JP4231134B2 - Highly dispersible magnesium hydroxide cake and method for producing the same - Google Patents
Highly dispersible magnesium hydroxide cake and method for producing the same Download PDFInfo
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Description
【０００１】
【発明の属する技術分野】
本発明は、高分散性水酸化マグネシウムケーク及びその製造方法に関するものである。
【０００２】
【従来の技術】
排煙の脱硫剤などに用いられている水酸化マグネシウムスラリーは、水酸化マグネシウム粒子を水に分散させたものであり、海水あるいは塩化マグネシウム水溶液（苦汁またはかん水）に水酸化カルシウムを加えて水酸化マグネシウムを生成させ、次いで、シックナーで濃縮して製造するのが一般的である。従って、水酸化マグネシウムスラリーは、海に近い場所で製造されて、使用場所へタンク等に入れて輸送されている。
【０００３】
水酸化マグネシウムスラリーは水酸化マグネシウムの含有量が３０％程度であり、その残りの成分は水である。従って、水酸化マグネシウムスラリーを濾過して水酸化マグネシウムケークにし、これを輸送して、そして使用の際に、水に分散させてスラリーに戻すことができれば、輸送コストを低減することができ、また、水酸化マグネシウムケークを梱包し保管することで保管場所も小さくすることができる。
しかし、水酸化マグネシウムケークを水に投入して攪拌機で攪拌しただけでは、水酸化マグネシウム粒子を均一に分散させてスラリーに戻しにくいことは既に知られている。
【０００４】
水に分散しやすい水酸化マグネシウムケークの検討がされており、例えば、特公昭５８−４３３２９号公報では、水酸化マグネシウムスラリーを加圧脱水し、含水率４０〜１５％の水酸化マグネシウムケークとした後、このケークを粒度２０ｍｍ以下に破砕する水酸化マグネシウムケークの製造方法が提案されている。この製造方法により製造した水酸化マグネシウムケークは、水に投入して攪拌機で攪拌するだけでスラリーにすることができるとされている。
【０００５】
【発明が解決しようとする課題】
本発明者の研究によると、水酸化マグネシウムケークを脱水する際の条件によって、分散性の高いケークと分散性の低いケークとが得られることが明らかになった。さらに検討を重ねた結果、分散性の低い水酸化マグネシウムケークは、ケークの通気率が分散性の高いケークと比較して低いことが判明した。このことから、分散性の低い水酸化マグネシウムケークは、水酸化マグネシウムの粒子と粒子との間に隙間がない（凝集している）ので、水がケーク内に侵入しにくいために分散性が低く、一方分散性の高いケークは、水酸化マグネシウムの粒子と粒子との間に隙間があり、水がその隙間からケーク内に侵入するので分散性が高くなると考えられる。
従って、本発明の目的は、水に投入して攪拌機で攪拌するだけで容易に分散する水酸化マグネシウムケーク、すなわち、通気率の高い水酸化マグネシウムケーク及び、その製造方法を提供することである。
【０００６】
【課題を解決するための手段】
本発明は、水分率が１０〜３５重量％の範囲内にあり、ＪＩＳ Ｒ ２１１５に記載された方法（但し、乾燥前処理は実施しない）で測定した通気率が、１×１０-4〜１×１０-1ｍ2の範囲内にあり、空隙率が１０〜６０％の範囲内にあることを特徴とする高分散性水酸化マグネシウムケークにある。
【０００７】
本発明は、上記の水酸化マグネシウムケークの製造方法と、上記の水酸化マグネシウムケークを用いた水酸化マグネシウムスラリーの製造方法にもある。
【０００８】
【発明の実施の形態】
本発明の高分散性水酸化マグネシウムケークは、水分率が１０〜３５％、好ましくは、１５〜３０％の範囲にあるので、水酸化マグネシウムスラリーと比較して輸送コストを低減することができ、ケークの状態で梱包し保管することで保管場所を小さくすることができる。なお、本発明における水分率とは、水酸化マグネシウムケークを１０５℃で乾燥したときの減量を乾燥前の水酸化マグネシウムケークの重量で割った値である。
