能になる。
【００３９】
また、請求項２の製塩方法のように、一次濃縮濃縮工程で、海水を１．５〜２．５倍に濃縮するとともに、二次濃縮工程で、石膏を含む析出塩の含有率（スラリー濃度）が３〜１０重量％になるまで濃縮するようにした場合、二次濃縮液の一部を一次濃縮液と混合して、二次濃縮液中に析出した石膏の主要部分を溶解させることなく塩（石膏以外の析出塩）を溶解させて、製品である塩に含まれる石膏の量を効率よく調整することが可能になり、水に溶かして使用する場合に濁りが生じないような、所望の石膏を含む塩を効率よく製造することが可能になるとともに、濁りのない苦汁を副成物として得ることが可能になる。
【００４０】
また、請求項３の製塩方法のように、二次濃縮液をスラリータンクに溜め、底部から粒径が大きく食塩リッチの固形分を含むスラリーを抜き出して塩回収工程に供するとともに、上部から粒径が小さく石膏リッチの固形分を含むスラリーを抜き出して塩溶解工程に供するようにした場合、石膏の分離効率を高めて、所望の石膏を含む塩を効率よく製造することが可能になる。
【００４１】
また、請求項４の製塩方法のように、二次濃縮液（塩スラリー液）の、(ａ)塩回収工程における固液分離に供される部分Ａと、(ｂ)塩溶解工程における一次濃縮液との混合による塩の溶解に供される部分Ｂの割合（Ａ：Ｂ）を重量比で、１：１〜１：３の範囲とした場合、水に溶かして使用する場合にも石膏による濁りが生じないような、実用に適した塩を効率よく製造することが可能になるとともに、濁りのない苦汁を副成物として得ることが可能になる。
【００４２】
また、請求項５の製塩方法のように、二次濃縮工程では５５〜６５℃の温度条件で蒸発濃縮・晶析を行い、塩溶解工程では４３〜５３℃の温度条件で塩の溶解を行うようにした場合、製品である塩に含まれる石膏の量を効率よく調整することが可能になり、水に溶かして使用する場合にも石膏による濁りが生じないような、実用に適した塩を効率よく製造することが可能になるとともに、濁りのない苦汁を副成物として得ることが可能になる。
【００４３】
また、本願発明（請求項６）の製塩装置は、一次濃縮手段と、蒸発晶析缶（二次濃縮手段）と、スラリータンクと、二次濃縮液の一部について固液分離を行い、製品となる塩を回収するとともに、塩が分離された後の塩分離液を蒸発晶析缶（二次濃縮手段）に循環供給する固液分離手段と、二次濃縮液（塩スラリー液）の一部を一次濃縮液と混合して、二次濃縮液中に析出した石膏の主要部分を溶解させることなく塩を溶解させる塩溶解タンクと、塩溶解タンク内の石膏を含む塩溶解液から石膏を分離するとともに、石膏が分離された石膏分離液を蒸発晶析缶（二次濃縮手段）に供給する石膏分離手段とを具備しているので、本願請求項１〜５のいずれかの製塩方法を効率よく実施して、水に溶かして使用する場合にも石膏による濁りが生じないような、実用に適した塩を効率よく製造することが可能になるとともに、濁りのない苦汁を副成物として得ることが可能になる。
【図面の簡単な説明】
【図１】本願発明の一実施形態にかかる製塩装置を示す図である。
【符号の説明】
１逆浸透膜法による濃縮装置（一次濃縮手段）
２蒸発晶析缶（二次濃縮手段）
３スラリータンク
４固液分離手段（遠心分離器）
５塩溶解タンク
６脱水濾過器（石膏分離手段）
１０濾液タンク
１１ヒータ
１２コンデンサ
１３母液タンク
１４一次濃縮液タンク[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a salt production method and a salt production apparatus, and more particularly, to a salt production method and a salt production apparatus capable of efficiently producing a salt containing a desired gypsum by controlling the content of gypsum.
