JP3924019B2 - Method for producing light calcium carbonate - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、軽質炭酸カルシウムの製造方法に関するものである。さらに詳しくいえば、本発明は、酸化カルシウムを原料とし、種晶を用いずに紡錘状軽質炭酸カルシウムを製造するに当り、反応開始温度を変えることにより、その粒径を制御する方法の改良に関するものである。
【０００２】
【従来の技術】
従来、炭酸カルシウムは工業的には石灰石を焼成して得た生石灰を原料に用いて、これを水と反応させて消石灰水性スラリーを調製し、これを二酸化炭素と反応させることにより軽質炭酸カルシウムとして製造され、０．１μｍ以下の膠質粒子から数μｍ〜数十μｍの粗大粒子までの種々の粒径のものや、紡錘状、角状、柱状、針状、球状などの種々の形態のものが生産されている。
【０００３】
この粒径の制御については、工業的には種晶添加法が知られており、例えば、粒径０．０１〜０．０９μｍの極微細種晶を炭酸化反応の途中で添加し、立方体状炭酸カルシウムを製造する方法（特公平３−１９１６５号公報）、カルシウム塩の水溶液に炭酸カルシウム種晶を特定比で加えたのち、二酸化炭素を導入することにより、種晶表面に析出する炭酸カルシウムの量を調整して平均粒径を制御する方法（特開昭６３−２３０５２０号公報）、一部炭酸化された膠質粒子状水酸化カルシウム水性懸濁液を所定割合で炭酸化率が所定値になるまでに添加して均一で分散性が良好な所定紡錘状炭酸カルシウムを製造する方法（特公平８−１８８２７号公報）、この方法を酸化カルシウムの湿式消化後液体サイクロン処理して調製した水酸化カルシウム水性懸濁液を原料に用いて行う方法（特開平６−５６４２２号公報）などが提案されている。
【０００４】
しかしながら、これらの方法では、粒径を制御するのに用いる種晶を生成させる反応を別に行わねばならないため煩雑となり、また反応器やタンク等の新たな設備が必要となるなどの問題を生じるのを免れない。
【０００５】
【発明が解決しようとする課題】
本発明は、このような種晶を用いて粒径を制御する従来法の欠点を克服し、操作を簡便にして効率よく粒径を制御し、紡錘状の炭酸カルシウムを製造する工業的な方法を提供することを目的としてなされたものである。
【０００６】
【課題を解決するための手段】
本発明者は、炭酸カルシウムの工業的製法を開発するために種々研究を重ねた結果、所定炭酸化反応で生成される炭酸カルシウム水性スラリーの脱水やろ過で生じる分離水やろ水を、その中の炭酸カルシウム濃度を調整して消化用の水の全部あるいは一部に用い、かつ３０〜７０℃の温度において炭酸化反応を行わせることにより、制御された粒径すなわち揃った粒径をもつ紡錘状の軽質炭酸カルシウムが得られることを見出し、この知見に基づいて本発明を完成するに至った。
【０００７】
すなわち、本発明は、酸化カルシウムに水を加え湿式消化させて水酸化カルシウム水性懸濁液を調製し、次いでこの水性懸濁液に二酸化炭素又は二酸化炭素含有ガスを吹き込み炭酸化することにより軽質炭酸カルシウムを製造するに当り、消化用の水として、水酸化カルシウム水性懸濁液の炭酸化反応で生成される炭酸カルシウム水性スラリーの分離脱水処理により得られる分離水及び該スラリーのろ過処理により得られるろ水の中から選ばれた少なくとも１種あるいはそれを混入させた水を生石灰濃度５０〜１５０ｇＣａＯ／リットル、炭酸カルシウム濃度０．１〜７ｇ／リットルに調整して用い、反応開始温度３０〜７０℃、平均滞留時間６０分以内の条件下で、種晶の添加なしに反応させ、この反応開始温度を変えることにより生成する紡錘状粒子の粒径を制御することを特徴とする紡錘状軽質炭酸カルシウムの製造方法を提供するものである。
【０００８】
【発明の実施の形態】
本発明方法においては、酸化カルシウムを所定の水で湿式消化させて水酸化カルシウム水性懸濁液を調製し、次いでこの水性懸濁液に二酸化炭素やそれを含有するガスを吹き込み炭酸化することにより軽質炭酸カルシウムが製造される。
【０００９】
この所定の消化用の水は、水酸化カルシウム水性懸濁液の炭酸化反応で生成される炭酸カルシウム水性スラリーの分離脱水処理により得られる分離水及び該スラリーのろ過処理により得られるろ水の中から選ばれた少なくとも１種あるいはそれを混入させた水である。この分離脱水処理としては、遠心分離処理や沈降分離処理が好適に用いられ、その他、浮上分離処理も用いられる。遠心分離処理は、通常、適当な装置、例えば遠心沈降機、遠心ろ過機、遠心分離機、遠心傾瀉機（デカンター）、遠心清澄機（クラリファイヤー）などを用いて行われる。ろ過処理として好適には加圧又は真空下に行う加圧ろ過処理又は真空ろ過処理が行われ、加圧ろ過処理はフィルタープレスやベルトプレスによるのが、また真空ろ過処理はオリバーフィルターやドラムフィルターによるのが好ましい。