本発明の水酸化マグネシウムケークは、通気率が１×１０-4〜１×１０-1（好ましくは、１×１０-3〜１×１０-2）ｍ2 の範囲内にあるので、ケークを水に投入すると水酸化マグネシウムの粒子間に水が侵入し、攪拌機で攪拌するだけで分散する。なお、本発明における通気率は、ＪＩＳ Ｒ ２１１５（耐火れんがの通気率の試験方法）に記載された方法に基づいて測定した値であり、水酸化マグネシウムケークを乾燥させないで、以下の方法により測定した値である。
（１）水酸化マグネシウムケークを直径５０ｍｍ、高さ１０〜５０ｍｍの円柱状にしたもの試験片とし、周囲を完全に密閉できる試料ホルダーに試験片を設置する。尚、試験片の通気方向は、濾過時の加圧方向と同一方向になるようにする。
（２）試験片の一方の面に気体（空気）を流し、試験片の二つの面の圧力を測定する。
（３）下記の式（１）より、気体の試験片の通気率（μ）を算出する。
式（１） μ＝Ｖ／ｔ×η×Ｌ／Ｓ×１／（Ｐ1 −Ｐ2 ）×２×Ｐ／（Ｐ1 ＋Ｐ2 ）
ここで、Ｐは絶対圧力（Ｎ／ｍｍ2 ）、ｔは試験時間（ｓ）、Ｖは絶対圧力Ｐにおいて、時間ｔ内に通過する気体の容積（ｍｍ3 ）、Ｓは気体が通過する試験片の面積（１９６０ｍｍ2 ）、Ｌは試験片の厚さ（ｍｍ）、Ｐ1 は気体を流した側の絶対圧力（Ｎ／ｍｍ2 ）、Ｐ2 は気体が通過した側の絶対圧力（Ｎ／ｍｍ2 、ηは試験温度での気体の動粘度（Ｐａ・ｓ）である。
【０００９】
さらに本発明の水酸化マグネシウムケークは、下記の式（２）で算出される空隙率が１０〜６０％（より好ましくは、１５〜３５％）の範囲内にあることが好ましい。
式（２） 空隙率（％）＝（Ｖ0 −ａ−ｂ）／Ｖ0 ×１００
ここで、Ｖ0 は水酸化マグネシウムケークの見かけ体積（ｃｍ3 ）、ａはケーク中に存在する水の体積（ｃｍ3 ）、ｂはケーク中の水酸化マグネシウムの体積（ｃｍ3 ）である。
【００１０】
本発明の高分散性水酸化マグネシウムケークは、水酸化マグネシウムスラリーを加圧濾過して得られたケークに、圧搾空気を吹き付けることにより製造することができる。すなわち、水酸化マグネシウム粒子間の空隙を維持できる程度に、水酸化マグネシウムスラリーを加圧濾過し、次いで加圧濾過して得られたケークに圧搾空気を吹き付けて、水酸化マグネシウム粒子間の空隙に付着している水分を吹き飛ばすことにより、本発明の高分散性水酸化マグネシウムケークを製造することができる。加圧濾過して得られたケークを水で洗浄して、圧搾空気を吹き付けても良い。
以上のようにして製造した水酸化マグネシウムケークは、圧搾空気を吹き付けることにより、ケーク内を空気が通過できるように空隙が形成されるので通気率が高くなる。また、水酸化マグネシウム粒子の凝集を起こりにくくするために、スラリーは、体積粒子径で０．５μｍ未満の粒子の含有量が３０％以下であることが好ましい。
【００１１】
加圧濾過では、水酸化マグネシウムスラリーを０．５〜５ＭＰａ、好ましくは１〜２ＭＰａの範囲内の圧力で濾過する。この加圧濾過により製造される水酸化マグネシウムケークの水分率は、３０〜４０％の範囲内であることが好ましい。水分率を低くしすぎると、水酸化マグネシウムケーク中の空隙がつぶれて、後に圧搾空気を吹き付けても粒子間に空隙が得られなくなり、ケークの通気率が低くなる。また、加圧濾過により製造された板状の水酸化マグネシウムケークの厚さは１０〜５０ｍｍの範囲内であることが好ましい。ケークの厚さが、厚すぎると空隙に付着している水分を除去するために、圧搾空気の圧力を高く設定する必要がある。
【００１２】
加圧濾過で得られた水酸化マグネシウムケークは、ケークの一方の面（加圧方向と同一の方向）に圧搾空気を吹き付けることによりさらに脱水する。この圧搾空気の圧力は２〜１５×１０5 Ｐａの範囲が好ましく、４〜７×１０5 Ｐａの範囲であることがより好ましい。
【００１３】
【実施例】
（水酸化マグネシウムスラリーの製造）
海水に水酸化カルシウムを加えて、水酸化マグネシウムを生成させ、次いで、シックナーで濃縮して水酸化マグネシウムスラリーを製造した。スラリー中の水酸化マグネシウム量は３６重量％、体積粒子径が０．５μｍ未満の水酸化マグネシウム粒子の含有率は５％であった。また、スラリーの粘度は１９４ｍＰａ・ｓ及び目開き４５μｍの篩に通過した水酸化マグネシウムの割合は９９．９％であった。粘度はＢ型粘度計で測定した（回転数６０ｒｐｍ、Ｎｏ．３ローター）。
【００１４】
（実施例１）
