JP4052432B2 - Method and apparatus for removing ions in liquid by crystallization method - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、晶析法による液中イオンの除去に係り、特に、液中からリン酸イオン、カルシウムイオン、フッ素イオン、炭酸イオン、硫酸イオン等の特定なイオンを除去する方法及び装置に関する。
【０００２】
【従来の技術】
従来、液中から特定なイオンを除去する方法の一つとして晶析法が用いられてきた。晶析法は、廃水中の特定のイオンと反応するイオンを薬品として添加したり、ｐＨを変化させることで廃水中を過飽和状態とし、特定イオンを含む結晶を析出させ分離する方法である。
晶析法の例を示すと、下水の２次処理水や汚泥処理系からの返流水などの廃水中のリン酸イオンを除去する場合には、カルシウムを添加し、リン酸カルシウムやヒドロキシアパタイト（以下、ＨＡＰ）の結晶を析出させている。
半導体工場の廃水には、フッ素イオンを多く含んでいる場合が多く、このときは、同じくカルシウム源を添加してフッ化カルシウムの結晶を析出させている。
地下水を原水とする用水、排水、ゴミ浸出水からカルシウムイオンを除去する場合では、ｐＨを上昇させたり、炭酸源を添加することで炭酸カルシウムの結晶を析出させている。
【０００３】
嫌気性消化汚泥の脱水ろ液や肥料工場廃水など、液中にリン酸イオンとアンモニアイオンを含有している廃水では、マグネシウムを添加してリン酸マグネシウムアンモニウム（以下、ＭＡＰという）の結晶を析出させている。
反応方式は、完全混合方式や流動層方式が用いられるが、固液分離性能を考慮すると後者の方が採用される場合が多い。流動層方式は、被処理水を上向流で通水し、流動層内で流動している結晶核の表面で生成物を析出させることで、反応と固液分離を同時に行うことができる。結晶核は、晶析生成物の構成物質を含むものが好ましく、砂や砂に生成物をコーティングしたものでもよい。この場合、流動槽内で流動している粒子は、粒子径が大きい方が沈降速度が速く、原水の上向流速度を速くすることができる。
【０００４】
晶析現象は、結晶核の発生がおこる核発生現象と、結晶核の成長がおこる成長現象からなる。一般に、難溶性塩の場合は、反応速度が速く、成長現象よりも核発生現象が支配的となり、粗大な結晶を得にくい。反応槽に結晶核を添加し、新たに結晶核（微細な結晶）を生成しないような過飽和度で運転を行うことで、生成物を添加した結晶核の表面で優先的に晶析させる技術が開発されている。
流動層方式で、反応槽内を上昇する液流速（以下、ＬＶという）は、反応槽内の結晶核の沈降速度で決まる。結晶核の沈降速度はストークスの式、アレンの式などで求められるが、通常、流動化に適したＬＶは結晶核沈降速度の１／１０程度である。
粒径の小さな結晶核及び生成した微細結晶は、沈降速度が遅いためにＬＶを高くすることが難しい。そのため、装置容積がきわめて大きくなる傾向があった。また、装置容積当たりの有効反応表面積が極めて大きく、結晶成長が遅いなどの問題点もあった。
【０００５】
粒径の比較的大きな結晶は、ＬＶを高くすることが可能であり、装置当たりの処理量を多くすることができる。しかし、装置当たりの有効反応表面積が小さく、結晶核が過大成長しやすい。
結晶核が過大成長すると、やがて流動しにくくなる。結晶核が流動しなくなると原水の偏流などにより反応効率が低下し、処理水質が悪くなるなどの問題が生じる。
再び流動させるには、ＬＶを高めるとよい。各槽の原水の供給量を増加させてＬＶを高めることができるが、それと共に薬品の添加量も増加させる必要があり、また、供給量を増加させるタイミングの制御が煩雑になるなどの問題点がある。
このような問題点を解決するために、特開昭６１−１６４６９６号公報によると、成長した結晶核を抜き出し、比較的粒径の小さな結晶核を添加する方法が提案されている。
【０００６】
添加する結晶核の粒径は、成長した結晶核の粒径に近いほど流出や膨張率を抑えられて効率がよい。しかし、晶析量が多い場合、添加する結晶核量が多くなる問題があった。また、添加する結晶核に生成物以外の物質を用いた場合、回収した生成物の純度が悪いという問題もあった。