上記消化用の水には、炭酸カルシウムが含有されているので、その濃度を０．１〜７ｇ／リットルの範囲に調整して用いる。また、この消化用の水は導電率が０．２〜１０ｍＳ／ｃｍであるものが好ましい。上記分離水やろ水を水に混入させる場合、この水としては通常、工業用水、井戸水、地下水などが用いられる。
【００１０】
本発明方法において、この生石灰の水による湿式消化は、濃度５０〜１５０ｇ‐ＣａＯ／リットル好ましくは６０〜１２０ｇ‐ＣａＯ／リットル、消化水温度すなわち反応開始温度を３０〜７０℃の範囲内で選び、平均滞留時間６０分以内好ましくは３〜３０分という消化条件下で行うことが必要である。この条件の範囲を逸脱すると所期の効果が得られない。すなわち、この濃度が高すぎると生成する消石灰水性スラリーの粘度が上昇し、残さが増大するし、また低すぎても効率的でなくなる。消化水温度が７０℃より高いと生成する消石灰水性スラリーの粘度が上昇し、操作がしにくくなるし、また３０℃より低いと消化に時間がかかり、効率的でなくなる。平均滞留時間が長すぎると消石灰の粒径の幅が大きくなり、炭酸カルシウムの粒度分布のばらつきや不揃いの原因となる。
また、湿式消化は連続湿式型のスレーカーを用いて行うのが好ましい。
【００１１】
このような湿式消化により消石灰水性スラリーが調製される。
本発明方法においては、この水性スラリーに二酸化炭素を吹き込み炭酸化することにより軽質炭酸カルシウムを製造することができる。
この炭酸化反応は通常用いられる方法により、例えば消石灰濃度５０〜２００ｇ／リットル、特に６０〜１５０ｇ／リットルの消石灰水性スラリーに、二酸化炭素濃度５〜４０容量％、特に１０〜３５容量％の二酸化炭素含有ガスを消石灰１ｋｇ当り標準状態で毎分１〜１２リットル、特に３〜１０リットルになる割合で、反応開始温度３０〜７０℃、特に３５〜６０℃で吹き込むことにより行われる。
【００１２】
本発明方法においては、炭酸化反応に二酸化炭素又は二酸化炭素含有ガスが用いられるが、工業的には二酸化炭素含有ガスが好ましい。
二酸化炭素含有ガスとして好適には、二酸化炭素を含有する混合ガス、例えば石灰石焼成キルン排ガスなどの石灰石焼成排ガス、パルプ製造プラントの石灰キルン排ガスなどの石灰焼成排ガス、発電ボイラー排ガス、ゴミ焼却排ガスなどが用いられる。
【００１３】
二酸化炭素含有ガスとして上記各種排ガスを用いる場合には、排ガス中に石灰石、石灰、硫黄酸化物、未燃焼カーボン等のダストが含まれているので、ダストを、バグフィルター、電気集塵機、湿式スクラバーあるいはそれらの組合せで除塵して排ガスを浄化するようにする。
上記排ガスは、乾性ガスであってもよいし、また湿性ガスであってもよく、乾性ガスの場合には前以てバグフィルターや電気集塵機である程度浄化したのち、さらに湿式スクラバーで所望程度まで浄化するのが好ましく、また湿性ガスの場合には多段の湿式スクラバーで所望程度まで浄化するかあるいは前以て湿式電気集塵機である程度浄化したのち、さらに湿式スクラバーで所望程度まで浄化するのが好ましい。
【００１４】
本発明方法においては、従来用いられていた種晶の添加なしに制御された粒径をもつ軽質炭酸カルシウムを形成させることができる。
【００１５】
このようにして、本発明方法によれば、制御された粒径をもつ紡錘状軽質炭酸カルシウムが得られる。
【００１６】
【実施例】
次に、実施例により本発明をさらに詳細に説明する。
各例に用いた酸化カルシウムは、天然産石灰石をＣサイズに粒度調整し、ベッケンバッハ炉で焼成したＪＩＳ特号相当品の酸化カルシウムを篩分けし、粒分をジョークラッシャーで粉砕したものである。
【００１７】
参考例
１０００リットルの容器に東京都西多摩郡瑞穂町の導電率０．１ｍＳ／ｃｍの水道水を６００リットル入れ、６０℃に調整した。撹拌機を用い５００ｒｐｍでかきまぜながら、生石灰４２ｋｇを加え、３０分後に３２５メッシュ篩でろ過し、８５ｇ／リットルの濃度の水酸化カルシウム水性スラリーを得た。
このスラリー３００リットルを半回分式反応器に仕込み、５０℃に調整したのち、この反応器中のスラリーに、０．５ｇ／Ｎｍ3のダスト濃度をバグフィルターで０．００５ｇ／Ｎｍ3に、さらに湿式スクラバーで０．００３ｇ／Ｎｍ3に減少させて除塵することによって浄化した、二酸化炭素濃度３０容量％のベッケンバッハ型石灰焼成炉排ガスを、水酸化カルシウム１ｋｇ当り１００容量％二酸化炭素換算で５Ｎリットル／分の割合で吹き込み、炭酸化率が１００％になるまで反応させて炭酸カルシウム水性懸濁液を得た。このものを３２５メッシュ篩でろ過して得た炭酸カルシウムは、ＳＥＭ写真（倍率×１００００）よりデジマチックノギスで粒径を測定したところ、平均長径４．１μｍ、平均短径１．５μｍの紡錘状粒子であった。
