JP4049493B2

JP4049493B2 - Flocculant

Info

Publication number: JP4049493B2
Application number: JP28488599A
Authority: JP
Inventors: 康広内山; 俊久丸田
Original assignee: Taiheiyo Cement Corp
Current assignee: Taiheiyo Cement Corp
Priority date: 1999-10-05
Filing date: 1999-10-05
Publication date: 2008-02-20
Anticipated expiration: 2019-10-05
Also published as: JP2001104711A

Description

【０００１】
【発明が属する技術分野】
本発明は、下水、産業廃水、浚渫土の処理の際に用いられる凝集剤に関する。より詳細には、これらに含まれる汚泥粒子を凝集する凝集剤であってセメント製造の中間処理工程から容易に得られる取り扱い性に優れた無機性の凝集剤に関する。
【０００２】
【従来技術】
河川、湖沼、海域等の浚渫土或いは下水や産業廃水は、一般に多量の汚泥粒子が懸濁した泥漿状の流体となっている。これらを処分する場合、昨今の埋立処分地の枯渇化に伴い、減容化即ちその容積をできるだけ減少させることが望まれる。また、これらを有効利用する場合もハンドリング性の向上のために減容化は不可欠である。減容化の方法としては、天日乾燥・サンドドレーン等の土木的脱水、真空濾過等の機械的脱水および凝集剤の添加或いはこれらの技術を組み合わせる方法がある。被脱水物が高含水率のものでは、直接土木的脱水処理を行うと処理時間が長くなり、その間対象物によっては異臭を発したり、また均一な減容化も行い難い為、まず凝集剤で沈降分離させ、これを土木的脱水処理や機械的脱水することが行われている。一方で、凝集剤を用いる方法は他の処理策と比較すると一般に処理コストが高いものとなりがちであり、とりわけ高分子系凝集剤は添加量は少なくて済むものの単価がかなり高い。このため、比較的安価な無機系の凝集剤、中でもより安価な凝集剤としてセメント中間品などから製造されたものの開発が進められている。
【０００３】
【発明が解決する課題】
セメント中間品から製造した凝集剤は、セメントクリンカー焼成物を原料とし、コスト増加を抑えるために物理的及び化学的処理を最小限度に留めたもので、従って新たな添加物を配合しない限り、その主成分がシリカと生石灰からなるものである。このため、凝集化処理効率を高める観点から従来の無機系凝集剤で一般に行われるように、凝集剤を水に加えて液状に調整した凝集剤溶液を使用しようとすると、生石灰と水とが反応し、顕著な発熱が起こる為、取り扱いに制約が生じた。
【０００４】
【課題を解決するための手段】
本発明者らは、前記課題の解決、即ちコストの増加を抑え、且つ凝集化能力も低下させず、発熱を抑制して取り扱い性の改善を検討した結果、前記のような凝集剤の主成分たる生石灰の一部又は全てを、水と反応しても顕著な発熱が起きない水酸化カルシウムに変換することで、かかる課題の解決を図ることができた。
【０００６】
即ち、本発明は、シリカおよびカルシウムを主成分とし、セメントクリンカー焼成キルンの途中から取り出されたクリンカー半焼成物であって、Ｃａ（ＯＨ）_２又はＣａ（ＯＨ）_２とＣａＯを４５〜７５重量％、ＳｉＯ_２５〜３０重量％、Ａｌ_２Ｏ_３１〜８重量％、Ｆｅ_２Ｏ_３０．５〜６重量％の鉱物成分を含み、且つＣａＯとＣａ（ＯＨ）_２の含有重量比がＣａＯ／Ｃａ（ＯＨ）_２＝０〜９であることを特徴とする凝集剤である。
【０００７】
【発明の実施の形態】
本発明は、例えば河川、湖沼、海域等の浚渫土、産業廃水、家庭等からの下水などの、懸濁粒子からなる泥漿を凝集対象とした凝集剤に関するものである。本発明の凝集剤は、シリカおよび水酸化カルシウムを主成分とし、アルミニウム分及び鉄分を酸化物換算でおのおの１〜８重量％、０．５〜６重量％含むものであり、本発明においてシリカおよび水酸化カルシウムを主成分とするとは、これら二成分の合計含有量が、他の含有化学成分中最大の含有量を示す成分の含有量よりも多いことを云う。
【０００８】
上記成分中、シリカ及び水酸化カルシウムは、高含水汚泥中の水分と各種の珪酸カルシウム化合物を生成することにより、脱水作用と固形化作用を発揮する。また、アルミニウム分と鉄分はアルミニウムイオン及び鉄イオンの供給源となり、カルシウムイオンと共に汚泥粒子表面の陰イオンを中和して凝集を誘発させる。アルミニウム分及び鉄分が酸化物換算で、各々１重量％未満、０．５重量％未満ではこの効果が十分ではない。一方、アルミニウム分及び鉄分が各々８重量％、６重量％を超えても上記効果は大差ない。アルミニウム分の含有量は１〜８重量％が適当であり、３〜７重量％が好ましい。また、鉄分の含有量は０．５〜６重量％が適当であり、１〜５重量％が好ましい。
