JP4763904B2 - Processing method of muddy water cake - Google Patents

Processing method of muddy water cake Download PDF

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Publication number
JP4763904B2
JP4763904B2 JP2001052080A JP2001052080A JP4763904B2 JP 4763904 B2 JP4763904 B2 JP 4763904B2 JP 2001052080 A JP2001052080 A JP 2001052080A JP 2001052080 A JP2001052080 A JP 2001052080A JP 4763904 B2 JP4763904 B2 JP 4763904B2
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Japan
Prior art keywords
muddy water
cake
mixture
mud
water cake
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JP2002248494A (en
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徹 井田
昇 中尾
毅 田中
理貴 長谷川
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Kobe Steel Ltd
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Kobe Steel Ltd
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Description

【0001】
【発明の属する技術分野】
本発明は、砕石プラントの湿式製砂設備で発生する濁水ケーキを処理して、用途が広く需要量の多いコンクリート用細骨材,道路用路盤材などとして利用可能な強度の高い固化品を得ることができる濁水ケーキの処理方法に関するものである。
【0002】
【従来の技術】
道路や建築用等の砕石,砕砂を生産する砕石プラントは、石切り場で発破した1m程度の大きさの石をプラント上流部分にある原料工場(破砕室)に投入し、破砕機により破砕し、篩で砕石の粒度別に篩分けし、規格外の大きな砕石については破砕と篩分け選別を繰り返して行き、最終的に規格粒度別に破砕選別された砕石,砕砂を製品として出荷するようにしたものであり、粒度5mm以下のコンクリート用細骨材を生産する製砂設備はプラント下流部分に設置されている。
【0003】
砕石プラントの製砂設備では、製品品質の向上を目的として付着泥分,不要微細石粒子などを除去すべく破砕品を水で洗浄するようにしている。特にコンクリート用細骨材(砕砂)では製品中に含まれる75μm以下の微細石粒子の含有量が制限されており、細骨材生産の際には、前記微細石粒子を除去するなどのために粒度5mmアンダーの破砕品の水洗が行われる。この水洗を行う湿式の設備での使用後の洗浄水は、75μm以下程度の微細な石粒子及び/又は泥分を重量で5〜10%程度含む泥水であり、「濁水」と呼ばれている。そして濁水は、シックナとフィルタプレス等の濃縮・脱水用の機械設備、あるいは沈殿池式設備により、水と分離された泥分が濃縮脱水されて、シリカを含有し水分を含む泥土スラッジである泥土ケーキにされる。なお、このような濁水の処理による泥土ケーキは「濁水ケーキ」と呼ばれており、例えばコンクリート用細骨材を生産する場合、重量で細骨材生産量の約10%程度発生する。
【0004】
そして近年、環境保全の観点から廃棄物の減少を図るべく、この泥土ケーキは生石灰、セメント等と単に混合されて、埋立て材,盛土材などの低強度材として利用されている。
【0005】
ところがこの方法では、得られる製品の強度(一軸圧縮強度)が10kg/cm程度以下と低く、用途が前述の埋立て材,盛土材など低強度の土木資材に限られてしまい、常時安定的に大量需要がなく利用量の拡大が期待できず、有効な廃棄物低減化になっていないのが実情である。
【0006】
次に、同じく副産物である石粉(乾燥石粉)について説明する。砕石プラントの製砂設備では、粒度5mmアンダーの破砕品について、前述した75μm以下の微細石粒子を除去するためにエアセパレータ等の乾式分級機で分級し、しかる後、除去仕切れずに残った微細石粒子の除去を前述の水洗により行うという製砂工程を採用している設備もある。このような製砂工程の場合、前記エアセパレータ等による分級によって主に75μm以下の微細石粒子が副産物として発生する。この微細な石粒子は石粉(乾燥石粉)と呼ばれている。コンクリート用細骨材を生産する場合、石粉は重量で細骨材生産量の約10%程度発生する。
【0007】
また、砕石プラントにおいて製砂設備の上流部分には、前述したように粒度別に砕石を生産するための破砕機や篩装置などが備えられており、これらの装置では集塵機によって捕集される集塵ダストとして微細な石粒子(粒度:平均15μm)である石粉(乾燥石粉)が副産物として発生する。
【0008】
ところがこのような石粉についても、高流動コンクリートの混合材である石灰石粉の代替え品として利用すべく開発が進められているものの、現状ではこれ以外には用途がなく、実質的に廃棄物となっているのが実情である。なお、河川の岩石を原石とするいわゆる砂利プラントで副産物として発生する濁水,石粉についても、資源として利用されていないのが実情であり、ここではこの砂利プラントをも含めて砕石プラントという。
【0009】