【００１８】
実施例１
参考例と同様にして得られた炭酸カルシウム水性懸濁液をフィルタープレスを用いてろ過し、含水率４０重量％の炭酸カルシウムケーキと炭酸カルシウム濃度５ｇ／リットル、導電率１．５ｍＳ／ｃｍのろ過水を得た。
このろ過水２００リットルを３００リットルの容器に入れ、６０℃に調整した。撹拌機を用い５００ｒｐｍでかきまぜながら、生石灰１４ｋｇを加え、３０分後に３２５メッシュ篩でろ過し、８５ｇ／リットルの濃度の水酸化カルシウム水性スラリーを得た。
このスラリー２００リットルを半回分式反応器に仕込み、５０℃に調整したのち、この反応器中のスラリーに、参考例と同様に浄化した二酸化炭素濃度３０容量％のベッケンバッハ型石灰焼成炉排ガスを、水酸化カルシウム１ｋｇ当り１００容量％二酸化炭素換算で５Ｎリットル／分の割合で吹き込み、炭酸化率が１００％になるまで反応させて炭酸カルシウム水性懸濁液を得た。このものを３２５メッシュ篩でろ過して得た炭酸カルシウムは、ＳＥＭ写真（倍率×３０００）よりデジマチックノギスで粒径を測定したところ、平均長径２．６μｍ、平均短径０．８μｍの紡錘状粒子であった。
【００１９】
実施例２
実施例１と同様にして得られた炭酸カルシウム水性懸濁液をフィルタープレスを用いてろ過し、含水率４０重量％の炭酸カルシウムケーキと炭酸カルシウム濃度６ｇ／リットル、導電率１．７ｍＳ／ｃｍのろ過水を得た。
このろ過水４０リットルを６０リットルの容器に入れ、６０℃に調整した。撹拌機を用い５００ｒｐｍでかきまぜながら、生石灰２．８ｋｇを加え、３０分後に３２５メッシュ篩でろ過し、８５ｇ／リットルの濃度の水酸化カルシウム水性スラリーを得た。
このスラリー３０リットルを半回分式反応器に仕込み、５０℃に調整したのち、この反応器中のスラリーに、参考例と同様に浄化した二酸化炭素濃度３０容量％のベッケンバッハ型石灰焼成炉排ガスを、水酸化カルシウム１ｋｇ当り１００容量％二酸化炭素換算で５Ｎｍ3／ｈｒの割合で吹き込み、炭酸化率が１００％になるまで反応させて炭酸カルシウム水性懸濁液を得た。このものを３２５メッシュ篩でろ過して得た炭酸カルシウムは、ＳＥＭ写真（倍率×１００００）よりデジマチックノギスで粒径を測定したところ、平均長径２．５μｍ、平均短径０．７μｍの紡錘状粒子であった。
【００２０】
実施例３
実施例２の容器に入れたろ過水４０リットルに代えて、実施例２と同様にして得られたろ過水３０リットルと水道水１０リットル（濃度４．５ｇ／リットルに相当）を消化水として用いた以外は、実施例２と同様にして消化、炭酸化反応を行い、３２５メッシュ篩いでろ過して得た炭酸カルシウムは、ＳＥＭ写真（倍率×１００００）よりデジマチックノギスで粒径を測定したところ、平均長径２．８μｍ、平均短径０．８μｍの紡錘状粒子であった。
【００２１】
実施例４
ろ過水と水道水の使用量をそれぞれ２０リットル（濃度３ｇ／リットルに相当）に変えた以外は、実施例２と同様にして消化、炭酸化反応を行い、３２５メッシュ篩いでろ過して得た炭酸カルシウムは、ＳＥＭ写真（倍率×１００００）よりデジマチックノギスで粒径を測定したところ、平均長径３．０μｍ、平均短径０．９μｍの紡錘状粒子であった。
【００２２】
実施例５
ろ過水と水道水の使用量をそれぞれ１０リットルと３０リットル（濃度１．５ｇ／リットルに相当）に変えた以外は、実施例２と同様にして消化、炭酸化反応を行い、３２５メッシュ篩いでろ過して得た炭酸カルシウムは、ＳＥＭ写真（倍率×１００００）よりデジマチックノギスで粒径を測定したところ、平均長径３．３μｍ、平均短径１．０μｍの紡錘状粒子であった。
【００２３】
実施例６
参考例と同様にして調製された水酸化カルシウム水性懸濁液を３０ｇ／リットルに濃度調整したものを３０リットル半回分式反応器に仕込み、１５℃に温度調節し、参考例と同様にして調製された二酸化炭素含有排ガスを、水酸化カルシウム１ｋｇ当り１００容量％二酸化炭素換算で８Ｎリットル／分の割合で吹き込んで炭酸化反応を行い、炭酸化率３５％のところで反応を停止し、一次炭酸化水酸化カルシウム水性スラリーを得た。
参考例と同様にして得られた炭酸カルシウム水性懸濁液をオリバーフィルターを用いてろ過して得た炭酸カルシウム濃度５ｇ／リットル、導電率１．３ｍＳ／ｃｍのろ過水と工業用水を３：１の割合で混合し（濃度３．７５ｇ／リットルに相当）、４０℃に調整したものを消化水として用い、連続式湿式消化方式のスレーカーにおいて、生石灰と共に定量供給を行い、スレーカーで未消化残さを除去し、８０ｇ／リットル濃度の水酸化カルシウム水性スラリーを得た。