成長した結晶核の粒径に比べ、添加する結晶核の粒径が５０％以下と小さい場合は、添加する結晶核にあわせてＬＶを抑えなければならず、装置容積が極めて大きくなるという問題点があった。また、ＬＶを抑えた結果、粒径の大きな結晶核の流動が悪くなり、処理水質が悪くなるという問題点もあった。この場合、反応槽底部の断面積を小さくすることでＬＶを高めることができるが、結局、装置上部の断面積は粒径の小さな結晶核に合わせる必要があり装置が大型化してしまう。
【０００７】
【発明が解決しようとする課題】
本発明は、上記従来技術の問題点を解消し、被処理液中の特定イオンを化学反応の結果、粒度の揃った難溶姓の結晶を析出させることにより、安定した除去性能を得ると共に、装置を極めて小型化することができる晶析法による液中イオンの除去方法及び装置を提供することを課題する。
【０００８】
【課題を解決するための手段】
上記課題を解決するために、本発明では、被処理液中の被除去イオンを晶析反応で除去する方法において、前記被処理液及び被除去イオンと反応するイオンを含む液及び／又は処理液の一部を、２槽以上からなる晶析反応槽の各々に供給して、各槽で反応晶析させるに際し、第一反応槽に結晶核を添加し成長させた後、該成長結晶核を順次後段の反応槽に移送させ、該成長結晶核を最終段の反応槽から抜き出して回収すると共に、後段の反応槽ほど被処理液の供給量を多くすることを特徴とする液中イオンの除去方法としたものである。
前記液中イオンの除去方法において、結晶核の移送及び抜き出しは、エアリフトで行うことができる。
また、本発明では、被処理液中の被除去イオンを晶析除去する装置において、２槽以上の晶析反応槽を設置し、該第一反応槽に結晶核を添加する手段を、最終段の反応槽に結晶核を抜き出す手段を設け、前記各反応槽に、被処理液供給管及び被除去イオンと反応するイオンを含む液の供給管及び／又は処理液の一部を供給する管と、エアリフト管とを設置すると共に、後段の反応槽ほど被処理液の供給量を多くする手段を有することを特徴とする液中イオンの除去装置としたものである。
【０００９】
【発明の実施の形態】
次に、本発明を図面を参照して詳細に説明する。
図１は、本発明を実施する処理系の１形態を示す断面構成図であり、反応槽は第一晶析反応槽、第二晶析反応槽、第三晶析反応槽からなる。各反応槽は図１のように分離していてよいし、図２に示す別の形態の断面構成図のように、反応槽の中に反応槽を入れてもよい。図２で、（ａ）は正面図、（ｂ）は平面図である。
以下、図１で説明する。
原水供給管、薬品及び／又は処理水の一部の供給管、及び空気の供給管は、各反応槽の底部に接続してある。原水の供給管及び薬品の供給管は、反応槽上部に接続しても良いが、原水を上向流で通水することで、各反応槽内に存在する結晶核を液流速のみで流動させることができる。結晶核を流動させる手段は、液の上昇流速のほかに、機械的攪拌、エア攪拌などがある。エアリフト管は、各晶析反応槽の上部から反応槽内に挿入してある。エアリフト管の底部には、気泡を集める気泡捕集傘を設けてある。エアリフト管内に空気を直接吹き込む場合は、気泡捕集傘を設けなくてもよい。
【００１０】
各反応槽上部には、処理水流出管を配置してある。各反応槽を流出した処理水に原水中の被除去イオン及び／又は被除去イオンと反応するイオン或いは化合物が残留している場合は、各反応槽の処理水流出管を同反応槽の底部及び／又は後段の反応槽に接続しても良い。
第一反応槽には、結晶核を添加する手段を設けている。結晶核は、晶析生成物の構成物費を含むものが好ましく、砂や砂に生成物をコーティングしたものでもよい。生成物がその表面で晶析するものとする。
最終段の反応槽には、成長した結晶核を抜き出す手段を設置し、成長した結晶核を回収する。
各反応槽は、原水中の被除去イオンと、被除去イオンと反応するイオン或いは化合物とを反応させることで、被除去イオン濃度を低下させる。最適な反応ｐＨは、生成させる物質によって異なるが、いずれの場合もｐＨが大きく変化しないように、反応槽内でｐＨ調整するとよい。
【００１１】
第一反応槽では、添加した結晶核の表面で晶析させる。原水の供給は、液側で微細な結晶を発生しない程度の過飽和度となるようにすることで、結晶核の成長を支配的にする。晶析が進むにつれ、ＬＶに比べ結晶核の沈降速度が非常に速くなる。
第二以降の反応槽では、前段で成長した結晶核を移送させた後、原水を通水する。ここでも同じく原水の供給は、液側で微細な結晶を発生しない程度の過飽和度となるようにすることで、結晶核の成長を支配的にする。晶析が進むにつれ、再びＬＶに比べ結晶核の沈降速度か非常に速くなる。このように成長した結晶を後段に移送し、更に成長させる。