また、他のシリカ含有副産物として、浚渫土処理濁水、建設汚泥がある。浚渫土処理濁水について説明すると、通常、浚渫土(湖沼,川,ダム湖など浚渫する際に発生する土砂)は含水率が高く、ふるい分け機などによって浚渫土を大・中・小の石、砂などに分離する際には、水洗に伴う濁水が発生する。また、建設汚泥は、周知のように、地中連続壁工法,泥水式シールド工法,高圧噴射攪拌工法などの土木建設工事に伴って発生する含水率が高く粒子の微細な泥状の掘削物である。
【0010】
ところが、このような浚渫土処理濁水や建設汚泥については、その大部分が減容化のためにシリカ含有泥土スラッジ(泥土ケーキ)にされているだけであり、環境保全の観点からも廃棄物の低減につながる有用なプロセスが強く希求されている。
【0011】
【発明が解決しようとする課題】
そこで本発明は、砕石プラントの湿式製砂設備で発生する濁水ケーキを処理して、用途が広く需要量の多いコンクリート用細骨材,道路用路盤材などとして利用可能な強度の高い固化品を得ることができる濁水ケーキの処理方法を提供することを課題とする。
【0012】
【課題を解決するための手段】
前記課題を解決する請求項1の発明は、砕石プラントの湿式製砂設備で発生する濁水ケーキと、生石灰とを、濁水ケーキに対して生石灰を5〜10重量%添加し、均一混合して泥土カルシウム均一混合物を得、しかる後、該泥土カルシウム均一混合物を水熱処理して一軸圧縮強度が200kg/cm以上の固化品を得る濁水ケーキの処理方法であって、前記濁水ケーキとして、前記泥土カルシウム均一混合物の含水率が5〜35%の範囲を満たす含水率の濁水ケーキを用いること、当該濁水ケーキと前記生石灰とを混合するに際し、その泥土カルシウム均一混合物の充填供試体の断面において各未混合部分の円形相当時の直径が2mm以下であることを満足するように均一混合を行うこと、水熱処理条件として温度130〜300℃の飽和水蒸気圧の下で1〜24時間にて前記水熱処理を行なうことを特徴とする濁水ケーキの処理方法である。
【0013】
【0014】
【0015】
【0016】
【発明の実施の形態】
本発明による濁水ケーキの処理方法は、濁水ケーキとカルシウム化合物とを均一混合して泥土カルシウム均一混合物を得、しかる後、該泥土カルシウム均一混合物を水熱処理により固化して固化品を得るようにしたものである。カルシウム化合物としては、酸化カルシウム(生石灰)を挙げることができる。ここで、シリカ含有泥土スラッジへのカルシウム化合物の添加は、後述の水熱処理によりトバモライト(5CaO・6SiO2 ・5H2 O)などのカルシウムシリケート(ケイ酸カルシウム)を生成させることにある。そして、トバモライトの結晶のCaとSiの重量比(Ca/Si)が5/6であることから、カルシウム化合物は、泥土カルシウム均一混合物における重量比(Ca/Si)が5/6以下となるように濁水ケーキに添加すればよい。なお、泥土カルシウム均一混合物は、水熱処理による固化品の圧縮強度の点から、含水率が5〜35%の範囲内のものが望ましい。
【0017】
ところで、濁水ケーキ生石灰との混合物において、CaとSiの重量比(Ca/Si)が平均して5/6であったとしても、該混合物の均一混合の度合いが低い場合には、該重量比の値が著しく小さい部分が生じてしまう。このため、後の水熱処理においてカルシウムシリケートの生成しない領域が残ってしまい、圧縮強度が高く、かつ、圧縮強度のバラツキが小さくて品質の安定した固化品が得られない。
【0018】
よって、本発明による濁水ケーキの処理方法においては、濁水ケーキと添加剤である生石灰とを均一混合して泥土カルシウム均一混合物を得るようにしている。この均一混合は、従来とは違って高速攪拌することによりなされる。この攪拌速度(攪拌ブレード回転速度)は処理しようとする濁水ケーキの含水率、粘着性などによって異なるため一概には規定できないものの、例えば機械攪拌式混合機により混合を行う場合、従来の攪拌ブレード回転速度(従来の攪拌ブレード回転速度は、濁水ケーキの水分を減らして流動性を低下させることに目的がおかれるとともに所要粒径範囲の造粒が可能なように設定されていた)に比較して、例えばその4〜5倍のブレード回転速度にて混合を行うようにすればよい。
【0019】
具体的には、以下の例に限定されないが、例えば、高速縦ブレード式混合機であれば、攪拌ブレードの回転速度を1250〜3000回転/分の範囲にて設定すればよく、スパイラル型混合機であれば、攪拌ブレードの回転速度を自転:200〜500回転/分,公転:自転回転速度の約半分にて設定すればよい。周知のように、高速縦ブレード式混合機は、固定された容器内において上下方向に延びる垂直回転軸を持つ1本の攪拌ブレードが回転するようになっている。また、スパイラル型混合機は、1本の攪拌ブレードをそのブレード軸が垂直上下方向に延びる姿勢で装着し、攪拌ブレードを容器の中心より偏心させて回転させるものであり、容器は回転せず固定されており、その攪拌ブレードが自転及び公転をしながら混合を行うようになっている。
【0020】
そして、本発明による処理方法において、濁水ケーキ生石灰との均一混合は、得られた泥土カルシウム均一混合物の充填供試体を作製したとき、該充填供試体の断面において各未混合部分の円形相当時の直径が2mm以下であることを満足するように混合を行うことがよい。ここで、泥土カルシウム均一混合物の充填供試体は、土質工学会基準に基づくものであり、泥土カルシウム均一混合物をモールド内に充填し突固め試験装置により突き固めて直径50mm×長さ100mmの円柱体に成形したものである。この供試体を輪切りにした供試体断面における平面視で円形状,島状などをなす各未混合部分それぞれについて、面積を測定してその形状が円形であると仮定して直径Diを計算して求める。なお、供試体の突き固めのバラツキによる影響を排除するため、未混合部分内に空隙が存在しているときの直径Diは、該空隙を除いた未混合部分における円形相当時の直径の値である。
【0021】
そして、これら個々の未混合部分それぞれの円形相当時の直径Diが2mm以下となるように混合を行って泥土カルシウム均一混合物を得、該泥土カルシウム均一混合物に水熱処理を施すことで、圧縮強度が高く、かつ、そのバラツキが小さくて品質が一定な固化品が得られる。
