JP2017095287A - Method for producing dihydrate gypsum with decreased amount of fluorine elution - Google Patents
Method for producing dihydrate gypsum with decreased amount of fluorine elution Download PDFInfo
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Abstract
Description
本発明は、石膏ボード廃材から、リサイクル可能な二水石膏を製造する方法に関する。詳しくは、石膏ボード廃材から得られる廃石膏から、フッ素を効率よく除去した二水石膏を製造する方法に関する。 The present invention relates to a method for producing recyclable dihydrate gypsum from gypsum board waste. Specifically, the present invention relates to a method for producing dihydrate gypsum from which fluorine has been efficiently removed from waste gypsum obtained from gypsum board waste material.
石膏ボードは、石膏芯材の両面を紙で張り合わせた複合材料であり、現在約４００万トン生産されている。それに対して、解体現場等で発生する廃石膏ボードは、年間約１００万トン排出され、その排出量は今後さらに増加することが予想されている。 The gypsum board is a composite material in which both sides of a gypsum core material are bonded together with paper, and currently about 4 million tons are produced. On the other hand, about 1 million tons of waste gypsum board generated at the site of dismantling is discharged annually, and the discharge amount is expected to increase further in the future.
上記廃石膏ボードを粉砕して得られる廃石膏（二水石膏）は、石膏ボードの再生原料としてリサイクルされているが、廃石膏の平均粒径が小さいため、そのリサイクル率は低い。さらに、廃石膏を加熱して得られる半水石膏は、土壌固化材用の原料として利用可能であるが、石膏ボードの原料である副生石膏由来のフッ素が、廃石膏には含まれているため、土壌固化材として使用した場合、土壌環境基準（０．８ｍｇ／Ｌ以下）を超えるフッ素が、土壌中に溶出してしまう。 The waste gypsum (dihydrate gypsum) obtained by pulverizing the waste gypsum board is recycled as a raw material for recycling the gypsum board. However, since the average particle size of the waste gypsum is small, the recycling rate is low. Furthermore, hemihydrate gypsum obtained by heating waste gypsum can be used as a raw material for soil solidification materials, but because waste gypsum contains fluorine derived from by-product gypsum, which is a raw material for gypsum board. When used as a soil solidifying material, fluorine exceeding the soil environmental standard (0.8 mg / L or less) is eluted into the soil.
以上のことから、廃石膏ボードの大半は埋立て処分されている。しかしながら、今後の廃石膏ボード排出量の増加、国内の最終処分場の逼迫、環境負荷の点から、新たな廃石膏ボードのリサイクル方法が求められている。 From the above, most of the waste gypsum board is disposed of in landfill. However, a new recycling method of waste gypsum board is required from the viewpoint of future increase in waste gypsum board discharge, tightness of domestic final disposal sites, and environmental burden.
従来、石膏ボードの原料として供し得ない小粒径の石膏を改質する方法を提案した例として、特許文献１では、加熱したＮａＣｌ、ＭｇＣｌを含有する溶液中に二水石膏を添加して溶解した後、種結晶を添加して徐冷することで、晶析反応を行い、大粒径の板状の二水石膏を製造する方法が開示されている。さらに特許文献２では、特許文献１の実施例１記載の方法を比較例５として実際行い、得られた石膏からのフッ素溶出量をＨ３環告第４６号に従い測定した結果を開示しているが、結果として、大粒径の石膏が得られたものの、フッ素溶出量は、３８．９ｍｇ／Ｌと土壌環境基準を大幅に超える値が得られており、土壌固化材用の原料としてリサイクルが困難な石膏が得られている。 Conventionally, as an example of proposing a method for modifying gypsum having a small particle size that cannot be used as a raw material for gypsum board, in Patent Document 1, dihydrate gypsum is added and dissolved in a solution containing heated NaCl and MgCl. Then, a method of producing a large particle size plate-like dihydrate gypsum by adding a seed crystal and slowly cooling to perform a crystallization reaction is disclosed. Further, Patent Document 2 discloses the result of actually carrying out the method described in Example 1 of Patent Document 1 as Comparative Example 5 and measuring the fluorine elution amount from the obtained gypsum according to H3 Circular No. 46. As a result, although gypsum with a large particle size was obtained, the fluorine elution amount was 38.9 mg / L, a value significantly exceeding the soil environmental standard, and it was difficult to recycle as a raw material for soil solidification material A plaster is obtained.