最終段の反応槽より結晶を抜き出すことで製品結晶とする。
【００１２】
各反応槽に供給する原水の割合は、粒径の小さな結晶核が流動している槽ほど少なくする。つまり、晶析量を少なくする。例えば、３段の反応槽を用いた場合で、各反応槽で結晶核を２倍（体積は２3＝８倍）にすることを考えると、前段反応槽から移送させる結晶核量は、後段反応槽に移送させる結晶核量に比べ１／８でよく、つまり、前段反応槽の晶析量は、後段反応槽の晶析量の１／８でよい。この場合、第一反応槽の供給量を１Ｑとすると、第二反応槽の供給量は８Ｑ、第三反応槽の供給量は６４Ｑとなる。
以上の操作を行うことで、粒径の小さな結晶核は順次後段の反応槽へ送られ、更に成長し製品結晶となる。製品結晶は、第一晶析反応槽に添加した結晶核の粒径にくらべ非常に大きくなっているため、不純物（第一晶析反応槽に添加した結晶核）の割合が極めて少なくなる。例えば、０．１ｍｍの砂を第一晶析反応槽に添加し、０．５ｍｍの製品結晶を得た場合、砂の製品結晶に占める割合はわずか０．８％である。本発明プロセスを用いると、容易に不純物の割合を極めて少なくすることができる。
【００１３】
また、従来技術にあるように、成長した結晶核の粒径に比べ５０％以下の結晶核を添加すると、装置容積が極めて大きくなる傾向があった。本発明によると、各粒径ごとに適したＬＶで流動させることができ、また、粒径の小さな結晶核ほど通水量を少なくすることが可能であり、装置の小型化に大きく貢献する。
本発明では、結晶核を後段に移送させる手段としてエアリフトを用いる。エアリフトを用いることで、本発明のように多段に移送手段を設置しなければならない場合、設置費用を低減させることができ、また、弁の開閉のみで結晶核の移送をすることができるので極めて安定した連続運転が可能となる。また、各反応槽内で粒径の大きな結晶核のみを選択的に移送させることが可能であり、しかもその操作は非常に簡単である。
【００１４】
【実施例】
以下本発明を実施例により更に具体的に説明する。
実施例１
生物処理系の処理水を用いて、図３に示す処理系で脱リン処理を行った。反応槽は、第一晶析反応槽と第二晶析反応槽からなる。第一反応槽は直径１０ｃｍ、高さ３ｍ、第二反応槽は直径２５ｃｍ、高さ３ｍとした。生物処理系の処理水に必要に応じてリン酸１カリウムを添加し、所定の温度となるように、リン濃度を調整した。以下、リン濃度を調整した液を原水とする。第一反応槽は平均粒径０．２ｍｍの砂を添加して結晶核とし、第二反応槽は第一反応槽で成長させた結晶核を移送させたものを結晶核とした。原水及び処理水の一部は、各反応槽底部より上向流で通水し、塩化カルシウムとｐＨを９に調整することで、結晶核表面にＨＡＰを晶析させた。原水の通水量は、第一反応槽が１ｍ3／ｄ、第二反応槽が１０ｍ3／ｄとした。表１に、通水条件を示す。
【００１５】
【表１】
【００１６】
【表２】
成長した結晶核の抜き出しは約３ヶ月に１度、以下の手順で行った。
▲１▼ 第二反応槽から成長した結晶核の抜き出し
４０ｍｍのエアリフト管を用いて、空気量３０ＮＬ／ｍｉｎで抜き出した。
なお、抜き出し中は原水の供給は止め、循環水のみ通水した。
▲２▼第一反応槽から第二反応槽に成長した結晶核の移送
空気弁を第一反応槽に切り替えて、同じく４０ｍｍのエアリフト管を用いて、空気６０ＮＬ／ｍｉｎで抜き出した。なお、抜き出し中は第二反応槽同様に原水の供給は止め、循環水のみ通水した。
▲３▼ 第一反応槽に新品の砂（０．２ｍｍ）の添加
平均粒径０．２ｍｍの新品の砂を約０．３ｍ分（約４ｋｇ）添加。
▲４▼ 原水通水
原水を再び通水開始した。
【００１８】
第一反応槽の砂の粒径は、初期粒径０．２ｍｍに対し０．２８〜０．３５ｍｍ（平均０．３０ｍｍ）まで成長し、また充填量も０．３ｍから約１ｍまで増加した。第二反応槽の結晶核は、第一反応槽で成長した結晶核の粒径０．２８〜０．３５ｍｍ（平均０．３０ｍｍ）のものが０．４０〜０．５０ｍｍ（平均０．４６ｍｍ）まで成長した。生成物中の砂（不純物）の割合は約８％であり、９０％以上が生成したＨＡＰであった。
実験期間中（１年間）に用いた砂は１７ｋｇで、回収した結晶核は約２２０ｋｇであった。
また、エアリフトを用いることにより容易に結晶核の抜き出しができた。