[0002]
[Prior art]
When seawater is concentrated to obtain a salt, the composition of the salt varies greatly depending on the production method and application.
Seawater contains many components in addition to NaCl, which is a representative component, and these components (hereinafter also referred to as minerals) are useful components for maintaining human life. Therefore, natural salt obtained by concentrating seawater as it is and drying the whole amount is desirable from the viewpoint of health because it contains all minerals in seawater.
[0003]
By the way, gypsum (CaSO ₄ ) is one of the minerals contained in seawater, and the presence of gypsum in the product salt is not only valuable as a mineral content but also highly valuable in terms of taste.
[0004]
[Problems to be solved by the invention]
However, gypsum may not be welcomed because it causes turbidity when salt is used in water.
[0005]
The presence of gypsum also causes turbidity of bitter juice, a valuable by-product produced simultaneously with salt.
[0006]
The present invention has been made in view of the above circumstances, and it is possible to efficiently produce a salt containing the desired gypsum by controlling the content of gypsum, and it is turbid when used by dissolving in water. An object of the present invention is to provide a salt production method and a salt production apparatus capable of obtaining bitter juice which does not occur and is not turbid as a by-product.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the salt production method of the present invention (Claim 1) comprises:
A primary concentration step of primarily concentrating seawater by a method without phase change such as reverse osmosis membrane method and ion exchange membrane method;
A secondary concentration step of precipitating a salt containing gypsum by evaporating and concentrating the primary concentrate concentrated in the primary concentration step;
Part of the secondary concentrated liquid from which the gypsum-containing salt is deposited from the secondary concentration process is subjected to solid-liquid separation to recover the product salt, and the salt separation liquid after the salt is separated A salt recovery step for circulating supply to the concentration step;
The main part of the gypsum deposited in the secondary concentrated liquid by mixing a part of the secondary concentrated liquid from which the salt containing gypsum was deposited from the secondary concentrated process with the primary concentrated liquid concentrated in the primary concentrated process. A salt dissolving step for dissolving the salt without dissolving the salt,
A gypsum separation step of separating the gypsum not dissolved in the salt dissolution step and supplying a gypsum separation liquid from which the gypsum has been separated to the secondary concentration step.
[0008]
As described above, the salt production method of the present invention (Claim 1) precipitates a salt containing gypsum by evaporating and concentrating the primary concentrated solution concentrated in the primary concentration step and the primary concentration step. A secondary concentration step and a part of the secondary concentrated solution (salt slurry solution) are subjected to solid-liquid separation to recover the salt as a product, and the salt separated solution after the salt is separated into the secondary concentration step A salt recovery step to circulate and a part of the secondary concentrated solution in which the gypsum-containing salt is deposited are mixed with the primary concentrated solution, so that the salt is removed without dissolving the main part of the gypsum deposited in the secondary concentrated solution. The gypsum separation step includes a salt dissolution step for dissolving and a gypsum separation step for separating the gypsum not dissolved in the salt dissolution step and supplying the gypsum separation liquid from which the gypsum has been separated to the secondary concentration step. Control the amount of gypsum to be separated in the product salt It is possible to adjust the amount of gypsum to be produced, and it is possible to efficiently produce a salt containing a desired gypsum that does not cause turbidity even when dissolved in water and used as a by-product. As a result, it becomes possible to obtain a bitter juice without turbidity.
[0009]
Further, a method for salt production claim 2, wherein the primary concentrate, which seawater is concentrated 1.5-2.5 times, the secondary concentrate, the content of precipitated salts containing gypsum It is characterized by being 3 to 10% by weight.
[0010]
In the primary concentration and concentration step, seawater is concentrated 1.5 to 2.5 times, and in the secondary concentration step, it is concentrated until the content rate (slurry concentration) of the precipitated salt including gypsum becomes 3 to 10% by weight. By mixing a part of the secondary concentrated liquid with the primary concentrated liquid and dissolving the main part of the gypsum deposited in the secondary concentrated liquid, the salt (deposited salt other than gypsum) is dissolved, and the product It is possible to efficiently adjust the amount of gypsum contained in the salt, and it is possible to efficiently produce a salt containing the desired gypsum that does not cause turbidity when dissolved in water. It becomes possible to obtain bitter juice without turbidity as a by-product.