【0022】
また、濁水ケーキと生石灰との均一混合は、未混合率Nmが6%以下であることを満足するように混合を行うことがよい。この未混合率Nmとは、泥土カルシウム均一混合物の充填供試体を作製したとき、該充填供試体の断面において、空隙部分を除いた断面面積に対する各未混合部分(ただし、各未混合部分はその大きさが円形相当時の直径Diが0.5mm以上のもの)の総計面積の比率を百分率で表したものである。なお、未混合部分の大きさとして円形相当時の直径Diが0.5mm以上の未混合部分についてそれらの総計面積を求めるようにした理由は、直径Diが0.5mm未満である微小な粒状の未混合部分については、水熱処理による固化品の品質に実質的に影響を与えないためである。
【0023】
ここで、未混合率Nmの求め方をより詳しく説明する。直径50mm×長さ100mmの円柱体をなす泥土カルシウム均一混合物の充填供試体を前述した要領にて作製し、この充填供試体を長さ方向において4等分して輪切りにする。得られた切断位置が異なる3つの供試体断面に関し、まず第1の供試体断面において、空隙部分を除いた断面面積Saと、この空隙部分を除いた断面面積Saのうちの各未混合部分(ただし、円形相当時の直径Diが0.5mm以上のもの)の総計面積Sbとを測定し、この比率(Sb/Sa)を百分率で未混合率として算出する。次に同様にして、残りの第2,第3の供試体断面において各未混合率をそれぞれ算出する。そしてこれら3つの各未混合率の平均値を当該泥土カルシウム均一混合物による充填供試体の未混合率Nmとしている。
【0024】
そして、この未混合率Nmが6%以下となるように混合を行って泥土カルシウム均一混合物を得、該泥土カルシウム均一混合物に水熱処理を施すことで、圧縮強度が高く、かつ、その圧縮強度のバラツキが小さくて品質が一定な固化品が得られる。より好ましくは、未混合率Nmが3%以下となるように混合を行うことがよい。
【0025】
さて次いで、得られた泥土カルシウム均一混合物を水熱処理であるオートクレーブ養生する。飽和蒸気圧下でのオートクレーブ養生により、泥土カルシウム均一混合物中のSiO2CaOとが反応してカルシウムシリケートが生成される。この結果、粒子同士が強固に固着し空隙率か小さくて、圧縮強度が高く、かつ、品質が一定であって、コンクリート用細骨材,道路用路盤材などとして利用しうる固化品が得られる。水熱処理では、カルシウムシリケートのうちでも、130〜300℃程度の比較的低温で結晶が成長し強度の高いトバモライトを生成させることがよい。水熱処理条件としては、反応温度(オートクレーブ養生温度):130〜300℃、反応時間(養生時間):1〜24時間が適切である。反応温度130〜300℃はトバモライトの結晶成長がよく促進される温度範囲であり、反応温度が高いほど反応速度は大きいので、同じ品質(強度、吸水率)のものであれば反応時間は短くてすむ。代表的水熱処理条件は、反応温度:180℃、反応時間:5時間、絶対圧力:1.01MPa(10気圧)である。
【0026】
【実施例】
以下、本発明の実施例について説明する。
【0027】
[実施例1] この実施例で用いた混合機Aと比較例で用いた混合機Bは、ともにスパイラル型混合機である1軸スパイラルミキサである。前述したように1軸スパイラルミキサは、攪拌ブレードを自転及び公転させながら混合を行うようになっている。混合機Aは高速用混合機でフック型の攪拌ブレードが装着されており、一方、混合機Bは低速用混合機でビータ型の攪拌ブレードが装着されている。
【0028】
実施例では、含水率25%の濁水ケーキを用いた。この濁水ケーキに対して生石灰を3〜10重量%添加し(5重量%未満は参考例)、前記混合機Aにより濁水ケーキと生石灰とを高速攪拌することにより均一混合して泥土カルシウム均一混合物を得た。混合機Aの運転条件は、攪拌ブレードの回転速度:自転288回転/分,公転135回転/分、処理時間:2分間である。
【0029】
そして、得られた泥土カルシウム均一混合物について、均一混合の度合いを調べるためにその充填供試体を作製し、前述した未混合部分の円形相当時の直径Diを測定した。充填供試体は、得られた泥土カルシウム均一混合物をモールド内に充填し突固め試験装置により突き固めて直径50mm×長さ100mmの円柱体に成形したものである。この充填供試体を長さ方向において4等分して輪切りにし、得られた切断位置が異なる3つの供試体断面に関し、まず第1の供試体断面における各未混合部分それぞれについて、面積を測定してその形状が円形であると仮定して直径Diを算出し求めた。未混合部分の面積と円形相当時の直径Diの測定には公知の画像解析装置(画像処理装置)を用いた。次に、これらの測定データDiから、〔Di>2mm〕:A1 %、〔0.5mm≦Di≦2mm〕:B1 %、〔Di<0.5mm〕:C1 %、というように整理して未混合部分の直径Diの分布を求めた。そして同様にして、残りの第2の供試体断面及び第3の供試体断面について、直径Diの値のこのような分布をそれぞれ求め、〔Di>2mm〕、〔0.5mm≦Di≦2mm〕及び〔Di<0.5mm〕に関するこれら3つの供試体断面についての平均値を求めた。実施例の結果を表1に示す。また、前述した未混合率Nmについても先に述べた手順にてこれを求め、その結果を同じく表1に示す。
【0030】
次いで、前記得られた泥土カルシウム均一混合物を用いてなる水熱固化品を作製し、その圧縮強度を測定した。すなわち、前記得られた泥土カルシウム均一混合物を用いて直径25mm、長さ50mmの円柱状の加圧成形体をつくり、これをオートクレーブにて反応温度:180℃、反応時間:5時間、絶対圧力:1.01MPaの条件で水熱処理して固化させた。得られたこの固化品の圧縮強度(一軸圧縮強度)を測定した。その結果を図1に示す。
【0031】