一方、特許文献３では、土壌中のフッ素を除去するフッ素除去剤として、リン酸一水素カルシウム二水和物（ＣａＨＰＯ４・２Ｈ２Ｏ）をフッ素汚染土壌に添加し、フッ素汚染土壌に含まれるフッ素と反応して、フッ素アパタイトを形成して不溶化させることにより、フッ素汚染土壌からのフッ素溶出量を土壌環境基準以下にまで低減可能な方法が開示されている。 On the other hand, in Patent Document 3, calcium monohydrogen phosphate dihydrate (CaHPO 4 .2H 2 O) is added to fluorine-contaminated soil as a fluorine removing agent for removing fluorine in the soil, and is contained in the fluorine-contaminated soil. A method is disclosed in which the amount of fluorine eluted from fluorine-contaminated soil can be reduced below the soil environmental standard by reacting with fluorine to form and insolubilize fluorine apatite.
従って、本発明の目的は、前記廃石膏ボードを大量にリサイクルするため、平均粒径が大きく、かつ土壌固化材として使用した際の土壌中へのフッ素の溶出量が、極めて少ない改質された二水石膏を製造する方法を提案することにある。 Therefore, the purpose of the present invention is to recycle the waste gypsum board in large quantities, so that the average particle size is large, and the amount of fluorine eluted into the soil when used as a soil solidifying material has been improved. It is to propose a method for producing dihydrate gypsum.
本発明者は、上記目的を達成すべく鋭意研究を重ねた。その結果、大粒径の石膏を得るための晶析反応槽に、フッ素除去剤として、リン酸一水素カルシウム二水和物を連続して添加することにより、平均粒径が大きく、かつフッ素溶出量が極めて少ない改質された二水石膏を連続的に製造可能であることを見出し、本発明を完成するに至った。 The present inventor has intensively studied to achieve the above object. As a result, by continuously adding calcium monohydrogen phosphate dihydrate as a fluorine removing agent to the crystallization reaction tank to obtain gypsum with a large particle size, the average particle size is large and fluorine elution is achieved. It has been found that a modified dihydrate gypsum with an extremely small amount can be continuously produced, and the present invention has been completed.
即ち、本発明は、廃石膏ボードから回収した二水石膏を半水石膏及び／又はIII型無水石膏へ変換する工程、及び晶析反応槽内で半水石膏及び／又はIII型無水石膏を水に溶解した後、二水石膏を析出させる工程を含む二水石膏の製造方法において、晶析反応槽内にリン酸一水素カルシウム二水和物を共存させることを特徴とする、フッ素溶出量の低減された二水石膏の製造方法である。 That is, the present invention includes a step of converting dihydrate gypsum recovered from waste gypsum board into hemihydrate gypsum and / or type III anhydrous gypsum, and hemihydrate gypsum and / or type III anhydrous gypsum in the crystallization reaction tank. In the method for producing dihydrate gypsum including the step of precipitating dihydrate gypsum after being dissolved in the solution, calcium monohydrogen phosphate dihydrate is allowed to coexist in the crystallization reaction tank. It is a manufacturing method of reduced dihydrate gypsum.
本発明によれば、晶析反応とフッ素除去反応を晶析反応槽で同時に行うことにより、平均粒径が大きく、かつフッ素が効率良く除去された二水石膏を安定的に得ることができる。 According to the present invention, dihydrate gypsum having a large average particle size and from which fluorine has been efficiently removed can be stably obtained by simultaneously performing the crystallization reaction and the fluorine removal reaction in the crystallization reaction tank.