【００１９】
比較例１
実施例と同様にして調整した原水を、図４に示す処理系で脱リン処理を行った。反応槽は直径２５ｃｍ、高さ３ｍのものを用いた。結晶核には０．３ｍｍの砂を用いた。原水及び／又は処理水の一部は、各反応槽底部より上向流で通水し、また、塩化カルシウムとｐＨを９に調整することで、砂表面にＨＡＰを晶析させた。原水の通水量は１０ｍ3／ｄとした。通水条件を表３に示す。
【表３】
【００２０】
約１２ヶ月通水させた原水と処理水の平均水質を表４に示す。原水のＴ−Ｐ１２．１ｍｇ／Ｌに対し、処理水のＴ−Ｐは５．０ｍｇ／Ｌであり、リンの回収率は５９％であった。
【表４】
実施例に比較し、回収率は２５ポイント低く、また使用した砂の量は４〜５倍であったにもかかわらず、回収量は約７０％であった。
【００２１】
【発明の効果】
本発明によると、装置容積を小さくすることが可能であり、また、結晶核の添加量を削減でき、しかも製品結晶の純度が高い液中のイオン除去方法及び装置を提供することができた。
【図面の簡単な説明】
【図１】本発明の装置の一例を示す断面構成図。
【図２】本発明の装置の他の例を示す断面構成図で、（ａ）正面図、（ｂ）平面図。
【図３】実施例１に用いた装置の断面構成図。
【図４】比較例１に用いた装置の断面構成図。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to removal of ions in a liquid by a crystallization method, and more particularly, to a method and apparatus for removing specific ions such as phosphate ions, calcium ions, fluorine ions, carbonate ions, and sulfate ions from a liquid.
[0002]
[Prior art]
Conventionally, a crystallization method has been used as one of methods for removing specific ions from a liquid. The crystallization method is a method in which ions that react with specific ions in wastewater are added as chemicals or the pH of the wastewater is changed to a supersaturated state, and crystals containing specific ions are precipitated and separated.
As an example of the crystallization method, when removing phosphate ions in wastewater such as secondary treated water of sewage and return water from the sludge treatment system, calcium is added and calcium phosphate or hydroxyapatite (hereinafter, HAP) crystals are precipitated.
In many cases, semiconductor factory wastewater contains a large amount of fluorine ions. At this time, calcium sources are also added to precipitate calcium fluoride crystals.
In the case of removing calcium ions from water, wastewater, and waste leachate using groundwater as raw water, calcium carbonate crystals are precipitated by raising the pH or adding a carbonic acid source.