次に、比較例について説明する。比較例では、前記した含水率25%の濁水ケーキに対して生石灰を5〜12重量%添加し、前記混合機Aに代えて前記混合機Bを用い濁水ケーキと生石灰とを混合してその混合物を得た。混合機Bの運転条件は、攪拌ブレードの回転速度:自転108回転/分,公転66回転/分、処理時間:2分間である。得られた前記混合物において未混合率Nmと未混合部分の直径Diとを求めた。その測定結果を表1に示す。また、前記混合物について、実施例と同手順・同条件にて水熱処理を行ってその固化品をつくり、該固化品の圧縮強度(一軸圧縮強度)を測定した。その結果を図1に示す。
【0032】
【表1】
【0033】
表1及び図1に示す結果よりわかるように、比較例では、混合物において未混合部分の直径Diが2mmを超えた部分があり、しかもその割合が23%と相当に高く、また、未混合率Nmも36%と相当に高く、濁水ケーキと生石灰とが均一混合されていないものであった。このため、水熱処理されたその固化品においては、図1に示すように、カルシウム添加量が同じであっても得られる圧縮強度のバラツキが極めて大きく、品質が不安定なものであった。
【0034】
これに対して実施例では、未混合部分の直径Diが2mm以下で、また、未混合率Nmが0.2%である泥土カルシウム均一混合物が得られた。この泥土カルシウム均一混合物を水熱処理してなる固化品は、図1に示すように、同じカルシウム添加量の比較例に比べて、圧縮強度が高く、かつ、圧縮強度のバラツキが小さくて品質が安定したものであった。このように本発明によれば、コンクリート用細骨材,道路用路盤材などとして利用可能な強度の高い固化品を得ることができる。
【0035】
[実施例2] この実施例ではコンクリート用細骨材として利用しうる固化品をつくった。まず、砕石プラントからの含水率25%の濁水ケーキにこの例では生石灰を5重量%添加し、前述した高速縦ブレード式混合機により濁水ケーキと生石灰とを高速攪拌することにより均一混合して泥土カルシウム均一混合物を得た。引き続いてこの高速縦ブレード式混合機を低速運転することにより、前記泥土カルシウム均一混合物を原料として造粒を行って粒状の泥土カルシウム均一混合物を得た。高速縦ブレード式混合機の運転条件は、均一混合時における攪拌ブレードの回転速度:1300〜2500回転/分、造粒時における攪拌ブレードの回転速度:400〜800回転/分である。この運転条件にて粒径(外径)が約1〜10mmの範囲の粒状をなす泥土カルシウム均一混合物が得られる。
【0036】
次いで、前記造粒された粒状の泥土カルシウム均一混合物を、オートクレーブにて反応温度:180℃、反応時間:5時間、絶対圧力:1.01MPaの条件により水熱処理して固化させた。その結果、比重:1.5以上(1.50〜1.95)、吸水率:25%以下(10.0〜24.4%)、圧縮強度:約200kg/cm2 である粒状の固化品が得られた。
【0037】
このようにして得られた粒状の固化品を破砕・分級して人工細骨材(人工砂)とし、製砂設備で生産される天然原料からの天然細骨材に重量で該細骨材の例えば約5%程度混ぜることにより比重:2.5以上、吸水率:3%以下というJIS規格(JIS A5005/1995)を満足するコンクリート用細骨材として用いることが可能である。また、前記粒状の固化品をそのまま道路用路盤材、埋戻し材として用いることが可能である。
【0038】
【発明の効果】
以上述べたように、本発明による濁水ケーキの処理方法によると、砕石プラントの湿式製砂設備で発生する濁水ケーキを処理して、用途が広く需要量の多いコンクリート用細骨材,道路用路盤材などとして利用可能な強度の高い固化品を得ることができ、ひいては廃棄物の減少化を図ることができる。
【図面の簡単な説明】
【図1】 実施例1における固化品の圧縮強度を示すグラフである。
[0001]
BACKGROUND OF THE INVENTION
The present invention processes a muddy water cake generated in a wet sand making facility of a crushed stone plant to obtain a solidified product with high strength that can be used as a fine aggregate for concrete, road base material, etc. that have a wide use and a large amount of demand. The present invention relates to a method for treating a muddy water cake .
[0002]
[Prior art]
A crushed stone plant that produces crushed stones and crushed sand for roads and buildings, etc. puts stones of about 1m size blasted at a quarry site into a raw material factory (crushing chamber) in the upstream part of the plant and crushes them with a crusher , Sieving according to the size of crushed stone with a sieve, repeatedly crushing and sieving and sorting out large non-standard crushed stones, and finally shipping crushed stones and crushed sand sorted by standard particle size as products A sand making facility for producing fine aggregate for concrete having a particle size of 5 mm or less is installed in the downstream part of the plant.