この水酸化カルシウム水性スラリー３０リットルと上記一次炭酸化水酸化カルシウム水性スラリー０．８リットルを反応器で混合し、参考例と同様にして炭酸化反応させて炭酸カルシウム水性懸濁液を得た。このものを３２５メッシュ篩でろ過して得た炭酸カルシウムは、ＳＥＭ写真（倍率×１００００）よりデジマチックノギスで粒径を測定したところ、平均長径１．５μｍ、平均短径０．４μｍの紡錘状粒子であった。
【００２４】
実施例７
参考例と同様にして得られた炭酸カルシウム水性懸濁液をスクリュウデカンターを用いてろ過して得た炭酸カルシウム濃度４ｇ／リットル、導電率１．０ｍＳ／ｃｍのろ過水と工業用水を３：１の割合で混合し（濃度３ｇ／リットルに相当）、４０℃に調整したものを消化水として用い、連続式湿式消化方式のスレーカーにおいて、生石灰と共に定量供給を行い、スレーカーで未消化残さを除去し、３２５メッシュ篩でろ過を行い、次いで公称カットポイントが１０μｍの２液分離型の液体サイクロン（Ｔ−１０：大石機械製）にかけ、トップから吐出された６０ｇ／リットル濃度の水酸化カルシウム水性スラリーを得た。
この水酸化カルシウム水性スラリー３０リットルと実施例６と同様にして得られた一次炭酸化水酸化カルシウム水性スラリー１．２リットルを反応器で混合し、参考例と同様にして炭酸化反応させて炭酸カルシウム水性懸濁液を得た。このものを３２５メッシュ篩でろ過して得た炭酸カルシウムは、ＳＥＭ写真（倍率×１００００）よりデジマチックノギスで粒径を測定したところ、平均長径０．８μｍ、平均短径０．２μｍの紡錘状粒子であった。
【００２５】
応用例
実施例２〜６及び参考例で得た炭酸カルシウム水性スラリーをフィルタープレスでろ過して固形分が４０重量％の炭酸カルシウムケーキとしたのち、適量の水を加えて炭酸カルシウム含量が４００ｇ／リットル（固形分３２重量％）の炭酸カルシウムスラリーを作製した。このスラリーを適当に希釈し、これを広葉樹クラフトパルプ（３５０ｃｓｆ）と針葉樹クラフトパルプ（４５０ｃｓｆ）を重量比７：３で混合したパルプ原料１００重量部に配合し、さらに紙力増強剤としてカチオン化デンプン０．５重量部、中性サイズ剤としてのアルキルケテンダイマー０．２重量部、歩留まり向上剤としてのポリアクリルアミド０．０２重量部を添加し、填料添加率をパルプに対し１５％とし、坪量４０ｇ／ｍ２で角型シートマシンを用いた手抄きにより、炭酸カルシウム内填紙を得た。このものの物性を表１に示す。
【００２６】
なお、表中の各物性は次のようにして測定した。
（１）歩留り：ＪＩＳ Ｐ ８１２９により測定。
（２）灰分 ：ＪＩＳ Ｐ ８１２８により測定。
（３）白色度：ＪＩＳ Ｐ ８１２３により測定。
（４）不透明度：ＪＩＳ Ｐ ８１３６により測定。
（５）引張強度：ＪＩＳ Ｐ ８１１３により測定。
【００２７】
【表１】
これより、実施例で得られた炭酸カルシウムはいずれも参考例のそれに比べ白色度や不透明度に優れていることが分る。
【００２９】
【発明の効果】
本発明方法によれば、従来の種晶添加法に比べ、種晶を生成させる反応を別に行わなくてすむため操作が簡便であり、水の使用量を節減でき、また反応器やタンク等の新たな設備を要しないためコストダウンを図れる上に、均一で分散性良好な軽質炭酸カルシウム、特にカルサイト系の軽質炭酸カルシウムを得ることができる。
この軽質炭酸カルシウムは分散性が高いため、高濃度スラリー化して紙の内填あるいは塗工に供すると、高い不透明性や隠蔽性を与えるし、またさらに適当な表面改質剤で表面処理が施されたものは、ゴムや樹脂の充填材として優れた機械特性を与えるという利点もある。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing light calcium carbonate. More particularly, the present invention, the calcium oxide as a starting material, per order to produce the spindle-shaped precipitated calcium carbonate without using a seed crystal, by changing the reaction initiation temperature, an improved method of controlling the particle size of its It is about.