また、晶析反応槽にリン酸一水素カルシウム二水和物を添加せずに製造した二水石膏のフッ素溶出量と比べ、本発明の方法により得られた二水石膏のフッ素溶出量は、格段に低減され、効率的にフッ素を除去した二水石膏を製造することが可能である。 In addition, compared with the amount of fluorine elution of dihydrate gypsum produced without adding calcium monohydrogen phosphate dihydrate to the crystallization reaction tank, the amount of fluorine elution of dihydrate gypsum obtained by the method of the present invention is It is possible to produce dihydrate gypsum that is remarkably reduced and efficiently removes fluorine.
従って、本発明の二水石膏の製造方法によれば、リサイクルが困難な廃石膏ボードを大量にリサイクルすることが可能となり、その経済的効果および環境面における効果が極めて高い。 Therefore, according to the method for producing dihydrate gypsum of the present invention, it is possible to recycle a large amount of waste gypsum board that is difficult to recycle, and its economic effect and environmental effect are extremely high.
本発明は、廃石膏ボード由来の二水石膏を原料とし、一旦半水石膏及び／又はIII型無水石膏へ変換した後、平均粒径が大きく、かつフッ素を効率よく除去した二水石膏を製造する方法である。以下順を追って説明する。 The present invention uses dihydrate gypsum derived from waste gypsum board as a raw material, and once converted to hemihydrate gypsum and / or type III anhydrous gypsum, produces dihydrate gypsum having a large average particle size and efficiently removing fluorine. It is a method to do. The following will be described in order.
（石膏粉末）
廃石膏ボードから原料となる二水石膏を回収する方法は特に限定されず、公知の方法を採用すれば良いが、一般的には、廃石膏ボードを破砕してボード紙と分離する破砕工程、前記破砕工程で分離された廃石膏を焼成する焼成工程、前記焼成工程で焼成された廃石膏を粉砕する粉砕工程からなる。
(Gypsum powder)
The method of collecting dihydrate gypsum as a raw material from waste gypsum board is not particularly limited, and a known method may be adopted, but in general, a crushing step of crushing waste gypsum board and separating it from board paper, It comprises a firing step for firing the waste gypsum separated in the crushing step, and a grinding step for grinding the waste gypsum fired in the firing step.
本発明において、改質に使用される石膏粉末の石膏は、特に限定されるものではなく、天然石膏、繊維状半水石膏、副生石膏および廃石膏ボードより回収される廃石膏等が挙げられる。 In the present invention, the gypsum of the gypsum powder used for modification is not particularly limited, and examples thereof include natural gypsum, fibrous hemihydrate gypsum, by-product gypsum, and waste gypsum recovered from waste gypsum board.
本発明において、前記石膏粉末のうち、経済的効果および環境面における効果を鑑み、廃石膏ボードから得られた廃石膏粉末を使用することが特に好ましい。 In the present invention, among the gypsum powders, it is particularly preferable to use waste gypsum powder obtained from waste gypsum board in view of economic effects and environmental effects.
廃石膏ボードは、二水石膏よりなる芯材の表面にボード原紙が付着したものが一般的であり、石膏ボードの生産工程もしくは建築現場で発生する端材、又は、残材からなる廃石膏ボード、リフォーム・解体工事で発生する廃石膏ボード等が制限無く使用される。 Waste gypsum board is generally made by attaching base paper to the surface of a core made of dihydrate gypsum, and waste gypsum board made of gypsum board at the production process or construction site, or remaining material. Waste gypsum board generated during renovation and demolition work is used without restriction.
（破砕工程）
上記廃石膏ボードを破砕してボード紙と分離する破砕工程においては、、廃石膏ボードの処理方法は特に制限されないが、好適な方法を例示すれば、以下の方法が挙げられる。
(Crushing process)
In the crushing step of crushing the waste gypsum board and separating it from the board paper, the processing method of the waste gypsum board is not particularly limited, but the following methods can be mentioned as examples of suitable methods.