[0003]
In the sand-making facility of the crushed stone plant, the crushed product is washed with water to remove adhered mud and unnecessary fine stone particles for the purpose of improving product quality. In particular, in concrete fine aggregate (crushed sand), the content of fine stone particles of 75 μm or less contained in the product is limited. For the production of fine aggregate, the fine stone particles are removed. The crushed product having a particle size of 5 mm or less is washed with water. The washing water after use in the wet equipment for performing this washing is muddy water containing about 5 to 10% by weight of fine stone particles and / or mud content of about 75 μm or less, and is called “turbid water”. . The muddy water is a mud sludge that is a mud sludge containing silica and containing water by concentrating and dewatering the mud separated from the water by a mechanical equipment for concentration / dehydration such as thickener and filter press, or a sedimentation basin type equipment. Made into a cake. The mud cake resulting from such muddy water treatment is called “turbid water cake”. For example, when producing fine aggregate for concrete, about 10% of the fine aggregate production is generated by weight.
[0004]
In recent years, in order to reduce waste from the viewpoint of environmental conservation, this mud cake is simply mixed with quick lime, cement and the like and used as a low-strength material such as landfill material and embankment material.
[0005]
However, in this method, the strength (uniaxial compressive strength) of the product obtained is as low as about 10 kg / cm 2 or less, and the use is limited to low-strength civil engineering materials such as the above-mentioned landfill materials and embankment materials, and is always stable. In fact, there is no mass demand, and the expansion of usage cannot be expected.
[0006]
Next, stone powder (dry stone powder) which is also a by-product will be described. In a sandmaking facility of a crushed stone plant, a crushed product having a particle size of 5 mm or less is classified by a dry classifier such as an air separator in order to remove the fine stone particles of 75 μm or less, and then the fine particles remaining without separation are removed. Some facilities employ a sand making process in which stone particles are removed by washing with water. In such a sand making process, fine stone particles of 75 μm or less are mainly generated as a by-product by classification with the air separator or the like. These fine stone particles are called stone powder (dry stone powder). When producing fine aggregate for concrete, about 10% of fine aggregate production is generated by weight.
[0007]
In addition, as described above, a crusher and a sieve device for producing crushed stone according to particle size are provided in the upstream portion of the sand making facility in the crushed stone plant, and in these devices, the dust collected by the dust collector is collected. Stone powder (dry stone powder) that is fine stone particles (particle size: average 15 μm) is generated as a by-product as dust.
[0008]
However, although such stone powder is also being developed to be used as a substitute for limestone powder, which is a mixture of high-fluidity concrete, it currently has no other use and is essentially waste. It is the actual situation. In addition, muddy water and stone powder generated as a by-product in a so-called gravel plant that uses river rocks as raw stones are not used as resources. Here, this gravel plant is also referred to as a crushed stone plant.
[0009]
Other silica-containing by-products include clay-treated muddy water and construction sludge. Explaining dredged turbid water, usually dredged soil (sediment generated when dredging lakes, rivers, dam lakes, etc.) has a high water content, and the dredged material is separated into large, medium and small stones and sand by a sieving machine. When it is separated, etc., turbid water accompanying water washing is generated. As is well known, construction sludge is a mud-like drilling that has a high water content and is finely divided due to civil engineering construction such as the underground continuous wall method, the muddy water shield method, and the high-pressure jet agitation method. is there.
[0010]
However, most of such dredged turbid water and construction sludge are made into silica-containing mud sludge (mud cake) for volume reduction, and from the viewpoint of environmental conservation, There is a strong need for useful processes that lead to reductions.
[0011]
[Problems to be solved by the invention]
Therefore, the present invention treats muddy water cake generated in the wet sand making facility of a crushed stone plant to produce a solidified product with high strength that can be used as a fine aggregate for concrete, road base material, etc. It aims at providing the processing method of the muddy water cake which can be obtained.
[0012]
[Means for Solving the Problems]
The invention of claim 1 which solves the above-mentioned problem is a mud clay by adding 5 to 10% by weight of quick lime to a muddy water cake and quick lime generated in a wet sand making facility of a crushed stone plant, and mixing uniformly. A method for treating a muddy water cake to obtain a homogeneous calcium mixture, and then hydrothermally treating the muddy calcium uniform mixture to obtain a solidified product having a uniaxial compressive strength of 200 kg / cm 2 or more , wherein the muddy calcium is used as the muddy water cake. When using a turbid water cake with a moisture content satisfying the range of 5 to 35% of the moisture content of the uniform mixture, and mixing the muddy water cake and the quicklime, each unmixed in the cross section of the specimen filled with the uniform mud calcium mixture Perform uniform mixing so that the diameter of the part corresponding to a circle is 2 mm or less, and saturation at a temperature of 130 to 300 ° C. as hydrothermal treatment conditions A method for treating a muddy water cake, characterized in that the hydrothermal treatment is performed under a water vapor pressure in 1 to 24 hours .