【０００９】
本発明の凝集剤は、セメント製造工程の中間品から好適に得ることができる。即ち、本発明はセメント製造工程でのクリンカー焼成中に取り出した中間品を消化することにより凝集剤として使用できるようにしたものである。ここで、セメント製造工程の中間品とは、セメントクリンカー焼成キルンの途中から取り出されたクリンカー半焼成物であり、セメント製造ではクリンカーに添加配合される他の原料成分は未配合としたものである。また、この中間品に粉砕等の物理的加工や加熱等を行う必要は特にない。即ち、適度の加水による消化のみを行えば良く、従って、極めて簡単に作製でき、製造コストも比較的安価である。
【００１０】
セメント製造工程の中間品から得られる本発明の上記凝集剤は、具体的には、ＳｉＯ₂：５〜３０重量％、Ａｌ₂Ｏ₃：１〜８重量％、Ｆｅ₂Ｏ₃：０．５〜６重量％の鉱物成分を含み、更にＣａ（ＯＨ）₂又はＣａ（ＯＨ）₂とＣａＯ：４５〜７５重量％、但し、ＣａＯの含有重量／Ｃａ（ＯＨ）₂の含有重量＝０〜９なる関係を満たす成分を含むものである。本凝集剤ではこれ以外の含有成分として、通常のセメントクリンカー焼成物に含まれる成分も含むことができる。
【００１１】
ＳｉＯ₂、Ａｌ₂Ｏ₃、Ｆｅ₂Ｏ₃の各成分の上記含有量範囲は、セメント製造の中間品中の成分含有量範囲でもあるため、前記成分の含有量は自ずと上記範囲に定まる。一方、カルシウム分も同様に中間品中に含まれるカルシウム分の含有範囲によって定まるものの、中間品中に含まれるカルシウム分の存在形態としては大部分が生石灰（ＣａＯ）及び遊離ＣａＯで存在する為、本発明の凝集剤ではこのＣａＯのうちの１０〜１００重量％をＣａ（ＯＨ）₂に変換して含有させたものとする。即ち、ＣａＯの含有重量／Ｃａ（ＯＨ）₂の含有重量＝０〜９なる関係を満たす必要がある。ＣａＯの含有重量／Ｃａ（ＯＨ）₂の含有重量の値が９を超えると水に加えた時の発熱反応が顕著となり、取り扱い性に支障を及ぼすことがあるので好ましくない。尚、ＣａＯの含有重量／Ｃａ（ＯＨ）₂の含有重量の値が０に近づくほど水を加えた時の反応は常温に近づくので、より好ましくは、ＣａＯの含有重量／Ｃａ（ＯＨ）₂の含有重量＝０〜２とする。カルシウム分は含水処理物中の固体粒子を固結化できると共に、比較的早期の凝集力にも優れる。
【００１２】
尚、中間品中に含有するＣａＯのＣａ（ＯＨ）₂への変換方法としては、公知の消化方法であれば特に限定されないが、例えば、常圧式消化装置や加圧式消化装置を用いた乾式消化、ロータリー式、クラリファイヤー式、粉砕消化機を用いた湿式消化、散水機を用いた散水による消化等の操作を行えば容易にできる。尚、消化操作に於いて、大量のＣａＯを水によって一気にＣａ（ＯＨ）₂にすると、Ｃａ（ＯＨ）₂への変換率を高めたものほど消化の際に発熱し易くなるので、その場合は前記例示した装置を使用し、比較的少量ずつ消化操作を行うのが望ましい。
【００１３】
本発明の凝集剤は、粉末のままでも使用できるが、水に加えて混合し、水溶液として使用すると良い。水溶液にすることで高含水の処理対象物にも均一且つ速やかに混ざり易く、凝集処理効率が格段に高まる。水溶液中の凝集剤濃度は特に限定されないが、好ましくは５〜４０％が良く、通常は外見的に乳濁状の溶液となれば使用できる。処理対象物に対する凝集剤溶液の使用量も特に限定されるものではないが、高含水処理物を凝集処理対象とする場合、処理対象物１００重量部に対し、固形分で概ね０．１〜１００重量部相当を加えるのが好ましい。これは０．１重量部未満では凝集作用が極めて乏しく、また１００重量部を超える添加量では凝集作用の向上が殆ど見られないため好ましくない。
【００１４】
凝集剤添加後の凝集物は、必要に応じ、濃縮、沈降、脱水等を公知手法で行うことによって、十分な減容化や一層の処理時間の短縮を行うことができる。尚、本凝集剤は他の公知無機系凝集剤と併用しても良い。
【００１５】
【実施例】
［実施例１〜３］普通セメント製造のクリンカー焼成中に取り出したクリンカー構成成分以外には配合物を加えてない中間品に、該中間品１００重量部に対し、水約１５重量部が加わるよう常圧式消化装置を用いて消化処理を行い、表１に記した含有成分のフレーク状の凝集剤を作製した。この凝集剤の表２に記した重量分をそれぞれ１００ｇの２５℃の水に添加し、攪拌混合して凝集剤溶液を作製した。凝集剤を水に添加してから約１分後の凝集剤溶液の温度を測定し、その結果を併せて表２に記す。次いで作製した各凝集剤溶液の全量を、表３に記した固形成分からなる泥水２５００ｇ（含水率約８０％）に投入し、攪拌機で約３分間攪拌した。攪拌混練物は約１リットルをメスシリンダーに移してこれを静置し、その間の混練物単位容積あたりの発生ブリージング水の容積比を減容化率として３０分〜３日間の経時変化で調べた。その結果を表２に併せて記す。
【００１６】
【表１】