[0003]
In wastewater containing phosphate ions and ammonia ions, such as dehydrated filtrate of anaerobic digested sludge and fertilizer factory wastewater, magnesium is added to precipitate crystals of magnesium ammonium phosphate (hereinafter referred to as MAP). I am letting.
As the reaction method, a complete mixing method or a fluidized bed method is used, but the latter is often adopted in view of solid-liquid separation performance. In the fluidized bed system, the water to be treated is passed in an upward flow, and the product is precipitated on the surface of crystal nuclei flowing in the fluidized bed, whereby the reaction and the solid-liquid separation can be performed simultaneously. The crystal nucleus preferably contains a constituent of the crystallization product, and may be sand or sand coated with the product. In this case, the particles flowing in the fluid tank have a larger sedimentation speed when the particle diameter is larger, and the upward flow speed of the raw water can be increased.
[0004]
The crystallization phenomenon consists of a nucleation phenomenon in which crystal nuclei occur and a growth phenomenon in which crystal nuclei grow. In general, in the case of a poorly soluble salt, the reaction rate is fast, the nucleation phenomenon is dominant over the growth phenomenon, and it is difficult to obtain coarse crystals. There is a technology to preferentially crystallize on the surface of the crystal nucleus to which the product has been added by adding crystal nuclei to the reactor and operating at a supersaturation level that does not generate new crystal nuclei (fine crystals). Has been developed.
In a fluidized bed system, the liquid flow rate (hereinafter referred to as LV) rising in the reaction vessel is determined by the sedimentation rate of crystal nuclei in the reaction vessel. The sedimentation rate of crystal nuclei can be determined by the Stokes equation, the Allen equation, and the like. Usually, the LV suitable for fluidization is about 1/10 of the crystal nucleus sedimentation rate.
The crystal nuclei having a small particle diameter and the generated fine crystals have a low sedimentation rate, so it is difficult to increase the LV. For this reason, the device volume tends to be extremely large. There are also problems such as an extremely large effective reaction surface area per unit volume and slow crystal growth.
[0005]
Crystals having a relatively large particle size can increase the LV and can increase the throughput per apparatus. However, the effective reaction surface area per apparatus is small, and crystal nuclei tend to grow excessively.
When crystal nuclei grow excessively, it becomes difficult to flow. If the crystal nuclei stop flowing, the reaction efficiency decreases due to the drift of raw water and the quality of treated water is deteriorated.
In order to make it flow again, it is good to raise LV. LV can be increased by increasing the supply amount of raw water in each tank, but it is also necessary to increase the addition amount of chemicals along with it, and problems such as complicated control of timing for increasing the supply amount There is.
In order to solve such problems, Japanese Patent Laid-Open No. 61-164696 proposes a method of extracting grown crystal nuclei and adding crystal nuclei having a relatively small grain size.
[0006]
As the grain size of the added crystal nuclei is closer to the grain size of the grown crystal nuclei, the outflow and expansion rate can be suppressed and efficiency is improved. However, when the amount of crystallization is large, there is a problem that the amount of crystal nuclei to be added increases. In addition, when a substance other than the product is used for the crystal nucleus to be added, there is a problem that the purity of the recovered product is poor.
When the grain size of the added crystal nuclei is as small as 50% or less compared to the grain size of the grown crystal nuclei, the LV must be suppressed according to the crystal nuclei to be added, and the apparatus volume becomes extremely large. was there. Further, as a result of suppressing the LV, there is a problem that the flow of crystal nuclei having a large particle diameter is deteriorated and the quality of treated water is deteriorated. In this case, the LV can be increased by reducing the cross-sectional area at the bottom of the reaction vessel, but eventually the cross-sectional area at the top of the apparatus needs to be matched to the crystal nuclei having a small particle size, resulting in an increase in the size of the apparatus.
[0007]
[Problems to be solved by the invention]
The present invention eliminates the above-mentioned problems of the prior art, and as a result of a chemical reaction of specific ions in the liquid to be treated, precipitates a slightly soluble crystal with uniform particle size, thereby obtaining stable removal performance, It is an object of the present invention to provide a method and an apparatus for removing ions in liquid by a crystallization method capable of extremely miniaturizing the apparatus.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, in the present invention, in a method for removing ions to be removed in a liquid to be treated by crystallization reaction, the liquid to be treated and a liquid containing ions that react with the ions to be removed and / or a treatment liquid Is supplied to each of the crystallization reaction tanks composed of two or more tanks, and when the reaction crystallization is performed in each tank, after adding crystal nuclei to the first reaction tank and growing, Removal of ions in liquid characterized by sequentially transferring to a subsequent reaction tank and extracting and recovering the grown crystal nuclei from the final reaction tank and increasing the supply amount of the liquid to be treated in the latter reaction tank It is a method.