[0011]
Further, in the salt production method of claim 3, the secondary concentrated liquid is stored in a slurry tank, and a slurry containing a large salt-rich solid content is extracted from the bottom and used for the salt recovery step. A small slurry containing a gypsum-rich solid content is extracted and used for the salt dissolution step.
[0012]
The secondary concentrated liquid is stored in a slurry tank, and the slurry containing a large salt-rich solid content is extracted from the bottom and used for the salt recovery process, and the slurry containing a small gypsum-rich solid content is extracted from the top. By using the salt dissolution step, it is possible to increase the separation efficiency of gypsum and efficiently produce a salt containing the desired gypsum.
[0013]
Moreover, the salt production method of Claim 4 is the ratio (A: B) of the part A of the secondary concentrated solution that is subjected to (a) the salt recovery step and (b) the portion B that is subjected to the salt dissolution step. Is in the range of 1: 1 to 1: 3 by weight.
[0014]
The secondary concentrated liquid (salt slurry liquid) is used for dissolution of salt by mixing (a) part A used for solid-liquid separation in the salt recovery step and (b) primary concentrated liquid in the salt dissolution step. By setting the ratio of part B (A: B) in the weight ratio range of 1: 1 to 1: 3, it is suitable for practical use so that turbidity due to gypsum does not occur even when dissolved in water. It becomes possible to produce a salt efficiently, and to obtain a bitter juice without turbidity as a by-product.
[0015]
Further, in the salt production method of claim 5, in the secondary concentration step, evaporation concentration and crystallization are performed under a temperature condition of 55 to 65 ° C, and in the salt dissolution step, a salt is dissolved under a temperature condition of 43 to 53 ° C. It is characterized by that.
[0016]
In the secondary concentration step, evaporation concentration and crystallization are performed under a temperature condition of 55 to 65 ° C., and in the salt dissolution step, the salt is dissolved under a temperature condition of 43 to 53 ° C., so that the gypsum contained in the product salt is dissolved. It is possible to adjust the amount efficiently, and it is possible to efficiently produce a salt suitable for practical use that does not cause turbidity due to gypsum even when dissolved in water, and there is no turbidity It becomes possible to obtain bitter juice as a by-product.
[0017]
In addition , by applying the salt production method according to claims 1 to 5, an arbitrary proportion of gypsum in seawater is included in the product salt (in other words, any proportion of gypsum in seawater The salt containing the desired gypsum can be efficiently produced.
[0018]
Moreover, the salt production apparatus of the present invention (Claim 6 ) is:
Primary concentration means for primarily concentrating seawater without phase change;
And evaporation crystallization cans for concentrating, crystallization of the primary concentrate is concentrated continuously evaporated to the primary concentration unit,
A slurry tank for storing the secondary concentrate to precipitate a salt containing Oite gypsum to the evaporation crystallization can,
Subjected to solid-liquid separation for some of the secondary concentrate in the slurry tank, thereby recovering the product salt, the salt separated liquid after the salt has been separated solid circulate and supply the evaporation crystallization bottom liquid separation Means,
A part of the secondary concentrated liquid in which the salt containing gypsum in the slurry tank is precipitated is mixed with the primary concentrated liquid concentrated by the primary concentration means, and the main part of the gypsum precipitated in the secondary concentrated liquid is dissolved. A salt dissolution tank that dissolves the salt without letting
With separating gypsum from a salt solution containing gypsum of the salt dissolution tank, gypsum is characterized by comprising a gypsum separation means for supplying gypsum separation liquid separated in evaporation crystallization can.