【００１７】
［比較例１］参考として他の条件は全て同じで、前記加水による消化、即ちＣａＯのＣａ（ＯＨ）₂への変換処理のみを行っていない表１記載含有成分の凝集剤を、固形分濃度がほぼ３０重量％の溶液となるよう２５℃の水に添加混合した。混合直後の凝集剤溶液の温度を測定し、更にこの凝集剤溶液についても前記と同様の泥水２．５Ｋｇに凝集剤溶液の全量を投入し、投入した際の減容化率を調べた。測定結果は表２に併せて記す。
【００１８】
【表２】

【００１９】
【表３】

【００２０】
【発明の効果】
本発明の凝集剤は、経済的にも安価であり、水と混ぜても顕著な発熱を生じることなく、ほぼ常温の溶液として得ることができるので、この溶液を用いることで大量の含水処理対象物に対しても、高い凝集力で斑無く短時間で安定した凝集処理を行うことができる。[0001]
[Technical field to which the invention belongs]
The present invention relates to a flocculant used in the treatment of sewage, industrial wastewater and dredged soil. More specifically, the present invention relates to an aggregating agent that agglomerates the sludge particles contained therein and is excellent in handleability easily obtained from an intermediate treatment step of cement production.
[0002]
[Prior art]
In general, dredged soil such as rivers, lakes, and marine areas, sewage, and industrial wastewater are in the form of a mud-like fluid in which a large amount of sludge particles are suspended. When disposing of these, it is desired to reduce the volume, that is, to reduce the volume as much as possible, in accordance with the recent depletion of landfill sites. Even when these are used effectively, volume reduction is indispensable for improving handling. As a method for volume reduction, there are methods of civil engineering dehydration such as sun drying and sand drain, mechanical dehydration such as vacuum filtration, addition of flocculant, or a combination of these techniques. If the material to be dehydrated has a high water content, the processing time will be longer if the direct civil engineering dehydration process is performed, and during that time, depending on the object, it may be difficult to produce a strange odor or to reduce the volume uniformly. A sedimentation separation is performed, and this is subjected to civil engineering dehydration or mechanical dehydration. On the other hand, the method using a flocculant generally tends to be high in processing cost as compared with other treatment measures. In particular, although the amount of the polymer flocculant is small, the unit price is considerably high. For this reason, the development of relatively inexpensive inorganic flocculants, especially those manufactured from cement intermediates or the like as cheaper flocculants, is underway.
[0003]
[Problems to be solved by the invention]
Flocculants produced from cement intermediates are made from cement clinker calcined material, with minimal physical and chemical treatments to reduce costs, so unless new additives are added The main component consists of silica and quicklime. For this reason, from the viewpoint of increasing the agglomeration efficiency, if an attempt is made to use a flocculant solution prepared by adding a flocculant to water, as is generally done with conventional inorganic flocculants, quick lime reacts with water. However, since significant heat generation occurred, the handling was restricted.
[0004]
[Means for Solving the Problems]
As a result of studying the solution of the above problems, that is, suppressing the increase in cost and reducing the agglomeration ability, suppressing the generation of heat and improving the handleability, the main components of the aggregating agent as described above. The problem could be solved by converting a part or all of the quick lime into calcium hydroxide that does not generate significant heat generation even when reacted with water.
[0006]
That is, the present invention is a clinker semi-calcined product mainly composed of silica and calcium and taken out from the cement clinker calcined kiln, and contains Ca (OH) ₂ or Ca (OH) ₂ and CaO in an amount of 45 to 75% by weight. _%, SiO 2 5 to 30 _wt%, Al ₂ O 3 1 to _8% by weight, include _Fe 2 O 3 0.5 to 6 wt% of the mineral component, and CaO and Ca _{(OH) 2} containing a weight ratio of It is a flocculant characterized by CaO / Ca (OH) ₂ = 0-9.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to an aggregating agent for agglomerating sludge composed of suspended particles such as dredged soil such as rivers, lakes, and marine areas, industrial wastewater, and sewage from households. The flocculant of the present invention is mainly composed of silica and calcium hydroxide, and contains 1 to 8% by weight and 0.5 to 6% by weight of aluminum and iron in terms of oxides. To have calcium hydroxide as a main component means that the total content of these two components is larger than the content of the component showing the maximum content among the other contained chemical components.
[0008]
Among the above components, silica and calcium hydroxide exhibit a dehydrating action and a solidifying action by generating water in the high water content sludge and various calcium silicate compounds. Further, aluminum and iron are sources of aluminum ions and iron ions, and together with calcium ions, the anions on the surface of the sludge particles are neutralized to induce aggregation. If the aluminum content and iron content are less than 1% by weight and less than 0.5% by weight, respectively, in terms of oxide, this effect is not sufficient. On the other hand, even if the aluminum content and the iron content exceed 8% by weight and 6% by weight, the above effects are not significantly different. The aluminum content is suitably 1 to 8% by weight, preferably 3 to 7% by weight. Moreover, 0.5-6 weight% is suitable for content of iron, and 1-5 weight% is preferable.
[0009]