前記廃石膏ボードを乾式で破砕することにより、ボード原紙と廃石膏とを分離し、分離された廃石膏を、必要に応じて更に乾式粉砕する方法が一般的である。上記破砕、或いは、粉砕を乾式で行うことにより、湿式で行った場合に比べ、得られる石膏粉末からの水分の除去に余分なエネルギーを必要とせず、工業的に有利に本発明を実施することができる。 In general, the waste gypsum board is crushed by a dry method to separate the board base paper and the waste gypsum, and the separated waste gypsum is further dry pulverized as necessary. By carrying out the above crushing or crushing in a dry manner, the present invention is advantageously carried out industrially without requiring extra energy for removing water from the obtained gypsum powder as compared with the case where it is carried out wet. Can do.
尚、リフォーム・解体工事で発生する廃石膏ボードには、ビス等の金属片が付着している場合があり、かかる金属片は、破砕機を用いて廃石膏ボードを破砕する際に、破砕機の故障を招く恐れがあるため、破砕の前に金属片を磁選機等を用いて除去しておくことが好ましい。 In addition, metal pieces such as screws may adhere to the waste gypsum board generated during renovation and demolition work, and this metal piece is used when crushing the waste gypsum board using a crusher. Therefore, it is preferable to remove the metal piece using a magnetic separator before crushing.
上記廃石膏ボードより石膏粉末を得るための工程を更に詳細に説明すれば、先ず、廃石膏ボードは、様々な大きさで回収された後、処理設備に搬入されるため、これを取り扱い易い適当な大きさに予備破砕することが好ましい。かかる予備破砕は、芯材(石膏の硬化体)は勿論、ボード原紙をも適当な大きさに破砕する破砕装置が好適に使用される。勿論、上記予備破砕も乾式で行うことが望ましい。具体的には、高速回転式衝撃破砕機、スクリューせん断式破砕機等が使用される。上記予備破砕後の破砕片の大きさは特に限定されないが、その後の破砕処理に投入する際の容易さを考慮して、廃石膏は粒径１５〜１００ｍｍ程度に、ボード原紙は５×１０−４〜０．０５ｍ２程度に破砕することが好ましい。 The process for obtaining gypsum powder from the above-mentioned waste gypsum board will be described in more detail. First, the waste gypsum board is collected in various sizes and then carried into a processing facility. It is preferable to preliminarily crush to a large size. For such preliminary crushing, a crushing apparatus that crushes not only the core material (hardened gypsum) but also board base paper into an appropriate size is preferably used. Of course, it is desirable that the preliminary crushing is also performed in a dry manner. Specifically, a high-speed rotary impact crusher, a screw shear crusher, or the like is used. The size of the crushed pieces after the preliminary crushing is not particularly limited, but considering the ease of putting into the subsequent crushing treatment, the waste gypsum has a particle size of about 15 to 100 mm, and the board base paper has 5 × 10 − It is preferable to crush to about 4 to 0.05 m 2 .
上記予備破砕処理により適当な大きさとされた廃石膏ボードは、乾式破砕によりボード原紙を分離することが好ましい。上記乾式破砕の際に、芯材の石膏硬化体は破砕するが、ボード原紙は破砕し難い圧縮式の破砕装置、例えば、ハンマーミル、ロールミル等を使用することが、ボード原紙を容易に除去するために好ましい。上記破砕処理は、芯材の石膏硬化体がボード原紙から脱離可能な大きさまで破砕することが好ましく、例えば、平均粒径２０ｍｍ以下、好ましくは、１０ｍｍ以下の大きさとなるまで、破砕することが好ましい。
そして、かかる廃石膏粉末は、公知の分離手段により、ボード原紙と容易に分離することが可能である。かかる分離手段としては、例えば、振動式、回転式の篩が挙げられる。かかる篩い目の大きさは、廃石膏粉末が通過でき、ボード原紙が通過し得なない大きさを選択すればよい。
The waste gypsum board having a suitable size by the preliminary crushing treatment is preferably separated from the board base paper by dry crushing. During the dry crushing, the core gypsum hardened body is crushed, but the board base paper is difficult to crush. For example, a hammer crusher, a roll mill, etc. can easily remove the board base paper. Therefore, it is preferable. In the crushing treatment, it is preferable that the hardened gypsum core material is crushed to such a size that the core can be detached from the board base paper. For example, crushing is performed until the average particle size is 20 mm or less, preferably 10 mm or less. preferable.