上記の水酸化マグネシウムスラリーを１．５ＭＰａで加圧濾過し厚さ３０ｍｍ、水分率３２％のケークとし、次いで、このケークに５．５×１０5 Ｐａの圧搾空気を加圧方向と同一の方向に１０分間吹き付けて脱水して水酸化マグネシウムケークを製造した。得られた水酸化マグネシウムケークは、水分率２０．９％、通気率４．８１×１０-3ｍ2 、空隙率２６％であった。
【００１５】
（実施例２）
上記の水酸化マグネシウムスラリーを、０．７ＭＰａで加圧濾過し厚さ４０ｍｍの水分率３５％のケークとし、次いで、このケークに４×１０5 Ｐａの圧搾空気を加圧方向と同一の方向に２０分間吹き付けて脱水して水酸化マグネシウムケークを製造した。得られた水酸化マグネシウムケークは、水分率２５．６％、通気率４．５４×１０-3ｍ2 、空隙率１７％であった。
【００１６】
（比較例１）
上記の水酸化マグネシウムスラリーを、チューブ型加圧脱水装置で１０ＭＰａで５分間、加圧して脱水し水酸化マグネシウムケークを製造した。得られた水酸化マグネシウムケークは、水分率２６％、通気率５×１０-15 ｍ2 以下、空隙率３％であった。
【００１７】
（比較例２）
上記の水酸化マグネシウムスラリーを、減圧濾過装置で１５分間濾過して水酸化マグネシウムケークを製造した。得られた水酸化マグネシウムケークは、水分率３５％、通気率５×１０-15 ｍ2 以下、空隙率１％以下であった。
【００１８】
（評価及び結果）
１．視覚評価
上記の実施例１及び比較例１で製造した水酸化マグネシウムケーク１００ｇを破砕しないで、水を５００ｍｌ入れた１Ｌビーカーに投入して静置し、投入後２時間までケークの状態を目視で観察した。そして４枚羽根攪拌機を用い、２５０ｒｐｍで５分間攪拌し、攪拌後１時間静置してその状態を目視で観察した。
その結果、実施例１の水酸化マグネシウムケークは、水に投入してから３０秒後には気泡の発生に伴いケークが分散し、投入してから６０秒後に気泡の発生は止まったが、その後もケークは徐々に崩れて、投入してから２時間後では投入前の形状を維持できなかった。そして、この状態のままで攪拌すると、水酸化マグネシウムケークは均一に分散し、攪拌後１時間静置すると、水酸化マグネシウムの粒子が均一に沈降した。
一方、比較例１の水酸化マグネシウムケークは、水に投入して１０分後でもケークにひびが入っている程度であり、投入してから２時間後でも、ほとんど投入前の形状を維持していた。そして、この状態のままで攪拌すると、水酸化マグネシウムケークはわずかに分散するが、ケークの一部は分散せずに残存し、攪拌だけではケークを完全に分散させることはできなかった。そして、攪拌後１時間静置しても、水酸化マグネシウムケークの残存物が確認できた。
【００１９】
２．分散性評価
水酸化マグネシウムの濃度が３６重量％になり、かつ水と水酸化マグネシウムとの総重量が１２８ｋｇになるように、上記の実施例１及び比較例１で製造した水酸化マグネシウムケークと水を量り取った。尚、実施例１の水酸化マグネシウムケークは破砕を行わずケークをそのまま（体積平均粒子径は５０ｍｍ以上）で使用し、一方、比較例１の水酸化マグネシウムケークは、分散性を高くするためにケークを破砕して目開き２０ｍｍの篩を通過したものを使用した。
量り取った水を容量２００Ｌの容器に入れ、次いで、直径１０ｃｍの３枚羽根を２４０ｒｐｍで回転させながら、量り取ったケーク全量を投入開始から４分間で投入完了するように容器に投入した。
ケーク投入後５、１０、２０、３０、６０分ごとにこの混合溶液をサンプリングして、上記スラリーと同様にして、混合溶液の粘度及び目開き４５μｍの篩透過率を測定した。その結果を表１に示す。
【００２０】
【表１】
表１より、実施例１の水酸化マグネシウムケークでは、破砕しなくてもケークを水に投入して５分で篩透過率及び粘度が脱水前のスラリーとほぼ同じ混合溶液（スラリー）になっていることがわかる。
【００２２】
【発明の効果】
本発明の高分散性水酸化マグネシウムケークは、破砕しなくても攪拌機で攪拌するだけで水に容易に分散し、本発明のケークを水に分散させて製造したスラリーは、篩通過率及び粘度が従来の排煙脱硫剤などに用いられている水酸化マグネシウムスラリー（脱水前のスラリー）と比較しても変化がない。従って、本発明の高分散性水酸化マグネシウムケークは、排煙脱硫剤用の水酸化マグネシウムスラリーの原料として使用することができる。