[0002]
[Prior art]
Conventionally, calcium carbonate is used as a raw calcium carbonate by reacting it with water and preparing slaked lime aqueous slurry by using quick lime obtained by calcining limestone as a raw material, and reacting it with carbon dioxide. Manufactured in various particle sizes from colloidal particles of 0.1 μm or less to coarse particles of several μm to several tens of μm, and in various forms such as spindle shape, square shape, columnar shape, needle shape, spherical shape, etc. Has been produced.
[0003]
Regarding the control of the particle size, a seed crystal addition method is known industrially. For example, an ultrafine seed crystal having a particle size of 0.01 to 0.09 μm is added in the middle of the carbonation reaction to form a cubic shape. A method for producing calcium carbonate (Japanese Patent Publication No. 3-19165), adding calcium carbonate seed crystals in a specific ratio to an aqueous solution of calcium salt, and then introducing carbon dioxide, thereby causing calcium carbonate to precipitate on the seed crystal surface. A method of controlling the average particle diameter by adjusting the amount (Japanese Patent Laid-Open No. 63-230520), a carbonation rate of a partially carbonated colloidal calcium hydroxide aqueous suspension at a predetermined ratio at a predetermined value A method for producing a predetermined spindle-shaped calcium carbonate having a uniform and good dispersibility by adding to the above (Japanese Patent Publication No. 8-18827), a hydroxide prepared by hydrocyclone treatment after wet digestion of calcium oxide Mosquito A method of performing Siumu aqueous suspension used as a raw material (Japanese Patent Laid-Open No. 6-56422) have been proposed.
[0004]
However, these methods are troublesome because a reaction for generating seed crystals used to control the particle size must be performed separately, and problems such as the need for new equipment such as a reactor and a tank arise. I can not escape.
[0005]
[Problems to be solved by the invention]
The present invention overcomes the disadvantages of the conventional method of controlling the particle size using such a seed crystal, and is an industrial method for producing spindle-shaped calcium carbonate by controlling the particle size efficiently by simplifying the operation. It was made for the purpose of providing.
[0006]
[Means for Solving the Problems]
The present inventor has conducted various studies to develop an industrial process for calcium carbonate, the separated water and filtered water produced by the dehydration and filtration of the calcium carbonate aqueous slurries produced at a predetermined carbonation reaction, therein A spindle shape having a controlled particle size, that is, a uniform particle size, by adjusting the concentration of calcium carbonate to be used for all or part of the water for digestion and allowing the carbonation reaction to be performed at a temperature of 30 to 70 ° C. The present inventors have found that a light calcium carbonate can be obtained, and have completed the present invention based on this finding.
[0007]
That is, the present invention prepares an aqueous calcium hydroxide suspension by adding water to calcium oxide and subjecting it to wet digestion, and then blowing carbon dioxide or a carbon dioxide-containing gas into the aqueous suspension to perform carbonation. In producing calcium, as water for digestion, it is obtained by separation water obtained by separation and dehydration treatment of an aqueous calcium carbonate slurry produced by a carbonation reaction of an aqueous calcium hydroxide suspension and filtration treatment of the slurry. At least one selected from filtered water or water mixed with it is used by adjusting the quick lime concentration to 50 to 150 g CaO / liter and the calcium carbonate concentration to 0.1 to 7 g / liter, and the reaction start temperature is 30 to 70 ° C. under conditions within 60 min average residence time, it reacted without addition of seed crystals, to produce by varying the reaction starting temperature There is provided a method for producing spindle-shaped precipitated calcium carbonate and controlling the particle size of the spindle-shaped particles.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
In the method of the present invention, calcium oxide is wet-digested with predetermined water to prepare an aqueous calcium hydroxide suspension, and then carbonized by blowing carbon dioxide or a gas containing the same into the aqueous suspension. Light calcium carbonate is produced.
[0009]
This predetermined water for digestion includes the separated water obtained by the separation and dehydration treatment of the calcium carbonate aqueous slurry produced by the carbonation reaction of the aqueous calcium hydroxide suspension and the filtered water obtained by the filtration treatment of the slurry. At least one selected from the above or water mixed with it. As the separation and dehydration treatment, a centrifugal separation treatment or a sedimentation separation treatment is preferably used, and a floating separation treatment is also used. Centrifugation is usually performed using an appropriate apparatus such as a centrifugal sedimentator, a centrifugal filter, a centrifugal separator, a centrifugal decanter, a centrifugal clarifier, or the like. As the filtration treatment, pressure filtration treatment or vacuum filtration treatment is preferably performed under pressure or vacuum. The pressure filtration treatment is performed by a filter press or a belt press, and the vacuum filtration treatment is performed by an oliver filter or a drum filter. Is preferred.
Since the water for digestion contains calcium carbonate , its concentration is adjusted to a range of 0.1 to 7 g / liter. The digestion water preferably has a conductivity of 0.2 to 10 mS / cm. When the separated water or filtered water is mixed in water, industrial water, well water, ground water, or the like is usually used as this water.