The waste gypsum powder can be easily separated from the board base paper by a known separation means. Examples of such separation means include vibration type and rotary type sieves. The size of the sieve mesh may be selected so that the waste gypsum powder can pass and the board base paper cannot pass.
（焼成工程）
本発明において、前記方法によって分離された廃石膏粉末は、適宜の装置により焼成を行い、半水石膏および/またはIII型無水石膏を得る。焼成装置は連続式でもバッチ式でも良い。この際の加熱温度は、１００℃〜３００℃が好ましく、１５０℃〜２００℃が特に好ましい。焼成する手段は、特に制限されないが、一般には、熱風乾燥機、スチームチューブドライヤー等の装置が使用される。また、この焼成工程は乾式であることが好ましいが、湿式焼成を採用してもよい。
(Baking process)
In the present invention, the waste gypsum powder separated by the above method is calcined with an appropriate apparatus to obtain hemihydrate gypsum and / or type III anhydrous gypsum. The baking apparatus may be a continuous type or a batch type. The heating temperature at this time is preferably from 100 ° C to 300 ° C, particularly preferably from 150 ° C to 200 ° C. The means for firing is not particularly limited, but generally, a device such as a hot air dryer or a steam tube dryer is used. Further, this firing step is preferably a dry method, but wet firing may be employed.
（粉砕工程）
本発明において、上記焼成した石膏は、適宜の装置により粉砕して粒度を調整することが好ましい。粉砕後の大きさとしては、好ましくは全累積細孔容積が１ｍｌ／ｇ以下、より好ましくは０．５〜１ｍＬ／ｇとなるようにする。この全累積細孔容積は、細孔径１ｎｍ〜１ｍｍの範囲の細孔について水銀ポロシメータによって測定した累積細孔容積である。粒径で表すと、レーザー回折・散乱式粒度分布計で測定した体積平均粒径で、０．５〜３０μｍ、更には１〜２０μｍ程度になるまで粉砕される。粉砕する手段は、特に制限されないが、一般には、ボールミル、ピンミル、高速回転衝撃粉砕機等の装置が使用される。
(Crushing process)
In the present invention, the calcined gypsum is preferably pulverized by an appropriate apparatus to adjust the particle size. The size after pulverization is preferably such that the total cumulative pore volume is 1 ml / g or less, more preferably 0.5 to 1 mL / g. This total cumulative pore volume is the cumulative pore volume measured with a mercury porosimeter for pores having a pore diameter in the range of 1 nm to 1 mm. When expressed in terms of particle size, the volume average particle size measured with a laser diffraction / scattering particle size distribution meter is 0.5 to 30 μm, and further pulverized to about 1 to 20 μm. The means for pulverization is not particularly limited, but generally, an apparatus such as a ball mill, a pin mill, a high-speed rotary impact pulverizer or the like is used.
なお、廃石膏ボードから半水石膏及び／又はIII型無水石膏を得る方法は上記した方法に限られるものではない。 The method for obtaining hemihydrate gypsum and / or type III anhydrous gypsum from waste gypsum board is not limited to the above-described method.