本発明の高分散性水酸化マグネシウムケークを排煙脱硫剤用の水酸化マグネシウムスラリーの原料として使用することで、輸送コストを低減することができ、さらに、水酸化マグネシウムケークの状態で梱包し保管することで保管場所も小さくすることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a highly dispersible magnesium hydroxide cake and a method for producing the same.
[0002]
[Prior art]
Magnesium hydroxide slurry used in flue gas desulfurization agents is a dispersion of magnesium hydroxide particles in water, and calcium hydroxide is added to seawater or magnesium chloride aqueous solution (bitter or brackish water) for hydroxylation. It is common to produce magnesium and then concentrate it with a thickener. Therefore, the magnesium hydroxide slurry is manufactured at a location close to the sea and transported in a tank or the like to a use location.
[0003]
The magnesium hydroxide slurry has a magnesium hydroxide content of about 30%, and the remaining component is water. Therefore, if the magnesium hydroxide slurry can be filtered into a magnesium hydroxide cake, which can be transported and dispersed in water and returned to the slurry for use, transportation costs can be reduced, and By packing and storing magnesium hydroxide cake, the storage location can be reduced.
However, it is already known that magnesium hydroxide particles are not easily dispersed and returned to a slurry simply by adding magnesium hydroxide cake into water and stirring with a stirrer.
[0004]
Magnesium hydroxide cake that is easy to disperse in water has been studied. For example, in Japanese Examined Patent Publication No. 58-43329, magnesium hydroxide slurry is pressurized and dehydrated to obtain a magnesium hydroxide cake having a water content of 40 to 15%. Thereafter, a method for producing a magnesium hydroxide cake is proposed in which the cake is crushed to a particle size of 20 mm or less. It is said that the magnesium hydroxide cake produced by this production method can be made into a slurry simply by adding it to water and stirring it with a stirrer.