[0013]
[0014]
[0015]
[0016]
DETAILED DESCRIPTION OF THE INVENTION
According to the method for treating a muddy water cake according to the present invention, a muddy water cake and a calcium compound are uniformly mixed to obtain a uniform mud calcium mixture, and then the mud calcium uniform mixture is solidified by hydrothermal treatment to obtain a solidified product. Is. An example of the calcium compound is calcium oxide (quick lime) . Here, the addition of the calcium compound to the silica-containing mud sludge is to generate calcium silicate (calcium silicate) such as tobermorite (5CaO · 6SiO 2 · 5H 2 O) by hydrothermal treatment described later. And since the weight ratio of Ca to Si (Ca / Si) of the tobermorite crystals is 5/6, the weight ratio (Ca / Si) in the homogeneous mud calcium mixture is 5/6 or less. Add to the muddy water cake . The homogeneous mud calcium mixture is preferably in the range of a moisture content of 5 to 35% from the viewpoint of the compressive strength of the solidified product by hydrothermal treatment.
[0017]
By the way, in the mixture of muddy water cake and quicklime , even if the weight ratio of Ca and Si (Ca / Si) is 5/6 on average, if the degree of uniform mixing of the mixture is low, the weight A portion having a remarkably small ratio value is generated. For this reason, a region where calcium silicate is not generated remains in the subsequent hydrothermal treatment, and the solidified product having high compressive strength and small compressive strength variation and stable quality cannot be obtained.
[0018]
Therefore, in the muddy water cake processing method according to the present invention, the muddy water cake and quicklime as an additive are uniformly mixed to obtain a uniform mud calcium mixture. This uniform mixing is performed by high-speed stirring unlike the conventional one. Although this stirring speed (stirring blade rotation speed) varies depending on the water content, tackiness, etc. of the muddy water cake to be treated, it cannot be specified unconditionally. For example, when mixing with a mechanical stirring mixer, the conventional stirring blade rotation Compared to the speed (the conventional rotating speed of the stirring blade was set so that the purpose of reducing the fluidity of the muddy water cake was to lower the fluidity and granulation within the required particle size range was possible) For example, the mixing may be performed at a blade rotation speed 4 to 5 times higher than that.
[0019]
Specifically, the present invention is not limited to the following examples. For example, in the case of a high-speed vertical blade type mixer, the rotational speed of the stirring blade may be set in a range of 1250 to 3000 rotations / minute. Then, the rotation speed of the stirring blade may be set at about half of the rotation speed: 200 to 500 rotations / minute and the revolution: rotation speed. As is well known, a high-speed vertical blade type mixer is configured such that a single stirring blade having a vertical rotating shaft extending in the vertical direction rotates in a fixed container. In addition, the spiral mixer is equipped with a single stirring blade mounted with its blade axis extending vertically and vertically, and the stirring blade is rotated eccentrically from the center of the container. The container is fixed without rotating. The stirring blade performs mixing while rotating and revolving.
[0020]
And, in the treatment method according to the present invention, the uniform mixing of the muddy water cake and quicklime is equivalent to the circular shape of each unmixed part in the cross section of the filled specimen when the filled specimen of the obtained uniform mud calcium mixture is prepared. It is good to mix so that the diameter of 2 mm or less may be satisfied. Here, the filling specimen of the uniform mud calcium mixture is based on the standards of the Japan Society of Geotechnical Engineers. The uniform mud calcium mixture is filled into a mold, and tamped by a tamping test device, and is a cylinder having a diameter of 50 mm and a length of 100 mm. It is molded into For each unmixed portion having a circular shape, an island shape, etc. in a plan view in a cross section of the specimen obtained by cutting the specimen, the area Di is measured and the diameter Di is calculated assuming that the shape is circular. Ask. In addition, in order to eliminate the influence due to the variation in the compaction of the specimen, the diameter Di when there is a gap in the unmixed portion is the value of the diameter corresponding to the circle in the unmixed portion excluding the gap. is there.
[0021]
And each of these individual unmixed portions is mixed so that the diameter Di at the time of the circle becomes 2 mm or less to obtain a mud calcium uniform mixture, and the compressive strength is obtained by subjecting the mud calcium uniform mixture to hydrothermal treatment. A solidified product having a high quality, a small variation, and a constant quality can be obtained.
[0022]
Further, the uniform mixing of the muddy water cake and quicklime is preferably performed so as to satisfy that the unmixing ratio Nm is 6% or less. The unmixed ratio Nm means that when a filled specimen of a uniform mud calcium mixture is prepared, each unmixed part relative to the cross-sectional area excluding voids in the section of the filled specimen (however, each unmixed part is The ratio of the total area of the diameter Di when the size corresponds to a circle is 0.5 mm or more) is expressed as a percentage. The reason why the total area of unmixed portions having a diameter Di of 0.5 mm or more as the size of the unmixed portion is determined is that the diameter Di is less than 0.5 mm. This is because the unmixed portion does not substantially affect the quality of the solidified product by hydrothermal treatment.
[0023]
Here, how to determine the unmixing ratio Nm will be described in more detail. A filled specimen of a uniform mud calcium mixture that forms a cylindrical body having a diameter of 50 mm and a length of 100 mm is prepared as described above, and this filled specimen is divided into four equal parts in the length direction and cut into round pieces. Regarding the three specimen cross sections having different cutting positions, first, in the first specimen cross section, the cross-sectional area Sa excluding the void portion and each unmixed portion of the cross-sectional area Sa excluding the void portion ( However, the total area Sb of the diameter Di when equivalent to a circle is 0.5 mm or more) is measured, and this ratio (Sb / Sa) is calculated as a percentage as an unmixed ratio. Next, in the same manner, each unmixed rate is calculated in the remaining second and third specimen cross sections. And the average value of each of these three unmixing rates is made into the unmixing rate Nm of the filling specimen by the said mud calcium uniform mixture.