（晶析工程）
本発明においては、上記例のようにして得た半水石膏及び／又はIII型無水石膏を晶析により二水石膏へと変換する。具体的には、水の存在する晶析反応槽内に半水石膏及び／又はIII型無水石膏を加えると、当該半水石膏及び／又はIII型無水石膏は一旦溶解し、再度析出してくる。この際、反応系の温度を９０℃以下にしておけば、析出してくる結晶は二水石膏となる。二水石膏の種結晶を反応系に存在させておくと、より効率的に二水石膏の析出が起きる。種結晶の量は半水石膏及び／又はIII型無水石膏１００質量部に対して２０〜１００質量部が好ましい。
(Crystallization process)
In the present invention, hemihydrate gypsum and / or type III anhydrous gypsum obtained as in the above example is converted into dihydrate gypsum by crystallization. Specifically, when hemihydrate gypsum and / or type III anhydrous gypsum is added to the crystallization reaction tank in the presence of water, the hemihydrate gypsum and / or type III anhydrous gypsum dissolves once and precipitates again. . Under the present circumstances, if the temperature of a reaction system shall be 90 degrees C or less, the crystal | crystallization which will precipitate will become dihydrate gypsum. When the seed crystal of dihydrate gypsum is present in the reaction system, precipitation of dihydrate gypsum occurs more efficiently. The amount of the seed crystal is preferably 20 to 100 parts by mass with respect to 100 parts by mass of hemihydrate gypsum and / or type III anhydrous gypsum.
晶析反応を行う反応槽は、連続式でもバッチ式でもよい。連続式の場合、単段式でもよいが、２槽以上の多段式で行ってもよい。多段式の場合、第１槽から次以降の晶析反応槽への送液は、オーバーフローで行っても良いし、ポンプにより送液しても良い。また、均一になるよう撹拌しながら反応を行うことが好ましい。 The reaction tank for performing the crystallization reaction may be a continuous type or a batch type. In the case of a continuous system, a single stage system may be used, but a multistage system having two or more tanks may be used. In the case of a multi-stage system, liquid feeding from the first tank to the subsequent crystallization reaction tanks may be performed by overflow or by a pump. Moreover, it is preferable to perform reaction, stirring so that it may become uniform.
反応槽のスラリー濃度は、２５〜５０質量％が好ましく、３０〜４０質量％が特に好ましい。 The slurry concentration in the reaction vessel is preferably 25 to 50% by mass, particularly preferably 30 to 40% by mass.
晶析反応を行う際の反応時間は、５〜１５時間が好ましく、反応温度は、９０℃以下、特に好ましくは、５０℃〜８０℃の範囲で行うことが好ましい。 The reaction time for carrying out the crystallization reaction is preferably 5 to 15 hours, and the reaction temperature is preferably 90 ° C. or lower, particularly preferably 50 ° C. to 80 ° C.
（フッ素除去剤）
本発明においては、リン酸一水素カルシウム二水和物をフッ素除去剤として使用し、上記晶析反応槽に共存させる点に最大の特徴を有する。晶析反応槽へのリン酸一水素カルシウム二水和物の添加は、二水石膏の析出が完了する前であれば良いが、特に好ましくは二水石膏の析出が開始すると同時またはその前である。これにより、フッ素を含む石膏の溶解により溶出したフッ素の除去が十分に行われる。従って、多段式の連続反応槽により晶析反応を行う場合には、リン酸一水素カルシウム二水和物は第１槽に添加することが好ましい。また晶析反応を連続式で行う場合には、晶析反応槽中で後述する好ましい濃度となるように、リン酸一水素カルシウム二水和物も連続式で加えることが好ましい。
(Fluorine removal agent)
The present invention has the greatest feature in that calcium monohydrogen phosphate dihydrate is used as a fluorine removing agent and coexists in the crystallization reaction tank. The addition of calcium monohydrogen phosphate dihydrate to the crystallization reaction tank may be performed before the precipitation of dihydrate gypsum is completed, and particularly preferably at the same time or before the start of precipitation of dihydrate gypsum. is there. Thereby, the fluorine eluted by dissolution of gypsum containing fluorine is sufficiently removed. Accordingly, when the crystallization reaction is performed in a multistage continuous reaction tank, it is preferable to add calcium monohydrogen phosphate dihydrate to the first tank. When the crystallization reaction is carried out continuously, it is preferable to add calcium monohydrogen phosphate dihydrate in a continuous manner so as to obtain a preferable concentration described later in the crystallization reaction tank.