[0005]
[Problems to be solved by the invention]
According to the research of the present inventors, it has been clarified that a highly dispersible cake and a low dispersible cake can be obtained depending on the conditions for dehydrating the magnesium hydroxide cake. As a result of further studies, it was found that a magnesium hydroxide cake with low dispersibility has a lower air permeability of the cake than a cake with high dispersibility. For this reason, a magnesium hydroxide cake with low dispersibility has no gap (aggregates) between the magnesium hydroxide particles, so that it is difficult for water to enter the cake. On the other hand, a highly dispersible cake has a gap between magnesium hydroxide particles, and water penetrates into the cake through the gap, so that the dispersibility is considered to be high.
Accordingly, an object of the present invention is to provide a magnesium hydroxide cake that can be easily dispersed by simply adding it to water and stirring it with a stirrer, that is, a magnesium hydroxide cake having a high air permeability, and a method for producing the same.
[0006]
[Means for Solving the Problems]
In the present invention, the moisture content is in the range of 10 to 35% by weight, and the air permeability measured by the method described in JIS R 2115 (however, pre-drying treatment is not performed) is 1 × 10 −4 to 1 × 10 -1 Ri range near the m 2, the highly dispersed magnesium hydroxide cake porosity and said near Rukoto within 10-60%.
[0007]
The present invention also resides in a method for producing the above magnesium hydroxide cake and a method for producing a magnesium hydroxide slurry using the above magnesium hydroxide cake .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The highly dispersible magnesium hydroxide cake of the present invention has a moisture content of 10 to 35%, preferably in the range of 15 to 30%. Therefore, the transportation cost can be reduced as compared with the magnesium hydroxide slurry. By packing and storing in the cake state, the storage location can be reduced. The moisture content in the present invention is a value obtained by dividing the weight loss when the magnesium hydroxide cake is dried at 105 ° C. by the weight of the magnesium hydroxide cake before drying.
The magnesium hydroxide cake of the present invention has an air permeability in the range of 1 × 10 −4 to 1 × 10 −1 (preferably 1 × 10 −3 to 1 × 10 −2 ) m 2. When it is put into water, water enters between the particles of magnesium hydroxide and is dispersed only by stirring with a stirrer. The air permeability in the present invention is a value measured based on the method described in JIS R 2115 (Test method for air permeability of refractory brick), and measured by the following method without drying the magnesium hydroxide cake. It is the value.
(1) A magnesium hydroxide cake having a cylindrical shape with a diameter of 50 mm and a height of 10 to 50 mm is used as a test piece, and the test piece is placed on a sample holder that can be completely sealed. It should be noted that the aeration direction of the test piece is set in the same direction as the pressure direction during filtration.
(2) A gas (air) is flowed on one side of the test piece, and the pressures on the two sides of the test piece are measured.
(3) The air permeability (μ) of the gas test piece is calculated from the following equation (1).
Formula (1) μ = V / t × η × L / S × 1 / (P 1 −P 2 ) × 2 × P / (P 1 + P 2 )
Here, P is the absolute pressure (N / mm 2 ), t is the test time (s), V is the volume of the gas passing in time t at the absolute pressure P (mm 3 ), and S is the test through which the gas passes. The area of the piece (1960 mm 2 ), L is the thickness of the test piece (mm), P 1 is the absolute pressure (N / mm 2 ) on the gas flow side, and P 2 is the absolute pressure (N / Mm 2 , η is the kinematic viscosity (Pa · s) of the gas at the test temperature.
[0009]
Further, in the magnesium hydroxide cake of the present invention, the porosity calculated by the following formula (2) is preferably in the range of 10 to 60% (more preferably 15 to 35%).
Formula (2) Porosity (%) = (V 0 −ab) / V 0 × 100
Here, V 0 is the apparent volume (cm 3 ) of the magnesium hydroxide cake, a is the volume of water present in the cake (cm 3 ), and b is the volume of magnesium hydroxide (cm 3 ) in the cake.
[0010]
The highly dispersible magnesium hydroxide cake of the present invention can be produced by blowing compressed air onto a cake obtained by pressure filtration of a magnesium hydroxide slurry. That is, the magnesium hydroxide slurry is pressure filtered to such an extent that the gaps between the magnesium hydroxide particles can be maintained, and then compressed air is blown onto the cake obtained by pressure filtration to form gaps between the magnesium hydroxide particles. By blowing off the adhering water, the highly dispersible magnesium hydroxide cake of the present invention can be produced. The cake obtained by pressure filtration may be washed with water and sprayed with compressed air.