[0024]
Then, mixing is performed so that the unmixed ratio Nm is 6% or less to obtain a mud calcium uniform mixture, and the mud calcium uniform mixture is subjected to hydrothermal treatment, so that the compressive strength is high and the compressive strength is high. Solidified products with small variations and constant quality can be obtained. More preferably, the mixing is performed so that the unmixing ratio Nm is 3% or less.
[0025]
Then, the obtained mud calcium uniform mixture is cured by an autoclave which is hydrothermal treatment. By autoclave curing under saturated vapor pressure, SiO 2 and CaO in the mud calcium homogeneous mixture react to produce calcium silicate. As a result, solidified products are obtained in which the particles are firmly fixed, the porosity is small, the compressive strength is high, the quality is constant, and the concrete can be used as fine aggregate for concrete, roadbed material for roads, etc. . In hydrothermal treatment, among calcium silicates, it is preferable that crystals grow at a relatively low temperature of about 130 to 300 ° C. to produce tobermorite having high strength. As hydrothermal treatment conditions, reaction temperature (autoclave curing temperature): 130 to 300 ° C., reaction time (curing time): 1 to 24 hours are appropriate. The reaction temperature of 130 to 300 ° C. is a temperature range in which the crystal growth of tobermorite is well promoted, and the higher the reaction temperature, the higher the reaction rate, so the reaction time is shorter if the same quality (strength, water absorption). I'm sorry. Typical hydrothermal treatment conditions are: reaction temperature: 180 ° C., reaction time: 5 hours, absolute pressure: 1.01 MPa (10 atm).
[0026]
【Example】
Examples of the present invention will be described below.
[0027]
[Example 1] The mixer A used in this example and the mixer B used in the comparative example are both single-shaft spiral mixers which are spiral mixers. As described above, the single-screw spiral mixer performs mixing while rotating and revolving the stirring blade. Mixer A is a high-speed mixer equipped with a hook-type stirring blade, while mixer B is a low-speed mixer equipped with a beater-type stirring blade.
[0028]
In the examples , a muddy water cake having a water content of 25% was used. 3-10% by weight of quicklime is added to the muddy water cake (less than 5% by weight is a reference example) , and the muddy water cake and quicklime are uniformly mixed by the mixer A to obtain a uniform mud calcium mixture. Obtained. The operating conditions of the mixer A are the rotation speed of the stirring blade: 288 rotations / minute for rotation, 135 rotations / minute for revolution, and the processing time: 2 minutes.
[0029]
And about the obtained mud calcium uniform mixture, in order to investigate the degree of uniform mixing, the filling test piece was produced, and the diameter Di at the time of circular equivalent of the unmixed part mentioned above was measured. The filled specimen is obtained by filling the obtained mud calcium uniform mixture into a mold, and tamping it with a tamping test device, and molding it into a cylinder having a diameter of 50 mm and a length of 100 mm. This filled specimen is divided into four equal parts in the length direction and cut into round pieces. Regarding the obtained specimen cross sections having different cutting positions, first, the area of each unmixed portion in the first specimen cross section is measured. Assuming that the shape is circular, the diameter Di was calculated and obtained. A known image analysis device (image processing device) was used to measure the area of the unmixed portion and the diameter Di when the circle was equivalent. Next, from these measurement data Di, [Di> 2 mm]: A 1 %, [0.5 mm ≦ Di ≦ 2 mm]: B 1 %, [Di <0.5 mm]: C 1 %, and so on. Thus, the distribution of the diameter Di of the unmixed portion was obtained. Similarly, for the remaining second specimen cross-section and third specimen cross-section, such distributions of the values of the diameter Di are obtained respectively, [Di> 2 mm], [0.5 mm ≦ Di ≦ 2 mm]. And the average value about these three specimen cross sections regarding [Di <0.5 mm] was obtained. The results of the examples are shown in Table 1. Further, the above-mentioned unmixing ratio Nm is obtained by the procedure described above, and the result is also shown in Table 1.
[0030]
Subsequently, the hydrothermal solidification product which uses the obtained mud calcium uniform mixture was produced, and the compressive strength was measured. That is, a cylindrical pressure-molded body having a diameter of 25 mm and a length of 50 mm was prepared using the obtained mud calcium uniform mixture, and this was subjected to reaction temperature: 180 ° C., reaction time: 5 hours, absolute pressure: It was solidified by hydrothermal treatment under the condition of 1.01 MPa. The compression strength (uniaxial compression strength) of the obtained solidified product was measured. The result is shown in FIG.
[0031]
Next, a comparative example will be described. In the comparative example, 5 to 12% by weight of quick lime is added to the muddy water cake having a water content of 25%, and the muddy water cake and quick lime are mixed using the mixer B instead of the mixer A, and the mixture. Got. The operating conditions of the mixer B are: the rotation speed of the stirring blade: 108 rotations / minute for rotation, 66 rotations / minute for revolution, and processing time: 2 minutes. In the obtained mixture, the unmixing ratio Nm and the diameter Di of the unmixed part were determined. The measurement results are shown in Table 1. Further, the mixture was hydrothermally treated under the same procedure and under the same conditions as in the Examples to produce a solidified product, and the compressive strength (uniaxial compressive strength) of the solidified product was measured. The result is shown in FIG.