リン酸一水素カルシウム二水和物は、粉末の状態で加えても良いし、水等の溶媒に分散させたスラリーの状態で行っても良い。また、半水石膏及び／又はIII型無水石膏の粉末と混合した後、晶析反応槽へと加えることも好ましい態様である。 Calcium monohydrogen phosphate dihydrate may be added in the form of a powder, or may be carried out in the form of a slurry dispersed in a solvent such as water. Moreover, after mixing with the powder of hemihydrate gypsum and / or type III anhydrous gypsum, it is also a preferable aspect to add to the crystallization reaction tank.
このリン酸一水素カルシウム二水和物の添加量は、晶析反応槽に添加する改質前の石膏１００質量部に対して、８質量部以下が好ましく、５質量部以下が特に好ましい。下限は好ましくは１質量部以上である。なおリン酸一水素カルシウム二水和物の添加量は、晶析反応槽に添加する改質前の石膏のフッ素溶出量を予め測定し、その溶出量から、適宜決定しても良い。 The amount of calcium monohydrogen phosphate dihydrate added is preferably 8 parts by mass or less, particularly preferably 5 parts by mass or less, based on 100 parts by mass of gypsum before modification added to the crystallization reaction tank. The lower limit is preferably 1 part by mass or more. Note that the amount of calcium monohydrogen phosphate dihydrate added may be appropriately determined from the amount of elution of pre-reformed gypsum to be added to the crystallization reaction tank in advance.
（ろ過工程）
本発明においては、上記方法により製造された二水石膏を含むスラリーは、該二水石膏と水とが分離回収されて製品となる。水との分離方法は公知の固液分離方法を適宜採用すればよいが、好ましくはろ過である。ろ過する手段は特に制限されないが、フィルタープレス、ベルトフィルター等のろ過機が好適に使用される。
(Filtration process)
In the present invention, the slurry containing dihydrate gypsum produced by the above method is separated and recovered from the dihydrate gypsum and water to obtain a product. A known solid-liquid separation method may be appropriately employed as a separation method from water, but filtration is preferable. The filtering means is not particularly limited, but a filter such as a filter press or a belt filter is preferably used.
なお、上記のように得られる二水石膏は、全部を製品として回収しても良く、あるいはその一部を種結晶として循環使用しても良い。 The dihydrate gypsum obtained as described above may be entirely recovered as a product, or a part thereof may be recycled as a seed crystal.
以下、実施例によって本発明をさらに詳細に説明するが、本発明はこれらの実施例に限定されるものではない。 EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.
実施例１
細田企画製プラスターボシリーズにて廃石膏ボードの破砕、廃石膏粉末とボード原紙との分離し、得られた廃石膏粉末を１８０℃の熱風乾燥機で焼成して半水石膏及び／又はIII型無水石膏とした後、ホソカワミクロン製粉砕機（ＡＣＭパルベライザ）で粉砕した。
Example 1
Crushing waste gypsum board with Hosoda Planning Plus Turbo series, separating waste gypsum powder and board base paper, and baking the obtained waste gypsum powder in a hot air dryer at 180 ° C to make half-water gypsum and / or type III After making anhydrous gypsum, it was pulverized with a Hosokawa Micron pulverizer (ACM Pulverizer).