In the method for removing ions in the liquid, the transfer and extraction of crystal nuclei can be performed by an air lift.
In the present invention, in the apparatus for crystallizing and removing ions to be removed from the liquid to be treated, two or more crystallization reaction tanks are installed, and means for adding crystal nuclei to the first reaction tank is provided at the final stage. A means for extracting crystal nuclei in the reaction tank, and a liquid supply pipe and / or a pipe for supplying a part of the processing liquid to the reaction liquid supply pipe and ions that react with the ions to be removed; In addition, an apparatus for removing ions in liquid is provided, which is provided with an air lift pipe and has means for increasing the supply amount of the liquid to be processed in the reaction tank at the latter stage.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view showing one embodiment of a processing system for carrying out the present invention, and the reaction tank is composed of a first crystallization reaction tank, a second crystallization reaction tank, and a third crystallization reaction tank. Each reaction vessel may be separated as shown in FIG. 1, or a reaction vessel may be placed in the reaction vessel as shown in a cross-sectional configuration diagram of another embodiment shown in FIG. 2A is a front view, and FIG. 2B is a plan view.
This will be described below with reference to FIG.
A raw water supply pipe, a supply pipe for some chemicals and / or treated water, and an air supply pipe are connected to the bottom of each reaction tank. The raw water supply pipe and the chemical supply pipe may be connected to the upper part of the reaction tank, but by passing the raw water in an upward flow, the crystal nuclei existing in each reaction tank are flowed only by the liquid flow rate. be able to. Means for causing crystal nuclei to flow include mechanical stirring and air stirring in addition to the rising speed of the liquid. The air lift pipe is inserted into the reaction tank from the top of each crystallization reaction tank. A bubble collecting umbrella for collecting bubbles is provided at the bottom of the air lift pipe. When air is directly blown into the air lift pipe, the bubble collecting umbrella need not be provided.
[0010]
A treated water outflow pipe is disposed at the top of each reaction tank. If the ions to be removed from the raw water and / or ions or compounds that react with the ions to be removed remain in the treated water that has flowed out of each reaction tank, the treated water outflow pipe of each reaction tank is connected to the bottom of the reaction tank and Alternatively, it may be connected to a subsequent reaction tank.
The first reaction tank is provided with means for adding crystal nuclei. The crystal nucleus preferably includes the component cost of the crystallization product, and may be sand or sand coated with the product. The product crystallizes on its surface.
A means for extracting the grown crystal nuclei is installed in the final reaction tank, and the grown crystal nuclei are collected.
Each reaction tank lowers the concentration of ions to be removed by reacting ions to be removed in the raw water with ions or compounds that react with the ions to be removed. The optimum reaction pH varies depending on the substance to be produced, but in any case, the pH may be adjusted in the reaction vessel so that the pH does not change greatly.
[0011]
In the first reaction tank, crystallization is performed on the surface of the added crystal nucleus. The supply of raw water makes the growth of crystal nuclei dominant by setting the degree of supersaturation to such an extent that fine crystals are not generated on the liquid side. As crystallization progresses, the sedimentation rate of crystal nuclei becomes much faster than LV.
In the second and subsequent reaction vessels, the crystal nuclei grown in the previous stage are transferred, and then raw water is passed. Here too, the supply of raw water makes the growth of crystal nuclei dominant by making the degree of supersaturation not to generate fine crystals on the liquid side. As crystallization progresses, the sedimentation rate of crystal nuclei becomes much faster than LV again. The crystal thus grown is transferred to the subsequent stage and further grown.
Crystals are extracted from the final reaction tank to obtain product crystals.