The flocculant of the present invention can be suitably obtained from an intermediate product in the cement manufacturing process. That is, in the present invention, an intermediate product taken out during clinker firing in a cement manufacturing process is digested so that it can be used as a flocculant. Here, the intermediate product of the cement manufacturing process is a clinker semi-fired product taken out from the middle of the cement clinker firing kiln, and other raw material components added and blended in the clinker in cement production are unblended. . Further, it is not particularly necessary to perform physical processing such as pulverization or heating on the intermediate product. That is, it is only necessary to carry out digestion with a moderate amount of water, so that it can be produced very easily and the production cost is relatively low.
[0010]
Specifically, the above-mentioned flocculant of the present invention obtained from an intermediate product in the cement production process is SiO ₂ : 5 to 30% by weight, Al ₂ O ₃ : 1 to 8% by weight, Fe ₂ O ₃ : 0.5 It contains -6% by weight of a mineral component, and further Ca (OH) ₂ or Ca (OH) ₂ and CaO: 45-75% by weight, provided that the content of CaO / the content of Ca (OH) ₂ = 0-9 The component which satisfy | fills this relationship is included. In the present flocculant, as a component other than this, a component contained in an ordinary cement clinker fired product can also be included.
[0011]
Since the above content range of each component of SiO ₂ , Al ₂ O ₃ , and Fe ₂ O ₃ is also a component content range in an intermediate product of cement production, the content of the component is naturally determined within the above range. On the other hand, although the calcium content is similarly determined by the content range of the calcium content contained in the intermediate product, the presence of the calcium content contained in the intermediate product is mostly present as quick lime (CaO) and free CaO, In the flocculant of the present invention, 10 to 100% by weight of CaO is converted into Ca (OH) ₂ and contained. That is, it is necessary to satisfy the relationship of CaO content / Ca (OH) ₂ content = 0-9. If the value of the content weight of CaO / weight of Ca (OH) ₂ exceeds 9, an exothermic reaction becomes remarkable when added to water, and this may be unfavorable for handling properties. In addition, since the reaction when water is added as the value of the content weight of CaO / the content weight of Ca (OH) ₂ approaches 0, the reaction becomes closer to normal temperature, and more preferably, the content of CaO content / Ca (OH) ₂ Content weight = 0-2. The calcium content can solidify the solid particles in the water-containing processed product and is excellent in relatively early cohesion.
[0012]
The method for converting CaO contained in the intermediate product into Ca (OH) ₂ is not particularly limited as long as it is a known digestion method. For example, dry digestion using an atmospheric digester or a pressurized digester It can be easily carried out by performing operations such as a rotary type, a clarifier type, a wet digestion using a pulverizing digester, and a watering digestion using a watering machine. In addition, in the digestion operation, if a large amount of CaO is made into Ca (OH) ₂ at once with water, the higher the conversion rate to Ca (OH) ₂ , the easier it is to generate heat during digestion. It is desirable to perform the digestion operation in a relatively small amount using the apparatus exemplified above.
[0013]
The flocculant of the present invention can be used as a powder, but it is preferable to use it as an aqueous solution by mixing in addition to water. By making it into an aqueous solution, it is easy to mix evenly and rapidly with a high water content treatment object, and the coagulation treatment efficiency is remarkably increased. The concentration of the flocculant in the aqueous solution is not particularly limited, but it is preferably 5 to 40%. Usually, it can be used if it becomes an emulsion-like solution in appearance. The amount of the flocculant solution used with respect to the object to be treated is not particularly limited, but when a high water content treated object is to be agglomerated, the solid content is generally about 0.1 to 100 parts per 100 parts by weight of the object to be treated. It is preferable to add the equivalent of parts by weight. If the amount is less than 0.1 parts by weight, the aggregating action is extremely poor, and if the amount is more than 100 parts by weight, the improvement of the aggregating action is hardly observed, which is not preferable.
[0014]
The aggregate after the addition of the flocculant can be sufficiently reduced in volume and further shortened in processing time by performing concentration, sedimentation, dehydration, and the like by a known method as necessary. The flocculant may be used in combination with other known inorganic flocculants.
[0015]
【Example】
[Examples 1 to 3] About 15 parts by weight of water is added to 100 parts by weight of the intermediate product to an intermediate product to which no compound is added other than the clinker component extracted during the clinker firing of ordinary cement. Digestion treatment was performed using a normal pressure digestion apparatus, and flaky flocculants having the components shown in Table 1 were prepared. The weight of the flocculant shown in Table 2 was added to 100 g of water at 25 ° C. and stirred to prepare a flocculant solution. The temperature of the flocculant solution is measured about 1 minute after adding the flocculant to water, and the results are also shown in Table 2. Next, the total amount of each of the prepared flocculant solutions was charged into 2500 g (water content: about 80%) of muddy water composed of the solid components shown in Table 3, and stirred with a stirrer for about 3 minutes. About 1 liter of the stirred kneaded product was transferred to a graduated cylinder and allowed to stand, and the volume ratio of the generated breathing water per unit volume of the kneaded product during that time was examined as a volume reduction rate, with a time course of 30 minutes to 3 days. . The results are also shown in Table 2.
[0016]
[Table 1]