[0019]
Further, as described above, the salt production apparatus of the present invention (Claim 6 ) is a solid-liquid solution for the primary concentration means, the evaporative crystallization can (secondary concentration means), the slurry tank, and a part of the secondary concentrate. A solid-liquid separation means for separating and recovering a salt as a product and circulatingly supplying the salt separation liquid after the salt is separated to an evaporative crystallization can (secondary concentration means); and a secondary concentrated liquid (salt) A salt dissolution tank in which a part of the slurry liquid is mixed with the primary concentrate to dissolve the salt without dissolving the main part of the gypsum deposited in the secondary concentrate, and the salt containing gypsum in the salt dissolution tank The gypsum separation means for separating the gypsum from the solution and supplying the gypsum separation liquid from which the gypsum has been separated to the evaporative crystallization can (secondary concentration means) is provided. When it is used and dissolved in water, it does not cause turbidity due to gypsum Thus, it is possible to efficiently produce a salt suitable for practical use and obtain a bitter juice without turbidity as a by-product.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the features of the present invention will be described in more detail with reference to embodiments of the present invention.
[0021]
FIG. 1 is a view showing a salt making apparatus used for carrying out a salt making method according to an embodiment of the present invention.
[0022]
This salt making device
(a) primary concentration means (primary concentration device by reverse osmosis membrane method in this embodiment) 1 for primarily concentrating seawater without phase change;
(b) an evaporative crystallization can (secondary concentrating means) 2 for concentrating and crystallizing by continuously evaporating the primary concentrated liquid supplied from the primary concentrated liquid tank 14;
(c) a slurry tank 3 for storing a secondary concentrated liquid (salt slurry liquid) in which a salt containing gypsum (CaSO ₄ ) is precipitated in the evaporative crystallization can (secondary concentration means) 2;
(d) A part of the secondary concentrated liquid in the slurry tank 3 is subjected to solid-liquid separation to collect a salt as a product, and the salt separated liquid after the salt is separated is evaporated and crystallized through the mother liquid tank 13. A solid-liquid separation means (in this embodiment, a centrifuge) 4 to be circulated and supplied to the can (secondary concentration means) 2;
(e) A part of the secondary concentrated liquid (salt slurry liquid) on which the salt containing gypsum in the slurry tank 3 is deposited is mixed with the primary concentrated liquid concentrated by the primary concentration means 1, and the resulting mixture is mixed into the secondary concentrated liquid. A salt dissolution tank 5 for dissolving the salt without dissolving the main part of the deposited gypsum,
(f) Gypsum is separated from the salt solution containing gypsum in the salt dissolution tank 5, and the gypsum separation solution from which the gypsum has been separated is supplied to the evaporative crystallization can (secondary concentration means) 2 through the filtrate tank 10. A gypsum separation means (dehydration filter) 6 is provided.
[0023]
The concentrated crystallization can 2 is continuously evaporated and crystallized as the liquid circulates while passing through the heater 11, so that the evaporated vapor is cooled by the condenser 12 and discharged out of the system as waste water. It is configured.
[0024]
Next, a method for producing salt using the salt production apparatus configured as described above will be described.
(1) Seawater having a composition as shown in Table 1 is concentrated 2.0 times by a concentrator (primary concentration means) 1 using a reverse osmosis membrane method to obtain a primary concentrated liquid having a composition as shown in Table 2.
[0025]
[Table 1]

[0026]
[Table 2]

[0027]
(2) Then, the seawater concentrated by the primary concentration means 1 is continuously evaporated in an evaporative crystallization can (secondary concentration means) 2 under the conditions of a vacuum degree of 83.7 Torr (11.2 kPa) and a temperature of 60 ° C. And concentrated to highly concentrated seawater (secondary concentrated liquid) containing 3 to 10 wt% of the slurry.
An example of the composition of the secondary concentrated liquid excluding the precipitated salts is shown in Table 3.