[0010]
In the method of the present invention, the wet digestion of quicklime with water is selected from a concentration of 50 to 150 g-CaO / liter, preferably 60 to 120 g-CaO / liter, and a digestion water temperature, that is, a reaction start temperature within a range of 30 to 70 ° C. It is necessary to carry out the digestion under an average residence time of 60 minutes or less, preferably 3 to 30 minutes. If it deviates from the range of this condition, the desired effect cannot be obtained. That is, if this concentration is too high, the viscosity of the resulting slaked lime aqueous slurry will increase, the residue will increase, and if it is too low, it will not be efficient. If the digestion water temperature is higher than 70 ° C., the viscosity of the slaked lime aqueous slurry produced increases, making it difficult to operate, and if it is lower than 30 ° C., digestion takes time and becomes inefficient. If the average residence time is too long, the width of the particle size of slaked lime becomes large, which causes variation and unevenness in the particle size distribution of calcium carbonate.
The wet digestion is preferably performed using a continuous wet type slaker.
[0011]
A slaked lime aqueous slurry is prepared by such wet digestion.
In the method of the present invention, light calcium carbonate can be produced by carbonation by blowing carbon dioxide into this aqueous slurry.
This carbonation reaction is carried out by a commonly used method , for example, a slaked lime aqueous slurry having a slaked lime concentration of 50 to 200 g / liter, particularly 60 to 150 g / liter, and a carbon dioxide concentration of 5 to 40% by volume, particularly 10 to 35% by volume. It is carried out by blowing the contained gas at a reaction starting temperature of 30 to 70 ° C., particularly 35 to 60 ° C. at a rate of 1 to 12 liters per minute, especially 3 to 10 liters per kg of slaked lime.
[0012]
In the method of the present invention, carbon dioxide or carbon dioxide-containing gas is used for the carbonation reaction, but industrially preferred is carbon dioxide-containing gas.
The carbon dioxide-containing gas is preferably a mixed gas containing carbon dioxide, for example, limestone fired exhaust gas such as limestone fired kiln exhaust gas, lime fired exhaust gas such as lime kiln exhaust gas of pulp manufacturing plant, power generation boiler exhaust gas, garbage incineration exhaust gas, etc. Used.
[0013]
When the above various exhaust gases are used as the carbon dioxide-containing gas, since dust such as limestone, lime, sulfur oxide, and unburned carbon is contained in the exhaust gas, the dust is removed by a bag filter, an electrostatic precipitator, a wet scrubber or Dust is removed in combination to purify the exhaust gas.
The exhaust gas may be a dry gas or a wet gas. In the case of a dry gas, it is first purified to some extent by a bag filter or an electrostatic precipitator, and further purified to a desired level by a wet scrubber. In the case of wet gas, it is preferable to purify to a desired level with a multistage wet scrubber, or after purifying to some extent with a wet electric dust collector in advance, and further purifying to a desired level with a wet scrubber.
[0014]
In the method of the present invention, light calcium carbonate having a controlled particle size can be formed without adding a seed crystal that has been conventionally used .
[0015]
Thus , according to the method of the present invention , spindle-shaped light calcium carbonate having a controlled particle size is obtained .
[0016]
【Example】
Next, the present invention will be described in more detail with reference to examples.
The calcium oxide used in each example is obtained by adjusting the particle size of natural limestone to C size, sieving calcium oxide of JIS special product baked in a Beckenbach furnace, and pulverizing the grain with a jaw crusher. .
[0017]
Reference Example 600 liters of tap water having a conductivity of 0.1 mS / cm in Mizuho-cho, Nishitama-gun, Tokyo was placed in a 1000-liter container and adjusted to 60 ° C. While stirring at 500 rpm using a stirrer, 42 kg of quicklime was added, and after 30 minutes, the mixture was filtered through a 325 mesh sieve to obtain an aqueous calcium hydroxide slurry having a concentration of 85 g / liter.
After charging 300 liters of this slurry into a semi-batch reactor and adjusting it to 50 ° C., the dust concentration of 0.5 g / Nm 3 was further reduced to 0.005 g / Nm 3 with a bag filter. Beckenbach-type lime calciner exhaust gas with a carbon dioxide concentration of 30% by volume, purified by reducing dust to 0.003g / Nm 3 with a wet scrubber, 5N liters in terms of 100% by volume carbon dioxide per kg of calcium hydroxide The mixture was blown at a rate of / min and reacted until the carbonation rate reached 100% to obtain an aqueous calcium carbonate suspension. Calcium carbonate obtained by filtering this with a 325 mesh sieve was measured with a digi caliper from a SEM photograph (magnification × 10000). As a result, a spindle shape having an average major axis of 4.1 μm and an average minor axis of 1.5 μm was obtained. It was a particle.
[0018]
Example 1
A calcium carbonate aqueous suspension obtained in the same manner as in the Reference Example was filtered using a filter press, and a calcium carbonate cake having a water content of 40% by weight, a calcium carbonate concentration of 5 g / liter, and a conductivity of 1.5 mS / cm was filtered. Got water.
200 liters of filtered water was placed in a 300 liter container and adjusted to 60 ° C. While stirring at 500 rpm using a stirrer, 14 kg of quicklime was added, and after 30 minutes, the mixture was filtered through a 325 mesh sieve to obtain an aqueous calcium hydroxide slurry having a concentration of 85 g / liter.