[0017]
[Comparative Example 1] For reference, all other conditions are the same, and the flocculant of the components described in Table 1 that has not been subjected to the above-described digestion by hydrolysis, that is, only the conversion treatment of CaO to Ca (OH) ₂ , was obtained. Was added to and mixed with water at 25 ° C. so that an approximately 30 wt% solution was obtained. The temperature of the flocculant solution immediately after mixing was measured, and also for this flocculant solution, the entire amount of the flocculant solution was charged into 2.5 kg of the same mud water as described above, and the volume reduction rate when charged was examined. The measurement results are also shown in Table 2.
[0018]
[Table 2]

[0019]
[Table 3]

[0020]
【The invention's effect】
The flocculant of the present invention is economical and inexpensive, and can be obtained as a solution at about room temperature without causing significant heat generation even when mixed with water. Even a product can be stably agglomerated in a short time without unevenness with a high agglomeration force.

Claims

A clinker semi-calcined product mainly composed of silica and calcium and taken out from the middle of a cement clinker calcined kiln, comprising Ca (OH) ₂ or Ca (OH) ₂ and CaO in an amount of 45 to 75% by weight, SiO ₂ 5 30% by weight, Al ₂ O ₃ 1-8% by weight, Fe ₂ O ₃ 0.5-6% by weight of mineral components, and the content ratio of CaO and Ca (OH) ₂ is CaO / Ca (OH) _2. A flocculant characterized by being 0-9.