[0028]
[Table 3]

[0029]
The so-called bitter juice is obtained by removing the precipitated salts from the highly concentrated seawater (secondary concentrate), and the bitter juice concentrated in this way has almost no solubility in gypsum.
[0030]
(3) Then, the secondary concentrated liquid (bitter juice) containing the precipitated salts (slurry) is extracted from the evaporative crystallization can 2 by a pump and supplied to the slurry tank 3. Here, crystals with a large particle size settle, and fine crystals hardly settle, so the crystals are classified.
[0031]
(4) The salt-rich crystals having a large particle diameter extracted from the bottom of the slurry tank are dehydrated and separated into a product salt by the centrifuge (solid-liquid separation means) 4. On the other hand, the separated filtrate is returned to the evaporation crystallization can 2 via the mother liquor tank 13. The filtrate after the salt-rich crystals are separated by the centrifuge (solid-liquid separation means) 4 can be recovered as bitter juice without turbidity.
[0032]
(5) The crystal extracted from the upper part of the slurry tank 3 is sent to the salt dissolution tank 5 and mixed with the primary concentrated liquid (double concentrated concentrated seawater) from the primary concentration means 1.
The extraction amount is set to about 2.3 times the extraction amount from the bottom of the slurry tank 3. Since the double-concentrated concentrated seawater has a low dissolved salt temperature, salt crystals dissolve in the salt dissolution tank 5. The gypsum also partially dissolves, but the main part remains undissolved and becomes a slurry liquid containing gypsum. In the salt dissolution tank 5, the salt dissolution operation is performed under the conditions of a liquid temperature of 48 ° C. and an average residence time of 20 minutes.
An example of the composition of this slurry liquid is shown in Table 4. As shown in Table 4, this slurry liquid contains 0.121% by weight of gypsum (CaSO ₄ ).
[0033]
[Table 4]

[0034]
(6) The slurry liquid containing gypsum is sent to a dehydration filter (gypsum separating means) 6 and separated into gypsum crystals and filtrate. The filtrate is sent to the evaporation crystal can (secondary concentration means) 2 and concentrated again.
[0035]
As described above, a part of the secondary concentrated liquid is supplied to the centrifuge 4 and subjected to solid-liquid separation to recover the salt as a product, and a part of the secondary concentrated liquid on which the salt containing gypsum is deposited is removed. The salt is dissolved without dissolving the main part of the gypsum precipitated in the secondary concentrated liquid by mixing with the primary concentrated liquid, and then the undissolved gypsum is separated by a dehydrating filter (gypsum separating means) 6. Therefore, by controlling the amount of gypsum to be separated in the gypsum separation process, it becomes possible to adjust the amount of gypsum contained in the salt that is the product, and it becomes turbid when dissolved in water and used. It becomes possible to efficiently produce a salt containing a desired gypsum that does not occur, and to obtain a bitter juice without turbidity as a by-product.
[0036]
In the above embodiment, a concentrating device using the reverse osmosis membrane method is used as the primary concentrating means 1, but other methods can also be used.
Moreover, in the said embodiment, although the primary concentration means 1 concentrates seawater 2.0 times, it is possible to adjust a concentration magnification in the range of this invention.
In the above embodiment, the evaporation crystallization operation is performed in the evaporative crystallization can (secondary concentration means) 2 under the conditions of 83.7 Torr and 60 ° C., but the conditions are changed within the scope of the present invention. Is possible.
In the above embodiment, the salt dissolution operation is performed in the salt dissolution tank 5 under the conditions of a liquid temperature of 48 ° C. and an average residence time of 20 minutes. However, the conditions can be adjusted within the scope of the present invention.
[0037]
The invention of the present application is not limited to the above embodiment in other points as well, and the configuration and model of the solid-liquid separation means and the gypsum separation means for recovering the salt as a product, and the specific salt making device Various applications and modifications can be made within the scope of the invention with respect to operating conditions and the like.