[0012]
The ratio of the raw water supplied to each reaction tank is decreased as the tank in which crystal nuclei having a small particle diameter are flowing. That is, the amount of crystallization is reduced. For example, in the case of using a three -stage reaction tank, considering that the number of crystal nuclei is doubled (volume is 2 3 = 8 times) in each reaction tank, the amount of crystal nuclei transferred from the front-stage reaction tank is The amount of crystal nuclei transferred to the reaction vessel may be 1/8, that is, the amount of crystallization in the former reaction vessel may be 1/8 of the amount of crystallization in the latter reaction vessel. In this case, if the supply amount of the first reaction tank is 1Q, the supply amount of the second reaction tank is 8Q, and the supply amount of the third reaction tank is 64Q.
By performing the above operation, the crystal nuclei having a small particle diameter are sequentially sent to the subsequent reaction tank and further grown to become product crystals. Since the product crystal is much larger than the grain size of the crystal nuclei added to the first crystallization reaction tank, the ratio of impurities (crystal nuclei added to the first crystallization reaction tank) is extremely small. For example, when 0.1 mm of sand is added to the first crystallization reaction tank to obtain 0.5 mm of product crystals, the proportion of sand in the product crystals is only 0.8%. When the process of the present invention is used, the ratio of impurities can be easily reduced.
[0013]
Further, as in the prior art, when 50% or less of crystal nuclei are added compared to the grain size of the grown crystal nuclei, the device volume tends to become extremely large. According to the present invention, it is possible to flow with an LV suitable for each particle size, and it is possible to reduce the amount of water passing through a crystal nucleus with a smaller particle size, which greatly contributes to downsizing of the apparatus.
In the present invention, an air lift is used as means for transferring crystal nuclei to the subsequent stage. By using an air lift, when it is necessary to install transfer means in multiple stages as in the present invention, the installation cost can be reduced, and crystal nuclei can be transferred only by opening and closing the valve. Stable and continuous operation is possible. In addition, it is possible to selectively transfer only crystal nuclei having a large particle size in each reaction tank, and the operation is very simple.
[0014]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples.
Example 1
Dephosphorization treatment was performed in the treatment system shown in FIG. 3 using treated water from a biological treatment system. The reaction tank comprises a first crystallization reaction tank and a second crystallization reaction tank. The first reaction tank had a diameter of 10 cm and a height of 3 m, and the second reaction tank had a diameter of 25 cm and a height of 3 m. If necessary, monopotassium phosphate was added to the treated water of the biological treatment system, and the phosphorus concentration was adjusted to a predetermined temperature. Hereinafter, the liquid whose phosphorus concentration is adjusted is referred to as raw water. In the first reaction tank, sand having an average particle size of 0.2 mm was added to form crystal nuclei, and in the second reaction tank, crystal nuclei transferred from the crystal nuclei grown in the first reaction tank were used as crystal nuclei. Part of the raw water and treated water was passed upward from the bottom of each reaction tank, and HAP was crystallized on the surface of the crystal nucleus by adjusting calcium chloride and pH to 9. Passing water of the raw water, the first reaction tank is 1 m 3 / d, the second reaction vessel was 10 m 3 / d. Table 1 shows the water flow conditions.
[0015]
[Table 1]
[0016]
[Table 2]
The grown crystal nuclei were extracted once every three months according to the following procedure.
(1) Extraction of crystal nuclei grown from the second reaction tank Using an air lift tube of 40 mm, the crystal nucleus was extracted at an air amount of 30 NL / min.
During extraction, the supply of raw water was stopped and only circulating water was passed.
{Circle around (2)} The transfer air valve for crystal nuclei grown from the first reaction tank to the second reaction tank was switched to the first reaction tank, and the air was extracted at 60 NL / min using the same 40 mm air lift pipe. During extraction, the supply of raw water was stopped as in the second reaction tank, and only circulating water was passed.
(3) Addition of new sand (0.2 mm) New sand with an average particle size of 0.2 mm was added to the first reaction tank for about 0.3 m (about 4 kg).
(4) Raw water flow Water flow was started again.
[0018]
The particle size of the sand in the first reaction tank grew from 0.28 to 0.35 mm (average 0.30 mm) with respect to the initial particle size of 0.2 mm, and the filling amount increased from 0.3 m to about 1 m. The crystal nuclei of the second reaction tank are those having a grain size of 0.28 to 0.35 mm (average 0.30 mm) grown in the first reaction tank, 0.40 to 0.50 mm (average 0.46 mm). Grew up. The ratio of sand (impurities) in the product was about 8%, and 90% or more of the produced HAP.