After charging 200 liters of this slurry into a semi-batch reactor and adjusting it to 50 ° C., the Beckenbach-type lime calciner exhaust gas with a carbon dioxide concentration of 30% by volume purified as in the reference example was added to the slurry in this reactor. Then, it was blown at a rate of 5 N liters / minute in terms of carbon dioxide equivalent of 100 volume% per 1 kg of calcium hydroxide, and reacted until the carbonation rate reached 100% to obtain an aqueous calcium carbonate suspension. Calcium carbonate obtained by filtering this with a 325 mesh sieve was measured with a digi caliper from a SEM photograph (magnification × 3000). As a result, a spindle shape having an average major axis of 2.6 μm and an average minor axis of 0.8 μm was obtained. It was a particle.
[0019]
Example 2
The aqueous calcium carbonate suspension obtained in the same manner as in Example 1 was filtered using a filter press, and a calcium carbonate cake having a water content of 40% by weight, a calcium carbonate concentration of 6 g / liter, and a conductivity of 1.7 mS / cm was obtained. Filtered water was obtained.
40 liters of this filtered water was put into a 60 liter container and adjusted to 60 ° C. While stirring at 500 rpm using a stirrer, 2.8 kg of quicklime was added, and after 30 minutes, it was filtered through a 325 mesh sieve to obtain a calcium hydroxide aqueous slurry having a concentration of 85 g / liter.
After charging 30 liters of this slurry into a semi-batch reactor and adjusting it to 50 ° C., the Beckenbach lime calciner exhaust gas with a carbon dioxide concentration of 30% by volume purified in the same manner as in the reference example was added to the slurry in this reactor. Then, it was blown at a rate of 5 Nm 3 / hr in terms of 100% by volume of carbon dioxide per 1 kg of calcium hydroxide and reacted until the carbonation rate reached 100% to obtain an aqueous calcium carbonate suspension. Calcium carbonate obtained by filtering this product through a 325 mesh sieve was measured in a spindle shape with an average major axis of 2.5 μm and an average minor axis of 0.7 μm when the particle size was measured with a Digimatic caliper from a SEM photograph (magnification × 10000). It was a particle.
[0020]
Example 3
Instead of 40 liters of filtered water in the container of Example 2, 30 liters of filtered water and 10 liters of tap water (corresponding to a concentration of 4.5 g / liter) obtained in the same manner as in Example 2 were used as digestion water. The calcium carbonate obtained by digestion and carbonation in the same manner as in Example 2 and filtering through a 325 mesh sieve was measured for the particle size with a digi caliper from a SEM photograph (magnification × 10000). Spindle-shaped particles having an average major axis of 2.8 μm and an average minor axis of 0.8 μm.
[0021]
Example 4
Digestion and carbonation were carried out in the same manner as in Example 2 except that the amounts of filtered water and tap water were changed to 20 liters (corresponding to a concentration of 3 g / liter) , respectively, and obtained by filtration through a 325 mesh sieve. Calcium carbonate was a spindle-shaped particle having an average major axis of 3.0 μm and an average minor axis of 0.9 μm as measured with a Digimatic caliper from an SEM photograph (magnification × 10000).
[0022]
Example 5
Digestion and carbonation were carried out in the same manner as in Example 2 except that the amounts of filtered water and tap water were changed to 10 liters and 30 liters (corresponding to a concentration of 1.5 g / liter) , respectively. The calcium carbonate obtained by filtration was measured with a digi caliper from a SEM photograph (magnification × 10000), and was a spindle-shaped particle having an average major axis of 3.3 μm and an average minor axis of 1.0 μm.
[0023]
Example 6
Charged that the calcium hydroxide aqueous suspension prepared in the same manner as in Reference Example was adjusted to a concentration of 30 g / liter 30 liter semi-batch reactor, thermostatted at 15 ° C., prepared in a manner similar to Reference Example The carbon dioxide-containing exhaust gas was blown at a rate of 8 N liters / minute in terms of 100% by volume of carbon dioxide per 1 kg of calcium hydroxide to perform a carbonation reaction, and when the carbonation rate was 35%, the reaction was stopped and primary carbonation was performed. A calcium hydroxide aqueous slurry was obtained.
Calcium carbonate aqueous suspension obtained in the same manner as in the Reference Example was filtered using an Oliver filter, and 3: 1 of filtered water and industrial water having a calcium carbonate concentration of 5 g / liter and a conductivity of 1.3 mS / cm was used. They were mixed in a ratio of (corresponding to a concentration 3.75 g / l), used after adjusted to 40 ° C. as a digestive water in the slaker the continuous wet digestion method performs dispensing with quicklime, undigested residue in slaker This was removed to obtain an aqueous calcium hydroxide slurry having a concentration of 80 g / liter.
30 liters of this calcium hydroxide aqueous slurry and 0.8 liters of the above primary carbonated calcium hydroxide aqueous slurry were mixed in a reactor and subjected to a carbonation reaction in the same manner as in the reference example to obtain an aqueous calcium carbonate suspension. Calcium carbonate obtained by filtering this with a 325 mesh sieve was measured with a digi caliper from a SEM photograph (magnification × 10000). As a result, it was spindle-shaped with an average major axis of 1.5 μm and an average minor axis of 0.4 μm. It was a particle.