[0038]
【The invention's effect】
As described above, the salt production method of the present invention (Claim 1) deposits a salt containing gypsum by evaporating and concentrating the primary concentrated solution concentrated in the primary concentration step and the primary concentration step. A secondary concentration step and a part of the secondary concentrated solution (salt slurry solution) are subjected to solid-liquid separation to recover the salt as a product, and the salt separated solution after the salt is separated into the secondary concentration step A salt recovery step to circulate and a part of the secondary concentrated solution in which the gypsum-containing salt is deposited are mixed with the primary concentrated solution, so that the salt is removed without dissolving the main part of the gypsum deposited in the secondary concentrated solution. The gypsum separation step includes a salt dissolution step for dissolving and a gypsum separation step for separating the gypsum not dissolved in the salt dissolution step and supplying the gypsum separation liquid from which the gypsum has been separated to the secondary concentration step. Control the amount of gypsum to be separated in the product salt It is possible to adjust the amount of gypsum to be produced, and it is possible to efficiently produce a salt containing a desired gypsum that does not cause turbidity even when dissolved in water and used as a by-product. As a result, it becomes possible to obtain a bitter juice without turbidity.
[0039]
Further, as in the salt production method according to claim 2, while concentrating seawater 1.5 to 2.5 times in the primary concentration step, the content of the precipitated salt containing gypsum (slurry concentration) in the secondary concentration step ) Is concentrated until it becomes 3 to 10% by weight, a part of the secondary concentrate is mixed with the primary concentrate without dissolving the main part of the gypsum deposited in the secondary concentrate. It is possible to dissolve the salt (deposited salt other than gypsum) and to adjust the amount of gypsum contained in the product salt efficiently, so that it does not become cloudy when used by dissolving in water It becomes possible to efficiently produce a salt containing gypsum of the above and to obtain a bitter juice without turbidity as a by-product.
[0040]
In addition, as in the salt production method of claim 3, the secondary concentrated liquid is stored in a slurry tank, and a slurry containing a large salt-rich solid content is extracted from the bottom and used for the salt recovery step. However, when a slurry containing a small amount of gypsum-rich solid is extracted and used for the salt dissolution step, it is possible to increase the separation efficiency of gypsum and to efficiently produce a salt containing the desired gypsum.
[0041]
Further, as in the salt production method of claim 4, the secondary concentrated liquid (salt slurry liquid) is subjected to (a) part A used for solid-liquid separation in the salt recovery step, and (b) primary concentration in the salt dissolution step. When the ratio of part B (A: B) used for dissolution of salt by mixing with liquid is in the range of 1: 1 to 1: 3 by weight, gypsum is also used when dissolved in water It is possible to efficiently produce a salt suitable for practical use that does not cause turbidity, and obtain bitter juice without turbidity as a by-product.
[0042]
Further, as in the salt production method of claim 5, in the secondary concentration step, evaporation concentration and crystallization are performed under a temperature condition of 55 to 65 ° C, and in the salt dissolution step, the salt is dissolved under a temperature condition of 43 to 53 ° C. In this case, it is possible to efficiently adjust the amount of gypsum contained in the salt that is the product, and when using it dissolved in water, a salt suitable for practical use that does not cause turbidity due to gypsum will be generated. It becomes possible to manufacture efficiently and to obtain bitter juice without turbidity as a by-product.
[0043]
The salt production apparatus of the present invention (Claim 6 ) performs solid-liquid separation on a primary concentration means, an evaporative crystallization can (secondary concentration means), a slurry tank, and a part of the secondary concentrate, A solid-liquid separation means that circulates the salt separation liquid after the salt is separated and supplies it to the evaporative crystallization can (secondary concentration means), and a secondary concentrated liquid (salt slurry liquid). The gypsum is mixed with the primary concentrated solution to dissolve the salt without dissolving the main part of the gypsum deposited in the secondary concentrated solution, and the salt dissolved solution containing gypsum in the salt dissolved tank. And a gypsum separation means for separating the gypsum separation liquid from which the gypsum has been separated into an evaporative crystallization can (secondary concentration means), so that the salt production method according to any one of claims 1 to 5 is performed. When used efficiently and dissolved in water, turbidity due to gypsum is not generated. No such practical salt it becomes possible to efficiently produce a suitable, it is possible to obtain a no turbidity bittern as-product thereof.