晶析反応のフローを図１に示す。体積平均粒径３４μｍの種結晶（二水石膏）が４０質量％含まれたスラリーを１．５Ｌずつ含んだ３槽の晶析反応槽を多段で設置し、前記焼成した石膏を１５０ｇ／ｈ、リン酸一水素カルシウム二水和物（和光純薬工業製）を７．５ｇ／ｈの供給速度で第１槽に添加した。この際、第１槽から次以降の晶析反応槽への送液は、オーバーフローで行い、第３槽のスラリーを１０８０ｇ／ｈの供給速度で第１槽に循環した。また、第1槽に７５℃の温水を３００ｇ／ｈの供給速度で添加して、水の蒸発分を補充した。各反応槽の反応温度は、６０℃で行い、第３槽の出口よりオーバーフローで排出された二水石膏スラリーをろ過して、二水石膏を得た。前記一連の操作を１日７時間、計１１日間行い、最終的に得られた二水石膏のフッ素溶出量をＨ３環告第４６号に従い測定した。結果を表１に示す。 The flow of the crystallization reaction is shown in FIG. Three crystallization reaction tanks each containing 1.5 L of a slurry containing 40% by mass of a seed crystal (dihydrate gypsum) having a volume average particle size of 34 μm were installed in multiple stages, and the calcined gypsum was 150 g / h, Calcium monohydrogen phosphate dihydrate (manufactured by Wako Pure Chemical Industries, Ltd.) was added to the first tank at a feed rate of 7.5 g / h. At this time, liquid feeding from the first tank to the subsequent crystallization reaction tank was performed by overflow, and the slurry in the third tank was circulated to the first tank at a supply rate of 1080 g / h. Moreover, 75 degreeC warm water was added to the 1st tank at the supply rate of 300 g / h, and the evaporation of water was replenished. The reaction temperature of each reaction tank was 60 ° C., and dihydrate gypsum slurry discharged by overflow from the outlet of the third tank was filtered to obtain dihydrate gypsum. The series of operations was performed for 7 hours a day for a total of 11 days, and the fluorine elution amount of the finally obtained dihydrate gypsum was measured in accordance with H3 Circular No. 46. The results are shown in Table 1.
晶析反応により、体積平均粒径が６５μｍの粒径の大きな二水石膏が得られた。さらに、フッ素溶出量を測定の結果、定量下限（０．１ｍｇ／Ｌ）未満となり、土壌環境基準を下回るフッ素溶出量が得られた。 By the crystallization reaction, a large dihydrate gypsum having a volume average particle diameter of 65 μm was obtained. Further, as a result of measuring the fluorine elution amount, the fluorine elution amount was less than the lower limit of quantification (0.1 mg / L), which was below the soil environment standard.
比較例１
実施例１において、１８０℃の熱風乾燥機で得られた廃石膏粉末のフッ素溶出量をＨ３環告第４６号に従い測定した。結果を表１に示す。測定の結果、４．８ｍｇ／Ｌのフッ素溶出量が得られた。
Comparative Example 1
In Example 1, the fluorine elution amount of the waste gypsum powder obtained with a hot air dryer at 180 ° C. was measured in accordance with H3 Ring No. 46. The results are shown in Table 1. As a result of the measurement, a fluorine elution amount of 4.8 mg / L was obtained.
比較例２
実施例１において、リン酸一水素カルシウム二水和物を添加せずに晶析反応を行った以外は、実施例１と同様の操作を行った。結果を表１に示す。晶析反応により、体積平均粒径が６３μｍの粒径の大きな二水石膏が得られた。得られた二水石膏のフッ素溶出量を測定の結果、２．４ｍｇ／Ｌであり、実施例1の結果よりも高い値が得られた。
Comparative Example 2
In Example 1, the same operation as in Example 1 was performed except that the crystallization reaction was performed without adding calcium monohydrogen phosphate dihydrate. The results are shown in Table 1. By the crystallization reaction, a large dihydrate gypsum having a volume average particle size of 63 μm was obtained. As a result of measuring the fluorine elution amount of the obtained dihydrate gypsum, it was 2.4 mg / L, which was higher than the result of Example 1.
比較例３
比較例２において、得られた二水石膏１００質量部に対して、リン酸一水素カルシウム二水和物を５質量部添加して混合した二水石膏のフッ素溶出量をＨ３環告第４６号に従い測定した。結果を表１に示す。測定の結果、フッ素溶出量は０．６ｍｇ／Ｌとなり、実施例１よりも高い値が得られた。
Comparative Example 3
In Comparative Example 2, with respect to 100 parts by mass of the obtained dihydrate gypsum, 5 mass parts of calcium monohydrogen phosphate dihydrate was added and mixed. Measured according to The results are shown in Table 1. As a result of the measurement, the fluorine elution amount was 0.6 mg / L, which was higher than Example 1.
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