[0024]
Example 7
A calcium carbonate aqueous suspension obtained in the same manner as in the reference example was filtered using a screw decanter, and the filtered water and industrial water having a calcium carbonate concentration of 4 g / liter and an electric conductivity of 1.0 mS / cm were mixed with industrial water at a ratio of 3: 1. It was mixed at a ratio of (corresponding to a concentration 3 g / l), used after adjusted to 40 ° C. as a digestive water in the slaker the continuous wet digestion method performs dispensing with quicklime to remove undigested residue in slaker Filter through a 325 mesh sieve, and then apply it to a two-component separation type hydrocyclone (T-10: manufactured by Oishi Machine) with a nominal cut point of 10 μm. The 60 g / liter calcium hydroxide aqueous slurry discharged from the top Obtained.
30 liters of this calcium hydroxide aqueous slurry and 1.2 liters of a primary carbonated calcium hydroxide aqueous slurry obtained in the same manner as in Example 6 were mixed in a reactor, followed by a carbonation reaction in the same manner as in the reference example to produce carbonic acid. An aqueous calcium suspension was obtained. Calcium carbonate obtained by filtering this with a 325 mesh sieve was measured with a digi caliper from a SEM photograph (magnification × 10000). As a result, it was spindle-shaped with an average major axis of 0.8 μm and an average minor axis of 0.2 μm. It was a particle.
[0025]
Application Example The calcium carbonate aqueous slurry obtained in Examples 2 to 6 and Reference Example was filtered with a filter press to obtain a calcium carbonate cake having a solid content of 40% by weight, and then an appropriate amount of water was added to obtain a calcium carbonate content of 400 g / A calcium carbonate slurry having a liter (solid content: 32% by weight) was prepared. This slurry is appropriately diluted and blended with 100 parts by weight of a pulp raw material in which hardwood kraft pulp (350 csf) and softwood kraft pulp (450 csf) are mixed at a weight ratio of 7: 3, and cationized starch as a paper strength enhancer. 0.5 part by weight, 0.2 part by weight of alkyl ketene dimer as a neutral sizing agent, 0.02 part by weight of polyacrylamide as a yield improver, and a filler addition rate of 15% with respect to the pulp, basis weight By papermaking using a square sheet machine at 40 g / m 2 , a calcium carbonate-incorporated paper was obtained. The physical properties of this product are shown in Table 1.
[0026]
Each physical property in the table was measured as follows.
(1) Yield: Measured according to JIS P 8129.
(2) Ash content: Measured according to JIS P 8128.
(3) Whiteness: Measured according to JIS P 8123.
(4) Opacity: Measured according to JIS P 8136.
(5) Tensile strength: Measured according to JIS P 8113.
[0027]
[Table 1]
From this, it can be seen that all the calcium carbonates obtained in the examples are superior in whiteness and opacity compared to those in the reference examples .
[0029]
【The invention's effect】
According to the method of the present invention, compared to the conventional seed crystal addition method, the reaction for generating seed crystals is not required to be performed separately, so that the operation is simple, the amount of water used can be reduced, and the reactor, tank, etc. on that attained the cost for not require new equipment, uniform dispersibility good light calcium carbonate, in particular can be obtained precipitated calcium carbonate calcite system.
Since this light calcium carbonate has high dispersibility, when it is slurried in high concentration and used for paper filling or coating, it gives high opacity and concealment, and surface treatment is performed with an appropriate surface modifier. The resulting product also has the advantage of providing excellent mechanical properties as a rubber or resin filler.
Claims (3)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12600996A JP3924019B2 (en) | 1996-05-21 | 1996-05-21 | Method for producing light calcium carbonate |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12600996A JP3924019B2 (en) | 1996-05-21 | 1996-05-21 | Method for producing light calcium carbonate |
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| JPH09309724A JPH09309724A (en) | 1997-12-02 |
| JP3924019B2 true JP3924019B2 (en) | 2007-06-06 |
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| FI122786B (en) * | 2007-07-20 | 2012-06-29 | Upm Kymmene Oyj | Use of carbon dioxide from synthetic hydrocarbon chains |
| JP5389491B2 (en) * | 2009-03-25 | 2014-01-15 | 太平洋セメント株式会社 | Method for producing high purity calcium carbonate |
| JP5426982B2 (en) * | 2009-09-29 | 2014-02-26 | 日本製紙株式会社 | Method for producing calcium carbonate |
| CN105217673B (en) * | 2015-10-21 | 2018-01-09 | 常山县南方碳酸钙有限公司 | A kind of preparation method of high thixotropic silicone adhesive special-purpose nanometer activated Calcium carbonate |
| CN114349036B (en) * | 2021-11-01 | 2023-11-24 | 山东宇信纳米科技有限公司 | Preparation method of nano calcium carbonate for MS glue |
| CN114620753B (en) * | 2021-11-29 | 2023-08-18 | 浙江天石纳米科技股份有限公司 | Low-carbon process method for producing light calcium carbonate by comprehensively utilizing chemical reaction heat |
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