[Brief description of the drawings]
FIG. 1 is a diagram showing a salt making apparatus according to an embodiment of the present invention.
[Explanation of symbols]
1 Concentrator by reverse osmosis membrane method (primary concentration means)
2 Evaporative crystallization can (secondary concentration means)
3 Slurry tank 4 Solid-liquid separation means (centrifugal separator)
5 Salt dissolution tank 6 Dehydration filter (gypsum separation means)
10 Filtrate tank 11 Heater 12 Condenser 13 Mother liquor tank 14 Primary concentrate tank

Claims

A primary concentration step of primarily concentrating seawater by a method without phase change such as reverse osmosis membrane method and ion exchange membrane method;
A secondary concentration step of precipitating a salt containing gypsum by evaporating and concentrating the primary concentrate concentrated in the primary concentration step;
Part of the secondary concentrated liquid from which the gypsum-containing salt is deposited from the secondary concentration process is subjected to solid-liquid separation to recover the product salt, and the salt separation liquid after the salt is separated A salt recovery step for circulating supply to the concentration step;
The main part of the gypsum deposited in the secondary concentrated liquid by mixing a part of the secondary concentrated liquid from which the salt containing gypsum was deposited from the secondary concentrated process with the primary concentrated liquid concentrated in the primary concentrated process. A salt dissolving step for dissolving the salt without dissolving the salt,
A gypsum separation step of separating gypsum that has not been dissolved in the salt dissolution step and supplying a gypsum separation liquid from which the gypsum has been separated to a secondary concentration step.

The primary concentrated solution is obtained by concentrating seawater 1.5 to 2.5 times, and the secondary concentrated solution has a content of precipitated salt containing gypsum of 3 to 10% by weight. The salt production method of Claim 1 characterized by these.

The secondary concentrated liquid is stored in a slurry tank, and a slurry containing a large salt-rich solid content is extracted from the bottom and used for the salt recovery step, and a slurry containing a small gypsum-rich solid content from the top. 3. The salt production method according to claim 1, wherein the salt is extracted and used for the salt dissolution step.

The ratio (A: B) of the portion (A) used for the salt recovery step and the portion B (B) used for the salt dissolution step (A: B) in the secondary concentrated solution is 1: 1-1. The salt production method according to any one of claims 1 to 3, wherein the salt production method is in a range of 3: 3.

5. The secondary concentration step performs evaporation concentration and crystallization under a temperature condition of 55 to 65 ° C., and the salt dissolution step performs salt dissolution under a temperature condition of 43 to 53 ° C. 5. The salt production method in any one of.

Primary concentration means for primarily concentrating seawater without phase change;
And evaporation crystallization cans for concentrating, crystallization of the primary concentrate is concentrated continuously evaporated to the primary concentration unit,
A slurry tank for storing the secondary concentrate to precipitate a salt containing Oite gypsum to the evaporation crystallization can,
Subjected to solid-liquid separation for some of the secondary concentrate in the slurry tank, thereby recovering the product salt, the salt separated liquid after the salt has been separated solid circulate and supply the evaporation crystallization bottom liquid separation Means,
A part of the secondary concentrated liquid in which the salt containing gypsum in the slurry tank is precipitated is mixed with the primary concentrated liquid concentrated by the primary concentration means, and the main part of the gypsum precipitated in the secondary concentrated liquid is dissolved. A salt dissolution tank that dissolves the salt without letting
Salt production apparatus characterized by comprising with separating gypsum from a salt solution containing gypsum of the salt dissolution tank, a gypsum separation means for supplying gypsum separation liquid gypsum is separated in evaporation crystallization can.