The sand used during the experiment (one year) was 17 kg, and the recovered crystal nuclei were about 220 kg.
In addition, crystal nuclei could be easily extracted by using an air lift.
[0019]
Comparative Example 1
The raw water prepared in the same manner as in Example was subjected to dephosphorization treatment in the treatment system shown in FIG. A reaction vessel having a diameter of 25 cm and a height of 3 m was used. 0.3 mm of sand was used for the crystal nucleus. Part of the raw water and / or treated water was passed upward from the bottom of each reaction tank, and HAP was crystallized on the sand surface by adjusting calcium chloride and pH to 9. The flow rate of the raw water was 10 m 3 / d. Table 3 shows the water flow conditions.
[Table 3]
[0020]
Table 4 shows the average water quality of the raw water and treated water passed through for about 12 months. The TP of the treated water was 5.0 mg / L against the TP of raw water of 12.1 mg / L, and the phosphorus recovery rate was 59%.
[Table 4]
Compared to the Examples, the recovery rate was 25 points lower, and the recovered amount was about 70%, although the amount of sand used was 4-5 times.
[0021]
【The invention's effect】
According to the present invention, it is possible to reduce the volume of the apparatus, to reduce the amount of crystal nuclei added, and to provide a method and apparatus for removing ions in a liquid in which the purity of product crystals is high.
[Brief description of the drawings]
FIG. 1 is a cross-sectional configuration diagram showing an example of an apparatus of the present invention.
2A and 2B are cross-sectional structural views showing another example of the apparatus of the present invention, in which FIG.
3 is a cross-sectional configuration diagram of the apparatus used in Example 1. FIG.
4 is a cross-sectional configuration diagram of an apparatus used in Comparative Example 1. FIG.
Claims (3)
Priority Applications (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001399269A JP4052432B2 (en) | 2001-12-28 | 2001-12-28 | Method and apparatus for removing ions in liquid by crystallization method |
| CNB028141628A CN1243588C (en) | 2001-10-12 | 2002-10-11 | Method and apparatus for removing ion present in solution by the crystallization method |
| PCT/JP2002/010596 WO2003033098A1 (en) | 2001-10-12 | 2002-10-11 | Method and apparatus for removing ion present in solution by the crystallization method |
| EP02801551A EP1435259B8 (en) | 2001-10-12 | 2002-10-11 | Method and apparatus for removing ion present in solution by the crystallization method |
| KR1020047000525A KR100949564B1 (en) | 2001-10-12 | 2002-10-11 | Method and apparatus for removing ion present in solution by the crystallization method |
| US10/483,429 US20040213713A1 (en) | 2001-10-12 | 2002-10-11 | Method and apparatus for removing ion present in solution by the crystallization method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001399269A JP4052432B2 (en) | 2001-12-28 | 2001-12-28 | Method and apparatus for removing ions in liquid by crystallization method |
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| JP2003190707A JP2003190707A (en) | 2003-07-08 |
| JP4052432B2 true JP4052432B2 (en) | 2008-02-27 |
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| JP4417056B2 (en) * | 2003-08-28 | 2010-02-17 | 株式会社荏原製作所 | Crystal recovery and transfer equipment |
| CA2917116A1 (en) | 2013-07-05 | 2015-01-08 | Mitsubishi Heavy Industries, Ltd. | Water treatment process and water treatment system |
| JP2019147126A (en) * | 2018-02-28 | 2019-09-05 | パナソニックＩｐマネジメント株式会社 | Ion removing system |
| JP2019147127A (en) * | 2018-02-28 | 2019-09-05 | パナソニックＩｐマネジメント株式会社 | Ion removing system |
| CN111741929A (en) * | 2018-02-28 | 2020-10-02 | 松下知识产权经营株式会社 | Ion removal system |
| JP7126113B2 (en) * | 2018-02-28 | 2022-08-26 | パナソニックＩｐマネジメント株式会社 | ion removal system |
| JP2019147128A (en) * | 2018-02-28 | 2019-09-05 | パナソニックＩｐマネジメント株式会社 | Ion removing system |
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