[0032]
[Table 1]
[0033]
As can be seen from the results shown in Table 1 and FIG. 1, in the comparative example, there was a portion where the diameter Di of the unmixed portion exceeded 2 mm in the mixture, and the ratio was considerably high at 23%. Nm was also as high as 36%, and the muddy water cake and quicklime were not uniformly mixed. For this reason, as shown in FIG. 1, the solidified product that has been hydrothermally treated has a very large variation in compressive strength even when the amount of added calcium is the same, and the quality is unstable.
[0034]
In contrast, in the examples, a uniform mud calcium mixture having an unmixed portion diameter Di of 2 mm or less and an unmixed ratio Nm of 0.2% was obtained. As shown in FIG. 1, the solidified product obtained by hydrothermally treating this uniform mud calcium mixture has a higher compressive strength and a smaller variation in compressive strength than the comparative example with the same calcium addition amount, and the quality is stable. Was. Thus, according to the present invention, it is possible to obtain a solidified product with high strength that can be used as fine aggregate for concrete, roadbed material for roads, and the like.
[0035]
Example 2 In this example, a solidified product that can be used as a fine aggregate for concrete was produced. First, in this example, 5% by weight of quicklime is added to a turbid water cake with a water content of 25% from a crushed stone plant, and the turbid water cake and quicklime are mixed at high speed with the above-mentioned high-speed vertical blade type mixer, and mud is mixed. A homogeneous mixture of calcium was obtained. Subsequently, the high-speed vertical blade type mixer was operated at a low speed to perform granulation using the mud calcium uniform mixture as a raw material to obtain a granular mud calcium uniform mixture. The operating conditions of the high-speed vertical blade mixer are: the rotation speed of the stirring blade during uniform mixing: 1300 to 2500 rotations / minute, and the rotation speed of the stirring blade during granulation: 400 to 800 rotations / minute. Under these operating conditions, a mud calcium uniform mixture having a particle size (outer diameter) in the range of about 1 to 10 mm is obtained.
[0036]
Subsequently, the granulated granular mud calcium homogeneous mixture was hydrothermally treated and solidified in an autoclave under the conditions of reaction temperature: 180 ° C., reaction time: 5 hours, absolute pressure: 1.01 MPa. As a result, a granular solidified product having a specific gravity of 1.5 or more (1.50 to 1.95), a water absorption rate of 25% or less (10.0 to 24.4%), and a compressive strength of about 200 kg / cm 2. was gotten.
[0037]
The granular solid product thus obtained is crushed and classified into an artificial fine aggregate (artificial sand). The natural fine aggregate from the natural raw material produced in the sand making facility is mixed with the fine aggregate by weight. For example, by mixing about 5%, it can be used as a fine aggregate for concrete satisfying the JIS standard (JIS A5005 / 1995) of specific gravity: 2.5 or more and water absorption: 3% or less. Moreover, it is possible to use the granular solidified product as it is as a roadbed material and a backfill material.
[0038]
【The invention's effect】
As described above, according to the method for treating muddy water cake according to the present invention, muddy water cake generated in a wet sand making facility of a crushed stone plant is treated, and the fine aggregate for concrete and road subbase having a wide use and high demand. A solidified product having high strength that can be used as a material can be obtained, and as a result, waste can be reduced.
[Brief description of the drawings]
1 is a graph showing the compressive strength of a solidified product in Example 1. FIG.

Claims (1)

砕石プラントの湿式製砂設備で発生する濁水ケーキと、生石灰とを、濁水ケーキに対して生石灰を5〜10重量%添加し、均一混合して泥土カルシウム均一混合物を得、しかる後、該泥土カルシウム均一混合物を水熱処理して一軸圧縮強度が200kg/cm以上の固化品を得る濁水ケーキの処理方法であって、前記濁水ケーキとして、前記泥土カルシウム均一混合物の含水率が5〜35%の範囲を満たす含水率の濁水ケーキを用いること、当該濁水ケーキと前記生石灰とを混合するに際し、その泥土カルシウム均一混合物の充填供試体の断面において各未混合部分の円形相当時の直径が2mm以下であることを満足するように均一混合を行うこと、水熱処理条件として温度130〜300℃の飽和水蒸気圧の下で1〜24時間にて前記水熱処理を行なうことを特徴とする濁水ケーキの処理方法。The muddy water cake generated in the wet sand making facility of the crushed stone plant and quick lime are added to the muddy water cake by adding 5 to 10% by weight of quick lime and uniformly mixed to obtain a uniform mixture of mud calcium, and then the mud calcium A method for treating a muddy water cake by hydrothermally treating a homogeneous mixture to obtain a solidified product having a uniaxial compressive strength of 200 kg / cm 2 or more, wherein the water content of the homogeneous mud calcium mixture is in the range of 5 to 35% as the muddy water cake. When the turbid water cake having a water content satisfying the above conditions is mixed, and when the turbid water cake and the quicklime are mixed, the diameter of each unmixed portion corresponding to a circle in the cross-section of the filled specimen of the mud calcium uniform mixture is 2 mm or less. The water is uniformly mixed so as to satisfy the above conditions, and the hydrothermal treatment conditions are carried out for 1 to 24 hours under a saturated water vapor pressure of 130 to 300 ° C. A method for treating a muddy water cake, characterized by performing a heat treatment .
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