The magnesium hydroxide cake produced as described above has a high air permeability because air gaps are formed so that air can pass through the cake by blowing compressed air. Moreover, in order to make aggregation of magnesium hydroxide particles difficult to occur, the slurry preferably has a content of particles having a volume particle diameter of less than 0.5 μm of 30% or less.
[0011]
In pressure filtration, the magnesium hydroxide slurry is filtered at a pressure in the range of 0.5 to 5 MPa, preferably 1 to 2 MPa. The moisture content of the magnesium hydroxide cake produced by this pressure filtration is preferably in the range of 30 to 40%. If the moisture content is too low, the voids in the magnesium hydroxide cake are crushed, and even if compressed air is blown later, voids cannot be obtained between the particles, and the air permeability of the cake becomes low. The thickness of the plate-like magnesium hydroxide cake produced by pressure filtration is preferably in the range of 10 to 50 mm. If the thickness of the cake is too thick, it is necessary to set the pressure of the compressed air high in order to remove moisture adhering to the gap.
[0012]
The magnesium hydroxide cake obtained by pressure filtration is further dehydrated by spraying compressed air on one side of the cake (the same direction as the pressure direction). The pressure of the compressed air is preferably in the range of 2-15 × 10 5 Pa, and more preferably in the range of 4-7 × 10 5 Pa.
[0013]
【Example】
(Manufacture of magnesium hydroxide slurry)
Calcium hydroxide was added to seawater to form magnesium hydroxide, and then concentrated with a thickener to produce a magnesium hydroxide slurry. The amount of magnesium hydroxide in the slurry was 36% by weight, and the content of magnesium hydroxide particles having a volume particle diameter of less than 0.5 μm was 5%. The slurry had a viscosity of 194 mPa · s and a ratio of magnesium hydroxide passed through a sieve having an opening of 45 μm was 99.9%. The viscosity was measured with a B-type viscometer (rotation speed: 60 rpm, No. 3 rotor).
[0014]
Example 1
The magnesium hydroxide slurry is subjected to pressure filtration at 1.5 MPa to obtain a cake having a thickness of 30 mm and a moisture content of 32%. Next, 5.5 × 10 5 Pa of compressed air is applied to the cake in the same direction as the pressure direction. And dried for 10 minutes to produce a magnesium hydroxide cake. The obtained magnesium hydroxide cake had a moisture content of 20.9%, an air permeability of 4.81 × 10 −3 m 2 and a porosity of 26%.
[0015]
(Example 2)
The magnesium hydroxide slurry is subjected to pressure filtration at 0.7 MPa to obtain a cake having a thickness of 35% and a moisture content of 35%. Next, 4 × 10 5 Pa of compressed air is applied to the cake in the same direction as the pressure direction. A magnesium hydroxide cake was produced by spraying for 20 minutes for dehydration. The obtained magnesium hydroxide cake had a moisture content of 25.6%, an air permeability of 4.54 × 10 −3 m 2 , and a porosity of 17%.
[0016]
(Comparative Example 1)
The magnesium hydroxide slurry was pressurized and dehydrated with a tube-type pressure dehydrator at 10 MPa for 5 minutes to produce a magnesium hydroxide cake. The obtained magnesium hydroxide cake had a moisture content of 26%, an air permeability of 5 × 10 −15 m 2 or less, and a porosity of 3%.
[0017]
(Comparative Example 2)
The magnesium hydroxide slurry was filtered with a vacuum filtration device for 15 minutes to produce a magnesium hydroxide cake. The obtained magnesium hydroxide cake had a moisture content of 35%, an air permeability of 5 × 10 −15 m 2 or less, and a porosity of 1% or less.
[0018]
(Evaluation and results)
1. Visual evaluation 100 g of the magnesium hydroxide cake produced in Example 1 and Comparative Example 1 was not crushed but placed in a 1 L beaker containing 500 ml of water and allowed to stand, and the state of the cake was visually observed for up to 2 hours after the addition. Observed. Then, using a four-blade stirrer, the mixture was stirred at 250 rpm for 5 minutes, allowed to stand for 1 hour after stirring, and the state was visually observed.
As a result, in the magnesium hydroxide cake of Example 1, the cake was dispersed with the generation of bubbles 30 seconds after the addition to water, and the generation of bubbles stopped 60 seconds after the addition. The cake gradually collapsed, and the shape before the addition could not be maintained 2 hours after the addition. When stirring in this state, the magnesium hydroxide cake was uniformly dispersed, and when allowed to stand for 1 hour after stirring, the magnesium hydroxide particles uniformly settled.
On the other hand, the magnesium hydroxide cake of Comparative Example 1 is only cracked in the cake even after 10 minutes after being put into water, and even before 2 hours after being thrown in, the shape before charging is almost maintained. It was. When stirring in this state, the magnesium hydroxide cake was slightly dispersed, but a part of the cake remained without being dispersed, and the cake could not be completely dispersed only by stirring. And even if it left still for 1 hour after stirring, the residue of magnesium hydroxide cake has been confirmed.
[0019]
2. Evaluation of Dispersibility Magnesium hydroxide cake and water produced in Example 1 and Comparative Example 1 above so that the concentration of magnesium hydroxide is 36% by weight and the total weight of water and magnesium hydroxide is 128 kg. Weighed out. In addition, the magnesium hydroxide cake of Example 1 is used without being crushed, and the cake is used as it is (volume average particle diameter is 50 mm or more), while the magnesium hydroxide cake of Comparative Example 1 is used to increase dispersibility. The cake was crushed and passed through a sieve having an opening of 20 mm.
The weighed water was put into a container with a capacity of 200 L, and then, the three pieces of 10 cm diameter blades were rotated at 240 rpm, and the whole amount of the cake weighed was put into the container so that the charging was completed in 4 minutes from the start of charging.
The mixed solution was sampled every 5, 10, 20, 30, and 60 minutes after the cake was added, and the viscosity of the mixed solution and the sieve transmittance of 45 μm were measured in the same manner as the slurry. The results are shown in Table 1.
[0020]
[Table 1]
From Table 1, in the magnesium hydroxide cake of Example 1, even if it is not crushed, the cake is put into water, and the mixed solution (slurry) becomes almost the same as the slurry before dehydration in 5 minutes after passing the cake into water. I understand that.
[0022]
【The invention's effect】
The highly dispersible magnesium hydroxide cake of the present invention is easily dispersed in water just by stirring with a stirrer without being crushed, and the slurry produced by dispersing the cake of the present invention in water has a sieve passing rate and viscosity. However, there is no change even when compared with a magnesium hydroxide slurry (slurry before dehydration) used in a conventional flue gas desulfurization agent. Therefore, the highly dispersible magnesium hydroxide cake of the present invention can be used as a raw material for magnesium hydroxide slurry for flue gas desulfurization agents.
By using the highly dispersible magnesium hydroxide cake of the present invention as a raw material of the magnesium hydroxide slurry for the flue gas desulfurization agent, the transportation cost can be reduced, and further, the magnesium hydroxide cake is packed and stored. By doing so, the storage location can also be reduced.
Claims (5)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP31836498A JP4231134B2 (en) | 1998-10-21 | 1998-10-21 | Highly dispersible magnesium hydroxide cake and method for producing the same |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP31836498A JP4231134B2 (en) | 1998-10-21 | 1998-10-21 | Highly dispersible magnesium hydroxide cake and method for producing the same |
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| Publication Number | Publication Date |
|---|---|
| JP2000128526A JP2000128526A (en) | 2000-05-09 |
| JP4231134B2 true JP4231134B2 (en) | 2009-02-25 |
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| JP31836498A Expired - Fee Related JP4231134B2 (en) | 1998-10-21 | 1998-10-21 | Highly dispersible magnesium hydroxide cake and method for producing the same |
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| Country | Link |
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